1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 * Swap reorganised 29.12.95, Stephen Tweedie.
6 * kswapd added: 7.1.96 sct
7 * Removed kswapd_ctl limits, and swap out as many pages as needed
8 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
9 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
10 * Multiqueue VM started 5.8.00, Rik van Riel.
13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
16 #include <linux/sched/mm.h>
17 #include <linux/module.h>
18 #include <linux/gfp.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/swap.h>
21 #include <linux/pagemap.h>
22 #include <linux/init.h>
23 #include <linux/highmem.h>
24 #include <linux/vmpressure.h>
25 #include <linux/vmstat.h>
26 #include <linux/file.h>
27 #include <linux/writeback.h>
28 #include <linux/blkdev.h>
29 #include <linux/buffer_head.h> /* for buffer_heads_over_limit */
30 #include <linux/mm_inline.h>
31 #include <linux/backing-dev.h>
32 #include <linux/rmap.h>
33 #include <linux/topology.h>
34 #include <linux/cpu.h>
35 #include <linux/cpuset.h>
36 #include <linux/compaction.h>
37 #include <linux/notifier.h>
38 #include <linux/rwsem.h>
39 #include <linux/delay.h>
40 #include <linux/kthread.h>
41 #include <linux/freezer.h>
42 #include <linux/memcontrol.h>
43 #include <linux/migrate.h>
44 #include <linux/delayacct.h>
45 #include <linux/sysctl.h>
46 #include <linux/memory-tiers.h>
47 #include <linux/oom.h>
48 #include <linux/pagevec.h>
49 #include <linux/prefetch.h>
50 #include <linux/printk.h>
51 #include <linux/dax.h>
52 #include <linux/psi.h>
53 #include <linux/pagewalk.h>
54 #include <linux/shmem_fs.h>
55 #include <linux/ctype.h>
56 #include <linux/debugfs.h>
57 #include <linux/khugepaged.h>
58 #include <linux/rculist_nulls.h>
59 #include <linux/random.h>
61 #include <asm/tlbflush.h>
62 #include <asm/div64.h>
64 #include <linux/swapops.h>
65 #include <linux/balloon_compaction.h>
66 #include <linux/sched/sysctl.h>
71 #define CREATE_TRACE_POINTS
72 #include <trace/events/vmscan.h>
75 /* How many pages shrink_list() should reclaim */
76 unsigned long nr_to_reclaim
;
79 * Nodemask of nodes allowed by the caller. If NULL, all nodes
85 * The memory cgroup that hit its limit and as a result is the
86 * primary target of this reclaim invocation.
88 struct mem_cgroup
*target_mem_cgroup
;
91 * Scan pressure balancing between anon and file LRUs
93 unsigned long anon_cost
;
94 unsigned long file_cost
;
96 /* Can active folios be deactivated as part of reclaim? */
97 #define DEACTIVATE_ANON 1
98 #define DEACTIVATE_FILE 2
99 unsigned int may_deactivate
:2;
100 unsigned int force_deactivate
:1;
101 unsigned int skipped_deactivate
:1;
103 /* Writepage batching in laptop mode; RECLAIM_WRITE */
104 unsigned int may_writepage
:1;
106 /* Can mapped folios be reclaimed? */
107 unsigned int may_unmap
:1;
109 /* Can folios be swapped as part of reclaim? */
110 unsigned int may_swap
:1;
112 /* Proactive reclaim invoked by userspace through memory.reclaim */
113 unsigned int proactive
:1;
116 * Cgroup memory below memory.low is protected as long as we
117 * don't threaten to OOM. If any cgroup is reclaimed at
118 * reduced force or passed over entirely due to its memory.low
119 * setting (memcg_low_skipped), and nothing is reclaimed as a
120 * result, then go back for one more cycle that reclaims the protected
121 * memory (memcg_low_reclaim) to avert OOM.
123 unsigned int memcg_low_reclaim
:1;
124 unsigned int memcg_low_skipped
:1;
126 unsigned int hibernation_mode
:1;
128 /* One of the zones is ready for compaction */
129 unsigned int compaction_ready
:1;
131 /* There is easily reclaimable cold cache in the current node */
132 unsigned int cache_trim_mode
:1;
134 /* The file folios on the current node are dangerously low */
135 unsigned int file_is_tiny
:1;
137 /* Always discard instead of demoting to lower tier memory */
138 unsigned int no_demotion
:1;
140 /* Allocation order */
143 /* Scan (total_size >> priority) pages at once */
146 /* The highest zone to isolate folios for reclaim from */
149 /* This context's GFP mask */
152 /* Incremented by the number of inactive pages that were scanned */
153 unsigned long nr_scanned
;
155 /* Number of pages freed so far during a call to shrink_zones() */
156 unsigned long nr_reclaimed
;
160 unsigned int unqueued_dirty
;
161 unsigned int congested
;
162 unsigned int writeback
;
163 unsigned int immediate
;
164 unsigned int file_taken
;
168 /* for recording the reclaimed slab by now */
169 struct reclaim_state reclaim_state
;
172 #ifdef ARCH_HAS_PREFETCHW
173 #define prefetchw_prev_lru_folio(_folio, _base, _field) \
175 if ((_folio)->lru.prev != _base) { \
176 struct folio *prev; \
178 prev = lru_to_folio(&(_folio->lru)); \
179 prefetchw(&prev->_field); \
183 #define prefetchw_prev_lru_folio(_folio, _base, _field) do { } while (0)
187 * From 0 .. 200. Higher means more swappy.
189 int vm_swappiness
= 60;
191 LIST_HEAD(shrinker_list
);
192 DECLARE_RWSEM(shrinker_rwsem
);
195 static int shrinker_nr_max
;
197 /* The shrinker_info is expanded in a batch of BITS_PER_LONG */
198 static inline int shrinker_map_size(int nr_items
)
200 return (DIV_ROUND_UP(nr_items
, BITS_PER_LONG
) * sizeof(unsigned long));
203 static inline int shrinker_defer_size(int nr_items
)
205 return (round_up(nr_items
, BITS_PER_LONG
) * sizeof(atomic_long_t
));
208 static struct shrinker_info
*shrinker_info_protected(struct mem_cgroup
*memcg
,
211 return rcu_dereference_protected(memcg
->nodeinfo
[nid
]->shrinker_info
,
212 lockdep_is_held(&shrinker_rwsem
));
215 static int expand_one_shrinker_info(struct mem_cgroup
*memcg
,
216 int map_size
, int defer_size
,
217 int old_map_size
, int old_defer_size
,
220 struct shrinker_info
*new, *old
;
221 struct mem_cgroup_per_node
*pn
;
223 int size
= map_size
+ defer_size
;
226 pn
= memcg
->nodeinfo
[nid
];
227 old
= shrinker_info_protected(memcg
, nid
);
228 /* Not yet online memcg */
232 /* Already expanded this shrinker_info */
233 if (new_nr_max
<= old
->map_nr_max
)
236 new = kvmalloc_node(sizeof(*new) + size
, GFP_KERNEL
, nid
);
240 new->nr_deferred
= (atomic_long_t
*)(new + 1);
241 new->map
= (void *)new->nr_deferred
+ defer_size
;
242 new->map_nr_max
= new_nr_max
;
244 /* map: set all old bits, clear all new bits */
245 memset(new->map
, (int)0xff, old_map_size
);
246 memset((void *)new->map
+ old_map_size
, 0, map_size
- old_map_size
);
247 /* nr_deferred: copy old values, clear all new values */
248 memcpy(new->nr_deferred
, old
->nr_deferred
, old_defer_size
);
249 memset((void *)new->nr_deferred
+ old_defer_size
, 0,
250 defer_size
- old_defer_size
);
252 rcu_assign_pointer(pn
->shrinker_info
, new);
253 kvfree_rcu(old
, rcu
);
259 void free_shrinker_info(struct mem_cgroup
*memcg
)
261 struct mem_cgroup_per_node
*pn
;
262 struct shrinker_info
*info
;
266 pn
= memcg
->nodeinfo
[nid
];
267 info
= rcu_dereference_protected(pn
->shrinker_info
, true);
269 rcu_assign_pointer(pn
->shrinker_info
, NULL
);
273 int alloc_shrinker_info(struct mem_cgroup
*memcg
)
275 struct shrinker_info
*info
;
276 int nid
, size
, ret
= 0;
277 int map_size
, defer_size
= 0;
279 down_write(&shrinker_rwsem
);
280 map_size
= shrinker_map_size(shrinker_nr_max
);
281 defer_size
= shrinker_defer_size(shrinker_nr_max
);
282 size
= map_size
+ defer_size
;
284 info
= kvzalloc_node(sizeof(*info
) + size
, GFP_KERNEL
, nid
);
286 free_shrinker_info(memcg
);
290 info
->nr_deferred
= (atomic_long_t
*)(info
+ 1);
291 info
->map
= (void *)info
->nr_deferred
+ defer_size
;
292 info
->map_nr_max
= shrinker_nr_max
;
293 rcu_assign_pointer(memcg
->nodeinfo
[nid
]->shrinker_info
, info
);
295 up_write(&shrinker_rwsem
);
300 static int expand_shrinker_info(int new_id
)
303 int new_nr_max
= round_up(new_id
+ 1, BITS_PER_LONG
);
304 int map_size
, defer_size
= 0;
305 int old_map_size
, old_defer_size
= 0;
306 struct mem_cgroup
*memcg
;
308 if (!root_mem_cgroup
)
311 lockdep_assert_held(&shrinker_rwsem
);
313 map_size
= shrinker_map_size(new_nr_max
);
314 defer_size
= shrinker_defer_size(new_nr_max
);
315 old_map_size
= shrinker_map_size(shrinker_nr_max
);
316 old_defer_size
= shrinker_defer_size(shrinker_nr_max
);
318 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
320 ret
= expand_one_shrinker_info(memcg
, map_size
, defer_size
,
321 old_map_size
, old_defer_size
,
324 mem_cgroup_iter_break(NULL
, memcg
);
327 } while ((memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
)) != NULL
);
330 shrinker_nr_max
= new_nr_max
;
335 void set_shrinker_bit(struct mem_cgroup
*memcg
, int nid
, int shrinker_id
)
337 if (shrinker_id
>= 0 && memcg
&& !mem_cgroup_is_root(memcg
)) {
338 struct shrinker_info
*info
;
341 info
= rcu_dereference(memcg
->nodeinfo
[nid
]->shrinker_info
);
342 if (!WARN_ON_ONCE(shrinker_id
>= info
->map_nr_max
)) {
343 /* Pairs with smp mb in shrink_slab() */
344 smp_mb__before_atomic();
345 set_bit(shrinker_id
, info
->map
);
351 static DEFINE_IDR(shrinker_idr
);
353 static int prealloc_memcg_shrinker(struct shrinker
*shrinker
)
355 int id
, ret
= -ENOMEM
;
357 if (mem_cgroup_disabled())
360 down_write(&shrinker_rwsem
);
361 /* This may call shrinker, so it must use down_read_trylock() */
362 id
= idr_alloc(&shrinker_idr
, shrinker
, 0, 0, GFP_KERNEL
);
366 if (id
>= shrinker_nr_max
) {
367 if (expand_shrinker_info(id
)) {
368 idr_remove(&shrinker_idr
, id
);
375 up_write(&shrinker_rwsem
);
379 static void unregister_memcg_shrinker(struct shrinker
*shrinker
)
381 int id
= shrinker
->id
;
385 lockdep_assert_held(&shrinker_rwsem
);
387 idr_remove(&shrinker_idr
, id
);
390 static long xchg_nr_deferred_memcg(int nid
, struct shrinker
*shrinker
,
391 struct mem_cgroup
*memcg
)
393 struct shrinker_info
*info
;
395 info
= shrinker_info_protected(memcg
, nid
);
396 return atomic_long_xchg(&info
->nr_deferred
[shrinker
->id
], 0);
399 static long add_nr_deferred_memcg(long nr
, int nid
, struct shrinker
*shrinker
,
400 struct mem_cgroup
*memcg
)
402 struct shrinker_info
*info
;
404 info
= shrinker_info_protected(memcg
, nid
);
405 return atomic_long_add_return(nr
, &info
->nr_deferred
[shrinker
->id
]);
408 void reparent_shrinker_deferred(struct mem_cgroup
*memcg
)
412 struct mem_cgroup
*parent
;
413 struct shrinker_info
*child_info
, *parent_info
;
415 parent
= parent_mem_cgroup(memcg
);
417 parent
= root_mem_cgroup
;
419 /* Prevent from concurrent shrinker_info expand */
420 down_read(&shrinker_rwsem
);
422 child_info
= shrinker_info_protected(memcg
, nid
);
423 parent_info
= shrinker_info_protected(parent
, nid
);
424 for (i
= 0; i
< child_info
->map_nr_max
; i
++) {
425 nr
= atomic_long_read(&child_info
->nr_deferred
[i
]);
426 atomic_long_add(nr
, &parent_info
->nr_deferred
[i
]);
429 up_read(&shrinker_rwsem
);
432 /* Returns true for reclaim through cgroup limits or cgroup interfaces. */
433 static bool cgroup_reclaim(struct scan_control
*sc
)
435 return sc
->target_mem_cgroup
;
439 * Returns true for reclaim on the root cgroup. This is true for direct
440 * allocator reclaim and reclaim through cgroup interfaces on the root cgroup.
442 static bool root_reclaim(struct scan_control
*sc
)
444 return !sc
->target_mem_cgroup
|| mem_cgroup_is_root(sc
->target_mem_cgroup
);
448 * writeback_throttling_sane - is the usual dirty throttling mechanism available?
449 * @sc: scan_control in question
451 * The normal page dirty throttling mechanism in balance_dirty_pages() is
452 * completely broken with the legacy memcg and direct stalling in
453 * shrink_folio_list() is used for throttling instead, which lacks all the
454 * niceties such as fairness, adaptive pausing, bandwidth proportional
455 * allocation and configurability.
457 * This function tests whether the vmscan currently in progress can assume
458 * that the normal dirty throttling mechanism is operational.
460 static bool writeback_throttling_sane(struct scan_control
*sc
)
462 if (!cgroup_reclaim(sc
))
464 #ifdef CONFIG_CGROUP_WRITEBACK
465 if (cgroup_subsys_on_dfl(memory_cgrp_subsys
))
471 static int prealloc_memcg_shrinker(struct shrinker
*shrinker
)
476 static void unregister_memcg_shrinker(struct shrinker
*shrinker
)
480 static long xchg_nr_deferred_memcg(int nid
, struct shrinker
*shrinker
,
481 struct mem_cgroup
*memcg
)
486 static long add_nr_deferred_memcg(long nr
, int nid
, struct shrinker
*shrinker
,
487 struct mem_cgroup
*memcg
)
492 static bool cgroup_reclaim(struct scan_control
*sc
)
497 static bool root_reclaim(struct scan_control
*sc
)
502 static bool writeback_throttling_sane(struct scan_control
*sc
)
508 static void set_task_reclaim_state(struct task_struct
*task
,
509 struct reclaim_state
*rs
)
511 /* Check for an overwrite */
512 WARN_ON_ONCE(rs
&& task
->reclaim_state
);
514 /* Check for the nulling of an already-nulled member */
515 WARN_ON_ONCE(!rs
&& !task
->reclaim_state
);
517 task
->reclaim_state
= rs
;
521 * flush_reclaim_state(): add pages reclaimed outside of LRU-based reclaim to
522 * scan_control->nr_reclaimed.
524 static void flush_reclaim_state(struct scan_control
*sc
)
527 * Currently, reclaim_state->reclaimed includes three types of pages
528 * freed outside of vmscan:
530 * (2) Clean file pages from pruned inodes (on highmem systems).
531 * (3) XFS freed buffer pages.
533 * For all of these cases, we cannot universally link the pages to a
534 * single memcg. For example, a memcg-aware shrinker can free one object
535 * charged to the target memcg, causing an entire page to be freed.
536 * If we count the entire page as reclaimed from the memcg, we end up
537 * overestimating the reclaimed amount (potentially under-reclaiming).
539 * Only count such pages for global reclaim to prevent under-reclaiming
540 * from the target memcg; preventing unnecessary retries during memcg
541 * charging and false positives from proactive reclaim.
543 * For uncommon cases where the freed pages were actually mostly
544 * charged to the target memcg, we end up underestimating the reclaimed
545 * amount. This should be fine. The freed pages will be uncharged
546 * anyway, even if they are not counted here properly, and we will be
547 * able to make forward progress in charging (which is usually in a
550 * We can go one step further, and report the uncharged objcg pages in
551 * memcg reclaim, to make reporting more accurate and reduce
552 * underestimation, but it's probably not worth the complexity for now.
554 if (current
->reclaim_state
&& root_reclaim(sc
)) {
555 sc
->nr_reclaimed
+= current
->reclaim_state
->reclaimed
;
556 current
->reclaim_state
->reclaimed
= 0;
560 static long xchg_nr_deferred(struct shrinker
*shrinker
,
561 struct shrink_control
*sc
)
565 if (!(shrinker
->flags
& SHRINKER_NUMA_AWARE
))
569 (shrinker
->flags
& SHRINKER_MEMCG_AWARE
))
570 return xchg_nr_deferred_memcg(nid
, shrinker
,
573 return atomic_long_xchg(&shrinker
->nr_deferred
[nid
], 0);
577 static long add_nr_deferred(long nr
, struct shrinker
*shrinker
,
578 struct shrink_control
*sc
)
582 if (!(shrinker
->flags
& SHRINKER_NUMA_AWARE
))
586 (shrinker
->flags
& SHRINKER_MEMCG_AWARE
))
587 return add_nr_deferred_memcg(nr
, nid
, shrinker
,
590 return atomic_long_add_return(nr
, &shrinker
->nr_deferred
[nid
]);
593 static bool can_demote(int nid
, struct scan_control
*sc
)
595 if (!numa_demotion_enabled
)
597 if (sc
&& sc
->no_demotion
)
599 if (next_demotion_node(nid
) == NUMA_NO_NODE
)
605 static inline bool can_reclaim_anon_pages(struct mem_cgroup
*memcg
,
607 struct scan_control
*sc
)
611 * For non-memcg reclaim, is there
612 * space in any swap device?
614 if (get_nr_swap_pages() > 0)
617 /* Is the memcg below its swap limit? */
618 if (mem_cgroup_get_nr_swap_pages(memcg
) > 0)
623 * The page can not be swapped.
625 * Can it be reclaimed from this node via demotion?
627 return can_demote(nid
, sc
);
631 * This misses isolated folios which are not accounted for to save counters.
632 * As the data only determines if reclaim or compaction continues, it is
633 * not expected that isolated folios will be a dominating factor.
635 unsigned long zone_reclaimable_pages(struct zone
*zone
)
639 nr
= zone_page_state_snapshot(zone
, NR_ZONE_INACTIVE_FILE
) +
640 zone_page_state_snapshot(zone
, NR_ZONE_ACTIVE_FILE
);
641 if (can_reclaim_anon_pages(NULL
, zone_to_nid(zone
), NULL
))
642 nr
+= zone_page_state_snapshot(zone
, NR_ZONE_INACTIVE_ANON
) +
643 zone_page_state_snapshot(zone
, NR_ZONE_ACTIVE_ANON
);
649 * lruvec_lru_size - Returns the number of pages on the given LRU list.
650 * @lruvec: lru vector
652 * @zone_idx: zones to consider (use MAX_NR_ZONES - 1 for the whole LRU list)
654 static unsigned long lruvec_lru_size(struct lruvec
*lruvec
, enum lru_list lru
,
657 unsigned long size
= 0;
660 for (zid
= 0; zid
<= zone_idx
; zid
++) {
661 struct zone
*zone
= &lruvec_pgdat(lruvec
)->node_zones
[zid
];
663 if (!managed_zone(zone
))
666 if (!mem_cgroup_disabled())
667 size
+= mem_cgroup_get_zone_lru_size(lruvec
, lru
, zid
);
669 size
+= zone_page_state(zone
, NR_ZONE_LRU_BASE
+ lru
);
675 * Add a shrinker callback to be called from the vm.
677 static int __prealloc_shrinker(struct shrinker
*shrinker
)
682 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
) {
683 err
= prealloc_memcg_shrinker(shrinker
);
687 shrinker
->flags
&= ~SHRINKER_MEMCG_AWARE
;
690 size
= sizeof(*shrinker
->nr_deferred
);
691 if (shrinker
->flags
& SHRINKER_NUMA_AWARE
)
694 shrinker
->nr_deferred
= kzalloc(size
, GFP_KERNEL
);
695 if (!shrinker
->nr_deferred
)
701 #ifdef CONFIG_SHRINKER_DEBUG
702 int prealloc_shrinker(struct shrinker
*shrinker
, const char *fmt
, ...)
708 shrinker
->name
= kvasprintf_const(GFP_KERNEL
, fmt
, ap
);
713 err
= __prealloc_shrinker(shrinker
);
715 kfree_const(shrinker
->name
);
716 shrinker
->name
= NULL
;
722 int prealloc_shrinker(struct shrinker
*shrinker
, const char *fmt
, ...)
724 return __prealloc_shrinker(shrinker
);
728 void free_prealloced_shrinker(struct shrinker
*shrinker
)
730 #ifdef CONFIG_SHRINKER_DEBUG
731 kfree_const(shrinker
->name
);
732 shrinker
->name
= NULL
;
734 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
) {
735 down_write(&shrinker_rwsem
);
736 unregister_memcg_shrinker(shrinker
);
737 up_write(&shrinker_rwsem
);
741 kfree(shrinker
->nr_deferred
);
742 shrinker
->nr_deferred
= NULL
;
745 void register_shrinker_prepared(struct shrinker
*shrinker
)
747 down_write(&shrinker_rwsem
);
748 list_add_tail(&shrinker
->list
, &shrinker_list
);
749 shrinker
->flags
|= SHRINKER_REGISTERED
;
750 shrinker_debugfs_add(shrinker
);
751 up_write(&shrinker_rwsem
);
754 static int __register_shrinker(struct shrinker
*shrinker
)
756 int err
= __prealloc_shrinker(shrinker
);
760 register_shrinker_prepared(shrinker
);
764 #ifdef CONFIG_SHRINKER_DEBUG
765 int register_shrinker(struct shrinker
*shrinker
, const char *fmt
, ...)
771 shrinker
->name
= kvasprintf_const(GFP_KERNEL
, fmt
, ap
);
776 err
= __register_shrinker(shrinker
);
778 kfree_const(shrinker
->name
);
779 shrinker
->name
= NULL
;
784 int register_shrinker(struct shrinker
*shrinker
, const char *fmt
, ...)
786 return __register_shrinker(shrinker
);
789 EXPORT_SYMBOL(register_shrinker
);
794 void unregister_shrinker(struct shrinker
*shrinker
)
796 struct dentry
*debugfs_entry
;
799 if (!(shrinker
->flags
& SHRINKER_REGISTERED
))
802 down_write(&shrinker_rwsem
);
803 list_del(&shrinker
->list
);
804 shrinker
->flags
&= ~SHRINKER_REGISTERED
;
805 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
)
806 unregister_memcg_shrinker(shrinker
);
807 debugfs_entry
= shrinker_debugfs_detach(shrinker
, &debugfs_id
);
808 up_write(&shrinker_rwsem
);
810 shrinker_debugfs_remove(debugfs_entry
, debugfs_id
);
812 kfree(shrinker
->nr_deferred
);
813 shrinker
->nr_deferred
= NULL
;
815 EXPORT_SYMBOL(unregister_shrinker
);
818 * synchronize_shrinkers - Wait for all running shrinkers to complete.
820 * This is equivalent to calling unregister_shrink() and register_shrinker(),
821 * but atomically and with less overhead. This is useful to guarantee that all
822 * shrinker invocations have seen an update, before freeing memory, similar to
825 void synchronize_shrinkers(void)
827 down_write(&shrinker_rwsem
);
828 up_write(&shrinker_rwsem
);
830 EXPORT_SYMBOL(synchronize_shrinkers
);
832 #define SHRINK_BATCH 128
834 static unsigned long do_shrink_slab(struct shrink_control
*shrinkctl
,
835 struct shrinker
*shrinker
, int priority
)
837 unsigned long freed
= 0;
838 unsigned long long delta
;
843 long batch_size
= shrinker
->batch
? shrinker
->batch
845 long scanned
= 0, next_deferred
;
847 freeable
= shrinker
->count_objects(shrinker
, shrinkctl
);
848 if (freeable
== 0 || freeable
== SHRINK_EMPTY
)
852 * copy the current shrinker scan count into a local variable
853 * and zero it so that other concurrent shrinker invocations
854 * don't also do this scanning work.
856 nr
= xchg_nr_deferred(shrinker
, shrinkctl
);
858 if (shrinker
->seeks
) {
859 delta
= freeable
>> priority
;
861 do_div(delta
, shrinker
->seeks
);
864 * These objects don't require any IO to create. Trim
865 * them aggressively under memory pressure to keep
866 * them from causing refetches in the IO caches.
868 delta
= freeable
/ 2;
871 total_scan
= nr
>> priority
;
873 total_scan
= min(total_scan
, (2 * freeable
));
875 trace_mm_shrink_slab_start(shrinker
, shrinkctl
, nr
,
876 freeable
, delta
, total_scan
, priority
);
879 * Normally, we should not scan less than batch_size objects in one
880 * pass to avoid too frequent shrinker calls, but if the slab has less
881 * than batch_size objects in total and we are really tight on memory,
882 * we will try to reclaim all available objects, otherwise we can end
883 * up failing allocations although there are plenty of reclaimable
884 * objects spread over several slabs with usage less than the
887 * We detect the "tight on memory" situations by looking at the total
888 * number of objects we want to scan (total_scan). If it is greater
889 * than the total number of objects on slab (freeable), we must be
890 * scanning at high prio and therefore should try to reclaim as much as
893 while (total_scan
>= batch_size
||
894 total_scan
>= freeable
) {
896 unsigned long nr_to_scan
= min(batch_size
, total_scan
);
898 shrinkctl
->nr_to_scan
= nr_to_scan
;
899 shrinkctl
->nr_scanned
= nr_to_scan
;
900 ret
= shrinker
->scan_objects(shrinker
, shrinkctl
);
901 if (ret
== SHRINK_STOP
)
905 count_vm_events(SLABS_SCANNED
, shrinkctl
->nr_scanned
);
906 total_scan
-= shrinkctl
->nr_scanned
;
907 scanned
+= shrinkctl
->nr_scanned
;
913 * The deferred work is increased by any new work (delta) that wasn't
914 * done, decreased by old deferred work that was done now.
916 * And it is capped to two times of the freeable items.
918 next_deferred
= max_t(long, (nr
+ delta
- scanned
), 0);
919 next_deferred
= min(next_deferred
, (2 * freeable
));
922 * move the unused scan count back into the shrinker in a
923 * manner that handles concurrent updates.
925 new_nr
= add_nr_deferred(next_deferred
, shrinker
, shrinkctl
);
927 trace_mm_shrink_slab_end(shrinker
, shrinkctl
->nid
, freed
, nr
, new_nr
, total_scan
);
932 static unsigned long shrink_slab_memcg(gfp_t gfp_mask
, int nid
,
933 struct mem_cgroup
*memcg
, int priority
)
935 struct shrinker_info
*info
;
936 unsigned long ret
, freed
= 0;
939 if (!mem_cgroup_online(memcg
))
942 if (!down_read_trylock(&shrinker_rwsem
))
945 info
= shrinker_info_protected(memcg
, nid
);
949 for_each_set_bit(i
, info
->map
, info
->map_nr_max
) {
950 struct shrink_control sc
= {
951 .gfp_mask
= gfp_mask
,
955 struct shrinker
*shrinker
;
957 shrinker
= idr_find(&shrinker_idr
, i
);
958 if (unlikely(!shrinker
|| !(shrinker
->flags
& SHRINKER_REGISTERED
))) {
960 clear_bit(i
, info
->map
);
964 /* Call non-slab shrinkers even though kmem is disabled */
965 if (!memcg_kmem_online() &&
966 !(shrinker
->flags
& SHRINKER_NONSLAB
))
969 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
970 if (ret
== SHRINK_EMPTY
) {
971 clear_bit(i
, info
->map
);
973 * After the shrinker reported that it had no objects to
974 * free, but before we cleared the corresponding bit in
975 * the memcg shrinker map, a new object might have been
976 * added. To make sure, we have the bit set in this
977 * case, we invoke the shrinker one more time and reset
978 * the bit if it reports that it is not empty anymore.
979 * The memory barrier here pairs with the barrier in
980 * set_shrinker_bit():
982 * list_lru_add() shrink_slab_memcg()
983 * list_add_tail() clear_bit()
985 * set_bit() do_shrink_slab()
987 smp_mb__after_atomic();
988 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
989 if (ret
== SHRINK_EMPTY
)
992 set_shrinker_bit(memcg
, nid
, i
);
996 if (rwsem_is_contended(&shrinker_rwsem
)) {
1002 up_read(&shrinker_rwsem
);
1005 #else /* CONFIG_MEMCG */
1006 static unsigned long shrink_slab_memcg(gfp_t gfp_mask
, int nid
,
1007 struct mem_cgroup
*memcg
, int priority
)
1011 #endif /* CONFIG_MEMCG */
1014 * shrink_slab - shrink slab caches
1015 * @gfp_mask: allocation context
1016 * @nid: node whose slab caches to target
1017 * @memcg: memory cgroup whose slab caches to target
1018 * @priority: the reclaim priority
1020 * Call the shrink functions to age shrinkable caches.
1022 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
1023 * unaware shrinkers will receive a node id of 0 instead.
1025 * @memcg specifies the memory cgroup to target. Unaware shrinkers
1026 * are called only if it is the root cgroup.
1028 * @priority is sc->priority, we take the number of objects and >> by priority
1029 * in order to get the scan target.
1031 * Returns the number of reclaimed slab objects.
1033 static unsigned long shrink_slab(gfp_t gfp_mask
, int nid
,
1034 struct mem_cgroup
*memcg
,
1037 unsigned long ret
, freed
= 0;
1038 struct shrinker
*shrinker
;
1041 * The root memcg might be allocated even though memcg is disabled
1042 * via "cgroup_disable=memory" boot parameter. This could make
1043 * mem_cgroup_is_root() return false, then just run memcg slab
1044 * shrink, but skip global shrink. This may result in premature
1047 if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg
))
1048 return shrink_slab_memcg(gfp_mask
, nid
, memcg
, priority
);
1050 if (!down_read_trylock(&shrinker_rwsem
))
1053 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
1054 struct shrink_control sc
= {
1055 .gfp_mask
= gfp_mask
,
1060 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
1061 if (ret
== SHRINK_EMPTY
)
1065 * Bail out if someone want to register a new shrinker to
1066 * prevent the registration from being stalled for long periods
1067 * by parallel ongoing shrinking.
1069 if (rwsem_is_contended(&shrinker_rwsem
)) {
1070 freed
= freed
? : 1;
1075 up_read(&shrinker_rwsem
);
1081 static unsigned long drop_slab_node(int nid
)
1083 unsigned long freed
= 0;
1084 struct mem_cgroup
*memcg
= NULL
;
1086 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
1088 freed
+= shrink_slab(GFP_KERNEL
, nid
, memcg
, 0);
1089 } while ((memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
)) != NULL
);
1094 void drop_slab(void)
1098 unsigned long freed
;
1102 for_each_online_node(nid
) {
1103 if (fatal_signal_pending(current
))
1106 freed
+= drop_slab_node(nid
);
1108 } while ((freed
>> shift
++) > 1);
1111 static int reclaimer_offset(void)
1113 BUILD_BUG_ON(PGSTEAL_DIRECT
- PGSTEAL_KSWAPD
!=
1114 PGDEMOTE_DIRECT
- PGDEMOTE_KSWAPD
);
1115 BUILD_BUG_ON(PGSTEAL_DIRECT
- PGSTEAL_KSWAPD
!=
1116 PGSCAN_DIRECT
- PGSCAN_KSWAPD
);
1117 BUILD_BUG_ON(PGSTEAL_KHUGEPAGED
- PGSTEAL_KSWAPD
!=
1118 PGDEMOTE_KHUGEPAGED
- PGDEMOTE_KSWAPD
);
1119 BUILD_BUG_ON(PGSTEAL_KHUGEPAGED
- PGSTEAL_KSWAPD
!=
1120 PGSCAN_KHUGEPAGED
- PGSCAN_KSWAPD
);
1122 if (current_is_kswapd())
1124 if (current_is_khugepaged())
1125 return PGSTEAL_KHUGEPAGED
- PGSTEAL_KSWAPD
;
1126 return PGSTEAL_DIRECT
- PGSTEAL_KSWAPD
;
1129 static inline int is_page_cache_freeable(struct folio
*folio
)
1132 * A freeable page cache folio is referenced only by the caller
1133 * that isolated the folio, the page cache and optional filesystem
1134 * private data at folio->private.
1136 return folio_ref_count(folio
) - folio_test_private(folio
) ==
1137 1 + folio_nr_pages(folio
);
1141 * We detected a synchronous write error writing a folio out. Probably
1142 * -ENOSPC. We need to propagate that into the address_space for a subsequent
1143 * fsync(), msync() or close().
1145 * The tricky part is that after writepage we cannot touch the mapping: nothing
1146 * prevents it from being freed up. But we have a ref on the folio and once
1147 * that folio is locked, the mapping is pinned.
1149 * We're allowed to run sleeping folio_lock() here because we know the caller has
1152 static void handle_write_error(struct address_space
*mapping
,
1153 struct folio
*folio
, int error
)
1156 if (folio_mapping(folio
) == mapping
)
1157 mapping_set_error(mapping
, error
);
1158 folio_unlock(folio
);
1161 static bool skip_throttle_noprogress(pg_data_t
*pgdat
)
1163 int reclaimable
= 0, write_pending
= 0;
1167 * If kswapd is disabled, reschedule if necessary but do not
1168 * throttle as the system is likely near OOM.
1170 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
1174 * If there are a lot of dirty/writeback folios then do not
1175 * throttle as throttling will occur when the folios cycle
1176 * towards the end of the LRU if still under writeback.
1178 for (i
= 0; i
< MAX_NR_ZONES
; i
++) {
1179 struct zone
*zone
= pgdat
->node_zones
+ i
;
1181 if (!managed_zone(zone
))
1184 reclaimable
+= zone_reclaimable_pages(zone
);
1185 write_pending
+= zone_page_state_snapshot(zone
,
1186 NR_ZONE_WRITE_PENDING
);
1188 if (2 * write_pending
<= reclaimable
)
1194 void reclaim_throttle(pg_data_t
*pgdat
, enum vmscan_throttle_state reason
)
1196 wait_queue_head_t
*wqh
= &pgdat
->reclaim_wait
[reason
];
1201 * Do not throttle user workers, kthreads other than kswapd or
1202 * workqueues. They may be required for reclaim to make
1203 * forward progress (e.g. journalling workqueues or kthreads).
1205 if (!current_is_kswapd() &&
1206 current
->flags
& (PF_USER_WORKER
|PF_KTHREAD
)) {
1212 * These figures are pulled out of thin air.
1213 * VMSCAN_THROTTLE_ISOLATED is a transient condition based on too many
1214 * parallel reclaimers which is a short-lived event so the timeout is
1215 * short. Failing to make progress or waiting on writeback are
1216 * potentially long-lived events so use a longer timeout. This is shaky
1217 * logic as a failure to make progress could be due to anything from
1218 * writeback to a slow device to excessive referenced folios at the tail
1219 * of the inactive LRU.
1222 case VMSCAN_THROTTLE_WRITEBACK
:
1225 if (atomic_inc_return(&pgdat
->nr_writeback_throttled
) == 1) {
1226 WRITE_ONCE(pgdat
->nr_reclaim_start
,
1227 node_page_state(pgdat
, NR_THROTTLED_WRITTEN
));
1231 case VMSCAN_THROTTLE_CONGESTED
:
1233 case VMSCAN_THROTTLE_NOPROGRESS
:
1234 if (skip_throttle_noprogress(pgdat
)) {
1242 case VMSCAN_THROTTLE_ISOLATED
:
1251 prepare_to_wait(wqh
, &wait
, TASK_UNINTERRUPTIBLE
);
1252 ret
= schedule_timeout(timeout
);
1253 finish_wait(wqh
, &wait
);
1255 if (reason
== VMSCAN_THROTTLE_WRITEBACK
)
1256 atomic_dec(&pgdat
->nr_writeback_throttled
);
1258 trace_mm_vmscan_throttled(pgdat
->node_id
, jiffies_to_usecs(timeout
),
1259 jiffies_to_usecs(timeout
- ret
),
1264 * Account for folios written if tasks are throttled waiting on dirty
1265 * folios to clean. If enough folios have been cleaned since throttling
1266 * started then wakeup the throttled tasks.
1268 void __acct_reclaim_writeback(pg_data_t
*pgdat
, struct folio
*folio
,
1271 unsigned long nr_written
;
1273 node_stat_add_folio(folio
, NR_THROTTLED_WRITTEN
);
1276 * This is an inaccurate read as the per-cpu deltas may not
1277 * be synchronised. However, given that the system is
1278 * writeback throttled, it is not worth taking the penalty
1279 * of getting an accurate count. At worst, the throttle
1280 * timeout guarantees forward progress.
1282 nr_written
= node_page_state(pgdat
, NR_THROTTLED_WRITTEN
) -
1283 READ_ONCE(pgdat
->nr_reclaim_start
);
1285 if (nr_written
> SWAP_CLUSTER_MAX
* nr_throttled
)
1286 wake_up(&pgdat
->reclaim_wait
[VMSCAN_THROTTLE_WRITEBACK
]);
1289 /* possible outcome of pageout() */
1291 /* failed to write folio out, folio is locked */
1293 /* move folio to the active list, folio is locked */
1295 /* folio has been sent to the disk successfully, folio is unlocked */
1297 /* folio is clean and locked */
1302 * pageout is called by shrink_folio_list() for each dirty folio.
1303 * Calls ->writepage().
1305 static pageout_t
pageout(struct folio
*folio
, struct address_space
*mapping
,
1306 struct swap_iocb
**plug
)
1309 * If the folio is dirty, only perform writeback if that write
1310 * will be non-blocking. To prevent this allocation from being
1311 * stalled by pagecache activity. But note that there may be
1312 * stalls if we need to run get_block(). We could test
1313 * PagePrivate for that.
1315 * If this process is currently in __generic_file_write_iter() against
1316 * this folio's queue, we can perform writeback even if that
1319 * If the folio is swapcache, write it back even if that would
1320 * block, for some throttling. This happens by accident, because
1321 * swap_backing_dev_info is bust: it doesn't reflect the
1322 * congestion state of the swapdevs. Easy to fix, if needed.
1324 if (!is_page_cache_freeable(folio
))
1328 * Some data journaling orphaned folios can have
1329 * folio->mapping == NULL while being dirty with clean buffers.
1331 if (folio_test_private(folio
)) {
1332 if (try_to_free_buffers(folio
)) {
1333 folio_clear_dirty(folio
);
1334 pr_info("%s: orphaned folio\n", __func__
);
1340 if (mapping
->a_ops
->writepage
== NULL
)
1341 return PAGE_ACTIVATE
;
1343 if (folio_clear_dirty_for_io(folio
)) {
1345 struct writeback_control wbc
= {
1346 .sync_mode
= WB_SYNC_NONE
,
1347 .nr_to_write
= SWAP_CLUSTER_MAX
,
1349 .range_end
= LLONG_MAX
,
1354 folio_set_reclaim(folio
);
1355 res
= mapping
->a_ops
->writepage(&folio
->page
, &wbc
);
1357 handle_write_error(mapping
, folio
, res
);
1358 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
1359 folio_clear_reclaim(folio
);
1360 return PAGE_ACTIVATE
;
1363 if (!folio_test_writeback(folio
)) {
1364 /* synchronous write or broken a_ops? */
1365 folio_clear_reclaim(folio
);
1367 trace_mm_vmscan_write_folio(folio
);
1368 node_stat_add_folio(folio
, NR_VMSCAN_WRITE
);
1369 return PAGE_SUCCESS
;
1376 * Same as remove_mapping, but if the folio is removed from the mapping, it
1377 * gets returned with a refcount of 0.
1379 static int __remove_mapping(struct address_space
*mapping
, struct folio
*folio
,
1380 bool reclaimed
, struct mem_cgroup
*target_memcg
)
1383 void *shadow
= NULL
;
1385 BUG_ON(!folio_test_locked(folio
));
1386 BUG_ON(mapping
!= folio_mapping(folio
));
1388 if (!folio_test_swapcache(folio
))
1389 spin_lock(&mapping
->host
->i_lock
);
1390 xa_lock_irq(&mapping
->i_pages
);
1392 * The non racy check for a busy folio.
1394 * Must be careful with the order of the tests. When someone has
1395 * a ref to the folio, it may be possible that they dirty it then
1396 * drop the reference. So if the dirty flag is tested before the
1397 * refcount here, then the following race may occur:
1399 * get_user_pages(&page);
1400 * [user mapping goes away]
1402 * !folio_test_dirty(folio) [good]
1403 * folio_set_dirty(folio);
1405 * !refcount(folio) [good, discard it]
1407 * [oops, our write_to data is lost]
1409 * Reversing the order of the tests ensures such a situation cannot
1410 * escape unnoticed. The smp_rmb is needed to ensure the folio->flags
1411 * load is not satisfied before that of folio->_refcount.
1413 * Note that if the dirty flag is always set via folio_mark_dirty,
1414 * and thus under the i_pages lock, then this ordering is not required.
1416 refcount
= 1 + folio_nr_pages(folio
);
1417 if (!folio_ref_freeze(folio
, refcount
))
1419 /* note: atomic_cmpxchg in folio_ref_freeze provides the smp_rmb */
1420 if (unlikely(folio_test_dirty(folio
))) {
1421 folio_ref_unfreeze(folio
, refcount
);
1425 if (folio_test_swapcache(folio
)) {
1426 swp_entry_t swap
= folio
->swap
;
1428 if (reclaimed
&& !mapping_exiting(mapping
))
1429 shadow
= workingset_eviction(folio
, target_memcg
);
1430 __delete_from_swap_cache(folio
, swap
, shadow
);
1431 mem_cgroup_swapout(folio
, swap
);
1432 xa_unlock_irq(&mapping
->i_pages
);
1433 put_swap_folio(folio
, swap
);
1435 void (*free_folio
)(struct folio
*);
1437 free_folio
= mapping
->a_ops
->free_folio
;
1439 * Remember a shadow entry for reclaimed file cache in
1440 * order to detect refaults, thus thrashing, later on.
1442 * But don't store shadows in an address space that is
1443 * already exiting. This is not just an optimization,
1444 * inode reclaim needs to empty out the radix tree or
1445 * the nodes are lost. Don't plant shadows behind its
1448 * We also don't store shadows for DAX mappings because the
1449 * only page cache folios found in these are zero pages
1450 * covering holes, and because we don't want to mix DAX
1451 * exceptional entries and shadow exceptional entries in the
1452 * same address_space.
1454 if (reclaimed
&& folio_is_file_lru(folio
) &&
1455 !mapping_exiting(mapping
) && !dax_mapping(mapping
))
1456 shadow
= workingset_eviction(folio
, target_memcg
);
1457 __filemap_remove_folio(folio
, shadow
);
1458 xa_unlock_irq(&mapping
->i_pages
);
1459 if (mapping_shrinkable(mapping
))
1460 inode_add_lru(mapping
->host
);
1461 spin_unlock(&mapping
->host
->i_lock
);
1470 xa_unlock_irq(&mapping
->i_pages
);
1471 if (!folio_test_swapcache(folio
))
1472 spin_unlock(&mapping
->host
->i_lock
);
1477 * remove_mapping() - Attempt to remove a folio from its mapping.
1478 * @mapping: The address space.
1479 * @folio: The folio to remove.
1481 * If the folio is dirty, under writeback or if someone else has a ref
1482 * on it, removal will fail.
1483 * Return: The number of pages removed from the mapping. 0 if the folio
1484 * could not be removed.
1485 * Context: The caller should have a single refcount on the folio and
1488 long remove_mapping(struct address_space
*mapping
, struct folio
*folio
)
1490 if (__remove_mapping(mapping
, folio
, false, NULL
)) {
1492 * Unfreezing the refcount with 1 effectively
1493 * drops the pagecache ref for us without requiring another
1496 folio_ref_unfreeze(folio
, 1);
1497 return folio_nr_pages(folio
);
1503 * folio_putback_lru - Put previously isolated folio onto appropriate LRU list.
1504 * @folio: Folio to be returned to an LRU list.
1506 * Add previously isolated @folio to appropriate LRU list.
1507 * The folio may still be unevictable for other reasons.
1509 * Context: lru_lock must not be held, interrupts must be enabled.
1511 void folio_putback_lru(struct folio
*folio
)
1513 folio_add_lru(folio
);
1514 folio_put(folio
); /* drop ref from isolate */
1517 enum folio_references
{
1519 FOLIOREF_RECLAIM_CLEAN
,
1524 static enum folio_references
folio_check_references(struct folio
*folio
,
1525 struct scan_control
*sc
)
1527 int referenced_ptes
, referenced_folio
;
1528 unsigned long vm_flags
;
1530 referenced_ptes
= folio_referenced(folio
, 1, sc
->target_mem_cgroup
,
1532 referenced_folio
= folio_test_clear_referenced(folio
);
1535 * The supposedly reclaimable folio was found to be in a VM_LOCKED vma.
1536 * Let the folio, now marked Mlocked, be moved to the unevictable list.
1538 if (vm_flags
& VM_LOCKED
)
1539 return FOLIOREF_ACTIVATE
;
1541 /* rmap lock contention: rotate */
1542 if (referenced_ptes
== -1)
1543 return FOLIOREF_KEEP
;
1545 if (referenced_ptes
) {
1547 * All mapped folios start out with page table
1548 * references from the instantiating fault, so we need
1549 * to look twice if a mapped file/anon folio is used more
1552 * Mark it and spare it for another trip around the
1553 * inactive list. Another page table reference will
1554 * lead to its activation.
1556 * Note: the mark is set for activated folios as well
1557 * so that recently deactivated but used folios are
1558 * quickly recovered.
1560 folio_set_referenced(folio
);
1562 if (referenced_folio
|| referenced_ptes
> 1)
1563 return FOLIOREF_ACTIVATE
;
1566 * Activate file-backed executable folios after first usage.
1568 if ((vm_flags
& VM_EXEC
) && folio_is_file_lru(folio
))
1569 return FOLIOREF_ACTIVATE
;
1571 return FOLIOREF_KEEP
;
1574 /* Reclaim if clean, defer dirty folios to writeback */
1575 if (referenced_folio
&& folio_is_file_lru(folio
))
1576 return FOLIOREF_RECLAIM_CLEAN
;
1578 return FOLIOREF_RECLAIM
;
1581 /* Check if a folio is dirty or under writeback */
1582 static void folio_check_dirty_writeback(struct folio
*folio
,
1583 bool *dirty
, bool *writeback
)
1585 struct address_space
*mapping
;
1588 * Anonymous folios are not handled by flushers and must be written
1589 * from reclaim context. Do not stall reclaim based on them.
1590 * MADV_FREE anonymous folios are put into inactive file list too.
1591 * They could be mistakenly treated as file lru. So further anon
1594 if (!folio_is_file_lru(folio
) ||
1595 (folio_test_anon(folio
) && !folio_test_swapbacked(folio
))) {
1601 /* By default assume that the folio flags are accurate */
1602 *dirty
= folio_test_dirty(folio
);
1603 *writeback
= folio_test_writeback(folio
);
1605 /* Verify dirty/writeback state if the filesystem supports it */
1606 if (!folio_test_private(folio
))
1609 mapping
= folio_mapping(folio
);
1610 if (mapping
&& mapping
->a_ops
->is_dirty_writeback
)
1611 mapping
->a_ops
->is_dirty_writeback(folio
, dirty
, writeback
);
1614 static struct folio
*alloc_demote_folio(struct folio
*src
,
1615 unsigned long private)
1618 nodemask_t
*allowed_mask
;
1619 struct migration_target_control
*mtc
;
1621 mtc
= (struct migration_target_control
*)private;
1623 allowed_mask
= mtc
->nmask
;
1625 * make sure we allocate from the target node first also trying to
1626 * demote or reclaim pages from the target node via kswapd if we are
1627 * low on free memory on target node. If we don't do this and if
1628 * we have free memory on the slower(lower) memtier, we would start
1629 * allocating pages from slower(lower) memory tiers without even forcing
1630 * a demotion of cold pages from the target memtier. This can result
1631 * in the kernel placing hot pages in slower(lower) memory tiers.
1634 mtc
->gfp_mask
|= __GFP_THISNODE
;
1635 dst
= alloc_migration_target(src
, (unsigned long)mtc
);
1639 mtc
->gfp_mask
&= ~__GFP_THISNODE
;
1640 mtc
->nmask
= allowed_mask
;
1642 return alloc_migration_target(src
, (unsigned long)mtc
);
1646 * Take folios on @demote_folios and attempt to demote them to another node.
1647 * Folios which are not demoted are left on @demote_folios.
1649 static unsigned int demote_folio_list(struct list_head
*demote_folios
,
1650 struct pglist_data
*pgdat
)
1652 int target_nid
= next_demotion_node(pgdat
->node_id
);
1653 unsigned int nr_succeeded
;
1654 nodemask_t allowed_mask
;
1656 struct migration_target_control mtc
= {
1658 * Allocate from 'node', or fail quickly and quietly.
1659 * When this happens, 'page' will likely just be discarded
1660 * instead of migrated.
1662 .gfp_mask
= (GFP_HIGHUSER_MOVABLE
& ~__GFP_RECLAIM
) | __GFP_NOWARN
|
1663 __GFP_NOMEMALLOC
| GFP_NOWAIT
,
1665 .nmask
= &allowed_mask
1668 if (list_empty(demote_folios
))
1671 if (target_nid
== NUMA_NO_NODE
)
1674 node_get_allowed_targets(pgdat
, &allowed_mask
);
1676 /* Demotion ignores all cpuset and mempolicy settings */
1677 migrate_pages(demote_folios
, alloc_demote_folio
, NULL
,
1678 (unsigned long)&mtc
, MIGRATE_ASYNC
, MR_DEMOTION
,
1681 __count_vm_events(PGDEMOTE_KSWAPD
+ reclaimer_offset(), nr_succeeded
);
1683 return nr_succeeded
;
1686 static bool may_enter_fs(struct folio
*folio
, gfp_t gfp_mask
)
1688 if (gfp_mask
& __GFP_FS
)
1690 if (!folio_test_swapcache(folio
) || !(gfp_mask
& __GFP_IO
))
1693 * We can "enter_fs" for swap-cache with only __GFP_IO
1694 * providing this isn't SWP_FS_OPS.
1695 * ->flags can be updated non-atomicially (scan_swap_map_slots),
1696 * but that will never affect SWP_FS_OPS, so the data_race
1699 return !data_race(folio_swap_flags(folio
) & SWP_FS_OPS
);
1703 * shrink_folio_list() returns the number of reclaimed pages
1705 static unsigned int shrink_folio_list(struct list_head
*folio_list
,
1706 struct pglist_data
*pgdat
, struct scan_control
*sc
,
1707 struct reclaim_stat
*stat
, bool ignore_references
)
1709 LIST_HEAD(ret_folios
);
1710 LIST_HEAD(free_folios
);
1711 LIST_HEAD(demote_folios
);
1712 unsigned int nr_reclaimed
= 0;
1713 unsigned int pgactivate
= 0;
1714 bool do_demote_pass
;
1715 struct swap_iocb
*plug
= NULL
;
1717 memset(stat
, 0, sizeof(*stat
));
1719 do_demote_pass
= can_demote(pgdat
->node_id
, sc
);
1722 while (!list_empty(folio_list
)) {
1723 struct address_space
*mapping
;
1724 struct folio
*folio
;
1725 enum folio_references references
= FOLIOREF_RECLAIM
;
1726 bool dirty
, writeback
;
1727 unsigned int nr_pages
;
1731 folio
= lru_to_folio(folio_list
);
1732 list_del(&folio
->lru
);
1734 if (!folio_trylock(folio
))
1737 VM_BUG_ON_FOLIO(folio_test_active(folio
), folio
);
1739 nr_pages
= folio_nr_pages(folio
);
1741 /* Account the number of base pages */
1742 sc
->nr_scanned
+= nr_pages
;
1744 if (unlikely(!folio_evictable(folio
)))
1745 goto activate_locked
;
1747 if (!sc
->may_unmap
&& folio_mapped(folio
))
1750 /* folio_update_gen() tried to promote this page? */
1751 if (lru_gen_enabled() && !ignore_references
&&
1752 folio_mapped(folio
) && folio_test_referenced(folio
))
1756 * The number of dirty pages determines if a node is marked
1757 * reclaim_congested. kswapd will stall and start writing
1758 * folios if the tail of the LRU is all dirty unqueued folios.
1760 folio_check_dirty_writeback(folio
, &dirty
, &writeback
);
1761 if (dirty
|| writeback
)
1762 stat
->nr_dirty
+= nr_pages
;
1764 if (dirty
&& !writeback
)
1765 stat
->nr_unqueued_dirty
+= nr_pages
;
1768 * Treat this folio as congested if folios are cycling
1769 * through the LRU so quickly that the folios marked
1770 * for immediate reclaim are making it to the end of
1771 * the LRU a second time.
1773 if (writeback
&& folio_test_reclaim(folio
))
1774 stat
->nr_congested
+= nr_pages
;
1777 * If a folio at the tail of the LRU is under writeback, there
1778 * are three cases to consider.
1780 * 1) If reclaim is encountering an excessive number
1781 * of folios under writeback and this folio has both
1782 * the writeback and reclaim flags set, then it
1783 * indicates that folios are being queued for I/O but
1784 * are being recycled through the LRU before the I/O
1785 * can complete. Waiting on the folio itself risks an
1786 * indefinite stall if it is impossible to writeback
1787 * the folio due to I/O error or disconnected storage
1788 * so instead note that the LRU is being scanned too
1789 * quickly and the caller can stall after the folio
1790 * list has been processed.
1792 * 2) Global or new memcg reclaim encounters a folio that is
1793 * not marked for immediate reclaim, or the caller does not
1794 * have __GFP_FS (or __GFP_IO if it's simply going to swap,
1795 * not to fs). In this case mark the folio for immediate
1796 * reclaim and continue scanning.
1798 * Require may_enter_fs() because we would wait on fs, which
1799 * may not have submitted I/O yet. And the loop driver might
1800 * enter reclaim, and deadlock if it waits on a folio for
1801 * which it is needed to do the write (loop masks off
1802 * __GFP_IO|__GFP_FS for this reason); but more thought
1803 * would probably show more reasons.
1805 * 3) Legacy memcg encounters a folio that already has the
1806 * reclaim flag set. memcg does not have any dirty folio
1807 * throttling so we could easily OOM just because too many
1808 * folios are in writeback and there is nothing else to
1809 * reclaim. Wait for the writeback to complete.
1811 * In cases 1) and 2) we activate the folios to get them out of
1812 * the way while we continue scanning for clean folios on the
1813 * inactive list and refilling from the active list. The
1814 * observation here is that waiting for disk writes is more
1815 * expensive than potentially causing reloads down the line.
1816 * Since they're marked for immediate reclaim, they won't put
1817 * memory pressure on the cache working set any longer than it
1818 * takes to write them to disk.
1820 if (folio_test_writeback(folio
)) {
1822 if (current_is_kswapd() &&
1823 folio_test_reclaim(folio
) &&
1824 test_bit(PGDAT_WRITEBACK
, &pgdat
->flags
)) {
1825 stat
->nr_immediate
+= nr_pages
;
1826 goto activate_locked
;
1829 } else if (writeback_throttling_sane(sc
) ||
1830 !folio_test_reclaim(folio
) ||
1831 !may_enter_fs(folio
, sc
->gfp_mask
)) {
1833 * This is slightly racy -
1834 * folio_end_writeback() might have
1835 * just cleared the reclaim flag, then
1836 * setting the reclaim flag here ends up
1837 * interpreted as the readahead flag - but
1838 * that does not matter enough to care.
1839 * What we do want is for this folio to
1840 * have the reclaim flag set next time
1841 * memcg reclaim reaches the tests above,
1842 * so it will then wait for writeback to
1843 * avoid OOM; and it's also appropriate
1844 * in global reclaim.
1846 folio_set_reclaim(folio
);
1847 stat
->nr_writeback
+= nr_pages
;
1848 goto activate_locked
;
1852 folio_unlock(folio
);
1853 folio_wait_writeback(folio
);
1854 /* then go back and try same folio again */
1855 list_add_tail(&folio
->lru
, folio_list
);
1860 if (!ignore_references
)
1861 references
= folio_check_references(folio
, sc
);
1863 switch (references
) {
1864 case FOLIOREF_ACTIVATE
:
1865 goto activate_locked
;
1867 stat
->nr_ref_keep
+= nr_pages
;
1869 case FOLIOREF_RECLAIM
:
1870 case FOLIOREF_RECLAIM_CLEAN
:
1871 ; /* try to reclaim the folio below */
1875 * Before reclaiming the folio, try to relocate
1876 * its contents to another node.
1878 if (do_demote_pass
&&
1879 (thp_migration_supported() || !folio_test_large(folio
))) {
1880 list_add(&folio
->lru
, &demote_folios
);
1881 folio_unlock(folio
);
1886 * Anonymous process memory has backing store?
1887 * Try to allocate it some swap space here.
1888 * Lazyfree folio could be freed directly
1890 if (folio_test_anon(folio
) && folio_test_swapbacked(folio
)) {
1891 if (!folio_test_swapcache(folio
)) {
1892 if (!(sc
->gfp_mask
& __GFP_IO
))
1894 if (folio_maybe_dma_pinned(folio
))
1896 if (folio_test_large(folio
)) {
1897 /* cannot split folio, skip it */
1898 if (!can_split_folio(folio
, NULL
))
1899 goto activate_locked
;
1901 * Split folios without a PMD map right
1902 * away. Chances are some or all of the
1903 * tail pages can be freed without IO.
1905 if (!folio_entire_mapcount(folio
) &&
1906 split_folio_to_list(folio
,
1908 goto activate_locked
;
1910 if (!add_to_swap(folio
)) {
1911 if (!folio_test_large(folio
))
1912 goto activate_locked_split
;
1913 /* Fallback to swap normal pages */
1914 if (split_folio_to_list(folio
,
1916 goto activate_locked
;
1917 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
1918 count_vm_event(THP_SWPOUT_FALLBACK
);
1920 if (!add_to_swap(folio
))
1921 goto activate_locked_split
;
1924 } else if (folio_test_swapbacked(folio
) &&
1925 folio_test_large(folio
)) {
1926 /* Split shmem folio */
1927 if (split_folio_to_list(folio
, folio_list
))
1932 * If the folio was split above, the tail pages will make
1933 * their own pass through this function and be accounted
1936 if ((nr_pages
> 1) && !folio_test_large(folio
)) {
1937 sc
->nr_scanned
-= (nr_pages
- 1);
1942 * The folio is mapped into the page tables of one or more
1943 * processes. Try to unmap it here.
1945 if (folio_mapped(folio
)) {
1946 enum ttu_flags flags
= TTU_BATCH_FLUSH
;
1947 bool was_swapbacked
= folio_test_swapbacked(folio
);
1949 if (folio_test_pmd_mappable(folio
))
1950 flags
|= TTU_SPLIT_HUGE_PMD
;
1952 try_to_unmap(folio
, flags
);
1953 if (folio_mapped(folio
)) {
1954 stat
->nr_unmap_fail
+= nr_pages
;
1955 if (!was_swapbacked
&&
1956 folio_test_swapbacked(folio
))
1957 stat
->nr_lazyfree_fail
+= nr_pages
;
1958 goto activate_locked
;
1963 * Folio is unmapped now so it cannot be newly pinned anymore.
1964 * No point in trying to reclaim folio if it is pinned.
1965 * Furthermore we don't want to reclaim underlying fs metadata
1966 * if the folio is pinned and thus potentially modified by the
1967 * pinning process as that may upset the filesystem.
1969 if (folio_maybe_dma_pinned(folio
))
1970 goto activate_locked
;
1972 mapping
= folio_mapping(folio
);
1973 if (folio_test_dirty(folio
)) {
1975 * Only kswapd can writeback filesystem folios
1976 * to avoid risk of stack overflow. But avoid
1977 * injecting inefficient single-folio I/O into
1978 * flusher writeback as much as possible: only
1979 * write folios when we've encountered many
1980 * dirty folios, and when we've already scanned
1981 * the rest of the LRU for clean folios and see
1982 * the same dirty folios again (with the reclaim
1985 if (folio_is_file_lru(folio
) &&
1986 (!current_is_kswapd() ||
1987 !folio_test_reclaim(folio
) ||
1988 !test_bit(PGDAT_DIRTY
, &pgdat
->flags
))) {
1990 * Immediately reclaim when written back.
1991 * Similar in principle to folio_deactivate()
1992 * except we already have the folio isolated
1993 * and know it's dirty
1995 node_stat_mod_folio(folio
, NR_VMSCAN_IMMEDIATE
,
1997 folio_set_reclaim(folio
);
1999 goto activate_locked
;
2002 if (references
== FOLIOREF_RECLAIM_CLEAN
)
2004 if (!may_enter_fs(folio
, sc
->gfp_mask
))
2006 if (!sc
->may_writepage
)
2010 * Folio is dirty. Flush the TLB if a writable entry
2011 * potentially exists to avoid CPU writes after I/O
2012 * starts and then write it out here.
2014 try_to_unmap_flush_dirty();
2015 switch (pageout(folio
, mapping
, &plug
)) {
2019 goto activate_locked
;
2021 stat
->nr_pageout
+= nr_pages
;
2023 if (folio_test_writeback(folio
))
2025 if (folio_test_dirty(folio
))
2029 * A synchronous write - probably a ramdisk. Go
2030 * ahead and try to reclaim the folio.
2032 if (!folio_trylock(folio
))
2034 if (folio_test_dirty(folio
) ||
2035 folio_test_writeback(folio
))
2037 mapping
= folio_mapping(folio
);
2040 ; /* try to free the folio below */
2045 * If the folio has buffers, try to free the buffer
2046 * mappings associated with this folio. If we succeed
2047 * we try to free the folio as well.
2049 * We do this even if the folio is dirty.
2050 * filemap_release_folio() does not perform I/O, but it
2051 * is possible for a folio to have the dirty flag set,
2052 * but it is actually clean (all its buffers are clean).
2053 * This happens if the buffers were written out directly,
2054 * with submit_bh(). ext3 will do this, as well as
2055 * the blockdev mapping. filemap_release_folio() will
2056 * discover that cleanness and will drop the buffers
2057 * and mark the folio clean - it can be freed.
2059 * Rarely, folios can have buffers and no ->mapping.
2060 * These are the folios which were not successfully
2061 * invalidated in truncate_cleanup_folio(). We try to
2062 * drop those buffers here and if that worked, and the
2063 * folio is no longer mapped into process address space
2064 * (refcount == 1) it can be freed. Otherwise, leave
2065 * the folio on the LRU so it is swappable.
2067 if (folio_needs_release(folio
)) {
2068 if (!filemap_release_folio(folio
, sc
->gfp_mask
))
2069 goto activate_locked
;
2070 if (!mapping
&& folio_ref_count(folio
) == 1) {
2071 folio_unlock(folio
);
2072 if (folio_put_testzero(folio
))
2076 * rare race with speculative reference.
2077 * the speculative reference will free
2078 * this folio shortly, so we may
2079 * increment nr_reclaimed here (and
2080 * leave it off the LRU).
2082 nr_reclaimed
+= nr_pages
;
2088 if (folio_test_anon(folio
) && !folio_test_swapbacked(folio
)) {
2089 /* follow __remove_mapping for reference */
2090 if (!folio_ref_freeze(folio
, 1))
2093 * The folio has only one reference left, which is
2094 * from the isolation. After the caller puts the
2095 * folio back on the lru and drops the reference, the
2096 * folio will be freed anyway. It doesn't matter
2097 * which lru it goes on. So we don't bother checking
2098 * the dirty flag here.
2100 count_vm_events(PGLAZYFREED
, nr_pages
);
2101 count_memcg_folio_events(folio
, PGLAZYFREED
, nr_pages
);
2102 } else if (!mapping
|| !__remove_mapping(mapping
, folio
, true,
2103 sc
->target_mem_cgroup
))
2106 folio_unlock(folio
);
2109 * Folio may get swapped out as a whole, need to account
2112 nr_reclaimed
+= nr_pages
;
2115 * Is there need to periodically free_folio_list? It would
2116 * appear not as the counts should be low
2118 if (unlikely(folio_test_large(folio
)))
2119 destroy_large_folio(folio
);
2121 list_add(&folio
->lru
, &free_folios
);
2124 activate_locked_split
:
2126 * The tail pages that are failed to add into swap cache
2127 * reach here. Fixup nr_scanned and nr_pages.
2130 sc
->nr_scanned
-= (nr_pages
- 1);
2134 /* Not a candidate for swapping, so reclaim swap space. */
2135 if (folio_test_swapcache(folio
) &&
2136 (mem_cgroup_swap_full(folio
) || folio_test_mlocked(folio
)))
2137 folio_free_swap(folio
);
2138 VM_BUG_ON_FOLIO(folio_test_active(folio
), folio
);
2139 if (!folio_test_mlocked(folio
)) {
2140 int type
= folio_is_file_lru(folio
);
2141 folio_set_active(folio
);
2142 stat
->nr_activate
[type
] += nr_pages
;
2143 count_memcg_folio_events(folio
, PGACTIVATE
, nr_pages
);
2146 folio_unlock(folio
);
2148 list_add(&folio
->lru
, &ret_folios
);
2149 VM_BUG_ON_FOLIO(folio_test_lru(folio
) ||
2150 folio_test_unevictable(folio
), folio
);
2152 /* 'folio_list' is always empty here */
2154 /* Migrate folios selected for demotion */
2155 nr_reclaimed
+= demote_folio_list(&demote_folios
, pgdat
);
2156 /* Folios that could not be demoted are still in @demote_folios */
2157 if (!list_empty(&demote_folios
)) {
2158 /* Folios which weren't demoted go back on @folio_list */
2159 list_splice_init(&demote_folios
, folio_list
);
2162 * goto retry to reclaim the undemoted folios in folio_list if
2165 * Reclaiming directly from top tier nodes is not often desired
2166 * due to it breaking the LRU ordering: in general memory
2167 * should be reclaimed from lower tier nodes and demoted from
2170 * However, disabling reclaim from top tier nodes entirely
2171 * would cause ooms in edge scenarios where lower tier memory
2172 * is unreclaimable for whatever reason, eg memory being
2173 * mlocked or too hot to reclaim. We can disable reclaim
2174 * from top tier nodes in proactive reclaim though as that is
2175 * not real memory pressure.
2177 if (!sc
->proactive
) {
2178 do_demote_pass
= false;
2183 pgactivate
= stat
->nr_activate
[0] + stat
->nr_activate
[1];
2185 mem_cgroup_uncharge_list(&free_folios
);
2186 try_to_unmap_flush();
2187 free_unref_page_list(&free_folios
);
2189 list_splice(&ret_folios
, folio_list
);
2190 count_vm_events(PGACTIVATE
, pgactivate
);
2193 swap_write_unplug(plug
);
2194 return nr_reclaimed
;
2197 unsigned int reclaim_clean_pages_from_list(struct zone
*zone
,
2198 struct list_head
*folio_list
)
2200 struct scan_control sc
= {
2201 .gfp_mask
= GFP_KERNEL
,
2204 struct reclaim_stat stat
;
2205 unsigned int nr_reclaimed
;
2206 struct folio
*folio
, *next
;
2207 LIST_HEAD(clean_folios
);
2208 unsigned int noreclaim_flag
;
2210 list_for_each_entry_safe(folio
, next
, folio_list
, lru
) {
2211 if (!folio_test_hugetlb(folio
) && folio_is_file_lru(folio
) &&
2212 !folio_test_dirty(folio
) && !__folio_test_movable(folio
) &&
2213 !folio_test_unevictable(folio
)) {
2214 folio_clear_active(folio
);
2215 list_move(&folio
->lru
, &clean_folios
);
2220 * We should be safe here since we are only dealing with file pages and
2221 * we are not kswapd and therefore cannot write dirty file pages. But
2222 * call memalloc_noreclaim_save() anyway, just in case these conditions
2223 * change in the future.
2225 noreclaim_flag
= memalloc_noreclaim_save();
2226 nr_reclaimed
= shrink_folio_list(&clean_folios
, zone
->zone_pgdat
, &sc
,
2228 memalloc_noreclaim_restore(noreclaim_flag
);
2230 list_splice(&clean_folios
, folio_list
);
2231 mod_node_page_state(zone
->zone_pgdat
, NR_ISOLATED_FILE
,
2232 -(long)nr_reclaimed
);
2234 * Since lazyfree pages are isolated from file LRU from the beginning,
2235 * they will rotate back to anonymous LRU in the end if it failed to
2236 * discard so isolated count will be mismatched.
2237 * Compensate the isolated count for both LRU lists.
2239 mod_node_page_state(zone
->zone_pgdat
, NR_ISOLATED_ANON
,
2240 stat
.nr_lazyfree_fail
);
2241 mod_node_page_state(zone
->zone_pgdat
, NR_ISOLATED_FILE
,
2242 -(long)stat
.nr_lazyfree_fail
);
2243 return nr_reclaimed
;
2247 * Update LRU sizes after isolating pages. The LRU size updates must
2248 * be complete before mem_cgroup_update_lru_size due to a sanity check.
2250 static __always_inline
void update_lru_sizes(struct lruvec
*lruvec
,
2251 enum lru_list lru
, unsigned long *nr_zone_taken
)
2255 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++) {
2256 if (!nr_zone_taken
[zid
])
2259 update_lru_size(lruvec
, lru
, zid
, -nr_zone_taken
[zid
]);
2266 * It is waste of effort to scan and reclaim CMA pages if it is not available
2267 * for current allocation context. Kswapd can not be enrolled as it can not
2268 * distinguish this scenario by using sc->gfp_mask = GFP_KERNEL
2270 static bool skip_cma(struct folio
*folio
, struct scan_control
*sc
)
2272 return !current_is_kswapd() &&
2273 gfp_migratetype(sc
->gfp_mask
) != MIGRATE_MOVABLE
&&
2274 get_pageblock_migratetype(&folio
->page
) == MIGRATE_CMA
;
2277 static bool skip_cma(struct folio
*folio
, struct scan_control
*sc
)
2284 * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
2286 * lruvec->lru_lock is heavily contended. Some of the functions that
2287 * shrink the lists perform better by taking out a batch of pages
2288 * and working on them outside the LRU lock.
2290 * For pagecache intensive workloads, this function is the hottest
2291 * spot in the kernel (apart from copy_*_user functions).
2293 * Lru_lock must be held before calling this function.
2295 * @nr_to_scan: The number of eligible pages to look through on the list.
2296 * @lruvec: The LRU vector to pull pages from.
2297 * @dst: The temp list to put pages on to.
2298 * @nr_scanned: The number of pages that were scanned.
2299 * @sc: The scan_control struct for this reclaim session
2300 * @lru: LRU list id for isolating
2302 * returns how many pages were moved onto *@dst.
2304 static unsigned long isolate_lru_folios(unsigned long nr_to_scan
,
2305 struct lruvec
*lruvec
, struct list_head
*dst
,
2306 unsigned long *nr_scanned
, struct scan_control
*sc
,
2309 struct list_head
*src
= &lruvec
->lists
[lru
];
2310 unsigned long nr_taken
= 0;
2311 unsigned long nr_zone_taken
[MAX_NR_ZONES
] = { 0 };
2312 unsigned long nr_skipped
[MAX_NR_ZONES
] = { 0, };
2313 unsigned long skipped
= 0;
2314 unsigned long scan
, total_scan
, nr_pages
;
2315 LIST_HEAD(folios_skipped
);
2319 while (scan
< nr_to_scan
&& !list_empty(src
)) {
2320 struct list_head
*move_to
= src
;
2321 struct folio
*folio
;
2323 folio
= lru_to_folio(src
);
2324 prefetchw_prev_lru_folio(folio
, src
, flags
);
2326 nr_pages
= folio_nr_pages(folio
);
2327 total_scan
+= nr_pages
;
2329 if (folio_zonenum(folio
) > sc
->reclaim_idx
||
2330 skip_cma(folio
, sc
)) {
2331 nr_skipped
[folio_zonenum(folio
)] += nr_pages
;
2332 move_to
= &folios_skipped
;
2337 * Do not count skipped folios because that makes the function
2338 * return with no isolated folios if the LRU mostly contains
2339 * ineligible folios. This causes the VM to not reclaim any
2340 * folios, triggering a premature OOM.
2341 * Account all pages in a folio.
2345 if (!folio_test_lru(folio
))
2347 if (!sc
->may_unmap
&& folio_mapped(folio
))
2351 * Be careful not to clear the lru flag until after we're
2352 * sure the folio is not being freed elsewhere -- the
2353 * folio release code relies on it.
2355 if (unlikely(!folio_try_get(folio
)))
2358 if (!folio_test_clear_lru(folio
)) {
2359 /* Another thread is already isolating this folio */
2364 nr_taken
+= nr_pages
;
2365 nr_zone_taken
[folio_zonenum(folio
)] += nr_pages
;
2368 list_move(&folio
->lru
, move_to
);
2372 * Splice any skipped folios to the start of the LRU list. Note that
2373 * this disrupts the LRU order when reclaiming for lower zones but
2374 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
2375 * scanning would soon rescan the same folios to skip and waste lots
2378 if (!list_empty(&folios_skipped
)) {
2381 list_splice(&folios_skipped
, src
);
2382 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++) {
2383 if (!nr_skipped
[zid
])
2386 __count_zid_vm_events(PGSCAN_SKIP
, zid
, nr_skipped
[zid
]);
2387 skipped
+= nr_skipped
[zid
];
2390 *nr_scanned
= total_scan
;
2391 trace_mm_vmscan_lru_isolate(sc
->reclaim_idx
, sc
->order
, nr_to_scan
,
2392 total_scan
, skipped
, nr_taken
,
2393 sc
->may_unmap
? 0 : ISOLATE_UNMAPPED
, lru
);
2394 update_lru_sizes(lruvec
, lru
, nr_zone_taken
);
2399 * folio_isolate_lru() - Try to isolate a folio from its LRU list.
2400 * @folio: Folio to isolate from its LRU list.
2402 * Isolate a @folio from an LRU list and adjust the vmstat statistic
2403 * corresponding to whatever LRU list the folio was on.
2405 * The folio will have its LRU flag cleared. If it was found on the
2406 * active list, it will have the Active flag set. If it was found on the
2407 * unevictable list, it will have the Unevictable flag set. These flags
2408 * may need to be cleared by the caller before letting the page go.
2412 * (1) Must be called with an elevated refcount on the folio. This is a
2413 * fundamental difference from isolate_lru_folios() (which is called
2414 * without a stable reference).
2415 * (2) The lru_lock must not be held.
2416 * (3) Interrupts must be enabled.
2418 * Return: true if the folio was removed from an LRU list.
2419 * false if the folio was not on an LRU list.
2421 bool folio_isolate_lru(struct folio
*folio
)
2425 VM_BUG_ON_FOLIO(!folio_ref_count(folio
), folio
);
2427 if (folio_test_clear_lru(folio
)) {
2428 struct lruvec
*lruvec
;
2431 lruvec
= folio_lruvec_lock_irq(folio
);
2432 lruvec_del_folio(lruvec
, folio
);
2433 unlock_page_lruvec_irq(lruvec
);
2441 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
2442 * then get rescheduled. When there are massive number of tasks doing page
2443 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
2444 * the LRU list will go small and be scanned faster than necessary, leading to
2445 * unnecessary swapping, thrashing and OOM.
2447 static int too_many_isolated(struct pglist_data
*pgdat
, int file
,
2448 struct scan_control
*sc
)
2450 unsigned long inactive
, isolated
;
2453 if (current_is_kswapd())
2456 if (!writeback_throttling_sane(sc
))
2460 inactive
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
2461 isolated
= node_page_state(pgdat
, NR_ISOLATED_FILE
);
2463 inactive
= node_page_state(pgdat
, NR_INACTIVE_ANON
);
2464 isolated
= node_page_state(pgdat
, NR_ISOLATED_ANON
);
2468 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
2469 * won't get blocked by normal direct-reclaimers, forming a circular
2472 if (gfp_has_io_fs(sc
->gfp_mask
))
2475 too_many
= isolated
> inactive
;
2477 /* Wake up tasks throttled due to too_many_isolated. */
2479 wake_throttle_isolated(pgdat
);
2485 * move_folios_to_lru() moves folios from private @list to appropriate LRU list.
2486 * On return, @list is reused as a list of folios to be freed by the caller.
2488 * Returns the number of pages moved to the given lruvec.
2490 static unsigned int move_folios_to_lru(struct lruvec
*lruvec
,
2491 struct list_head
*list
)
2493 int nr_pages
, nr_moved
= 0;
2494 LIST_HEAD(folios_to_free
);
2496 while (!list_empty(list
)) {
2497 struct folio
*folio
= lru_to_folio(list
);
2499 VM_BUG_ON_FOLIO(folio_test_lru(folio
), folio
);
2500 list_del(&folio
->lru
);
2501 if (unlikely(!folio_evictable(folio
))) {
2502 spin_unlock_irq(&lruvec
->lru_lock
);
2503 folio_putback_lru(folio
);
2504 spin_lock_irq(&lruvec
->lru_lock
);
2509 * The folio_set_lru needs to be kept here for list integrity.
2511 * #0 move_folios_to_lru #1 release_pages
2512 * if (!folio_put_testzero())
2513 * if (folio_put_testzero())
2514 * !lru //skip lru_lock
2516 * list_add(&folio->lru,)
2517 * list_add(&folio->lru,)
2519 folio_set_lru(folio
);
2521 if (unlikely(folio_put_testzero(folio
))) {
2522 __folio_clear_lru_flags(folio
);
2524 if (unlikely(folio_test_large(folio
))) {
2525 spin_unlock_irq(&lruvec
->lru_lock
);
2526 destroy_large_folio(folio
);
2527 spin_lock_irq(&lruvec
->lru_lock
);
2529 list_add(&folio
->lru
, &folios_to_free
);
2535 * All pages were isolated from the same lruvec (and isolation
2536 * inhibits memcg migration).
2538 VM_BUG_ON_FOLIO(!folio_matches_lruvec(folio
, lruvec
), folio
);
2539 lruvec_add_folio(lruvec
, folio
);
2540 nr_pages
= folio_nr_pages(folio
);
2541 nr_moved
+= nr_pages
;
2542 if (folio_test_active(folio
))
2543 workingset_age_nonresident(lruvec
, nr_pages
);
2547 * To save our caller's stack, now use input list for pages to free.
2549 list_splice(&folios_to_free
, list
);
2555 * If a kernel thread (such as nfsd for loop-back mounts) services a backing
2556 * device by writing to the page cache it sets PF_LOCAL_THROTTLE. In this case
2557 * we should not throttle. Otherwise it is safe to do so.
2559 static int current_may_throttle(void)
2561 return !(current
->flags
& PF_LOCAL_THROTTLE
);
2565 * shrink_inactive_list() is a helper for shrink_node(). It returns the number
2566 * of reclaimed pages
2568 static unsigned long shrink_inactive_list(unsigned long nr_to_scan
,
2569 struct lruvec
*lruvec
, struct scan_control
*sc
,
2572 LIST_HEAD(folio_list
);
2573 unsigned long nr_scanned
;
2574 unsigned int nr_reclaimed
= 0;
2575 unsigned long nr_taken
;
2576 struct reclaim_stat stat
;
2577 bool file
= is_file_lru(lru
);
2578 enum vm_event_item item
;
2579 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2580 bool stalled
= false;
2582 while (unlikely(too_many_isolated(pgdat
, file
, sc
))) {
2586 /* wait a bit for the reclaimer. */
2588 reclaim_throttle(pgdat
, VMSCAN_THROTTLE_ISOLATED
);
2590 /* We are about to die and free our memory. Return now. */
2591 if (fatal_signal_pending(current
))
2592 return SWAP_CLUSTER_MAX
;
2597 spin_lock_irq(&lruvec
->lru_lock
);
2599 nr_taken
= isolate_lru_folios(nr_to_scan
, lruvec
, &folio_list
,
2600 &nr_scanned
, sc
, lru
);
2602 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, nr_taken
);
2603 item
= PGSCAN_KSWAPD
+ reclaimer_offset();
2604 if (!cgroup_reclaim(sc
))
2605 __count_vm_events(item
, nr_scanned
);
2606 __count_memcg_events(lruvec_memcg(lruvec
), item
, nr_scanned
);
2607 __count_vm_events(PGSCAN_ANON
+ file
, nr_scanned
);
2609 spin_unlock_irq(&lruvec
->lru_lock
);
2614 nr_reclaimed
= shrink_folio_list(&folio_list
, pgdat
, sc
, &stat
, false);
2616 spin_lock_irq(&lruvec
->lru_lock
);
2617 move_folios_to_lru(lruvec
, &folio_list
);
2619 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
2620 item
= PGSTEAL_KSWAPD
+ reclaimer_offset();
2621 if (!cgroup_reclaim(sc
))
2622 __count_vm_events(item
, nr_reclaimed
);
2623 __count_memcg_events(lruvec_memcg(lruvec
), item
, nr_reclaimed
);
2624 __count_vm_events(PGSTEAL_ANON
+ file
, nr_reclaimed
);
2625 spin_unlock_irq(&lruvec
->lru_lock
);
2627 lru_note_cost(lruvec
, file
, stat
.nr_pageout
, nr_scanned
- nr_reclaimed
);
2628 mem_cgroup_uncharge_list(&folio_list
);
2629 free_unref_page_list(&folio_list
);
2632 * If dirty folios are scanned that are not queued for IO, it
2633 * implies that flushers are not doing their job. This can
2634 * happen when memory pressure pushes dirty folios to the end of
2635 * the LRU before the dirty limits are breached and the dirty
2636 * data has expired. It can also happen when the proportion of
2637 * dirty folios grows not through writes but through memory
2638 * pressure reclaiming all the clean cache. And in some cases,
2639 * the flushers simply cannot keep up with the allocation
2640 * rate. Nudge the flusher threads in case they are asleep.
2642 if (stat
.nr_unqueued_dirty
== nr_taken
) {
2643 wakeup_flusher_threads(WB_REASON_VMSCAN
);
2645 * For cgroupv1 dirty throttling is achieved by waking up
2646 * the kernel flusher here and later waiting on folios
2647 * which are in writeback to finish (see shrink_folio_list()).
2649 * Flusher may not be able to issue writeback quickly
2650 * enough for cgroupv1 writeback throttling to work
2651 * on a large system.
2653 if (!writeback_throttling_sane(sc
))
2654 reclaim_throttle(pgdat
, VMSCAN_THROTTLE_WRITEBACK
);
2657 sc
->nr
.dirty
+= stat
.nr_dirty
;
2658 sc
->nr
.congested
+= stat
.nr_congested
;
2659 sc
->nr
.unqueued_dirty
+= stat
.nr_unqueued_dirty
;
2660 sc
->nr
.writeback
+= stat
.nr_writeback
;
2661 sc
->nr
.immediate
+= stat
.nr_immediate
;
2662 sc
->nr
.taken
+= nr_taken
;
2664 sc
->nr
.file_taken
+= nr_taken
;
2666 trace_mm_vmscan_lru_shrink_inactive(pgdat
->node_id
,
2667 nr_scanned
, nr_reclaimed
, &stat
, sc
->priority
, file
);
2668 return nr_reclaimed
;
2672 * shrink_active_list() moves folios from the active LRU to the inactive LRU.
2674 * We move them the other way if the folio is referenced by one or more
2677 * If the folios are mostly unmapped, the processing is fast and it is
2678 * appropriate to hold lru_lock across the whole operation. But if
2679 * the folios are mapped, the processing is slow (folio_referenced()), so
2680 * we should drop lru_lock around each folio. It's impossible to balance
2681 * this, so instead we remove the folios from the LRU while processing them.
2682 * It is safe to rely on the active flag against the non-LRU folios in here
2683 * because nobody will play with that bit on a non-LRU folio.
2685 * The downside is that we have to touch folio->_refcount against each folio.
2686 * But we had to alter folio->flags anyway.
2688 static void shrink_active_list(unsigned long nr_to_scan
,
2689 struct lruvec
*lruvec
,
2690 struct scan_control
*sc
,
2693 unsigned long nr_taken
;
2694 unsigned long nr_scanned
;
2695 unsigned long vm_flags
;
2696 LIST_HEAD(l_hold
); /* The folios which were snipped off */
2697 LIST_HEAD(l_active
);
2698 LIST_HEAD(l_inactive
);
2699 unsigned nr_deactivate
, nr_activate
;
2700 unsigned nr_rotated
= 0;
2701 int file
= is_file_lru(lru
);
2702 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2706 spin_lock_irq(&lruvec
->lru_lock
);
2708 nr_taken
= isolate_lru_folios(nr_to_scan
, lruvec
, &l_hold
,
2709 &nr_scanned
, sc
, lru
);
2711 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, nr_taken
);
2713 if (!cgroup_reclaim(sc
))
2714 __count_vm_events(PGREFILL
, nr_scanned
);
2715 __count_memcg_events(lruvec_memcg(lruvec
), PGREFILL
, nr_scanned
);
2717 spin_unlock_irq(&lruvec
->lru_lock
);
2719 while (!list_empty(&l_hold
)) {
2720 struct folio
*folio
;
2723 folio
= lru_to_folio(&l_hold
);
2724 list_del(&folio
->lru
);
2726 if (unlikely(!folio_evictable(folio
))) {
2727 folio_putback_lru(folio
);
2731 if (unlikely(buffer_heads_over_limit
)) {
2732 if (folio_needs_release(folio
) &&
2733 folio_trylock(folio
)) {
2734 filemap_release_folio(folio
, 0);
2735 folio_unlock(folio
);
2739 /* Referenced or rmap lock contention: rotate */
2740 if (folio_referenced(folio
, 0, sc
->target_mem_cgroup
,
2743 * Identify referenced, file-backed active folios and
2744 * give them one more trip around the active list. So
2745 * that executable code get better chances to stay in
2746 * memory under moderate memory pressure. Anon folios
2747 * are not likely to be evicted by use-once streaming
2748 * IO, plus JVM can create lots of anon VM_EXEC folios,
2749 * so we ignore them here.
2751 if ((vm_flags
& VM_EXEC
) && folio_is_file_lru(folio
)) {
2752 nr_rotated
+= folio_nr_pages(folio
);
2753 list_add(&folio
->lru
, &l_active
);
2758 folio_clear_active(folio
); /* we are de-activating */
2759 folio_set_workingset(folio
);
2760 list_add(&folio
->lru
, &l_inactive
);
2764 * Move folios back to the lru list.
2766 spin_lock_irq(&lruvec
->lru_lock
);
2768 nr_activate
= move_folios_to_lru(lruvec
, &l_active
);
2769 nr_deactivate
= move_folios_to_lru(lruvec
, &l_inactive
);
2770 /* Keep all free folios in l_active list */
2771 list_splice(&l_inactive
, &l_active
);
2773 __count_vm_events(PGDEACTIVATE
, nr_deactivate
);
2774 __count_memcg_events(lruvec_memcg(lruvec
), PGDEACTIVATE
, nr_deactivate
);
2776 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
2777 spin_unlock_irq(&lruvec
->lru_lock
);
2780 lru_note_cost(lruvec
, file
, 0, nr_rotated
);
2781 mem_cgroup_uncharge_list(&l_active
);
2782 free_unref_page_list(&l_active
);
2783 trace_mm_vmscan_lru_shrink_active(pgdat
->node_id
, nr_taken
, nr_activate
,
2784 nr_deactivate
, nr_rotated
, sc
->priority
, file
);
2787 static unsigned int reclaim_folio_list(struct list_head
*folio_list
,
2788 struct pglist_data
*pgdat
)
2790 struct reclaim_stat dummy_stat
;
2791 unsigned int nr_reclaimed
;
2792 struct folio
*folio
;
2793 struct scan_control sc
= {
2794 .gfp_mask
= GFP_KERNEL
,
2801 nr_reclaimed
= shrink_folio_list(folio_list
, pgdat
, &sc
, &dummy_stat
, false);
2802 while (!list_empty(folio_list
)) {
2803 folio
= lru_to_folio(folio_list
);
2804 list_del(&folio
->lru
);
2805 folio_putback_lru(folio
);
2808 return nr_reclaimed
;
2811 unsigned long reclaim_pages(struct list_head
*folio_list
)
2814 unsigned int nr_reclaimed
= 0;
2815 LIST_HEAD(node_folio_list
);
2816 unsigned int noreclaim_flag
;
2818 if (list_empty(folio_list
))
2819 return nr_reclaimed
;
2821 noreclaim_flag
= memalloc_noreclaim_save();
2823 nid
= folio_nid(lru_to_folio(folio_list
));
2825 struct folio
*folio
= lru_to_folio(folio_list
);
2827 if (nid
== folio_nid(folio
)) {
2828 folio_clear_active(folio
);
2829 list_move(&folio
->lru
, &node_folio_list
);
2833 nr_reclaimed
+= reclaim_folio_list(&node_folio_list
, NODE_DATA(nid
));
2834 nid
= folio_nid(lru_to_folio(folio_list
));
2835 } while (!list_empty(folio_list
));
2837 nr_reclaimed
+= reclaim_folio_list(&node_folio_list
, NODE_DATA(nid
));
2839 memalloc_noreclaim_restore(noreclaim_flag
);
2841 return nr_reclaimed
;
2844 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
2845 struct lruvec
*lruvec
, struct scan_control
*sc
)
2847 if (is_active_lru(lru
)) {
2848 if (sc
->may_deactivate
& (1 << is_file_lru(lru
)))
2849 shrink_active_list(nr_to_scan
, lruvec
, sc
, lru
);
2851 sc
->skipped_deactivate
= 1;
2855 return shrink_inactive_list(nr_to_scan
, lruvec
, sc
, lru
);
2859 * The inactive anon list should be small enough that the VM never has
2860 * to do too much work.
2862 * The inactive file list should be small enough to leave most memory
2863 * to the established workingset on the scan-resistant active list,
2864 * but large enough to avoid thrashing the aggregate readahead window.
2866 * Both inactive lists should also be large enough that each inactive
2867 * folio has a chance to be referenced again before it is reclaimed.
2869 * If that fails and refaulting is observed, the inactive list grows.
2871 * The inactive_ratio is the target ratio of ACTIVE to INACTIVE folios
2872 * on this LRU, maintained by the pageout code. An inactive_ratio
2873 * of 3 means 3:1 or 25% of the folios are kept on the inactive list.
2876 * memory ratio inactive
2877 * -------------------------------------
2886 static bool inactive_is_low(struct lruvec
*lruvec
, enum lru_list inactive_lru
)
2888 enum lru_list active_lru
= inactive_lru
+ LRU_ACTIVE
;
2889 unsigned long inactive
, active
;
2890 unsigned long inactive_ratio
;
2893 inactive
= lruvec_page_state(lruvec
, NR_LRU_BASE
+ inactive_lru
);
2894 active
= lruvec_page_state(lruvec
, NR_LRU_BASE
+ active_lru
);
2896 gb
= (inactive
+ active
) >> (30 - PAGE_SHIFT
);
2898 inactive_ratio
= int_sqrt(10 * gb
);
2902 return inactive
* inactive_ratio
< active
;
2912 static void prepare_scan_count(pg_data_t
*pgdat
, struct scan_control
*sc
)
2915 struct lruvec
*target_lruvec
;
2917 if (lru_gen_enabled())
2920 target_lruvec
= mem_cgroup_lruvec(sc
->target_mem_cgroup
, pgdat
);
2923 * Flush the memory cgroup stats, so that we read accurate per-memcg
2924 * lruvec stats for heuristics.
2926 mem_cgroup_flush_stats();
2929 * Determine the scan balance between anon and file LRUs.
2931 spin_lock_irq(&target_lruvec
->lru_lock
);
2932 sc
->anon_cost
= target_lruvec
->anon_cost
;
2933 sc
->file_cost
= target_lruvec
->file_cost
;
2934 spin_unlock_irq(&target_lruvec
->lru_lock
);
2937 * Target desirable inactive:active list ratios for the anon
2938 * and file LRU lists.
2940 if (!sc
->force_deactivate
) {
2941 unsigned long refaults
;
2944 * When refaults are being observed, it means a new
2945 * workingset is being established. Deactivate to get
2946 * rid of any stale active pages quickly.
2948 refaults
= lruvec_page_state(target_lruvec
,
2949 WORKINGSET_ACTIVATE_ANON
);
2950 if (refaults
!= target_lruvec
->refaults
[WORKINGSET_ANON
] ||
2951 inactive_is_low(target_lruvec
, LRU_INACTIVE_ANON
))
2952 sc
->may_deactivate
|= DEACTIVATE_ANON
;
2954 sc
->may_deactivate
&= ~DEACTIVATE_ANON
;
2956 refaults
= lruvec_page_state(target_lruvec
,
2957 WORKINGSET_ACTIVATE_FILE
);
2958 if (refaults
!= target_lruvec
->refaults
[WORKINGSET_FILE
] ||
2959 inactive_is_low(target_lruvec
, LRU_INACTIVE_FILE
))
2960 sc
->may_deactivate
|= DEACTIVATE_FILE
;
2962 sc
->may_deactivate
&= ~DEACTIVATE_FILE
;
2964 sc
->may_deactivate
= DEACTIVATE_ANON
| DEACTIVATE_FILE
;
2967 * If we have plenty of inactive file pages that aren't
2968 * thrashing, try to reclaim those first before touching
2971 file
= lruvec_page_state(target_lruvec
, NR_INACTIVE_FILE
);
2972 if (file
>> sc
->priority
&& !(sc
->may_deactivate
& DEACTIVATE_FILE
))
2973 sc
->cache_trim_mode
= 1;
2975 sc
->cache_trim_mode
= 0;
2978 * Prevent the reclaimer from falling into the cache trap: as
2979 * cache pages start out inactive, every cache fault will tip
2980 * the scan balance towards the file LRU. And as the file LRU
2981 * shrinks, so does the window for rotation from references.
2982 * This means we have a runaway feedback loop where a tiny
2983 * thrashing file LRU becomes infinitely more attractive than
2984 * anon pages. Try to detect this based on file LRU size.
2986 if (!cgroup_reclaim(sc
)) {
2987 unsigned long total_high_wmark
= 0;
2988 unsigned long free
, anon
;
2991 free
= sum_zone_node_page_state(pgdat
->node_id
, NR_FREE_PAGES
);
2992 file
= node_page_state(pgdat
, NR_ACTIVE_FILE
) +
2993 node_page_state(pgdat
, NR_INACTIVE_FILE
);
2995 for (z
= 0; z
< MAX_NR_ZONES
; z
++) {
2996 struct zone
*zone
= &pgdat
->node_zones
[z
];
2998 if (!managed_zone(zone
))
3001 total_high_wmark
+= high_wmark_pages(zone
);
3005 * Consider anon: if that's low too, this isn't a
3006 * runaway file reclaim problem, but rather just
3007 * extreme pressure. Reclaim as per usual then.
3009 anon
= node_page_state(pgdat
, NR_INACTIVE_ANON
);
3012 file
+ free
<= total_high_wmark
&&
3013 !(sc
->may_deactivate
& DEACTIVATE_ANON
) &&
3014 anon
>> sc
->priority
;
3019 * Determine how aggressively the anon and file LRU lists should be
3022 * nr[0] = anon inactive folios to scan; nr[1] = anon active folios to scan
3023 * nr[2] = file inactive folios to scan; nr[3] = file active folios to scan
3025 static void get_scan_count(struct lruvec
*lruvec
, struct scan_control
*sc
,
3028 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
3029 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
3030 unsigned long anon_cost
, file_cost
, total_cost
;
3031 int swappiness
= mem_cgroup_swappiness(memcg
);
3032 u64 fraction
[ANON_AND_FILE
];
3033 u64 denominator
= 0; /* gcc */
3034 enum scan_balance scan_balance
;
3035 unsigned long ap
, fp
;
3038 /* If we have no swap space, do not bother scanning anon folios. */
3039 if (!sc
->may_swap
|| !can_reclaim_anon_pages(memcg
, pgdat
->node_id
, sc
)) {
3040 scan_balance
= SCAN_FILE
;
3045 * Global reclaim will swap to prevent OOM even with no
3046 * swappiness, but memcg users want to use this knob to
3047 * disable swapping for individual groups completely when
3048 * using the memory controller's swap limit feature would be
3051 if (cgroup_reclaim(sc
) && !swappiness
) {
3052 scan_balance
= SCAN_FILE
;
3057 * Do not apply any pressure balancing cleverness when the
3058 * system is close to OOM, scan both anon and file equally
3059 * (unless the swappiness setting disagrees with swapping).
3061 if (!sc
->priority
&& swappiness
) {
3062 scan_balance
= SCAN_EQUAL
;
3067 * If the system is almost out of file pages, force-scan anon.
3069 if (sc
->file_is_tiny
) {
3070 scan_balance
= SCAN_ANON
;
3075 * If there is enough inactive page cache, we do not reclaim
3076 * anything from the anonymous working right now.
3078 if (sc
->cache_trim_mode
) {
3079 scan_balance
= SCAN_FILE
;
3083 scan_balance
= SCAN_FRACT
;
3085 * Calculate the pressure balance between anon and file pages.
3087 * The amount of pressure we put on each LRU is inversely
3088 * proportional to the cost of reclaiming each list, as
3089 * determined by the share of pages that are refaulting, times
3090 * the relative IO cost of bringing back a swapped out
3091 * anonymous page vs reloading a filesystem page (swappiness).
3093 * Although we limit that influence to ensure no list gets
3094 * left behind completely: at least a third of the pressure is
3095 * applied, before swappiness.
3097 * With swappiness at 100, anon and file have equal IO cost.
3099 total_cost
= sc
->anon_cost
+ sc
->file_cost
;
3100 anon_cost
= total_cost
+ sc
->anon_cost
;
3101 file_cost
= total_cost
+ sc
->file_cost
;
3102 total_cost
= anon_cost
+ file_cost
;
3104 ap
= swappiness
* (total_cost
+ 1);
3105 ap
/= anon_cost
+ 1;
3107 fp
= (200 - swappiness
) * (total_cost
+ 1);
3108 fp
/= file_cost
+ 1;
3112 denominator
= ap
+ fp
;
3114 for_each_evictable_lru(lru
) {
3115 int file
= is_file_lru(lru
);
3116 unsigned long lruvec_size
;
3117 unsigned long low
, min
;
3120 lruvec_size
= lruvec_lru_size(lruvec
, lru
, sc
->reclaim_idx
);
3121 mem_cgroup_protection(sc
->target_mem_cgroup
, memcg
,
3126 * Scale a cgroup's reclaim pressure by proportioning
3127 * its current usage to its memory.low or memory.min
3130 * This is important, as otherwise scanning aggression
3131 * becomes extremely binary -- from nothing as we
3132 * approach the memory protection threshold, to totally
3133 * nominal as we exceed it. This results in requiring
3134 * setting extremely liberal protection thresholds. It
3135 * also means we simply get no protection at all if we
3136 * set it too low, which is not ideal.
3138 * If there is any protection in place, we reduce scan
3139 * pressure by how much of the total memory used is
3140 * within protection thresholds.
3142 * There is one special case: in the first reclaim pass,
3143 * we skip over all groups that are within their low
3144 * protection. If that fails to reclaim enough pages to
3145 * satisfy the reclaim goal, we come back and override
3146 * the best-effort low protection. However, we still
3147 * ideally want to honor how well-behaved groups are in
3148 * that case instead of simply punishing them all
3149 * equally. As such, we reclaim them based on how much
3150 * memory they are using, reducing the scan pressure
3151 * again by how much of the total memory used is under
3154 unsigned long cgroup_size
= mem_cgroup_size(memcg
);
3155 unsigned long protection
;
3157 /* memory.low scaling, make sure we retry before OOM */
3158 if (!sc
->memcg_low_reclaim
&& low
> min
) {
3160 sc
->memcg_low_skipped
= 1;
3165 /* Avoid TOCTOU with earlier protection check */
3166 cgroup_size
= max(cgroup_size
, protection
);
3168 scan
= lruvec_size
- lruvec_size
* protection
/
3172 * Minimally target SWAP_CLUSTER_MAX pages to keep
3173 * reclaim moving forwards, avoiding decrementing
3174 * sc->priority further than desirable.
3176 scan
= max(scan
, SWAP_CLUSTER_MAX
);
3181 scan
>>= sc
->priority
;
3184 * If the cgroup's already been deleted, make sure to
3185 * scrape out the remaining cache.
3187 if (!scan
&& !mem_cgroup_online(memcg
))
3188 scan
= min(lruvec_size
, SWAP_CLUSTER_MAX
);
3190 switch (scan_balance
) {
3192 /* Scan lists relative to size */
3196 * Scan types proportional to swappiness and
3197 * their relative recent reclaim efficiency.
3198 * Make sure we don't miss the last page on
3199 * the offlined memory cgroups because of a
3202 scan
= mem_cgroup_online(memcg
) ?
3203 div64_u64(scan
* fraction
[file
], denominator
) :
3204 DIV64_U64_ROUND_UP(scan
* fraction
[file
],
3209 /* Scan one type exclusively */
3210 if ((scan_balance
== SCAN_FILE
) != file
)
3214 /* Look ma, no brain */
3223 * Anonymous LRU management is a waste if there is
3224 * ultimately no way to reclaim the memory.
3226 static bool can_age_anon_pages(struct pglist_data
*pgdat
,
3227 struct scan_control
*sc
)
3229 /* Aging the anon LRU is valuable if swap is present: */
3230 if (total_swap_pages
> 0)
3233 /* Also valuable if anon pages can be demoted: */
3234 return can_demote(pgdat
->node_id
, sc
);
3237 #ifdef CONFIG_LRU_GEN
3239 #ifdef CONFIG_LRU_GEN_ENABLED
3240 DEFINE_STATIC_KEY_ARRAY_TRUE(lru_gen_caps
, NR_LRU_GEN_CAPS
);
3241 #define get_cap(cap) static_branch_likely(&lru_gen_caps[cap])
3243 DEFINE_STATIC_KEY_ARRAY_FALSE(lru_gen_caps
, NR_LRU_GEN_CAPS
);
3244 #define get_cap(cap) static_branch_unlikely(&lru_gen_caps[cap])
3247 static bool should_walk_mmu(void)
3249 return arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK
);
3252 static bool should_clear_pmd_young(void)
3254 return arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG
);
3257 /******************************************************************************
3259 ******************************************************************************/
3261 #define LRU_REFS_FLAGS (BIT(PG_referenced) | BIT(PG_workingset))
3263 #define DEFINE_MAX_SEQ(lruvec) \
3264 unsigned long max_seq = READ_ONCE((lruvec)->lrugen.max_seq)
3266 #define DEFINE_MIN_SEQ(lruvec) \
3267 unsigned long min_seq[ANON_AND_FILE] = { \
3268 READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_ANON]), \
3269 READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_FILE]), \
3272 #define for_each_gen_type_zone(gen, type, zone) \
3273 for ((gen) = 0; (gen) < MAX_NR_GENS; (gen)++) \
3274 for ((type) = 0; (type) < ANON_AND_FILE; (type)++) \
3275 for ((zone) = 0; (zone) < MAX_NR_ZONES; (zone)++)
3277 #define get_memcg_gen(seq) ((seq) % MEMCG_NR_GENS)
3278 #define get_memcg_bin(bin) ((bin) % MEMCG_NR_BINS)
3280 static struct lruvec
*get_lruvec(struct mem_cgroup
*memcg
, int nid
)
3282 struct pglist_data
*pgdat
= NODE_DATA(nid
);
3286 struct lruvec
*lruvec
= &memcg
->nodeinfo
[nid
]->lruvec
;
3288 /* see the comment in mem_cgroup_lruvec() */
3290 lruvec
->pgdat
= pgdat
;
3295 VM_WARN_ON_ONCE(!mem_cgroup_disabled());
3297 return &pgdat
->__lruvec
;
3300 static int get_swappiness(struct lruvec
*lruvec
, struct scan_control
*sc
)
3302 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
3303 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
3308 if (!can_demote(pgdat
->node_id
, sc
) &&
3309 mem_cgroup_get_nr_swap_pages(memcg
) < MIN_LRU_BATCH
)
3312 return mem_cgroup_swappiness(memcg
);
3315 static int get_nr_gens(struct lruvec
*lruvec
, int type
)
3317 return lruvec
->lrugen
.max_seq
- lruvec
->lrugen
.min_seq
[type
] + 1;
3320 static bool __maybe_unused
seq_is_valid(struct lruvec
*lruvec
)
3322 /* see the comment on lru_gen_folio */
3323 return get_nr_gens(lruvec
, LRU_GEN_FILE
) >= MIN_NR_GENS
&&
3324 get_nr_gens(lruvec
, LRU_GEN_FILE
) <= get_nr_gens(lruvec
, LRU_GEN_ANON
) &&
3325 get_nr_gens(lruvec
, LRU_GEN_ANON
) <= MAX_NR_GENS
;
3328 /******************************************************************************
3330 ******************************************************************************/
3333 * Bloom filters with m=1<<15, k=2 and the false positive rates of ~1/5 when
3334 * n=10,000 and ~1/2 when n=20,000, where, conventionally, m is the number of
3335 * bits in a bitmap, k is the number of hash functions and n is the number of
3338 * Page table walkers use one of the two filters to reduce their search space.
3339 * To get rid of non-leaf entries that no longer have enough leaf entries, the
3340 * aging uses the double-buffering technique to flip to the other filter each
3341 * time it produces a new generation. For non-leaf entries that have enough
3342 * leaf entries, the aging carries them over to the next generation in
3343 * walk_pmd_range(); the eviction also report them when walking the rmap
3344 * in lru_gen_look_around().
3346 * For future optimizations:
3347 * 1. It's not necessary to keep both filters all the time. The spare one can be
3348 * freed after the RCU grace period and reallocated if needed again.
3349 * 2. And when reallocating, it's worth scaling its size according to the number
3350 * of inserted entries in the other filter, to reduce the memory overhead on
3351 * small systems and false positives on large systems.
3352 * 3. Jenkins' hash function is an alternative to Knuth's.
3354 #define BLOOM_FILTER_SHIFT 15
3356 static inline int filter_gen_from_seq(unsigned long seq
)
3358 return seq
% NR_BLOOM_FILTERS
;
3361 static void get_item_key(void *item
, int *key
)
3363 u32 hash
= hash_ptr(item
, BLOOM_FILTER_SHIFT
* 2);
3365 BUILD_BUG_ON(BLOOM_FILTER_SHIFT
* 2 > BITS_PER_TYPE(u32
));
3367 key
[0] = hash
& (BIT(BLOOM_FILTER_SHIFT
) - 1);
3368 key
[1] = hash
>> BLOOM_FILTER_SHIFT
;
3371 static bool test_bloom_filter(struct lruvec
*lruvec
, unsigned long seq
, void *item
)
3374 unsigned long *filter
;
3375 int gen
= filter_gen_from_seq(seq
);
3377 filter
= READ_ONCE(lruvec
->mm_state
.filters
[gen
]);
3381 get_item_key(item
, key
);
3383 return test_bit(key
[0], filter
) && test_bit(key
[1], filter
);
3386 static void update_bloom_filter(struct lruvec
*lruvec
, unsigned long seq
, void *item
)
3389 unsigned long *filter
;
3390 int gen
= filter_gen_from_seq(seq
);
3392 filter
= READ_ONCE(lruvec
->mm_state
.filters
[gen
]);
3396 get_item_key(item
, key
);
3398 if (!test_bit(key
[0], filter
))
3399 set_bit(key
[0], filter
);
3400 if (!test_bit(key
[1], filter
))
3401 set_bit(key
[1], filter
);
3404 static void reset_bloom_filter(struct lruvec
*lruvec
, unsigned long seq
)
3406 unsigned long *filter
;
3407 int gen
= filter_gen_from_seq(seq
);
3409 filter
= lruvec
->mm_state
.filters
[gen
];
3411 bitmap_clear(filter
, 0, BIT(BLOOM_FILTER_SHIFT
));
3415 filter
= bitmap_zalloc(BIT(BLOOM_FILTER_SHIFT
),
3416 __GFP_HIGH
| __GFP_NOMEMALLOC
| __GFP_NOWARN
);
3417 WRITE_ONCE(lruvec
->mm_state
.filters
[gen
], filter
);
3420 /******************************************************************************
3422 ******************************************************************************/
3424 static struct lru_gen_mm_list
*get_mm_list(struct mem_cgroup
*memcg
)
3426 static struct lru_gen_mm_list mm_list
= {
3427 .fifo
= LIST_HEAD_INIT(mm_list
.fifo
),
3428 .lock
= __SPIN_LOCK_UNLOCKED(mm_list
.lock
),
3433 return &memcg
->mm_list
;
3435 VM_WARN_ON_ONCE(!mem_cgroup_disabled());
3440 void lru_gen_add_mm(struct mm_struct
*mm
)
3443 struct mem_cgroup
*memcg
= get_mem_cgroup_from_mm(mm
);
3444 struct lru_gen_mm_list
*mm_list
= get_mm_list(memcg
);
3446 VM_WARN_ON_ONCE(!list_empty(&mm
->lru_gen
.list
));
3448 VM_WARN_ON_ONCE(mm
->lru_gen
.memcg
);
3449 mm
->lru_gen
.memcg
= memcg
;
3451 spin_lock(&mm_list
->lock
);
3453 for_each_node_state(nid
, N_MEMORY
) {
3454 struct lruvec
*lruvec
= get_lruvec(memcg
, nid
);
3456 /* the first addition since the last iteration */
3457 if (lruvec
->mm_state
.tail
== &mm_list
->fifo
)
3458 lruvec
->mm_state
.tail
= &mm
->lru_gen
.list
;
3461 list_add_tail(&mm
->lru_gen
.list
, &mm_list
->fifo
);
3463 spin_unlock(&mm_list
->lock
);
3466 void lru_gen_del_mm(struct mm_struct
*mm
)
3469 struct lru_gen_mm_list
*mm_list
;
3470 struct mem_cgroup
*memcg
= NULL
;
3472 if (list_empty(&mm
->lru_gen
.list
))
3476 memcg
= mm
->lru_gen
.memcg
;
3478 mm_list
= get_mm_list(memcg
);
3480 spin_lock(&mm_list
->lock
);
3482 for_each_node(nid
) {
3483 struct lruvec
*lruvec
= get_lruvec(memcg
, nid
);
3485 /* where the current iteration continues after */
3486 if (lruvec
->mm_state
.head
== &mm
->lru_gen
.list
)
3487 lruvec
->mm_state
.head
= lruvec
->mm_state
.head
->prev
;
3489 /* where the last iteration ended before */
3490 if (lruvec
->mm_state
.tail
== &mm
->lru_gen
.list
)
3491 lruvec
->mm_state
.tail
= lruvec
->mm_state
.tail
->next
;
3494 list_del_init(&mm
->lru_gen
.list
);
3496 spin_unlock(&mm_list
->lock
);
3499 mem_cgroup_put(mm
->lru_gen
.memcg
);
3500 mm
->lru_gen
.memcg
= NULL
;
3505 void lru_gen_migrate_mm(struct mm_struct
*mm
)
3507 struct mem_cgroup
*memcg
;
3508 struct task_struct
*task
= rcu_dereference_protected(mm
->owner
, true);
3510 VM_WARN_ON_ONCE(task
->mm
!= mm
);
3511 lockdep_assert_held(&task
->alloc_lock
);
3513 /* for mm_update_next_owner() */
3514 if (mem_cgroup_disabled())
3517 /* migration can happen before addition */
3518 if (!mm
->lru_gen
.memcg
)
3522 memcg
= mem_cgroup_from_task(task
);
3524 if (memcg
== mm
->lru_gen
.memcg
)
3527 VM_WARN_ON_ONCE(list_empty(&mm
->lru_gen
.list
));
3534 static void reset_mm_stats(struct lruvec
*lruvec
, struct lru_gen_mm_walk
*walk
, bool last
)
3539 lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec
))->lock
);
3542 hist
= lru_hist_from_seq(walk
->max_seq
);
3544 for (i
= 0; i
< NR_MM_STATS
; i
++) {
3545 WRITE_ONCE(lruvec
->mm_state
.stats
[hist
][i
],
3546 lruvec
->mm_state
.stats
[hist
][i
] + walk
->mm_stats
[i
]);
3547 walk
->mm_stats
[i
] = 0;
3551 if (NR_HIST_GENS
> 1 && last
) {
3552 hist
= lru_hist_from_seq(lruvec
->mm_state
.seq
+ 1);
3554 for (i
= 0; i
< NR_MM_STATS
; i
++)
3555 WRITE_ONCE(lruvec
->mm_state
.stats
[hist
][i
], 0);
3559 static bool should_skip_mm(struct mm_struct
*mm
, struct lru_gen_mm_walk
*walk
)
3562 unsigned long size
= 0;
3563 struct pglist_data
*pgdat
= lruvec_pgdat(walk
->lruvec
);
3564 int key
= pgdat
->node_id
% BITS_PER_TYPE(mm
->lru_gen
.bitmap
);
3566 if (!walk
->force_scan
&& !test_bit(key
, &mm
->lru_gen
.bitmap
))
3569 clear_bit(key
, &mm
->lru_gen
.bitmap
);
3571 for (type
= !walk
->can_swap
; type
< ANON_AND_FILE
; type
++) {
3572 size
+= type
? get_mm_counter(mm
, MM_FILEPAGES
) :
3573 get_mm_counter(mm
, MM_ANONPAGES
) +
3574 get_mm_counter(mm
, MM_SHMEMPAGES
);
3577 if (size
< MIN_LRU_BATCH
)
3580 return !mmget_not_zero(mm
);
3583 static bool iterate_mm_list(struct lruvec
*lruvec
, struct lru_gen_mm_walk
*walk
,
3584 struct mm_struct
**iter
)
3588 struct mm_struct
*mm
= NULL
;
3589 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
3590 struct lru_gen_mm_list
*mm_list
= get_mm_list(memcg
);
3591 struct lru_gen_mm_state
*mm_state
= &lruvec
->mm_state
;
3594 * mm_state->seq is incremented after each iteration of mm_list. There
3595 * are three interesting cases for this page table walker:
3596 * 1. It tries to start a new iteration with a stale max_seq: there is
3597 * nothing left to do.
3598 * 2. It started the next iteration: it needs to reset the Bloom filter
3599 * so that a fresh set of PTE tables can be recorded.
3600 * 3. It ended the current iteration: it needs to reset the mm stats
3601 * counters and tell its caller to increment max_seq.
3603 spin_lock(&mm_list
->lock
);
3605 VM_WARN_ON_ONCE(mm_state
->seq
+ 1 < walk
->max_seq
);
3607 if (walk
->max_seq
<= mm_state
->seq
)
3610 if (!mm_state
->head
)
3611 mm_state
->head
= &mm_list
->fifo
;
3613 if (mm_state
->head
== &mm_list
->fifo
)
3617 mm_state
->head
= mm_state
->head
->next
;
3618 if (mm_state
->head
== &mm_list
->fifo
) {
3619 WRITE_ONCE(mm_state
->seq
, mm_state
->seq
+ 1);
3624 /* force scan for those added after the last iteration */
3625 if (!mm_state
->tail
|| mm_state
->tail
== mm_state
->head
) {
3626 mm_state
->tail
= mm_state
->head
->next
;
3627 walk
->force_scan
= true;
3630 mm
= list_entry(mm_state
->head
, struct mm_struct
, lru_gen
.list
);
3631 if (should_skip_mm(mm
, walk
))
3636 reset_mm_stats(lruvec
, walk
, last
);
3638 spin_unlock(&mm_list
->lock
);
3641 reset_bloom_filter(lruvec
, walk
->max_seq
+ 1);
3651 static bool iterate_mm_list_nowalk(struct lruvec
*lruvec
, unsigned long max_seq
)
3653 bool success
= false;
3654 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
3655 struct lru_gen_mm_list
*mm_list
= get_mm_list(memcg
);
3656 struct lru_gen_mm_state
*mm_state
= &lruvec
->mm_state
;
3658 spin_lock(&mm_list
->lock
);
3660 VM_WARN_ON_ONCE(mm_state
->seq
+ 1 < max_seq
);
3662 if (max_seq
> mm_state
->seq
) {
3663 mm_state
->head
= NULL
;
3664 mm_state
->tail
= NULL
;
3665 WRITE_ONCE(mm_state
->seq
, mm_state
->seq
+ 1);
3666 reset_mm_stats(lruvec
, NULL
, true);
3670 spin_unlock(&mm_list
->lock
);
3675 /******************************************************************************
3677 ******************************************************************************/
3680 * A feedback loop based on Proportional-Integral-Derivative (PID) controller.
3682 * The P term is refaulted/(evicted+protected) from a tier in the generation
3683 * currently being evicted; the I term is the exponential moving average of the
3684 * P term over the generations previously evicted, using the smoothing factor
3685 * 1/2; the D term isn't supported.
3687 * The setpoint (SP) is always the first tier of one type; the process variable
3688 * (PV) is either any tier of the other type or any other tier of the same
3691 * The error is the difference between the SP and the PV; the correction is to
3692 * turn off protection when SP>PV or turn on protection when SP<PV.
3694 * For future optimizations:
3695 * 1. The D term may discount the other two terms over time so that long-lived
3696 * generations can resist stale information.
3699 unsigned long refaulted
;
3700 unsigned long total
;
3704 static void read_ctrl_pos(struct lruvec
*lruvec
, int type
, int tier
, int gain
,
3705 struct ctrl_pos
*pos
)
3707 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
3708 int hist
= lru_hist_from_seq(lrugen
->min_seq
[type
]);
3710 pos
->refaulted
= lrugen
->avg_refaulted
[type
][tier
] +
3711 atomic_long_read(&lrugen
->refaulted
[hist
][type
][tier
]);
3712 pos
->total
= lrugen
->avg_total
[type
][tier
] +
3713 atomic_long_read(&lrugen
->evicted
[hist
][type
][tier
]);
3715 pos
->total
+= lrugen
->protected[hist
][type
][tier
- 1];
3719 static void reset_ctrl_pos(struct lruvec
*lruvec
, int type
, bool carryover
)
3722 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
3723 bool clear
= carryover
? NR_HIST_GENS
== 1 : NR_HIST_GENS
> 1;
3724 unsigned long seq
= carryover
? lrugen
->min_seq
[type
] : lrugen
->max_seq
+ 1;
3726 lockdep_assert_held(&lruvec
->lru_lock
);
3728 if (!carryover
&& !clear
)
3731 hist
= lru_hist_from_seq(seq
);
3733 for (tier
= 0; tier
< MAX_NR_TIERS
; tier
++) {
3737 sum
= lrugen
->avg_refaulted
[type
][tier
] +
3738 atomic_long_read(&lrugen
->refaulted
[hist
][type
][tier
]);
3739 WRITE_ONCE(lrugen
->avg_refaulted
[type
][tier
], sum
/ 2);
3741 sum
= lrugen
->avg_total
[type
][tier
] +
3742 atomic_long_read(&lrugen
->evicted
[hist
][type
][tier
]);
3744 sum
+= lrugen
->protected[hist
][type
][tier
- 1];
3745 WRITE_ONCE(lrugen
->avg_total
[type
][tier
], sum
/ 2);
3749 atomic_long_set(&lrugen
->refaulted
[hist
][type
][tier
], 0);
3750 atomic_long_set(&lrugen
->evicted
[hist
][type
][tier
], 0);
3752 WRITE_ONCE(lrugen
->protected[hist
][type
][tier
- 1], 0);
3757 static bool positive_ctrl_err(struct ctrl_pos
*sp
, struct ctrl_pos
*pv
)
3760 * Return true if the PV has a limited number of refaults or a lower
3761 * refaulted/total than the SP.
3763 return pv
->refaulted
< MIN_LRU_BATCH
||
3764 pv
->refaulted
* (sp
->total
+ MIN_LRU_BATCH
) * sp
->gain
<=
3765 (sp
->refaulted
+ 1) * pv
->total
* pv
->gain
;
3768 /******************************************************************************
3770 ******************************************************************************/
3772 /* promote pages accessed through page tables */
3773 static int folio_update_gen(struct folio
*folio
, int gen
)
3775 unsigned long new_flags
, old_flags
= READ_ONCE(folio
->flags
);
3777 VM_WARN_ON_ONCE(gen
>= MAX_NR_GENS
);
3778 VM_WARN_ON_ONCE(!rcu_read_lock_held());
3781 /* lru_gen_del_folio() has isolated this page? */
3782 if (!(old_flags
& LRU_GEN_MASK
)) {
3783 /* for shrink_folio_list() */
3784 new_flags
= old_flags
| BIT(PG_referenced
);
3788 new_flags
= old_flags
& ~(LRU_GEN_MASK
| LRU_REFS_MASK
| LRU_REFS_FLAGS
);
3789 new_flags
|= (gen
+ 1UL) << LRU_GEN_PGOFF
;
3790 } while (!try_cmpxchg(&folio
->flags
, &old_flags
, new_flags
));
3792 return ((old_flags
& LRU_GEN_MASK
) >> LRU_GEN_PGOFF
) - 1;
3795 /* protect pages accessed multiple times through file descriptors */
3796 static int folio_inc_gen(struct lruvec
*lruvec
, struct folio
*folio
, bool reclaiming
)
3798 int type
= folio_is_file_lru(folio
);
3799 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
3800 int new_gen
, old_gen
= lru_gen_from_seq(lrugen
->min_seq
[type
]);
3801 unsigned long new_flags
, old_flags
= READ_ONCE(folio
->flags
);
3803 VM_WARN_ON_ONCE_FOLIO(!(old_flags
& LRU_GEN_MASK
), folio
);
3806 new_gen
= ((old_flags
& LRU_GEN_MASK
) >> LRU_GEN_PGOFF
) - 1;
3807 /* folio_update_gen() has promoted this page? */
3808 if (new_gen
>= 0 && new_gen
!= old_gen
)
3811 new_gen
= (old_gen
+ 1) % MAX_NR_GENS
;
3813 new_flags
= old_flags
& ~(LRU_GEN_MASK
| LRU_REFS_MASK
| LRU_REFS_FLAGS
);
3814 new_flags
|= (new_gen
+ 1UL) << LRU_GEN_PGOFF
;
3815 /* for folio_end_writeback() */
3817 new_flags
|= BIT(PG_reclaim
);
3818 } while (!try_cmpxchg(&folio
->flags
, &old_flags
, new_flags
));
3820 lru_gen_update_size(lruvec
, folio
, old_gen
, new_gen
);
3825 static void update_batch_size(struct lru_gen_mm_walk
*walk
, struct folio
*folio
,
3826 int old_gen
, int new_gen
)
3828 int type
= folio_is_file_lru(folio
);
3829 int zone
= folio_zonenum(folio
);
3830 int delta
= folio_nr_pages(folio
);
3832 VM_WARN_ON_ONCE(old_gen
>= MAX_NR_GENS
);
3833 VM_WARN_ON_ONCE(new_gen
>= MAX_NR_GENS
);
3837 walk
->nr_pages
[old_gen
][type
][zone
] -= delta
;
3838 walk
->nr_pages
[new_gen
][type
][zone
] += delta
;
3841 static void reset_batch_size(struct lruvec
*lruvec
, struct lru_gen_mm_walk
*walk
)
3843 int gen
, type
, zone
;
3844 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
3848 for_each_gen_type_zone(gen
, type
, zone
) {
3849 enum lru_list lru
= type
* LRU_INACTIVE_FILE
;
3850 int delta
= walk
->nr_pages
[gen
][type
][zone
];
3855 walk
->nr_pages
[gen
][type
][zone
] = 0;
3856 WRITE_ONCE(lrugen
->nr_pages
[gen
][type
][zone
],
3857 lrugen
->nr_pages
[gen
][type
][zone
] + delta
);
3859 if (lru_gen_is_active(lruvec
, gen
))
3861 __update_lru_size(lruvec
, lru
, zone
, delta
);
3865 static int should_skip_vma(unsigned long start
, unsigned long end
, struct mm_walk
*args
)
3867 struct address_space
*mapping
;
3868 struct vm_area_struct
*vma
= args
->vma
;
3869 struct lru_gen_mm_walk
*walk
= args
->private;
3871 if (!vma_is_accessible(vma
))
3874 if (is_vm_hugetlb_page(vma
))
3877 if (!vma_has_recency(vma
))
3880 if (vma
->vm_flags
& (VM_LOCKED
| VM_SPECIAL
))
3883 if (vma
== get_gate_vma(vma
->vm_mm
))
3886 if (vma_is_anonymous(vma
))
3887 return !walk
->can_swap
;
3889 if (WARN_ON_ONCE(!vma
->vm_file
|| !vma
->vm_file
->f_mapping
))
3892 mapping
= vma
->vm_file
->f_mapping
;
3893 if (mapping_unevictable(mapping
))
3896 if (shmem_mapping(mapping
))
3897 return !walk
->can_swap
;
3899 /* to exclude special mappings like dax, etc. */
3900 return !mapping
->a_ops
->read_folio
;
3904 * Some userspace memory allocators map many single-page VMAs. Instead of
3905 * returning back to the PGD table for each of such VMAs, finish an entire PMD
3906 * table to reduce zigzags and improve cache performance.
3908 static bool get_next_vma(unsigned long mask
, unsigned long size
, struct mm_walk
*args
,
3909 unsigned long *vm_start
, unsigned long *vm_end
)
3911 unsigned long start
= round_up(*vm_end
, size
);
3912 unsigned long end
= (start
| ~mask
) + 1;
3913 VMA_ITERATOR(vmi
, args
->mm
, start
);
3915 VM_WARN_ON_ONCE(mask
& size
);
3916 VM_WARN_ON_ONCE((start
& mask
) != (*vm_start
& mask
));
3918 for_each_vma(vmi
, args
->vma
) {
3919 if (end
&& end
<= args
->vma
->vm_start
)
3922 if (should_skip_vma(args
->vma
->vm_start
, args
->vma
->vm_end
, args
))
3925 *vm_start
= max(start
, args
->vma
->vm_start
);
3926 *vm_end
= min(end
- 1, args
->vma
->vm_end
- 1) + 1;
3934 static unsigned long get_pte_pfn(pte_t pte
, struct vm_area_struct
*vma
, unsigned long addr
)
3936 unsigned long pfn
= pte_pfn(pte
);
3938 VM_WARN_ON_ONCE(addr
< vma
->vm_start
|| addr
>= vma
->vm_end
);
3940 if (!pte_present(pte
) || is_zero_pfn(pfn
))
3943 if (WARN_ON_ONCE(pte_devmap(pte
) || pte_special(pte
)))
3946 if (WARN_ON_ONCE(!pfn_valid(pfn
)))
3952 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)
3953 static unsigned long get_pmd_pfn(pmd_t pmd
, struct vm_area_struct
*vma
, unsigned long addr
)
3955 unsigned long pfn
= pmd_pfn(pmd
);
3957 VM_WARN_ON_ONCE(addr
< vma
->vm_start
|| addr
>= vma
->vm_end
);
3959 if (!pmd_present(pmd
) || is_huge_zero_pmd(pmd
))
3962 if (WARN_ON_ONCE(pmd_devmap(pmd
)))
3965 if (WARN_ON_ONCE(!pfn_valid(pfn
)))
3972 static struct folio
*get_pfn_folio(unsigned long pfn
, struct mem_cgroup
*memcg
,
3973 struct pglist_data
*pgdat
, bool can_swap
)
3975 struct folio
*folio
;
3977 /* try to avoid unnecessary memory loads */
3978 if (pfn
< pgdat
->node_start_pfn
|| pfn
>= pgdat_end_pfn(pgdat
))
3981 folio
= pfn_folio(pfn
);
3982 if (folio_nid(folio
) != pgdat
->node_id
)
3985 if (folio_memcg_rcu(folio
) != memcg
)
3988 /* file VMAs can contain anon pages from COW */
3989 if (!folio_is_file_lru(folio
) && !can_swap
)
3995 static bool suitable_to_scan(int total
, int young
)
3997 int n
= clamp_t(int, cache_line_size() / sizeof(pte_t
), 2, 8);
3999 /* suitable if the average number of young PTEs per cacheline is >=1 */
4000 return young
* n
>= total
;
4003 static bool walk_pte_range(pmd_t
*pmd
, unsigned long start
, unsigned long end
,
4004 struct mm_walk
*args
)
4012 struct lru_gen_mm_walk
*walk
= args
->private;
4013 struct mem_cgroup
*memcg
= lruvec_memcg(walk
->lruvec
);
4014 struct pglist_data
*pgdat
= lruvec_pgdat(walk
->lruvec
);
4015 int old_gen
, new_gen
= lru_gen_from_seq(walk
->max_seq
);
4017 pte
= pte_offset_map_nolock(args
->mm
, pmd
, start
& PMD_MASK
, &ptl
);
4020 if (!spin_trylock(ptl
)) {
4025 arch_enter_lazy_mmu_mode();
4027 for (i
= pte_index(start
), addr
= start
; addr
!= end
; i
++, addr
+= PAGE_SIZE
) {
4029 struct folio
*folio
;
4030 pte_t ptent
= ptep_get(pte
+ i
);
4033 walk
->mm_stats
[MM_LEAF_TOTAL
]++;
4035 pfn
= get_pte_pfn(ptent
, args
->vma
, addr
);
4039 if (!pte_young(ptent
)) {
4040 walk
->mm_stats
[MM_LEAF_OLD
]++;
4044 folio
= get_pfn_folio(pfn
, memcg
, pgdat
, walk
->can_swap
);
4048 if (!ptep_test_and_clear_young(args
->vma
, addr
, pte
+ i
))
4049 VM_WARN_ON_ONCE(true);
4052 walk
->mm_stats
[MM_LEAF_YOUNG
]++;
4054 if (pte_dirty(ptent
) && !folio_test_dirty(folio
) &&
4055 !(folio_test_anon(folio
) && folio_test_swapbacked(folio
) &&
4056 !folio_test_swapcache(folio
)))
4057 folio_mark_dirty(folio
);
4059 old_gen
= folio_update_gen(folio
, new_gen
);
4060 if (old_gen
>= 0 && old_gen
!= new_gen
)
4061 update_batch_size(walk
, folio
, old_gen
, new_gen
);
4064 if (i
< PTRS_PER_PTE
&& get_next_vma(PMD_MASK
, PAGE_SIZE
, args
, &start
, &end
))
4067 arch_leave_lazy_mmu_mode();
4068 pte_unmap_unlock(pte
, ptl
);
4070 return suitable_to_scan(total
, young
);
4073 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)
4074 static void walk_pmd_range_locked(pud_t
*pud
, unsigned long addr
, struct vm_area_struct
*vma
,
4075 struct mm_walk
*args
, unsigned long *bitmap
, unsigned long *first
)
4080 struct lru_gen_mm_walk
*walk
= args
->private;
4081 struct mem_cgroup
*memcg
= lruvec_memcg(walk
->lruvec
);
4082 struct pglist_data
*pgdat
= lruvec_pgdat(walk
->lruvec
);
4083 int old_gen
, new_gen
= lru_gen_from_seq(walk
->max_seq
);
4085 VM_WARN_ON_ONCE(pud_leaf(*pud
));
4087 /* try to batch at most 1+MIN_LRU_BATCH+1 entries */
4090 bitmap_zero(bitmap
, MIN_LRU_BATCH
);
4094 i
= addr
== -1 ? 0 : pmd_index(addr
) - pmd_index(*first
);
4095 if (i
&& i
<= MIN_LRU_BATCH
) {
4096 __set_bit(i
- 1, bitmap
);
4100 pmd
= pmd_offset(pud
, *first
);
4102 ptl
= pmd_lockptr(args
->mm
, pmd
);
4103 if (!spin_trylock(ptl
))
4106 arch_enter_lazy_mmu_mode();
4110 struct folio
*folio
;
4112 /* don't round down the first address */
4113 addr
= i
? (*first
& PMD_MASK
) + i
* PMD_SIZE
: *first
;
4115 pfn
= get_pmd_pfn(pmd
[i
], vma
, addr
);
4119 if (!pmd_trans_huge(pmd
[i
])) {
4120 if (should_clear_pmd_young())
4121 pmdp_test_and_clear_young(vma
, addr
, pmd
+ i
);
4125 folio
= get_pfn_folio(pfn
, memcg
, pgdat
, walk
->can_swap
);
4129 if (!pmdp_test_and_clear_young(vma
, addr
, pmd
+ i
))
4132 walk
->mm_stats
[MM_LEAF_YOUNG
]++;
4134 if (pmd_dirty(pmd
[i
]) && !folio_test_dirty(folio
) &&
4135 !(folio_test_anon(folio
) && folio_test_swapbacked(folio
) &&
4136 !folio_test_swapcache(folio
)))
4137 folio_mark_dirty(folio
);
4139 old_gen
= folio_update_gen(folio
, new_gen
);
4140 if (old_gen
>= 0 && old_gen
!= new_gen
)
4141 update_batch_size(walk
, folio
, old_gen
, new_gen
);
4143 i
= i
> MIN_LRU_BATCH
? 0 : find_next_bit(bitmap
, MIN_LRU_BATCH
, i
) + 1;
4144 } while (i
<= MIN_LRU_BATCH
);
4146 arch_leave_lazy_mmu_mode();
4152 static void walk_pmd_range_locked(pud_t
*pud
, unsigned long addr
, struct vm_area_struct
*vma
,
4153 struct mm_walk
*args
, unsigned long *bitmap
, unsigned long *first
)
4158 static void walk_pmd_range(pud_t
*pud
, unsigned long start
, unsigned long end
,
4159 struct mm_walk
*args
)
4165 struct vm_area_struct
*vma
;
4166 DECLARE_BITMAP(bitmap
, MIN_LRU_BATCH
);
4167 unsigned long first
= -1;
4168 struct lru_gen_mm_walk
*walk
= args
->private;
4170 VM_WARN_ON_ONCE(pud_leaf(*pud
));
4173 * Finish an entire PMD in two passes: the first only reaches to PTE
4174 * tables to avoid taking the PMD lock; the second, if necessary, takes
4175 * the PMD lock to clear the accessed bit in PMD entries.
4177 pmd
= pmd_offset(pud
, start
& PUD_MASK
);
4179 /* walk_pte_range() may call get_next_vma() */
4181 for (i
= pmd_index(start
), addr
= start
; addr
!= end
; i
++, addr
= next
) {
4182 pmd_t val
= pmdp_get_lockless(pmd
+ i
);
4184 next
= pmd_addr_end(addr
, end
);
4186 if (!pmd_present(val
) || is_huge_zero_pmd(val
)) {
4187 walk
->mm_stats
[MM_LEAF_TOTAL
]++;
4191 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
4192 if (pmd_trans_huge(val
)) {
4193 unsigned long pfn
= pmd_pfn(val
);
4194 struct pglist_data
*pgdat
= lruvec_pgdat(walk
->lruvec
);
4196 walk
->mm_stats
[MM_LEAF_TOTAL
]++;
4198 if (!pmd_young(val
)) {
4199 walk
->mm_stats
[MM_LEAF_OLD
]++;
4203 /* try to avoid unnecessary memory loads */
4204 if (pfn
< pgdat
->node_start_pfn
|| pfn
>= pgdat_end_pfn(pgdat
))
4207 walk_pmd_range_locked(pud
, addr
, vma
, args
, bitmap
, &first
);
4211 walk
->mm_stats
[MM_NONLEAF_TOTAL
]++;
4213 if (should_clear_pmd_young()) {
4214 if (!pmd_young(val
))
4217 walk_pmd_range_locked(pud
, addr
, vma
, args
, bitmap
, &first
);
4220 if (!walk
->force_scan
&& !test_bloom_filter(walk
->lruvec
, walk
->max_seq
, pmd
+ i
))
4223 walk
->mm_stats
[MM_NONLEAF_FOUND
]++;
4225 if (!walk_pte_range(&val
, addr
, next
, args
))
4228 walk
->mm_stats
[MM_NONLEAF_ADDED
]++;
4230 /* carry over to the next generation */
4231 update_bloom_filter(walk
->lruvec
, walk
->max_seq
+ 1, pmd
+ i
);
4234 walk_pmd_range_locked(pud
, -1, vma
, args
, bitmap
, &first
);
4236 if (i
< PTRS_PER_PMD
&& get_next_vma(PUD_MASK
, PMD_SIZE
, args
, &start
, &end
))
4240 static int walk_pud_range(p4d_t
*p4d
, unsigned long start
, unsigned long end
,
4241 struct mm_walk
*args
)
4247 struct lru_gen_mm_walk
*walk
= args
->private;
4249 VM_WARN_ON_ONCE(p4d_leaf(*p4d
));
4251 pud
= pud_offset(p4d
, start
& P4D_MASK
);
4253 for (i
= pud_index(start
), addr
= start
; addr
!= end
; i
++, addr
= next
) {
4254 pud_t val
= READ_ONCE(pud
[i
]);
4256 next
= pud_addr_end(addr
, end
);
4258 if (!pud_present(val
) || WARN_ON_ONCE(pud_leaf(val
)))
4261 walk_pmd_range(&val
, addr
, next
, args
);
4263 if (need_resched() || walk
->batched
>= MAX_LRU_BATCH
) {
4264 end
= (addr
| ~PUD_MASK
) + 1;
4269 if (i
< PTRS_PER_PUD
&& get_next_vma(P4D_MASK
, PUD_SIZE
, args
, &start
, &end
))
4272 end
= round_up(end
, P4D_SIZE
);
4274 if (!end
|| !args
->vma
)
4277 walk
->next_addr
= max(end
, args
->vma
->vm_start
);
4282 static void walk_mm(struct lruvec
*lruvec
, struct mm_struct
*mm
, struct lru_gen_mm_walk
*walk
)
4284 static const struct mm_walk_ops mm_walk_ops
= {
4285 .test_walk
= should_skip_vma
,
4286 .p4d_entry
= walk_pud_range
,
4287 .walk_lock
= PGWALK_RDLOCK
,
4291 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
4293 walk
->next_addr
= FIRST_USER_ADDRESS
;
4296 DEFINE_MAX_SEQ(lruvec
);
4300 /* another thread might have called inc_max_seq() */
4301 if (walk
->max_seq
!= max_seq
)
4304 /* folio_update_gen() requires stable folio_memcg() */
4305 if (!mem_cgroup_trylock_pages(memcg
))
4308 /* the caller might be holding the lock for write */
4309 if (mmap_read_trylock(mm
)) {
4310 err
= walk_page_range(mm
, walk
->next_addr
, ULONG_MAX
, &mm_walk_ops
, walk
);
4312 mmap_read_unlock(mm
);
4315 mem_cgroup_unlock_pages();
4317 if (walk
->batched
) {
4318 spin_lock_irq(&lruvec
->lru_lock
);
4319 reset_batch_size(lruvec
, walk
);
4320 spin_unlock_irq(&lruvec
->lru_lock
);
4324 } while (err
== -EAGAIN
);
4327 static struct lru_gen_mm_walk
*set_mm_walk(struct pglist_data
*pgdat
, bool force_alloc
)
4329 struct lru_gen_mm_walk
*walk
= current
->reclaim_state
->mm_walk
;
4331 if (pgdat
&& current_is_kswapd()) {
4332 VM_WARN_ON_ONCE(walk
);
4334 walk
= &pgdat
->mm_walk
;
4335 } else if (!walk
&& force_alloc
) {
4336 VM_WARN_ON_ONCE(current_is_kswapd());
4338 walk
= kzalloc(sizeof(*walk
), __GFP_HIGH
| __GFP_NOMEMALLOC
| __GFP_NOWARN
);
4341 current
->reclaim_state
->mm_walk
= walk
;
4346 static void clear_mm_walk(void)
4348 struct lru_gen_mm_walk
*walk
= current
->reclaim_state
->mm_walk
;
4350 VM_WARN_ON_ONCE(walk
&& memchr_inv(walk
->nr_pages
, 0, sizeof(walk
->nr_pages
)));
4351 VM_WARN_ON_ONCE(walk
&& memchr_inv(walk
->mm_stats
, 0, sizeof(walk
->mm_stats
)));
4353 current
->reclaim_state
->mm_walk
= NULL
;
4355 if (!current_is_kswapd())
4359 static bool inc_min_seq(struct lruvec
*lruvec
, int type
, bool can_swap
)
4362 int remaining
= MAX_LRU_BATCH
;
4363 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
4364 int new_gen
, old_gen
= lru_gen_from_seq(lrugen
->min_seq
[type
]);
4366 if (type
== LRU_GEN_ANON
&& !can_swap
)
4369 /* prevent cold/hot inversion if force_scan is true */
4370 for (zone
= 0; zone
< MAX_NR_ZONES
; zone
++) {
4371 struct list_head
*head
= &lrugen
->folios
[old_gen
][type
][zone
];
4373 while (!list_empty(head
)) {
4374 struct folio
*folio
= lru_to_folio(head
);
4376 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio
), folio
);
4377 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio
), folio
);
4378 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio
) != type
, folio
);
4379 VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio
) != zone
, folio
);
4381 new_gen
= folio_inc_gen(lruvec
, folio
, false);
4382 list_move_tail(&folio
->lru
, &lrugen
->folios
[new_gen
][type
][zone
]);
4389 reset_ctrl_pos(lruvec
, type
, true);
4390 WRITE_ONCE(lrugen
->min_seq
[type
], lrugen
->min_seq
[type
] + 1);
4395 static bool try_to_inc_min_seq(struct lruvec
*lruvec
, bool can_swap
)
4397 int gen
, type
, zone
;
4398 bool success
= false;
4399 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
4400 DEFINE_MIN_SEQ(lruvec
);
4402 VM_WARN_ON_ONCE(!seq_is_valid(lruvec
));
4404 /* find the oldest populated generation */
4405 for (type
= !can_swap
; type
< ANON_AND_FILE
; type
++) {
4406 while (min_seq
[type
] + MIN_NR_GENS
<= lrugen
->max_seq
) {
4407 gen
= lru_gen_from_seq(min_seq
[type
]);
4409 for (zone
= 0; zone
< MAX_NR_ZONES
; zone
++) {
4410 if (!list_empty(&lrugen
->folios
[gen
][type
][zone
]))
4420 /* see the comment on lru_gen_folio */
4422 min_seq
[LRU_GEN_ANON
] = min(min_seq
[LRU_GEN_ANON
], min_seq
[LRU_GEN_FILE
]);
4423 min_seq
[LRU_GEN_FILE
] = max(min_seq
[LRU_GEN_ANON
], lrugen
->min_seq
[LRU_GEN_FILE
]);
4426 for (type
= !can_swap
; type
< ANON_AND_FILE
; type
++) {
4427 if (min_seq
[type
] == lrugen
->min_seq
[type
])
4430 reset_ctrl_pos(lruvec
, type
, true);
4431 WRITE_ONCE(lrugen
->min_seq
[type
], min_seq
[type
]);
4438 static void inc_max_seq(struct lruvec
*lruvec
, bool can_swap
, bool force_scan
)
4442 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
4444 spin_lock_irq(&lruvec
->lru_lock
);
4446 VM_WARN_ON_ONCE(!seq_is_valid(lruvec
));
4448 for (type
= ANON_AND_FILE
- 1; type
>= 0; type
--) {
4449 if (get_nr_gens(lruvec
, type
) != MAX_NR_GENS
)
4452 VM_WARN_ON_ONCE(!force_scan
&& (type
== LRU_GEN_FILE
|| can_swap
));
4454 if (inc_min_seq(lruvec
, type
, can_swap
))
4457 spin_unlock_irq(&lruvec
->lru_lock
);
4463 * Update the active/inactive LRU sizes for compatibility. Both sides of
4464 * the current max_seq need to be covered, since max_seq+1 can overlap
4465 * with min_seq[LRU_GEN_ANON] if swapping is constrained. And if they do
4466 * overlap, cold/hot inversion happens.
4468 prev
= lru_gen_from_seq(lrugen
->max_seq
- 1);
4469 next
= lru_gen_from_seq(lrugen
->max_seq
+ 1);
4471 for (type
= 0; type
< ANON_AND_FILE
; type
++) {
4472 for (zone
= 0; zone
< MAX_NR_ZONES
; zone
++) {
4473 enum lru_list lru
= type
* LRU_INACTIVE_FILE
;
4474 long delta
= lrugen
->nr_pages
[prev
][type
][zone
] -
4475 lrugen
->nr_pages
[next
][type
][zone
];
4480 __update_lru_size(lruvec
, lru
, zone
, delta
);
4481 __update_lru_size(lruvec
, lru
+ LRU_ACTIVE
, zone
, -delta
);
4485 for (type
= 0; type
< ANON_AND_FILE
; type
++)
4486 reset_ctrl_pos(lruvec
, type
, false);
4488 WRITE_ONCE(lrugen
->timestamps
[next
], jiffies
);
4489 /* make sure preceding modifications appear */
4490 smp_store_release(&lrugen
->max_seq
, lrugen
->max_seq
+ 1);
4492 spin_unlock_irq(&lruvec
->lru_lock
);
4495 static bool try_to_inc_max_seq(struct lruvec
*lruvec
, unsigned long max_seq
,
4496 struct scan_control
*sc
, bool can_swap
, bool force_scan
)
4499 struct lru_gen_mm_walk
*walk
;
4500 struct mm_struct
*mm
= NULL
;
4501 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
4503 VM_WARN_ON_ONCE(max_seq
> READ_ONCE(lrugen
->max_seq
));
4505 /* see the comment in iterate_mm_list() */
4506 if (max_seq
<= READ_ONCE(lruvec
->mm_state
.seq
)) {
4512 * If the hardware doesn't automatically set the accessed bit, fallback
4513 * to lru_gen_look_around(), which only clears the accessed bit in a
4514 * handful of PTEs. Spreading the work out over a period of time usually
4515 * is less efficient, but it avoids bursty page faults.
4517 if (!should_walk_mmu()) {
4518 success
= iterate_mm_list_nowalk(lruvec
, max_seq
);
4522 walk
= set_mm_walk(NULL
, true);
4524 success
= iterate_mm_list_nowalk(lruvec
, max_seq
);
4528 walk
->lruvec
= lruvec
;
4529 walk
->max_seq
= max_seq
;
4530 walk
->can_swap
= can_swap
;
4531 walk
->force_scan
= force_scan
;
4534 success
= iterate_mm_list(lruvec
, walk
, &mm
);
4536 walk_mm(lruvec
, mm
, walk
);
4540 inc_max_seq(lruvec
, can_swap
, force_scan
);
4545 /******************************************************************************
4546 * working set protection
4547 ******************************************************************************/
4549 static bool lruvec_is_sizable(struct lruvec
*lruvec
, struct scan_control
*sc
)
4551 int gen
, type
, zone
;
4552 unsigned long total
= 0;
4553 bool can_swap
= get_swappiness(lruvec
, sc
);
4554 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
4555 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
4556 DEFINE_MAX_SEQ(lruvec
);
4557 DEFINE_MIN_SEQ(lruvec
);
4559 for (type
= !can_swap
; type
< ANON_AND_FILE
; type
++) {
4562 for (seq
= min_seq
[type
]; seq
<= max_seq
; seq
++) {
4563 gen
= lru_gen_from_seq(seq
);
4565 for (zone
= 0; zone
< MAX_NR_ZONES
; zone
++)
4566 total
+= max(READ_ONCE(lrugen
->nr_pages
[gen
][type
][zone
]), 0L);
4570 /* whether the size is big enough to be helpful */
4571 return mem_cgroup_online(memcg
) ? (total
>> sc
->priority
) : total
;
4574 static bool lruvec_is_reclaimable(struct lruvec
*lruvec
, struct scan_control
*sc
,
4575 unsigned long min_ttl
)
4578 unsigned long birth
;
4579 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
4580 DEFINE_MIN_SEQ(lruvec
);
4582 /* see the comment on lru_gen_folio */
4583 gen
= lru_gen_from_seq(min_seq
[LRU_GEN_FILE
]);
4584 birth
= READ_ONCE(lruvec
->lrugen
.timestamps
[gen
]);
4586 if (time_is_after_jiffies(birth
+ min_ttl
))
4589 if (!lruvec_is_sizable(lruvec
, sc
))
4592 mem_cgroup_calculate_protection(NULL
, memcg
);
4594 return !mem_cgroup_below_min(NULL
, memcg
);
4597 /* to protect the working set of the last N jiffies */
4598 static unsigned long lru_gen_min_ttl __read_mostly
;
4600 static void lru_gen_age_node(struct pglist_data
*pgdat
, struct scan_control
*sc
)
4602 struct mem_cgroup
*memcg
;
4603 unsigned long min_ttl
= READ_ONCE(lru_gen_min_ttl
);
4605 VM_WARN_ON_ONCE(!current_is_kswapd());
4607 /* check the order to exclude compaction-induced reclaim */
4608 if (!min_ttl
|| sc
->order
|| sc
->priority
== DEF_PRIORITY
)
4611 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
4613 struct lruvec
*lruvec
= mem_cgroup_lruvec(memcg
, pgdat
);
4615 if (lruvec_is_reclaimable(lruvec
, sc
, min_ttl
)) {
4616 mem_cgroup_iter_break(NULL
, memcg
);
4621 } while ((memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
)));
4624 * The main goal is to OOM kill if every generation from all memcgs is
4625 * younger than min_ttl. However, another possibility is all memcgs are
4626 * either too small or below min.
4628 if (mutex_trylock(&oom_lock
)) {
4629 struct oom_control oc
= {
4630 .gfp_mask
= sc
->gfp_mask
,
4635 mutex_unlock(&oom_lock
);
4639 /******************************************************************************
4640 * rmap/PT walk feedback
4641 ******************************************************************************/
4644 * This function exploits spatial locality when shrink_folio_list() walks the
4645 * rmap. It scans the adjacent PTEs of a young PTE and promotes hot pages. If
4646 * the scan was done cacheline efficiently, it adds the PMD entry pointing to
4647 * the PTE table to the Bloom filter. This forms a feedback loop between the
4648 * eviction and the aging.
4650 void lru_gen_look_around(struct page_vma_mapped_walk
*pvmw
)
4653 unsigned long start
;
4655 struct lru_gen_mm_walk
*walk
;
4657 pte_t
*pte
= pvmw
->pte
;
4658 unsigned long addr
= pvmw
->address
;
4659 struct folio
*folio
= pfn_folio(pvmw
->pfn
);
4660 bool can_swap
= !folio_is_file_lru(folio
);
4661 struct mem_cgroup
*memcg
= folio_memcg(folio
);
4662 struct pglist_data
*pgdat
= folio_pgdat(folio
);
4663 struct lruvec
*lruvec
= mem_cgroup_lruvec(memcg
, pgdat
);
4664 DEFINE_MAX_SEQ(lruvec
);
4665 int old_gen
, new_gen
= lru_gen_from_seq(max_seq
);
4667 lockdep_assert_held(pvmw
->ptl
);
4668 VM_WARN_ON_ONCE_FOLIO(folio_test_lru(folio
), folio
);
4670 if (spin_is_contended(pvmw
->ptl
))
4673 /* avoid taking the LRU lock under the PTL when possible */
4674 walk
= current
->reclaim_state
? current
->reclaim_state
->mm_walk
: NULL
;
4676 start
= max(addr
& PMD_MASK
, pvmw
->vma
->vm_start
);
4677 end
= min(addr
| ~PMD_MASK
, pvmw
->vma
->vm_end
- 1) + 1;
4679 if (end
- start
> MIN_LRU_BATCH
* PAGE_SIZE
) {
4680 if (addr
- start
< MIN_LRU_BATCH
* PAGE_SIZE
/ 2)
4681 end
= start
+ MIN_LRU_BATCH
* PAGE_SIZE
;
4682 else if (end
- addr
< MIN_LRU_BATCH
* PAGE_SIZE
/ 2)
4683 start
= end
- MIN_LRU_BATCH
* PAGE_SIZE
;
4685 start
= addr
- MIN_LRU_BATCH
* PAGE_SIZE
/ 2;
4686 end
= addr
+ MIN_LRU_BATCH
* PAGE_SIZE
/ 2;
4690 /* folio_update_gen() requires stable folio_memcg() */
4691 if (!mem_cgroup_trylock_pages(memcg
))
4694 arch_enter_lazy_mmu_mode();
4696 pte
-= (addr
- start
) / PAGE_SIZE
;
4698 for (i
= 0, addr
= start
; addr
!= end
; i
++, addr
+= PAGE_SIZE
) {
4700 pte_t ptent
= ptep_get(pte
+ i
);
4702 pfn
= get_pte_pfn(ptent
, pvmw
->vma
, addr
);
4706 if (!pte_young(ptent
))
4709 folio
= get_pfn_folio(pfn
, memcg
, pgdat
, can_swap
);
4713 if (!ptep_test_and_clear_young(pvmw
->vma
, addr
, pte
+ i
))
4714 VM_WARN_ON_ONCE(true);
4718 if (pte_dirty(ptent
) && !folio_test_dirty(folio
) &&
4719 !(folio_test_anon(folio
) && folio_test_swapbacked(folio
) &&
4720 !folio_test_swapcache(folio
)))
4721 folio_mark_dirty(folio
);
4724 old_gen
= folio_update_gen(folio
, new_gen
);
4725 if (old_gen
>= 0 && old_gen
!= new_gen
)
4726 update_batch_size(walk
, folio
, old_gen
, new_gen
);
4731 old_gen
= folio_lru_gen(folio
);
4733 folio_set_referenced(folio
);
4734 else if (old_gen
!= new_gen
)
4735 folio_activate(folio
);
4738 arch_leave_lazy_mmu_mode();
4739 mem_cgroup_unlock_pages();
4741 /* feedback from rmap walkers to page table walkers */
4742 if (suitable_to_scan(i
, young
))
4743 update_bloom_filter(lruvec
, max_seq
, pvmw
->pmd
);
4746 /******************************************************************************
4748 ******************************************************************************/
4750 /* see the comment on MEMCG_NR_GENS */
4761 static int lru_gen_memcg_seg(struct lruvec
*lruvec
)
4763 return READ_ONCE(lruvec
->lrugen
.seg
);
4766 static void lru_gen_rotate_memcg(struct lruvec
*lruvec
, int op
)
4770 unsigned long flags
;
4771 int bin
= get_random_u32_below(MEMCG_NR_BINS
);
4772 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
4774 spin_lock_irqsave(&pgdat
->memcg_lru
.lock
, flags
);
4776 VM_WARN_ON_ONCE(hlist_nulls_unhashed(&lruvec
->lrugen
.list
));
4779 new = old
= lruvec
->lrugen
.gen
;
4781 /* see the comment on MEMCG_NR_GENS */
4782 if (op
== MEMCG_LRU_HEAD
)
4783 seg
= MEMCG_LRU_HEAD
;
4784 else if (op
== MEMCG_LRU_TAIL
)
4785 seg
= MEMCG_LRU_TAIL
;
4786 else if (op
== MEMCG_LRU_OLD
)
4787 new = get_memcg_gen(pgdat
->memcg_lru
.seq
);
4788 else if (op
== MEMCG_LRU_YOUNG
)
4789 new = get_memcg_gen(pgdat
->memcg_lru
.seq
+ 1);
4791 VM_WARN_ON_ONCE(true);
4793 hlist_nulls_del_rcu(&lruvec
->lrugen
.list
);
4795 if (op
== MEMCG_LRU_HEAD
|| op
== MEMCG_LRU_OLD
)
4796 hlist_nulls_add_head_rcu(&lruvec
->lrugen
.list
, &pgdat
->memcg_lru
.fifo
[new][bin
]);
4798 hlist_nulls_add_tail_rcu(&lruvec
->lrugen
.list
, &pgdat
->memcg_lru
.fifo
[new][bin
]);
4800 pgdat
->memcg_lru
.nr_memcgs
[old
]--;
4801 pgdat
->memcg_lru
.nr_memcgs
[new]++;
4803 lruvec
->lrugen
.gen
= new;
4804 WRITE_ONCE(lruvec
->lrugen
.seg
, seg
);
4806 if (!pgdat
->memcg_lru
.nr_memcgs
[old
] && old
== get_memcg_gen(pgdat
->memcg_lru
.seq
))
4807 WRITE_ONCE(pgdat
->memcg_lru
.seq
, pgdat
->memcg_lru
.seq
+ 1);
4809 spin_unlock_irqrestore(&pgdat
->memcg_lru
.lock
, flags
);
4812 void lru_gen_online_memcg(struct mem_cgroup
*memcg
)
4816 int bin
= get_random_u32_below(MEMCG_NR_BINS
);
4818 for_each_node(nid
) {
4819 struct pglist_data
*pgdat
= NODE_DATA(nid
);
4820 struct lruvec
*lruvec
= get_lruvec(memcg
, nid
);
4822 spin_lock_irq(&pgdat
->memcg_lru
.lock
);
4824 VM_WARN_ON_ONCE(!hlist_nulls_unhashed(&lruvec
->lrugen
.list
));
4826 gen
= get_memcg_gen(pgdat
->memcg_lru
.seq
);
4828 hlist_nulls_add_tail_rcu(&lruvec
->lrugen
.list
, &pgdat
->memcg_lru
.fifo
[gen
][bin
]);
4829 pgdat
->memcg_lru
.nr_memcgs
[gen
]++;
4831 lruvec
->lrugen
.gen
= gen
;
4833 spin_unlock_irq(&pgdat
->memcg_lru
.lock
);
4837 void lru_gen_offline_memcg(struct mem_cgroup
*memcg
)
4841 for_each_node(nid
) {
4842 struct lruvec
*lruvec
= get_lruvec(memcg
, nid
);
4844 lru_gen_rotate_memcg(lruvec
, MEMCG_LRU_OLD
);
4848 void lru_gen_release_memcg(struct mem_cgroup
*memcg
)
4853 for_each_node(nid
) {
4854 struct pglist_data
*pgdat
= NODE_DATA(nid
);
4855 struct lruvec
*lruvec
= get_lruvec(memcg
, nid
);
4857 spin_lock_irq(&pgdat
->memcg_lru
.lock
);
4859 if (hlist_nulls_unhashed(&lruvec
->lrugen
.list
))
4862 gen
= lruvec
->lrugen
.gen
;
4864 hlist_nulls_del_init_rcu(&lruvec
->lrugen
.list
);
4865 pgdat
->memcg_lru
.nr_memcgs
[gen
]--;
4867 if (!pgdat
->memcg_lru
.nr_memcgs
[gen
] && gen
== get_memcg_gen(pgdat
->memcg_lru
.seq
))
4868 WRITE_ONCE(pgdat
->memcg_lru
.seq
, pgdat
->memcg_lru
.seq
+ 1);
4870 spin_unlock_irq(&pgdat
->memcg_lru
.lock
);
4874 void lru_gen_soft_reclaim(struct mem_cgroup
*memcg
, int nid
)
4876 struct lruvec
*lruvec
= get_lruvec(memcg
, nid
);
4878 /* see the comment on MEMCG_NR_GENS */
4879 if (lru_gen_memcg_seg(lruvec
) != MEMCG_LRU_HEAD
)
4880 lru_gen_rotate_memcg(lruvec
, MEMCG_LRU_HEAD
);
4883 #else /* !CONFIG_MEMCG */
4885 static int lru_gen_memcg_seg(struct lruvec
*lruvec
)
4892 /******************************************************************************
4894 ******************************************************************************/
4896 static bool sort_folio(struct lruvec
*lruvec
, struct folio
*folio
, struct scan_control
*sc
,
4900 int gen
= folio_lru_gen(folio
);
4901 int type
= folio_is_file_lru(folio
);
4902 int zone
= folio_zonenum(folio
);
4903 int delta
= folio_nr_pages(folio
);
4904 int refs
= folio_lru_refs(folio
);
4905 int tier
= lru_tier_from_refs(refs
);
4906 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
4908 VM_WARN_ON_ONCE_FOLIO(gen
>= MAX_NR_GENS
, folio
);
4911 if (!folio_evictable(folio
)) {
4912 success
= lru_gen_del_folio(lruvec
, folio
, true);
4913 VM_WARN_ON_ONCE_FOLIO(!success
, folio
);
4914 folio_set_unevictable(folio
);
4915 lruvec_add_folio(lruvec
, folio
);
4916 __count_vm_events(UNEVICTABLE_PGCULLED
, delta
);
4920 /* dirty lazyfree */
4921 if (type
== LRU_GEN_FILE
&& folio_test_anon(folio
) && folio_test_dirty(folio
)) {
4922 success
= lru_gen_del_folio(lruvec
, folio
, true);
4923 VM_WARN_ON_ONCE_FOLIO(!success
, folio
);
4924 folio_set_swapbacked(folio
);
4925 lruvec_add_folio_tail(lruvec
, folio
);
4930 if (gen
!= lru_gen_from_seq(lrugen
->min_seq
[type
])) {
4931 list_move(&folio
->lru
, &lrugen
->folios
[gen
][type
][zone
]);
4936 if (tier
> tier_idx
) {
4937 int hist
= lru_hist_from_seq(lrugen
->min_seq
[type
]);
4939 gen
= folio_inc_gen(lruvec
, folio
, false);
4940 list_move_tail(&folio
->lru
, &lrugen
->folios
[gen
][type
][zone
]);
4942 WRITE_ONCE(lrugen
->protected[hist
][type
][tier
- 1],
4943 lrugen
->protected[hist
][type
][tier
- 1] + delta
);
4948 if (zone
> sc
->reclaim_idx
|| skip_cma(folio
, sc
)) {
4949 gen
= folio_inc_gen(lruvec
, folio
, false);
4950 list_move_tail(&folio
->lru
, &lrugen
->folios
[gen
][type
][zone
]);
4954 /* waiting for writeback */
4955 if (folio_test_locked(folio
) || folio_test_writeback(folio
) ||
4956 (type
== LRU_GEN_FILE
&& folio_test_dirty(folio
))) {
4957 gen
= folio_inc_gen(lruvec
, folio
, true);
4958 list_move(&folio
->lru
, &lrugen
->folios
[gen
][type
][zone
]);
4965 static bool isolate_folio(struct lruvec
*lruvec
, struct folio
*folio
, struct scan_control
*sc
)
4969 /* swapping inhibited */
4970 if (!(sc
->gfp_mask
& __GFP_IO
) &&
4971 (folio_test_dirty(folio
) ||
4972 (folio_test_anon(folio
) && !folio_test_swapcache(folio
))))
4975 /* raced with release_pages() */
4976 if (!folio_try_get(folio
))
4979 /* raced with another isolation */
4980 if (!folio_test_clear_lru(folio
)) {
4985 /* see the comment on MAX_NR_TIERS */
4986 if (!folio_test_referenced(folio
))
4987 set_mask_bits(&folio
->flags
, LRU_REFS_MASK
| LRU_REFS_FLAGS
, 0);
4989 /* for shrink_folio_list() */
4990 folio_clear_reclaim(folio
);
4991 folio_clear_referenced(folio
);
4993 success
= lru_gen_del_folio(lruvec
, folio
, true);
4994 VM_WARN_ON_ONCE_FOLIO(!success
, folio
);
4999 static int scan_folios(struct lruvec
*lruvec
, struct scan_control
*sc
,
5000 int type
, int tier
, struct list_head
*list
)
5004 enum vm_event_item item
;
5008 int remaining
= MAX_LRU_BATCH
;
5009 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
5010 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
5012 VM_WARN_ON_ONCE(!list_empty(list
));
5014 if (get_nr_gens(lruvec
, type
) == MIN_NR_GENS
)
5017 gen
= lru_gen_from_seq(lrugen
->min_seq
[type
]);
5019 for (i
= MAX_NR_ZONES
; i
> 0; i
--) {
5022 int zone
= (sc
->reclaim_idx
+ i
) % MAX_NR_ZONES
;
5023 struct list_head
*head
= &lrugen
->folios
[gen
][type
][zone
];
5025 while (!list_empty(head
)) {
5026 struct folio
*folio
= lru_to_folio(head
);
5027 int delta
= folio_nr_pages(folio
);
5029 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio
), folio
);
5030 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio
), folio
);
5031 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio
) != type
, folio
);
5032 VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio
) != zone
, folio
);
5036 if (sort_folio(lruvec
, folio
, sc
, tier
))
5038 else if (isolate_folio(lruvec
, folio
, sc
)) {
5039 list_add(&folio
->lru
, list
);
5042 list_move(&folio
->lru
, &moved
);
5046 if (!--remaining
|| max(isolated
, skipped
) >= MIN_LRU_BATCH
)
5051 list_splice(&moved
, head
);
5052 __count_zid_vm_events(PGSCAN_SKIP
, zone
, skipped
);
5055 if (!remaining
|| isolated
>= MIN_LRU_BATCH
)
5059 item
= PGSCAN_KSWAPD
+ reclaimer_offset();
5060 if (!cgroup_reclaim(sc
)) {
5061 __count_vm_events(item
, isolated
);
5062 __count_vm_events(PGREFILL
, sorted
);
5064 __count_memcg_events(memcg
, item
, isolated
);
5065 __count_memcg_events(memcg
, PGREFILL
, sorted
);
5066 __count_vm_events(PGSCAN_ANON
+ type
, isolated
);
5069 * There might not be eligible folios due to reclaim_idx. Check the
5070 * remaining to prevent livelock if it's not making progress.
5072 return isolated
|| !remaining
? scanned
: 0;
5075 static int get_tier_idx(struct lruvec
*lruvec
, int type
)
5078 struct ctrl_pos sp
, pv
;
5081 * To leave a margin for fluctuations, use a larger gain factor (1:2).
5082 * This value is chosen because any other tier would have at least twice
5083 * as many refaults as the first tier.
5085 read_ctrl_pos(lruvec
, type
, 0, 1, &sp
);
5086 for (tier
= 1; tier
< MAX_NR_TIERS
; tier
++) {
5087 read_ctrl_pos(lruvec
, type
, tier
, 2, &pv
);
5088 if (!positive_ctrl_err(&sp
, &pv
))
5095 static int get_type_to_scan(struct lruvec
*lruvec
, int swappiness
, int *tier_idx
)
5098 struct ctrl_pos sp
, pv
;
5099 int gain
[ANON_AND_FILE
] = { swappiness
, 200 - swappiness
};
5102 * Compare the first tier of anon with that of file to determine which
5103 * type to scan. Also need to compare other tiers of the selected type
5104 * with the first tier of the other type to determine the last tier (of
5105 * the selected type) to evict.
5107 read_ctrl_pos(lruvec
, LRU_GEN_ANON
, 0, gain
[LRU_GEN_ANON
], &sp
);
5108 read_ctrl_pos(lruvec
, LRU_GEN_FILE
, 0, gain
[LRU_GEN_FILE
], &pv
);
5109 type
= positive_ctrl_err(&sp
, &pv
);
5111 read_ctrl_pos(lruvec
, !type
, 0, gain
[!type
], &sp
);
5112 for (tier
= 1; tier
< MAX_NR_TIERS
; tier
++) {
5113 read_ctrl_pos(lruvec
, type
, tier
, gain
[type
], &pv
);
5114 if (!positive_ctrl_err(&sp
, &pv
))
5118 *tier_idx
= tier
- 1;
5123 static int isolate_folios(struct lruvec
*lruvec
, struct scan_control
*sc
, int swappiness
,
5124 int *type_scanned
, struct list_head
*list
)
5130 DEFINE_MIN_SEQ(lruvec
);
5133 * Try to make the obvious choice first. When anon and file are both
5134 * available from the same generation, interpret swappiness 1 as file
5135 * first and 200 as anon first.
5138 type
= LRU_GEN_FILE
;
5139 else if (min_seq
[LRU_GEN_ANON
] < min_seq
[LRU_GEN_FILE
])
5140 type
= LRU_GEN_ANON
;
5141 else if (swappiness
== 1)
5142 type
= LRU_GEN_FILE
;
5143 else if (swappiness
== 200)
5144 type
= LRU_GEN_ANON
;
5146 type
= get_type_to_scan(lruvec
, swappiness
, &tier
);
5148 for (i
= !swappiness
; i
< ANON_AND_FILE
; i
++) {
5150 tier
= get_tier_idx(lruvec
, type
);
5152 scanned
= scan_folios(lruvec
, sc
, type
, tier
, list
);
5160 *type_scanned
= type
;
5165 static int evict_folios(struct lruvec
*lruvec
, struct scan_control
*sc
, int swappiness
)
5172 struct folio
*folio
;
5174 enum vm_event_item item
;
5175 struct reclaim_stat stat
;
5176 struct lru_gen_mm_walk
*walk
;
5177 bool skip_retry
= false;
5178 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
5179 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
5181 spin_lock_irq(&lruvec
->lru_lock
);
5183 scanned
= isolate_folios(lruvec
, sc
, swappiness
, &type
, &list
);
5185 scanned
+= try_to_inc_min_seq(lruvec
, swappiness
);
5187 if (get_nr_gens(lruvec
, !swappiness
) == MIN_NR_GENS
)
5190 spin_unlock_irq(&lruvec
->lru_lock
);
5192 if (list_empty(&list
))
5195 reclaimed
= shrink_folio_list(&list
, pgdat
, sc
, &stat
, false);
5196 sc
->nr_reclaimed
+= reclaimed
;
5198 list_for_each_entry_safe_reverse(folio
, next
, &list
, lru
) {
5199 if (!folio_evictable(folio
)) {
5200 list_del(&folio
->lru
);
5201 folio_putback_lru(folio
);
5205 if (folio_test_reclaim(folio
) &&
5206 (folio_test_dirty(folio
) || folio_test_writeback(folio
))) {
5207 /* restore LRU_REFS_FLAGS cleared by isolate_folio() */
5208 if (folio_test_workingset(folio
))
5209 folio_set_referenced(folio
);
5213 if (skip_retry
|| folio_test_active(folio
) || folio_test_referenced(folio
) ||
5214 folio_mapped(folio
) || folio_test_locked(folio
) ||
5215 folio_test_dirty(folio
) || folio_test_writeback(folio
)) {
5216 /* don't add rejected folios to the oldest generation */
5217 set_mask_bits(&folio
->flags
, LRU_REFS_MASK
| LRU_REFS_FLAGS
,
5222 /* retry folios that may have missed folio_rotate_reclaimable() */
5223 list_move(&folio
->lru
, &clean
);
5224 sc
->nr_scanned
-= folio_nr_pages(folio
);
5227 spin_lock_irq(&lruvec
->lru_lock
);
5229 move_folios_to_lru(lruvec
, &list
);
5231 walk
= current
->reclaim_state
->mm_walk
;
5232 if (walk
&& walk
->batched
)
5233 reset_batch_size(lruvec
, walk
);
5235 item
= PGSTEAL_KSWAPD
+ reclaimer_offset();
5236 if (!cgroup_reclaim(sc
))
5237 __count_vm_events(item
, reclaimed
);
5238 __count_memcg_events(memcg
, item
, reclaimed
);
5239 __count_vm_events(PGSTEAL_ANON
+ type
, reclaimed
);
5241 spin_unlock_irq(&lruvec
->lru_lock
);
5243 mem_cgroup_uncharge_list(&list
);
5244 free_unref_page_list(&list
);
5246 INIT_LIST_HEAD(&list
);
5247 list_splice_init(&clean
, &list
);
5249 if (!list_empty(&list
)) {
5257 static bool should_run_aging(struct lruvec
*lruvec
, unsigned long max_seq
,
5258 struct scan_control
*sc
, bool can_swap
, unsigned long *nr_to_scan
)
5260 int gen
, type
, zone
;
5261 unsigned long old
= 0;
5262 unsigned long young
= 0;
5263 unsigned long total
= 0;
5264 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
5265 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
5266 DEFINE_MIN_SEQ(lruvec
);
5268 /* whether this lruvec is completely out of cold folios */
5269 if (min_seq
[!can_swap
] + MIN_NR_GENS
> max_seq
) {
5274 for (type
= !can_swap
; type
< ANON_AND_FILE
; type
++) {
5277 for (seq
= min_seq
[type
]; seq
<= max_seq
; seq
++) {
5278 unsigned long size
= 0;
5280 gen
= lru_gen_from_seq(seq
);
5282 for (zone
= 0; zone
< MAX_NR_ZONES
; zone
++)
5283 size
+= max(READ_ONCE(lrugen
->nr_pages
[gen
][type
][zone
]), 0L);
5288 else if (seq
+ MIN_NR_GENS
== max_seq
)
5293 /* try to scrape all its memory if this memcg was deleted */
5294 *nr_to_scan
= mem_cgroup_online(memcg
) ? (total
>> sc
->priority
) : total
;
5297 * The aging tries to be lazy to reduce the overhead, while the eviction
5298 * stalls when the number of generations reaches MIN_NR_GENS. Hence, the
5299 * ideal number of generations is MIN_NR_GENS+1.
5301 if (min_seq
[!can_swap
] + MIN_NR_GENS
< max_seq
)
5305 * It's also ideal to spread pages out evenly, i.e., 1/(MIN_NR_GENS+1)
5306 * of the total number of pages for each generation. A reasonable range
5307 * for this average portion is [1/MIN_NR_GENS, 1/(MIN_NR_GENS+2)]. The
5308 * aging cares about the upper bound of hot pages, while the eviction
5309 * cares about the lower bound of cold pages.
5311 if (young
* MIN_NR_GENS
> total
)
5313 if (old
* (MIN_NR_GENS
+ 2) < total
)
5320 * For future optimizations:
5321 * 1. Defer try_to_inc_max_seq() to workqueues to reduce latency for memcg
5324 static long get_nr_to_scan(struct lruvec
*lruvec
, struct scan_control
*sc
, bool can_swap
)
5326 unsigned long nr_to_scan
;
5327 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
5328 DEFINE_MAX_SEQ(lruvec
);
5330 if (mem_cgroup_below_min(sc
->target_mem_cgroup
, memcg
))
5333 if (!should_run_aging(lruvec
, max_seq
, sc
, can_swap
, &nr_to_scan
))
5336 /* skip the aging path at the default priority */
5337 if (sc
->priority
== DEF_PRIORITY
)
5340 /* skip this lruvec as it's low on cold folios */
5341 return try_to_inc_max_seq(lruvec
, max_seq
, sc
, can_swap
, false) ? -1 : 0;
5344 static unsigned long get_nr_to_reclaim(struct scan_control
*sc
)
5346 /* don't abort memcg reclaim to ensure fairness */
5347 if (!root_reclaim(sc
))
5350 return max(sc
->nr_to_reclaim
, compact_gap(sc
->order
));
5353 static bool try_to_shrink_lruvec(struct lruvec
*lruvec
, struct scan_control
*sc
)
5356 unsigned long scanned
= 0;
5357 unsigned long nr_to_reclaim
= get_nr_to_reclaim(sc
);
5358 int swappiness
= get_swappiness(lruvec
, sc
);
5360 /* clean file folios are more likely to exist */
5361 if (swappiness
&& !(sc
->gfp_mask
& __GFP_IO
))
5367 nr_to_scan
= get_nr_to_scan(lruvec
, sc
, swappiness
);
5368 if (nr_to_scan
<= 0)
5371 delta
= evict_folios(lruvec
, sc
, swappiness
);
5376 if (scanned
>= nr_to_scan
)
5379 if (sc
->nr_reclaimed
>= nr_to_reclaim
)
5385 /* whether try_to_inc_max_seq() was successful */
5386 return nr_to_scan
< 0;
5389 static int shrink_one(struct lruvec
*lruvec
, struct scan_control
*sc
)
5392 unsigned long scanned
= sc
->nr_scanned
;
5393 unsigned long reclaimed
= sc
->nr_reclaimed
;
5394 int seg
= lru_gen_memcg_seg(lruvec
);
5395 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
5396 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
5398 /* see the comment on MEMCG_NR_GENS */
5399 if (!lruvec_is_sizable(lruvec
, sc
))
5400 return seg
!= MEMCG_LRU_TAIL
? MEMCG_LRU_TAIL
: MEMCG_LRU_YOUNG
;
5402 mem_cgroup_calculate_protection(NULL
, memcg
);
5404 if (mem_cgroup_below_min(NULL
, memcg
))
5405 return MEMCG_LRU_YOUNG
;
5407 if (mem_cgroup_below_low(NULL
, memcg
)) {
5408 /* see the comment on MEMCG_NR_GENS */
5409 if (seg
!= MEMCG_LRU_TAIL
)
5410 return MEMCG_LRU_TAIL
;
5412 memcg_memory_event(memcg
, MEMCG_LOW
);
5415 success
= try_to_shrink_lruvec(lruvec
, sc
);
5417 shrink_slab(sc
->gfp_mask
, pgdat
->node_id
, memcg
, sc
->priority
);
5420 vmpressure(sc
->gfp_mask
, memcg
, false, sc
->nr_scanned
- scanned
,
5421 sc
->nr_reclaimed
- reclaimed
);
5423 flush_reclaim_state(sc
);
5425 return success
? MEMCG_LRU_YOUNG
: 0;
5430 static void shrink_many(struct pglist_data
*pgdat
, struct scan_control
*sc
)
5436 struct lruvec
*lruvec
;
5437 struct lru_gen_folio
*lrugen
;
5438 struct mem_cgroup
*memcg
;
5439 const struct hlist_nulls_node
*pos
;
5440 unsigned long nr_to_reclaim
= get_nr_to_reclaim(sc
);
5442 bin
= first_bin
= get_random_u32_below(MEMCG_NR_BINS
);
5446 gen
= get_memcg_gen(READ_ONCE(pgdat
->memcg_lru
.seq
));
5450 hlist_nulls_for_each_entry_rcu(lrugen
, pos
, &pgdat
->memcg_lru
.fifo
[gen
][bin
], list
) {
5452 lru_gen_rotate_memcg(lruvec
, op
);
5456 mem_cgroup_put(memcg
);
5458 lruvec
= container_of(lrugen
, struct lruvec
, lrugen
);
5459 memcg
= lruvec_memcg(lruvec
);
5461 if (!mem_cgroup_tryget(memcg
)) {
5462 lru_gen_release_memcg(memcg
);
5469 op
= shrink_one(lruvec
, sc
);
5473 if (sc
->nr_reclaimed
>= nr_to_reclaim
)
5480 lru_gen_rotate_memcg(lruvec
, op
);
5482 mem_cgroup_put(memcg
);
5484 if (sc
->nr_reclaimed
>= nr_to_reclaim
)
5487 /* restart if raced with lru_gen_rotate_memcg() */
5488 if (gen
!= get_nulls_value(pos
))
5491 /* try the rest of the bins of the current generation */
5492 bin
= get_memcg_bin(bin
+ 1);
5493 if (bin
!= first_bin
)
5497 static void lru_gen_shrink_lruvec(struct lruvec
*lruvec
, struct scan_control
*sc
)
5499 struct blk_plug plug
;
5501 VM_WARN_ON_ONCE(root_reclaim(sc
));
5502 VM_WARN_ON_ONCE(!sc
->may_writepage
|| !sc
->may_unmap
);
5506 blk_start_plug(&plug
);
5508 set_mm_walk(NULL
, sc
->proactive
);
5510 if (try_to_shrink_lruvec(lruvec
, sc
))
5511 lru_gen_rotate_memcg(lruvec
, MEMCG_LRU_YOUNG
);
5515 blk_finish_plug(&plug
);
5518 #else /* !CONFIG_MEMCG */
5520 static void shrink_many(struct pglist_data
*pgdat
, struct scan_control
*sc
)
5525 static void lru_gen_shrink_lruvec(struct lruvec
*lruvec
, struct scan_control
*sc
)
5532 static void set_initial_priority(struct pglist_data
*pgdat
, struct scan_control
*sc
)
5535 unsigned long reclaimable
;
5536 struct lruvec
*lruvec
= mem_cgroup_lruvec(NULL
, pgdat
);
5538 if (sc
->priority
!= DEF_PRIORITY
|| sc
->nr_to_reclaim
< MIN_LRU_BATCH
)
5541 * Determine the initial priority based on ((total / MEMCG_NR_GENS) >>
5542 * priority) * reclaimed_to_scanned_ratio = nr_to_reclaim, where the
5543 * estimated reclaimed_to_scanned_ratio = inactive / total.
5545 reclaimable
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
5546 if (get_swappiness(lruvec
, sc
))
5547 reclaimable
+= node_page_state(pgdat
, NR_INACTIVE_ANON
);
5549 reclaimable
/= MEMCG_NR_GENS
;
5551 /* round down reclaimable and round up sc->nr_to_reclaim */
5552 priority
= fls_long(reclaimable
) - 1 - fls_long(sc
->nr_to_reclaim
- 1);
5554 sc
->priority
= clamp(priority
, 0, DEF_PRIORITY
);
5557 static void lru_gen_shrink_node(struct pglist_data
*pgdat
, struct scan_control
*sc
)
5559 struct blk_plug plug
;
5560 unsigned long reclaimed
= sc
->nr_reclaimed
;
5562 VM_WARN_ON_ONCE(!root_reclaim(sc
));
5565 * Unmapped clean folios are already prioritized. Scanning for more of
5566 * them is likely futile and can cause high reclaim latency when there
5567 * is a large number of memcgs.
5569 if (!sc
->may_writepage
|| !sc
->may_unmap
)
5574 blk_start_plug(&plug
);
5576 set_mm_walk(pgdat
, sc
->proactive
);
5578 set_initial_priority(pgdat
, sc
);
5580 if (current_is_kswapd())
5581 sc
->nr_reclaimed
= 0;
5583 if (mem_cgroup_disabled())
5584 shrink_one(&pgdat
->__lruvec
, sc
);
5586 shrink_many(pgdat
, sc
);
5588 if (current_is_kswapd())
5589 sc
->nr_reclaimed
+= reclaimed
;
5593 blk_finish_plug(&plug
);
5595 /* kswapd should never fail */
5596 pgdat
->kswapd_failures
= 0;
5599 /******************************************************************************
5601 ******************************************************************************/
5603 static bool __maybe_unused
state_is_valid(struct lruvec
*lruvec
)
5605 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
5607 if (lrugen
->enabled
) {
5610 for_each_evictable_lru(lru
) {
5611 if (!list_empty(&lruvec
->lists
[lru
]))
5615 int gen
, type
, zone
;
5617 for_each_gen_type_zone(gen
, type
, zone
) {
5618 if (!list_empty(&lrugen
->folios
[gen
][type
][zone
]))
5626 static bool fill_evictable(struct lruvec
*lruvec
)
5629 int remaining
= MAX_LRU_BATCH
;
5631 for_each_evictable_lru(lru
) {
5632 int type
= is_file_lru(lru
);
5633 bool active
= is_active_lru(lru
);
5634 struct list_head
*head
= &lruvec
->lists
[lru
];
5636 while (!list_empty(head
)) {
5638 struct folio
*folio
= lru_to_folio(head
);
5640 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio
), folio
);
5641 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio
) != active
, folio
);
5642 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio
) != type
, folio
);
5643 VM_WARN_ON_ONCE_FOLIO(folio_lru_gen(folio
) != -1, folio
);
5645 lruvec_del_folio(lruvec
, folio
);
5646 success
= lru_gen_add_folio(lruvec
, folio
, false);
5647 VM_WARN_ON_ONCE(!success
);
5657 static bool drain_evictable(struct lruvec
*lruvec
)
5659 int gen
, type
, zone
;
5660 int remaining
= MAX_LRU_BATCH
;
5662 for_each_gen_type_zone(gen
, type
, zone
) {
5663 struct list_head
*head
= &lruvec
->lrugen
.folios
[gen
][type
][zone
];
5665 while (!list_empty(head
)) {
5667 struct folio
*folio
= lru_to_folio(head
);
5669 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio
), folio
);
5670 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio
), folio
);
5671 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio
) != type
, folio
);
5672 VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio
) != zone
, folio
);
5674 success
= lru_gen_del_folio(lruvec
, folio
, false);
5675 VM_WARN_ON_ONCE(!success
);
5676 lruvec_add_folio(lruvec
, folio
);
5686 static void lru_gen_change_state(bool enabled
)
5688 static DEFINE_MUTEX(state_mutex
);
5690 struct mem_cgroup
*memcg
;
5695 mutex_lock(&state_mutex
);
5697 if (enabled
== lru_gen_enabled())
5701 static_branch_enable_cpuslocked(&lru_gen_caps
[LRU_GEN_CORE
]);
5703 static_branch_disable_cpuslocked(&lru_gen_caps
[LRU_GEN_CORE
]);
5705 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
5709 for_each_node(nid
) {
5710 struct lruvec
*lruvec
= get_lruvec(memcg
, nid
);
5712 spin_lock_irq(&lruvec
->lru_lock
);
5714 VM_WARN_ON_ONCE(!seq_is_valid(lruvec
));
5715 VM_WARN_ON_ONCE(!state_is_valid(lruvec
));
5717 lruvec
->lrugen
.enabled
= enabled
;
5719 while (!(enabled
? fill_evictable(lruvec
) : drain_evictable(lruvec
))) {
5720 spin_unlock_irq(&lruvec
->lru_lock
);
5722 spin_lock_irq(&lruvec
->lru_lock
);
5725 spin_unlock_irq(&lruvec
->lru_lock
);
5729 } while ((memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
)));
5731 mutex_unlock(&state_mutex
);
5737 /******************************************************************************
5739 ******************************************************************************/
5741 static ssize_t
min_ttl_ms_show(struct kobject
*kobj
, struct kobj_attribute
*attr
, char *buf
)
5743 return sysfs_emit(buf
, "%u\n", jiffies_to_msecs(READ_ONCE(lru_gen_min_ttl
)));
5746 /* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5747 static ssize_t
min_ttl_ms_store(struct kobject
*kobj
, struct kobj_attribute
*attr
,
5748 const char *buf
, size_t len
)
5752 if (kstrtouint(buf
, 0, &msecs
))
5755 WRITE_ONCE(lru_gen_min_ttl
, msecs_to_jiffies(msecs
));
5760 static struct kobj_attribute lru_gen_min_ttl_attr
= __ATTR_RW(min_ttl_ms
);
5762 static ssize_t
enabled_show(struct kobject
*kobj
, struct kobj_attribute
*attr
, char *buf
)
5764 unsigned int caps
= 0;
5766 if (get_cap(LRU_GEN_CORE
))
5767 caps
|= BIT(LRU_GEN_CORE
);
5769 if (should_walk_mmu())
5770 caps
|= BIT(LRU_GEN_MM_WALK
);
5772 if (should_clear_pmd_young())
5773 caps
|= BIT(LRU_GEN_NONLEAF_YOUNG
);
5775 return sysfs_emit(buf
, "0x%04x\n", caps
);
5778 /* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5779 static ssize_t
enabled_store(struct kobject
*kobj
, struct kobj_attribute
*attr
,
5780 const char *buf
, size_t len
)
5785 if (tolower(*buf
) == 'n')
5787 else if (tolower(*buf
) == 'y')
5789 else if (kstrtouint(buf
, 0, &caps
))
5792 for (i
= 0; i
< NR_LRU_GEN_CAPS
; i
++) {
5793 bool enabled
= caps
& BIT(i
);
5795 if (i
== LRU_GEN_CORE
)
5796 lru_gen_change_state(enabled
);
5798 static_branch_enable(&lru_gen_caps
[i
]);
5800 static_branch_disable(&lru_gen_caps
[i
]);
5806 static struct kobj_attribute lru_gen_enabled_attr
= __ATTR_RW(enabled
);
5808 static struct attribute
*lru_gen_attrs
[] = {
5809 &lru_gen_min_ttl_attr
.attr
,
5810 &lru_gen_enabled_attr
.attr
,
5814 static const struct attribute_group lru_gen_attr_group
= {
5816 .attrs
= lru_gen_attrs
,
5819 /******************************************************************************
5821 ******************************************************************************/
5823 static void *lru_gen_seq_start(struct seq_file
*m
, loff_t
*pos
)
5825 struct mem_cgroup
*memcg
;
5826 loff_t nr_to_skip
= *pos
;
5828 m
->private = kvmalloc(PATH_MAX
, GFP_KERNEL
);
5830 return ERR_PTR(-ENOMEM
);
5832 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
5836 for_each_node_state(nid
, N_MEMORY
) {
5838 return get_lruvec(memcg
, nid
);
5840 } while ((memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
)));
5845 static void lru_gen_seq_stop(struct seq_file
*m
, void *v
)
5847 if (!IS_ERR_OR_NULL(v
))
5848 mem_cgroup_iter_break(NULL
, lruvec_memcg(v
));
5854 static void *lru_gen_seq_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
5856 int nid
= lruvec_pgdat(v
)->node_id
;
5857 struct mem_cgroup
*memcg
= lruvec_memcg(v
);
5861 nid
= next_memory_node(nid
);
5862 if (nid
== MAX_NUMNODES
) {
5863 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
5867 nid
= first_memory_node
;
5870 return get_lruvec(memcg
, nid
);
5873 static void lru_gen_seq_show_full(struct seq_file
*m
, struct lruvec
*lruvec
,
5874 unsigned long max_seq
, unsigned long *min_seq
,
5879 int hist
= lru_hist_from_seq(seq
);
5880 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
5882 for (tier
= 0; tier
< MAX_NR_TIERS
; tier
++) {
5883 seq_printf(m
, " %10d", tier
);
5884 for (type
= 0; type
< ANON_AND_FILE
; type
++) {
5885 const char *s
= " ";
5886 unsigned long n
[3] = {};
5888 if (seq
== max_seq
) {
5890 n
[0] = READ_ONCE(lrugen
->avg_refaulted
[type
][tier
]);
5891 n
[1] = READ_ONCE(lrugen
->avg_total
[type
][tier
]);
5892 } else if (seq
== min_seq
[type
] || NR_HIST_GENS
> 1) {
5894 n
[0] = atomic_long_read(&lrugen
->refaulted
[hist
][type
][tier
]);
5895 n
[1] = atomic_long_read(&lrugen
->evicted
[hist
][type
][tier
]);
5897 n
[2] = READ_ONCE(lrugen
->protected[hist
][type
][tier
- 1]);
5900 for (i
= 0; i
< 3; i
++)
5901 seq_printf(m
, " %10lu%c", n
[i
], s
[i
]);
5907 for (i
= 0; i
< NR_MM_STATS
; i
++) {
5908 const char *s
= " ";
5909 unsigned long n
= 0;
5911 if (seq
== max_seq
&& NR_HIST_GENS
== 1) {
5913 n
= READ_ONCE(lruvec
->mm_state
.stats
[hist
][i
]);
5914 } else if (seq
!= max_seq
&& NR_HIST_GENS
> 1) {
5916 n
= READ_ONCE(lruvec
->mm_state
.stats
[hist
][i
]);
5919 seq_printf(m
, " %10lu%c", n
, s
[i
]);
5924 /* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5925 static int lru_gen_seq_show(struct seq_file
*m
, void *v
)
5928 bool full
= !debugfs_real_fops(m
->file
)->write
;
5929 struct lruvec
*lruvec
= v
;
5930 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
5931 int nid
= lruvec_pgdat(lruvec
)->node_id
;
5932 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
5933 DEFINE_MAX_SEQ(lruvec
);
5934 DEFINE_MIN_SEQ(lruvec
);
5936 if (nid
== first_memory_node
) {
5937 const char *path
= memcg
? m
->private : "";
5941 cgroup_path(memcg
->css
.cgroup
, m
->private, PATH_MAX
);
5943 seq_printf(m
, "memcg %5hu %s\n", mem_cgroup_id(memcg
), path
);
5946 seq_printf(m
, " node %5d\n", nid
);
5949 seq
= min_seq
[LRU_GEN_ANON
];
5950 else if (max_seq
>= MAX_NR_GENS
)
5951 seq
= max_seq
- MAX_NR_GENS
+ 1;
5955 for (; seq
<= max_seq
; seq
++) {
5957 int gen
= lru_gen_from_seq(seq
);
5958 unsigned long birth
= READ_ONCE(lruvec
->lrugen
.timestamps
[gen
]);
5960 seq_printf(m
, " %10lu %10u", seq
, jiffies_to_msecs(jiffies
- birth
));
5962 for (type
= 0; type
< ANON_AND_FILE
; type
++) {
5963 unsigned long size
= 0;
5964 char mark
= full
&& seq
< min_seq
[type
] ? 'x' : ' ';
5966 for (zone
= 0; zone
< MAX_NR_ZONES
; zone
++)
5967 size
+= max(READ_ONCE(lrugen
->nr_pages
[gen
][type
][zone
]), 0L);
5969 seq_printf(m
, " %10lu%c", size
, mark
);
5975 lru_gen_seq_show_full(m
, lruvec
, max_seq
, min_seq
, seq
);
5981 static const struct seq_operations lru_gen_seq_ops
= {
5982 .start
= lru_gen_seq_start
,
5983 .stop
= lru_gen_seq_stop
,
5984 .next
= lru_gen_seq_next
,
5985 .show
= lru_gen_seq_show
,
5988 static int run_aging(struct lruvec
*lruvec
, unsigned long seq
, struct scan_control
*sc
,
5989 bool can_swap
, bool force_scan
)
5991 DEFINE_MAX_SEQ(lruvec
);
5992 DEFINE_MIN_SEQ(lruvec
);
6000 if (!force_scan
&& min_seq
[!can_swap
] + MAX_NR_GENS
- 1 <= max_seq
)
6003 try_to_inc_max_seq(lruvec
, max_seq
, sc
, can_swap
, force_scan
);
6008 static int run_eviction(struct lruvec
*lruvec
, unsigned long seq
, struct scan_control
*sc
,
6009 int swappiness
, unsigned long nr_to_reclaim
)
6011 DEFINE_MAX_SEQ(lruvec
);
6013 if (seq
+ MIN_NR_GENS
> max_seq
)
6016 sc
->nr_reclaimed
= 0;
6018 while (!signal_pending(current
)) {
6019 DEFINE_MIN_SEQ(lruvec
);
6021 if (seq
< min_seq
[!swappiness
])
6024 if (sc
->nr_reclaimed
>= nr_to_reclaim
)
6027 if (!evict_folios(lruvec
, sc
, swappiness
))
6036 static int run_cmd(char cmd
, int memcg_id
, int nid
, unsigned long seq
,
6037 struct scan_control
*sc
, int swappiness
, unsigned long opt
)
6039 struct lruvec
*lruvec
;
6041 struct mem_cgroup
*memcg
= NULL
;
6043 if (nid
< 0 || nid
>= MAX_NUMNODES
|| !node_state(nid
, N_MEMORY
))
6046 if (!mem_cgroup_disabled()) {
6049 memcg
= mem_cgroup_from_id(memcg_id
);
6050 if (!mem_cgroup_tryget(memcg
))
6059 if (memcg_id
!= mem_cgroup_id(memcg
))
6062 lruvec
= get_lruvec(memcg
, nid
);
6065 swappiness
= get_swappiness(lruvec
, sc
);
6066 else if (swappiness
> 200)
6071 err
= run_aging(lruvec
, seq
, sc
, swappiness
, opt
);
6074 err
= run_eviction(lruvec
, seq
, sc
, swappiness
, opt
);
6078 mem_cgroup_put(memcg
);
6083 /* see Documentation/admin-guide/mm/multigen_lru.rst for details */
6084 static ssize_t
lru_gen_seq_write(struct file
*file
, const char __user
*src
,
6085 size_t len
, loff_t
*pos
)
6090 struct blk_plug plug
;
6092 struct scan_control sc
= {
6093 .may_writepage
= true,
6096 .reclaim_idx
= MAX_NR_ZONES
- 1,
6097 .gfp_mask
= GFP_KERNEL
,
6100 buf
= kvmalloc(len
+ 1, GFP_KERNEL
);
6104 if (copy_from_user(buf
, src
, len
)) {
6109 set_task_reclaim_state(current
, &sc
.reclaim_state
);
6110 flags
= memalloc_noreclaim_save();
6111 blk_start_plug(&plug
);
6112 if (!set_mm_walk(NULL
, true)) {
6120 while ((cur
= strsep(&next
, ",;\n"))) {
6124 unsigned int memcg_id
;
6127 unsigned int swappiness
= -1;
6128 unsigned long opt
= -1;
6130 cur
= skip_spaces(cur
);
6134 n
= sscanf(cur
, "%c %u %u %lu %n %u %n %lu %n", &cmd
, &memcg_id
, &nid
,
6135 &seq
, &end
, &swappiness
, &end
, &opt
, &end
);
6136 if (n
< 4 || cur
[end
]) {
6141 err
= run_cmd(cmd
, memcg_id
, nid
, seq
, &sc
, swappiness
, opt
);
6147 blk_finish_plug(&plug
);
6148 memalloc_noreclaim_restore(flags
);
6149 set_task_reclaim_state(current
, NULL
);
6156 static int lru_gen_seq_open(struct inode
*inode
, struct file
*file
)
6158 return seq_open(file
, &lru_gen_seq_ops
);
6161 static const struct file_operations lru_gen_rw_fops
= {
6162 .open
= lru_gen_seq_open
,
6164 .write
= lru_gen_seq_write
,
6165 .llseek
= seq_lseek
,
6166 .release
= seq_release
,
6169 static const struct file_operations lru_gen_ro_fops
= {
6170 .open
= lru_gen_seq_open
,
6172 .llseek
= seq_lseek
,
6173 .release
= seq_release
,
6176 /******************************************************************************
6178 ******************************************************************************/
6180 void lru_gen_init_lruvec(struct lruvec
*lruvec
)
6183 int gen
, type
, zone
;
6184 struct lru_gen_folio
*lrugen
= &lruvec
->lrugen
;
6186 lrugen
->max_seq
= MIN_NR_GENS
+ 1;
6187 lrugen
->enabled
= lru_gen_enabled();
6189 for (i
= 0; i
<= MIN_NR_GENS
+ 1; i
++)
6190 lrugen
->timestamps
[i
] = jiffies
;
6192 for_each_gen_type_zone(gen
, type
, zone
)
6193 INIT_LIST_HEAD(&lrugen
->folios
[gen
][type
][zone
]);
6195 lruvec
->mm_state
.seq
= MIN_NR_GENS
;
6200 void lru_gen_init_pgdat(struct pglist_data
*pgdat
)
6204 spin_lock_init(&pgdat
->memcg_lru
.lock
);
6206 for (i
= 0; i
< MEMCG_NR_GENS
; i
++) {
6207 for (j
= 0; j
< MEMCG_NR_BINS
; j
++)
6208 INIT_HLIST_NULLS_HEAD(&pgdat
->memcg_lru
.fifo
[i
][j
], i
);
6212 void lru_gen_init_memcg(struct mem_cgroup
*memcg
)
6214 INIT_LIST_HEAD(&memcg
->mm_list
.fifo
);
6215 spin_lock_init(&memcg
->mm_list
.lock
);
6218 void lru_gen_exit_memcg(struct mem_cgroup
*memcg
)
6223 VM_WARN_ON_ONCE(!list_empty(&memcg
->mm_list
.fifo
));
6225 for_each_node(nid
) {
6226 struct lruvec
*lruvec
= get_lruvec(memcg
, nid
);
6228 VM_WARN_ON_ONCE(memchr_inv(lruvec
->lrugen
.nr_pages
, 0,
6229 sizeof(lruvec
->lrugen
.nr_pages
)));
6231 lruvec
->lrugen
.list
.next
= LIST_POISON1
;
6233 for (i
= 0; i
< NR_BLOOM_FILTERS
; i
++) {
6234 bitmap_free(lruvec
->mm_state
.filters
[i
]);
6235 lruvec
->mm_state
.filters
[i
] = NULL
;
6240 #endif /* CONFIG_MEMCG */
6242 static int __init
init_lru_gen(void)
6244 BUILD_BUG_ON(MIN_NR_GENS
+ 1 >= MAX_NR_GENS
);
6245 BUILD_BUG_ON(BIT(LRU_GEN_WIDTH
) <= MAX_NR_GENS
);
6247 if (sysfs_create_group(mm_kobj
, &lru_gen_attr_group
))
6248 pr_err("lru_gen: failed to create sysfs group\n");
6250 debugfs_create_file("lru_gen", 0644, NULL
, NULL
, &lru_gen_rw_fops
);
6251 debugfs_create_file("lru_gen_full", 0444, NULL
, NULL
, &lru_gen_ro_fops
);
6255 late_initcall(init_lru_gen
);
6257 #else /* !CONFIG_LRU_GEN */
6259 static void lru_gen_age_node(struct pglist_data
*pgdat
, struct scan_control
*sc
)
6263 static void lru_gen_shrink_lruvec(struct lruvec
*lruvec
, struct scan_control
*sc
)
6267 static void lru_gen_shrink_node(struct pglist_data
*pgdat
, struct scan_control
*sc
)
6271 #endif /* CONFIG_LRU_GEN */
6273 static void shrink_lruvec(struct lruvec
*lruvec
, struct scan_control
*sc
)
6275 unsigned long nr
[NR_LRU_LISTS
];
6276 unsigned long targets
[NR_LRU_LISTS
];
6277 unsigned long nr_to_scan
;
6279 unsigned long nr_reclaimed
= 0;
6280 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
6281 bool proportional_reclaim
;
6282 struct blk_plug plug
;
6284 if (lru_gen_enabled() && !root_reclaim(sc
)) {
6285 lru_gen_shrink_lruvec(lruvec
, sc
);
6289 get_scan_count(lruvec
, sc
, nr
);
6291 /* Record the original scan target for proportional adjustments later */
6292 memcpy(targets
, nr
, sizeof(nr
));
6295 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
6296 * event that can occur when there is little memory pressure e.g.
6297 * multiple streaming readers/writers. Hence, we do not abort scanning
6298 * when the requested number of pages are reclaimed when scanning at
6299 * DEF_PRIORITY on the assumption that the fact we are direct
6300 * reclaiming implies that kswapd is not keeping up and it is best to
6301 * do a batch of work at once. For memcg reclaim one check is made to
6302 * abort proportional reclaim if either the file or anon lru has already
6303 * dropped to zero at the first pass.
6305 proportional_reclaim
= (!cgroup_reclaim(sc
) && !current_is_kswapd() &&
6306 sc
->priority
== DEF_PRIORITY
);
6308 blk_start_plug(&plug
);
6309 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
6310 nr
[LRU_INACTIVE_FILE
]) {
6311 unsigned long nr_anon
, nr_file
, percentage
;
6312 unsigned long nr_scanned
;
6314 for_each_evictable_lru(lru
) {
6316 nr_to_scan
= min(nr
[lru
], SWAP_CLUSTER_MAX
);
6317 nr
[lru
] -= nr_to_scan
;
6319 nr_reclaimed
+= shrink_list(lru
, nr_to_scan
,
6326 if (nr_reclaimed
< nr_to_reclaim
|| proportional_reclaim
)
6330 * For kswapd and memcg, reclaim at least the number of pages
6331 * requested. Ensure that the anon and file LRUs are scanned
6332 * proportionally what was requested by get_scan_count(). We
6333 * stop reclaiming one LRU and reduce the amount scanning
6334 * proportional to the original scan target.
6336 nr_file
= nr
[LRU_INACTIVE_FILE
] + nr
[LRU_ACTIVE_FILE
];
6337 nr_anon
= nr
[LRU_INACTIVE_ANON
] + nr
[LRU_ACTIVE_ANON
];
6340 * It's just vindictive to attack the larger once the smaller
6341 * has gone to zero. And given the way we stop scanning the
6342 * smaller below, this makes sure that we only make one nudge
6343 * towards proportionality once we've got nr_to_reclaim.
6345 if (!nr_file
|| !nr_anon
)
6348 if (nr_file
> nr_anon
) {
6349 unsigned long scan_target
= targets
[LRU_INACTIVE_ANON
] +
6350 targets
[LRU_ACTIVE_ANON
] + 1;
6352 percentage
= nr_anon
* 100 / scan_target
;
6354 unsigned long scan_target
= targets
[LRU_INACTIVE_FILE
] +
6355 targets
[LRU_ACTIVE_FILE
] + 1;
6357 percentage
= nr_file
* 100 / scan_target
;
6360 /* Stop scanning the smaller of the LRU */
6362 nr
[lru
+ LRU_ACTIVE
] = 0;
6365 * Recalculate the other LRU scan count based on its original
6366 * scan target and the percentage scanning already complete
6368 lru
= (lru
== LRU_FILE
) ? LRU_BASE
: LRU_FILE
;
6369 nr_scanned
= targets
[lru
] - nr
[lru
];
6370 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
6371 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
6374 nr_scanned
= targets
[lru
] - nr
[lru
];
6375 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
6376 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
6378 blk_finish_plug(&plug
);
6379 sc
->nr_reclaimed
+= nr_reclaimed
;
6382 * Even if we did not try to evict anon pages at all, we want to
6383 * rebalance the anon lru active/inactive ratio.
6385 if (can_age_anon_pages(lruvec_pgdat(lruvec
), sc
) &&
6386 inactive_is_low(lruvec
, LRU_INACTIVE_ANON
))
6387 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
6388 sc
, LRU_ACTIVE_ANON
);
6391 /* Use reclaim/compaction for costly allocs or under memory pressure */
6392 static bool in_reclaim_compaction(struct scan_control
*sc
)
6394 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
6395 (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
||
6396 sc
->priority
< DEF_PRIORITY
- 2))
6403 * Reclaim/compaction is used for high-order allocation requests. It reclaims
6404 * order-0 pages before compacting the zone. should_continue_reclaim() returns
6405 * true if more pages should be reclaimed such that when the page allocator
6406 * calls try_to_compact_pages() that it will have enough free pages to succeed.
6407 * It will give up earlier than that if there is difficulty reclaiming pages.
6409 static inline bool should_continue_reclaim(struct pglist_data
*pgdat
,
6410 unsigned long nr_reclaimed
,
6411 struct scan_control
*sc
)
6413 unsigned long pages_for_compaction
;
6414 unsigned long inactive_lru_pages
;
6417 /* If not in reclaim/compaction mode, stop */
6418 if (!in_reclaim_compaction(sc
))
6422 * Stop if we failed to reclaim any pages from the last SWAP_CLUSTER_MAX
6423 * number of pages that were scanned. This will return to the caller
6424 * with the risk reclaim/compaction and the resulting allocation attempt
6425 * fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL
6426 * allocations through requiring that the full LRU list has been scanned
6427 * first, by assuming that zero delta of sc->nr_scanned means full LRU
6428 * scan, but that approximation was wrong, and there were corner cases
6429 * where always a non-zero amount of pages were scanned.
6434 /* If compaction would go ahead or the allocation would succeed, stop */
6435 for (z
= 0; z
<= sc
->reclaim_idx
; z
++) {
6436 struct zone
*zone
= &pgdat
->node_zones
[z
];
6437 if (!managed_zone(zone
))
6440 /* Allocation can already succeed, nothing to do */
6441 if (zone_watermark_ok(zone
, sc
->order
, min_wmark_pages(zone
),
6442 sc
->reclaim_idx
, 0))
6445 if (compaction_suitable(zone
, sc
->order
, sc
->reclaim_idx
))
6450 * If we have not reclaimed enough pages for compaction and the
6451 * inactive lists are large enough, continue reclaiming
6453 pages_for_compaction
= compact_gap(sc
->order
);
6454 inactive_lru_pages
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
6455 if (can_reclaim_anon_pages(NULL
, pgdat
->node_id
, sc
))
6456 inactive_lru_pages
+= node_page_state(pgdat
, NR_INACTIVE_ANON
);
6458 return inactive_lru_pages
> pages_for_compaction
;
6461 static void shrink_node_memcgs(pg_data_t
*pgdat
, struct scan_control
*sc
)
6463 struct mem_cgroup
*target_memcg
= sc
->target_mem_cgroup
;
6464 struct mem_cgroup
*memcg
;
6466 memcg
= mem_cgroup_iter(target_memcg
, NULL
, NULL
);
6468 struct lruvec
*lruvec
= mem_cgroup_lruvec(memcg
, pgdat
);
6469 unsigned long reclaimed
;
6470 unsigned long scanned
;
6473 * This loop can become CPU-bound when target memcgs
6474 * aren't eligible for reclaim - either because they
6475 * don't have any reclaimable pages, or because their
6476 * memory is explicitly protected. Avoid soft lockups.
6480 mem_cgroup_calculate_protection(target_memcg
, memcg
);
6482 if (mem_cgroup_below_min(target_memcg
, memcg
)) {
6485 * If there is no reclaimable memory, OOM.
6488 } else if (mem_cgroup_below_low(target_memcg
, memcg
)) {
6491 * Respect the protection only as long as
6492 * there is an unprotected supply
6493 * of reclaimable memory from other cgroups.
6495 if (!sc
->memcg_low_reclaim
) {
6496 sc
->memcg_low_skipped
= 1;
6499 memcg_memory_event(memcg
, MEMCG_LOW
);
6502 reclaimed
= sc
->nr_reclaimed
;
6503 scanned
= sc
->nr_scanned
;
6505 shrink_lruvec(lruvec
, sc
);
6507 shrink_slab(sc
->gfp_mask
, pgdat
->node_id
, memcg
,
6510 /* Record the group's reclaim efficiency */
6512 vmpressure(sc
->gfp_mask
, memcg
, false,
6513 sc
->nr_scanned
- scanned
,
6514 sc
->nr_reclaimed
- reclaimed
);
6516 } while ((memcg
= mem_cgroup_iter(target_memcg
, memcg
, NULL
)));
6519 static void shrink_node(pg_data_t
*pgdat
, struct scan_control
*sc
)
6521 unsigned long nr_reclaimed
, nr_scanned
, nr_node_reclaimed
;
6522 struct lruvec
*target_lruvec
;
6523 bool reclaimable
= false;
6525 if (lru_gen_enabled() && root_reclaim(sc
)) {
6526 lru_gen_shrink_node(pgdat
, sc
);
6530 target_lruvec
= mem_cgroup_lruvec(sc
->target_mem_cgroup
, pgdat
);
6533 memset(&sc
->nr
, 0, sizeof(sc
->nr
));
6535 nr_reclaimed
= sc
->nr_reclaimed
;
6536 nr_scanned
= sc
->nr_scanned
;
6538 prepare_scan_count(pgdat
, sc
);
6540 shrink_node_memcgs(pgdat
, sc
);
6542 flush_reclaim_state(sc
);
6544 nr_node_reclaimed
= sc
->nr_reclaimed
- nr_reclaimed
;
6546 /* Record the subtree's reclaim efficiency */
6548 vmpressure(sc
->gfp_mask
, sc
->target_mem_cgroup
, true,
6549 sc
->nr_scanned
- nr_scanned
, nr_node_reclaimed
);
6551 if (nr_node_reclaimed
)
6554 if (current_is_kswapd()) {
6556 * If reclaim is isolating dirty pages under writeback,
6557 * it implies that the long-lived page allocation rate
6558 * is exceeding the page laundering rate. Either the
6559 * global limits are not being effective at throttling
6560 * processes due to the page distribution throughout
6561 * zones or there is heavy usage of a slow backing
6562 * device. The only option is to throttle from reclaim
6563 * context which is not ideal as there is no guarantee
6564 * the dirtying process is throttled in the same way
6565 * balance_dirty_pages() manages.
6567 * Once a node is flagged PGDAT_WRITEBACK, kswapd will
6568 * count the number of pages under pages flagged for
6569 * immediate reclaim and stall if any are encountered
6570 * in the nr_immediate check below.
6572 if (sc
->nr
.writeback
&& sc
->nr
.writeback
== sc
->nr
.taken
)
6573 set_bit(PGDAT_WRITEBACK
, &pgdat
->flags
);
6575 /* Allow kswapd to start writing pages during reclaim.*/
6576 if (sc
->nr
.unqueued_dirty
== sc
->nr
.file_taken
)
6577 set_bit(PGDAT_DIRTY
, &pgdat
->flags
);
6580 * If kswapd scans pages marked for immediate
6581 * reclaim and under writeback (nr_immediate), it
6582 * implies that pages are cycling through the LRU
6583 * faster than they are written so forcibly stall
6584 * until some pages complete writeback.
6586 if (sc
->nr
.immediate
)
6587 reclaim_throttle(pgdat
, VMSCAN_THROTTLE_WRITEBACK
);
6591 * Tag a node/memcg as congested if all the dirty pages were marked
6592 * for writeback and immediate reclaim (counted in nr.congested).
6594 * Legacy memcg will stall in page writeback so avoid forcibly
6595 * stalling in reclaim_throttle().
6597 if (sc
->nr
.dirty
&& sc
->nr
.dirty
== sc
->nr
.congested
) {
6598 if (cgroup_reclaim(sc
) && writeback_throttling_sane(sc
))
6599 set_bit(LRUVEC_CGROUP_CONGESTED
, &target_lruvec
->flags
);
6601 if (current_is_kswapd())
6602 set_bit(LRUVEC_NODE_CONGESTED
, &target_lruvec
->flags
);
6606 * Stall direct reclaim for IO completions if the lruvec is
6607 * node is congested. Allow kswapd to continue until it
6608 * starts encountering unqueued dirty pages or cycling through
6609 * the LRU too quickly.
6611 if (!current_is_kswapd() && current_may_throttle() &&
6612 !sc
->hibernation_mode
&&
6613 (test_bit(LRUVEC_CGROUP_CONGESTED
, &target_lruvec
->flags
) ||
6614 test_bit(LRUVEC_NODE_CONGESTED
, &target_lruvec
->flags
)))
6615 reclaim_throttle(pgdat
, VMSCAN_THROTTLE_CONGESTED
);
6617 if (should_continue_reclaim(pgdat
, nr_node_reclaimed
, sc
))
6621 * Kswapd gives up on balancing particular nodes after too
6622 * many failures to reclaim anything from them and goes to
6623 * sleep. On reclaim progress, reset the failure counter. A
6624 * successful direct reclaim run will revive a dormant kswapd.
6627 pgdat
->kswapd_failures
= 0;
6631 * Returns true if compaction should go ahead for a costly-order request, or
6632 * the allocation would already succeed without compaction. Return false if we
6633 * should reclaim first.
6635 static inline bool compaction_ready(struct zone
*zone
, struct scan_control
*sc
)
6637 unsigned long watermark
;
6639 /* Allocation can already succeed, nothing to do */
6640 if (zone_watermark_ok(zone
, sc
->order
, min_wmark_pages(zone
),
6641 sc
->reclaim_idx
, 0))
6644 /* Compaction cannot yet proceed. Do reclaim. */
6645 if (!compaction_suitable(zone
, sc
->order
, sc
->reclaim_idx
))
6649 * Compaction is already possible, but it takes time to run and there
6650 * are potentially other callers using the pages just freed. So proceed
6651 * with reclaim to make a buffer of free pages available to give
6652 * compaction a reasonable chance of completing and allocating the page.
6653 * Note that we won't actually reclaim the whole buffer in one attempt
6654 * as the target watermark in should_continue_reclaim() is lower. But if
6655 * we are already above the high+gap watermark, don't reclaim at all.
6657 watermark
= high_wmark_pages(zone
) + compact_gap(sc
->order
);
6659 return zone_watermark_ok_safe(zone
, 0, watermark
, sc
->reclaim_idx
);
6662 static void consider_reclaim_throttle(pg_data_t
*pgdat
, struct scan_control
*sc
)
6665 * If reclaim is making progress greater than 12% efficiency then
6666 * wake all the NOPROGRESS throttled tasks.
6668 if (sc
->nr_reclaimed
> (sc
->nr_scanned
>> 3)) {
6669 wait_queue_head_t
*wqh
;
6671 wqh
= &pgdat
->reclaim_wait
[VMSCAN_THROTTLE_NOPROGRESS
];
6672 if (waitqueue_active(wqh
))
6679 * Do not throttle kswapd or cgroup reclaim on NOPROGRESS as it will
6680 * throttle on VMSCAN_THROTTLE_WRITEBACK if there are too many pages
6681 * under writeback and marked for immediate reclaim at the tail of the
6684 if (current_is_kswapd() || cgroup_reclaim(sc
))
6687 /* Throttle if making no progress at high prioities. */
6688 if (sc
->priority
== 1 && !sc
->nr_reclaimed
)
6689 reclaim_throttle(pgdat
, VMSCAN_THROTTLE_NOPROGRESS
);
6693 * This is the direct reclaim path, for page-allocating processes. We only
6694 * try to reclaim pages from zones which will satisfy the caller's allocation
6697 * If a zone is deemed to be full of pinned pages then just give it a light
6698 * scan then give up on it.
6700 static void shrink_zones(struct zonelist
*zonelist
, struct scan_control
*sc
)
6704 unsigned long nr_soft_reclaimed
;
6705 unsigned long nr_soft_scanned
;
6707 pg_data_t
*last_pgdat
= NULL
;
6708 pg_data_t
*first_pgdat
= NULL
;
6711 * If the number of buffer_heads in the machine exceeds the maximum
6712 * allowed level, force direct reclaim to scan the highmem zone as
6713 * highmem pages could be pinning lowmem pages storing buffer_heads
6715 orig_mask
= sc
->gfp_mask
;
6716 if (buffer_heads_over_limit
) {
6717 sc
->gfp_mask
|= __GFP_HIGHMEM
;
6718 sc
->reclaim_idx
= gfp_zone(sc
->gfp_mask
);
6721 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
6722 sc
->reclaim_idx
, sc
->nodemask
) {
6724 * Take care memory controller reclaiming has small influence
6727 if (!cgroup_reclaim(sc
)) {
6728 if (!cpuset_zone_allowed(zone
,
6729 GFP_KERNEL
| __GFP_HARDWALL
))
6733 * If we already have plenty of memory free for
6734 * compaction in this zone, don't free any more.
6735 * Even though compaction is invoked for any
6736 * non-zero order, only frequent costly order
6737 * reclamation is disruptive enough to become a
6738 * noticeable problem, like transparent huge
6741 if (IS_ENABLED(CONFIG_COMPACTION
) &&
6742 sc
->order
> PAGE_ALLOC_COSTLY_ORDER
&&
6743 compaction_ready(zone
, sc
)) {
6744 sc
->compaction_ready
= true;
6749 * Shrink each node in the zonelist once. If the
6750 * zonelist is ordered by zone (not the default) then a
6751 * node may be shrunk multiple times but in that case
6752 * the user prefers lower zones being preserved.
6754 if (zone
->zone_pgdat
== last_pgdat
)
6758 * This steals pages from memory cgroups over softlimit
6759 * and returns the number of reclaimed pages and
6760 * scanned pages. This works for global memory pressure
6761 * and balancing, not for a memcg's limit.
6763 nr_soft_scanned
= 0;
6764 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
->zone_pgdat
,
6765 sc
->order
, sc
->gfp_mask
,
6767 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
6768 sc
->nr_scanned
+= nr_soft_scanned
;
6769 /* need some check for avoid more shrink_zone() */
6773 first_pgdat
= zone
->zone_pgdat
;
6775 /* See comment about same check for global reclaim above */
6776 if (zone
->zone_pgdat
== last_pgdat
)
6778 last_pgdat
= zone
->zone_pgdat
;
6779 shrink_node(zone
->zone_pgdat
, sc
);
6783 consider_reclaim_throttle(first_pgdat
, sc
);
6786 * Restore to original mask to avoid the impact on the caller if we
6787 * promoted it to __GFP_HIGHMEM.
6789 sc
->gfp_mask
= orig_mask
;
6792 static void snapshot_refaults(struct mem_cgroup
*target_memcg
, pg_data_t
*pgdat
)
6794 struct lruvec
*target_lruvec
;
6795 unsigned long refaults
;
6797 if (lru_gen_enabled())
6800 target_lruvec
= mem_cgroup_lruvec(target_memcg
, pgdat
);
6801 refaults
= lruvec_page_state(target_lruvec
, WORKINGSET_ACTIVATE_ANON
);
6802 target_lruvec
->refaults
[WORKINGSET_ANON
] = refaults
;
6803 refaults
= lruvec_page_state(target_lruvec
, WORKINGSET_ACTIVATE_FILE
);
6804 target_lruvec
->refaults
[WORKINGSET_FILE
] = refaults
;
6808 * This is the main entry point to direct page reclaim.
6810 * If a full scan of the inactive list fails to free enough memory then we
6811 * are "out of memory" and something needs to be killed.
6813 * If the caller is !__GFP_FS then the probability of a failure is reasonably
6814 * high - the zone may be full of dirty or under-writeback pages, which this
6815 * caller can't do much about. We kick the writeback threads and take explicit
6816 * naps in the hope that some of these pages can be written. But if the
6817 * allocating task holds filesystem locks which prevent writeout this might not
6818 * work, and the allocation attempt will fail.
6820 * returns: 0, if no pages reclaimed
6821 * else, the number of pages reclaimed
6823 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
6824 struct scan_control
*sc
)
6826 int initial_priority
= sc
->priority
;
6827 pg_data_t
*last_pgdat
;
6831 delayacct_freepages_start();
6833 if (!cgroup_reclaim(sc
))
6834 __count_zid_vm_events(ALLOCSTALL
, sc
->reclaim_idx
, 1);
6838 vmpressure_prio(sc
->gfp_mask
, sc
->target_mem_cgroup
,
6841 shrink_zones(zonelist
, sc
);
6843 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
6846 if (sc
->compaction_ready
)
6850 * If we're getting trouble reclaiming, start doing
6851 * writepage even in laptop mode.
6853 if (sc
->priority
< DEF_PRIORITY
- 2)
6854 sc
->may_writepage
= 1;
6855 } while (--sc
->priority
>= 0);
6858 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
, sc
->reclaim_idx
,
6860 if (zone
->zone_pgdat
== last_pgdat
)
6862 last_pgdat
= zone
->zone_pgdat
;
6864 snapshot_refaults(sc
->target_mem_cgroup
, zone
->zone_pgdat
);
6866 if (cgroup_reclaim(sc
)) {
6867 struct lruvec
*lruvec
;
6869 lruvec
= mem_cgroup_lruvec(sc
->target_mem_cgroup
,
6871 clear_bit(LRUVEC_CGROUP_CONGESTED
, &lruvec
->flags
);
6875 delayacct_freepages_end();
6877 if (sc
->nr_reclaimed
)
6878 return sc
->nr_reclaimed
;
6880 /* Aborted reclaim to try compaction? don't OOM, then */
6881 if (sc
->compaction_ready
)
6885 * We make inactive:active ratio decisions based on the node's
6886 * composition of memory, but a restrictive reclaim_idx or a
6887 * memory.low cgroup setting can exempt large amounts of
6888 * memory from reclaim. Neither of which are very common, so
6889 * instead of doing costly eligibility calculations of the
6890 * entire cgroup subtree up front, we assume the estimates are
6891 * good, and retry with forcible deactivation if that fails.
6893 if (sc
->skipped_deactivate
) {
6894 sc
->priority
= initial_priority
;
6895 sc
->force_deactivate
= 1;
6896 sc
->skipped_deactivate
= 0;
6900 /* Untapped cgroup reserves? Don't OOM, retry. */
6901 if (sc
->memcg_low_skipped
) {
6902 sc
->priority
= initial_priority
;
6903 sc
->force_deactivate
= 0;
6904 sc
->memcg_low_reclaim
= 1;
6905 sc
->memcg_low_skipped
= 0;
6912 static bool allow_direct_reclaim(pg_data_t
*pgdat
)
6915 unsigned long pfmemalloc_reserve
= 0;
6916 unsigned long free_pages
= 0;
6920 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
6923 for (i
= 0; i
<= ZONE_NORMAL
; i
++) {
6924 zone
= &pgdat
->node_zones
[i
];
6925 if (!managed_zone(zone
))
6928 if (!zone_reclaimable_pages(zone
))
6931 pfmemalloc_reserve
+= min_wmark_pages(zone
);
6932 free_pages
+= zone_page_state_snapshot(zone
, NR_FREE_PAGES
);
6935 /* If there are no reserves (unexpected config) then do not throttle */
6936 if (!pfmemalloc_reserve
)
6939 wmark_ok
= free_pages
> pfmemalloc_reserve
/ 2;
6941 /* kswapd must be awake if processes are being throttled */
6942 if (!wmark_ok
&& waitqueue_active(&pgdat
->kswapd_wait
)) {
6943 if (READ_ONCE(pgdat
->kswapd_highest_zoneidx
) > ZONE_NORMAL
)
6944 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, ZONE_NORMAL
);
6946 wake_up_interruptible(&pgdat
->kswapd_wait
);
6953 * Throttle direct reclaimers if backing storage is backed by the network
6954 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
6955 * depleted. kswapd will continue to make progress and wake the processes
6956 * when the low watermark is reached.
6958 * Returns true if a fatal signal was delivered during throttling. If this
6959 * happens, the page allocator should not consider triggering the OOM killer.
6961 static bool throttle_direct_reclaim(gfp_t gfp_mask
, struct zonelist
*zonelist
,
6962 nodemask_t
*nodemask
)
6966 pg_data_t
*pgdat
= NULL
;
6969 * Kernel threads should not be throttled as they may be indirectly
6970 * responsible for cleaning pages necessary for reclaim to make forward
6971 * progress. kjournald for example may enter direct reclaim while
6972 * committing a transaction where throttling it could forcing other
6973 * processes to block on log_wait_commit().
6975 if (current
->flags
& PF_KTHREAD
)
6979 * If a fatal signal is pending, this process should not throttle.
6980 * It should return quickly so it can exit and free its memory
6982 if (fatal_signal_pending(current
))
6986 * Check if the pfmemalloc reserves are ok by finding the first node
6987 * with a usable ZONE_NORMAL or lower zone. The expectation is that
6988 * GFP_KERNEL will be required for allocating network buffers when
6989 * swapping over the network so ZONE_HIGHMEM is unusable.
6991 * Throttling is based on the first usable node and throttled processes
6992 * wait on a queue until kswapd makes progress and wakes them. There
6993 * is an affinity then between processes waking up and where reclaim
6994 * progress has been made assuming the process wakes on the same node.
6995 * More importantly, processes running on remote nodes will not compete
6996 * for remote pfmemalloc reserves and processes on different nodes
6997 * should make reasonable progress.
6999 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
7000 gfp_zone(gfp_mask
), nodemask
) {
7001 if (zone_idx(zone
) > ZONE_NORMAL
)
7004 /* Throttle based on the first usable node */
7005 pgdat
= zone
->zone_pgdat
;
7006 if (allow_direct_reclaim(pgdat
))
7011 /* If no zone was usable by the allocation flags then do not throttle */
7015 /* Account for the throttling */
7016 count_vm_event(PGSCAN_DIRECT_THROTTLE
);
7019 * If the caller cannot enter the filesystem, it's possible that it
7020 * is due to the caller holding an FS lock or performing a journal
7021 * transaction in the case of a filesystem like ext[3|4]. In this case,
7022 * it is not safe to block on pfmemalloc_wait as kswapd could be
7023 * blocked waiting on the same lock. Instead, throttle for up to a
7024 * second before continuing.
7026 if (!(gfp_mask
& __GFP_FS
))
7027 wait_event_interruptible_timeout(pgdat
->pfmemalloc_wait
,
7028 allow_direct_reclaim(pgdat
), HZ
);
7030 /* Throttle until kswapd wakes the process */
7031 wait_event_killable(zone
->zone_pgdat
->pfmemalloc_wait
,
7032 allow_direct_reclaim(pgdat
));
7034 if (fatal_signal_pending(current
))
7041 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
7042 gfp_t gfp_mask
, nodemask_t
*nodemask
)
7044 unsigned long nr_reclaimed
;
7045 struct scan_control sc
= {
7046 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
7047 .gfp_mask
= current_gfp_context(gfp_mask
),
7048 .reclaim_idx
= gfp_zone(gfp_mask
),
7050 .nodemask
= nodemask
,
7051 .priority
= DEF_PRIORITY
,
7052 .may_writepage
= !laptop_mode
,
7058 * scan_control uses s8 fields for order, priority, and reclaim_idx.
7059 * Confirm they are large enough for max values.
7061 BUILD_BUG_ON(MAX_ORDER
>= S8_MAX
);
7062 BUILD_BUG_ON(DEF_PRIORITY
> S8_MAX
);
7063 BUILD_BUG_ON(MAX_NR_ZONES
> S8_MAX
);
7066 * Do not enter reclaim if fatal signal was delivered while throttled.
7067 * 1 is returned so that the page allocator does not OOM kill at this
7070 if (throttle_direct_reclaim(sc
.gfp_mask
, zonelist
, nodemask
))
7073 set_task_reclaim_state(current
, &sc
.reclaim_state
);
7074 trace_mm_vmscan_direct_reclaim_begin(order
, sc
.gfp_mask
);
7076 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
7078 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
7079 set_task_reclaim_state(current
, NULL
);
7081 return nr_reclaimed
;
7086 /* Only used by soft limit reclaim. Do not reuse for anything else. */
7087 unsigned long mem_cgroup_shrink_node(struct mem_cgroup
*memcg
,
7088 gfp_t gfp_mask
, bool noswap
,
7090 unsigned long *nr_scanned
)
7092 struct lruvec
*lruvec
= mem_cgroup_lruvec(memcg
, pgdat
);
7093 struct scan_control sc
= {
7094 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
7095 .target_mem_cgroup
= memcg
,
7096 .may_writepage
= !laptop_mode
,
7098 .reclaim_idx
= MAX_NR_ZONES
- 1,
7099 .may_swap
= !noswap
,
7102 WARN_ON_ONCE(!current
->reclaim_state
);
7104 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
7105 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
7107 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc
.order
,
7111 * NOTE: Although we can get the priority field, using it
7112 * here is not a good idea, since it limits the pages we can scan.
7113 * if we don't reclaim here, the shrink_node from balance_pgdat
7114 * will pick up pages from other mem cgroup's as well. We hack
7115 * the priority and make it zero.
7117 shrink_lruvec(lruvec
, &sc
);
7119 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
7121 *nr_scanned
= sc
.nr_scanned
;
7123 return sc
.nr_reclaimed
;
7126 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*memcg
,
7127 unsigned long nr_pages
,
7129 unsigned int reclaim_options
)
7131 unsigned long nr_reclaimed
;
7132 unsigned int noreclaim_flag
;
7133 struct scan_control sc
= {
7134 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
7135 .gfp_mask
= (current_gfp_context(gfp_mask
) & GFP_RECLAIM_MASK
) |
7136 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
7137 .reclaim_idx
= MAX_NR_ZONES
- 1,
7138 .target_mem_cgroup
= memcg
,
7139 .priority
= DEF_PRIORITY
,
7140 .may_writepage
= !laptop_mode
,
7142 .may_swap
= !!(reclaim_options
& MEMCG_RECLAIM_MAY_SWAP
),
7143 .proactive
= !!(reclaim_options
& MEMCG_RECLAIM_PROACTIVE
),
7146 * Traverse the ZONELIST_FALLBACK zonelist of the current node to put
7147 * equal pressure on all the nodes. This is based on the assumption that
7148 * the reclaim does not bail out early.
7150 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
7152 set_task_reclaim_state(current
, &sc
.reclaim_state
);
7153 trace_mm_vmscan_memcg_reclaim_begin(0, sc
.gfp_mask
);
7154 noreclaim_flag
= memalloc_noreclaim_save();
7156 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
7158 memalloc_noreclaim_restore(noreclaim_flag
);
7159 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
7160 set_task_reclaim_state(current
, NULL
);
7162 return nr_reclaimed
;
7166 static void kswapd_age_node(struct pglist_data
*pgdat
, struct scan_control
*sc
)
7168 struct mem_cgroup
*memcg
;
7169 struct lruvec
*lruvec
;
7171 if (lru_gen_enabled()) {
7172 lru_gen_age_node(pgdat
, sc
);
7176 if (!can_age_anon_pages(pgdat
, sc
))
7179 lruvec
= mem_cgroup_lruvec(NULL
, pgdat
);
7180 if (!inactive_is_low(lruvec
, LRU_INACTIVE_ANON
))
7183 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
7185 lruvec
= mem_cgroup_lruvec(memcg
, pgdat
);
7186 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
7187 sc
, LRU_ACTIVE_ANON
);
7188 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
7192 static bool pgdat_watermark_boosted(pg_data_t
*pgdat
, int highest_zoneidx
)
7198 * Check for watermark boosts top-down as the higher zones
7199 * are more likely to be boosted. Both watermarks and boosts
7200 * should not be checked at the same time as reclaim would
7201 * start prematurely when there is no boosting and a lower
7204 for (i
= highest_zoneidx
; i
>= 0; i
--) {
7205 zone
= pgdat
->node_zones
+ i
;
7206 if (!managed_zone(zone
))
7209 if (zone
->watermark_boost
)
7217 * Returns true if there is an eligible zone balanced for the request order
7218 * and highest_zoneidx
7220 static bool pgdat_balanced(pg_data_t
*pgdat
, int order
, int highest_zoneidx
)
7223 unsigned long mark
= -1;
7227 * Check watermarks bottom-up as lower zones are more likely to
7230 for (i
= 0; i
<= highest_zoneidx
; i
++) {
7231 zone
= pgdat
->node_zones
+ i
;
7233 if (!managed_zone(zone
))
7236 if (sysctl_numa_balancing_mode
& NUMA_BALANCING_MEMORY_TIERING
)
7237 mark
= wmark_pages(zone
, WMARK_PROMO
);
7239 mark
= high_wmark_pages(zone
);
7240 if (zone_watermark_ok_safe(zone
, order
, mark
, highest_zoneidx
))
7245 * If a node has no managed zone within highest_zoneidx, it does not
7246 * need balancing by definition. This can happen if a zone-restricted
7247 * allocation tries to wake a remote kswapd.
7255 /* Clear pgdat state for congested, dirty or under writeback. */
7256 static void clear_pgdat_congested(pg_data_t
*pgdat
)
7258 struct lruvec
*lruvec
= mem_cgroup_lruvec(NULL
, pgdat
);
7260 clear_bit(LRUVEC_NODE_CONGESTED
, &lruvec
->flags
);
7261 clear_bit(LRUVEC_CGROUP_CONGESTED
, &lruvec
->flags
);
7262 clear_bit(PGDAT_DIRTY
, &pgdat
->flags
);
7263 clear_bit(PGDAT_WRITEBACK
, &pgdat
->flags
);
7267 * Prepare kswapd for sleeping. This verifies that there are no processes
7268 * waiting in throttle_direct_reclaim() and that watermarks have been met.
7270 * Returns true if kswapd is ready to sleep
7272 static bool prepare_kswapd_sleep(pg_data_t
*pgdat
, int order
,
7273 int highest_zoneidx
)
7276 * The throttled processes are normally woken up in balance_pgdat() as
7277 * soon as allow_direct_reclaim() is true. But there is a potential
7278 * race between when kswapd checks the watermarks and a process gets
7279 * throttled. There is also a potential race if processes get
7280 * throttled, kswapd wakes, a large process exits thereby balancing the
7281 * zones, which causes kswapd to exit balance_pgdat() before reaching
7282 * the wake up checks. If kswapd is going to sleep, no process should
7283 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
7284 * the wake up is premature, processes will wake kswapd and get
7285 * throttled again. The difference from wake ups in balance_pgdat() is
7286 * that here we are under prepare_to_wait().
7288 if (waitqueue_active(&pgdat
->pfmemalloc_wait
))
7289 wake_up_all(&pgdat
->pfmemalloc_wait
);
7291 /* Hopeless node, leave it to direct reclaim */
7292 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
7295 if (pgdat_balanced(pgdat
, order
, highest_zoneidx
)) {
7296 clear_pgdat_congested(pgdat
);
7304 * kswapd shrinks a node of pages that are at or below the highest usable
7305 * zone that is currently unbalanced.
7307 * Returns true if kswapd scanned at least the requested number of pages to
7308 * reclaim or if the lack of progress was due to pages under writeback.
7309 * This is used to determine if the scanning priority needs to be raised.
7311 static bool kswapd_shrink_node(pg_data_t
*pgdat
,
7312 struct scan_control
*sc
)
7317 /* Reclaim a number of pages proportional to the number of zones */
7318 sc
->nr_to_reclaim
= 0;
7319 for (z
= 0; z
<= sc
->reclaim_idx
; z
++) {
7320 zone
= pgdat
->node_zones
+ z
;
7321 if (!managed_zone(zone
))
7324 sc
->nr_to_reclaim
+= max(high_wmark_pages(zone
), SWAP_CLUSTER_MAX
);
7328 * Historically care was taken to put equal pressure on all zones but
7329 * now pressure is applied based on node LRU order.
7331 shrink_node(pgdat
, sc
);
7334 * Fragmentation may mean that the system cannot be rebalanced for
7335 * high-order allocations. If twice the allocation size has been
7336 * reclaimed then recheck watermarks only at order-0 to prevent
7337 * excessive reclaim. Assume that a process requested a high-order
7338 * can direct reclaim/compact.
7340 if (sc
->order
&& sc
->nr_reclaimed
>= compact_gap(sc
->order
))
7343 return sc
->nr_scanned
>= sc
->nr_to_reclaim
;
7346 /* Page allocator PCP high watermark is lowered if reclaim is active. */
7348 update_reclaim_active(pg_data_t
*pgdat
, int highest_zoneidx
, bool active
)
7353 for (i
= 0; i
<= highest_zoneidx
; i
++) {
7354 zone
= pgdat
->node_zones
+ i
;
7356 if (!managed_zone(zone
))
7360 set_bit(ZONE_RECLAIM_ACTIVE
, &zone
->flags
);
7362 clear_bit(ZONE_RECLAIM_ACTIVE
, &zone
->flags
);
7367 set_reclaim_active(pg_data_t
*pgdat
, int highest_zoneidx
)
7369 update_reclaim_active(pgdat
, highest_zoneidx
, true);
7373 clear_reclaim_active(pg_data_t
*pgdat
, int highest_zoneidx
)
7375 update_reclaim_active(pgdat
, highest_zoneidx
, false);
7379 * For kswapd, balance_pgdat() will reclaim pages across a node from zones
7380 * that are eligible for use by the caller until at least one zone is
7383 * Returns the order kswapd finished reclaiming at.
7385 * kswapd scans the zones in the highmem->normal->dma direction. It skips
7386 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
7387 * found to have free_pages <= high_wmark_pages(zone), any page in that zone
7388 * or lower is eligible for reclaim until at least one usable zone is
7391 static int balance_pgdat(pg_data_t
*pgdat
, int order
, int highest_zoneidx
)
7394 unsigned long nr_soft_reclaimed
;
7395 unsigned long nr_soft_scanned
;
7396 unsigned long pflags
;
7397 unsigned long nr_boost_reclaim
;
7398 unsigned long zone_boosts
[MAX_NR_ZONES
] = { 0, };
7401 struct scan_control sc
= {
7402 .gfp_mask
= GFP_KERNEL
,
7407 set_task_reclaim_state(current
, &sc
.reclaim_state
);
7408 psi_memstall_enter(&pflags
);
7409 __fs_reclaim_acquire(_THIS_IP_
);
7411 count_vm_event(PAGEOUTRUN
);
7414 * Account for the reclaim boost. Note that the zone boost is left in
7415 * place so that parallel allocations that are near the watermark will
7416 * stall or direct reclaim until kswapd is finished.
7418 nr_boost_reclaim
= 0;
7419 for (i
= 0; i
<= highest_zoneidx
; i
++) {
7420 zone
= pgdat
->node_zones
+ i
;
7421 if (!managed_zone(zone
))
7424 nr_boost_reclaim
+= zone
->watermark_boost
;
7425 zone_boosts
[i
] = zone
->watermark_boost
;
7427 boosted
= nr_boost_reclaim
;
7430 set_reclaim_active(pgdat
, highest_zoneidx
);
7431 sc
.priority
= DEF_PRIORITY
;
7433 unsigned long nr_reclaimed
= sc
.nr_reclaimed
;
7434 bool raise_priority
= true;
7438 sc
.reclaim_idx
= highest_zoneidx
;
7441 * If the number of buffer_heads exceeds the maximum allowed
7442 * then consider reclaiming from all zones. This has a dual
7443 * purpose -- on 64-bit systems it is expected that
7444 * buffer_heads are stripped during active rotation. On 32-bit
7445 * systems, highmem pages can pin lowmem memory and shrinking
7446 * buffers can relieve lowmem pressure. Reclaim may still not
7447 * go ahead if all eligible zones for the original allocation
7448 * request are balanced to avoid excessive reclaim from kswapd.
7450 if (buffer_heads_over_limit
) {
7451 for (i
= MAX_NR_ZONES
- 1; i
>= 0; i
--) {
7452 zone
= pgdat
->node_zones
+ i
;
7453 if (!managed_zone(zone
))
7462 * If the pgdat is imbalanced then ignore boosting and preserve
7463 * the watermarks for a later time and restart. Note that the
7464 * zone watermarks will be still reset at the end of balancing
7465 * on the grounds that the normal reclaim should be enough to
7466 * re-evaluate if boosting is required when kswapd next wakes.
7468 balanced
= pgdat_balanced(pgdat
, sc
.order
, highest_zoneidx
);
7469 if (!balanced
&& nr_boost_reclaim
) {
7470 nr_boost_reclaim
= 0;
7475 * If boosting is not active then only reclaim if there are no
7476 * eligible zones. Note that sc.reclaim_idx is not used as
7477 * buffer_heads_over_limit may have adjusted it.
7479 if (!nr_boost_reclaim
&& balanced
)
7482 /* Limit the priority of boosting to avoid reclaim writeback */
7483 if (nr_boost_reclaim
&& sc
.priority
== DEF_PRIORITY
- 2)
7484 raise_priority
= false;
7487 * Do not writeback or swap pages for boosted reclaim. The
7488 * intent is to relieve pressure not issue sub-optimal IO
7489 * from reclaim context. If no pages are reclaimed, the
7490 * reclaim will be aborted.
7492 sc
.may_writepage
= !laptop_mode
&& !nr_boost_reclaim
;
7493 sc
.may_swap
= !nr_boost_reclaim
;
7496 * Do some background aging, to give pages a chance to be
7497 * referenced before reclaiming. All pages are rotated
7498 * regardless of classzone as this is about consistent aging.
7500 kswapd_age_node(pgdat
, &sc
);
7503 * If we're getting trouble reclaiming, start doing writepage
7504 * even in laptop mode.
7506 if (sc
.priority
< DEF_PRIORITY
- 2)
7507 sc
.may_writepage
= 1;
7509 /* Call soft limit reclaim before calling shrink_node. */
7511 nr_soft_scanned
= 0;
7512 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(pgdat
, sc
.order
,
7513 sc
.gfp_mask
, &nr_soft_scanned
);
7514 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
7517 * There should be no need to raise the scanning priority if
7518 * enough pages are already being scanned that that high
7519 * watermark would be met at 100% efficiency.
7521 if (kswapd_shrink_node(pgdat
, &sc
))
7522 raise_priority
= false;
7525 * If the low watermark is met there is no need for processes
7526 * to be throttled on pfmemalloc_wait as they should not be
7527 * able to safely make forward progress. Wake them
7529 if (waitqueue_active(&pgdat
->pfmemalloc_wait
) &&
7530 allow_direct_reclaim(pgdat
))
7531 wake_up_all(&pgdat
->pfmemalloc_wait
);
7533 /* Check if kswapd should be suspending */
7534 __fs_reclaim_release(_THIS_IP_
);
7535 ret
= try_to_freeze();
7536 __fs_reclaim_acquire(_THIS_IP_
);
7537 if (ret
|| kthread_should_stop())
7541 * Raise priority if scanning rate is too low or there was no
7542 * progress in reclaiming pages
7544 nr_reclaimed
= sc
.nr_reclaimed
- nr_reclaimed
;
7545 nr_boost_reclaim
-= min(nr_boost_reclaim
, nr_reclaimed
);
7548 * If reclaim made no progress for a boost, stop reclaim as
7549 * IO cannot be queued and it could be an infinite loop in
7550 * extreme circumstances.
7552 if (nr_boost_reclaim
&& !nr_reclaimed
)
7555 if (raise_priority
|| !nr_reclaimed
)
7557 } while (sc
.priority
>= 1);
7559 if (!sc
.nr_reclaimed
)
7560 pgdat
->kswapd_failures
++;
7563 clear_reclaim_active(pgdat
, highest_zoneidx
);
7565 /* If reclaim was boosted, account for the reclaim done in this pass */
7567 unsigned long flags
;
7569 for (i
= 0; i
<= highest_zoneidx
; i
++) {
7570 if (!zone_boosts
[i
])
7573 /* Increments are under the zone lock */
7574 zone
= pgdat
->node_zones
+ i
;
7575 spin_lock_irqsave(&zone
->lock
, flags
);
7576 zone
->watermark_boost
-= min(zone
->watermark_boost
, zone_boosts
[i
]);
7577 spin_unlock_irqrestore(&zone
->lock
, flags
);
7581 * As there is now likely space, wakeup kcompact to defragment
7584 wakeup_kcompactd(pgdat
, pageblock_order
, highest_zoneidx
);
7587 snapshot_refaults(NULL
, pgdat
);
7588 __fs_reclaim_release(_THIS_IP_
);
7589 psi_memstall_leave(&pflags
);
7590 set_task_reclaim_state(current
, NULL
);
7593 * Return the order kswapd stopped reclaiming at as
7594 * prepare_kswapd_sleep() takes it into account. If another caller
7595 * entered the allocator slow path while kswapd was awake, order will
7596 * remain at the higher level.
7602 * The pgdat->kswapd_highest_zoneidx is used to pass the highest zone index to
7603 * be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is
7604 * not a valid index then either kswapd runs for first time or kswapd couldn't
7605 * sleep after previous reclaim attempt (node is still unbalanced). In that
7606 * case return the zone index of the previous kswapd reclaim cycle.
7608 static enum zone_type
kswapd_highest_zoneidx(pg_data_t
*pgdat
,
7609 enum zone_type prev_highest_zoneidx
)
7611 enum zone_type curr_idx
= READ_ONCE(pgdat
->kswapd_highest_zoneidx
);
7613 return curr_idx
== MAX_NR_ZONES
? prev_highest_zoneidx
: curr_idx
;
7616 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int alloc_order
, int reclaim_order
,
7617 unsigned int highest_zoneidx
)
7622 if (freezing(current
) || kthread_should_stop())
7625 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
7628 * Try to sleep for a short interval. Note that kcompactd will only be
7629 * woken if it is possible to sleep for a short interval. This is
7630 * deliberate on the assumption that if reclaim cannot keep an
7631 * eligible zone balanced that it's also unlikely that compaction will
7634 if (prepare_kswapd_sleep(pgdat
, reclaim_order
, highest_zoneidx
)) {
7636 * Compaction records what page blocks it recently failed to
7637 * isolate pages from and skips them in the future scanning.
7638 * When kswapd is going to sleep, it is reasonable to assume
7639 * that pages and compaction may succeed so reset the cache.
7641 reset_isolation_suitable(pgdat
);
7644 * We have freed the memory, now we should compact it to make
7645 * allocation of the requested order possible.
7647 wakeup_kcompactd(pgdat
, alloc_order
, highest_zoneidx
);
7649 remaining
= schedule_timeout(HZ
/10);
7652 * If woken prematurely then reset kswapd_highest_zoneidx and
7653 * order. The values will either be from a wakeup request or
7654 * the previous request that slept prematurely.
7657 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
,
7658 kswapd_highest_zoneidx(pgdat
,
7661 if (READ_ONCE(pgdat
->kswapd_order
) < reclaim_order
)
7662 WRITE_ONCE(pgdat
->kswapd_order
, reclaim_order
);
7665 finish_wait(&pgdat
->kswapd_wait
, &wait
);
7666 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
7670 * After a short sleep, check if it was a premature sleep. If not, then
7671 * go fully to sleep until explicitly woken up.
7674 prepare_kswapd_sleep(pgdat
, reclaim_order
, highest_zoneidx
)) {
7675 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
7678 * vmstat counters are not perfectly accurate and the estimated
7679 * value for counters such as NR_FREE_PAGES can deviate from the
7680 * true value by nr_online_cpus * threshold. To avoid the zone
7681 * watermarks being breached while under pressure, we reduce the
7682 * per-cpu vmstat threshold while kswapd is awake and restore
7683 * them before going back to sleep.
7685 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
7687 if (!kthread_should_stop())
7690 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
7693 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
7695 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
7697 finish_wait(&pgdat
->kswapd_wait
, &wait
);
7701 * The background pageout daemon, started as a kernel thread
7702 * from the init process.
7704 * This basically trickles out pages so that we have _some_
7705 * free memory available even if there is no other activity
7706 * that frees anything up. This is needed for things like routing
7707 * etc, where we otherwise might have all activity going on in
7708 * asynchronous contexts that cannot page things out.
7710 * If there are applications that are active memory-allocators
7711 * (most normal use), this basically shouldn't matter.
7713 static int kswapd(void *p
)
7715 unsigned int alloc_order
, reclaim_order
;
7716 unsigned int highest_zoneidx
= MAX_NR_ZONES
- 1;
7717 pg_data_t
*pgdat
= (pg_data_t
*)p
;
7718 struct task_struct
*tsk
= current
;
7719 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
7721 if (!cpumask_empty(cpumask
))
7722 set_cpus_allowed_ptr(tsk
, cpumask
);
7725 * Tell the memory management that we're a "memory allocator",
7726 * and that if we need more memory we should get access to it
7727 * regardless (see "__alloc_pages()"). "kswapd" should
7728 * never get caught in the normal page freeing logic.
7730 * (Kswapd normally doesn't need memory anyway, but sometimes
7731 * you need a small amount of memory in order to be able to
7732 * page out something else, and this flag essentially protects
7733 * us from recursively trying to free more memory as we're
7734 * trying to free the first piece of memory in the first place).
7736 tsk
->flags
|= PF_MEMALLOC
| PF_KSWAPD
;
7739 WRITE_ONCE(pgdat
->kswapd_order
, 0);
7740 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, MAX_NR_ZONES
);
7741 atomic_set(&pgdat
->nr_writeback_throttled
, 0);
7745 alloc_order
= reclaim_order
= READ_ONCE(pgdat
->kswapd_order
);
7746 highest_zoneidx
= kswapd_highest_zoneidx(pgdat
,
7750 kswapd_try_to_sleep(pgdat
, alloc_order
, reclaim_order
,
7753 /* Read the new order and highest_zoneidx */
7754 alloc_order
= READ_ONCE(pgdat
->kswapd_order
);
7755 highest_zoneidx
= kswapd_highest_zoneidx(pgdat
,
7757 WRITE_ONCE(pgdat
->kswapd_order
, 0);
7758 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, MAX_NR_ZONES
);
7760 ret
= try_to_freeze();
7761 if (kthread_should_stop())
7765 * We can speed up thawing tasks if we don't call balance_pgdat
7766 * after returning from the refrigerator
7772 * Reclaim begins at the requested order but if a high-order
7773 * reclaim fails then kswapd falls back to reclaiming for
7774 * order-0. If that happens, kswapd will consider sleeping
7775 * for the order it finished reclaiming at (reclaim_order)
7776 * but kcompactd is woken to compact for the original
7777 * request (alloc_order).
7779 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, highest_zoneidx
,
7781 reclaim_order
= balance_pgdat(pgdat
, alloc_order
,
7783 if (reclaim_order
< alloc_order
)
7784 goto kswapd_try_sleep
;
7787 tsk
->flags
&= ~(PF_MEMALLOC
| PF_KSWAPD
);
7793 * A zone is low on free memory or too fragmented for high-order memory. If
7794 * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
7795 * pgdat. It will wake up kcompactd after reclaiming memory. If kswapd reclaim
7796 * has failed or is not needed, still wake up kcompactd if only compaction is
7799 void wakeup_kswapd(struct zone
*zone
, gfp_t gfp_flags
, int order
,
7800 enum zone_type highest_zoneidx
)
7803 enum zone_type curr_idx
;
7805 if (!managed_zone(zone
))
7808 if (!cpuset_zone_allowed(zone
, gfp_flags
))
7811 pgdat
= zone
->zone_pgdat
;
7812 curr_idx
= READ_ONCE(pgdat
->kswapd_highest_zoneidx
);
7814 if (curr_idx
== MAX_NR_ZONES
|| curr_idx
< highest_zoneidx
)
7815 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, highest_zoneidx
);
7817 if (READ_ONCE(pgdat
->kswapd_order
) < order
)
7818 WRITE_ONCE(pgdat
->kswapd_order
, order
);
7820 if (!waitqueue_active(&pgdat
->kswapd_wait
))
7823 /* Hopeless node, leave it to direct reclaim if possible */
7824 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
||
7825 (pgdat_balanced(pgdat
, order
, highest_zoneidx
) &&
7826 !pgdat_watermark_boosted(pgdat
, highest_zoneidx
))) {
7828 * There may be plenty of free memory available, but it's too
7829 * fragmented for high-order allocations. Wake up kcompactd
7830 * and rely on compaction_suitable() to determine if it's
7831 * needed. If it fails, it will defer subsequent attempts to
7832 * ratelimit its work.
7834 if (!(gfp_flags
& __GFP_DIRECT_RECLAIM
))
7835 wakeup_kcompactd(pgdat
, order
, highest_zoneidx
);
7839 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, highest_zoneidx
, order
,
7841 wake_up_interruptible(&pgdat
->kswapd_wait
);
7844 #ifdef CONFIG_HIBERNATION
7846 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
7849 * Rather than trying to age LRUs the aim is to preserve the overall
7850 * LRU order by reclaiming preferentially
7851 * inactive > active > active referenced > active mapped
7853 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
7855 struct scan_control sc
= {
7856 .nr_to_reclaim
= nr_to_reclaim
,
7857 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
7858 .reclaim_idx
= MAX_NR_ZONES
- 1,
7859 .priority
= DEF_PRIORITY
,
7863 .hibernation_mode
= 1,
7865 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
7866 unsigned long nr_reclaimed
;
7867 unsigned int noreclaim_flag
;
7869 fs_reclaim_acquire(sc
.gfp_mask
);
7870 noreclaim_flag
= memalloc_noreclaim_save();
7871 set_task_reclaim_state(current
, &sc
.reclaim_state
);
7873 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
7875 set_task_reclaim_state(current
, NULL
);
7876 memalloc_noreclaim_restore(noreclaim_flag
);
7877 fs_reclaim_release(sc
.gfp_mask
);
7879 return nr_reclaimed
;
7881 #endif /* CONFIG_HIBERNATION */
7884 * This kswapd start function will be called by init and node-hot-add.
7886 void __meminit
kswapd_run(int nid
)
7888 pg_data_t
*pgdat
= NODE_DATA(nid
);
7890 pgdat_kswapd_lock(pgdat
);
7891 if (!pgdat
->kswapd
) {
7892 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
7893 if (IS_ERR(pgdat
->kswapd
)) {
7894 /* failure at boot is fatal */
7895 BUG_ON(system_state
< SYSTEM_RUNNING
);
7896 pr_err("Failed to start kswapd on node %d\n", nid
);
7897 pgdat
->kswapd
= NULL
;
7900 pgdat_kswapd_unlock(pgdat
);
7904 * Called by memory hotplug when all memory in a node is offlined. Caller must
7905 * be holding mem_hotplug_begin/done().
7907 void __meminit
kswapd_stop(int nid
)
7909 pg_data_t
*pgdat
= NODE_DATA(nid
);
7910 struct task_struct
*kswapd
;
7912 pgdat_kswapd_lock(pgdat
);
7913 kswapd
= pgdat
->kswapd
;
7915 kthread_stop(kswapd
);
7916 pgdat
->kswapd
= NULL
;
7918 pgdat_kswapd_unlock(pgdat
);
7921 static int __init
kswapd_init(void)
7926 for_each_node_state(nid
, N_MEMORY
)
7931 module_init(kswapd_init
)
7937 * If non-zero call node_reclaim when the number of free pages falls below
7940 int node_reclaim_mode __read_mostly
;
7943 * Priority for NODE_RECLAIM. This determines the fraction of pages
7944 * of a node considered for each zone_reclaim. 4 scans 1/16th of
7947 #define NODE_RECLAIM_PRIORITY 4
7950 * Percentage of pages in a zone that must be unmapped for node_reclaim to
7953 int sysctl_min_unmapped_ratio
= 1;
7956 * If the number of slab pages in a zone grows beyond this percentage then
7957 * slab reclaim needs to occur.
7959 int sysctl_min_slab_ratio
= 5;
7961 static inline unsigned long node_unmapped_file_pages(struct pglist_data
*pgdat
)
7963 unsigned long file_mapped
= node_page_state(pgdat
, NR_FILE_MAPPED
);
7964 unsigned long file_lru
= node_page_state(pgdat
, NR_INACTIVE_FILE
) +
7965 node_page_state(pgdat
, NR_ACTIVE_FILE
);
7968 * It's possible for there to be more file mapped pages than
7969 * accounted for by the pages on the file LRU lists because
7970 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
7972 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
7975 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
7976 static unsigned long node_pagecache_reclaimable(struct pglist_data
*pgdat
)
7978 unsigned long nr_pagecache_reclaimable
;
7979 unsigned long delta
= 0;
7982 * If RECLAIM_UNMAP is set, then all file pages are considered
7983 * potentially reclaimable. Otherwise, we have to worry about
7984 * pages like swapcache and node_unmapped_file_pages() provides
7987 if (node_reclaim_mode
& RECLAIM_UNMAP
)
7988 nr_pagecache_reclaimable
= node_page_state(pgdat
, NR_FILE_PAGES
);
7990 nr_pagecache_reclaimable
= node_unmapped_file_pages(pgdat
);
7992 /* If we can't clean pages, remove dirty pages from consideration */
7993 if (!(node_reclaim_mode
& RECLAIM_WRITE
))
7994 delta
+= node_page_state(pgdat
, NR_FILE_DIRTY
);
7996 /* Watch for any possible underflows due to delta */
7997 if (unlikely(delta
> nr_pagecache_reclaimable
))
7998 delta
= nr_pagecache_reclaimable
;
8000 return nr_pagecache_reclaimable
- delta
;
8004 * Try to free up some pages from this node through reclaim.
8006 static int __node_reclaim(struct pglist_data
*pgdat
, gfp_t gfp_mask
, unsigned int order
)
8008 /* Minimum pages needed in order to stay on node */
8009 const unsigned long nr_pages
= 1 << order
;
8010 struct task_struct
*p
= current
;
8011 unsigned int noreclaim_flag
;
8012 struct scan_control sc
= {
8013 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
8014 .gfp_mask
= current_gfp_context(gfp_mask
),
8016 .priority
= NODE_RECLAIM_PRIORITY
,
8017 .may_writepage
= !!(node_reclaim_mode
& RECLAIM_WRITE
),
8018 .may_unmap
= !!(node_reclaim_mode
& RECLAIM_UNMAP
),
8020 .reclaim_idx
= gfp_zone(gfp_mask
),
8022 unsigned long pflags
;
8024 trace_mm_vmscan_node_reclaim_begin(pgdat
->node_id
, order
,
8028 psi_memstall_enter(&pflags
);
8029 fs_reclaim_acquire(sc
.gfp_mask
);
8031 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
8033 noreclaim_flag
= memalloc_noreclaim_save();
8034 set_task_reclaim_state(p
, &sc
.reclaim_state
);
8036 if (node_pagecache_reclaimable(pgdat
) > pgdat
->min_unmapped_pages
||
8037 node_page_state_pages(pgdat
, NR_SLAB_RECLAIMABLE_B
) > pgdat
->min_slab_pages
) {
8039 * Free memory by calling shrink node with increasing
8040 * priorities until we have enough memory freed.
8043 shrink_node(pgdat
, &sc
);
8044 } while (sc
.nr_reclaimed
< nr_pages
&& --sc
.priority
>= 0);
8047 set_task_reclaim_state(p
, NULL
);
8048 memalloc_noreclaim_restore(noreclaim_flag
);
8049 fs_reclaim_release(sc
.gfp_mask
);
8050 psi_memstall_leave(&pflags
);
8052 trace_mm_vmscan_node_reclaim_end(sc
.nr_reclaimed
);
8054 return sc
.nr_reclaimed
>= nr_pages
;
8057 int node_reclaim(struct pglist_data
*pgdat
, gfp_t gfp_mask
, unsigned int order
)
8062 * Node reclaim reclaims unmapped file backed pages and
8063 * slab pages if we are over the defined limits.
8065 * A small portion of unmapped file backed pages is needed for
8066 * file I/O otherwise pages read by file I/O will be immediately
8067 * thrown out if the node is overallocated. So we do not reclaim
8068 * if less than a specified percentage of the node is used by
8069 * unmapped file backed pages.
8071 if (node_pagecache_reclaimable(pgdat
) <= pgdat
->min_unmapped_pages
&&
8072 node_page_state_pages(pgdat
, NR_SLAB_RECLAIMABLE_B
) <=
8073 pgdat
->min_slab_pages
)
8074 return NODE_RECLAIM_FULL
;
8077 * Do not scan if the allocation should not be delayed.
8079 if (!gfpflags_allow_blocking(gfp_mask
) || (current
->flags
& PF_MEMALLOC
))
8080 return NODE_RECLAIM_NOSCAN
;
8083 * Only run node reclaim on the local node or on nodes that do not
8084 * have associated processors. This will favor the local processor
8085 * over remote processors and spread off node memory allocations
8086 * as wide as possible.
8088 if (node_state(pgdat
->node_id
, N_CPU
) && pgdat
->node_id
!= numa_node_id())
8089 return NODE_RECLAIM_NOSCAN
;
8091 if (test_and_set_bit(PGDAT_RECLAIM_LOCKED
, &pgdat
->flags
))
8092 return NODE_RECLAIM_NOSCAN
;
8094 ret
= __node_reclaim(pgdat
, gfp_mask
, order
);
8095 clear_bit(PGDAT_RECLAIM_LOCKED
, &pgdat
->flags
);
8098 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
8105 * check_move_unevictable_folios - Move evictable folios to appropriate zone
8107 * @fbatch: Batch of lru folios to check.
8109 * Checks folios for evictability, if an evictable folio is in the unevictable
8110 * lru list, moves it to the appropriate evictable lru list. This function
8111 * should be only used for lru folios.
8113 void check_move_unevictable_folios(struct folio_batch
*fbatch
)
8115 struct lruvec
*lruvec
= NULL
;
8120 for (i
= 0; i
< fbatch
->nr
; i
++) {
8121 struct folio
*folio
= fbatch
->folios
[i
];
8122 int nr_pages
= folio_nr_pages(folio
);
8124 pgscanned
+= nr_pages
;
8126 /* block memcg migration while the folio moves between lrus */
8127 if (!folio_test_clear_lru(folio
))
8130 lruvec
= folio_lruvec_relock_irq(folio
, lruvec
);
8131 if (folio_evictable(folio
) && folio_test_unevictable(folio
)) {
8132 lruvec_del_folio(lruvec
, folio
);
8133 folio_clear_unevictable(folio
);
8134 lruvec_add_folio(lruvec
, folio
);
8135 pgrescued
+= nr_pages
;
8137 folio_set_lru(folio
);
8141 __count_vm_events(UNEVICTABLE_PGRESCUED
, pgrescued
);
8142 __count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
8143 unlock_page_lruvec_irq(lruvec
);
8144 } else if (pgscanned
) {
8145 count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
8148 EXPORT_SYMBOL_GPL(check_move_unevictable_folios
);