4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 * Swap reorganised 29.12.95, Stephen Tweedie.
7 * kswapd added: 7.1.96 sct
8 * Removed kswapd_ctl limits, and swap out as many pages as needed
9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11 * Multiqueue VM started 5.8.00, Rik van Riel.
14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17 #include <linux/sched/mm.h>
18 #include <linux/module.h>
19 #include <linux/gfp.h>
20 #include <linux/kernel_stat.h>
21 #include <linux/swap.h>
22 #include <linux/pagemap.h>
23 #include <linux/init.h>
24 #include <linux/highmem.h>
25 #include <linux/vmpressure.h>
26 #include <linux/vmstat.h>
27 #include <linux/file.h>
28 #include <linux/writeback.h>
29 #include <linux/blkdev.h>
30 #include <linux/buffer_head.h> /* for try_to_release_page(),
31 buffer_heads_over_limit */
32 #include <linux/mm_inline.h>
33 #include <linux/backing-dev.h>
34 #include <linux/rmap.h>
35 #include <linux/topology.h>
36 #include <linux/cpu.h>
37 #include <linux/cpuset.h>
38 #include <linux/compaction.h>
39 #include <linux/notifier.h>
40 #include <linux/rwsem.h>
41 #include <linux/delay.h>
42 #include <linux/kthread.h>
43 #include <linux/freezer.h>
44 #include <linux/memcontrol.h>
45 #include <linux/delayacct.h>
46 #include <linux/sysctl.h>
47 #include <linux/oom.h>
48 #include <linux/prefetch.h>
49 #include <linux/printk.h>
50 #include <linux/dax.h>
52 #include <asm/tlbflush.h>
53 #include <asm/div64.h>
55 #include <linux/swapops.h>
56 #include <linux/balloon_compaction.h>
60 #define CREATE_TRACE_POINTS
61 #include <trace/events/vmscan.h>
64 /* How many pages shrink_list() should reclaim */
65 unsigned long nr_to_reclaim
;
67 /* This context's GFP mask */
70 /* Allocation order */
74 * Nodemask of nodes allowed by the caller. If NULL, all nodes
80 * The memory cgroup that hit its limit and as a result is the
81 * primary target of this reclaim invocation.
83 struct mem_cgroup
*target_mem_cgroup
;
85 /* Scan (total_size >> priority) pages at once */
88 /* The highest zone to isolate pages for reclaim from */
89 enum zone_type reclaim_idx
;
91 /* Writepage batching in laptop mode; RECLAIM_WRITE */
92 unsigned int may_writepage
:1;
94 /* Can mapped pages be reclaimed? */
95 unsigned int may_unmap
:1;
97 /* Can pages be swapped as part of reclaim? */
98 unsigned int may_swap
:1;
100 /* Can cgroups be reclaimed below their normal consumption range? */
101 unsigned int may_thrash
:1;
103 unsigned int hibernation_mode
:1;
105 /* One of the zones is ready for compaction */
106 unsigned int compaction_ready
:1;
108 /* Incremented by the number of inactive pages that were scanned */
109 unsigned long nr_scanned
;
111 /* Number of pages freed so far during a call to shrink_zones() */
112 unsigned long nr_reclaimed
;
115 #ifdef ARCH_HAS_PREFETCH
116 #define prefetch_prev_lru_page(_page, _base, _field) \
118 if ((_page)->lru.prev != _base) { \
121 prev = lru_to_page(&(_page->lru)); \
122 prefetch(&prev->_field); \
126 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
129 #ifdef ARCH_HAS_PREFETCHW
130 #define prefetchw_prev_lru_page(_page, _base, _field) \
132 if ((_page)->lru.prev != _base) { \
135 prev = lru_to_page(&(_page->lru)); \
136 prefetchw(&prev->_field); \
140 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
144 * From 0 .. 100. Higher means more swappy.
146 int vm_swappiness
= 60;
148 * The total number of pages which are beyond the high watermark within all
151 unsigned long vm_total_pages
;
153 static LIST_HEAD(shrinker_list
);
154 static DECLARE_RWSEM(shrinker_rwsem
);
157 static bool global_reclaim(struct scan_control
*sc
)
159 return !sc
->target_mem_cgroup
;
163 * sane_reclaim - is the usual dirty throttling mechanism operational?
164 * @sc: scan_control in question
166 * The normal page dirty throttling mechanism in balance_dirty_pages() is
167 * completely broken with the legacy memcg and direct stalling in
168 * shrink_page_list() is used for throttling instead, which lacks all the
169 * niceties such as fairness, adaptive pausing, bandwidth proportional
170 * allocation and configurability.
172 * This function tests whether the vmscan currently in progress can assume
173 * that the normal dirty throttling mechanism is operational.
175 static bool sane_reclaim(struct scan_control
*sc
)
177 struct mem_cgroup
*memcg
= sc
->target_mem_cgroup
;
181 #ifdef CONFIG_CGROUP_WRITEBACK
182 if (cgroup_subsys_on_dfl(memory_cgrp_subsys
))
188 static bool global_reclaim(struct scan_control
*sc
)
193 static bool sane_reclaim(struct scan_control
*sc
)
200 * This misses isolated pages which are not accounted for to save counters.
201 * As the data only determines if reclaim or compaction continues, it is
202 * not expected that isolated pages will be a dominating factor.
204 unsigned long zone_reclaimable_pages(struct zone
*zone
)
208 nr
= zone_page_state_snapshot(zone
, NR_ZONE_INACTIVE_FILE
) +
209 zone_page_state_snapshot(zone
, NR_ZONE_ACTIVE_FILE
);
210 if (get_nr_swap_pages() > 0)
211 nr
+= zone_page_state_snapshot(zone
, NR_ZONE_INACTIVE_ANON
) +
212 zone_page_state_snapshot(zone
, NR_ZONE_ACTIVE_ANON
);
217 unsigned long pgdat_reclaimable_pages(struct pglist_data
*pgdat
)
221 nr
= node_page_state_snapshot(pgdat
, NR_ACTIVE_FILE
) +
222 node_page_state_snapshot(pgdat
, NR_INACTIVE_FILE
) +
223 node_page_state_snapshot(pgdat
, NR_ISOLATED_FILE
);
225 if (get_nr_swap_pages() > 0)
226 nr
+= node_page_state_snapshot(pgdat
, NR_ACTIVE_ANON
) +
227 node_page_state_snapshot(pgdat
, NR_INACTIVE_ANON
) +
228 node_page_state_snapshot(pgdat
, NR_ISOLATED_ANON
);
234 * lruvec_lru_size - Returns the number of pages on the given LRU list.
235 * @lruvec: lru vector
237 * @zone_idx: zones to consider (use MAX_NR_ZONES for the whole LRU list)
239 unsigned long lruvec_lru_size(struct lruvec
*lruvec
, enum lru_list lru
, int zone_idx
)
241 unsigned long lru_size
;
244 if (!mem_cgroup_disabled())
245 lru_size
= mem_cgroup_get_lru_size(lruvec
, lru
);
247 lru_size
= node_page_state(lruvec_pgdat(lruvec
), NR_LRU_BASE
+ lru
);
249 for (zid
= zone_idx
+ 1; zid
< MAX_NR_ZONES
; zid
++) {
250 struct zone
*zone
= &lruvec_pgdat(lruvec
)->node_zones
[zid
];
253 if (!managed_zone(zone
))
256 if (!mem_cgroup_disabled())
257 size
= mem_cgroup_get_zone_lru_size(lruvec
, lru
, zid
);
259 size
= zone_page_state(&lruvec_pgdat(lruvec
)->node_zones
[zid
],
260 NR_ZONE_LRU_BASE
+ lru
);
261 lru_size
-= min(size
, lru_size
);
269 * Add a shrinker callback to be called from the vm.
271 int register_shrinker(struct shrinker
*shrinker
)
273 size_t size
= sizeof(*shrinker
->nr_deferred
);
275 if (shrinker
->flags
& SHRINKER_NUMA_AWARE
)
278 shrinker
->nr_deferred
= kzalloc(size
, GFP_KERNEL
);
279 if (!shrinker
->nr_deferred
)
282 down_write(&shrinker_rwsem
);
283 list_add_tail(&shrinker
->list
, &shrinker_list
);
284 up_write(&shrinker_rwsem
);
287 EXPORT_SYMBOL(register_shrinker
);
292 void unregister_shrinker(struct shrinker
*shrinker
)
294 down_write(&shrinker_rwsem
);
295 list_del(&shrinker
->list
);
296 up_write(&shrinker_rwsem
);
297 kfree(shrinker
->nr_deferred
);
299 EXPORT_SYMBOL(unregister_shrinker
);
301 #define SHRINK_BATCH 128
303 static unsigned long do_shrink_slab(struct shrink_control
*shrinkctl
,
304 struct shrinker
*shrinker
,
305 unsigned long nr_scanned
,
306 unsigned long nr_eligible
)
308 unsigned long freed
= 0;
309 unsigned long long delta
;
314 int nid
= shrinkctl
->nid
;
315 long batch_size
= shrinker
->batch
? shrinker
->batch
317 long scanned
= 0, next_deferred
;
319 freeable
= shrinker
->count_objects(shrinker
, shrinkctl
);
324 * copy the current shrinker scan count into a local variable
325 * and zero it so that other concurrent shrinker invocations
326 * don't also do this scanning work.
328 nr
= atomic_long_xchg(&shrinker
->nr_deferred
[nid
], 0);
331 delta
= (4 * nr_scanned
) / shrinker
->seeks
;
333 do_div(delta
, nr_eligible
+ 1);
335 if (total_scan
< 0) {
336 pr_err("shrink_slab: %pF negative objects to delete nr=%ld\n",
337 shrinker
->scan_objects
, total_scan
);
338 total_scan
= freeable
;
341 next_deferred
= total_scan
;
344 * We need to avoid excessive windup on filesystem shrinkers
345 * due to large numbers of GFP_NOFS allocations causing the
346 * shrinkers to return -1 all the time. This results in a large
347 * nr being built up so when a shrink that can do some work
348 * comes along it empties the entire cache due to nr >>>
349 * freeable. This is bad for sustaining a working set in
352 * Hence only allow the shrinker to scan the entire cache when
353 * a large delta change is calculated directly.
355 if (delta
< freeable
/ 4)
356 total_scan
= min(total_scan
, freeable
/ 2);
359 * Avoid risking looping forever due to too large nr value:
360 * never try to free more than twice the estimate number of
363 if (total_scan
> freeable
* 2)
364 total_scan
= freeable
* 2;
366 trace_mm_shrink_slab_start(shrinker
, shrinkctl
, nr
,
367 nr_scanned
, nr_eligible
,
368 freeable
, delta
, total_scan
);
371 * Normally, we should not scan less than batch_size objects in one
372 * pass to avoid too frequent shrinker calls, but if the slab has less
373 * than batch_size objects in total and we are really tight on memory,
374 * we will try to reclaim all available objects, otherwise we can end
375 * up failing allocations although there are plenty of reclaimable
376 * objects spread over several slabs with usage less than the
379 * We detect the "tight on memory" situations by looking at the total
380 * number of objects we want to scan (total_scan). If it is greater
381 * than the total number of objects on slab (freeable), we must be
382 * scanning at high prio and therefore should try to reclaim as much as
385 while (total_scan
>= batch_size
||
386 total_scan
>= freeable
) {
388 unsigned long nr_to_scan
= min(batch_size
, total_scan
);
390 shrinkctl
->nr_to_scan
= nr_to_scan
;
391 ret
= shrinker
->scan_objects(shrinker
, shrinkctl
);
392 if (ret
== SHRINK_STOP
)
396 count_vm_events(SLABS_SCANNED
, nr_to_scan
);
397 total_scan
-= nr_to_scan
;
398 scanned
+= nr_to_scan
;
403 if (next_deferred
>= scanned
)
404 next_deferred
-= scanned
;
408 * move the unused scan count back into the shrinker in a
409 * manner that handles concurrent updates. If we exhausted the
410 * scan, there is no need to do an update.
412 if (next_deferred
> 0)
413 new_nr
= atomic_long_add_return(next_deferred
,
414 &shrinker
->nr_deferred
[nid
]);
416 new_nr
= atomic_long_read(&shrinker
->nr_deferred
[nid
]);
418 trace_mm_shrink_slab_end(shrinker
, nid
, freed
, nr
, new_nr
, total_scan
);
423 * shrink_slab - shrink slab caches
424 * @gfp_mask: allocation context
425 * @nid: node whose slab caches to target
426 * @memcg: memory cgroup whose slab caches to target
427 * @nr_scanned: pressure numerator
428 * @nr_eligible: pressure denominator
430 * Call the shrink functions to age shrinkable caches.
432 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
433 * unaware shrinkers will receive a node id of 0 instead.
435 * @memcg specifies the memory cgroup to target. If it is not NULL,
436 * only shrinkers with SHRINKER_MEMCG_AWARE set will be called to scan
437 * objects from the memory cgroup specified. Otherwise, only unaware
438 * shrinkers are called.
440 * @nr_scanned and @nr_eligible form a ratio that indicate how much of
441 * the available objects should be scanned. Page reclaim for example
442 * passes the number of pages scanned and the number of pages on the
443 * LRU lists that it considered on @nid, plus a bias in @nr_scanned
444 * when it encountered mapped pages. The ratio is further biased by
445 * the ->seeks setting of the shrink function, which indicates the
446 * cost to recreate an object relative to that of an LRU page.
448 * Returns the number of reclaimed slab objects.
450 static unsigned long shrink_slab(gfp_t gfp_mask
, int nid
,
451 struct mem_cgroup
*memcg
,
452 unsigned long nr_scanned
,
453 unsigned long nr_eligible
)
455 struct shrinker
*shrinker
;
456 unsigned long freed
= 0;
458 if (memcg
&& (!memcg_kmem_enabled() || !mem_cgroup_online(memcg
)))
462 nr_scanned
= SWAP_CLUSTER_MAX
;
464 if (!down_read_trylock(&shrinker_rwsem
)) {
466 * If we would return 0, our callers would understand that we
467 * have nothing else to shrink and give up trying. By returning
468 * 1 we keep it going and assume we'll be able to shrink next
475 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
476 struct shrink_control sc
= {
477 .gfp_mask
= gfp_mask
,
483 * If kernel memory accounting is disabled, we ignore
484 * SHRINKER_MEMCG_AWARE flag and call all shrinkers
485 * passing NULL for memcg.
487 if (memcg_kmem_enabled() &&
488 !!memcg
!= !!(shrinker
->flags
& SHRINKER_MEMCG_AWARE
))
491 if (!(shrinker
->flags
& SHRINKER_NUMA_AWARE
))
494 freed
+= do_shrink_slab(&sc
, shrinker
, nr_scanned
, nr_eligible
);
497 up_read(&shrinker_rwsem
);
503 void drop_slab_node(int nid
)
508 struct mem_cgroup
*memcg
= NULL
;
512 freed
+= shrink_slab(GFP_KERNEL
, nid
, memcg
,
514 } while ((memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
)) != NULL
);
515 } while (freed
> 10);
522 for_each_online_node(nid
)
526 static inline int is_page_cache_freeable(struct page
*page
)
529 * A freeable page cache page is referenced only by the caller
530 * that isolated the page, the page cache radix tree and
531 * optional buffer heads at page->private.
533 return page_count(page
) - page_has_private(page
) == 2;
536 static int may_write_to_inode(struct inode
*inode
, struct scan_control
*sc
)
538 if (current
->flags
& PF_SWAPWRITE
)
540 if (!inode_write_congested(inode
))
542 if (inode_to_bdi(inode
) == current
->backing_dev_info
)
548 * We detected a synchronous write error writing a page out. Probably
549 * -ENOSPC. We need to propagate that into the address_space for a subsequent
550 * fsync(), msync() or close().
552 * The tricky part is that after writepage we cannot touch the mapping: nothing
553 * prevents it from being freed up. But we have a ref on the page and once
554 * that page is locked, the mapping is pinned.
556 * We're allowed to run sleeping lock_page() here because we know the caller has
559 static void handle_write_error(struct address_space
*mapping
,
560 struct page
*page
, int error
)
563 if (page_mapping(page
) == mapping
)
564 mapping_set_error(mapping
, error
);
568 /* possible outcome of pageout() */
570 /* failed to write page out, page is locked */
572 /* move page to the active list, page is locked */
574 /* page has been sent to the disk successfully, page is unlocked */
576 /* page is clean and locked */
581 * pageout is called by shrink_page_list() for each dirty page.
582 * Calls ->writepage().
584 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
585 struct scan_control
*sc
)
588 * If the page is dirty, only perform writeback if that write
589 * will be non-blocking. To prevent this allocation from being
590 * stalled by pagecache activity. But note that there may be
591 * stalls if we need to run get_block(). We could test
592 * PagePrivate for that.
594 * If this process is currently in __generic_file_write_iter() against
595 * this page's queue, we can perform writeback even if that
598 * If the page is swapcache, write it back even if that would
599 * block, for some throttling. This happens by accident, because
600 * swap_backing_dev_info is bust: it doesn't reflect the
601 * congestion state of the swapdevs. Easy to fix, if needed.
603 if (!is_page_cache_freeable(page
))
607 * Some data journaling orphaned pages can have
608 * page->mapping == NULL while being dirty with clean buffers.
610 if (page_has_private(page
)) {
611 if (try_to_free_buffers(page
)) {
612 ClearPageDirty(page
);
613 pr_info("%s: orphaned page\n", __func__
);
619 if (mapping
->a_ops
->writepage
== NULL
)
620 return PAGE_ACTIVATE
;
621 if (!may_write_to_inode(mapping
->host
, sc
))
624 if (clear_page_dirty_for_io(page
)) {
626 struct writeback_control wbc
= {
627 .sync_mode
= WB_SYNC_NONE
,
628 .nr_to_write
= SWAP_CLUSTER_MAX
,
630 .range_end
= LLONG_MAX
,
634 SetPageReclaim(page
);
635 res
= mapping
->a_ops
->writepage(page
, &wbc
);
637 handle_write_error(mapping
, page
, res
);
638 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
639 ClearPageReclaim(page
);
640 return PAGE_ACTIVATE
;
643 if (!PageWriteback(page
)) {
644 /* synchronous write or broken a_ops? */
645 ClearPageReclaim(page
);
647 trace_mm_vmscan_writepage(page
);
648 inc_node_page_state(page
, NR_VMSCAN_WRITE
);
656 * Same as remove_mapping, but if the page is removed from the mapping, it
657 * gets returned with a refcount of 0.
659 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
,
664 BUG_ON(!PageLocked(page
));
665 BUG_ON(mapping
!= page_mapping(page
));
667 spin_lock_irqsave(&mapping
->tree_lock
, flags
);
669 * The non racy check for a busy page.
671 * Must be careful with the order of the tests. When someone has
672 * a ref to the page, it may be possible that they dirty it then
673 * drop the reference. So if PageDirty is tested before page_count
674 * here, then the following race may occur:
676 * get_user_pages(&page);
677 * [user mapping goes away]
679 * !PageDirty(page) [good]
680 * SetPageDirty(page);
682 * !page_count(page) [good, discard it]
684 * [oops, our write_to data is lost]
686 * Reversing the order of the tests ensures such a situation cannot
687 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
688 * load is not satisfied before that of page->_refcount.
690 * Note that if SetPageDirty is always performed via set_page_dirty,
691 * and thus under tree_lock, then this ordering is not required.
693 if (!page_ref_freeze(page
, 2))
695 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
696 if (unlikely(PageDirty(page
))) {
697 page_ref_unfreeze(page
, 2);
701 if (PageSwapCache(page
)) {
702 swp_entry_t swap
= { .val
= page_private(page
) };
703 mem_cgroup_swapout(page
, swap
);
704 __delete_from_swap_cache(page
);
705 spin_unlock_irqrestore(&mapping
->tree_lock
, flags
);
706 swapcache_free(swap
);
708 void (*freepage
)(struct page
*);
711 freepage
= mapping
->a_ops
->freepage
;
713 * Remember a shadow entry for reclaimed file cache in
714 * order to detect refaults, thus thrashing, later on.
716 * But don't store shadows in an address space that is
717 * already exiting. This is not just an optizimation,
718 * inode reclaim needs to empty out the radix tree or
719 * the nodes are lost. Don't plant shadows behind its
722 * We also don't store shadows for DAX mappings because the
723 * only page cache pages found in these are zero pages
724 * covering holes, and because we don't want to mix DAX
725 * exceptional entries and shadow exceptional entries in the
728 if (reclaimed
&& page_is_file_cache(page
) &&
729 !mapping_exiting(mapping
) && !dax_mapping(mapping
))
730 shadow
= workingset_eviction(mapping
, page
);
731 __delete_from_page_cache(page
, shadow
);
732 spin_unlock_irqrestore(&mapping
->tree_lock
, flags
);
734 if (freepage
!= NULL
)
741 spin_unlock_irqrestore(&mapping
->tree_lock
, flags
);
746 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
747 * someone else has a ref on the page, abort and return 0. If it was
748 * successfully detached, return 1. Assumes the caller has a single ref on
751 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
753 if (__remove_mapping(mapping
, page
, false)) {
755 * Unfreezing the refcount with 1 rather than 2 effectively
756 * drops the pagecache ref for us without requiring another
759 page_ref_unfreeze(page
, 1);
766 * putback_lru_page - put previously isolated page onto appropriate LRU list
767 * @page: page to be put back to appropriate lru list
769 * Add previously isolated @page to appropriate LRU list.
770 * Page may still be unevictable for other reasons.
772 * lru_lock must not be held, interrupts must be enabled.
774 void putback_lru_page(struct page
*page
)
777 int was_unevictable
= PageUnevictable(page
);
779 VM_BUG_ON_PAGE(PageLRU(page
), page
);
782 ClearPageUnevictable(page
);
784 if (page_evictable(page
)) {
786 * For evictable pages, we can use the cache.
787 * In event of a race, worst case is we end up with an
788 * unevictable page on [in]active list.
789 * We know how to handle that.
791 is_unevictable
= false;
795 * Put unevictable pages directly on zone's unevictable
798 is_unevictable
= true;
799 add_page_to_unevictable_list(page
);
801 * When racing with an mlock or AS_UNEVICTABLE clearing
802 * (page is unlocked) make sure that if the other thread
803 * does not observe our setting of PG_lru and fails
804 * isolation/check_move_unevictable_pages,
805 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
806 * the page back to the evictable list.
808 * The other side is TestClearPageMlocked() or shmem_lock().
814 * page's status can change while we move it among lru. If an evictable
815 * page is on unevictable list, it never be freed. To avoid that,
816 * check after we added it to the list, again.
818 if (is_unevictable
&& page_evictable(page
)) {
819 if (!isolate_lru_page(page
)) {
823 /* This means someone else dropped this page from LRU
824 * So, it will be freed or putback to LRU again. There is
825 * nothing to do here.
829 if (was_unevictable
&& !is_unevictable
)
830 count_vm_event(UNEVICTABLE_PGRESCUED
);
831 else if (!was_unevictable
&& is_unevictable
)
832 count_vm_event(UNEVICTABLE_PGCULLED
);
834 put_page(page
); /* drop ref from isolate */
837 enum page_references
{
839 PAGEREF_RECLAIM_CLEAN
,
844 static enum page_references
page_check_references(struct page
*page
,
845 struct scan_control
*sc
)
847 int referenced_ptes
, referenced_page
;
848 unsigned long vm_flags
;
850 referenced_ptes
= page_referenced(page
, 1, sc
->target_mem_cgroup
,
852 referenced_page
= TestClearPageReferenced(page
);
855 * Mlock lost the isolation race with us. Let try_to_unmap()
856 * move the page to the unevictable list.
858 if (vm_flags
& VM_LOCKED
)
859 return PAGEREF_RECLAIM
;
861 if (referenced_ptes
) {
862 if (PageSwapBacked(page
))
863 return PAGEREF_ACTIVATE
;
865 * All mapped pages start out with page table
866 * references from the instantiating fault, so we need
867 * to look twice if a mapped file page is used more
870 * Mark it and spare it for another trip around the
871 * inactive list. Another page table reference will
872 * lead to its activation.
874 * Note: the mark is set for activated pages as well
875 * so that recently deactivated but used pages are
878 SetPageReferenced(page
);
880 if (referenced_page
|| referenced_ptes
> 1)
881 return PAGEREF_ACTIVATE
;
884 * Activate file-backed executable pages after first usage.
886 if (vm_flags
& VM_EXEC
)
887 return PAGEREF_ACTIVATE
;
892 /* Reclaim if clean, defer dirty pages to writeback */
893 if (referenced_page
&& !PageSwapBacked(page
))
894 return PAGEREF_RECLAIM_CLEAN
;
896 return PAGEREF_RECLAIM
;
899 /* Check if a page is dirty or under writeback */
900 static void page_check_dirty_writeback(struct page
*page
,
901 bool *dirty
, bool *writeback
)
903 struct address_space
*mapping
;
906 * Anonymous pages are not handled by flushers and must be written
907 * from reclaim context. Do not stall reclaim based on them
909 if (!page_is_file_cache(page
) ||
910 (PageAnon(page
) && !PageSwapBacked(page
))) {
916 /* By default assume that the page flags are accurate */
917 *dirty
= PageDirty(page
);
918 *writeback
= PageWriteback(page
);
920 /* Verify dirty/writeback state if the filesystem supports it */
921 if (!page_has_private(page
))
924 mapping
= page_mapping(page
);
925 if (mapping
&& mapping
->a_ops
->is_dirty_writeback
)
926 mapping
->a_ops
->is_dirty_writeback(page
, dirty
, writeback
);
929 struct reclaim_stat
{
931 unsigned nr_unqueued_dirty
;
932 unsigned nr_congested
;
933 unsigned nr_writeback
;
934 unsigned nr_immediate
;
935 unsigned nr_activate
;
936 unsigned nr_ref_keep
;
937 unsigned nr_unmap_fail
;
941 * shrink_page_list() returns the number of reclaimed pages
943 static unsigned long shrink_page_list(struct list_head
*page_list
,
944 struct pglist_data
*pgdat
,
945 struct scan_control
*sc
,
946 enum ttu_flags ttu_flags
,
947 struct reclaim_stat
*stat
,
950 LIST_HEAD(ret_pages
);
951 LIST_HEAD(free_pages
);
953 unsigned nr_unqueued_dirty
= 0;
954 unsigned nr_dirty
= 0;
955 unsigned nr_congested
= 0;
956 unsigned nr_reclaimed
= 0;
957 unsigned nr_writeback
= 0;
958 unsigned nr_immediate
= 0;
959 unsigned nr_ref_keep
= 0;
960 unsigned nr_unmap_fail
= 0;
964 while (!list_empty(page_list
)) {
965 struct address_space
*mapping
;
968 enum page_references references
= PAGEREF_RECLAIM_CLEAN
;
969 bool dirty
, writeback
;
970 int ret
= SWAP_SUCCESS
;
974 page
= lru_to_page(page_list
);
975 list_del(&page
->lru
);
977 if (!trylock_page(page
))
980 VM_BUG_ON_PAGE(PageActive(page
), page
);
984 if (unlikely(!page_evictable(page
)))
987 if (!sc
->may_unmap
&& page_mapped(page
))
990 /* Double the slab pressure for mapped and swapcache pages */
991 if ((page_mapped(page
) || PageSwapCache(page
)) &&
992 !(PageAnon(page
) && !PageSwapBacked(page
)))
995 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
996 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
999 * The number of dirty pages determines if a zone is marked
1000 * reclaim_congested which affects wait_iff_congested. kswapd
1001 * will stall and start writing pages if the tail of the LRU
1002 * is all dirty unqueued pages.
1004 page_check_dirty_writeback(page
, &dirty
, &writeback
);
1005 if (dirty
|| writeback
)
1008 if (dirty
&& !writeback
)
1009 nr_unqueued_dirty
++;
1012 * Treat this page as congested if the underlying BDI is or if
1013 * pages are cycling through the LRU so quickly that the
1014 * pages marked for immediate reclaim are making it to the
1015 * end of the LRU a second time.
1017 mapping
= page_mapping(page
);
1018 if (((dirty
|| writeback
) && mapping
&&
1019 inode_write_congested(mapping
->host
)) ||
1020 (writeback
&& PageReclaim(page
)))
1024 * If a page at the tail of the LRU is under writeback, there
1025 * are three cases to consider.
1027 * 1) If reclaim is encountering an excessive number of pages
1028 * under writeback and this page is both under writeback and
1029 * PageReclaim then it indicates that pages are being queued
1030 * for IO but are being recycled through the LRU before the
1031 * IO can complete. Waiting on the page itself risks an
1032 * indefinite stall if it is impossible to writeback the
1033 * page due to IO error or disconnected storage so instead
1034 * note that the LRU is being scanned too quickly and the
1035 * caller can stall after page list has been processed.
1037 * 2) Global or new memcg reclaim encounters a page that is
1038 * not marked for immediate reclaim, or the caller does not
1039 * have __GFP_FS (or __GFP_IO if it's simply going to swap,
1040 * not to fs). In this case mark the page for immediate
1041 * reclaim and continue scanning.
1043 * Require may_enter_fs because we would wait on fs, which
1044 * may not have submitted IO yet. And the loop driver might
1045 * enter reclaim, and deadlock if it waits on a page for
1046 * which it is needed to do the write (loop masks off
1047 * __GFP_IO|__GFP_FS for this reason); but more thought
1048 * would probably show more reasons.
1050 * 3) Legacy memcg encounters a page that is already marked
1051 * PageReclaim. memcg does not have any dirty pages
1052 * throttling so we could easily OOM just because too many
1053 * pages are in writeback and there is nothing else to
1054 * reclaim. Wait for the writeback to complete.
1056 * In cases 1) and 2) we activate the pages to get them out of
1057 * the way while we continue scanning for clean pages on the
1058 * inactive list and refilling from the active list. The
1059 * observation here is that waiting for disk writes is more
1060 * expensive than potentially causing reloads down the line.
1061 * Since they're marked for immediate reclaim, they won't put
1062 * memory pressure on the cache working set any longer than it
1063 * takes to write them to disk.
1065 if (PageWriteback(page
)) {
1067 if (current_is_kswapd() &&
1068 PageReclaim(page
) &&
1069 test_bit(PGDAT_WRITEBACK
, &pgdat
->flags
)) {
1071 goto activate_locked
;
1074 } else if (sane_reclaim(sc
) ||
1075 !PageReclaim(page
) || !may_enter_fs
) {
1077 * This is slightly racy - end_page_writeback()
1078 * might have just cleared PageReclaim, then
1079 * setting PageReclaim here end up interpreted
1080 * as PageReadahead - but that does not matter
1081 * enough to care. What we do want is for this
1082 * page to have PageReclaim set next time memcg
1083 * reclaim reaches the tests above, so it will
1084 * then wait_on_page_writeback() to avoid OOM;
1085 * and it's also appropriate in global reclaim.
1087 SetPageReclaim(page
);
1089 goto activate_locked
;
1094 wait_on_page_writeback(page
);
1095 /* then go back and try same page again */
1096 list_add_tail(&page
->lru
, page_list
);
1102 references
= page_check_references(page
, sc
);
1104 switch (references
) {
1105 case PAGEREF_ACTIVATE
:
1106 goto activate_locked
;
1110 case PAGEREF_RECLAIM
:
1111 case PAGEREF_RECLAIM_CLEAN
:
1112 ; /* try to reclaim the page below */
1116 * Anonymous process memory has backing store?
1117 * Try to allocate it some swap space here.
1118 * Lazyfree page could be freed directly
1120 if (PageAnon(page
) && PageSwapBacked(page
) &&
1121 !PageSwapCache(page
)) {
1122 if (!(sc
->gfp_mask
& __GFP_IO
))
1124 if (!add_to_swap(page
, page_list
))
1125 goto activate_locked
;
1128 /* Adding to swap updated mapping */
1129 mapping
= page_mapping(page
);
1130 } else if (unlikely(PageTransHuge(page
))) {
1131 /* Split file THP */
1132 if (split_huge_page_to_list(page
, page_list
))
1136 VM_BUG_ON_PAGE(PageTransHuge(page
), page
);
1139 * The page is mapped into the page tables of one or more
1140 * processes. Try to unmap it here.
1142 if (page_mapped(page
)) {
1143 switch (ret
= try_to_unmap(page
,
1144 ttu_flags
| TTU_BATCH_FLUSH
)) {
1146 SetPageSwapBacked(page
);
1150 goto activate_locked
;
1156 ; /* try to free the page below */
1160 if (PageDirty(page
)) {
1162 * Only kswapd can writeback filesystem pages
1163 * to avoid risk of stack overflow. But avoid
1164 * injecting inefficient single-page IO into
1165 * flusher writeback as much as possible: only
1166 * write pages when we've encountered many
1167 * dirty pages, and when we've already scanned
1168 * the rest of the LRU for clean pages and see
1169 * the same dirty pages again (PageReclaim).
1171 if (page_is_file_cache(page
) &&
1172 (!current_is_kswapd() || !PageReclaim(page
) ||
1173 !test_bit(PGDAT_DIRTY
, &pgdat
->flags
))) {
1175 * Immediately reclaim when written back.
1176 * Similar in principal to deactivate_page()
1177 * except we already have the page isolated
1178 * and know it's dirty
1180 inc_node_page_state(page
, NR_VMSCAN_IMMEDIATE
);
1181 SetPageReclaim(page
);
1183 goto activate_locked
;
1186 if (references
== PAGEREF_RECLAIM_CLEAN
)
1190 if (!sc
->may_writepage
)
1194 * Page is dirty. Flush the TLB if a writable entry
1195 * potentially exists to avoid CPU writes after IO
1196 * starts and then write it out here.
1198 try_to_unmap_flush_dirty();
1199 switch (pageout(page
, mapping
, sc
)) {
1203 goto activate_locked
;
1205 if (PageWriteback(page
))
1207 if (PageDirty(page
))
1211 * A synchronous write - probably a ramdisk. Go
1212 * ahead and try to reclaim the page.
1214 if (!trylock_page(page
))
1216 if (PageDirty(page
) || PageWriteback(page
))
1218 mapping
= page_mapping(page
);
1220 ; /* try to free the page below */
1225 * If the page has buffers, try to free the buffer mappings
1226 * associated with this page. If we succeed we try to free
1229 * We do this even if the page is PageDirty().
1230 * try_to_release_page() does not perform I/O, but it is
1231 * possible for a page to have PageDirty set, but it is actually
1232 * clean (all its buffers are clean). This happens if the
1233 * buffers were written out directly, with submit_bh(). ext3
1234 * will do this, as well as the blockdev mapping.
1235 * try_to_release_page() will discover that cleanness and will
1236 * drop the buffers and mark the page clean - it can be freed.
1238 * Rarely, pages can have buffers and no ->mapping. These are
1239 * the pages which were not successfully invalidated in
1240 * truncate_complete_page(). We try to drop those buffers here
1241 * and if that worked, and the page is no longer mapped into
1242 * process address space (page_count == 1) it can be freed.
1243 * Otherwise, leave the page on the LRU so it is swappable.
1245 if (page_has_private(page
)) {
1246 if (!try_to_release_page(page
, sc
->gfp_mask
))
1247 goto activate_locked
;
1248 if (!mapping
&& page_count(page
) == 1) {
1250 if (put_page_testzero(page
))
1254 * rare race with speculative reference.
1255 * the speculative reference will free
1256 * this page shortly, so we may
1257 * increment nr_reclaimed here (and
1258 * leave it off the LRU).
1266 if (PageAnon(page
) && !PageSwapBacked(page
)) {
1267 /* follow __remove_mapping for reference */
1268 if (!page_ref_freeze(page
, 1))
1270 if (PageDirty(page
)) {
1271 page_ref_unfreeze(page
, 1);
1275 count_vm_event(PGLAZYFREED
);
1276 } else if (!mapping
|| !__remove_mapping(mapping
, page
, true))
1279 * At this point, we have no other references and there is
1280 * no way to pick any more up (removed from LRU, removed
1281 * from pagecache). Can use non-atomic bitops now (and
1282 * we obviously don't have to worry about waking up a process
1283 * waiting on the page lock, because there are no references.
1285 __ClearPageLocked(page
);
1290 * Is there need to periodically free_page_list? It would
1291 * appear not as the counts should be low
1293 list_add(&page
->lru
, &free_pages
);
1297 if (PageSwapCache(page
))
1298 try_to_free_swap(page
);
1300 list_add(&page
->lru
, &ret_pages
);
1304 /* Not a candidate for swapping, so reclaim swap space. */
1305 if (PageSwapCache(page
) && mem_cgroup_swap_full(page
))
1306 try_to_free_swap(page
);
1307 VM_BUG_ON_PAGE(PageActive(page
), page
);
1308 SetPageActive(page
);
1313 list_add(&page
->lru
, &ret_pages
);
1314 VM_BUG_ON_PAGE(PageLRU(page
) || PageUnevictable(page
), page
);
1317 mem_cgroup_uncharge_list(&free_pages
);
1318 try_to_unmap_flush();
1319 free_hot_cold_page_list(&free_pages
, true);
1321 list_splice(&ret_pages
, page_list
);
1322 count_vm_events(PGACTIVATE
, pgactivate
);
1325 stat
->nr_dirty
= nr_dirty
;
1326 stat
->nr_congested
= nr_congested
;
1327 stat
->nr_unqueued_dirty
= nr_unqueued_dirty
;
1328 stat
->nr_writeback
= nr_writeback
;
1329 stat
->nr_immediate
= nr_immediate
;
1330 stat
->nr_activate
= pgactivate
;
1331 stat
->nr_ref_keep
= nr_ref_keep
;
1332 stat
->nr_unmap_fail
= nr_unmap_fail
;
1334 return nr_reclaimed
;
1337 unsigned long reclaim_clean_pages_from_list(struct zone
*zone
,
1338 struct list_head
*page_list
)
1340 struct scan_control sc
= {
1341 .gfp_mask
= GFP_KERNEL
,
1342 .priority
= DEF_PRIORITY
,
1346 struct page
*page
, *next
;
1347 LIST_HEAD(clean_pages
);
1349 list_for_each_entry_safe(page
, next
, page_list
, lru
) {
1350 if (page_is_file_cache(page
) && !PageDirty(page
) &&
1351 !__PageMovable(page
)) {
1352 ClearPageActive(page
);
1353 list_move(&page
->lru
, &clean_pages
);
1357 ret
= shrink_page_list(&clean_pages
, zone
->zone_pgdat
, &sc
,
1358 TTU_IGNORE_ACCESS
, NULL
, true);
1359 list_splice(&clean_pages
, page_list
);
1360 mod_node_page_state(zone
->zone_pgdat
, NR_ISOLATED_FILE
, -ret
);
1365 * Attempt to remove the specified page from its LRU. Only take this page
1366 * if it is of the appropriate PageActive status. Pages which are being
1367 * freed elsewhere are also ignored.
1369 * page: page to consider
1370 * mode: one of the LRU isolation modes defined above
1372 * returns 0 on success, -ve errno on failure.
1374 int __isolate_lru_page(struct page
*page
, isolate_mode_t mode
)
1378 /* Only take pages on the LRU. */
1382 /* Compaction should not handle unevictable pages but CMA can do so */
1383 if (PageUnevictable(page
) && !(mode
& ISOLATE_UNEVICTABLE
))
1389 * To minimise LRU disruption, the caller can indicate that it only
1390 * wants to isolate pages it will be able to operate on without
1391 * blocking - clean pages for the most part.
1393 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1394 * that it is possible to migrate without blocking
1396 if (mode
& ISOLATE_ASYNC_MIGRATE
) {
1397 /* All the caller can do on PageWriteback is block */
1398 if (PageWriteback(page
))
1401 if (PageDirty(page
)) {
1402 struct address_space
*mapping
;
1405 * Only pages without mappings or that have a
1406 * ->migratepage callback are possible to migrate
1409 mapping
= page_mapping(page
);
1410 if (mapping
&& !mapping
->a_ops
->migratepage
)
1415 if ((mode
& ISOLATE_UNMAPPED
) && page_mapped(page
))
1418 if (likely(get_page_unless_zero(page
))) {
1420 * Be careful not to clear PageLRU until after we're
1421 * sure the page is not being freed elsewhere -- the
1422 * page release code relies on it.
1433 * Update LRU sizes after isolating pages. The LRU size updates must
1434 * be complete before mem_cgroup_update_lru_size due to a santity check.
1436 static __always_inline
void update_lru_sizes(struct lruvec
*lruvec
,
1437 enum lru_list lru
, unsigned long *nr_zone_taken
)
1441 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++) {
1442 if (!nr_zone_taken
[zid
])
1445 __update_lru_size(lruvec
, lru
, zid
, -nr_zone_taken
[zid
]);
1447 mem_cgroup_update_lru_size(lruvec
, lru
, zid
, -nr_zone_taken
[zid
]);
1454 * zone_lru_lock is heavily contended. Some of the functions that
1455 * shrink the lists perform better by taking out a batch of pages
1456 * and working on them outside the LRU lock.
1458 * For pagecache intensive workloads, this function is the hottest
1459 * spot in the kernel (apart from copy_*_user functions).
1461 * Appropriate locks must be held before calling this function.
1463 * @nr_to_scan: The number of pages to look through on the list.
1464 * @lruvec: The LRU vector to pull pages from.
1465 * @dst: The temp list to put pages on to.
1466 * @nr_scanned: The number of pages that were scanned.
1467 * @sc: The scan_control struct for this reclaim session
1468 * @mode: One of the LRU isolation modes
1469 * @lru: LRU list id for isolating
1471 * returns how many pages were moved onto *@dst.
1473 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1474 struct lruvec
*lruvec
, struct list_head
*dst
,
1475 unsigned long *nr_scanned
, struct scan_control
*sc
,
1476 isolate_mode_t mode
, enum lru_list lru
)
1478 struct list_head
*src
= &lruvec
->lists
[lru
];
1479 unsigned long nr_taken
= 0;
1480 unsigned long nr_zone_taken
[MAX_NR_ZONES
] = { 0 };
1481 unsigned long nr_skipped
[MAX_NR_ZONES
] = { 0, };
1482 unsigned long skipped
= 0;
1483 unsigned long scan
, nr_pages
;
1484 LIST_HEAD(pages_skipped
);
1486 for (scan
= 0; scan
< nr_to_scan
&& nr_taken
< nr_to_scan
&&
1487 !list_empty(src
); scan
++) {
1490 page
= lru_to_page(src
);
1491 prefetchw_prev_lru_page(page
, src
, flags
);
1493 VM_BUG_ON_PAGE(!PageLRU(page
), page
);
1495 if (page_zonenum(page
) > sc
->reclaim_idx
) {
1496 list_move(&page
->lru
, &pages_skipped
);
1497 nr_skipped
[page_zonenum(page
)]++;
1501 switch (__isolate_lru_page(page
, mode
)) {
1503 nr_pages
= hpage_nr_pages(page
);
1504 nr_taken
+= nr_pages
;
1505 nr_zone_taken
[page_zonenum(page
)] += nr_pages
;
1506 list_move(&page
->lru
, dst
);
1510 /* else it is being freed elsewhere */
1511 list_move(&page
->lru
, src
);
1520 * Splice any skipped pages to the start of the LRU list. Note that
1521 * this disrupts the LRU order when reclaiming for lower zones but
1522 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
1523 * scanning would soon rescan the same pages to skip and put the
1524 * system at risk of premature OOM.
1526 if (!list_empty(&pages_skipped
)) {
1529 list_splice(&pages_skipped
, src
);
1530 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++) {
1531 if (!nr_skipped
[zid
])
1534 __count_zid_vm_events(PGSCAN_SKIP
, zid
, nr_skipped
[zid
]);
1535 skipped
+= nr_skipped
[zid
];
1539 trace_mm_vmscan_lru_isolate(sc
->reclaim_idx
, sc
->order
, nr_to_scan
,
1540 scan
, skipped
, nr_taken
, mode
, lru
);
1541 update_lru_sizes(lruvec
, lru
, nr_zone_taken
);
1546 * isolate_lru_page - tries to isolate a page from its LRU list
1547 * @page: page to isolate from its LRU list
1549 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1550 * vmstat statistic corresponding to whatever LRU list the page was on.
1552 * Returns 0 if the page was removed from an LRU list.
1553 * Returns -EBUSY if the page was not on an LRU list.
1555 * The returned page will have PageLRU() cleared. If it was found on
1556 * the active list, it will have PageActive set. If it was found on
1557 * the unevictable list, it will have the PageUnevictable bit set. That flag
1558 * may need to be cleared by the caller before letting the page go.
1560 * The vmstat statistic corresponding to the list on which the page was
1561 * found will be decremented.
1564 * (1) Must be called with an elevated refcount on the page. This is a
1565 * fundamentnal difference from isolate_lru_pages (which is called
1566 * without a stable reference).
1567 * (2) the lru_lock must not be held.
1568 * (3) interrupts must be enabled.
1570 int isolate_lru_page(struct page
*page
)
1574 VM_BUG_ON_PAGE(!page_count(page
), page
);
1575 WARN_RATELIMIT(PageTail(page
), "trying to isolate tail page");
1577 if (PageLRU(page
)) {
1578 struct zone
*zone
= page_zone(page
);
1579 struct lruvec
*lruvec
;
1581 spin_lock_irq(zone_lru_lock(zone
));
1582 lruvec
= mem_cgroup_page_lruvec(page
, zone
->zone_pgdat
);
1583 if (PageLRU(page
)) {
1584 int lru
= page_lru(page
);
1587 del_page_from_lru_list(page
, lruvec
, lru
);
1590 spin_unlock_irq(zone_lru_lock(zone
));
1596 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1597 * then get resheduled. When there are massive number of tasks doing page
1598 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1599 * the LRU list will go small and be scanned faster than necessary, leading to
1600 * unnecessary swapping, thrashing and OOM.
1602 static int too_many_isolated(struct pglist_data
*pgdat
, int file
,
1603 struct scan_control
*sc
)
1605 unsigned long inactive
, isolated
;
1607 if (current_is_kswapd())
1610 if (!sane_reclaim(sc
))
1614 inactive
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
1615 isolated
= node_page_state(pgdat
, NR_ISOLATED_FILE
);
1617 inactive
= node_page_state(pgdat
, NR_INACTIVE_ANON
);
1618 isolated
= node_page_state(pgdat
, NR_ISOLATED_ANON
);
1622 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1623 * won't get blocked by normal direct-reclaimers, forming a circular
1626 if ((sc
->gfp_mask
& (__GFP_IO
| __GFP_FS
)) == (__GFP_IO
| __GFP_FS
))
1629 return isolated
> inactive
;
1632 static noinline_for_stack
void
1633 putback_inactive_pages(struct lruvec
*lruvec
, struct list_head
*page_list
)
1635 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1636 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
1637 LIST_HEAD(pages_to_free
);
1640 * Put back any unfreeable pages.
1642 while (!list_empty(page_list
)) {
1643 struct page
*page
= lru_to_page(page_list
);
1646 VM_BUG_ON_PAGE(PageLRU(page
), page
);
1647 list_del(&page
->lru
);
1648 if (unlikely(!page_evictable(page
))) {
1649 spin_unlock_irq(&pgdat
->lru_lock
);
1650 putback_lru_page(page
);
1651 spin_lock_irq(&pgdat
->lru_lock
);
1655 lruvec
= mem_cgroup_page_lruvec(page
, pgdat
);
1658 lru
= page_lru(page
);
1659 add_page_to_lru_list(page
, lruvec
, lru
);
1661 if (is_active_lru(lru
)) {
1662 int file
= is_file_lru(lru
);
1663 int numpages
= hpage_nr_pages(page
);
1664 reclaim_stat
->recent_rotated
[file
] += numpages
;
1666 if (put_page_testzero(page
)) {
1667 __ClearPageLRU(page
);
1668 __ClearPageActive(page
);
1669 del_page_from_lru_list(page
, lruvec
, lru
);
1671 if (unlikely(PageCompound(page
))) {
1672 spin_unlock_irq(&pgdat
->lru_lock
);
1673 mem_cgroup_uncharge(page
);
1674 (*get_compound_page_dtor(page
))(page
);
1675 spin_lock_irq(&pgdat
->lru_lock
);
1677 list_add(&page
->lru
, &pages_to_free
);
1682 * To save our caller's stack, now use input list for pages to free.
1684 list_splice(&pages_to_free
, page_list
);
1688 * If a kernel thread (such as nfsd for loop-back mounts) services
1689 * a backing device by writing to the page cache it sets PF_LESS_THROTTLE.
1690 * In that case we should only throttle if the backing device it is
1691 * writing to is congested. In other cases it is safe to throttle.
1693 static int current_may_throttle(void)
1695 return !(current
->flags
& PF_LESS_THROTTLE
) ||
1696 current
->backing_dev_info
== NULL
||
1697 bdi_write_congested(current
->backing_dev_info
);
1701 * shrink_inactive_list() is a helper for shrink_node(). It returns the number
1702 * of reclaimed pages
1704 static noinline_for_stack
unsigned long
1705 shrink_inactive_list(unsigned long nr_to_scan
, struct lruvec
*lruvec
,
1706 struct scan_control
*sc
, enum lru_list lru
)
1708 LIST_HEAD(page_list
);
1709 unsigned long nr_scanned
;
1710 unsigned long nr_reclaimed
= 0;
1711 unsigned long nr_taken
;
1712 struct reclaim_stat stat
= {};
1713 isolate_mode_t isolate_mode
= 0;
1714 int file
= is_file_lru(lru
);
1715 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
1716 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1718 while (unlikely(too_many_isolated(pgdat
, file
, sc
))) {
1719 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1721 /* We are about to die and free our memory. Return now. */
1722 if (fatal_signal_pending(current
))
1723 return SWAP_CLUSTER_MAX
;
1729 isolate_mode
|= ISOLATE_UNMAPPED
;
1731 spin_lock_irq(&pgdat
->lru_lock
);
1733 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &page_list
,
1734 &nr_scanned
, sc
, isolate_mode
, lru
);
1736 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1737 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1739 if (global_reclaim(sc
)) {
1740 if (current_is_kswapd())
1741 __count_vm_events(PGSCAN_KSWAPD
, nr_scanned
);
1743 __count_vm_events(PGSCAN_DIRECT
, nr_scanned
);
1745 spin_unlock_irq(&pgdat
->lru_lock
);
1750 nr_reclaimed
= shrink_page_list(&page_list
, pgdat
, sc
, 0,
1753 spin_lock_irq(&pgdat
->lru_lock
);
1755 if (global_reclaim(sc
)) {
1756 if (current_is_kswapd())
1757 __count_vm_events(PGSTEAL_KSWAPD
, nr_reclaimed
);
1759 __count_vm_events(PGSTEAL_DIRECT
, nr_reclaimed
);
1762 putback_inactive_pages(lruvec
, &page_list
);
1764 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1766 spin_unlock_irq(&pgdat
->lru_lock
);
1768 mem_cgroup_uncharge_list(&page_list
);
1769 free_hot_cold_page_list(&page_list
, true);
1772 * If reclaim is isolating dirty pages under writeback, it implies
1773 * that the long-lived page allocation rate is exceeding the page
1774 * laundering rate. Either the global limits are not being effective
1775 * at throttling processes due to the page distribution throughout
1776 * zones or there is heavy usage of a slow backing device. The
1777 * only option is to throttle from reclaim context which is not ideal
1778 * as there is no guarantee the dirtying process is throttled in the
1779 * same way balance_dirty_pages() manages.
1781 * Once a zone is flagged ZONE_WRITEBACK, kswapd will count the number
1782 * of pages under pages flagged for immediate reclaim and stall if any
1783 * are encountered in the nr_immediate check below.
1785 if (stat
.nr_writeback
&& stat
.nr_writeback
== nr_taken
)
1786 set_bit(PGDAT_WRITEBACK
, &pgdat
->flags
);
1789 * Legacy memcg will stall in page writeback so avoid forcibly
1792 if (sane_reclaim(sc
)) {
1794 * Tag a zone as congested if all the dirty pages scanned were
1795 * backed by a congested BDI and wait_iff_congested will stall.
1797 if (stat
.nr_dirty
&& stat
.nr_dirty
== stat
.nr_congested
)
1798 set_bit(PGDAT_CONGESTED
, &pgdat
->flags
);
1801 * If dirty pages are scanned that are not queued for IO, it
1802 * implies that flushers are not doing their job. This can
1803 * happen when memory pressure pushes dirty pages to the end of
1804 * the LRU before the dirty limits are breached and the dirty
1805 * data has expired. It can also happen when the proportion of
1806 * dirty pages grows not through writes but through memory
1807 * pressure reclaiming all the clean cache. And in some cases,
1808 * the flushers simply cannot keep up with the allocation
1809 * rate. Nudge the flusher threads in case they are asleep, but
1810 * also allow kswapd to start writing pages during reclaim.
1812 if (stat
.nr_unqueued_dirty
== nr_taken
) {
1813 wakeup_flusher_threads(0, WB_REASON_VMSCAN
);
1814 set_bit(PGDAT_DIRTY
, &pgdat
->flags
);
1818 * If kswapd scans pages marked marked for immediate
1819 * reclaim and under writeback (nr_immediate), it implies
1820 * that pages are cycling through the LRU faster than
1821 * they are written so also forcibly stall.
1823 if (stat
.nr_immediate
&& current_may_throttle())
1824 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1828 * Stall direct reclaim for IO completions if underlying BDIs or zone
1829 * is congested. Allow kswapd to continue until it starts encountering
1830 * unqueued dirty pages or cycling through the LRU too quickly.
1832 if (!sc
->hibernation_mode
&& !current_is_kswapd() &&
1833 current_may_throttle())
1834 wait_iff_congested(pgdat
, BLK_RW_ASYNC
, HZ
/10);
1836 trace_mm_vmscan_lru_shrink_inactive(pgdat
->node_id
,
1837 nr_scanned
, nr_reclaimed
,
1838 stat
.nr_dirty
, stat
.nr_writeback
,
1839 stat
.nr_congested
, stat
.nr_immediate
,
1840 stat
.nr_activate
, stat
.nr_ref_keep
,
1842 sc
->priority
, file
);
1843 return nr_reclaimed
;
1847 * This moves pages from the active list to the inactive list.
1849 * We move them the other way if the page is referenced by one or more
1850 * processes, from rmap.
1852 * If the pages are mostly unmapped, the processing is fast and it is
1853 * appropriate to hold zone_lru_lock across the whole operation. But if
1854 * the pages are mapped, the processing is slow (page_referenced()) so we
1855 * should drop zone_lru_lock around each page. It's impossible to balance
1856 * this, so instead we remove the pages from the LRU while processing them.
1857 * It is safe to rely on PG_active against the non-LRU pages in here because
1858 * nobody will play with that bit on a non-LRU page.
1860 * The downside is that we have to touch page->_refcount against each page.
1861 * But we had to alter page->flags anyway.
1863 * Returns the number of pages moved to the given lru.
1866 static unsigned move_active_pages_to_lru(struct lruvec
*lruvec
,
1867 struct list_head
*list
,
1868 struct list_head
*pages_to_free
,
1871 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
1876 while (!list_empty(list
)) {
1877 page
= lru_to_page(list
);
1878 lruvec
= mem_cgroup_page_lruvec(page
, pgdat
);
1880 VM_BUG_ON_PAGE(PageLRU(page
), page
);
1883 nr_pages
= hpage_nr_pages(page
);
1884 update_lru_size(lruvec
, lru
, page_zonenum(page
), nr_pages
);
1885 list_move(&page
->lru
, &lruvec
->lists
[lru
]);
1887 if (put_page_testzero(page
)) {
1888 __ClearPageLRU(page
);
1889 __ClearPageActive(page
);
1890 del_page_from_lru_list(page
, lruvec
, lru
);
1892 if (unlikely(PageCompound(page
))) {
1893 spin_unlock_irq(&pgdat
->lru_lock
);
1894 mem_cgroup_uncharge(page
);
1895 (*get_compound_page_dtor(page
))(page
);
1896 spin_lock_irq(&pgdat
->lru_lock
);
1898 list_add(&page
->lru
, pages_to_free
);
1900 nr_moved
+= nr_pages
;
1904 if (!is_active_lru(lru
))
1905 __count_vm_events(PGDEACTIVATE
, nr_moved
);
1910 static void shrink_active_list(unsigned long nr_to_scan
,
1911 struct lruvec
*lruvec
,
1912 struct scan_control
*sc
,
1915 unsigned long nr_taken
;
1916 unsigned long nr_scanned
;
1917 unsigned long vm_flags
;
1918 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1919 LIST_HEAD(l_active
);
1920 LIST_HEAD(l_inactive
);
1922 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1923 unsigned nr_deactivate
, nr_activate
;
1924 unsigned nr_rotated
= 0;
1925 isolate_mode_t isolate_mode
= 0;
1926 int file
= is_file_lru(lru
);
1927 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
1932 isolate_mode
|= ISOLATE_UNMAPPED
;
1934 spin_lock_irq(&pgdat
->lru_lock
);
1936 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &l_hold
,
1937 &nr_scanned
, sc
, isolate_mode
, lru
);
1939 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1940 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1942 __count_vm_events(PGREFILL
, nr_scanned
);
1944 spin_unlock_irq(&pgdat
->lru_lock
);
1946 while (!list_empty(&l_hold
)) {
1948 page
= lru_to_page(&l_hold
);
1949 list_del(&page
->lru
);
1951 if (unlikely(!page_evictable(page
))) {
1952 putback_lru_page(page
);
1956 if (unlikely(buffer_heads_over_limit
)) {
1957 if (page_has_private(page
) && trylock_page(page
)) {
1958 if (page_has_private(page
))
1959 try_to_release_page(page
, 0);
1964 if (page_referenced(page
, 0, sc
->target_mem_cgroup
,
1966 nr_rotated
+= hpage_nr_pages(page
);
1968 * Identify referenced, file-backed active pages and
1969 * give them one more trip around the active list. So
1970 * that executable code get better chances to stay in
1971 * memory under moderate memory pressure. Anon pages
1972 * are not likely to be evicted by use-once streaming
1973 * IO, plus JVM can create lots of anon VM_EXEC pages,
1974 * so we ignore them here.
1976 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1977 list_add(&page
->lru
, &l_active
);
1982 ClearPageActive(page
); /* we are de-activating */
1983 list_add(&page
->lru
, &l_inactive
);
1987 * Move pages back to the lru list.
1989 spin_lock_irq(&pgdat
->lru_lock
);
1991 * Count referenced pages from currently used mappings as rotated,
1992 * even though only some of them are actually re-activated. This
1993 * helps balance scan pressure between file and anonymous pages in
1996 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1998 nr_activate
= move_active_pages_to_lru(lruvec
, &l_active
, &l_hold
, lru
);
1999 nr_deactivate
= move_active_pages_to_lru(lruvec
, &l_inactive
, &l_hold
, lru
- LRU_ACTIVE
);
2000 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
2001 spin_unlock_irq(&pgdat
->lru_lock
);
2003 mem_cgroup_uncharge_list(&l_hold
);
2004 free_hot_cold_page_list(&l_hold
, true);
2005 trace_mm_vmscan_lru_shrink_active(pgdat
->node_id
, nr_taken
, nr_activate
,
2006 nr_deactivate
, nr_rotated
, sc
->priority
, file
);
2010 * The inactive anon list should be small enough that the VM never has
2011 * to do too much work.
2013 * The inactive file list should be small enough to leave most memory
2014 * to the established workingset on the scan-resistant active list,
2015 * but large enough to avoid thrashing the aggregate readahead window.
2017 * Both inactive lists should also be large enough that each inactive
2018 * page has a chance to be referenced again before it is reclaimed.
2020 * The inactive_ratio is the target ratio of ACTIVE to INACTIVE pages
2021 * on this LRU, maintained by the pageout code. A zone->inactive_ratio
2022 * of 3 means 3:1 or 25% of the pages are kept on the inactive list.
2025 * memory ratio inactive
2026 * -------------------------------------
2035 static bool inactive_list_is_low(struct lruvec
*lruvec
, bool file
,
2036 struct scan_control
*sc
, bool trace
)
2038 unsigned long inactive_ratio
;
2039 unsigned long inactive
, active
;
2040 enum lru_list inactive_lru
= file
* LRU_FILE
;
2041 enum lru_list active_lru
= file
* LRU_FILE
+ LRU_ACTIVE
;
2045 * If we don't have swap space, anonymous page deactivation
2048 if (!file
&& !total_swap_pages
)
2051 inactive
= lruvec_lru_size(lruvec
, inactive_lru
, sc
->reclaim_idx
);
2052 active
= lruvec_lru_size(lruvec
, active_lru
, sc
->reclaim_idx
);
2054 gb
= (inactive
+ active
) >> (30 - PAGE_SHIFT
);
2056 inactive_ratio
= int_sqrt(10 * gb
);
2061 trace_mm_vmscan_inactive_list_is_low(lruvec_pgdat(lruvec
)->node_id
,
2063 lruvec_lru_size(lruvec
, inactive_lru
, MAX_NR_ZONES
), inactive
,
2064 lruvec_lru_size(lruvec
, active_lru
, MAX_NR_ZONES
), active
,
2065 inactive_ratio
, file
);
2067 return inactive
* inactive_ratio
< active
;
2070 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
2071 struct lruvec
*lruvec
, struct scan_control
*sc
)
2073 if (is_active_lru(lru
)) {
2074 if (inactive_list_is_low(lruvec
, is_file_lru(lru
), sc
, true))
2075 shrink_active_list(nr_to_scan
, lruvec
, sc
, lru
);
2079 return shrink_inactive_list(nr_to_scan
, lruvec
, sc
, lru
);
2090 * Determine how aggressively the anon and file LRU lists should be
2091 * scanned. The relative value of each set of LRU lists is determined
2092 * by looking at the fraction of the pages scanned we did rotate back
2093 * onto the active list instead of evict.
2095 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
2096 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
2098 static void get_scan_count(struct lruvec
*lruvec
, struct mem_cgroup
*memcg
,
2099 struct scan_control
*sc
, unsigned long *nr
,
2100 unsigned long *lru_pages
)
2102 int swappiness
= mem_cgroup_swappiness(memcg
);
2103 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
2105 u64 denominator
= 0; /* gcc */
2106 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2107 unsigned long anon_prio
, file_prio
;
2108 enum scan_balance scan_balance
;
2109 unsigned long anon
, file
;
2110 unsigned long ap
, fp
;
2113 /* If we have no swap space, do not bother scanning anon pages. */
2114 if (!sc
->may_swap
|| mem_cgroup_get_nr_swap_pages(memcg
) <= 0) {
2115 scan_balance
= SCAN_FILE
;
2120 * Global reclaim will swap to prevent OOM even with no
2121 * swappiness, but memcg users want to use this knob to
2122 * disable swapping for individual groups completely when
2123 * using the memory controller's swap limit feature would be
2126 if (!global_reclaim(sc
) && !swappiness
) {
2127 scan_balance
= SCAN_FILE
;
2132 * Do not apply any pressure balancing cleverness when the
2133 * system is close to OOM, scan both anon and file equally
2134 * (unless the swappiness setting disagrees with swapping).
2136 if (!sc
->priority
&& swappiness
) {
2137 scan_balance
= SCAN_EQUAL
;
2142 * Prevent the reclaimer from falling into the cache trap: as
2143 * cache pages start out inactive, every cache fault will tip
2144 * the scan balance towards the file LRU. And as the file LRU
2145 * shrinks, so does the window for rotation from references.
2146 * This means we have a runaway feedback loop where a tiny
2147 * thrashing file LRU becomes infinitely more attractive than
2148 * anon pages. Try to detect this based on file LRU size.
2150 if (global_reclaim(sc
)) {
2151 unsigned long pgdatfile
;
2152 unsigned long pgdatfree
;
2154 unsigned long total_high_wmark
= 0;
2156 pgdatfree
= sum_zone_node_page_state(pgdat
->node_id
, NR_FREE_PAGES
);
2157 pgdatfile
= node_page_state(pgdat
, NR_ACTIVE_FILE
) +
2158 node_page_state(pgdat
, NR_INACTIVE_FILE
);
2160 for (z
= 0; z
< MAX_NR_ZONES
; z
++) {
2161 struct zone
*zone
= &pgdat
->node_zones
[z
];
2162 if (!managed_zone(zone
))
2165 total_high_wmark
+= high_wmark_pages(zone
);
2168 if (unlikely(pgdatfile
+ pgdatfree
<= total_high_wmark
)) {
2169 scan_balance
= SCAN_ANON
;
2175 * If there is enough inactive page cache, i.e. if the size of the
2176 * inactive list is greater than that of the active list *and* the
2177 * inactive list actually has some pages to scan on this priority, we
2178 * do not reclaim anything from the anonymous working set right now.
2179 * Without the second condition we could end up never scanning an
2180 * lruvec even if it has plenty of old anonymous pages unless the
2181 * system is under heavy pressure.
2183 if (!inactive_list_is_low(lruvec
, true, sc
, false) &&
2184 lruvec_lru_size(lruvec
, LRU_INACTIVE_FILE
, sc
->reclaim_idx
) >> sc
->priority
) {
2185 scan_balance
= SCAN_FILE
;
2189 scan_balance
= SCAN_FRACT
;
2192 * With swappiness at 100, anonymous and file have the same priority.
2193 * This scanning priority is essentially the inverse of IO cost.
2195 anon_prio
= swappiness
;
2196 file_prio
= 200 - anon_prio
;
2199 * OK, so we have swap space and a fair amount of page cache
2200 * pages. We use the recently rotated / recently scanned
2201 * ratios to determine how valuable each cache is.
2203 * Because workloads change over time (and to avoid overflow)
2204 * we keep these statistics as a floating average, which ends
2205 * up weighing recent references more than old ones.
2207 * anon in [0], file in [1]
2210 anon
= lruvec_lru_size(lruvec
, LRU_ACTIVE_ANON
, MAX_NR_ZONES
) +
2211 lruvec_lru_size(lruvec
, LRU_INACTIVE_ANON
, MAX_NR_ZONES
);
2212 file
= lruvec_lru_size(lruvec
, LRU_ACTIVE_FILE
, MAX_NR_ZONES
) +
2213 lruvec_lru_size(lruvec
, LRU_INACTIVE_FILE
, MAX_NR_ZONES
);
2215 spin_lock_irq(&pgdat
->lru_lock
);
2216 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
2217 reclaim_stat
->recent_scanned
[0] /= 2;
2218 reclaim_stat
->recent_rotated
[0] /= 2;
2221 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
2222 reclaim_stat
->recent_scanned
[1] /= 2;
2223 reclaim_stat
->recent_rotated
[1] /= 2;
2227 * The amount of pressure on anon vs file pages is inversely
2228 * proportional to the fraction of recently scanned pages on
2229 * each list that were recently referenced and in active use.
2231 ap
= anon_prio
* (reclaim_stat
->recent_scanned
[0] + 1);
2232 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
2234 fp
= file_prio
* (reclaim_stat
->recent_scanned
[1] + 1);
2235 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
2236 spin_unlock_irq(&pgdat
->lru_lock
);
2240 denominator
= ap
+ fp
+ 1;
2243 for_each_evictable_lru(lru
) {
2244 int file
= is_file_lru(lru
);
2248 size
= lruvec_lru_size(lruvec
, lru
, sc
->reclaim_idx
);
2249 scan
= size
>> sc
->priority
;
2251 * If the cgroup's already been deleted, make sure to
2252 * scrape out the remaining cache.
2254 if (!scan
&& !mem_cgroup_online(memcg
))
2255 scan
= min(size
, SWAP_CLUSTER_MAX
);
2257 switch (scan_balance
) {
2259 /* Scan lists relative to size */
2263 * Scan types proportional to swappiness and
2264 * their relative recent reclaim efficiency.
2266 scan
= div64_u64(scan
* fraction
[file
],
2271 /* Scan one type exclusively */
2272 if ((scan_balance
== SCAN_FILE
) != file
) {
2278 /* Look ma, no brain */
2288 * This is a basic per-node page freer. Used by both kswapd and direct reclaim.
2290 static void shrink_node_memcg(struct pglist_data
*pgdat
, struct mem_cgroup
*memcg
,
2291 struct scan_control
*sc
, unsigned long *lru_pages
)
2293 struct lruvec
*lruvec
= mem_cgroup_lruvec(pgdat
, memcg
);
2294 unsigned long nr
[NR_LRU_LISTS
];
2295 unsigned long targets
[NR_LRU_LISTS
];
2296 unsigned long nr_to_scan
;
2298 unsigned long nr_reclaimed
= 0;
2299 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
2300 struct blk_plug plug
;
2303 get_scan_count(lruvec
, memcg
, sc
, nr
, lru_pages
);
2305 /* Record the original scan target for proportional adjustments later */
2306 memcpy(targets
, nr
, sizeof(nr
));
2309 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
2310 * event that can occur when there is little memory pressure e.g.
2311 * multiple streaming readers/writers. Hence, we do not abort scanning
2312 * when the requested number of pages are reclaimed when scanning at
2313 * DEF_PRIORITY on the assumption that the fact we are direct
2314 * reclaiming implies that kswapd is not keeping up and it is best to
2315 * do a batch of work at once. For memcg reclaim one check is made to
2316 * abort proportional reclaim if either the file or anon lru has already
2317 * dropped to zero at the first pass.
2319 scan_adjusted
= (global_reclaim(sc
) && !current_is_kswapd() &&
2320 sc
->priority
== DEF_PRIORITY
);
2322 blk_start_plug(&plug
);
2323 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
2324 nr
[LRU_INACTIVE_FILE
]) {
2325 unsigned long nr_anon
, nr_file
, percentage
;
2326 unsigned long nr_scanned
;
2328 for_each_evictable_lru(lru
) {
2330 nr_to_scan
= min(nr
[lru
], SWAP_CLUSTER_MAX
);
2331 nr
[lru
] -= nr_to_scan
;
2333 nr_reclaimed
+= shrink_list(lru
, nr_to_scan
,
2340 if (nr_reclaimed
< nr_to_reclaim
|| scan_adjusted
)
2344 * For kswapd and memcg, reclaim at least the number of pages
2345 * requested. Ensure that the anon and file LRUs are scanned
2346 * proportionally what was requested by get_scan_count(). We
2347 * stop reclaiming one LRU and reduce the amount scanning
2348 * proportional to the original scan target.
2350 nr_file
= nr
[LRU_INACTIVE_FILE
] + nr
[LRU_ACTIVE_FILE
];
2351 nr_anon
= nr
[LRU_INACTIVE_ANON
] + nr
[LRU_ACTIVE_ANON
];
2354 * It's just vindictive to attack the larger once the smaller
2355 * has gone to zero. And given the way we stop scanning the
2356 * smaller below, this makes sure that we only make one nudge
2357 * towards proportionality once we've got nr_to_reclaim.
2359 if (!nr_file
|| !nr_anon
)
2362 if (nr_file
> nr_anon
) {
2363 unsigned long scan_target
= targets
[LRU_INACTIVE_ANON
] +
2364 targets
[LRU_ACTIVE_ANON
] + 1;
2366 percentage
= nr_anon
* 100 / scan_target
;
2368 unsigned long scan_target
= targets
[LRU_INACTIVE_FILE
] +
2369 targets
[LRU_ACTIVE_FILE
] + 1;
2371 percentage
= nr_file
* 100 / scan_target
;
2374 /* Stop scanning the smaller of the LRU */
2376 nr
[lru
+ LRU_ACTIVE
] = 0;
2379 * Recalculate the other LRU scan count based on its original
2380 * scan target and the percentage scanning already complete
2382 lru
= (lru
== LRU_FILE
) ? LRU_BASE
: LRU_FILE
;
2383 nr_scanned
= targets
[lru
] - nr
[lru
];
2384 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2385 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2388 nr_scanned
= targets
[lru
] - nr
[lru
];
2389 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2390 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2392 scan_adjusted
= true;
2394 blk_finish_plug(&plug
);
2395 sc
->nr_reclaimed
+= nr_reclaimed
;
2398 * Even if we did not try to evict anon pages at all, we want to
2399 * rebalance the anon lru active/inactive ratio.
2401 if (inactive_list_is_low(lruvec
, false, sc
, true))
2402 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
2403 sc
, LRU_ACTIVE_ANON
);
2406 /* Use reclaim/compaction for costly allocs or under memory pressure */
2407 static bool in_reclaim_compaction(struct scan_control
*sc
)
2409 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
2410 (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
||
2411 sc
->priority
< DEF_PRIORITY
- 2))
2418 * Reclaim/compaction is used for high-order allocation requests. It reclaims
2419 * order-0 pages before compacting the zone. should_continue_reclaim() returns
2420 * true if more pages should be reclaimed such that when the page allocator
2421 * calls try_to_compact_zone() that it will have enough free pages to succeed.
2422 * It will give up earlier than that if there is difficulty reclaiming pages.
2424 static inline bool should_continue_reclaim(struct pglist_data
*pgdat
,
2425 unsigned long nr_reclaimed
,
2426 unsigned long nr_scanned
,
2427 struct scan_control
*sc
)
2429 unsigned long pages_for_compaction
;
2430 unsigned long inactive_lru_pages
;
2433 /* If not in reclaim/compaction mode, stop */
2434 if (!in_reclaim_compaction(sc
))
2437 /* Consider stopping depending on scan and reclaim activity */
2438 if (sc
->gfp_mask
& __GFP_REPEAT
) {
2440 * For __GFP_REPEAT allocations, stop reclaiming if the
2441 * full LRU list has been scanned and we are still failing
2442 * to reclaim pages. This full LRU scan is potentially
2443 * expensive but a __GFP_REPEAT caller really wants to succeed
2445 if (!nr_reclaimed
&& !nr_scanned
)
2449 * For non-__GFP_REPEAT allocations which can presumably
2450 * fail without consequence, stop if we failed to reclaim
2451 * any pages from the last SWAP_CLUSTER_MAX number of
2452 * pages that were scanned. This will return to the
2453 * caller faster at the risk reclaim/compaction and
2454 * the resulting allocation attempt fails
2461 * If we have not reclaimed enough pages for compaction and the
2462 * inactive lists are large enough, continue reclaiming
2464 pages_for_compaction
= compact_gap(sc
->order
);
2465 inactive_lru_pages
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
2466 if (get_nr_swap_pages() > 0)
2467 inactive_lru_pages
+= node_page_state(pgdat
, NR_INACTIVE_ANON
);
2468 if (sc
->nr_reclaimed
< pages_for_compaction
&&
2469 inactive_lru_pages
> pages_for_compaction
)
2472 /* If compaction would go ahead or the allocation would succeed, stop */
2473 for (z
= 0; z
<= sc
->reclaim_idx
; z
++) {
2474 struct zone
*zone
= &pgdat
->node_zones
[z
];
2475 if (!managed_zone(zone
))
2478 switch (compaction_suitable(zone
, sc
->order
, 0, sc
->reclaim_idx
)) {
2479 case COMPACT_SUCCESS
:
2480 case COMPACT_CONTINUE
:
2483 /* check next zone */
2490 static bool shrink_node(pg_data_t
*pgdat
, struct scan_control
*sc
)
2492 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2493 unsigned long nr_reclaimed
, nr_scanned
;
2494 bool reclaimable
= false;
2497 struct mem_cgroup
*root
= sc
->target_mem_cgroup
;
2498 struct mem_cgroup_reclaim_cookie reclaim
= {
2500 .priority
= sc
->priority
,
2502 unsigned long node_lru_pages
= 0;
2503 struct mem_cgroup
*memcg
;
2505 nr_reclaimed
= sc
->nr_reclaimed
;
2506 nr_scanned
= sc
->nr_scanned
;
2508 memcg
= mem_cgroup_iter(root
, NULL
, &reclaim
);
2510 unsigned long lru_pages
;
2511 unsigned long reclaimed
;
2512 unsigned long scanned
;
2514 if (mem_cgroup_low(root
, memcg
)) {
2515 if (!sc
->may_thrash
)
2517 mem_cgroup_events(memcg
, MEMCG_LOW
, 1);
2520 reclaimed
= sc
->nr_reclaimed
;
2521 scanned
= sc
->nr_scanned
;
2523 shrink_node_memcg(pgdat
, memcg
, sc
, &lru_pages
);
2524 node_lru_pages
+= lru_pages
;
2527 shrink_slab(sc
->gfp_mask
, pgdat
->node_id
,
2528 memcg
, sc
->nr_scanned
- scanned
,
2531 /* Record the group's reclaim efficiency */
2532 vmpressure(sc
->gfp_mask
, memcg
, false,
2533 sc
->nr_scanned
- scanned
,
2534 sc
->nr_reclaimed
- reclaimed
);
2537 * Direct reclaim and kswapd have to scan all memory
2538 * cgroups to fulfill the overall scan target for the
2541 * Limit reclaim, on the other hand, only cares about
2542 * nr_to_reclaim pages to be reclaimed and it will
2543 * retry with decreasing priority if one round over the
2544 * whole hierarchy is not sufficient.
2546 if (!global_reclaim(sc
) &&
2547 sc
->nr_reclaimed
>= sc
->nr_to_reclaim
) {
2548 mem_cgroup_iter_break(root
, memcg
);
2551 } while ((memcg
= mem_cgroup_iter(root
, memcg
, &reclaim
)));
2554 * Shrink the slab caches in the same proportion that
2555 * the eligible LRU pages were scanned.
2557 if (global_reclaim(sc
))
2558 shrink_slab(sc
->gfp_mask
, pgdat
->node_id
, NULL
,
2559 sc
->nr_scanned
- nr_scanned
,
2562 if (reclaim_state
) {
2563 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2564 reclaim_state
->reclaimed_slab
= 0;
2567 /* Record the subtree's reclaim efficiency */
2568 vmpressure(sc
->gfp_mask
, sc
->target_mem_cgroup
, true,
2569 sc
->nr_scanned
- nr_scanned
,
2570 sc
->nr_reclaimed
- nr_reclaimed
);
2572 if (sc
->nr_reclaimed
- nr_reclaimed
)
2575 } while (should_continue_reclaim(pgdat
, sc
->nr_reclaimed
- nr_reclaimed
,
2576 sc
->nr_scanned
- nr_scanned
, sc
));
2579 * Kswapd gives up on balancing particular nodes after too
2580 * many failures to reclaim anything from them and goes to
2581 * sleep. On reclaim progress, reset the failure counter. A
2582 * successful direct reclaim run will revive a dormant kswapd.
2585 pgdat
->kswapd_failures
= 0;
2591 * Returns true if compaction should go ahead for a costly-order request, or
2592 * the allocation would already succeed without compaction. Return false if we
2593 * should reclaim first.
2595 static inline bool compaction_ready(struct zone
*zone
, struct scan_control
*sc
)
2597 unsigned long watermark
;
2598 enum compact_result suitable
;
2600 suitable
= compaction_suitable(zone
, sc
->order
, 0, sc
->reclaim_idx
);
2601 if (suitable
== COMPACT_SUCCESS
)
2602 /* Allocation should succeed already. Don't reclaim. */
2604 if (suitable
== COMPACT_SKIPPED
)
2605 /* Compaction cannot yet proceed. Do reclaim. */
2609 * Compaction is already possible, but it takes time to run and there
2610 * are potentially other callers using the pages just freed. So proceed
2611 * with reclaim to make a buffer of free pages available to give
2612 * compaction a reasonable chance of completing and allocating the page.
2613 * Note that we won't actually reclaim the whole buffer in one attempt
2614 * as the target watermark in should_continue_reclaim() is lower. But if
2615 * we are already above the high+gap watermark, don't reclaim at all.
2617 watermark
= high_wmark_pages(zone
) + compact_gap(sc
->order
);
2619 return zone_watermark_ok_safe(zone
, 0, watermark
, sc
->reclaim_idx
);
2623 * This is the direct reclaim path, for page-allocating processes. We only
2624 * try to reclaim pages from zones which will satisfy the caller's allocation
2627 * If a zone is deemed to be full of pinned pages then just give it a light
2628 * scan then give up on it.
2630 static void shrink_zones(struct zonelist
*zonelist
, struct scan_control
*sc
)
2634 unsigned long nr_soft_reclaimed
;
2635 unsigned long nr_soft_scanned
;
2637 pg_data_t
*last_pgdat
= NULL
;
2640 * If the number of buffer_heads in the machine exceeds the maximum
2641 * allowed level, force direct reclaim to scan the highmem zone as
2642 * highmem pages could be pinning lowmem pages storing buffer_heads
2644 orig_mask
= sc
->gfp_mask
;
2645 if (buffer_heads_over_limit
) {
2646 sc
->gfp_mask
|= __GFP_HIGHMEM
;
2647 sc
->reclaim_idx
= gfp_zone(sc
->gfp_mask
);
2650 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2651 sc
->reclaim_idx
, sc
->nodemask
) {
2653 * Take care memory controller reclaiming has small influence
2656 if (global_reclaim(sc
)) {
2657 if (!cpuset_zone_allowed(zone
,
2658 GFP_KERNEL
| __GFP_HARDWALL
))
2662 * If we already have plenty of memory free for
2663 * compaction in this zone, don't free any more.
2664 * Even though compaction is invoked for any
2665 * non-zero order, only frequent costly order
2666 * reclamation is disruptive enough to become a
2667 * noticeable problem, like transparent huge
2670 if (IS_ENABLED(CONFIG_COMPACTION
) &&
2671 sc
->order
> PAGE_ALLOC_COSTLY_ORDER
&&
2672 compaction_ready(zone
, sc
)) {
2673 sc
->compaction_ready
= true;
2678 * Shrink each node in the zonelist once. If the
2679 * zonelist is ordered by zone (not the default) then a
2680 * node may be shrunk multiple times but in that case
2681 * the user prefers lower zones being preserved.
2683 if (zone
->zone_pgdat
== last_pgdat
)
2687 * This steals pages from memory cgroups over softlimit
2688 * and returns the number of reclaimed pages and
2689 * scanned pages. This works for global memory pressure
2690 * and balancing, not for a memcg's limit.
2692 nr_soft_scanned
= 0;
2693 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
->zone_pgdat
,
2694 sc
->order
, sc
->gfp_mask
,
2696 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
2697 sc
->nr_scanned
+= nr_soft_scanned
;
2698 /* need some check for avoid more shrink_zone() */
2701 /* See comment about same check for global reclaim above */
2702 if (zone
->zone_pgdat
== last_pgdat
)
2704 last_pgdat
= zone
->zone_pgdat
;
2705 shrink_node(zone
->zone_pgdat
, sc
);
2709 * Restore to original mask to avoid the impact on the caller if we
2710 * promoted it to __GFP_HIGHMEM.
2712 sc
->gfp_mask
= orig_mask
;
2716 * This is the main entry point to direct page reclaim.
2718 * If a full scan of the inactive list fails to free enough memory then we
2719 * are "out of memory" and something needs to be killed.
2721 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2722 * high - the zone may be full of dirty or under-writeback pages, which this
2723 * caller can't do much about. We kick the writeback threads and take explicit
2724 * naps in the hope that some of these pages can be written. But if the
2725 * allocating task holds filesystem locks which prevent writeout this might not
2726 * work, and the allocation attempt will fail.
2728 * returns: 0, if no pages reclaimed
2729 * else, the number of pages reclaimed
2731 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2732 struct scan_control
*sc
)
2734 int initial_priority
= sc
->priority
;
2736 delayacct_freepages_start();
2738 if (global_reclaim(sc
))
2739 __count_zid_vm_events(ALLOCSTALL
, sc
->reclaim_idx
, 1);
2742 vmpressure_prio(sc
->gfp_mask
, sc
->target_mem_cgroup
,
2745 shrink_zones(zonelist
, sc
);
2747 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
2750 if (sc
->compaction_ready
)
2754 * If we're getting trouble reclaiming, start doing
2755 * writepage even in laptop mode.
2757 if (sc
->priority
< DEF_PRIORITY
- 2)
2758 sc
->may_writepage
= 1;
2759 } while (--sc
->priority
>= 0);
2761 delayacct_freepages_end();
2763 if (sc
->nr_reclaimed
)
2764 return sc
->nr_reclaimed
;
2766 /* Aborted reclaim to try compaction? don't OOM, then */
2767 if (sc
->compaction_ready
)
2770 /* Untapped cgroup reserves? Don't OOM, retry. */
2771 if (!sc
->may_thrash
) {
2772 sc
->priority
= initial_priority
;
2780 static bool allow_direct_reclaim(pg_data_t
*pgdat
)
2783 unsigned long pfmemalloc_reserve
= 0;
2784 unsigned long free_pages
= 0;
2788 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
2791 for (i
= 0; i
<= ZONE_NORMAL
; i
++) {
2792 zone
= &pgdat
->node_zones
[i
];
2793 if (!managed_zone(zone
))
2796 if (!zone_reclaimable_pages(zone
))
2799 pfmemalloc_reserve
+= min_wmark_pages(zone
);
2800 free_pages
+= zone_page_state(zone
, NR_FREE_PAGES
);
2803 /* If there are no reserves (unexpected config) then do not throttle */
2804 if (!pfmemalloc_reserve
)
2807 wmark_ok
= free_pages
> pfmemalloc_reserve
/ 2;
2809 /* kswapd must be awake if processes are being throttled */
2810 if (!wmark_ok
&& waitqueue_active(&pgdat
->kswapd_wait
)) {
2811 pgdat
->kswapd_classzone_idx
= min(pgdat
->kswapd_classzone_idx
,
2812 (enum zone_type
)ZONE_NORMAL
);
2813 wake_up_interruptible(&pgdat
->kswapd_wait
);
2820 * Throttle direct reclaimers if backing storage is backed by the network
2821 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
2822 * depleted. kswapd will continue to make progress and wake the processes
2823 * when the low watermark is reached.
2825 * Returns true if a fatal signal was delivered during throttling. If this
2826 * happens, the page allocator should not consider triggering the OOM killer.
2828 static bool throttle_direct_reclaim(gfp_t gfp_mask
, struct zonelist
*zonelist
,
2829 nodemask_t
*nodemask
)
2833 pg_data_t
*pgdat
= NULL
;
2836 * Kernel threads should not be throttled as they may be indirectly
2837 * responsible for cleaning pages necessary for reclaim to make forward
2838 * progress. kjournald for example may enter direct reclaim while
2839 * committing a transaction where throttling it could forcing other
2840 * processes to block on log_wait_commit().
2842 if (current
->flags
& PF_KTHREAD
)
2846 * If a fatal signal is pending, this process should not throttle.
2847 * It should return quickly so it can exit and free its memory
2849 if (fatal_signal_pending(current
))
2853 * Check if the pfmemalloc reserves are ok by finding the first node
2854 * with a usable ZONE_NORMAL or lower zone. The expectation is that
2855 * GFP_KERNEL will be required for allocating network buffers when
2856 * swapping over the network so ZONE_HIGHMEM is unusable.
2858 * Throttling is based on the first usable node and throttled processes
2859 * wait on a queue until kswapd makes progress and wakes them. There
2860 * is an affinity then between processes waking up and where reclaim
2861 * progress has been made assuming the process wakes on the same node.
2862 * More importantly, processes running on remote nodes will not compete
2863 * for remote pfmemalloc reserves and processes on different nodes
2864 * should make reasonable progress.
2866 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2867 gfp_zone(gfp_mask
), nodemask
) {
2868 if (zone_idx(zone
) > ZONE_NORMAL
)
2871 /* Throttle based on the first usable node */
2872 pgdat
= zone
->zone_pgdat
;
2873 if (allow_direct_reclaim(pgdat
))
2878 /* If no zone was usable by the allocation flags then do not throttle */
2882 /* Account for the throttling */
2883 count_vm_event(PGSCAN_DIRECT_THROTTLE
);
2886 * If the caller cannot enter the filesystem, it's possible that it
2887 * is due to the caller holding an FS lock or performing a journal
2888 * transaction in the case of a filesystem like ext[3|4]. In this case,
2889 * it is not safe to block on pfmemalloc_wait as kswapd could be
2890 * blocked waiting on the same lock. Instead, throttle for up to a
2891 * second before continuing.
2893 if (!(gfp_mask
& __GFP_FS
)) {
2894 wait_event_interruptible_timeout(pgdat
->pfmemalloc_wait
,
2895 allow_direct_reclaim(pgdat
), HZ
);
2900 /* Throttle until kswapd wakes the process */
2901 wait_event_killable(zone
->zone_pgdat
->pfmemalloc_wait
,
2902 allow_direct_reclaim(pgdat
));
2905 if (fatal_signal_pending(current
))
2912 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
2913 gfp_t gfp_mask
, nodemask_t
*nodemask
)
2915 unsigned long nr_reclaimed
;
2916 struct scan_control sc
= {
2917 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2918 .gfp_mask
= (gfp_mask
= current_gfp_context(gfp_mask
)),
2919 .reclaim_idx
= gfp_zone(gfp_mask
),
2921 .nodemask
= nodemask
,
2922 .priority
= DEF_PRIORITY
,
2923 .may_writepage
= !laptop_mode
,
2929 * Do not enter reclaim if fatal signal was delivered while throttled.
2930 * 1 is returned so that the page allocator does not OOM kill at this
2933 if (throttle_direct_reclaim(gfp_mask
, zonelist
, nodemask
))
2936 trace_mm_vmscan_direct_reclaim_begin(order
,
2941 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2943 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
2945 return nr_reclaimed
;
2950 unsigned long mem_cgroup_shrink_node(struct mem_cgroup
*memcg
,
2951 gfp_t gfp_mask
, bool noswap
,
2953 unsigned long *nr_scanned
)
2955 struct scan_control sc
= {
2956 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2957 .target_mem_cgroup
= memcg
,
2958 .may_writepage
= !laptop_mode
,
2960 .reclaim_idx
= MAX_NR_ZONES
- 1,
2961 .may_swap
= !noswap
,
2963 unsigned long lru_pages
;
2965 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2966 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2968 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc
.order
,
2974 * NOTE: Although we can get the priority field, using it
2975 * here is not a good idea, since it limits the pages we can scan.
2976 * if we don't reclaim here, the shrink_node from balance_pgdat
2977 * will pick up pages from other mem cgroup's as well. We hack
2978 * the priority and make it zero.
2980 shrink_node_memcg(pgdat
, memcg
, &sc
, &lru_pages
);
2982 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
2984 *nr_scanned
= sc
.nr_scanned
;
2985 return sc
.nr_reclaimed
;
2988 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*memcg
,
2989 unsigned long nr_pages
,
2993 struct zonelist
*zonelist
;
2994 unsigned long nr_reclaimed
;
2996 struct scan_control sc
= {
2997 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
2998 .gfp_mask
= (current_gfp_context(gfp_mask
) & GFP_RECLAIM_MASK
) |
2999 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
3000 .reclaim_idx
= MAX_NR_ZONES
- 1,
3001 .target_mem_cgroup
= memcg
,
3002 .priority
= DEF_PRIORITY
,
3003 .may_writepage
= !laptop_mode
,
3005 .may_swap
= may_swap
,
3009 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
3010 * take care of from where we get pages. So the node where we start the
3011 * scan does not need to be the current node.
3013 nid
= mem_cgroup_select_victim_node(memcg
);
3015 zonelist
= &NODE_DATA(nid
)->node_zonelists
[ZONELIST_FALLBACK
];
3017 trace_mm_vmscan_memcg_reclaim_begin(0,
3022 current
->flags
|= PF_MEMALLOC
;
3023 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3024 current
->flags
&= ~PF_MEMALLOC
;
3026 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
3028 return nr_reclaimed
;
3032 static void age_active_anon(struct pglist_data
*pgdat
,
3033 struct scan_control
*sc
)
3035 struct mem_cgroup
*memcg
;
3037 if (!total_swap_pages
)
3040 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
3042 struct lruvec
*lruvec
= mem_cgroup_lruvec(pgdat
, memcg
);
3044 if (inactive_list_is_low(lruvec
, false, sc
, true))
3045 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
3046 sc
, LRU_ACTIVE_ANON
);
3048 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
3052 static bool zone_balanced(struct zone
*zone
, int order
, int classzone_idx
)
3054 unsigned long mark
= high_wmark_pages(zone
);
3056 if (!zone_watermark_ok_safe(zone
, order
, mark
, classzone_idx
))
3060 * If any eligible zone is balanced then the node is not considered
3061 * to be congested or dirty
3063 clear_bit(PGDAT_CONGESTED
, &zone
->zone_pgdat
->flags
);
3064 clear_bit(PGDAT_DIRTY
, &zone
->zone_pgdat
->flags
);
3065 clear_bit(PGDAT_WRITEBACK
, &zone
->zone_pgdat
->flags
);
3071 * Prepare kswapd for sleeping. This verifies that there are no processes
3072 * waiting in throttle_direct_reclaim() and that watermarks have been met.
3074 * Returns true if kswapd is ready to sleep
3076 static bool prepare_kswapd_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
3081 * The throttled processes are normally woken up in balance_pgdat() as
3082 * soon as allow_direct_reclaim() is true. But there is a potential
3083 * race between when kswapd checks the watermarks and a process gets
3084 * throttled. There is also a potential race if processes get
3085 * throttled, kswapd wakes, a large process exits thereby balancing the
3086 * zones, which causes kswapd to exit balance_pgdat() before reaching
3087 * the wake up checks. If kswapd is going to sleep, no process should
3088 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
3089 * the wake up is premature, processes will wake kswapd and get
3090 * throttled again. The difference from wake ups in balance_pgdat() is
3091 * that here we are under prepare_to_wait().
3093 if (waitqueue_active(&pgdat
->pfmemalloc_wait
))
3094 wake_up_all(&pgdat
->pfmemalloc_wait
);
3096 /* Hopeless node, leave it to direct reclaim */
3097 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
3100 for (i
= 0; i
<= classzone_idx
; i
++) {
3101 struct zone
*zone
= pgdat
->node_zones
+ i
;
3103 if (!managed_zone(zone
))
3106 if (!zone_balanced(zone
, order
, classzone_idx
))
3114 * kswapd shrinks a node of pages that are at or below the highest usable
3115 * zone that is currently unbalanced.
3117 * Returns true if kswapd scanned at least the requested number of pages to
3118 * reclaim or if the lack of progress was due to pages under writeback.
3119 * This is used to determine if the scanning priority needs to be raised.
3121 static bool kswapd_shrink_node(pg_data_t
*pgdat
,
3122 struct scan_control
*sc
)
3127 /* Reclaim a number of pages proportional to the number of zones */
3128 sc
->nr_to_reclaim
= 0;
3129 for (z
= 0; z
<= sc
->reclaim_idx
; z
++) {
3130 zone
= pgdat
->node_zones
+ z
;
3131 if (!managed_zone(zone
))
3134 sc
->nr_to_reclaim
+= max(high_wmark_pages(zone
), SWAP_CLUSTER_MAX
);
3138 * Historically care was taken to put equal pressure on all zones but
3139 * now pressure is applied based on node LRU order.
3141 shrink_node(pgdat
, sc
);
3144 * Fragmentation may mean that the system cannot be rebalanced for
3145 * high-order allocations. If twice the allocation size has been
3146 * reclaimed then recheck watermarks only at order-0 to prevent
3147 * excessive reclaim. Assume that a process requested a high-order
3148 * can direct reclaim/compact.
3150 if (sc
->order
&& sc
->nr_reclaimed
>= compact_gap(sc
->order
))
3153 return sc
->nr_scanned
>= sc
->nr_to_reclaim
;
3157 * For kswapd, balance_pgdat() will reclaim pages across a node from zones
3158 * that are eligible for use by the caller until at least one zone is
3161 * Returns the order kswapd finished reclaiming at.
3163 * kswapd scans the zones in the highmem->normal->dma direction. It skips
3164 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
3165 * found to have free_pages <= high_wmark_pages(zone), any page is that zone
3166 * or lower is eligible for reclaim until at least one usable zone is
3169 static int balance_pgdat(pg_data_t
*pgdat
, int order
, int classzone_idx
)
3172 unsigned long nr_soft_reclaimed
;
3173 unsigned long nr_soft_scanned
;
3175 struct scan_control sc
= {
3176 .gfp_mask
= GFP_KERNEL
,
3178 .priority
= DEF_PRIORITY
,
3179 .may_writepage
= !laptop_mode
,
3183 count_vm_event(PAGEOUTRUN
);
3186 unsigned long nr_reclaimed
= sc
.nr_reclaimed
;
3187 bool raise_priority
= true;
3189 sc
.reclaim_idx
= classzone_idx
;
3192 * If the number of buffer_heads exceeds the maximum allowed
3193 * then consider reclaiming from all zones. This has a dual
3194 * purpose -- on 64-bit systems it is expected that
3195 * buffer_heads are stripped during active rotation. On 32-bit
3196 * systems, highmem pages can pin lowmem memory and shrinking
3197 * buffers can relieve lowmem pressure. Reclaim may still not
3198 * go ahead if all eligible zones for the original allocation
3199 * request are balanced to avoid excessive reclaim from kswapd.
3201 if (buffer_heads_over_limit
) {
3202 for (i
= MAX_NR_ZONES
- 1; i
>= 0; i
--) {
3203 zone
= pgdat
->node_zones
+ i
;
3204 if (!managed_zone(zone
))
3213 * Only reclaim if there are no eligible zones. Check from
3214 * high to low zone as allocations prefer higher zones.
3215 * Scanning from low to high zone would allow congestion to be
3216 * cleared during a very small window when a small low
3217 * zone was balanced even under extreme pressure when the
3218 * overall node may be congested. Note that sc.reclaim_idx
3219 * is not used as buffer_heads_over_limit may have adjusted
3222 for (i
= classzone_idx
; i
>= 0; i
--) {
3223 zone
= pgdat
->node_zones
+ i
;
3224 if (!managed_zone(zone
))
3227 if (zone_balanced(zone
, sc
.order
, classzone_idx
))
3232 * Do some background aging of the anon list, to give
3233 * pages a chance to be referenced before reclaiming. All
3234 * pages are rotated regardless of classzone as this is
3235 * about consistent aging.
3237 age_active_anon(pgdat
, &sc
);
3240 * If we're getting trouble reclaiming, start doing writepage
3241 * even in laptop mode.
3243 if (sc
.priority
< DEF_PRIORITY
- 2)
3244 sc
.may_writepage
= 1;
3246 /* Call soft limit reclaim before calling shrink_node. */
3248 nr_soft_scanned
= 0;
3249 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(pgdat
, sc
.order
,
3250 sc
.gfp_mask
, &nr_soft_scanned
);
3251 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
3254 * There should be no need to raise the scanning priority if
3255 * enough pages are already being scanned that that high
3256 * watermark would be met at 100% efficiency.
3258 if (kswapd_shrink_node(pgdat
, &sc
))
3259 raise_priority
= false;
3262 * If the low watermark is met there is no need for processes
3263 * to be throttled on pfmemalloc_wait as they should not be
3264 * able to safely make forward progress. Wake them
3266 if (waitqueue_active(&pgdat
->pfmemalloc_wait
) &&
3267 allow_direct_reclaim(pgdat
))
3268 wake_up_all(&pgdat
->pfmemalloc_wait
);
3270 /* Check if kswapd should be suspending */
3271 if (try_to_freeze() || kthread_should_stop())
3275 * Raise priority if scanning rate is too low or there was no
3276 * progress in reclaiming pages
3278 nr_reclaimed
= sc
.nr_reclaimed
- nr_reclaimed
;
3279 if (raise_priority
|| !nr_reclaimed
)
3281 } while (sc
.priority
>= 1);
3283 if (!sc
.nr_reclaimed
)
3284 pgdat
->kswapd_failures
++;
3288 * Return the order kswapd stopped reclaiming at as
3289 * prepare_kswapd_sleep() takes it into account. If another caller
3290 * entered the allocator slow path while kswapd was awake, order will
3291 * remain at the higher level.
3296 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int alloc_order
, int reclaim_order
,
3297 unsigned int classzone_idx
)
3302 if (freezing(current
) || kthread_should_stop())
3305 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
3307 /* Try to sleep for a short interval */
3308 if (prepare_kswapd_sleep(pgdat
, reclaim_order
, classzone_idx
)) {
3310 * Compaction records what page blocks it recently failed to
3311 * isolate pages from and skips them in the future scanning.
3312 * When kswapd is going to sleep, it is reasonable to assume
3313 * that pages and compaction may succeed so reset the cache.
3315 reset_isolation_suitable(pgdat
);
3318 * We have freed the memory, now we should compact it to make
3319 * allocation of the requested order possible.
3321 wakeup_kcompactd(pgdat
, alloc_order
, classzone_idx
);
3323 remaining
= schedule_timeout(HZ
/10);
3326 * If woken prematurely then reset kswapd_classzone_idx and
3327 * order. The values will either be from a wakeup request or
3328 * the previous request that slept prematurely.
3331 pgdat
->kswapd_classzone_idx
= max(pgdat
->kswapd_classzone_idx
, classzone_idx
);
3332 pgdat
->kswapd_order
= max(pgdat
->kswapd_order
, reclaim_order
);
3335 finish_wait(&pgdat
->kswapd_wait
, &wait
);
3336 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
3340 * After a short sleep, check if it was a premature sleep. If not, then
3341 * go fully to sleep until explicitly woken up.
3344 prepare_kswapd_sleep(pgdat
, reclaim_order
, classzone_idx
)) {
3345 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
3348 * vmstat counters are not perfectly accurate and the estimated
3349 * value for counters such as NR_FREE_PAGES can deviate from the
3350 * true value by nr_online_cpus * threshold. To avoid the zone
3351 * watermarks being breached while under pressure, we reduce the
3352 * per-cpu vmstat threshold while kswapd is awake and restore
3353 * them before going back to sleep.
3355 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
3357 if (!kthread_should_stop())
3360 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
3363 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
3365 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
3367 finish_wait(&pgdat
->kswapd_wait
, &wait
);
3371 * The background pageout daemon, started as a kernel thread
3372 * from the init process.
3374 * This basically trickles out pages so that we have _some_
3375 * free memory available even if there is no other activity
3376 * that frees anything up. This is needed for things like routing
3377 * etc, where we otherwise might have all activity going on in
3378 * asynchronous contexts that cannot page things out.
3380 * If there are applications that are active memory-allocators
3381 * (most normal use), this basically shouldn't matter.
3383 static int kswapd(void *p
)
3385 unsigned int alloc_order
, reclaim_order
, classzone_idx
;
3386 pg_data_t
*pgdat
= (pg_data_t
*)p
;
3387 struct task_struct
*tsk
= current
;
3389 struct reclaim_state reclaim_state
= {
3390 .reclaimed_slab
= 0,
3392 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
3394 lockdep_set_current_reclaim_state(GFP_KERNEL
);
3396 if (!cpumask_empty(cpumask
))
3397 set_cpus_allowed_ptr(tsk
, cpumask
);
3398 current
->reclaim_state
= &reclaim_state
;
3401 * Tell the memory management that we're a "memory allocator",
3402 * and that if we need more memory we should get access to it
3403 * regardless (see "__alloc_pages()"). "kswapd" should
3404 * never get caught in the normal page freeing logic.
3406 * (Kswapd normally doesn't need memory anyway, but sometimes
3407 * you need a small amount of memory in order to be able to
3408 * page out something else, and this flag essentially protects
3409 * us from recursively trying to free more memory as we're
3410 * trying to free the first piece of memory in the first place).
3412 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
3415 pgdat
->kswapd_order
= alloc_order
= reclaim_order
= 0;
3416 pgdat
->kswapd_classzone_idx
= classzone_idx
= 0;
3421 kswapd_try_to_sleep(pgdat
, alloc_order
, reclaim_order
,
3424 /* Read the new order and classzone_idx */
3425 alloc_order
= reclaim_order
= pgdat
->kswapd_order
;
3426 classzone_idx
= pgdat
->kswapd_classzone_idx
;
3427 pgdat
->kswapd_order
= 0;
3428 pgdat
->kswapd_classzone_idx
= 0;
3430 ret
= try_to_freeze();
3431 if (kthread_should_stop())
3435 * We can speed up thawing tasks if we don't call balance_pgdat
3436 * after returning from the refrigerator
3442 * Reclaim begins at the requested order but if a high-order
3443 * reclaim fails then kswapd falls back to reclaiming for
3444 * order-0. If that happens, kswapd will consider sleeping
3445 * for the order it finished reclaiming at (reclaim_order)
3446 * but kcompactd is woken to compact for the original
3447 * request (alloc_order).
3449 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, classzone_idx
,
3451 reclaim_order
= balance_pgdat(pgdat
, alloc_order
, classzone_idx
);
3452 if (reclaim_order
< alloc_order
)
3453 goto kswapd_try_sleep
;
3455 alloc_order
= reclaim_order
= pgdat
->kswapd_order
;
3456 classzone_idx
= pgdat
->kswapd_classzone_idx
;
3459 tsk
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
);
3460 current
->reclaim_state
= NULL
;
3461 lockdep_clear_current_reclaim_state();
3467 * A zone is low on free memory, so wake its kswapd task to service it.
3469 void wakeup_kswapd(struct zone
*zone
, int order
, enum zone_type classzone_idx
)
3474 if (!managed_zone(zone
))
3477 if (!cpuset_zone_allowed(zone
, GFP_KERNEL
| __GFP_HARDWALL
))
3479 pgdat
= zone
->zone_pgdat
;
3480 pgdat
->kswapd_classzone_idx
= max(pgdat
->kswapd_classzone_idx
, classzone_idx
);
3481 pgdat
->kswapd_order
= max(pgdat
->kswapd_order
, order
);
3482 if (!waitqueue_active(&pgdat
->kswapd_wait
))
3485 /* Hopeless node, leave it to direct reclaim */
3486 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
3489 /* Only wake kswapd if all zones are unbalanced */
3490 for (z
= 0; z
<= classzone_idx
; z
++) {
3491 zone
= pgdat
->node_zones
+ z
;
3492 if (!managed_zone(zone
))
3495 if (zone_balanced(zone
, order
, classzone_idx
))
3499 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, zone_idx(zone
), order
);
3500 wake_up_interruptible(&pgdat
->kswapd_wait
);
3503 #ifdef CONFIG_HIBERNATION
3505 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3508 * Rather than trying to age LRUs the aim is to preserve the overall
3509 * LRU order by reclaiming preferentially
3510 * inactive > active > active referenced > active mapped
3512 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
3514 struct reclaim_state reclaim_state
;
3515 struct scan_control sc
= {
3516 .nr_to_reclaim
= nr_to_reclaim
,
3517 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
3518 .reclaim_idx
= MAX_NR_ZONES
- 1,
3519 .priority
= DEF_PRIORITY
,
3523 .hibernation_mode
= 1,
3525 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
3526 struct task_struct
*p
= current
;
3527 unsigned long nr_reclaimed
;
3529 p
->flags
|= PF_MEMALLOC
;
3530 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
3531 reclaim_state
.reclaimed_slab
= 0;
3532 p
->reclaim_state
= &reclaim_state
;
3534 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3536 p
->reclaim_state
= NULL
;
3537 lockdep_clear_current_reclaim_state();
3538 p
->flags
&= ~PF_MEMALLOC
;
3540 return nr_reclaimed
;
3542 #endif /* CONFIG_HIBERNATION */
3544 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3545 not required for correctness. So if the last cpu in a node goes
3546 away, we get changed to run anywhere: as the first one comes back,
3547 restore their cpu bindings. */
3548 static int kswapd_cpu_online(unsigned int cpu
)
3552 for_each_node_state(nid
, N_MEMORY
) {
3553 pg_data_t
*pgdat
= NODE_DATA(nid
);
3554 const struct cpumask
*mask
;
3556 mask
= cpumask_of_node(pgdat
->node_id
);
3558 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
3559 /* One of our CPUs online: restore mask */
3560 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
3566 * This kswapd start function will be called by init and node-hot-add.
3567 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3569 int kswapd_run(int nid
)
3571 pg_data_t
*pgdat
= NODE_DATA(nid
);
3577 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
3578 if (IS_ERR(pgdat
->kswapd
)) {
3579 /* failure at boot is fatal */
3580 BUG_ON(system_state
== SYSTEM_BOOTING
);
3581 pr_err("Failed to start kswapd on node %d\n", nid
);
3582 ret
= PTR_ERR(pgdat
->kswapd
);
3583 pgdat
->kswapd
= NULL
;
3589 * Called by memory hotplug when all memory in a node is offlined. Caller must
3590 * hold mem_hotplug_begin/end().
3592 void kswapd_stop(int nid
)
3594 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
3597 kthread_stop(kswapd
);
3598 NODE_DATA(nid
)->kswapd
= NULL
;
3602 static int __init
kswapd_init(void)
3607 for_each_node_state(nid
, N_MEMORY
)
3609 ret
= cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN
,
3610 "mm/vmscan:online", kswapd_cpu_online
,
3616 module_init(kswapd_init
)
3622 * If non-zero call node_reclaim when the number of free pages falls below
3625 int node_reclaim_mode __read_mostly
;
3627 #define RECLAIM_OFF 0
3628 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3629 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3630 #define RECLAIM_UNMAP (1<<2) /* Unmap pages during reclaim */
3633 * Priority for NODE_RECLAIM. This determines the fraction of pages
3634 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3637 #define NODE_RECLAIM_PRIORITY 4
3640 * Percentage of pages in a zone that must be unmapped for node_reclaim to
3643 int sysctl_min_unmapped_ratio
= 1;
3646 * If the number of slab pages in a zone grows beyond this percentage then
3647 * slab reclaim needs to occur.
3649 int sysctl_min_slab_ratio
= 5;
3651 static inline unsigned long node_unmapped_file_pages(struct pglist_data
*pgdat
)
3653 unsigned long file_mapped
= node_page_state(pgdat
, NR_FILE_MAPPED
);
3654 unsigned long file_lru
= node_page_state(pgdat
, NR_INACTIVE_FILE
) +
3655 node_page_state(pgdat
, NR_ACTIVE_FILE
);
3658 * It's possible for there to be more file mapped pages than
3659 * accounted for by the pages on the file LRU lists because
3660 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3662 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
3665 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3666 static unsigned long node_pagecache_reclaimable(struct pglist_data
*pgdat
)
3668 unsigned long nr_pagecache_reclaimable
;
3669 unsigned long delta
= 0;
3672 * If RECLAIM_UNMAP is set, then all file pages are considered
3673 * potentially reclaimable. Otherwise, we have to worry about
3674 * pages like swapcache and node_unmapped_file_pages() provides
3677 if (node_reclaim_mode
& RECLAIM_UNMAP
)
3678 nr_pagecache_reclaimable
= node_page_state(pgdat
, NR_FILE_PAGES
);
3680 nr_pagecache_reclaimable
= node_unmapped_file_pages(pgdat
);
3682 /* If we can't clean pages, remove dirty pages from consideration */
3683 if (!(node_reclaim_mode
& RECLAIM_WRITE
))
3684 delta
+= node_page_state(pgdat
, NR_FILE_DIRTY
);
3686 /* Watch for any possible underflows due to delta */
3687 if (unlikely(delta
> nr_pagecache_reclaimable
))
3688 delta
= nr_pagecache_reclaimable
;
3690 return nr_pagecache_reclaimable
- delta
;
3694 * Try to free up some pages from this node through reclaim.
3696 static int __node_reclaim(struct pglist_data
*pgdat
, gfp_t gfp_mask
, unsigned int order
)
3698 /* Minimum pages needed in order to stay on node */
3699 const unsigned long nr_pages
= 1 << order
;
3700 struct task_struct
*p
= current
;
3701 struct reclaim_state reclaim_state
;
3702 int classzone_idx
= gfp_zone(gfp_mask
);
3703 struct scan_control sc
= {
3704 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
3705 .gfp_mask
= (gfp_mask
= current_gfp_context(gfp_mask
)),
3707 .priority
= NODE_RECLAIM_PRIORITY
,
3708 .may_writepage
= !!(node_reclaim_mode
& RECLAIM_WRITE
),
3709 .may_unmap
= !!(node_reclaim_mode
& RECLAIM_UNMAP
),
3711 .reclaim_idx
= classzone_idx
,
3716 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
3717 * and we also need to be able to write out pages for RECLAIM_WRITE
3718 * and RECLAIM_UNMAP.
3720 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
3721 lockdep_set_current_reclaim_state(gfp_mask
);
3722 reclaim_state
.reclaimed_slab
= 0;
3723 p
->reclaim_state
= &reclaim_state
;
3725 if (node_pagecache_reclaimable(pgdat
) > pgdat
->min_unmapped_pages
) {
3727 * Free memory by calling shrink zone with increasing
3728 * priorities until we have enough memory freed.
3731 shrink_node(pgdat
, &sc
);
3732 } while (sc
.nr_reclaimed
< nr_pages
&& --sc
.priority
>= 0);
3735 p
->reclaim_state
= NULL
;
3736 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
3737 lockdep_clear_current_reclaim_state();
3738 return sc
.nr_reclaimed
>= nr_pages
;
3741 int node_reclaim(struct pglist_data
*pgdat
, gfp_t gfp_mask
, unsigned int order
)
3746 * Node reclaim reclaims unmapped file backed pages and
3747 * slab pages if we are over the defined limits.
3749 * A small portion of unmapped file backed pages is needed for
3750 * file I/O otherwise pages read by file I/O will be immediately
3751 * thrown out if the node is overallocated. So we do not reclaim
3752 * if less than a specified percentage of the node is used by
3753 * unmapped file backed pages.
3755 if (node_pagecache_reclaimable(pgdat
) <= pgdat
->min_unmapped_pages
&&
3756 sum_zone_node_page_state(pgdat
->node_id
, NR_SLAB_RECLAIMABLE
) <= pgdat
->min_slab_pages
)
3757 return NODE_RECLAIM_FULL
;
3760 * Do not scan if the allocation should not be delayed.
3762 if (!gfpflags_allow_blocking(gfp_mask
) || (current
->flags
& PF_MEMALLOC
))
3763 return NODE_RECLAIM_NOSCAN
;
3766 * Only run node reclaim on the local node or on nodes that do not
3767 * have associated processors. This will favor the local processor
3768 * over remote processors and spread off node memory allocations
3769 * as wide as possible.
3771 if (node_state(pgdat
->node_id
, N_CPU
) && pgdat
->node_id
!= numa_node_id())
3772 return NODE_RECLAIM_NOSCAN
;
3774 if (test_and_set_bit(PGDAT_RECLAIM_LOCKED
, &pgdat
->flags
))
3775 return NODE_RECLAIM_NOSCAN
;
3777 ret
= __node_reclaim(pgdat
, gfp_mask
, order
);
3778 clear_bit(PGDAT_RECLAIM_LOCKED
, &pgdat
->flags
);
3781 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
3788 * page_evictable - test whether a page is evictable
3789 * @page: the page to test
3791 * Test whether page is evictable--i.e., should be placed on active/inactive
3792 * lists vs unevictable list.
3794 * Reasons page might not be evictable:
3795 * (1) page's mapping marked unevictable
3796 * (2) page is part of an mlocked VMA
3799 int page_evictable(struct page
*page
)
3801 return !mapping_unevictable(page_mapping(page
)) && !PageMlocked(page
);
3806 * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
3807 * @pages: array of pages to check
3808 * @nr_pages: number of pages to check
3810 * Checks pages for evictability and moves them to the appropriate lru list.
3812 * This function is only used for SysV IPC SHM_UNLOCK.
3814 void check_move_unevictable_pages(struct page
**pages
, int nr_pages
)
3816 struct lruvec
*lruvec
;
3817 struct pglist_data
*pgdat
= NULL
;
3822 for (i
= 0; i
< nr_pages
; i
++) {
3823 struct page
*page
= pages
[i
];
3824 struct pglist_data
*pagepgdat
= page_pgdat(page
);
3827 if (pagepgdat
!= pgdat
) {
3829 spin_unlock_irq(&pgdat
->lru_lock
);
3831 spin_lock_irq(&pgdat
->lru_lock
);
3833 lruvec
= mem_cgroup_page_lruvec(page
, pgdat
);
3835 if (!PageLRU(page
) || !PageUnevictable(page
))
3838 if (page_evictable(page
)) {
3839 enum lru_list lru
= page_lru_base_type(page
);
3841 VM_BUG_ON_PAGE(PageActive(page
), page
);
3842 ClearPageUnevictable(page
);
3843 del_page_from_lru_list(page
, lruvec
, LRU_UNEVICTABLE
);
3844 add_page_to_lru_list(page
, lruvec
, lru
);
3850 __count_vm_events(UNEVICTABLE_PGRESCUED
, pgrescued
);
3851 __count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
3852 spin_unlock_irq(&pgdat
->lru_lock
);
3855 #endif /* CONFIG_SHMEM */