1 // SPDX-License-Identifier: GPL-2.0
3 * linux/mm/compaction.c
5 * Memory compaction for the reduction of external fragmentation. Note that
6 * this heavily depends upon page migration to do all the real heavy
9 * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
11 #include <linux/cpu.h>
12 #include <linux/swap.h>
13 #include <linux/migrate.h>
14 #include <linux/compaction.h>
15 #include <linux/mm_inline.h>
16 #include <linux/sched/signal.h>
17 #include <linux/backing-dev.h>
18 #include <linux/sysctl.h>
19 #include <linux/sysfs.h>
20 #include <linux/page-isolation.h>
21 #include <linux/kasan.h>
22 #include <linux/kthread.h>
23 #include <linux/freezer.h>
24 #include <linux/page_owner.h>
25 #include <linux/psi.h>
28 #ifdef CONFIG_COMPACTION
30 * Fragmentation score check interval for proactive compaction purposes.
32 #define HPAGE_FRAG_CHECK_INTERVAL_MSEC (500)
34 static inline void count_compact_event(enum vm_event_item item
)
39 static inline void count_compact_events(enum vm_event_item item
, long delta
)
41 count_vm_events(item
, delta
);
44 #define count_compact_event(item) do { } while (0)
45 #define count_compact_events(item, delta) do { } while (0)
48 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
50 #define CREATE_TRACE_POINTS
51 #include <trace/events/compaction.h>
53 #define block_start_pfn(pfn, order) round_down(pfn, 1UL << (order))
54 #define block_end_pfn(pfn, order) ALIGN((pfn) + 1, 1UL << (order))
57 * Page order with-respect-to which proactive compaction
58 * calculates external fragmentation, which is used as
59 * the "fragmentation score" of a node/zone.
61 #if defined CONFIG_TRANSPARENT_HUGEPAGE
62 #define COMPACTION_HPAGE_ORDER HPAGE_PMD_ORDER
63 #elif defined CONFIG_HUGETLBFS
64 #define COMPACTION_HPAGE_ORDER HUGETLB_PAGE_ORDER
66 #define COMPACTION_HPAGE_ORDER (PMD_SHIFT - PAGE_SHIFT)
69 static unsigned long release_freepages(struct list_head
*freelist
)
71 struct page
*page
, *next
;
72 unsigned long high_pfn
= 0;
74 list_for_each_entry_safe(page
, next
, freelist
, lru
) {
75 unsigned long pfn
= page_to_pfn(page
);
85 static void split_map_pages(struct list_head
*list
)
87 unsigned int i
, order
, nr_pages
;
88 struct page
*page
, *next
;
91 list_for_each_entry_safe(page
, next
, list
, lru
) {
94 order
= page_private(page
);
95 nr_pages
= 1 << order
;
97 post_alloc_hook(page
, order
, __GFP_MOVABLE
);
99 split_page(page
, order
);
101 for (i
= 0; i
< nr_pages
; i
++) {
102 list_add(&page
->lru
, &tmp_list
);
107 list_splice(&tmp_list
, list
);
110 #ifdef CONFIG_COMPACTION
111 bool PageMovable(struct page
*page
)
113 const struct movable_operations
*mops
;
115 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
116 if (!__PageMovable(page
))
119 mops
= page_movable_ops(page
);
126 void __SetPageMovable(struct page
*page
, const struct movable_operations
*mops
)
128 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
129 VM_BUG_ON_PAGE((unsigned long)mops
& PAGE_MAPPING_MOVABLE
, page
);
130 page
->mapping
= (void *)((unsigned long)mops
| PAGE_MAPPING_MOVABLE
);
132 EXPORT_SYMBOL(__SetPageMovable
);
134 void __ClearPageMovable(struct page
*page
)
136 VM_BUG_ON_PAGE(!PageMovable(page
), page
);
138 * This page still has the type of a movable page, but it's
139 * actually not movable any more.
141 page
->mapping
= (void *)PAGE_MAPPING_MOVABLE
;
143 EXPORT_SYMBOL(__ClearPageMovable
);
145 /* Do not skip compaction more than 64 times */
146 #define COMPACT_MAX_DEFER_SHIFT 6
149 * Compaction is deferred when compaction fails to result in a page
150 * allocation success. 1 << compact_defer_shift, compactions are skipped up
151 * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
153 static void defer_compaction(struct zone
*zone
, int order
)
155 zone
->compact_considered
= 0;
156 zone
->compact_defer_shift
++;
158 if (order
< zone
->compact_order_failed
)
159 zone
->compact_order_failed
= order
;
161 if (zone
->compact_defer_shift
> COMPACT_MAX_DEFER_SHIFT
)
162 zone
->compact_defer_shift
= COMPACT_MAX_DEFER_SHIFT
;
164 trace_mm_compaction_defer_compaction(zone
, order
);
167 /* Returns true if compaction should be skipped this time */
168 static bool compaction_deferred(struct zone
*zone
, int order
)
170 unsigned long defer_limit
= 1UL << zone
->compact_defer_shift
;
172 if (order
< zone
->compact_order_failed
)
175 /* Avoid possible overflow */
176 if (++zone
->compact_considered
>= defer_limit
) {
177 zone
->compact_considered
= defer_limit
;
181 trace_mm_compaction_deferred(zone
, order
);
187 * Update defer tracking counters after successful compaction of given order,
188 * which means an allocation either succeeded (alloc_success == true) or is
189 * expected to succeed.
191 void compaction_defer_reset(struct zone
*zone
, int order
,
195 zone
->compact_considered
= 0;
196 zone
->compact_defer_shift
= 0;
198 if (order
>= zone
->compact_order_failed
)
199 zone
->compact_order_failed
= order
+ 1;
201 trace_mm_compaction_defer_reset(zone
, order
);
204 /* Returns true if restarting compaction after many failures */
205 static bool compaction_restarting(struct zone
*zone
, int order
)
207 if (order
< zone
->compact_order_failed
)
210 return zone
->compact_defer_shift
== COMPACT_MAX_DEFER_SHIFT
&&
211 zone
->compact_considered
>= 1UL << zone
->compact_defer_shift
;
214 /* Returns true if the pageblock should be scanned for pages to isolate. */
215 static inline bool isolation_suitable(struct compact_control
*cc
,
218 if (cc
->ignore_skip_hint
)
221 return !get_pageblock_skip(page
);
224 static void reset_cached_positions(struct zone
*zone
)
226 zone
->compact_cached_migrate_pfn
[0] = zone
->zone_start_pfn
;
227 zone
->compact_cached_migrate_pfn
[1] = zone
->zone_start_pfn
;
228 zone
->compact_cached_free_pfn
=
229 pageblock_start_pfn(zone_end_pfn(zone
) - 1);
232 #ifdef CONFIG_SPARSEMEM
234 * If the PFN falls into an offline section, return the start PFN of the
235 * next online section. If the PFN falls into an online section or if
236 * there is no next online section, return 0.
238 static unsigned long skip_offline_sections(unsigned long start_pfn
)
240 unsigned long start_nr
= pfn_to_section_nr(start_pfn
);
242 if (online_section_nr(start_nr
))
245 while (++start_nr
<= __highest_present_section_nr
) {
246 if (online_section_nr(start_nr
))
247 return section_nr_to_pfn(start_nr
);
254 * If the PFN falls into an offline section, return the end PFN of the
255 * next online section in reverse. If the PFN falls into an online section
256 * or if there is no next online section in reverse, return 0.
258 static unsigned long skip_offline_sections_reverse(unsigned long start_pfn
)
260 unsigned long start_nr
= pfn_to_section_nr(start_pfn
);
262 if (!start_nr
|| online_section_nr(start_nr
))
265 while (start_nr
-- > 0) {
266 if (online_section_nr(start_nr
))
267 return section_nr_to_pfn(start_nr
) + PAGES_PER_SECTION
;
273 static unsigned long skip_offline_sections(unsigned long start_pfn
)
278 static unsigned long skip_offline_sections_reverse(unsigned long start_pfn
)
285 * Compound pages of >= pageblock_order should consistently be skipped until
286 * released. It is always pointless to compact pages of such order (if they are
287 * migratable), and the pageblocks they occupy cannot contain any free pages.
289 static bool pageblock_skip_persistent(struct page
*page
)
291 if (!PageCompound(page
))
294 page
= compound_head(page
);
296 if (compound_order(page
) >= pageblock_order
)
303 __reset_isolation_pfn(struct zone
*zone
, unsigned long pfn
, bool check_source
,
306 struct page
*page
= pfn_to_online_page(pfn
);
307 struct page
*block_page
;
308 struct page
*end_page
;
309 unsigned long block_pfn
;
313 if (zone
!= page_zone(page
))
315 if (pageblock_skip_persistent(page
))
319 * If skip is already cleared do no further checking once the
320 * restart points have been set.
322 if (check_source
&& check_target
&& !get_pageblock_skip(page
))
326 * If clearing skip for the target scanner, do not select a
327 * non-movable pageblock as the starting point.
329 if (!check_source
&& check_target
&&
330 get_pageblock_migratetype(page
) != MIGRATE_MOVABLE
)
333 /* Ensure the start of the pageblock or zone is online and valid */
334 block_pfn
= pageblock_start_pfn(pfn
);
335 block_pfn
= max(block_pfn
, zone
->zone_start_pfn
);
336 block_page
= pfn_to_online_page(block_pfn
);
342 /* Ensure the end of the pageblock or zone is online and valid */
343 block_pfn
= pageblock_end_pfn(pfn
) - 1;
344 block_pfn
= min(block_pfn
, zone_end_pfn(zone
) - 1);
345 end_page
= pfn_to_online_page(block_pfn
);
350 * Only clear the hint if a sample indicates there is either a
351 * free page or an LRU page in the block. One or other condition
352 * is necessary for the block to be a migration source/target.
355 if (check_source
&& PageLRU(page
)) {
356 clear_pageblock_skip(page
);
360 if (check_target
&& PageBuddy(page
)) {
361 clear_pageblock_skip(page
);
365 page
+= (1 << PAGE_ALLOC_COSTLY_ORDER
);
366 } while (page
<= end_page
);
372 * This function is called to clear all cached information on pageblocks that
373 * should be skipped for page isolation when the migrate and free page scanner
376 static void __reset_isolation_suitable(struct zone
*zone
)
378 unsigned long migrate_pfn
= zone
->zone_start_pfn
;
379 unsigned long free_pfn
= zone_end_pfn(zone
) - 1;
380 unsigned long reset_migrate
= free_pfn
;
381 unsigned long reset_free
= migrate_pfn
;
382 bool source_set
= false;
383 bool free_set
= false;
385 if (!zone
->compact_blockskip_flush
)
388 zone
->compact_blockskip_flush
= false;
391 * Walk the zone and update pageblock skip information. Source looks
392 * for PageLRU while target looks for PageBuddy. When the scanner
393 * is found, both PageBuddy and PageLRU are checked as the pageblock
394 * is suitable as both source and target.
396 for (; migrate_pfn
< free_pfn
; migrate_pfn
+= pageblock_nr_pages
,
397 free_pfn
-= pageblock_nr_pages
) {
400 /* Update the migrate PFN */
401 if (__reset_isolation_pfn(zone
, migrate_pfn
, true, source_set
) &&
402 migrate_pfn
< reset_migrate
) {
404 reset_migrate
= migrate_pfn
;
405 zone
->compact_init_migrate_pfn
= reset_migrate
;
406 zone
->compact_cached_migrate_pfn
[0] = reset_migrate
;
407 zone
->compact_cached_migrate_pfn
[1] = reset_migrate
;
410 /* Update the free PFN */
411 if (__reset_isolation_pfn(zone
, free_pfn
, free_set
, true) &&
412 free_pfn
> reset_free
) {
414 reset_free
= free_pfn
;
415 zone
->compact_init_free_pfn
= reset_free
;
416 zone
->compact_cached_free_pfn
= reset_free
;
420 /* Leave no distance if no suitable block was reset */
421 if (reset_migrate
>= reset_free
) {
422 zone
->compact_cached_migrate_pfn
[0] = migrate_pfn
;
423 zone
->compact_cached_migrate_pfn
[1] = migrate_pfn
;
424 zone
->compact_cached_free_pfn
= free_pfn
;
428 void reset_isolation_suitable(pg_data_t
*pgdat
)
432 for (zoneid
= 0; zoneid
< MAX_NR_ZONES
; zoneid
++) {
433 struct zone
*zone
= &pgdat
->node_zones
[zoneid
];
434 if (!populated_zone(zone
))
437 /* Only flush if a full compaction finished recently */
438 if (zone
->compact_blockskip_flush
)
439 __reset_isolation_suitable(zone
);
444 * Sets the pageblock skip bit if it was clear. Note that this is a hint as
445 * locks are not required for read/writers. Returns true if it was already set.
447 static bool test_and_set_skip(struct compact_control
*cc
, struct page
*page
)
451 /* Do not update if skip hint is being ignored */
452 if (cc
->ignore_skip_hint
)
455 skip
= get_pageblock_skip(page
);
456 if (!skip
&& !cc
->no_set_skip_hint
)
457 set_pageblock_skip(page
);
462 static void update_cached_migrate(struct compact_control
*cc
, unsigned long pfn
)
464 struct zone
*zone
= cc
->zone
;
466 /* Set for isolation rather than compaction */
467 if (cc
->no_set_skip_hint
)
470 pfn
= pageblock_end_pfn(pfn
);
472 /* Update where async and sync compaction should restart */
473 if (pfn
> zone
->compact_cached_migrate_pfn
[0])
474 zone
->compact_cached_migrate_pfn
[0] = pfn
;
475 if (cc
->mode
!= MIGRATE_ASYNC
&&
476 pfn
> zone
->compact_cached_migrate_pfn
[1])
477 zone
->compact_cached_migrate_pfn
[1] = pfn
;
481 * If no pages were isolated then mark this pageblock to be skipped in the
482 * future. The information is later cleared by __reset_isolation_suitable().
484 static void update_pageblock_skip(struct compact_control
*cc
,
485 struct page
*page
, unsigned long pfn
)
487 struct zone
*zone
= cc
->zone
;
489 if (cc
->no_set_skip_hint
)
492 set_pageblock_skip(page
);
494 if (pfn
< zone
->compact_cached_free_pfn
)
495 zone
->compact_cached_free_pfn
= pfn
;
498 static inline bool isolation_suitable(struct compact_control
*cc
,
504 static inline bool pageblock_skip_persistent(struct page
*page
)
509 static inline void update_pageblock_skip(struct compact_control
*cc
,
510 struct page
*page
, unsigned long pfn
)
514 static void update_cached_migrate(struct compact_control
*cc
, unsigned long pfn
)
518 static bool test_and_set_skip(struct compact_control
*cc
, struct page
*page
)
522 #endif /* CONFIG_COMPACTION */
525 * Compaction requires the taking of some coarse locks that are potentially
526 * very heavily contended. For async compaction, trylock and record if the
527 * lock is contended. The lock will still be acquired but compaction will
528 * abort when the current block is finished regardless of success rate.
529 * Sync compaction acquires the lock.
531 * Always returns true which makes it easier to track lock state in callers.
533 static bool compact_lock_irqsave(spinlock_t
*lock
, unsigned long *flags
,
534 struct compact_control
*cc
)
537 /* Track if the lock is contended in async mode */
538 if (cc
->mode
== MIGRATE_ASYNC
&& !cc
->contended
) {
539 if (spin_trylock_irqsave(lock
, *flags
))
542 cc
->contended
= true;
545 spin_lock_irqsave(lock
, *flags
);
550 * Compaction requires the taking of some coarse locks that are potentially
551 * very heavily contended. The lock should be periodically unlocked to avoid
552 * having disabled IRQs for a long time, even when there is nobody waiting on
553 * the lock. It might also be that allowing the IRQs will result in
554 * need_resched() becoming true. If scheduling is needed, compaction schedules.
555 * Either compaction type will also abort if a fatal signal is pending.
556 * In either case if the lock was locked, it is dropped and not regained.
558 * Returns true if compaction should abort due to fatal signal pending.
559 * Returns false when compaction can continue.
561 static bool compact_unlock_should_abort(spinlock_t
*lock
,
562 unsigned long flags
, bool *locked
, struct compact_control
*cc
)
565 spin_unlock_irqrestore(lock
, flags
);
569 if (fatal_signal_pending(current
)) {
570 cc
->contended
= true;
580 * Isolate free pages onto a private freelist. If @strict is true, will abort
581 * returning 0 on any invalid PFNs or non-free pages inside of the pageblock
582 * (even though it may still end up isolating some pages).
584 static unsigned long isolate_freepages_block(struct compact_control
*cc
,
585 unsigned long *start_pfn
,
586 unsigned long end_pfn
,
587 struct list_head
*freelist
,
591 int nr_scanned
= 0, total_isolated
= 0;
593 unsigned long flags
= 0;
595 unsigned long blockpfn
= *start_pfn
;
598 /* Strict mode is for isolation, speed is secondary */
602 page
= pfn_to_page(blockpfn
);
604 /* Isolate free pages. */
605 for (; blockpfn
< end_pfn
; blockpfn
+= stride
, page
+= stride
) {
609 * Periodically drop the lock (if held) regardless of its
610 * contention, to give chance to IRQs. Abort if fatal signal
613 if (!(blockpfn
% COMPACT_CLUSTER_MAX
)
614 && compact_unlock_should_abort(&cc
->zone
->lock
, flags
,
621 * For compound pages such as THP and hugetlbfs, we can save
622 * potentially a lot of iterations if we skip them at once.
623 * The check is racy, but we can consider only valid values
624 * and the only danger is skipping too much.
626 if (PageCompound(page
)) {
627 const unsigned int order
= compound_order(page
);
629 if (likely(order
<= MAX_ORDER
)) {
630 blockpfn
+= (1UL << order
) - 1;
631 page
+= (1UL << order
) - 1;
632 nr_scanned
+= (1UL << order
) - 1;
637 if (!PageBuddy(page
))
640 /* If we already hold the lock, we can skip some rechecking. */
642 locked
= compact_lock_irqsave(&cc
->zone
->lock
,
645 /* Recheck this is a buddy page under lock */
646 if (!PageBuddy(page
))
650 /* Found a free page, will break it into order-0 pages */
651 order
= buddy_order(page
);
652 isolated
= __isolate_free_page(page
, order
);
655 set_page_private(page
, order
);
657 nr_scanned
+= isolated
- 1;
658 total_isolated
+= isolated
;
659 cc
->nr_freepages
+= isolated
;
660 list_add_tail(&page
->lru
, freelist
);
662 if (!strict
&& cc
->nr_migratepages
<= cc
->nr_freepages
) {
663 blockpfn
+= isolated
;
666 /* Advance to the end of split page */
667 blockpfn
+= isolated
- 1;
668 page
+= isolated
- 1;
678 spin_unlock_irqrestore(&cc
->zone
->lock
, flags
);
681 * There is a tiny chance that we have read bogus compound_order(),
682 * so be careful to not go outside of the pageblock.
684 if (unlikely(blockpfn
> end_pfn
))
687 trace_mm_compaction_isolate_freepages(*start_pfn
, blockpfn
,
688 nr_scanned
, total_isolated
);
690 /* Record how far we have got within the block */
691 *start_pfn
= blockpfn
;
694 * If strict isolation is requested by CMA then check that all the
695 * pages requested were isolated. If there were any failures, 0 is
696 * returned and CMA will fail.
698 if (strict
&& blockpfn
< end_pfn
)
701 cc
->total_free_scanned
+= nr_scanned
;
703 count_compact_events(COMPACTISOLATED
, total_isolated
);
704 return total_isolated
;
708 * isolate_freepages_range() - isolate free pages.
709 * @cc: Compaction control structure.
710 * @start_pfn: The first PFN to start isolating.
711 * @end_pfn: The one-past-last PFN.
713 * Non-free pages, invalid PFNs, or zone boundaries within the
714 * [start_pfn, end_pfn) range are considered errors, cause function to
715 * undo its actions and return zero.
717 * Otherwise, function returns one-past-the-last PFN of isolated page
718 * (which may be greater then end_pfn if end fell in a middle of
722 isolate_freepages_range(struct compact_control
*cc
,
723 unsigned long start_pfn
, unsigned long end_pfn
)
725 unsigned long isolated
, pfn
, block_start_pfn
, block_end_pfn
;
729 block_start_pfn
= pageblock_start_pfn(pfn
);
730 if (block_start_pfn
< cc
->zone
->zone_start_pfn
)
731 block_start_pfn
= cc
->zone
->zone_start_pfn
;
732 block_end_pfn
= pageblock_end_pfn(pfn
);
734 for (; pfn
< end_pfn
; pfn
+= isolated
,
735 block_start_pfn
= block_end_pfn
,
736 block_end_pfn
+= pageblock_nr_pages
) {
737 /* Protect pfn from changing by isolate_freepages_block */
738 unsigned long isolate_start_pfn
= pfn
;
741 * pfn could pass the block_end_pfn if isolated freepage
742 * is more than pageblock order. In this case, we adjust
743 * scanning range to right one.
745 if (pfn
>= block_end_pfn
) {
746 block_start_pfn
= pageblock_start_pfn(pfn
);
747 block_end_pfn
= pageblock_end_pfn(pfn
);
750 block_end_pfn
= min(block_end_pfn
, end_pfn
);
752 if (!pageblock_pfn_to_page(block_start_pfn
,
753 block_end_pfn
, cc
->zone
))
756 isolated
= isolate_freepages_block(cc
, &isolate_start_pfn
,
757 block_end_pfn
, &freelist
, 0, true);
760 * In strict mode, isolate_freepages_block() returns 0 if
761 * there are any holes in the block (ie. invalid PFNs or
768 * If we managed to isolate pages, it is always (1 << n) *
769 * pageblock_nr_pages for some non-negative n. (Max order
770 * page may span two pageblocks).
774 /* __isolate_free_page() does not map the pages */
775 split_map_pages(&freelist
);
778 /* Loop terminated early, cleanup. */
779 release_freepages(&freelist
);
783 /* We don't use freelists for anything. */
787 /* Similar to reclaim, but different enough that they don't share logic */
788 static bool too_many_isolated(struct compact_control
*cc
)
790 pg_data_t
*pgdat
= cc
->zone
->zone_pgdat
;
793 unsigned long active
, inactive
, isolated
;
795 inactive
= node_page_state(pgdat
, NR_INACTIVE_FILE
) +
796 node_page_state(pgdat
, NR_INACTIVE_ANON
);
797 active
= node_page_state(pgdat
, NR_ACTIVE_FILE
) +
798 node_page_state(pgdat
, NR_ACTIVE_ANON
);
799 isolated
= node_page_state(pgdat
, NR_ISOLATED_FILE
) +
800 node_page_state(pgdat
, NR_ISOLATED_ANON
);
803 * Allow GFP_NOFS to isolate past the limit set for regular
804 * compaction runs. This prevents an ABBA deadlock when other
805 * compactors have already isolated to the limit, but are
806 * blocked on filesystem locks held by the GFP_NOFS thread.
808 if (cc
->gfp_mask
& __GFP_FS
) {
813 too_many
= isolated
> (inactive
+ active
) / 2;
815 wake_throttle_isolated(pgdat
);
821 * isolate_migratepages_block() - isolate all migrate-able pages within
823 * @cc: Compaction control structure.
824 * @low_pfn: The first PFN to isolate
825 * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
826 * @mode: Isolation mode to be used.
828 * Isolate all pages that can be migrated from the range specified by
829 * [low_pfn, end_pfn). The range is expected to be within same pageblock.
830 * Returns errno, like -EAGAIN or -EINTR in case e.g signal pending or congestion,
831 * -ENOMEM in case we could not allocate a page, or 0.
832 * cc->migrate_pfn will contain the next pfn to scan.
834 * The pages are isolated on cc->migratepages list (not required to be empty),
835 * and cc->nr_migratepages is updated accordingly.
838 isolate_migratepages_block(struct compact_control
*cc
, unsigned long low_pfn
,
839 unsigned long end_pfn
, isolate_mode_t mode
)
841 pg_data_t
*pgdat
= cc
->zone
->zone_pgdat
;
842 unsigned long nr_scanned
= 0, nr_isolated
= 0;
843 struct lruvec
*lruvec
;
844 unsigned long flags
= 0;
845 struct lruvec
*locked
= NULL
;
846 struct folio
*folio
= NULL
;
847 struct page
*page
= NULL
, *valid_page
= NULL
;
848 struct address_space
*mapping
;
849 unsigned long start_pfn
= low_pfn
;
850 bool skip_on_failure
= false;
851 unsigned long next_skip_pfn
= 0;
852 bool skip_updated
= false;
855 cc
->migrate_pfn
= low_pfn
;
858 * Ensure that there are not too many pages isolated from the LRU
859 * list by either parallel reclaimers or compaction. If there are,
860 * delay for some time until fewer pages are isolated
862 while (unlikely(too_many_isolated(cc
))) {
863 /* stop isolation if there are still pages not migrated */
864 if (cc
->nr_migratepages
)
867 /* async migration should just abort */
868 if (cc
->mode
== MIGRATE_ASYNC
)
871 reclaim_throttle(pgdat
, VMSCAN_THROTTLE_ISOLATED
);
873 if (fatal_signal_pending(current
))
879 if (cc
->direct_compaction
&& (cc
->mode
== MIGRATE_ASYNC
)) {
880 skip_on_failure
= true;
881 next_skip_pfn
= block_end_pfn(low_pfn
, cc
->order
);
884 /* Time to isolate some pages for migration */
885 for (; low_pfn
< end_pfn
; low_pfn
++) {
887 if (skip_on_failure
&& low_pfn
>= next_skip_pfn
) {
889 * We have isolated all migration candidates in the
890 * previous order-aligned block, and did not skip it due
891 * to failure. We should migrate the pages now and
892 * hopefully succeed compaction.
898 * We failed to isolate in the previous order-aligned
899 * block. Set the new boundary to the end of the
900 * current block. Note we can't simply increase
901 * next_skip_pfn by 1 << order, as low_pfn might have
902 * been incremented by a higher number due to skipping
903 * a compound or a high-order buddy page in the
904 * previous loop iteration.
906 next_skip_pfn
= block_end_pfn(low_pfn
, cc
->order
);
910 * Periodically drop the lock (if held) regardless of its
911 * contention, to give chance to IRQs. Abort completely if
912 * a fatal signal is pending.
914 if (!(low_pfn
% COMPACT_CLUSTER_MAX
)) {
916 unlock_page_lruvec_irqrestore(locked
, flags
);
920 if (fatal_signal_pending(current
)) {
921 cc
->contended
= true;
932 page
= pfn_to_page(low_pfn
);
935 * Check if the pageblock has already been marked skipped.
936 * Only the first PFN is checked as the caller isolates
937 * COMPACT_CLUSTER_MAX at a time so the second call must
938 * not falsely conclude that the block should be skipped.
940 if (!valid_page
&& (pageblock_aligned(low_pfn
) ||
941 low_pfn
== cc
->zone
->zone_start_pfn
)) {
942 if (!isolation_suitable(cc
, page
)) {
950 if (PageHuge(page
) && cc
->alloc_contig
) {
952 unlock_page_lruvec_irqrestore(locked
, flags
);
956 ret
= isolate_or_dissolve_huge_page(page
, &cc
->migratepages
);
959 * Fail isolation in case isolate_or_dissolve_huge_page()
960 * reports an error. In case of -ENOMEM, abort right away.
963 /* Do not report -EBUSY down the chain */
966 low_pfn
+= compound_nr(page
) - 1;
967 nr_scanned
+= compound_nr(page
) - 1;
971 if (PageHuge(page
)) {
973 * Hugepage was successfully isolated and placed
974 * on the cc->migratepages list.
976 folio
= page_folio(page
);
977 low_pfn
+= folio_nr_pages(folio
) - 1;
978 goto isolate_success_no_list
;
982 * Ok, the hugepage was dissolved. Now these pages are
983 * Buddy and cannot be re-allocated because they are
984 * isolated. Fall-through as the check below handles
990 * Skip if free. We read page order here without zone lock
991 * which is generally unsafe, but the race window is small and
992 * the worst thing that can happen is that we skip some
993 * potential isolation targets.
995 if (PageBuddy(page
)) {
996 unsigned long freepage_order
= buddy_order_unsafe(page
);
999 * Without lock, we cannot be sure that what we got is
1000 * a valid page order. Consider only values in the
1001 * valid order range to prevent low_pfn overflow.
1003 if (freepage_order
> 0 && freepage_order
<= MAX_ORDER
) {
1004 low_pfn
+= (1UL << freepage_order
) - 1;
1005 nr_scanned
+= (1UL << freepage_order
) - 1;
1011 * Regardless of being on LRU, compound pages such as THP and
1012 * hugetlbfs are not to be compacted unless we are attempting
1013 * an allocation much larger than the huge page size (eg CMA).
1014 * We can potentially save a lot of iterations if we skip them
1015 * at once. The check is racy, but we can consider only valid
1016 * values and the only danger is skipping too much.
1018 if (PageCompound(page
) && !cc
->alloc_contig
) {
1019 const unsigned int order
= compound_order(page
);
1021 if (likely(order
<= MAX_ORDER
)) {
1022 low_pfn
+= (1UL << order
) - 1;
1023 nr_scanned
+= (1UL << order
) - 1;
1029 * Check may be lockless but that's ok as we recheck later.
1030 * It's possible to migrate LRU and non-lru movable pages.
1031 * Skip any other type of page
1033 if (!PageLRU(page
)) {
1035 * __PageMovable can return false positive so we need
1036 * to verify it under page_lock.
1038 if (unlikely(__PageMovable(page
)) &&
1039 !PageIsolated(page
)) {
1041 unlock_page_lruvec_irqrestore(locked
, flags
);
1045 if (isolate_movable_page(page
, mode
)) {
1046 folio
= page_folio(page
);
1047 goto isolate_success
;
1055 * Be careful not to clear PageLRU until after we're
1056 * sure the page is not being freed elsewhere -- the
1057 * page release code relies on it.
1059 folio
= folio_get_nontail_page(page
);
1060 if (unlikely(!folio
))
1064 * Migration will fail if an anonymous page is pinned in memory,
1065 * so avoid taking lru_lock and isolating it unnecessarily in an
1066 * admittedly racy check.
1068 mapping
= folio_mapping(folio
);
1069 if (!mapping
&& (folio_ref_count(folio
) - 1) > folio_mapcount(folio
))
1070 goto isolate_fail_put
;
1073 * Only allow to migrate anonymous pages in GFP_NOFS context
1074 * because those do not depend on fs locks.
1076 if (!(cc
->gfp_mask
& __GFP_FS
) && mapping
)
1077 goto isolate_fail_put
;
1079 /* Only take pages on LRU: a check now makes later tests safe */
1080 if (!folio_test_lru(folio
))
1081 goto isolate_fail_put
;
1083 /* Compaction might skip unevictable pages but CMA takes them */
1084 if (!(mode
& ISOLATE_UNEVICTABLE
) && folio_test_unevictable(folio
))
1085 goto isolate_fail_put
;
1088 * To minimise LRU disruption, the caller can indicate with
1089 * ISOLATE_ASYNC_MIGRATE that it only wants to isolate pages
1090 * it will be able to migrate without blocking - clean pages
1091 * for the most part. PageWriteback would require blocking.
1093 if ((mode
& ISOLATE_ASYNC_MIGRATE
) && folio_test_writeback(folio
))
1094 goto isolate_fail_put
;
1096 if ((mode
& ISOLATE_ASYNC_MIGRATE
) && folio_test_dirty(folio
)) {
1100 * Only folios without mappings or that have
1101 * a ->migrate_folio callback are possible to
1102 * migrate without blocking. However, we may
1103 * be racing with truncation, which can free
1104 * the mapping. Truncation holds the folio lock
1105 * until after the folio is removed from the page
1106 * cache so holding it ourselves is sufficient.
1108 if (!folio_trylock(folio
))
1109 goto isolate_fail_put
;
1111 mapping
= folio_mapping(folio
);
1112 migrate_dirty
= !mapping
||
1113 mapping
->a_ops
->migrate_folio
;
1114 folio_unlock(folio
);
1116 goto isolate_fail_put
;
1119 /* Try isolate the folio */
1120 if (!folio_test_clear_lru(folio
))
1121 goto isolate_fail_put
;
1123 lruvec
= folio_lruvec(folio
);
1125 /* If we already hold the lock, we can skip some rechecking */
1126 if (lruvec
!= locked
) {
1128 unlock_page_lruvec_irqrestore(locked
, flags
);
1130 compact_lock_irqsave(&lruvec
->lru_lock
, &flags
, cc
);
1133 lruvec_memcg_debug(lruvec
, folio
);
1136 * Try get exclusive access under lock. If marked for
1137 * skip, the scan is aborted unless the current context
1138 * is a rescan to reach the end of the pageblock.
1140 if (!skip_updated
&& valid_page
) {
1141 skip_updated
= true;
1142 if (test_and_set_skip(cc
, valid_page
) &&
1143 !cc
->finish_pageblock
) {
1150 * folio become large since the non-locked check,
1153 if (unlikely(folio_test_large(folio
) && !cc
->alloc_contig
)) {
1154 low_pfn
+= folio_nr_pages(folio
) - 1;
1155 nr_scanned
+= folio_nr_pages(folio
) - 1;
1156 folio_set_lru(folio
);
1157 goto isolate_fail_put
;
1161 /* The folio is taken off the LRU */
1162 if (folio_test_large(folio
))
1163 low_pfn
+= folio_nr_pages(folio
) - 1;
1165 /* Successfully isolated */
1166 lruvec_del_folio(lruvec
, folio
);
1167 node_stat_mod_folio(folio
,
1168 NR_ISOLATED_ANON
+ folio_is_file_lru(folio
),
1169 folio_nr_pages(folio
));
1172 list_add(&folio
->lru
, &cc
->migratepages
);
1173 isolate_success_no_list
:
1174 cc
->nr_migratepages
+= folio_nr_pages(folio
);
1175 nr_isolated
+= folio_nr_pages(folio
);
1176 nr_scanned
+= folio_nr_pages(folio
) - 1;
1179 * Avoid isolating too much unless this block is being
1180 * fully scanned (e.g. dirty/writeback pages, parallel allocation)
1181 * or a lock is contended. For contention, isolate quickly to
1182 * potentially remove one source of contention.
1184 if (cc
->nr_migratepages
>= COMPACT_CLUSTER_MAX
&&
1185 !cc
->finish_pageblock
&& !cc
->contended
) {
1193 /* Avoid potential deadlock in freeing page under lru_lock */
1195 unlock_page_lruvec_irqrestore(locked
, flags
);
1201 if (!skip_on_failure
&& ret
!= -ENOMEM
)
1205 * We have isolated some pages, but then failed. Release them
1206 * instead of migrating, as we cannot form the cc->order buddy
1211 unlock_page_lruvec_irqrestore(locked
, flags
);
1214 putback_movable_pages(&cc
->migratepages
);
1215 cc
->nr_migratepages
= 0;
1219 if (low_pfn
< next_skip_pfn
) {
1220 low_pfn
= next_skip_pfn
- 1;
1222 * The check near the loop beginning would have updated
1223 * next_skip_pfn too, but this is a bit simpler.
1225 next_skip_pfn
+= 1UL << cc
->order
;
1233 * The PageBuddy() check could have potentially brought us outside
1234 * the range to be scanned.
1236 if (unlikely(low_pfn
> end_pfn
))
1243 unlock_page_lruvec_irqrestore(locked
, flags
);
1245 folio_set_lru(folio
);
1250 * Update the cached scanner pfn once the pageblock has been scanned.
1251 * Pages will either be migrated in which case there is no point
1252 * scanning in the near future or migration failed in which case the
1253 * failure reason may persist. The block is marked for skipping if
1254 * there were no pages isolated in the block or if the block is
1255 * rescanned twice in a row.
1257 if (low_pfn
== end_pfn
&& (!nr_isolated
|| cc
->finish_pageblock
)) {
1258 if (!cc
->no_set_skip_hint
&& valid_page
&& !skip_updated
)
1259 set_pageblock_skip(valid_page
);
1260 update_cached_migrate(cc
, low_pfn
);
1263 trace_mm_compaction_isolate_migratepages(start_pfn
, low_pfn
,
1264 nr_scanned
, nr_isolated
);
1267 cc
->total_migrate_scanned
+= nr_scanned
;
1269 count_compact_events(COMPACTISOLATED
, nr_isolated
);
1271 cc
->migrate_pfn
= low_pfn
;
1277 * isolate_migratepages_range() - isolate migrate-able pages in a PFN range
1278 * @cc: Compaction control structure.
1279 * @start_pfn: The first PFN to start isolating.
1280 * @end_pfn: The one-past-last PFN.
1282 * Returns -EAGAIN when contented, -EINTR in case of a signal pending, -ENOMEM
1283 * in case we could not allocate a page, or 0.
1286 isolate_migratepages_range(struct compact_control
*cc
, unsigned long start_pfn
,
1287 unsigned long end_pfn
)
1289 unsigned long pfn
, block_start_pfn
, block_end_pfn
;
1292 /* Scan block by block. First and last block may be incomplete */
1294 block_start_pfn
= pageblock_start_pfn(pfn
);
1295 if (block_start_pfn
< cc
->zone
->zone_start_pfn
)
1296 block_start_pfn
= cc
->zone
->zone_start_pfn
;
1297 block_end_pfn
= pageblock_end_pfn(pfn
);
1299 for (; pfn
< end_pfn
; pfn
= block_end_pfn
,
1300 block_start_pfn
= block_end_pfn
,
1301 block_end_pfn
+= pageblock_nr_pages
) {
1303 block_end_pfn
= min(block_end_pfn
, end_pfn
);
1305 if (!pageblock_pfn_to_page(block_start_pfn
,
1306 block_end_pfn
, cc
->zone
))
1309 ret
= isolate_migratepages_block(cc
, pfn
, block_end_pfn
,
1310 ISOLATE_UNEVICTABLE
);
1315 if (cc
->nr_migratepages
>= COMPACT_CLUSTER_MAX
)
1322 #endif /* CONFIG_COMPACTION || CONFIG_CMA */
1323 #ifdef CONFIG_COMPACTION
1325 static bool suitable_migration_source(struct compact_control
*cc
,
1330 if (pageblock_skip_persistent(page
))
1333 if ((cc
->mode
!= MIGRATE_ASYNC
) || !cc
->direct_compaction
)
1336 block_mt
= get_pageblock_migratetype(page
);
1338 if (cc
->migratetype
== MIGRATE_MOVABLE
)
1339 return is_migrate_movable(block_mt
);
1341 return block_mt
== cc
->migratetype
;
1344 /* Returns true if the page is within a block suitable for migration to */
1345 static bool suitable_migration_target(struct compact_control
*cc
,
1348 /* If the page is a large free page, then disallow migration */
1349 if (PageBuddy(page
)) {
1351 * We are checking page_order without zone->lock taken. But
1352 * the only small danger is that we skip a potentially suitable
1353 * pageblock, so it's not worth to check order for valid range.
1355 if (buddy_order_unsafe(page
) >= pageblock_order
)
1359 if (cc
->ignore_block_suitable
)
1362 /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
1363 if (is_migrate_movable(get_pageblock_migratetype(page
)))
1366 /* Otherwise skip the block */
1370 static inline unsigned int
1371 freelist_scan_limit(struct compact_control
*cc
)
1373 unsigned short shift
= BITS_PER_LONG
- 1;
1375 return (COMPACT_CLUSTER_MAX
>> min(shift
, cc
->fast_search_fail
)) + 1;
1379 * Test whether the free scanner has reached the same or lower pageblock than
1380 * the migration scanner, and compaction should thus terminate.
1382 static inline bool compact_scanners_met(struct compact_control
*cc
)
1384 return (cc
->free_pfn
>> pageblock_order
)
1385 <= (cc
->migrate_pfn
>> pageblock_order
);
1389 * Used when scanning for a suitable migration target which scans freelists
1390 * in reverse. Reorders the list such as the unscanned pages are scanned
1391 * first on the next iteration of the free scanner
1394 move_freelist_head(struct list_head
*freelist
, struct page
*freepage
)
1398 if (!list_is_last(freelist
, &freepage
->lru
)) {
1399 list_cut_before(&sublist
, freelist
, &freepage
->lru
);
1400 list_splice_tail(&sublist
, freelist
);
1405 * Similar to move_freelist_head except used by the migration scanner
1406 * when scanning forward. It's possible for these list operations to
1407 * move against each other if they search the free list exactly in
1411 move_freelist_tail(struct list_head
*freelist
, struct page
*freepage
)
1415 if (!list_is_first(freelist
, &freepage
->lru
)) {
1416 list_cut_position(&sublist
, freelist
, &freepage
->lru
);
1417 list_splice_tail(&sublist
, freelist
);
1422 fast_isolate_around(struct compact_control
*cc
, unsigned long pfn
)
1424 unsigned long start_pfn
, end_pfn
;
1427 /* Do not search around if there are enough pages already */
1428 if (cc
->nr_freepages
>= cc
->nr_migratepages
)
1431 /* Minimise scanning during async compaction */
1432 if (cc
->direct_compaction
&& cc
->mode
== MIGRATE_ASYNC
)
1435 /* Pageblock boundaries */
1436 start_pfn
= max(pageblock_start_pfn(pfn
), cc
->zone
->zone_start_pfn
);
1437 end_pfn
= min(pageblock_end_pfn(pfn
), zone_end_pfn(cc
->zone
));
1439 page
= pageblock_pfn_to_page(start_pfn
, end_pfn
, cc
->zone
);
1443 isolate_freepages_block(cc
, &start_pfn
, end_pfn
, &cc
->freepages
, 1, false);
1445 /* Skip this pageblock in the future as it's full or nearly full */
1446 if (start_pfn
== end_pfn
&& !cc
->no_set_skip_hint
)
1447 set_pageblock_skip(page
);
1450 /* Search orders in round-robin fashion */
1451 static int next_search_order(struct compact_control
*cc
, int order
)
1455 order
= cc
->order
- 1;
1457 /* Search wrapped around? */
1458 if (order
== cc
->search_order
) {
1460 if (cc
->search_order
< 0)
1461 cc
->search_order
= cc
->order
- 1;
1468 static void fast_isolate_freepages(struct compact_control
*cc
)
1470 unsigned int limit
= max(1U, freelist_scan_limit(cc
) >> 1);
1471 unsigned int nr_scanned
= 0, total_isolated
= 0;
1472 unsigned long low_pfn
, min_pfn
, highest
= 0;
1473 unsigned long nr_isolated
= 0;
1474 unsigned long distance
;
1475 struct page
*page
= NULL
;
1476 bool scan_start
= false;
1479 /* Full compaction passes in a negative order */
1484 * If starting the scan, use a deeper search and use the highest
1485 * PFN found if a suitable one is not found.
1487 if (cc
->free_pfn
>= cc
->zone
->compact_init_free_pfn
) {
1488 limit
= pageblock_nr_pages
>> 1;
1493 * Preferred point is in the top quarter of the scan space but take
1494 * a pfn from the top half if the search is problematic.
1496 distance
= (cc
->free_pfn
- cc
->migrate_pfn
);
1497 low_pfn
= pageblock_start_pfn(cc
->free_pfn
- (distance
>> 2));
1498 min_pfn
= pageblock_start_pfn(cc
->free_pfn
- (distance
>> 1));
1500 if (WARN_ON_ONCE(min_pfn
> low_pfn
))
1504 * Search starts from the last successful isolation order or the next
1505 * order to search after a previous failure
1507 cc
->search_order
= min_t(unsigned int, cc
->order
- 1, cc
->search_order
);
1509 for (order
= cc
->search_order
;
1510 !page
&& order
>= 0;
1511 order
= next_search_order(cc
, order
)) {
1512 struct free_area
*area
= &cc
->zone
->free_area
[order
];
1513 struct list_head
*freelist
;
1514 struct page
*freepage
;
1515 unsigned long flags
;
1516 unsigned int order_scanned
= 0;
1517 unsigned long high_pfn
= 0;
1522 spin_lock_irqsave(&cc
->zone
->lock
, flags
);
1523 freelist
= &area
->free_list
[MIGRATE_MOVABLE
];
1524 list_for_each_entry_reverse(freepage
, freelist
, buddy_list
) {
1529 pfn
= page_to_pfn(freepage
);
1532 highest
= max(pageblock_start_pfn(pfn
),
1533 cc
->zone
->zone_start_pfn
);
1535 if (pfn
>= low_pfn
) {
1536 cc
->fast_search_fail
= 0;
1537 cc
->search_order
= order
;
1542 if (pfn
>= min_pfn
&& pfn
> high_pfn
) {
1545 /* Shorten the scan if a candidate is found */
1549 if (order_scanned
>= limit
)
1553 /* Use a maximum candidate pfn if a preferred one was not found */
1554 if (!page
&& high_pfn
) {
1555 page
= pfn_to_page(high_pfn
);
1557 /* Update freepage for the list reorder below */
1561 /* Reorder to so a future search skips recent pages */
1562 move_freelist_head(freelist
, freepage
);
1564 /* Isolate the page if available */
1566 if (__isolate_free_page(page
, order
)) {
1567 set_page_private(page
, order
);
1568 nr_isolated
= 1 << order
;
1569 nr_scanned
+= nr_isolated
- 1;
1570 total_isolated
+= nr_isolated
;
1571 cc
->nr_freepages
+= nr_isolated
;
1572 list_add_tail(&page
->lru
, &cc
->freepages
);
1573 count_compact_events(COMPACTISOLATED
, nr_isolated
);
1575 /* If isolation fails, abort the search */
1576 order
= cc
->search_order
+ 1;
1581 spin_unlock_irqrestore(&cc
->zone
->lock
, flags
);
1583 /* Skip fast search if enough freepages isolated */
1584 if (cc
->nr_freepages
>= cc
->nr_migratepages
)
1588 * Smaller scan on next order so the total scan is related
1589 * to freelist_scan_limit.
1591 if (order_scanned
>= limit
)
1592 limit
= max(1U, limit
>> 1);
1595 trace_mm_compaction_fast_isolate_freepages(min_pfn
, cc
->free_pfn
,
1596 nr_scanned
, total_isolated
);
1599 cc
->fast_search_fail
++;
1602 * Use the highest PFN found above min. If one was
1603 * not found, be pessimistic for direct compaction
1604 * and use the min mark.
1606 if (highest
>= min_pfn
) {
1607 page
= pfn_to_page(highest
);
1608 cc
->free_pfn
= highest
;
1610 if (cc
->direct_compaction
&& pfn_valid(min_pfn
)) {
1611 page
= pageblock_pfn_to_page(min_pfn
,
1612 min(pageblock_end_pfn(min_pfn
),
1613 zone_end_pfn(cc
->zone
)),
1615 cc
->free_pfn
= min_pfn
;
1621 if (highest
&& highest
>= cc
->zone
->compact_cached_free_pfn
) {
1622 highest
-= pageblock_nr_pages
;
1623 cc
->zone
->compact_cached_free_pfn
= highest
;
1626 cc
->total_free_scanned
+= nr_scanned
;
1630 low_pfn
= page_to_pfn(page
);
1631 fast_isolate_around(cc
, low_pfn
);
1635 * Based on information in the current compact_control, find blocks
1636 * suitable for isolating free pages from and then isolate them.
1638 static void isolate_freepages(struct compact_control
*cc
)
1640 struct zone
*zone
= cc
->zone
;
1642 unsigned long block_start_pfn
; /* start of current pageblock */
1643 unsigned long isolate_start_pfn
; /* exact pfn we start at */
1644 unsigned long block_end_pfn
; /* end of current pageblock */
1645 unsigned long low_pfn
; /* lowest pfn scanner is able to scan */
1646 struct list_head
*freelist
= &cc
->freepages
;
1647 unsigned int stride
;
1649 /* Try a small search of the free lists for a candidate */
1650 fast_isolate_freepages(cc
);
1651 if (cc
->nr_freepages
)
1655 * Initialise the free scanner. The starting point is where we last
1656 * successfully isolated from, zone-cached value, or the end of the
1657 * zone when isolating for the first time. For looping we also need
1658 * this pfn aligned down to the pageblock boundary, because we do
1659 * block_start_pfn -= pageblock_nr_pages in the for loop.
1660 * For ending point, take care when isolating in last pageblock of a
1661 * zone which ends in the middle of a pageblock.
1662 * The low boundary is the end of the pageblock the migration scanner
1665 isolate_start_pfn
= cc
->free_pfn
;
1666 block_start_pfn
= pageblock_start_pfn(isolate_start_pfn
);
1667 block_end_pfn
= min(block_start_pfn
+ pageblock_nr_pages
,
1668 zone_end_pfn(zone
));
1669 low_pfn
= pageblock_end_pfn(cc
->migrate_pfn
);
1670 stride
= cc
->mode
== MIGRATE_ASYNC
? COMPACT_CLUSTER_MAX
: 1;
1673 * Isolate free pages until enough are available to migrate the
1674 * pages on cc->migratepages. We stop searching if the migrate
1675 * and free page scanners meet or enough free pages are isolated.
1677 for (; block_start_pfn
>= low_pfn
;
1678 block_end_pfn
= block_start_pfn
,
1679 block_start_pfn
-= pageblock_nr_pages
,
1680 isolate_start_pfn
= block_start_pfn
) {
1681 unsigned long nr_isolated
;
1684 * This can iterate a massively long zone without finding any
1685 * suitable migration targets, so periodically check resched.
1687 if (!(block_start_pfn
% (COMPACT_CLUSTER_MAX
* pageblock_nr_pages
)))
1690 page
= pageblock_pfn_to_page(block_start_pfn
, block_end_pfn
,
1693 unsigned long next_pfn
;
1695 next_pfn
= skip_offline_sections_reverse(block_start_pfn
);
1697 block_start_pfn
= max(next_pfn
, low_pfn
);
1702 /* Check the block is suitable for migration */
1703 if (!suitable_migration_target(cc
, page
))
1706 /* If isolation recently failed, do not retry */
1707 if (!isolation_suitable(cc
, page
))
1710 /* Found a block suitable for isolating free pages from. */
1711 nr_isolated
= isolate_freepages_block(cc
, &isolate_start_pfn
,
1712 block_end_pfn
, freelist
, stride
, false);
1714 /* Update the skip hint if the full pageblock was scanned */
1715 if (isolate_start_pfn
== block_end_pfn
)
1716 update_pageblock_skip(cc
, page
, block_start_pfn
-
1717 pageblock_nr_pages
);
1719 /* Are enough freepages isolated? */
1720 if (cc
->nr_freepages
>= cc
->nr_migratepages
) {
1721 if (isolate_start_pfn
>= block_end_pfn
) {
1723 * Restart at previous pageblock if more
1724 * freepages can be isolated next time.
1727 block_start_pfn
- pageblock_nr_pages
;
1730 } else if (isolate_start_pfn
< block_end_pfn
) {
1732 * If isolation failed early, do not continue
1738 /* Adjust stride depending on isolation */
1743 stride
= min_t(unsigned int, COMPACT_CLUSTER_MAX
, stride
<< 1);
1747 * Record where the free scanner will restart next time. Either we
1748 * broke from the loop and set isolate_start_pfn based on the last
1749 * call to isolate_freepages_block(), or we met the migration scanner
1750 * and the loop terminated due to isolate_start_pfn < low_pfn
1752 cc
->free_pfn
= isolate_start_pfn
;
1755 /* __isolate_free_page() does not map the pages */
1756 split_map_pages(freelist
);
1760 * This is a migrate-callback that "allocates" freepages by taking pages
1761 * from the isolated freelists in the block we are migrating to.
1763 static struct folio
*compaction_alloc(struct folio
*src
, unsigned long data
)
1765 struct compact_control
*cc
= (struct compact_control
*)data
;
1768 if (list_empty(&cc
->freepages
)) {
1769 isolate_freepages(cc
);
1771 if (list_empty(&cc
->freepages
))
1775 dst
= list_entry(cc
->freepages
.next
, struct folio
, lru
);
1776 list_del(&dst
->lru
);
1783 * This is a migrate-callback that "frees" freepages back to the isolated
1784 * freelist. All pages on the freelist are from the same zone, so there is no
1785 * special handling needed for NUMA.
1787 static void compaction_free(struct folio
*dst
, unsigned long data
)
1789 struct compact_control
*cc
= (struct compact_control
*)data
;
1791 list_add(&dst
->lru
, &cc
->freepages
);
1795 /* possible outcome of isolate_migratepages */
1797 ISOLATE_ABORT
, /* Abort compaction now */
1798 ISOLATE_NONE
, /* No pages isolated, continue scanning */
1799 ISOLATE_SUCCESS
, /* Pages isolated, migrate */
1800 } isolate_migrate_t
;
1803 * Allow userspace to control policy on scanning the unevictable LRU for
1804 * compactable pages.
1806 static int sysctl_compact_unevictable_allowed __read_mostly
= CONFIG_COMPACT_UNEVICTABLE_DEFAULT
;
1808 * Tunable for proactive compaction. It determines how
1809 * aggressively the kernel should compact memory in the
1810 * background. It takes values in the range [0, 100].
1812 static unsigned int __read_mostly sysctl_compaction_proactiveness
= 20;
1813 static int sysctl_extfrag_threshold
= 500;
1814 static int __read_mostly sysctl_compact_memory
;
1817 update_fast_start_pfn(struct compact_control
*cc
, unsigned long pfn
)
1819 if (cc
->fast_start_pfn
== ULONG_MAX
)
1822 if (!cc
->fast_start_pfn
)
1823 cc
->fast_start_pfn
= pfn
;
1825 cc
->fast_start_pfn
= min(cc
->fast_start_pfn
, pfn
);
1828 static inline unsigned long
1829 reinit_migrate_pfn(struct compact_control
*cc
)
1831 if (!cc
->fast_start_pfn
|| cc
->fast_start_pfn
== ULONG_MAX
)
1832 return cc
->migrate_pfn
;
1834 cc
->migrate_pfn
= cc
->fast_start_pfn
;
1835 cc
->fast_start_pfn
= ULONG_MAX
;
1837 return cc
->migrate_pfn
;
1841 * Briefly search the free lists for a migration source that already has
1842 * some free pages to reduce the number of pages that need migration
1843 * before a pageblock is free.
1845 static unsigned long fast_find_migrateblock(struct compact_control
*cc
)
1847 unsigned int limit
= freelist_scan_limit(cc
);
1848 unsigned int nr_scanned
= 0;
1849 unsigned long distance
;
1850 unsigned long pfn
= cc
->migrate_pfn
;
1851 unsigned long high_pfn
;
1853 bool found_block
= false;
1855 /* Skip hints are relied on to avoid repeats on the fast search */
1856 if (cc
->ignore_skip_hint
)
1860 * If the pageblock should be finished then do not select a different
1863 if (cc
->finish_pageblock
)
1867 * If the migrate_pfn is not at the start of a zone or the start
1868 * of a pageblock then assume this is a continuation of a previous
1869 * scan restarted due to COMPACT_CLUSTER_MAX.
1871 if (pfn
!= cc
->zone
->zone_start_pfn
&& pfn
!= pageblock_start_pfn(pfn
))
1875 * For smaller orders, just linearly scan as the number of pages
1876 * to migrate should be relatively small and does not necessarily
1877 * justify freeing up a large block for a small allocation.
1879 if (cc
->order
<= PAGE_ALLOC_COSTLY_ORDER
)
1883 * Only allow kcompactd and direct requests for movable pages to
1884 * quickly clear out a MOVABLE pageblock for allocation. This
1885 * reduces the risk that a large movable pageblock is freed for
1886 * an unmovable/reclaimable small allocation.
1888 if (cc
->direct_compaction
&& cc
->migratetype
!= MIGRATE_MOVABLE
)
1892 * When starting the migration scanner, pick any pageblock within the
1893 * first half of the search space. Otherwise try and pick a pageblock
1894 * within the first eighth to reduce the chances that a migration
1895 * target later becomes a source.
1897 distance
= (cc
->free_pfn
- cc
->migrate_pfn
) >> 1;
1898 if (cc
->migrate_pfn
!= cc
->zone
->zone_start_pfn
)
1900 high_pfn
= pageblock_start_pfn(cc
->migrate_pfn
+ distance
);
1902 for (order
= cc
->order
- 1;
1903 order
>= PAGE_ALLOC_COSTLY_ORDER
&& !found_block
&& nr_scanned
< limit
;
1905 struct free_area
*area
= &cc
->zone
->free_area
[order
];
1906 struct list_head
*freelist
;
1907 unsigned long flags
;
1908 struct page
*freepage
;
1913 spin_lock_irqsave(&cc
->zone
->lock
, flags
);
1914 freelist
= &area
->free_list
[MIGRATE_MOVABLE
];
1915 list_for_each_entry(freepage
, freelist
, buddy_list
) {
1916 unsigned long free_pfn
;
1918 if (nr_scanned
++ >= limit
) {
1919 move_freelist_tail(freelist
, freepage
);
1923 free_pfn
= page_to_pfn(freepage
);
1924 if (free_pfn
< high_pfn
) {
1926 * Avoid if skipped recently. Ideally it would
1927 * move to the tail but even safe iteration of
1928 * the list assumes an entry is deleted, not
1931 if (get_pageblock_skip(freepage
))
1934 /* Reorder to so a future search skips recent pages */
1935 move_freelist_tail(freelist
, freepage
);
1937 update_fast_start_pfn(cc
, free_pfn
);
1938 pfn
= pageblock_start_pfn(free_pfn
);
1939 if (pfn
< cc
->zone
->zone_start_pfn
)
1940 pfn
= cc
->zone
->zone_start_pfn
;
1941 cc
->fast_search_fail
= 0;
1946 spin_unlock_irqrestore(&cc
->zone
->lock
, flags
);
1949 cc
->total_migrate_scanned
+= nr_scanned
;
1952 * If fast scanning failed then use a cached entry for a page block
1953 * that had free pages as the basis for starting a linear scan.
1956 cc
->fast_search_fail
++;
1957 pfn
= reinit_migrate_pfn(cc
);
1963 * Isolate all pages that can be migrated from the first suitable block,
1964 * starting at the block pointed to by the migrate scanner pfn within
1967 static isolate_migrate_t
isolate_migratepages(struct compact_control
*cc
)
1969 unsigned long block_start_pfn
;
1970 unsigned long block_end_pfn
;
1971 unsigned long low_pfn
;
1973 const isolate_mode_t isolate_mode
=
1974 (sysctl_compact_unevictable_allowed
? ISOLATE_UNEVICTABLE
: 0) |
1975 (cc
->mode
!= MIGRATE_SYNC
? ISOLATE_ASYNC_MIGRATE
: 0);
1976 bool fast_find_block
;
1979 * Start at where we last stopped, or beginning of the zone as
1980 * initialized by compact_zone(). The first failure will use
1981 * the lowest PFN as the starting point for linear scanning.
1983 low_pfn
= fast_find_migrateblock(cc
);
1984 block_start_pfn
= pageblock_start_pfn(low_pfn
);
1985 if (block_start_pfn
< cc
->zone
->zone_start_pfn
)
1986 block_start_pfn
= cc
->zone
->zone_start_pfn
;
1989 * fast_find_migrateblock() has already ensured the pageblock is not
1990 * set with a skipped flag, so to avoid the isolation_suitable check
1991 * below again, check whether the fast search was successful.
1993 fast_find_block
= low_pfn
!= cc
->migrate_pfn
&& !cc
->fast_search_fail
;
1995 /* Only scan within a pageblock boundary */
1996 block_end_pfn
= pageblock_end_pfn(low_pfn
);
1999 * Iterate over whole pageblocks until we find the first suitable.
2000 * Do not cross the free scanner.
2002 for (; block_end_pfn
<= cc
->free_pfn
;
2003 fast_find_block
= false,
2004 cc
->migrate_pfn
= low_pfn
= block_end_pfn
,
2005 block_start_pfn
= block_end_pfn
,
2006 block_end_pfn
+= pageblock_nr_pages
) {
2009 * This can potentially iterate a massively long zone with
2010 * many pageblocks unsuitable, so periodically check if we
2013 if (!(low_pfn
% (COMPACT_CLUSTER_MAX
* pageblock_nr_pages
)))
2016 page
= pageblock_pfn_to_page(block_start_pfn
,
2017 block_end_pfn
, cc
->zone
);
2019 unsigned long next_pfn
;
2021 next_pfn
= skip_offline_sections(block_start_pfn
);
2023 block_end_pfn
= min(next_pfn
, cc
->free_pfn
);
2028 * If isolation recently failed, do not retry. Only check the
2029 * pageblock once. COMPACT_CLUSTER_MAX causes a pageblock
2030 * to be visited multiple times. Assume skip was checked
2031 * before making it "skip" so other compaction instances do
2032 * not scan the same block.
2034 if ((pageblock_aligned(low_pfn
) ||
2035 low_pfn
== cc
->zone
->zone_start_pfn
) &&
2036 !fast_find_block
&& !isolation_suitable(cc
, page
))
2040 * For async direct compaction, only scan the pageblocks of the
2041 * same migratetype without huge pages. Async direct compaction
2042 * is optimistic to see if the minimum amount of work satisfies
2043 * the allocation. The cached PFN is updated as it's possible
2044 * that all remaining blocks between source and target are
2045 * unsuitable and the compaction scanners fail to meet.
2047 if (!suitable_migration_source(cc
, page
)) {
2048 update_cached_migrate(cc
, block_end_pfn
);
2052 /* Perform the isolation */
2053 if (isolate_migratepages_block(cc
, low_pfn
, block_end_pfn
,
2055 return ISOLATE_ABORT
;
2058 * Either we isolated something and proceed with migration. Or
2059 * we failed and compact_zone should decide if we should
2065 return cc
->nr_migratepages
? ISOLATE_SUCCESS
: ISOLATE_NONE
;
2069 * order == -1 is expected when compacting via
2070 * /proc/sys/vm/compact_memory
2072 static inline bool is_via_compact_memory(int order
)
2078 * Determine whether kswapd is (or recently was!) running on this node.
2080 * pgdat_kswapd_lock() pins pgdat->kswapd, so a concurrent kswapd_stop() can't
2083 static bool kswapd_is_running(pg_data_t
*pgdat
)
2087 pgdat_kswapd_lock(pgdat
);
2088 running
= pgdat
->kswapd
&& task_is_running(pgdat
->kswapd
);
2089 pgdat_kswapd_unlock(pgdat
);
2095 * A zone's fragmentation score is the external fragmentation wrt to the
2096 * COMPACTION_HPAGE_ORDER. It returns a value in the range [0, 100].
2098 static unsigned int fragmentation_score_zone(struct zone
*zone
)
2100 return extfrag_for_order(zone
, COMPACTION_HPAGE_ORDER
);
2104 * A weighted zone's fragmentation score is the external fragmentation
2105 * wrt to the COMPACTION_HPAGE_ORDER scaled by the zone's size. It
2106 * returns a value in the range [0, 100].
2108 * The scaling factor ensures that proactive compaction focuses on larger
2109 * zones like ZONE_NORMAL, rather than smaller, specialized zones like
2110 * ZONE_DMA32. For smaller zones, the score value remains close to zero,
2111 * and thus never exceeds the high threshold for proactive compaction.
2113 static unsigned int fragmentation_score_zone_weighted(struct zone
*zone
)
2115 unsigned long score
;
2117 score
= zone
->present_pages
* fragmentation_score_zone(zone
);
2118 return div64_ul(score
, zone
->zone_pgdat
->node_present_pages
+ 1);
2122 * The per-node proactive (background) compaction process is started by its
2123 * corresponding kcompactd thread when the node's fragmentation score
2124 * exceeds the high threshold. The compaction process remains active till
2125 * the node's score falls below the low threshold, or one of the back-off
2126 * conditions is met.
2128 static unsigned int fragmentation_score_node(pg_data_t
*pgdat
)
2130 unsigned int score
= 0;
2133 for (zoneid
= 0; zoneid
< MAX_NR_ZONES
; zoneid
++) {
2136 zone
= &pgdat
->node_zones
[zoneid
];
2137 if (!populated_zone(zone
))
2139 score
+= fragmentation_score_zone_weighted(zone
);
2145 static unsigned int fragmentation_score_wmark(bool low
)
2147 unsigned int wmark_low
;
2150 * Cap the low watermark to avoid excessive compaction
2151 * activity in case a user sets the proactiveness tunable
2152 * close to 100 (maximum).
2154 wmark_low
= max(100U - sysctl_compaction_proactiveness
, 5U);
2155 return low
? wmark_low
: min(wmark_low
+ 10, 100U);
2158 static bool should_proactive_compact_node(pg_data_t
*pgdat
)
2162 if (!sysctl_compaction_proactiveness
|| kswapd_is_running(pgdat
))
2165 wmark_high
= fragmentation_score_wmark(false);
2166 return fragmentation_score_node(pgdat
) > wmark_high
;
2169 static enum compact_result
__compact_finished(struct compact_control
*cc
)
2172 const int migratetype
= cc
->migratetype
;
2175 /* Compaction run completes if the migrate and free scanner meet */
2176 if (compact_scanners_met(cc
)) {
2177 /* Let the next compaction start anew. */
2178 reset_cached_positions(cc
->zone
);
2181 * Mark that the PG_migrate_skip information should be cleared
2182 * by kswapd when it goes to sleep. kcompactd does not set the
2183 * flag itself as the decision to be clear should be directly
2184 * based on an allocation request.
2186 if (cc
->direct_compaction
)
2187 cc
->zone
->compact_blockskip_flush
= true;
2190 return COMPACT_COMPLETE
;
2192 return COMPACT_PARTIAL_SKIPPED
;
2195 if (cc
->proactive_compaction
) {
2196 int score
, wmark_low
;
2199 pgdat
= cc
->zone
->zone_pgdat
;
2200 if (kswapd_is_running(pgdat
))
2201 return COMPACT_PARTIAL_SKIPPED
;
2203 score
= fragmentation_score_zone(cc
->zone
);
2204 wmark_low
= fragmentation_score_wmark(true);
2206 if (score
> wmark_low
)
2207 ret
= COMPACT_CONTINUE
;
2209 ret
= COMPACT_SUCCESS
;
2214 if (is_via_compact_memory(cc
->order
))
2215 return COMPACT_CONTINUE
;
2218 * Always finish scanning a pageblock to reduce the possibility of
2219 * fallbacks in the future. This is particularly important when
2220 * migration source is unmovable/reclaimable but it's not worth
2223 if (!pageblock_aligned(cc
->migrate_pfn
))
2224 return COMPACT_CONTINUE
;
2226 /* Direct compactor: Is a suitable page free? */
2227 ret
= COMPACT_NO_SUITABLE_PAGE
;
2228 for (order
= cc
->order
; order
<= MAX_ORDER
; order
++) {
2229 struct free_area
*area
= &cc
->zone
->free_area
[order
];
2232 /* Job done if page is free of the right migratetype */
2233 if (!free_area_empty(area
, migratetype
))
2234 return COMPACT_SUCCESS
;
2237 /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
2238 if (migratetype
== MIGRATE_MOVABLE
&&
2239 !free_area_empty(area
, MIGRATE_CMA
))
2240 return COMPACT_SUCCESS
;
2243 * Job done if allocation would steal freepages from
2244 * other migratetype buddy lists.
2246 if (find_suitable_fallback(area
, order
, migratetype
,
2247 true, &can_steal
) != -1)
2249 * Movable pages are OK in any pageblock. If we are
2250 * stealing for a non-movable allocation, make sure
2251 * we finish compacting the current pageblock first
2252 * (which is assured by the above migrate_pfn align
2253 * check) so it is as free as possible and we won't
2254 * have to steal another one soon.
2256 return COMPACT_SUCCESS
;
2260 if (cc
->contended
|| fatal_signal_pending(current
))
2261 ret
= COMPACT_CONTENDED
;
2266 static enum compact_result
compact_finished(struct compact_control
*cc
)
2270 ret
= __compact_finished(cc
);
2271 trace_mm_compaction_finished(cc
->zone
, cc
->order
, ret
);
2272 if (ret
== COMPACT_NO_SUITABLE_PAGE
)
2273 ret
= COMPACT_CONTINUE
;
2278 static bool __compaction_suitable(struct zone
*zone
, int order
,
2279 int highest_zoneidx
,
2280 unsigned long wmark_target
)
2282 unsigned long watermark
;
2284 * Watermarks for order-0 must be met for compaction to be able to
2285 * isolate free pages for migration targets. This means that the
2286 * watermark and alloc_flags have to match, or be more pessimistic than
2287 * the check in __isolate_free_page(). We don't use the direct
2288 * compactor's alloc_flags, as they are not relevant for freepage
2289 * isolation. We however do use the direct compactor's highest_zoneidx
2290 * to skip over zones where lowmem reserves would prevent allocation
2291 * even if compaction succeeds.
2292 * For costly orders, we require low watermark instead of min for
2293 * compaction to proceed to increase its chances.
2294 * ALLOC_CMA is used, as pages in CMA pageblocks are considered
2295 * suitable migration targets
2297 watermark
= (order
> PAGE_ALLOC_COSTLY_ORDER
) ?
2298 low_wmark_pages(zone
) : min_wmark_pages(zone
);
2299 watermark
+= compact_gap(order
);
2300 return __zone_watermark_ok(zone
, 0, watermark
, highest_zoneidx
,
2301 ALLOC_CMA
, wmark_target
);
2305 * compaction_suitable: Is this suitable to run compaction on this zone now?
2307 bool compaction_suitable(struct zone
*zone
, int order
, int highest_zoneidx
)
2309 enum compact_result compact_result
;
2312 suitable
= __compaction_suitable(zone
, order
, highest_zoneidx
,
2313 zone_page_state(zone
, NR_FREE_PAGES
));
2315 * fragmentation index determines if allocation failures are due to
2316 * low memory or external fragmentation
2318 * index of -1000 would imply allocations might succeed depending on
2319 * watermarks, but we already failed the high-order watermark check
2320 * index towards 0 implies failure is due to lack of memory
2321 * index towards 1000 implies failure is due to fragmentation
2323 * Only compact if a failure would be due to fragmentation. Also
2324 * ignore fragindex for non-costly orders where the alternative to
2325 * a successful reclaim/compaction is OOM. Fragindex and the
2326 * vm.extfrag_threshold sysctl is meant as a heuristic to prevent
2327 * excessive compaction for costly orders, but it should not be at the
2328 * expense of system stability.
2331 compact_result
= COMPACT_CONTINUE
;
2332 if (order
> PAGE_ALLOC_COSTLY_ORDER
) {
2333 int fragindex
= fragmentation_index(zone
, order
);
2335 if (fragindex
>= 0 &&
2336 fragindex
<= sysctl_extfrag_threshold
) {
2338 compact_result
= COMPACT_NOT_SUITABLE_ZONE
;
2342 compact_result
= COMPACT_SKIPPED
;
2345 trace_mm_compaction_suitable(zone
, order
, compact_result
);
2350 bool compaction_zonelist_suitable(struct alloc_context
*ac
, int order
,
2357 * Make sure at least one zone would pass __compaction_suitable if we continue
2358 * retrying the reclaim.
2360 for_each_zone_zonelist_nodemask(zone
, z
, ac
->zonelist
,
2361 ac
->highest_zoneidx
, ac
->nodemask
) {
2362 unsigned long available
;
2365 * Do not consider all the reclaimable memory because we do not
2366 * want to trash just for a single high order allocation which
2367 * is even not guaranteed to appear even if __compaction_suitable
2368 * is happy about the watermark check.
2370 available
= zone_reclaimable_pages(zone
) / order
;
2371 available
+= zone_page_state_snapshot(zone
, NR_FREE_PAGES
);
2372 if (__compaction_suitable(zone
, order
, ac
->highest_zoneidx
,
2380 static enum compact_result
2381 compact_zone(struct compact_control
*cc
, struct capture_control
*capc
)
2383 enum compact_result ret
;
2384 unsigned long start_pfn
= cc
->zone
->zone_start_pfn
;
2385 unsigned long end_pfn
= zone_end_pfn(cc
->zone
);
2386 unsigned long last_migrated_pfn
;
2387 const bool sync
= cc
->mode
!= MIGRATE_ASYNC
;
2389 unsigned int nr_succeeded
= 0;
2392 * These counters track activities during zone compaction. Initialize
2393 * them before compacting a new zone.
2395 cc
->total_migrate_scanned
= 0;
2396 cc
->total_free_scanned
= 0;
2397 cc
->nr_migratepages
= 0;
2398 cc
->nr_freepages
= 0;
2399 INIT_LIST_HEAD(&cc
->freepages
);
2400 INIT_LIST_HEAD(&cc
->migratepages
);
2402 cc
->migratetype
= gfp_migratetype(cc
->gfp_mask
);
2404 if (!is_via_compact_memory(cc
->order
)) {
2405 unsigned long watermark
;
2407 /* Allocation can already succeed, nothing to do */
2408 watermark
= wmark_pages(cc
->zone
,
2409 cc
->alloc_flags
& ALLOC_WMARK_MASK
);
2410 if (zone_watermark_ok(cc
->zone
, cc
->order
, watermark
,
2411 cc
->highest_zoneidx
, cc
->alloc_flags
))
2412 return COMPACT_SUCCESS
;
2414 /* Compaction is likely to fail */
2415 if (!compaction_suitable(cc
->zone
, cc
->order
,
2416 cc
->highest_zoneidx
))
2417 return COMPACT_SKIPPED
;
2421 * Clear pageblock skip if there were failures recently and compaction
2422 * is about to be retried after being deferred.
2424 if (compaction_restarting(cc
->zone
, cc
->order
))
2425 __reset_isolation_suitable(cc
->zone
);
2428 * Setup to move all movable pages to the end of the zone. Used cached
2429 * information on where the scanners should start (unless we explicitly
2430 * want to compact the whole zone), but check that it is initialised
2431 * by ensuring the values are within zone boundaries.
2433 cc
->fast_start_pfn
= 0;
2434 if (cc
->whole_zone
) {
2435 cc
->migrate_pfn
= start_pfn
;
2436 cc
->free_pfn
= pageblock_start_pfn(end_pfn
- 1);
2438 cc
->migrate_pfn
= cc
->zone
->compact_cached_migrate_pfn
[sync
];
2439 cc
->free_pfn
= cc
->zone
->compact_cached_free_pfn
;
2440 if (cc
->free_pfn
< start_pfn
|| cc
->free_pfn
>= end_pfn
) {
2441 cc
->free_pfn
= pageblock_start_pfn(end_pfn
- 1);
2442 cc
->zone
->compact_cached_free_pfn
= cc
->free_pfn
;
2444 if (cc
->migrate_pfn
< start_pfn
|| cc
->migrate_pfn
>= end_pfn
) {
2445 cc
->migrate_pfn
= start_pfn
;
2446 cc
->zone
->compact_cached_migrate_pfn
[0] = cc
->migrate_pfn
;
2447 cc
->zone
->compact_cached_migrate_pfn
[1] = cc
->migrate_pfn
;
2450 if (cc
->migrate_pfn
<= cc
->zone
->compact_init_migrate_pfn
)
2451 cc
->whole_zone
= true;
2454 last_migrated_pfn
= 0;
2457 * Migrate has separate cached PFNs for ASYNC and SYNC* migration on
2458 * the basis that some migrations will fail in ASYNC mode. However,
2459 * if the cached PFNs match and pageblocks are skipped due to having
2460 * no isolation candidates, then the sync state does not matter.
2461 * Until a pageblock with isolation candidates is found, keep the
2462 * cached PFNs in sync to avoid revisiting the same blocks.
2464 update_cached
= !sync
&&
2465 cc
->zone
->compact_cached_migrate_pfn
[0] == cc
->zone
->compact_cached_migrate_pfn
[1];
2467 trace_mm_compaction_begin(cc
, start_pfn
, end_pfn
, sync
);
2469 /* lru_add_drain_all could be expensive with involving other CPUs */
2472 while ((ret
= compact_finished(cc
)) == COMPACT_CONTINUE
) {
2474 unsigned long iteration_start_pfn
= cc
->migrate_pfn
;
2477 * Avoid multiple rescans of the same pageblock which can
2478 * happen if a page cannot be isolated (dirty/writeback in
2479 * async mode) or if the migrated pages are being allocated
2480 * before the pageblock is cleared. The first rescan will
2481 * capture the entire pageblock for migration. If it fails,
2482 * it'll be marked skip and scanning will proceed as normal.
2484 cc
->finish_pageblock
= false;
2485 if (pageblock_start_pfn(last_migrated_pfn
) ==
2486 pageblock_start_pfn(iteration_start_pfn
)) {
2487 cc
->finish_pageblock
= true;
2491 switch (isolate_migratepages(cc
)) {
2493 ret
= COMPACT_CONTENDED
;
2494 putback_movable_pages(&cc
->migratepages
);
2495 cc
->nr_migratepages
= 0;
2498 if (update_cached
) {
2499 cc
->zone
->compact_cached_migrate_pfn
[1] =
2500 cc
->zone
->compact_cached_migrate_pfn
[0];
2504 * We haven't isolated and migrated anything, but
2505 * there might still be unflushed migrations from
2506 * previous cc->order aligned block.
2509 case ISOLATE_SUCCESS
:
2510 update_cached
= false;
2511 last_migrated_pfn
= max(cc
->zone
->zone_start_pfn
,
2512 pageblock_start_pfn(cc
->migrate_pfn
- 1));
2515 err
= migrate_pages(&cc
->migratepages
, compaction_alloc
,
2516 compaction_free
, (unsigned long)cc
, cc
->mode
,
2517 MR_COMPACTION
, &nr_succeeded
);
2519 trace_mm_compaction_migratepages(cc
, nr_succeeded
);
2521 /* All pages were either migrated or will be released */
2522 cc
->nr_migratepages
= 0;
2524 putback_movable_pages(&cc
->migratepages
);
2526 * migrate_pages() may return -ENOMEM when scanners meet
2527 * and we want compact_finished() to detect it
2529 if (err
== -ENOMEM
&& !compact_scanners_met(cc
)) {
2530 ret
= COMPACT_CONTENDED
;
2534 * If an ASYNC or SYNC_LIGHT fails to migrate a page
2535 * within the pageblock_order-aligned block and
2536 * fast_find_migrateblock may be used then scan the
2537 * remainder of the pageblock. This will mark the
2538 * pageblock "skip" to avoid rescanning in the near
2539 * future. This will isolate more pages than necessary
2540 * for the request but avoid loops due to
2541 * fast_find_migrateblock revisiting blocks that were
2542 * recently partially scanned.
2544 if (!pageblock_aligned(cc
->migrate_pfn
) &&
2545 !cc
->ignore_skip_hint
&& !cc
->finish_pageblock
&&
2546 (cc
->mode
< MIGRATE_SYNC
)) {
2547 cc
->finish_pageblock
= true;
2550 * Draining pcplists does not help THP if
2551 * any page failed to migrate. Even after
2552 * drain, the pageblock will not be free.
2554 if (cc
->order
== COMPACTION_HPAGE_ORDER
)
2555 last_migrated_pfn
= 0;
2561 /* Stop if a page has been captured */
2562 if (capc
&& capc
->page
) {
2563 ret
= COMPACT_SUCCESS
;
2569 * Has the migration scanner moved away from the previous
2570 * cc->order aligned block where we migrated from? If yes,
2571 * flush the pages that were freed, so that they can merge and
2572 * compact_finished() can detect immediately if allocation
2575 if (cc
->order
> 0 && last_migrated_pfn
) {
2576 unsigned long current_block_start
=
2577 block_start_pfn(cc
->migrate_pfn
, cc
->order
);
2579 if (last_migrated_pfn
< current_block_start
) {
2580 lru_add_drain_cpu_zone(cc
->zone
);
2581 /* No more flushing until we migrate again */
2582 last_migrated_pfn
= 0;
2589 * Release free pages and update where the free scanner should restart,
2590 * so we don't leave any returned pages behind in the next attempt.
2592 if (cc
->nr_freepages
> 0) {
2593 unsigned long free_pfn
= release_freepages(&cc
->freepages
);
2595 cc
->nr_freepages
= 0;
2596 VM_BUG_ON(free_pfn
== 0);
2597 /* The cached pfn is always the first in a pageblock */
2598 free_pfn
= pageblock_start_pfn(free_pfn
);
2600 * Only go back, not forward. The cached pfn might have been
2601 * already reset to zone end in compact_finished()
2603 if (free_pfn
> cc
->zone
->compact_cached_free_pfn
)
2604 cc
->zone
->compact_cached_free_pfn
= free_pfn
;
2607 count_compact_events(COMPACTMIGRATE_SCANNED
, cc
->total_migrate_scanned
);
2608 count_compact_events(COMPACTFREE_SCANNED
, cc
->total_free_scanned
);
2610 trace_mm_compaction_end(cc
, start_pfn
, end_pfn
, sync
, ret
);
2612 VM_BUG_ON(!list_empty(&cc
->freepages
));
2613 VM_BUG_ON(!list_empty(&cc
->migratepages
));
2618 static enum compact_result
compact_zone_order(struct zone
*zone
, int order
,
2619 gfp_t gfp_mask
, enum compact_priority prio
,
2620 unsigned int alloc_flags
, int highest_zoneidx
,
2621 struct page
**capture
)
2623 enum compact_result ret
;
2624 struct compact_control cc
= {
2626 .search_order
= order
,
2627 .gfp_mask
= gfp_mask
,
2629 .mode
= (prio
== COMPACT_PRIO_ASYNC
) ?
2630 MIGRATE_ASYNC
: MIGRATE_SYNC_LIGHT
,
2631 .alloc_flags
= alloc_flags
,
2632 .highest_zoneidx
= highest_zoneidx
,
2633 .direct_compaction
= true,
2634 .whole_zone
= (prio
== MIN_COMPACT_PRIORITY
),
2635 .ignore_skip_hint
= (prio
== MIN_COMPACT_PRIORITY
),
2636 .ignore_block_suitable
= (prio
== MIN_COMPACT_PRIORITY
)
2638 struct capture_control capc
= {
2644 * Make sure the structs are really initialized before we expose the
2645 * capture control, in case we are interrupted and the interrupt handler
2649 WRITE_ONCE(current
->capture_control
, &capc
);
2651 ret
= compact_zone(&cc
, &capc
);
2654 * Make sure we hide capture control first before we read the captured
2655 * page pointer, otherwise an interrupt could free and capture a page
2656 * and we would leak it.
2658 WRITE_ONCE(current
->capture_control
, NULL
);
2659 *capture
= READ_ONCE(capc
.page
);
2661 * Technically, it is also possible that compaction is skipped but
2662 * the page is still captured out of luck(IRQ came and freed the page).
2663 * Returning COMPACT_SUCCESS in such cases helps in properly accounting
2664 * the COMPACT[STALL|FAIL] when compaction is skipped.
2667 ret
= COMPACT_SUCCESS
;
2673 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
2674 * @gfp_mask: The GFP mask of the current allocation
2675 * @order: The order of the current allocation
2676 * @alloc_flags: The allocation flags of the current allocation
2677 * @ac: The context of current allocation
2678 * @prio: Determines how hard direct compaction should try to succeed
2679 * @capture: Pointer to free page created by compaction will be stored here
2681 * This is the main entry point for direct page compaction.
2683 enum compact_result
try_to_compact_pages(gfp_t gfp_mask
, unsigned int order
,
2684 unsigned int alloc_flags
, const struct alloc_context
*ac
,
2685 enum compact_priority prio
, struct page
**capture
)
2687 int may_perform_io
= (__force
int)(gfp_mask
& __GFP_IO
);
2690 enum compact_result rc
= COMPACT_SKIPPED
;
2693 * Check if the GFP flags allow compaction - GFP_NOIO is really
2694 * tricky context because the migration might require IO
2696 if (!may_perform_io
)
2697 return COMPACT_SKIPPED
;
2699 trace_mm_compaction_try_to_compact_pages(order
, gfp_mask
, prio
);
2701 /* Compact each zone in the list */
2702 for_each_zone_zonelist_nodemask(zone
, z
, ac
->zonelist
,
2703 ac
->highest_zoneidx
, ac
->nodemask
) {
2704 enum compact_result status
;
2706 if (prio
> MIN_COMPACT_PRIORITY
2707 && compaction_deferred(zone
, order
)) {
2708 rc
= max_t(enum compact_result
, COMPACT_DEFERRED
, rc
);
2712 status
= compact_zone_order(zone
, order
, gfp_mask
, prio
,
2713 alloc_flags
, ac
->highest_zoneidx
, capture
);
2714 rc
= max(status
, rc
);
2716 /* The allocation should succeed, stop compacting */
2717 if (status
== COMPACT_SUCCESS
) {
2719 * We think the allocation will succeed in this zone,
2720 * but it is not certain, hence the false. The caller
2721 * will repeat this with true if allocation indeed
2722 * succeeds in this zone.
2724 compaction_defer_reset(zone
, order
, false);
2729 if (prio
!= COMPACT_PRIO_ASYNC
&& (status
== COMPACT_COMPLETE
||
2730 status
== COMPACT_PARTIAL_SKIPPED
))
2732 * We think that allocation won't succeed in this zone
2733 * so we defer compaction there. If it ends up
2734 * succeeding after all, it will be reset.
2736 defer_compaction(zone
, order
);
2739 * We might have stopped compacting due to need_resched() in
2740 * async compaction, or due to a fatal signal detected. In that
2741 * case do not try further zones
2743 if ((prio
== COMPACT_PRIO_ASYNC
&& need_resched())
2744 || fatal_signal_pending(current
))
2752 * Compact all zones within a node till each zone's fragmentation score
2753 * reaches within proactive compaction thresholds (as determined by the
2754 * proactiveness tunable).
2756 * It is possible that the function returns before reaching score targets
2757 * due to various back-off conditions, such as, contention on per-node or
2760 static void proactive_compact_node(pg_data_t
*pgdat
)
2764 struct compact_control cc
= {
2766 .mode
= MIGRATE_SYNC_LIGHT
,
2767 .ignore_skip_hint
= true,
2769 .gfp_mask
= GFP_KERNEL
,
2770 .proactive_compaction
= true,
2773 for (zoneid
= 0; zoneid
< MAX_NR_ZONES
; zoneid
++) {
2774 zone
= &pgdat
->node_zones
[zoneid
];
2775 if (!populated_zone(zone
))
2780 compact_zone(&cc
, NULL
);
2782 count_compact_events(KCOMPACTD_MIGRATE_SCANNED
,
2783 cc
.total_migrate_scanned
);
2784 count_compact_events(KCOMPACTD_FREE_SCANNED
,
2785 cc
.total_free_scanned
);
2789 /* Compact all zones within a node */
2790 static void compact_node(int nid
)
2792 pg_data_t
*pgdat
= NODE_DATA(nid
);
2795 struct compact_control cc
= {
2797 .mode
= MIGRATE_SYNC
,
2798 .ignore_skip_hint
= true,
2800 .gfp_mask
= GFP_KERNEL
,
2804 for (zoneid
= 0; zoneid
< MAX_NR_ZONES
; zoneid
++) {
2806 zone
= &pgdat
->node_zones
[zoneid
];
2807 if (!populated_zone(zone
))
2812 compact_zone(&cc
, NULL
);
2816 /* Compact all nodes in the system */
2817 static void compact_nodes(void)
2821 /* Flush pending updates to the LRU lists */
2822 lru_add_drain_all();
2824 for_each_online_node(nid
)
2828 static int compaction_proactiveness_sysctl_handler(struct ctl_table
*table
, int write
,
2829 void *buffer
, size_t *length
, loff_t
*ppos
)
2833 rc
= proc_dointvec_minmax(table
, write
, buffer
, length
, ppos
);
2837 if (write
&& sysctl_compaction_proactiveness
) {
2838 for_each_online_node(nid
) {
2839 pg_data_t
*pgdat
= NODE_DATA(nid
);
2841 if (pgdat
->proactive_compact_trigger
)
2844 pgdat
->proactive_compact_trigger
= true;
2845 trace_mm_compaction_wakeup_kcompactd(pgdat
->node_id
, -1,
2846 pgdat
->nr_zones
- 1);
2847 wake_up_interruptible(&pgdat
->kcompactd_wait
);
2855 * This is the entry point for compacting all nodes via
2856 * /proc/sys/vm/compact_memory
2858 static int sysctl_compaction_handler(struct ctl_table
*table
, int write
,
2859 void *buffer
, size_t *length
, loff_t
*ppos
)
2863 ret
= proc_dointvec(table
, write
, buffer
, length
, ppos
);
2867 if (sysctl_compact_memory
!= 1)
2876 #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
2877 static ssize_t
compact_store(struct device
*dev
,
2878 struct device_attribute
*attr
,
2879 const char *buf
, size_t count
)
2883 if (nid
>= 0 && nid
< nr_node_ids
&& node_online(nid
)) {
2884 /* Flush pending updates to the LRU lists */
2885 lru_add_drain_all();
2892 static DEVICE_ATTR_WO(compact
);
2894 int compaction_register_node(struct node
*node
)
2896 return device_create_file(&node
->dev
, &dev_attr_compact
);
2899 void compaction_unregister_node(struct node
*node
)
2901 device_remove_file(&node
->dev
, &dev_attr_compact
);
2903 #endif /* CONFIG_SYSFS && CONFIG_NUMA */
2905 static inline bool kcompactd_work_requested(pg_data_t
*pgdat
)
2907 return pgdat
->kcompactd_max_order
> 0 || kthread_should_stop() ||
2908 pgdat
->proactive_compact_trigger
;
2911 static bool kcompactd_node_suitable(pg_data_t
*pgdat
)
2915 enum zone_type highest_zoneidx
= pgdat
->kcompactd_highest_zoneidx
;
2917 for (zoneid
= 0; zoneid
<= highest_zoneidx
; zoneid
++) {
2918 zone
= &pgdat
->node_zones
[zoneid
];
2920 if (!populated_zone(zone
))
2923 /* Allocation can already succeed, check other zones */
2924 if (zone_watermark_ok(zone
, pgdat
->kcompactd_max_order
,
2925 min_wmark_pages(zone
),
2926 highest_zoneidx
, 0))
2929 if (compaction_suitable(zone
, pgdat
->kcompactd_max_order
,
2937 static void kcompactd_do_work(pg_data_t
*pgdat
)
2940 * With no special task, compact all zones so that a page of requested
2941 * order is allocatable.
2945 struct compact_control cc
= {
2946 .order
= pgdat
->kcompactd_max_order
,
2947 .search_order
= pgdat
->kcompactd_max_order
,
2948 .highest_zoneidx
= pgdat
->kcompactd_highest_zoneidx
,
2949 .mode
= MIGRATE_SYNC_LIGHT
,
2950 .ignore_skip_hint
= false,
2951 .gfp_mask
= GFP_KERNEL
,
2953 trace_mm_compaction_kcompactd_wake(pgdat
->node_id
, cc
.order
,
2954 cc
.highest_zoneidx
);
2955 count_compact_event(KCOMPACTD_WAKE
);
2957 for (zoneid
= 0; zoneid
<= cc
.highest_zoneidx
; zoneid
++) {
2960 zone
= &pgdat
->node_zones
[zoneid
];
2961 if (!populated_zone(zone
))
2964 if (compaction_deferred(zone
, cc
.order
))
2967 /* Allocation can already succeed, nothing to do */
2968 if (zone_watermark_ok(zone
, cc
.order
,
2969 min_wmark_pages(zone
), zoneid
, 0))
2972 if (!compaction_suitable(zone
, cc
.order
, zoneid
))
2975 if (kthread_should_stop())
2979 status
= compact_zone(&cc
, NULL
);
2981 if (status
== COMPACT_SUCCESS
) {
2982 compaction_defer_reset(zone
, cc
.order
, false);
2983 } else if (status
== COMPACT_PARTIAL_SKIPPED
|| status
== COMPACT_COMPLETE
) {
2985 * Buddy pages may become stranded on pcps that could
2986 * otherwise coalesce on the zone's free area for
2987 * order >= cc.order. This is ratelimited by the
2988 * upcoming deferral.
2990 drain_all_pages(zone
);
2993 * We use sync migration mode here, so we defer like
2994 * sync direct compaction does.
2996 defer_compaction(zone
, cc
.order
);
2999 count_compact_events(KCOMPACTD_MIGRATE_SCANNED
,
3000 cc
.total_migrate_scanned
);
3001 count_compact_events(KCOMPACTD_FREE_SCANNED
,
3002 cc
.total_free_scanned
);
3006 * Regardless of success, we are done until woken up next. But remember
3007 * the requested order/highest_zoneidx in case it was higher/tighter
3008 * than our current ones
3010 if (pgdat
->kcompactd_max_order
<= cc
.order
)
3011 pgdat
->kcompactd_max_order
= 0;
3012 if (pgdat
->kcompactd_highest_zoneidx
>= cc
.highest_zoneidx
)
3013 pgdat
->kcompactd_highest_zoneidx
= pgdat
->nr_zones
- 1;
3016 void wakeup_kcompactd(pg_data_t
*pgdat
, int order
, int highest_zoneidx
)
3021 if (pgdat
->kcompactd_max_order
< order
)
3022 pgdat
->kcompactd_max_order
= order
;
3024 if (pgdat
->kcompactd_highest_zoneidx
> highest_zoneidx
)
3025 pgdat
->kcompactd_highest_zoneidx
= highest_zoneidx
;
3028 * Pairs with implicit barrier in wait_event_freezable()
3029 * such that wakeups are not missed.
3031 if (!wq_has_sleeper(&pgdat
->kcompactd_wait
))
3034 if (!kcompactd_node_suitable(pgdat
))
3037 trace_mm_compaction_wakeup_kcompactd(pgdat
->node_id
, order
,
3039 wake_up_interruptible(&pgdat
->kcompactd_wait
);
3043 * The background compaction daemon, started as a kernel thread
3044 * from the init process.
3046 static int kcompactd(void *p
)
3048 pg_data_t
*pgdat
= (pg_data_t
*)p
;
3049 struct task_struct
*tsk
= current
;
3050 long default_timeout
= msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC
);
3051 long timeout
= default_timeout
;
3053 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
3055 if (!cpumask_empty(cpumask
))
3056 set_cpus_allowed_ptr(tsk
, cpumask
);
3060 pgdat
->kcompactd_max_order
= 0;
3061 pgdat
->kcompactd_highest_zoneidx
= pgdat
->nr_zones
- 1;
3063 while (!kthread_should_stop()) {
3064 unsigned long pflags
;
3067 * Avoid the unnecessary wakeup for proactive compaction
3068 * when it is disabled.
3070 if (!sysctl_compaction_proactiveness
)
3071 timeout
= MAX_SCHEDULE_TIMEOUT
;
3072 trace_mm_compaction_kcompactd_sleep(pgdat
->node_id
);
3073 if (wait_event_freezable_timeout(pgdat
->kcompactd_wait
,
3074 kcompactd_work_requested(pgdat
), timeout
) &&
3075 !pgdat
->proactive_compact_trigger
) {
3077 psi_memstall_enter(&pflags
);
3078 kcompactd_do_work(pgdat
);
3079 psi_memstall_leave(&pflags
);
3081 * Reset the timeout value. The defer timeout from
3082 * proactive compaction is lost here but that is fine
3083 * as the condition of the zone changing substantionally
3084 * then carrying on with the previous defer interval is
3087 timeout
= default_timeout
;
3092 * Start the proactive work with default timeout. Based
3093 * on the fragmentation score, this timeout is updated.
3095 timeout
= default_timeout
;
3096 if (should_proactive_compact_node(pgdat
)) {
3097 unsigned int prev_score
, score
;
3099 prev_score
= fragmentation_score_node(pgdat
);
3100 proactive_compact_node(pgdat
);
3101 score
= fragmentation_score_node(pgdat
);
3103 * Defer proactive compaction if the fragmentation
3104 * score did not go down i.e. no progress made.
3106 if (unlikely(score
>= prev_score
))
3108 default_timeout
<< COMPACT_MAX_DEFER_SHIFT
;
3110 if (unlikely(pgdat
->proactive_compact_trigger
))
3111 pgdat
->proactive_compact_trigger
= false;
3118 * This kcompactd start function will be called by init and node-hot-add.
3119 * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added.
3121 void __meminit
kcompactd_run(int nid
)
3123 pg_data_t
*pgdat
= NODE_DATA(nid
);
3125 if (pgdat
->kcompactd
)
3128 pgdat
->kcompactd
= kthread_run(kcompactd
, pgdat
, "kcompactd%d", nid
);
3129 if (IS_ERR(pgdat
->kcompactd
)) {
3130 pr_err("Failed to start kcompactd on node %d\n", nid
);
3131 pgdat
->kcompactd
= NULL
;
3136 * Called by memory hotplug when all memory in a node is offlined. Caller must
3137 * be holding mem_hotplug_begin/done().
3139 void __meminit
kcompactd_stop(int nid
)
3141 struct task_struct
*kcompactd
= NODE_DATA(nid
)->kcompactd
;
3144 kthread_stop(kcompactd
);
3145 NODE_DATA(nid
)->kcompactd
= NULL
;
3150 * It's optimal to keep kcompactd on the same CPUs as their memory, but
3151 * not required for correctness. So if the last cpu in a node goes
3152 * away, we get changed to run anywhere: as the first one comes back,
3153 * restore their cpu bindings.
3155 static int kcompactd_cpu_online(unsigned int cpu
)
3159 for_each_node_state(nid
, N_MEMORY
) {
3160 pg_data_t
*pgdat
= NODE_DATA(nid
);
3161 const struct cpumask
*mask
;
3163 mask
= cpumask_of_node(pgdat
->node_id
);
3165 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
3166 /* One of our CPUs online: restore mask */
3167 if (pgdat
->kcompactd
)
3168 set_cpus_allowed_ptr(pgdat
->kcompactd
, mask
);
3173 static int proc_dointvec_minmax_warn_RT_change(struct ctl_table
*table
,
3174 int write
, void *buffer
, size_t *lenp
, loff_t
*ppos
)
3178 if (!IS_ENABLED(CONFIG_PREEMPT_RT
) || !write
)
3179 return proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
3181 old
= *(int *)table
->data
;
3182 ret
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
3185 if (old
!= *(int *)table
->data
)
3186 pr_warn_once("sysctl attribute %s changed by %s[%d]\n",
3187 table
->procname
, current
->comm
,
3188 task_pid_nr(current
));
3192 static struct ctl_table vm_compaction
[] = {
3194 .procname
= "compact_memory",
3195 .data
= &sysctl_compact_memory
,
3196 .maxlen
= sizeof(int),
3198 .proc_handler
= sysctl_compaction_handler
,
3201 .procname
= "compaction_proactiveness",
3202 .data
= &sysctl_compaction_proactiveness
,
3203 .maxlen
= sizeof(sysctl_compaction_proactiveness
),
3205 .proc_handler
= compaction_proactiveness_sysctl_handler
,
3206 .extra1
= SYSCTL_ZERO
,
3207 .extra2
= SYSCTL_ONE_HUNDRED
,
3210 .procname
= "extfrag_threshold",
3211 .data
= &sysctl_extfrag_threshold
,
3212 .maxlen
= sizeof(int),
3214 .proc_handler
= proc_dointvec_minmax
,
3215 .extra1
= SYSCTL_ZERO
,
3216 .extra2
= SYSCTL_ONE_THOUSAND
,
3219 .procname
= "compact_unevictable_allowed",
3220 .data
= &sysctl_compact_unevictable_allowed
,
3221 .maxlen
= sizeof(int),
3223 .proc_handler
= proc_dointvec_minmax_warn_RT_change
,
3224 .extra1
= SYSCTL_ZERO
,
3225 .extra2
= SYSCTL_ONE
,
3230 static int __init
kcompactd_init(void)
3235 ret
= cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN
,
3236 "mm/compaction:online",
3237 kcompactd_cpu_online
, NULL
);
3239 pr_err("kcompactd: failed to register hotplug callbacks.\n");
3243 for_each_node_state(nid
, N_MEMORY
)
3245 register_sysctl_init("vm", vm_compaction
);
3248 subsys_initcall(kcompactd_init
)
3250 #endif /* CONFIG_COMPACTION */