2 * linux/mm/compaction.c
4 * Memory compaction for the reduction of external fragmentation. Note that
5 * this heavily depends upon page migration to do all the real heavy
8 * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
10 #include <linux/swap.h>
11 #include <linux/migrate.h>
12 #include <linux/compaction.h>
13 #include <linux/mm_inline.h>
14 #include <linux/backing-dev.h>
15 #include <linux/sysctl.h>
16 #include <linux/sysfs.h>
17 #include <linux/balloon_compaction.h>
18 #include <linux/page-isolation.h>
19 #include <linux/kasan.h>
22 #ifdef CONFIG_COMPACTION
23 static inline void count_compact_event(enum vm_event_item item
)
28 static inline void count_compact_events(enum vm_event_item item
, long delta
)
30 count_vm_events(item
, delta
);
33 #define count_compact_event(item) do { } while (0)
34 #define count_compact_events(item, delta) do { } while (0)
37 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
38 #ifdef CONFIG_TRACEPOINTS
39 static const char *const compaction_status_string
[] = {
50 #define CREATE_TRACE_POINTS
51 #include <trace/events/compaction.h>
53 static unsigned long release_freepages(struct list_head
*freelist
)
55 struct page
*page
, *next
;
56 unsigned long high_pfn
= 0;
58 list_for_each_entry_safe(page
, next
, freelist
, lru
) {
59 unsigned long pfn
= page_to_pfn(page
);
69 static void map_pages(struct list_head
*list
)
73 list_for_each_entry(page
, list
, lru
) {
74 arch_alloc_page(page
, 0);
75 kernel_map_pages(page
, 1, 1);
76 kasan_alloc_pages(page
, 0);
80 static inline bool migrate_async_suitable(int migratetype
)
82 return is_migrate_cma(migratetype
) || migratetype
== MIGRATE_MOVABLE
;
86 * Check that the whole (or subset of) a pageblock given by the interval of
87 * [start_pfn, end_pfn) is valid and within the same zone, before scanning it
88 * with the migration of free compaction scanner. The scanners then need to
89 * use only pfn_valid_within() check for arches that allow holes within
92 * Return struct page pointer of start_pfn, or NULL if checks were not passed.
94 * It's possible on some configurations to have a setup like node0 node1 node0
95 * i.e. it's possible that all pages within a zones range of pages do not
96 * belong to a single zone. We assume that a border between node0 and node1
97 * can occur within a single pageblock, but not a node0 node1 node0
98 * interleaving within a single pageblock. It is therefore sufficient to check
99 * the first and last page of a pageblock and avoid checking each individual
100 * page in a pageblock.
102 static struct page
*pageblock_pfn_to_page(unsigned long start_pfn
,
103 unsigned long end_pfn
, struct zone
*zone
)
105 struct page
*start_page
;
106 struct page
*end_page
;
108 /* end_pfn is one past the range we are checking */
111 if (!pfn_valid(start_pfn
) || !pfn_valid(end_pfn
))
114 start_page
= pfn_to_page(start_pfn
);
116 if (page_zone(start_page
) != zone
)
119 end_page
= pfn_to_page(end_pfn
);
121 /* This gives a shorter code than deriving page_zone(end_page) */
122 if (page_zone_id(start_page
) != page_zone_id(end_page
))
128 #ifdef CONFIG_COMPACTION
130 /* Do not skip compaction more than 64 times */
131 #define COMPACT_MAX_DEFER_SHIFT 6
134 * Compaction is deferred when compaction fails to result in a page
135 * allocation success. 1 << compact_defer_limit compactions are skipped up
136 * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
138 void defer_compaction(struct zone
*zone
, int order
)
140 zone
->compact_considered
= 0;
141 zone
->compact_defer_shift
++;
143 if (order
< zone
->compact_order_failed
)
144 zone
->compact_order_failed
= order
;
146 if (zone
->compact_defer_shift
> COMPACT_MAX_DEFER_SHIFT
)
147 zone
->compact_defer_shift
= COMPACT_MAX_DEFER_SHIFT
;
149 trace_mm_compaction_defer_compaction(zone
, order
);
152 /* Returns true if compaction should be skipped this time */
153 bool compaction_deferred(struct zone
*zone
, int order
)
155 unsigned long defer_limit
= 1UL << zone
->compact_defer_shift
;
157 if (order
< zone
->compact_order_failed
)
160 /* Avoid possible overflow */
161 if (++zone
->compact_considered
> defer_limit
)
162 zone
->compact_considered
= defer_limit
;
164 if (zone
->compact_considered
>= defer_limit
)
167 trace_mm_compaction_deferred(zone
, order
);
173 * Update defer tracking counters after successful compaction of given order,
174 * which means an allocation either succeeded (alloc_success == true) or is
175 * expected to succeed.
177 void compaction_defer_reset(struct zone
*zone
, int order
,
181 zone
->compact_considered
= 0;
182 zone
->compact_defer_shift
= 0;
184 if (order
>= zone
->compact_order_failed
)
185 zone
->compact_order_failed
= order
+ 1;
187 trace_mm_compaction_defer_reset(zone
, order
);
190 /* Returns true if restarting compaction after many failures */
191 bool compaction_restarting(struct zone
*zone
, int order
)
193 if (order
< zone
->compact_order_failed
)
196 return zone
->compact_defer_shift
== COMPACT_MAX_DEFER_SHIFT
&&
197 zone
->compact_considered
>= 1UL << zone
->compact_defer_shift
;
200 /* Returns true if the pageblock should be scanned for pages to isolate. */
201 static inline bool isolation_suitable(struct compact_control
*cc
,
204 if (cc
->ignore_skip_hint
)
207 return !get_pageblock_skip(page
);
210 static void reset_cached_positions(struct zone
*zone
)
212 zone
->compact_cached_migrate_pfn
[0] = zone
->zone_start_pfn
;
213 zone
->compact_cached_migrate_pfn
[1] = zone
->zone_start_pfn
;
214 zone
->compact_cached_free_pfn
= zone_end_pfn(zone
);
218 * This function is called to clear all cached information on pageblocks that
219 * should be skipped for page isolation when the migrate and free page scanner
222 static void __reset_isolation_suitable(struct zone
*zone
)
224 unsigned long start_pfn
= zone
->zone_start_pfn
;
225 unsigned long end_pfn
= zone_end_pfn(zone
);
228 zone
->compact_blockskip_flush
= false;
230 /* Walk the zone and mark every pageblock as suitable for isolation */
231 for (pfn
= start_pfn
; pfn
< end_pfn
; pfn
+= pageblock_nr_pages
) {
239 page
= pfn_to_page(pfn
);
240 if (zone
!= page_zone(page
))
243 clear_pageblock_skip(page
);
246 reset_cached_positions(zone
);
249 void reset_isolation_suitable(pg_data_t
*pgdat
)
253 for (zoneid
= 0; zoneid
< MAX_NR_ZONES
; zoneid
++) {
254 struct zone
*zone
= &pgdat
->node_zones
[zoneid
];
255 if (!populated_zone(zone
))
258 /* Only flush if a full compaction finished recently */
259 if (zone
->compact_blockskip_flush
)
260 __reset_isolation_suitable(zone
);
265 * If no pages were isolated then mark this pageblock to be skipped in the
266 * future. The information is later cleared by __reset_isolation_suitable().
268 static void update_pageblock_skip(struct compact_control
*cc
,
269 struct page
*page
, unsigned long nr_isolated
,
270 bool migrate_scanner
)
272 struct zone
*zone
= cc
->zone
;
275 if (cc
->ignore_skip_hint
)
284 set_pageblock_skip(page
);
286 pfn
= page_to_pfn(page
);
288 /* Update where async and sync compaction should restart */
289 if (migrate_scanner
) {
290 if (pfn
> zone
->compact_cached_migrate_pfn
[0])
291 zone
->compact_cached_migrate_pfn
[0] = pfn
;
292 if (cc
->mode
!= MIGRATE_ASYNC
&&
293 pfn
> zone
->compact_cached_migrate_pfn
[1])
294 zone
->compact_cached_migrate_pfn
[1] = pfn
;
296 if (pfn
< zone
->compact_cached_free_pfn
)
297 zone
->compact_cached_free_pfn
= pfn
;
301 static inline bool isolation_suitable(struct compact_control
*cc
,
307 static void update_pageblock_skip(struct compact_control
*cc
,
308 struct page
*page
, unsigned long nr_isolated
,
309 bool migrate_scanner
)
312 #endif /* CONFIG_COMPACTION */
315 * Compaction requires the taking of some coarse locks that are potentially
316 * very heavily contended. For async compaction, back out if the lock cannot
317 * be taken immediately. For sync compaction, spin on the lock if needed.
319 * Returns true if the lock is held
320 * Returns false if the lock is not held and compaction should abort
322 static bool compact_trylock_irqsave(spinlock_t
*lock
, unsigned long *flags
,
323 struct compact_control
*cc
)
325 if (cc
->mode
== MIGRATE_ASYNC
) {
326 if (!spin_trylock_irqsave(lock
, *flags
)) {
327 cc
->contended
= COMPACT_CONTENDED_LOCK
;
331 spin_lock_irqsave(lock
, *flags
);
338 * Compaction requires the taking of some coarse locks that are potentially
339 * very heavily contended. The lock should be periodically unlocked to avoid
340 * having disabled IRQs for a long time, even when there is nobody waiting on
341 * the lock. It might also be that allowing the IRQs will result in
342 * need_resched() becoming true. If scheduling is needed, async compaction
343 * aborts. Sync compaction schedules.
344 * Either compaction type will also abort if a fatal signal is pending.
345 * In either case if the lock was locked, it is dropped and not regained.
347 * Returns true if compaction should abort due to fatal signal pending, or
348 * async compaction due to need_resched()
349 * Returns false when compaction can continue (sync compaction might have
352 static bool compact_unlock_should_abort(spinlock_t
*lock
,
353 unsigned long flags
, bool *locked
, struct compact_control
*cc
)
356 spin_unlock_irqrestore(lock
, flags
);
360 if (fatal_signal_pending(current
)) {
361 cc
->contended
= COMPACT_CONTENDED_SCHED
;
365 if (need_resched()) {
366 if (cc
->mode
== MIGRATE_ASYNC
) {
367 cc
->contended
= COMPACT_CONTENDED_SCHED
;
377 * Aside from avoiding lock contention, compaction also periodically checks
378 * need_resched() and either schedules in sync compaction or aborts async
379 * compaction. This is similar to what compact_unlock_should_abort() does, but
380 * is used where no lock is concerned.
382 * Returns false when no scheduling was needed, or sync compaction scheduled.
383 * Returns true when async compaction should abort.
385 static inline bool compact_should_abort(struct compact_control
*cc
)
387 /* async compaction aborts if contended */
388 if (need_resched()) {
389 if (cc
->mode
== MIGRATE_ASYNC
) {
390 cc
->contended
= COMPACT_CONTENDED_SCHED
;
401 * Isolate free pages onto a private freelist. If @strict is true, will abort
402 * returning 0 on any invalid PFNs or non-free pages inside of the pageblock
403 * (even though it may still end up isolating some pages).
405 static unsigned long isolate_freepages_block(struct compact_control
*cc
,
406 unsigned long *start_pfn
,
407 unsigned long end_pfn
,
408 struct list_head
*freelist
,
411 int nr_scanned
= 0, total_isolated
= 0;
412 struct page
*cursor
, *valid_page
= NULL
;
413 unsigned long flags
= 0;
415 unsigned long blockpfn
= *start_pfn
;
417 cursor
= pfn_to_page(blockpfn
);
419 /* Isolate free pages. */
420 for (; blockpfn
< end_pfn
; blockpfn
++, cursor
++) {
422 struct page
*page
= cursor
;
425 * Periodically drop the lock (if held) regardless of its
426 * contention, to give chance to IRQs. Abort if fatal signal
427 * pending or async compaction detects need_resched()
429 if (!(blockpfn
% SWAP_CLUSTER_MAX
)
430 && compact_unlock_should_abort(&cc
->zone
->lock
, flags
,
435 if (!pfn_valid_within(blockpfn
))
442 * For compound pages such as THP and hugetlbfs, we can save
443 * potentially a lot of iterations if we skip them at once.
444 * The check is racy, but we can consider only valid values
445 * and the only danger is skipping too much.
447 if (PageCompound(page
)) {
448 unsigned int comp_order
= compound_order(page
);
450 if (likely(comp_order
< MAX_ORDER
)) {
451 blockpfn
+= (1UL << comp_order
) - 1;
452 cursor
+= (1UL << comp_order
) - 1;
458 if (!PageBuddy(page
))
462 * If we already hold the lock, we can skip some rechecking.
463 * Note that if we hold the lock now, checked_pageblock was
464 * already set in some previous iteration (or strict is true),
465 * so it is correct to skip the suitable migration target
470 * The zone lock must be held to isolate freepages.
471 * Unfortunately this is a very coarse lock and can be
472 * heavily contended if there are parallel allocations
473 * or parallel compactions. For async compaction do not
474 * spin on the lock and we acquire the lock as late as
477 locked
= compact_trylock_irqsave(&cc
->zone
->lock
,
482 /* Recheck this is a buddy page under lock */
483 if (!PageBuddy(page
))
487 /* Found a free page, break it into order-0 pages */
488 isolated
= split_free_page(page
);
489 total_isolated
+= isolated
;
490 for (i
= 0; i
< isolated
; i
++) {
491 list_add(&page
->lru
, freelist
);
495 /* If a page was split, advance to the end of it */
497 cc
->nr_freepages
+= isolated
;
499 cc
->nr_migratepages
<= cc
->nr_freepages
) {
500 blockpfn
+= isolated
;
504 blockpfn
+= isolated
- 1;
505 cursor
+= isolated
- 1;
518 * There is a tiny chance that we have read bogus compound_order(),
519 * so be careful to not go outside of the pageblock.
521 if (unlikely(blockpfn
> end_pfn
))
524 trace_mm_compaction_isolate_freepages(*start_pfn
, blockpfn
,
525 nr_scanned
, total_isolated
);
527 /* Record how far we have got within the block */
528 *start_pfn
= blockpfn
;
531 * If strict isolation is requested by CMA then check that all the
532 * pages requested were isolated. If there were any failures, 0 is
533 * returned and CMA will fail.
535 if (strict
&& blockpfn
< end_pfn
)
539 spin_unlock_irqrestore(&cc
->zone
->lock
, flags
);
541 /* Update the pageblock-skip if the whole pageblock was scanned */
542 if (blockpfn
== end_pfn
)
543 update_pageblock_skip(cc
, valid_page
, total_isolated
, false);
545 count_compact_events(COMPACTFREE_SCANNED
, nr_scanned
);
547 count_compact_events(COMPACTISOLATED
, total_isolated
);
548 return total_isolated
;
552 * isolate_freepages_range() - isolate free pages.
553 * @start_pfn: The first PFN to start isolating.
554 * @end_pfn: The one-past-last PFN.
556 * Non-free pages, invalid PFNs, or zone boundaries within the
557 * [start_pfn, end_pfn) range are considered errors, cause function to
558 * undo its actions and return zero.
560 * Otherwise, function returns one-past-the-last PFN of isolated page
561 * (which may be greater then end_pfn if end fell in a middle of
565 isolate_freepages_range(struct compact_control
*cc
,
566 unsigned long start_pfn
, unsigned long end_pfn
)
568 unsigned long isolated
, pfn
, block_end_pfn
;
572 block_end_pfn
= ALIGN(pfn
+ 1, pageblock_nr_pages
);
574 for (; pfn
< end_pfn
; pfn
+= isolated
,
575 block_end_pfn
+= pageblock_nr_pages
) {
576 /* Protect pfn from changing by isolate_freepages_block */
577 unsigned long isolate_start_pfn
= pfn
;
579 block_end_pfn
= min(block_end_pfn
, end_pfn
);
582 * pfn could pass the block_end_pfn if isolated freepage
583 * is more than pageblock order. In this case, we adjust
584 * scanning range to right one.
586 if (pfn
>= block_end_pfn
) {
587 block_end_pfn
= ALIGN(pfn
+ 1, pageblock_nr_pages
);
588 block_end_pfn
= min(block_end_pfn
, end_pfn
);
591 if (!pageblock_pfn_to_page(pfn
, block_end_pfn
, cc
->zone
))
594 isolated
= isolate_freepages_block(cc
, &isolate_start_pfn
,
595 block_end_pfn
, &freelist
, true);
598 * In strict mode, isolate_freepages_block() returns 0 if
599 * there are any holes in the block (ie. invalid PFNs or
606 * If we managed to isolate pages, it is always (1 << n) *
607 * pageblock_nr_pages for some non-negative n. (Max order
608 * page may span two pageblocks).
612 /* split_free_page does not map the pages */
613 map_pages(&freelist
);
616 /* Loop terminated early, cleanup. */
617 release_freepages(&freelist
);
621 /* We don't use freelists for anything. */
625 /* Update the number of anon and file isolated pages in the zone */
626 static void acct_isolated(struct zone
*zone
, struct compact_control
*cc
)
629 unsigned int count
[2] = { 0, };
631 if (list_empty(&cc
->migratepages
))
634 list_for_each_entry(page
, &cc
->migratepages
, lru
)
635 count
[!!page_is_file_cache(page
)]++;
637 mod_zone_page_state(zone
, NR_ISOLATED_ANON
, count
[0]);
638 mod_zone_page_state(zone
, NR_ISOLATED_FILE
, count
[1]);
641 /* Similar to reclaim, but different enough that they don't share logic */
642 static bool too_many_isolated(struct zone
*zone
)
644 unsigned long active
, inactive
, isolated
;
646 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
647 zone_page_state(zone
, NR_INACTIVE_ANON
);
648 active
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
649 zone_page_state(zone
, NR_ACTIVE_ANON
);
650 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
) +
651 zone_page_state(zone
, NR_ISOLATED_ANON
);
653 return isolated
> (inactive
+ active
) / 2;
657 * isolate_migratepages_block() - isolate all migrate-able pages within
659 * @cc: Compaction control structure.
660 * @low_pfn: The first PFN to isolate
661 * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
662 * @isolate_mode: Isolation mode to be used.
664 * Isolate all pages that can be migrated from the range specified by
665 * [low_pfn, end_pfn). The range is expected to be within same pageblock.
666 * Returns zero if there is a fatal signal pending, otherwise PFN of the
667 * first page that was not scanned (which may be both less, equal to or more
670 * The pages are isolated on cc->migratepages list (not required to be empty),
671 * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field
672 * is neither read nor updated.
675 isolate_migratepages_block(struct compact_control
*cc
, unsigned long low_pfn
,
676 unsigned long end_pfn
, isolate_mode_t isolate_mode
)
678 struct zone
*zone
= cc
->zone
;
679 unsigned long nr_scanned
= 0, nr_isolated
= 0;
680 struct list_head
*migratelist
= &cc
->migratepages
;
681 struct lruvec
*lruvec
;
682 unsigned long flags
= 0;
684 struct page
*page
= NULL
, *valid_page
= NULL
;
685 unsigned long start_pfn
= low_pfn
;
688 * Ensure that there are not too many pages isolated from the LRU
689 * list by either parallel reclaimers or compaction. If there are,
690 * delay for some time until fewer pages are isolated
692 while (unlikely(too_many_isolated(zone
))) {
693 /* async migration should just abort */
694 if (cc
->mode
== MIGRATE_ASYNC
)
697 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
699 if (fatal_signal_pending(current
))
703 if (compact_should_abort(cc
))
706 /* Time to isolate some pages for migration */
707 for (; low_pfn
< end_pfn
; low_pfn
++) {
711 * Periodically drop the lock (if held) regardless of its
712 * contention, to give chance to IRQs. Abort async compaction
715 if (!(low_pfn
% SWAP_CLUSTER_MAX
)
716 && compact_unlock_should_abort(&zone
->lru_lock
, flags
,
720 if (!pfn_valid_within(low_pfn
))
724 page
= pfn_to_page(low_pfn
);
730 * Skip if free. We read page order here without zone lock
731 * which is generally unsafe, but the race window is small and
732 * the worst thing that can happen is that we skip some
733 * potential isolation targets.
735 if (PageBuddy(page
)) {
736 unsigned long freepage_order
= page_order_unsafe(page
);
739 * Without lock, we cannot be sure that what we got is
740 * a valid page order. Consider only values in the
741 * valid order range to prevent low_pfn overflow.
743 if (freepage_order
> 0 && freepage_order
< MAX_ORDER
)
744 low_pfn
+= (1UL << freepage_order
) - 1;
749 * Check may be lockless but that's ok as we recheck later.
750 * It's possible to migrate LRU pages and balloon pages
751 * Skip any other type of page
753 is_lru
= PageLRU(page
);
755 if (unlikely(balloon_page_movable(page
))) {
756 if (balloon_page_isolate(page
)) {
757 /* Successfully isolated */
758 goto isolate_success
;
764 * Regardless of being on LRU, compound pages such as THP and
765 * hugetlbfs are not to be compacted. We can potentially save
766 * a lot of iterations if we skip them at once. The check is
767 * racy, but we can consider only valid values and the only
768 * danger is skipping too much.
770 if (PageCompound(page
)) {
771 unsigned int comp_order
= compound_order(page
);
773 if (likely(comp_order
< MAX_ORDER
))
774 low_pfn
+= (1UL << comp_order
) - 1;
783 * Migration will fail if an anonymous page is pinned in memory,
784 * so avoid taking lru_lock and isolating it unnecessarily in an
785 * admittedly racy check.
787 if (!page_mapping(page
) &&
788 page_count(page
) > page_mapcount(page
))
791 /* If we already hold the lock, we can skip some rechecking */
793 locked
= compact_trylock_irqsave(&zone
->lru_lock
,
798 /* Recheck PageLRU and PageCompound under lock */
803 * Page become compound since the non-locked check,
804 * and it's on LRU. It can only be a THP so the order
805 * is safe to read and it's 0 for tail pages.
807 if (unlikely(PageCompound(page
))) {
808 low_pfn
+= (1UL << compound_order(page
)) - 1;
813 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
815 /* Try isolate the page */
816 if (__isolate_lru_page(page
, isolate_mode
) != 0)
819 VM_BUG_ON_PAGE(PageCompound(page
), page
);
821 /* Successfully isolated */
822 del_page_from_lru_list(page
, lruvec
, page_lru(page
));
825 list_add(&page
->lru
, migratelist
);
826 cc
->nr_migratepages
++;
829 /* Avoid isolating too much */
830 if (cc
->nr_migratepages
== COMPACT_CLUSTER_MAX
) {
837 * The PageBuddy() check could have potentially brought us outside
838 * the range to be scanned.
840 if (unlikely(low_pfn
> end_pfn
))
844 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
847 * Update the pageblock-skip information and cached scanner pfn,
848 * if the whole pageblock was scanned without isolating any page.
850 if (low_pfn
== end_pfn
)
851 update_pageblock_skip(cc
, valid_page
, nr_isolated
, true);
853 trace_mm_compaction_isolate_migratepages(start_pfn
, low_pfn
,
854 nr_scanned
, nr_isolated
);
856 count_compact_events(COMPACTMIGRATE_SCANNED
, nr_scanned
);
858 count_compact_events(COMPACTISOLATED
, nr_isolated
);
864 * isolate_migratepages_range() - isolate migrate-able pages in a PFN range
865 * @cc: Compaction control structure.
866 * @start_pfn: The first PFN to start isolating.
867 * @end_pfn: The one-past-last PFN.
869 * Returns zero if isolation fails fatally due to e.g. pending signal.
870 * Otherwise, function returns one-past-the-last PFN of isolated page
871 * (which may be greater than end_pfn if end fell in a middle of a THP page).
874 isolate_migratepages_range(struct compact_control
*cc
, unsigned long start_pfn
,
875 unsigned long end_pfn
)
877 unsigned long pfn
, block_end_pfn
;
879 /* Scan block by block. First and last block may be incomplete */
881 block_end_pfn
= ALIGN(pfn
+ 1, pageblock_nr_pages
);
883 for (; pfn
< end_pfn
; pfn
= block_end_pfn
,
884 block_end_pfn
+= pageblock_nr_pages
) {
886 block_end_pfn
= min(block_end_pfn
, end_pfn
);
888 if (!pageblock_pfn_to_page(pfn
, block_end_pfn
, cc
->zone
))
891 pfn
= isolate_migratepages_block(cc
, pfn
, block_end_pfn
,
892 ISOLATE_UNEVICTABLE
);
895 * In case of fatal failure, release everything that might
896 * have been isolated in the previous iteration, and signal
897 * the failure back to caller.
900 putback_movable_pages(&cc
->migratepages
);
901 cc
->nr_migratepages
= 0;
905 if (cc
->nr_migratepages
== COMPACT_CLUSTER_MAX
)
908 acct_isolated(cc
->zone
, cc
);
913 #endif /* CONFIG_COMPACTION || CONFIG_CMA */
914 #ifdef CONFIG_COMPACTION
916 /* Returns true if the page is within a block suitable for migration to */
917 static bool suitable_migration_target(struct page
*page
)
919 /* If the page is a large free page, then disallow migration */
920 if (PageBuddy(page
)) {
922 * We are checking page_order without zone->lock taken. But
923 * the only small danger is that we skip a potentially suitable
924 * pageblock, so it's not worth to check order for valid range.
926 if (page_order_unsafe(page
) >= pageblock_order
)
930 /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
931 if (migrate_async_suitable(get_pageblock_migratetype(page
)))
934 /* Otherwise skip the block */
939 * Test whether the free scanner has reached the same or lower pageblock than
940 * the migration scanner, and compaction should thus terminate.
942 static inline bool compact_scanners_met(struct compact_control
*cc
)
944 return (cc
->free_pfn
>> pageblock_order
)
945 <= (cc
->migrate_pfn
>> pageblock_order
);
949 * Based on information in the current compact_control, find blocks
950 * suitable for isolating free pages from and then isolate them.
952 static void isolate_freepages(struct compact_control
*cc
)
954 struct zone
*zone
= cc
->zone
;
956 unsigned long block_start_pfn
; /* start of current pageblock */
957 unsigned long isolate_start_pfn
; /* exact pfn we start at */
958 unsigned long block_end_pfn
; /* end of current pageblock */
959 unsigned long low_pfn
; /* lowest pfn scanner is able to scan */
960 struct list_head
*freelist
= &cc
->freepages
;
963 * Initialise the free scanner. The starting point is where we last
964 * successfully isolated from, zone-cached value, or the end of the
965 * zone when isolating for the first time. For looping we also need
966 * this pfn aligned down to the pageblock boundary, because we do
967 * block_start_pfn -= pageblock_nr_pages in the for loop.
968 * For ending point, take care when isolating in last pageblock of a
969 * a zone which ends in the middle of a pageblock.
970 * The low boundary is the end of the pageblock the migration scanner
973 isolate_start_pfn
= cc
->free_pfn
;
974 block_start_pfn
= cc
->free_pfn
& ~(pageblock_nr_pages
-1);
975 block_end_pfn
= min(block_start_pfn
+ pageblock_nr_pages
,
977 low_pfn
= ALIGN(cc
->migrate_pfn
+ 1, pageblock_nr_pages
);
980 * Isolate free pages until enough are available to migrate the
981 * pages on cc->migratepages. We stop searching if the migrate
982 * and free page scanners meet or enough free pages are isolated.
984 for (; block_start_pfn
>= low_pfn
;
985 block_end_pfn
= block_start_pfn
,
986 block_start_pfn
-= pageblock_nr_pages
,
987 isolate_start_pfn
= block_start_pfn
) {
990 * This can iterate a massively long zone without finding any
991 * suitable migration targets, so periodically check if we need
992 * to schedule, or even abort async compaction.
994 if (!(block_start_pfn
% (SWAP_CLUSTER_MAX
* pageblock_nr_pages
))
995 && compact_should_abort(cc
))
998 page
= pageblock_pfn_to_page(block_start_pfn
, block_end_pfn
,
1003 /* Check the block is suitable for migration */
1004 if (!suitable_migration_target(page
))
1007 /* If isolation recently failed, do not retry */
1008 if (!isolation_suitable(cc
, page
))
1011 /* Found a block suitable for isolating free pages from. */
1012 isolate_freepages_block(cc
, &isolate_start_pfn
,
1013 block_end_pfn
, freelist
, false);
1016 * If we isolated enough freepages, or aborted due to async
1017 * compaction being contended, terminate the loop.
1018 * Remember where the free scanner should restart next time,
1019 * which is where isolate_freepages_block() left off.
1020 * But if it scanned the whole pageblock, isolate_start_pfn
1021 * now points at block_end_pfn, which is the start of the next
1023 * In that case we will however want to restart at the start
1024 * of the previous pageblock.
1026 if ((cc
->nr_freepages
>= cc
->nr_migratepages
)
1028 if (isolate_start_pfn
>= block_end_pfn
)
1030 block_start_pfn
- pageblock_nr_pages
;
1034 * isolate_freepages_block() should not terminate
1035 * prematurely unless contended, or isolated enough
1037 VM_BUG_ON(isolate_start_pfn
< block_end_pfn
);
1041 /* split_free_page does not map the pages */
1042 map_pages(freelist
);
1045 * Record where the free scanner will restart next time. Either we
1046 * broke from the loop and set isolate_start_pfn based on the last
1047 * call to isolate_freepages_block(), or we met the migration scanner
1048 * and the loop terminated due to isolate_start_pfn < low_pfn
1050 cc
->free_pfn
= isolate_start_pfn
;
1054 * This is a migrate-callback that "allocates" freepages by taking pages
1055 * from the isolated freelists in the block we are migrating to.
1057 static struct page
*compaction_alloc(struct page
*migratepage
,
1061 struct compact_control
*cc
= (struct compact_control
*)data
;
1062 struct page
*freepage
;
1065 * Isolate free pages if necessary, and if we are not aborting due to
1068 if (list_empty(&cc
->freepages
)) {
1070 isolate_freepages(cc
);
1072 if (list_empty(&cc
->freepages
))
1076 freepage
= list_entry(cc
->freepages
.next
, struct page
, lru
);
1077 list_del(&freepage
->lru
);
1084 * This is a migrate-callback that "frees" freepages back to the isolated
1085 * freelist. All pages on the freelist are from the same zone, so there is no
1086 * special handling needed for NUMA.
1088 static void compaction_free(struct page
*page
, unsigned long data
)
1090 struct compact_control
*cc
= (struct compact_control
*)data
;
1092 list_add(&page
->lru
, &cc
->freepages
);
1096 /* possible outcome of isolate_migratepages */
1098 ISOLATE_ABORT
, /* Abort compaction now */
1099 ISOLATE_NONE
, /* No pages isolated, continue scanning */
1100 ISOLATE_SUCCESS
, /* Pages isolated, migrate */
1101 } isolate_migrate_t
;
1104 * Allow userspace to control policy on scanning the unevictable LRU for
1105 * compactable pages.
1107 int sysctl_compact_unevictable_allowed __read_mostly
= 1;
1110 * Isolate all pages that can be migrated from the first suitable block,
1111 * starting at the block pointed to by the migrate scanner pfn within
1114 static isolate_migrate_t
isolate_migratepages(struct zone
*zone
,
1115 struct compact_control
*cc
)
1117 unsigned long low_pfn
, end_pfn
;
1118 unsigned long isolate_start_pfn
;
1120 const isolate_mode_t isolate_mode
=
1121 (sysctl_compact_unevictable_allowed
? ISOLATE_UNEVICTABLE
: 0) |
1122 (cc
->mode
== MIGRATE_ASYNC
? ISOLATE_ASYNC_MIGRATE
: 0);
1125 * Start at where we last stopped, or beginning of the zone as
1126 * initialized by compact_zone()
1128 low_pfn
= cc
->migrate_pfn
;
1130 /* Only scan within a pageblock boundary */
1131 end_pfn
= ALIGN(low_pfn
+ 1, pageblock_nr_pages
);
1134 * Iterate over whole pageblocks until we find the first suitable.
1135 * Do not cross the free scanner.
1137 for (; end_pfn
<= cc
->free_pfn
;
1138 low_pfn
= end_pfn
, end_pfn
+= pageblock_nr_pages
) {
1141 * This can potentially iterate a massively long zone with
1142 * many pageblocks unsuitable, so periodically check if we
1143 * need to schedule, or even abort async compaction.
1145 if (!(low_pfn
% (SWAP_CLUSTER_MAX
* pageblock_nr_pages
))
1146 && compact_should_abort(cc
))
1149 page
= pageblock_pfn_to_page(low_pfn
, end_pfn
, zone
);
1153 /* If isolation recently failed, do not retry */
1154 if (!isolation_suitable(cc
, page
))
1158 * For async compaction, also only scan in MOVABLE blocks.
1159 * Async compaction is optimistic to see if the minimum amount
1160 * of work satisfies the allocation.
1162 if (cc
->mode
== MIGRATE_ASYNC
&&
1163 !migrate_async_suitable(get_pageblock_migratetype(page
)))
1166 /* Perform the isolation */
1167 isolate_start_pfn
= low_pfn
;
1168 low_pfn
= isolate_migratepages_block(cc
, low_pfn
, end_pfn
,
1171 if (!low_pfn
|| cc
->contended
) {
1172 acct_isolated(zone
, cc
);
1173 return ISOLATE_ABORT
;
1177 * Record where we could have freed pages by migration and not
1178 * yet flushed them to buddy allocator.
1179 * - this is the lowest page that could have been isolated and
1180 * then freed by migration.
1182 if (cc
->nr_migratepages
&& !cc
->last_migrated_pfn
)
1183 cc
->last_migrated_pfn
= isolate_start_pfn
;
1186 * Either we isolated something and proceed with migration. Or
1187 * we failed and compact_zone should decide if we should
1193 acct_isolated(zone
, cc
);
1194 /* Record where migration scanner will be restarted. */
1195 cc
->migrate_pfn
= low_pfn
;
1197 return cc
->nr_migratepages
? ISOLATE_SUCCESS
: ISOLATE_NONE
;
1200 static int __compact_finished(struct zone
*zone
, struct compact_control
*cc
,
1201 const int migratetype
)
1204 unsigned long watermark
;
1206 if (cc
->contended
|| fatal_signal_pending(current
))
1207 return COMPACT_PARTIAL
;
1209 /* Compaction run completes if the migrate and free scanner meet */
1210 if (compact_scanners_met(cc
)) {
1211 /* Let the next compaction start anew. */
1212 reset_cached_positions(zone
);
1215 * Mark that the PG_migrate_skip information should be cleared
1216 * by kswapd when it goes to sleep. kswapd does not set the
1217 * flag itself as the decision to be clear should be directly
1218 * based on an allocation request.
1220 if (!current_is_kswapd())
1221 zone
->compact_blockskip_flush
= true;
1223 return COMPACT_COMPLETE
;
1227 * order == -1 is expected when compacting via
1228 * /proc/sys/vm/compact_memory
1230 if (cc
->order
== -1)
1231 return COMPACT_CONTINUE
;
1233 /* Compaction run is not finished if the watermark is not met */
1234 watermark
= low_wmark_pages(zone
);
1236 if (!zone_watermark_ok(zone
, cc
->order
, watermark
, cc
->classzone_idx
,
1238 return COMPACT_CONTINUE
;
1240 /* Direct compactor: Is a suitable page free? */
1241 for (order
= cc
->order
; order
< MAX_ORDER
; order
++) {
1242 struct free_area
*area
= &zone
->free_area
[order
];
1245 /* Job done if page is free of the right migratetype */
1246 if (!list_empty(&area
->free_list
[migratetype
]))
1247 return COMPACT_PARTIAL
;
1250 /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
1251 if (migratetype
== MIGRATE_MOVABLE
&&
1252 !list_empty(&area
->free_list
[MIGRATE_CMA
]))
1253 return COMPACT_PARTIAL
;
1256 * Job done if allocation would steal freepages from
1257 * other migratetype buddy lists.
1259 if (find_suitable_fallback(area
, order
, migratetype
,
1260 true, &can_steal
) != -1)
1261 return COMPACT_PARTIAL
;
1264 return COMPACT_NO_SUITABLE_PAGE
;
1267 static int compact_finished(struct zone
*zone
, struct compact_control
*cc
,
1268 const int migratetype
)
1272 ret
= __compact_finished(zone
, cc
, migratetype
);
1273 trace_mm_compaction_finished(zone
, cc
->order
, ret
);
1274 if (ret
== COMPACT_NO_SUITABLE_PAGE
)
1275 ret
= COMPACT_CONTINUE
;
1281 * compaction_suitable: Is this suitable to run compaction on this zone now?
1283 * COMPACT_SKIPPED - If there are too few free pages for compaction
1284 * COMPACT_PARTIAL - If the allocation would succeed without compaction
1285 * COMPACT_CONTINUE - If compaction should run now
1287 static unsigned long __compaction_suitable(struct zone
*zone
, int order
,
1288 int alloc_flags
, int classzone_idx
)
1291 unsigned long watermark
;
1294 * order == -1 is expected when compacting via
1295 * /proc/sys/vm/compact_memory
1298 return COMPACT_CONTINUE
;
1300 watermark
= low_wmark_pages(zone
);
1302 * If watermarks for high-order allocation are already met, there
1303 * should be no need for compaction at all.
1305 if (zone_watermark_ok(zone
, order
, watermark
, classzone_idx
,
1307 return COMPACT_PARTIAL
;
1310 * Watermarks for order-0 must be met for compaction. Note the 2UL.
1311 * This is because during migration, copies of pages need to be
1312 * allocated and for a short time, the footprint is higher
1314 watermark
+= (2UL << order
);
1315 if (!zone_watermark_ok(zone
, 0, watermark
, classzone_idx
, alloc_flags
))
1316 return COMPACT_SKIPPED
;
1319 * fragmentation index determines if allocation failures are due to
1320 * low memory or external fragmentation
1322 * index of -1000 would imply allocations might succeed depending on
1323 * watermarks, but we already failed the high-order watermark check
1324 * index towards 0 implies failure is due to lack of memory
1325 * index towards 1000 implies failure is due to fragmentation
1327 * Only compact if a failure would be due to fragmentation.
1329 fragindex
= fragmentation_index(zone
, order
);
1330 if (fragindex
>= 0 && fragindex
<= sysctl_extfrag_threshold
)
1331 return COMPACT_NOT_SUITABLE_ZONE
;
1333 return COMPACT_CONTINUE
;
1336 unsigned long compaction_suitable(struct zone
*zone
, int order
,
1337 int alloc_flags
, int classzone_idx
)
1341 ret
= __compaction_suitable(zone
, order
, alloc_flags
, classzone_idx
);
1342 trace_mm_compaction_suitable(zone
, order
, ret
);
1343 if (ret
== COMPACT_NOT_SUITABLE_ZONE
)
1344 ret
= COMPACT_SKIPPED
;
1349 static int compact_zone(struct zone
*zone
, struct compact_control
*cc
)
1352 unsigned long start_pfn
= zone
->zone_start_pfn
;
1353 unsigned long end_pfn
= zone_end_pfn(zone
);
1354 const int migratetype
= gfpflags_to_migratetype(cc
->gfp_mask
);
1355 const bool sync
= cc
->mode
!= MIGRATE_ASYNC
;
1357 ret
= compaction_suitable(zone
, cc
->order
, cc
->alloc_flags
,
1360 case COMPACT_PARTIAL
:
1361 case COMPACT_SKIPPED
:
1362 /* Compaction is likely to fail */
1364 case COMPACT_CONTINUE
:
1365 /* Fall through to compaction */
1370 * Clear pageblock skip if there were failures recently and compaction
1371 * is about to be retried after being deferred. kswapd does not do
1372 * this reset as it'll reset the cached information when going to sleep.
1374 if (compaction_restarting(zone
, cc
->order
) && !current_is_kswapd())
1375 __reset_isolation_suitable(zone
);
1378 * Setup to move all movable pages to the end of the zone. Used cached
1379 * information on where the scanners should start but check that it
1380 * is initialised by ensuring the values are within zone boundaries.
1382 cc
->migrate_pfn
= zone
->compact_cached_migrate_pfn
[sync
];
1383 cc
->free_pfn
= zone
->compact_cached_free_pfn
;
1384 if (cc
->free_pfn
< start_pfn
|| cc
->free_pfn
> end_pfn
) {
1385 cc
->free_pfn
= end_pfn
& ~(pageblock_nr_pages
-1);
1386 zone
->compact_cached_free_pfn
= cc
->free_pfn
;
1388 if (cc
->migrate_pfn
< start_pfn
|| cc
->migrate_pfn
> end_pfn
) {
1389 cc
->migrate_pfn
= start_pfn
;
1390 zone
->compact_cached_migrate_pfn
[0] = cc
->migrate_pfn
;
1391 zone
->compact_cached_migrate_pfn
[1] = cc
->migrate_pfn
;
1393 cc
->last_migrated_pfn
= 0;
1395 trace_mm_compaction_begin(start_pfn
, cc
->migrate_pfn
,
1396 cc
->free_pfn
, end_pfn
, sync
);
1398 migrate_prep_local();
1400 while ((ret
= compact_finished(zone
, cc
, migratetype
)) ==
1404 switch (isolate_migratepages(zone
, cc
)) {
1406 ret
= COMPACT_PARTIAL
;
1407 putback_movable_pages(&cc
->migratepages
);
1408 cc
->nr_migratepages
= 0;
1412 * We haven't isolated and migrated anything, but
1413 * there might still be unflushed migrations from
1414 * previous cc->order aligned block.
1417 case ISOLATE_SUCCESS
:
1421 err
= migrate_pages(&cc
->migratepages
, compaction_alloc
,
1422 compaction_free
, (unsigned long)cc
, cc
->mode
,
1425 trace_mm_compaction_migratepages(cc
->nr_migratepages
, err
,
1428 /* All pages were either migrated or will be released */
1429 cc
->nr_migratepages
= 0;
1431 putback_movable_pages(&cc
->migratepages
);
1433 * migrate_pages() may return -ENOMEM when scanners meet
1434 * and we want compact_finished() to detect it
1436 if (err
== -ENOMEM
&& !compact_scanners_met(cc
)) {
1437 ret
= COMPACT_PARTIAL
;
1444 * Has the migration scanner moved away from the previous
1445 * cc->order aligned block where we migrated from? If yes,
1446 * flush the pages that were freed, so that they can merge and
1447 * compact_finished() can detect immediately if allocation
1450 if (cc
->order
> 0 && cc
->last_migrated_pfn
) {
1452 unsigned long current_block_start
=
1453 cc
->migrate_pfn
& ~((1UL << cc
->order
) - 1);
1455 if (cc
->last_migrated_pfn
< current_block_start
) {
1457 lru_add_drain_cpu(cpu
);
1458 drain_local_pages(zone
);
1460 /* No more flushing until we migrate again */
1461 cc
->last_migrated_pfn
= 0;
1469 * Release free pages and update where the free scanner should restart,
1470 * so we don't leave any returned pages behind in the next attempt.
1472 if (cc
->nr_freepages
> 0) {
1473 unsigned long free_pfn
= release_freepages(&cc
->freepages
);
1475 cc
->nr_freepages
= 0;
1476 VM_BUG_ON(free_pfn
== 0);
1477 /* The cached pfn is always the first in a pageblock */
1478 free_pfn
&= ~(pageblock_nr_pages
-1);
1480 * Only go back, not forward. The cached pfn might have been
1481 * already reset to zone end in compact_finished()
1483 if (free_pfn
> zone
->compact_cached_free_pfn
)
1484 zone
->compact_cached_free_pfn
= free_pfn
;
1487 trace_mm_compaction_end(start_pfn
, cc
->migrate_pfn
,
1488 cc
->free_pfn
, end_pfn
, sync
, ret
);
1493 static unsigned long compact_zone_order(struct zone
*zone
, int order
,
1494 gfp_t gfp_mask
, enum migrate_mode mode
, int *contended
,
1495 int alloc_flags
, int classzone_idx
)
1498 struct compact_control cc
= {
1500 .nr_migratepages
= 0,
1502 .gfp_mask
= gfp_mask
,
1505 .alloc_flags
= alloc_flags
,
1506 .classzone_idx
= classzone_idx
,
1508 INIT_LIST_HEAD(&cc
.freepages
);
1509 INIT_LIST_HEAD(&cc
.migratepages
);
1511 ret
= compact_zone(zone
, &cc
);
1513 VM_BUG_ON(!list_empty(&cc
.freepages
));
1514 VM_BUG_ON(!list_empty(&cc
.migratepages
));
1516 *contended
= cc
.contended
;
1520 int sysctl_extfrag_threshold
= 500;
1523 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
1524 * @gfp_mask: The GFP mask of the current allocation
1525 * @order: The order of the current allocation
1526 * @alloc_flags: The allocation flags of the current allocation
1527 * @ac: The context of current allocation
1528 * @mode: The migration mode for async, sync light, or sync migration
1529 * @contended: Return value that determines if compaction was aborted due to
1530 * need_resched() or lock contention
1532 * This is the main entry point for direct page compaction.
1534 unsigned long try_to_compact_pages(gfp_t gfp_mask
, unsigned int order
,
1535 int alloc_flags
, const struct alloc_context
*ac
,
1536 enum migrate_mode mode
, int *contended
)
1538 int may_enter_fs
= gfp_mask
& __GFP_FS
;
1539 int may_perform_io
= gfp_mask
& __GFP_IO
;
1542 int rc
= COMPACT_DEFERRED
;
1543 int all_zones_contended
= COMPACT_CONTENDED_LOCK
; /* init for &= op */
1545 *contended
= COMPACT_CONTENDED_NONE
;
1547 /* Check if the GFP flags allow compaction */
1548 if (!order
|| !may_enter_fs
|| !may_perform_io
)
1549 return COMPACT_SKIPPED
;
1551 trace_mm_compaction_try_to_compact_pages(order
, gfp_mask
, mode
);
1553 /* Compact each zone in the list */
1554 for_each_zone_zonelist_nodemask(zone
, z
, ac
->zonelist
, ac
->high_zoneidx
,
1559 if (compaction_deferred(zone
, order
))
1562 status
= compact_zone_order(zone
, order
, gfp_mask
, mode
,
1563 &zone_contended
, alloc_flags
,
1565 rc
= max(status
, rc
);
1567 * It takes at least one zone that wasn't lock contended
1568 * to clear all_zones_contended.
1570 all_zones_contended
&= zone_contended
;
1572 /* If a normal allocation would succeed, stop compacting */
1573 if (zone_watermark_ok(zone
, order
, low_wmark_pages(zone
),
1574 ac
->classzone_idx
, alloc_flags
)) {
1576 * We think the allocation will succeed in this zone,
1577 * but it is not certain, hence the false. The caller
1578 * will repeat this with true if allocation indeed
1579 * succeeds in this zone.
1581 compaction_defer_reset(zone
, order
, false);
1583 * It is possible that async compaction aborted due to
1584 * need_resched() and the watermarks were ok thanks to
1585 * somebody else freeing memory. The allocation can
1586 * however still fail so we better signal the
1587 * need_resched() contention anyway (this will not
1588 * prevent the allocation attempt).
1590 if (zone_contended
== COMPACT_CONTENDED_SCHED
)
1591 *contended
= COMPACT_CONTENDED_SCHED
;
1596 if (mode
!= MIGRATE_ASYNC
&& status
== COMPACT_COMPLETE
) {
1598 * We think that allocation won't succeed in this zone
1599 * so we defer compaction there. If it ends up
1600 * succeeding after all, it will be reset.
1602 defer_compaction(zone
, order
);
1606 * We might have stopped compacting due to need_resched() in
1607 * async compaction, or due to a fatal signal detected. In that
1608 * case do not try further zones and signal need_resched()
1611 if ((zone_contended
== COMPACT_CONTENDED_SCHED
)
1612 || fatal_signal_pending(current
)) {
1613 *contended
= COMPACT_CONTENDED_SCHED
;
1620 * We might not have tried all the zones, so be conservative
1621 * and assume they are not all lock contended.
1623 all_zones_contended
= 0;
1628 * If at least one zone wasn't deferred or skipped, we report if all
1629 * zones that were tried were lock contended.
1631 if (rc
> COMPACT_SKIPPED
&& all_zones_contended
)
1632 *contended
= COMPACT_CONTENDED_LOCK
;
1638 /* Compact all zones within a node */
1639 static void __compact_pgdat(pg_data_t
*pgdat
, struct compact_control
*cc
)
1644 for (zoneid
= 0; zoneid
< MAX_NR_ZONES
; zoneid
++) {
1646 zone
= &pgdat
->node_zones
[zoneid
];
1647 if (!populated_zone(zone
))
1650 cc
->nr_freepages
= 0;
1651 cc
->nr_migratepages
= 0;
1653 INIT_LIST_HEAD(&cc
->freepages
);
1654 INIT_LIST_HEAD(&cc
->migratepages
);
1657 * When called via /proc/sys/vm/compact_memory
1658 * this makes sure we compact the whole zone regardless of
1659 * cached scanner positions.
1661 if (cc
->order
== -1)
1662 __reset_isolation_suitable(zone
);
1664 if (cc
->order
== -1 || !compaction_deferred(zone
, cc
->order
))
1665 compact_zone(zone
, cc
);
1667 if (cc
->order
> 0) {
1668 if (zone_watermark_ok(zone
, cc
->order
,
1669 low_wmark_pages(zone
), 0, 0))
1670 compaction_defer_reset(zone
, cc
->order
, false);
1673 VM_BUG_ON(!list_empty(&cc
->freepages
));
1674 VM_BUG_ON(!list_empty(&cc
->migratepages
));
1678 void compact_pgdat(pg_data_t
*pgdat
, int order
)
1680 struct compact_control cc
= {
1682 .mode
= MIGRATE_ASYNC
,
1688 __compact_pgdat(pgdat
, &cc
);
1691 static void compact_node(int nid
)
1693 struct compact_control cc
= {
1695 .mode
= MIGRATE_SYNC
,
1696 .ignore_skip_hint
= true,
1699 __compact_pgdat(NODE_DATA(nid
), &cc
);
1702 /* Compact all nodes in the system */
1703 static void compact_nodes(void)
1707 /* Flush pending updates to the LRU lists */
1708 lru_add_drain_all();
1710 for_each_online_node(nid
)
1714 /* The written value is actually unused, all memory is compacted */
1715 int sysctl_compact_memory
;
1717 /* This is the entry point for compacting all nodes via /proc/sys/vm */
1718 int sysctl_compaction_handler(struct ctl_table
*table
, int write
,
1719 void __user
*buffer
, size_t *length
, loff_t
*ppos
)
1727 int sysctl_extfrag_handler(struct ctl_table
*table
, int write
,
1728 void __user
*buffer
, size_t *length
, loff_t
*ppos
)
1730 proc_dointvec_minmax(table
, write
, buffer
, length
, ppos
);
1735 #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
1736 static ssize_t
sysfs_compact_node(struct device
*dev
,
1737 struct device_attribute
*attr
,
1738 const char *buf
, size_t count
)
1742 if (nid
>= 0 && nid
< nr_node_ids
&& node_online(nid
)) {
1743 /* Flush pending updates to the LRU lists */
1744 lru_add_drain_all();
1751 static DEVICE_ATTR(compact
, S_IWUSR
, NULL
, sysfs_compact_node
);
1753 int compaction_register_node(struct node
*node
)
1755 return device_create_file(&node
->dev
, &dev_attr_compact
);
1758 void compaction_unregister_node(struct node
*node
)
1760 return device_remove_file(&node
->dev
, &dev_attr_compact
);
1762 #endif /* CONFIG_SYSFS && CONFIG_NUMA */
1764 #endif /* CONFIG_COMPACTION */