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>
19 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
21 #define CREATE_TRACE_POINTS
22 #include <trace/events/compaction.h>
24 static unsigned long release_freepages(struct list_head
*freelist
)
26 struct page
*page
, *next
;
27 unsigned long count
= 0;
29 list_for_each_entry_safe(page
, next
, freelist
, lru
) {
38 static void map_pages(struct list_head
*list
)
42 list_for_each_entry(page
, list
, lru
) {
43 arch_alloc_page(page
, 0);
44 kernel_map_pages(page
, 1, 1);
48 static inline bool migrate_async_suitable(int migratetype
)
50 return is_migrate_cma(migratetype
) || migratetype
== MIGRATE_MOVABLE
;
53 #ifdef CONFIG_COMPACTION
54 /* Returns true if the pageblock should be scanned for pages to isolate. */
55 static inline bool isolation_suitable(struct compact_control
*cc
,
58 if (cc
->ignore_skip_hint
)
61 return !get_pageblock_skip(page
);
65 * This function is called to clear all cached information on pageblocks that
66 * should be skipped for page isolation when the migrate and free page scanner
69 static void reset_isolation_suitable(struct zone
*zone
)
71 unsigned long start_pfn
= zone
->zone_start_pfn
;
72 unsigned long end_pfn
= zone
->zone_start_pfn
+ zone
->spanned_pages
;
76 * Do not reset more than once every five seconds. If allocations are
77 * failing sufficiently quickly to allow this to happen then continually
78 * scanning for compaction is not going to help. The choice of five
79 * seconds is arbitrary but will mitigate excessive scanning.
81 if (time_before(jiffies
, zone
->compact_blockskip_expire
))
84 zone
->compact_cached_migrate_pfn
= start_pfn
;
85 zone
->compact_cached_free_pfn
= end_pfn
;
86 zone
->compact_blockskip_expire
= jiffies
+ (HZ
* 5);
88 /* Walk the zone and mark every pageblock as suitable for isolation */
89 for (pfn
= start_pfn
; pfn
< end_pfn
; pfn
+= pageblock_nr_pages
) {
97 page
= pfn_to_page(pfn
);
98 if (zone
!= page_zone(page
))
101 clear_pageblock_skip(page
);
106 * If no pages were isolated then mark this pageblock to be skipped in the
107 * future. The information is later cleared by reset_isolation_suitable().
109 static void update_pageblock_skip(struct compact_control
*cc
,
110 struct page
*page
, unsigned long nr_isolated
,
111 bool migrate_scanner
)
113 struct zone
*zone
= cc
->zone
;
118 unsigned long pfn
= page_to_pfn(page
);
119 set_pageblock_skip(page
);
121 /* Update where compaction should restart */
122 if (migrate_scanner
) {
123 if (!cc
->finished_update_migrate
&&
124 pfn
> zone
->compact_cached_migrate_pfn
)
125 zone
->compact_cached_migrate_pfn
= pfn
;
127 if (!cc
->finished_update_free
&&
128 pfn
< zone
->compact_cached_free_pfn
)
129 zone
->compact_cached_free_pfn
= pfn
;
134 static inline bool isolation_suitable(struct compact_control
*cc
,
140 static void update_pageblock_skip(struct compact_control
*cc
,
141 struct page
*page
, unsigned long nr_isolated
,
142 bool migrate_scanner
)
145 #endif /* CONFIG_COMPACTION */
147 static inline bool should_release_lock(spinlock_t
*lock
)
149 return need_resched() || spin_is_contended(lock
);
153 * Compaction requires the taking of some coarse locks that are potentially
154 * very heavily contended. Check if the process needs to be scheduled or
155 * if the lock is contended. For async compaction, back out in the event
156 * if contention is severe. For sync compaction, schedule.
158 * Returns true if the lock is held.
159 * Returns false if the lock is released and compaction should abort
161 static bool compact_checklock_irqsave(spinlock_t
*lock
, unsigned long *flags
,
162 bool locked
, struct compact_control
*cc
)
164 if (should_release_lock(lock
)) {
166 spin_unlock_irqrestore(lock
, *flags
);
170 /* async aborts if taking too long or contended */
172 cc
->contended
= true;
180 spin_lock_irqsave(lock
, *flags
);
184 static inline bool compact_trylock_irqsave(spinlock_t
*lock
,
185 unsigned long *flags
, struct compact_control
*cc
)
187 return compact_checklock_irqsave(lock
, flags
, false, cc
);
190 /* Returns true if the page is within a block suitable for migration to */
191 static bool suitable_migration_target(struct page
*page
)
193 int migratetype
= get_pageblock_migratetype(page
);
195 /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
196 if (migratetype
== MIGRATE_ISOLATE
|| migratetype
== MIGRATE_RESERVE
)
199 /* If the page is a large free page, then allow migration */
200 if (PageBuddy(page
) && page_order(page
) >= pageblock_order
)
203 /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
204 if (migrate_async_suitable(migratetype
))
207 /* Otherwise skip the block */
211 static void compact_capture_page(struct compact_control
*cc
)
214 int mtype
, mtype_low
, mtype_high
;
216 if (!cc
->page
|| *cc
->page
)
220 * For MIGRATE_MOVABLE allocations we capture a suitable page ASAP
221 * regardless of the migratetype of the freelist is is captured from.
222 * This is fine because the order for a high-order MIGRATE_MOVABLE
223 * allocation is typically at least a pageblock size and overall
224 * fragmentation is not impaired. Other allocation types must
225 * capture pages from their own migratelist because otherwise they
226 * could pollute other pageblocks like MIGRATE_MOVABLE with
227 * difficult to move pages and making fragmentation worse overall.
229 if (cc
->migratetype
== MIGRATE_MOVABLE
) {
231 mtype_high
= MIGRATE_PCPTYPES
;
233 mtype_low
= cc
->migratetype
;
234 mtype_high
= cc
->migratetype
+ 1;
237 /* Speculatively examine the free lists without zone lock */
238 for (mtype
= mtype_low
; mtype
< mtype_high
; mtype
++) {
240 for (order
= cc
->order
; order
< MAX_ORDER
; order
++) {
242 struct free_area
*area
;
243 area
= &(cc
->zone
->free_area
[order
]);
244 if (list_empty(&area
->free_list
[mtype
]))
247 /* Take the lock and attempt capture of the page */
248 if (!compact_trylock_irqsave(&cc
->zone
->lock
, &flags
, cc
))
250 if (!list_empty(&area
->free_list
[mtype
])) {
251 page
= list_entry(area
->free_list
[mtype
].next
,
253 if (capture_free_page(page
, cc
->order
, mtype
)) {
254 spin_unlock_irqrestore(&cc
->zone
->lock
,
260 spin_unlock_irqrestore(&cc
->zone
->lock
, flags
);
266 * Isolate free pages onto a private freelist. Caller must hold zone->lock.
267 * If @strict is true, will abort returning 0 on any invalid PFNs or non-free
268 * pages inside of the pageblock (even though it may still end up isolating
271 static unsigned long isolate_freepages_block(struct compact_control
*cc
,
272 unsigned long blockpfn
,
273 unsigned long end_pfn
,
274 struct list_head
*freelist
,
277 int nr_scanned
= 0, total_isolated
= 0;
278 struct page
*cursor
, *valid_page
= NULL
;
279 unsigned long nr_strict_required
= end_pfn
- blockpfn
;
283 cursor
= pfn_to_page(blockpfn
);
285 /* Isolate free pages. */
286 for (; blockpfn
< end_pfn
; blockpfn
++, cursor
++) {
288 struct page
*page
= cursor
;
291 if (!pfn_valid_within(blockpfn
))
295 if (!PageBuddy(page
))
299 * The zone lock must be held to isolate freepages.
300 * Unfortunately this is a very coarse lock and can be
301 * heavily contended if there are parallel allocations
302 * or parallel compactions. For async compaction do not
303 * spin on the lock and we acquire the lock as late as
306 locked
= compact_checklock_irqsave(&cc
->zone
->lock
, &flags
,
311 /* Recheck this is a suitable migration target under lock */
312 if (!strict
&& !suitable_migration_target(page
))
315 /* Recheck this is a buddy page under lock */
316 if (!PageBuddy(page
))
319 /* Found a free page, break it into order-0 pages */
320 isolated
= split_free_page(page
);
321 if (!isolated
&& strict
)
323 total_isolated
+= isolated
;
324 for (i
= 0; i
< isolated
; i
++) {
325 list_add(&page
->lru
, freelist
);
329 /* If a page was split, advance to the end of it */
331 blockpfn
+= isolated
- 1;
332 cursor
+= isolated
- 1;
336 trace_mm_compaction_isolate_freepages(nr_scanned
, total_isolated
);
339 * If strict isolation is requested by CMA then check that all the
340 * pages requested were isolated. If there were any failures, 0 is
341 * returned and CMA will fail.
343 if (strict
&& nr_strict_required
!= total_isolated
)
347 spin_unlock_irqrestore(&cc
->zone
->lock
, flags
);
349 /* Update the pageblock-skip if the whole pageblock was scanned */
350 if (blockpfn
== end_pfn
)
351 update_pageblock_skip(cc
, valid_page
, total_isolated
, false);
353 return total_isolated
;
357 * isolate_freepages_range() - isolate free pages.
358 * @start_pfn: The first PFN to start isolating.
359 * @end_pfn: The one-past-last PFN.
361 * Non-free pages, invalid PFNs, or zone boundaries within the
362 * [start_pfn, end_pfn) range are considered errors, cause function to
363 * undo its actions and return zero.
365 * Otherwise, function returns one-past-the-last PFN of isolated page
366 * (which may be greater then end_pfn if end fell in a middle of
370 isolate_freepages_range(struct compact_control
*cc
,
371 unsigned long start_pfn
, unsigned long end_pfn
)
373 unsigned long isolated
, pfn
, block_end_pfn
;
376 for (pfn
= start_pfn
; pfn
< end_pfn
; pfn
+= isolated
) {
377 if (!pfn_valid(pfn
) || cc
->zone
!= page_zone(pfn_to_page(pfn
)))
381 * On subsequent iterations ALIGN() is actually not needed,
382 * but we keep it that we not to complicate the code.
384 block_end_pfn
= ALIGN(pfn
+ 1, pageblock_nr_pages
);
385 block_end_pfn
= min(block_end_pfn
, end_pfn
);
387 isolated
= isolate_freepages_block(cc
, pfn
, block_end_pfn
,
391 * In strict mode, isolate_freepages_block() returns 0 if
392 * there are any holes in the block (ie. invalid PFNs or
399 * If we managed to isolate pages, it is always (1 << n) *
400 * pageblock_nr_pages for some non-negative n. (Max order
401 * page may span two pageblocks).
405 /* split_free_page does not map the pages */
406 map_pages(&freelist
);
409 /* Loop terminated early, cleanup. */
410 release_freepages(&freelist
);
414 /* We don't use freelists for anything. */
418 /* Update the number of anon and file isolated pages in the zone */
419 static void acct_isolated(struct zone
*zone
, bool locked
, struct compact_control
*cc
)
422 unsigned int count
[2] = { 0, };
424 list_for_each_entry(page
, &cc
->migratepages
, lru
)
425 count
[!!page_is_file_cache(page
)]++;
427 /* If locked we can use the interrupt unsafe versions */
429 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, count
[0]);
430 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, count
[1]);
432 mod_zone_page_state(zone
, NR_ISOLATED_ANON
, count
[0]);
433 mod_zone_page_state(zone
, NR_ISOLATED_FILE
, count
[1]);
437 /* Similar to reclaim, but different enough that they don't share logic */
438 static bool too_many_isolated(struct zone
*zone
)
440 unsigned long active
, inactive
, isolated
;
442 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
443 zone_page_state(zone
, NR_INACTIVE_ANON
);
444 active
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
445 zone_page_state(zone
, NR_ACTIVE_ANON
);
446 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
) +
447 zone_page_state(zone
, NR_ISOLATED_ANON
);
449 return isolated
> (inactive
+ active
) / 2;
453 * isolate_migratepages_range() - isolate all migrate-able pages in range.
454 * @zone: Zone pages are in.
455 * @cc: Compaction control structure.
456 * @low_pfn: The first PFN of the range.
457 * @end_pfn: The one-past-the-last PFN of the range.
459 * Isolate all pages that can be migrated from the range specified by
460 * [low_pfn, end_pfn). Returns zero if there is a fatal signal
461 * pending), otherwise PFN of the first page that was not scanned
462 * (which may be both less, equal to or more then end_pfn).
464 * Assumes that cc->migratepages is empty and cc->nr_migratepages is
467 * Apart from cc->migratepages and cc->nr_migratetypes this function
468 * does not modify any cc's fields, in particular it does not modify
469 * (or read for that matter) cc->migrate_pfn.
472 isolate_migratepages_range(struct zone
*zone
, struct compact_control
*cc
,
473 unsigned long low_pfn
, unsigned long end_pfn
)
475 unsigned long last_pageblock_nr
= 0, pageblock_nr
;
476 unsigned long nr_scanned
= 0, nr_isolated
= 0;
477 struct list_head
*migratelist
= &cc
->migratepages
;
478 isolate_mode_t mode
= 0;
479 struct lruvec
*lruvec
;
482 struct page
*page
= NULL
, *valid_page
= NULL
;
485 * Ensure that there are not too many pages isolated from the LRU
486 * list by either parallel reclaimers or compaction. If there are,
487 * delay for some time until fewer pages are isolated
489 while (unlikely(too_many_isolated(zone
))) {
490 /* async migration should just abort */
494 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
496 if (fatal_signal_pending(current
))
500 /* Time to isolate some pages for migration */
502 for (; low_pfn
< end_pfn
; low_pfn
++) {
503 /* give a chance to irqs before checking need_resched() */
504 if (locked
&& !((low_pfn
+1) % SWAP_CLUSTER_MAX
)) {
505 if (should_release_lock(&zone
->lru_lock
)) {
506 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
512 * migrate_pfn does not necessarily start aligned to a
513 * pageblock. Ensure that pfn_valid is called when moving
514 * into a new MAX_ORDER_NR_PAGES range in case of large
515 * memory holes within the zone
517 if ((low_pfn
& (MAX_ORDER_NR_PAGES
- 1)) == 0) {
518 if (!pfn_valid(low_pfn
)) {
519 low_pfn
+= MAX_ORDER_NR_PAGES
- 1;
524 if (!pfn_valid_within(low_pfn
))
529 * Get the page and ensure the page is within the same zone.
530 * See the comment in isolate_freepages about overlapping
531 * nodes. It is deliberate that the new zone lock is not taken
532 * as memory compaction should not move pages between nodes.
534 page
= pfn_to_page(low_pfn
);
535 if (page_zone(page
) != zone
)
541 /* If isolation recently failed, do not retry */
542 pageblock_nr
= low_pfn
>> pageblock_order
;
543 if (!isolation_suitable(cc
, page
))
551 * For async migration, also only scan in MOVABLE blocks. Async
552 * migration is optimistic to see if the minimum amount of work
553 * satisfies the allocation
555 if (!cc
->sync
&& last_pageblock_nr
!= pageblock_nr
&&
556 !migrate_async_suitable(get_pageblock_migratetype(page
))) {
557 cc
->finished_update_migrate
= true;
561 /* Check may be lockless but that's ok as we recheck later */
566 * PageLRU is set. lru_lock normally excludes isolation
567 * splitting and collapsing (collapsing has already happened
568 * if PageLRU is set) but the lock is not necessarily taken
569 * here and it is wasteful to take it just to check transhuge.
570 * Check TransHuge without lock and skip the whole pageblock if
571 * it's either a transhuge or hugetlbfs page, as calling
572 * compound_order() without preventing THP from splitting the
573 * page underneath us may return surprising results.
575 if (PageTransHuge(page
)) {
578 low_pfn
+= (1 << compound_order(page
)) - 1;
582 /* Check if it is ok to still hold the lock */
583 locked
= compact_checklock_irqsave(&zone
->lru_lock
, &flags
,
585 if (!locked
|| fatal_signal_pending(current
))
588 /* Recheck PageLRU and PageTransHuge under lock */
591 if (PageTransHuge(page
)) {
592 low_pfn
+= (1 << compound_order(page
)) - 1;
597 mode
|= ISOLATE_ASYNC_MIGRATE
;
599 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
601 /* Try isolate the page */
602 if (__isolate_lru_page(page
, mode
) != 0)
605 VM_BUG_ON(PageTransCompound(page
));
607 /* Successfully isolated */
608 cc
->finished_update_migrate
= true;
609 del_page_from_lru_list(page
, lruvec
, page_lru(page
));
610 list_add(&page
->lru
, migratelist
);
611 cc
->nr_migratepages
++;
614 /* Avoid isolating too much */
615 if (cc
->nr_migratepages
== COMPACT_CLUSTER_MAX
) {
623 low_pfn
+= pageblock_nr_pages
;
624 low_pfn
= ALIGN(low_pfn
, pageblock_nr_pages
) - 1;
625 last_pageblock_nr
= pageblock_nr
;
628 acct_isolated(zone
, locked
, cc
);
631 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
633 /* Update the pageblock-skip if the whole pageblock was scanned */
634 if (low_pfn
== end_pfn
)
635 update_pageblock_skip(cc
, valid_page
, nr_isolated
, true);
637 trace_mm_compaction_isolate_migratepages(nr_scanned
, nr_isolated
);
642 #endif /* CONFIG_COMPACTION || CONFIG_CMA */
643 #ifdef CONFIG_COMPACTION
645 * Based on information in the current compact_control, find blocks
646 * suitable for isolating free pages from and then isolate them.
648 static void isolate_freepages(struct zone
*zone
,
649 struct compact_control
*cc
)
652 unsigned long high_pfn
, low_pfn
, pfn
, zone_end_pfn
, end_pfn
;
653 int nr_freepages
= cc
->nr_freepages
;
654 struct list_head
*freelist
= &cc
->freepages
;
657 * Initialise the free scanner. The starting point is where we last
658 * scanned from (or the end of the zone if starting). The low point
659 * is the end of the pageblock the migration scanner is using.
662 low_pfn
= cc
->migrate_pfn
+ pageblock_nr_pages
;
665 * Take care that if the migration scanner is at the end of the zone
666 * that the free scanner does not accidentally move to the next zone
667 * in the next isolation cycle.
669 high_pfn
= min(low_pfn
, pfn
);
671 zone_end_pfn
= zone
->zone_start_pfn
+ zone
->spanned_pages
;
674 * Isolate free pages until enough are available to migrate the
675 * pages on cc->migratepages. We stop searching if the migrate
676 * and free page scanners meet or enough free pages are isolated.
678 for (; pfn
> low_pfn
&& cc
->nr_migratepages
> nr_freepages
;
679 pfn
-= pageblock_nr_pages
) {
680 unsigned long isolated
;
686 * Check for overlapping nodes/zones. It's possible on some
687 * configurations to have a setup like
689 * i.e. it's possible that all pages within a zones range of
690 * pages do not belong to a single zone.
692 page
= pfn_to_page(pfn
);
693 if (page_zone(page
) != zone
)
696 /* Check the block is suitable for migration */
697 if (!suitable_migration_target(page
))
700 /* If isolation recently failed, do not retry */
701 if (!isolation_suitable(cc
, page
))
704 /* Found a block suitable for isolating free pages from */
706 end_pfn
= min(pfn
+ pageblock_nr_pages
, zone_end_pfn
);
707 isolated
= isolate_freepages_block(cc
, pfn
, end_pfn
,
709 nr_freepages
+= isolated
;
712 * Record the highest PFN we isolated pages from. When next
713 * looking for free pages, the search will restart here as
714 * page migration may have returned some pages to the allocator
717 cc
->finished_update_free
= true;
718 high_pfn
= max(high_pfn
, pfn
);
722 /* split_free_page does not map the pages */
725 cc
->free_pfn
= high_pfn
;
726 cc
->nr_freepages
= nr_freepages
;
730 * This is a migrate-callback that "allocates" freepages by taking pages
731 * from the isolated freelists in the block we are migrating to.
733 static struct page
*compaction_alloc(struct page
*migratepage
,
737 struct compact_control
*cc
= (struct compact_control
*)data
;
738 struct page
*freepage
;
740 /* Isolate free pages if necessary */
741 if (list_empty(&cc
->freepages
)) {
742 isolate_freepages(cc
->zone
, cc
);
744 if (list_empty(&cc
->freepages
))
748 freepage
= list_entry(cc
->freepages
.next
, struct page
, lru
);
749 list_del(&freepage
->lru
);
756 * We cannot control nr_migratepages and nr_freepages fully when migration is
757 * running as migrate_pages() has no knowledge of compact_control. When
758 * migration is complete, we count the number of pages on the lists by hand.
760 static void update_nr_listpages(struct compact_control
*cc
)
762 int nr_migratepages
= 0;
763 int nr_freepages
= 0;
766 list_for_each_entry(page
, &cc
->migratepages
, lru
)
768 list_for_each_entry(page
, &cc
->freepages
, lru
)
771 cc
->nr_migratepages
= nr_migratepages
;
772 cc
->nr_freepages
= nr_freepages
;
775 /* possible outcome of isolate_migratepages */
777 ISOLATE_ABORT
, /* Abort compaction now */
778 ISOLATE_NONE
, /* No pages isolated, continue scanning */
779 ISOLATE_SUCCESS
, /* Pages isolated, migrate */
783 * Isolate all pages that can be migrated from the block pointed to by
784 * the migrate scanner within compact_control.
786 static isolate_migrate_t
isolate_migratepages(struct zone
*zone
,
787 struct compact_control
*cc
)
789 unsigned long low_pfn
, end_pfn
;
791 /* Do not scan outside zone boundaries */
792 low_pfn
= max(cc
->migrate_pfn
, zone
->zone_start_pfn
);
794 /* Only scan within a pageblock boundary */
795 end_pfn
= ALIGN(low_pfn
+ pageblock_nr_pages
, pageblock_nr_pages
);
797 /* Do not cross the free scanner or scan within a memory hole */
798 if (end_pfn
> cc
->free_pfn
|| !pfn_valid(low_pfn
)) {
799 cc
->migrate_pfn
= end_pfn
;
803 /* Perform the isolation */
804 low_pfn
= isolate_migratepages_range(zone
, cc
, low_pfn
, end_pfn
);
805 if (!low_pfn
|| cc
->contended
)
806 return ISOLATE_ABORT
;
808 cc
->migrate_pfn
= low_pfn
;
810 return ISOLATE_SUCCESS
;
813 static int compact_finished(struct zone
*zone
,
814 struct compact_control
*cc
)
816 unsigned long watermark
;
818 if (fatal_signal_pending(current
))
819 return COMPACT_PARTIAL
;
821 /* Compaction run completes if the migrate and free scanner meet */
822 if (cc
->free_pfn
<= cc
->migrate_pfn
) {
823 reset_isolation_suitable(cc
->zone
);
824 return COMPACT_COMPLETE
;
828 * order == -1 is expected when compacting via
829 * /proc/sys/vm/compact_memory
832 return COMPACT_CONTINUE
;
834 /* Compaction run is not finished if the watermark is not met */
835 watermark
= low_wmark_pages(zone
);
836 watermark
+= (1 << cc
->order
);
838 if (!zone_watermark_ok(zone
, cc
->order
, watermark
, 0, 0))
839 return COMPACT_CONTINUE
;
841 /* Direct compactor: Is a suitable page free? */
843 /* Was a suitable page captured? */
845 return COMPACT_PARTIAL
;
848 for (order
= cc
->order
; order
< MAX_ORDER
; order
++) {
849 struct free_area
*area
= &zone
->free_area
[cc
->order
];
850 /* Job done if page is free of the right migratetype */
851 if (!list_empty(&area
->free_list
[cc
->migratetype
]))
852 return COMPACT_PARTIAL
;
854 /* Job done if allocation would set block type */
855 if (cc
->order
>= pageblock_order
&& area
->nr_free
)
856 return COMPACT_PARTIAL
;
860 return COMPACT_CONTINUE
;
864 * compaction_suitable: Is this suitable to run compaction on this zone now?
866 * COMPACT_SKIPPED - If there are too few free pages for compaction
867 * COMPACT_PARTIAL - If the allocation would succeed without compaction
868 * COMPACT_CONTINUE - If compaction should run now
870 unsigned long compaction_suitable(struct zone
*zone
, int order
)
873 unsigned long watermark
;
876 * order == -1 is expected when compacting via
877 * /proc/sys/vm/compact_memory
880 return COMPACT_CONTINUE
;
883 * Watermarks for order-0 must be met for compaction. Note the 2UL.
884 * This is because during migration, copies of pages need to be
885 * allocated and for a short time, the footprint is higher
887 watermark
= low_wmark_pages(zone
) + (2UL << order
);
888 if (!zone_watermark_ok(zone
, 0, watermark
, 0, 0))
889 return COMPACT_SKIPPED
;
892 * fragmentation index determines if allocation failures are due to
893 * low memory or external fragmentation
895 * index of -1000 implies allocations might succeed depending on
897 * index towards 0 implies failure is due to lack of memory
898 * index towards 1000 implies failure is due to fragmentation
900 * Only compact if a failure would be due to fragmentation.
902 fragindex
= fragmentation_index(zone
, order
);
903 if (fragindex
>= 0 && fragindex
<= sysctl_extfrag_threshold
)
904 return COMPACT_SKIPPED
;
906 if (fragindex
== -1000 && zone_watermark_ok(zone
, order
, watermark
,
908 return COMPACT_PARTIAL
;
910 return COMPACT_CONTINUE
;
913 static int compact_zone(struct zone
*zone
, struct compact_control
*cc
)
916 unsigned long start_pfn
= zone
->zone_start_pfn
;
917 unsigned long end_pfn
= zone
->zone_start_pfn
+ zone
->spanned_pages
;
919 ret
= compaction_suitable(zone
, cc
->order
);
921 case COMPACT_PARTIAL
:
922 case COMPACT_SKIPPED
:
923 /* Compaction is likely to fail */
925 case COMPACT_CONTINUE
:
926 /* Fall through to compaction */
931 * Setup to move all movable pages to the end of the zone. Used cached
932 * information on where the scanners should start but check that it
933 * is initialised by ensuring the values are within zone boundaries.
935 cc
->migrate_pfn
= zone
->compact_cached_migrate_pfn
;
936 cc
->free_pfn
= zone
->compact_cached_free_pfn
;
937 if (cc
->free_pfn
< start_pfn
|| cc
->free_pfn
> end_pfn
) {
938 cc
->free_pfn
= end_pfn
& ~(pageblock_nr_pages
-1);
939 zone
->compact_cached_free_pfn
= cc
->free_pfn
;
941 if (cc
->migrate_pfn
< start_pfn
|| cc
->migrate_pfn
> end_pfn
) {
942 cc
->migrate_pfn
= start_pfn
;
943 zone
->compact_cached_migrate_pfn
= cc
->migrate_pfn
;
946 /* Clear pageblock skip if there are numerous alloc failures */
947 if (zone
->compact_defer_shift
== COMPACT_MAX_DEFER_SHIFT
)
948 reset_isolation_suitable(zone
);
950 migrate_prep_local();
952 while ((ret
= compact_finished(zone
, cc
)) == COMPACT_CONTINUE
) {
953 unsigned long nr_migrate
, nr_remaining
;
956 switch (isolate_migratepages(zone
, cc
)) {
958 ret
= COMPACT_PARTIAL
;
959 putback_lru_pages(&cc
->migratepages
);
960 cc
->nr_migratepages
= 0;
964 case ISOLATE_SUCCESS
:
968 nr_migrate
= cc
->nr_migratepages
;
969 err
= migrate_pages(&cc
->migratepages
, compaction_alloc
,
970 (unsigned long)cc
, false,
971 cc
->sync
? MIGRATE_SYNC_LIGHT
: MIGRATE_ASYNC
);
972 update_nr_listpages(cc
);
973 nr_remaining
= cc
->nr_migratepages
;
975 count_vm_event(COMPACTBLOCKS
);
976 count_vm_events(COMPACTPAGES
, nr_migrate
- nr_remaining
);
978 count_vm_events(COMPACTPAGEFAILED
, nr_remaining
);
979 trace_mm_compaction_migratepages(nr_migrate
- nr_remaining
,
982 /* Release LRU pages not migrated */
984 putback_lru_pages(&cc
->migratepages
);
985 cc
->nr_migratepages
= 0;
986 if (err
== -ENOMEM
) {
987 ret
= COMPACT_PARTIAL
;
992 /* Capture a page now if it is a suitable size */
993 compact_capture_page(cc
);
997 /* Release free pages and check accounting */
998 cc
->nr_freepages
-= release_freepages(&cc
->freepages
);
999 VM_BUG_ON(cc
->nr_freepages
!= 0);
1004 static unsigned long compact_zone_order(struct zone
*zone
,
1005 int order
, gfp_t gfp_mask
,
1006 bool sync
, bool *contended
,
1010 struct compact_control cc
= {
1012 .nr_migratepages
= 0,
1014 .migratetype
= allocflags_to_migratetype(gfp_mask
),
1019 INIT_LIST_HEAD(&cc
.freepages
);
1020 INIT_LIST_HEAD(&cc
.migratepages
);
1022 ret
= compact_zone(zone
, &cc
);
1024 VM_BUG_ON(!list_empty(&cc
.freepages
));
1025 VM_BUG_ON(!list_empty(&cc
.migratepages
));
1027 *contended
= cc
.contended
;
1031 int sysctl_extfrag_threshold
= 500;
1034 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
1035 * @zonelist: The zonelist used for the current allocation
1036 * @order: The order of the current allocation
1037 * @gfp_mask: The GFP mask of the current allocation
1038 * @nodemask: The allowed nodes to allocate from
1039 * @sync: Whether migration is synchronous or not
1040 * @contended: Return value that is true if compaction was aborted due to lock contention
1041 * @page: Optionally capture a free page of the requested order during compaction
1043 * This is the main entry point for direct page compaction.
1045 unsigned long try_to_compact_pages(struct zonelist
*zonelist
,
1046 int order
, gfp_t gfp_mask
, nodemask_t
*nodemask
,
1047 bool sync
, bool *contended
, struct page
**page
)
1049 enum zone_type high_zoneidx
= gfp_zone(gfp_mask
);
1050 int may_enter_fs
= gfp_mask
& __GFP_FS
;
1051 int may_perform_io
= gfp_mask
& __GFP_IO
;
1054 int rc
= COMPACT_SKIPPED
;
1055 int alloc_flags
= 0;
1057 /* Check if the GFP flags allow compaction */
1058 if (!order
|| !may_enter_fs
|| !may_perform_io
)
1061 count_vm_event(COMPACTSTALL
);
1064 if (allocflags_to_migratetype(gfp_mask
) == MIGRATE_MOVABLE
)
1065 alloc_flags
|= ALLOC_CMA
;
1067 /* Compact each zone in the list */
1068 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
, high_zoneidx
,
1072 status
= compact_zone_order(zone
, order
, gfp_mask
, sync
,
1074 rc
= max(status
, rc
);
1076 /* If a normal allocation would succeed, stop compacting */
1077 if (zone_watermark_ok(zone
, order
, low_wmark_pages(zone
), 0,
1086 /* Compact all zones within a node */
1087 static int __compact_pgdat(pg_data_t
*pgdat
, struct compact_control
*cc
)
1092 for (zoneid
= 0; zoneid
< MAX_NR_ZONES
; zoneid
++) {
1094 zone
= &pgdat
->node_zones
[zoneid
];
1095 if (!populated_zone(zone
))
1098 cc
->nr_freepages
= 0;
1099 cc
->nr_migratepages
= 0;
1101 INIT_LIST_HEAD(&cc
->freepages
);
1102 INIT_LIST_HEAD(&cc
->migratepages
);
1104 if (cc
->order
== -1 || !compaction_deferred(zone
, cc
->order
))
1105 compact_zone(zone
, cc
);
1107 if (cc
->order
> 0) {
1108 int ok
= zone_watermark_ok(zone
, cc
->order
,
1109 low_wmark_pages(zone
), 0, 0);
1110 if (ok
&& cc
->order
>= zone
->compact_order_failed
)
1111 zone
->compact_order_failed
= cc
->order
+ 1;
1112 /* Currently async compaction is never deferred. */
1113 else if (!ok
&& cc
->sync
)
1114 defer_compaction(zone
, cc
->order
);
1117 VM_BUG_ON(!list_empty(&cc
->freepages
));
1118 VM_BUG_ON(!list_empty(&cc
->migratepages
));
1124 int compact_pgdat(pg_data_t
*pgdat
, int order
)
1126 struct compact_control cc
= {
1132 return __compact_pgdat(pgdat
, &cc
);
1135 static int compact_node(int nid
)
1137 struct compact_control cc
= {
1143 return __compact_pgdat(NODE_DATA(nid
), &cc
);
1146 /* Compact all nodes in the system */
1147 static int compact_nodes(void)
1151 /* Flush pending updates to the LRU lists */
1152 lru_add_drain_all();
1154 for_each_online_node(nid
)
1157 return COMPACT_COMPLETE
;
1160 /* The written value is actually unused, all memory is compacted */
1161 int sysctl_compact_memory
;
1163 /* This is the entry point for compacting all nodes via /proc/sys/vm */
1164 int sysctl_compaction_handler(struct ctl_table
*table
, int write
,
1165 void __user
*buffer
, size_t *length
, loff_t
*ppos
)
1168 return compact_nodes();
1173 int sysctl_extfrag_handler(struct ctl_table
*table
, int write
,
1174 void __user
*buffer
, size_t *length
, loff_t
*ppos
)
1176 proc_dointvec_minmax(table
, write
, buffer
, length
, ppos
);
1181 #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
1182 ssize_t
sysfs_compact_node(struct device
*dev
,
1183 struct device_attribute
*attr
,
1184 const char *buf
, size_t count
)
1188 if (nid
>= 0 && nid
< nr_node_ids
&& node_online(nid
)) {
1189 /* Flush pending updates to the LRU lists */
1190 lru_add_drain_all();
1197 static DEVICE_ATTR(compact
, S_IWUSR
, NULL
, sysfs_compact_node
);
1199 int compaction_register_node(struct node
*node
)
1201 return device_create_file(&node
->dev
, &dev_attr_compact
);
1204 void compaction_unregister_node(struct node
*node
)
1206 return device_remove_file(&node
->dev
, &dev_attr_compact
);
1208 #endif /* CONFIG_SYSFS && CONFIG_NUMA */
1210 #endif /* CONFIG_COMPACTION */