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
;
54 * Compaction requires the taking of some coarse locks that are potentially
55 * very heavily contended. Check if the process needs to be scheduled or
56 * if the lock is contended. For async compaction, back out in the event
57 * if contention is severe. For sync compaction, schedule.
59 * Returns true if the lock is held.
60 * Returns false if the lock is released and compaction should abort
62 static bool compact_checklock_irqsave(spinlock_t
*lock
, unsigned long *flags
,
63 bool locked
, struct compact_control
*cc
)
65 if (need_resched() || spin_is_contended(lock
)) {
67 spin_unlock_irqrestore(lock
, *flags
);
71 /* async aborts if taking too long or contended */
78 if (fatal_signal_pending(current
))
83 spin_lock_irqsave(lock
, *flags
);
87 static inline bool compact_trylock_irqsave(spinlock_t
*lock
,
88 unsigned long *flags
, struct compact_control
*cc
)
90 return compact_checklock_irqsave(lock
, flags
, false, cc
);
93 static void compact_capture_page(struct compact_control
*cc
)
96 int mtype
, mtype_low
, mtype_high
;
98 if (!cc
->page
|| *cc
->page
)
102 * For MIGRATE_MOVABLE allocations we capture a suitable page ASAP
103 * regardless of the migratetype of the freelist is is captured from.
104 * This is fine because the order for a high-order MIGRATE_MOVABLE
105 * allocation is typically at least a pageblock size and overall
106 * fragmentation is not impaired. Other allocation types must
107 * capture pages from their own migratelist because otherwise they
108 * could pollute other pageblocks like MIGRATE_MOVABLE with
109 * difficult to move pages and making fragmentation worse overall.
111 if (cc
->migratetype
== MIGRATE_MOVABLE
) {
113 mtype_high
= MIGRATE_PCPTYPES
;
115 mtype_low
= cc
->migratetype
;
116 mtype_high
= cc
->migratetype
+ 1;
119 /* Speculatively examine the free lists without zone lock */
120 for (mtype
= mtype_low
; mtype
< mtype_high
; mtype
++) {
122 for (order
= cc
->order
; order
< MAX_ORDER
; order
++) {
124 struct free_area
*area
;
125 area
= &(cc
->zone
->free_area
[order
]);
126 if (list_empty(&area
->free_list
[mtype
]))
129 /* Take the lock and attempt capture of the page */
130 if (!compact_trylock_irqsave(&cc
->zone
->lock
, &flags
, cc
))
132 if (!list_empty(&area
->free_list
[mtype
])) {
133 page
= list_entry(area
->free_list
[mtype
].next
,
135 if (capture_free_page(page
, cc
->order
, mtype
)) {
136 spin_unlock_irqrestore(&cc
->zone
->lock
,
142 spin_unlock_irqrestore(&cc
->zone
->lock
, flags
);
148 * Isolate free pages onto a private freelist. Caller must hold zone->lock.
149 * If @strict is true, will abort returning 0 on any invalid PFNs or non-free
150 * pages inside of the pageblock (even though it may still end up isolating
153 static unsigned long isolate_freepages_block(unsigned long blockpfn
,
154 unsigned long end_pfn
,
155 struct list_head
*freelist
,
158 int nr_scanned
= 0, total_isolated
= 0;
161 cursor
= pfn_to_page(blockpfn
);
163 /* Isolate free pages. This assumes the block is valid */
164 for (; blockpfn
< end_pfn
; blockpfn
++, cursor
++) {
166 struct page
*page
= cursor
;
168 if (!pfn_valid_within(blockpfn
)) {
175 if (!PageBuddy(page
)) {
181 /* Found a free page, break it into order-0 pages */
182 isolated
= split_free_page(page
);
183 if (!isolated
&& strict
)
185 total_isolated
+= isolated
;
186 for (i
= 0; i
< isolated
; i
++) {
187 list_add(&page
->lru
, freelist
);
191 /* If a page was split, advance to the end of it */
193 blockpfn
+= isolated
- 1;
194 cursor
+= isolated
- 1;
198 trace_mm_compaction_isolate_freepages(nr_scanned
, total_isolated
);
199 return total_isolated
;
203 * isolate_freepages_range() - isolate free pages.
204 * @start_pfn: The first PFN to start isolating.
205 * @end_pfn: The one-past-last PFN.
207 * Non-free pages, invalid PFNs, or zone boundaries within the
208 * [start_pfn, end_pfn) range are considered errors, cause function to
209 * undo its actions and return zero.
211 * Otherwise, function returns one-past-the-last PFN of isolated page
212 * (which may be greater then end_pfn if end fell in a middle of
216 isolate_freepages_range(unsigned long start_pfn
, unsigned long end_pfn
)
218 unsigned long isolated
, pfn
, block_end_pfn
, flags
;
219 struct zone
*zone
= NULL
;
222 if (pfn_valid(start_pfn
))
223 zone
= page_zone(pfn_to_page(start_pfn
));
225 for (pfn
= start_pfn
; pfn
< end_pfn
; pfn
+= isolated
) {
226 if (!pfn_valid(pfn
) || zone
!= page_zone(pfn_to_page(pfn
)))
230 * On subsequent iterations ALIGN() is actually not needed,
231 * but we keep it that we not to complicate the code.
233 block_end_pfn
= ALIGN(pfn
+ 1, pageblock_nr_pages
);
234 block_end_pfn
= min(block_end_pfn
, end_pfn
);
236 spin_lock_irqsave(&zone
->lock
, flags
);
237 isolated
= isolate_freepages_block(pfn
, block_end_pfn
,
239 spin_unlock_irqrestore(&zone
->lock
, flags
);
242 * In strict mode, isolate_freepages_block() returns 0 if
243 * there are any holes in the block (ie. invalid PFNs or
250 * If we managed to isolate pages, it is always (1 << n) *
251 * pageblock_nr_pages for some non-negative n. (Max order
252 * page may span two pageblocks).
256 /* split_free_page does not map the pages */
257 map_pages(&freelist
);
260 /* Loop terminated early, cleanup. */
261 release_freepages(&freelist
);
265 /* We don't use freelists for anything. */
269 /* Update the number of anon and file isolated pages in the zone */
270 static void acct_isolated(struct zone
*zone
, bool locked
, struct compact_control
*cc
)
273 unsigned int count
[2] = { 0, };
275 list_for_each_entry(page
, &cc
->migratepages
, lru
)
276 count
[!!page_is_file_cache(page
)]++;
278 /* If locked we can use the interrupt unsafe versions */
280 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, count
[0]);
281 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, count
[1]);
283 mod_zone_page_state(zone
, NR_ISOLATED_ANON
, count
[0]);
284 mod_zone_page_state(zone
, NR_ISOLATED_FILE
, count
[1]);
288 /* Similar to reclaim, but different enough that they don't share logic */
289 static bool too_many_isolated(struct zone
*zone
)
291 unsigned long active
, inactive
, isolated
;
293 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
294 zone_page_state(zone
, NR_INACTIVE_ANON
);
295 active
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
296 zone_page_state(zone
, NR_ACTIVE_ANON
);
297 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
) +
298 zone_page_state(zone
, NR_ISOLATED_ANON
);
300 return isolated
> (inactive
+ active
) / 2;
304 * isolate_migratepages_range() - isolate all migrate-able pages in range.
305 * @zone: Zone pages are in.
306 * @cc: Compaction control structure.
307 * @low_pfn: The first PFN of the range.
308 * @end_pfn: The one-past-the-last PFN of the range.
310 * Isolate all pages that can be migrated from the range specified by
311 * [low_pfn, end_pfn). Returns zero if there is a fatal signal
312 * pending), otherwise PFN of the first page that was not scanned
313 * (which may be both less, equal to or more then end_pfn).
315 * Assumes that cc->migratepages is empty and cc->nr_migratepages is
318 * Apart from cc->migratepages and cc->nr_migratetypes this function
319 * does not modify any cc's fields, in particular it does not modify
320 * (or read for that matter) cc->migrate_pfn.
323 isolate_migratepages_range(struct zone
*zone
, struct compact_control
*cc
,
324 unsigned long low_pfn
, unsigned long end_pfn
)
326 unsigned long last_pageblock_nr
= 0, pageblock_nr
;
327 unsigned long nr_scanned
= 0, nr_isolated
= 0;
328 struct list_head
*migratelist
= &cc
->migratepages
;
329 isolate_mode_t mode
= 0;
330 struct lruvec
*lruvec
;
335 * Ensure that there are not too many pages isolated from the LRU
336 * list by either parallel reclaimers or compaction. If there are,
337 * delay for some time until fewer pages are isolated
339 while (unlikely(too_many_isolated(zone
))) {
340 /* async migration should just abort */
344 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
346 if (fatal_signal_pending(current
))
350 /* Time to isolate some pages for migration */
352 spin_lock_irqsave(&zone
->lru_lock
, flags
);
354 for (; low_pfn
< end_pfn
; low_pfn
++) {
357 /* give a chance to irqs before checking need_resched() */
358 if (!((low_pfn
+1) % SWAP_CLUSTER_MAX
)) {
359 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
363 /* Check if it is ok to still hold the lock */
364 locked
= compact_checklock_irqsave(&zone
->lru_lock
, &flags
,
370 * migrate_pfn does not necessarily start aligned to a
371 * pageblock. Ensure that pfn_valid is called when moving
372 * into a new MAX_ORDER_NR_PAGES range in case of large
373 * memory holes within the zone
375 if ((low_pfn
& (MAX_ORDER_NR_PAGES
- 1)) == 0) {
376 if (!pfn_valid(low_pfn
)) {
377 low_pfn
+= MAX_ORDER_NR_PAGES
- 1;
382 if (!pfn_valid_within(low_pfn
))
387 * Get the page and ensure the page is within the same zone.
388 * See the comment in isolate_freepages about overlapping
389 * nodes. It is deliberate that the new zone lock is not taken
390 * as memory compaction should not move pages between nodes.
392 page
= pfn_to_page(low_pfn
);
393 if (page_zone(page
) != zone
)
401 * For async migration, also only scan in MOVABLE blocks. Async
402 * migration is optimistic to see if the minimum amount of work
403 * satisfies the allocation
405 pageblock_nr
= low_pfn
>> pageblock_order
;
406 if (!cc
->sync
&& last_pageblock_nr
!= pageblock_nr
&&
407 !migrate_async_suitable(get_pageblock_migratetype(page
))) {
408 low_pfn
+= pageblock_nr_pages
;
409 low_pfn
= ALIGN(low_pfn
, pageblock_nr_pages
) - 1;
410 last_pageblock_nr
= pageblock_nr
;
418 * PageLRU is set, and lru_lock excludes isolation,
419 * splitting and collapsing (collapsing has already
420 * happened if PageLRU is set).
422 if (PageTransHuge(page
)) {
423 low_pfn
+= (1 << compound_order(page
)) - 1;
428 mode
|= ISOLATE_ASYNC_MIGRATE
;
430 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
432 /* Try isolate the page */
433 if (__isolate_lru_page(page
, mode
) != 0)
436 VM_BUG_ON(PageTransCompound(page
));
438 /* Successfully isolated */
439 del_page_from_lru_list(page
, lruvec
, page_lru(page
));
440 list_add(&page
->lru
, migratelist
);
441 cc
->nr_migratepages
++;
444 /* Avoid isolating too much */
445 if (cc
->nr_migratepages
== COMPACT_CLUSTER_MAX
) {
451 acct_isolated(zone
, locked
, cc
);
454 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
456 trace_mm_compaction_isolate_migratepages(nr_scanned
, nr_isolated
);
461 #endif /* CONFIG_COMPACTION || CONFIG_CMA */
462 #ifdef CONFIG_COMPACTION
464 /* Returns true if the page is within a block suitable for migration to */
465 static bool suitable_migration_target(struct page
*page
)
468 int migratetype
= get_pageblock_migratetype(page
);
470 /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
471 if (migratetype
== MIGRATE_ISOLATE
|| migratetype
== MIGRATE_RESERVE
)
474 /* If the page is a large free page, then allow migration */
475 if (PageBuddy(page
) && page_order(page
) >= pageblock_order
)
478 /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
479 if (migrate_async_suitable(migratetype
))
482 /* Otherwise skip the block */
487 * Returns the start pfn of the last page block in a zone. This is the starting
488 * point for full compaction of a zone. Compaction searches for free pages from
489 * the end of each zone, while isolate_freepages_block scans forward inside each
492 static unsigned long start_free_pfn(struct zone
*zone
)
494 unsigned long free_pfn
;
495 free_pfn
= zone
->zone_start_pfn
+ zone
->spanned_pages
;
496 free_pfn
&= ~(pageblock_nr_pages
-1);
501 * Based on information in the current compact_control, find blocks
502 * suitable for isolating free pages from and then isolate them.
504 static void isolate_freepages(struct zone
*zone
,
505 struct compact_control
*cc
)
508 unsigned long high_pfn
, low_pfn
, pfn
, zone_end_pfn
, end_pfn
;
510 int nr_freepages
= cc
->nr_freepages
;
511 struct list_head
*freelist
= &cc
->freepages
;
514 * Initialise the free scanner. The starting point is where we last
515 * scanned from (or the end of the zone if starting). The low point
516 * is the end of the pageblock the migration scanner is using.
519 low_pfn
= cc
->migrate_pfn
+ pageblock_nr_pages
;
522 * Take care that if the migration scanner is at the end of the zone
523 * that the free scanner does not accidentally move to the next zone
524 * in the next isolation cycle.
526 high_pfn
= min(low_pfn
, pfn
);
528 zone_end_pfn
= zone
->zone_start_pfn
+ zone
->spanned_pages
;
531 * Isolate free pages until enough are available to migrate the
532 * pages on cc->migratepages. We stop searching if the migrate
533 * and free page scanners meet or enough free pages are isolated.
535 for (; pfn
> low_pfn
&& cc
->nr_migratepages
> nr_freepages
;
536 pfn
-= pageblock_nr_pages
) {
537 unsigned long isolated
;
543 * Check for overlapping nodes/zones. It's possible on some
544 * configurations to have a setup like
546 * i.e. it's possible that all pages within a zones range of
547 * pages do not belong to a single zone.
549 page
= pfn_to_page(pfn
);
550 if (page_zone(page
) != zone
)
553 /* Check the block is suitable for migration */
554 if (!suitable_migration_target(page
))
558 * Found a block suitable for isolating free pages from. Now
559 * we disabled interrupts, double check things are ok and
560 * isolate the pages. This is to minimise the time IRQs
566 * The zone lock must be held to isolate freepages. This
567 * unfortunately this is a very coarse lock and can be
568 * heavily contended if there are parallel allocations
569 * or parallel compactions. For async compaction do not
572 if (!compact_trylock_irqsave(&zone
->lock
, &flags
, cc
))
574 if (suitable_migration_target(page
)) {
575 end_pfn
= min(pfn
+ pageblock_nr_pages
, zone_end_pfn
);
576 isolated
= isolate_freepages_block(pfn
, end_pfn
,
578 nr_freepages
+= isolated
;
580 spin_unlock_irqrestore(&zone
->lock
, flags
);
583 * Record the highest PFN we isolated pages from. When next
584 * looking for free pages, the search will restart here as
585 * page migration may have returned some pages to the allocator
588 high_pfn
= max(high_pfn
, pfn
);
591 * If the free scanner has wrapped, update
592 * compact_cached_free_pfn to point to the highest
593 * pageblock with free pages. This reduces excessive
594 * scanning of full pageblocks near the end of the
597 if (cc
->order
> 0 && cc
->wrapped
)
598 zone
->compact_cached_free_pfn
= high_pfn
;
602 /* split_free_page does not map the pages */
605 cc
->free_pfn
= high_pfn
;
606 cc
->nr_freepages
= nr_freepages
;
608 /* If compact_cached_free_pfn is reset then set it now */
609 if (cc
->order
> 0 && !cc
->wrapped
&&
610 zone
->compact_cached_free_pfn
== start_free_pfn(zone
))
611 zone
->compact_cached_free_pfn
= high_pfn
;
615 * This is a migrate-callback that "allocates" freepages by taking pages
616 * from the isolated freelists in the block we are migrating to.
618 static struct page
*compaction_alloc(struct page
*migratepage
,
622 struct compact_control
*cc
= (struct compact_control
*)data
;
623 struct page
*freepage
;
625 /* Isolate free pages if necessary */
626 if (list_empty(&cc
->freepages
)) {
627 isolate_freepages(cc
->zone
, cc
);
629 if (list_empty(&cc
->freepages
))
633 freepage
= list_entry(cc
->freepages
.next
, struct page
, lru
);
634 list_del(&freepage
->lru
);
641 * We cannot control nr_migratepages and nr_freepages fully when migration is
642 * running as migrate_pages() has no knowledge of compact_control. When
643 * migration is complete, we count the number of pages on the lists by hand.
645 static void update_nr_listpages(struct compact_control
*cc
)
647 int nr_migratepages
= 0;
648 int nr_freepages
= 0;
651 list_for_each_entry(page
, &cc
->migratepages
, lru
)
653 list_for_each_entry(page
, &cc
->freepages
, lru
)
656 cc
->nr_migratepages
= nr_migratepages
;
657 cc
->nr_freepages
= nr_freepages
;
660 /* possible outcome of isolate_migratepages */
662 ISOLATE_ABORT
, /* Abort compaction now */
663 ISOLATE_NONE
, /* No pages isolated, continue scanning */
664 ISOLATE_SUCCESS
, /* Pages isolated, migrate */
668 * Isolate all pages that can be migrated from the block pointed to by
669 * the migrate scanner within compact_control.
671 static isolate_migrate_t
isolate_migratepages(struct zone
*zone
,
672 struct compact_control
*cc
)
674 unsigned long low_pfn
, end_pfn
;
676 /* Do not scan outside zone boundaries */
677 low_pfn
= max(cc
->migrate_pfn
, zone
->zone_start_pfn
);
679 /* Only scan within a pageblock boundary */
680 end_pfn
= ALIGN(low_pfn
+ pageblock_nr_pages
, pageblock_nr_pages
);
682 /* Do not cross the free scanner or scan within a memory hole */
683 if (end_pfn
> cc
->free_pfn
|| !pfn_valid(low_pfn
)) {
684 cc
->migrate_pfn
= end_pfn
;
688 /* Perform the isolation */
689 low_pfn
= isolate_migratepages_range(zone
, cc
, low_pfn
, end_pfn
);
690 if (!low_pfn
|| cc
->contended
)
691 return ISOLATE_ABORT
;
693 cc
->migrate_pfn
= low_pfn
;
695 return ISOLATE_SUCCESS
;
698 static int compact_finished(struct zone
*zone
,
699 struct compact_control
*cc
)
701 unsigned long watermark
;
703 if (fatal_signal_pending(current
))
704 return COMPACT_PARTIAL
;
707 * A full (order == -1) compaction run starts at the beginning and
708 * end of a zone; it completes when the migrate and free scanner meet.
709 * A partial (order > 0) compaction can start with the free scanner
710 * at a random point in the zone, and may have to restart.
712 if (cc
->free_pfn
<= cc
->migrate_pfn
) {
713 if (cc
->order
> 0 && !cc
->wrapped
) {
714 /* We started partway through; restart at the end. */
715 unsigned long free_pfn
= start_free_pfn(zone
);
716 zone
->compact_cached_free_pfn
= free_pfn
;
717 cc
->free_pfn
= free_pfn
;
719 return COMPACT_CONTINUE
;
721 return COMPACT_COMPLETE
;
724 /* We wrapped around and ended up where we started. */
725 if (cc
->wrapped
&& cc
->free_pfn
<= cc
->start_free_pfn
)
726 return COMPACT_COMPLETE
;
729 * order == -1 is expected when compacting via
730 * /proc/sys/vm/compact_memory
733 return COMPACT_CONTINUE
;
735 /* Compaction run is not finished if the watermark is not met */
736 watermark
= low_wmark_pages(zone
);
737 watermark
+= (1 << cc
->order
);
739 if (!zone_watermark_ok(zone
, cc
->order
, watermark
, 0, 0))
740 return COMPACT_CONTINUE
;
742 /* Direct compactor: Is a suitable page free? */
744 /* Was a suitable page captured? */
746 return COMPACT_PARTIAL
;
749 for (order
= cc
->order
; order
< MAX_ORDER
; order
++) {
750 struct free_area
*area
= &zone
->free_area
[cc
->order
];
751 /* Job done if page is free of the right migratetype */
752 if (!list_empty(&area
->free_list
[cc
->migratetype
]))
753 return COMPACT_PARTIAL
;
755 /* Job done if allocation would set block type */
756 if (cc
->order
>= pageblock_order
&& area
->nr_free
)
757 return COMPACT_PARTIAL
;
761 return COMPACT_CONTINUE
;
765 * compaction_suitable: Is this suitable to run compaction on this zone now?
767 * COMPACT_SKIPPED - If there are too few free pages for compaction
768 * COMPACT_PARTIAL - If the allocation would succeed without compaction
769 * COMPACT_CONTINUE - If compaction should run now
771 unsigned long compaction_suitable(struct zone
*zone
, int order
)
774 unsigned long watermark
;
777 * order == -1 is expected when compacting via
778 * /proc/sys/vm/compact_memory
781 return COMPACT_CONTINUE
;
784 * Watermarks for order-0 must be met for compaction. Note the 2UL.
785 * This is because during migration, copies of pages need to be
786 * allocated and for a short time, the footprint is higher
788 watermark
= low_wmark_pages(zone
) + (2UL << order
);
789 if (!zone_watermark_ok(zone
, 0, watermark
, 0, 0))
790 return COMPACT_SKIPPED
;
793 * fragmentation index determines if allocation failures are due to
794 * low memory or external fragmentation
796 * index of -1000 implies allocations might succeed depending on
798 * index towards 0 implies failure is due to lack of memory
799 * index towards 1000 implies failure is due to fragmentation
801 * Only compact if a failure would be due to fragmentation.
803 fragindex
= fragmentation_index(zone
, order
);
804 if (fragindex
>= 0 && fragindex
<= sysctl_extfrag_threshold
)
805 return COMPACT_SKIPPED
;
807 if (fragindex
== -1000 && zone_watermark_ok(zone
, order
, watermark
,
809 return COMPACT_PARTIAL
;
811 return COMPACT_CONTINUE
;
814 static int compact_zone(struct zone
*zone
, struct compact_control
*cc
)
818 ret
= compaction_suitable(zone
, cc
->order
);
820 case COMPACT_PARTIAL
:
821 case COMPACT_SKIPPED
:
822 /* Compaction is likely to fail */
824 case COMPACT_CONTINUE
:
825 /* Fall through to compaction */
829 /* Setup to move all movable pages to the end of the zone */
830 cc
->migrate_pfn
= zone
->zone_start_pfn
;
833 /* Incremental compaction. Start where the last one stopped. */
834 cc
->free_pfn
= zone
->compact_cached_free_pfn
;
835 cc
->start_free_pfn
= cc
->free_pfn
;
837 /* Order == -1 starts at the end of the zone. */
838 cc
->free_pfn
= start_free_pfn(zone
);
841 migrate_prep_local();
843 while ((ret
= compact_finished(zone
, cc
)) == COMPACT_CONTINUE
) {
844 unsigned long nr_migrate
, nr_remaining
;
847 switch (isolate_migratepages(zone
, cc
)) {
849 ret
= COMPACT_PARTIAL
;
850 putback_lru_pages(&cc
->migratepages
);
851 cc
->nr_migratepages
= 0;
855 case ISOLATE_SUCCESS
:
859 nr_migrate
= cc
->nr_migratepages
;
860 err
= migrate_pages(&cc
->migratepages
, compaction_alloc
,
861 (unsigned long)cc
, false,
862 cc
->sync
? MIGRATE_SYNC_LIGHT
: MIGRATE_ASYNC
);
863 update_nr_listpages(cc
);
864 nr_remaining
= cc
->nr_migratepages
;
866 count_vm_event(COMPACTBLOCKS
);
867 count_vm_events(COMPACTPAGES
, nr_migrate
- nr_remaining
);
869 count_vm_events(COMPACTPAGEFAILED
, nr_remaining
);
870 trace_mm_compaction_migratepages(nr_migrate
- nr_remaining
,
873 /* Release LRU pages not migrated */
875 putback_lru_pages(&cc
->migratepages
);
876 cc
->nr_migratepages
= 0;
877 if (err
== -ENOMEM
) {
878 ret
= COMPACT_PARTIAL
;
883 /* Capture a page now if it is a suitable size */
884 compact_capture_page(cc
);
888 /* Release free pages and check accounting */
889 cc
->nr_freepages
-= release_freepages(&cc
->freepages
);
890 VM_BUG_ON(cc
->nr_freepages
!= 0);
895 static unsigned long compact_zone_order(struct zone
*zone
,
896 int order
, gfp_t gfp_mask
,
897 bool sync
, bool *contended
,
901 struct compact_control cc
= {
903 .nr_migratepages
= 0,
905 .migratetype
= allocflags_to_migratetype(gfp_mask
),
910 INIT_LIST_HEAD(&cc
.freepages
);
911 INIT_LIST_HEAD(&cc
.migratepages
);
913 ret
= compact_zone(zone
, &cc
);
915 VM_BUG_ON(!list_empty(&cc
.freepages
));
916 VM_BUG_ON(!list_empty(&cc
.migratepages
));
918 *contended
= cc
.contended
;
922 int sysctl_extfrag_threshold
= 500;
925 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
926 * @zonelist: The zonelist used for the current allocation
927 * @order: The order of the current allocation
928 * @gfp_mask: The GFP mask of the current allocation
929 * @nodemask: The allowed nodes to allocate from
930 * @sync: Whether migration is synchronous or not
932 * This is the main entry point for direct page compaction.
934 unsigned long try_to_compact_pages(struct zonelist
*zonelist
,
935 int order
, gfp_t gfp_mask
, nodemask_t
*nodemask
,
936 bool sync
, bool *contended
, struct page
**page
)
938 enum zone_type high_zoneidx
= gfp_zone(gfp_mask
);
939 int may_enter_fs
= gfp_mask
& __GFP_FS
;
940 int may_perform_io
= gfp_mask
& __GFP_IO
;
943 int rc
= COMPACT_SKIPPED
;
946 /* Check if the GFP flags allow compaction */
947 if (!order
|| !may_enter_fs
|| !may_perform_io
)
950 count_vm_event(COMPACTSTALL
);
953 if (allocflags_to_migratetype(gfp_mask
) == MIGRATE_MOVABLE
)
954 alloc_flags
|= ALLOC_CMA
;
956 /* Compact each zone in the list */
957 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
, high_zoneidx
,
961 status
= compact_zone_order(zone
, order
, gfp_mask
, sync
,
963 rc
= max(status
, rc
);
965 /* If a normal allocation would succeed, stop compacting */
966 if (zone_watermark_ok(zone
, order
, low_wmark_pages(zone
), 0,
975 /* Compact all zones within a node */
976 static int __compact_pgdat(pg_data_t
*pgdat
, struct compact_control
*cc
)
981 for (zoneid
= 0; zoneid
< MAX_NR_ZONES
; zoneid
++) {
983 zone
= &pgdat
->node_zones
[zoneid
];
984 if (!populated_zone(zone
))
987 cc
->nr_freepages
= 0;
988 cc
->nr_migratepages
= 0;
990 INIT_LIST_HEAD(&cc
->freepages
);
991 INIT_LIST_HEAD(&cc
->migratepages
);
993 if (cc
->order
== -1 || !compaction_deferred(zone
, cc
->order
))
994 compact_zone(zone
, cc
);
997 int ok
= zone_watermark_ok(zone
, cc
->order
,
998 low_wmark_pages(zone
), 0, 0);
999 if (ok
&& cc
->order
>= zone
->compact_order_failed
)
1000 zone
->compact_order_failed
= cc
->order
+ 1;
1001 /* Currently async compaction is never deferred. */
1002 else if (!ok
&& cc
->sync
)
1003 defer_compaction(zone
, cc
->order
);
1006 VM_BUG_ON(!list_empty(&cc
->freepages
));
1007 VM_BUG_ON(!list_empty(&cc
->migratepages
));
1013 int compact_pgdat(pg_data_t
*pgdat
, int order
)
1015 struct compact_control cc
= {
1021 return __compact_pgdat(pgdat
, &cc
);
1024 static int compact_node(int nid
)
1026 struct compact_control cc
= {
1032 return __compact_pgdat(NODE_DATA(nid
), &cc
);
1035 /* Compact all nodes in the system */
1036 static int compact_nodes(void)
1040 /* Flush pending updates to the LRU lists */
1041 lru_add_drain_all();
1043 for_each_online_node(nid
)
1046 return COMPACT_COMPLETE
;
1049 /* The written value is actually unused, all memory is compacted */
1050 int sysctl_compact_memory
;
1052 /* This is the entry point for compacting all nodes via /proc/sys/vm */
1053 int sysctl_compaction_handler(struct ctl_table
*table
, int write
,
1054 void __user
*buffer
, size_t *length
, loff_t
*ppos
)
1057 return compact_nodes();
1062 int sysctl_extfrag_handler(struct ctl_table
*table
, int write
,
1063 void __user
*buffer
, size_t *length
, loff_t
*ppos
)
1065 proc_dointvec_minmax(table
, write
, buffer
, length
, ppos
);
1070 #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
1071 ssize_t
sysfs_compact_node(struct device
*dev
,
1072 struct device_attribute
*attr
,
1073 const char *buf
, size_t count
)
1077 if (nid
>= 0 && nid
< nr_node_ids
&& node_online(nid
)) {
1078 /* Flush pending updates to the LRU lists */
1079 lru_add_drain_all();
1086 static DEVICE_ATTR(compact
, S_IWUSR
, NULL
, sysfs_compact_node
);
1088 int compaction_register_node(struct node
*node
)
1090 return device_create_file(&node
->dev
, &dev_attr_compact
);
1093 void compaction_unregister_node(struct node
*node
)
1095 return device_remove_file(&node
->dev
, &dev_attr_compact
);
1097 #endif /* CONFIG_SYSFS && CONFIG_NUMA */
1099 #endif /* CONFIG_COMPACTION */
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