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 * Isolate free pages onto a private freelist. Caller must hold zone->lock.
55 * If @strict is true, will abort returning 0 on any invalid PFNs or non-free
56 * pages inside of the pageblock (even though it may still end up isolating
59 static unsigned long isolate_freepages_block(unsigned long blockpfn
,
60 unsigned long end_pfn
,
61 struct list_head
*freelist
,
64 int nr_scanned
= 0, total_isolated
= 0;
67 cursor
= pfn_to_page(blockpfn
);
69 /* Isolate free pages. This assumes the block is valid */
70 for (; blockpfn
< end_pfn
; blockpfn
++, cursor
++) {
72 struct page
*page
= cursor
;
74 if (!pfn_valid_within(blockpfn
)) {
81 if (!PageBuddy(page
)) {
87 /* Found a free page, break it into order-0 pages */
88 isolated
= split_free_page(page
);
89 if (!isolated
&& strict
)
91 total_isolated
+= isolated
;
92 for (i
= 0; i
< isolated
; i
++) {
93 list_add(&page
->lru
, freelist
);
97 /* If a page was split, advance to the end of it */
99 blockpfn
+= isolated
- 1;
100 cursor
+= isolated
- 1;
104 trace_mm_compaction_isolate_freepages(nr_scanned
, total_isolated
);
105 return total_isolated
;
109 * isolate_freepages_range() - isolate free pages.
110 * @start_pfn: The first PFN to start isolating.
111 * @end_pfn: The one-past-last PFN.
113 * Non-free pages, invalid PFNs, or zone boundaries within the
114 * [start_pfn, end_pfn) range are considered errors, cause function to
115 * undo its actions and return zero.
117 * Otherwise, function returns one-past-the-last PFN of isolated page
118 * (which may be greater then end_pfn if end fell in a middle of
122 isolate_freepages_range(unsigned long start_pfn
, unsigned long end_pfn
)
124 unsigned long isolated
, pfn
, block_end_pfn
, flags
;
125 struct zone
*zone
= NULL
;
128 if (pfn_valid(start_pfn
))
129 zone
= page_zone(pfn_to_page(start_pfn
));
131 for (pfn
= start_pfn
; pfn
< end_pfn
; pfn
+= isolated
) {
132 if (!pfn_valid(pfn
) || zone
!= page_zone(pfn_to_page(pfn
)))
136 * On subsequent iterations ALIGN() is actually not needed,
137 * but we keep it that we not to complicate the code.
139 block_end_pfn
= ALIGN(pfn
+ 1, pageblock_nr_pages
);
140 block_end_pfn
= min(block_end_pfn
, end_pfn
);
142 spin_lock_irqsave(&zone
->lock
, flags
);
143 isolated
= isolate_freepages_block(pfn
, block_end_pfn
,
145 spin_unlock_irqrestore(&zone
->lock
, flags
);
148 * In strict mode, isolate_freepages_block() returns 0 if
149 * there are any holes in the block (ie. invalid PFNs or
156 * If we managed to isolate pages, it is always (1 << n) *
157 * pageblock_nr_pages for some non-negative n. (Max order
158 * page may span two pageblocks).
162 /* split_free_page does not map the pages */
163 map_pages(&freelist
);
166 /* Loop terminated early, cleanup. */
167 release_freepages(&freelist
);
171 /* We don't use freelists for anything. */
175 /* Update the number of anon and file isolated pages in the zone */
176 static void acct_isolated(struct zone
*zone
, struct compact_control
*cc
)
179 unsigned int count
[2] = { 0, };
181 list_for_each_entry(page
, &cc
->migratepages
, lru
)
182 count
[!!page_is_file_cache(page
)]++;
184 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, count
[0]);
185 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, count
[1]);
188 /* Similar to reclaim, but different enough that they don't share logic */
189 static bool too_many_isolated(struct zone
*zone
)
191 unsigned long active
, inactive
, isolated
;
193 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
194 zone_page_state(zone
, NR_INACTIVE_ANON
);
195 active
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
196 zone_page_state(zone
, NR_ACTIVE_ANON
);
197 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
) +
198 zone_page_state(zone
, NR_ISOLATED_ANON
);
200 return isolated
> (inactive
+ active
) / 2;
204 * isolate_migratepages_range() - isolate all migrate-able pages in range.
205 * @zone: Zone pages are in.
206 * @cc: Compaction control structure.
207 * @low_pfn: The first PFN of the range.
208 * @end_pfn: The one-past-the-last PFN of the range.
210 * Isolate all pages that can be migrated from the range specified by
211 * [low_pfn, end_pfn). Returns zero if there is a fatal signal
212 * pending), otherwise PFN of the first page that was not scanned
213 * (which may be both less, equal to or more then end_pfn).
215 * Assumes that cc->migratepages is empty and cc->nr_migratepages is
218 * Apart from cc->migratepages and cc->nr_migratetypes this function
219 * does not modify any cc's fields, in particular it does not modify
220 * (or read for that matter) cc->migrate_pfn.
223 isolate_migratepages_range(struct zone
*zone
, struct compact_control
*cc
,
224 unsigned long low_pfn
, unsigned long end_pfn
)
226 unsigned long last_pageblock_nr
= 0, pageblock_nr
;
227 unsigned long nr_scanned
= 0, nr_isolated
= 0;
228 struct list_head
*migratelist
= &cc
->migratepages
;
229 isolate_mode_t mode
= 0;
230 struct lruvec
*lruvec
;
233 * Ensure that there are not too many pages isolated from the LRU
234 * list by either parallel reclaimers or compaction. If there are,
235 * delay for some time until fewer pages are isolated
237 while (unlikely(too_many_isolated(zone
))) {
238 /* async migration should just abort */
239 if (cc
->mode
!= COMPACT_SYNC
)
242 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
244 if (fatal_signal_pending(current
))
248 /* Time to isolate some pages for migration */
250 spin_lock_irq(&zone
->lru_lock
);
251 for (; low_pfn
< end_pfn
; low_pfn
++) {
255 /* give a chance to irqs before checking need_resched() */
256 if (!((low_pfn
+1) % SWAP_CLUSTER_MAX
)) {
257 spin_unlock_irq(&zone
->lru_lock
);
260 if (need_resched() || spin_is_contended(&zone
->lru_lock
)) {
262 spin_unlock_irq(&zone
->lru_lock
);
264 spin_lock_irq(&zone
->lru_lock
);
265 if (fatal_signal_pending(current
))
268 spin_lock_irq(&zone
->lru_lock
);
271 * migrate_pfn does not necessarily start aligned to a
272 * pageblock. Ensure that pfn_valid is called when moving
273 * into a new MAX_ORDER_NR_PAGES range in case of large
274 * memory holes within the zone
276 if ((low_pfn
& (MAX_ORDER_NR_PAGES
- 1)) == 0) {
277 if (!pfn_valid(low_pfn
)) {
278 low_pfn
+= MAX_ORDER_NR_PAGES
- 1;
283 if (!pfn_valid_within(low_pfn
))
288 * Get the page and ensure the page is within the same zone.
289 * See the comment in isolate_freepages about overlapping
290 * nodes. It is deliberate that the new zone lock is not taken
291 * as memory compaction should not move pages between nodes.
293 page
= pfn_to_page(low_pfn
);
294 if (page_zone(page
) != zone
)
302 * For async migration, also only scan in MOVABLE blocks. Async
303 * migration is optimistic to see if the minimum amount of work
304 * satisfies the allocation
306 pageblock_nr
= low_pfn
>> pageblock_order
;
307 if (cc
->mode
!= COMPACT_SYNC
&&
308 last_pageblock_nr
!= pageblock_nr
&&
309 !migrate_async_suitable(get_pageblock_migratetype(page
))) {
310 low_pfn
+= pageblock_nr_pages
;
311 low_pfn
= ALIGN(low_pfn
, pageblock_nr_pages
) - 1;
312 last_pageblock_nr
= pageblock_nr
;
320 * PageLRU is set, and lru_lock excludes isolation,
321 * splitting and collapsing (collapsing has already
322 * happened if PageLRU is set).
324 if (PageTransHuge(page
)) {
325 low_pfn
+= (1 << compound_order(page
)) - 1;
329 if (cc
->mode
!= COMPACT_SYNC
)
330 mode
|= ISOLATE_ASYNC_MIGRATE
;
332 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
334 /* Try isolate the page */
335 if (__isolate_lru_page(page
, mode
) != 0)
338 VM_BUG_ON(PageTransCompound(page
));
340 /* Successfully isolated */
341 del_page_from_lru_list(page
, lruvec
, page_lru(page
));
342 list_add(&page
->lru
, migratelist
);
343 cc
->nr_migratepages
++;
346 /* Avoid isolating too much */
347 if (cc
->nr_migratepages
== COMPACT_CLUSTER_MAX
) {
353 acct_isolated(zone
, cc
);
355 spin_unlock_irq(&zone
->lru_lock
);
357 trace_mm_compaction_isolate_migratepages(nr_scanned
, nr_isolated
);
362 #endif /* CONFIG_COMPACTION || CONFIG_CMA */
363 #ifdef CONFIG_COMPACTION
365 * Returns true if MIGRATE_UNMOVABLE pageblock was successfully
366 * converted to MIGRATE_MOVABLE type, false otherwise.
368 static bool rescue_unmovable_pageblock(struct page
*page
)
370 unsigned long pfn
, start_pfn
, end_pfn
;
371 struct page
*start_page
, *end_page
;
373 pfn
= page_to_pfn(page
);
374 start_pfn
= pfn
& ~(pageblock_nr_pages
- 1);
375 end_pfn
= start_pfn
+ pageblock_nr_pages
;
377 start_page
= pfn_to_page(start_pfn
);
378 end_page
= pfn_to_page(end_pfn
);
380 /* Do not deal with pageblocks that overlap zones */
381 if (page_zone(start_page
) != page_zone(end_page
))
384 for (page
= start_page
, pfn
= start_pfn
; page
< end_page
; pfn
++,
386 if (!pfn_valid_within(pfn
))
389 if (PageBuddy(page
)) {
390 int order
= page_order(page
);
392 pfn
+= (1 << order
) - 1;
393 page
+= (1 << order
) - 1;
396 } else if (page_count(page
) == 0 || PageLRU(page
))
402 set_pageblock_migratetype(page
, MIGRATE_MOVABLE
);
403 move_freepages_block(page_zone(page
), page
, MIGRATE_MOVABLE
);
408 GOOD_AS_MIGRATION_TARGET
,
409 FAIL_UNMOVABLE_TARGET
,
414 * Returns GOOD_AS_MIGRATION_TARGET if the page is within a block
415 * suitable for migration to, FAIL_UNMOVABLE_TARGET if the page
416 * is within a MIGRATE_UNMOVABLE block, FAIL_BAD_TARGET otherwise.
418 static enum smt_result
suitable_migration_target(struct page
*page
,
419 struct compact_control
*cc
)
422 int migratetype
= get_pageblock_migratetype(page
);
424 /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
425 if (migratetype
== MIGRATE_ISOLATE
|| migratetype
== MIGRATE_RESERVE
)
426 return FAIL_BAD_TARGET
;
428 /* If the page is a large free page, then allow migration */
429 if (PageBuddy(page
) && page_order(page
) >= pageblock_order
)
430 return GOOD_AS_MIGRATION_TARGET
;
432 /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
433 if (cc
->mode
!= COMPACT_ASYNC_UNMOVABLE
&&
434 migrate_async_suitable(migratetype
))
435 return GOOD_AS_MIGRATION_TARGET
;
437 if (cc
->mode
== COMPACT_ASYNC_MOVABLE
&&
438 migratetype
== MIGRATE_UNMOVABLE
)
439 return FAIL_UNMOVABLE_TARGET
;
441 if (cc
->mode
!= COMPACT_ASYNC_MOVABLE
&&
442 migratetype
== MIGRATE_UNMOVABLE
&&
443 rescue_unmovable_pageblock(page
))
444 return GOOD_AS_MIGRATION_TARGET
;
446 /* Otherwise skip the block */
447 return FAIL_BAD_TARGET
;
451 * Based on information in the current compact_control, find blocks
452 * suitable for isolating free pages from and then isolate them.
454 static void isolate_freepages(struct zone
*zone
,
455 struct compact_control
*cc
)
458 unsigned long high_pfn
, low_pfn
, pfn
, zone_end_pfn
, end_pfn
;
460 int nr_freepages
= cc
->nr_freepages
;
461 struct list_head
*freelist
= &cc
->freepages
;
464 * Initialise the free scanner. The starting point is where we last
465 * scanned from (or the end of the zone if starting). The low point
466 * is the end of the pageblock the migration scanner is using.
469 low_pfn
= cc
->migrate_pfn
+ pageblock_nr_pages
;
472 * Take care that if the migration scanner is at the end of the zone
473 * that the free scanner does not accidentally move to the next zone
474 * in the next isolation cycle.
476 high_pfn
= min(low_pfn
, pfn
);
478 zone_end_pfn
= zone
->zone_start_pfn
+ zone
->spanned_pages
;
481 * isolate_freepages() may be called more than once during
482 * compact_zone_order() run and we want only the most recent
485 cc
->nr_pageblocks_skipped
= 0;
488 * Isolate free pages until enough are available to migrate the
489 * pages on cc->migratepages. We stop searching if the migrate
490 * and free page scanners meet or enough free pages are isolated.
492 for (; pfn
> low_pfn
&& cc
->nr_migratepages
> nr_freepages
;
493 pfn
-= pageblock_nr_pages
) {
494 unsigned long isolated
;
501 * Check for overlapping nodes/zones. It's possible on some
502 * configurations to have a setup like
504 * i.e. it's possible that all pages within a zones range of
505 * pages do not belong to a single zone.
507 page
= pfn_to_page(pfn
);
508 if (page_zone(page
) != zone
)
511 /* Check the block is suitable for migration */
512 ret
= suitable_migration_target(page
, cc
);
513 if (ret
!= GOOD_AS_MIGRATION_TARGET
) {
514 if (ret
== FAIL_UNMOVABLE_TARGET
)
515 cc
->nr_pageblocks_skipped
++;
519 * Found a block suitable for isolating free pages from. Now
520 * we disabled interrupts, double check things are ok and
521 * isolate the pages. This is to minimise the time IRQs
525 spin_lock_irqsave(&zone
->lock
, flags
);
526 ret
= suitable_migration_target(page
, cc
);
527 if (ret
== GOOD_AS_MIGRATION_TARGET
) {
528 end_pfn
= min(pfn
+ pageblock_nr_pages
, zone_end_pfn
);
529 isolated
= isolate_freepages_block(pfn
, end_pfn
,
531 nr_freepages
+= isolated
;
532 } else if (ret
== FAIL_UNMOVABLE_TARGET
)
533 cc
->nr_pageblocks_skipped
++;
534 spin_unlock_irqrestore(&zone
->lock
, flags
);
537 * Record the highest PFN we isolated pages from. When next
538 * looking for free pages, the search will restart here as
539 * page migration may have returned some pages to the allocator
542 high_pfn
= max(high_pfn
, pfn
);
545 /* split_free_page does not map the pages */
548 cc
->free_pfn
= high_pfn
;
549 cc
->nr_freepages
= nr_freepages
;
553 * This is a migrate-callback that "allocates" freepages by taking pages
554 * from the isolated freelists in the block we are migrating to.
556 static struct page
*compaction_alloc(struct page
*migratepage
,
560 struct compact_control
*cc
= (struct compact_control
*)data
;
561 struct page
*freepage
;
563 /* Isolate free pages if necessary */
564 if (list_empty(&cc
->freepages
)) {
565 isolate_freepages(cc
->zone
, cc
);
567 if (list_empty(&cc
->freepages
))
571 freepage
= list_entry(cc
->freepages
.next
, struct page
, lru
);
572 list_del(&freepage
->lru
);
579 * We cannot control nr_migratepages and nr_freepages fully when migration is
580 * running as migrate_pages() has no knowledge of compact_control. When
581 * migration is complete, we count the number of pages on the lists by hand.
583 static void update_nr_listpages(struct compact_control
*cc
)
585 int nr_migratepages
= 0;
586 int nr_freepages
= 0;
589 list_for_each_entry(page
, &cc
->migratepages
, lru
)
591 list_for_each_entry(page
, &cc
->freepages
, lru
)
594 cc
->nr_migratepages
= nr_migratepages
;
595 cc
->nr_freepages
= nr_freepages
;
598 /* possible outcome of isolate_migratepages */
600 ISOLATE_ABORT
, /* Abort compaction now */
601 ISOLATE_NONE
, /* No pages isolated, continue scanning */
602 ISOLATE_SUCCESS
, /* Pages isolated, migrate */
606 * Isolate all pages that can be migrated from the block pointed to by
607 * the migrate scanner within compact_control.
609 static isolate_migrate_t
isolate_migratepages(struct zone
*zone
,
610 struct compact_control
*cc
)
612 unsigned long low_pfn
, end_pfn
;
614 /* Do not scan outside zone boundaries */
615 low_pfn
= max(cc
->migrate_pfn
, zone
->zone_start_pfn
);
617 /* Only scan within a pageblock boundary */
618 end_pfn
= ALIGN(low_pfn
+ pageblock_nr_pages
, pageblock_nr_pages
);
620 /* Do not cross the free scanner or scan within a memory hole */
621 if (end_pfn
> cc
->free_pfn
|| !pfn_valid(low_pfn
)) {
622 cc
->migrate_pfn
= end_pfn
;
626 /* Perform the isolation */
627 low_pfn
= isolate_migratepages_range(zone
, cc
, low_pfn
, end_pfn
);
629 return ISOLATE_ABORT
;
631 cc
->migrate_pfn
= low_pfn
;
633 return ISOLATE_SUCCESS
;
636 static int compact_finished(struct zone
*zone
,
637 struct compact_control
*cc
)
640 unsigned long watermark
;
642 if (fatal_signal_pending(current
))
643 return COMPACT_PARTIAL
;
645 /* Compaction run completes if the migrate and free scanner meet */
646 if (cc
->free_pfn
<= cc
->migrate_pfn
)
647 return COMPACT_COMPLETE
;
650 * order == -1 is expected when compacting via
651 * /proc/sys/vm/compact_memory
654 return COMPACT_CONTINUE
;
656 /* Compaction run is not finished if the watermark is not met */
657 watermark
= low_wmark_pages(zone
);
658 watermark
+= (1 << cc
->order
);
660 if (!zone_watermark_ok(zone
, cc
->order
, watermark
, 0, 0))
661 return COMPACT_CONTINUE
;
663 /* Direct compactor: Is a suitable page free? */
664 for (order
= cc
->order
; order
< MAX_ORDER
; order
++) {
665 /* Job done if page is free of the right migratetype */
666 if (!list_empty(&zone
->free_area
[order
].free_list
[cc
->migratetype
]))
667 return COMPACT_PARTIAL
;
669 /* Job done if allocation would set block type */
670 if (order
>= pageblock_order
&& zone
->free_area
[order
].nr_free
)
671 return COMPACT_PARTIAL
;
674 return COMPACT_CONTINUE
;
678 * compaction_suitable: Is this suitable to run compaction on this zone now?
680 * COMPACT_SKIPPED - If there are too few free pages for compaction
681 * COMPACT_PARTIAL - If the allocation would succeed without compaction
682 * COMPACT_CONTINUE - If compaction should run now
684 unsigned long compaction_suitable(struct zone
*zone
, int order
)
687 unsigned long watermark
;
690 * order == -1 is expected when compacting via
691 * /proc/sys/vm/compact_memory
694 return COMPACT_CONTINUE
;
697 * Watermarks for order-0 must be met for compaction. Note the 2UL.
698 * This is because during migration, copies of pages need to be
699 * allocated and for a short time, the footprint is higher
701 watermark
= low_wmark_pages(zone
) + (2UL << order
);
702 if (!zone_watermark_ok(zone
, 0, watermark
, 0, 0))
703 return COMPACT_SKIPPED
;
706 * fragmentation index determines if allocation failures are due to
707 * low memory or external fragmentation
709 * index of -1000 implies allocations might succeed depending on
711 * index towards 0 implies failure is due to lack of memory
712 * index towards 1000 implies failure is due to fragmentation
714 * Only compact if a failure would be due to fragmentation.
716 fragindex
= fragmentation_index(zone
, order
);
717 if (fragindex
>= 0 && fragindex
<= sysctl_extfrag_threshold
)
718 return COMPACT_SKIPPED
;
720 if (fragindex
== -1000 && zone_watermark_ok(zone
, order
, watermark
,
722 return COMPACT_PARTIAL
;
724 return COMPACT_CONTINUE
;
727 static int compact_zone(struct zone
*zone
, struct compact_control
*cc
)
731 ret
= compaction_suitable(zone
, cc
->order
);
733 case COMPACT_PARTIAL
:
734 case COMPACT_SKIPPED
:
735 /* Compaction is likely to fail */
737 case COMPACT_CONTINUE
:
738 /* Fall through to compaction */
742 /* Setup to move all movable pages to the end of the zone */
743 cc
->migrate_pfn
= zone
->zone_start_pfn
;
744 cc
->free_pfn
= cc
->migrate_pfn
+ zone
->spanned_pages
;
745 cc
->free_pfn
&= ~(pageblock_nr_pages
-1);
747 migrate_prep_local();
749 while ((ret
= compact_finished(zone
, cc
)) == COMPACT_CONTINUE
) {
750 unsigned long nr_migrate
, nr_remaining
;
753 switch (isolate_migratepages(zone
, cc
)) {
755 ret
= COMPACT_PARTIAL
;
759 case ISOLATE_SUCCESS
:
763 nr_migrate
= cc
->nr_migratepages
;
764 err
= migrate_pages(&cc
->migratepages
, compaction_alloc
,
765 (unsigned long)&cc
->freepages
, false,
766 (cc
->mode
== COMPACT_SYNC
) ? MIGRATE_SYNC_LIGHT
768 update_nr_listpages(cc
);
769 nr_remaining
= cc
->nr_migratepages
;
771 count_vm_event(COMPACTBLOCKS
);
772 count_vm_events(COMPACTPAGES
, nr_migrate
- nr_remaining
);
774 count_vm_events(COMPACTPAGEFAILED
, nr_remaining
);
775 trace_mm_compaction_migratepages(nr_migrate
- nr_remaining
,
778 /* Release LRU pages not migrated */
780 putback_lru_pages(&cc
->migratepages
);
781 cc
->nr_migratepages
= 0;
787 /* Release free pages and check accounting */
788 cc
->nr_freepages
-= release_freepages(&cc
->freepages
);
789 VM_BUG_ON(cc
->nr_freepages
!= 0);
794 static unsigned long compact_zone_order(struct zone
*zone
,
795 int order
, gfp_t gfp_mask
,
796 enum compact_mode mode
,
797 unsigned long *nr_pageblocks_skipped
)
799 struct compact_control cc
= {
801 .nr_migratepages
= 0,
803 .migratetype
= allocflags_to_migratetype(gfp_mask
),
809 INIT_LIST_HEAD(&cc
.freepages
);
810 INIT_LIST_HEAD(&cc
.migratepages
);
812 rc
= compact_zone(zone
, &cc
);
813 *nr_pageblocks_skipped
= cc
.nr_pageblocks_skipped
;
818 int sysctl_extfrag_threshold
= 500;
821 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
822 * @zonelist: The zonelist used for the current allocation
823 * @order: The order of the current allocation
824 * @gfp_mask: The GFP mask of the current allocation
825 * @nodemask: The allowed nodes to allocate from
826 * @sync: Whether migration is synchronous or not
828 * This is the main entry point for direct page compaction.
830 unsigned long try_to_compact_pages(struct zonelist
*zonelist
,
831 int order
, gfp_t gfp_mask
, nodemask_t
*nodemask
,
834 enum zone_type high_zoneidx
= gfp_zone(gfp_mask
);
835 int may_enter_fs
= gfp_mask
& __GFP_FS
;
836 int may_perform_io
= gfp_mask
& __GFP_IO
;
839 int rc
= COMPACT_SKIPPED
;
840 unsigned long nr_pageblocks_skipped
;
841 enum compact_mode mode
;
844 * Check whether it is worth even starting compaction. The order check is
845 * made because an assumption is made that the page allocator can satisfy
846 * the "cheaper" orders without taking special steps
848 if (!order
|| !may_enter_fs
|| !may_perform_io
)
851 count_vm_event(COMPACTSTALL
);
853 /* Compact each zone in the list */
854 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
, high_zoneidx
,
858 mode
= sync
? COMPACT_SYNC
: COMPACT_ASYNC_MOVABLE
;
860 status
= compact_zone_order(zone
, order
, gfp_mask
, mode
,
861 &nr_pageblocks_skipped
);
862 rc
= max(status
, rc
);
864 /* If a normal allocation would succeed, stop compacting */
865 if (zone_watermark_ok(zone
, order
, low_wmark_pages(zone
), 0, 0))
868 if (rc
== COMPACT_COMPLETE
&& mode
== COMPACT_ASYNC_MOVABLE
) {
869 if (nr_pageblocks_skipped
) {
870 mode
= COMPACT_ASYNC_UNMOVABLE
;
880 /* Compact all zones within a node */
881 static int __compact_pgdat(pg_data_t
*pgdat
, struct compact_control
*cc
)
886 for (zoneid
= 0; zoneid
< MAX_NR_ZONES
; zoneid
++) {
888 zone
= &pgdat
->node_zones
[zoneid
];
889 if (!populated_zone(zone
))
892 cc
->nr_freepages
= 0;
893 cc
->nr_migratepages
= 0;
895 INIT_LIST_HEAD(&cc
->freepages
);
896 INIT_LIST_HEAD(&cc
->migratepages
);
898 if (cc
->order
== -1 || !compaction_deferred(zone
, cc
->order
))
899 compact_zone(zone
, cc
);
902 int ok
= zone_watermark_ok(zone
, cc
->order
,
903 low_wmark_pages(zone
), 0, 0);
904 if (ok
&& cc
->order
> zone
->compact_order_failed
)
905 zone
->compact_order_failed
= cc
->order
+ 1;
906 /* Currently async compaction is never deferred. */
907 else if (!ok
&& cc
->mode
== COMPACT_SYNC
)
908 defer_compaction(zone
, cc
->order
);
911 VM_BUG_ON(!list_empty(&cc
->freepages
));
912 VM_BUG_ON(!list_empty(&cc
->migratepages
));
918 int compact_pgdat(pg_data_t
*pgdat
, int order
)
920 struct compact_control cc
= {
922 .mode
= COMPACT_ASYNC_MOVABLE
,
925 return __compact_pgdat(pgdat
, &cc
);
928 static int compact_node(int nid
)
930 struct compact_control cc
= {
932 .mode
= COMPACT_SYNC
,
935 return __compact_pgdat(NODE_DATA(nid
), &cc
);
938 /* Compact all nodes in the system */
939 static int compact_nodes(void)
943 /* Flush pending updates to the LRU lists */
946 for_each_online_node(nid
)
949 return COMPACT_COMPLETE
;
952 /* The written value is actually unused, all memory is compacted */
953 int sysctl_compact_memory
;
955 /* This is the entry point for compacting all nodes via /proc/sys/vm */
956 int sysctl_compaction_handler(struct ctl_table
*table
, int write
,
957 void __user
*buffer
, size_t *length
, loff_t
*ppos
)
960 return compact_nodes();
965 int sysctl_extfrag_handler(struct ctl_table
*table
, int write
,
966 void __user
*buffer
, size_t *length
, loff_t
*ppos
)
968 proc_dointvec_minmax(table
, write
, buffer
, length
, ppos
);
973 #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
974 ssize_t
sysfs_compact_node(struct device
*dev
,
975 struct device_attribute
*attr
,
976 const char *buf
, size_t count
)
980 if (nid
>= 0 && nid
< nr_node_ids
&& node_online(nid
)) {
981 /* Flush pending updates to the LRU lists */
989 static DEVICE_ATTR(compact
, S_IWUSR
, NULL
, sysfs_compact_node
);
991 int compaction_register_node(struct node
*node
)
993 return device_create_file(&node
->dev
, &dev_attr_compact
);
996 void compaction_unregister_node(struct node
*node
)
998 return device_remove_file(&node
->dev
, &dev_attr_compact
);
1000 #endif /* CONFIG_SYSFS && CONFIG_NUMA */
1002 #endif /* CONFIG_COMPACTION */