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1/*
2 * linux/mm/compaction.c
3 *
4 * Memory compaction for the reduction of external fragmentation. Note that
5 * this heavily depends upon page migration to do all the real heavy
6 * lifting
7 *
8 * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
9 */
10#include <linux/cpu.h>
11#include <linux/swap.h>
12#include <linux/migrate.h>
13#include <linux/compaction.h>
14#include <linux/mm_inline.h>
15#include <linux/backing-dev.h>
16#include <linux/sysctl.h>
17#include <linux/sysfs.h>
18#include <linux/balloon_compaction.h>
19#include <linux/page-isolation.h>
20#include <linux/kasan.h>
21#include <linux/kthread.h>
22#include <linux/freezer.h>
23#include "internal.h"
24
25#ifdef CONFIG_COMPACTION
26static inline void count_compact_event(enum vm_event_item item)
27{
28 count_vm_event(item);
29}
30
31static inline void count_compact_events(enum vm_event_item item, long delta)
32{
33 count_vm_events(item, delta);
34}
35#else
36#define count_compact_event(item) do { } while (0)
37#define count_compact_events(item, delta) do { } while (0)
38#endif
39
40#if defined CONFIG_COMPACTION || defined CONFIG_CMA
41
42#define CREATE_TRACE_POINTS
43#include <trace/events/compaction.h>
44
45static unsigned long release_freepages(struct list_head *freelist)
46{
47 struct page *page, *next;
48 unsigned long high_pfn = 0;
49
50 list_for_each_entry_safe(page, next, freelist, lru) {
51 unsigned long pfn = page_to_pfn(page);
52 list_del(&page->lru);
53 __free_page(page);
54 if (pfn > high_pfn)
55 high_pfn = pfn;
56 }
57
58 return high_pfn;
59}
60
61static void map_pages(struct list_head *list)
62{
63 struct page *page;
64
65 list_for_each_entry(page, list, lru) {
66 arch_alloc_page(page, 0);
67 kernel_map_pages(page, 1, 1);
68 kasan_alloc_pages(page, 0);
69 }
70}
71
72static inline bool migrate_async_suitable(int migratetype)
73{
74 return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE;
75}
76
77#ifdef CONFIG_COMPACTION
78
79/* Do not skip compaction more than 64 times */
80#define COMPACT_MAX_DEFER_SHIFT 6
81
82/*
83 * Compaction is deferred when compaction fails to result in a page
84 * allocation success. 1 << compact_defer_limit compactions are skipped up
85 * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
86 */
87void defer_compaction(struct zone *zone, int order)
88{
89 zone->compact_considered = 0;
90 zone->compact_defer_shift++;
91
92 if (order < zone->compact_order_failed)
93 zone->compact_order_failed = order;
94
95 if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
96 zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
97
98 trace_mm_compaction_defer_compaction(zone, order);
99}
100
101/* Returns true if compaction should be skipped this time */
102bool compaction_deferred(struct zone *zone, int order)
103{
104 unsigned long defer_limit = 1UL << zone->compact_defer_shift;
105
106 if (order < zone->compact_order_failed)
107 return false;
108
109 /* Avoid possible overflow */
110 if (++zone->compact_considered > defer_limit)
111 zone->compact_considered = defer_limit;
112
113 if (zone->compact_considered >= defer_limit)
114 return false;
115
116 trace_mm_compaction_deferred(zone, order);
117
118 return true;
119}
120
121/*
122 * Update defer tracking counters after successful compaction of given order,
123 * which means an allocation either succeeded (alloc_success == true) or is
124 * expected to succeed.
125 */
126void compaction_defer_reset(struct zone *zone, int order,
127 bool alloc_success)
128{
129 if (alloc_success) {
130 zone->compact_considered = 0;
131 zone->compact_defer_shift = 0;
132 }
133 if (order >= zone->compact_order_failed)
134 zone->compact_order_failed = order + 1;
135
136 trace_mm_compaction_defer_reset(zone, order);
137}
138
139/* Returns true if restarting compaction after many failures */
140bool compaction_restarting(struct zone *zone, int order)
141{
142 if (order < zone->compact_order_failed)
143 return false;
144
145 return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
146 zone->compact_considered >= 1UL << zone->compact_defer_shift;
147}
148
149/* Returns true if the pageblock should be scanned for pages to isolate. */
150static inline bool isolation_suitable(struct compact_control *cc,
151 struct page *page)
152{
153 if (cc->ignore_skip_hint)
154 return true;
155
156 return !get_pageblock_skip(page);
157}
158
159static void reset_cached_positions(struct zone *zone)
160{
161 zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn;
162 zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn;
163 zone->compact_cached_free_pfn =
164 round_down(zone_end_pfn(zone) - 1, pageblock_nr_pages);
165}
166
167/*
168 * This function is called to clear all cached information on pageblocks that
169 * should be skipped for page isolation when the migrate and free page scanner
170 * meet.
171 */
172static void __reset_isolation_suitable(struct zone *zone)
173{
174 unsigned long start_pfn = zone->zone_start_pfn;
175 unsigned long end_pfn = zone_end_pfn(zone);
176 unsigned long pfn;
177
178 zone->compact_blockskip_flush = false;
179
180 /* Walk the zone and mark every pageblock as suitable for isolation */
181 for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
182 struct page *page;
183
184 cond_resched();
185
186 if (!pfn_valid(pfn))
187 continue;
188
189 page = pfn_to_page(pfn);
190 if (zone != page_zone(page))
191 continue;
192
193 clear_pageblock_skip(page);
194 }
195
196 reset_cached_positions(zone);
197}
198
199void reset_isolation_suitable(pg_data_t *pgdat)
200{
201 int zoneid;
202
203 for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
204 struct zone *zone = &pgdat->node_zones[zoneid];
205 if (!populated_zone(zone))
206 continue;
207
208 /* Only flush if a full compaction finished recently */
209 if (zone->compact_blockskip_flush)
210 __reset_isolation_suitable(zone);
211 }
212}
213
214/*
215 * If no pages were isolated then mark this pageblock to be skipped in the
216 * future. The information is later cleared by __reset_isolation_suitable().
217 */
218static void update_pageblock_skip(struct compact_control *cc,
219 struct page *page, unsigned long nr_isolated,
220 bool migrate_scanner)
221{
222 struct zone *zone = cc->zone;
223 unsigned long pfn;
224
225 if (cc->ignore_skip_hint)
226 return;
227
228 if (!page)
229 return;
230
231 if (nr_isolated)
232 return;
233
234 set_pageblock_skip(page);
235
236 pfn = page_to_pfn(page);
237
238 /* Update where async and sync compaction should restart */
239 if (migrate_scanner) {
240 if (pfn > zone->compact_cached_migrate_pfn[0])
241 zone->compact_cached_migrate_pfn[0] = pfn;
242 if (cc->mode != MIGRATE_ASYNC &&
243 pfn > zone->compact_cached_migrate_pfn[1])
244 zone->compact_cached_migrate_pfn[1] = pfn;
245 } else {
246 if (pfn < zone->compact_cached_free_pfn)
247 zone->compact_cached_free_pfn = pfn;
248 }
249}
250#else
251static inline bool isolation_suitable(struct compact_control *cc,
252 struct page *page)
253{
254 return true;
255}
256
257static void update_pageblock_skip(struct compact_control *cc,
258 struct page *page, unsigned long nr_isolated,
259 bool migrate_scanner)
260{
261}
262#endif /* CONFIG_COMPACTION */
263
264/*
265 * Compaction requires the taking of some coarse locks that are potentially
266 * very heavily contended. For async compaction, back out if the lock cannot
267 * be taken immediately. For sync compaction, spin on the lock if needed.
268 *
269 * Returns true if the lock is held
270 * Returns false if the lock is not held and compaction should abort
271 */
272static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags,
273 struct compact_control *cc)
274{
275 if (cc->mode == MIGRATE_ASYNC) {
276 if (!spin_trylock_irqsave(lock, *flags)) {
277 cc->contended = COMPACT_CONTENDED_LOCK;
278 return false;
279 }
280 } else {
281 spin_lock_irqsave(lock, *flags);
282 }
283
284 return true;
285}
286
287/*
288 * Compaction requires the taking of some coarse locks that are potentially
289 * very heavily contended. The lock should be periodically unlocked to avoid
290 * having disabled IRQs for a long time, even when there is nobody waiting on
291 * the lock. It might also be that allowing the IRQs will result in
292 * need_resched() becoming true. If scheduling is needed, async compaction
293 * aborts. Sync compaction schedules.
294 * Either compaction type will also abort if a fatal signal is pending.
295 * In either case if the lock was locked, it is dropped and not regained.
296 *
297 * Returns true if compaction should abort due to fatal signal pending, or
298 * async compaction due to need_resched()
299 * Returns false when compaction can continue (sync compaction might have
300 * scheduled)
301 */
302static bool compact_unlock_should_abort(spinlock_t *lock,
303 unsigned long flags, bool *locked, struct compact_control *cc)
304{
305 if (*locked) {
306 spin_unlock_irqrestore(lock, flags);
307 *locked = false;
308 }
309
310 if (fatal_signal_pending(current)) {
311 cc->contended = COMPACT_CONTENDED_SCHED;
312 return true;
313 }
314
315 if (need_resched()) {
316 if (cc->mode == MIGRATE_ASYNC) {
317 cc->contended = COMPACT_CONTENDED_SCHED;
318 return true;
319 }
320 cond_resched();
321 }
322
323 return false;
324}
325
326/*
327 * Aside from avoiding lock contention, compaction also periodically checks
328 * need_resched() and either schedules in sync compaction or aborts async
329 * compaction. This is similar to what compact_unlock_should_abort() does, but
330 * is used where no lock is concerned.
331 *
332 * Returns false when no scheduling was needed, or sync compaction scheduled.
333 * Returns true when async compaction should abort.
334 */
335static inline bool compact_should_abort(struct compact_control *cc)
336{
337 /* async compaction aborts if contended */
338 if (need_resched()) {
339 if (cc->mode == MIGRATE_ASYNC) {
340 cc->contended = COMPACT_CONTENDED_SCHED;
341 return true;
342 }
343
344 cond_resched();
345 }
346
347 return false;
348}
349
350/*
351 * Isolate free pages onto a private freelist. If @strict is true, will abort
352 * returning 0 on any invalid PFNs or non-free pages inside of the pageblock
353 * (even though it may still end up isolating some pages).
354 */
355static unsigned long isolate_freepages_block(struct compact_control *cc,
356 unsigned long *start_pfn,
357 unsigned long end_pfn,
358 struct list_head *freelist,
359 bool strict)
360{
361 int nr_scanned = 0, total_isolated = 0;
362 struct page *cursor, *valid_page = NULL;
363 unsigned long flags = 0;
364 bool locked = false;
365 unsigned long blockpfn = *start_pfn;
366
367 cursor = pfn_to_page(blockpfn);
368
369 /* Isolate free pages. */
370 for (; blockpfn < end_pfn; blockpfn++, cursor++) {
371 int isolated, i;
372 struct page *page = cursor;
373
374 /*
375 * Periodically drop the lock (if held) regardless of its
376 * contention, to give chance to IRQs. Abort if fatal signal
377 * pending or async compaction detects need_resched()
378 */
379 if (!(blockpfn % SWAP_CLUSTER_MAX)
380 && compact_unlock_should_abort(&cc->zone->lock, flags,
381 &locked, cc))
382 break;
383
384 nr_scanned++;
385 if (!pfn_valid_within(blockpfn))
386 goto isolate_fail;
387
388 if (!valid_page)
389 valid_page = page;
390
391 /*
392 * For compound pages such as THP and hugetlbfs, we can save
393 * potentially a lot of iterations if we skip them at once.
394 * The check is racy, but we can consider only valid values
395 * and the only danger is skipping too much.
396 */
397 if (PageCompound(page)) {
398 unsigned int comp_order = compound_order(page);
399
400 if (likely(comp_order < MAX_ORDER)) {
401 blockpfn += (1UL << comp_order) - 1;
402 cursor += (1UL << comp_order) - 1;
403 }
404
405 goto isolate_fail;
406 }
407
408 if (!PageBuddy(page))
409 goto isolate_fail;
410
411 /*
412 * If we already hold the lock, we can skip some rechecking.
413 * Note that if we hold the lock now, checked_pageblock was
414 * already set in some previous iteration (or strict is true),
415 * so it is correct to skip the suitable migration target
416 * recheck as well.
417 */
418 if (!locked) {
419 /*
420 * The zone lock must be held to isolate freepages.
421 * Unfortunately this is a very coarse lock and can be
422 * heavily contended if there are parallel allocations
423 * or parallel compactions. For async compaction do not
424 * spin on the lock and we acquire the lock as late as
425 * possible.
426 */
427 locked = compact_trylock_irqsave(&cc->zone->lock,
428 &flags, cc);
429 if (!locked)
430 break;
431
432 /* Recheck this is a buddy page under lock */
433 if (!PageBuddy(page))
434 goto isolate_fail;
435 }
436
437 /* Found a free page, break it into order-0 pages */
438 isolated = split_free_page(page);
439 total_isolated += isolated;
440 for (i = 0; i < isolated; i++) {
441 list_add(&page->lru, freelist);
442 page++;
443 }
444
445 /* If a page was split, advance to the end of it */
446 if (isolated) {
447 cc->nr_freepages += isolated;
448 if (!strict &&
449 cc->nr_migratepages <= cc->nr_freepages) {
450 blockpfn += isolated;
451 break;
452 }
453
454 blockpfn += isolated - 1;
455 cursor += isolated - 1;
456 continue;
457 }
458
459isolate_fail:
460 if (strict)
461 break;
462 else
463 continue;
464
465 }
466
467 /*
468 * There is a tiny chance that we have read bogus compound_order(),
469 * so be careful to not go outside of the pageblock.
470 */
471 if (unlikely(blockpfn > end_pfn))
472 blockpfn = end_pfn;
473
474 trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn,
475 nr_scanned, total_isolated);
476
477 /* Record how far we have got within the block */
478 *start_pfn = blockpfn;
479
480 /*
481 * If strict isolation is requested by CMA then check that all the
482 * pages requested were isolated. If there were any failures, 0 is
483 * returned and CMA will fail.
484 */
485 if (strict && blockpfn < end_pfn)
486 total_isolated = 0;
487
488 if (locked)
489 spin_unlock_irqrestore(&cc->zone->lock, flags);
490
491 /* Update the pageblock-skip if the whole pageblock was scanned */
492 if (blockpfn == end_pfn)
493 update_pageblock_skip(cc, valid_page, total_isolated, false);
494
495 count_compact_events(COMPACTFREE_SCANNED, nr_scanned);
496 if (total_isolated)
497 count_compact_events(COMPACTISOLATED, total_isolated);
498 return total_isolated;
499}
500
501/**
502 * isolate_freepages_range() - isolate free pages.
503 * @start_pfn: The first PFN to start isolating.
504 * @end_pfn: The one-past-last PFN.
505 *
506 * Non-free pages, invalid PFNs, or zone boundaries within the
507 * [start_pfn, end_pfn) range are considered errors, cause function to
508 * undo its actions and return zero.
509 *
510 * Otherwise, function returns one-past-the-last PFN of isolated page
511 * (which may be greater then end_pfn if end fell in a middle of
512 * a free page).
513 */
514unsigned long
515isolate_freepages_range(struct compact_control *cc,
516 unsigned long start_pfn, unsigned long end_pfn)
517{
518 unsigned long isolated, pfn, block_start_pfn, block_end_pfn;
519 LIST_HEAD(freelist);
520
521 pfn = start_pfn;
522 block_start_pfn = pfn & ~(pageblock_nr_pages - 1);
523 if (block_start_pfn < cc->zone->zone_start_pfn)
524 block_start_pfn = cc->zone->zone_start_pfn;
525 block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
526
527 for (; pfn < end_pfn; pfn += isolated,
528 block_start_pfn = block_end_pfn,
529 block_end_pfn += pageblock_nr_pages) {
530 /* Protect pfn from changing by isolate_freepages_block */
531 unsigned long isolate_start_pfn = pfn;
532
533 block_end_pfn = min(block_end_pfn, end_pfn);
534
535 /*
536 * pfn could pass the block_end_pfn if isolated freepage
537 * is more than pageblock order. In this case, we adjust
538 * scanning range to right one.
539 */
540 if (pfn >= block_end_pfn) {
541 block_start_pfn = pfn & ~(pageblock_nr_pages - 1);
542 block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
543 block_end_pfn = min(block_end_pfn, end_pfn);
544 }
545
546 if (!pageblock_pfn_to_page(block_start_pfn,
547 block_end_pfn, cc->zone))
548 break;
549
550 isolated = isolate_freepages_block(cc, &isolate_start_pfn,
551 block_end_pfn, &freelist, true);
552
553 /*
554 * In strict mode, isolate_freepages_block() returns 0 if
555 * there are any holes in the block (ie. invalid PFNs or
556 * non-free pages).
557 */
558 if (!isolated)
559 break;
560
561 /*
562 * If we managed to isolate pages, it is always (1 << n) *
563 * pageblock_nr_pages for some non-negative n. (Max order
564 * page may span two pageblocks).
565 */
566 }
567
568 /* split_free_page does not map the pages */
569 map_pages(&freelist);
570
571 if (pfn < end_pfn) {
572 /* Loop terminated early, cleanup. */
573 release_freepages(&freelist);
574 return 0;
575 }
576
577 /* We don't use freelists for anything. */
578 return pfn;
579}
580
581/* Update the number of anon and file isolated pages in the zone */
582static void acct_isolated(struct zone *zone, struct compact_control *cc)
583{
584 struct page *page;
585 unsigned int count[2] = { 0, };
586
587 if (list_empty(&cc->migratepages))
588 return;
589
590 list_for_each_entry(page, &cc->migratepages, lru)
591 count[!!page_is_file_cache(page)]++;
592
593 mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
594 mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
595}
596
597/* Similar to reclaim, but different enough that they don't share logic */
598static bool too_many_isolated(struct zone *zone)
599{
600 unsigned long active, inactive, isolated;
601
602 inactive = zone_page_state(zone, NR_INACTIVE_FILE) +
603 zone_page_state(zone, NR_INACTIVE_ANON);
604 active = zone_page_state(zone, NR_ACTIVE_FILE) +
605 zone_page_state(zone, NR_ACTIVE_ANON);
606 isolated = zone_page_state(zone, NR_ISOLATED_FILE) +
607 zone_page_state(zone, NR_ISOLATED_ANON);
608
609 return isolated > (inactive + active) / 2;
610}
611
612/**
613 * isolate_migratepages_block() - isolate all migrate-able pages within
614 * a single pageblock
615 * @cc: Compaction control structure.
616 * @low_pfn: The first PFN to isolate
617 * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
618 * @isolate_mode: Isolation mode to be used.
619 *
620 * Isolate all pages that can be migrated from the range specified by
621 * [low_pfn, end_pfn). The range is expected to be within same pageblock.
622 * Returns zero if there is a fatal signal pending, otherwise PFN of the
623 * first page that was not scanned (which may be both less, equal to or more
624 * than end_pfn).
625 *
626 * The pages are isolated on cc->migratepages list (not required to be empty),
627 * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field
628 * is neither read nor updated.
629 */
630static unsigned long
631isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
632 unsigned long end_pfn, isolate_mode_t isolate_mode)
633{
634 struct zone *zone = cc->zone;
635 unsigned long nr_scanned = 0, nr_isolated = 0;
636 struct list_head *migratelist = &cc->migratepages;
637 struct lruvec *lruvec;
638 unsigned long flags = 0;
639 bool locked = false;
640 struct page *page = NULL, *valid_page = NULL;
641 unsigned long start_pfn = low_pfn;
642
643 /*
644 * Ensure that there are not too many pages isolated from the LRU
645 * list by either parallel reclaimers or compaction. If there are,
646 * delay for some time until fewer pages are isolated
647 */
648 while (unlikely(too_many_isolated(zone))) {
649 /* async migration should just abort */
650 if (cc->mode == MIGRATE_ASYNC)
651 return 0;
652
653 congestion_wait(BLK_RW_ASYNC, HZ/10);
654
655 if (fatal_signal_pending(current))
656 return 0;
657 }
658
659 if (compact_should_abort(cc))
660 return 0;
661
662 /* Time to isolate some pages for migration */
663 for (; low_pfn < end_pfn; low_pfn++) {
664 bool is_lru;
665
666 /*
667 * Periodically drop the lock (if held) regardless of its
668 * contention, to give chance to IRQs. Abort async compaction
669 * if contended.
670 */
671 if (!(low_pfn % SWAP_CLUSTER_MAX)
672 && compact_unlock_should_abort(&zone->lru_lock, flags,
673 &locked, cc))
674 break;
675
676 if (!pfn_valid_within(low_pfn))
677 continue;
678 nr_scanned++;
679
680 page = pfn_to_page(low_pfn);
681
682 if (!valid_page)
683 valid_page = page;
684
685 /*
686 * Skip if free. We read page order here without zone lock
687 * which is generally unsafe, but the race window is small and
688 * the worst thing that can happen is that we skip some
689 * potential isolation targets.
690 */
691 if (PageBuddy(page)) {
692 unsigned long freepage_order = page_order_unsafe(page);
693
694 /*
695 * Without lock, we cannot be sure that what we got is
696 * a valid page order. Consider only values in the
697 * valid order range to prevent low_pfn overflow.
698 */
699 if (freepage_order > 0 && freepage_order < MAX_ORDER)
700 low_pfn += (1UL << freepage_order) - 1;
701 continue;
702 }
703
704 /*
705 * Check may be lockless but that's ok as we recheck later.
706 * It's possible to migrate LRU pages and balloon pages
707 * Skip any other type of page
708 */
709 is_lru = PageLRU(page);
710 if (!is_lru) {
711 if (unlikely(balloon_page_movable(page))) {
712 if (balloon_page_isolate(page)) {
713 /* Successfully isolated */
714 goto isolate_success;
715 }
716 }
717 }
718
719 /*
720 * Regardless of being on LRU, compound pages such as THP and
721 * hugetlbfs are not to be compacted. We can potentially save
722 * a lot of iterations if we skip them at once. The check is
723 * racy, but we can consider only valid values and the only
724 * danger is skipping too much.
725 */
726 if (PageCompound(page)) {
727 unsigned int comp_order = compound_order(page);
728
729 if (likely(comp_order < MAX_ORDER))
730 low_pfn += (1UL << comp_order) - 1;
731
732 continue;
733 }
734
735 if (!is_lru)
736 continue;
737
738 /*
739 * Migration will fail if an anonymous page is pinned in memory,
740 * so avoid taking lru_lock and isolating it unnecessarily in an
741 * admittedly racy check.
742 */
743 if (!page_mapping(page) &&
744 page_count(page) > page_mapcount(page))
745 continue;
746
747 /* If we already hold the lock, we can skip some rechecking */
748 if (!locked) {
749 locked = compact_trylock_irqsave(&zone->lru_lock,
750 &flags, cc);
751 if (!locked)
752 break;
753
754 /* Recheck PageLRU and PageCompound under lock */
755 if (!PageLRU(page))
756 continue;
757
758 /*
759 * Page become compound since the non-locked check,
760 * and it's on LRU. It can only be a THP so the order
761 * is safe to read and it's 0 for tail pages.
762 */
763 if (unlikely(PageCompound(page))) {
764 low_pfn += (1UL << compound_order(page)) - 1;
765 continue;
766 }
767 }
768
769 lruvec = mem_cgroup_page_lruvec(page, zone);
770
771 /* Try isolate the page */
772 if (__isolate_lru_page(page, isolate_mode) != 0)
773 continue;
774
775 VM_BUG_ON_PAGE(PageCompound(page), page);
776
777 /* Successfully isolated */
778 del_page_from_lru_list(page, lruvec, page_lru(page));
779
780isolate_success:
781 list_add(&page->lru, migratelist);
782 cc->nr_migratepages++;
783 nr_isolated++;
784
785 /* Avoid isolating too much */
786 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
787 ++low_pfn;
788 break;
789 }
790 }
791
792 /*
793 * The PageBuddy() check could have potentially brought us outside
794 * the range to be scanned.
795 */
796 if (unlikely(low_pfn > end_pfn))
797 low_pfn = end_pfn;
798
799 if (locked)
800 spin_unlock_irqrestore(&zone->lru_lock, flags);
801
802 /*
803 * Update the pageblock-skip information and cached scanner pfn,
804 * if the whole pageblock was scanned without isolating any page.
805 */
806 if (low_pfn == end_pfn)
807 update_pageblock_skip(cc, valid_page, nr_isolated, true);
808
809 trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn,
810 nr_scanned, nr_isolated);
811
812 count_compact_events(COMPACTMIGRATE_SCANNED, nr_scanned);
813 if (nr_isolated)
814 count_compact_events(COMPACTISOLATED, nr_isolated);
815
816 return low_pfn;
817}
818
819/**
820 * isolate_migratepages_range() - isolate migrate-able pages in a PFN range
821 * @cc: Compaction control structure.
822 * @start_pfn: The first PFN to start isolating.
823 * @end_pfn: The one-past-last PFN.
824 *
825 * Returns zero if isolation fails fatally due to e.g. pending signal.
826 * Otherwise, function returns one-past-the-last PFN of isolated page
827 * (which may be greater than end_pfn if end fell in a middle of a THP page).
828 */
829unsigned long
830isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
831 unsigned long end_pfn)
832{
833 unsigned long pfn, block_start_pfn, block_end_pfn;
834
835 /* Scan block by block. First and last block may be incomplete */
836 pfn = start_pfn;
837 block_start_pfn = pfn & ~(pageblock_nr_pages - 1);
838 if (block_start_pfn < cc->zone->zone_start_pfn)
839 block_start_pfn = cc->zone->zone_start_pfn;
840 block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
841
842 for (; pfn < end_pfn; pfn = block_end_pfn,
843 block_start_pfn = block_end_pfn,
844 block_end_pfn += pageblock_nr_pages) {
845
846 block_end_pfn = min(block_end_pfn, end_pfn);
847
848 if (!pageblock_pfn_to_page(block_start_pfn,
849 block_end_pfn, cc->zone))
850 continue;
851
852 pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
853 ISOLATE_UNEVICTABLE);
854
855 if (!pfn)
856 break;
857
858 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
859 break;
860 }
861 acct_isolated(cc->zone, cc);
862
863 return pfn;
864}
865
866#endif /* CONFIG_COMPACTION || CONFIG_CMA */
867#ifdef CONFIG_COMPACTION
868
869/* Returns true if the page is within a block suitable for migration to */
870static bool suitable_migration_target(struct page *page)
871{
872 /* If the page is a large free page, then disallow migration */
873 if (PageBuddy(page)) {
874 /*
875 * We are checking page_order without zone->lock taken. But
876 * the only small danger is that we skip a potentially suitable
877 * pageblock, so it's not worth to check order for valid range.
878 */
879 if (page_order_unsafe(page) >= pageblock_order)
880 return false;
881 }
882
883 /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
884 if (migrate_async_suitable(get_pageblock_migratetype(page)))
885 return true;
886
887 /* Otherwise skip the block */
888 return false;
889}
890
891/*
892 * Test whether the free scanner has reached the same or lower pageblock than
893 * the migration scanner, and compaction should thus terminate.
894 */
895static inline bool compact_scanners_met(struct compact_control *cc)
896{
897 return (cc->free_pfn >> pageblock_order)
898 <= (cc->migrate_pfn >> pageblock_order);
899}
900
901/*
902 * Based on information in the current compact_control, find blocks
903 * suitable for isolating free pages from and then isolate them.
904 */
905static void isolate_freepages(struct compact_control *cc)
906{
907 struct zone *zone = cc->zone;
908 struct page *page;
909 unsigned long block_start_pfn; /* start of current pageblock */
910 unsigned long isolate_start_pfn; /* exact pfn we start at */
911 unsigned long block_end_pfn; /* end of current pageblock */
912 unsigned long low_pfn; /* lowest pfn scanner is able to scan */
913 struct list_head *freelist = &cc->freepages;
914
915 /*
916 * Initialise the free scanner. The starting point is where we last
917 * successfully isolated from, zone-cached value, or the end of the
918 * zone when isolating for the first time. For looping we also need
919 * this pfn aligned down to the pageblock boundary, because we do
920 * block_start_pfn -= pageblock_nr_pages in the for loop.
921 * For ending point, take care when isolating in last pageblock of a
922 * a zone which ends in the middle of a pageblock.
923 * The low boundary is the end of the pageblock the migration scanner
924 * is using.
925 */
926 isolate_start_pfn = cc->free_pfn;
927 block_start_pfn = cc->free_pfn & ~(pageblock_nr_pages-1);
928 block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
929 zone_end_pfn(zone));
930 low_pfn = ALIGN(cc->migrate_pfn + 1, pageblock_nr_pages);
931
932 /*
933 * Isolate free pages until enough are available to migrate the
934 * pages on cc->migratepages. We stop searching if the migrate
935 * and free page scanners meet or enough free pages are isolated.
936 */
937 for (; block_start_pfn >= low_pfn;
938 block_end_pfn = block_start_pfn,
939 block_start_pfn -= pageblock_nr_pages,
940 isolate_start_pfn = block_start_pfn) {
941
942 /*
943 * This can iterate a massively long zone without finding any
944 * suitable migration targets, so periodically check if we need
945 * to schedule, or even abort async compaction.
946 */
947 if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
948 && compact_should_abort(cc))
949 break;
950
951 page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
952 zone);
953 if (!page)
954 continue;
955
956 /* Check the block is suitable for migration */
957 if (!suitable_migration_target(page))
958 continue;
959
960 /* If isolation recently failed, do not retry */
961 if (!isolation_suitable(cc, page))
962 continue;
963
964 /* Found a block suitable for isolating free pages from. */
965 isolate_freepages_block(cc, &isolate_start_pfn,
966 block_end_pfn, freelist, false);
967
968 /*
969 * If we isolated enough freepages, or aborted due to async
970 * compaction being contended, terminate the loop.
971 * Remember where the free scanner should restart next time,
972 * which is where isolate_freepages_block() left off.
973 * But if it scanned the whole pageblock, isolate_start_pfn
974 * now points at block_end_pfn, which is the start of the next
975 * pageblock.
976 * In that case we will however want to restart at the start
977 * of the previous pageblock.
978 */
979 if ((cc->nr_freepages >= cc->nr_migratepages)
980 || cc->contended) {
981 if (isolate_start_pfn >= block_end_pfn)
982 isolate_start_pfn =
983 block_start_pfn - pageblock_nr_pages;
984 break;
985 } else {
986 /*
987 * isolate_freepages_block() should not terminate
988 * prematurely unless contended, or isolated enough
989 */
990 VM_BUG_ON(isolate_start_pfn < block_end_pfn);
991 }
992 }
993
994 /* split_free_page does not map the pages */
995 map_pages(freelist);
996
997 /*
998 * Record where the free scanner will restart next time. Either we
999 * broke from the loop and set isolate_start_pfn based on the last
1000 * call to isolate_freepages_block(), or we met the migration scanner
1001 * and the loop terminated due to isolate_start_pfn < low_pfn
1002 */
1003 cc->free_pfn = isolate_start_pfn;
1004}
1005
1006/*
1007 * This is a migrate-callback that "allocates" freepages by taking pages
1008 * from the isolated freelists in the block we are migrating to.
1009 */
1010static struct page *compaction_alloc(struct page *migratepage,
1011 unsigned long data,
1012 int **result)
1013{
1014 struct compact_control *cc = (struct compact_control *)data;
1015 struct page *freepage;
1016
1017 /*
1018 * Isolate free pages if necessary, and if we are not aborting due to
1019 * contention.
1020 */
1021 if (list_empty(&cc->freepages)) {
1022 if (!cc->contended)
1023 isolate_freepages(cc);
1024
1025 if (list_empty(&cc->freepages))
1026 return NULL;
1027 }
1028
1029 freepage = list_entry(cc->freepages.next, struct page, lru);
1030 list_del(&freepage->lru);
1031 cc->nr_freepages--;
1032
1033 return freepage;
1034}
1035
1036/*
1037 * This is a migrate-callback that "frees" freepages back to the isolated
1038 * freelist. All pages on the freelist are from the same zone, so there is no
1039 * special handling needed for NUMA.
1040 */
1041static void compaction_free(struct page *page, unsigned long data)
1042{
1043 struct compact_control *cc = (struct compact_control *)data;
1044
1045 list_add(&page->lru, &cc->freepages);
1046 cc->nr_freepages++;
1047}
1048
1049/* possible outcome of isolate_migratepages */
1050typedef enum {
1051 ISOLATE_ABORT, /* Abort compaction now */
1052 ISOLATE_NONE, /* No pages isolated, continue scanning */
1053 ISOLATE_SUCCESS, /* Pages isolated, migrate */
1054} isolate_migrate_t;
1055
1056/*
1057 * Allow userspace to control policy on scanning the unevictable LRU for
1058 * compactable pages.
1059 */
1060int sysctl_compact_unevictable_allowed __read_mostly = 1;
1061
1062/*
1063 * Isolate all pages that can be migrated from the first suitable block,
1064 * starting at the block pointed to by the migrate scanner pfn within
1065 * compact_control.
1066 */
1067static isolate_migrate_t isolate_migratepages(struct zone *zone,
1068 struct compact_control *cc)
1069{
1070 unsigned long block_start_pfn;
1071 unsigned long block_end_pfn;
1072 unsigned long low_pfn;
1073 unsigned long isolate_start_pfn;
1074 struct page *page;
1075 const isolate_mode_t isolate_mode =
1076 (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
1077 (cc->mode == MIGRATE_ASYNC ? ISOLATE_ASYNC_MIGRATE : 0);
1078
1079 /*
1080 * Start at where we last stopped, or beginning of the zone as
1081 * initialized by compact_zone()
1082 */
1083 low_pfn = cc->migrate_pfn;
1084 block_start_pfn = cc->migrate_pfn & ~(pageblock_nr_pages - 1);
1085 if (block_start_pfn < zone->zone_start_pfn)
1086 block_start_pfn = zone->zone_start_pfn;
1087
1088 /* Only scan within a pageblock boundary */
1089 block_end_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages);
1090
1091 /*
1092 * Iterate over whole pageblocks until we find the first suitable.
1093 * Do not cross the free scanner.
1094 */
1095 for (; block_end_pfn <= cc->free_pfn;
1096 low_pfn = block_end_pfn,
1097 block_start_pfn = block_end_pfn,
1098 block_end_pfn += pageblock_nr_pages) {
1099
1100 /*
1101 * This can potentially iterate a massively long zone with
1102 * many pageblocks unsuitable, so periodically check if we
1103 * need to schedule, or even abort async compaction.
1104 */
1105 if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
1106 && compact_should_abort(cc))
1107 break;
1108
1109 page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
1110 zone);
1111 if (!page)
1112 continue;
1113
1114 /* If isolation recently failed, do not retry */
1115 if (!isolation_suitable(cc, page))
1116 continue;
1117
1118 /*
1119 * For async compaction, also only scan in MOVABLE blocks.
1120 * Async compaction is optimistic to see if the minimum amount
1121 * of work satisfies the allocation.
1122 */
1123 if (cc->mode == MIGRATE_ASYNC &&
1124 !migrate_async_suitable(get_pageblock_migratetype(page)))
1125 continue;
1126
1127 /* Perform the isolation */
1128 isolate_start_pfn = low_pfn;
1129 low_pfn = isolate_migratepages_block(cc, low_pfn,
1130 block_end_pfn, isolate_mode);
1131
1132 if (!low_pfn || cc->contended) {
1133 acct_isolated(zone, cc);
1134 return ISOLATE_ABORT;
1135 }
1136
1137 /*
1138 * Record where we could have freed pages by migration and not
1139 * yet flushed them to buddy allocator.
1140 * - this is the lowest page that could have been isolated and
1141 * then freed by migration.
1142 */
1143 if (cc->nr_migratepages && !cc->last_migrated_pfn)
1144 cc->last_migrated_pfn = isolate_start_pfn;
1145
1146 /*
1147 * Either we isolated something and proceed with migration. Or
1148 * we failed and compact_zone should decide if we should
1149 * continue or not.
1150 */
1151 break;
1152 }
1153
1154 acct_isolated(zone, cc);
1155 /* Record where migration scanner will be restarted. */
1156 cc->migrate_pfn = low_pfn;
1157
1158 return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
1159}
1160
1161/*
1162 * order == -1 is expected when compacting via
1163 * /proc/sys/vm/compact_memory
1164 */
1165static inline bool is_via_compact_memory(int order)
1166{
1167 return order == -1;
1168}
1169
1170static int __compact_finished(struct zone *zone, struct compact_control *cc,
1171 const int migratetype)
1172{
1173 unsigned int order;
1174 unsigned long watermark;
1175
1176 if (cc->contended || fatal_signal_pending(current))
1177 return COMPACT_CONTENDED;
1178
1179 /* Compaction run completes if the migrate and free scanner meet */
1180 if (compact_scanners_met(cc)) {
1181 /* Let the next compaction start anew. */
1182 reset_cached_positions(zone);
1183
1184 /*
1185 * Mark that the PG_migrate_skip information should be cleared
1186 * by kswapd when it goes to sleep. kcompactd does not set the
1187 * flag itself as the decision to be clear should be directly
1188 * based on an allocation request.
1189 */
1190 if (cc->direct_compaction)
1191 zone->compact_blockskip_flush = true;
1192
1193 return COMPACT_COMPLETE;
1194 }
1195
1196 if (is_via_compact_memory(cc->order))
1197 return COMPACT_CONTINUE;
1198
1199 /* Compaction run is not finished if the watermark is not met */
1200 watermark = low_wmark_pages(zone);
1201
1202 if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx,
1203 cc->alloc_flags))
1204 return COMPACT_CONTINUE;
1205
1206 /* Direct compactor: Is a suitable page free? */
1207 for (order = cc->order; order < MAX_ORDER; order++) {
1208 struct free_area *area = &zone->free_area[order];
1209 bool can_steal;
1210
1211 /* Job done if page is free of the right migratetype */
1212 if (!list_empty(&area->free_list[migratetype]))
1213 return COMPACT_PARTIAL;
1214
1215#ifdef CONFIG_CMA
1216 /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
1217 if (migratetype == MIGRATE_MOVABLE &&
1218 !list_empty(&area->free_list[MIGRATE_CMA]))
1219 return COMPACT_PARTIAL;
1220#endif
1221 /*
1222 * Job done if allocation would steal freepages from
1223 * other migratetype buddy lists.
1224 */
1225 if (find_suitable_fallback(area, order, migratetype,
1226 true, &can_steal) != -1)
1227 return COMPACT_PARTIAL;
1228 }
1229
1230 return COMPACT_NO_SUITABLE_PAGE;
1231}
1232
1233static int compact_finished(struct zone *zone, struct compact_control *cc,
1234 const int migratetype)
1235{
1236 int ret;
1237
1238 ret = __compact_finished(zone, cc, migratetype);
1239 trace_mm_compaction_finished(zone, cc->order, ret);
1240 if (ret == COMPACT_NO_SUITABLE_PAGE)
1241 ret = COMPACT_CONTINUE;
1242
1243 return ret;
1244}
1245
1246/*
1247 * compaction_suitable: Is this suitable to run compaction on this zone now?
1248 * Returns
1249 * COMPACT_SKIPPED - If there are too few free pages for compaction
1250 * COMPACT_PARTIAL - If the allocation would succeed without compaction
1251 * COMPACT_CONTINUE - If compaction should run now
1252 */
1253static unsigned long __compaction_suitable(struct zone *zone, int order,
1254 int alloc_flags, int classzone_idx)
1255{
1256 int fragindex;
1257 unsigned long watermark;
1258
1259 if (is_via_compact_memory(order))
1260 return COMPACT_CONTINUE;
1261
1262 watermark = low_wmark_pages(zone);
1263 /*
1264 * If watermarks for high-order allocation are already met, there
1265 * should be no need for compaction at all.
1266 */
1267 if (zone_watermark_ok(zone, order, watermark, classzone_idx,
1268 alloc_flags))
1269 return COMPACT_PARTIAL;
1270
1271 /*
1272 * Watermarks for order-0 must be met for compaction. Note the 2UL.
1273 * This is because during migration, copies of pages need to be
1274 * allocated and for a short time, the footprint is higher
1275 */
1276 watermark += (2UL << order);
1277 if (!zone_watermark_ok(zone, 0, watermark, classzone_idx, alloc_flags))
1278 return COMPACT_SKIPPED;
1279
1280 /*
1281 * fragmentation index determines if allocation failures are due to
1282 * low memory or external fragmentation
1283 *
1284 * index of -1000 would imply allocations might succeed depending on
1285 * watermarks, but we already failed the high-order watermark check
1286 * index towards 0 implies failure is due to lack of memory
1287 * index towards 1000 implies failure is due to fragmentation
1288 *
1289 * Only compact if a failure would be due to fragmentation.
1290 */
1291 fragindex = fragmentation_index(zone, order);
1292 if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
1293 return COMPACT_NOT_SUITABLE_ZONE;
1294
1295 return COMPACT_CONTINUE;
1296}
1297
1298unsigned long compaction_suitable(struct zone *zone, int order,
1299 int alloc_flags, int classzone_idx)
1300{
1301 unsigned long ret;
1302
1303 ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx);
1304 trace_mm_compaction_suitable(zone, order, ret);
1305 if (ret == COMPACT_NOT_SUITABLE_ZONE)
1306 ret = COMPACT_SKIPPED;
1307
1308 return ret;
1309}
1310
1311static int compact_zone(struct zone *zone, struct compact_control *cc)
1312{
1313 int ret;
1314 unsigned long start_pfn = zone->zone_start_pfn;
1315 unsigned long end_pfn = zone_end_pfn(zone);
1316 const int migratetype = gfpflags_to_migratetype(cc->gfp_mask);
1317 const bool sync = cc->mode != MIGRATE_ASYNC;
1318
1319 ret = compaction_suitable(zone, cc->order, cc->alloc_flags,
1320 cc->classzone_idx);
1321 switch (ret) {
1322 case COMPACT_PARTIAL:
1323 case COMPACT_SKIPPED:
1324 /* Compaction is likely to fail */
1325 return ret;
1326 case COMPACT_CONTINUE:
1327 /* Fall through to compaction */
1328 ;
1329 }
1330
1331 /*
1332 * Clear pageblock skip if there were failures recently and compaction
1333 * is about to be retried after being deferred.
1334 */
1335 if (compaction_restarting(zone, cc->order))
1336 __reset_isolation_suitable(zone);
1337
1338 /*
1339 * Setup to move all movable pages to the end of the zone. Used cached
1340 * information on where the scanners should start but check that it
1341 * is initialised by ensuring the values are within zone boundaries.
1342 */
1343 cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync];
1344 cc->free_pfn = zone->compact_cached_free_pfn;
1345 if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) {
1346 cc->free_pfn = round_down(end_pfn - 1, pageblock_nr_pages);
1347 zone->compact_cached_free_pfn = cc->free_pfn;
1348 }
1349 if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) {
1350 cc->migrate_pfn = start_pfn;
1351 zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
1352 zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
1353 }
1354 cc->last_migrated_pfn = 0;
1355
1356 trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
1357 cc->free_pfn, end_pfn, sync);
1358
1359 migrate_prep_local();
1360
1361 while ((ret = compact_finished(zone, cc, migratetype)) ==
1362 COMPACT_CONTINUE) {
1363 int err;
1364
1365 switch (isolate_migratepages(zone, cc)) {
1366 case ISOLATE_ABORT:
1367 ret = COMPACT_CONTENDED;
1368 putback_movable_pages(&cc->migratepages);
1369 cc->nr_migratepages = 0;
1370 goto out;
1371 case ISOLATE_NONE:
1372 /*
1373 * We haven't isolated and migrated anything, but
1374 * there might still be unflushed migrations from
1375 * previous cc->order aligned block.
1376 */
1377 goto check_drain;
1378 case ISOLATE_SUCCESS:
1379 ;
1380 }
1381
1382 err = migrate_pages(&cc->migratepages, compaction_alloc,
1383 compaction_free, (unsigned long)cc, cc->mode,
1384 MR_COMPACTION);
1385
1386 trace_mm_compaction_migratepages(cc->nr_migratepages, err,
1387 &cc->migratepages);
1388
1389 /* All pages were either migrated or will be released */
1390 cc->nr_migratepages = 0;
1391 if (err) {
1392 putback_movable_pages(&cc->migratepages);
1393 /*
1394 * migrate_pages() may return -ENOMEM when scanners meet
1395 * and we want compact_finished() to detect it
1396 */
1397 if (err == -ENOMEM && !compact_scanners_met(cc)) {
1398 ret = COMPACT_CONTENDED;
1399 goto out;
1400 }
1401 }
1402
1403check_drain:
1404 /*
1405 * Has the migration scanner moved away from the previous
1406 * cc->order aligned block where we migrated from? If yes,
1407 * flush the pages that were freed, so that they can merge and
1408 * compact_finished() can detect immediately if allocation
1409 * would succeed.
1410 */
1411 if (cc->order > 0 && cc->last_migrated_pfn) {
1412 int cpu;
1413 unsigned long current_block_start =
1414 cc->migrate_pfn & ~((1UL << cc->order) - 1);
1415
1416 if (cc->last_migrated_pfn < current_block_start) {
1417 cpu = get_cpu();
1418 lru_add_drain_cpu(cpu);
1419 drain_local_pages(zone);
1420 put_cpu();
1421 /* No more flushing until we migrate again */
1422 cc->last_migrated_pfn = 0;
1423 }
1424 }
1425
1426 }
1427
1428out:
1429 /*
1430 * Release free pages and update where the free scanner should restart,
1431 * so we don't leave any returned pages behind in the next attempt.
1432 */
1433 if (cc->nr_freepages > 0) {
1434 unsigned long free_pfn = release_freepages(&cc->freepages);
1435
1436 cc->nr_freepages = 0;
1437 VM_BUG_ON(free_pfn == 0);
1438 /* The cached pfn is always the first in a pageblock */
1439 free_pfn &= ~(pageblock_nr_pages-1);
1440 /*
1441 * Only go back, not forward. The cached pfn might have been
1442 * already reset to zone end in compact_finished()
1443 */
1444 if (free_pfn > zone->compact_cached_free_pfn)
1445 zone->compact_cached_free_pfn = free_pfn;
1446 }
1447
1448 trace_mm_compaction_end(start_pfn, cc->migrate_pfn,
1449 cc->free_pfn, end_pfn, sync, ret);
1450
1451 if (ret == COMPACT_CONTENDED)
1452 ret = COMPACT_PARTIAL;
1453
1454 return ret;
1455}
1456
1457static unsigned long compact_zone_order(struct zone *zone, int order,
1458 gfp_t gfp_mask, enum migrate_mode mode, int *contended,
1459 int alloc_flags, int classzone_idx)
1460{
1461 unsigned long ret;
1462 struct compact_control cc = {
1463 .nr_freepages = 0,
1464 .nr_migratepages = 0,
1465 .order = order,
1466 .gfp_mask = gfp_mask,
1467 .zone = zone,
1468 .mode = mode,
1469 .alloc_flags = alloc_flags,
1470 .classzone_idx = classzone_idx,
1471 .direct_compaction = true,
1472 };
1473 INIT_LIST_HEAD(&cc.freepages);
1474 INIT_LIST_HEAD(&cc.migratepages);
1475
1476 ret = compact_zone(zone, &cc);
1477
1478 VM_BUG_ON(!list_empty(&cc.freepages));
1479 VM_BUG_ON(!list_empty(&cc.migratepages));
1480
1481 *contended = cc.contended;
1482 return ret;
1483}
1484
1485int sysctl_extfrag_threshold = 500;
1486
1487/**
1488 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
1489 * @gfp_mask: The GFP mask of the current allocation
1490 * @order: The order of the current allocation
1491 * @alloc_flags: The allocation flags of the current allocation
1492 * @ac: The context of current allocation
1493 * @mode: The migration mode for async, sync light, or sync migration
1494 * @contended: Return value that determines if compaction was aborted due to
1495 * need_resched() or lock contention
1496 *
1497 * This is the main entry point for direct page compaction.
1498 */
1499unsigned long try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
1500 int alloc_flags, const struct alloc_context *ac,
1501 enum migrate_mode mode, int *contended)
1502{
1503 int may_enter_fs = gfp_mask & __GFP_FS;
1504 int may_perform_io = gfp_mask & __GFP_IO;
1505 struct zoneref *z;
1506 struct zone *zone;
1507 int rc = COMPACT_DEFERRED;
1508 int all_zones_contended = COMPACT_CONTENDED_LOCK; /* init for &= op */
1509
1510 *contended = COMPACT_CONTENDED_NONE;
1511
1512 /* Check if the GFP flags allow compaction */
1513 if (!order || !may_enter_fs || !may_perform_io)
1514 return COMPACT_SKIPPED;
1515
1516 trace_mm_compaction_try_to_compact_pages(order, gfp_mask, mode);
1517
1518 /* Compact each zone in the list */
1519 for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
1520 ac->nodemask) {
1521 int status;
1522 int zone_contended;
1523
1524 if (compaction_deferred(zone, order))
1525 continue;
1526
1527 status = compact_zone_order(zone, order, gfp_mask, mode,
1528 &zone_contended, alloc_flags,
1529 ac->classzone_idx);
1530 rc = max(status, rc);
1531 /*
1532 * It takes at least one zone that wasn't lock contended
1533 * to clear all_zones_contended.
1534 */
1535 all_zones_contended &= zone_contended;
1536
1537 /* If a normal allocation would succeed, stop compacting */
1538 if (zone_watermark_ok(zone, order, low_wmark_pages(zone),
1539 ac->classzone_idx, alloc_flags)) {
1540 /*
1541 * We think the allocation will succeed in this zone,
1542 * but it is not certain, hence the false. The caller
1543 * will repeat this with true if allocation indeed
1544 * succeeds in this zone.
1545 */
1546 compaction_defer_reset(zone, order, false);
1547 /*
1548 * It is possible that async compaction aborted due to
1549 * need_resched() and the watermarks were ok thanks to
1550 * somebody else freeing memory. The allocation can
1551 * however still fail so we better signal the
1552 * need_resched() contention anyway (this will not
1553 * prevent the allocation attempt).
1554 */
1555 if (zone_contended == COMPACT_CONTENDED_SCHED)
1556 *contended = COMPACT_CONTENDED_SCHED;
1557
1558 goto break_loop;
1559 }
1560
1561 if (mode != MIGRATE_ASYNC && status == COMPACT_COMPLETE) {
1562 /*
1563 * We think that allocation won't succeed in this zone
1564 * so we defer compaction there. If it ends up
1565 * succeeding after all, it will be reset.
1566 */
1567 defer_compaction(zone, order);
1568 }
1569
1570 /*
1571 * We might have stopped compacting due to need_resched() in
1572 * async compaction, or due to a fatal signal detected. In that
1573 * case do not try further zones and signal need_resched()
1574 * contention.
1575 */
1576 if ((zone_contended == COMPACT_CONTENDED_SCHED)
1577 || fatal_signal_pending(current)) {
1578 *contended = COMPACT_CONTENDED_SCHED;
1579 goto break_loop;
1580 }
1581
1582 continue;
1583break_loop:
1584 /*
1585 * We might not have tried all the zones, so be conservative
1586 * and assume they are not all lock contended.
1587 */
1588 all_zones_contended = 0;
1589 break;
1590 }
1591
1592 /*
1593 * If at least one zone wasn't deferred or skipped, we report if all
1594 * zones that were tried were lock contended.
1595 */
1596 if (rc > COMPACT_SKIPPED && all_zones_contended)
1597 *contended = COMPACT_CONTENDED_LOCK;
1598
1599 return rc;
1600}
1601
1602
1603/* Compact all zones within a node */
1604static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
1605{
1606 int zoneid;
1607 struct zone *zone;
1608
1609 for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
1610
1611 zone = &pgdat->node_zones[zoneid];
1612 if (!populated_zone(zone))
1613 continue;
1614
1615 cc->nr_freepages = 0;
1616 cc->nr_migratepages = 0;
1617 cc->zone = zone;
1618 INIT_LIST_HEAD(&cc->freepages);
1619 INIT_LIST_HEAD(&cc->migratepages);
1620
1621 /*
1622 * When called via /proc/sys/vm/compact_memory
1623 * this makes sure we compact the whole zone regardless of
1624 * cached scanner positions.
1625 */
1626 if (is_via_compact_memory(cc->order))
1627 __reset_isolation_suitable(zone);
1628
1629 if (is_via_compact_memory(cc->order) ||
1630 !compaction_deferred(zone, cc->order))
1631 compact_zone(zone, cc);
1632
1633 VM_BUG_ON(!list_empty(&cc->freepages));
1634 VM_BUG_ON(!list_empty(&cc->migratepages));
1635
1636 if (is_via_compact_memory(cc->order))
1637 continue;
1638
1639 if (zone_watermark_ok(zone, cc->order,
1640 low_wmark_pages(zone), 0, 0))
1641 compaction_defer_reset(zone, cc->order, false);
1642 }
1643}
1644
1645void compact_pgdat(pg_data_t *pgdat, int order)
1646{
1647 struct compact_control cc = {
1648 .order = order,
1649 .mode = MIGRATE_ASYNC,
1650 };
1651
1652 if (!order)
1653 return;
1654
1655 __compact_pgdat(pgdat, &cc);
1656}
1657
1658static void compact_node(int nid)
1659{
1660 struct compact_control cc = {
1661 .order = -1,
1662 .mode = MIGRATE_SYNC,
1663 .ignore_skip_hint = true,
1664 };
1665
1666 __compact_pgdat(NODE_DATA(nid), &cc);
1667}
1668
1669/* Compact all nodes in the system */
1670static void compact_nodes(void)
1671{
1672 int nid;
1673
1674 /* Flush pending updates to the LRU lists */
1675 lru_add_drain_all();
1676
1677 for_each_online_node(nid)
1678 compact_node(nid);
1679}
1680
1681/* The written value is actually unused, all memory is compacted */
1682int sysctl_compact_memory;
1683
1684/*
1685 * This is the entry point for compacting all nodes via
1686 * /proc/sys/vm/compact_memory
1687 */
1688int sysctl_compaction_handler(struct ctl_table *table, int write,
1689 void __user *buffer, size_t *length, loff_t *ppos)
1690{
1691 if (write)
1692 compact_nodes();
1693
1694 return 0;
1695}
1696
1697int sysctl_extfrag_handler(struct ctl_table *table, int write,
1698 void __user *buffer, size_t *length, loff_t *ppos)
1699{
1700 proc_dointvec_minmax(table, write, buffer, length, ppos);
1701
1702 return 0;
1703}
1704
1705#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
1706static ssize_t sysfs_compact_node(struct device *dev,
1707 struct device_attribute *attr,
1708 const char *buf, size_t count)
1709{
1710 int nid = dev->id;
1711
1712 if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
1713 /* Flush pending updates to the LRU lists */
1714 lru_add_drain_all();
1715
1716 compact_node(nid);
1717 }
1718
1719 return count;
1720}
1721static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
1722
1723int compaction_register_node(struct node *node)
1724{
1725 return device_create_file(&node->dev, &dev_attr_compact);
1726}
1727
1728void compaction_unregister_node(struct node *node)
1729{
1730 return device_remove_file(&node->dev, &dev_attr_compact);
1731}
1732#endif /* CONFIG_SYSFS && CONFIG_NUMA */
1733
1734static inline bool kcompactd_work_requested(pg_data_t *pgdat)
1735{
1736 return pgdat->kcompactd_max_order > 0 || kthread_should_stop();
1737}
1738
1739static bool kcompactd_node_suitable(pg_data_t *pgdat)
1740{
1741 int zoneid;
1742 struct zone *zone;
1743 enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx;
1744
1745 for (zoneid = 0; zoneid < classzone_idx; zoneid++) {
1746 zone = &pgdat->node_zones[zoneid];
1747
1748 if (!populated_zone(zone))
1749 continue;
1750
1751 if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0,
1752 classzone_idx) == COMPACT_CONTINUE)
1753 return true;
1754 }
1755
1756 return false;
1757}
1758
1759static void kcompactd_do_work(pg_data_t *pgdat)
1760{
1761 /*
1762 * With no special task, compact all zones so that a page of requested
1763 * order is allocatable.
1764 */
1765 int zoneid;
1766 struct zone *zone;
1767 struct compact_control cc = {
1768 .order = pgdat->kcompactd_max_order,
1769 .classzone_idx = pgdat->kcompactd_classzone_idx,
1770 .mode = MIGRATE_SYNC_LIGHT,
1771 .ignore_skip_hint = true,
1772
1773 };
1774 bool success = false;
1775
1776 trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order,
1777 cc.classzone_idx);
1778 count_vm_event(KCOMPACTD_WAKE);
1779
1780 for (zoneid = 0; zoneid < cc.classzone_idx; zoneid++) {
1781 int status;
1782
1783 zone = &pgdat->node_zones[zoneid];
1784 if (!populated_zone(zone))
1785 continue;
1786
1787 if (compaction_deferred(zone, cc.order))
1788 continue;
1789
1790 if (compaction_suitable(zone, cc.order, 0, zoneid) !=
1791 COMPACT_CONTINUE)
1792 continue;
1793
1794 cc.nr_freepages = 0;
1795 cc.nr_migratepages = 0;
1796 cc.zone = zone;
1797 INIT_LIST_HEAD(&cc.freepages);
1798 INIT_LIST_HEAD(&cc.migratepages);
1799
1800 if (kthread_should_stop())
1801 return;
1802 status = compact_zone(zone, &cc);
1803
1804 if (zone_watermark_ok(zone, cc.order, low_wmark_pages(zone),
1805 cc.classzone_idx, 0)) {
1806 success = true;
1807 compaction_defer_reset(zone, cc.order, false);
1808 } else if (status == COMPACT_COMPLETE) {
1809 /*
1810 * We use sync migration mode here, so we defer like
1811 * sync direct compaction does.
1812 */
1813 defer_compaction(zone, cc.order);
1814 }
1815
1816 VM_BUG_ON(!list_empty(&cc.freepages));
1817 VM_BUG_ON(!list_empty(&cc.migratepages));
1818 }
1819
1820 /*
1821 * Regardless of success, we are done until woken up next. But remember
1822 * the requested order/classzone_idx in case it was higher/tighter than
1823 * our current ones
1824 */
1825 if (pgdat->kcompactd_max_order <= cc.order)
1826 pgdat->kcompactd_max_order = 0;
1827 if (pgdat->kcompactd_classzone_idx >= cc.classzone_idx)
1828 pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
1829}
1830
1831void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
1832{
1833 if (!order)
1834 return;
1835
1836 if (pgdat->kcompactd_max_order < order)
1837 pgdat->kcompactd_max_order = order;
1838
1839 if (pgdat->kcompactd_classzone_idx > classzone_idx)
1840 pgdat->kcompactd_classzone_idx = classzone_idx;
1841
1842 if (!waitqueue_active(&pgdat->kcompactd_wait))
1843 return;
1844
1845 if (!kcompactd_node_suitable(pgdat))
1846 return;
1847
1848 trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order,
1849 classzone_idx);
1850 wake_up_interruptible(&pgdat->kcompactd_wait);
1851}
1852
1853/*
1854 * The background compaction daemon, started as a kernel thread
1855 * from the init process.
1856 */
1857static int kcompactd(void *p)
1858{
1859 pg_data_t *pgdat = (pg_data_t*)p;
1860 struct task_struct *tsk = current;
1861
1862 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
1863
1864 if (!cpumask_empty(cpumask))
1865 set_cpus_allowed_ptr(tsk, cpumask);
1866
1867 set_freezable();
1868
1869 pgdat->kcompactd_max_order = 0;
1870 pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
1871
1872 while (!kthread_should_stop()) {
1873 trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
1874 wait_event_freezable(pgdat->kcompactd_wait,
1875 kcompactd_work_requested(pgdat));
1876
1877 kcompactd_do_work(pgdat);
1878 }
1879
1880 return 0;
1881}
1882
1883/*
1884 * This kcompactd start function will be called by init and node-hot-add.
1885 * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added.
1886 */
1887int kcompactd_run(int nid)
1888{
1889 pg_data_t *pgdat = NODE_DATA(nid);
1890 int ret = 0;
1891
1892 if (pgdat->kcompactd)
1893 return 0;
1894
1895 pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid);
1896 if (IS_ERR(pgdat->kcompactd)) {
1897 pr_err("Failed to start kcompactd on node %d\n", nid);
1898 ret = PTR_ERR(pgdat->kcompactd);
1899 pgdat->kcompactd = NULL;
1900 }
1901 return ret;
1902}
1903
1904/*
1905 * Called by memory hotplug when all memory in a node is offlined. Caller must
1906 * hold mem_hotplug_begin/end().
1907 */
1908void kcompactd_stop(int nid)
1909{
1910 struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd;
1911
1912 if (kcompactd) {
1913 kthread_stop(kcompactd);
1914 NODE_DATA(nid)->kcompactd = NULL;
1915 }
1916}
1917
1918/*
1919 * It's optimal to keep kcompactd on the same CPUs as their memory, but
1920 * not required for correctness. So if the last cpu in a node goes
1921 * away, we get changed to run anywhere: as the first one comes back,
1922 * restore their cpu bindings.
1923 */
1924static int cpu_callback(struct notifier_block *nfb, unsigned long action,
1925 void *hcpu)
1926{
1927 int nid;
1928
1929 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
1930 for_each_node_state(nid, N_MEMORY) {
1931 pg_data_t *pgdat = NODE_DATA(nid);
1932 const struct cpumask *mask;
1933
1934 mask = cpumask_of_node(pgdat->node_id);
1935
1936 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
1937 /* One of our CPUs online: restore mask */
1938 set_cpus_allowed_ptr(pgdat->kcompactd, mask);
1939 }
1940 }
1941 return NOTIFY_OK;
1942}
1943
1944static int __init kcompactd_init(void)
1945{
1946 int nid;
1947
1948 for_each_node_state(nid, N_MEMORY)
1949 kcompactd_run(nid);
1950 hotcpu_notifier(cpu_callback, 0);
1951 return 0;
1952}
1953subsys_initcall(kcompactd_init)
1954
1955#endif /* CONFIG_COMPACTION */
1/*
2 * linux/mm/compaction.c
3 *
4 * Memory compaction for the reduction of external fragmentation. Note that
5 * this heavily depends upon page migration to do all the real heavy
6 * lifting
7 *
8 * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
9 */
10#include <linux/cpu.h>
11#include <linux/swap.h>
12#include <linux/migrate.h>
13#include <linux/compaction.h>
14#include <linux/mm_inline.h>
15#include <linux/backing-dev.h>
16#include <linux/sysctl.h>
17#include <linux/sysfs.h>
18#include <linux/page-isolation.h>
19#include <linux/kasan.h>
20#include <linux/kthread.h>
21#include <linux/freezer.h>
22#include <linux/page_owner.h>
23#include "internal.h"
24
25#ifdef CONFIG_COMPACTION
26static inline void count_compact_event(enum vm_event_item item)
27{
28 count_vm_event(item);
29}
30
31static inline void count_compact_events(enum vm_event_item item, long delta)
32{
33 count_vm_events(item, delta);
34}
35#else
36#define count_compact_event(item) do { } while (0)
37#define count_compact_events(item, delta) do { } while (0)
38#endif
39
40#if defined CONFIG_COMPACTION || defined CONFIG_CMA
41
42#define CREATE_TRACE_POINTS
43#include <trace/events/compaction.h>
44
45#define block_start_pfn(pfn, order) round_down(pfn, 1UL << (order))
46#define block_end_pfn(pfn, order) ALIGN((pfn) + 1, 1UL << (order))
47#define pageblock_start_pfn(pfn) block_start_pfn(pfn, pageblock_order)
48#define pageblock_end_pfn(pfn) block_end_pfn(pfn, pageblock_order)
49
50static unsigned long release_freepages(struct list_head *freelist)
51{
52 struct page *page, *next;
53 unsigned long high_pfn = 0;
54
55 list_for_each_entry_safe(page, next, freelist, lru) {
56 unsigned long pfn = page_to_pfn(page);
57 list_del(&page->lru);
58 __free_page(page);
59 if (pfn > high_pfn)
60 high_pfn = pfn;
61 }
62
63 return high_pfn;
64}
65
66static void map_pages(struct list_head *list)
67{
68 unsigned int i, order, nr_pages;
69 struct page *page, *next;
70 LIST_HEAD(tmp_list);
71
72 list_for_each_entry_safe(page, next, list, lru) {
73 list_del(&page->lru);
74
75 order = page_private(page);
76 nr_pages = 1 << order;
77
78 post_alloc_hook(page, order, __GFP_MOVABLE);
79 if (order)
80 split_page(page, order);
81
82 for (i = 0; i < nr_pages; i++) {
83 list_add(&page->lru, &tmp_list);
84 page++;
85 }
86 }
87
88 list_splice(&tmp_list, list);
89}
90
91static inline bool migrate_async_suitable(int migratetype)
92{
93 return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE;
94}
95
96#ifdef CONFIG_COMPACTION
97
98int PageMovable(struct page *page)
99{
100 struct address_space *mapping;
101
102 VM_BUG_ON_PAGE(!PageLocked(page), page);
103 if (!__PageMovable(page))
104 return 0;
105
106 mapping = page_mapping(page);
107 if (mapping && mapping->a_ops && mapping->a_ops->isolate_page)
108 return 1;
109
110 return 0;
111}
112EXPORT_SYMBOL(PageMovable);
113
114void __SetPageMovable(struct page *page, struct address_space *mapping)
115{
116 VM_BUG_ON_PAGE(!PageLocked(page), page);
117 VM_BUG_ON_PAGE((unsigned long)mapping & PAGE_MAPPING_MOVABLE, page);
118 page->mapping = (void *)((unsigned long)mapping | PAGE_MAPPING_MOVABLE);
119}
120EXPORT_SYMBOL(__SetPageMovable);
121
122void __ClearPageMovable(struct page *page)
123{
124 VM_BUG_ON_PAGE(!PageLocked(page), page);
125 VM_BUG_ON_PAGE(!PageMovable(page), page);
126 /*
127 * Clear registered address_space val with keeping PAGE_MAPPING_MOVABLE
128 * flag so that VM can catch up released page by driver after isolation.
129 * With it, VM migration doesn't try to put it back.
130 */
131 page->mapping = (void *)((unsigned long)page->mapping &
132 PAGE_MAPPING_MOVABLE);
133}
134EXPORT_SYMBOL(__ClearPageMovable);
135
136/* Do not skip compaction more than 64 times */
137#define COMPACT_MAX_DEFER_SHIFT 6
138
139/*
140 * Compaction is deferred when compaction fails to result in a page
141 * allocation success. 1 << compact_defer_limit compactions are skipped up
142 * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
143 */
144void defer_compaction(struct zone *zone, int order)
145{
146 zone->compact_considered = 0;
147 zone->compact_defer_shift++;
148
149 if (order < zone->compact_order_failed)
150 zone->compact_order_failed = order;
151
152 if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
153 zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
154
155 trace_mm_compaction_defer_compaction(zone, order);
156}
157
158/* Returns true if compaction should be skipped this time */
159bool compaction_deferred(struct zone *zone, int order)
160{
161 unsigned long defer_limit = 1UL << zone->compact_defer_shift;
162
163 if (order < zone->compact_order_failed)
164 return false;
165
166 /* Avoid possible overflow */
167 if (++zone->compact_considered > defer_limit)
168 zone->compact_considered = defer_limit;
169
170 if (zone->compact_considered >= defer_limit)
171 return false;
172
173 trace_mm_compaction_deferred(zone, order);
174
175 return true;
176}
177
178/*
179 * Update defer tracking counters after successful compaction of given order,
180 * which means an allocation either succeeded (alloc_success == true) or is
181 * expected to succeed.
182 */
183void compaction_defer_reset(struct zone *zone, int order,
184 bool alloc_success)
185{
186 if (alloc_success) {
187 zone->compact_considered = 0;
188 zone->compact_defer_shift = 0;
189 }
190 if (order >= zone->compact_order_failed)
191 zone->compact_order_failed = order + 1;
192
193 trace_mm_compaction_defer_reset(zone, order);
194}
195
196/* Returns true if restarting compaction after many failures */
197bool compaction_restarting(struct zone *zone, int order)
198{
199 if (order < zone->compact_order_failed)
200 return false;
201
202 return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
203 zone->compact_considered >= 1UL << zone->compact_defer_shift;
204}
205
206/* Returns true if the pageblock should be scanned for pages to isolate. */
207static inline bool isolation_suitable(struct compact_control *cc,
208 struct page *page)
209{
210 if (cc->ignore_skip_hint)
211 return true;
212
213 return !get_pageblock_skip(page);
214}
215
216static void reset_cached_positions(struct zone *zone)
217{
218 zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn;
219 zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn;
220 zone->compact_cached_free_pfn =
221 pageblock_start_pfn(zone_end_pfn(zone) - 1);
222}
223
224/*
225 * This function is called to clear all cached information on pageblocks that
226 * should be skipped for page isolation when the migrate and free page scanner
227 * meet.
228 */
229static void __reset_isolation_suitable(struct zone *zone)
230{
231 unsigned long start_pfn = zone->zone_start_pfn;
232 unsigned long end_pfn = zone_end_pfn(zone);
233 unsigned long pfn;
234
235 zone->compact_blockskip_flush = false;
236
237 /* Walk the zone and mark every pageblock as suitable for isolation */
238 for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
239 struct page *page;
240
241 cond_resched();
242
243 if (!pfn_valid(pfn))
244 continue;
245
246 page = pfn_to_page(pfn);
247 if (zone != page_zone(page))
248 continue;
249
250 clear_pageblock_skip(page);
251 }
252
253 reset_cached_positions(zone);
254}
255
256void reset_isolation_suitable(pg_data_t *pgdat)
257{
258 int zoneid;
259
260 for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
261 struct zone *zone = &pgdat->node_zones[zoneid];
262 if (!populated_zone(zone))
263 continue;
264
265 /* Only flush if a full compaction finished recently */
266 if (zone->compact_blockskip_flush)
267 __reset_isolation_suitable(zone);
268 }
269}
270
271/*
272 * If no pages were isolated then mark this pageblock to be skipped in the
273 * future. The information is later cleared by __reset_isolation_suitable().
274 */
275static void update_pageblock_skip(struct compact_control *cc,
276 struct page *page, unsigned long nr_isolated,
277 bool migrate_scanner)
278{
279 struct zone *zone = cc->zone;
280 unsigned long pfn;
281
282 if (cc->ignore_skip_hint)
283 return;
284
285 if (!page)
286 return;
287
288 if (nr_isolated)
289 return;
290
291 set_pageblock_skip(page);
292
293 pfn = page_to_pfn(page);
294
295 /* Update where async and sync compaction should restart */
296 if (migrate_scanner) {
297 if (pfn > zone->compact_cached_migrate_pfn[0])
298 zone->compact_cached_migrate_pfn[0] = pfn;
299 if (cc->mode != MIGRATE_ASYNC &&
300 pfn > zone->compact_cached_migrate_pfn[1])
301 zone->compact_cached_migrate_pfn[1] = pfn;
302 } else {
303 if (pfn < zone->compact_cached_free_pfn)
304 zone->compact_cached_free_pfn = pfn;
305 }
306}
307#else
308static inline bool isolation_suitable(struct compact_control *cc,
309 struct page *page)
310{
311 return true;
312}
313
314static void update_pageblock_skip(struct compact_control *cc,
315 struct page *page, unsigned long nr_isolated,
316 bool migrate_scanner)
317{
318}
319#endif /* CONFIG_COMPACTION */
320
321/*
322 * Compaction requires the taking of some coarse locks that are potentially
323 * very heavily contended. For async compaction, back out if the lock cannot
324 * be taken immediately. For sync compaction, spin on the lock if needed.
325 *
326 * Returns true if the lock is held
327 * Returns false if the lock is not held and compaction should abort
328 */
329static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags,
330 struct compact_control *cc)
331{
332 if (cc->mode == MIGRATE_ASYNC) {
333 if (!spin_trylock_irqsave(lock, *flags)) {
334 cc->contended = true;
335 return false;
336 }
337 } else {
338 spin_lock_irqsave(lock, *flags);
339 }
340
341 return true;
342}
343
344/*
345 * Compaction requires the taking of some coarse locks that are potentially
346 * very heavily contended. The lock should be periodically unlocked to avoid
347 * having disabled IRQs for a long time, even when there is nobody waiting on
348 * the lock. It might also be that allowing the IRQs will result in
349 * need_resched() becoming true. If scheduling is needed, async compaction
350 * aborts. Sync compaction schedules.
351 * Either compaction type will also abort if a fatal signal is pending.
352 * In either case if the lock was locked, it is dropped and not regained.
353 *
354 * Returns true if compaction should abort due to fatal signal pending, or
355 * async compaction due to need_resched()
356 * Returns false when compaction can continue (sync compaction might have
357 * scheduled)
358 */
359static bool compact_unlock_should_abort(spinlock_t *lock,
360 unsigned long flags, bool *locked, struct compact_control *cc)
361{
362 if (*locked) {
363 spin_unlock_irqrestore(lock, flags);
364 *locked = false;
365 }
366
367 if (fatal_signal_pending(current)) {
368 cc->contended = true;
369 return true;
370 }
371
372 if (need_resched()) {
373 if (cc->mode == MIGRATE_ASYNC) {
374 cc->contended = true;
375 return true;
376 }
377 cond_resched();
378 }
379
380 return false;
381}
382
383/*
384 * Aside from avoiding lock contention, compaction also periodically checks
385 * need_resched() and either schedules in sync compaction or aborts async
386 * compaction. This is similar to what compact_unlock_should_abort() does, but
387 * is used where no lock is concerned.
388 *
389 * Returns false when no scheduling was needed, or sync compaction scheduled.
390 * Returns true when async compaction should abort.
391 */
392static inline bool compact_should_abort(struct compact_control *cc)
393{
394 /* async compaction aborts if contended */
395 if (need_resched()) {
396 if (cc->mode == MIGRATE_ASYNC) {
397 cc->contended = true;
398 return true;
399 }
400
401 cond_resched();
402 }
403
404 return false;
405}
406
407/*
408 * Isolate free pages onto a private freelist. If @strict is true, will abort
409 * returning 0 on any invalid PFNs or non-free pages inside of the pageblock
410 * (even though it may still end up isolating some pages).
411 */
412static unsigned long isolate_freepages_block(struct compact_control *cc,
413 unsigned long *start_pfn,
414 unsigned long end_pfn,
415 struct list_head *freelist,
416 bool strict)
417{
418 int nr_scanned = 0, total_isolated = 0;
419 struct page *cursor, *valid_page = NULL;
420 unsigned long flags = 0;
421 bool locked = false;
422 unsigned long blockpfn = *start_pfn;
423 unsigned int order;
424
425 cursor = pfn_to_page(blockpfn);
426
427 /* Isolate free pages. */
428 for (; blockpfn < end_pfn; blockpfn++, cursor++) {
429 int isolated;
430 struct page *page = cursor;
431
432 /*
433 * Periodically drop the lock (if held) regardless of its
434 * contention, to give chance to IRQs. Abort if fatal signal
435 * pending or async compaction detects need_resched()
436 */
437 if (!(blockpfn % SWAP_CLUSTER_MAX)
438 && compact_unlock_should_abort(&cc->zone->lock, flags,
439 &locked, cc))
440 break;
441
442 nr_scanned++;
443 if (!pfn_valid_within(blockpfn))
444 goto isolate_fail;
445
446 if (!valid_page)
447 valid_page = page;
448
449 /*
450 * For compound pages such as THP and hugetlbfs, we can save
451 * potentially a lot of iterations if we skip them at once.
452 * The check is racy, but we can consider only valid values
453 * and the only danger is skipping too much.
454 */
455 if (PageCompound(page)) {
456 unsigned int comp_order = compound_order(page);
457
458 if (likely(comp_order < MAX_ORDER)) {
459 blockpfn += (1UL << comp_order) - 1;
460 cursor += (1UL << comp_order) - 1;
461 }
462
463 goto isolate_fail;
464 }
465
466 if (!PageBuddy(page))
467 goto isolate_fail;
468
469 /*
470 * If we already hold the lock, we can skip some rechecking.
471 * Note that if we hold the lock now, checked_pageblock was
472 * already set in some previous iteration (or strict is true),
473 * so it is correct to skip the suitable migration target
474 * recheck as well.
475 */
476 if (!locked) {
477 /*
478 * The zone lock must be held to isolate freepages.
479 * Unfortunately this is a very coarse lock and can be
480 * heavily contended if there are parallel allocations
481 * or parallel compactions. For async compaction do not
482 * spin on the lock and we acquire the lock as late as
483 * possible.
484 */
485 locked = compact_trylock_irqsave(&cc->zone->lock,
486 &flags, cc);
487 if (!locked)
488 break;
489
490 /* Recheck this is a buddy page under lock */
491 if (!PageBuddy(page))
492 goto isolate_fail;
493 }
494
495 /* Found a free page, will break it into order-0 pages */
496 order = page_order(page);
497 isolated = __isolate_free_page(page, order);
498 if (!isolated)
499 break;
500 set_page_private(page, order);
501
502 total_isolated += isolated;
503 cc->nr_freepages += isolated;
504 list_add_tail(&page->lru, freelist);
505
506 if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
507 blockpfn += isolated;
508 break;
509 }
510 /* Advance to the end of split page */
511 blockpfn += isolated - 1;
512 cursor += isolated - 1;
513 continue;
514
515isolate_fail:
516 if (strict)
517 break;
518 else
519 continue;
520
521 }
522
523 if (locked)
524 spin_unlock_irqrestore(&cc->zone->lock, flags);
525
526 /*
527 * There is a tiny chance that we have read bogus compound_order(),
528 * so be careful to not go outside of the pageblock.
529 */
530 if (unlikely(blockpfn > end_pfn))
531 blockpfn = end_pfn;
532
533 trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn,
534 nr_scanned, total_isolated);
535
536 /* Record how far we have got within the block */
537 *start_pfn = blockpfn;
538
539 /*
540 * If strict isolation is requested by CMA then check that all the
541 * pages requested were isolated. If there were any failures, 0 is
542 * returned and CMA will fail.
543 */
544 if (strict && blockpfn < end_pfn)
545 total_isolated = 0;
546
547 /* Update the pageblock-skip if the whole pageblock was scanned */
548 if (blockpfn == end_pfn)
549 update_pageblock_skip(cc, valid_page, total_isolated, false);
550
551 count_compact_events(COMPACTFREE_SCANNED, nr_scanned);
552 if (total_isolated)
553 count_compact_events(COMPACTISOLATED, total_isolated);
554 return total_isolated;
555}
556
557/**
558 * isolate_freepages_range() - isolate free pages.
559 * @start_pfn: The first PFN to start isolating.
560 * @end_pfn: The one-past-last PFN.
561 *
562 * Non-free pages, invalid PFNs, or zone boundaries within the
563 * [start_pfn, end_pfn) range are considered errors, cause function to
564 * undo its actions and return zero.
565 *
566 * Otherwise, function returns one-past-the-last PFN of isolated page
567 * (which may be greater then end_pfn if end fell in a middle of
568 * a free page).
569 */
570unsigned long
571isolate_freepages_range(struct compact_control *cc,
572 unsigned long start_pfn, unsigned long end_pfn)
573{
574 unsigned long isolated, pfn, block_start_pfn, block_end_pfn;
575 LIST_HEAD(freelist);
576
577 pfn = start_pfn;
578 block_start_pfn = pageblock_start_pfn(pfn);
579 if (block_start_pfn < cc->zone->zone_start_pfn)
580 block_start_pfn = cc->zone->zone_start_pfn;
581 block_end_pfn = pageblock_end_pfn(pfn);
582
583 for (; pfn < end_pfn; pfn += isolated,
584 block_start_pfn = block_end_pfn,
585 block_end_pfn += pageblock_nr_pages) {
586 /* Protect pfn from changing by isolate_freepages_block */
587 unsigned long isolate_start_pfn = pfn;
588
589 block_end_pfn = min(block_end_pfn, end_pfn);
590
591 /*
592 * pfn could pass the block_end_pfn if isolated freepage
593 * is more than pageblock order. In this case, we adjust
594 * scanning range to right one.
595 */
596 if (pfn >= block_end_pfn) {
597 block_start_pfn = pageblock_start_pfn(pfn);
598 block_end_pfn = pageblock_end_pfn(pfn);
599 block_end_pfn = min(block_end_pfn, end_pfn);
600 }
601
602 if (!pageblock_pfn_to_page(block_start_pfn,
603 block_end_pfn, cc->zone))
604 break;
605
606 isolated = isolate_freepages_block(cc, &isolate_start_pfn,
607 block_end_pfn, &freelist, true);
608
609 /*
610 * In strict mode, isolate_freepages_block() returns 0 if
611 * there are any holes in the block (ie. invalid PFNs or
612 * non-free pages).
613 */
614 if (!isolated)
615 break;
616
617 /*
618 * If we managed to isolate pages, it is always (1 << n) *
619 * pageblock_nr_pages for some non-negative n. (Max order
620 * page may span two pageblocks).
621 */
622 }
623
624 /* __isolate_free_page() does not map the pages */
625 map_pages(&freelist);
626
627 if (pfn < end_pfn) {
628 /* Loop terminated early, cleanup. */
629 release_freepages(&freelist);
630 return 0;
631 }
632
633 /* We don't use freelists for anything. */
634 return pfn;
635}
636
637/* Similar to reclaim, but different enough that they don't share logic */
638static bool too_many_isolated(struct zone *zone)
639{
640 unsigned long active, inactive, isolated;
641
642 inactive = node_page_state(zone->zone_pgdat, NR_INACTIVE_FILE) +
643 node_page_state(zone->zone_pgdat, NR_INACTIVE_ANON);
644 active = node_page_state(zone->zone_pgdat, NR_ACTIVE_FILE) +
645 node_page_state(zone->zone_pgdat, NR_ACTIVE_ANON);
646 isolated = node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE) +
647 node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON);
648
649 return isolated > (inactive + active) / 2;
650}
651
652/**
653 * isolate_migratepages_block() - isolate all migrate-able pages within
654 * a single pageblock
655 * @cc: Compaction control structure.
656 * @low_pfn: The first PFN to isolate
657 * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
658 * @isolate_mode: Isolation mode to be used.
659 *
660 * Isolate all pages that can be migrated from the range specified by
661 * [low_pfn, end_pfn). The range is expected to be within same pageblock.
662 * Returns zero if there is a fatal signal pending, otherwise PFN of the
663 * first page that was not scanned (which may be both less, equal to or more
664 * than end_pfn).
665 *
666 * The pages are isolated on cc->migratepages list (not required to be empty),
667 * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field
668 * is neither read nor updated.
669 */
670static unsigned long
671isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
672 unsigned long end_pfn, isolate_mode_t isolate_mode)
673{
674 struct zone *zone = cc->zone;
675 unsigned long nr_scanned = 0, nr_isolated = 0;
676 struct lruvec *lruvec;
677 unsigned long flags = 0;
678 bool locked = false;
679 struct page *page = NULL, *valid_page = NULL;
680 unsigned long start_pfn = low_pfn;
681 bool skip_on_failure = false;
682 unsigned long next_skip_pfn = 0;
683
684 /*
685 * Ensure that there are not too many pages isolated from the LRU
686 * list by either parallel reclaimers or compaction. If there are,
687 * delay for some time until fewer pages are isolated
688 */
689 while (unlikely(too_many_isolated(zone))) {
690 /* async migration should just abort */
691 if (cc->mode == MIGRATE_ASYNC)
692 return 0;
693
694 congestion_wait(BLK_RW_ASYNC, HZ/10);
695
696 if (fatal_signal_pending(current))
697 return 0;
698 }
699
700 if (compact_should_abort(cc))
701 return 0;
702
703 if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) {
704 skip_on_failure = true;
705 next_skip_pfn = block_end_pfn(low_pfn, cc->order);
706 }
707
708 /* Time to isolate some pages for migration */
709 for (; low_pfn < end_pfn; low_pfn++) {
710
711 if (skip_on_failure && low_pfn >= next_skip_pfn) {
712 /*
713 * We have isolated all migration candidates in the
714 * previous order-aligned block, and did not skip it due
715 * to failure. We should migrate the pages now and
716 * hopefully succeed compaction.
717 */
718 if (nr_isolated)
719 break;
720
721 /*
722 * We failed to isolate in the previous order-aligned
723 * block. Set the new boundary to the end of the
724 * current block. Note we can't simply increase
725 * next_skip_pfn by 1 << order, as low_pfn might have
726 * been incremented by a higher number due to skipping
727 * a compound or a high-order buddy page in the
728 * previous loop iteration.
729 */
730 next_skip_pfn = block_end_pfn(low_pfn, cc->order);
731 }
732
733 /*
734 * Periodically drop the lock (if held) regardless of its
735 * contention, to give chance to IRQs. Abort async compaction
736 * if contended.
737 */
738 if (!(low_pfn % SWAP_CLUSTER_MAX)
739 && compact_unlock_should_abort(zone_lru_lock(zone), flags,
740 &locked, cc))
741 break;
742
743 if (!pfn_valid_within(low_pfn))
744 goto isolate_fail;
745 nr_scanned++;
746
747 page = pfn_to_page(low_pfn);
748
749 if (!valid_page)
750 valid_page = page;
751
752 /*
753 * Skip if free. We read page order here without zone lock
754 * which is generally unsafe, but the race window is small and
755 * the worst thing that can happen is that we skip some
756 * potential isolation targets.
757 */
758 if (PageBuddy(page)) {
759 unsigned long freepage_order = page_order_unsafe(page);
760
761 /*
762 * Without lock, we cannot be sure that what we got is
763 * a valid page order. Consider only values in the
764 * valid order range to prevent low_pfn overflow.
765 */
766 if (freepage_order > 0 && freepage_order < MAX_ORDER)
767 low_pfn += (1UL << freepage_order) - 1;
768 continue;
769 }
770
771 /*
772 * Regardless of being on LRU, compound pages such as THP and
773 * hugetlbfs are not to be compacted. We can potentially save
774 * a lot of iterations if we skip them at once. The check is
775 * racy, but we can consider only valid values and the only
776 * danger is skipping too much.
777 */
778 if (PageCompound(page)) {
779 unsigned int comp_order = compound_order(page);
780
781 if (likely(comp_order < MAX_ORDER))
782 low_pfn += (1UL << comp_order) - 1;
783
784 goto isolate_fail;
785 }
786
787 /*
788 * Check may be lockless but that's ok as we recheck later.
789 * It's possible to migrate LRU and non-lru movable pages.
790 * Skip any other type of page
791 */
792 if (!PageLRU(page)) {
793 /*
794 * __PageMovable can return false positive so we need
795 * to verify it under page_lock.
796 */
797 if (unlikely(__PageMovable(page)) &&
798 !PageIsolated(page)) {
799 if (locked) {
800 spin_unlock_irqrestore(zone_lru_lock(zone),
801 flags);
802 locked = false;
803 }
804
805 if (isolate_movable_page(page, isolate_mode))
806 goto isolate_success;
807 }
808
809 goto isolate_fail;
810 }
811
812 /*
813 * Migration will fail if an anonymous page is pinned in memory,
814 * so avoid taking lru_lock and isolating it unnecessarily in an
815 * admittedly racy check.
816 */
817 if (!page_mapping(page) &&
818 page_count(page) > page_mapcount(page))
819 goto isolate_fail;
820
821 /*
822 * Only allow to migrate anonymous pages in GFP_NOFS context
823 * because those do not depend on fs locks.
824 */
825 if (!(cc->gfp_mask & __GFP_FS) && page_mapping(page))
826 goto isolate_fail;
827
828 /* If we already hold the lock, we can skip some rechecking */
829 if (!locked) {
830 locked = compact_trylock_irqsave(zone_lru_lock(zone),
831 &flags, cc);
832 if (!locked)
833 break;
834
835 /* Recheck PageLRU and PageCompound under lock */
836 if (!PageLRU(page))
837 goto isolate_fail;
838
839 /*
840 * Page become compound since the non-locked check,
841 * and it's on LRU. It can only be a THP so the order
842 * is safe to read and it's 0 for tail pages.
843 */
844 if (unlikely(PageCompound(page))) {
845 low_pfn += (1UL << compound_order(page)) - 1;
846 goto isolate_fail;
847 }
848 }
849
850 lruvec = mem_cgroup_page_lruvec(page, zone->zone_pgdat);
851
852 /* Try isolate the page */
853 if (__isolate_lru_page(page, isolate_mode) != 0)
854 goto isolate_fail;
855
856 VM_BUG_ON_PAGE(PageCompound(page), page);
857
858 /* Successfully isolated */
859 del_page_from_lru_list(page, lruvec, page_lru(page));
860 inc_node_page_state(page,
861 NR_ISOLATED_ANON + page_is_file_cache(page));
862
863isolate_success:
864 list_add(&page->lru, &cc->migratepages);
865 cc->nr_migratepages++;
866 nr_isolated++;
867
868 /*
869 * Record where we could have freed pages by migration and not
870 * yet flushed them to buddy allocator.
871 * - this is the lowest page that was isolated and likely be
872 * then freed by migration.
873 */
874 if (!cc->last_migrated_pfn)
875 cc->last_migrated_pfn = low_pfn;
876
877 /* Avoid isolating too much */
878 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
879 ++low_pfn;
880 break;
881 }
882
883 continue;
884isolate_fail:
885 if (!skip_on_failure)
886 continue;
887
888 /*
889 * We have isolated some pages, but then failed. Release them
890 * instead of migrating, as we cannot form the cc->order buddy
891 * page anyway.
892 */
893 if (nr_isolated) {
894 if (locked) {
895 spin_unlock_irqrestore(zone_lru_lock(zone), flags);
896 locked = false;
897 }
898 putback_movable_pages(&cc->migratepages);
899 cc->nr_migratepages = 0;
900 cc->last_migrated_pfn = 0;
901 nr_isolated = 0;
902 }
903
904 if (low_pfn < next_skip_pfn) {
905 low_pfn = next_skip_pfn - 1;
906 /*
907 * The check near the loop beginning would have updated
908 * next_skip_pfn too, but this is a bit simpler.
909 */
910 next_skip_pfn += 1UL << cc->order;
911 }
912 }
913
914 /*
915 * The PageBuddy() check could have potentially brought us outside
916 * the range to be scanned.
917 */
918 if (unlikely(low_pfn > end_pfn))
919 low_pfn = end_pfn;
920
921 if (locked)
922 spin_unlock_irqrestore(zone_lru_lock(zone), flags);
923
924 /*
925 * Update the pageblock-skip information and cached scanner pfn,
926 * if the whole pageblock was scanned without isolating any page.
927 */
928 if (low_pfn == end_pfn)
929 update_pageblock_skip(cc, valid_page, nr_isolated, true);
930
931 trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn,
932 nr_scanned, nr_isolated);
933
934 count_compact_events(COMPACTMIGRATE_SCANNED, nr_scanned);
935 if (nr_isolated)
936 count_compact_events(COMPACTISOLATED, nr_isolated);
937
938 return low_pfn;
939}
940
941/**
942 * isolate_migratepages_range() - isolate migrate-able pages in a PFN range
943 * @cc: Compaction control structure.
944 * @start_pfn: The first PFN to start isolating.
945 * @end_pfn: The one-past-last PFN.
946 *
947 * Returns zero if isolation fails fatally due to e.g. pending signal.
948 * Otherwise, function returns one-past-the-last PFN of isolated page
949 * (which may be greater than end_pfn if end fell in a middle of a THP page).
950 */
951unsigned long
952isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
953 unsigned long end_pfn)
954{
955 unsigned long pfn, block_start_pfn, block_end_pfn;
956
957 /* Scan block by block. First and last block may be incomplete */
958 pfn = start_pfn;
959 block_start_pfn = pageblock_start_pfn(pfn);
960 if (block_start_pfn < cc->zone->zone_start_pfn)
961 block_start_pfn = cc->zone->zone_start_pfn;
962 block_end_pfn = pageblock_end_pfn(pfn);
963
964 for (; pfn < end_pfn; pfn = block_end_pfn,
965 block_start_pfn = block_end_pfn,
966 block_end_pfn += pageblock_nr_pages) {
967
968 block_end_pfn = min(block_end_pfn, end_pfn);
969
970 if (!pageblock_pfn_to_page(block_start_pfn,
971 block_end_pfn, cc->zone))
972 continue;
973
974 pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
975 ISOLATE_UNEVICTABLE);
976
977 if (!pfn)
978 break;
979
980 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
981 break;
982 }
983
984 return pfn;
985}
986
987#endif /* CONFIG_COMPACTION || CONFIG_CMA */
988#ifdef CONFIG_COMPACTION
989
990/* Returns true if the page is within a block suitable for migration to */
991static bool suitable_migration_target(struct compact_control *cc,
992 struct page *page)
993{
994 if (cc->ignore_block_suitable)
995 return true;
996
997 /* If the page is a large free page, then disallow migration */
998 if (PageBuddy(page)) {
999 /*
1000 * We are checking page_order without zone->lock taken. But
1001 * the only small danger is that we skip a potentially suitable
1002 * pageblock, so it's not worth to check order for valid range.
1003 */
1004 if (page_order_unsafe(page) >= pageblock_order)
1005 return false;
1006 }
1007
1008 /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
1009 if (migrate_async_suitable(get_pageblock_migratetype(page)))
1010 return true;
1011
1012 /* Otherwise skip the block */
1013 return false;
1014}
1015
1016/*
1017 * Test whether the free scanner has reached the same or lower pageblock than
1018 * the migration scanner, and compaction should thus terminate.
1019 */
1020static inline bool compact_scanners_met(struct compact_control *cc)
1021{
1022 return (cc->free_pfn >> pageblock_order)
1023 <= (cc->migrate_pfn >> pageblock_order);
1024}
1025
1026/*
1027 * Based on information in the current compact_control, find blocks
1028 * suitable for isolating free pages from and then isolate them.
1029 */
1030static void isolate_freepages(struct compact_control *cc)
1031{
1032 struct zone *zone = cc->zone;
1033 struct page *page;
1034 unsigned long block_start_pfn; /* start of current pageblock */
1035 unsigned long isolate_start_pfn; /* exact pfn we start at */
1036 unsigned long block_end_pfn; /* end of current pageblock */
1037 unsigned long low_pfn; /* lowest pfn scanner is able to scan */
1038 struct list_head *freelist = &cc->freepages;
1039
1040 /*
1041 * Initialise the free scanner. The starting point is where we last
1042 * successfully isolated from, zone-cached value, or the end of the
1043 * zone when isolating for the first time. For looping we also need
1044 * this pfn aligned down to the pageblock boundary, because we do
1045 * block_start_pfn -= pageblock_nr_pages in the for loop.
1046 * For ending point, take care when isolating in last pageblock of a
1047 * a zone which ends in the middle of a pageblock.
1048 * The low boundary is the end of the pageblock the migration scanner
1049 * is using.
1050 */
1051 isolate_start_pfn = cc->free_pfn;
1052 block_start_pfn = pageblock_start_pfn(cc->free_pfn);
1053 block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
1054 zone_end_pfn(zone));
1055 low_pfn = pageblock_end_pfn(cc->migrate_pfn);
1056
1057 /*
1058 * Isolate free pages until enough are available to migrate the
1059 * pages on cc->migratepages. We stop searching if the migrate
1060 * and free page scanners meet or enough free pages are isolated.
1061 */
1062 for (; block_start_pfn >= low_pfn;
1063 block_end_pfn = block_start_pfn,
1064 block_start_pfn -= pageblock_nr_pages,
1065 isolate_start_pfn = block_start_pfn) {
1066 /*
1067 * This can iterate a massively long zone without finding any
1068 * suitable migration targets, so periodically check if we need
1069 * to schedule, or even abort async compaction.
1070 */
1071 if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
1072 && compact_should_abort(cc))
1073 break;
1074
1075 page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
1076 zone);
1077 if (!page)
1078 continue;
1079
1080 /* Check the block is suitable for migration */
1081 if (!suitable_migration_target(cc, page))
1082 continue;
1083
1084 /* If isolation recently failed, do not retry */
1085 if (!isolation_suitable(cc, page))
1086 continue;
1087
1088 /* Found a block suitable for isolating free pages from. */
1089 isolate_freepages_block(cc, &isolate_start_pfn, block_end_pfn,
1090 freelist, false);
1091
1092 /*
1093 * If we isolated enough freepages, or aborted due to lock
1094 * contention, terminate.
1095 */
1096 if ((cc->nr_freepages >= cc->nr_migratepages)
1097 || cc->contended) {
1098 if (isolate_start_pfn >= block_end_pfn) {
1099 /*
1100 * Restart at previous pageblock if more
1101 * freepages can be isolated next time.
1102 */
1103 isolate_start_pfn =
1104 block_start_pfn - pageblock_nr_pages;
1105 }
1106 break;
1107 } else if (isolate_start_pfn < block_end_pfn) {
1108 /*
1109 * If isolation failed early, do not continue
1110 * needlessly.
1111 */
1112 break;
1113 }
1114 }
1115
1116 /* __isolate_free_page() does not map the pages */
1117 map_pages(freelist);
1118
1119 /*
1120 * Record where the free scanner will restart next time. Either we
1121 * broke from the loop and set isolate_start_pfn based on the last
1122 * call to isolate_freepages_block(), or we met the migration scanner
1123 * and the loop terminated due to isolate_start_pfn < low_pfn
1124 */
1125 cc->free_pfn = isolate_start_pfn;
1126}
1127
1128/*
1129 * This is a migrate-callback that "allocates" freepages by taking pages
1130 * from the isolated freelists in the block we are migrating to.
1131 */
1132static struct page *compaction_alloc(struct page *migratepage,
1133 unsigned long data,
1134 int **result)
1135{
1136 struct compact_control *cc = (struct compact_control *)data;
1137 struct page *freepage;
1138
1139 /*
1140 * Isolate free pages if necessary, and if we are not aborting due to
1141 * contention.
1142 */
1143 if (list_empty(&cc->freepages)) {
1144 if (!cc->contended)
1145 isolate_freepages(cc);
1146
1147 if (list_empty(&cc->freepages))
1148 return NULL;
1149 }
1150
1151 freepage = list_entry(cc->freepages.next, struct page, lru);
1152 list_del(&freepage->lru);
1153 cc->nr_freepages--;
1154
1155 return freepage;
1156}
1157
1158/*
1159 * This is a migrate-callback that "frees" freepages back to the isolated
1160 * freelist. All pages on the freelist are from the same zone, so there is no
1161 * special handling needed for NUMA.
1162 */
1163static void compaction_free(struct page *page, unsigned long data)
1164{
1165 struct compact_control *cc = (struct compact_control *)data;
1166
1167 list_add(&page->lru, &cc->freepages);
1168 cc->nr_freepages++;
1169}
1170
1171/* possible outcome of isolate_migratepages */
1172typedef enum {
1173 ISOLATE_ABORT, /* Abort compaction now */
1174 ISOLATE_NONE, /* No pages isolated, continue scanning */
1175 ISOLATE_SUCCESS, /* Pages isolated, migrate */
1176} isolate_migrate_t;
1177
1178/*
1179 * Allow userspace to control policy on scanning the unevictable LRU for
1180 * compactable pages.
1181 */
1182int sysctl_compact_unevictable_allowed __read_mostly = 1;
1183
1184/*
1185 * Isolate all pages that can be migrated from the first suitable block,
1186 * starting at the block pointed to by the migrate scanner pfn within
1187 * compact_control.
1188 */
1189static isolate_migrate_t isolate_migratepages(struct zone *zone,
1190 struct compact_control *cc)
1191{
1192 unsigned long block_start_pfn;
1193 unsigned long block_end_pfn;
1194 unsigned long low_pfn;
1195 struct page *page;
1196 const isolate_mode_t isolate_mode =
1197 (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
1198 (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0);
1199
1200 /*
1201 * Start at where we last stopped, or beginning of the zone as
1202 * initialized by compact_zone()
1203 */
1204 low_pfn = cc->migrate_pfn;
1205 block_start_pfn = pageblock_start_pfn(low_pfn);
1206 if (block_start_pfn < zone->zone_start_pfn)
1207 block_start_pfn = zone->zone_start_pfn;
1208
1209 /* Only scan within a pageblock boundary */
1210 block_end_pfn = pageblock_end_pfn(low_pfn);
1211
1212 /*
1213 * Iterate over whole pageblocks until we find the first suitable.
1214 * Do not cross the free scanner.
1215 */
1216 for (; block_end_pfn <= cc->free_pfn;
1217 low_pfn = block_end_pfn,
1218 block_start_pfn = block_end_pfn,
1219 block_end_pfn += pageblock_nr_pages) {
1220
1221 /*
1222 * This can potentially iterate a massively long zone with
1223 * many pageblocks unsuitable, so periodically check if we
1224 * need to schedule, or even abort async compaction.
1225 */
1226 if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
1227 && compact_should_abort(cc))
1228 break;
1229
1230 page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
1231 zone);
1232 if (!page)
1233 continue;
1234
1235 /* If isolation recently failed, do not retry */
1236 if (!isolation_suitable(cc, page))
1237 continue;
1238
1239 /*
1240 * For async compaction, also only scan in MOVABLE blocks.
1241 * Async compaction is optimistic to see if the minimum amount
1242 * of work satisfies the allocation.
1243 */
1244 if (cc->mode == MIGRATE_ASYNC &&
1245 !migrate_async_suitable(get_pageblock_migratetype(page)))
1246 continue;
1247
1248 /* Perform the isolation */
1249 low_pfn = isolate_migratepages_block(cc, low_pfn,
1250 block_end_pfn, isolate_mode);
1251
1252 if (!low_pfn || cc->contended)
1253 return ISOLATE_ABORT;
1254
1255 /*
1256 * Either we isolated something and proceed with migration. Or
1257 * we failed and compact_zone should decide if we should
1258 * continue or not.
1259 */
1260 break;
1261 }
1262
1263 /* Record where migration scanner will be restarted. */
1264 cc->migrate_pfn = low_pfn;
1265
1266 return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
1267}
1268
1269/*
1270 * order == -1 is expected when compacting via
1271 * /proc/sys/vm/compact_memory
1272 */
1273static inline bool is_via_compact_memory(int order)
1274{
1275 return order == -1;
1276}
1277
1278static enum compact_result __compact_finished(struct zone *zone, struct compact_control *cc,
1279 const int migratetype)
1280{
1281 unsigned int order;
1282 unsigned long watermark;
1283
1284 if (cc->contended || fatal_signal_pending(current))
1285 return COMPACT_CONTENDED;
1286
1287 /* Compaction run completes if the migrate and free scanner meet */
1288 if (compact_scanners_met(cc)) {
1289 /* Let the next compaction start anew. */
1290 reset_cached_positions(zone);
1291
1292 /*
1293 * Mark that the PG_migrate_skip information should be cleared
1294 * by kswapd when it goes to sleep. kcompactd does not set the
1295 * flag itself as the decision to be clear should be directly
1296 * based on an allocation request.
1297 */
1298 if (cc->direct_compaction)
1299 zone->compact_blockskip_flush = true;
1300
1301 if (cc->whole_zone)
1302 return COMPACT_COMPLETE;
1303 else
1304 return COMPACT_PARTIAL_SKIPPED;
1305 }
1306
1307 if (is_via_compact_memory(cc->order))
1308 return COMPACT_CONTINUE;
1309
1310 /* Compaction run is not finished if the watermark is not met */
1311 watermark = zone->watermark[cc->alloc_flags & ALLOC_WMARK_MASK];
1312
1313 if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx,
1314 cc->alloc_flags))
1315 return COMPACT_CONTINUE;
1316
1317 /* Direct compactor: Is a suitable page free? */
1318 for (order = cc->order; order < MAX_ORDER; order++) {
1319 struct free_area *area = &zone->free_area[order];
1320 bool can_steal;
1321
1322 /* Job done if page is free of the right migratetype */
1323 if (!list_empty(&area->free_list[migratetype]))
1324 return COMPACT_SUCCESS;
1325
1326#ifdef CONFIG_CMA
1327 /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
1328 if (migratetype == MIGRATE_MOVABLE &&
1329 !list_empty(&area->free_list[MIGRATE_CMA]))
1330 return COMPACT_SUCCESS;
1331#endif
1332 /*
1333 * Job done if allocation would steal freepages from
1334 * other migratetype buddy lists.
1335 */
1336 if (find_suitable_fallback(area, order, migratetype,
1337 true, &can_steal) != -1)
1338 return COMPACT_SUCCESS;
1339 }
1340
1341 return COMPACT_NO_SUITABLE_PAGE;
1342}
1343
1344static enum compact_result compact_finished(struct zone *zone,
1345 struct compact_control *cc,
1346 const int migratetype)
1347{
1348 int ret;
1349
1350 ret = __compact_finished(zone, cc, migratetype);
1351 trace_mm_compaction_finished(zone, cc->order, ret);
1352 if (ret == COMPACT_NO_SUITABLE_PAGE)
1353 ret = COMPACT_CONTINUE;
1354
1355 return ret;
1356}
1357
1358/*
1359 * compaction_suitable: Is this suitable to run compaction on this zone now?
1360 * Returns
1361 * COMPACT_SKIPPED - If there are too few free pages for compaction
1362 * COMPACT_SUCCESS - If the allocation would succeed without compaction
1363 * COMPACT_CONTINUE - If compaction should run now
1364 */
1365static enum compact_result __compaction_suitable(struct zone *zone, int order,
1366 unsigned int alloc_flags,
1367 int classzone_idx,
1368 unsigned long wmark_target)
1369{
1370 unsigned long watermark;
1371
1372 if (is_via_compact_memory(order))
1373 return COMPACT_CONTINUE;
1374
1375 watermark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
1376 /*
1377 * If watermarks for high-order allocation are already met, there
1378 * should be no need for compaction at all.
1379 */
1380 if (zone_watermark_ok(zone, order, watermark, classzone_idx,
1381 alloc_flags))
1382 return COMPACT_SUCCESS;
1383
1384 /*
1385 * Watermarks for order-0 must be met for compaction to be able to
1386 * isolate free pages for migration targets. This means that the
1387 * watermark and alloc_flags have to match, or be more pessimistic than
1388 * the check in __isolate_free_page(). We don't use the direct
1389 * compactor's alloc_flags, as they are not relevant for freepage
1390 * isolation. We however do use the direct compactor's classzone_idx to
1391 * skip over zones where lowmem reserves would prevent allocation even
1392 * if compaction succeeds.
1393 * For costly orders, we require low watermark instead of min for
1394 * compaction to proceed to increase its chances.
1395 * ALLOC_CMA is used, as pages in CMA pageblocks are considered
1396 * suitable migration targets
1397 */
1398 watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ?
1399 low_wmark_pages(zone) : min_wmark_pages(zone);
1400 watermark += compact_gap(order);
1401 if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx,
1402 ALLOC_CMA, wmark_target))
1403 return COMPACT_SKIPPED;
1404
1405 return COMPACT_CONTINUE;
1406}
1407
1408enum compact_result compaction_suitable(struct zone *zone, int order,
1409 unsigned int alloc_flags,
1410 int classzone_idx)
1411{
1412 enum compact_result ret;
1413 int fragindex;
1414
1415 ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx,
1416 zone_page_state(zone, NR_FREE_PAGES));
1417 /*
1418 * fragmentation index determines if allocation failures are due to
1419 * low memory or external fragmentation
1420 *
1421 * index of -1000 would imply allocations might succeed depending on
1422 * watermarks, but we already failed the high-order watermark check
1423 * index towards 0 implies failure is due to lack of memory
1424 * index towards 1000 implies failure is due to fragmentation
1425 *
1426 * Only compact if a failure would be due to fragmentation. Also
1427 * ignore fragindex for non-costly orders where the alternative to
1428 * a successful reclaim/compaction is OOM. Fragindex and the
1429 * vm.extfrag_threshold sysctl is meant as a heuristic to prevent
1430 * excessive compaction for costly orders, but it should not be at the
1431 * expense of system stability.
1432 */
1433 if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) {
1434 fragindex = fragmentation_index(zone, order);
1435 if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
1436 ret = COMPACT_NOT_SUITABLE_ZONE;
1437 }
1438
1439 trace_mm_compaction_suitable(zone, order, ret);
1440 if (ret == COMPACT_NOT_SUITABLE_ZONE)
1441 ret = COMPACT_SKIPPED;
1442
1443 return ret;
1444}
1445
1446bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
1447 int alloc_flags)
1448{
1449 struct zone *zone;
1450 struct zoneref *z;
1451
1452 /*
1453 * Make sure at least one zone would pass __compaction_suitable if we continue
1454 * retrying the reclaim.
1455 */
1456 for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
1457 ac->nodemask) {
1458 unsigned long available;
1459 enum compact_result compact_result;
1460
1461 /*
1462 * Do not consider all the reclaimable memory because we do not
1463 * want to trash just for a single high order allocation which
1464 * is even not guaranteed to appear even if __compaction_suitable
1465 * is happy about the watermark check.
1466 */
1467 available = zone_reclaimable_pages(zone) / order;
1468 available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
1469 compact_result = __compaction_suitable(zone, order, alloc_flags,
1470 ac_classzone_idx(ac), available);
1471 if (compact_result != COMPACT_SKIPPED)
1472 return true;
1473 }
1474
1475 return false;
1476}
1477
1478static enum compact_result compact_zone(struct zone *zone, struct compact_control *cc)
1479{
1480 enum compact_result ret;
1481 unsigned long start_pfn = zone->zone_start_pfn;
1482 unsigned long end_pfn = zone_end_pfn(zone);
1483 const int migratetype = gfpflags_to_migratetype(cc->gfp_mask);
1484 const bool sync = cc->mode != MIGRATE_ASYNC;
1485
1486 ret = compaction_suitable(zone, cc->order, cc->alloc_flags,
1487 cc->classzone_idx);
1488 /* Compaction is likely to fail */
1489 if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
1490 return ret;
1491
1492 /* huh, compaction_suitable is returning something unexpected */
1493 VM_BUG_ON(ret != COMPACT_CONTINUE);
1494
1495 /*
1496 * Clear pageblock skip if there were failures recently and compaction
1497 * is about to be retried after being deferred.
1498 */
1499 if (compaction_restarting(zone, cc->order))
1500 __reset_isolation_suitable(zone);
1501
1502 /*
1503 * Setup to move all movable pages to the end of the zone. Used cached
1504 * information on where the scanners should start (unless we explicitly
1505 * want to compact the whole zone), but check that it is initialised
1506 * by ensuring the values are within zone boundaries.
1507 */
1508 if (cc->whole_zone) {
1509 cc->migrate_pfn = start_pfn;
1510 cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
1511 } else {
1512 cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync];
1513 cc->free_pfn = zone->compact_cached_free_pfn;
1514 if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) {
1515 cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
1516 zone->compact_cached_free_pfn = cc->free_pfn;
1517 }
1518 if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) {
1519 cc->migrate_pfn = start_pfn;
1520 zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
1521 zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
1522 }
1523
1524 if (cc->migrate_pfn == start_pfn)
1525 cc->whole_zone = true;
1526 }
1527
1528 cc->last_migrated_pfn = 0;
1529
1530 trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
1531 cc->free_pfn, end_pfn, sync);
1532
1533 migrate_prep_local();
1534
1535 while ((ret = compact_finished(zone, cc, migratetype)) ==
1536 COMPACT_CONTINUE) {
1537 int err;
1538
1539 switch (isolate_migratepages(zone, cc)) {
1540 case ISOLATE_ABORT:
1541 ret = COMPACT_CONTENDED;
1542 putback_movable_pages(&cc->migratepages);
1543 cc->nr_migratepages = 0;
1544 goto out;
1545 case ISOLATE_NONE:
1546 /*
1547 * We haven't isolated and migrated anything, but
1548 * there might still be unflushed migrations from
1549 * previous cc->order aligned block.
1550 */
1551 goto check_drain;
1552 case ISOLATE_SUCCESS:
1553 ;
1554 }
1555
1556 err = migrate_pages(&cc->migratepages, compaction_alloc,
1557 compaction_free, (unsigned long)cc, cc->mode,
1558 MR_COMPACTION);
1559
1560 trace_mm_compaction_migratepages(cc->nr_migratepages, err,
1561 &cc->migratepages);
1562
1563 /* All pages were either migrated or will be released */
1564 cc->nr_migratepages = 0;
1565 if (err) {
1566 putback_movable_pages(&cc->migratepages);
1567 /*
1568 * migrate_pages() may return -ENOMEM when scanners meet
1569 * and we want compact_finished() to detect it
1570 */
1571 if (err == -ENOMEM && !compact_scanners_met(cc)) {
1572 ret = COMPACT_CONTENDED;
1573 goto out;
1574 }
1575 /*
1576 * We failed to migrate at least one page in the current
1577 * order-aligned block, so skip the rest of it.
1578 */
1579 if (cc->direct_compaction &&
1580 (cc->mode == MIGRATE_ASYNC)) {
1581 cc->migrate_pfn = block_end_pfn(
1582 cc->migrate_pfn - 1, cc->order);
1583 /* Draining pcplists is useless in this case */
1584 cc->last_migrated_pfn = 0;
1585
1586 }
1587 }
1588
1589check_drain:
1590 /*
1591 * Has the migration scanner moved away from the previous
1592 * cc->order aligned block where we migrated from? If yes,
1593 * flush the pages that were freed, so that they can merge and
1594 * compact_finished() can detect immediately if allocation
1595 * would succeed.
1596 */
1597 if (cc->order > 0 && cc->last_migrated_pfn) {
1598 int cpu;
1599 unsigned long current_block_start =
1600 block_start_pfn(cc->migrate_pfn, cc->order);
1601
1602 if (cc->last_migrated_pfn < current_block_start) {
1603 cpu = get_cpu();
1604 lru_add_drain_cpu(cpu);
1605 drain_local_pages(zone);
1606 put_cpu();
1607 /* No more flushing until we migrate again */
1608 cc->last_migrated_pfn = 0;
1609 }
1610 }
1611
1612 }
1613
1614out:
1615 /*
1616 * Release free pages and update where the free scanner should restart,
1617 * so we don't leave any returned pages behind in the next attempt.
1618 */
1619 if (cc->nr_freepages > 0) {
1620 unsigned long free_pfn = release_freepages(&cc->freepages);
1621
1622 cc->nr_freepages = 0;
1623 VM_BUG_ON(free_pfn == 0);
1624 /* The cached pfn is always the first in a pageblock */
1625 free_pfn = pageblock_start_pfn(free_pfn);
1626 /*
1627 * Only go back, not forward. The cached pfn might have been
1628 * already reset to zone end in compact_finished()
1629 */
1630 if (free_pfn > zone->compact_cached_free_pfn)
1631 zone->compact_cached_free_pfn = free_pfn;
1632 }
1633
1634 trace_mm_compaction_end(start_pfn, cc->migrate_pfn,
1635 cc->free_pfn, end_pfn, sync, ret);
1636
1637 return ret;
1638}
1639
1640static enum compact_result compact_zone_order(struct zone *zone, int order,
1641 gfp_t gfp_mask, enum compact_priority prio,
1642 unsigned int alloc_flags, int classzone_idx)
1643{
1644 enum compact_result ret;
1645 struct compact_control cc = {
1646 .nr_freepages = 0,
1647 .nr_migratepages = 0,
1648 .order = order,
1649 .gfp_mask = gfp_mask,
1650 .zone = zone,
1651 .mode = (prio == COMPACT_PRIO_ASYNC) ?
1652 MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT,
1653 .alloc_flags = alloc_flags,
1654 .classzone_idx = classzone_idx,
1655 .direct_compaction = true,
1656 .whole_zone = (prio == MIN_COMPACT_PRIORITY),
1657 .ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY),
1658 .ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY)
1659 };
1660 INIT_LIST_HEAD(&cc.freepages);
1661 INIT_LIST_HEAD(&cc.migratepages);
1662
1663 ret = compact_zone(zone, &cc);
1664
1665 VM_BUG_ON(!list_empty(&cc.freepages));
1666 VM_BUG_ON(!list_empty(&cc.migratepages));
1667
1668 return ret;
1669}
1670
1671int sysctl_extfrag_threshold = 500;
1672
1673/**
1674 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
1675 * @gfp_mask: The GFP mask of the current allocation
1676 * @order: The order of the current allocation
1677 * @alloc_flags: The allocation flags of the current allocation
1678 * @ac: The context of current allocation
1679 * @mode: The migration mode for async, sync light, or sync migration
1680 *
1681 * This is the main entry point for direct page compaction.
1682 */
1683enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
1684 unsigned int alloc_flags, const struct alloc_context *ac,
1685 enum compact_priority prio)
1686{
1687 int may_perform_io = gfp_mask & __GFP_IO;
1688 struct zoneref *z;
1689 struct zone *zone;
1690 enum compact_result rc = COMPACT_SKIPPED;
1691
1692 /*
1693 * Check if the GFP flags allow compaction - GFP_NOIO is really
1694 * tricky context because the migration might require IO
1695 */
1696 if (!may_perform_io)
1697 return COMPACT_SKIPPED;
1698
1699 trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio);
1700
1701 /* Compact each zone in the list */
1702 for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
1703 ac->nodemask) {
1704 enum compact_result status;
1705
1706 if (prio > MIN_COMPACT_PRIORITY
1707 && compaction_deferred(zone, order)) {
1708 rc = max_t(enum compact_result, COMPACT_DEFERRED, rc);
1709 continue;
1710 }
1711
1712 status = compact_zone_order(zone, order, gfp_mask, prio,
1713 alloc_flags, ac_classzone_idx(ac));
1714 rc = max(status, rc);
1715
1716 /* The allocation should succeed, stop compacting */
1717 if (status == COMPACT_SUCCESS) {
1718 /*
1719 * We think the allocation will succeed in this zone,
1720 * but it is not certain, hence the false. The caller
1721 * will repeat this with true if allocation indeed
1722 * succeeds in this zone.
1723 */
1724 compaction_defer_reset(zone, order, false);
1725
1726 break;
1727 }
1728
1729 if (prio != COMPACT_PRIO_ASYNC && (status == COMPACT_COMPLETE ||
1730 status == COMPACT_PARTIAL_SKIPPED))
1731 /*
1732 * We think that allocation won't succeed in this zone
1733 * so we defer compaction there. If it ends up
1734 * succeeding after all, it will be reset.
1735 */
1736 defer_compaction(zone, order);
1737
1738 /*
1739 * We might have stopped compacting due to need_resched() in
1740 * async compaction, or due to a fatal signal detected. In that
1741 * case do not try further zones
1742 */
1743 if ((prio == COMPACT_PRIO_ASYNC && need_resched())
1744 || fatal_signal_pending(current))
1745 break;
1746 }
1747
1748 return rc;
1749}
1750
1751
1752/* Compact all zones within a node */
1753static void compact_node(int nid)
1754{
1755 pg_data_t *pgdat = NODE_DATA(nid);
1756 int zoneid;
1757 struct zone *zone;
1758 struct compact_control cc = {
1759 .order = -1,
1760 .mode = MIGRATE_SYNC,
1761 .ignore_skip_hint = true,
1762 .whole_zone = true,
1763 .gfp_mask = GFP_KERNEL,
1764 };
1765
1766
1767 for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
1768
1769 zone = &pgdat->node_zones[zoneid];
1770 if (!populated_zone(zone))
1771 continue;
1772
1773 cc.nr_freepages = 0;
1774 cc.nr_migratepages = 0;
1775 cc.zone = zone;
1776 INIT_LIST_HEAD(&cc.freepages);
1777 INIT_LIST_HEAD(&cc.migratepages);
1778
1779 compact_zone(zone, &cc);
1780
1781 VM_BUG_ON(!list_empty(&cc.freepages));
1782 VM_BUG_ON(!list_empty(&cc.migratepages));
1783 }
1784}
1785
1786/* Compact all nodes in the system */
1787static void compact_nodes(void)
1788{
1789 int nid;
1790
1791 /* Flush pending updates to the LRU lists */
1792 lru_add_drain_all();
1793
1794 for_each_online_node(nid)
1795 compact_node(nid);
1796}
1797
1798/* The written value is actually unused, all memory is compacted */
1799int sysctl_compact_memory;
1800
1801/*
1802 * This is the entry point for compacting all nodes via
1803 * /proc/sys/vm/compact_memory
1804 */
1805int sysctl_compaction_handler(struct ctl_table *table, int write,
1806 void __user *buffer, size_t *length, loff_t *ppos)
1807{
1808 if (write)
1809 compact_nodes();
1810
1811 return 0;
1812}
1813
1814int sysctl_extfrag_handler(struct ctl_table *table, int write,
1815 void __user *buffer, size_t *length, loff_t *ppos)
1816{
1817 proc_dointvec_minmax(table, write, buffer, length, ppos);
1818
1819 return 0;
1820}
1821
1822#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
1823static ssize_t sysfs_compact_node(struct device *dev,
1824 struct device_attribute *attr,
1825 const char *buf, size_t count)
1826{
1827 int nid = dev->id;
1828
1829 if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
1830 /* Flush pending updates to the LRU lists */
1831 lru_add_drain_all();
1832
1833 compact_node(nid);
1834 }
1835
1836 return count;
1837}
1838static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
1839
1840int compaction_register_node(struct node *node)
1841{
1842 return device_create_file(&node->dev, &dev_attr_compact);
1843}
1844
1845void compaction_unregister_node(struct node *node)
1846{
1847 return device_remove_file(&node->dev, &dev_attr_compact);
1848}
1849#endif /* CONFIG_SYSFS && CONFIG_NUMA */
1850
1851static inline bool kcompactd_work_requested(pg_data_t *pgdat)
1852{
1853 return pgdat->kcompactd_max_order > 0 || kthread_should_stop();
1854}
1855
1856static bool kcompactd_node_suitable(pg_data_t *pgdat)
1857{
1858 int zoneid;
1859 struct zone *zone;
1860 enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx;
1861
1862 for (zoneid = 0; zoneid <= classzone_idx; zoneid++) {
1863 zone = &pgdat->node_zones[zoneid];
1864
1865 if (!populated_zone(zone))
1866 continue;
1867
1868 if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0,
1869 classzone_idx) == COMPACT_CONTINUE)
1870 return true;
1871 }
1872
1873 return false;
1874}
1875
1876static void kcompactd_do_work(pg_data_t *pgdat)
1877{
1878 /*
1879 * With no special task, compact all zones so that a page of requested
1880 * order is allocatable.
1881 */
1882 int zoneid;
1883 struct zone *zone;
1884 struct compact_control cc = {
1885 .order = pgdat->kcompactd_max_order,
1886 .classzone_idx = pgdat->kcompactd_classzone_idx,
1887 .mode = MIGRATE_SYNC_LIGHT,
1888 .ignore_skip_hint = true,
1889 .gfp_mask = GFP_KERNEL,
1890
1891 };
1892 trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order,
1893 cc.classzone_idx);
1894 count_vm_event(KCOMPACTD_WAKE);
1895
1896 for (zoneid = 0; zoneid <= cc.classzone_idx; zoneid++) {
1897 int status;
1898
1899 zone = &pgdat->node_zones[zoneid];
1900 if (!populated_zone(zone))
1901 continue;
1902
1903 if (compaction_deferred(zone, cc.order))
1904 continue;
1905
1906 if (compaction_suitable(zone, cc.order, 0, zoneid) !=
1907 COMPACT_CONTINUE)
1908 continue;
1909
1910 cc.nr_freepages = 0;
1911 cc.nr_migratepages = 0;
1912 cc.zone = zone;
1913 INIT_LIST_HEAD(&cc.freepages);
1914 INIT_LIST_HEAD(&cc.migratepages);
1915
1916 if (kthread_should_stop())
1917 return;
1918 status = compact_zone(zone, &cc);
1919
1920 if (status == COMPACT_SUCCESS) {
1921 compaction_defer_reset(zone, cc.order, false);
1922 } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) {
1923 /*
1924 * We use sync migration mode here, so we defer like
1925 * sync direct compaction does.
1926 */
1927 defer_compaction(zone, cc.order);
1928 }
1929
1930 VM_BUG_ON(!list_empty(&cc.freepages));
1931 VM_BUG_ON(!list_empty(&cc.migratepages));
1932 }
1933
1934 /*
1935 * Regardless of success, we are done until woken up next. But remember
1936 * the requested order/classzone_idx in case it was higher/tighter than
1937 * our current ones
1938 */
1939 if (pgdat->kcompactd_max_order <= cc.order)
1940 pgdat->kcompactd_max_order = 0;
1941 if (pgdat->kcompactd_classzone_idx >= cc.classzone_idx)
1942 pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
1943}
1944
1945void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
1946{
1947 if (!order)
1948 return;
1949
1950 if (pgdat->kcompactd_max_order < order)
1951 pgdat->kcompactd_max_order = order;
1952
1953 if (pgdat->kcompactd_classzone_idx > classzone_idx)
1954 pgdat->kcompactd_classzone_idx = classzone_idx;
1955
1956 if (!waitqueue_active(&pgdat->kcompactd_wait))
1957 return;
1958
1959 if (!kcompactd_node_suitable(pgdat))
1960 return;
1961
1962 trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order,
1963 classzone_idx);
1964 wake_up_interruptible(&pgdat->kcompactd_wait);
1965}
1966
1967/*
1968 * The background compaction daemon, started as a kernel thread
1969 * from the init process.
1970 */
1971static int kcompactd(void *p)
1972{
1973 pg_data_t *pgdat = (pg_data_t*)p;
1974 struct task_struct *tsk = current;
1975
1976 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
1977
1978 if (!cpumask_empty(cpumask))
1979 set_cpus_allowed_ptr(tsk, cpumask);
1980
1981 set_freezable();
1982
1983 pgdat->kcompactd_max_order = 0;
1984 pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
1985
1986 while (!kthread_should_stop()) {
1987 trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
1988 wait_event_freezable(pgdat->kcompactd_wait,
1989 kcompactd_work_requested(pgdat));
1990
1991 kcompactd_do_work(pgdat);
1992 }
1993
1994 return 0;
1995}
1996
1997/*
1998 * This kcompactd start function will be called by init and node-hot-add.
1999 * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added.
2000 */
2001int kcompactd_run(int nid)
2002{
2003 pg_data_t *pgdat = NODE_DATA(nid);
2004 int ret = 0;
2005
2006 if (pgdat->kcompactd)
2007 return 0;
2008
2009 pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid);
2010 if (IS_ERR(pgdat->kcompactd)) {
2011 pr_err("Failed to start kcompactd on node %d\n", nid);
2012 ret = PTR_ERR(pgdat->kcompactd);
2013 pgdat->kcompactd = NULL;
2014 }
2015 return ret;
2016}
2017
2018/*
2019 * Called by memory hotplug when all memory in a node is offlined. Caller must
2020 * hold mem_hotplug_begin/end().
2021 */
2022void kcompactd_stop(int nid)
2023{
2024 struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd;
2025
2026 if (kcompactd) {
2027 kthread_stop(kcompactd);
2028 NODE_DATA(nid)->kcompactd = NULL;
2029 }
2030}
2031
2032/*
2033 * It's optimal to keep kcompactd on the same CPUs as their memory, but
2034 * not required for correctness. So if the last cpu in a node goes
2035 * away, we get changed to run anywhere: as the first one comes back,
2036 * restore their cpu bindings.
2037 */
2038static int kcompactd_cpu_online(unsigned int cpu)
2039{
2040 int nid;
2041
2042 for_each_node_state(nid, N_MEMORY) {
2043 pg_data_t *pgdat = NODE_DATA(nid);
2044 const struct cpumask *mask;
2045
2046 mask = cpumask_of_node(pgdat->node_id);
2047
2048 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2049 /* One of our CPUs online: restore mask */
2050 set_cpus_allowed_ptr(pgdat->kcompactd, mask);
2051 }
2052 return 0;
2053}
2054
2055static int __init kcompactd_init(void)
2056{
2057 int nid;
2058 int ret;
2059
2060 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
2061 "mm/compaction:online",
2062 kcompactd_cpu_online, NULL);
2063 if (ret < 0) {
2064 pr_err("kcompactd: failed to register hotplug callbacks.\n");
2065 return ret;
2066 }
2067
2068 for_each_node_state(nid, N_MEMORY)
2069 kcompactd_run(nid);
2070 return 0;
2071}
2072subsys_initcall(kcompactd_init)
2073
2074#endif /* CONFIG_COMPACTION */