ccf97b02b85f32d38f6f68a41bedf89b9a1ee596
[deliverable/linux.git] / mm / compaction.c
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
26 static inline void count_compact_event(enum vm_event_item item)
27 {
28 count_vm_event(item);
29 }
30
31 static 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 static 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
61 static 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
72 static 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 */
87 void 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 */
102 bool 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 */
126 void 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 */
140 bool 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. */
150 static 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
159 static 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 */
172 static 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
199 void 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 */
218 static 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
251 static inline bool isolation_suitable(struct compact_control *cc,
252 struct page *page)
253 {
254 return true;
255 }
256
257 static 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 */
272 static 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 */
302 static 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 */
335 static 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 */
355 static 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
459 isolate_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 */
514 unsigned long
515 isolate_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 */
582 static 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 */
598 static 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 */
630 static unsigned long
631 isolate_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
780 isolate_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 */
829 unsigned long
830 isolate_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 /*
856 * In case of fatal failure, release everything that might
857 * have been isolated in the previous iteration, and signal
858 * the failure back to caller.
859 */
860 if (!pfn) {
861 putback_movable_pages(&cc->migratepages);
862 cc->nr_migratepages = 0;
863 break;
864 }
865
866 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
867 break;
868 }
869 acct_isolated(cc->zone, cc);
870
871 return pfn;
872 }
873
874 #endif /* CONFIG_COMPACTION || CONFIG_CMA */
875 #ifdef CONFIG_COMPACTION
876
877 /* Returns true if the page is within a block suitable for migration to */
878 static bool suitable_migration_target(struct page *page)
879 {
880 /* If the page is a large free page, then disallow migration */
881 if (PageBuddy(page)) {
882 /*
883 * We are checking page_order without zone->lock taken. But
884 * the only small danger is that we skip a potentially suitable
885 * pageblock, so it's not worth to check order for valid range.
886 */
887 if (page_order_unsafe(page) >= pageblock_order)
888 return false;
889 }
890
891 /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
892 if (migrate_async_suitable(get_pageblock_migratetype(page)))
893 return true;
894
895 /* Otherwise skip the block */
896 return false;
897 }
898
899 /*
900 * Test whether the free scanner has reached the same or lower pageblock than
901 * the migration scanner, and compaction should thus terminate.
902 */
903 static inline bool compact_scanners_met(struct compact_control *cc)
904 {
905 return (cc->free_pfn >> pageblock_order)
906 <= (cc->migrate_pfn >> pageblock_order);
907 }
908
909 /*
910 * Based on information in the current compact_control, find blocks
911 * suitable for isolating free pages from and then isolate them.
912 */
913 static void isolate_freepages(struct compact_control *cc)
914 {
915 struct zone *zone = cc->zone;
916 struct page *page;
917 unsigned long block_start_pfn; /* start of current pageblock */
918 unsigned long isolate_start_pfn; /* exact pfn we start at */
919 unsigned long block_end_pfn; /* end of current pageblock */
920 unsigned long low_pfn; /* lowest pfn scanner is able to scan */
921 struct list_head *freelist = &cc->freepages;
922
923 /*
924 * Initialise the free scanner. The starting point is where we last
925 * successfully isolated from, zone-cached value, or the end of the
926 * zone when isolating for the first time. For looping we also need
927 * this pfn aligned down to the pageblock boundary, because we do
928 * block_start_pfn -= pageblock_nr_pages in the for loop.
929 * For ending point, take care when isolating in last pageblock of a
930 * a zone which ends in the middle of a pageblock.
931 * The low boundary is the end of the pageblock the migration scanner
932 * is using.
933 */
934 isolate_start_pfn = cc->free_pfn;
935 block_start_pfn = cc->free_pfn & ~(pageblock_nr_pages-1);
936 block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
937 zone_end_pfn(zone));
938 low_pfn = ALIGN(cc->migrate_pfn + 1, pageblock_nr_pages);
939
940 /*
941 * Isolate free pages until enough are available to migrate the
942 * pages on cc->migratepages. We stop searching if the migrate
943 * and free page scanners meet or enough free pages are isolated.
944 */
945 for (; block_start_pfn >= low_pfn;
946 block_end_pfn = block_start_pfn,
947 block_start_pfn -= pageblock_nr_pages,
948 isolate_start_pfn = block_start_pfn) {
949
950 /*
951 * This can iterate a massively long zone without finding any
952 * suitable migration targets, so periodically check if we need
953 * to schedule, or even abort async compaction.
954 */
955 if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
956 && compact_should_abort(cc))
957 break;
958
959 page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
960 zone);
961 if (!page)
962 continue;
963
964 /* Check the block is suitable for migration */
965 if (!suitable_migration_target(page))
966 continue;
967
968 /* If isolation recently failed, do not retry */
969 if (!isolation_suitable(cc, page))
970 continue;
971
972 /* Found a block suitable for isolating free pages from. */
973 isolate_freepages_block(cc, &isolate_start_pfn,
974 block_end_pfn, freelist, false);
975
976 /*
977 * If we isolated enough freepages, or aborted due to async
978 * compaction being contended, terminate the loop.
979 * Remember where the free scanner should restart next time,
980 * which is where isolate_freepages_block() left off.
981 * But if it scanned the whole pageblock, isolate_start_pfn
982 * now points at block_end_pfn, which is the start of the next
983 * pageblock.
984 * In that case we will however want to restart at the start
985 * of the previous pageblock.
986 */
987 if ((cc->nr_freepages >= cc->nr_migratepages)
988 || cc->contended) {
989 if (isolate_start_pfn >= block_end_pfn)
990 isolate_start_pfn =
991 block_start_pfn - pageblock_nr_pages;
992 break;
993 } else {
994 /*
995 * isolate_freepages_block() should not terminate
996 * prematurely unless contended, or isolated enough
997 */
998 VM_BUG_ON(isolate_start_pfn < block_end_pfn);
999 }
1000 }
1001
1002 /* split_free_page does not map the pages */
1003 map_pages(freelist);
1004
1005 /*
1006 * Record where the free scanner will restart next time. Either we
1007 * broke from the loop and set isolate_start_pfn based on the last
1008 * call to isolate_freepages_block(), or we met the migration scanner
1009 * and the loop terminated due to isolate_start_pfn < low_pfn
1010 */
1011 cc->free_pfn = isolate_start_pfn;
1012 }
1013
1014 /*
1015 * This is a migrate-callback that "allocates" freepages by taking pages
1016 * from the isolated freelists in the block we are migrating to.
1017 */
1018 static struct page *compaction_alloc(struct page *migratepage,
1019 unsigned long data,
1020 int **result)
1021 {
1022 struct compact_control *cc = (struct compact_control *)data;
1023 struct page *freepage;
1024
1025 /*
1026 * Isolate free pages if necessary, and if we are not aborting due to
1027 * contention.
1028 */
1029 if (list_empty(&cc->freepages)) {
1030 if (!cc->contended)
1031 isolate_freepages(cc);
1032
1033 if (list_empty(&cc->freepages))
1034 return NULL;
1035 }
1036
1037 freepage = list_entry(cc->freepages.next, struct page, lru);
1038 list_del(&freepage->lru);
1039 cc->nr_freepages--;
1040
1041 return freepage;
1042 }
1043
1044 /*
1045 * This is a migrate-callback that "frees" freepages back to the isolated
1046 * freelist. All pages on the freelist are from the same zone, so there is no
1047 * special handling needed for NUMA.
1048 */
1049 static void compaction_free(struct page *page, unsigned long data)
1050 {
1051 struct compact_control *cc = (struct compact_control *)data;
1052
1053 list_add(&page->lru, &cc->freepages);
1054 cc->nr_freepages++;
1055 }
1056
1057 /* possible outcome of isolate_migratepages */
1058 typedef enum {
1059 ISOLATE_ABORT, /* Abort compaction now */
1060 ISOLATE_NONE, /* No pages isolated, continue scanning */
1061 ISOLATE_SUCCESS, /* Pages isolated, migrate */
1062 } isolate_migrate_t;
1063
1064 /*
1065 * Allow userspace to control policy on scanning the unevictable LRU for
1066 * compactable pages.
1067 */
1068 int sysctl_compact_unevictable_allowed __read_mostly = 1;
1069
1070 /*
1071 * Isolate all pages that can be migrated from the first suitable block,
1072 * starting at the block pointed to by the migrate scanner pfn within
1073 * compact_control.
1074 */
1075 static isolate_migrate_t isolate_migratepages(struct zone *zone,
1076 struct compact_control *cc)
1077 {
1078 unsigned long block_start_pfn;
1079 unsigned long block_end_pfn;
1080 unsigned long low_pfn;
1081 unsigned long isolate_start_pfn;
1082 struct page *page;
1083 const isolate_mode_t isolate_mode =
1084 (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
1085 (cc->mode == MIGRATE_ASYNC ? ISOLATE_ASYNC_MIGRATE : 0);
1086
1087 /*
1088 * Start at where we last stopped, or beginning of the zone as
1089 * initialized by compact_zone()
1090 */
1091 low_pfn = cc->migrate_pfn;
1092 block_start_pfn = cc->migrate_pfn & ~(pageblock_nr_pages - 1);
1093 if (block_start_pfn < zone->zone_start_pfn)
1094 block_start_pfn = zone->zone_start_pfn;
1095
1096 /* Only scan within a pageblock boundary */
1097 block_end_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages);
1098
1099 /*
1100 * Iterate over whole pageblocks until we find the first suitable.
1101 * Do not cross the free scanner.
1102 */
1103 for (; block_end_pfn <= cc->free_pfn;
1104 low_pfn = block_end_pfn,
1105 block_start_pfn = block_end_pfn,
1106 block_end_pfn += pageblock_nr_pages) {
1107
1108 /*
1109 * This can potentially iterate a massively long zone with
1110 * many pageblocks unsuitable, so periodically check if we
1111 * need to schedule, or even abort async compaction.
1112 */
1113 if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
1114 && compact_should_abort(cc))
1115 break;
1116
1117 page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
1118 zone);
1119 if (!page)
1120 continue;
1121
1122 /* If isolation recently failed, do not retry */
1123 if (!isolation_suitable(cc, page))
1124 continue;
1125
1126 /*
1127 * For async compaction, also only scan in MOVABLE blocks.
1128 * Async compaction is optimistic to see if the minimum amount
1129 * of work satisfies the allocation.
1130 */
1131 if (cc->mode == MIGRATE_ASYNC &&
1132 !migrate_async_suitable(get_pageblock_migratetype(page)))
1133 continue;
1134
1135 /* Perform the isolation */
1136 isolate_start_pfn = low_pfn;
1137 low_pfn = isolate_migratepages_block(cc, low_pfn,
1138 block_end_pfn, isolate_mode);
1139
1140 if (!low_pfn || cc->contended) {
1141 acct_isolated(zone, cc);
1142 return ISOLATE_ABORT;
1143 }
1144
1145 /*
1146 * Record where we could have freed pages by migration and not
1147 * yet flushed them to buddy allocator.
1148 * - this is the lowest page that could have been isolated and
1149 * then freed by migration.
1150 */
1151 if (cc->nr_migratepages && !cc->last_migrated_pfn)
1152 cc->last_migrated_pfn = isolate_start_pfn;
1153
1154 /*
1155 * Either we isolated something and proceed with migration. Or
1156 * we failed and compact_zone should decide if we should
1157 * continue or not.
1158 */
1159 break;
1160 }
1161
1162 acct_isolated(zone, cc);
1163 /* Record where migration scanner will be restarted. */
1164 cc->migrate_pfn = low_pfn;
1165
1166 return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
1167 }
1168
1169 /*
1170 * order == -1 is expected when compacting via
1171 * /proc/sys/vm/compact_memory
1172 */
1173 static inline bool is_via_compact_memory(int order)
1174 {
1175 return order == -1;
1176 }
1177
1178 static int __compact_finished(struct zone *zone, struct compact_control *cc,
1179 const int migratetype)
1180 {
1181 unsigned int order;
1182 unsigned long watermark;
1183
1184 if (cc->contended || fatal_signal_pending(current))
1185 return COMPACT_CONTENDED;
1186
1187 /* Compaction run completes if the migrate and free scanner meet */
1188 if (compact_scanners_met(cc)) {
1189 /* Let the next compaction start anew. */
1190 reset_cached_positions(zone);
1191
1192 /*
1193 * Mark that the PG_migrate_skip information should be cleared
1194 * by kswapd when it goes to sleep. kcompactd does not set the
1195 * flag itself as the decision to be clear should be directly
1196 * based on an allocation request.
1197 */
1198 if (cc->direct_compaction)
1199 zone->compact_blockskip_flush = true;
1200
1201 return COMPACT_COMPLETE;
1202 }
1203
1204 if (is_via_compact_memory(cc->order))
1205 return COMPACT_CONTINUE;
1206
1207 /* Compaction run is not finished if the watermark is not met */
1208 watermark = low_wmark_pages(zone);
1209
1210 if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx,
1211 cc->alloc_flags))
1212 return COMPACT_CONTINUE;
1213
1214 /* Direct compactor: Is a suitable page free? */
1215 for (order = cc->order; order < MAX_ORDER; order++) {
1216 struct free_area *area = &zone->free_area[order];
1217 bool can_steal;
1218
1219 /* Job done if page is free of the right migratetype */
1220 if (!list_empty(&area->free_list[migratetype]))
1221 return COMPACT_PARTIAL;
1222
1223 #ifdef CONFIG_CMA
1224 /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
1225 if (migratetype == MIGRATE_MOVABLE &&
1226 !list_empty(&area->free_list[MIGRATE_CMA]))
1227 return COMPACT_PARTIAL;
1228 #endif
1229 /*
1230 * Job done if allocation would steal freepages from
1231 * other migratetype buddy lists.
1232 */
1233 if (find_suitable_fallback(area, order, migratetype,
1234 true, &can_steal) != -1)
1235 return COMPACT_PARTIAL;
1236 }
1237
1238 return COMPACT_NO_SUITABLE_PAGE;
1239 }
1240
1241 static int compact_finished(struct zone *zone, struct compact_control *cc,
1242 const int migratetype)
1243 {
1244 int ret;
1245
1246 ret = __compact_finished(zone, cc, migratetype);
1247 trace_mm_compaction_finished(zone, cc->order, ret);
1248 if (ret == COMPACT_NO_SUITABLE_PAGE)
1249 ret = COMPACT_CONTINUE;
1250
1251 return ret;
1252 }
1253
1254 /*
1255 * compaction_suitable: Is this suitable to run compaction on this zone now?
1256 * Returns
1257 * COMPACT_SKIPPED - If there are too few free pages for compaction
1258 * COMPACT_PARTIAL - If the allocation would succeed without compaction
1259 * COMPACT_CONTINUE - If compaction should run now
1260 */
1261 static unsigned long __compaction_suitable(struct zone *zone, int order,
1262 int alloc_flags, int classzone_idx)
1263 {
1264 int fragindex;
1265 unsigned long watermark;
1266
1267 if (is_via_compact_memory(order))
1268 return COMPACT_CONTINUE;
1269
1270 watermark = low_wmark_pages(zone);
1271 /*
1272 * If watermarks for high-order allocation are already met, there
1273 * should be no need for compaction at all.
1274 */
1275 if (zone_watermark_ok(zone, order, watermark, classzone_idx,
1276 alloc_flags))
1277 return COMPACT_PARTIAL;
1278
1279 /*
1280 * Watermarks for order-0 must be met for compaction. Note the 2UL.
1281 * This is because during migration, copies of pages need to be
1282 * allocated and for a short time, the footprint is higher
1283 */
1284 watermark += (2UL << order);
1285 if (!zone_watermark_ok(zone, 0, watermark, classzone_idx, alloc_flags))
1286 return COMPACT_SKIPPED;
1287
1288 /*
1289 * fragmentation index determines if allocation failures are due to
1290 * low memory or external fragmentation
1291 *
1292 * index of -1000 would imply allocations might succeed depending on
1293 * watermarks, but we already failed the high-order watermark check
1294 * index towards 0 implies failure is due to lack of memory
1295 * index towards 1000 implies failure is due to fragmentation
1296 *
1297 * Only compact if a failure would be due to fragmentation.
1298 */
1299 fragindex = fragmentation_index(zone, order);
1300 if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
1301 return COMPACT_NOT_SUITABLE_ZONE;
1302
1303 return COMPACT_CONTINUE;
1304 }
1305
1306 unsigned long compaction_suitable(struct zone *zone, int order,
1307 int alloc_flags, int classzone_idx)
1308 {
1309 unsigned long ret;
1310
1311 ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx);
1312 trace_mm_compaction_suitable(zone, order, ret);
1313 if (ret == COMPACT_NOT_SUITABLE_ZONE)
1314 ret = COMPACT_SKIPPED;
1315
1316 return ret;
1317 }
1318
1319 static int compact_zone(struct zone *zone, struct compact_control *cc)
1320 {
1321 int ret;
1322 unsigned long start_pfn = zone->zone_start_pfn;
1323 unsigned long end_pfn = zone_end_pfn(zone);
1324 const int migratetype = gfpflags_to_migratetype(cc->gfp_mask);
1325 const bool sync = cc->mode != MIGRATE_ASYNC;
1326
1327 ret = compaction_suitable(zone, cc->order, cc->alloc_flags,
1328 cc->classzone_idx);
1329 switch (ret) {
1330 case COMPACT_PARTIAL:
1331 case COMPACT_SKIPPED:
1332 /* Compaction is likely to fail */
1333 return ret;
1334 case COMPACT_CONTINUE:
1335 /* Fall through to compaction */
1336 ;
1337 }
1338
1339 /*
1340 * Clear pageblock skip if there were failures recently and compaction
1341 * is about to be retried after being deferred.
1342 */
1343 if (compaction_restarting(zone, cc->order))
1344 __reset_isolation_suitable(zone);
1345
1346 /*
1347 * Setup to move all movable pages to the end of the zone. Used cached
1348 * information on where the scanners should start but check that it
1349 * is initialised by ensuring the values are within zone boundaries.
1350 */
1351 cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync];
1352 cc->free_pfn = zone->compact_cached_free_pfn;
1353 if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) {
1354 cc->free_pfn = round_down(end_pfn - 1, pageblock_nr_pages);
1355 zone->compact_cached_free_pfn = cc->free_pfn;
1356 }
1357 if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) {
1358 cc->migrate_pfn = start_pfn;
1359 zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
1360 zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
1361 }
1362 cc->last_migrated_pfn = 0;
1363
1364 trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
1365 cc->free_pfn, end_pfn, sync);
1366
1367 migrate_prep_local();
1368
1369 while ((ret = compact_finished(zone, cc, migratetype)) ==
1370 COMPACT_CONTINUE) {
1371 int err;
1372
1373 switch (isolate_migratepages(zone, cc)) {
1374 case ISOLATE_ABORT:
1375 ret = COMPACT_CONTENDED;
1376 putback_movable_pages(&cc->migratepages);
1377 cc->nr_migratepages = 0;
1378 goto out;
1379 case ISOLATE_NONE:
1380 /*
1381 * We haven't isolated and migrated anything, but
1382 * there might still be unflushed migrations from
1383 * previous cc->order aligned block.
1384 */
1385 goto check_drain;
1386 case ISOLATE_SUCCESS:
1387 ;
1388 }
1389
1390 err = migrate_pages(&cc->migratepages, compaction_alloc,
1391 compaction_free, (unsigned long)cc, cc->mode,
1392 MR_COMPACTION);
1393
1394 trace_mm_compaction_migratepages(cc->nr_migratepages, err,
1395 &cc->migratepages);
1396
1397 /* All pages were either migrated or will be released */
1398 cc->nr_migratepages = 0;
1399 if (err) {
1400 putback_movable_pages(&cc->migratepages);
1401 /*
1402 * migrate_pages() may return -ENOMEM when scanners meet
1403 * and we want compact_finished() to detect it
1404 */
1405 if (err == -ENOMEM && !compact_scanners_met(cc)) {
1406 ret = COMPACT_CONTENDED;
1407 goto out;
1408 }
1409 }
1410
1411 check_drain:
1412 /*
1413 * Has the migration scanner moved away from the previous
1414 * cc->order aligned block where we migrated from? If yes,
1415 * flush the pages that were freed, so that they can merge and
1416 * compact_finished() can detect immediately if allocation
1417 * would succeed.
1418 */
1419 if (cc->order > 0 && cc->last_migrated_pfn) {
1420 int cpu;
1421 unsigned long current_block_start =
1422 cc->migrate_pfn & ~((1UL << cc->order) - 1);
1423
1424 if (cc->last_migrated_pfn < current_block_start) {
1425 cpu = get_cpu();
1426 lru_add_drain_cpu(cpu);
1427 drain_local_pages(zone);
1428 put_cpu();
1429 /* No more flushing until we migrate again */
1430 cc->last_migrated_pfn = 0;
1431 }
1432 }
1433
1434 }
1435
1436 out:
1437 /*
1438 * Release free pages and update where the free scanner should restart,
1439 * so we don't leave any returned pages behind in the next attempt.
1440 */
1441 if (cc->nr_freepages > 0) {
1442 unsigned long free_pfn = release_freepages(&cc->freepages);
1443
1444 cc->nr_freepages = 0;
1445 VM_BUG_ON(free_pfn == 0);
1446 /* The cached pfn is always the first in a pageblock */
1447 free_pfn &= ~(pageblock_nr_pages-1);
1448 /*
1449 * Only go back, not forward. The cached pfn might have been
1450 * already reset to zone end in compact_finished()
1451 */
1452 if (free_pfn > zone->compact_cached_free_pfn)
1453 zone->compact_cached_free_pfn = free_pfn;
1454 }
1455
1456 trace_mm_compaction_end(start_pfn, cc->migrate_pfn,
1457 cc->free_pfn, end_pfn, sync, ret);
1458
1459 if (ret == COMPACT_CONTENDED)
1460 ret = COMPACT_PARTIAL;
1461
1462 return ret;
1463 }
1464
1465 static unsigned long compact_zone_order(struct zone *zone, int order,
1466 gfp_t gfp_mask, enum migrate_mode mode, int *contended,
1467 int alloc_flags, int classzone_idx)
1468 {
1469 unsigned long ret;
1470 struct compact_control cc = {
1471 .nr_freepages = 0,
1472 .nr_migratepages = 0,
1473 .order = order,
1474 .gfp_mask = gfp_mask,
1475 .zone = zone,
1476 .mode = mode,
1477 .alloc_flags = alloc_flags,
1478 .classzone_idx = classzone_idx,
1479 .direct_compaction = true,
1480 };
1481 INIT_LIST_HEAD(&cc.freepages);
1482 INIT_LIST_HEAD(&cc.migratepages);
1483
1484 ret = compact_zone(zone, &cc);
1485
1486 VM_BUG_ON(!list_empty(&cc.freepages));
1487 VM_BUG_ON(!list_empty(&cc.migratepages));
1488
1489 *contended = cc.contended;
1490 return ret;
1491 }
1492
1493 int sysctl_extfrag_threshold = 500;
1494
1495 /**
1496 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
1497 * @gfp_mask: The GFP mask of the current allocation
1498 * @order: The order of the current allocation
1499 * @alloc_flags: The allocation flags of the current allocation
1500 * @ac: The context of current allocation
1501 * @mode: The migration mode for async, sync light, or sync migration
1502 * @contended: Return value that determines if compaction was aborted due to
1503 * need_resched() or lock contention
1504 *
1505 * This is the main entry point for direct page compaction.
1506 */
1507 unsigned long try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
1508 int alloc_flags, const struct alloc_context *ac,
1509 enum migrate_mode mode, int *contended)
1510 {
1511 int may_enter_fs = gfp_mask & __GFP_FS;
1512 int may_perform_io = gfp_mask & __GFP_IO;
1513 struct zoneref *z;
1514 struct zone *zone;
1515 int rc = COMPACT_DEFERRED;
1516 int all_zones_contended = COMPACT_CONTENDED_LOCK; /* init for &= op */
1517
1518 *contended = COMPACT_CONTENDED_NONE;
1519
1520 /* Check if the GFP flags allow compaction */
1521 if (!order || !may_enter_fs || !may_perform_io)
1522 return COMPACT_SKIPPED;
1523
1524 trace_mm_compaction_try_to_compact_pages(order, gfp_mask, mode);
1525
1526 /* Compact each zone in the list */
1527 for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
1528 ac->nodemask) {
1529 int status;
1530 int zone_contended;
1531
1532 if (compaction_deferred(zone, order))
1533 continue;
1534
1535 status = compact_zone_order(zone, order, gfp_mask, mode,
1536 &zone_contended, alloc_flags,
1537 ac->classzone_idx);
1538 rc = max(status, rc);
1539 /*
1540 * It takes at least one zone that wasn't lock contended
1541 * to clear all_zones_contended.
1542 */
1543 all_zones_contended &= zone_contended;
1544
1545 /* If a normal allocation would succeed, stop compacting */
1546 if (zone_watermark_ok(zone, order, low_wmark_pages(zone),
1547 ac->classzone_idx, alloc_flags)) {
1548 /*
1549 * We think the allocation will succeed in this zone,
1550 * but it is not certain, hence the false. The caller
1551 * will repeat this with true if allocation indeed
1552 * succeeds in this zone.
1553 */
1554 compaction_defer_reset(zone, order, false);
1555 /*
1556 * It is possible that async compaction aborted due to
1557 * need_resched() and the watermarks were ok thanks to
1558 * somebody else freeing memory. The allocation can
1559 * however still fail so we better signal the
1560 * need_resched() contention anyway (this will not
1561 * prevent the allocation attempt).
1562 */
1563 if (zone_contended == COMPACT_CONTENDED_SCHED)
1564 *contended = COMPACT_CONTENDED_SCHED;
1565
1566 goto break_loop;
1567 }
1568
1569 if (mode != MIGRATE_ASYNC && status == COMPACT_COMPLETE) {
1570 /*
1571 * We think that allocation won't succeed in this zone
1572 * so we defer compaction there. If it ends up
1573 * succeeding after all, it will be reset.
1574 */
1575 defer_compaction(zone, order);
1576 }
1577
1578 /*
1579 * We might have stopped compacting due to need_resched() in
1580 * async compaction, or due to a fatal signal detected. In that
1581 * case do not try further zones and signal need_resched()
1582 * contention.
1583 */
1584 if ((zone_contended == COMPACT_CONTENDED_SCHED)
1585 || fatal_signal_pending(current)) {
1586 *contended = COMPACT_CONTENDED_SCHED;
1587 goto break_loop;
1588 }
1589
1590 continue;
1591 break_loop:
1592 /*
1593 * We might not have tried all the zones, so be conservative
1594 * and assume they are not all lock contended.
1595 */
1596 all_zones_contended = 0;
1597 break;
1598 }
1599
1600 /*
1601 * If at least one zone wasn't deferred or skipped, we report if all
1602 * zones that were tried were lock contended.
1603 */
1604 if (rc > COMPACT_SKIPPED && all_zones_contended)
1605 *contended = COMPACT_CONTENDED_LOCK;
1606
1607 return rc;
1608 }
1609
1610
1611 /* Compact all zones within a node */
1612 static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
1613 {
1614 int zoneid;
1615 struct zone *zone;
1616
1617 for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
1618
1619 zone = &pgdat->node_zones[zoneid];
1620 if (!populated_zone(zone))
1621 continue;
1622
1623 cc->nr_freepages = 0;
1624 cc->nr_migratepages = 0;
1625 cc->zone = zone;
1626 INIT_LIST_HEAD(&cc->freepages);
1627 INIT_LIST_HEAD(&cc->migratepages);
1628
1629 /*
1630 * When called via /proc/sys/vm/compact_memory
1631 * this makes sure we compact the whole zone regardless of
1632 * cached scanner positions.
1633 */
1634 if (is_via_compact_memory(cc->order))
1635 __reset_isolation_suitable(zone);
1636
1637 if (is_via_compact_memory(cc->order) ||
1638 !compaction_deferred(zone, cc->order))
1639 compact_zone(zone, cc);
1640
1641 VM_BUG_ON(!list_empty(&cc->freepages));
1642 VM_BUG_ON(!list_empty(&cc->migratepages));
1643
1644 if (is_via_compact_memory(cc->order))
1645 continue;
1646
1647 if (zone_watermark_ok(zone, cc->order,
1648 low_wmark_pages(zone), 0, 0))
1649 compaction_defer_reset(zone, cc->order, false);
1650 }
1651 }
1652
1653 void compact_pgdat(pg_data_t *pgdat, int order)
1654 {
1655 struct compact_control cc = {
1656 .order = order,
1657 .mode = MIGRATE_ASYNC,
1658 };
1659
1660 if (!order)
1661 return;
1662
1663 __compact_pgdat(pgdat, &cc);
1664 }
1665
1666 static void compact_node(int nid)
1667 {
1668 struct compact_control cc = {
1669 .order = -1,
1670 .mode = MIGRATE_SYNC,
1671 .ignore_skip_hint = true,
1672 };
1673
1674 __compact_pgdat(NODE_DATA(nid), &cc);
1675 }
1676
1677 /* Compact all nodes in the system */
1678 static void compact_nodes(void)
1679 {
1680 int nid;
1681
1682 /* Flush pending updates to the LRU lists */
1683 lru_add_drain_all();
1684
1685 for_each_online_node(nid)
1686 compact_node(nid);
1687 }
1688
1689 /* The written value is actually unused, all memory is compacted */
1690 int sysctl_compact_memory;
1691
1692 /*
1693 * This is the entry point for compacting all nodes via
1694 * /proc/sys/vm/compact_memory
1695 */
1696 int sysctl_compaction_handler(struct ctl_table *table, int write,
1697 void __user *buffer, size_t *length, loff_t *ppos)
1698 {
1699 if (write)
1700 compact_nodes();
1701
1702 return 0;
1703 }
1704
1705 int sysctl_extfrag_handler(struct ctl_table *table, int write,
1706 void __user *buffer, size_t *length, loff_t *ppos)
1707 {
1708 proc_dointvec_minmax(table, write, buffer, length, ppos);
1709
1710 return 0;
1711 }
1712
1713 #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
1714 static ssize_t sysfs_compact_node(struct device *dev,
1715 struct device_attribute *attr,
1716 const char *buf, size_t count)
1717 {
1718 int nid = dev->id;
1719
1720 if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
1721 /* Flush pending updates to the LRU lists */
1722 lru_add_drain_all();
1723
1724 compact_node(nid);
1725 }
1726
1727 return count;
1728 }
1729 static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
1730
1731 int compaction_register_node(struct node *node)
1732 {
1733 return device_create_file(&node->dev, &dev_attr_compact);
1734 }
1735
1736 void compaction_unregister_node(struct node *node)
1737 {
1738 return device_remove_file(&node->dev, &dev_attr_compact);
1739 }
1740 #endif /* CONFIG_SYSFS && CONFIG_NUMA */
1741
1742 static inline bool kcompactd_work_requested(pg_data_t *pgdat)
1743 {
1744 return pgdat->kcompactd_max_order > 0;
1745 }
1746
1747 static bool kcompactd_node_suitable(pg_data_t *pgdat)
1748 {
1749 int zoneid;
1750 struct zone *zone;
1751 enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx;
1752
1753 for (zoneid = 0; zoneid < classzone_idx; zoneid++) {
1754 zone = &pgdat->node_zones[zoneid];
1755
1756 if (!populated_zone(zone))
1757 continue;
1758
1759 if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0,
1760 classzone_idx) == COMPACT_CONTINUE)
1761 return true;
1762 }
1763
1764 return false;
1765 }
1766
1767 static void kcompactd_do_work(pg_data_t *pgdat)
1768 {
1769 /*
1770 * With no special task, compact all zones so that a page of requested
1771 * order is allocatable.
1772 */
1773 int zoneid;
1774 struct zone *zone;
1775 struct compact_control cc = {
1776 .order = pgdat->kcompactd_max_order,
1777 .classzone_idx = pgdat->kcompactd_classzone_idx,
1778 .mode = MIGRATE_SYNC_LIGHT,
1779 .ignore_skip_hint = true,
1780
1781 };
1782 bool success = false;
1783
1784 trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order,
1785 cc.classzone_idx);
1786 count_vm_event(KCOMPACTD_WAKE);
1787
1788 for (zoneid = 0; zoneid < cc.classzone_idx; zoneid++) {
1789 int status;
1790
1791 zone = &pgdat->node_zones[zoneid];
1792 if (!populated_zone(zone))
1793 continue;
1794
1795 if (compaction_deferred(zone, cc.order))
1796 continue;
1797
1798 if (compaction_suitable(zone, cc.order, 0, zoneid) !=
1799 COMPACT_CONTINUE)
1800 continue;
1801
1802 cc.nr_freepages = 0;
1803 cc.nr_migratepages = 0;
1804 cc.zone = zone;
1805 INIT_LIST_HEAD(&cc.freepages);
1806 INIT_LIST_HEAD(&cc.migratepages);
1807
1808 status = compact_zone(zone, &cc);
1809
1810 if (zone_watermark_ok(zone, cc.order, low_wmark_pages(zone),
1811 cc.classzone_idx, 0)) {
1812 success = true;
1813 compaction_defer_reset(zone, cc.order, false);
1814 } else if (status == COMPACT_COMPLETE) {
1815 /*
1816 * We use sync migration mode here, so we defer like
1817 * sync direct compaction does.
1818 */
1819 defer_compaction(zone, cc.order);
1820 }
1821
1822 VM_BUG_ON(!list_empty(&cc.freepages));
1823 VM_BUG_ON(!list_empty(&cc.migratepages));
1824 }
1825
1826 /*
1827 * Regardless of success, we are done until woken up next. But remember
1828 * the requested order/classzone_idx in case it was higher/tighter than
1829 * our current ones
1830 */
1831 if (pgdat->kcompactd_max_order <= cc.order)
1832 pgdat->kcompactd_max_order = 0;
1833 if (pgdat->kcompactd_classzone_idx >= cc.classzone_idx)
1834 pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
1835 }
1836
1837 void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
1838 {
1839 if (!order)
1840 return;
1841
1842 if (pgdat->kcompactd_max_order < order)
1843 pgdat->kcompactd_max_order = order;
1844
1845 if (pgdat->kcompactd_classzone_idx > classzone_idx)
1846 pgdat->kcompactd_classzone_idx = classzone_idx;
1847
1848 if (!waitqueue_active(&pgdat->kcompactd_wait))
1849 return;
1850
1851 if (!kcompactd_node_suitable(pgdat))
1852 return;
1853
1854 trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order,
1855 classzone_idx);
1856 wake_up_interruptible(&pgdat->kcompactd_wait);
1857 }
1858
1859 /*
1860 * The background compaction daemon, started as a kernel thread
1861 * from the init process.
1862 */
1863 static int kcompactd(void *p)
1864 {
1865 pg_data_t *pgdat = (pg_data_t*)p;
1866 struct task_struct *tsk = current;
1867
1868 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
1869
1870 if (!cpumask_empty(cpumask))
1871 set_cpus_allowed_ptr(tsk, cpumask);
1872
1873 set_freezable();
1874
1875 pgdat->kcompactd_max_order = 0;
1876 pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
1877
1878 while (!kthread_should_stop()) {
1879 trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
1880 wait_event_freezable(pgdat->kcompactd_wait,
1881 kcompactd_work_requested(pgdat));
1882
1883 kcompactd_do_work(pgdat);
1884 }
1885
1886 return 0;
1887 }
1888
1889 /*
1890 * This kcompactd start function will be called by init and node-hot-add.
1891 * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added.
1892 */
1893 int kcompactd_run(int nid)
1894 {
1895 pg_data_t *pgdat = NODE_DATA(nid);
1896 int ret = 0;
1897
1898 if (pgdat->kcompactd)
1899 return 0;
1900
1901 pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid);
1902 if (IS_ERR(pgdat->kcompactd)) {
1903 pr_err("Failed to start kcompactd on node %d\n", nid);
1904 ret = PTR_ERR(pgdat->kcompactd);
1905 pgdat->kcompactd = NULL;
1906 }
1907 return ret;
1908 }
1909
1910 /*
1911 * Called by memory hotplug when all memory in a node is offlined. Caller must
1912 * hold mem_hotplug_begin/end().
1913 */
1914 void kcompactd_stop(int nid)
1915 {
1916 struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd;
1917
1918 if (kcompactd) {
1919 kthread_stop(kcompactd);
1920 NODE_DATA(nid)->kcompactd = NULL;
1921 }
1922 }
1923
1924 /*
1925 * It's optimal to keep kcompactd on the same CPUs as their memory, but
1926 * not required for correctness. So if the last cpu in a node goes
1927 * away, we get changed to run anywhere: as the first one comes back,
1928 * restore their cpu bindings.
1929 */
1930 static int cpu_callback(struct notifier_block *nfb, unsigned long action,
1931 void *hcpu)
1932 {
1933 int nid;
1934
1935 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
1936 for_each_node_state(nid, N_MEMORY) {
1937 pg_data_t *pgdat = NODE_DATA(nid);
1938 const struct cpumask *mask;
1939
1940 mask = cpumask_of_node(pgdat->node_id);
1941
1942 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
1943 /* One of our CPUs online: restore mask */
1944 set_cpus_allowed_ptr(pgdat->kcompactd, mask);
1945 }
1946 }
1947 return NOTIFY_OK;
1948 }
1949
1950 static int __init kcompactd_init(void)
1951 {
1952 int nid;
1953
1954 for_each_node_state(nid, N_MEMORY)
1955 kcompactd_run(nid);
1956 hotcpu_notifier(cpu_callback, 0);
1957 return 0;
1958 }
1959 subsys_initcall(kcompactd_init)
1960
1961 #endif /* CONFIG_COMPACTION */
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