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748446bb
MG
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 */
698b1b30 10#include <linux/cpu.h>
748446bb
MG
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>
76ab0f53 16#include <linux/sysctl.h>
ed4a6d7f 17#include <linux/sysfs.h>
bf6bddf1 18#include <linux/balloon_compaction.h>
194159fb 19#include <linux/page-isolation.h>
b8c73fc2 20#include <linux/kasan.h>
698b1b30
VB
21#include <linux/kthread.h>
22#include <linux/freezer.h>
748446bb
MG
23#include "internal.h"
24
010fc29a
MK
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
ff9543fd
MN
40#if defined CONFIG_COMPACTION || defined CONFIG_CMA
41
b7aba698
MG
42#define CREATE_TRACE_POINTS
43#include <trace/events/compaction.h>
44
06b6640a
VB
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
748446bb
MG
50static unsigned long release_freepages(struct list_head *freelist)
51{
52 struct page *page, *next;
6bace090 53 unsigned long high_pfn = 0;
748446bb
MG
54
55 list_for_each_entry_safe(page, next, freelist, lru) {
6bace090 56 unsigned long pfn = page_to_pfn(page);
748446bb
MG
57 list_del(&page->lru);
58 __free_page(page);
6bace090
VB
59 if (pfn > high_pfn)
60 high_pfn = pfn;
748446bb
MG
61 }
62
6bace090 63 return high_pfn;
748446bb
MG
64}
65
ff9543fd
MN
66static void map_pages(struct list_head *list)
67{
68 struct page *page;
69
70 list_for_each_entry(page, list, lru) {
71 arch_alloc_page(page, 0);
72 kernel_map_pages(page, 1, 1);
b8c73fc2 73 kasan_alloc_pages(page, 0);
ff9543fd
MN
74 }
75}
76
47118af0
MN
77static inline bool migrate_async_suitable(int migratetype)
78{
79 return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE;
80}
81
bb13ffeb 82#ifdef CONFIG_COMPACTION
24e2716f
JK
83
84/* Do not skip compaction more than 64 times */
85#define COMPACT_MAX_DEFER_SHIFT 6
86
87/*
88 * Compaction is deferred when compaction fails to result in a page
89 * allocation success. 1 << compact_defer_limit compactions are skipped up
90 * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
91 */
92void defer_compaction(struct zone *zone, int order)
93{
94 zone->compact_considered = 0;
95 zone->compact_defer_shift++;
96
97 if (order < zone->compact_order_failed)
98 zone->compact_order_failed = order;
99
100 if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
101 zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
102
103 trace_mm_compaction_defer_compaction(zone, order);
104}
105
106/* Returns true if compaction should be skipped this time */
107bool compaction_deferred(struct zone *zone, int order)
108{
109 unsigned long defer_limit = 1UL << zone->compact_defer_shift;
110
111 if (order < zone->compact_order_failed)
112 return false;
113
114 /* Avoid possible overflow */
115 if (++zone->compact_considered > defer_limit)
116 zone->compact_considered = defer_limit;
117
118 if (zone->compact_considered >= defer_limit)
119 return false;
120
121 trace_mm_compaction_deferred(zone, order);
122
123 return true;
124}
125
126/*
127 * Update defer tracking counters after successful compaction of given order,
128 * which means an allocation either succeeded (alloc_success == true) or is
129 * expected to succeed.
130 */
131void compaction_defer_reset(struct zone *zone, int order,
132 bool alloc_success)
133{
134 if (alloc_success) {
135 zone->compact_considered = 0;
136 zone->compact_defer_shift = 0;
137 }
138 if (order >= zone->compact_order_failed)
139 zone->compact_order_failed = order + 1;
140
141 trace_mm_compaction_defer_reset(zone, order);
142}
143
144/* Returns true if restarting compaction after many failures */
145bool compaction_restarting(struct zone *zone, int order)
146{
147 if (order < zone->compact_order_failed)
148 return false;
149
150 return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
151 zone->compact_considered >= 1UL << zone->compact_defer_shift;
152}
153
bb13ffeb
MG
154/* Returns true if the pageblock should be scanned for pages to isolate. */
155static inline bool isolation_suitable(struct compact_control *cc,
156 struct page *page)
157{
158 if (cc->ignore_skip_hint)
159 return true;
160
161 return !get_pageblock_skip(page);
162}
163
02333641
VB
164static void reset_cached_positions(struct zone *zone)
165{
166 zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn;
167 zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn;
623446e4 168 zone->compact_cached_free_pfn =
06b6640a 169 pageblock_start_pfn(zone_end_pfn(zone) - 1);
02333641
VB
170}
171
bb13ffeb
MG
172/*
173 * This function is called to clear all cached information on pageblocks that
174 * should be skipped for page isolation when the migrate and free page scanner
175 * meet.
176 */
62997027 177static void __reset_isolation_suitable(struct zone *zone)
bb13ffeb
MG
178{
179 unsigned long start_pfn = zone->zone_start_pfn;
108bcc96 180 unsigned long end_pfn = zone_end_pfn(zone);
bb13ffeb
MG
181 unsigned long pfn;
182
62997027 183 zone->compact_blockskip_flush = false;
bb13ffeb
MG
184
185 /* Walk the zone and mark every pageblock as suitable for isolation */
186 for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
187 struct page *page;
188
189 cond_resched();
190
191 if (!pfn_valid(pfn))
192 continue;
193
194 page = pfn_to_page(pfn);
195 if (zone != page_zone(page))
196 continue;
197
198 clear_pageblock_skip(page);
199 }
02333641
VB
200
201 reset_cached_positions(zone);
bb13ffeb
MG
202}
203
62997027
MG
204void reset_isolation_suitable(pg_data_t *pgdat)
205{
206 int zoneid;
207
208 for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
209 struct zone *zone = &pgdat->node_zones[zoneid];
210 if (!populated_zone(zone))
211 continue;
212
213 /* Only flush if a full compaction finished recently */
214 if (zone->compact_blockskip_flush)
215 __reset_isolation_suitable(zone);
216 }
217}
218
bb13ffeb
MG
219/*
220 * If no pages were isolated then mark this pageblock to be skipped in the
62997027 221 * future. The information is later cleared by __reset_isolation_suitable().
bb13ffeb 222 */
c89511ab
MG
223static void update_pageblock_skip(struct compact_control *cc,
224 struct page *page, unsigned long nr_isolated,
edc2ca61 225 bool migrate_scanner)
bb13ffeb 226{
c89511ab 227 struct zone *zone = cc->zone;
35979ef3 228 unsigned long pfn;
6815bf3f
JK
229
230 if (cc->ignore_skip_hint)
231 return;
232
bb13ffeb
MG
233 if (!page)
234 return;
235
35979ef3
DR
236 if (nr_isolated)
237 return;
238
edc2ca61 239 set_pageblock_skip(page);
c89511ab 240
35979ef3
DR
241 pfn = page_to_pfn(page);
242
243 /* Update where async and sync compaction should restart */
244 if (migrate_scanner) {
35979ef3
DR
245 if (pfn > zone->compact_cached_migrate_pfn[0])
246 zone->compact_cached_migrate_pfn[0] = pfn;
e0b9daeb
DR
247 if (cc->mode != MIGRATE_ASYNC &&
248 pfn > zone->compact_cached_migrate_pfn[1])
35979ef3
DR
249 zone->compact_cached_migrate_pfn[1] = pfn;
250 } else {
35979ef3
DR
251 if (pfn < zone->compact_cached_free_pfn)
252 zone->compact_cached_free_pfn = pfn;
c89511ab 253 }
bb13ffeb
MG
254}
255#else
256static inline bool isolation_suitable(struct compact_control *cc,
257 struct page *page)
258{
259 return true;
260}
261
c89511ab
MG
262static void update_pageblock_skip(struct compact_control *cc,
263 struct page *page, unsigned long nr_isolated,
edc2ca61 264 bool migrate_scanner)
bb13ffeb
MG
265{
266}
267#endif /* CONFIG_COMPACTION */
268
8b44d279
VB
269/*
270 * Compaction requires the taking of some coarse locks that are potentially
271 * very heavily contended. For async compaction, back out if the lock cannot
272 * be taken immediately. For sync compaction, spin on the lock if needed.
273 *
274 * Returns true if the lock is held
275 * Returns false if the lock is not held and compaction should abort
276 */
277static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags,
278 struct compact_control *cc)
2a1402aa 279{
8b44d279
VB
280 if (cc->mode == MIGRATE_ASYNC) {
281 if (!spin_trylock_irqsave(lock, *flags)) {
282 cc->contended = COMPACT_CONTENDED_LOCK;
283 return false;
284 }
285 } else {
286 spin_lock_irqsave(lock, *flags);
287 }
1f9efdef 288
8b44d279 289 return true;
2a1402aa
MG
290}
291
c67fe375
MG
292/*
293 * Compaction requires the taking of some coarse locks that are potentially
8b44d279
VB
294 * very heavily contended. The lock should be periodically unlocked to avoid
295 * having disabled IRQs for a long time, even when there is nobody waiting on
296 * the lock. It might also be that allowing the IRQs will result in
297 * need_resched() becoming true. If scheduling is needed, async compaction
298 * aborts. Sync compaction schedules.
299 * Either compaction type will also abort if a fatal signal is pending.
300 * In either case if the lock was locked, it is dropped and not regained.
c67fe375 301 *
8b44d279
VB
302 * Returns true if compaction should abort due to fatal signal pending, or
303 * async compaction due to need_resched()
304 * Returns false when compaction can continue (sync compaction might have
305 * scheduled)
c67fe375 306 */
8b44d279
VB
307static bool compact_unlock_should_abort(spinlock_t *lock,
308 unsigned long flags, bool *locked, struct compact_control *cc)
c67fe375 309{
8b44d279
VB
310 if (*locked) {
311 spin_unlock_irqrestore(lock, flags);
312 *locked = false;
313 }
1f9efdef 314
8b44d279
VB
315 if (fatal_signal_pending(current)) {
316 cc->contended = COMPACT_CONTENDED_SCHED;
317 return true;
318 }
c67fe375 319
8b44d279 320 if (need_resched()) {
e0b9daeb 321 if (cc->mode == MIGRATE_ASYNC) {
8b44d279
VB
322 cc->contended = COMPACT_CONTENDED_SCHED;
323 return true;
c67fe375 324 }
c67fe375 325 cond_resched();
c67fe375
MG
326 }
327
8b44d279 328 return false;
c67fe375
MG
329}
330
be976572
VB
331/*
332 * Aside from avoiding lock contention, compaction also periodically checks
333 * need_resched() and either schedules in sync compaction or aborts async
8b44d279 334 * compaction. This is similar to what compact_unlock_should_abort() does, but
be976572
VB
335 * is used where no lock is concerned.
336 *
337 * Returns false when no scheduling was needed, or sync compaction scheduled.
338 * Returns true when async compaction should abort.
339 */
340static inline bool compact_should_abort(struct compact_control *cc)
341{
342 /* async compaction aborts if contended */
343 if (need_resched()) {
344 if (cc->mode == MIGRATE_ASYNC) {
1f9efdef 345 cc->contended = COMPACT_CONTENDED_SCHED;
be976572
VB
346 return true;
347 }
348
349 cond_resched();
350 }
351
352 return false;
353}
354
85aa125f 355/*
9e4be470
JM
356 * Isolate free pages onto a private freelist. If @strict is true, will abort
357 * returning 0 on any invalid PFNs or non-free pages inside of the pageblock
358 * (even though it may still end up isolating some pages).
85aa125f 359 */
f40d1e42 360static unsigned long isolate_freepages_block(struct compact_control *cc,
e14c720e 361 unsigned long *start_pfn,
85aa125f
MN
362 unsigned long end_pfn,
363 struct list_head *freelist,
364 bool strict)
748446bb 365{
b7aba698 366 int nr_scanned = 0, total_isolated = 0;
bb13ffeb 367 struct page *cursor, *valid_page = NULL;
b8b2d825 368 unsigned long flags = 0;
f40d1e42 369 bool locked = false;
e14c720e 370 unsigned long blockpfn = *start_pfn;
748446bb 371
748446bb
MG
372 cursor = pfn_to_page(blockpfn);
373
f40d1e42 374 /* Isolate free pages. */
748446bb
MG
375 for (; blockpfn < end_pfn; blockpfn++, cursor++) {
376 int isolated, i;
377 struct page *page = cursor;
378
8b44d279
VB
379 /*
380 * Periodically drop the lock (if held) regardless of its
381 * contention, to give chance to IRQs. Abort if fatal signal
382 * pending or async compaction detects need_resched()
383 */
384 if (!(blockpfn % SWAP_CLUSTER_MAX)
385 && compact_unlock_should_abort(&cc->zone->lock, flags,
386 &locked, cc))
387 break;
388
b7aba698 389 nr_scanned++;
f40d1e42 390 if (!pfn_valid_within(blockpfn))
2af120bc
LA
391 goto isolate_fail;
392
bb13ffeb
MG
393 if (!valid_page)
394 valid_page = page;
9fcd6d2e
VB
395
396 /*
397 * For compound pages such as THP and hugetlbfs, we can save
398 * potentially a lot of iterations if we skip them at once.
399 * The check is racy, but we can consider only valid values
400 * and the only danger is skipping too much.
401 */
402 if (PageCompound(page)) {
403 unsigned int comp_order = compound_order(page);
404
405 if (likely(comp_order < MAX_ORDER)) {
406 blockpfn += (1UL << comp_order) - 1;
407 cursor += (1UL << comp_order) - 1;
408 }
409
410 goto isolate_fail;
411 }
412
f40d1e42 413 if (!PageBuddy(page))
2af120bc 414 goto isolate_fail;
f40d1e42
MG
415
416 /*
69b7189f
VB
417 * If we already hold the lock, we can skip some rechecking.
418 * Note that if we hold the lock now, checked_pageblock was
419 * already set in some previous iteration (or strict is true),
420 * so it is correct to skip the suitable migration target
421 * recheck as well.
f40d1e42 422 */
69b7189f
VB
423 if (!locked) {
424 /*
425 * The zone lock must be held to isolate freepages.
426 * Unfortunately this is a very coarse lock and can be
427 * heavily contended if there are parallel allocations
428 * or parallel compactions. For async compaction do not
429 * spin on the lock and we acquire the lock as late as
430 * possible.
431 */
8b44d279
VB
432 locked = compact_trylock_irqsave(&cc->zone->lock,
433 &flags, cc);
69b7189f
VB
434 if (!locked)
435 break;
f40d1e42 436
69b7189f
VB
437 /* Recheck this is a buddy page under lock */
438 if (!PageBuddy(page))
439 goto isolate_fail;
440 }
748446bb
MG
441
442 /* Found a free page, break it into order-0 pages */
443 isolated = split_free_page(page);
444 total_isolated += isolated;
445 for (i = 0; i < isolated; i++) {
446 list_add(&page->lru, freelist);
447 page++;
448 }
449
450 /* If a page was split, advance to the end of it */
451 if (isolated) {
932ff6bb
JK
452 cc->nr_freepages += isolated;
453 if (!strict &&
454 cc->nr_migratepages <= cc->nr_freepages) {
455 blockpfn += isolated;
456 break;
457 }
458
748446bb
MG
459 blockpfn += isolated - 1;
460 cursor += isolated - 1;
2af120bc 461 continue;
748446bb 462 }
2af120bc
LA
463
464isolate_fail:
465 if (strict)
466 break;
467 else
468 continue;
469
748446bb
MG
470 }
471
9fcd6d2e
VB
472 /*
473 * There is a tiny chance that we have read bogus compound_order(),
474 * so be careful to not go outside of the pageblock.
475 */
476 if (unlikely(blockpfn > end_pfn))
477 blockpfn = end_pfn;
478
e34d85f0
JK
479 trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn,
480 nr_scanned, total_isolated);
481
e14c720e
VB
482 /* Record how far we have got within the block */
483 *start_pfn = blockpfn;
484
f40d1e42
MG
485 /*
486 * If strict isolation is requested by CMA then check that all the
487 * pages requested were isolated. If there were any failures, 0 is
488 * returned and CMA will fail.
489 */
2af120bc 490 if (strict && blockpfn < end_pfn)
f40d1e42
MG
491 total_isolated = 0;
492
493 if (locked)
494 spin_unlock_irqrestore(&cc->zone->lock, flags);
495
bb13ffeb
MG
496 /* Update the pageblock-skip if the whole pageblock was scanned */
497 if (blockpfn == end_pfn)
edc2ca61 498 update_pageblock_skip(cc, valid_page, total_isolated, false);
bb13ffeb 499
010fc29a 500 count_compact_events(COMPACTFREE_SCANNED, nr_scanned);
397487db 501 if (total_isolated)
010fc29a 502 count_compact_events(COMPACTISOLATED, total_isolated);
748446bb
MG
503 return total_isolated;
504}
505
85aa125f
MN
506/**
507 * isolate_freepages_range() - isolate free pages.
508 * @start_pfn: The first PFN to start isolating.
509 * @end_pfn: The one-past-last PFN.
510 *
511 * Non-free pages, invalid PFNs, or zone boundaries within the
512 * [start_pfn, end_pfn) range are considered errors, cause function to
513 * undo its actions and return zero.
514 *
515 * Otherwise, function returns one-past-the-last PFN of isolated page
516 * (which may be greater then end_pfn if end fell in a middle of
517 * a free page).
518 */
ff9543fd 519unsigned long
bb13ffeb
MG
520isolate_freepages_range(struct compact_control *cc,
521 unsigned long start_pfn, unsigned long end_pfn)
85aa125f 522{
e1409c32 523 unsigned long isolated, pfn, block_start_pfn, block_end_pfn;
85aa125f
MN
524 LIST_HEAD(freelist);
525
7d49d886 526 pfn = start_pfn;
06b6640a 527 block_start_pfn = pageblock_start_pfn(pfn);
e1409c32
JK
528 if (block_start_pfn < cc->zone->zone_start_pfn)
529 block_start_pfn = cc->zone->zone_start_pfn;
06b6640a 530 block_end_pfn = pageblock_end_pfn(pfn);
7d49d886
VB
531
532 for (; pfn < end_pfn; pfn += isolated,
e1409c32 533 block_start_pfn = block_end_pfn,
7d49d886 534 block_end_pfn += pageblock_nr_pages) {
e14c720e
VB
535 /* Protect pfn from changing by isolate_freepages_block */
536 unsigned long isolate_start_pfn = pfn;
85aa125f 537
85aa125f
MN
538 block_end_pfn = min(block_end_pfn, end_pfn);
539
58420016
JK
540 /*
541 * pfn could pass the block_end_pfn if isolated freepage
542 * is more than pageblock order. In this case, we adjust
543 * scanning range to right one.
544 */
545 if (pfn >= block_end_pfn) {
06b6640a
VB
546 block_start_pfn = pageblock_start_pfn(pfn);
547 block_end_pfn = pageblock_end_pfn(pfn);
58420016
JK
548 block_end_pfn = min(block_end_pfn, end_pfn);
549 }
550
e1409c32
JK
551 if (!pageblock_pfn_to_page(block_start_pfn,
552 block_end_pfn, cc->zone))
7d49d886
VB
553 break;
554
e14c720e
VB
555 isolated = isolate_freepages_block(cc, &isolate_start_pfn,
556 block_end_pfn, &freelist, true);
85aa125f
MN
557
558 /*
559 * In strict mode, isolate_freepages_block() returns 0 if
560 * there are any holes in the block (ie. invalid PFNs or
561 * non-free pages).
562 */
563 if (!isolated)
564 break;
565
566 /*
567 * If we managed to isolate pages, it is always (1 << n) *
568 * pageblock_nr_pages for some non-negative n. (Max order
569 * page may span two pageblocks).
570 */
571 }
572
573 /* split_free_page does not map the pages */
574 map_pages(&freelist);
575
576 if (pfn < end_pfn) {
577 /* Loop terminated early, cleanup. */
578 release_freepages(&freelist);
579 return 0;
580 }
581
582 /* We don't use freelists for anything. */
583 return pfn;
584}
585
748446bb 586/* Update the number of anon and file isolated pages in the zone */
edc2ca61 587static void acct_isolated(struct zone *zone, struct compact_control *cc)
748446bb
MG
588{
589 struct page *page;
b9e84ac1 590 unsigned int count[2] = { 0, };
748446bb 591
edc2ca61
VB
592 if (list_empty(&cc->migratepages))
593 return;
594
b9e84ac1
MK
595 list_for_each_entry(page, &cc->migratepages, lru)
596 count[!!page_is_file_cache(page)]++;
748446bb 597
edc2ca61
VB
598 mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
599 mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
748446bb
MG
600}
601
602/* Similar to reclaim, but different enough that they don't share logic */
603static bool too_many_isolated(struct zone *zone)
604{
bc693045 605 unsigned long active, inactive, isolated;
748446bb
MG
606
607 inactive = zone_page_state(zone, NR_INACTIVE_FILE) +
608 zone_page_state(zone, NR_INACTIVE_ANON);
bc693045
MK
609 active = zone_page_state(zone, NR_ACTIVE_FILE) +
610 zone_page_state(zone, NR_ACTIVE_ANON);
748446bb
MG
611 isolated = zone_page_state(zone, NR_ISOLATED_FILE) +
612 zone_page_state(zone, NR_ISOLATED_ANON);
613
bc693045 614 return isolated > (inactive + active) / 2;
748446bb
MG
615}
616
2fe86e00 617/**
edc2ca61
VB
618 * isolate_migratepages_block() - isolate all migrate-able pages within
619 * a single pageblock
2fe86e00 620 * @cc: Compaction control structure.
edc2ca61
VB
621 * @low_pfn: The first PFN to isolate
622 * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
623 * @isolate_mode: Isolation mode to be used.
2fe86e00
MN
624 *
625 * Isolate all pages that can be migrated from the range specified by
edc2ca61
VB
626 * [low_pfn, end_pfn). The range is expected to be within same pageblock.
627 * Returns zero if there is a fatal signal pending, otherwise PFN of the
628 * first page that was not scanned (which may be both less, equal to or more
629 * than end_pfn).
2fe86e00 630 *
edc2ca61
VB
631 * The pages are isolated on cc->migratepages list (not required to be empty),
632 * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field
633 * is neither read nor updated.
748446bb 634 */
edc2ca61
VB
635static unsigned long
636isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
637 unsigned long end_pfn, isolate_mode_t isolate_mode)
748446bb 638{
edc2ca61 639 struct zone *zone = cc->zone;
b7aba698 640 unsigned long nr_scanned = 0, nr_isolated = 0;
fa9add64 641 struct lruvec *lruvec;
b8b2d825 642 unsigned long flags = 0;
2a1402aa 643 bool locked = false;
bb13ffeb 644 struct page *page = NULL, *valid_page = NULL;
e34d85f0 645 unsigned long start_pfn = low_pfn;
fdd048e1
VB
646 bool skip_on_failure = false;
647 unsigned long next_skip_pfn = 0;
748446bb 648
748446bb
MG
649 /*
650 * Ensure that there are not too many pages isolated from the LRU
651 * list by either parallel reclaimers or compaction. If there are,
652 * delay for some time until fewer pages are isolated
653 */
654 while (unlikely(too_many_isolated(zone))) {
f9e35b3b 655 /* async migration should just abort */
e0b9daeb 656 if (cc->mode == MIGRATE_ASYNC)
2fe86e00 657 return 0;
f9e35b3b 658
748446bb
MG
659 congestion_wait(BLK_RW_ASYNC, HZ/10);
660
661 if (fatal_signal_pending(current))
2fe86e00 662 return 0;
748446bb
MG
663 }
664
be976572
VB
665 if (compact_should_abort(cc))
666 return 0;
aeef4b83 667
fdd048e1
VB
668 if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) {
669 skip_on_failure = true;
670 next_skip_pfn = block_end_pfn(low_pfn, cc->order);
671 }
672
748446bb 673 /* Time to isolate some pages for migration */
748446bb 674 for (; low_pfn < end_pfn; low_pfn++) {
29c0dde8
VB
675 bool is_lru;
676
fdd048e1
VB
677 if (skip_on_failure && low_pfn >= next_skip_pfn) {
678 /*
679 * We have isolated all migration candidates in the
680 * previous order-aligned block, and did not skip it due
681 * to failure. We should migrate the pages now and
682 * hopefully succeed compaction.
683 */
684 if (nr_isolated)
685 break;
686
687 /*
688 * We failed to isolate in the previous order-aligned
689 * block. Set the new boundary to the end of the
690 * current block. Note we can't simply increase
691 * next_skip_pfn by 1 << order, as low_pfn might have
692 * been incremented by a higher number due to skipping
693 * a compound or a high-order buddy page in the
694 * previous loop iteration.
695 */
696 next_skip_pfn = block_end_pfn(low_pfn, cc->order);
697 }
698
8b44d279
VB
699 /*
700 * Periodically drop the lock (if held) regardless of its
701 * contention, to give chance to IRQs. Abort async compaction
702 * if contended.
703 */
704 if (!(low_pfn % SWAP_CLUSTER_MAX)
705 && compact_unlock_should_abort(&zone->lru_lock, flags,
706 &locked, cc))
707 break;
c67fe375 708
748446bb 709 if (!pfn_valid_within(low_pfn))
fdd048e1 710 goto isolate_fail;
b7aba698 711 nr_scanned++;
748446bb 712
748446bb 713 page = pfn_to_page(low_pfn);
dc908600 714
bb13ffeb
MG
715 if (!valid_page)
716 valid_page = page;
717
6c14466c 718 /*
99c0fd5e
VB
719 * Skip if free. We read page order here without zone lock
720 * which is generally unsafe, but the race window is small and
721 * the worst thing that can happen is that we skip some
722 * potential isolation targets.
6c14466c 723 */
99c0fd5e
VB
724 if (PageBuddy(page)) {
725 unsigned long freepage_order = page_order_unsafe(page);
726
727 /*
728 * Without lock, we cannot be sure that what we got is
729 * a valid page order. Consider only values in the
730 * valid order range to prevent low_pfn overflow.
731 */
732 if (freepage_order > 0 && freepage_order < MAX_ORDER)
733 low_pfn += (1UL << freepage_order) - 1;
748446bb 734 continue;
99c0fd5e 735 }
748446bb 736
bf6bddf1
RA
737 /*
738 * Check may be lockless but that's ok as we recheck later.
739 * It's possible to migrate LRU pages and balloon pages
740 * Skip any other type of page
741 */
29c0dde8
VB
742 is_lru = PageLRU(page);
743 if (!is_lru) {
bf6bddf1 744 if (unlikely(balloon_page_movable(page))) {
d6d86c0a 745 if (balloon_page_isolate(page)) {
bf6bddf1 746 /* Successfully isolated */
b6c75016 747 goto isolate_success;
bf6bddf1
RA
748 }
749 }
bf6bddf1 750 }
bc835011
AA
751
752 /*
29c0dde8
VB
753 * Regardless of being on LRU, compound pages such as THP and
754 * hugetlbfs are not to be compacted. We can potentially save
755 * a lot of iterations if we skip them at once. The check is
756 * racy, but we can consider only valid values and the only
757 * danger is skipping too much.
bc835011 758 */
29c0dde8
VB
759 if (PageCompound(page)) {
760 unsigned int comp_order = compound_order(page);
761
762 if (likely(comp_order < MAX_ORDER))
763 low_pfn += (1UL << comp_order) - 1;
edc2ca61 764
fdd048e1 765 goto isolate_fail;
2a1402aa
MG
766 }
767
29c0dde8 768 if (!is_lru)
fdd048e1 769 goto isolate_fail;
29c0dde8 770
119d6d59
DR
771 /*
772 * Migration will fail if an anonymous page is pinned in memory,
773 * so avoid taking lru_lock and isolating it unnecessarily in an
774 * admittedly racy check.
775 */
776 if (!page_mapping(page) &&
777 page_count(page) > page_mapcount(page))
fdd048e1 778 goto isolate_fail;
119d6d59 779
69b7189f
VB
780 /* If we already hold the lock, we can skip some rechecking */
781 if (!locked) {
8b44d279
VB
782 locked = compact_trylock_irqsave(&zone->lru_lock,
783 &flags, cc);
69b7189f
VB
784 if (!locked)
785 break;
2a1402aa 786
29c0dde8 787 /* Recheck PageLRU and PageCompound under lock */
69b7189f 788 if (!PageLRU(page))
fdd048e1 789 goto isolate_fail;
29c0dde8
VB
790
791 /*
792 * Page become compound since the non-locked check,
793 * and it's on LRU. It can only be a THP so the order
794 * is safe to read and it's 0 for tail pages.
795 */
796 if (unlikely(PageCompound(page))) {
797 low_pfn += (1UL << compound_order(page)) - 1;
fdd048e1 798 goto isolate_fail;
69b7189f 799 }
bc835011
AA
800 }
801
fa9add64
HD
802 lruvec = mem_cgroup_page_lruvec(page, zone);
803
748446bb 804 /* Try isolate the page */
edc2ca61 805 if (__isolate_lru_page(page, isolate_mode) != 0)
fdd048e1 806 goto isolate_fail;
748446bb 807
29c0dde8 808 VM_BUG_ON_PAGE(PageCompound(page), page);
bc835011 809
748446bb 810 /* Successfully isolated */
fa9add64 811 del_page_from_lru_list(page, lruvec, page_lru(page));
b6c75016
JK
812
813isolate_success:
fdd048e1 814 list_add(&page->lru, &cc->migratepages);
748446bb 815 cc->nr_migratepages++;
b7aba698 816 nr_isolated++;
748446bb 817
a34753d2
VB
818 /*
819 * Record where we could have freed pages by migration and not
820 * yet flushed them to buddy allocator.
821 * - this is the lowest page that was isolated and likely be
822 * then freed by migration.
823 */
824 if (!cc->last_migrated_pfn)
825 cc->last_migrated_pfn = low_pfn;
826
748446bb 827 /* Avoid isolating too much */
31b8384a
HD
828 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
829 ++low_pfn;
748446bb 830 break;
31b8384a 831 }
fdd048e1
VB
832
833 continue;
834isolate_fail:
835 if (!skip_on_failure)
836 continue;
837
838 /*
839 * We have isolated some pages, but then failed. Release them
840 * instead of migrating, as we cannot form the cc->order buddy
841 * page anyway.
842 */
843 if (nr_isolated) {
844 if (locked) {
845 spin_unlock_irqrestore(&zone->lru_lock, flags);
846 locked = false;
847 }
848 acct_isolated(zone, cc);
849 putback_movable_pages(&cc->migratepages);
850 cc->nr_migratepages = 0;
851 cc->last_migrated_pfn = 0;
852 nr_isolated = 0;
853 }
854
855 if (low_pfn < next_skip_pfn) {
856 low_pfn = next_skip_pfn - 1;
857 /*
858 * The check near the loop beginning would have updated
859 * next_skip_pfn too, but this is a bit simpler.
860 */
861 next_skip_pfn += 1UL << cc->order;
862 }
748446bb
MG
863 }
864
99c0fd5e
VB
865 /*
866 * The PageBuddy() check could have potentially brought us outside
867 * the range to be scanned.
868 */
869 if (unlikely(low_pfn > end_pfn))
870 low_pfn = end_pfn;
871
c67fe375
MG
872 if (locked)
873 spin_unlock_irqrestore(&zone->lru_lock, flags);
748446bb 874
50b5b094
VB
875 /*
876 * Update the pageblock-skip information and cached scanner pfn,
877 * if the whole pageblock was scanned without isolating any page.
50b5b094 878 */
35979ef3 879 if (low_pfn == end_pfn)
edc2ca61 880 update_pageblock_skip(cc, valid_page, nr_isolated, true);
bb13ffeb 881
e34d85f0
JK
882 trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn,
883 nr_scanned, nr_isolated);
b7aba698 884
010fc29a 885 count_compact_events(COMPACTMIGRATE_SCANNED, nr_scanned);
397487db 886 if (nr_isolated)
010fc29a 887 count_compact_events(COMPACTISOLATED, nr_isolated);
397487db 888
2fe86e00
MN
889 return low_pfn;
890}
891
edc2ca61
VB
892/**
893 * isolate_migratepages_range() - isolate migrate-able pages in a PFN range
894 * @cc: Compaction control structure.
895 * @start_pfn: The first PFN to start isolating.
896 * @end_pfn: The one-past-last PFN.
897 *
898 * Returns zero if isolation fails fatally due to e.g. pending signal.
899 * Otherwise, function returns one-past-the-last PFN of isolated page
900 * (which may be greater than end_pfn if end fell in a middle of a THP page).
901 */
902unsigned long
903isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
904 unsigned long end_pfn)
905{
e1409c32 906 unsigned long pfn, block_start_pfn, block_end_pfn;
edc2ca61
VB
907
908 /* Scan block by block. First and last block may be incomplete */
909 pfn = start_pfn;
06b6640a 910 block_start_pfn = pageblock_start_pfn(pfn);
e1409c32
JK
911 if (block_start_pfn < cc->zone->zone_start_pfn)
912 block_start_pfn = cc->zone->zone_start_pfn;
06b6640a 913 block_end_pfn = pageblock_end_pfn(pfn);
edc2ca61
VB
914
915 for (; pfn < end_pfn; pfn = block_end_pfn,
e1409c32 916 block_start_pfn = block_end_pfn,
edc2ca61
VB
917 block_end_pfn += pageblock_nr_pages) {
918
919 block_end_pfn = min(block_end_pfn, end_pfn);
920
e1409c32
JK
921 if (!pageblock_pfn_to_page(block_start_pfn,
922 block_end_pfn, cc->zone))
edc2ca61
VB
923 continue;
924
925 pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
926 ISOLATE_UNEVICTABLE);
927
14af4a5e 928 if (!pfn)
edc2ca61 929 break;
6ea41c0c
JK
930
931 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
932 break;
edc2ca61
VB
933 }
934 acct_isolated(cc->zone, cc);
935
936 return pfn;
937}
938
ff9543fd
MN
939#endif /* CONFIG_COMPACTION || CONFIG_CMA */
940#ifdef CONFIG_COMPACTION
018e9a49
AM
941
942/* Returns true if the page is within a block suitable for migration to */
943static bool suitable_migration_target(struct page *page)
944{
945 /* If the page is a large free page, then disallow migration */
946 if (PageBuddy(page)) {
947 /*
948 * We are checking page_order without zone->lock taken. But
949 * the only small danger is that we skip a potentially suitable
950 * pageblock, so it's not worth to check order for valid range.
951 */
952 if (page_order_unsafe(page) >= pageblock_order)
953 return false;
954 }
955
956 /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
957 if (migrate_async_suitable(get_pageblock_migratetype(page)))
958 return true;
959
960 /* Otherwise skip the block */
961 return false;
962}
963
f2849aa0
VB
964/*
965 * Test whether the free scanner has reached the same or lower pageblock than
966 * the migration scanner, and compaction should thus terminate.
967 */
968static inline bool compact_scanners_met(struct compact_control *cc)
969{
970 return (cc->free_pfn >> pageblock_order)
971 <= (cc->migrate_pfn >> pageblock_order);
972}
973
2fe86e00 974/*
ff9543fd
MN
975 * Based on information in the current compact_control, find blocks
976 * suitable for isolating free pages from and then isolate them.
2fe86e00 977 */
edc2ca61 978static void isolate_freepages(struct compact_control *cc)
2fe86e00 979{
edc2ca61 980 struct zone *zone = cc->zone;
ff9543fd 981 struct page *page;
c96b9e50 982 unsigned long block_start_pfn; /* start of current pageblock */
e14c720e 983 unsigned long isolate_start_pfn; /* exact pfn we start at */
c96b9e50
VB
984 unsigned long block_end_pfn; /* end of current pageblock */
985 unsigned long low_pfn; /* lowest pfn scanner is able to scan */
ff9543fd 986 struct list_head *freelist = &cc->freepages;
2fe86e00 987
ff9543fd
MN
988 /*
989 * Initialise the free scanner. The starting point is where we last
49e068f0 990 * successfully isolated from, zone-cached value, or the end of the
e14c720e
VB
991 * zone when isolating for the first time. For looping we also need
992 * this pfn aligned down to the pageblock boundary, because we do
c96b9e50
VB
993 * block_start_pfn -= pageblock_nr_pages in the for loop.
994 * For ending point, take care when isolating in last pageblock of a
995 * a zone which ends in the middle of a pageblock.
49e068f0
VB
996 * The low boundary is the end of the pageblock the migration scanner
997 * is using.
ff9543fd 998 */
e14c720e 999 isolate_start_pfn = cc->free_pfn;
06b6640a 1000 block_start_pfn = pageblock_start_pfn(cc->free_pfn);
c96b9e50
VB
1001 block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
1002 zone_end_pfn(zone));
06b6640a 1003 low_pfn = pageblock_end_pfn(cc->migrate_pfn);
2fe86e00 1004
ff9543fd
MN
1005 /*
1006 * Isolate free pages until enough are available to migrate the
1007 * pages on cc->migratepages. We stop searching if the migrate
1008 * and free page scanners meet or enough free pages are isolated.
1009 */
f5f61a32 1010 for (; block_start_pfn >= low_pfn;
c96b9e50 1011 block_end_pfn = block_start_pfn,
e14c720e
VB
1012 block_start_pfn -= pageblock_nr_pages,
1013 isolate_start_pfn = block_start_pfn) {
2fe86e00 1014
f6ea3adb
DR
1015 /*
1016 * This can iterate a massively long zone without finding any
1017 * suitable migration targets, so periodically check if we need
be976572 1018 * to schedule, or even abort async compaction.
f6ea3adb 1019 */
be976572
VB
1020 if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
1021 && compact_should_abort(cc))
1022 break;
f6ea3adb 1023
7d49d886
VB
1024 page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
1025 zone);
1026 if (!page)
ff9543fd
MN
1027 continue;
1028
1029 /* Check the block is suitable for migration */
68e3e926 1030 if (!suitable_migration_target(page))
ff9543fd 1031 continue;
68e3e926 1032
bb13ffeb
MG
1033 /* If isolation recently failed, do not retry */
1034 if (!isolation_suitable(cc, page))
1035 continue;
1036
e14c720e 1037 /* Found a block suitable for isolating free pages from. */
932ff6bb 1038 isolate_freepages_block(cc, &isolate_start_pfn,
c96b9e50 1039 block_end_pfn, freelist, false);
ff9543fd 1040
e14c720e 1041 /*
f5f61a32
VB
1042 * If we isolated enough freepages, or aborted due to async
1043 * compaction being contended, terminate the loop.
e14c720e
VB
1044 * Remember where the free scanner should restart next time,
1045 * which is where isolate_freepages_block() left off.
1046 * But if it scanned the whole pageblock, isolate_start_pfn
1047 * now points at block_end_pfn, which is the start of the next
1048 * pageblock.
1049 * In that case we will however want to restart at the start
1050 * of the previous pageblock.
1051 */
f5f61a32
VB
1052 if ((cc->nr_freepages >= cc->nr_migratepages)
1053 || cc->contended) {
1054 if (isolate_start_pfn >= block_end_pfn)
1055 isolate_start_pfn =
1056 block_start_pfn - pageblock_nr_pages;
be976572 1057 break;
f5f61a32
VB
1058 } else {
1059 /*
1060 * isolate_freepages_block() should not terminate
1061 * prematurely unless contended, or isolated enough
1062 */
1063 VM_BUG_ON(isolate_start_pfn < block_end_pfn);
1064 }
ff9543fd
MN
1065 }
1066
1067 /* split_free_page does not map the pages */
1068 map_pages(freelist);
1069
7ed695e0 1070 /*
f5f61a32
VB
1071 * Record where the free scanner will restart next time. Either we
1072 * broke from the loop and set isolate_start_pfn based on the last
1073 * call to isolate_freepages_block(), or we met the migration scanner
1074 * and the loop terminated due to isolate_start_pfn < low_pfn
7ed695e0 1075 */
f5f61a32 1076 cc->free_pfn = isolate_start_pfn;
748446bb
MG
1077}
1078
1079/*
1080 * This is a migrate-callback that "allocates" freepages by taking pages
1081 * from the isolated freelists in the block we are migrating to.
1082 */
1083static struct page *compaction_alloc(struct page *migratepage,
1084 unsigned long data,
1085 int **result)
1086{
1087 struct compact_control *cc = (struct compact_control *)data;
1088 struct page *freepage;
1089
be976572
VB
1090 /*
1091 * Isolate free pages if necessary, and if we are not aborting due to
1092 * contention.
1093 */
748446bb 1094 if (list_empty(&cc->freepages)) {
be976572 1095 if (!cc->contended)
edc2ca61 1096 isolate_freepages(cc);
748446bb
MG
1097
1098 if (list_empty(&cc->freepages))
1099 return NULL;
1100 }
1101
1102 freepage = list_entry(cc->freepages.next, struct page, lru);
1103 list_del(&freepage->lru);
1104 cc->nr_freepages--;
1105
1106 return freepage;
1107}
1108
1109/*
d53aea3d
DR
1110 * This is a migrate-callback that "frees" freepages back to the isolated
1111 * freelist. All pages on the freelist are from the same zone, so there is no
1112 * special handling needed for NUMA.
1113 */
1114static void compaction_free(struct page *page, unsigned long data)
1115{
1116 struct compact_control *cc = (struct compact_control *)data;
1117
1118 list_add(&page->lru, &cc->freepages);
1119 cc->nr_freepages++;
1120}
1121
ff9543fd
MN
1122/* possible outcome of isolate_migratepages */
1123typedef enum {
1124 ISOLATE_ABORT, /* Abort compaction now */
1125 ISOLATE_NONE, /* No pages isolated, continue scanning */
1126 ISOLATE_SUCCESS, /* Pages isolated, migrate */
1127} isolate_migrate_t;
1128
5bbe3547
EM
1129/*
1130 * Allow userspace to control policy on scanning the unevictable LRU for
1131 * compactable pages.
1132 */
1133int sysctl_compact_unevictable_allowed __read_mostly = 1;
1134
ff9543fd 1135/*
edc2ca61
VB
1136 * Isolate all pages that can be migrated from the first suitable block,
1137 * starting at the block pointed to by the migrate scanner pfn within
1138 * compact_control.
ff9543fd
MN
1139 */
1140static isolate_migrate_t isolate_migratepages(struct zone *zone,
1141 struct compact_control *cc)
1142{
e1409c32
JK
1143 unsigned long block_start_pfn;
1144 unsigned long block_end_pfn;
1145 unsigned long low_pfn;
edc2ca61
VB
1146 struct page *page;
1147 const isolate_mode_t isolate_mode =
5bbe3547 1148 (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
edc2ca61 1149 (cc->mode == MIGRATE_ASYNC ? ISOLATE_ASYNC_MIGRATE : 0);
ff9543fd 1150
edc2ca61
VB
1151 /*
1152 * Start at where we last stopped, or beginning of the zone as
1153 * initialized by compact_zone()
1154 */
1155 low_pfn = cc->migrate_pfn;
06b6640a 1156 block_start_pfn = pageblock_start_pfn(low_pfn);
e1409c32
JK
1157 if (block_start_pfn < zone->zone_start_pfn)
1158 block_start_pfn = zone->zone_start_pfn;
ff9543fd
MN
1159
1160 /* Only scan within a pageblock boundary */
06b6640a 1161 block_end_pfn = pageblock_end_pfn(low_pfn);
ff9543fd 1162
edc2ca61
VB
1163 /*
1164 * Iterate over whole pageblocks until we find the first suitable.
1165 * Do not cross the free scanner.
1166 */
e1409c32
JK
1167 for (; block_end_pfn <= cc->free_pfn;
1168 low_pfn = block_end_pfn,
1169 block_start_pfn = block_end_pfn,
1170 block_end_pfn += pageblock_nr_pages) {
ff9543fd 1171
edc2ca61
VB
1172 /*
1173 * This can potentially iterate a massively long zone with
1174 * many pageblocks unsuitable, so periodically check if we
1175 * need to schedule, or even abort async compaction.
1176 */
1177 if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
1178 && compact_should_abort(cc))
1179 break;
ff9543fd 1180
e1409c32
JK
1181 page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
1182 zone);
7d49d886 1183 if (!page)
edc2ca61
VB
1184 continue;
1185
edc2ca61
VB
1186 /* If isolation recently failed, do not retry */
1187 if (!isolation_suitable(cc, page))
1188 continue;
1189
1190 /*
1191 * For async compaction, also only scan in MOVABLE blocks.
1192 * Async compaction is optimistic to see if the minimum amount
1193 * of work satisfies the allocation.
1194 */
1195 if (cc->mode == MIGRATE_ASYNC &&
1196 !migrate_async_suitable(get_pageblock_migratetype(page)))
1197 continue;
1198
1199 /* Perform the isolation */
e1409c32
JK
1200 low_pfn = isolate_migratepages_block(cc, low_pfn,
1201 block_end_pfn, isolate_mode);
edc2ca61 1202
ff59909a
HD
1203 if (!low_pfn || cc->contended) {
1204 acct_isolated(zone, cc);
edc2ca61 1205 return ISOLATE_ABORT;
ff59909a 1206 }
edc2ca61
VB
1207
1208 /*
1209 * Either we isolated something and proceed with migration. Or
1210 * we failed and compact_zone should decide if we should
1211 * continue or not.
1212 */
1213 break;
1214 }
1215
1216 acct_isolated(zone, cc);
f2849aa0
VB
1217 /* Record where migration scanner will be restarted. */
1218 cc->migrate_pfn = low_pfn;
ff9543fd 1219
edc2ca61 1220 return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
ff9543fd
MN
1221}
1222
21c527a3
YB
1223/*
1224 * order == -1 is expected when compacting via
1225 * /proc/sys/vm/compact_memory
1226 */
1227static inline bool is_via_compact_memory(int order)
1228{
1229 return order == -1;
1230}
1231
ea7ab982 1232static enum compact_result __compact_finished(struct zone *zone, struct compact_control *cc,
6d7ce559 1233 const int migratetype)
748446bb 1234{
8fb74b9f 1235 unsigned int order;
5a03b051 1236 unsigned long watermark;
56de7263 1237
be976572 1238 if (cc->contended || fatal_signal_pending(current))
2d1e1041 1239 return COMPACT_CONTENDED;
748446bb 1240
753341a4 1241 /* Compaction run completes if the migrate and free scanner meet */
f2849aa0 1242 if (compact_scanners_met(cc)) {
55b7c4c9 1243 /* Let the next compaction start anew. */
02333641 1244 reset_cached_positions(zone);
55b7c4c9 1245
62997027
MG
1246 /*
1247 * Mark that the PG_migrate_skip information should be cleared
accf6242 1248 * by kswapd when it goes to sleep. kcompactd does not set the
62997027
MG
1249 * flag itself as the decision to be clear should be directly
1250 * based on an allocation request.
1251 */
accf6242 1252 if (cc->direct_compaction)
62997027
MG
1253 zone->compact_blockskip_flush = true;
1254
c8f7de0b
MH
1255 if (cc->whole_zone)
1256 return COMPACT_COMPLETE;
1257 else
1258 return COMPACT_PARTIAL_SKIPPED;
bb13ffeb 1259 }
748446bb 1260
21c527a3 1261 if (is_via_compact_memory(cc->order))
56de7263
MG
1262 return COMPACT_CONTINUE;
1263
3957c776
MH
1264 /* Compaction run is not finished if the watermark is not met */
1265 watermark = low_wmark_pages(zone);
3957c776 1266
ebff3980
VB
1267 if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx,
1268 cc->alloc_flags))
3957c776
MH
1269 return COMPACT_CONTINUE;
1270
56de7263 1271 /* Direct compactor: Is a suitable page free? */
8fb74b9f
MG
1272 for (order = cc->order; order < MAX_ORDER; order++) {
1273 struct free_area *area = &zone->free_area[order];
2149cdae 1274 bool can_steal;
8fb74b9f
MG
1275
1276 /* Job done if page is free of the right migratetype */
6d7ce559 1277 if (!list_empty(&area->free_list[migratetype]))
8fb74b9f
MG
1278 return COMPACT_PARTIAL;
1279
2149cdae
JK
1280#ifdef CONFIG_CMA
1281 /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
1282 if (migratetype == MIGRATE_MOVABLE &&
1283 !list_empty(&area->free_list[MIGRATE_CMA]))
1284 return COMPACT_PARTIAL;
1285#endif
1286 /*
1287 * Job done if allocation would steal freepages from
1288 * other migratetype buddy lists.
1289 */
1290 if (find_suitable_fallback(area, order, migratetype,
1291 true, &can_steal) != -1)
56de7263
MG
1292 return COMPACT_PARTIAL;
1293 }
1294
837d026d
JK
1295 return COMPACT_NO_SUITABLE_PAGE;
1296}
1297
ea7ab982
MH
1298static enum compact_result compact_finished(struct zone *zone,
1299 struct compact_control *cc,
1300 const int migratetype)
837d026d
JK
1301{
1302 int ret;
1303
1304 ret = __compact_finished(zone, cc, migratetype);
1305 trace_mm_compaction_finished(zone, cc->order, ret);
1306 if (ret == COMPACT_NO_SUITABLE_PAGE)
1307 ret = COMPACT_CONTINUE;
1308
1309 return ret;
748446bb
MG
1310}
1311
3e7d3449
MG
1312/*
1313 * compaction_suitable: Is this suitable to run compaction on this zone now?
1314 * Returns
1315 * COMPACT_SKIPPED - If there are too few free pages for compaction
1316 * COMPACT_PARTIAL - If the allocation would succeed without compaction
1317 * COMPACT_CONTINUE - If compaction should run now
1318 */
ea7ab982 1319static enum compact_result __compaction_suitable(struct zone *zone, int order,
c603844b 1320 unsigned int alloc_flags,
86a294a8
MH
1321 int classzone_idx,
1322 unsigned long wmark_target)
3e7d3449
MG
1323{
1324 int fragindex;
1325 unsigned long watermark;
1326
21c527a3 1327 if (is_via_compact_memory(order))
3957c776
MH
1328 return COMPACT_CONTINUE;
1329
ebff3980
VB
1330 watermark = low_wmark_pages(zone);
1331 /*
1332 * If watermarks for high-order allocation are already met, there
1333 * should be no need for compaction at all.
1334 */
1335 if (zone_watermark_ok(zone, order, watermark, classzone_idx,
1336 alloc_flags))
1337 return COMPACT_PARTIAL;
1338
3e7d3449
MG
1339 /*
1340 * Watermarks for order-0 must be met for compaction. Note the 2UL.
1341 * This is because during migration, copies of pages need to be
1342 * allocated and for a short time, the footprint is higher
1343 */
ebff3980 1344 watermark += (2UL << order);
86a294a8
MH
1345 if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx,
1346 alloc_flags, wmark_target))
3e7d3449
MG
1347 return COMPACT_SKIPPED;
1348
1349 /*
1350 * fragmentation index determines if allocation failures are due to
1351 * low memory or external fragmentation
1352 *
ebff3980
VB
1353 * index of -1000 would imply allocations might succeed depending on
1354 * watermarks, but we already failed the high-order watermark check
3e7d3449
MG
1355 * index towards 0 implies failure is due to lack of memory
1356 * index towards 1000 implies failure is due to fragmentation
1357 *
1358 * Only compact if a failure would be due to fragmentation.
1359 */
1360 fragindex = fragmentation_index(zone, order);
1361 if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
837d026d 1362 return COMPACT_NOT_SUITABLE_ZONE;
3e7d3449 1363
3e7d3449
MG
1364 return COMPACT_CONTINUE;
1365}
1366
ea7ab982 1367enum compact_result compaction_suitable(struct zone *zone, int order,
c603844b
MG
1368 unsigned int alloc_flags,
1369 int classzone_idx)
837d026d 1370{
ea7ab982 1371 enum compact_result ret;
837d026d 1372
86a294a8
MH
1373 ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx,
1374 zone_page_state(zone, NR_FREE_PAGES));
837d026d
JK
1375 trace_mm_compaction_suitable(zone, order, ret);
1376 if (ret == COMPACT_NOT_SUITABLE_ZONE)
1377 ret = COMPACT_SKIPPED;
1378
1379 return ret;
1380}
1381
86a294a8
MH
1382bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
1383 int alloc_flags)
1384{
1385 struct zone *zone;
1386 struct zoneref *z;
1387
1388 /*
1389 * Make sure at least one zone would pass __compaction_suitable if we continue
1390 * retrying the reclaim.
1391 */
1392 for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
1393 ac->nodemask) {
1394 unsigned long available;
1395 enum compact_result compact_result;
1396
1397 /*
1398 * Do not consider all the reclaimable memory because we do not
1399 * want to trash just for a single high order allocation which
1400 * is even not guaranteed to appear even if __compaction_suitable
1401 * is happy about the watermark check.
1402 */
1403 available = zone_reclaimable_pages(zone) / order;
1404 available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
1405 compact_result = __compaction_suitable(zone, order, alloc_flags,
1406 ac_classzone_idx(ac), available);
1407 if (compact_result != COMPACT_SKIPPED &&
1408 compact_result != COMPACT_NOT_SUITABLE_ZONE)
1409 return true;
1410 }
1411
1412 return false;
1413}
1414
ea7ab982 1415static enum compact_result compact_zone(struct zone *zone, struct compact_control *cc)
748446bb 1416{
ea7ab982 1417 enum compact_result ret;
c89511ab 1418 unsigned long start_pfn = zone->zone_start_pfn;
108bcc96 1419 unsigned long end_pfn = zone_end_pfn(zone);
6d7ce559 1420 const int migratetype = gfpflags_to_migratetype(cc->gfp_mask);
e0b9daeb 1421 const bool sync = cc->mode != MIGRATE_ASYNC;
748446bb 1422
ebff3980
VB
1423 ret = compaction_suitable(zone, cc->order, cc->alloc_flags,
1424 cc->classzone_idx);
c46649de
MH
1425 /* Compaction is likely to fail */
1426 if (ret == COMPACT_PARTIAL || ret == COMPACT_SKIPPED)
3e7d3449 1427 return ret;
c46649de
MH
1428
1429 /* huh, compaction_suitable is returning something unexpected */
1430 VM_BUG_ON(ret != COMPACT_CONTINUE);
3e7d3449 1431
d3132e4b
VB
1432 /*
1433 * Clear pageblock skip if there were failures recently and compaction
accf6242 1434 * is about to be retried after being deferred.
d3132e4b 1435 */
accf6242 1436 if (compaction_restarting(zone, cc->order))
d3132e4b
VB
1437 __reset_isolation_suitable(zone);
1438
c89511ab
MG
1439 /*
1440 * Setup to move all movable pages to the end of the zone. Used cached
1441 * information on where the scanners should start but check that it
1442 * is initialised by ensuring the values are within zone boundaries.
1443 */
e0b9daeb 1444 cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync];
c89511ab 1445 cc->free_pfn = zone->compact_cached_free_pfn;
623446e4 1446 if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) {
06b6640a 1447 cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
c89511ab
MG
1448 zone->compact_cached_free_pfn = cc->free_pfn;
1449 }
623446e4 1450 if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) {
c89511ab 1451 cc->migrate_pfn = start_pfn;
35979ef3
DR
1452 zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
1453 zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
c89511ab 1454 }
c8f7de0b
MH
1455
1456 if (cc->migrate_pfn == start_pfn)
1457 cc->whole_zone = true;
1458
1a16718c 1459 cc->last_migrated_pfn = 0;
748446bb 1460
16c4a097
JK
1461 trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
1462 cc->free_pfn, end_pfn, sync);
0eb927c0 1463
748446bb
MG
1464 migrate_prep_local();
1465
6d7ce559
DR
1466 while ((ret = compact_finished(zone, cc, migratetype)) ==
1467 COMPACT_CONTINUE) {
9d502c1c 1468 int err;
748446bb 1469
f9e35b3b
MG
1470 switch (isolate_migratepages(zone, cc)) {
1471 case ISOLATE_ABORT:
2d1e1041 1472 ret = COMPACT_CONTENDED;
5733c7d1 1473 putback_movable_pages(&cc->migratepages);
e64c5237 1474 cc->nr_migratepages = 0;
f9e35b3b
MG
1475 goto out;
1476 case ISOLATE_NONE:
fdaf7f5c
VB
1477 /*
1478 * We haven't isolated and migrated anything, but
1479 * there might still be unflushed migrations from
1480 * previous cc->order aligned block.
1481 */
1482 goto check_drain;
f9e35b3b
MG
1483 case ISOLATE_SUCCESS:
1484 ;
1485 }
748446bb 1486
d53aea3d 1487 err = migrate_pages(&cc->migratepages, compaction_alloc,
e0b9daeb 1488 compaction_free, (unsigned long)cc, cc->mode,
7b2a2d4a 1489 MR_COMPACTION);
748446bb 1490
f8c9301f
VB
1491 trace_mm_compaction_migratepages(cc->nr_migratepages, err,
1492 &cc->migratepages);
748446bb 1493
f8c9301f
VB
1494 /* All pages were either migrated or will be released */
1495 cc->nr_migratepages = 0;
9d502c1c 1496 if (err) {
5733c7d1 1497 putback_movable_pages(&cc->migratepages);
7ed695e0
VB
1498 /*
1499 * migrate_pages() may return -ENOMEM when scanners meet
1500 * and we want compact_finished() to detect it
1501 */
f2849aa0 1502 if (err == -ENOMEM && !compact_scanners_met(cc)) {
2d1e1041 1503 ret = COMPACT_CONTENDED;
4bf2bba3
DR
1504 goto out;
1505 }
fdd048e1
VB
1506 /*
1507 * We failed to migrate at least one page in the current
1508 * order-aligned block, so skip the rest of it.
1509 */
1510 if (cc->direct_compaction &&
1511 (cc->mode == MIGRATE_ASYNC)) {
1512 cc->migrate_pfn = block_end_pfn(
1513 cc->migrate_pfn - 1, cc->order);
1514 /* Draining pcplists is useless in this case */
1515 cc->last_migrated_pfn = 0;
1516
1517 }
748446bb 1518 }
fdaf7f5c 1519
fdaf7f5c
VB
1520check_drain:
1521 /*
1522 * Has the migration scanner moved away from the previous
1523 * cc->order aligned block where we migrated from? If yes,
1524 * flush the pages that were freed, so that they can merge and
1525 * compact_finished() can detect immediately if allocation
1526 * would succeed.
1527 */
1a16718c 1528 if (cc->order > 0 && cc->last_migrated_pfn) {
fdaf7f5c
VB
1529 int cpu;
1530 unsigned long current_block_start =
06b6640a 1531 block_start_pfn(cc->migrate_pfn, cc->order);
fdaf7f5c 1532
1a16718c 1533 if (cc->last_migrated_pfn < current_block_start) {
fdaf7f5c
VB
1534 cpu = get_cpu();
1535 lru_add_drain_cpu(cpu);
1536 drain_local_pages(zone);
1537 put_cpu();
1538 /* No more flushing until we migrate again */
1a16718c 1539 cc->last_migrated_pfn = 0;
fdaf7f5c
VB
1540 }
1541 }
1542
748446bb
MG
1543 }
1544
f9e35b3b 1545out:
6bace090
VB
1546 /*
1547 * Release free pages and update where the free scanner should restart,
1548 * so we don't leave any returned pages behind in the next attempt.
1549 */
1550 if (cc->nr_freepages > 0) {
1551 unsigned long free_pfn = release_freepages(&cc->freepages);
1552
1553 cc->nr_freepages = 0;
1554 VM_BUG_ON(free_pfn == 0);
1555 /* The cached pfn is always the first in a pageblock */
06b6640a 1556 free_pfn = pageblock_start_pfn(free_pfn);
6bace090
VB
1557 /*
1558 * Only go back, not forward. The cached pfn might have been
1559 * already reset to zone end in compact_finished()
1560 */
1561 if (free_pfn > zone->compact_cached_free_pfn)
1562 zone->compact_cached_free_pfn = free_pfn;
1563 }
748446bb 1564
16c4a097
JK
1565 trace_mm_compaction_end(start_pfn, cc->migrate_pfn,
1566 cc->free_pfn, end_pfn, sync, ret);
0eb927c0 1567
2d1e1041
VB
1568 if (ret == COMPACT_CONTENDED)
1569 ret = COMPACT_PARTIAL;
1570
748446bb
MG
1571 return ret;
1572}
76ab0f53 1573
ea7ab982 1574static enum compact_result compact_zone_order(struct zone *zone, int order,
ebff3980 1575 gfp_t gfp_mask, enum migrate_mode mode, int *contended,
c603844b 1576 unsigned int alloc_flags, int classzone_idx)
56de7263 1577{
ea7ab982 1578 enum compact_result ret;
56de7263
MG
1579 struct compact_control cc = {
1580 .nr_freepages = 0,
1581 .nr_migratepages = 0,
1582 .order = order,
6d7ce559 1583 .gfp_mask = gfp_mask,
56de7263 1584 .zone = zone,
e0b9daeb 1585 .mode = mode,
ebff3980
VB
1586 .alloc_flags = alloc_flags,
1587 .classzone_idx = classzone_idx,
accf6242 1588 .direct_compaction = true,
56de7263
MG
1589 };
1590 INIT_LIST_HEAD(&cc.freepages);
1591 INIT_LIST_HEAD(&cc.migratepages);
1592
e64c5237
SL
1593 ret = compact_zone(zone, &cc);
1594
1595 VM_BUG_ON(!list_empty(&cc.freepages));
1596 VM_BUG_ON(!list_empty(&cc.migratepages));
1597
1598 *contended = cc.contended;
1599 return ret;
56de7263
MG
1600}
1601
5e771905
MG
1602int sysctl_extfrag_threshold = 500;
1603
56de7263
MG
1604/**
1605 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
56de7263 1606 * @gfp_mask: The GFP mask of the current allocation
1a6d53a1
VB
1607 * @order: The order of the current allocation
1608 * @alloc_flags: The allocation flags of the current allocation
1609 * @ac: The context of current allocation
e0b9daeb 1610 * @mode: The migration mode for async, sync light, or sync migration
1f9efdef
VB
1611 * @contended: Return value that determines if compaction was aborted due to
1612 * need_resched() or lock contention
56de7263
MG
1613 *
1614 * This is the main entry point for direct page compaction.
1615 */
ea7ab982 1616enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
c603844b
MG
1617 unsigned int alloc_flags, const struct alloc_context *ac,
1618 enum migrate_mode mode, int *contended)
56de7263 1619{
56de7263
MG
1620 int may_enter_fs = gfp_mask & __GFP_FS;
1621 int may_perform_io = gfp_mask & __GFP_IO;
56de7263
MG
1622 struct zoneref *z;
1623 struct zone *zone;
1d4746d3 1624 enum compact_result rc = COMPACT_SKIPPED;
1f9efdef
VB
1625 int all_zones_contended = COMPACT_CONTENDED_LOCK; /* init for &= op */
1626
1627 *contended = COMPACT_CONTENDED_NONE;
56de7263 1628
4ffb6335 1629 /* Check if the GFP flags allow compaction */
c5a73c3d 1630 if (!order || !may_enter_fs || !may_perform_io)
53853e2d 1631 return COMPACT_SKIPPED;
56de7263 1632
837d026d
JK
1633 trace_mm_compaction_try_to_compact_pages(order, gfp_mask, mode);
1634
56de7263 1635 /* Compact each zone in the list */
1a6d53a1
VB
1636 for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
1637 ac->nodemask) {
ea7ab982 1638 enum compact_result status;
1f9efdef 1639 int zone_contended;
56de7263 1640
1d4746d3
MH
1641 if (compaction_deferred(zone, order)) {
1642 rc = max_t(enum compact_result, COMPACT_DEFERRED, rc);
53853e2d 1643 continue;
1d4746d3 1644 }
53853e2d 1645
e0b9daeb 1646 status = compact_zone_order(zone, order, gfp_mask, mode,
1a6d53a1 1647 &zone_contended, alloc_flags,
93ea9964 1648 ac_classzone_idx(ac));
56de7263 1649 rc = max(status, rc);
1f9efdef
VB
1650 /*
1651 * It takes at least one zone that wasn't lock contended
1652 * to clear all_zones_contended.
1653 */
1654 all_zones_contended &= zone_contended;
56de7263 1655
3e7d3449 1656 /* If a normal allocation would succeed, stop compacting */
ebff3980 1657 if (zone_watermark_ok(zone, order, low_wmark_pages(zone),
93ea9964 1658 ac_classzone_idx(ac), alloc_flags)) {
53853e2d
VB
1659 /*
1660 * We think the allocation will succeed in this zone,
1661 * but it is not certain, hence the false. The caller
1662 * will repeat this with true if allocation indeed
1663 * succeeds in this zone.
1664 */
1665 compaction_defer_reset(zone, order, false);
1f9efdef
VB
1666 /*
1667 * It is possible that async compaction aborted due to
1668 * need_resched() and the watermarks were ok thanks to
1669 * somebody else freeing memory. The allocation can
1670 * however still fail so we better signal the
1671 * need_resched() contention anyway (this will not
1672 * prevent the allocation attempt).
1673 */
1674 if (zone_contended == COMPACT_CONTENDED_SCHED)
1675 *contended = COMPACT_CONTENDED_SCHED;
1676
1677 goto break_loop;
1678 }
1679
c8f7de0b
MH
1680 if (mode != MIGRATE_ASYNC && (status == COMPACT_COMPLETE ||
1681 status == COMPACT_PARTIAL_SKIPPED)) {
53853e2d
VB
1682 /*
1683 * We think that allocation won't succeed in this zone
1684 * so we defer compaction there. If it ends up
1685 * succeeding after all, it will be reset.
1686 */
1687 defer_compaction(zone, order);
1688 }
1f9efdef
VB
1689
1690 /*
1691 * We might have stopped compacting due to need_resched() in
1692 * async compaction, or due to a fatal signal detected. In that
1693 * case do not try further zones and signal need_resched()
1694 * contention.
1695 */
1696 if ((zone_contended == COMPACT_CONTENDED_SCHED)
1697 || fatal_signal_pending(current)) {
1698 *contended = COMPACT_CONTENDED_SCHED;
1699 goto break_loop;
1700 }
1701
1702 continue;
1703break_loop:
1704 /*
1705 * We might not have tried all the zones, so be conservative
1706 * and assume they are not all lock contended.
1707 */
1708 all_zones_contended = 0;
1709 break;
56de7263
MG
1710 }
1711
1f9efdef
VB
1712 /*
1713 * If at least one zone wasn't deferred or skipped, we report if all
1714 * zones that were tried were lock contended.
1715 */
1d4746d3 1716 if (rc > COMPACT_INACTIVE && all_zones_contended)
1f9efdef
VB
1717 *contended = COMPACT_CONTENDED_LOCK;
1718
56de7263
MG
1719 return rc;
1720}
1721
1722
76ab0f53 1723/* Compact all zones within a node */
7103f16d 1724static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
76ab0f53
MG
1725{
1726 int zoneid;
76ab0f53
MG
1727 struct zone *zone;
1728
76ab0f53 1729 for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
76ab0f53
MG
1730
1731 zone = &pgdat->node_zones[zoneid];
1732 if (!populated_zone(zone))
1733 continue;
1734
7be62de9
RR
1735 cc->nr_freepages = 0;
1736 cc->nr_migratepages = 0;
1737 cc->zone = zone;
1738 INIT_LIST_HEAD(&cc->freepages);
1739 INIT_LIST_HEAD(&cc->migratepages);
76ab0f53 1740
195b0c60
GK
1741 /*
1742 * When called via /proc/sys/vm/compact_memory
1743 * this makes sure we compact the whole zone regardless of
1744 * cached scanner positions.
1745 */
21c527a3 1746 if (is_via_compact_memory(cc->order))
195b0c60
GK
1747 __reset_isolation_suitable(zone);
1748
21c527a3
YB
1749 if (is_via_compact_memory(cc->order) ||
1750 !compaction_deferred(zone, cc->order))
7be62de9 1751 compact_zone(zone, cc);
76ab0f53 1752
7be62de9
RR
1753 VM_BUG_ON(!list_empty(&cc->freepages));
1754 VM_BUG_ON(!list_empty(&cc->migratepages));
75469345
JK
1755
1756 if (is_via_compact_memory(cc->order))
1757 continue;
1758
1759 if (zone_watermark_ok(zone, cc->order,
1760 low_wmark_pages(zone), 0, 0))
1761 compaction_defer_reset(zone, cc->order, false);
76ab0f53 1762 }
76ab0f53
MG
1763}
1764
7103f16d 1765void compact_pgdat(pg_data_t *pgdat, int order)
7be62de9
RR
1766{
1767 struct compact_control cc = {
1768 .order = order,
e0b9daeb 1769 .mode = MIGRATE_ASYNC,
7be62de9
RR
1770 };
1771
3a7200af
MG
1772 if (!order)
1773 return;
1774
7103f16d 1775 __compact_pgdat(pgdat, &cc);
7be62de9
RR
1776}
1777
7103f16d 1778static void compact_node(int nid)
7be62de9 1779{
7be62de9
RR
1780 struct compact_control cc = {
1781 .order = -1,
e0b9daeb 1782 .mode = MIGRATE_SYNC,
91ca9186 1783 .ignore_skip_hint = true,
7be62de9
RR
1784 };
1785
7103f16d 1786 __compact_pgdat(NODE_DATA(nid), &cc);
7be62de9
RR
1787}
1788
76ab0f53 1789/* Compact all nodes in the system */
7964c06d 1790static void compact_nodes(void)
76ab0f53
MG
1791{
1792 int nid;
1793
8575ec29
HD
1794 /* Flush pending updates to the LRU lists */
1795 lru_add_drain_all();
1796
76ab0f53
MG
1797 for_each_online_node(nid)
1798 compact_node(nid);
76ab0f53
MG
1799}
1800
1801/* The written value is actually unused, all memory is compacted */
1802int sysctl_compact_memory;
1803
fec4eb2c
YB
1804/*
1805 * This is the entry point for compacting all nodes via
1806 * /proc/sys/vm/compact_memory
1807 */
76ab0f53
MG
1808int sysctl_compaction_handler(struct ctl_table *table, int write,
1809 void __user *buffer, size_t *length, loff_t *ppos)
1810{
1811 if (write)
7964c06d 1812 compact_nodes();
76ab0f53
MG
1813
1814 return 0;
1815}
ed4a6d7f 1816
5e771905
MG
1817int sysctl_extfrag_handler(struct ctl_table *table, int write,
1818 void __user *buffer, size_t *length, loff_t *ppos)
1819{
1820 proc_dointvec_minmax(table, write, buffer, length, ppos);
1821
1822 return 0;
1823}
1824
ed4a6d7f 1825#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
74e77fb9 1826static ssize_t sysfs_compact_node(struct device *dev,
10fbcf4c 1827 struct device_attribute *attr,
ed4a6d7f
MG
1828 const char *buf, size_t count)
1829{
8575ec29
HD
1830 int nid = dev->id;
1831
1832 if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
1833 /* Flush pending updates to the LRU lists */
1834 lru_add_drain_all();
1835
1836 compact_node(nid);
1837 }
ed4a6d7f
MG
1838
1839 return count;
1840}
10fbcf4c 1841static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
ed4a6d7f
MG
1842
1843int compaction_register_node(struct node *node)
1844{
10fbcf4c 1845 return device_create_file(&node->dev, &dev_attr_compact);
ed4a6d7f
MG
1846}
1847
1848void compaction_unregister_node(struct node *node)
1849{
10fbcf4c 1850 return device_remove_file(&node->dev, &dev_attr_compact);
ed4a6d7f
MG
1851}
1852#endif /* CONFIG_SYSFS && CONFIG_NUMA */
ff9543fd 1853
698b1b30
VB
1854static inline bool kcompactd_work_requested(pg_data_t *pgdat)
1855{
172400c6 1856 return pgdat->kcompactd_max_order > 0 || kthread_should_stop();
698b1b30
VB
1857}
1858
1859static bool kcompactd_node_suitable(pg_data_t *pgdat)
1860{
1861 int zoneid;
1862 struct zone *zone;
1863 enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx;
1864
6cd9dc3e 1865 for (zoneid = 0; zoneid <= classzone_idx; zoneid++) {
698b1b30
VB
1866 zone = &pgdat->node_zones[zoneid];
1867
1868 if (!populated_zone(zone))
1869 continue;
1870
1871 if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0,
1872 classzone_idx) == COMPACT_CONTINUE)
1873 return true;
1874 }
1875
1876 return false;
1877}
1878
1879static void kcompactd_do_work(pg_data_t *pgdat)
1880{
1881 /*
1882 * With no special task, compact all zones so that a page of requested
1883 * order is allocatable.
1884 */
1885 int zoneid;
1886 struct zone *zone;
1887 struct compact_control cc = {
1888 .order = pgdat->kcompactd_max_order,
1889 .classzone_idx = pgdat->kcompactd_classzone_idx,
1890 .mode = MIGRATE_SYNC_LIGHT,
1891 .ignore_skip_hint = true,
1892
1893 };
1894 bool success = false;
1895
1896 trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order,
1897 cc.classzone_idx);
1898 count_vm_event(KCOMPACTD_WAKE);
1899
6cd9dc3e 1900 for (zoneid = 0; zoneid <= cc.classzone_idx; zoneid++) {
698b1b30
VB
1901 int status;
1902
1903 zone = &pgdat->node_zones[zoneid];
1904 if (!populated_zone(zone))
1905 continue;
1906
1907 if (compaction_deferred(zone, cc.order))
1908 continue;
1909
1910 if (compaction_suitable(zone, cc.order, 0, zoneid) !=
1911 COMPACT_CONTINUE)
1912 continue;
1913
1914 cc.nr_freepages = 0;
1915 cc.nr_migratepages = 0;
1916 cc.zone = zone;
1917 INIT_LIST_HEAD(&cc.freepages);
1918 INIT_LIST_HEAD(&cc.migratepages);
1919
172400c6
VB
1920 if (kthread_should_stop())
1921 return;
698b1b30
VB
1922 status = compact_zone(zone, &cc);
1923
1924 if (zone_watermark_ok(zone, cc.order, low_wmark_pages(zone),
1925 cc.classzone_idx, 0)) {
1926 success = true;
1927 compaction_defer_reset(zone, cc.order, false);
c8f7de0b 1928 } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) {
698b1b30
VB
1929 /*
1930 * We use sync migration mode here, so we defer like
1931 * sync direct compaction does.
1932 */
1933 defer_compaction(zone, cc.order);
1934 }
1935
1936 VM_BUG_ON(!list_empty(&cc.freepages));
1937 VM_BUG_ON(!list_empty(&cc.migratepages));
1938 }
1939
1940 /*
1941 * Regardless of success, we are done until woken up next. But remember
1942 * the requested order/classzone_idx in case it was higher/tighter than
1943 * our current ones
1944 */
1945 if (pgdat->kcompactd_max_order <= cc.order)
1946 pgdat->kcompactd_max_order = 0;
1947 if (pgdat->kcompactd_classzone_idx >= cc.classzone_idx)
1948 pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
1949}
1950
1951void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
1952{
1953 if (!order)
1954 return;
1955
1956 if (pgdat->kcompactd_max_order < order)
1957 pgdat->kcompactd_max_order = order;
1958
1959 if (pgdat->kcompactd_classzone_idx > classzone_idx)
1960 pgdat->kcompactd_classzone_idx = classzone_idx;
1961
1962 if (!waitqueue_active(&pgdat->kcompactd_wait))
1963 return;
1964
1965 if (!kcompactd_node_suitable(pgdat))
1966 return;
1967
1968 trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order,
1969 classzone_idx);
1970 wake_up_interruptible(&pgdat->kcompactd_wait);
1971}
1972
1973/*
1974 * The background compaction daemon, started as a kernel thread
1975 * from the init process.
1976 */
1977static int kcompactd(void *p)
1978{
1979 pg_data_t *pgdat = (pg_data_t*)p;
1980 struct task_struct *tsk = current;
1981
1982 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
1983
1984 if (!cpumask_empty(cpumask))
1985 set_cpus_allowed_ptr(tsk, cpumask);
1986
1987 set_freezable();
1988
1989 pgdat->kcompactd_max_order = 0;
1990 pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
1991
1992 while (!kthread_should_stop()) {
1993 trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
1994 wait_event_freezable(pgdat->kcompactd_wait,
1995 kcompactd_work_requested(pgdat));
1996
1997 kcompactd_do_work(pgdat);
1998 }
1999
2000 return 0;
2001}
2002
2003/*
2004 * This kcompactd start function will be called by init and node-hot-add.
2005 * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added.
2006 */
2007int kcompactd_run(int nid)
2008{
2009 pg_data_t *pgdat = NODE_DATA(nid);
2010 int ret = 0;
2011
2012 if (pgdat->kcompactd)
2013 return 0;
2014
2015 pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid);
2016 if (IS_ERR(pgdat->kcompactd)) {
2017 pr_err("Failed to start kcompactd on node %d\n", nid);
2018 ret = PTR_ERR(pgdat->kcompactd);
2019 pgdat->kcompactd = NULL;
2020 }
2021 return ret;
2022}
2023
2024/*
2025 * Called by memory hotplug when all memory in a node is offlined. Caller must
2026 * hold mem_hotplug_begin/end().
2027 */
2028void kcompactd_stop(int nid)
2029{
2030 struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd;
2031
2032 if (kcompactd) {
2033 kthread_stop(kcompactd);
2034 NODE_DATA(nid)->kcompactd = NULL;
2035 }
2036}
2037
2038/*
2039 * It's optimal to keep kcompactd on the same CPUs as their memory, but
2040 * not required for correctness. So if the last cpu in a node goes
2041 * away, we get changed to run anywhere: as the first one comes back,
2042 * restore their cpu bindings.
2043 */
2044static int cpu_callback(struct notifier_block *nfb, unsigned long action,
2045 void *hcpu)
2046{
2047 int nid;
2048
2049 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2050 for_each_node_state(nid, N_MEMORY) {
2051 pg_data_t *pgdat = NODE_DATA(nid);
2052 const struct cpumask *mask;
2053
2054 mask = cpumask_of_node(pgdat->node_id);
2055
2056 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2057 /* One of our CPUs online: restore mask */
2058 set_cpus_allowed_ptr(pgdat->kcompactd, mask);
2059 }
2060 }
2061 return NOTIFY_OK;
2062}
2063
2064static int __init kcompactd_init(void)
2065{
2066 int nid;
2067
2068 for_each_node_state(nid, N_MEMORY)
2069 kcompactd_run(nid);
2070 hotcpu_notifier(cpu_callback, 0);
2071 return 0;
2072}
2073subsys_initcall(kcompactd_init)
2074
ff9543fd 2075#endif /* CONFIG_COMPACTION */