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1 | /* | |
2 | * linux/mm/compaction.c | |
3 | * | |
4 | * Memory compaction for the reduction of external fragmentation. Note that | |
5 | * this heavily depends upon page migration to do all the real heavy | |
6 | * lifting | |
7 | * | |
8 | * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie> | |
9 | */ | |
10 | #include <linux/swap.h> | |
11 | #include <linux/migrate.h> | |
12 | #include <linux/compaction.h> | |
13 | #include <linux/mm_inline.h> | |
14 | #include <linux/backing-dev.h> | |
15 | #include <linux/sysctl.h> | |
16 | #include <linux/sysfs.h> | |
17 | #include <linux/balloon_compaction.h> | |
18 | #include <linux/page-isolation.h> | |
19 | #include <linux/kasan.h> | |
20 | #include "internal.h" | |
21 | ||
22 | #ifdef CONFIG_COMPACTION | |
23 | static inline void count_compact_event(enum vm_event_item item) | |
24 | { | |
25 | count_vm_event(item); | |
26 | } | |
27 | ||
28 | static inline void count_compact_events(enum vm_event_item item, long delta) | |
29 | { | |
30 | count_vm_events(item, delta); | |
31 | } | |
32 | #else | |
33 | #define count_compact_event(item) do { } while (0) | |
34 | #define count_compact_events(item, delta) do { } while (0) | |
35 | #endif | |
36 | ||
37 | #if defined CONFIG_COMPACTION || defined CONFIG_CMA | |
38 | #ifdef CONFIG_TRACEPOINTS | |
39 | static const char *const compaction_status_string[] = { | |
40 | "deferred", | |
41 | "skipped", | |
42 | "continue", | |
43 | "partial", | |
44 | "complete", | |
45 | "no_suitable_page", | |
46 | "not_suitable_zone", | |
47 | }; | |
48 | #endif | |
49 | ||
50 | #define CREATE_TRACE_POINTS | |
51 | #include <trace/events/compaction.h> | |
52 | ||
53 | static unsigned long release_freepages(struct list_head *freelist) | |
54 | { | |
55 | struct page *page, *next; | |
56 | unsigned long high_pfn = 0; | |
57 | ||
58 | list_for_each_entry_safe(page, next, freelist, lru) { | |
59 | unsigned long pfn = page_to_pfn(page); | |
60 | list_del(&page->lru); | |
61 | __free_page(page); | |
62 | if (pfn > high_pfn) | |
63 | high_pfn = pfn; | |
64 | } | |
65 | ||
66 | return high_pfn; | |
67 | } | |
68 | ||
69 | static void map_pages(struct list_head *list) | |
70 | { | |
71 | struct page *page; | |
72 | ||
73 | list_for_each_entry(page, list, lru) { | |
74 | arch_alloc_page(page, 0); | |
75 | kernel_map_pages(page, 1, 1); | |
76 | kasan_alloc_pages(page, 0); | |
77 | } | |
78 | } | |
79 | ||
80 | static inline bool migrate_async_suitable(int migratetype) | |
81 | { | |
82 | return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE; | |
83 | } | |
84 | ||
85 | /* | |
86 | * Check that the whole (or subset of) a pageblock given by the interval of | |
87 | * [start_pfn, end_pfn) is valid and within the same zone, before scanning it | |
88 | * with the migration of free compaction scanner. The scanners then need to | |
89 | * use only pfn_valid_within() check for arches that allow holes within | |
90 | * pageblocks. | |
91 | * | |
92 | * Return struct page pointer of start_pfn, or NULL if checks were not passed. | |
93 | * | |
94 | * It's possible on some configurations to have a setup like node0 node1 node0 | |
95 | * i.e. it's possible that all pages within a zones range of pages do not | |
96 | * belong to a single zone. We assume that a border between node0 and node1 | |
97 | * can occur within a single pageblock, but not a node0 node1 node0 | |
98 | * interleaving within a single pageblock. It is therefore sufficient to check | |
99 | * the first and last page of a pageblock and avoid checking each individual | |
100 | * page in a pageblock. | |
101 | */ | |
102 | static struct page *pageblock_pfn_to_page(unsigned long start_pfn, | |
103 | unsigned long end_pfn, struct zone *zone) | |
104 | { | |
105 | struct page *start_page; | |
106 | struct page *end_page; | |
107 | ||
108 | /* end_pfn is one past the range we are checking */ | |
109 | end_pfn--; | |
110 | ||
111 | if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) | |
112 | return NULL; | |
113 | ||
114 | start_page = pfn_to_page(start_pfn); | |
115 | ||
116 | if (page_zone(start_page) != zone) | |
117 | return NULL; | |
118 | ||
119 | end_page = pfn_to_page(end_pfn); | |
120 | ||
121 | /* This gives a shorter code than deriving page_zone(end_page) */ | |
122 | if (page_zone_id(start_page) != page_zone_id(end_page)) | |
123 | return NULL; | |
124 | ||
125 | return start_page; | |
126 | } | |
127 | ||
128 | #ifdef CONFIG_COMPACTION | |
129 | ||
130 | /* Do not skip compaction more than 64 times */ | |
131 | #define COMPACT_MAX_DEFER_SHIFT 6 | |
132 | ||
133 | /* | |
134 | * Compaction is deferred when compaction fails to result in a page | |
135 | * allocation success. 1 << compact_defer_limit compactions are skipped up | |
136 | * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT | |
137 | */ | |
138 | void defer_compaction(struct zone *zone, int order) | |
139 | { | |
140 | zone->compact_considered = 0; | |
141 | zone->compact_defer_shift++; | |
142 | ||
143 | if (order < zone->compact_order_failed) | |
144 | zone->compact_order_failed = order; | |
145 | ||
146 | if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT) | |
147 | zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT; | |
148 | ||
149 | trace_mm_compaction_defer_compaction(zone, order); | |
150 | } | |
151 | ||
152 | /* Returns true if compaction should be skipped this time */ | |
153 | bool compaction_deferred(struct zone *zone, int order) | |
154 | { | |
155 | unsigned long defer_limit = 1UL << zone->compact_defer_shift; | |
156 | ||
157 | if (order < zone->compact_order_failed) | |
158 | return false; | |
159 | ||
160 | /* Avoid possible overflow */ | |
161 | if (++zone->compact_considered > defer_limit) | |
162 | zone->compact_considered = defer_limit; | |
163 | ||
164 | if (zone->compact_considered >= defer_limit) | |
165 | return false; | |
166 | ||
167 | trace_mm_compaction_deferred(zone, order); | |
168 | ||
169 | return true; | |
170 | } | |
171 | ||
172 | /* | |
173 | * Update defer tracking counters after successful compaction of given order, | |
174 | * which means an allocation either succeeded (alloc_success == true) or is | |
175 | * expected to succeed. | |
176 | */ | |
177 | void compaction_defer_reset(struct zone *zone, int order, | |
178 | bool alloc_success) | |
179 | { | |
180 | if (alloc_success) { | |
181 | zone->compact_considered = 0; | |
182 | zone->compact_defer_shift = 0; | |
183 | } | |
184 | if (order >= zone->compact_order_failed) | |
185 | zone->compact_order_failed = order + 1; | |
186 | ||
187 | trace_mm_compaction_defer_reset(zone, order); | |
188 | } | |
189 | ||
190 | /* Returns true if restarting compaction after many failures */ | |
191 | bool compaction_restarting(struct zone *zone, int order) | |
192 | { | |
193 | if (order < zone->compact_order_failed) | |
194 | return false; | |
195 | ||
196 | return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT && | |
197 | zone->compact_considered >= 1UL << zone->compact_defer_shift; | |
198 | } | |
199 | ||
200 | /* Returns true if the pageblock should be scanned for pages to isolate. */ | |
201 | static inline bool isolation_suitable(struct compact_control *cc, | |
202 | struct page *page) | |
203 | { | |
204 | if (cc->ignore_skip_hint) | |
205 | return true; | |
206 | ||
207 | return !get_pageblock_skip(page); | |
208 | } | |
209 | ||
210 | /* | |
211 | * This function is called to clear all cached information on pageblocks that | |
212 | * should be skipped for page isolation when the migrate and free page scanner | |
213 | * meet. | |
214 | */ | |
215 | static void __reset_isolation_suitable(struct zone *zone) | |
216 | { | |
217 | unsigned long start_pfn = zone->zone_start_pfn; | |
218 | unsigned long end_pfn = zone_end_pfn(zone); | |
219 | unsigned long pfn; | |
220 | ||
221 | zone->compact_cached_migrate_pfn[0] = start_pfn; | |
222 | zone->compact_cached_migrate_pfn[1] = start_pfn; | |
223 | zone->compact_cached_free_pfn = end_pfn; | |
224 | zone->compact_blockskip_flush = false; | |
225 | ||
226 | /* Walk the zone and mark every pageblock as suitable for isolation */ | |
227 | for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) { | |
228 | struct page *page; | |
229 | ||
230 | cond_resched(); | |
231 | ||
232 | if (!pfn_valid(pfn)) | |
233 | continue; | |
234 | ||
235 | page = pfn_to_page(pfn); | |
236 | if (zone != page_zone(page)) | |
237 | continue; | |
238 | ||
239 | clear_pageblock_skip(page); | |
240 | } | |
241 | } | |
242 | ||
243 | void reset_isolation_suitable(pg_data_t *pgdat) | |
244 | { | |
245 | int zoneid; | |
246 | ||
247 | for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { | |
248 | struct zone *zone = &pgdat->node_zones[zoneid]; | |
249 | if (!populated_zone(zone)) | |
250 | continue; | |
251 | ||
252 | /* Only flush if a full compaction finished recently */ | |
253 | if (zone->compact_blockskip_flush) | |
254 | __reset_isolation_suitable(zone); | |
255 | } | |
256 | } | |
257 | ||
258 | /* | |
259 | * If no pages were isolated then mark this pageblock to be skipped in the | |
260 | * future. The information is later cleared by __reset_isolation_suitable(). | |
261 | */ | |
262 | static void update_pageblock_skip(struct compact_control *cc, | |
263 | struct page *page, unsigned long nr_isolated, | |
264 | bool migrate_scanner) | |
265 | { | |
266 | struct zone *zone = cc->zone; | |
267 | unsigned long pfn; | |
268 | ||
269 | if (cc->ignore_skip_hint) | |
270 | return; | |
271 | ||
272 | if (!page) | |
273 | return; | |
274 | ||
275 | if (nr_isolated) | |
276 | return; | |
277 | ||
278 | set_pageblock_skip(page); | |
279 | ||
280 | pfn = page_to_pfn(page); | |
281 | ||
282 | /* Update where async and sync compaction should restart */ | |
283 | if (migrate_scanner) { | |
284 | if (pfn > zone->compact_cached_migrate_pfn[0]) | |
285 | zone->compact_cached_migrate_pfn[0] = pfn; | |
286 | if (cc->mode != MIGRATE_ASYNC && | |
287 | pfn > zone->compact_cached_migrate_pfn[1]) | |
288 | zone->compact_cached_migrate_pfn[1] = pfn; | |
289 | } else { | |
290 | if (pfn < zone->compact_cached_free_pfn) | |
291 | zone->compact_cached_free_pfn = pfn; | |
292 | } | |
293 | } | |
294 | #else | |
295 | static inline bool isolation_suitable(struct compact_control *cc, | |
296 | struct page *page) | |
297 | { | |
298 | return true; | |
299 | } | |
300 | ||
301 | static void update_pageblock_skip(struct compact_control *cc, | |
302 | struct page *page, unsigned long nr_isolated, | |
303 | bool migrate_scanner) | |
304 | { | |
305 | } | |
306 | #endif /* CONFIG_COMPACTION */ | |
307 | ||
308 | /* | |
309 | * Compaction requires the taking of some coarse locks that are potentially | |
310 | * very heavily contended. For async compaction, back out if the lock cannot | |
311 | * be taken immediately. For sync compaction, spin on the lock if needed. | |
312 | * | |
313 | * Returns true if the lock is held | |
314 | * Returns false if the lock is not held and compaction should abort | |
315 | */ | |
316 | static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags, | |
317 | struct compact_control *cc) | |
318 | { | |
319 | if (cc->mode == MIGRATE_ASYNC) { | |
320 | if (!spin_trylock_irqsave(lock, *flags)) { | |
321 | cc->contended = COMPACT_CONTENDED_LOCK; | |
322 | return false; | |
323 | } | |
324 | } else { | |
325 | spin_lock_irqsave(lock, *flags); | |
326 | } | |
327 | ||
328 | return true; | |
329 | } | |
330 | ||
331 | /* | |
332 | * Compaction requires the taking of some coarse locks that are potentially | |
333 | * very heavily contended. The lock should be periodically unlocked to avoid | |
334 | * having disabled IRQs for a long time, even when there is nobody waiting on | |
335 | * the lock. It might also be that allowing the IRQs will result in | |
336 | * need_resched() becoming true. If scheduling is needed, async compaction | |
337 | * aborts. Sync compaction schedules. | |
338 | * Either compaction type will also abort if a fatal signal is pending. | |
339 | * In either case if the lock was locked, it is dropped and not regained. | |
340 | * | |
341 | * Returns true if compaction should abort due to fatal signal pending, or | |
342 | * async compaction due to need_resched() | |
343 | * Returns false when compaction can continue (sync compaction might have | |
344 | * scheduled) | |
345 | */ | |
346 | static bool compact_unlock_should_abort(spinlock_t *lock, | |
347 | unsigned long flags, bool *locked, struct compact_control *cc) | |
348 | { | |
349 | if (*locked) { | |
350 | spin_unlock_irqrestore(lock, flags); | |
351 | *locked = false; | |
352 | } | |
353 | ||
354 | if (fatal_signal_pending(current)) { | |
355 | cc->contended = COMPACT_CONTENDED_SCHED; | |
356 | return true; | |
357 | } | |
358 | ||
359 | if (need_resched()) { | |
360 | if (cc->mode == MIGRATE_ASYNC) { | |
361 | cc->contended = COMPACT_CONTENDED_SCHED; | |
362 | return true; | |
363 | } | |
364 | cond_resched(); | |
365 | } | |
366 | ||
367 | return false; | |
368 | } | |
369 | ||
370 | /* | |
371 | * Aside from avoiding lock contention, compaction also periodically checks | |
372 | * need_resched() and either schedules in sync compaction or aborts async | |
373 | * compaction. This is similar to what compact_unlock_should_abort() does, but | |
374 | * is used where no lock is concerned. | |
375 | * | |
376 | * Returns false when no scheduling was needed, or sync compaction scheduled. | |
377 | * Returns true when async compaction should abort. | |
378 | */ | |
379 | static inline bool compact_should_abort(struct compact_control *cc) | |
380 | { | |
381 | /* async compaction aborts if contended */ | |
382 | if (need_resched()) { | |
383 | if (cc->mode == MIGRATE_ASYNC) { | |
384 | cc->contended = COMPACT_CONTENDED_SCHED; | |
385 | return true; | |
386 | } | |
387 | ||
388 | cond_resched(); | |
389 | } | |
390 | ||
391 | return false; | |
392 | } | |
393 | ||
394 | /* | |
395 | * Isolate free pages onto a private freelist. If @strict is true, will abort | |
396 | * returning 0 on any invalid PFNs or non-free pages inside of the pageblock | |
397 | * (even though it may still end up isolating some pages). | |
398 | */ | |
399 | static unsigned long isolate_freepages_block(struct compact_control *cc, | |
400 | unsigned long *start_pfn, | |
401 | unsigned long end_pfn, | |
402 | struct list_head *freelist, | |
403 | bool strict) | |
404 | { | |
405 | int nr_scanned = 0, total_isolated = 0; | |
406 | struct page *cursor, *valid_page = NULL; | |
407 | unsigned long flags = 0; | |
408 | bool locked = false; | |
409 | unsigned long blockpfn = *start_pfn; | |
410 | ||
411 | cursor = pfn_to_page(blockpfn); | |
412 | ||
413 | /* Isolate free pages. */ | |
414 | for (; blockpfn < end_pfn; blockpfn++, cursor++) { | |
415 | int isolated, i; | |
416 | struct page *page = cursor; | |
417 | ||
418 | /* | |
419 | * Periodically drop the lock (if held) regardless of its | |
420 | * contention, to give chance to IRQs. Abort if fatal signal | |
421 | * pending or async compaction detects need_resched() | |
422 | */ | |
423 | if (!(blockpfn % SWAP_CLUSTER_MAX) | |
424 | && compact_unlock_should_abort(&cc->zone->lock, flags, | |
425 | &locked, cc)) | |
426 | break; | |
427 | ||
428 | nr_scanned++; | |
429 | if (!pfn_valid_within(blockpfn)) | |
430 | goto isolate_fail; | |
431 | ||
432 | if (!valid_page) | |
433 | valid_page = page; | |
434 | if (!PageBuddy(page)) | |
435 | goto isolate_fail; | |
436 | ||
437 | /* | |
438 | * If we already hold the lock, we can skip some rechecking. | |
439 | * Note that if we hold the lock now, checked_pageblock was | |
440 | * already set in some previous iteration (or strict is true), | |
441 | * so it is correct to skip the suitable migration target | |
442 | * recheck as well. | |
443 | */ | |
444 | if (!locked) { | |
445 | /* | |
446 | * The zone lock must be held to isolate freepages. | |
447 | * Unfortunately this is a very coarse lock and can be | |
448 | * heavily contended if there are parallel allocations | |
449 | * or parallel compactions. For async compaction do not | |
450 | * spin on the lock and we acquire the lock as late as | |
451 | * possible. | |
452 | */ | |
453 | locked = compact_trylock_irqsave(&cc->zone->lock, | |
454 | &flags, cc); | |
455 | if (!locked) | |
456 | break; | |
457 | ||
458 | /* Recheck this is a buddy page under lock */ | |
459 | if (!PageBuddy(page)) | |
460 | goto isolate_fail; | |
461 | } | |
462 | ||
463 | /* Found a free page, break it into order-0 pages */ | |
464 | isolated = split_free_page(page); | |
465 | total_isolated += isolated; | |
466 | for (i = 0; i < isolated; i++) { | |
467 | list_add(&page->lru, freelist); | |
468 | page++; | |
469 | } | |
470 | ||
471 | /* If a page was split, advance to the end of it */ | |
472 | if (isolated) { | |
473 | cc->nr_freepages += isolated; | |
474 | if (!strict && | |
475 | cc->nr_migratepages <= cc->nr_freepages) { | |
476 | blockpfn += isolated; | |
477 | break; | |
478 | } | |
479 | ||
480 | blockpfn += isolated - 1; | |
481 | cursor += isolated - 1; | |
482 | continue; | |
483 | } | |
484 | ||
485 | isolate_fail: | |
486 | if (strict) | |
487 | break; | |
488 | else | |
489 | continue; | |
490 | ||
491 | } | |
492 | ||
493 | trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn, | |
494 | nr_scanned, total_isolated); | |
495 | ||
496 | /* Record how far we have got within the block */ | |
497 | *start_pfn = blockpfn; | |
498 | ||
499 | /* | |
500 | * If strict isolation is requested by CMA then check that all the | |
501 | * pages requested were isolated. If there were any failures, 0 is | |
502 | * returned and CMA will fail. | |
503 | */ | |
504 | if (strict && blockpfn < end_pfn) | |
505 | total_isolated = 0; | |
506 | ||
507 | if (locked) | |
508 | spin_unlock_irqrestore(&cc->zone->lock, flags); | |
509 | ||
510 | /* Update the pageblock-skip if the whole pageblock was scanned */ | |
511 | if (blockpfn == end_pfn) | |
512 | update_pageblock_skip(cc, valid_page, total_isolated, false); | |
513 | ||
514 | count_compact_events(COMPACTFREE_SCANNED, nr_scanned); | |
515 | if (total_isolated) | |
516 | count_compact_events(COMPACTISOLATED, total_isolated); | |
517 | return total_isolated; | |
518 | } | |
519 | ||
520 | /** | |
521 | * isolate_freepages_range() - isolate free pages. | |
522 | * @start_pfn: The first PFN to start isolating. | |
523 | * @end_pfn: The one-past-last PFN. | |
524 | * | |
525 | * Non-free pages, invalid PFNs, or zone boundaries within the | |
526 | * [start_pfn, end_pfn) range are considered errors, cause function to | |
527 | * undo its actions and return zero. | |
528 | * | |
529 | * Otherwise, function returns one-past-the-last PFN of isolated page | |
530 | * (which may be greater then end_pfn if end fell in a middle of | |
531 | * a free page). | |
532 | */ | |
533 | unsigned long | |
534 | isolate_freepages_range(struct compact_control *cc, | |
535 | unsigned long start_pfn, unsigned long end_pfn) | |
536 | { | |
537 | unsigned long isolated, pfn, block_end_pfn; | |
538 | LIST_HEAD(freelist); | |
539 | ||
540 | pfn = start_pfn; | |
541 | block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages); | |
542 | ||
543 | for (; pfn < end_pfn; pfn += isolated, | |
544 | block_end_pfn += pageblock_nr_pages) { | |
545 | /* Protect pfn from changing by isolate_freepages_block */ | |
546 | unsigned long isolate_start_pfn = pfn; | |
547 | ||
548 | block_end_pfn = min(block_end_pfn, end_pfn); | |
549 | ||
550 | /* | |
551 | * pfn could pass the block_end_pfn if isolated freepage | |
552 | * is more than pageblock order. In this case, we adjust | |
553 | * scanning range to right one. | |
554 | */ | |
555 | if (pfn >= block_end_pfn) { | |
556 | block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages); | |
557 | block_end_pfn = min(block_end_pfn, end_pfn); | |
558 | } | |
559 | ||
560 | if (!pageblock_pfn_to_page(pfn, block_end_pfn, cc->zone)) | |
561 | break; | |
562 | ||
563 | isolated = isolate_freepages_block(cc, &isolate_start_pfn, | |
564 | block_end_pfn, &freelist, true); | |
565 | ||
566 | /* | |
567 | * In strict mode, isolate_freepages_block() returns 0 if | |
568 | * there are any holes in the block (ie. invalid PFNs or | |
569 | * non-free pages). | |
570 | */ | |
571 | if (!isolated) | |
572 | break; | |
573 | ||
574 | /* | |
575 | * If we managed to isolate pages, it is always (1 << n) * | |
576 | * pageblock_nr_pages for some non-negative n. (Max order | |
577 | * page may span two pageblocks). | |
578 | */ | |
579 | } | |
580 | ||
581 | /* split_free_page does not map the pages */ | |
582 | map_pages(&freelist); | |
583 | ||
584 | if (pfn < end_pfn) { | |
585 | /* Loop terminated early, cleanup. */ | |
586 | release_freepages(&freelist); | |
587 | return 0; | |
588 | } | |
589 | ||
590 | /* We don't use freelists for anything. */ | |
591 | return pfn; | |
592 | } | |
593 | ||
594 | /* Update the number of anon and file isolated pages in the zone */ | |
595 | static void acct_isolated(struct zone *zone, struct compact_control *cc) | |
596 | { | |
597 | struct page *page; | |
598 | unsigned int count[2] = { 0, }; | |
599 | ||
600 | if (list_empty(&cc->migratepages)) | |
601 | return; | |
602 | ||
603 | list_for_each_entry(page, &cc->migratepages, lru) | |
604 | count[!!page_is_file_cache(page)]++; | |
605 | ||
606 | mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]); | |
607 | mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]); | |
608 | } | |
609 | ||
610 | /* Similar to reclaim, but different enough that they don't share logic */ | |
611 | static bool too_many_isolated(struct zone *zone) | |
612 | { | |
613 | unsigned long active, inactive, isolated; | |
614 | ||
615 | inactive = zone_page_state(zone, NR_INACTIVE_FILE) + | |
616 | zone_page_state(zone, NR_INACTIVE_ANON); | |
617 | active = zone_page_state(zone, NR_ACTIVE_FILE) + | |
618 | zone_page_state(zone, NR_ACTIVE_ANON); | |
619 | isolated = zone_page_state(zone, NR_ISOLATED_FILE) + | |
620 | zone_page_state(zone, NR_ISOLATED_ANON); | |
621 | ||
622 | return isolated > (inactive + active) / 2; | |
623 | } | |
624 | ||
625 | /** | |
626 | * isolate_migratepages_block() - isolate all migrate-able pages within | |
627 | * a single pageblock | |
628 | * @cc: Compaction control structure. | |
629 | * @low_pfn: The first PFN to isolate | |
630 | * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock | |
631 | * @isolate_mode: Isolation mode to be used. | |
632 | * | |
633 | * Isolate all pages that can be migrated from the range specified by | |
634 | * [low_pfn, end_pfn). The range is expected to be within same pageblock. | |
635 | * Returns zero if there is a fatal signal pending, otherwise PFN of the | |
636 | * first page that was not scanned (which may be both less, equal to or more | |
637 | * than end_pfn). | |
638 | * | |
639 | * The pages are isolated on cc->migratepages list (not required to be empty), | |
640 | * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field | |
641 | * is neither read nor updated. | |
642 | */ | |
643 | static unsigned long | |
644 | isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, | |
645 | unsigned long end_pfn, isolate_mode_t isolate_mode) | |
646 | { | |
647 | struct zone *zone = cc->zone; | |
648 | unsigned long nr_scanned = 0, nr_isolated = 0; | |
649 | struct list_head *migratelist = &cc->migratepages; | |
650 | struct lruvec *lruvec; | |
651 | unsigned long flags = 0; | |
652 | bool locked = false; | |
653 | struct page *page = NULL, *valid_page = NULL; | |
654 | unsigned long start_pfn = low_pfn; | |
655 | ||
656 | /* | |
657 | * Ensure that there are not too many pages isolated from the LRU | |
658 | * list by either parallel reclaimers or compaction. If there are, | |
659 | * delay for some time until fewer pages are isolated | |
660 | */ | |
661 | while (unlikely(too_many_isolated(zone))) { | |
662 | /* async migration should just abort */ | |
663 | if (cc->mode == MIGRATE_ASYNC) | |
664 | return 0; | |
665 | ||
666 | congestion_wait(BLK_RW_ASYNC, HZ/10); | |
667 | ||
668 | if (fatal_signal_pending(current)) | |
669 | return 0; | |
670 | } | |
671 | ||
672 | if (compact_should_abort(cc)) | |
673 | return 0; | |
674 | ||
675 | /* Time to isolate some pages for migration */ | |
676 | for (; low_pfn < end_pfn; low_pfn++) { | |
677 | /* | |
678 | * Periodically drop the lock (if held) regardless of its | |
679 | * contention, to give chance to IRQs. Abort async compaction | |
680 | * if contended. | |
681 | */ | |
682 | if (!(low_pfn % SWAP_CLUSTER_MAX) | |
683 | && compact_unlock_should_abort(&zone->lru_lock, flags, | |
684 | &locked, cc)) | |
685 | break; | |
686 | ||
687 | if (!pfn_valid_within(low_pfn)) | |
688 | continue; | |
689 | nr_scanned++; | |
690 | ||
691 | page = pfn_to_page(low_pfn); | |
692 | ||
693 | if (!valid_page) | |
694 | valid_page = page; | |
695 | ||
696 | /* | |
697 | * Skip if free. We read page order here without zone lock | |
698 | * which is generally unsafe, but the race window is small and | |
699 | * the worst thing that can happen is that we skip some | |
700 | * potential isolation targets. | |
701 | */ | |
702 | if (PageBuddy(page)) { | |
703 | unsigned long freepage_order = page_order_unsafe(page); | |
704 | ||
705 | /* | |
706 | * Without lock, we cannot be sure that what we got is | |
707 | * a valid page order. Consider only values in the | |
708 | * valid order range to prevent low_pfn overflow. | |
709 | */ | |
710 | if (freepage_order > 0 && freepage_order < MAX_ORDER) | |
711 | low_pfn += (1UL << freepage_order) - 1; | |
712 | continue; | |
713 | } | |
714 | ||
715 | /* | |
716 | * Check may be lockless but that's ok as we recheck later. | |
717 | * It's possible to migrate LRU pages and balloon pages | |
718 | * Skip any other type of page | |
719 | */ | |
720 | if (!PageLRU(page)) { | |
721 | if (unlikely(balloon_page_movable(page))) { | |
722 | if (balloon_page_isolate(page)) { | |
723 | /* Successfully isolated */ | |
724 | goto isolate_success; | |
725 | } | |
726 | } | |
727 | continue; | |
728 | } | |
729 | ||
730 | /* | |
731 | * PageLRU is set. lru_lock normally excludes isolation | |
732 | * splitting and collapsing (collapsing has already happened | |
733 | * if PageLRU is set) but the lock is not necessarily taken | |
734 | * here and it is wasteful to take it just to check transhuge. | |
735 | * Check TransHuge without lock and skip the whole pageblock if | |
736 | * it's either a transhuge or hugetlbfs page, as calling | |
737 | * compound_order() without preventing THP from splitting the | |
738 | * page underneath us may return surprising results. | |
739 | */ | |
740 | if (PageTransHuge(page)) { | |
741 | if (!locked) | |
742 | low_pfn = ALIGN(low_pfn + 1, | |
743 | pageblock_nr_pages) - 1; | |
744 | else | |
745 | low_pfn += (1 << compound_order(page)) - 1; | |
746 | ||
747 | continue; | |
748 | } | |
749 | ||
750 | /* | |
751 | * Migration will fail if an anonymous page is pinned in memory, | |
752 | * so avoid taking lru_lock and isolating it unnecessarily in an | |
753 | * admittedly racy check. | |
754 | */ | |
755 | if (!page_mapping(page) && | |
756 | page_count(page) > page_mapcount(page)) | |
757 | continue; | |
758 | ||
759 | /* If we already hold the lock, we can skip some rechecking */ | |
760 | if (!locked) { | |
761 | locked = compact_trylock_irqsave(&zone->lru_lock, | |
762 | &flags, cc); | |
763 | if (!locked) | |
764 | break; | |
765 | ||
766 | /* Recheck PageLRU and PageTransHuge under lock */ | |
767 | if (!PageLRU(page)) | |
768 | continue; | |
769 | if (PageTransHuge(page)) { | |
770 | low_pfn += (1 << compound_order(page)) - 1; | |
771 | continue; | |
772 | } | |
773 | } | |
774 | ||
775 | lruvec = mem_cgroup_page_lruvec(page, zone); | |
776 | ||
777 | /* Try isolate the page */ | |
778 | if (__isolate_lru_page(page, isolate_mode) != 0) | |
779 | continue; | |
780 | ||
781 | VM_BUG_ON_PAGE(PageTransCompound(page), page); | |
782 | ||
783 | /* Successfully isolated */ | |
784 | del_page_from_lru_list(page, lruvec, page_lru(page)); | |
785 | ||
786 | isolate_success: | |
787 | list_add(&page->lru, migratelist); | |
788 | cc->nr_migratepages++; | |
789 | nr_isolated++; | |
790 | ||
791 | /* Avoid isolating too much */ | |
792 | if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) { | |
793 | ++low_pfn; | |
794 | break; | |
795 | } | |
796 | } | |
797 | ||
798 | /* | |
799 | * The PageBuddy() check could have potentially brought us outside | |
800 | * the range to be scanned. | |
801 | */ | |
802 | if (unlikely(low_pfn > end_pfn)) | |
803 | low_pfn = end_pfn; | |
804 | ||
805 | if (locked) | |
806 | spin_unlock_irqrestore(&zone->lru_lock, flags); | |
807 | ||
808 | /* | |
809 | * Update the pageblock-skip information and cached scanner pfn, | |
810 | * if the whole pageblock was scanned without isolating any page. | |
811 | */ | |
812 | if (low_pfn == end_pfn) | |
813 | update_pageblock_skip(cc, valid_page, nr_isolated, true); | |
814 | ||
815 | trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn, | |
816 | nr_scanned, nr_isolated); | |
817 | ||
818 | count_compact_events(COMPACTMIGRATE_SCANNED, nr_scanned); | |
819 | if (nr_isolated) | |
820 | count_compact_events(COMPACTISOLATED, nr_isolated); | |
821 | ||
822 | return low_pfn; | |
823 | } | |
824 | ||
825 | /** | |
826 | * isolate_migratepages_range() - isolate migrate-able pages in a PFN range | |
827 | * @cc: Compaction control structure. | |
828 | * @start_pfn: The first PFN to start isolating. | |
829 | * @end_pfn: The one-past-last PFN. | |
830 | * | |
831 | * Returns zero if isolation fails fatally due to e.g. pending signal. | |
832 | * Otherwise, function returns one-past-the-last PFN of isolated page | |
833 | * (which may be greater than end_pfn if end fell in a middle of a THP page). | |
834 | */ | |
835 | unsigned long | |
836 | isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, | |
837 | unsigned long end_pfn) | |
838 | { | |
839 | unsigned long pfn, block_end_pfn; | |
840 | ||
841 | /* Scan block by block. First and last block may be incomplete */ | |
842 | pfn = start_pfn; | |
843 | block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages); | |
844 | ||
845 | for (; pfn < end_pfn; pfn = block_end_pfn, | |
846 | block_end_pfn += pageblock_nr_pages) { | |
847 | ||
848 | block_end_pfn = min(block_end_pfn, end_pfn); | |
849 | ||
850 | if (!pageblock_pfn_to_page(pfn, block_end_pfn, cc->zone)) | |
851 | continue; | |
852 | ||
853 | pfn = isolate_migratepages_block(cc, pfn, block_end_pfn, | |
854 | ISOLATE_UNEVICTABLE); | |
855 | ||
856 | /* | |
857 | * In case of fatal failure, release everything that might | |
858 | * have been isolated in the previous iteration, and signal | |
859 | * the failure back to caller. | |
860 | */ | |
861 | if (!pfn) { | |
862 | putback_movable_pages(&cc->migratepages); | |
863 | cc->nr_migratepages = 0; | |
864 | break; | |
865 | } | |
866 | ||
867 | if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) | |
868 | break; | |
869 | } | |
870 | acct_isolated(cc->zone, cc); | |
871 | ||
872 | return pfn; | |
873 | } | |
874 | ||
875 | #endif /* CONFIG_COMPACTION || CONFIG_CMA */ | |
876 | #ifdef CONFIG_COMPACTION | |
877 | ||
878 | /* Returns true if the page is within a block suitable for migration to */ | |
879 | static bool suitable_migration_target(struct page *page) | |
880 | { | |
881 | /* If the page is a large free page, then disallow migration */ | |
882 | if (PageBuddy(page)) { | |
883 | /* | |
884 | * We are checking page_order without zone->lock taken. But | |
885 | * the only small danger is that we skip a potentially suitable | |
886 | * pageblock, so it's not worth to check order for valid range. | |
887 | */ | |
888 | if (page_order_unsafe(page) >= pageblock_order) | |
889 | return false; | |
890 | } | |
891 | ||
892 | /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */ | |
893 | if (migrate_async_suitable(get_pageblock_migratetype(page))) | |
894 | return true; | |
895 | ||
896 | /* Otherwise skip the block */ | |
897 | return false; | |
898 | } | |
899 | ||
900 | /* | |
901 | * Based on information in the current compact_control, find blocks | |
902 | * suitable for isolating free pages from and then isolate them. | |
903 | */ | |
904 | static void isolate_freepages(struct compact_control *cc) | |
905 | { | |
906 | struct zone *zone = cc->zone; | |
907 | struct page *page; | |
908 | unsigned long block_start_pfn; /* start of current pageblock */ | |
909 | unsigned long isolate_start_pfn; /* exact pfn we start at */ | |
910 | unsigned long block_end_pfn; /* end of current pageblock */ | |
911 | unsigned long low_pfn; /* lowest pfn scanner is able to scan */ | |
912 | struct list_head *freelist = &cc->freepages; | |
913 | ||
914 | /* | |
915 | * Initialise the free scanner. The starting point is where we last | |
916 | * successfully isolated from, zone-cached value, or the end of the | |
917 | * zone when isolating for the first time. For looping we also need | |
918 | * this pfn aligned down to the pageblock boundary, because we do | |
919 | * block_start_pfn -= pageblock_nr_pages in the for loop. | |
920 | * For ending point, take care when isolating in last pageblock of a | |
921 | * a zone which ends in the middle of a pageblock. | |
922 | * The low boundary is the end of the pageblock the migration scanner | |
923 | * is using. | |
924 | */ | |
925 | isolate_start_pfn = cc->free_pfn; | |
926 | block_start_pfn = cc->free_pfn & ~(pageblock_nr_pages-1); | |
927 | block_end_pfn = min(block_start_pfn + pageblock_nr_pages, | |
928 | zone_end_pfn(zone)); | |
929 | low_pfn = ALIGN(cc->migrate_pfn + 1, pageblock_nr_pages); | |
930 | ||
931 | /* | |
932 | * Isolate free pages until enough are available to migrate the | |
933 | * pages on cc->migratepages. We stop searching if the migrate | |
934 | * and free page scanners meet or enough free pages are isolated. | |
935 | */ | |
936 | for (; block_start_pfn >= low_pfn && | |
937 | cc->nr_migratepages > cc->nr_freepages; | |
938 | block_end_pfn = block_start_pfn, | |
939 | block_start_pfn -= pageblock_nr_pages, | |
940 | isolate_start_pfn = block_start_pfn) { | |
941 | ||
942 | /* | |
943 | * This can iterate a massively long zone without finding any | |
944 | * suitable migration targets, so periodically check if we need | |
945 | * to schedule, or even abort async compaction. | |
946 | */ | |
947 | if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)) | |
948 | && compact_should_abort(cc)) | |
949 | break; | |
950 | ||
951 | page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn, | |
952 | zone); | |
953 | if (!page) | |
954 | continue; | |
955 | ||
956 | /* Check the block is suitable for migration */ | |
957 | if (!suitable_migration_target(page)) | |
958 | continue; | |
959 | ||
960 | /* If isolation recently failed, do not retry */ | |
961 | if (!isolation_suitable(cc, page)) | |
962 | continue; | |
963 | ||
964 | /* Found a block suitable for isolating free pages from. */ | |
965 | isolate_freepages_block(cc, &isolate_start_pfn, | |
966 | block_end_pfn, freelist, false); | |
967 | ||
968 | /* | |
969 | * Remember where the free scanner should restart next time, | |
970 | * which is where isolate_freepages_block() left off. | |
971 | * But if it scanned the whole pageblock, isolate_start_pfn | |
972 | * now points at block_end_pfn, which is the start of the next | |
973 | * pageblock. | |
974 | * In that case we will however want to restart at the start | |
975 | * of the previous pageblock. | |
976 | */ | |
977 | cc->free_pfn = (isolate_start_pfn < block_end_pfn) ? | |
978 | isolate_start_pfn : | |
979 | block_start_pfn - pageblock_nr_pages; | |
980 | ||
981 | /* | |
982 | * isolate_freepages_block() might have aborted due to async | |
983 | * compaction being contended | |
984 | */ | |
985 | if (cc->contended) | |
986 | break; | |
987 | } | |
988 | ||
989 | /* split_free_page does not map the pages */ | |
990 | map_pages(freelist); | |
991 | ||
992 | /* | |
993 | * If we crossed the migrate scanner, we want to keep it that way | |
994 | * so that compact_finished() may detect this | |
995 | */ | |
996 | if (block_start_pfn < low_pfn) | |
997 | cc->free_pfn = cc->migrate_pfn; | |
998 | } | |
999 | ||
1000 | /* | |
1001 | * This is a migrate-callback that "allocates" freepages by taking pages | |
1002 | * from the isolated freelists in the block we are migrating to. | |
1003 | */ | |
1004 | static struct page *compaction_alloc(struct page *migratepage, | |
1005 | unsigned long data, | |
1006 | int **result) | |
1007 | { | |
1008 | struct compact_control *cc = (struct compact_control *)data; | |
1009 | struct page *freepage; | |
1010 | ||
1011 | /* | |
1012 | * Isolate free pages if necessary, and if we are not aborting due to | |
1013 | * contention. | |
1014 | */ | |
1015 | if (list_empty(&cc->freepages)) { | |
1016 | if (!cc->contended) | |
1017 | isolate_freepages(cc); | |
1018 | ||
1019 | if (list_empty(&cc->freepages)) | |
1020 | return NULL; | |
1021 | } | |
1022 | ||
1023 | freepage = list_entry(cc->freepages.next, struct page, lru); | |
1024 | list_del(&freepage->lru); | |
1025 | cc->nr_freepages--; | |
1026 | ||
1027 | return freepage; | |
1028 | } | |
1029 | ||
1030 | /* | |
1031 | * This is a migrate-callback that "frees" freepages back to the isolated | |
1032 | * freelist. All pages on the freelist are from the same zone, so there is no | |
1033 | * special handling needed for NUMA. | |
1034 | */ | |
1035 | static void compaction_free(struct page *page, unsigned long data) | |
1036 | { | |
1037 | struct compact_control *cc = (struct compact_control *)data; | |
1038 | ||
1039 | list_add(&page->lru, &cc->freepages); | |
1040 | cc->nr_freepages++; | |
1041 | } | |
1042 | ||
1043 | /* possible outcome of isolate_migratepages */ | |
1044 | typedef enum { | |
1045 | ISOLATE_ABORT, /* Abort compaction now */ | |
1046 | ISOLATE_NONE, /* No pages isolated, continue scanning */ | |
1047 | ISOLATE_SUCCESS, /* Pages isolated, migrate */ | |
1048 | } isolate_migrate_t; | |
1049 | ||
1050 | /* | |
1051 | * Allow userspace to control policy on scanning the unevictable LRU for | |
1052 | * compactable pages. | |
1053 | */ | |
1054 | int sysctl_compact_unevictable_allowed __read_mostly = 1; | |
1055 | ||
1056 | /* | |
1057 | * Isolate all pages that can be migrated from the first suitable block, | |
1058 | * starting at the block pointed to by the migrate scanner pfn within | |
1059 | * compact_control. | |
1060 | */ | |
1061 | static isolate_migrate_t isolate_migratepages(struct zone *zone, | |
1062 | struct compact_control *cc) | |
1063 | { | |
1064 | unsigned long low_pfn, end_pfn; | |
1065 | struct page *page; | |
1066 | const isolate_mode_t isolate_mode = | |
1067 | (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | | |
1068 | (cc->mode == MIGRATE_ASYNC ? ISOLATE_ASYNC_MIGRATE : 0); | |
1069 | ||
1070 | /* | |
1071 | * Start at where we last stopped, or beginning of the zone as | |
1072 | * initialized by compact_zone() | |
1073 | */ | |
1074 | low_pfn = cc->migrate_pfn; | |
1075 | ||
1076 | /* Only scan within a pageblock boundary */ | |
1077 | end_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages); | |
1078 | ||
1079 | /* | |
1080 | * Iterate over whole pageblocks until we find the first suitable. | |
1081 | * Do not cross the free scanner. | |
1082 | */ | |
1083 | for (; end_pfn <= cc->free_pfn; | |
1084 | low_pfn = end_pfn, end_pfn += pageblock_nr_pages) { | |
1085 | ||
1086 | /* | |
1087 | * This can potentially iterate a massively long zone with | |
1088 | * many pageblocks unsuitable, so periodically check if we | |
1089 | * need to schedule, or even abort async compaction. | |
1090 | */ | |
1091 | if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)) | |
1092 | && compact_should_abort(cc)) | |
1093 | break; | |
1094 | ||
1095 | page = pageblock_pfn_to_page(low_pfn, end_pfn, zone); | |
1096 | if (!page) | |
1097 | continue; | |
1098 | ||
1099 | /* If isolation recently failed, do not retry */ | |
1100 | if (!isolation_suitable(cc, page)) | |
1101 | continue; | |
1102 | ||
1103 | /* | |
1104 | * For async compaction, also only scan in MOVABLE blocks. | |
1105 | * Async compaction is optimistic to see if the minimum amount | |
1106 | * of work satisfies the allocation. | |
1107 | */ | |
1108 | if (cc->mode == MIGRATE_ASYNC && | |
1109 | !migrate_async_suitable(get_pageblock_migratetype(page))) | |
1110 | continue; | |
1111 | ||
1112 | /* Perform the isolation */ | |
1113 | low_pfn = isolate_migratepages_block(cc, low_pfn, end_pfn, | |
1114 | isolate_mode); | |
1115 | ||
1116 | if (!low_pfn || cc->contended) { | |
1117 | acct_isolated(zone, cc); | |
1118 | return ISOLATE_ABORT; | |
1119 | } | |
1120 | ||
1121 | /* | |
1122 | * Either we isolated something and proceed with migration. Or | |
1123 | * we failed and compact_zone should decide if we should | |
1124 | * continue or not. | |
1125 | */ | |
1126 | break; | |
1127 | } | |
1128 | ||
1129 | acct_isolated(zone, cc); | |
1130 | /* | |
1131 | * Record where migration scanner will be restarted. If we end up in | |
1132 | * the same pageblock as the free scanner, make the scanners fully | |
1133 | * meet so that compact_finished() terminates compaction. | |
1134 | */ | |
1135 | cc->migrate_pfn = (end_pfn <= cc->free_pfn) ? low_pfn : cc->free_pfn; | |
1136 | ||
1137 | return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE; | |
1138 | } | |
1139 | ||
1140 | static int __compact_finished(struct zone *zone, struct compact_control *cc, | |
1141 | const int migratetype) | |
1142 | { | |
1143 | unsigned int order; | |
1144 | unsigned long watermark; | |
1145 | ||
1146 | if (cc->contended || fatal_signal_pending(current)) | |
1147 | return COMPACT_PARTIAL; | |
1148 | ||
1149 | /* Compaction run completes if the migrate and free scanner meet */ | |
1150 | if (cc->free_pfn <= cc->migrate_pfn) { | |
1151 | /* Let the next compaction start anew. */ | |
1152 | zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn; | |
1153 | zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn; | |
1154 | zone->compact_cached_free_pfn = zone_end_pfn(zone); | |
1155 | ||
1156 | /* | |
1157 | * Mark that the PG_migrate_skip information should be cleared | |
1158 | * by kswapd when it goes to sleep. kswapd does not set the | |
1159 | * flag itself as the decision to be clear should be directly | |
1160 | * based on an allocation request. | |
1161 | */ | |
1162 | if (!current_is_kswapd()) | |
1163 | zone->compact_blockskip_flush = true; | |
1164 | ||
1165 | return COMPACT_COMPLETE; | |
1166 | } | |
1167 | ||
1168 | /* | |
1169 | * order == -1 is expected when compacting via | |
1170 | * /proc/sys/vm/compact_memory | |
1171 | */ | |
1172 | if (cc->order == -1) | |
1173 | return COMPACT_CONTINUE; | |
1174 | ||
1175 | /* Compaction run is not finished if the watermark is not met */ | |
1176 | watermark = low_wmark_pages(zone); | |
1177 | ||
1178 | if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx, | |
1179 | cc->alloc_flags)) | |
1180 | return COMPACT_CONTINUE; | |
1181 | ||
1182 | /* Direct compactor: Is a suitable page free? */ | |
1183 | for (order = cc->order; order < MAX_ORDER; order++) { | |
1184 | struct free_area *area = &zone->free_area[order]; | |
1185 | bool can_steal; | |
1186 | ||
1187 | /* Job done if page is free of the right migratetype */ | |
1188 | if (!list_empty(&area->free_list[migratetype])) | |
1189 | return COMPACT_PARTIAL; | |
1190 | ||
1191 | #ifdef CONFIG_CMA | |
1192 | /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */ | |
1193 | if (migratetype == MIGRATE_MOVABLE && | |
1194 | !list_empty(&area->free_list[MIGRATE_CMA])) | |
1195 | return COMPACT_PARTIAL; | |
1196 | #endif | |
1197 | /* | |
1198 | * Job done if allocation would steal freepages from | |
1199 | * other migratetype buddy lists. | |
1200 | */ | |
1201 | if (find_suitable_fallback(area, order, migratetype, | |
1202 | true, &can_steal) != -1) | |
1203 | return COMPACT_PARTIAL; | |
1204 | } | |
1205 | ||
1206 | return COMPACT_NO_SUITABLE_PAGE; | |
1207 | } | |
1208 | ||
1209 | static int compact_finished(struct zone *zone, struct compact_control *cc, | |
1210 | const int migratetype) | |
1211 | { | |
1212 | int ret; | |
1213 | ||
1214 | ret = __compact_finished(zone, cc, migratetype); | |
1215 | trace_mm_compaction_finished(zone, cc->order, ret); | |
1216 | if (ret == COMPACT_NO_SUITABLE_PAGE) | |
1217 | ret = COMPACT_CONTINUE; | |
1218 | ||
1219 | return ret; | |
1220 | } | |
1221 | ||
1222 | /* | |
1223 | * compaction_suitable: Is this suitable to run compaction on this zone now? | |
1224 | * Returns | |
1225 | * COMPACT_SKIPPED - If there are too few free pages for compaction | |
1226 | * COMPACT_PARTIAL - If the allocation would succeed without compaction | |
1227 | * COMPACT_CONTINUE - If compaction should run now | |
1228 | */ | |
1229 | static unsigned long __compaction_suitable(struct zone *zone, int order, | |
1230 | int alloc_flags, int classzone_idx) | |
1231 | { | |
1232 | int fragindex; | |
1233 | unsigned long watermark; | |
1234 | ||
1235 | /* | |
1236 | * order == -1 is expected when compacting via | |
1237 | * /proc/sys/vm/compact_memory | |
1238 | */ | |
1239 | if (order == -1) | |
1240 | return COMPACT_CONTINUE; | |
1241 | ||
1242 | watermark = low_wmark_pages(zone); | |
1243 | /* | |
1244 | * If watermarks for high-order allocation are already met, there | |
1245 | * should be no need for compaction at all. | |
1246 | */ | |
1247 | if (zone_watermark_ok(zone, order, watermark, classzone_idx, | |
1248 | alloc_flags)) | |
1249 | return COMPACT_PARTIAL; | |
1250 | ||
1251 | /* | |
1252 | * Watermarks for order-0 must be met for compaction. Note the 2UL. | |
1253 | * This is because during migration, copies of pages need to be | |
1254 | * allocated and for a short time, the footprint is higher | |
1255 | */ | |
1256 | watermark += (2UL << order); | |
1257 | if (!zone_watermark_ok(zone, 0, watermark, classzone_idx, alloc_flags)) | |
1258 | return COMPACT_SKIPPED; | |
1259 | ||
1260 | /* | |
1261 | * fragmentation index determines if allocation failures are due to | |
1262 | * low memory or external fragmentation | |
1263 | * | |
1264 | * index of -1000 would imply allocations might succeed depending on | |
1265 | * watermarks, but we already failed the high-order watermark check | |
1266 | * index towards 0 implies failure is due to lack of memory | |
1267 | * index towards 1000 implies failure is due to fragmentation | |
1268 | * | |
1269 | * Only compact if a failure would be due to fragmentation. | |
1270 | */ | |
1271 | fragindex = fragmentation_index(zone, order); | |
1272 | if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold) | |
1273 | return COMPACT_NOT_SUITABLE_ZONE; | |
1274 | ||
1275 | return COMPACT_CONTINUE; | |
1276 | } | |
1277 | ||
1278 | unsigned long compaction_suitable(struct zone *zone, int order, | |
1279 | int alloc_flags, int classzone_idx) | |
1280 | { | |
1281 | unsigned long ret; | |
1282 | ||
1283 | ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx); | |
1284 | trace_mm_compaction_suitable(zone, order, ret); | |
1285 | if (ret == COMPACT_NOT_SUITABLE_ZONE) | |
1286 | ret = COMPACT_SKIPPED; | |
1287 | ||
1288 | return ret; | |
1289 | } | |
1290 | ||
1291 | static int compact_zone(struct zone *zone, struct compact_control *cc) | |
1292 | { | |
1293 | int ret; | |
1294 | unsigned long start_pfn = zone->zone_start_pfn; | |
1295 | unsigned long end_pfn = zone_end_pfn(zone); | |
1296 | const int migratetype = gfpflags_to_migratetype(cc->gfp_mask); | |
1297 | const bool sync = cc->mode != MIGRATE_ASYNC; | |
1298 | unsigned long last_migrated_pfn = 0; | |
1299 | ||
1300 | ret = compaction_suitable(zone, cc->order, cc->alloc_flags, | |
1301 | cc->classzone_idx); | |
1302 | switch (ret) { | |
1303 | case COMPACT_PARTIAL: | |
1304 | case COMPACT_SKIPPED: | |
1305 | /* Compaction is likely to fail */ | |
1306 | return ret; | |
1307 | case COMPACT_CONTINUE: | |
1308 | /* Fall through to compaction */ | |
1309 | ; | |
1310 | } | |
1311 | ||
1312 | /* | |
1313 | * Clear pageblock skip if there were failures recently and compaction | |
1314 | * is about to be retried after being deferred. kswapd does not do | |
1315 | * this reset as it'll reset the cached information when going to sleep. | |
1316 | */ | |
1317 | if (compaction_restarting(zone, cc->order) && !current_is_kswapd()) | |
1318 | __reset_isolation_suitable(zone); | |
1319 | ||
1320 | /* | |
1321 | * Setup to move all movable pages to the end of the zone. Used cached | |
1322 | * information on where the scanners should start but check that it | |
1323 | * is initialised by ensuring the values are within zone boundaries. | |
1324 | */ | |
1325 | cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync]; | |
1326 | cc->free_pfn = zone->compact_cached_free_pfn; | |
1327 | if (cc->free_pfn < start_pfn || cc->free_pfn > end_pfn) { | |
1328 | cc->free_pfn = end_pfn & ~(pageblock_nr_pages-1); | |
1329 | zone->compact_cached_free_pfn = cc->free_pfn; | |
1330 | } | |
1331 | if (cc->migrate_pfn < start_pfn || cc->migrate_pfn > end_pfn) { | |
1332 | cc->migrate_pfn = start_pfn; | |
1333 | zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn; | |
1334 | zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn; | |
1335 | } | |
1336 | ||
1337 | trace_mm_compaction_begin(start_pfn, cc->migrate_pfn, | |
1338 | cc->free_pfn, end_pfn, sync); | |
1339 | ||
1340 | migrate_prep_local(); | |
1341 | ||
1342 | while ((ret = compact_finished(zone, cc, migratetype)) == | |
1343 | COMPACT_CONTINUE) { | |
1344 | int err; | |
1345 | unsigned long isolate_start_pfn = cc->migrate_pfn; | |
1346 | ||
1347 | switch (isolate_migratepages(zone, cc)) { | |
1348 | case ISOLATE_ABORT: | |
1349 | ret = COMPACT_PARTIAL; | |
1350 | putback_movable_pages(&cc->migratepages); | |
1351 | cc->nr_migratepages = 0; | |
1352 | goto out; | |
1353 | case ISOLATE_NONE: | |
1354 | /* | |
1355 | * We haven't isolated and migrated anything, but | |
1356 | * there might still be unflushed migrations from | |
1357 | * previous cc->order aligned block. | |
1358 | */ | |
1359 | goto check_drain; | |
1360 | case ISOLATE_SUCCESS: | |
1361 | ; | |
1362 | } | |
1363 | ||
1364 | err = migrate_pages(&cc->migratepages, compaction_alloc, | |
1365 | compaction_free, (unsigned long)cc, cc->mode, | |
1366 | MR_COMPACTION); | |
1367 | ||
1368 | trace_mm_compaction_migratepages(cc->nr_migratepages, err, | |
1369 | &cc->migratepages); | |
1370 | ||
1371 | /* All pages were either migrated or will be released */ | |
1372 | cc->nr_migratepages = 0; | |
1373 | if (err) { | |
1374 | putback_movable_pages(&cc->migratepages); | |
1375 | /* | |
1376 | * migrate_pages() may return -ENOMEM when scanners meet | |
1377 | * and we want compact_finished() to detect it | |
1378 | */ | |
1379 | if (err == -ENOMEM && cc->free_pfn > cc->migrate_pfn) { | |
1380 | ret = COMPACT_PARTIAL; | |
1381 | goto out; | |
1382 | } | |
1383 | } | |
1384 | ||
1385 | /* | |
1386 | * Record where we could have freed pages by migration and not | |
1387 | * yet flushed them to buddy allocator. We use the pfn that | |
1388 | * isolate_migratepages() started from in this loop iteration | |
1389 | * - this is the lowest page that could have been isolated and | |
1390 | * then freed by migration. | |
1391 | */ | |
1392 | if (!last_migrated_pfn) | |
1393 | last_migrated_pfn = isolate_start_pfn; | |
1394 | ||
1395 | check_drain: | |
1396 | /* | |
1397 | * Has the migration scanner moved away from the previous | |
1398 | * cc->order aligned block where we migrated from? If yes, | |
1399 | * flush the pages that were freed, so that they can merge and | |
1400 | * compact_finished() can detect immediately if allocation | |
1401 | * would succeed. | |
1402 | */ | |
1403 | if (cc->order > 0 && last_migrated_pfn) { | |
1404 | int cpu; | |
1405 | unsigned long current_block_start = | |
1406 | cc->migrate_pfn & ~((1UL << cc->order) - 1); | |
1407 | ||
1408 | if (last_migrated_pfn < current_block_start) { | |
1409 | cpu = get_cpu(); | |
1410 | lru_add_drain_cpu(cpu); | |
1411 | drain_local_pages(zone); | |
1412 | put_cpu(); | |
1413 | /* No more flushing until we migrate again */ | |
1414 | last_migrated_pfn = 0; | |
1415 | } | |
1416 | } | |
1417 | ||
1418 | } | |
1419 | ||
1420 | out: | |
1421 | /* | |
1422 | * Release free pages and update where the free scanner should restart, | |
1423 | * so we don't leave any returned pages behind in the next attempt. | |
1424 | */ | |
1425 | if (cc->nr_freepages > 0) { | |
1426 | unsigned long free_pfn = release_freepages(&cc->freepages); | |
1427 | ||
1428 | cc->nr_freepages = 0; | |
1429 | VM_BUG_ON(free_pfn == 0); | |
1430 | /* The cached pfn is always the first in a pageblock */ | |
1431 | free_pfn &= ~(pageblock_nr_pages-1); | |
1432 | /* | |
1433 | * Only go back, not forward. The cached pfn might have been | |
1434 | * already reset to zone end in compact_finished() | |
1435 | */ | |
1436 | if (free_pfn > zone->compact_cached_free_pfn) | |
1437 | zone->compact_cached_free_pfn = free_pfn; | |
1438 | } | |
1439 | ||
1440 | trace_mm_compaction_end(start_pfn, cc->migrate_pfn, | |
1441 | cc->free_pfn, end_pfn, sync, ret); | |
1442 | ||
1443 | return ret; | |
1444 | } | |
1445 | ||
1446 | static unsigned long compact_zone_order(struct zone *zone, int order, | |
1447 | gfp_t gfp_mask, enum migrate_mode mode, int *contended, | |
1448 | int alloc_flags, int classzone_idx) | |
1449 | { | |
1450 | unsigned long ret; | |
1451 | struct compact_control cc = { | |
1452 | .nr_freepages = 0, | |
1453 | .nr_migratepages = 0, | |
1454 | .order = order, | |
1455 | .gfp_mask = gfp_mask, | |
1456 | .zone = zone, | |
1457 | .mode = mode, | |
1458 | .alloc_flags = alloc_flags, | |
1459 | .classzone_idx = classzone_idx, | |
1460 | }; | |
1461 | INIT_LIST_HEAD(&cc.freepages); | |
1462 | INIT_LIST_HEAD(&cc.migratepages); | |
1463 | ||
1464 | ret = compact_zone(zone, &cc); | |
1465 | ||
1466 | VM_BUG_ON(!list_empty(&cc.freepages)); | |
1467 | VM_BUG_ON(!list_empty(&cc.migratepages)); | |
1468 | ||
1469 | *contended = cc.contended; | |
1470 | return ret; | |
1471 | } | |
1472 | ||
1473 | int sysctl_extfrag_threshold = 500; | |
1474 | ||
1475 | /** | |
1476 | * try_to_compact_pages - Direct compact to satisfy a high-order allocation | |
1477 | * @gfp_mask: The GFP mask of the current allocation | |
1478 | * @order: The order of the current allocation | |
1479 | * @alloc_flags: The allocation flags of the current allocation | |
1480 | * @ac: The context of current allocation | |
1481 | * @mode: The migration mode for async, sync light, or sync migration | |
1482 | * @contended: Return value that determines if compaction was aborted due to | |
1483 | * need_resched() or lock contention | |
1484 | * | |
1485 | * This is the main entry point for direct page compaction. | |
1486 | */ | |
1487 | unsigned long try_to_compact_pages(gfp_t gfp_mask, unsigned int order, | |
1488 | int alloc_flags, const struct alloc_context *ac, | |
1489 | enum migrate_mode mode, int *contended) | |
1490 | { | |
1491 | int may_enter_fs = gfp_mask & __GFP_FS; | |
1492 | int may_perform_io = gfp_mask & __GFP_IO; | |
1493 | struct zoneref *z; | |
1494 | struct zone *zone; | |
1495 | int rc = COMPACT_DEFERRED; | |
1496 | int all_zones_contended = COMPACT_CONTENDED_LOCK; /* init for &= op */ | |
1497 | ||
1498 | *contended = COMPACT_CONTENDED_NONE; | |
1499 | ||
1500 | /* Check if the GFP flags allow compaction */ | |
1501 | if (!order || !may_enter_fs || !may_perform_io) | |
1502 | return COMPACT_SKIPPED; | |
1503 | ||
1504 | trace_mm_compaction_try_to_compact_pages(order, gfp_mask, mode); | |
1505 | ||
1506 | /* Compact each zone in the list */ | |
1507 | for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx, | |
1508 | ac->nodemask) { | |
1509 | int status; | |
1510 | int zone_contended; | |
1511 | ||
1512 | if (compaction_deferred(zone, order)) | |
1513 | continue; | |
1514 | ||
1515 | status = compact_zone_order(zone, order, gfp_mask, mode, | |
1516 | &zone_contended, alloc_flags, | |
1517 | ac->classzone_idx); | |
1518 | rc = max(status, rc); | |
1519 | /* | |
1520 | * It takes at least one zone that wasn't lock contended | |
1521 | * to clear all_zones_contended. | |
1522 | */ | |
1523 | all_zones_contended &= zone_contended; | |
1524 | ||
1525 | /* If a normal allocation would succeed, stop compacting */ | |
1526 | if (zone_watermark_ok(zone, order, low_wmark_pages(zone), | |
1527 | ac->classzone_idx, alloc_flags)) { | |
1528 | /* | |
1529 | * We think the allocation will succeed in this zone, | |
1530 | * but it is not certain, hence the false. The caller | |
1531 | * will repeat this with true if allocation indeed | |
1532 | * succeeds in this zone. | |
1533 | */ | |
1534 | compaction_defer_reset(zone, order, false); | |
1535 | /* | |
1536 | * It is possible that async compaction aborted due to | |
1537 | * need_resched() and the watermarks were ok thanks to | |
1538 | * somebody else freeing memory. The allocation can | |
1539 | * however still fail so we better signal the | |
1540 | * need_resched() contention anyway (this will not | |
1541 | * prevent the allocation attempt). | |
1542 | */ | |
1543 | if (zone_contended == COMPACT_CONTENDED_SCHED) | |
1544 | *contended = COMPACT_CONTENDED_SCHED; | |
1545 | ||
1546 | goto break_loop; | |
1547 | } | |
1548 | ||
1549 | if (mode != MIGRATE_ASYNC && status == COMPACT_COMPLETE) { | |
1550 | /* | |
1551 | * We think that allocation won't succeed in this zone | |
1552 | * so we defer compaction there. If it ends up | |
1553 | * succeeding after all, it will be reset. | |
1554 | */ | |
1555 | defer_compaction(zone, order); | |
1556 | } | |
1557 | ||
1558 | /* | |
1559 | * We might have stopped compacting due to need_resched() in | |
1560 | * async compaction, or due to a fatal signal detected. In that | |
1561 | * case do not try further zones and signal need_resched() | |
1562 | * contention. | |
1563 | */ | |
1564 | if ((zone_contended == COMPACT_CONTENDED_SCHED) | |
1565 | || fatal_signal_pending(current)) { | |
1566 | *contended = COMPACT_CONTENDED_SCHED; | |
1567 | goto break_loop; | |
1568 | } | |
1569 | ||
1570 | continue; | |
1571 | break_loop: | |
1572 | /* | |
1573 | * We might not have tried all the zones, so be conservative | |
1574 | * and assume they are not all lock contended. | |
1575 | */ | |
1576 | all_zones_contended = 0; | |
1577 | break; | |
1578 | } | |
1579 | ||
1580 | /* | |
1581 | * If at least one zone wasn't deferred or skipped, we report if all | |
1582 | * zones that were tried were lock contended. | |
1583 | */ | |
1584 | if (rc > COMPACT_SKIPPED && all_zones_contended) | |
1585 | *contended = COMPACT_CONTENDED_LOCK; | |
1586 | ||
1587 | return rc; | |
1588 | } | |
1589 | ||
1590 | ||
1591 | /* Compact all zones within a node */ | |
1592 | static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc) | |
1593 | { | |
1594 | int zoneid; | |
1595 | struct zone *zone; | |
1596 | ||
1597 | for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { | |
1598 | ||
1599 | zone = &pgdat->node_zones[zoneid]; | |
1600 | if (!populated_zone(zone)) | |
1601 | continue; | |
1602 | ||
1603 | cc->nr_freepages = 0; | |
1604 | cc->nr_migratepages = 0; | |
1605 | cc->zone = zone; | |
1606 | INIT_LIST_HEAD(&cc->freepages); | |
1607 | INIT_LIST_HEAD(&cc->migratepages); | |
1608 | ||
1609 | /* | |
1610 | * When called via /proc/sys/vm/compact_memory | |
1611 | * this makes sure we compact the whole zone regardless of | |
1612 | * cached scanner positions. | |
1613 | */ | |
1614 | if (cc->order == -1) | |
1615 | __reset_isolation_suitable(zone); | |
1616 | ||
1617 | if (cc->order == -1 || !compaction_deferred(zone, cc->order)) | |
1618 | compact_zone(zone, cc); | |
1619 | ||
1620 | if (cc->order > 0) { | |
1621 | if (zone_watermark_ok(zone, cc->order, | |
1622 | low_wmark_pages(zone), 0, 0)) | |
1623 | compaction_defer_reset(zone, cc->order, false); | |
1624 | } | |
1625 | ||
1626 | VM_BUG_ON(!list_empty(&cc->freepages)); | |
1627 | VM_BUG_ON(!list_empty(&cc->migratepages)); | |
1628 | } | |
1629 | } | |
1630 | ||
1631 | void compact_pgdat(pg_data_t *pgdat, int order) | |
1632 | { | |
1633 | struct compact_control cc = { | |
1634 | .order = order, | |
1635 | .mode = MIGRATE_ASYNC, | |
1636 | }; | |
1637 | ||
1638 | if (!order) | |
1639 | return; | |
1640 | ||
1641 | __compact_pgdat(pgdat, &cc); | |
1642 | } | |
1643 | ||
1644 | static void compact_node(int nid) | |
1645 | { | |
1646 | struct compact_control cc = { | |
1647 | .order = -1, | |
1648 | .mode = MIGRATE_SYNC, | |
1649 | .ignore_skip_hint = true, | |
1650 | }; | |
1651 | ||
1652 | __compact_pgdat(NODE_DATA(nid), &cc); | |
1653 | } | |
1654 | ||
1655 | /* Compact all nodes in the system */ | |
1656 | static void compact_nodes(void) | |
1657 | { | |
1658 | int nid; | |
1659 | ||
1660 | /* Flush pending updates to the LRU lists */ | |
1661 | lru_add_drain_all(); | |
1662 | ||
1663 | for_each_online_node(nid) | |
1664 | compact_node(nid); | |
1665 | } | |
1666 | ||
1667 | /* The written value is actually unused, all memory is compacted */ | |
1668 | int sysctl_compact_memory; | |
1669 | ||
1670 | /* This is the entry point for compacting all nodes via /proc/sys/vm */ | |
1671 | int sysctl_compaction_handler(struct ctl_table *table, int write, | |
1672 | void __user *buffer, size_t *length, loff_t *ppos) | |
1673 | { | |
1674 | if (write) | |
1675 | compact_nodes(); | |
1676 | ||
1677 | return 0; | |
1678 | } | |
1679 | ||
1680 | int sysctl_extfrag_handler(struct ctl_table *table, int write, | |
1681 | void __user *buffer, size_t *length, loff_t *ppos) | |
1682 | { | |
1683 | proc_dointvec_minmax(table, write, buffer, length, ppos); | |
1684 | ||
1685 | return 0; | |
1686 | } | |
1687 | ||
1688 | #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) | |
1689 | static ssize_t sysfs_compact_node(struct device *dev, | |
1690 | struct device_attribute *attr, | |
1691 | const char *buf, size_t count) | |
1692 | { | |
1693 | int nid = dev->id; | |
1694 | ||
1695 | if (nid >= 0 && nid < nr_node_ids && node_online(nid)) { | |
1696 | /* Flush pending updates to the LRU lists */ | |
1697 | lru_add_drain_all(); | |
1698 | ||
1699 | compact_node(nid); | |
1700 | } | |
1701 | ||
1702 | return count; | |
1703 | } | |
1704 | static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node); | |
1705 | ||
1706 | int compaction_register_node(struct node *node) | |
1707 | { | |
1708 | return device_create_file(&node->dev, &dev_attr_compact); | |
1709 | } | |
1710 | ||
1711 | void compaction_unregister_node(struct node *node) | |
1712 | { | |
1713 | return device_remove_file(&node->dev, &dev_attr_compact); | |
1714 | } | |
1715 | #endif /* CONFIG_SYSFS && CONFIG_NUMA */ | |
1716 | ||
1717 | #endif /* CONFIG_COMPACTION */ |