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