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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/page-isolation.h> | |
19 | #include <linux/kasan.h> | |
20 | #include <linux/kthread.h> | |
21 | #include <linux/freezer.h> | |
22 | #include <linux/page_owner.h> | |
23 | #include "internal.h" | |
24 | ||
25 | #ifdef CONFIG_COMPACTION | |
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 | #define block_start_pfn(pfn, order) round_down(pfn, 1UL << (order)) | |
46 | #define block_end_pfn(pfn, order) ALIGN((pfn) + 1, 1UL << (order)) | |
47 | #define pageblock_start_pfn(pfn) block_start_pfn(pfn, pageblock_order) | |
48 | #define pageblock_end_pfn(pfn) block_end_pfn(pfn, pageblock_order) | |
49 | ||
50 | static unsigned long release_freepages(struct list_head *freelist) | |
51 | { | |
52 | struct page *page, *next; | |
53 | unsigned long high_pfn = 0; | |
54 | ||
55 | list_for_each_entry_safe(page, next, freelist, lru) { | |
56 | unsigned long pfn = page_to_pfn(page); | |
57 | list_del(&page->lru); | |
58 | __free_page(page); | |
59 | if (pfn > high_pfn) | |
60 | high_pfn = pfn; | |
61 | } | |
62 | ||
63 | return high_pfn; | |
64 | } | |
65 | ||
66 | static void map_pages(struct list_head *list) | |
67 | { | |
68 | unsigned int i, order, nr_pages; | |
69 | struct page *page, *next; | |
70 | LIST_HEAD(tmp_list); | |
71 | ||
72 | list_for_each_entry_safe(page, next, list, lru) { | |
73 | list_del(&page->lru); | |
74 | ||
75 | order = page_private(page); | |
76 | nr_pages = 1 << order; | |
77 | ||
78 | post_alloc_hook(page, order, __GFP_MOVABLE); | |
79 | if (order) | |
80 | split_page(page, order); | |
81 | ||
82 | for (i = 0; i < nr_pages; i++) { | |
83 | list_add(&page->lru, &tmp_list); | |
84 | page++; | |
85 | } | |
86 | } | |
87 | ||
88 | list_splice(&tmp_list, list); | |
89 | } | |
90 | ||
91 | static inline bool migrate_async_suitable(int migratetype) | |
92 | { | |
93 | return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE; | |
94 | } | |
95 | ||
96 | #ifdef CONFIG_COMPACTION | |
97 | ||
98 | int PageMovable(struct page *page) | |
99 | { | |
100 | struct address_space *mapping; | |
101 | ||
102 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
103 | if (!__PageMovable(page)) | |
104 | return 0; | |
105 | ||
106 | mapping = page_mapping(page); | |
107 | if (mapping && mapping->a_ops && mapping->a_ops->isolate_page) | |
108 | return 1; | |
109 | ||
110 | return 0; | |
111 | } | |
112 | EXPORT_SYMBOL(PageMovable); | |
113 | ||
114 | void __SetPageMovable(struct page *page, struct address_space *mapping) | |
115 | { | |
116 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
117 | VM_BUG_ON_PAGE((unsigned long)mapping & PAGE_MAPPING_MOVABLE, page); | |
118 | page->mapping = (void *)((unsigned long)mapping | PAGE_MAPPING_MOVABLE); | |
119 | } | |
120 | EXPORT_SYMBOL(__SetPageMovable); | |
121 | ||
122 | void __ClearPageMovable(struct page *page) | |
123 | { | |
124 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
125 | VM_BUG_ON_PAGE(!PageMovable(page), page); | |
126 | /* | |
127 | * Clear registered address_space val with keeping PAGE_MAPPING_MOVABLE | |
128 | * flag so that VM can catch up released page by driver after isolation. | |
129 | * With it, VM migration doesn't try to put it back. | |
130 | */ | |
131 | page->mapping = (void *)((unsigned long)page->mapping & | |
132 | PAGE_MAPPING_MOVABLE); | |
133 | } | |
134 | EXPORT_SYMBOL(__ClearPageMovable); | |
135 | ||
136 | /* Do not skip compaction more than 64 times */ | |
137 | #define COMPACT_MAX_DEFER_SHIFT 6 | |
138 | ||
139 | /* | |
140 | * Compaction is deferred when compaction fails to result in a page | |
141 | * allocation success. 1 << compact_defer_limit compactions are skipped up | |
142 | * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT | |
143 | */ | |
144 | void defer_compaction(struct zone *zone, int order) | |
145 | { | |
146 | zone->compact_considered = 0; | |
147 | zone->compact_defer_shift++; | |
148 | ||
149 | if (order < zone->compact_order_failed) | |
150 | zone->compact_order_failed = order; | |
151 | ||
152 | if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT) | |
153 | zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT; | |
154 | ||
155 | trace_mm_compaction_defer_compaction(zone, order); | |
156 | } | |
157 | ||
158 | /* Returns true if compaction should be skipped this time */ | |
159 | bool compaction_deferred(struct zone *zone, int order) | |
160 | { | |
161 | unsigned long defer_limit = 1UL << zone->compact_defer_shift; | |
162 | ||
163 | if (order < zone->compact_order_failed) | |
164 | return false; | |
165 | ||
166 | /* Avoid possible overflow */ | |
167 | if (++zone->compact_considered > defer_limit) | |
168 | zone->compact_considered = defer_limit; | |
169 | ||
170 | if (zone->compact_considered >= defer_limit) | |
171 | return false; | |
172 | ||
173 | trace_mm_compaction_deferred(zone, order); | |
174 | ||
175 | return true; | |
176 | } | |
177 | ||
178 | /* | |
179 | * Update defer tracking counters after successful compaction of given order, | |
180 | * which means an allocation either succeeded (alloc_success == true) or is | |
181 | * expected to succeed. | |
182 | */ | |
183 | void compaction_defer_reset(struct zone *zone, int order, | |
184 | bool alloc_success) | |
185 | { | |
186 | if (alloc_success) { | |
187 | zone->compact_considered = 0; | |
188 | zone->compact_defer_shift = 0; | |
189 | } | |
190 | if (order >= zone->compact_order_failed) | |
191 | zone->compact_order_failed = order + 1; | |
192 | ||
193 | trace_mm_compaction_defer_reset(zone, order); | |
194 | } | |
195 | ||
196 | /* Returns true if restarting compaction after many failures */ | |
197 | bool compaction_restarting(struct zone *zone, int order) | |
198 | { | |
199 | if (order < zone->compact_order_failed) | |
200 | return false; | |
201 | ||
202 | return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT && | |
203 | zone->compact_considered >= 1UL << zone->compact_defer_shift; | |
204 | } | |
205 | ||
206 | /* Returns true if the pageblock should be scanned for pages to isolate. */ | |
207 | static inline bool isolation_suitable(struct compact_control *cc, | |
208 | struct page *page) | |
209 | { | |
210 | if (cc->ignore_skip_hint) | |
211 | return true; | |
212 | ||
213 | return !get_pageblock_skip(page); | |
214 | } | |
215 | ||
216 | static void reset_cached_positions(struct zone *zone) | |
217 | { | |
218 | zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn; | |
219 | zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn; | |
220 | zone->compact_cached_free_pfn = | |
221 | pageblock_start_pfn(zone_end_pfn(zone) - 1); | |
222 | } | |
223 | ||
224 | /* | |
225 | * This function is called to clear all cached information on pageblocks that | |
226 | * should be skipped for page isolation when the migrate and free page scanner | |
227 | * meet. | |
228 | */ | |
229 | static void __reset_isolation_suitable(struct zone *zone) | |
230 | { | |
231 | unsigned long start_pfn = zone->zone_start_pfn; | |
232 | unsigned long end_pfn = zone_end_pfn(zone); | |
233 | unsigned long pfn; | |
234 | ||
235 | zone->compact_blockskip_flush = false; | |
236 | ||
237 | /* Walk the zone and mark every pageblock as suitable for isolation */ | |
238 | for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) { | |
239 | struct page *page; | |
240 | ||
241 | cond_resched(); | |
242 | ||
243 | if (!pfn_valid(pfn)) | |
244 | continue; | |
245 | ||
246 | page = pfn_to_page(pfn); | |
247 | if (zone != page_zone(page)) | |
248 | continue; | |
249 | ||
250 | clear_pageblock_skip(page); | |
251 | } | |
252 | ||
253 | reset_cached_positions(zone); | |
254 | } | |
255 | ||
256 | void reset_isolation_suitable(pg_data_t *pgdat) | |
257 | { | |
258 | int zoneid; | |
259 | ||
260 | for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { | |
261 | struct zone *zone = &pgdat->node_zones[zoneid]; | |
262 | if (!populated_zone(zone)) | |
263 | continue; | |
264 | ||
265 | /* Only flush if a full compaction finished recently */ | |
266 | if (zone->compact_blockskip_flush) | |
267 | __reset_isolation_suitable(zone); | |
268 | } | |
269 | } | |
270 | ||
271 | /* | |
272 | * If no pages were isolated then mark this pageblock to be skipped in the | |
273 | * future. The information is later cleared by __reset_isolation_suitable(). | |
274 | */ | |
275 | static void update_pageblock_skip(struct compact_control *cc, | |
276 | struct page *page, unsigned long nr_isolated, | |
277 | bool migrate_scanner) | |
278 | { | |
279 | struct zone *zone = cc->zone; | |
280 | unsigned long pfn; | |
281 | ||
282 | if (cc->ignore_skip_hint) | |
283 | return; | |
284 | ||
285 | if (!page) | |
286 | return; | |
287 | ||
288 | if (nr_isolated) | |
289 | return; | |
290 | ||
291 | set_pageblock_skip(page); | |
292 | ||
293 | pfn = page_to_pfn(page); | |
294 | ||
295 | /* Update where async and sync compaction should restart */ | |
296 | if (migrate_scanner) { | |
297 | if (pfn > zone->compact_cached_migrate_pfn[0]) | |
298 | zone->compact_cached_migrate_pfn[0] = pfn; | |
299 | if (cc->mode != MIGRATE_ASYNC && | |
300 | pfn > zone->compact_cached_migrate_pfn[1]) | |
301 | zone->compact_cached_migrate_pfn[1] = pfn; | |
302 | } else { | |
303 | if (pfn < zone->compact_cached_free_pfn) | |
304 | zone->compact_cached_free_pfn = pfn; | |
305 | } | |
306 | } | |
307 | #else | |
308 | static inline bool isolation_suitable(struct compact_control *cc, | |
309 | struct page *page) | |
310 | { | |
311 | return true; | |
312 | } | |
313 | ||
314 | static void update_pageblock_skip(struct compact_control *cc, | |
315 | struct page *page, unsigned long nr_isolated, | |
316 | bool migrate_scanner) | |
317 | { | |
318 | } | |
319 | #endif /* CONFIG_COMPACTION */ | |
320 | ||
321 | /* | |
322 | * Compaction requires the taking of some coarse locks that are potentially | |
323 | * very heavily contended. For async compaction, back out if the lock cannot | |
324 | * be taken immediately. For sync compaction, spin on the lock if needed. | |
325 | * | |
326 | * Returns true if the lock is held | |
327 | * Returns false if the lock is not held and compaction should abort | |
328 | */ | |
329 | static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags, | |
330 | struct compact_control *cc) | |
331 | { | |
332 | if (cc->mode == MIGRATE_ASYNC) { | |
333 | if (!spin_trylock_irqsave(lock, *flags)) { | |
334 | cc->contended = COMPACT_CONTENDED_LOCK; | |
335 | return false; | |
336 | } | |
337 | } else { | |
338 | spin_lock_irqsave(lock, *flags); | |
339 | } | |
340 | ||
341 | return true; | |
342 | } | |
343 | ||
344 | /* | |
345 | * Compaction requires the taking of some coarse locks that are potentially | |
346 | * very heavily contended. The lock should be periodically unlocked to avoid | |
347 | * having disabled IRQs for a long time, even when there is nobody waiting on | |
348 | * the lock. It might also be that allowing the IRQs will result in | |
349 | * need_resched() becoming true. If scheduling is needed, async compaction | |
350 | * aborts. Sync compaction schedules. | |
351 | * Either compaction type will also abort if a fatal signal is pending. | |
352 | * In either case if the lock was locked, it is dropped and not regained. | |
353 | * | |
354 | * Returns true if compaction should abort due to fatal signal pending, or | |
355 | * async compaction due to need_resched() | |
356 | * Returns false when compaction can continue (sync compaction might have | |
357 | * scheduled) | |
358 | */ | |
359 | static bool compact_unlock_should_abort(spinlock_t *lock, | |
360 | unsigned long flags, bool *locked, struct compact_control *cc) | |
361 | { | |
362 | if (*locked) { | |
363 | spin_unlock_irqrestore(lock, flags); | |
364 | *locked = false; | |
365 | } | |
366 | ||
367 | if (fatal_signal_pending(current)) { | |
368 | cc->contended = COMPACT_CONTENDED_SCHED; | |
369 | return true; | |
370 | } | |
371 | ||
372 | if (need_resched()) { | |
373 | if (cc->mode == MIGRATE_ASYNC) { | |
374 | cc->contended = COMPACT_CONTENDED_SCHED; | |
375 | return true; | |
376 | } | |
377 | cond_resched(); | |
378 | } | |
379 | ||
380 | return false; | |
381 | } | |
382 | ||
383 | /* | |
384 | * Aside from avoiding lock contention, compaction also periodically checks | |
385 | * need_resched() and either schedules in sync compaction or aborts async | |
386 | * compaction. This is similar to what compact_unlock_should_abort() does, but | |
387 | * is used where no lock is concerned. | |
388 | * | |
389 | * Returns false when no scheduling was needed, or sync compaction scheduled. | |
390 | * Returns true when async compaction should abort. | |
391 | */ | |
392 | static inline bool compact_should_abort(struct compact_control *cc) | |
393 | { | |
394 | /* async compaction aborts if contended */ | |
395 | if (need_resched()) { | |
396 | if (cc->mode == MIGRATE_ASYNC) { | |
397 | cc->contended = COMPACT_CONTENDED_SCHED; | |
398 | return true; | |
399 | } | |
400 | ||
401 | cond_resched(); | |
402 | } | |
403 | ||
404 | return false; | |
405 | } | |
406 | ||
407 | /* | |
408 | * Isolate free pages onto a private freelist. If @strict is true, will abort | |
409 | * returning 0 on any invalid PFNs or non-free pages inside of the pageblock | |
410 | * (even though it may still end up isolating some pages). | |
411 | */ | |
412 | static unsigned long isolate_freepages_block(struct compact_control *cc, | |
413 | unsigned long *start_pfn, | |
414 | unsigned long end_pfn, | |
415 | struct list_head *freelist, | |
416 | bool strict) | |
417 | { | |
418 | int nr_scanned = 0, total_isolated = 0; | |
419 | struct page *cursor, *valid_page = NULL; | |
420 | unsigned long flags = 0; | |
421 | bool locked = false; | |
422 | unsigned long blockpfn = *start_pfn; | |
423 | unsigned int order; | |
424 | ||
425 | cursor = pfn_to_page(blockpfn); | |
426 | ||
427 | /* Isolate free pages. */ | |
428 | for (; blockpfn < end_pfn; blockpfn++, cursor++) { | |
429 | int isolated; | |
430 | struct page *page = cursor; | |
431 | ||
432 | /* | |
433 | * Periodically drop the lock (if held) regardless of its | |
434 | * contention, to give chance to IRQs. Abort if fatal signal | |
435 | * pending or async compaction detects need_resched() | |
436 | */ | |
437 | if (!(blockpfn % SWAP_CLUSTER_MAX) | |
438 | && compact_unlock_should_abort(&cc->zone->lock, flags, | |
439 | &locked, cc)) | |
440 | break; | |
441 | ||
442 | nr_scanned++; | |
443 | if (!pfn_valid_within(blockpfn)) | |
444 | goto isolate_fail; | |
445 | ||
446 | if (!valid_page) | |
447 | valid_page = page; | |
448 | ||
449 | /* | |
450 | * For compound pages such as THP and hugetlbfs, we can save | |
451 | * potentially a lot of iterations if we skip them at once. | |
452 | * The check is racy, but we can consider only valid values | |
453 | * and the only danger is skipping too much. | |
454 | */ | |
455 | if (PageCompound(page)) { | |
456 | unsigned int comp_order = compound_order(page); | |
457 | ||
458 | if (likely(comp_order < MAX_ORDER)) { | |
459 | blockpfn += (1UL << comp_order) - 1; | |
460 | cursor += (1UL << comp_order) - 1; | |
461 | } | |
462 | ||
463 | goto isolate_fail; | |
464 | } | |
465 | ||
466 | if (!PageBuddy(page)) | |
467 | goto isolate_fail; | |
468 | ||
469 | /* | |
470 | * If we already hold the lock, we can skip some rechecking. | |
471 | * Note that if we hold the lock now, checked_pageblock was | |
472 | * already set in some previous iteration (or strict is true), | |
473 | * so it is correct to skip the suitable migration target | |
474 | * recheck as well. | |
475 | */ | |
476 | if (!locked) { | |
477 | /* | |
478 | * The zone lock must be held to isolate freepages. | |
479 | * Unfortunately this is a very coarse lock and can be | |
480 | * heavily contended if there are parallel allocations | |
481 | * or parallel compactions. For async compaction do not | |
482 | * spin on the lock and we acquire the lock as late as | |
483 | * possible. | |
484 | */ | |
485 | locked = compact_trylock_irqsave(&cc->zone->lock, | |
486 | &flags, cc); | |
487 | if (!locked) | |
488 | break; | |
489 | ||
490 | /* Recheck this is a buddy page under lock */ | |
491 | if (!PageBuddy(page)) | |
492 | goto isolate_fail; | |
493 | } | |
494 | ||
495 | /* Found a free page, will break it into order-0 pages */ | |
496 | order = page_order(page); | |
497 | isolated = __isolate_free_page(page, order); | |
498 | if (!isolated) | |
499 | break; | |
500 | set_page_private(page, order); | |
501 | ||
502 | total_isolated += isolated; | |
503 | cc->nr_freepages += isolated; | |
504 | list_add_tail(&page->lru, freelist); | |
505 | ||
506 | if (!strict && cc->nr_migratepages <= cc->nr_freepages) { | |
507 | blockpfn += isolated; | |
508 | break; | |
509 | } | |
510 | /* Advance to the end of split page */ | |
511 | blockpfn += isolated - 1; | |
512 | cursor += isolated - 1; | |
513 | continue; | |
514 | ||
515 | isolate_fail: | |
516 | if (strict) | |
517 | break; | |
518 | else | |
519 | continue; | |
520 | ||
521 | } | |
522 | ||
523 | if (locked) | |
524 | spin_unlock_irqrestore(&cc->zone->lock, flags); | |
525 | ||
526 | /* | |
527 | * There is a tiny chance that we have read bogus compound_order(), | |
528 | * so be careful to not go outside of the pageblock. | |
529 | */ | |
530 | if (unlikely(blockpfn > end_pfn)) | |
531 | blockpfn = end_pfn; | |
532 | ||
533 | trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn, | |
534 | nr_scanned, total_isolated); | |
535 | ||
536 | /* Record how far we have got within the block */ | |
537 | *start_pfn = blockpfn; | |
538 | ||
539 | /* | |
540 | * If strict isolation is requested by CMA then check that all the | |
541 | * pages requested were isolated. If there were any failures, 0 is | |
542 | * returned and CMA will fail. | |
543 | */ | |
544 | if (strict && blockpfn < end_pfn) | |
545 | total_isolated = 0; | |
546 | ||
547 | /* Update the pageblock-skip if the whole pageblock was scanned */ | |
548 | if (blockpfn == end_pfn) | |
549 | update_pageblock_skip(cc, valid_page, total_isolated, false); | |
550 | ||
551 | count_compact_events(COMPACTFREE_SCANNED, nr_scanned); | |
552 | if (total_isolated) | |
553 | count_compact_events(COMPACTISOLATED, total_isolated); | |
554 | return total_isolated; | |
555 | } | |
556 | ||
557 | /** | |
558 | * isolate_freepages_range() - isolate free pages. | |
559 | * @start_pfn: The first PFN to start isolating. | |
560 | * @end_pfn: The one-past-last PFN. | |
561 | * | |
562 | * Non-free pages, invalid PFNs, or zone boundaries within the | |
563 | * [start_pfn, end_pfn) range are considered errors, cause function to | |
564 | * undo its actions and return zero. | |
565 | * | |
566 | * Otherwise, function returns one-past-the-last PFN of isolated page | |
567 | * (which may be greater then end_pfn if end fell in a middle of | |
568 | * a free page). | |
569 | */ | |
570 | unsigned long | |
571 | isolate_freepages_range(struct compact_control *cc, | |
572 | unsigned long start_pfn, unsigned long end_pfn) | |
573 | { | |
574 | unsigned long isolated, pfn, block_start_pfn, block_end_pfn; | |
575 | LIST_HEAD(freelist); | |
576 | ||
577 | pfn = start_pfn; | |
578 | block_start_pfn = pageblock_start_pfn(pfn); | |
579 | if (block_start_pfn < cc->zone->zone_start_pfn) | |
580 | block_start_pfn = cc->zone->zone_start_pfn; | |
581 | block_end_pfn = pageblock_end_pfn(pfn); | |
582 | ||
583 | for (; pfn < end_pfn; pfn += isolated, | |
584 | block_start_pfn = block_end_pfn, | |
585 | block_end_pfn += pageblock_nr_pages) { | |
586 | /* Protect pfn from changing by isolate_freepages_block */ | |
587 | unsigned long isolate_start_pfn = pfn; | |
588 | ||
589 | block_end_pfn = min(block_end_pfn, end_pfn); | |
590 | ||
591 | /* | |
592 | * pfn could pass the block_end_pfn if isolated freepage | |
593 | * is more than pageblock order. In this case, we adjust | |
594 | * scanning range to right one. | |
595 | */ | |
596 | if (pfn >= block_end_pfn) { | |
597 | block_start_pfn = pageblock_start_pfn(pfn); | |
598 | block_end_pfn = pageblock_end_pfn(pfn); | |
599 | block_end_pfn = min(block_end_pfn, end_pfn); | |
600 | } | |
601 | ||
602 | if (!pageblock_pfn_to_page(block_start_pfn, | |
603 | block_end_pfn, cc->zone)) | |
604 | break; | |
605 | ||
606 | isolated = isolate_freepages_block(cc, &isolate_start_pfn, | |
607 | block_end_pfn, &freelist, true); | |
608 | ||
609 | /* | |
610 | * In strict mode, isolate_freepages_block() returns 0 if | |
611 | * there are any holes in the block (ie. invalid PFNs or | |
612 | * non-free pages). | |
613 | */ | |
614 | if (!isolated) | |
615 | break; | |
616 | ||
617 | /* | |
618 | * If we managed to isolate pages, it is always (1 << n) * | |
619 | * pageblock_nr_pages for some non-negative n. (Max order | |
620 | * page may span two pageblocks). | |
621 | */ | |
622 | } | |
623 | ||
624 | /* __isolate_free_page() does not map the pages */ | |
625 | map_pages(&freelist); | |
626 | ||
627 | if (pfn < end_pfn) { | |
628 | /* Loop terminated early, cleanup. */ | |
629 | release_freepages(&freelist); | |
630 | return 0; | |
631 | } | |
632 | ||
633 | /* We don't use freelists for anything. */ | |
634 | return pfn; | |
635 | } | |
636 | ||
637 | /* Update the number of anon and file isolated pages in the zone */ | |
638 | static void acct_isolated(struct zone *zone, struct compact_control *cc) | |
639 | { | |
640 | struct page *page; | |
641 | unsigned int count[2] = { 0, }; | |
642 | ||
643 | if (list_empty(&cc->migratepages)) | |
644 | return; | |
645 | ||
646 | list_for_each_entry(page, &cc->migratepages, lru) | |
647 | count[!!page_is_file_cache(page)]++; | |
648 | ||
649 | mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON, count[0]); | |
650 | mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, count[1]); | |
651 | } | |
652 | ||
653 | /* Similar to reclaim, but different enough that they don't share logic */ | |
654 | static bool too_many_isolated(struct zone *zone) | |
655 | { | |
656 | unsigned long active, inactive, isolated; | |
657 | ||
658 | inactive = node_page_state(zone->zone_pgdat, NR_INACTIVE_FILE) + | |
659 | node_page_state(zone->zone_pgdat, NR_INACTIVE_ANON); | |
660 | active = node_page_state(zone->zone_pgdat, NR_ACTIVE_FILE) + | |
661 | node_page_state(zone->zone_pgdat, NR_ACTIVE_ANON); | |
662 | isolated = node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE) + | |
663 | node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON); | |
664 | ||
665 | return isolated > (inactive + active) / 2; | |
666 | } | |
667 | ||
668 | /** | |
669 | * isolate_migratepages_block() - isolate all migrate-able pages within | |
670 | * a single pageblock | |
671 | * @cc: Compaction control structure. | |
672 | * @low_pfn: The first PFN to isolate | |
673 | * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock | |
674 | * @isolate_mode: Isolation mode to be used. | |
675 | * | |
676 | * Isolate all pages that can be migrated from the range specified by | |
677 | * [low_pfn, end_pfn). The range is expected to be within same pageblock. | |
678 | * Returns zero if there is a fatal signal pending, otherwise PFN of the | |
679 | * first page that was not scanned (which may be both less, equal to or more | |
680 | * than end_pfn). | |
681 | * | |
682 | * The pages are isolated on cc->migratepages list (not required to be empty), | |
683 | * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field | |
684 | * is neither read nor updated. | |
685 | */ | |
686 | static unsigned long | |
687 | isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, | |
688 | unsigned long end_pfn, isolate_mode_t isolate_mode) | |
689 | { | |
690 | struct zone *zone = cc->zone; | |
691 | unsigned long nr_scanned = 0, nr_isolated = 0; | |
692 | struct lruvec *lruvec; | |
693 | unsigned long flags = 0; | |
694 | bool locked = false; | |
695 | struct page *page = NULL, *valid_page = NULL; | |
696 | unsigned long start_pfn = low_pfn; | |
697 | bool skip_on_failure = false; | |
698 | unsigned long next_skip_pfn = 0; | |
699 | ||
700 | /* | |
701 | * Ensure that there are not too many pages isolated from the LRU | |
702 | * list by either parallel reclaimers or compaction. If there are, | |
703 | * delay for some time until fewer pages are isolated | |
704 | */ | |
705 | while (unlikely(too_many_isolated(zone))) { | |
706 | /* async migration should just abort */ | |
707 | if (cc->mode == MIGRATE_ASYNC) | |
708 | return 0; | |
709 | ||
710 | congestion_wait(BLK_RW_ASYNC, HZ/10); | |
711 | ||
712 | if (fatal_signal_pending(current)) | |
713 | return 0; | |
714 | } | |
715 | ||
716 | if (compact_should_abort(cc)) | |
717 | return 0; | |
718 | ||
719 | if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) { | |
720 | skip_on_failure = true; | |
721 | next_skip_pfn = block_end_pfn(low_pfn, cc->order); | |
722 | } | |
723 | ||
724 | /* Time to isolate some pages for migration */ | |
725 | for (; low_pfn < end_pfn; low_pfn++) { | |
726 | ||
727 | if (skip_on_failure && low_pfn >= next_skip_pfn) { | |
728 | /* | |
729 | * We have isolated all migration candidates in the | |
730 | * previous order-aligned block, and did not skip it due | |
731 | * to failure. We should migrate the pages now and | |
732 | * hopefully succeed compaction. | |
733 | */ | |
734 | if (nr_isolated) | |
735 | break; | |
736 | ||
737 | /* | |
738 | * We failed to isolate in the previous order-aligned | |
739 | * block. Set the new boundary to the end of the | |
740 | * current block. Note we can't simply increase | |
741 | * next_skip_pfn by 1 << order, as low_pfn might have | |
742 | * been incremented by a higher number due to skipping | |
743 | * a compound or a high-order buddy page in the | |
744 | * previous loop iteration. | |
745 | */ | |
746 | next_skip_pfn = block_end_pfn(low_pfn, cc->order); | |
747 | } | |
748 | ||
749 | /* | |
750 | * Periodically drop the lock (if held) regardless of its | |
751 | * contention, to give chance to IRQs. Abort async compaction | |
752 | * if contended. | |
753 | */ | |
754 | if (!(low_pfn % SWAP_CLUSTER_MAX) | |
755 | && compact_unlock_should_abort(zone_lru_lock(zone), flags, | |
756 | &locked, cc)) | |
757 | break; | |
758 | ||
759 | if (!pfn_valid_within(low_pfn)) | |
760 | goto isolate_fail; | |
761 | nr_scanned++; | |
762 | ||
763 | page = pfn_to_page(low_pfn); | |
764 | ||
765 | if (!valid_page) | |
766 | valid_page = page; | |
767 | ||
768 | /* | |
769 | * Skip if free. We read page order here without zone lock | |
770 | * which is generally unsafe, but the race window is small and | |
771 | * the worst thing that can happen is that we skip some | |
772 | * potential isolation targets. | |
773 | */ | |
774 | if (PageBuddy(page)) { | |
775 | unsigned long freepage_order = page_order_unsafe(page); | |
776 | ||
777 | /* | |
778 | * Without lock, we cannot be sure that what we got is | |
779 | * a valid page order. Consider only values in the | |
780 | * valid order range to prevent low_pfn overflow. | |
781 | */ | |
782 | if (freepage_order > 0 && freepage_order < MAX_ORDER) | |
783 | low_pfn += (1UL << freepage_order) - 1; | |
784 | continue; | |
785 | } | |
786 | ||
787 | /* | |
788 | * Regardless of being on LRU, compound pages such as THP and | |
789 | * hugetlbfs are not to be compacted. We can potentially save | |
790 | * a lot of iterations if we skip them at once. The check is | |
791 | * racy, but we can consider only valid values and the only | |
792 | * danger is skipping too much. | |
793 | */ | |
794 | if (PageCompound(page)) { | |
795 | unsigned int comp_order = compound_order(page); | |
796 | ||
797 | if (likely(comp_order < MAX_ORDER)) | |
798 | low_pfn += (1UL << comp_order) - 1; | |
799 | ||
800 | goto isolate_fail; | |
801 | } | |
802 | ||
803 | /* | |
804 | * Check may be lockless but that's ok as we recheck later. | |
805 | * It's possible to migrate LRU and non-lru movable pages. | |
806 | * Skip any other type of page | |
807 | */ | |
808 | if (!PageLRU(page)) { | |
809 | /* | |
810 | * __PageMovable can return false positive so we need | |
811 | * to verify it under page_lock. | |
812 | */ | |
813 | if (unlikely(__PageMovable(page)) && | |
814 | !PageIsolated(page)) { | |
815 | if (locked) { | |
816 | spin_unlock_irqrestore(zone_lru_lock(zone), | |
817 | flags); | |
818 | locked = false; | |
819 | } | |
820 | ||
821 | if (isolate_movable_page(page, isolate_mode)) | |
822 | goto isolate_success; | |
823 | } | |
824 | ||
825 | goto isolate_fail; | |
826 | } | |
827 | ||
828 | /* | |
829 | * Migration will fail if an anonymous page is pinned in memory, | |
830 | * so avoid taking lru_lock and isolating it unnecessarily in an | |
831 | * admittedly racy check. | |
832 | */ | |
833 | if (!page_mapping(page) && | |
834 | page_count(page) > page_mapcount(page)) | |
835 | goto isolate_fail; | |
836 | ||
837 | /* If we already hold the lock, we can skip some rechecking */ | |
838 | if (!locked) { | |
839 | locked = compact_trylock_irqsave(zone_lru_lock(zone), | |
840 | &flags, cc); | |
841 | if (!locked) | |
842 | break; | |
843 | ||
844 | /* Recheck PageLRU and PageCompound under lock */ | |
845 | if (!PageLRU(page)) | |
846 | goto isolate_fail; | |
847 | ||
848 | /* | |
849 | * Page become compound since the non-locked check, | |
850 | * and it's on LRU. It can only be a THP so the order | |
851 | * is safe to read and it's 0 for tail pages. | |
852 | */ | |
853 | if (unlikely(PageCompound(page))) { | |
854 | low_pfn += (1UL << compound_order(page)) - 1; | |
855 | goto isolate_fail; | |
856 | } | |
857 | } | |
858 | ||
859 | lruvec = mem_cgroup_page_lruvec(page, zone->zone_pgdat); | |
860 | ||
861 | /* Try isolate the page */ | |
862 | if (__isolate_lru_page(page, isolate_mode) != 0) | |
863 | goto isolate_fail; | |
864 | ||
865 | VM_BUG_ON_PAGE(PageCompound(page), page); | |
866 | ||
867 | /* Successfully isolated */ | |
868 | del_page_from_lru_list(page, lruvec, page_lru(page)); | |
869 | ||
870 | isolate_success: | |
871 | list_add(&page->lru, &cc->migratepages); | |
872 | cc->nr_migratepages++; | |
873 | nr_isolated++; | |
874 | ||
875 | /* | |
876 | * Record where we could have freed pages by migration and not | |
877 | * yet flushed them to buddy allocator. | |
878 | * - this is the lowest page that was isolated and likely be | |
879 | * then freed by migration. | |
880 | */ | |
881 | if (!cc->last_migrated_pfn) | |
882 | cc->last_migrated_pfn = low_pfn; | |
883 | ||
884 | /* Avoid isolating too much */ | |
885 | if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) { | |
886 | ++low_pfn; | |
887 | break; | |
888 | } | |
889 | ||
890 | continue; | |
891 | isolate_fail: | |
892 | if (!skip_on_failure) | |
893 | continue; | |
894 | ||
895 | /* | |
896 | * We have isolated some pages, but then failed. Release them | |
897 | * instead of migrating, as we cannot form the cc->order buddy | |
898 | * page anyway. | |
899 | */ | |
900 | if (nr_isolated) { | |
901 | if (locked) { | |
902 | spin_unlock_irqrestore(zone_lru_lock(zone), flags); | |
903 | locked = false; | |
904 | } | |
905 | acct_isolated(zone, cc); | |
906 | putback_movable_pages(&cc->migratepages); | |
907 | cc->nr_migratepages = 0; | |
908 | cc->last_migrated_pfn = 0; | |
909 | nr_isolated = 0; | |
910 | } | |
911 | ||
912 | if (low_pfn < next_skip_pfn) { | |
913 | low_pfn = next_skip_pfn - 1; | |
914 | /* | |
915 | * The check near the loop beginning would have updated | |
916 | * next_skip_pfn too, but this is a bit simpler. | |
917 | */ | |
918 | next_skip_pfn += 1UL << cc->order; | |
919 | } | |
920 | } | |
921 | ||
922 | /* | |
923 | * The PageBuddy() check could have potentially brought us outside | |
924 | * the range to be scanned. | |
925 | */ | |
926 | if (unlikely(low_pfn > end_pfn)) | |
927 | low_pfn = end_pfn; | |
928 | ||
929 | if (locked) | |
930 | spin_unlock_irqrestore(zone_lru_lock(zone), flags); | |
931 | ||
932 | /* | |
933 | * Update the pageblock-skip information and cached scanner pfn, | |
934 | * if the whole pageblock was scanned without isolating any page. | |
935 | */ | |
936 | if (low_pfn == end_pfn) | |
937 | update_pageblock_skip(cc, valid_page, nr_isolated, true); | |
938 | ||
939 | trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn, | |
940 | nr_scanned, nr_isolated); | |
941 | ||
942 | count_compact_events(COMPACTMIGRATE_SCANNED, nr_scanned); | |
943 | if (nr_isolated) | |
944 | count_compact_events(COMPACTISOLATED, nr_isolated); | |
945 | ||
946 | return low_pfn; | |
947 | } | |
948 | ||
949 | /** | |
950 | * isolate_migratepages_range() - isolate migrate-able pages in a PFN range | |
951 | * @cc: Compaction control structure. | |
952 | * @start_pfn: The first PFN to start isolating. | |
953 | * @end_pfn: The one-past-last PFN. | |
954 | * | |
955 | * Returns zero if isolation fails fatally due to e.g. pending signal. | |
956 | * Otherwise, function returns one-past-the-last PFN of isolated page | |
957 | * (which may be greater than end_pfn if end fell in a middle of a THP page). | |
958 | */ | |
959 | unsigned long | |
960 | isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, | |
961 | unsigned long end_pfn) | |
962 | { | |
963 | unsigned long pfn, block_start_pfn, block_end_pfn; | |
964 | ||
965 | /* Scan block by block. First and last block may be incomplete */ | |
966 | pfn = start_pfn; | |
967 | block_start_pfn = pageblock_start_pfn(pfn); | |
968 | if (block_start_pfn < cc->zone->zone_start_pfn) | |
969 | block_start_pfn = cc->zone->zone_start_pfn; | |
970 | block_end_pfn = pageblock_end_pfn(pfn); | |
971 | ||
972 | for (; pfn < end_pfn; pfn = block_end_pfn, | |
973 | block_start_pfn = block_end_pfn, | |
974 | block_end_pfn += pageblock_nr_pages) { | |
975 | ||
976 | block_end_pfn = min(block_end_pfn, end_pfn); | |
977 | ||
978 | if (!pageblock_pfn_to_page(block_start_pfn, | |
979 | block_end_pfn, cc->zone)) | |
980 | continue; | |
981 | ||
982 | pfn = isolate_migratepages_block(cc, pfn, block_end_pfn, | |
983 | ISOLATE_UNEVICTABLE); | |
984 | ||
985 | if (!pfn) | |
986 | break; | |
987 | ||
988 | if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) | |
989 | break; | |
990 | } | |
991 | acct_isolated(cc->zone, cc); | |
992 | ||
993 | return pfn; | |
994 | } | |
995 | ||
996 | #endif /* CONFIG_COMPACTION || CONFIG_CMA */ | |
997 | #ifdef CONFIG_COMPACTION | |
998 | ||
999 | /* Returns true if the page is within a block suitable for migration to */ | |
1000 | static bool suitable_migration_target(struct page *page) | |
1001 | { | |
1002 | /* If the page is a large free page, then disallow migration */ | |
1003 | if (PageBuddy(page)) { | |
1004 | /* | |
1005 | * We are checking page_order without zone->lock taken. But | |
1006 | * the only small danger is that we skip a potentially suitable | |
1007 | * pageblock, so it's not worth to check order for valid range. | |
1008 | */ | |
1009 | if (page_order_unsafe(page) >= pageblock_order) | |
1010 | return false; | |
1011 | } | |
1012 | ||
1013 | /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */ | |
1014 | if (migrate_async_suitable(get_pageblock_migratetype(page))) | |
1015 | return true; | |
1016 | ||
1017 | /* Otherwise skip the block */ | |
1018 | return false; | |
1019 | } | |
1020 | ||
1021 | /* | |
1022 | * Test whether the free scanner has reached the same or lower pageblock than | |
1023 | * the migration scanner, and compaction should thus terminate. | |
1024 | */ | |
1025 | static inline bool compact_scanners_met(struct compact_control *cc) | |
1026 | { | |
1027 | return (cc->free_pfn >> pageblock_order) | |
1028 | <= (cc->migrate_pfn >> pageblock_order); | |
1029 | } | |
1030 | ||
1031 | /* | |
1032 | * Based on information in the current compact_control, find blocks | |
1033 | * suitable for isolating free pages from and then isolate them. | |
1034 | */ | |
1035 | static void isolate_freepages(struct compact_control *cc) | |
1036 | { | |
1037 | struct zone *zone = cc->zone; | |
1038 | struct page *page; | |
1039 | unsigned long block_start_pfn; /* start of current pageblock */ | |
1040 | unsigned long isolate_start_pfn; /* exact pfn we start at */ | |
1041 | unsigned long block_end_pfn; /* end of current pageblock */ | |
1042 | unsigned long low_pfn; /* lowest pfn scanner is able to scan */ | |
1043 | struct list_head *freelist = &cc->freepages; | |
1044 | ||
1045 | /* | |
1046 | * Initialise the free scanner. The starting point is where we last | |
1047 | * successfully isolated from, zone-cached value, or the end of the | |
1048 | * zone when isolating for the first time. For looping we also need | |
1049 | * this pfn aligned down to the pageblock boundary, because we do | |
1050 | * block_start_pfn -= pageblock_nr_pages in the for loop. | |
1051 | * For ending point, take care when isolating in last pageblock of a | |
1052 | * a zone which ends in the middle of a pageblock. | |
1053 | * The low boundary is the end of the pageblock the migration scanner | |
1054 | * is using. | |
1055 | */ | |
1056 | isolate_start_pfn = cc->free_pfn; | |
1057 | block_start_pfn = pageblock_start_pfn(cc->free_pfn); | |
1058 | block_end_pfn = min(block_start_pfn + pageblock_nr_pages, | |
1059 | zone_end_pfn(zone)); | |
1060 | low_pfn = pageblock_end_pfn(cc->migrate_pfn); | |
1061 | ||
1062 | /* | |
1063 | * Isolate free pages until enough are available to migrate the | |
1064 | * pages on cc->migratepages. We stop searching if the migrate | |
1065 | * and free page scanners meet or enough free pages are isolated. | |
1066 | */ | |
1067 | for (; block_start_pfn >= low_pfn; | |
1068 | block_end_pfn = block_start_pfn, | |
1069 | block_start_pfn -= pageblock_nr_pages, | |
1070 | isolate_start_pfn = block_start_pfn) { | |
1071 | /* | |
1072 | * This can iterate a massively long zone without finding any | |
1073 | * suitable migration targets, so periodically check if we need | |
1074 | * to schedule, or even abort async compaction. | |
1075 | */ | |
1076 | if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)) | |
1077 | && compact_should_abort(cc)) | |
1078 | break; | |
1079 | ||
1080 | page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn, | |
1081 | zone); | |
1082 | if (!page) | |
1083 | continue; | |
1084 | ||
1085 | /* Check the block is suitable for migration */ | |
1086 | if (!suitable_migration_target(page)) | |
1087 | continue; | |
1088 | ||
1089 | /* If isolation recently failed, do not retry */ | |
1090 | if (!isolation_suitable(cc, page)) | |
1091 | continue; | |
1092 | ||
1093 | /* Found a block suitable for isolating free pages from. */ | |
1094 | isolate_freepages_block(cc, &isolate_start_pfn, block_end_pfn, | |
1095 | freelist, false); | |
1096 | ||
1097 | /* | |
1098 | * If we isolated enough freepages, or aborted due to lock | |
1099 | * contention, terminate. | |
1100 | */ | |
1101 | if ((cc->nr_freepages >= cc->nr_migratepages) | |
1102 | || cc->contended) { | |
1103 | if (isolate_start_pfn >= block_end_pfn) { | |
1104 | /* | |
1105 | * Restart at previous pageblock if more | |
1106 | * freepages can be isolated next time. | |
1107 | */ | |
1108 | isolate_start_pfn = | |
1109 | block_start_pfn - pageblock_nr_pages; | |
1110 | } | |
1111 | break; | |
1112 | } else if (isolate_start_pfn < block_end_pfn) { | |
1113 | /* | |
1114 | * If isolation failed early, do not continue | |
1115 | * needlessly. | |
1116 | */ | |
1117 | break; | |
1118 | } | |
1119 | } | |
1120 | ||
1121 | /* __isolate_free_page() does not map the pages */ | |
1122 | map_pages(freelist); | |
1123 | ||
1124 | /* | |
1125 | * Record where the free scanner will restart next time. Either we | |
1126 | * broke from the loop and set isolate_start_pfn based on the last | |
1127 | * call to isolate_freepages_block(), or we met the migration scanner | |
1128 | * and the loop terminated due to isolate_start_pfn < low_pfn | |
1129 | */ | |
1130 | cc->free_pfn = isolate_start_pfn; | |
1131 | } | |
1132 | ||
1133 | /* | |
1134 | * This is a migrate-callback that "allocates" freepages by taking pages | |
1135 | * from the isolated freelists in the block we are migrating to. | |
1136 | */ | |
1137 | static struct page *compaction_alloc(struct page *migratepage, | |
1138 | unsigned long data, | |
1139 | int **result) | |
1140 | { | |
1141 | struct compact_control *cc = (struct compact_control *)data; | |
1142 | struct page *freepage; | |
1143 | ||
1144 | /* | |
1145 | * Isolate free pages if necessary, and if we are not aborting due to | |
1146 | * contention. | |
1147 | */ | |
1148 | if (list_empty(&cc->freepages)) { | |
1149 | if (!cc->contended) | |
1150 | isolate_freepages(cc); | |
1151 | ||
1152 | if (list_empty(&cc->freepages)) | |
1153 | return NULL; | |
1154 | } | |
1155 | ||
1156 | freepage = list_entry(cc->freepages.next, struct page, lru); | |
1157 | list_del(&freepage->lru); | |
1158 | cc->nr_freepages--; | |
1159 | ||
1160 | return freepage; | |
1161 | } | |
1162 | ||
1163 | /* | |
1164 | * This is a migrate-callback that "frees" freepages back to the isolated | |
1165 | * freelist. All pages on the freelist are from the same zone, so there is no | |
1166 | * special handling needed for NUMA. | |
1167 | */ | |
1168 | static void compaction_free(struct page *page, unsigned long data) | |
1169 | { | |
1170 | struct compact_control *cc = (struct compact_control *)data; | |
1171 | ||
1172 | list_add(&page->lru, &cc->freepages); | |
1173 | cc->nr_freepages++; | |
1174 | } | |
1175 | ||
1176 | /* possible outcome of isolate_migratepages */ | |
1177 | typedef enum { | |
1178 | ISOLATE_ABORT, /* Abort compaction now */ | |
1179 | ISOLATE_NONE, /* No pages isolated, continue scanning */ | |
1180 | ISOLATE_SUCCESS, /* Pages isolated, migrate */ | |
1181 | } isolate_migrate_t; | |
1182 | ||
1183 | /* | |
1184 | * Allow userspace to control policy on scanning the unevictable LRU for | |
1185 | * compactable pages. | |
1186 | */ | |
1187 | int sysctl_compact_unevictable_allowed __read_mostly = 1; | |
1188 | ||
1189 | /* | |
1190 | * Isolate all pages that can be migrated from the first suitable block, | |
1191 | * starting at the block pointed to by the migrate scanner pfn within | |
1192 | * compact_control. | |
1193 | */ | |
1194 | static isolate_migrate_t isolate_migratepages(struct zone *zone, | |
1195 | struct compact_control *cc) | |
1196 | { | |
1197 | unsigned long block_start_pfn; | |
1198 | unsigned long block_end_pfn; | |
1199 | unsigned long low_pfn; | |
1200 | struct page *page; | |
1201 | const isolate_mode_t isolate_mode = | |
1202 | (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | | |
1203 | (cc->mode == MIGRATE_ASYNC ? ISOLATE_ASYNC_MIGRATE : 0); | |
1204 | ||
1205 | /* | |
1206 | * Start at where we last stopped, or beginning of the zone as | |
1207 | * initialized by compact_zone() | |
1208 | */ | |
1209 | low_pfn = cc->migrate_pfn; | |
1210 | block_start_pfn = pageblock_start_pfn(low_pfn); | |
1211 | if (block_start_pfn < zone->zone_start_pfn) | |
1212 | block_start_pfn = zone->zone_start_pfn; | |
1213 | ||
1214 | /* Only scan within a pageblock boundary */ | |
1215 | block_end_pfn = pageblock_end_pfn(low_pfn); | |
1216 | ||
1217 | /* | |
1218 | * Iterate over whole pageblocks until we find the first suitable. | |
1219 | * Do not cross the free scanner. | |
1220 | */ | |
1221 | for (; block_end_pfn <= cc->free_pfn; | |
1222 | low_pfn = block_end_pfn, | |
1223 | block_start_pfn = block_end_pfn, | |
1224 | block_end_pfn += pageblock_nr_pages) { | |
1225 | ||
1226 | /* | |
1227 | * This can potentially iterate a massively long zone with | |
1228 | * many pageblocks unsuitable, so periodically check if we | |
1229 | * need to schedule, or even abort async compaction. | |
1230 | */ | |
1231 | if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)) | |
1232 | && compact_should_abort(cc)) | |
1233 | break; | |
1234 | ||
1235 | page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn, | |
1236 | zone); | |
1237 | if (!page) | |
1238 | continue; | |
1239 | ||
1240 | /* If isolation recently failed, do not retry */ | |
1241 | if (!isolation_suitable(cc, page)) | |
1242 | continue; | |
1243 | ||
1244 | /* | |
1245 | * For async compaction, also only scan in MOVABLE blocks. | |
1246 | * Async compaction is optimistic to see if the minimum amount | |
1247 | * of work satisfies the allocation. | |
1248 | */ | |
1249 | if (cc->mode == MIGRATE_ASYNC && | |
1250 | !migrate_async_suitable(get_pageblock_migratetype(page))) | |
1251 | continue; | |
1252 | ||
1253 | /* Perform the isolation */ | |
1254 | low_pfn = isolate_migratepages_block(cc, low_pfn, | |
1255 | block_end_pfn, isolate_mode); | |
1256 | ||
1257 | if (!low_pfn || cc->contended) { | |
1258 | acct_isolated(zone, cc); | |
1259 | return ISOLATE_ABORT; | |
1260 | } | |
1261 | ||
1262 | /* | |
1263 | * Either we isolated something and proceed with migration. Or | |
1264 | * we failed and compact_zone should decide if we should | |
1265 | * continue or not. | |
1266 | */ | |
1267 | break; | |
1268 | } | |
1269 | ||
1270 | acct_isolated(zone, cc); | |
1271 | /* Record where migration scanner will be restarted. */ | |
1272 | cc->migrate_pfn = low_pfn; | |
1273 | ||
1274 | return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE; | |
1275 | } | |
1276 | ||
1277 | /* | |
1278 | * order == -1 is expected when compacting via | |
1279 | * /proc/sys/vm/compact_memory | |
1280 | */ | |
1281 | static inline bool is_via_compact_memory(int order) | |
1282 | { | |
1283 | return order == -1; | |
1284 | } | |
1285 | ||
1286 | static enum compact_result __compact_finished(struct zone *zone, struct compact_control *cc, | |
1287 | const int migratetype) | |
1288 | { | |
1289 | unsigned int order; | |
1290 | unsigned long watermark; | |
1291 | ||
1292 | if (cc->contended || fatal_signal_pending(current)) | |
1293 | return COMPACT_CONTENDED; | |
1294 | ||
1295 | /* Compaction run completes if the migrate and free scanner meet */ | |
1296 | if (compact_scanners_met(cc)) { | |
1297 | /* Let the next compaction start anew. */ | |
1298 | reset_cached_positions(zone); | |
1299 | ||
1300 | /* | |
1301 | * Mark that the PG_migrate_skip information should be cleared | |
1302 | * by kswapd when it goes to sleep. kcompactd does not set the | |
1303 | * flag itself as the decision to be clear should be directly | |
1304 | * based on an allocation request. | |
1305 | */ | |
1306 | if (cc->direct_compaction) | |
1307 | zone->compact_blockskip_flush = true; | |
1308 | ||
1309 | if (cc->whole_zone) | |
1310 | return COMPACT_COMPLETE; | |
1311 | else | |
1312 | return COMPACT_PARTIAL_SKIPPED; | |
1313 | } | |
1314 | ||
1315 | if (is_via_compact_memory(cc->order)) | |
1316 | return COMPACT_CONTINUE; | |
1317 | ||
1318 | /* Compaction run is not finished if the watermark is not met */ | |
1319 | watermark = low_wmark_pages(zone); | |
1320 | ||
1321 | if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx, | |
1322 | cc->alloc_flags)) | |
1323 | return COMPACT_CONTINUE; | |
1324 | ||
1325 | /* Direct compactor: Is a suitable page free? */ | |
1326 | for (order = cc->order; order < MAX_ORDER; order++) { | |
1327 | struct free_area *area = &zone->free_area[order]; | |
1328 | bool can_steal; | |
1329 | ||
1330 | /* Job done if page is free of the right migratetype */ | |
1331 | if (!list_empty(&area->free_list[migratetype])) | |
1332 | return COMPACT_PARTIAL; | |
1333 | ||
1334 | #ifdef CONFIG_CMA | |
1335 | /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */ | |
1336 | if (migratetype == MIGRATE_MOVABLE && | |
1337 | !list_empty(&area->free_list[MIGRATE_CMA])) | |
1338 | return COMPACT_PARTIAL; | |
1339 | #endif | |
1340 | /* | |
1341 | * Job done if allocation would steal freepages from | |
1342 | * other migratetype buddy lists. | |
1343 | */ | |
1344 | if (find_suitable_fallback(area, order, migratetype, | |
1345 | true, &can_steal) != -1) | |
1346 | return COMPACT_PARTIAL; | |
1347 | } | |
1348 | ||
1349 | return COMPACT_NO_SUITABLE_PAGE; | |
1350 | } | |
1351 | ||
1352 | static enum compact_result compact_finished(struct zone *zone, | |
1353 | struct compact_control *cc, | |
1354 | const int migratetype) | |
1355 | { | |
1356 | int ret; | |
1357 | ||
1358 | ret = __compact_finished(zone, cc, migratetype); | |
1359 | trace_mm_compaction_finished(zone, cc->order, ret); | |
1360 | if (ret == COMPACT_NO_SUITABLE_PAGE) | |
1361 | ret = COMPACT_CONTINUE; | |
1362 | ||
1363 | return ret; | |
1364 | } | |
1365 | ||
1366 | /* | |
1367 | * compaction_suitable: Is this suitable to run compaction on this zone now? | |
1368 | * Returns | |
1369 | * COMPACT_SKIPPED - If there are too few free pages for compaction | |
1370 | * COMPACT_PARTIAL - If the allocation would succeed without compaction | |
1371 | * COMPACT_CONTINUE - If compaction should run now | |
1372 | */ | |
1373 | static enum compact_result __compaction_suitable(struct zone *zone, int order, | |
1374 | unsigned int alloc_flags, | |
1375 | int classzone_idx, | |
1376 | unsigned long wmark_target) | |
1377 | { | |
1378 | int fragindex; | |
1379 | unsigned long watermark; | |
1380 | ||
1381 | if (is_via_compact_memory(order)) | |
1382 | return COMPACT_CONTINUE; | |
1383 | ||
1384 | watermark = low_wmark_pages(zone); | |
1385 | /* | |
1386 | * If watermarks for high-order allocation are already met, there | |
1387 | * should be no need for compaction at all. | |
1388 | */ | |
1389 | if (zone_watermark_ok(zone, order, watermark, classzone_idx, | |
1390 | alloc_flags)) | |
1391 | return COMPACT_PARTIAL; | |
1392 | ||
1393 | /* | |
1394 | * Watermarks for order-0 must be met for compaction. Note the 2UL. | |
1395 | * This is because during migration, copies of pages need to be | |
1396 | * allocated and for a short time, the footprint is higher | |
1397 | */ | |
1398 | watermark += (2UL << order); | |
1399 | if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx, | |
1400 | alloc_flags, wmark_target)) | |
1401 | return COMPACT_SKIPPED; | |
1402 | ||
1403 | /* | |
1404 | * fragmentation index determines if allocation failures are due to | |
1405 | * low memory or external fragmentation | |
1406 | * | |
1407 | * index of -1000 would imply allocations might succeed depending on | |
1408 | * watermarks, but we already failed the high-order watermark check | |
1409 | * index towards 0 implies failure is due to lack of memory | |
1410 | * index towards 1000 implies failure is due to fragmentation | |
1411 | * | |
1412 | * Only compact if a failure would be due to fragmentation. | |
1413 | */ | |
1414 | fragindex = fragmentation_index(zone, order); | |
1415 | if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold) | |
1416 | return COMPACT_NOT_SUITABLE_ZONE; | |
1417 | ||
1418 | return COMPACT_CONTINUE; | |
1419 | } | |
1420 | ||
1421 | enum compact_result compaction_suitable(struct zone *zone, int order, | |
1422 | unsigned int alloc_flags, | |
1423 | int classzone_idx) | |
1424 | { | |
1425 | enum compact_result ret; | |
1426 | ||
1427 | ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx, | |
1428 | zone_page_state(zone, NR_FREE_PAGES)); | |
1429 | trace_mm_compaction_suitable(zone, order, ret); | |
1430 | if (ret == COMPACT_NOT_SUITABLE_ZONE) | |
1431 | ret = COMPACT_SKIPPED; | |
1432 | ||
1433 | return ret; | |
1434 | } | |
1435 | ||
1436 | bool compaction_zonelist_suitable(struct alloc_context *ac, int order, | |
1437 | int alloc_flags) | |
1438 | { | |
1439 | struct zone *zone; | |
1440 | struct zoneref *z; | |
1441 | pg_data_t *last_pgdat = NULL; | |
1442 | ||
1443 | /* Do not retry compaction for zone-constrained allocations */ | |
1444 | if (ac->high_zoneidx < ZONE_NORMAL) | |
1445 | return false; | |
1446 | ||
1447 | /* | |
1448 | * Make sure at least one zone would pass __compaction_suitable if we continue | |
1449 | * retrying the reclaim. | |
1450 | */ | |
1451 | for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx, | |
1452 | ac->nodemask) { | |
1453 | unsigned long available; | |
1454 | enum compact_result compact_result; | |
1455 | ||
1456 | if (last_pgdat == zone->zone_pgdat) | |
1457 | continue; | |
1458 | ||
1459 | /* | |
1460 | * This over-estimates the number of pages available for | |
1461 | * reclaim/compaction but walking the LRU would take too | |
1462 | * long. The consequences are that compaction may retry | |
1463 | * longer than it should for a zone-constrained allocation | |
1464 | * request. | |
1465 | */ | |
1466 | last_pgdat = zone->zone_pgdat; | |
1467 | available = pgdat_reclaimable_pages(zone->zone_pgdat) / order; | |
1468 | ||
1469 | /* | |
1470 | * Do not consider all the reclaimable memory because we do not | |
1471 | * want to trash just for a single high order allocation which | |
1472 | * is even not guaranteed to appear even if __compaction_suitable | |
1473 | * is happy about the watermark check. | |
1474 | */ | |
1475 | available += zone_page_state_snapshot(zone, NR_FREE_PAGES); | |
1476 | available = min(zone->managed_pages, available); | |
1477 | compact_result = __compaction_suitable(zone, order, alloc_flags, | |
1478 | ac_classzone_idx(ac), available); | |
1479 | if (compact_result != COMPACT_SKIPPED && | |
1480 | compact_result != COMPACT_NOT_SUITABLE_ZONE) | |
1481 | return true; | |
1482 | } | |
1483 | ||
1484 | return false; | |
1485 | } | |
1486 | ||
1487 | static enum compact_result compact_zone(struct zone *zone, struct compact_control *cc) | |
1488 | { | |
1489 | enum compact_result ret; | |
1490 | unsigned long start_pfn = zone->zone_start_pfn; | |
1491 | unsigned long end_pfn = zone_end_pfn(zone); | |
1492 | const int migratetype = gfpflags_to_migratetype(cc->gfp_mask); | |
1493 | const bool sync = cc->mode != MIGRATE_ASYNC; | |
1494 | ||
1495 | ret = compaction_suitable(zone, cc->order, cc->alloc_flags, | |
1496 | cc->classzone_idx); | |
1497 | /* Compaction is likely to fail */ | |
1498 | if (ret == COMPACT_PARTIAL || ret == COMPACT_SKIPPED) | |
1499 | return ret; | |
1500 | ||
1501 | /* huh, compaction_suitable is returning something unexpected */ | |
1502 | VM_BUG_ON(ret != COMPACT_CONTINUE); | |
1503 | ||
1504 | /* | |
1505 | * Clear pageblock skip if there were failures recently and compaction | |
1506 | * is about to be retried after being deferred. | |
1507 | */ | |
1508 | if (compaction_restarting(zone, cc->order)) | |
1509 | __reset_isolation_suitable(zone); | |
1510 | ||
1511 | /* | |
1512 | * Setup to move all movable pages to the end of the zone. Used cached | |
1513 | * information on where the scanners should start but check that it | |
1514 | * is initialised by ensuring the values are within zone boundaries. | |
1515 | */ | |
1516 | cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync]; | |
1517 | cc->free_pfn = zone->compact_cached_free_pfn; | |
1518 | if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) { | |
1519 | cc->free_pfn = pageblock_start_pfn(end_pfn - 1); | |
1520 | zone->compact_cached_free_pfn = cc->free_pfn; | |
1521 | } | |
1522 | if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) { | |
1523 | cc->migrate_pfn = start_pfn; | |
1524 | zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn; | |
1525 | zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn; | |
1526 | } | |
1527 | ||
1528 | if (cc->migrate_pfn == start_pfn) | |
1529 | cc->whole_zone = true; | |
1530 | ||
1531 | cc->last_migrated_pfn = 0; | |
1532 | ||
1533 | trace_mm_compaction_begin(start_pfn, cc->migrate_pfn, | |
1534 | cc->free_pfn, end_pfn, sync); | |
1535 | ||
1536 | migrate_prep_local(); | |
1537 | ||
1538 | while ((ret = compact_finished(zone, cc, migratetype)) == | |
1539 | COMPACT_CONTINUE) { | |
1540 | int err; | |
1541 | ||
1542 | switch (isolate_migratepages(zone, cc)) { | |
1543 | case ISOLATE_ABORT: | |
1544 | ret = COMPACT_CONTENDED; | |
1545 | putback_movable_pages(&cc->migratepages); | |
1546 | cc->nr_migratepages = 0; | |
1547 | goto out; | |
1548 | case ISOLATE_NONE: | |
1549 | /* | |
1550 | * We haven't isolated and migrated anything, but | |
1551 | * there might still be unflushed migrations from | |
1552 | * previous cc->order aligned block. | |
1553 | */ | |
1554 | goto check_drain; | |
1555 | case ISOLATE_SUCCESS: | |
1556 | ; | |
1557 | } | |
1558 | ||
1559 | err = migrate_pages(&cc->migratepages, compaction_alloc, | |
1560 | compaction_free, (unsigned long)cc, cc->mode, | |
1561 | MR_COMPACTION); | |
1562 | ||
1563 | trace_mm_compaction_migratepages(cc->nr_migratepages, err, | |
1564 | &cc->migratepages); | |
1565 | ||
1566 | /* All pages were either migrated or will be released */ | |
1567 | cc->nr_migratepages = 0; | |
1568 | if (err) { | |
1569 | putback_movable_pages(&cc->migratepages); | |
1570 | /* | |
1571 | * migrate_pages() may return -ENOMEM when scanners meet | |
1572 | * and we want compact_finished() to detect it | |
1573 | */ | |
1574 | if (err == -ENOMEM && !compact_scanners_met(cc)) { | |
1575 | ret = COMPACT_CONTENDED; | |
1576 | goto out; | |
1577 | } | |
1578 | /* | |
1579 | * We failed to migrate at least one page in the current | |
1580 | * order-aligned block, so skip the rest of it. | |
1581 | */ | |
1582 | if (cc->direct_compaction && | |
1583 | (cc->mode == MIGRATE_ASYNC)) { | |
1584 | cc->migrate_pfn = block_end_pfn( | |
1585 | cc->migrate_pfn - 1, cc->order); | |
1586 | /* Draining pcplists is useless in this case */ | |
1587 | cc->last_migrated_pfn = 0; | |
1588 | ||
1589 | } | |
1590 | } | |
1591 | ||
1592 | check_drain: | |
1593 | /* | |
1594 | * Has the migration scanner moved away from the previous | |
1595 | * cc->order aligned block where we migrated from? If yes, | |
1596 | * flush the pages that were freed, so that they can merge and | |
1597 | * compact_finished() can detect immediately if allocation | |
1598 | * would succeed. | |
1599 | */ | |
1600 | if (cc->order > 0 && cc->last_migrated_pfn) { | |
1601 | int cpu; | |
1602 | unsigned long current_block_start = | |
1603 | block_start_pfn(cc->migrate_pfn, cc->order); | |
1604 | ||
1605 | if (cc->last_migrated_pfn < current_block_start) { | |
1606 | cpu = get_cpu(); | |
1607 | lru_add_drain_cpu(cpu); | |
1608 | drain_local_pages(zone); | |
1609 | put_cpu(); | |
1610 | /* No more flushing until we migrate again */ | |
1611 | cc->last_migrated_pfn = 0; | |
1612 | } | |
1613 | } | |
1614 | ||
1615 | } | |
1616 | ||
1617 | out: | |
1618 | /* | |
1619 | * Release free pages and update where the free scanner should restart, | |
1620 | * so we don't leave any returned pages behind in the next attempt. | |
1621 | */ | |
1622 | if (cc->nr_freepages > 0) { | |
1623 | unsigned long free_pfn = release_freepages(&cc->freepages); | |
1624 | ||
1625 | cc->nr_freepages = 0; | |
1626 | VM_BUG_ON(free_pfn == 0); | |
1627 | /* The cached pfn is always the first in a pageblock */ | |
1628 | free_pfn = pageblock_start_pfn(free_pfn); | |
1629 | /* | |
1630 | * Only go back, not forward. The cached pfn might have been | |
1631 | * already reset to zone end in compact_finished() | |
1632 | */ | |
1633 | if (free_pfn > zone->compact_cached_free_pfn) | |
1634 | zone->compact_cached_free_pfn = free_pfn; | |
1635 | } | |
1636 | ||
1637 | trace_mm_compaction_end(start_pfn, cc->migrate_pfn, | |
1638 | cc->free_pfn, end_pfn, sync, ret); | |
1639 | ||
1640 | if (ret == COMPACT_CONTENDED) | |
1641 | ret = COMPACT_PARTIAL; | |
1642 | ||
1643 | return ret; | |
1644 | } | |
1645 | ||
1646 | static enum compact_result compact_zone_order(struct zone *zone, int order, | |
1647 | gfp_t gfp_mask, enum migrate_mode mode, int *contended, | |
1648 | unsigned int alloc_flags, int classzone_idx) | |
1649 | { | |
1650 | enum compact_result ret; | |
1651 | struct compact_control cc = { | |
1652 | .nr_freepages = 0, | |
1653 | .nr_migratepages = 0, | |
1654 | .order = order, | |
1655 | .gfp_mask = gfp_mask, | |
1656 | .zone = zone, | |
1657 | .mode = mode, | |
1658 | .alloc_flags = alloc_flags, | |
1659 | .classzone_idx = classzone_idx, | |
1660 | .direct_compaction = true, | |
1661 | }; | |
1662 | INIT_LIST_HEAD(&cc.freepages); | |
1663 | INIT_LIST_HEAD(&cc.migratepages); | |
1664 | ||
1665 | ret = compact_zone(zone, &cc); | |
1666 | ||
1667 | VM_BUG_ON(!list_empty(&cc.freepages)); | |
1668 | VM_BUG_ON(!list_empty(&cc.migratepages)); | |
1669 | ||
1670 | *contended = cc.contended; | |
1671 | return ret; | |
1672 | } | |
1673 | ||
1674 | int sysctl_extfrag_threshold = 500; | |
1675 | ||
1676 | /** | |
1677 | * try_to_compact_pages - Direct compact to satisfy a high-order allocation | |
1678 | * @gfp_mask: The GFP mask of the current allocation | |
1679 | * @order: The order of the current allocation | |
1680 | * @alloc_flags: The allocation flags of the current allocation | |
1681 | * @ac: The context of current allocation | |
1682 | * @mode: The migration mode for async, sync light, or sync migration | |
1683 | * @contended: Return value that determines if compaction was aborted due to | |
1684 | * need_resched() or lock contention | |
1685 | * | |
1686 | * This is the main entry point for direct page compaction. | |
1687 | */ | |
1688 | enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order, | |
1689 | unsigned int alloc_flags, const struct alloc_context *ac, | |
1690 | enum migrate_mode mode, int *contended) | |
1691 | { | |
1692 | int may_enter_fs = gfp_mask & __GFP_FS; | |
1693 | int may_perform_io = gfp_mask & __GFP_IO; | |
1694 | struct zoneref *z; | |
1695 | struct zone *zone; | |
1696 | enum compact_result rc = COMPACT_SKIPPED; | |
1697 | int all_zones_contended = COMPACT_CONTENDED_LOCK; /* init for &= op */ | |
1698 | ||
1699 | *contended = COMPACT_CONTENDED_NONE; | |
1700 | ||
1701 | /* Check if the GFP flags allow compaction */ | |
1702 | if (!may_enter_fs || !may_perform_io) | |
1703 | return COMPACT_SKIPPED; | |
1704 | ||
1705 | trace_mm_compaction_try_to_compact_pages(order, gfp_mask, mode); | |
1706 | ||
1707 | /* Compact each zone in the list */ | |
1708 | for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx, | |
1709 | ac->nodemask) { | |
1710 | enum compact_result status; | |
1711 | int zone_contended; | |
1712 | ||
1713 | if (compaction_deferred(zone, order)) { | |
1714 | rc = max_t(enum compact_result, COMPACT_DEFERRED, rc); | |
1715 | continue; | |
1716 | } | |
1717 | ||
1718 | status = compact_zone_order(zone, order, gfp_mask, mode, | |
1719 | &zone_contended, alloc_flags, | |
1720 | ac_classzone_idx(ac)); | |
1721 | rc = max(status, rc); | |
1722 | /* | |
1723 | * It takes at least one zone that wasn't lock contended | |
1724 | * to clear all_zones_contended. | |
1725 | */ | |
1726 | all_zones_contended &= zone_contended; | |
1727 | ||
1728 | /* If a normal allocation would succeed, stop compacting */ | |
1729 | if (zone_watermark_ok(zone, order, low_wmark_pages(zone), | |
1730 | ac_classzone_idx(ac), alloc_flags)) { | |
1731 | /* | |
1732 | * We think the allocation will succeed in this zone, | |
1733 | * but it is not certain, hence the false. The caller | |
1734 | * will repeat this with true if allocation indeed | |
1735 | * succeeds in this zone. | |
1736 | */ | |
1737 | compaction_defer_reset(zone, order, false); | |
1738 | /* | |
1739 | * It is possible that async compaction aborted due to | |
1740 | * need_resched() and the watermarks were ok thanks to | |
1741 | * somebody else freeing memory. The allocation can | |
1742 | * however still fail so we better signal the | |
1743 | * need_resched() contention anyway (this will not | |
1744 | * prevent the allocation attempt). | |
1745 | */ | |
1746 | if (zone_contended == COMPACT_CONTENDED_SCHED) | |
1747 | *contended = COMPACT_CONTENDED_SCHED; | |
1748 | ||
1749 | goto break_loop; | |
1750 | } | |
1751 | ||
1752 | if (mode != MIGRATE_ASYNC && (status == COMPACT_COMPLETE || | |
1753 | status == COMPACT_PARTIAL_SKIPPED)) { | |
1754 | /* | |
1755 | * We think that allocation won't succeed in this zone | |
1756 | * so we defer compaction there. If it ends up | |
1757 | * succeeding after all, it will be reset. | |
1758 | */ | |
1759 | defer_compaction(zone, order); | |
1760 | } | |
1761 | ||
1762 | /* | |
1763 | * We might have stopped compacting due to need_resched() in | |
1764 | * async compaction, or due to a fatal signal detected. In that | |
1765 | * case do not try further zones and signal need_resched() | |
1766 | * contention. | |
1767 | */ | |
1768 | if ((zone_contended == COMPACT_CONTENDED_SCHED) | |
1769 | || fatal_signal_pending(current)) { | |
1770 | *contended = COMPACT_CONTENDED_SCHED; | |
1771 | goto break_loop; | |
1772 | } | |
1773 | ||
1774 | continue; | |
1775 | break_loop: | |
1776 | /* | |
1777 | * We might not have tried all the zones, so be conservative | |
1778 | * and assume they are not all lock contended. | |
1779 | */ | |
1780 | all_zones_contended = 0; | |
1781 | break; | |
1782 | } | |
1783 | ||
1784 | /* | |
1785 | * If at least one zone wasn't deferred or skipped, we report if all | |
1786 | * zones that were tried were lock contended. | |
1787 | */ | |
1788 | if (rc > COMPACT_INACTIVE && all_zones_contended) | |
1789 | *contended = COMPACT_CONTENDED_LOCK; | |
1790 | ||
1791 | return rc; | |
1792 | } | |
1793 | ||
1794 | ||
1795 | /* Compact all zones within a node */ | |
1796 | static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc) | |
1797 | { | |
1798 | int zoneid; | |
1799 | struct zone *zone; | |
1800 | ||
1801 | for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { | |
1802 | ||
1803 | zone = &pgdat->node_zones[zoneid]; | |
1804 | if (!populated_zone(zone)) | |
1805 | continue; | |
1806 | ||
1807 | cc->nr_freepages = 0; | |
1808 | cc->nr_migratepages = 0; | |
1809 | cc->zone = zone; | |
1810 | INIT_LIST_HEAD(&cc->freepages); | |
1811 | INIT_LIST_HEAD(&cc->migratepages); | |
1812 | ||
1813 | /* | |
1814 | * When called via /proc/sys/vm/compact_memory | |
1815 | * this makes sure we compact the whole zone regardless of | |
1816 | * cached scanner positions. | |
1817 | */ | |
1818 | if (is_via_compact_memory(cc->order)) | |
1819 | __reset_isolation_suitable(zone); | |
1820 | ||
1821 | if (is_via_compact_memory(cc->order) || | |
1822 | !compaction_deferred(zone, cc->order)) | |
1823 | compact_zone(zone, cc); | |
1824 | ||
1825 | VM_BUG_ON(!list_empty(&cc->freepages)); | |
1826 | VM_BUG_ON(!list_empty(&cc->migratepages)); | |
1827 | ||
1828 | if (is_via_compact_memory(cc->order)) | |
1829 | continue; | |
1830 | ||
1831 | if (zone_watermark_ok(zone, cc->order, | |
1832 | low_wmark_pages(zone), 0, 0)) | |
1833 | compaction_defer_reset(zone, cc->order, false); | |
1834 | } | |
1835 | } | |
1836 | ||
1837 | void compact_pgdat(pg_data_t *pgdat, int order) | |
1838 | { | |
1839 | struct compact_control cc = { | |
1840 | .order = order, | |
1841 | .mode = MIGRATE_ASYNC, | |
1842 | }; | |
1843 | ||
1844 | if (!order) | |
1845 | return; | |
1846 | ||
1847 | __compact_pgdat(pgdat, &cc); | |
1848 | } | |
1849 | ||
1850 | static void compact_node(int nid) | |
1851 | { | |
1852 | struct compact_control cc = { | |
1853 | .order = -1, | |
1854 | .mode = MIGRATE_SYNC, | |
1855 | .ignore_skip_hint = true, | |
1856 | }; | |
1857 | ||
1858 | __compact_pgdat(NODE_DATA(nid), &cc); | |
1859 | } | |
1860 | ||
1861 | /* Compact all nodes in the system */ | |
1862 | static void compact_nodes(void) | |
1863 | { | |
1864 | int nid; | |
1865 | ||
1866 | /* Flush pending updates to the LRU lists */ | |
1867 | lru_add_drain_all(); | |
1868 | ||
1869 | for_each_online_node(nid) | |
1870 | compact_node(nid); | |
1871 | } | |
1872 | ||
1873 | /* The written value is actually unused, all memory is compacted */ | |
1874 | int sysctl_compact_memory; | |
1875 | ||
1876 | /* | |
1877 | * This is the entry point for compacting all nodes via | |
1878 | * /proc/sys/vm/compact_memory | |
1879 | */ | |
1880 | int sysctl_compaction_handler(struct ctl_table *table, int write, | |
1881 | void __user *buffer, size_t *length, loff_t *ppos) | |
1882 | { | |
1883 | if (write) | |
1884 | compact_nodes(); | |
1885 | ||
1886 | return 0; | |
1887 | } | |
1888 | ||
1889 | int sysctl_extfrag_handler(struct ctl_table *table, int write, | |
1890 | void __user *buffer, size_t *length, loff_t *ppos) | |
1891 | { | |
1892 | proc_dointvec_minmax(table, write, buffer, length, ppos); | |
1893 | ||
1894 | return 0; | |
1895 | } | |
1896 | ||
1897 | #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) | |
1898 | static ssize_t sysfs_compact_node(struct device *dev, | |
1899 | struct device_attribute *attr, | |
1900 | const char *buf, size_t count) | |
1901 | { | |
1902 | int nid = dev->id; | |
1903 | ||
1904 | if (nid >= 0 && nid < nr_node_ids && node_online(nid)) { | |
1905 | /* Flush pending updates to the LRU lists */ | |
1906 | lru_add_drain_all(); | |
1907 | ||
1908 | compact_node(nid); | |
1909 | } | |
1910 | ||
1911 | return count; | |
1912 | } | |
1913 | static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node); | |
1914 | ||
1915 | int compaction_register_node(struct node *node) | |
1916 | { | |
1917 | return device_create_file(&node->dev, &dev_attr_compact); | |
1918 | } | |
1919 | ||
1920 | void compaction_unregister_node(struct node *node) | |
1921 | { | |
1922 | return device_remove_file(&node->dev, &dev_attr_compact); | |
1923 | } | |
1924 | #endif /* CONFIG_SYSFS && CONFIG_NUMA */ | |
1925 | ||
1926 | static inline bool kcompactd_work_requested(pg_data_t *pgdat) | |
1927 | { | |
1928 | return pgdat->kcompactd_max_order > 0 || kthread_should_stop(); | |
1929 | } | |
1930 | ||
1931 | static bool kcompactd_node_suitable(pg_data_t *pgdat) | |
1932 | { | |
1933 | int zoneid; | |
1934 | struct zone *zone; | |
1935 | enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx; | |
1936 | ||
1937 | for (zoneid = 0; zoneid <= classzone_idx; zoneid++) { | |
1938 | zone = &pgdat->node_zones[zoneid]; | |
1939 | ||
1940 | if (!populated_zone(zone)) | |
1941 | continue; | |
1942 | ||
1943 | if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0, | |
1944 | classzone_idx) == COMPACT_CONTINUE) | |
1945 | return true; | |
1946 | } | |
1947 | ||
1948 | return false; | |
1949 | } | |
1950 | ||
1951 | static void kcompactd_do_work(pg_data_t *pgdat) | |
1952 | { | |
1953 | /* | |
1954 | * With no special task, compact all zones so that a page of requested | |
1955 | * order is allocatable. | |
1956 | */ | |
1957 | int zoneid; | |
1958 | struct zone *zone; | |
1959 | struct compact_control cc = { | |
1960 | .order = pgdat->kcompactd_max_order, | |
1961 | .classzone_idx = pgdat->kcompactd_classzone_idx, | |
1962 | .mode = MIGRATE_SYNC_LIGHT, | |
1963 | .ignore_skip_hint = true, | |
1964 | ||
1965 | }; | |
1966 | bool success = false; | |
1967 | ||
1968 | trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order, | |
1969 | cc.classzone_idx); | |
1970 | count_vm_event(KCOMPACTD_WAKE); | |
1971 | ||
1972 | for (zoneid = 0; zoneid <= cc.classzone_idx; zoneid++) { | |
1973 | int status; | |
1974 | ||
1975 | zone = &pgdat->node_zones[zoneid]; | |
1976 | if (!populated_zone(zone)) | |
1977 | continue; | |
1978 | ||
1979 | if (compaction_deferred(zone, cc.order)) | |
1980 | continue; | |
1981 | ||
1982 | if (compaction_suitable(zone, cc.order, 0, zoneid) != | |
1983 | COMPACT_CONTINUE) | |
1984 | continue; | |
1985 | ||
1986 | cc.nr_freepages = 0; | |
1987 | cc.nr_migratepages = 0; | |
1988 | cc.zone = zone; | |
1989 | INIT_LIST_HEAD(&cc.freepages); | |
1990 | INIT_LIST_HEAD(&cc.migratepages); | |
1991 | ||
1992 | if (kthread_should_stop()) | |
1993 | return; | |
1994 | status = compact_zone(zone, &cc); | |
1995 | ||
1996 | if (zone_watermark_ok(zone, cc.order, low_wmark_pages(zone), | |
1997 | cc.classzone_idx, 0)) { | |
1998 | success = true; | |
1999 | compaction_defer_reset(zone, cc.order, false); | |
2000 | } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) { | |
2001 | /* | |
2002 | * We use sync migration mode here, so we defer like | |
2003 | * sync direct compaction does. | |
2004 | */ | |
2005 | defer_compaction(zone, cc.order); | |
2006 | } | |
2007 | ||
2008 | VM_BUG_ON(!list_empty(&cc.freepages)); | |
2009 | VM_BUG_ON(!list_empty(&cc.migratepages)); | |
2010 | } | |
2011 | ||
2012 | /* | |
2013 | * Regardless of success, we are done until woken up next. But remember | |
2014 | * the requested order/classzone_idx in case it was higher/tighter than | |
2015 | * our current ones | |
2016 | */ | |
2017 | if (pgdat->kcompactd_max_order <= cc.order) | |
2018 | pgdat->kcompactd_max_order = 0; | |
2019 | if (pgdat->kcompactd_classzone_idx >= cc.classzone_idx) | |
2020 | pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1; | |
2021 | } | |
2022 | ||
2023 | void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx) | |
2024 | { | |
2025 | if (!order) | |
2026 | return; | |
2027 | ||
2028 | if (pgdat->kcompactd_max_order < order) | |
2029 | pgdat->kcompactd_max_order = order; | |
2030 | ||
2031 | if (pgdat->kcompactd_classzone_idx > classzone_idx) | |
2032 | pgdat->kcompactd_classzone_idx = classzone_idx; | |
2033 | ||
2034 | if (!waitqueue_active(&pgdat->kcompactd_wait)) | |
2035 | return; | |
2036 | ||
2037 | if (!kcompactd_node_suitable(pgdat)) | |
2038 | return; | |
2039 | ||
2040 | trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order, | |
2041 | classzone_idx); | |
2042 | wake_up_interruptible(&pgdat->kcompactd_wait); | |
2043 | } | |
2044 | ||
2045 | /* | |
2046 | * The background compaction daemon, started as a kernel thread | |
2047 | * from the init process. | |
2048 | */ | |
2049 | static int kcompactd(void *p) | |
2050 | { | |
2051 | pg_data_t *pgdat = (pg_data_t*)p; | |
2052 | struct task_struct *tsk = current; | |
2053 | ||
2054 | const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); | |
2055 | ||
2056 | if (!cpumask_empty(cpumask)) | |
2057 | set_cpus_allowed_ptr(tsk, cpumask); | |
2058 | ||
2059 | set_freezable(); | |
2060 | ||
2061 | pgdat->kcompactd_max_order = 0; | |
2062 | pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1; | |
2063 | ||
2064 | while (!kthread_should_stop()) { | |
2065 | trace_mm_compaction_kcompactd_sleep(pgdat->node_id); | |
2066 | wait_event_freezable(pgdat->kcompactd_wait, | |
2067 | kcompactd_work_requested(pgdat)); | |
2068 | ||
2069 | kcompactd_do_work(pgdat); | |
2070 | } | |
2071 | ||
2072 | return 0; | |
2073 | } | |
2074 | ||
2075 | /* | |
2076 | * This kcompactd start function will be called by init and node-hot-add. | |
2077 | * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added. | |
2078 | */ | |
2079 | int kcompactd_run(int nid) | |
2080 | { | |
2081 | pg_data_t *pgdat = NODE_DATA(nid); | |
2082 | int ret = 0; | |
2083 | ||
2084 | if (pgdat->kcompactd) | |
2085 | return 0; | |
2086 | ||
2087 | pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid); | |
2088 | if (IS_ERR(pgdat->kcompactd)) { | |
2089 | pr_err("Failed to start kcompactd on node %d\n", nid); | |
2090 | ret = PTR_ERR(pgdat->kcompactd); | |
2091 | pgdat->kcompactd = NULL; | |
2092 | } | |
2093 | return ret; | |
2094 | } | |
2095 | ||
2096 | /* | |
2097 | * Called by memory hotplug when all memory in a node is offlined. Caller must | |
2098 | * hold mem_hotplug_begin/end(). | |
2099 | */ | |
2100 | void kcompactd_stop(int nid) | |
2101 | { | |
2102 | struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd; | |
2103 | ||
2104 | if (kcompactd) { | |
2105 | kthread_stop(kcompactd); | |
2106 | NODE_DATA(nid)->kcompactd = NULL; | |
2107 | } | |
2108 | } | |
2109 | ||
2110 | /* | |
2111 | * It's optimal to keep kcompactd on the same CPUs as their memory, but | |
2112 | * not required for correctness. So if the last cpu in a node goes | |
2113 | * away, we get changed to run anywhere: as the first one comes back, | |
2114 | * restore their cpu bindings. | |
2115 | */ | |
2116 | static int cpu_callback(struct notifier_block *nfb, unsigned long action, | |
2117 | void *hcpu) | |
2118 | { | |
2119 | int nid; | |
2120 | ||
2121 | if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { | |
2122 | for_each_node_state(nid, N_MEMORY) { | |
2123 | pg_data_t *pgdat = NODE_DATA(nid); | |
2124 | const struct cpumask *mask; | |
2125 | ||
2126 | mask = cpumask_of_node(pgdat->node_id); | |
2127 | ||
2128 | if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) | |
2129 | /* One of our CPUs online: restore mask */ | |
2130 | set_cpus_allowed_ptr(pgdat->kcompactd, mask); | |
2131 | } | |
2132 | } | |
2133 | return NOTIFY_OK; | |
2134 | } | |
2135 | ||
2136 | static int __init kcompactd_init(void) | |
2137 | { | |
2138 | int nid; | |
2139 | ||
2140 | for_each_node_state(nid, N_MEMORY) | |
2141 | kcompactd_run(nid); | |
2142 | hotcpu_notifier(cpu_callback, 0); | |
2143 | return 0; | |
2144 | } | |
2145 | subsys_initcall(kcompactd_init) | |
2146 | ||
2147 | #endif /* CONFIG_COMPACTION */ |