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1 | // SPDX-License-Identifier: GPL-2.0 | |
2 | /* | |
3 | * linux/mm/compaction.c | |
4 | * | |
5 | * Memory compaction for the reduction of external fragmentation. Note that | |
6 | * this heavily depends upon page migration to do all the real heavy | |
7 | * lifting | |
8 | * | |
9 | * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie> | |
10 | */ | |
11 | #include <linux/cpu.h> | |
12 | #include <linux/swap.h> | |
13 | #include <linux/migrate.h> | |
14 | #include <linux/compaction.h> | |
15 | #include <linux/mm_inline.h> | |
16 | #include <linux/sched/signal.h> | |
17 | #include <linux/backing-dev.h> | |
18 | #include <linux/sysctl.h> | |
19 | #include <linux/sysfs.h> | |
20 | #include <linux/page-isolation.h> | |
21 | #include <linux/kasan.h> | |
22 | #include <linux/kthread.h> | |
23 | #include <linux/freezer.h> | |
24 | #include <linux/page_owner.h> | |
25 | #include "internal.h" | |
26 | ||
27 | #ifdef CONFIG_COMPACTION | |
28 | static inline void count_compact_event(enum vm_event_item item) | |
29 | { | |
30 | count_vm_event(item); | |
31 | } | |
32 | ||
33 | static inline void count_compact_events(enum vm_event_item item, long delta) | |
34 | { | |
35 | count_vm_events(item, delta); | |
36 | } | |
37 | #else | |
38 | #define count_compact_event(item) do { } while (0) | |
39 | #define count_compact_events(item, delta) do { } while (0) | |
40 | #endif | |
41 | ||
42 | #if defined CONFIG_COMPACTION || defined CONFIG_CMA | |
43 | ||
44 | #define CREATE_TRACE_POINTS | |
45 | #include <trace/events/compaction.h> | |
46 | ||
47 | #define block_start_pfn(pfn, order) round_down(pfn, 1UL << (order)) | |
48 | #define block_end_pfn(pfn, order) ALIGN((pfn) + 1, 1UL << (order)) | |
49 | #define pageblock_start_pfn(pfn) block_start_pfn(pfn, pageblock_order) | |
50 | #define pageblock_end_pfn(pfn) block_end_pfn(pfn, pageblock_order) | |
51 | ||
52 | static unsigned long release_freepages(struct list_head *freelist) | |
53 | { | |
54 | struct page *page, *next; | |
55 | unsigned long high_pfn = 0; | |
56 | ||
57 | list_for_each_entry_safe(page, next, freelist, lru) { | |
58 | unsigned long pfn = page_to_pfn(page); | |
59 | list_del(&page->lru); | |
60 | __free_page(page); | |
61 | if (pfn > high_pfn) | |
62 | high_pfn = pfn; | |
63 | } | |
64 | ||
65 | return high_pfn; | |
66 | } | |
67 | ||
68 | static void map_pages(struct list_head *list) | |
69 | { | |
70 | unsigned int i, order, nr_pages; | |
71 | struct page *page, *next; | |
72 | LIST_HEAD(tmp_list); | |
73 | ||
74 | list_for_each_entry_safe(page, next, list, lru) { | |
75 | list_del(&page->lru); | |
76 | ||
77 | order = page_private(page); | |
78 | nr_pages = 1 << order; | |
79 | ||
80 | post_alloc_hook(page, order, __GFP_MOVABLE); | |
81 | if (order) | |
82 | split_page(page, order); | |
83 | ||
84 | for (i = 0; i < nr_pages; i++) { | |
85 | list_add(&page->lru, &tmp_list); | |
86 | page++; | |
87 | } | |
88 | } | |
89 | ||
90 | list_splice(&tmp_list, list); | |
91 | } | |
92 | ||
93 | #ifdef CONFIG_COMPACTION | |
94 | ||
95 | int PageMovable(struct page *page) | |
96 | { | |
97 | struct address_space *mapping; | |
98 | ||
99 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
100 | if (!__PageMovable(page)) | |
101 | return 0; | |
102 | ||
103 | mapping = page_mapping(page); | |
104 | if (mapping && mapping->a_ops && mapping->a_ops->isolate_page) | |
105 | return 1; | |
106 | ||
107 | return 0; | |
108 | } | |
109 | EXPORT_SYMBOL(PageMovable); | |
110 | ||
111 | void __SetPageMovable(struct page *page, struct address_space *mapping) | |
112 | { | |
113 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
114 | VM_BUG_ON_PAGE((unsigned long)mapping & PAGE_MAPPING_MOVABLE, page); | |
115 | page->mapping = (void *)((unsigned long)mapping | PAGE_MAPPING_MOVABLE); | |
116 | } | |
117 | EXPORT_SYMBOL(__SetPageMovable); | |
118 | ||
119 | void __ClearPageMovable(struct page *page) | |
120 | { | |
121 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
122 | VM_BUG_ON_PAGE(!PageMovable(page), page); | |
123 | /* | |
124 | * Clear registered address_space val with keeping PAGE_MAPPING_MOVABLE | |
125 | * flag so that VM can catch up released page by driver after isolation. | |
126 | * With it, VM migration doesn't try to put it back. | |
127 | */ | |
128 | page->mapping = (void *)((unsigned long)page->mapping & | |
129 | PAGE_MAPPING_MOVABLE); | |
130 | } | |
131 | EXPORT_SYMBOL(__ClearPageMovable); | |
132 | ||
133 | /* Do not skip compaction more than 64 times */ | |
134 | #define COMPACT_MAX_DEFER_SHIFT 6 | |
135 | ||
136 | /* | |
137 | * Compaction is deferred when compaction fails to result in a page | |
138 | * allocation success. 1 << compact_defer_limit compactions are skipped up | |
139 | * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT | |
140 | */ | |
141 | void defer_compaction(struct zone *zone, int order) | |
142 | { | |
143 | zone->compact_considered = 0; | |
144 | zone->compact_defer_shift++; | |
145 | ||
146 | if (order < zone->compact_order_failed) | |
147 | zone->compact_order_failed = order; | |
148 | ||
149 | if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT) | |
150 | zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT; | |
151 | ||
152 | trace_mm_compaction_defer_compaction(zone, order); | |
153 | } | |
154 | ||
155 | /* Returns true if compaction should be skipped this time */ | |
156 | bool compaction_deferred(struct zone *zone, int order) | |
157 | { | |
158 | unsigned long defer_limit = 1UL << zone->compact_defer_shift; | |
159 | ||
160 | if (order < zone->compact_order_failed) | |
161 | return false; | |
162 | ||
163 | /* Avoid possible overflow */ | |
164 | if (++zone->compact_considered > defer_limit) | |
165 | zone->compact_considered = defer_limit; | |
166 | ||
167 | if (zone->compact_considered >= defer_limit) | |
168 | return false; | |
169 | ||
170 | trace_mm_compaction_deferred(zone, order); | |
171 | ||
172 | return true; | |
173 | } | |
174 | ||
175 | /* | |
176 | * Update defer tracking counters after successful compaction of given order, | |
177 | * which means an allocation either succeeded (alloc_success == true) or is | |
178 | * expected to succeed. | |
179 | */ | |
180 | void compaction_defer_reset(struct zone *zone, int order, | |
181 | bool alloc_success) | |
182 | { | |
183 | if (alloc_success) { | |
184 | zone->compact_considered = 0; | |
185 | zone->compact_defer_shift = 0; | |
186 | } | |
187 | if (order >= zone->compact_order_failed) | |
188 | zone->compact_order_failed = order + 1; | |
189 | ||
190 | trace_mm_compaction_defer_reset(zone, order); | |
191 | } | |
192 | ||
193 | /* Returns true if restarting compaction after many failures */ | |
194 | bool compaction_restarting(struct zone *zone, int order) | |
195 | { | |
196 | if (order < zone->compact_order_failed) | |
197 | return false; | |
198 | ||
199 | return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT && | |
200 | zone->compact_considered >= 1UL << zone->compact_defer_shift; | |
201 | } | |
202 | ||
203 | /* Returns true if the pageblock should be scanned for pages to isolate. */ | |
204 | static inline bool isolation_suitable(struct compact_control *cc, | |
205 | struct page *page) | |
206 | { | |
207 | if (cc->ignore_skip_hint) | |
208 | return true; | |
209 | ||
210 | return !get_pageblock_skip(page); | |
211 | } | |
212 | ||
213 | static void reset_cached_positions(struct zone *zone) | |
214 | { | |
215 | zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn; | |
216 | zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn; | |
217 | zone->compact_cached_free_pfn = | |
218 | pageblock_start_pfn(zone_end_pfn(zone) - 1); | |
219 | } | |
220 | ||
221 | /* | |
222 | * Compound pages of >= pageblock_order should consistenly be skipped until | |
223 | * released. It is always pointless to compact pages of such order (if they are | |
224 | * migratable), and the pageblocks they occupy cannot contain any free pages. | |
225 | */ | |
226 | static bool pageblock_skip_persistent(struct page *page) | |
227 | { | |
228 | if (!PageCompound(page)) | |
229 | return false; | |
230 | ||
231 | page = compound_head(page); | |
232 | ||
233 | if (compound_order(page) >= pageblock_order) | |
234 | return true; | |
235 | ||
236 | return false; | |
237 | } | |
238 | ||
239 | /* | |
240 | * This function is called to clear all cached information on pageblocks that | |
241 | * should be skipped for page isolation when the migrate and free page scanner | |
242 | * meet. | |
243 | */ | |
244 | static void __reset_isolation_suitable(struct zone *zone) | |
245 | { | |
246 | unsigned long start_pfn = zone->zone_start_pfn; | |
247 | unsigned long end_pfn = zone_end_pfn(zone); | |
248 | unsigned long pfn; | |
249 | ||
250 | zone->compact_blockskip_flush = false; | |
251 | ||
252 | /* Walk the zone and mark every pageblock as suitable for isolation */ | |
253 | for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) { | |
254 | struct page *page; | |
255 | ||
256 | cond_resched(); | |
257 | ||
258 | page = pfn_to_online_page(pfn); | |
259 | if (!page) | |
260 | continue; | |
261 | if (zone != page_zone(page)) | |
262 | continue; | |
263 | if (pageblock_skip_persistent(page)) | |
264 | continue; | |
265 | ||
266 | clear_pageblock_skip(page); | |
267 | } | |
268 | ||
269 | reset_cached_positions(zone); | |
270 | } | |
271 | ||
272 | void reset_isolation_suitable(pg_data_t *pgdat) | |
273 | { | |
274 | int zoneid; | |
275 | ||
276 | for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { | |
277 | struct zone *zone = &pgdat->node_zones[zoneid]; | |
278 | if (!populated_zone(zone)) | |
279 | continue; | |
280 | ||
281 | /* Only flush if a full compaction finished recently */ | |
282 | if (zone->compact_blockskip_flush) | |
283 | __reset_isolation_suitable(zone); | |
284 | } | |
285 | } | |
286 | ||
287 | /* | |
288 | * If no pages were isolated then mark this pageblock to be skipped in the | |
289 | * future. The information is later cleared by __reset_isolation_suitable(). | |
290 | */ | |
291 | static void update_pageblock_skip(struct compact_control *cc, | |
292 | struct page *page, unsigned long nr_isolated, | |
293 | bool migrate_scanner) | |
294 | { | |
295 | struct zone *zone = cc->zone; | |
296 | unsigned long pfn; | |
297 | ||
298 | if (cc->no_set_skip_hint) | |
299 | return; | |
300 | ||
301 | if (!page) | |
302 | return; | |
303 | ||
304 | if (nr_isolated) | |
305 | return; | |
306 | ||
307 | set_pageblock_skip(page); | |
308 | ||
309 | pfn = page_to_pfn(page); | |
310 | ||
311 | /* Update where async and sync compaction should restart */ | |
312 | if (migrate_scanner) { | |
313 | if (pfn > zone->compact_cached_migrate_pfn[0]) | |
314 | zone->compact_cached_migrate_pfn[0] = pfn; | |
315 | if (cc->mode != MIGRATE_ASYNC && | |
316 | pfn > zone->compact_cached_migrate_pfn[1]) | |
317 | zone->compact_cached_migrate_pfn[1] = pfn; | |
318 | } else { | |
319 | if (pfn < zone->compact_cached_free_pfn) | |
320 | zone->compact_cached_free_pfn = pfn; | |
321 | } | |
322 | } | |
323 | #else | |
324 | static inline bool isolation_suitable(struct compact_control *cc, | |
325 | struct page *page) | |
326 | { | |
327 | return true; | |
328 | } | |
329 | ||
330 | static inline bool pageblock_skip_persistent(struct page *page) | |
331 | { | |
332 | return false; | |
333 | } | |
334 | ||
335 | static inline void update_pageblock_skip(struct compact_control *cc, | |
336 | struct page *page, unsigned long nr_isolated, | |
337 | bool migrate_scanner) | |
338 | { | |
339 | } | |
340 | #endif /* CONFIG_COMPACTION */ | |
341 | ||
342 | /* | |
343 | * Compaction requires the taking of some coarse locks that are potentially | |
344 | * very heavily contended. For async compaction, back out if the lock cannot | |
345 | * be taken immediately. For sync compaction, spin on the lock if needed. | |
346 | * | |
347 | * Returns true if the lock is held | |
348 | * Returns false if the lock is not held and compaction should abort | |
349 | */ | |
350 | static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags, | |
351 | struct compact_control *cc) | |
352 | { | |
353 | if (cc->mode == MIGRATE_ASYNC) { | |
354 | if (!spin_trylock_irqsave(lock, *flags)) { | |
355 | cc->contended = true; | |
356 | return false; | |
357 | } | |
358 | } else { | |
359 | spin_lock_irqsave(lock, *flags); | |
360 | } | |
361 | ||
362 | return true; | |
363 | } | |
364 | ||
365 | /* | |
366 | * Compaction requires the taking of some coarse locks that are potentially | |
367 | * very heavily contended. The lock should be periodically unlocked to avoid | |
368 | * having disabled IRQs for a long time, even when there is nobody waiting on | |
369 | * the lock. It might also be that allowing the IRQs will result in | |
370 | * need_resched() becoming true. If scheduling is needed, async compaction | |
371 | * aborts. Sync compaction schedules. | |
372 | * Either compaction type will also abort if a fatal signal is pending. | |
373 | * In either case if the lock was locked, it is dropped and not regained. | |
374 | * | |
375 | * Returns true if compaction should abort due to fatal signal pending, or | |
376 | * async compaction due to need_resched() | |
377 | * Returns false when compaction can continue (sync compaction might have | |
378 | * scheduled) | |
379 | */ | |
380 | static bool compact_unlock_should_abort(spinlock_t *lock, | |
381 | unsigned long flags, bool *locked, struct compact_control *cc) | |
382 | { | |
383 | if (*locked) { | |
384 | spin_unlock_irqrestore(lock, flags); | |
385 | *locked = false; | |
386 | } | |
387 | ||
388 | if (fatal_signal_pending(current)) { | |
389 | cc->contended = true; | |
390 | return true; | |
391 | } | |
392 | ||
393 | if (need_resched()) { | |
394 | if (cc->mode == MIGRATE_ASYNC) { | |
395 | cc->contended = true; | |
396 | return true; | |
397 | } | |
398 | cond_resched(); | |
399 | } | |
400 | ||
401 | return false; | |
402 | } | |
403 | ||
404 | /* | |
405 | * Aside from avoiding lock contention, compaction also periodically checks | |
406 | * need_resched() and either schedules in sync compaction or aborts async | |
407 | * compaction. This is similar to what compact_unlock_should_abort() does, but | |
408 | * is used where no lock is concerned. | |
409 | * | |
410 | * Returns false when no scheduling was needed, or sync compaction scheduled. | |
411 | * Returns true when async compaction should abort. | |
412 | */ | |
413 | static inline bool compact_should_abort(struct compact_control *cc) | |
414 | { | |
415 | /* async compaction aborts if contended */ | |
416 | if (need_resched()) { | |
417 | if (cc->mode == MIGRATE_ASYNC) { | |
418 | cc->contended = true; | |
419 | return true; | |
420 | } | |
421 | ||
422 | cond_resched(); | |
423 | } | |
424 | ||
425 | return false; | |
426 | } | |
427 | ||
428 | /* | |
429 | * Isolate free pages onto a private freelist. If @strict is true, will abort | |
430 | * returning 0 on any invalid PFNs or non-free pages inside of the pageblock | |
431 | * (even though it may still end up isolating some pages). | |
432 | */ | |
433 | static unsigned long isolate_freepages_block(struct compact_control *cc, | |
434 | unsigned long *start_pfn, | |
435 | unsigned long end_pfn, | |
436 | struct list_head *freelist, | |
437 | bool strict) | |
438 | { | |
439 | int nr_scanned = 0, total_isolated = 0; | |
440 | struct page *cursor, *valid_page = NULL; | |
441 | unsigned long flags = 0; | |
442 | bool locked = false; | |
443 | unsigned long blockpfn = *start_pfn; | |
444 | unsigned int order; | |
445 | ||
446 | cursor = pfn_to_page(blockpfn); | |
447 | ||
448 | /* Isolate free pages. */ | |
449 | for (; blockpfn < end_pfn; blockpfn++, cursor++) { | |
450 | int isolated; | |
451 | struct page *page = cursor; | |
452 | ||
453 | /* | |
454 | * Periodically drop the lock (if held) regardless of its | |
455 | * contention, to give chance to IRQs. Abort if fatal signal | |
456 | * pending or async compaction detects need_resched() | |
457 | */ | |
458 | if (!(blockpfn % SWAP_CLUSTER_MAX) | |
459 | && compact_unlock_should_abort(&cc->zone->lock, flags, | |
460 | &locked, cc)) | |
461 | break; | |
462 | ||
463 | nr_scanned++; | |
464 | if (!pfn_valid_within(blockpfn)) | |
465 | goto isolate_fail; | |
466 | ||
467 | if (!valid_page) | |
468 | valid_page = page; | |
469 | ||
470 | /* | |
471 | * For compound pages such as THP and hugetlbfs, we can save | |
472 | * potentially a lot of iterations if we skip them at once. | |
473 | * The check is racy, but we can consider only valid values | |
474 | * and the only danger is skipping too much. | |
475 | */ | |
476 | if (PageCompound(page)) { | |
477 | const unsigned int order = compound_order(page); | |
478 | ||
479 | if (likely(order < MAX_ORDER)) { | |
480 | blockpfn += (1UL << order) - 1; | |
481 | cursor += (1UL << order) - 1; | |
482 | } | |
483 | goto isolate_fail; | |
484 | } | |
485 | ||
486 | if (!PageBuddy(page)) | |
487 | goto isolate_fail; | |
488 | ||
489 | /* | |
490 | * If we already hold the lock, we can skip some rechecking. | |
491 | * Note that if we hold the lock now, checked_pageblock was | |
492 | * already set in some previous iteration (or strict is true), | |
493 | * so it is correct to skip the suitable migration target | |
494 | * recheck as well. | |
495 | */ | |
496 | if (!locked) { | |
497 | /* | |
498 | * The zone lock must be held to isolate freepages. | |
499 | * Unfortunately this is a very coarse lock and can be | |
500 | * heavily contended if there are parallel allocations | |
501 | * or parallel compactions. For async compaction do not | |
502 | * spin on the lock and we acquire the lock as late as | |
503 | * possible. | |
504 | */ | |
505 | locked = compact_trylock_irqsave(&cc->zone->lock, | |
506 | &flags, cc); | |
507 | if (!locked) | |
508 | break; | |
509 | ||
510 | /* Recheck this is a buddy page under lock */ | |
511 | if (!PageBuddy(page)) | |
512 | goto isolate_fail; | |
513 | } | |
514 | ||
515 | /* Found a free page, will break it into order-0 pages */ | |
516 | order = page_order(page); | |
517 | isolated = __isolate_free_page(page, order); | |
518 | if (!isolated) | |
519 | break; | |
520 | set_page_private(page, order); | |
521 | ||
522 | total_isolated += isolated; | |
523 | cc->nr_freepages += isolated; | |
524 | list_add_tail(&page->lru, freelist); | |
525 | ||
526 | if (!strict && cc->nr_migratepages <= cc->nr_freepages) { | |
527 | blockpfn += isolated; | |
528 | break; | |
529 | } | |
530 | /* Advance to the end of split page */ | |
531 | blockpfn += isolated - 1; | |
532 | cursor += isolated - 1; | |
533 | continue; | |
534 | ||
535 | isolate_fail: | |
536 | if (strict) | |
537 | break; | |
538 | else | |
539 | continue; | |
540 | ||
541 | } | |
542 | ||
543 | if (locked) | |
544 | spin_unlock_irqrestore(&cc->zone->lock, flags); | |
545 | ||
546 | /* | |
547 | * There is a tiny chance that we have read bogus compound_order(), | |
548 | * so be careful to not go outside of the pageblock. | |
549 | */ | |
550 | if (unlikely(blockpfn > end_pfn)) | |
551 | blockpfn = end_pfn; | |
552 | ||
553 | trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn, | |
554 | nr_scanned, total_isolated); | |
555 | ||
556 | /* Record how far we have got within the block */ | |
557 | *start_pfn = blockpfn; | |
558 | ||
559 | /* | |
560 | * If strict isolation is requested by CMA then check that all the | |
561 | * pages requested were isolated. If there were any failures, 0 is | |
562 | * returned and CMA will fail. | |
563 | */ | |
564 | if (strict && blockpfn < end_pfn) | |
565 | total_isolated = 0; | |
566 | ||
567 | /* Update the pageblock-skip if the whole pageblock was scanned */ | |
568 | if (blockpfn == end_pfn) | |
569 | update_pageblock_skip(cc, valid_page, total_isolated, false); | |
570 | ||
571 | cc->total_free_scanned += nr_scanned; | |
572 | if (total_isolated) | |
573 | count_compact_events(COMPACTISOLATED, total_isolated); | |
574 | return total_isolated; | |
575 | } | |
576 | ||
577 | /** | |
578 | * isolate_freepages_range() - isolate free pages. | |
579 | * @start_pfn: The first PFN to start isolating. | |
580 | * @end_pfn: The one-past-last PFN. | |
581 | * | |
582 | * Non-free pages, invalid PFNs, or zone boundaries within the | |
583 | * [start_pfn, end_pfn) range are considered errors, cause function to | |
584 | * undo its actions and return zero. | |
585 | * | |
586 | * Otherwise, function returns one-past-the-last PFN of isolated page | |
587 | * (which may be greater then end_pfn if end fell in a middle of | |
588 | * a free page). | |
589 | */ | |
590 | unsigned long | |
591 | isolate_freepages_range(struct compact_control *cc, | |
592 | unsigned long start_pfn, unsigned long end_pfn) | |
593 | { | |
594 | unsigned long isolated, pfn, block_start_pfn, block_end_pfn; | |
595 | LIST_HEAD(freelist); | |
596 | ||
597 | pfn = start_pfn; | |
598 | block_start_pfn = pageblock_start_pfn(pfn); | |
599 | if (block_start_pfn < cc->zone->zone_start_pfn) | |
600 | block_start_pfn = cc->zone->zone_start_pfn; | |
601 | block_end_pfn = pageblock_end_pfn(pfn); | |
602 | ||
603 | for (; pfn < end_pfn; pfn += isolated, | |
604 | block_start_pfn = block_end_pfn, | |
605 | block_end_pfn += pageblock_nr_pages) { | |
606 | /* Protect pfn from changing by isolate_freepages_block */ | |
607 | unsigned long isolate_start_pfn = pfn; | |
608 | ||
609 | block_end_pfn = min(block_end_pfn, end_pfn); | |
610 | ||
611 | /* | |
612 | * pfn could pass the block_end_pfn if isolated freepage | |
613 | * is more than pageblock order. In this case, we adjust | |
614 | * scanning range to right one. | |
615 | */ | |
616 | if (pfn >= block_end_pfn) { | |
617 | block_start_pfn = pageblock_start_pfn(pfn); | |
618 | block_end_pfn = pageblock_end_pfn(pfn); | |
619 | block_end_pfn = min(block_end_pfn, end_pfn); | |
620 | } | |
621 | ||
622 | if (!pageblock_pfn_to_page(block_start_pfn, | |
623 | block_end_pfn, cc->zone)) | |
624 | break; | |
625 | ||
626 | isolated = isolate_freepages_block(cc, &isolate_start_pfn, | |
627 | block_end_pfn, &freelist, true); | |
628 | ||
629 | /* | |
630 | * In strict mode, isolate_freepages_block() returns 0 if | |
631 | * there are any holes in the block (ie. invalid PFNs or | |
632 | * non-free pages). | |
633 | */ | |
634 | if (!isolated) | |
635 | break; | |
636 | ||
637 | /* | |
638 | * If we managed to isolate pages, it is always (1 << n) * | |
639 | * pageblock_nr_pages for some non-negative n. (Max order | |
640 | * page may span two pageblocks). | |
641 | */ | |
642 | } | |
643 | ||
644 | /* __isolate_free_page() does not map the pages */ | |
645 | map_pages(&freelist); | |
646 | ||
647 | if (pfn < end_pfn) { | |
648 | /* Loop terminated early, cleanup. */ | |
649 | release_freepages(&freelist); | |
650 | return 0; | |
651 | } | |
652 | ||
653 | /* We don't use freelists for anything. */ | |
654 | return pfn; | |
655 | } | |
656 | ||
657 | /* Similar to reclaim, but different enough that they don't share logic */ | |
658 | static bool too_many_isolated(struct zone *zone) | |
659 | { | |
660 | unsigned long active, inactive, isolated; | |
661 | ||
662 | inactive = node_page_state(zone->zone_pgdat, NR_INACTIVE_FILE) + | |
663 | node_page_state(zone->zone_pgdat, NR_INACTIVE_ANON); | |
664 | active = node_page_state(zone->zone_pgdat, NR_ACTIVE_FILE) + | |
665 | node_page_state(zone->zone_pgdat, NR_ACTIVE_ANON); | |
666 | isolated = node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE) + | |
667 | node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON); | |
668 | ||
669 | return isolated > (inactive + active) / 2; | |
670 | } | |
671 | ||
672 | /** | |
673 | * isolate_migratepages_block() - isolate all migrate-able pages within | |
674 | * a single pageblock | |
675 | * @cc: Compaction control structure. | |
676 | * @low_pfn: The first PFN to isolate | |
677 | * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock | |
678 | * @isolate_mode: Isolation mode to be used. | |
679 | * | |
680 | * Isolate all pages that can be migrated from the range specified by | |
681 | * [low_pfn, end_pfn). The range is expected to be within same pageblock. | |
682 | * Returns zero if there is a fatal signal pending, otherwise PFN of the | |
683 | * first page that was not scanned (which may be both less, equal to or more | |
684 | * than end_pfn). | |
685 | * | |
686 | * The pages are isolated on cc->migratepages list (not required to be empty), | |
687 | * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field | |
688 | * is neither read nor updated. | |
689 | */ | |
690 | static unsigned long | |
691 | isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, | |
692 | unsigned long end_pfn, isolate_mode_t isolate_mode) | |
693 | { | |
694 | struct zone *zone = cc->zone; | |
695 | unsigned long nr_scanned = 0, nr_isolated = 0; | |
696 | struct lruvec *lruvec; | |
697 | unsigned long flags = 0; | |
698 | bool locked = false; | |
699 | struct page *page = NULL, *valid_page = NULL; | |
700 | unsigned long start_pfn = low_pfn; | |
701 | bool skip_on_failure = false; | |
702 | unsigned long next_skip_pfn = 0; | |
703 | ||
704 | /* | |
705 | * Ensure that there are not too many pages isolated from the LRU | |
706 | * list by either parallel reclaimers or compaction. If there are, | |
707 | * delay for some time until fewer pages are isolated | |
708 | */ | |
709 | while (unlikely(too_many_isolated(zone))) { | |
710 | /* async migration should just abort */ | |
711 | if (cc->mode == MIGRATE_ASYNC) | |
712 | return 0; | |
713 | ||
714 | congestion_wait(BLK_RW_ASYNC, HZ/10); | |
715 | ||
716 | if (fatal_signal_pending(current)) | |
717 | return 0; | |
718 | } | |
719 | ||
720 | if (compact_should_abort(cc)) | |
721 | return 0; | |
722 | ||
723 | if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) { | |
724 | skip_on_failure = true; | |
725 | next_skip_pfn = block_end_pfn(low_pfn, cc->order); | |
726 | } | |
727 | ||
728 | /* Time to isolate some pages for migration */ | |
729 | for (; low_pfn < end_pfn; low_pfn++) { | |
730 | ||
731 | if (skip_on_failure && low_pfn >= next_skip_pfn) { | |
732 | /* | |
733 | * We have isolated all migration candidates in the | |
734 | * previous order-aligned block, and did not skip it due | |
735 | * to failure. We should migrate the pages now and | |
736 | * hopefully succeed compaction. | |
737 | */ | |
738 | if (nr_isolated) | |
739 | break; | |
740 | ||
741 | /* | |
742 | * We failed to isolate in the previous order-aligned | |
743 | * block. Set the new boundary to the end of the | |
744 | * current block. Note we can't simply increase | |
745 | * next_skip_pfn by 1 << order, as low_pfn might have | |
746 | * been incremented by a higher number due to skipping | |
747 | * a compound or a high-order buddy page in the | |
748 | * previous loop iteration. | |
749 | */ | |
750 | next_skip_pfn = block_end_pfn(low_pfn, cc->order); | |
751 | } | |
752 | ||
753 | /* | |
754 | * Periodically drop the lock (if held) regardless of its | |
755 | * contention, to give chance to IRQs. Abort async compaction | |
756 | * if contended. | |
757 | */ | |
758 | if (!(low_pfn % SWAP_CLUSTER_MAX) | |
759 | && compact_unlock_should_abort(zone_lru_lock(zone), flags, | |
760 | &locked, cc)) | |
761 | break; | |
762 | ||
763 | if (!pfn_valid_within(low_pfn)) | |
764 | goto isolate_fail; | |
765 | nr_scanned++; | |
766 | ||
767 | page = pfn_to_page(low_pfn); | |
768 | ||
769 | if (!valid_page) | |
770 | valid_page = page; | |
771 | ||
772 | /* | |
773 | * Skip if free. We read page order here without zone lock | |
774 | * which is generally unsafe, but the race window is small and | |
775 | * the worst thing that can happen is that we skip some | |
776 | * potential isolation targets. | |
777 | */ | |
778 | if (PageBuddy(page)) { | |
779 | unsigned long freepage_order = page_order_unsafe(page); | |
780 | ||
781 | /* | |
782 | * Without lock, we cannot be sure that what we got is | |
783 | * a valid page order. Consider only values in the | |
784 | * valid order range to prevent low_pfn overflow. | |
785 | */ | |
786 | if (freepage_order > 0 && freepage_order < MAX_ORDER) | |
787 | low_pfn += (1UL << freepage_order) - 1; | |
788 | continue; | |
789 | } | |
790 | ||
791 | /* | |
792 | * Regardless of being on LRU, compound pages such as THP and | |
793 | * hugetlbfs are not to be compacted. We can potentially save | |
794 | * a lot of iterations if we skip them at once. The check is | |
795 | * racy, but we can consider only valid values and the only | |
796 | * danger is skipping too much. | |
797 | */ | |
798 | if (PageCompound(page)) { | |
799 | const unsigned int order = compound_order(page); | |
800 | ||
801 | if (likely(order < MAX_ORDER)) | |
802 | low_pfn += (1UL << order) - 1; | |
803 | goto isolate_fail; | |
804 | } | |
805 | ||
806 | /* | |
807 | * Check may be lockless but that's ok as we recheck later. | |
808 | * It's possible to migrate LRU and non-lru movable pages. | |
809 | * Skip any other type of page | |
810 | */ | |
811 | if (!PageLRU(page)) { | |
812 | /* | |
813 | * __PageMovable can return false positive so we need | |
814 | * to verify it under page_lock. | |
815 | */ | |
816 | if (unlikely(__PageMovable(page)) && | |
817 | !PageIsolated(page)) { | |
818 | if (locked) { | |
819 | spin_unlock_irqrestore(zone_lru_lock(zone), | |
820 | flags); | |
821 | locked = false; | |
822 | } | |
823 | ||
824 | if (!isolate_movable_page(page, isolate_mode)) | |
825 | goto isolate_success; | |
826 | } | |
827 | ||
828 | goto isolate_fail; | |
829 | } | |
830 | ||
831 | /* | |
832 | * Migration will fail if an anonymous page is pinned in memory, | |
833 | * so avoid taking lru_lock and isolating it unnecessarily in an | |
834 | * admittedly racy check. | |
835 | */ | |
836 | if (!page_mapping(page) && | |
837 | page_count(page) > page_mapcount(page)) | |
838 | goto isolate_fail; | |
839 | ||
840 | /* | |
841 | * Only allow to migrate anonymous pages in GFP_NOFS context | |
842 | * because those do not depend on fs locks. | |
843 | */ | |
844 | if (!(cc->gfp_mask & __GFP_FS) && page_mapping(page)) | |
845 | goto isolate_fail; | |
846 | ||
847 | /* If we already hold the lock, we can skip some rechecking */ | |
848 | if (!locked) { | |
849 | locked = compact_trylock_irqsave(zone_lru_lock(zone), | |
850 | &flags, cc); | |
851 | if (!locked) | |
852 | break; | |
853 | ||
854 | /* Recheck PageLRU and PageCompound under lock */ | |
855 | if (!PageLRU(page)) | |
856 | goto isolate_fail; | |
857 | ||
858 | /* | |
859 | * Page become compound since the non-locked check, | |
860 | * and it's on LRU. It can only be a THP so the order | |
861 | * is safe to read and it's 0 for tail pages. | |
862 | */ | |
863 | if (unlikely(PageCompound(page))) { | |
864 | low_pfn += (1UL << compound_order(page)) - 1; | |
865 | goto isolate_fail; | |
866 | } | |
867 | } | |
868 | ||
869 | lruvec = mem_cgroup_page_lruvec(page, zone->zone_pgdat); | |
870 | ||
871 | /* Try isolate the page */ | |
872 | if (__isolate_lru_page(page, isolate_mode) != 0) | |
873 | goto isolate_fail; | |
874 | ||
875 | VM_BUG_ON_PAGE(PageCompound(page), page); | |
876 | ||
877 | /* Successfully isolated */ | |
878 | del_page_from_lru_list(page, lruvec, page_lru(page)); | |
879 | inc_node_page_state(page, | |
880 | NR_ISOLATED_ANON + page_is_file_cache(page)); | |
881 | ||
882 | isolate_success: | |
883 | list_add(&page->lru, &cc->migratepages); | |
884 | cc->nr_migratepages++; | |
885 | nr_isolated++; | |
886 | ||
887 | /* | |
888 | * Record where we could have freed pages by migration and not | |
889 | * yet flushed them to buddy allocator. | |
890 | * - this is the lowest page that was isolated and likely be | |
891 | * then freed by migration. | |
892 | */ | |
893 | if (!cc->last_migrated_pfn) | |
894 | cc->last_migrated_pfn = low_pfn; | |
895 | ||
896 | /* Avoid isolating too much */ | |
897 | if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) { | |
898 | ++low_pfn; | |
899 | break; | |
900 | } | |
901 | ||
902 | continue; | |
903 | isolate_fail: | |
904 | if (!skip_on_failure) | |
905 | continue; | |
906 | ||
907 | /* | |
908 | * We have isolated some pages, but then failed. Release them | |
909 | * instead of migrating, as we cannot form the cc->order buddy | |
910 | * page anyway. | |
911 | */ | |
912 | if (nr_isolated) { | |
913 | if (locked) { | |
914 | spin_unlock_irqrestore(zone_lru_lock(zone), flags); | |
915 | locked = false; | |
916 | } | |
917 | putback_movable_pages(&cc->migratepages); | |
918 | cc->nr_migratepages = 0; | |
919 | cc->last_migrated_pfn = 0; | |
920 | nr_isolated = 0; | |
921 | } | |
922 | ||
923 | if (low_pfn < next_skip_pfn) { | |
924 | low_pfn = next_skip_pfn - 1; | |
925 | /* | |
926 | * The check near the loop beginning would have updated | |
927 | * next_skip_pfn too, but this is a bit simpler. | |
928 | */ | |
929 | next_skip_pfn += 1UL << cc->order; | |
930 | } | |
931 | } | |
932 | ||
933 | /* | |
934 | * The PageBuddy() check could have potentially brought us outside | |
935 | * the range to be scanned. | |
936 | */ | |
937 | if (unlikely(low_pfn > end_pfn)) | |
938 | low_pfn = end_pfn; | |
939 | ||
940 | if (locked) | |
941 | spin_unlock_irqrestore(zone_lru_lock(zone), flags); | |
942 | ||
943 | /* | |
944 | * Update the pageblock-skip information and cached scanner pfn, | |
945 | * if the whole pageblock was scanned without isolating any page. | |
946 | */ | |
947 | if (low_pfn == end_pfn) | |
948 | update_pageblock_skip(cc, valid_page, nr_isolated, true); | |
949 | ||
950 | trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn, | |
951 | nr_scanned, nr_isolated); | |
952 | ||
953 | cc->total_migrate_scanned += nr_scanned; | |
954 | if (nr_isolated) | |
955 | count_compact_events(COMPACTISOLATED, nr_isolated); | |
956 | ||
957 | return low_pfn; | |
958 | } | |
959 | ||
960 | /** | |
961 | * isolate_migratepages_range() - isolate migrate-able pages in a PFN range | |
962 | * @cc: Compaction control structure. | |
963 | * @start_pfn: The first PFN to start isolating. | |
964 | * @end_pfn: The one-past-last PFN. | |
965 | * | |
966 | * Returns zero if isolation fails fatally due to e.g. pending signal. | |
967 | * Otherwise, function returns one-past-the-last PFN of isolated page | |
968 | * (which may be greater than end_pfn if end fell in a middle of a THP page). | |
969 | */ | |
970 | unsigned long | |
971 | isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, | |
972 | unsigned long end_pfn) | |
973 | { | |
974 | unsigned long pfn, block_start_pfn, block_end_pfn; | |
975 | ||
976 | /* Scan block by block. First and last block may be incomplete */ | |
977 | pfn = start_pfn; | |
978 | block_start_pfn = pageblock_start_pfn(pfn); | |
979 | if (block_start_pfn < cc->zone->zone_start_pfn) | |
980 | block_start_pfn = cc->zone->zone_start_pfn; | |
981 | block_end_pfn = pageblock_end_pfn(pfn); | |
982 | ||
983 | for (; pfn < end_pfn; pfn = block_end_pfn, | |
984 | block_start_pfn = block_end_pfn, | |
985 | block_end_pfn += pageblock_nr_pages) { | |
986 | ||
987 | block_end_pfn = min(block_end_pfn, end_pfn); | |
988 | ||
989 | if (!pageblock_pfn_to_page(block_start_pfn, | |
990 | block_end_pfn, cc->zone)) | |
991 | continue; | |
992 | ||
993 | pfn = isolate_migratepages_block(cc, pfn, block_end_pfn, | |
994 | ISOLATE_UNEVICTABLE); | |
995 | ||
996 | if (!pfn) | |
997 | break; | |
998 | ||
999 | if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) | |
1000 | break; | |
1001 | } | |
1002 | ||
1003 | return pfn; | |
1004 | } | |
1005 | ||
1006 | #endif /* CONFIG_COMPACTION || CONFIG_CMA */ | |
1007 | #ifdef CONFIG_COMPACTION | |
1008 | ||
1009 | static bool suitable_migration_source(struct compact_control *cc, | |
1010 | struct page *page) | |
1011 | { | |
1012 | int block_mt; | |
1013 | ||
1014 | if ((cc->mode != MIGRATE_ASYNC) || !cc->direct_compaction) | |
1015 | return true; | |
1016 | ||
1017 | block_mt = get_pageblock_migratetype(page); | |
1018 | ||
1019 | if (cc->migratetype == MIGRATE_MOVABLE) | |
1020 | return is_migrate_movable(block_mt); | |
1021 | else | |
1022 | return block_mt == cc->migratetype; | |
1023 | } | |
1024 | ||
1025 | /* Returns true if the page is within a block suitable for migration to */ | |
1026 | static bool suitable_migration_target(struct compact_control *cc, | |
1027 | struct page *page) | |
1028 | { | |
1029 | /* If the page is a large free page, then disallow migration */ | |
1030 | if (PageBuddy(page)) { | |
1031 | /* | |
1032 | * We are checking page_order without zone->lock taken. But | |
1033 | * the only small danger is that we skip a potentially suitable | |
1034 | * pageblock, so it's not worth to check order for valid range. | |
1035 | */ | |
1036 | if (page_order_unsafe(page) >= pageblock_order) | |
1037 | return false; | |
1038 | } | |
1039 | ||
1040 | if (cc->ignore_block_suitable) | |
1041 | return true; | |
1042 | ||
1043 | /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */ | |
1044 | if (is_migrate_movable(get_pageblock_migratetype(page))) | |
1045 | return true; | |
1046 | ||
1047 | /* Otherwise skip the block */ | |
1048 | return false; | |
1049 | } | |
1050 | ||
1051 | /* | |
1052 | * Test whether the free scanner has reached the same or lower pageblock than | |
1053 | * the migration scanner, and compaction should thus terminate. | |
1054 | */ | |
1055 | static inline bool compact_scanners_met(struct compact_control *cc) | |
1056 | { | |
1057 | return (cc->free_pfn >> pageblock_order) | |
1058 | <= (cc->migrate_pfn >> pageblock_order); | |
1059 | } | |
1060 | ||
1061 | /* | |
1062 | * Based on information in the current compact_control, find blocks | |
1063 | * suitable for isolating free pages from and then isolate them. | |
1064 | */ | |
1065 | static void isolate_freepages(struct compact_control *cc) | |
1066 | { | |
1067 | struct zone *zone = cc->zone; | |
1068 | struct page *page; | |
1069 | unsigned long block_start_pfn; /* start of current pageblock */ | |
1070 | unsigned long isolate_start_pfn; /* exact pfn we start at */ | |
1071 | unsigned long block_end_pfn; /* end of current pageblock */ | |
1072 | unsigned long low_pfn; /* lowest pfn scanner is able to scan */ | |
1073 | struct list_head *freelist = &cc->freepages; | |
1074 | ||
1075 | /* | |
1076 | * Initialise the free scanner. The starting point is where we last | |
1077 | * successfully isolated from, zone-cached value, or the end of the | |
1078 | * zone when isolating for the first time. For looping we also need | |
1079 | * this pfn aligned down to the pageblock boundary, because we do | |
1080 | * block_start_pfn -= pageblock_nr_pages in the for loop. | |
1081 | * For ending point, take care when isolating in last pageblock of a | |
1082 | * a zone which ends in the middle of a pageblock. | |
1083 | * The low boundary is the end of the pageblock the migration scanner | |
1084 | * is using. | |
1085 | */ | |
1086 | isolate_start_pfn = cc->free_pfn; | |
1087 | block_start_pfn = pageblock_start_pfn(cc->free_pfn); | |
1088 | block_end_pfn = min(block_start_pfn + pageblock_nr_pages, | |
1089 | zone_end_pfn(zone)); | |
1090 | low_pfn = pageblock_end_pfn(cc->migrate_pfn); | |
1091 | ||
1092 | /* | |
1093 | * Isolate free pages until enough are available to migrate the | |
1094 | * pages on cc->migratepages. We stop searching if the migrate | |
1095 | * and free page scanners meet or enough free pages are isolated. | |
1096 | */ | |
1097 | for (; block_start_pfn >= low_pfn; | |
1098 | block_end_pfn = block_start_pfn, | |
1099 | block_start_pfn -= pageblock_nr_pages, | |
1100 | isolate_start_pfn = block_start_pfn) { | |
1101 | /* | |
1102 | * This can iterate a massively long zone without finding any | |
1103 | * suitable migration targets, so periodically check if we need | |
1104 | * to schedule, or even abort async compaction. | |
1105 | */ | |
1106 | if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)) | |
1107 | && compact_should_abort(cc)) | |
1108 | break; | |
1109 | ||
1110 | page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn, | |
1111 | zone); | |
1112 | if (!page) | |
1113 | continue; | |
1114 | ||
1115 | /* Check the block is suitable for migration */ | |
1116 | if (!suitable_migration_target(cc, page)) | |
1117 | continue; | |
1118 | ||
1119 | /* If isolation recently failed, do not retry */ | |
1120 | if (!isolation_suitable(cc, page)) | |
1121 | continue; | |
1122 | ||
1123 | /* Found a block suitable for isolating free pages from. */ | |
1124 | isolate_freepages_block(cc, &isolate_start_pfn, block_end_pfn, | |
1125 | freelist, false); | |
1126 | ||
1127 | /* | |
1128 | * If we isolated enough freepages, or aborted due to lock | |
1129 | * contention, terminate. | |
1130 | */ | |
1131 | if ((cc->nr_freepages >= cc->nr_migratepages) | |
1132 | || cc->contended) { | |
1133 | if (isolate_start_pfn >= block_end_pfn) { | |
1134 | /* | |
1135 | * Restart at previous pageblock if more | |
1136 | * freepages can be isolated next time. | |
1137 | */ | |
1138 | isolate_start_pfn = | |
1139 | block_start_pfn - pageblock_nr_pages; | |
1140 | } | |
1141 | break; | |
1142 | } else if (isolate_start_pfn < block_end_pfn) { | |
1143 | /* | |
1144 | * If isolation failed early, do not continue | |
1145 | * needlessly. | |
1146 | */ | |
1147 | break; | |
1148 | } | |
1149 | } | |
1150 | ||
1151 | /* __isolate_free_page() does not map the pages */ | |
1152 | map_pages(freelist); | |
1153 | ||
1154 | /* | |
1155 | * Record where the free scanner will restart next time. Either we | |
1156 | * broke from the loop and set isolate_start_pfn based on the last | |
1157 | * call to isolate_freepages_block(), or we met the migration scanner | |
1158 | * and the loop terminated due to isolate_start_pfn < low_pfn | |
1159 | */ | |
1160 | cc->free_pfn = isolate_start_pfn; | |
1161 | } | |
1162 | ||
1163 | /* | |
1164 | * This is a migrate-callback that "allocates" freepages by taking pages | |
1165 | * from the isolated freelists in the block we are migrating to. | |
1166 | */ | |
1167 | static struct page *compaction_alloc(struct page *migratepage, | |
1168 | unsigned long data, | |
1169 | int **result) | |
1170 | { | |
1171 | struct compact_control *cc = (struct compact_control *)data; | |
1172 | struct page *freepage; | |
1173 | ||
1174 | /* | |
1175 | * Isolate free pages if necessary, and if we are not aborting due to | |
1176 | * contention. | |
1177 | */ | |
1178 | if (list_empty(&cc->freepages)) { | |
1179 | if (!cc->contended) | |
1180 | isolate_freepages(cc); | |
1181 | ||
1182 | if (list_empty(&cc->freepages)) | |
1183 | return NULL; | |
1184 | } | |
1185 | ||
1186 | freepage = list_entry(cc->freepages.next, struct page, lru); | |
1187 | list_del(&freepage->lru); | |
1188 | cc->nr_freepages--; | |
1189 | ||
1190 | return freepage; | |
1191 | } | |
1192 | ||
1193 | /* | |
1194 | * This is a migrate-callback that "frees" freepages back to the isolated | |
1195 | * freelist. All pages on the freelist are from the same zone, so there is no | |
1196 | * special handling needed for NUMA. | |
1197 | */ | |
1198 | static void compaction_free(struct page *page, unsigned long data) | |
1199 | { | |
1200 | struct compact_control *cc = (struct compact_control *)data; | |
1201 | ||
1202 | list_add(&page->lru, &cc->freepages); | |
1203 | cc->nr_freepages++; | |
1204 | } | |
1205 | ||
1206 | /* possible outcome of isolate_migratepages */ | |
1207 | typedef enum { | |
1208 | ISOLATE_ABORT, /* Abort compaction now */ | |
1209 | ISOLATE_NONE, /* No pages isolated, continue scanning */ | |
1210 | ISOLATE_SUCCESS, /* Pages isolated, migrate */ | |
1211 | } isolate_migrate_t; | |
1212 | ||
1213 | /* | |
1214 | * Allow userspace to control policy on scanning the unevictable LRU for | |
1215 | * compactable pages. | |
1216 | */ | |
1217 | int sysctl_compact_unevictable_allowed __read_mostly = 1; | |
1218 | ||
1219 | /* | |
1220 | * Isolate all pages that can be migrated from the first suitable block, | |
1221 | * starting at the block pointed to by the migrate scanner pfn within | |
1222 | * compact_control. | |
1223 | */ | |
1224 | static isolate_migrate_t isolate_migratepages(struct zone *zone, | |
1225 | struct compact_control *cc) | |
1226 | { | |
1227 | unsigned long block_start_pfn; | |
1228 | unsigned long block_end_pfn; | |
1229 | unsigned long low_pfn; | |
1230 | struct page *page; | |
1231 | const isolate_mode_t isolate_mode = | |
1232 | (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | | |
1233 | (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0); | |
1234 | ||
1235 | /* | |
1236 | * Start at where we last stopped, or beginning of the zone as | |
1237 | * initialized by compact_zone() | |
1238 | */ | |
1239 | low_pfn = cc->migrate_pfn; | |
1240 | block_start_pfn = pageblock_start_pfn(low_pfn); | |
1241 | if (block_start_pfn < zone->zone_start_pfn) | |
1242 | block_start_pfn = zone->zone_start_pfn; | |
1243 | ||
1244 | /* Only scan within a pageblock boundary */ | |
1245 | block_end_pfn = pageblock_end_pfn(low_pfn); | |
1246 | ||
1247 | /* | |
1248 | * Iterate over whole pageblocks until we find the first suitable. | |
1249 | * Do not cross the free scanner. | |
1250 | */ | |
1251 | for (; block_end_pfn <= cc->free_pfn; | |
1252 | low_pfn = block_end_pfn, | |
1253 | block_start_pfn = block_end_pfn, | |
1254 | block_end_pfn += pageblock_nr_pages) { | |
1255 | ||
1256 | /* | |
1257 | * This can potentially iterate a massively long zone with | |
1258 | * many pageblocks unsuitable, so periodically check if we | |
1259 | * need to schedule, or even abort async compaction. | |
1260 | */ | |
1261 | if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)) | |
1262 | && compact_should_abort(cc)) | |
1263 | break; | |
1264 | ||
1265 | page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn, | |
1266 | zone); | |
1267 | if (!page) | |
1268 | continue; | |
1269 | ||
1270 | /* If isolation recently failed, do not retry */ | |
1271 | if (!isolation_suitable(cc, page)) | |
1272 | continue; | |
1273 | ||
1274 | /* | |
1275 | * For async compaction, also only scan in MOVABLE blocks. | |
1276 | * Async compaction is optimistic to see if the minimum amount | |
1277 | * of work satisfies the allocation. | |
1278 | */ | |
1279 | if (!suitable_migration_source(cc, page)) | |
1280 | continue; | |
1281 | ||
1282 | /* Perform the isolation */ | |
1283 | low_pfn = isolate_migratepages_block(cc, low_pfn, | |
1284 | block_end_pfn, isolate_mode); | |
1285 | ||
1286 | if (!low_pfn || cc->contended) | |
1287 | return ISOLATE_ABORT; | |
1288 | ||
1289 | /* | |
1290 | * Either we isolated something and proceed with migration. Or | |
1291 | * we failed and compact_zone should decide if we should | |
1292 | * continue or not. | |
1293 | */ | |
1294 | break; | |
1295 | } | |
1296 | ||
1297 | /* Record where migration scanner will be restarted. */ | |
1298 | cc->migrate_pfn = low_pfn; | |
1299 | ||
1300 | return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE; | |
1301 | } | |
1302 | ||
1303 | /* | |
1304 | * order == -1 is expected when compacting via | |
1305 | * /proc/sys/vm/compact_memory | |
1306 | */ | |
1307 | static inline bool is_via_compact_memory(int order) | |
1308 | { | |
1309 | return order == -1; | |
1310 | } | |
1311 | ||
1312 | static enum compact_result __compact_finished(struct zone *zone, | |
1313 | struct compact_control *cc) | |
1314 | { | |
1315 | unsigned int order; | |
1316 | const int migratetype = cc->migratetype; | |
1317 | ||
1318 | if (cc->contended || fatal_signal_pending(current)) | |
1319 | return COMPACT_CONTENDED; | |
1320 | ||
1321 | /* Compaction run completes if the migrate and free scanner meet */ | |
1322 | if (compact_scanners_met(cc)) { | |
1323 | /* Let the next compaction start anew. */ | |
1324 | reset_cached_positions(zone); | |
1325 | ||
1326 | /* | |
1327 | * Mark that the PG_migrate_skip information should be cleared | |
1328 | * by kswapd when it goes to sleep. kcompactd does not set the | |
1329 | * flag itself as the decision to be clear should be directly | |
1330 | * based on an allocation request. | |
1331 | */ | |
1332 | if (cc->direct_compaction) | |
1333 | zone->compact_blockskip_flush = true; | |
1334 | ||
1335 | if (cc->whole_zone) | |
1336 | return COMPACT_COMPLETE; | |
1337 | else | |
1338 | return COMPACT_PARTIAL_SKIPPED; | |
1339 | } | |
1340 | ||
1341 | if (is_via_compact_memory(cc->order)) | |
1342 | return COMPACT_CONTINUE; | |
1343 | ||
1344 | if (cc->finishing_block) { | |
1345 | /* | |
1346 | * We have finished the pageblock, but better check again that | |
1347 | * we really succeeded. | |
1348 | */ | |
1349 | if (IS_ALIGNED(cc->migrate_pfn, pageblock_nr_pages)) | |
1350 | cc->finishing_block = false; | |
1351 | else | |
1352 | return COMPACT_CONTINUE; | |
1353 | } | |
1354 | ||
1355 | /* Direct compactor: Is a suitable page free? */ | |
1356 | for (order = cc->order; order < MAX_ORDER; order++) { | |
1357 | struct free_area *area = &zone->free_area[order]; | |
1358 | bool can_steal; | |
1359 | ||
1360 | /* Job done if page is free of the right migratetype */ | |
1361 | if (!list_empty(&area->free_list[migratetype])) | |
1362 | return COMPACT_SUCCESS; | |
1363 | ||
1364 | #ifdef CONFIG_CMA | |
1365 | /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */ | |
1366 | if (migratetype == MIGRATE_MOVABLE && | |
1367 | !list_empty(&area->free_list[MIGRATE_CMA])) | |
1368 | return COMPACT_SUCCESS; | |
1369 | #endif | |
1370 | /* | |
1371 | * Job done if allocation would steal freepages from | |
1372 | * other migratetype buddy lists. | |
1373 | */ | |
1374 | if (find_suitable_fallback(area, order, migratetype, | |
1375 | true, &can_steal) != -1) { | |
1376 | ||
1377 | /* movable pages are OK in any pageblock */ | |
1378 | if (migratetype == MIGRATE_MOVABLE) | |
1379 | return COMPACT_SUCCESS; | |
1380 | ||
1381 | /* | |
1382 | * We are stealing for a non-movable allocation. Make | |
1383 | * sure we finish compacting the current pageblock | |
1384 | * first so it is as free as possible and we won't | |
1385 | * have to steal another one soon. This only applies | |
1386 | * to sync compaction, as async compaction operates | |
1387 | * on pageblocks of the same migratetype. | |
1388 | */ | |
1389 | if (cc->mode == MIGRATE_ASYNC || | |
1390 | IS_ALIGNED(cc->migrate_pfn, | |
1391 | pageblock_nr_pages)) { | |
1392 | return COMPACT_SUCCESS; | |
1393 | } | |
1394 | ||
1395 | cc->finishing_block = true; | |
1396 | return COMPACT_CONTINUE; | |
1397 | } | |
1398 | } | |
1399 | ||
1400 | return COMPACT_NO_SUITABLE_PAGE; | |
1401 | } | |
1402 | ||
1403 | static enum compact_result compact_finished(struct zone *zone, | |
1404 | struct compact_control *cc) | |
1405 | { | |
1406 | int ret; | |
1407 | ||
1408 | ret = __compact_finished(zone, cc); | |
1409 | trace_mm_compaction_finished(zone, cc->order, ret); | |
1410 | if (ret == COMPACT_NO_SUITABLE_PAGE) | |
1411 | ret = COMPACT_CONTINUE; | |
1412 | ||
1413 | return ret; | |
1414 | } | |
1415 | ||
1416 | /* | |
1417 | * compaction_suitable: Is this suitable to run compaction on this zone now? | |
1418 | * Returns | |
1419 | * COMPACT_SKIPPED - If there are too few free pages for compaction | |
1420 | * COMPACT_SUCCESS - If the allocation would succeed without compaction | |
1421 | * COMPACT_CONTINUE - If compaction should run now | |
1422 | */ | |
1423 | static enum compact_result __compaction_suitable(struct zone *zone, int order, | |
1424 | unsigned int alloc_flags, | |
1425 | int classzone_idx, | |
1426 | unsigned long wmark_target) | |
1427 | { | |
1428 | unsigned long watermark; | |
1429 | ||
1430 | if (is_via_compact_memory(order)) | |
1431 | return COMPACT_CONTINUE; | |
1432 | ||
1433 | watermark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK]; | |
1434 | /* | |
1435 | * If watermarks for high-order allocation are already met, there | |
1436 | * should be no need for compaction at all. | |
1437 | */ | |
1438 | if (zone_watermark_ok(zone, order, watermark, classzone_idx, | |
1439 | alloc_flags)) | |
1440 | return COMPACT_SUCCESS; | |
1441 | ||
1442 | /* | |
1443 | * Watermarks for order-0 must be met for compaction to be able to | |
1444 | * isolate free pages for migration targets. This means that the | |
1445 | * watermark and alloc_flags have to match, or be more pessimistic than | |
1446 | * the check in __isolate_free_page(). We don't use the direct | |
1447 | * compactor's alloc_flags, as they are not relevant for freepage | |
1448 | * isolation. We however do use the direct compactor's classzone_idx to | |
1449 | * skip over zones where lowmem reserves would prevent allocation even | |
1450 | * if compaction succeeds. | |
1451 | * For costly orders, we require low watermark instead of min for | |
1452 | * compaction to proceed to increase its chances. | |
1453 | * ALLOC_CMA is used, as pages in CMA pageblocks are considered | |
1454 | * suitable migration targets | |
1455 | */ | |
1456 | watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ? | |
1457 | low_wmark_pages(zone) : min_wmark_pages(zone); | |
1458 | watermark += compact_gap(order); | |
1459 | if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx, | |
1460 | ALLOC_CMA, wmark_target)) | |
1461 | return COMPACT_SKIPPED; | |
1462 | ||
1463 | return COMPACT_CONTINUE; | |
1464 | } | |
1465 | ||
1466 | enum compact_result compaction_suitable(struct zone *zone, int order, | |
1467 | unsigned int alloc_flags, | |
1468 | int classzone_idx) | |
1469 | { | |
1470 | enum compact_result ret; | |
1471 | int fragindex; | |
1472 | ||
1473 | ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx, | |
1474 | zone_page_state(zone, NR_FREE_PAGES)); | |
1475 | /* | |
1476 | * fragmentation index determines if allocation failures are due to | |
1477 | * low memory or external fragmentation | |
1478 | * | |
1479 | * index of -1000 would imply allocations might succeed depending on | |
1480 | * watermarks, but we already failed the high-order watermark check | |
1481 | * index towards 0 implies failure is due to lack of memory | |
1482 | * index towards 1000 implies failure is due to fragmentation | |
1483 | * | |
1484 | * Only compact if a failure would be due to fragmentation. Also | |
1485 | * ignore fragindex for non-costly orders where the alternative to | |
1486 | * a successful reclaim/compaction is OOM. Fragindex and the | |
1487 | * vm.extfrag_threshold sysctl is meant as a heuristic to prevent | |
1488 | * excessive compaction for costly orders, but it should not be at the | |
1489 | * expense of system stability. | |
1490 | */ | |
1491 | if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) { | |
1492 | fragindex = fragmentation_index(zone, order); | |
1493 | if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold) | |
1494 | ret = COMPACT_NOT_SUITABLE_ZONE; | |
1495 | } | |
1496 | ||
1497 | trace_mm_compaction_suitable(zone, order, ret); | |
1498 | if (ret == COMPACT_NOT_SUITABLE_ZONE) | |
1499 | ret = COMPACT_SKIPPED; | |
1500 | ||
1501 | return ret; | |
1502 | } | |
1503 | ||
1504 | bool compaction_zonelist_suitable(struct alloc_context *ac, int order, | |
1505 | int alloc_flags) | |
1506 | { | |
1507 | struct zone *zone; | |
1508 | struct zoneref *z; | |
1509 | ||
1510 | /* | |
1511 | * Make sure at least one zone would pass __compaction_suitable if we continue | |
1512 | * retrying the reclaim. | |
1513 | */ | |
1514 | for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx, | |
1515 | ac->nodemask) { | |
1516 | unsigned long available; | |
1517 | enum compact_result compact_result; | |
1518 | ||
1519 | /* | |
1520 | * Do not consider all the reclaimable memory because we do not | |
1521 | * want to trash just for a single high order allocation which | |
1522 | * is even not guaranteed to appear even if __compaction_suitable | |
1523 | * is happy about the watermark check. | |
1524 | */ | |
1525 | available = zone_reclaimable_pages(zone) / order; | |
1526 | available += zone_page_state_snapshot(zone, NR_FREE_PAGES); | |
1527 | compact_result = __compaction_suitable(zone, order, alloc_flags, | |
1528 | ac_classzone_idx(ac), available); | |
1529 | if (compact_result != COMPACT_SKIPPED) | |
1530 | return true; | |
1531 | } | |
1532 | ||
1533 | return false; | |
1534 | } | |
1535 | ||
1536 | static enum compact_result compact_zone(struct zone *zone, struct compact_control *cc) | |
1537 | { | |
1538 | enum compact_result ret; | |
1539 | unsigned long start_pfn = zone->zone_start_pfn; | |
1540 | unsigned long end_pfn = zone_end_pfn(zone); | |
1541 | const bool sync = cc->mode != MIGRATE_ASYNC; | |
1542 | ||
1543 | cc->migratetype = gfpflags_to_migratetype(cc->gfp_mask); | |
1544 | ret = compaction_suitable(zone, cc->order, cc->alloc_flags, | |
1545 | cc->classzone_idx); | |
1546 | /* Compaction is likely to fail */ | |
1547 | if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED) | |
1548 | return ret; | |
1549 | ||
1550 | /* huh, compaction_suitable is returning something unexpected */ | |
1551 | VM_BUG_ON(ret != COMPACT_CONTINUE); | |
1552 | ||
1553 | /* | |
1554 | * Clear pageblock skip if there were failures recently and compaction | |
1555 | * is about to be retried after being deferred. | |
1556 | */ | |
1557 | if (compaction_restarting(zone, cc->order)) | |
1558 | __reset_isolation_suitable(zone); | |
1559 | ||
1560 | /* | |
1561 | * Setup to move all movable pages to the end of the zone. Used cached | |
1562 | * information on where the scanners should start (unless we explicitly | |
1563 | * want to compact the whole zone), but check that it is initialised | |
1564 | * by ensuring the values are within zone boundaries. | |
1565 | */ | |
1566 | if (cc->whole_zone) { | |
1567 | cc->migrate_pfn = start_pfn; | |
1568 | cc->free_pfn = pageblock_start_pfn(end_pfn - 1); | |
1569 | } else { | |
1570 | cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync]; | |
1571 | cc->free_pfn = zone->compact_cached_free_pfn; | |
1572 | if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) { | |
1573 | cc->free_pfn = pageblock_start_pfn(end_pfn - 1); | |
1574 | zone->compact_cached_free_pfn = cc->free_pfn; | |
1575 | } | |
1576 | if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) { | |
1577 | cc->migrate_pfn = start_pfn; | |
1578 | zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn; | |
1579 | zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn; | |
1580 | } | |
1581 | ||
1582 | if (cc->migrate_pfn == start_pfn) | |
1583 | cc->whole_zone = true; | |
1584 | } | |
1585 | ||
1586 | cc->last_migrated_pfn = 0; | |
1587 | ||
1588 | trace_mm_compaction_begin(start_pfn, cc->migrate_pfn, | |
1589 | cc->free_pfn, end_pfn, sync); | |
1590 | ||
1591 | migrate_prep_local(); | |
1592 | ||
1593 | while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) { | |
1594 | int err; | |
1595 | ||
1596 | switch (isolate_migratepages(zone, cc)) { | |
1597 | case ISOLATE_ABORT: | |
1598 | ret = COMPACT_CONTENDED; | |
1599 | putback_movable_pages(&cc->migratepages); | |
1600 | cc->nr_migratepages = 0; | |
1601 | goto out; | |
1602 | case ISOLATE_NONE: | |
1603 | /* | |
1604 | * We haven't isolated and migrated anything, but | |
1605 | * there might still be unflushed migrations from | |
1606 | * previous cc->order aligned block. | |
1607 | */ | |
1608 | goto check_drain; | |
1609 | case ISOLATE_SUCCESS: | |
1610 | ; | |
1611 | } | |
1612 | ||
1613 | err = migrate_pages(&cc->migratepages, compaction_alloc, | |
1614 | compaction_free, (unsigned long)cc, cc->mode, | |
1615 | MR_COMPACTION); | |
1616 | ||
1617 | trace_mm_compaction_migratepages(cc->nr_migratepages, err, | |
1618 | &cc->migratepages); | |
1619 | ||
1620 | /* All pages were either migrated or will be released */ | |
1621 | cc->nr_migratepages = 0; | |
1622 | if (err) { | |
1623 | putback_movable_pages(&cc->migratepages); | |
1624 | /* | |
1625 | * migrate_pages() may return -ENOMEM when scanners meet | |
1626 | * and we want compact_finished() to detect it | |
1627 | */ | |
1628 | if (err == -ENOMEM && !compact_scanners_met(cc)) { | |
1629 | ret = COMPACT_CONTENDED; | |
1630 | goto out; | |
1631 | } | |
1632 | /* | |
1633 | * We failed to migrate at least one page in the current | |
1634 | * order-aligned block, so skip the rest of it. | |
1635 | */ | |
1636 | if (cc->direct_compaction && | |
1637 | (cc->mode == MIGRATE_ASYNC)) { | |
1638 | cc->migrate_pfn = block_end_pfn( | |
1639 | cc->migrate_pfn - 1, cc->order); | |
1640 | /* Draining pcplists is useless in this case */ | |
1641 | cc->last_migrated_pfn = 0; | |
1642 | ||
1643 | } | |
1644 | } | |
1645 | ||
1646 | check_drain: | |
1647 | /* | |
1648 | * Has the migration scanner moved away from the previous | |
1649 | * cc->order aligned block where we migrated from? If yes, | |
1650 | * flush the pages that were freed, so that they can merge and | |
1651 | * compact_finished() can detect immediately if allocation | |
1652 | * would succeed. | |
1653 | */ | |
1654 | if (cc->order > 0 && cc->last_migrated_pfn) { | |
1655 | int cpu; | |
1656 | unsigned long current_block_start = | |
1657 | block_start_pfn(cc->migrate_pfn, cc->order); | |
1658 | ||
1659 | if (cc->last_migrated_pfn < current_block_start) { | |
1660 | cpu = get_cpu(); | |
1661 | lru_add_drain_cpu(cpu); | |
1662 | drain_local_pages(zone); | |
1663 | put_cpu(); | |
1664 | /* No more flushing until we migrate again */ | |
1665 | cc->last_migrated_pfn = 0; | |
1666 | } | |
1667 | } | |
1668 | ||
1669 | } | |
1670 | ||
1671 | out: | |
1672 | /* | |
1673 | * Release free pages and update where the free scanner should restart, | |
1674 | * so we don't leave any returned pages behind in the next attempt. | |
1675 | */ | |
1676 | if (cc->nr_freepages > 0) { | |
1677 | unsigned long free_pfn = release_freepages(&cc->freepages); | |
1678 | ||
1679 | cc->nr_freepages = 0; | |
1680 | VM_BUG_ON(free_pfn == 0); | |
1681 | /* The cached pfn is always the first in a pageblock */ | |
1682 | free_pfn = pageblock_start_pfn(free_pfn); | |
1683 | /* | |
1684 | * Only go back, not forward. The cached pfn might have been | |
1685 | * already reset to zone end in compact_finished() | |
1686 | */ | |
1687 | if (free_pfn > zone->compact_cached_free_pfn) | |
1688 | zone->compact_cached_free_pfn = free_pfn; | |
1689 | } | |
1690 | ||
1691 | count_compact_events(COMPACTMIGRATE_SCANNED, cc->total_migrate_scanned); | |
1692 | count_compact_events(COMPACTFREE_SCANNED, cc->total_free_scanned); | |
1693 | ||
1694 | trace_mm_compaction_end(start_pfn, cc->migrate_pfn, | |
1695 | cc->free_pfn, end_pfn, sync, ret); | |
1696 | ||
1697 | return ret; | |
1698 | } | |
1699 | ||
1700 | static enum compact_result compact_zone_order(struct zone *zone, int order, | |
1701 | gfp_t gfp_mask, enum compact_priority prio, | |
1702 | unsigned int alloc_flags, int classzone_idx) | |
1703 | { | |
1704 | enum compact_result ret; | |
1705 | struct compact_control cc = { | |
1706 | .nr_freepages = 0, | |
1707 | .nr_migratepages = 0, | |
1708 | .total_migrate_scanned = 0, | |
1709 | .total_free_scanned = 0, | |
1710 | .order = order, | |
1711 | .gfp_mask = gfp_mask, | |
1712 | .zone = zone, | |
1713 | .mode = (prio == COMPACT_PRIO_ASYNC) ? | |
1714 | MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT, | |
1715 | .alloc_flags = alloc_flags, | |
1716 | .classzone_idx = classzone_idx, | |
1717 | .direct_compaction = true, | |
1718 | .whole_zone = (prio == MIN_COMPACT_PRIORITY), | |
1719 | .ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY), | |
1720 | .ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY) | |
1721 | }; | |
1722 | INIT_LIST_HEAD(&cc.freepages); | |
1723 | INIT_LIST_HEAD(&cc.migratepages); | |
1724 | ||
1725 | ret = compact_zone(zone, &cc); | |
1726 | ||
1727 | VM_BUG_ON(!list_empty(&cc.freepages)); | |
1728 | VM_BUG_ON(!list_empty(&cc.migratepages)); | |
1729 | ||
1730 | return ret; | |
1731 | } | |
1732 | ||
1733 | int sysctl_extfrag_threshold = 500; | |
1734 | ||
1735 | /** | |
1736 | * try_to_compact_pages - Direct compact to satisfy a high-order allocation | |
1737 | * @gfp_mask: The GFP mask of the current allocation | |
1738 | * @order: The order of the current allocation | |
1739 | * @alloc_flags: The allocation flags of the current allocation | |
1740 | * @ac: The context of current allocation | |
1741 | * @mode: The migration mode for async, sync light, or sync migration | |
1742 | * | |
1743 | * This is the main entry point for direct page compaction. | |
1744 | */ | |
1745 | enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order, | |
1746 | unsigned int alloc_flags, const struct alloc_context *ac, | |
1747 | enum compact_priority prio) | |
1748 | { | |
1749 | int may_perform_io = gfp_mask & __GFP_IO; | |
1750 | struct zoneref *z; | |
1751 | struct zone *zone; | |
1752 | enum compact_result rc = COMPACT_SKIPPED; | |
1753 | ||
1754 | /* | |
1755 | * Check if the GFP flags allow compaction - GFP_NOIO is really | |
1756 | * tricky context because the migration might require IO | |
1757 | */ | |
1758 | if (!may_perform_io) | |
1759 | return COMPACT_SKIPPED; | |
1760 | ||
1761 | trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio); | |
1762 | ||
1763 | /* Compact each zone in the list */ | |
1764 | for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx, | |
1765 | ac->nodemask) { | |
1766 | enum compact_result status; | |
1767 | ||
1768 | if (prio > MIN_COMPACT_PRIORITY | |
1769 | && compaction_deferred(zone, order)) { | |
1770 | rc = max_t(enum compact_result, COMPACT_DEFERRED, rc); | |
1771 | continue; | |
1772 | } | |
1773 | ||
1774 | status = compact_zone_order(zone, order, gfp_mask, prio, | |
1775 | alloc_flags, ac_classzone_idx(ac)); | |
1776 | rc = max(status, rc); | |
1777 | ||
1778 | /* The allocation should succeed, stop compacting */ | |
1779 | if (status == COMPACT_SUCCESS) { | |
1780 | /* | |
1781 | * We think the allocation will succeed in this zone, | |
1782 | * but it is not certain, hence the false. The caller | |
1783 | * will repeat this with true if allocation indeed | |
1784 | * succeeds in this zone. | |
1785 | */ | |
1786 | compaction_defer_reset(zone, order, false); | |
1787 | ||
1788 | break; | |
1789 | } | |
1790 | ||
1791 | if (prio != COMPACT_PRIO_ASYNC && (status == COMPACT_COMPLETE || | |
1792 | status == COMPACT_PARTIAL_SKIPPED)) | |
1793 | /* | |
1794 | * We think that allocation won't succeed in this zone | |
1795 | * so we defer compaction there. If it ends up | |
1796 | * succeeding after all, it will be reset. | |
1797 | */ | |
1798 | defer_compaction(zone, order); | |
1799 | ||
1800 | /* | |
1801 | * We might have stopped compacting due to need_resched() in | |
1802 | * async compaction, or due to a fatal signal detected. In that | |
1803 | * case do not try further zones | |
1804 | */ | |
1805 | if ((prio == COMPACT_PRIO_ASYNC && need_resched()) | |
1806 | || fatal_signal_pending(current)) | |
1807 | break; | |
1808 | } | |
1809 | ||
1810 | return rc; | |
1811 | } | |
1812 | ||
1813 | ||
1814 | /* Compact all zones within a node */ | |
1815 | static void compact_node(int nid) | |
1816 | { | |
1817 | pg_data_t *pgdat = NODE_DATA(nid); | |
1818 | int zoneid; | |
1819 | struct zone *zone; | |
1820 | struct compact_control cc = { | |
1821 | .order = -1, | |
1822 | .total_migrate_scanned = 0, | |
1823 | .total_free_scanned = 0, | |
1824 | .mode = MIGRATE_SYNC, | |
1825 | .ignore_skip_hint = true, | |
1826 | .whole_zone = true, | |
1827 | .gfp_mask = GFP_KERNEL, | |
1828 | }; | |
1829 | ||
1830 | ||
1831 | for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { | |
1832 | ||
1833 | zone = &pgdat->node_zones[zoneid]; | |
1834 | if (!populated_zone(zone)) | |
1835 | continue; | |
1836 | ||
1837 | cc.nr_freepages = 0; | |
1838 | cc.nr_migratepages = 0; | |
1839 | cc.zone = zone; | |
1840 | INIT_LIST_HEAD(&cc.freepages); | |
1841 | INIT_LIST_HEAD(&cc.migratepages); | |
1842 | ||
1843 | compact_zone(zone, &cc); | |
1844 | ||
1845 | VM_BUG_ON(!list_empty(&cc.freepages)); | |
1846 | VM_BUG_ON(!list_empty(&cc.migratepages)); | |
1847 | } | |
1848 | } | |
1849 | ||
1850 | /* Compact all nodes in the system */ | |
1851 | static void compact_nodes(void) | |
1852 | { | |
1853 | int nid; | |
1854 | ||
1855 | /* Flush pending updates to the LRU lists */ | |
1856 | lru_add_drain_all(); | |
1857 | ||
1858 | for_each_online_node(nid) | |
1859 | compact_node(nid); | |
1860 | } | |
1861 | ||
1862 | /* The written value is actually unused, all memory is compacted */ | |
1863 | int sysctl_compact_memory; | |
1864 | ||
1865 | /* | |
1866 | * This is the entry point for compacting all nodes via | |
1867 | * /proc/sys/vm/compact_memory | |
1868 | */ | |
1869 | int sysctl_compaction_handler(struct ctl_table *table, int write, | |
1870 | void __user *buffer, size_t *length, loff_t *ppos) | |
1871 | { | |
1872 | if (write) | |
1873 | compact_nodes(); | |
1874 | ||
1875 | return 0; | |
1876 | } | |
1877 | ||
1878 | int sysctl_extfrag_handler(struct ctl_table *table, int write, | |
1879 | void __user *buffer, size_t *length, loff_t *ppos) | |
1880 | { | |
1881 | proc_dointvec_minmax(table, write, buffer, length, ppos); | |
1882 | ||
1883 | return 0; | |
1884 | } | |
1885 | ||
1886 | #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) | |
1887 | static ssize_t sysfs_compact_node(struct device *dev, | |
1888 | struct device_attribute *attr, | |
1889 | const char *buf, size_t count) | |
1890 | { | |
1891 | int nid = dev->id; | |
1892 | ||
1893 | if (nid >= 0 && nid < nr_node_ids && node_online(nid)) { | |
1894 | /* Flush pending updates to the LRU lists */ | |
1895 | lru_add_drain_all(); | |
1896 | ||
1897 | compact_node(nid); | |
1898 | } | |
1899 | ||
1900 | return count; | |
1901 | } | |
1902 | static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node); | |
1903 | ||
1904 | int compaction_register_node(struct node *node) | |
1905 | { | |
1906 | return device_create_file(&node->dev, &dev_attr_compact); | |
1907 | } | |
1908 | ||
1909 | void compaction_unregister_node(struct node *node) | |
1910 | { | |
1911 | return device_remove_file(&node->dev, &dev_attr_compact); | |
1912 | } | |
1913 | #endif /* CONFIG_SYSFS && CONFIG_NUMA */ | |
1914 | ||
1915 | static inline bool kcompactd_work_requested(pg_data_t *pgdat) | |
1916 | { | |
1917 | return pgdat->kcompactd_max_order > 0 || kthread_should_stop(); | |
1918 | } | |
1919 | ||
1920 | static bool kcompactd_node_suitable(pg_data_t *pgdat) | |
1921 | { | |
1922 | int zoneid; | |
1923 | struct zone *zone; | |
1924 | enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx; | |
1925 | ||
1926 | for (zoneid = 0; zoneid <= classzone_idx; zoneid++) { | |
1927 | zone = &pgdat->node_zones[zoneid]; | |
1928 | ||
1929 | if (!populated_zone(zone)) | |
1930 | continue; | |
1931 | ||
1932 | if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0, | |
1933 | classzone_idx) == COMPACT_CONTINUE) | |
1934 | return true; | |
1935 | } | |
1936 | ||
1937 | return false; | |
1938 | } | |
1939 | ||
1940 | static void kcompactd_do_work(pg_data_t *pgdat) | |
1941 | { | |
1942 | /* | |
1943 | * With no special task, compact all zones so that a page of requested | |
1944 | * order is allocatable. | |
1945 | */ | |
1946 | int zoneid; | |
1947 | struct zone *zone; | |
1948 | struct compact_control cc = { | |
1949 | .order = pgdat->kcompactd_max_order, | |
1950 | .total_migrate_scanned = 0, | |
1951 | .total_free_scanned = 0, | |
1952 | .classzone_idx = pgdat->kcompactd_classzone_idx, | |
1953 | .mode = MIGRATE_SYNC_LIGHT, | |
1954 | .ignore_skip_hint = false, | |
1955 | .gfp_mask = GFP_KERNEL, | |
1956 | }; | |
1957 | trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order, | |
1958 | cc.classzone_idx); | |
1959 | count_compact_event(KCOMPACTD_WAKE); | |
1960 | ||
1961 | for (zoneid = 0; zoneid <= cc.classzone_idx; zoneid++) { | |
1962 | int status; | |
1963 | ||
1964 | zone = &pgdat->node_zones[zoneid]; | |
1965 | if (!populated_zone(zone)) | |
1966 | continue; | |
1967 | ||
1968 | if (compaction_deferred(zone, cc.order)) | |
1969 | continue; | |
1970 | ||
1971 | if (compaction_suitable(zone, cc.order, 0, zoneid) != | |
1972 | COMPACT_CONTINUE) | |
1973 | continue; | |
1974 | ||
1975 | cc.nr_freepages = 0; | |
1976 | cc.nr_migratepages = 0; | |
1977 | cc.total_migrate_scanned = 0; | |
1978 | cc.total_free_scanned = 0; | |
1979 | cc.zone = zone; | |
1980 | INIT_LIST_HEAD(&cc.freepages); | |
1981 | INIT_LIST_HEAD(&cc.migratepages); | |
1982 | ||
1983 | if (kthread_should_stop()) | |
1984 | return; | |
1985 | status = compact_zone(zone, &cc); | |
1986 | ||
1987 | if (status == COMPACT_SUCCESS) { | |
1988 | compaction_defer_reset(zone, cc.order, false); | |
1989 | } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) { | |
1990 | /* | |
1991 | * We use sync migration mode here, so we defer like | |
1992 | * sync direct compaction does. | |
1993 | */ | |
1994 | defer_compaction(zone, cc.order); | |
1995 | } | |
1996 | ||
1997 | count_compact_events(KCOMPACTD_MIGRATE_SCANNED, | |
1998 | cc.total_migrate_scanned); | |
1999 | count_compact_events(KCOMPACTD_FREE_SCANNED, | |
2000 | cc.total_free_scanned); | |
2001 | ||
2002 | VM_BUG_ON(!list_empty(&cc.freepages)); | |
2003 | VM_BUG_ON(!list_empty(&cc.migratepages)); | |
2004 | } | |
2005 | ||
2006 | /* | |
2007 | * Regardless of success, we are done until woken up next. But remember | |
2008 | * the requested order/classzone_idx in case it was higher/tighter than | |
2009 | * our current ones | |
2010 | */ | |
2011 | if (pgdat->kcompactd_max_order <= cc.order) | |
2012 | pgdat->kcompactd_max_order = 0; | |
2013 | if (pgdat->kcompactd_classzone_idx >= cc.classzone_idx) | |
2014 | pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1; | |
2015 | } | |
2016 | ||
2017 | void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx) | |
2018 | { | |
2019 | if (!order) | |
2020 | return; | |
2021 | ||
2022 | if (pgdat->kcompactd_max_order < order) | |
2023 | pgdat->kcompactd_max_order = order; | |
2024 | ||
2025 | if (pgdat->kcompactd_classzone_idx > classzone_idx) | |
2026 | pgdat->kcompactd_classzone_idx = classzone_idx; | |
2027 | ||
2028 | /* | |
2029 | * Pairs with implicit barrier in wait_event_freezable() | |
2030 | * such that wakeups are not missed. | |
2031 | */ | |
2032 | if (!wq_has_sleeper(&pgdat->kcompactd_wait)) | |
2033 | return; | |
2034 | ||
2035 | if (!kcompactd_node_suitable(pgdat)) | |
2036 | return; | |
2037 | ||
2038 | trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order, | |
2039 | classzone_idx); | |
2040 | wake_up_interruptible(&pgdat->kcompactd_wait); | |
2041 | } | |
2042 | ||
2043 | /* | |
2044 | * The background compaction daemon, started as a kernel thread | |
2045 | * from the init process. | |
2046 | */ | |
2047 | static int kcompactd(void *p) | |
2048 | { | |
2049 | pg_data_t *pgdat = (pg_data_t*)p; | |
2050 | struct task_struct *tsk = current; | |
2051 | ||
2052 | const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); | |
2053 | ||
2054 | if (!cpumask_empty(cpumask)) | |
2055 | set_cpus_allowed_ptr(tsk, cpumask); | |
2056 | ||
2057 | set_freezable(); | |
2058 | ||
2059 | pgdat->kcompactd_max_order = 0; | |
2060 | pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1; | |
2061 | ||
2062 | while (!kthread_should_stop()) { | |
2063 | trace_mm_compaction_kcompactd_sleep(pgdat->node_id); | |
2064 | wait_event_freezable(pgdat->kcompactd_wait, | |
2065 | kcompactd_work_requested(pgdat)); | |
2066 | ||
2067 | kcompactd_do_work(pgdat); | |
2068 | } | |
2069 | ||
2070 | return 0; | |
2071 | } | |
2072 | ||
2073 | /* | |
2074 | * This kcompactd start function will be called by init and node-hot-add. | |
2075 | * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added. | |
2076 | */ | |
2077 | int kcompactd_run(int nid) | |
2078 | { | |
2079 | pg_data_t *pgdat = NODE_DATA(nid); | |
2080 | int ret = 0; | |
2081 | ||
2082 | if (pgdat->kcompactd) | |
2083 | return 0; | |
2084 | ||
2085 | pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid); | |
2086 | if (IS_ERR(pgdat->kcompactd)) { | |
2087 | pr_err("Failed to start kcompactd on node %d\n", nid); | |
2088 | ret = PTR_ERR(pgdat->kcompactd); | |
2089 | pgdat->kcompactd = NULL; | |
2090 | } | |
2091 | return ret; | |
2092 | } | |
2093 | ||
2094 | /* | |
2095 | * Called by memory hotplug when all memory in a node is offlined. Caller must | |
2096 | * hold mem_hotplug_begin/end(). | |
2097 | */ | |
2098 | void kcompactd_stop(int nid) | |
2099 | { | |
2100 | struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd; | |
2101 | ||
2102 | if (kcompactd) { | |
2103 | kthread_stop(kcompactd); | |
2104 | NODE_DATA(nid)->kcompactd = NULL; | |
2105 | } | |
2106 | } | |
2107 | ||
2108 | /* | |
2109 | * It's optimal to keep kcompactd on the same CPUs as their memory, but | |
2110 | * not required for correctness. So if the last cpu in a node goes | |
2111 | * away, we get changed to run anywhere: as the first one comes back, | |
2112 | * restore their cpu bindings. | |
2113 | */ | |
2114 | static int kcompactd_cpu_online(unsigned int cpu) | |
2115 | { | |
2116 | int nid; | |
2117 | ||
2118 | for_each_node_state(nid, N_MEMORY) { | |
2119 | pg_data_t *pgdat = NODE_DATA(nid); | |
2120 | const struct cpumask *mask; | |
2121 | ||
2122 | mask = cpumask_of_node(pgdat->node_id); | |
2123 | ||
2124 | if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) | |
2125 | /* One of our CPUs online: restore mask */ | |
2126 | set_cpus_allowed_ptr(pgdat->kcompactd, mask); | |
2127 | } | |
2128 | return 0; | |
2129 | } | |
2130 | ||
2131 | static int __init kcompactd_init(void) | |
2132 | { | |
2133 | int nid; | |
2134 | int ret; | |
2135 | ||
2136 | ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, | |
2137 | "mm/compaction:online", | |
2138 | kcompactd_cpu_online, NULL); | |
2139 | if (ret < 0) { | |
2140 | pr_err("kcompactd: failed to register hotplug callbacks.\n"); | |
2141 | return ret; | |
2142 | } | |
2143 | ||
2144 | for_each_node_state(nid, N_MEMORY) | |
2145 | kcompactd_run(nid); | |
2146 | return 0; | |
2147 | } | |
2148 | subsys_initcall(kcompactd_init) | |
2149 | ||
2150 | #endif /* CONFIG_COMPACTION */ |