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 <linux/psi.h> |
26 | #include "internal.h" |
27 | |
28 | #ifdef CONFIG_COMPACTION |
29 | /* |
30 | * Fragmentation score check interval for proactive compaction purposes. |
31 | */ |
32 | #define HPAGE_FRAG_CHECK_INTERVAL_MSEC (500) |
33 | |
34 | static inline void count_compact_event(enum vm_event_item item) |
35 | { |
36 | count_vm_event(item); |
37 | } |
38 | |
39 | static inline void count_compact_events(enum vm_event_item item, long delta) |
40 | { |
41 | count_vm_events(item, delta); |
42 | } |
43 | #else |
44 | #define count_compact_event(item) do { } while (0) |
45 | #define count_compact_events(item, delta) do { } while (0) |
46 | #endif |
47 | |
48 | #if defined CONFIG_COMPACTION || defined CONFIG_CMA |
49 | |
50 | #define CREATE_TRACE_POINTS |
51 | #include <trace/events/compaction.h> |
52 | |
53 | #define block_start_pfn(pfn, order) round_down(pfn, 1UL << (order)) |
54 | #define block_end_pfn(pfn, order) ALIGN((pfn) + 1, 1UL << (order)) |
55 | |
56 | /* |
57 | * Page order with-respect-to which proactive compaction |
58 | * calculates external fragmentation, which is used as |
59 | * the "fragmentation score" of a node/zone. |
60 | */ |
61 | #if defined CONFIG_TRANSPARENT_HUGEPAGE |
62 | #define COMPACTION_HPAGE_ORDER HPAGE_PMD_ORDER |
63 | #elif defined CONFIG_HUGETLBFS |
64 | #define COMPACTION_HPAGE_ORDER HUGETLB_PAGE_ORDER |
65 | #else |
66 | #define COMPACTION_HPAGE_ORDER (PMD_SHIFT - PAGE_SHIFT) |
67 | #endif |
68 | |
69 | static unsigned long release_freepages(struct list_head *freelist) |
70 | { |
71 | struct page *page, *next; |
72 | unsigned long high_pfn = 0; |
73 | |
74 | list_for_each_entry_safe(page, next, freelist, lru) { |
75 | unsigned long pfn = page_to_pfn(page); |
76 | list_del(entry: &page->lru); |
77 | __free_page(page); |
78 | if (pfn > high_pfn) |
79 | high_pfn = pfn; |
80 | } |
81 | |
82 | return high_pfn; |
83 | } |
84 | |
85 | static void split_map_pages(struct list_head *list) |
86 | { |
87 | unsigned int i, order, nr_pages; |
88 | struct page *page, *next; |
89 | LIST_HEAD(tmp_list); |
90 | |
91 | list_for_each_entry_safe(page, next, list, lru) { |
92 | list_del(entry: &page->lru); |
93 | |
94 | order = page_private(page); |
95 | nr_pages = 1 << order; |
96 | |
97 | post_alloc_hook(page, order, __GFP_MOVABLE); |
98 | if (order) |
99 | split_page(page, order); |
100 | |
101 | for (i = 0; i < nr_pages; i++) { |
102 | list_add(new: &page->lru, head: &tmp_list); |
103 | page++; |
104 | } |
105 | } |
106 | |
107 | list_splice(list: &tmp_list, head: list); |
108 | } |
109 | |
110 | #ifdef CONFIG_COMPACTION |
111 | bool PageMovable(struct page *page) |
112 | { |
113 | const struct movable_operations *mops; |
114 | |
115 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
116 | if (!__PageMovable(page)) |
117 | return false; |
118 | |
119 | mops = page_movable_ops(page); |
120 | if (mops) |
121 | return true; |
122 | |
123 | return false; |
124 | } |
125 | |
126 | void __SetPageMovable(struct page *page, const struct movable_operations *mops) |
127 | { |
128 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
129 | VM_BUG_ON_PAGE((unsigned long)mops & PAGE_MAPPING_MOVABLE, page); |
130 | page->mapping = (void *)((unsigned long)mops | PAGE_MAPPING_MOVABLE); |
131 | } |
132 | EXPORT_SYMBOL(__SetPageMovable); |
133 | |
134 | void __ClearPageMovable(struct page *page) |
135 | { |
136 | VM_BUG_ON_PAGE(!PageMovable(page), page); |
137 | /* |
138 | * This page still has the type of a movable page, but it's |
139 | * actually not movable any more. |
140 | */ |
141 | page->mapping = (void *)PAGE_MAPPING_MOVABLE; |
142 | } |
143 | EXPORT_SYMBOL(__ClearPageMovable); |
144 | |
145 | /* Do not skip compaction more than 64 times */ |
146 | #define COMPACT_MAX_DEFER_SHIFT 6 |
147 | |
148 | /* |
149 | * Compaction is deferred when compaction fails to result in a page |
150 | * allocation success. 1 << compact_defer_shift, compactions are skipped up |
151 | * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT |
152 | */ |
153 | static void defer_compaction(struct zone *zone, int order) |
154 | { |
155 | zone->compact_considered = 0; |
156 | zone->compact_defer_shift++; |
157 | |
158 | if (order < zone->compact_order_failed) |
159 | zone->compact_order_failed = order; |
160 | |
161 | if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT) |
162 | zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT; |
163 | |
164 | trace_mm_compaction_defer_compaction(zone, order); |
165 | } |
166 | |
167 | /* Returns true if compaction should be skipped this time */ |
168 | static bool compaction_deferred(struct zone *zone, int order) |
169 | { |
170 | unsigned long defer_limit = 1UL << zone->compact_defer_shift; |
171 | |
172 | if (order < zone->compact_order_failed) |
173 | return false; |
174 | |
175 | /* Avoid possible overflow */ |
176 | if (++zone->compact_considered >= defer_limit) { |
177 | zone->compact_considered = defer_limit; |
178 | return false; |
179 | } |
180 | |
181 | trace_mm_compaction_deferred(zone, order); |
182 | |
183 | return true; |
184 | } |
185 | |
186 | /* |
187 | * Update defer tracking counters after successful compaction of given order, |
188 | * which means an allocation either succeeded (alloc_success == true) or is |
189 | * expected to succeed. |
190 | */ |
191 | void compaction_defer_reset(struct zone *zone, int order, |
192 | bool alloc_success) |
193 | { |
194 | if (alloc_success) { |
195 | zone->compact_considered = 0; |
196 | zone->compact_defer_shift = 0; |
197 | } |
198 | if (order >= zone->compact_order_failed) |
199 | zone->compact_order_failed = order + 1; |
200 | |
201 | trace_mm_compaction_defer_reset(zone, order); |
202 | } |
203 | |
204 | /* Returns true if restarting compaction after many failures */ |
205 | static bool compaction_restarting(struct zone *zone, int order) |
206 | { |
207 | if (order < zone->compact_order_failed) |
208 | return false; |
209 | |
210 | return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT && |
211 | zone->compact_considered >= 1UL << zone->compact_defer_shift; |
212 | } |
213 | |
214 | /* Returns true if the pageblock should be scanned for pages to isolate. */ |
215 | static inline bool isolation_suitable(struct compact_control *cc, |
216 | struct page *page) |
217 | { |
218 | if (cc->ignore_skip_hint) |
219 | return true; |
220 | |
221 | return !get_pageblock_skip(page); |
222 | } |
223 | |
224 | static void reset_cached_positions(struct zone *zone) |
225 | { |
226 | zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn; |
227 | zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn; |
228 | zone->compact_cached_free_pfn = |
229 | pageblock_start_pfn(zone_end_pfn(zone) - 1); |
230 | } |
231 | |
232 | #ifdef CONFIG_SPARSEMEM |
233 | /* |
234 | * If the PFN falls into an offline section, return the start PFN of the |
235 | * next online section. If the PFN falls into an online section or if |
236 | * there is no next online section, return 0. |
237 | */ |
238 | static unsigned long skip_offline_sections(unsigned long start_pfn) |
239 | { |
240 | unsigned long start_nr = pfn_to_section_nr(pfn: start_pfn); |
241 | |
242 | if (online_section_nr(nr: start_nr)) |
243 | return 0; |
244 | |
245 | while (++start_nr <= __highest_present_section_nr) { |
246 | if (online_section_nr(nr: start_nr)) |
247 | return section_nr_to_pfn(sec: start_nr); |
248 | } |
249 | |
250 | return 0; |
251 | } |
252 | |
253 | /* |
254 | * If the PFN falls into an offline section, return the end PFN of the |
255 | * next online section in reverse. If the PFN falls into an online section |
256 | * or if there is no next online section in reverse, return 0. |
257 | */ |
258 | static unsigned long skip_offline_sections_reverse(unsigned long start_pfn) |
259 | { |
260 | unsigned long start_nr = pfn_to_section_nr(pfn: start_pfn); |
261 | |
262 | if (!start_nr || online_section_nr(nr: start_nr)) |
263 | return 0; |
264 | |
265 | while (start_nr-- > 0) { |
266 | if (online_section_nr(nr: start_nr)) |
267 | return section_nr_to_pfn(sec: start_nr) + PAGES_PER_SECTION; |
268 | } |
269 | |
270 | return 0; |
271 | } |
272 | #else |
273 | static unsigned long skip_offline_sections(unsigned long start_pfn) |
274 | { |
275 | return 0; |
276 | } |
277 | |
278 | static unsigned long skip_offline_sections_reverse(unsigned long start_pfn) |
279 | { |
280 | return 0; |
281 | } |
282 | #endif |
283 | |
284 | /* |
285 | * Compound pages of >= pageblock_order should consistently be skipped until |
286 | * released. It is always pointless to compact pages of such order (if they are |
287 | * migratable), and the pageblocks they occupy cannot contain any free pages. |
288 | */ |
289 | static bool pageblock_skip_persistent(struct page *page) |
290 | { |
291 | if (!PageCompound(page)) |
292 | return false; |
293 | |
294 | page = compound_head(page); |
295 | |
296 | if (compound_order(page) >= pageblock_order) |
297 | return true; |
298 | |
299 | return false; |
300 | } |
301 | |
302 | static bool |
303 | __reset_isolation_pfn(struct zone *zone, unsigned long pfn, bool check_source, |
304 | bool check_target) |
305 | { |
306 | struct page *page = pfn_to_online_page(pfn); |
307 | struct page *block_page; |
308 | struct page *end_page; |
309 | unsigned long block_pfn; |
310 | |
311 | if (!page) |
312 | return false; |
313 | if (zone != page_zone(page)) |
314 | return false; |
315 | if (pageblock_skip_persistent(page)) |
316 | return false; |
317 | |
318 | /* |
319 | * If skip is already cleared do no further checking once the |
320 | * restart points have been set. |
321 | */ |
322 | if (check_source && check_target && !get_pageblock_skip(page)) |
323 | return true; |
324 | |
325 | /* |
326 | * If clearing skip for the target scanner, do not select a |
327 | * non-movable pageblock as the starting point. |
328 | */ |
329 | if (!check_source && check_target && |
330 | get_pageblock_migratetype(page) != MIGRATE_MOVABLE) |
331 | return false; |
332 | |
333 | /* Ensure the start of the pageblock or zone is online and valid */ |
334 | block_pfn = pageblock_start_pfn(pfn); |
335 | block_pfn = max(block_pfn, zone->zone_start_pfn); |
336 | block_page = pfn_to_online_page(pfn: block_pfn); |
337 | if (block_page) { |
338 | page = block_page; |
339 | pfn = block_pfn; |
340 | } |
341 | |
342 | /* Ensure the end of the pageblock or zone is online and valid */ |
343 | block_pfn = pageblock_end_pfn(pfn) - 1; |
344 | block_pfn = min(block_pfn, zone_end_pfn(zone) - 1); |
345 | end_page = pfn_to_online_page(pfn: block_pfn); |
346 | if (!end_page) |
347 | return false; |
348 | |
349 | /* |
350 | * Only clear the hint if a sample indicates there is either a |
351 | * free page or an LRU page in the block. One or other condition |
352 | * is necessary for the block to be a migration source/target. |
353 | */ |
354 | do { |
355 | if (check_source && PageLRU(page)) { |
356 | clear_pageblock_skip(page); |
357 | return true; |
358 | } |
359 | |
360 | if (check_target && PageBuddy(page)) { |
361 | clear_pageblock_skip(page); |
362 | return true; |
363 | } |
364 | |
365 | page += (1 << PAGE_ALLOC_COSTLY_ORDER); |
366 | } while (page <= end_page); |
367 | |
368 | return false; |
369 | } |
370 | |
371 | /* |
372 | * This function is called to clear all cached information on pageblocks that |
373 | * should be skipped for page isolation when the migrate and free page scanner |
374 | * meet. |
375 | */ |
376 | static void __reset_isolation_suitable(struct zone *zone) |
377 | { |
378 | unsigned long migrate_pfn = zone->zone_start_pfn; |
379 | unsigned long free_pfn = zone_end_pfn(zone) - 1; |
380 | unsigned long reset_migrate = free_pfn; |
381 | unsigned long reset_free = migrate_pfn; |
382 | bool source_set = false; |
383 | bool free_set = false; |
384 | |
385 | /* Only flush if a full compaction finished recently */ |
386 | if (!zone->compact_blockskip_flush) |
387 | return; |
388 | |
389 | zone->compact_blockskip_flush = false; |
390 | |
391 | /* |
392 | * Walk the zone and update pageblock skip information. Source looks |
393 | * for PageLRU while target looks for PageBuddy. When the scanner |
394 | * is found, both PageBuddy and PageLRU are checked as the pageblock |
395 | * is suitable as both source and target. |
396 | */ |
397 | for (; migrate_pfn < free_pfn; migrate_pfn += pageblock_nr_pages, |
398 | free_pfn -= pageblock_nr_pages) { |
399 | cond_resched(); |
400 | |
401 | /* Update the migrate PFN */ |
402 | if (__reset_isolation_pfn(zone, pfn: migrate_pfn, check_source: true, check_target: source_set) && |
403 | migrate_pfn < reset_migrate) { |
404 | source_set = true; |
405 | reset_migrate = migrate_pfn; |
406 | zone->compact_init_migrate_pfn = reset_migrate; |
407 | zone->compact_cached_migrate_pfn[0] = reset_migrate; |
408 | zone->compact_cached_migrate_pfn[1] = reset_migrate; |
409 | } |
410 | |
411 | /* Update the free PFN */ |
412 | if (__reset_isolation_pfn(zone, pfn: free_pfn, check_source: free_set, check_target: true) && |
413 | free_pfn > reset_free) { |
414 | free_set = true; |
415 | reset_free = free_pfn; |
416 | zone->compact_init_free_pfn = reset_free; |
417 | zone->compact_cached_free_pfn = reset_free; |
418 | } |
419 | } |
420 | |
421 | /* Leave no distance if no suitable block was reset */ |
422 | if (reset_migrate >= reset_free) { |
423 | zone->compact_cached_migrate_pfn[0] = migrate_pfn; |
424 | zone->compact_cached_migrate_pfn[1] = migrate_pfn; |
425 | zone->compact_cached_free_pfn = free_pfn; |
426 | } |
427 | } |
428 | |
429 | void reset_isolation_suitable(pg_data_t *pgdat) |
430 | { |
431 | int zoneid; |
432 | |
433 | for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
434 | struct zone *zone = &pgdat->node_zones[zoneid]; |
435 | if (!populated_zone(zone)) |
436 | continue; |
437 | |
438 | __reset_isolation_suitable(zone); |
439 | } |
440 | } |
441 | |
442 | /* |
443 | * Sets the pageblock skip bit if it was clear. Note that this is a hint as |
444 | * locks are not required for read/writers. Returns true if it was already set. |
445 | */ |
446 | static bool test_and_set_skip(struct compact_control *cc, struct page *page) |
447 | { |
448 | bool skip; |
449 | |
450 | /* Do not update if skip hint is being ignored */ |
451 | if (cc->ignore_skip_hint) |
452 | return false; |
453 | |
454 | skip = get_pageblock_skip(page); |
455 | if (!skip && !cc->no_set_skip_hint) |
456 | set_pageblock_skip(page); |
457 | |
458 | return skip; |
459 | } |
460 | |
461 | static void update_cached_migrate(struct compact_control *cc, unsigned long pfn) |
462 | { |
463 | struct zone *zone = cc->zone; |
464 | |
465 | /* Set for isolation rather than compaction */ |
466 | if (cc->no_set_skip_hint) |
467 | return; |
468 | |
469 | pfn = pageblock_end_pfn(pfn); |
470 | |
471 | /* Update where async and sync compaction should restart */ |
472 | if (pfn > zone->compact_cached_migrate_pfn[0]) |
473 | zone->compact_cached_migrate_pfn[0] = pfn; |
474 | if (cc->mode != MIGRATE_ASYNC && |
475 | pfn > zone->compact_cached_migrate_pfn[1]) |
476 | zone->compact_cached_migrate_pfn[1] = pfn; |
477 | } |
478 | |
479 | /* |
480 | * If no pages were isolated then mark this pageblock to be skipped in the |
481 | * future. The information is later cleared by __reset_isolation_suitable(). |
482 | */ |
483 | static void update_pageblock_skip(struct compact_control *cc, |
484 | struct page *page, unsigned long pfn) |
485 | { |
486 | struct zone *zone = cc->zone; |
487 | |
488 | if (cc->no_set_skip_hint) |
489 | return; |
490 | |
491 | set_pageblock_skip(page); |
492 | |
493 | if (pfn < zone->compact_cached_free_pfn) |
494 | zone->compact_cached_free_pfn = pfn; |
495 | } |
496 | #else |
497 | static inline bool isolation_suitable(struct compact_control *cc, |
498 | struct page *page) |
499 | { |
500 | return true; |
501 | } |
502 | |
503 | static inline bool pageblock_skip_persistent(struct page *page) |
504 | { |
505 | return false; |
506 | } |
507 | |
508 | static inline void update_pageblock_skip(struct compact_control *cc, |
509 | struct page *page, unsigned long pfn) |
510 | { |
511 | } |
512 | |
513 | static void update_cached_migrate(struct compact_control *cc, unsigned long pfn) |
514 | { |
515 | } |
516 | |
517 | static bool test_and_set_skip(struct compact_control *cc, struct page *page) |
518 | { |
519 | return false; |
520 | } |
521 | #endif /* CONFIG_COMPACTION */ |
522 | |
523 | /* |
524 | * Compaction requires the taking of some coarse locks that are potentially |
525 | * very heavily contended. For async compaction, trylock and record if the |
526 | * lock is contended. The lock will still be acquired but compaction will |
527 | * abort when the current block is finished regardless of success rate. |
528 | * Sync compaction acquires the lock. |
529 | * |
530 | * Always returns true which makes it easier to track lock state in callers. |
531 | */ |
532 | static bool compact_lock_irqsave(spinlock_t *lock, unsigned long *flags, |
533 | struct compact_control *cc) |
534 | __acquires(lock) |
535 | { |
536 | /* Track if the lock is contended in async mode */ |
537 | if (cc->mode == MIGRATE_ASYNC && !cc->contended) { |
538 | if (spin_trylock_irqsave(lock, *flags)) |
539 | return true; |
540 | |
541 | cc->contended = true; |
542 | } |
543 | |
544 | spin_lock_irqsave(lock, *flags); |
545 | return true; |
546 | } |
547 | |
548 | /* |
549 | * Compaction requires the taking of some coarse locks that are potentially |
550 | * very heavily contended. The lock should be periodically unlocked to avoid |
551 | * having disabled IRQs for a long time, even when there is nobody waiting on |
552 | * the lock. It might also be that allowing the IRQs will result in |
553 | * need_resched() becoming true. If scheduling is needed, compaction schedules. |
554 | * Either compaction type will also abort if a fatal signal is pending. |
555 | * In either case if the lock was locked, it is dropped and not regained. |
556 | * |
557 | * Returns true if compaction should abort due to fatal signal pending. |
558 | * Returns false when compaction can continue. |
559 | */ |
560 | static bool compact_unlock_should_abort(spinlock_t *lock, |
561 | unsigned long flags, bool *locked, struct compact_control *cc) |
562 | { |
563 | if (*locked) { |
564 | spin_unlock_irqrestore(lock, flags); |
565 | *locked = false; |
566 | } |
567 | |
568 | if (fatal_signal_pending(current)) { |
569 | cc->contended = true; |
570 | return true; |
571 | } |
572 | |
573 | cond_resched(); |
574 | |
575 | return false; |
576 | } |
577 | |
578 | /* |
579 | * Isolate free pages onto a private freelist. If @strict is true, will abort |
580 | * returning 0 on any invalid PFNs or non-free pages inside of the pageblock |
581 | * (even though it may still end up isolating some pages). |
582 | */ |
583 | static unsigned long isolate_freepages_block(struct compact_control *cc, |
584 | unsigned long *start_pfn, |
585 | unsigned long end_pfn, |
586 | struct list_head *freelist, |
587 | unsigned int stride, |
588 | bool strict) |
589 | { |
590 | int nr_scanned = 0, total_isolated = 0; |
591 | struct page *page; |
592 | unsigned long flags = 0; |
593 | bool locked = false; |
594 | unsigned long blockpfn = *start_pfn; |
595 | unsigned int order; |
596 | |
597 | /* Strict mode is for isolation, speed is secondary */ |
598 | if (strict) |
599 | stride = 1; |
600 | |
601 | page = pfn_to_page(blockpfn); |
602 | |
603 | /* Isolate free pages. */ |
604 | for (; blockpfn < end_pfn; blockpfn += stride, page += stride) { |
605 | int isolated; |
606 | |
607 | /* |
608 | * Periodically drop the lock (if held) regardless of its |
609 | * contention, to give chance to IRQs. Abort if fatal signal |
610 | * pending. |
611 | */ |
612 | if (!(blockpfn % COMPACT_CLUSTER_MAX) |
613 | && compact_unlock_should_abort(lock: &cc->zone->lock, flags, |
614 | locked: &locked, cc)) |
615 | break; |
616 | |
617 | nr_scanned++; |
618 | |
619 | /* |
620 | * For compound pages such as THP and hugetlbfs, we can save |
621 | * potentially a lot of iterations if we skip them at once. |
622 | * The check is racy, but we can consider only valid values |
623 | * and the only danger is skipping too much. |
624 | */ |
625 | if (PageCompound(page)) { |
626 | const unsigned int order = compound_order(page); |
627 | |
628 | if (blockpfn + (1UL << order) <= end_pfn) { |
629 | blockpfn += (1UL << order) - 1; |
630 | page += (1UL << order) - 1; |
631 | nr_scanned += (1UL << order) - 1; |
632 | } |
633 | |
634 | goto isolate_fail; |
635 | } |
636 | |
637 | if (!PageBuddy(page)) |
638 | goto isolate_fail; |
639 | |
640 | /* If we already hold the lock, we can skip some rechecking. */ |
641 | if (!locked) { |
642 | locked = compact_lock_irqsave(lock: &cc->zone->lock, |
643 | flags: &flags, cc); |
644 | |
645 | /* Recheck this is a buddy page under lock */ |
646 | if (!PageBuddy(page)) |
647 | goto isolate_fail; |
648 | } |
649 | |
650 | /* Found a free page, will break it into order-0 pages */ |
651 | order = buddy_order(page); |
652 | isolated = __isolate_free_page(page, order); |
653 | if (!isolated) |
654 | break; |
655 | set_page_private(page, private: order); |
656 | |
657 | nr_scanned += isolated - 1; |
658 | total_isolated += isolated; |
659 | cc->nr_freepages += isolated; |
660 | list_add_tail(new: &page->lru, head: freelist); |
661 | |
662 | if (!strict && cc->nr_migratepages <= cc->nr_freepages) { |
663 | blockpfn += isolated; |
664 | break; |
665 | } |
666 | /* Advance to the end of split page */ |
667 | blockpfn += isolated - 1; |
668 | page += isolated - 1; |
669 | continue; |
670 | |
671 | isolate_fail: |
672 | if (strict) |
673 | break; |
674 | |
675 | } |
676 | |
677 | if (locked) |
678 | spin_unlock_irqrestore(lock: &cc->zone->lock, flags); |
679 | |
680 | /* |
681 | * Be careful to not go outside of the pageblock. |
682 | */ |
683 | if (unlikely(blockpfn > end_pfn)) |
684 | blockpfn = end_pfn; |
685 | |
686 | trace_mm_compaction_isolate_freepages(start_pfn: *start_pfn, end_pfn: blockpfn, |
687 | nr_scanned, nr_taken: total_isolated); |
688 | |
689 | /* Record how far we have got within the block */ |
690 | *start_pfn = blockpfn; |
691 | |
692 | /* |
693 | * If strict isolation is requested by CMA then check that all the |
694 | * pages requested were isolated. If there were any failures, 0 is |
695 | * returned and CMA will fail. |
696 | */ |
697 | if (strict && blockpfn < end_pfn) |
698 | total_isolated = 0; |
699 | |
700 | cc->total_free_scanned += nr_scanned; |
701 | if (total_isolated) |
702 | count_compact_events(item: COMPACTISOLATED, delta: total_isolated); |
703 | return total_isolated; |
704 | } |
705 | |
706 | /** |
707 | * isolate_freepages_range() - isolate free pages. |
708 | * @cc: Compaction control structure. |
709 | * @start_pfn: The first PFN to start isolating. |
710 | * @end_pfn: The one-past-last PFN. |
711 | * |
712 | * Non-free pages, invalid PFNs, or zone boundaries within the |
713 | * [start_pfn, end_pfn) range are considered errors, cause function to |
714 | * undo its actions and return zero. |
715 | * |
716 | * Otherwise, function returns one-past-the-last PFN of isolated page |
717 | * (which may be greater then end_pfn if end fell in a middle of |
718 | * a free page). |
719 | */ |
720 | unsigned long |
721 | isolate_freepages_range(struct compact_control *cc, |
722 | unsigned long start_pfn, unsigned long end_pfn) |
723 | { |
724 | unsigned long isolated, pfn, block_start_pfn, block_end_pfn; |
725 | LIST_HEAD(freelist); |
726 | |
727 | pfn = start_pfn; |
728 | block_start_pfn = pageblock_start_pfn(pfn); |
729 | if (block_start_pfn < cc->zone->zone_start_pfn) |
730 | block_start_pfn = cc->zone->zone_start_pfn; |
731 | block_end_pfn = pageblock_end_pfn(pfn); |
732 | |
733 | for (; pfn < end_pfn; pfn += isolated, |
734 | block_start_pfn = block_end_pfn, |
735 | block_end_pfn += pageblock_nr_pages) { |
736 | /* Protect pfn from changing by isolate_freepages_block */ |
737 | unsigned long isolate_start_pfn = pfn; |
738 | |
739 | /* |
740 | * pfn could pass the block_end_pfn if isolated freepage |
741 | * is more than pageblock order. In this case, we adjust |
742 | * scanning range to right one. |
743 | */ |
744 | if (pfn >= block_end_pfn) { |
745 | block_start_pfn = pageblock_start_pfn(pfn); |
746 | block_end_pfn = pageblock_end_pfn(pfn); |
747 | } |
748 | |
749 | block_end_pfn = min(block_end_pfn, end_pfn); |
750 | |
751 | if (!pageblock_pfn_to_page(start_pfn: block_start_pfn, |
752 | end_pfn: block_end_pfn, zone: cc->zone)) |
753 | break; |
754 | |
755 | isolated = isolate_freepages_block(cc, start_pfn: &isolate_start_pfn, |
756 | end_pfn: block_end_pfn, freelist: &freelist, stride: 0, strict: true); |
757 | |
758 | /* |
759 | * In strict mode, isolate_freepages_block() returns 0 if |
760 | * there are any holes in the block (ie. invalid PFNs or |
761 | * non-free pages). |
762 | */ |
763 | if (!isolated) |
764 | break; |
765 | |
766 | /* |
767 | * If we managed to isolate pages, it is always (1 << n) * |
768 | * pageblock_nr_pages for some non-negative n. (Max order |
769 | * page may span two pageblocks). |
770 | */ |
771 | } |
772 | |
773 | /* __isolate_free_page() does not map the pages */ |
774 | split_map_pages(list: &freelist); |
775 | |
776 | if (pfn < end_pfn) { |
777 | /* Loop terminated early, cleanup. */ |
778 | release_freepages(freelist: &freelist); |
779 | return 0; |
780 | } |
781 | |
782 | /* We don't use freelists for anything. */ |
783 | return pfn; |
784 | } |
785 | |
786 | /* Similar to reclaim, but different enough that they don't share logic */ |
787 | static bool too_many_isolated(struct compact_control *cc) |
788 | { |
789 | pg_data_t *pgdat = cc->zone->zone_pgdat; |
790 | bool too_many; |
791 | |
792 | unsigned long active, inactive, isolated; |
793 | |
794 | inactive = node_page_state(pgdat, item: NR_INACTIVE_FILE) + |
795 | node_page_state(pgdat, item: NR_INACTIVE_ANON); |
796 | active = node_page_state(pgdat, item: NR_ACTIVE_FILE) + |
797 | node_page_state(pgdat, item: NR_ACTIVE_ANON); |
798 | isolated = node_page_state(pgdat, item: NR_ISOLATED_FILE) + |
799 | node_page_state(pgdat, item: NR_ISOLATED_ANON); |
800 | |
801 | /* |
802 | * Allow GFP_NOFS to isolate past the limit set for regular |
803 | * compaction runs. This prevents an ABBA deadlock when other |
804 | * compactors have already isolated to the limit, but are |
805 | * blocked on filesystem locks held by the GFP_NOFS thread. |
806 | */ |
807 | if (cc->gfp_mask & __GFP_FS) { |
808 | inactive >>= 3; |
809 | active >>= 3; |
810 | } |
811 | |
812 | too_many = isolated > (inactive + active) / 2; |
813 | if (!too_many) |
814 | wake_throttle_isolated(pgdat); |
815 | |
816 | return too_many; |
817 | } |
818 | |
819 | /** |
820 | * isolate_migratepages_block() - isolate all migrate-able pages within |
821 | * a single pageblock |
822 | * @cc: Compaction control structure. |
823 | * @low_pfn: The first PFN to isolate |
824 | * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock |
825 | * @mode: Isolation mode to be used. |
826 | * |
827 | * Isolate all pages that can be migrated from the range specified by |
828 | * [low_pfn, end_pfn). The range is expected to be within same pageblock. |
829 | * Returns errno, like -EAGAIN or -EINTR in case e.g signal pending or congestion, |
830 | * -ENOMEM in case we could not allocate a page, or 0. |
831 | * cc->migrate_pfn will contain the next pfn to scan. |
832 | * |
833 | * The pages are isolated on cc->migratepages list (not required to be empty), |
834 | * and cc->nr_migratepages is updated accordingly. |
835 | */ |
836 | static int |
837 | isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, |
838 | unsigned long end_pfn, isolate_mode_t mode) |
839 | { |
840 | pg_data_t *pgdat = cc->zone->zone_pgdat; |
841 | unsigned long nr_scanned = 0, nr_isolated = 0; |
842 | struct lruvec *lruvec; |
843 | unsigned long flags = 0; |
844 | struct lruvec *locked = NULL; |
845 | struct folio *folio = NULL; |
846 | struct page *page = NULL, *valid_page = NULL; |
847 | struct address_space *mapping; |
848 | unsigned long start_pfn = low_pfn; |
849 | bool skip_on_failure = false; |
850 | unsigned long next_skip_pfn = 0; |
851 | bool skip_updated = false; |
852 | int ret = 0; |
853 | |
854 | cc->migrate_pfn = low_pfn; |
855 | |
856 | /* |
857 | * Ensure that there are not too many pages isolated from the LRU |
858 | * list by either parallel reclaimers or compaction. If there are, |
859 | * delay for some time until fewer pages are isolated |
860 | */ |
861 | while (unlikely(too_many_isolated(cc))) { |
862 | /* stop isolation if there are still pages not migrated */ |
863 | if (cc->nr_migratepages) |
864 | return -EAGAIN; |
865 | |
866 | /* async migration should just abort */ |
867 | if (cc->mode == MIGRATE_ASYNC) |
868 | return -EAGAIN; |
869 | |
870 | reclaim_throttle(pgdat, reason: VMSCAN_THROTTLE_ISOLATED); |
871 | |
872 | if (fatal_signal_pending(current)) |
873 | return -EINTR; |
874 | } |
875 | |
876 | cond_resched(); |
877 | |
878 | if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) { |
879 | skip_on_failure = true; |
880 | next_skip_pfn = block_end_pfn(low_pfn, cc->order); |
881 | } |
882 | |
883 | /* Time to isolate some pages for migration */ |
884 | for (; low_pfn < end_pfn; low_pfn++) { |
885 | |
886 | if (skip_on_failure && low_pfn >= next_skip_pfn) { |
887 | /* |
888 | * We have isolated all migration candidates in the |
889 | * previous order-aligned block, and did not skip it due |
890 | * to failure. We should migrate the pages now and |
891 | * hopefully succeed compaction. |
892 | */ |
893 | if (nr_isolated) |
894 | break; |
895 | |
896 | /* |
897 | * We failed to isolate in the previous order-aligned |
898 | * block. Set the new boundary to the end of the |
899 | * current block. Note we can't simply increase |
900 | * next_skip_pfn by 1 << order, as low_pfn might have |
901 | * been incremented by a higher number due to skipping |
902 | * a compound or a high-order buddy page in the |
903 | * previous loop iteration. |
904 | */ |
905 | next_skip_pfn = block_end_pfn(low_pfn, cc->order); |
906 | } |
907 | |
908 | /* |
909 | * Periodically drop the lock (if held) regardless of its |
910 | * contention, to give chance to IRQs. Abort completely if |
911 | * a fatal signal is pending. |
912 | */ |
913 | if (!(low_pfn % COMPACT_CLUSTER_MAX)) { |
914 | if (locked) { |
915 | unlock_page_lruvec_irqrestore(lruvec: locked, flags); |
916 | locked = NULL; |
917 | } |
918 | |
919 | if (fatal_signal_pending(current)) { |
920 | cc->contended = true; |
921 | ret = -EINTR; |
922 | |
923 | goto fatal_pending; |
924 | } |
925 | |
926 | cond_resched(); |
927 | } |
928 | |
929 | nr_scanned++; |
930 | |
931 | page = pfn_to_page(low_pfn); |
932 | |
933 | /* |
934 | * Check if the pageblock has already been marked skipped. |
935 | * Only the first PFN is checked as the caller isolates |
936 | * COMPACT_CLUSTER_MAX at a time so the second call must |
937 | * not falsely conclude that the block should be skipped. |
938 | */ |
939 | if (!valid_page && (pageblock_aligned(low_pfn) || |
940 | low_pfn == cc->zone->zone_start_pfn)) { |
941 | if (!isolation_suitable(cc, page)) { |
942 | low_pfn = end_pfn; |
943 | folio = NULL; |
944 | goto isolate_abort; |
945 | } |
946 | valid_page = page; |
947 | } |
948 | |
949 | if (PageHuge(page) && cc->alloc_contig) { |
950 | if (locked) { |
951 | unlock_page_lruvec_irqrestore(lruvec: locked, flags); |
952 | locked = NULL; |
953 | } |
954 | |
955 | ret = isolate_or_dissolve_huge_page(page, list: &cc->migratepages); |
956 | |
957 | /* |
958 | * Fail isolation in case isolate_or_dissolve_huge_page() |
959 | * reports an error. In case of -ENOMEM, abort right away. |
960 | */ |
961 | if (ret < 0) { |
962 | /* Do not report -EBUSY down the chain */ |
963 | if (ret == -EBUSY) |
964 | ret = 0; |
965 | low_pfn += compound_nr(page) - 1; |
966 | nr_scanned += compound_nr(page) - 1; |
967 | goto isolate_fail; |
968 | } |
969 | |
970 | if (PageHuge(page)) { |
971 | /* |
972 | * Hugepage was successfully isolated and placed |
973 | * on the cc->migratepages list. |
974 | */ |
975 | folio = page_folio(page); |
976 | low_pfn += folio_nr_pages(folio) - 1; |
977 | goto isolate_success_no_list; |
978 | } |
979 | |
980 | /* |
981 | * Ok, the hugepage was dissolved. Now these pages are |
982 | * Buddy and cannot be re-allocated because they are |
983 | * isolated. Fall-through as the check below handles |
984 | * Buddy pages. |
985 | */ |
986 | } |
987 | |
988 | /* |
989 | * Skip if free. We read page order here without zone lock |
990 | * which is generally unsafe, but the race window is small and |
991 | * the worst thing that can happen is that we skip some |
992 | * potential isolation targets. |
993 | */ |
994 | if (PageBuddy(page)) { |
995 | unsigned long freepage_order = buddy_order_unsafe(page); |
996 | |
997 | /* |
998 | * Without lock, we cannot be sure that what we got is |
999 | * a valid page order. Consider only values in the |
1000 | * valid order range to prevent low_pfn overflow. |
1001 | */ |
1002 | if (freepage_order > 0 && freepage_order <= MAX_ORDER) { |
1003 | low_pfn += (1UL << freepage_order) - 1; |
1004 | nr_scanned += (1UL << freepage_order) - 1; |
1005 | } |
1006 | continue; |
1007 | } |
1008 | |
1009 | /* |
1010 | * Regardless of being on LRU, compound pages such as THP and |
1011 | * hugetlbfs are not to be compacted unless we are attempting |
1012 | * an allocation much larger than the huge page size (eg CMA). |
1013 | * We can potentially save a lot of iterations if we skip them |
1014 | * at once. The check is racy, but we can consider only valid |
1015 | * values and the only danger is skipping too much. |
1016 | */ |
1017 | if (PageCompound(page) && !cc->alloc_contig) { |
1018 | const unsigned int order = compound_order(page); |
1019 | |
1020 | if (likely(order <= MAX_ORDER)) { |
1021 | low_pfn += (1UL << order) - 1; |
1022 | nr_scanned += (1UL << order) - 1; |
1023 | } |
1024 | goto isolate_fail; |
1025 | } |
1026 | |
1027 | /* |
1028 | * Check may be lockless but that's ok as we recheck later. |
1029 | * It's possible to migrate LRU and non-lru movable pages. |
1030 | * Skip any other type of page |
1031 | */ |
1032 | if (!PageLRU(page)) { |
1033 | /* |
1034 | * __PageMovable can return false positive so we need |
1035 | * to verify it under page_lock. |
1036 | */ |
1037 | if (unlikely(__PageMovable(page)) && |
1038 | !PageIsolated(page)) { |
1039 | if (locked) { |
1040 | unlock_page_lruvec_irqrestore(lruvec: locked, flags); |
1041 | locked = NULL; |
1042 | } |
1043 | |
1044 | if (isolate_movable_page(page, mode)) { |
1045 | folio = page_folio(page); |
1046 | goto isolate_success; |
1047 | } |
1048 | } |
1049 | |
1050 | goto isolate_fail; |
1051 | } |
1052 | |
1053 | /* |
1054 | * Be careful not to clear PageLRU until after we're |
1055 | * sure the page is not being freed elsewhere -- the |
1056 | * page release code relies on it. |
1057 | */ |
1058 | folio = folio_get_nontail_page(page); |
1059 | if (unlikely(!folio)) |
1060 | goto isolate_fail; |
1061 | |
1062 | /* |
1063 | * Migration will fail if an anonymous page is pinned in memory, |
1064 | * so avoid taking lru_lock and isolating it unnecessarily in an |
1065 | * admittedly racy check. |
1066 | */ |
1067 | mapping = folio_mapping(folio); |
1068 | if (!mapping && (folio_ref_count(folio) - 1) > folio_mapcount(folio)) |
1069 | goto isolate_fail_put; |
1070 | |
1071 | /* |
1072 | * Only allow to migrate anonymous pages in GFP_NOFS context |
1073 | * because those do not depend on fs locks. |
1074 | */ |
1075 | if (!(cc->gfp_mask & __GFP_FS) && mapping) |
1076 | goto isolate_fail_put; |
1077 | |
1078 | /* Only take pages on LRU: a check now makes later tests safe */ |
1079 | if (!folio_test_lru(folio)) |
1080 | goto isolate_fail_put; |
1081 | |
1082 | /* Compaction might skip unevictable pages but CMA takes them */ |
1083 | if (!(mode & ISOLATE_UNEVICTABLE) && folio_test_unevictable(folio)) |
1084 | goto isolate_fail_put; |
1085 | |
1086 | /* |
1087 | * To minimise LRU disruption, the caller can indicate with |
1088 | * ISOLATE_ASYNC_MIGRATE that it only wants to isolate pages |
1089 | * it will be able to migrate without blocking - clean pages |
1090 | * for the most part. PageWriteback would require blocking. |
1091 | */ |
1092 | if ((mode & ISOLATE_ASYNC_MIGRATE) && folio_test_writeback(folio)) |
1093 | goto isolate_fail_put; |
1094 | |
1095 | if ((mode & ISOLATE_ASYNC_MIGRATE) && folio_test_dirty(folio)) { |
1096 | bool migrate_dirty; |
1097 | |
1098 | /* |
1099 | * Only folios without mappings or that have |
1100 | * a ->migrate_folio callback are possible to |
1101 | * migrate without blocking. However, we may |
1102 | * be racing with truncation, which can free |
1103 | * the mapping. Truncation holds the folio lock |
1104 | * until after the folio is removed from the page |
1105 | * cache so holding it ourselves is sufficient. |
1106 | */ |
1107 | if (!folio_trylock(folio)) |
1108 | goto isolate_fail_put; |
1109 | |
1110 | mapping = folio_mapping(folio); |
1111 | migrate_dirty = !mapping || |
1112 | mapping->a_ops->migrate_folio; |
1113 | folio_unlock(folio); |
1114 | if (!migrate_dirty) |
1115 | goto isolate_fail_put; |
1116 | } |
1117 | |
1118 | /* Try isolate the folio */ |
1119 | if (!folio_test_clear_lru(folio)) |
1120 | goto isolate_fail_put; |
1121 | |
1122 | lruvec = folio_lruvec(folio); |
1123 | |
1124 | /* If we already hold the lock, we can skip some rechecking */ |
1125 | if (lruvec != locked) { |
1126 | if (locked) |
1127 | unlock_page_lruvec_irqrestore(lruvec: locked, flags); |
1128 | |
1129 | compact_lock_irqsave(lock: &lruvec->lru_lock, flags: &flags, cc); |
1130 | locked = lruvec; |
1131 | |
1132 | lruvec_memcg_debug(lruvec, folio); |
1133 | |
1134 | /* |
1135 | * Try get exclusive access under lock. If marked for |
1136 | * skip, the scan is aborted unless the current context |
1137 | * is a rescan to reach the end of the pageblock. |
1138 | */ |
1139 | if (!skip_updated && valid_page) { |
1140 | skip_updated = true; |
1141 | if (test_and_set_skip(cc, page: valid_page) && |
1142 | !cc->finish_pageblock) { |
1143 | low_pfn = end_pfn; |
1144 | goto isolate_abort; |
1145 | } |
1146 | } |
1147 | |
1148 | /* |
1149 | * folio become large since the non-locked check, |
1150 | * and it's on LRU. |
1151 | */ |
1152 | if (unlikely(folio_test_large(folio) && !cc->alloc_contig)) { |
1153 | low_pfn += folio_nr_pages(folio) - 1; |
1154 | nr_scanned += folio_nr_pages(folio) - 1; |
1155 | folio_set_lru(folio); |
1156 | goto isolate_fail_put; |
1157 | } |
1158 | } |
1159 | |
1160 | /* The folio is taken off the LRU */ |
1161 | if (folio_test_large(folio)) |
1162 | low_pfn += folio_nr_pages(folio) - 1; |
1163 | |
1164 | /* Successfully isolated */ |
1165 | lruvec_del_folio(lruvec, folio); |
1166 | node_stat_mod_folio(folio, |
1167 | item: NR_ISOLATED_ANON + folio_is_file_lru(folio), |
1168 | nr: folio_nr_pages(folio)); |
1169 | |
1170 | isolate_success: |
1171 | list_add(new: &folio->lru, head: &cc->migratepages); |
1172 | isolate_success_no_list: |
1173 | cc->nr_migratepages += folio_nr_pages(folio); |
1174 | nr_isolated += folio_nr_pages(folio); |
1175 | nr_scanned += folio_nr_pages(folio) - 1; |
1176 | |
1177 | /* |
1178 | * Avoid isolating too much unless this block is being |
1179 | * fully scanned (e.g. dirty/writeback pages, parallel allocation) |
1180 | * or a lock is contended. For contention, isolate quickly to |
1181 | * potentially remove one source of contention. |
1182 | */ |
1183 | if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX && |
1184 | !cc->finish_pageblock && !cc->contended) { |
1185 | ++low_pfn; |
1186 | break; |
1187 | } |
1188 | |
1189 | continue; |
1190 | |
1191 | isolate_fail_put: |
1192 | /* Avoid potential deadlock in freeing page under lru_lock */ |
1193 | if (locked) { |
1194 | unlock_page_lruvec_irqrestore(lruvec: locked, flags); |
1195 | locked = NULL; |
1196 | } |
1197 | folio_put(folio); |
1198 | |
1199 | isolate_fail: |
1200 | if (!skip_on_failure && ret != -ENOMEM) |
1201 | continue; |
1202 | |
1203 | /* |
1204 | * We have isolated some pages, but then failed. Release them |
1205 | * instead of migrating, as we cannot form the cc->order buddy |
1206 | * page anyway. |
1207 | */ |
1208 | if (nr_isolated) { |
1209 | if (locked) { |
1210 | unlock_page_lruvec_irqrestore(lruvec: locked, flags); |
1211 | locked = NULL; |
1212 | } |
1213 | putback_movable_pages(l: &cc->migratepages); |
1214 | cc->nr_migratepages = 0; |
1215 | nr_isolated = 0; |
1216 | } |
1217 | |
1218 | if (low_pfn < next_skip_pfn) { |
1219 | low_pfn = next_skip_pfn - 1; |
1220 | /* |
1221 | * The check near the loop beginning would have updated |
1222 | * next_skip_pfn too, but this is a bit simpler. |
1223 | */ |
1224 | next_skip_pfn += 1UL << cc->order; |
1225 | } |
1226 | |
1227 | if (ret == -ENOMEM) |
1228 | break; |
1229 | } |
1230 | |
1231 | /* |
1232 | * The PageBuddy() check could have potentially brought us outside |
1233 | * the range to be scanned. |
1234 | */ |
1235 | if (unlikely(low_pfn > end_pfn)) |
1236 | low_pfn = end_pfn; |
1237 | |
1238 | folio = NULL; |
1239 | |
1240 | isolate_abort: |
1241 | if (locked) |
1242 | unlock_page_lruvec_irqrestore(lruvec: locked, flags); |
1243 | if (folio) { |
1244 | folio_set_lru(folio); |
1245 | folio_put(folio); |
1246 | } |
1247 | |
1248 | /* |
1249 | * Update the cached scanner pfn once the pageblock has been scanned. |
1250 | * Pages will either be migrated in which case there is no point |
1251 | * scanning in the near future or migration failed in which case the |
1252 | * failure reason may persist. The block is marked for skipping if |
1253 | * there were no pages isolated in the block or if the block is |
1254 | * rescanned twice in a row. |
1255 | */ |
1256 | if (low_pfn == end_pfn && (!nr_isolated || cc->finish_pageblock)) { |
1257 | if (!cc->no_set_skip_hint && valid_page && !skip_updated) |
1258 | set_pageblock_skip(valid_page); |
1259 | update_cached_migrate(cc, pfn: low_pfn); |
1260 | } |
1261 | |
1262 | trace_mm_compaction_isolate_migratepages(start_pfn, end_pfn: low_pfn, |
1263 | nr_scanned, nr_taken: nr_isolated); |
1264 | |
1265 | fatal_pending: |
1266 | cc->total_migrate_scanned += nr_scanned; |
1267 | if (nr_isolated) |
1268 | count_compact_events(item: COMPACTISOLATED, delta: nr_isolated); |
1269 | |
1270 | cc->migrate_pfn = low_pfn; |
1271 | |
1272 | return ret; |
1273 | } |
1274 | |
1275 | /** |
1276 | * isolate_migratepages_range() - isolate migrate-able pages in a PFN range |
1277 | * @cc: Compaction control structure. |
1278 | * @start_pfn: The first PFN to start isolating. |
1279 | * @end_pfn: The one-past-last PFN. |
1280 | * |
1281 | * Returns -EAGAIN when contented, -EINTR in case of a signal pending, -ENOMEM |
1282 | * in case we could not allocate a page, or 0. |
1283 | */ |
1284 | int |
1285 | isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, |
1286 | unsigned long end_pfn) |
1287 | { |
1288 | unsigned long pfn, block_start_pfn, block_end_pfn; |
1289 | int ret = 0; |
1290 | |
1291 | /* Scan block by block. First and last block may be incomplete */ |
1292 | pfn = start_pfn; |
1293 | block_start_pfn = pageblock_start_pfn(pfn); |
1294 | if (block_start_pfn < cc->zone->zone_start_pfn) |
1295 | block_start_pfn = cc->zone->zone_start_pfn; |
1296 | block_end_pfn = pageblock_end_pfn(pfn); |
1297 | |
1298 | for (; pfn < end_pfn; pfn = block_end_pfn, |
1299 | block_start_pfn = block_end_pfn, |
1300 | block_end_pfn += pageblock_nr_pages) { |
1301 | |
1302 | block_end_pfn = min(block_end_pfn, end_pfn); |
1303 | |
1304 | if (!pageblock_pfn_to_page(start_pfn: block_start_pfn, |
1305 | end_pfn: block_end_pfn, zone: cc->zone)) |
1306 | continue; |
1307 | |
1308 | ret = isolate_migratepages_block(cc, low_pfn: pfn, end_pfn: block_end_pfn, |
1309 | ISOLATE_UNEVICTABLE); |
1310 | |
1311 | if (ret) |
1312 | break; |
1313 | |
1314 | if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX) |
1315 | break; |
1316 | } |
1317 | |
1318 | return ret; |
1319 | } |
1320 | |
1321 | #endif /* CONFIG_COMPACTION || CONFIG_CMA */ |
1322 | #ifdef CONFIG_COMPACTION |
1323 | |
1324 | static bool suitable_migration_source(struct compact_control *cc, |
1325 | struct page *page) |
1326 | { |
1327 | int block_mt; |
1328 | |
1329 | if (pageblock_skip_persistent(page)) |
1330 | return false; |
1331 | |
1332 | if ((cc->mode != MIGRATE_ASYNC) || !cc->direct_compaction) |
1333 | return true; |
1334 | |
1335 | block_mt = get_pageblock_migratetype(page); |
1336 | |
1337 | if (cc->migratetype == MIGRATE_MOVABLE) |
1338 | return is_migrate_movable(mt: block_mt); |
1339 | else |
1340 | return block_mt == cc->migratetype; |
1341 | } |
1342 | |
1343 | /* Returns true if the page is within a block suitable for migration to */ |
1344 | static bool suitable_migration_target(struct compact_control *cc, |
1345 | struct page *page) |
1346 | { |
1347 | /* If the page is a large free page, then disallow migration */ |
1348 | if (PageBuddy(page)) { |
1349 | /* |
1350 | * We are checking page_order without zone->lock taken. But |
1351 | * the only small danger is that we skip a potentially suitable |
1352 | * pageblock, so it's not worth to check order for valid range. |
1353 | */ |
1354 | if (buddy_order_unsafe(page) >= pageblock_order) |
1355 | return false; |
1356 | } |
1357 | |
1358 | if (cc->ignore_block_suitable) |
1359 | return true; |
1360 | |
1361 | /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */ |
1362 | if (is_migrate_movable(get_pageblock_migratetype(page))) |
1363 | return true; |
1364 | |
1365 | /* Otherwise skip the block */ |
1366 | return false; |
1367 | } |
1368 | |
1369 | static inline unsigned int |
1370 | freelist_scan_limit(struct compact_control *cc) |
1371 | { |
1372 | unsigned short shift = BITS_PER_LONG - 1; |
1373 | |
1374 | return (COMPACT_CLUSTER_MAX >> min(shift, cc->fast_search_fail)) + 1; |
1375 | } |
1376 | |
1377 | /* |
1378 | * Test whether the free scanner has reached the same or lower pageblock than |
1379 | * the migration scanner, and compaction should thus terminate. |
1380 | */ |
1381 | static inline bool compact_scanners_met(struct compact_control *cc) |
1382 | { |
1383 | return (cc->free_pfn >> pageblock_order) |
1384 | <= (cc->migrate_pfn >> pageblock_order); |
1385 | } |
1386 | |
1387 | /* |
1388 | * Used when scanning for a suitable migration target which scans freelists |
1389 | * in reverse. Reorders the list such as the unscanned pages are scanned |
1390 | * first on the next iteration of the free scanner |
1391 | */ |
1392 | static void |
1393 | move_freelist_head(struct list_head *freelist, struct page *freepage) |
1394 | { |
1395 | LIST_HEAD(sublist); |
1396 | |
1397 | if (!list_is_first(list: &freepage->buddy_list, head: freelist)) { |
1398 | list_cut_before(list: &sublist, head: freelist, entry: &freepage->buddy_list); |
1399 | list_splice_tail(list: &sublist, head: freelist); |
1400 | } |
1401 | } |
1402 | |
1403 | /* |
1404 | * Similar to move_freelist_head except used by the migration scanner |
1405 | * when scanning forward. It's possible for these list operations to |
1406 | * move against each other if they search the free list exactly in |
1407 | * lockstep. |
1408 | */ |
1409 | static void |
1410 | move_freelist_tail(struct list_head *freelist, struct page *freepage) |
1411 | { |
1412 | LIST_HEAD(sublist); |
1413 | |
1414 | if (!list_is_last(list: &freepage->buddy_list, head: freelist)) { |
1415 | list_cut_position(list: &sublist, head: freelist, entry: &freepage->buddy_list); |
1416 | list_splice_tail(list: &sublist, head: freelist); |
1417 | } |
1418 | } |
1419 | |
1420 | static void |
1421 | fast_isolate_around(struct compact_control *cc, unsigned long pfn) |
1422 | { |
1423 | unsigned long start_pfn, end_pfn; |
1424 | struct page *page; |
1425 | |
1426 | /* Do not search around if there are enough pages already */ |
1427 | if (cc->nr_freepages >= cc->nr_migratepages) |
1428 | return; |
1429 | |
1430 | /* Minimise scanning during async compaction */ |
1431 | if (cc->direct_compaction && cc->mode == MIGRATE_ASYNC) |
1432 | return; |
1433 | |
1434 | /* Pageblock boundaries */ |
1435 | start_pfn = max(pageblock_start_pfn(pfn), cc->zone->zone_start_pfn); |
1436 | end_pfn = min(pageblock_end_pfn(pfn), zone_end_pfn(cc->zone)); |
1437 | |
1438 | page = pageblock_pfn_to_page(start_pfn, end_pfn, zone: cc->zone); |
1439 | if (!page) |
1440 | return; |
1441 | |
1442 | isolate_freepages_block(cc, start_pfn: &start_pfn, end_pfn, freelist: &cc->freepages, stride: 1, strict: false); |
1443 | |
1444 | /* Skip this pageblock in the future as it's full or nearly full */ |
1445 | if (start_pfn == end_pfn && !cc->no_set_skip_hint) |
1446 | set_pageblock_skip(page); |
1447 | } |
1448 | |
1449 | /* Search orders in round-robin fashion */ |
1450 | static int next_search_order(struct compact_control *cc, int order) |
1451 | { |
1452 | order--; |
1453 | if (order < 0) |
1454 | order = cc->order - 1; |
1455 | |
1456 | /* Search wrapped around? */ |
1457 | if (order == cc->search_order) { |
1458 | cc->search_order--; |
1459 | if (cc->search_order < 0) |
1460 | cc->search_order = cc->order - 1; |
1461 | return -1; |
1462 | } |
1463 | |
1464 | return order; |
1465 | } |
1466 | |
1467 | static void fast_isolate_freepages(struct compact_control *cc) |
1468 | { |
1469 | unsigned int limit = max(1U, freelist_scan_limit(cc) >> 1); |
1470 | unsigned int nr_scanned = 0, total_isolated = 0; |
1471 | unsigned long low_pfn, min_pfn, highest = 0; |
1472 | unsigned long nr_isolated = 0; |
1473 | unsigned long distance; |
1474 | struct page *page = NULL; |
1475 | bool scan_start = false; |
1476 | int order; |
1477 | |
1478 | /* Full compaction passes in a negative order */ |
1479 | if (cc->order <= 0) |
1480 | return; |
1481 | |
1482 | /* |
1483 | * If starting the scan, use a deeper search and use the highest |
1484 | * PFN found if a suitable one is not found. |
1485 | */ |
1486 | if (cc->free_pfn >= cc->zone->compact_init_free_pfn) { |
1487 | limit = pageblock_nr_pages >> 1; |
1488 | scan_start = true; |
1489 | } |
1490 | |
1491 | /* |
1492 | * Preferred point is in the top quarter of the scan space but take |
1493 | * a pfn from the top half if the search is problematic. |
1494 | */ |
1495 | distance = (cc->free_pfn - cc->migrate_pfn); |
1496 | low_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 2)); |
1497 | min_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 1)); |
1498 | |
1499 | if (WARN_ON_ONCE(min_pfn > low_pfn)) |
1500 | low_pfn = min_pfn; |
1501 | |
1502 | /* |
1503 | * Search starts from the last successful isolation order or the next |
1504 | * order to search after a previous failure |
1505 | */ |
1506 | cc->search_order = min_t(unsigned int, cc->order - 1, cc->search_order); |
1507 | |
1508 | for (order = cc->search_order; |
1509 | !page && order >= 0; |
1510 | order = next_search_order(cc, order)) { |
1511 | struct free_area *area = &cc->zone->free_area[order]; |
1512 | struct list_head *freelist; |
1513 | struct page *freepage; |
1514 | unsigned long flags; |
1515 | unsigned int order_scanned = 0; |
1516 | unsigned long high_pfn = 0; |
1517 | |
1518 | if (!area->nr_free) |
1519 | continue; |
1520 | |
1521 | spin_lock_irqsave(&cc->zone->lock, flags); |
1522 | freelist = &area->free_list[MIGRATE_MOVABLE]; |
1523 | list_for_each_entry_reverse(freepage, freelist, buddy_list) { |
1524 | unsigned long pfn; |
1525 | |
1526 | order_scanned++; |
1527 | nr_scanned++; |
1528 | pfn = page_to_pfn(freepage); |
1529 | |
1530 | if (pfn >= highest) |
1531 | highest = max(pageblock_start_pfn(pfn), |
1532 | cc->zone->zone_start_pfn); |
1533 | |
1534 | if (pfn >= low_pfn) { |
1535 | cc->fast_search_fail = 0; |
1536 | cc->search_order = order; |
1537 | page = freepage; |
1538 | break; |
1539 | } |
1540 | |
1541 | if (pfn >= min_pfn && pfn > high_pfn) { |
1542 | high_pfn = pfn; |
1543 | |
1544 | /* Shorten the scan if a candidate is found */ |
1545 | limit >>= 1; |
1546 | } |
1547 | |
1548 | if (order_scanned >= limit) |
1549 | break; |
1550 | } |
1551 | |
1552 | /* Use a maximum candidate pfn if a preferred one was not found */ |
1553 | if (!page && high_pfn) { |
1554 | page = pfn_to_page(high_pfn); |
1555 | |
1556 | /* Update freepage for the list reorder below */ |
1557 | freepage = page; |
1558 | } |
1559 | |
1560 | /* Reorder to so a future search skips recent pages */ |
1561 | move_freelist_head(freelist, freepage); |
1562 | |
1563 | /* Isolate the page if available */ |
1564 | if (page) { |
1565 | if (__isolate_free_page(page, order)) { |
1566 | set_page_private(page, private: order); |
1567 | nr_isolated = 1 << order; |
1568 | nr_scanned += nr_isolated - 1; |
1569 | total_isolated += nr_isolated; |
1570 | cc->nr_freepages += nr_isolated; |
1571 | list_add_tail(new: &page->lru, head: &cc->freepages); |
1572 | count_compact_events(item: COMPACTISOLATED, delta: nr_isolated); |
1573 | } else { |
1574 | /* If isolation fails, abort the search */ |
1575 | order = cc->search_order + 1; |
1576 | page = NULL; |
1577 | } |
1578 | } |
1579 | |
1580 | spin_unlock_irqrestore(lock: &cc->zone->lock, flags); |
1581 | |
1582 | /* Skip fast search if enough freepages isolated */ |
1583 | if (cc->nr_freepages >= cc->nr_migratepages) |
1584 | break; |
1585 | |
1586 | /* |
1587 | * Smaller scan on next order so the total scan is related |
1588 | * to freelist_scan_limit. |
1589 | */ |
1590 | if (order_scanned >= limit) |
1591 | limit = max(1U, limit >> 1); |
1592 | } |
1593 | |
1594 | trace_mm_compaction_fast_isolate_freepages(start_pfn: min_pfn, end_pfn: cc->free_pfn, |
1595 | nr_scanned, nr_taken: total_isolated); |
1596 | |
1597 | if (!page) { |
1598 | cc->fast_search_fail++; |
1599 | if (scan_start) { |
1600 | /* |
1601 | * Use the highest PFN found above min. If one was |
1602 | * not found, be pessimistic for direct compaction |
1603 | * and use the min mark. |
1604 | */ |
1605 | if (highest >= min_pfn) { |
1606 | page = pfn_to_page(highest); |
1607 | cc->free_pfn = highest; |
1608 | } else { |
1609 | if (cc->direct_compaction && pfn_valid(pfn: min_pfn)) { |
1610 | page = pageblock_pfn_to_page(start_pfn: min_pfn, |
1611 | min(pageblock_end_pfn(min_pfn), |
1612 | zone_end_pfn(cc->zone)), |
1613 | zone: cc->zone); |
1614 | cc->free_pfn = min_pfn; |
1615 | } |
1616 | } |
1617 | } |
1618 | } |
1619 | |
1620 | if (highest && highest >= cc->zone->compact_cached_free_pfn) { |
1621 | highest -= pageblock_nr_pages; |
1622 | cc->zone->compact_cached_free_pfn = highest; |
1623 | } |
1624 | |
1625 | cc->total_free_scanned += nr_scanned; |
1626 | if (!page) |
1627 | return; |
1628 | |
1629 | low_pfn = page_to_pfn(page); |
1630 | fast_isolate_around(cc, pfn: low_pfn); |
1631 | } |
1632 | |
1633 | /* |
1634 | * Based on information in the current compact_control, find blocks |
1635 | * suitable for isolating free pages from and then isolate them. |
1636 | */ |
1637 | static void isolate_freepages(struct compact_control *cc) |
1638 | { |
1639 | struct zone *zone = cc->zone; |
1640 | struct page *page; |
1641 | unsigned long block_start_pfn; /* start of current pageblock */ |
1642 | unsigned long isolate_start_pfn; /* exact pfn we start at */ |
1643 | unsigned long block_end_pfn; /* end of current pageblock */ |
1644 | unsigned long low_pfn; /* lowest pfn scanner is able to scan */ |
1645 | struct list_head *freelist = &cc->freepages; |
1646 | unsigned int stride; |
1647 | |
1648 | /* Try a small search of the free lists for a candidate */ |
1649 | fast_isolate_freepages(cc); |
1650 | if (cc->nr_freepages) |
1651 | goto splitmap; |
1652 | |
1653 | /* |
1654 | * Initialise the free scanner. The starting point is where we last |
1655 | * successfully isolated from, zone-cached value, or the end of the |
1656 | * zone when isolating for the first time. For looping we also need |
1657 | * this pfn aligned down to the pageblock boundary, because we do |
1658 | * block_start_pfn -= pageblock_nr_pages in the for loop. |
1659 | * For ending point, take care when isolating in last pageblock of a |
1660 | * zone which ends in the middle of a pageblock. |
1661 | * The low boundary is the end of the pageblock the migration scanner |
1662 | * is using. |
1663 | */ |
1664 | isolate_start_pfn = cc->free_pfn; |
1665 | block_start_pfn = pageblock_start_pfn(isolate_start_pfn); |
1666 | block_end_pfn = min(block_start_pfn + pageblock_nr_pages, |
1667 | zone_end_pfn(zone)); |
1668 | low_pfn = pageblock_end_pfn(cc->migrate_pfn); |
1669 | stride = cc->mode == MIGRATE_ASYNC ? COMPACT_CLUSTER_MAX : 1; |
1670 | |
1671 | /* |
1672 | * Isolate free pages until enough are available to migrate the |
1673 | * pages on cc->migratepages. We stop searching if the migrate |
1674 | * and free page scanners meet or enough free pages are isolated. |
1675 | */ |
1676 | for (; block_start_pfn >= low_pfn; |
1677 | block_end_pfn = block_start_pfn, |
1678 | block_start_pfn -= pageblock_nr_pages, |
1679 | isolate_start_pfn = block_start_pfn) { |
1680 | unsigned long nr_isolated; |
1681 | |
1682 | /* |
1683 | * This can iterate a massively long zone without finding any |
1684 | * suitable migration targets, so periodically check resched. |
1685 | */ |
1686 | if (!(block_start_pfn % (COMPACT_CLUSTER_MAX * pageblock_nr_pages))) |
1687 | cond_resched(); |
1688 | |
1689 | page = pageblock_pfn_to_page(start_pfn: block_start_pfn, end_pfn: block_end_pfn, |
1690 | zone); |
1691 | if (!page) { |
1692 | unsigned long next_pfn; |
1693 | |
1694 | next_pfn = skip_offline_sections_reverse(start_pfn: block_start_pfn); |
1695 | if (next_pfn) |
1696 | block_start_pfn = max(next_pfn, low_pfn); |
1697 | |
1698 | continue; |
1699 | } |
1700 | |
1701 | /* Check the block is suitable for migration */ |
1702 | if (!suitable_migration_target(cc, page)) |
1703 | continue; |
1704 | |
1705 | /* If isolation recently failed, do not retry */ |
1706 | if (!isolation_suitable(cc, page)) |
1707 | continue; |
1708 | |
1709 | /* Found a block suitable for isolating free pages from. */ |
1710 | nr_isolated = isolate_freepages_block(cc, start_pfn: &isolate_start_pfn, |
1711 | end_pfn: block_end_pfn, freelist, stride, strict: false); |
1712 | |
1713 | /* Update the skip hint if the full pageblock was scanned */ |
1714 | if (isolate_start_pfn == block_end_pfn) |
1715 | update_pageblock_skip(cc, page, pfn: block_start_pfn - |
1716 | pageblock_nr_pages); |
1717 | |
1718 | /* Are enough freepages isolated? */ |
1719 | if (cc->nr_freepages >= cc->nr_migratepages) { |
1720 | if (isolate_start_pfn >= block_end_pfn) { |
1721 | /* |
1722 | * Restart at previous pageblock if more |
1723 | * freepages can be isolated next time. |
1724 | */ |
1725 | isolate_start_pfn = |
1726 | block_start_pfn - pageblock_nr_pages; |
1727 | } |
1728 | break; |
1729 | } else if (isolate_start_pfn < block_end_pfn) { |
1730 | /* |
1731 | * If isolation failed early, do not continue |
1732 | * needlessly. |
1733 | */ |
1734 | break; |
1735 | } |
1736 | |
1737 | /* Adjust stride depending on isolation */ |
1738 | if (nr_isolated) { |
1739 | stride = 1; |
1740 | continue; |
1741 | } |
1742 | stride = min_t(unsigned int, COMPACT_CLUSTER_MAX, stride << 1); |
1743 | } |
1744 | |
1745 | /* |
1746 | * Record where the free scanner will restart next time. Either we |
1747 | * broke from the loop and set isolate_start_pfn based on the last |
1748 | * call to isolate_freepages_block(), or we met the migration scanner |
1749 | * and the loop terminated due to isolate_start_pfn < low_pfn |
1750 | */ |
1751 | cc->free_pfn = isolate_start_pfn; |
1752 | |
1753 | splitmap: |
1754 | /* __isolate_free_page() does not map the pages */ |
1755 | split_map_pages(list: freelist); |
1756 | } |
1757 | |
1758 | /* |
1759 | * This is a migrate-callback that "allocates" freepages by taking pages |
1760 | * from the isolated freelists in the block we are migrating to. |
1761 | */ |
1762 | static struct folio *compaction_alloc(struct folio *src, unsigned long data) |
1763 | { |
1764 | struct compact_control *cc = (struct compact_control *)data; |
1765 | struct folio *dst; |
1766 | |
1767 | if (list_empty(head: &cc->freepages)) { |
1768 | isolate_freepages(cc); |
1769 | |
1770 | if (list_empty(head: &cc->freepages)) |
1771 | return NULL; |
1772 | } |
1773 | |
1774 | dst = list_entry(cc->freepages.next, struct folio, lru); |
1775 | list_del(entry: &dst->lru); |
1776 | cc->nr_freepages--; |
1777 | |
1778 | return dst; |
1779 | } |
1780 | |
1781 | /* |
1782 | * This is a migrate-callback that "frees" freepages back to the isolated |
1783 | * freelist. All pages on the freelist are from the same zone, so there is no |
1784 | * special handling needed for NUMA. |
1785 | */ |
1786 | static void compaction_free(struct folio *dst, unsigned long data) |
1787 | { |
1788 | struct compact_control *cc = (struct compact_control *)data; |
1789 | |
1790 | list_add(new: &dst->lru, head: &cc->freepages); |
1791 | cc->nr_freepages++; |
1792 | } |
1793 | |
1794 | /* possible outcome of isolate_migratepages */ |
1795 | typedef enum { |
1796 | ISOLATE_ABORT, /* Abort compaction now */ |
1797 | ISOLATE_NONE, /* No pages isolated, continue scanning */ |
1798 | ISOLATE_SUCCESS, /* Pages isolated, migrate */ |
1799 | } isolate_migrate_t; |
1800 | |
1801 | /* |
1802 | * Allow userspace to control policy on scanning the unevictable LRU for |
1803 | * compactable pages. |
1804 | */ |
1805 | static int sysctl_compact_unevictable_allowed __read_mostly = CONFIG_COMPACT_UNEVICTABLE_DEFAULT; |
1806 | /* |
1807 | * Tunable for proactive compaction. It determines how |
1808 | * aggressively the kernel should compact memory in the |
1809 | * background. It takes values in the range [0, 100]. |
1810 | */ |
1811 | static unsigned int __read_mostly sysctl_compaction_proactiveness = 20; |
1812 | static int sysctl_extfrag_threshold = 500; |
1813 | static int __read_mostly sysctl_compact_memory; |
1814 | |
1815 | static inline void |
1816 | update_fast_start_pfn(struct compact_control *cc, unsigned long pfn) |
1817 | { |
1818 | if (cc->fast_start_pfn == ULONG_MAX) |
1819 | return; |
1820 | |
1821 | if (!cc->fast_start_pfn) |
1822 | cc->fast_start_pfn = pfn; |
1823 | |
1824 | cc->fast_start_pfn = min(cc->fast_start_pfn, pfn); |
1825 | } |
1826 | |
1827 | static inline unsigned long |
1828 | reinit_migrate_pfn(struct compact_control *cc) |
1829 | { |
1830 | if (!cc->fast_start_pfn || cc->fast_start_pfn == ULONG_MAX) |
1831 | return cc->migrate_pfn; |
1832 | |
1833 | cc->migrate_pfn = cc->fast_start_pfn; |
1834 | cc->fast_start_pfn = ULONG_MAX; |
1835 | |
1836 | return cc->migrate_pfn; |
1837 | } |
1838 | |
1839 | /* |
1840 | * Briefly search the free lists for a migration source that already has |
1841 | * some free pages to reduce the number of pages that need migration |
1842 | * before a pageblock is free. |
1843 | */ |
1844 | static unsigned long fast_find_migrateblock(struct compact_control *cc) |
1845 | { |
1846 | unsigned int limit = freelist_scan_limit(cc); |
1847 | unsigned int nr_scanned = 0; |
1848 | unsigned long distance; |
1849 | unsigned long pfn = cc->migrate_pfn; |
1850 | unsigned long high_pfn; |
1851 | int order; |
1852 | bool found_block = false; |
1853 | |
1854 | /* Skip hints are relied on to avoid repeats on the fast search */ |
1855 | if (cc->ignore_skip_hint) |
1856 | return pfn; |
1857 | |
1858 | /* |
1859 | * If the pageblock should be finished then do not select a different |
1860 | * pageblock. |
1861 | */ |
1862 | if (cc->finish_pageblock) |
1863 | return pfn; |
1864 | |
1865 | /* |
1866 | * If the migrate_pfn is not at the start of a zone or the start |
1867 | * of a pageblock then assume this is a continuation of a previous |
1868 | * scan restarted due to COMPACT_CLUSTER_MAX. |
1869 | */ |
1870 | if (pfn != cc->zone->zone_start_pfn && pfn != pageblock_start_pfn(pfn)) |
1871 | return pfn; |
1872 | |
1873 | /* |
1874 | * For smaller orders, just linearly scan as the number of pages |
1875 | * to migrate should be relatively small and does not necessarily |
1876 | * justify freeing up a large block for a small allocation. |
1877 | */ |
1878 | if (cc->order <= PAGE_ALLOC_COSTLY_ORDER) |
1879 | return pfn; |
1880 | |
1881 | /* |
1882 | * Only allow kcompactd and direct requests for movable pages to |
1883 | * quickly clear out a MOVABLE pageblock for allocation. This |
1884 | * reduces the risk that a large movable pageblock is freed for |
1885 | * an unmovable/reclaimable small allocation. |
1886 | */ |
1887 | if (cc->direct_compaction && cc->migratetype != MIGRATE_MOVABLE) |
1888 | return pfn; |
1889 | |
1890 | /* |
1891 | * When starting the migration scanner, pick any pageblock within the |
1892 | * first half of the search space. Otherwise try and pick a pageblock |
1893 | * within the first eighth to reduce the chances that a migration |
1894 | * target later becomes a source. |
1895 | */ |
1896 | distance = (cc->free_pfn - cc->migrate_pfn) >> 1; |
1897 | if (cc->migrate_pfn != cc->zone->zone_start_pfn) |
1898 | distance >>= 2; |
1899 | high_pfn = pageblock_start_pfn(cc->migrate_pfn + distance); |
1900 | |
1901 | for (order = cc->order - 1; |
1902 | order >= PAGE_ALLOC_COSTLY_ORDER && !found_block && nr_scanned < limit; |
1903 | order--) { |
1904 | struct free_area *area = &cc->zone->free_area[order]; |
1905 | struct list_head *freelist; |
1906 | unsigned long flags; |
1907 | struct page *freepage; |
1908 | |
1909 | if (!area->nr_free) |
1910 | continue; |
1911 | |
1912 | spin_lock_irqsave(&cc->zone->lock, flags); |
1913 | freelist = &area->free_list[MIGRATE_MOVABLE]; |
1914 | list_for_each_entry(freepage, freelist, buddy_list) { |
1915 | unsigned long free_pfn; |
1916 | |
1917 | if (nr_scanned++ >= limit) { |
1918 | move_freelist_tail(freelist, freepage); |
1919 | break; |
1920 | } |
1921 | |
1922 | free_pfn = page_to_pfn(freepage); |
1923 | if (free_pfn < high_pfn) { |
1924 | /* |
1925 | * Avoid if skipped recently. Ideally it would |
1926 | * move to the tail but even safe iteration of |
1927 | * the list assumes an entry is deleted, not |
1928 | * reordered. |
1929 | */ |
1930 | if (get_pageblock_skip(freepage)) |
1931 | continue; |
1932 | |
1933 | /* Reorder to so a future search skips recent pages */ |
1934 | move_freelist_tail(freelist, freepage); |
1935 | |
1936 | update_fast_start_pfn(cc, pfn: free_pfn); |
1937 | pfn = pageblock_start_pfn(free_pfn); |
1938 | if (pfn < cc->zone->zone_start_pfn) |
1939 | pfn = cc->zone->zone_start_pfn; |
1940 | cc->fast_search_fail = 0; |
1941 | found_block = true; |
1942 | break; |
1943 | } |
1944 | } |
1945 | spin_unlock_irqrestore(lock: &cc->zone->lock, flags); |
1946 | } |
1947 | |
1948 | cc->total_migrate_scanned += nr_scanned; |
1949 | |
1950 | /* |
1951 | * If fast scanning failed then use a cached entry for a page block |
1952 | * that had free pages as the basis for starting a linear scan. |
1953 | */ |
1954 | if (!found_block) { |
1955 | cc->fast_search_fail++; |
1956 | pfn = reinit_migrate_pfn(cc); |
1957 | } |
1958 | return pfn; |
1959 | } |
1960 | |
1961 | /* |
1962 | * Isolate all pages that can be migrated from the first suitable block, |
1963 | * starting at the block pointed to by the migrate scanner pfn within |
1964 | * compact_control. |
1965 | */ |
1966 | static isolate_migrate_t isolate_migratepages(struct compact_control *cc) |
1967 | { |
1968 | unsigned long block_start_pfn; |
1969 | unsigned long block_end_pfn; |
1970 | unsigned long low_pfn; |
1971 | struct page *page; |
1972 | const isolate_mode_t isolate_mode = |
1973 | (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | |
1974 | (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0); |
1975 | bool fast_find_block; |
1976 | |
1977 | /* |
1978 | * Start at where we last stopped, or beginning of the zone as |
1979 | * initialized by compact_zone(). The first failure will use |
1980 | * the lowest PFN as the starting point for linear scanning. |
1981 | */ |
1982 | low_pfn = fast_find_migrateblock(cc); |
1983 | block_start_pfn = pageblock_start_pfn(low_pfn); |
1984 | if (block_start_pfn < cc->zone->zone_start_pfn) |
1985 | block_start_pfn = cc->zone->zone_start_pfn; |
1986 | |
1987 | /* |
1988 | * fast_find_migrateblock() has already ensured the pageblock is not |
1989 | * set with a skipped flag, so to avoid the isolation_suitable check |
1990 | * below again, check whether the fast search was successful. |
1991 | */ |
1992 | fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail; |
1993 | |
1994 | /* Only scan within a pageblock boundary */ |
1995 | block_end_pfn = pageblock_end_pfn(low_pfn); |
1996 | |
1997 | /* |
1998 | * Iterate over whole pageblocks until we find the first suitable. |
1999 | * Do not cross the free scanner. |
2000 | */ |
2001 | for (; block_end_pfn <= cc->free_pfn; |
2002 | fast_find_block = false, |
2003 | cc->migrate_pfn = low_pfn = block_end_pfn, |
2004 | block_start_pfn = block_end_pfn, |
2005 | block_end_pfn += pageblock_nr_pages) { |
2006 | |
2007 | /* |
2008 | * This can potentially iterate a massively long zone with |
2009 | * many pageblocks unsuitable, so periodically check if we |
2010 | * need to schedule. |
2011 | */ |
2012 | if (!(low_pfn % (COMPACT_CLUSTER_MAX * pageblock_nr_pages))) |
2013 | cond_resched(); |
2014 | |
2015 | page = pageblock_pfn_to_page(start_pfn: block_start_pfn, |
2016 | end_pfn: block_end_pfn, zone: cc->zone); |
2017 | if (!page) { |
2018 | unsigned long next_pfn; |
2019 | |
2020 | next_pfn = skip_offline_sections(start_pfn: block_start_pfn); |
2021 | if (next_pfn) |
2022 | block_end_pfn = min(next_pfn, cc->free_pfn); |
2023 | continue; |
2024 | } |
2025 | |
2026 | /* |
2027 | * If isolation recently failed, do not retry. Only check the |
2028 | * pageblock once. COMPACT_CLUSTER_MAX causes a pageblock |
2029 | * to be visited multiple times. Assume skip was checked |
2030 | * before making it "skip" so other compaction instances do |
2031 | * not scan the same block. |
2032 | */ |
2033 | if ((pageblock_aligned(low_pfn) || |
2034 | low_pfn == cc->zone->zone_start_pfn) && |
2035 | !fast_find_block && !isolation_suitable(cc, page)) |
2036 | continue; |
2037 | |
2038 | /* |
2039 | * For async direct compaction, only scan the pageblocks of the |
2040 | * same migratetype without huge pages. Async direct compaction |
2041 | * is optimistic to see if the minimum amount of work satisfies |
2042 | * the allocation. The cached PFN is updated as it's possible |
2043 | * that all remaining blocks between source and target are |
2044 | * unsuitable and the compaction scanners fail to meet. |
2045 | */ |
2046 | if (!suitable_migration_source(cc, page)) { |
2047 | update_cached_migrate(cc, pfn: block_end_pfn); |
2048 | continue; |
2049 | } |
2050 | |
2051 | /* Perform the isolation */ |
2052 | if (isolate_migratepages_block(cc, low_pfn, end_pfn: block_end_pfn, |
2053 | mode: isolate_mode)) |
2054 | return ISOLATE_ABORT; |
2055 | |
2056 | /* |
2057 | * Either we isolated something and proceed with migration. Or |
2058 | * we failed and compact_zone should decide if we should |
2059 | * continue or not. |
2060 | */ |
2061 | break; |
2062 | } |
2063 | |
2064 | return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE; |
2065 | } |
2066 | |
2067 | /* |
2068 | * order == -1 is expected when compacting proactively via |
2069 | * 1. /proc/sys/vm/compact_memory |
2070 | * 2. /sys/devices/system/node/nodex/compact |
2071 | * 3. /proc/sys/vm/compaction_proactiveness |
2072 | */ |
2073 | static inline bool is_via_compact_memory(int order) |
2074 | { |
2075 | return order == -1; |
2076 | } |
2077 | |
2078 | /* |
2079 | * Determine whether kswapd is (or recently was!) running on this node. |
2080 | * |
2081 | * pgdat_kswapd_lock() pins pgdat->kswapd, so a concurrent kswapd_stop() can't |
2082 | * zero it. |
2083 | */ |
2084 | static bool kswapd_is_running(pg_data_t *pgdat) |
2085 | { |
2086 | bool running; |
2087 | |
2088 | pgdat_kswapd_lock(pgdat); |
2089 | running = pgdat->kswapd && task_is_running(pgdat->kswapd); |
2090 | pgdat_kswapd_unlock(pgdat); |
2091 | |
2092 | return running; |
2093 | } |
2094 | |
2095 | /* |
2096 | * A zone's fragmentation score is the external fragmentation wrt to the |
2097 | * COMPACTION_HPAGE_ORDER. It returns a value in the range [0, 100]. |
2098 | */ |
2099 | static unsigned int fragmentation_score_zone(struct zone *zone) |
2100 | { |
2101 | return extfrag_for_order(zone, COMPACTION_HPAGE_ORDER); |
2102 | } |
2103 | |
2104 | /* |
2105 | * A weighted zone's fragmentation score is the external fragmentation |
2106 | * wrt to the COMPACTION_HPAGE_ORDER scaled by the zone's size. It |
2107 | * returns a value in the range [0, 100]. |
2108 | * |
2109 | * The scaling factor ensures that proactive compaction focuses on larger |
2110 | * zones like ZONE_NORMAL, rather than smaller, specialized zones like |
2111 | * ZONE_DMA32. For smaller zones, the score value remains close to zero, |
2112 | * and thus never exceeds the high threshold for proactive compaction. |
2113 | */ |
2114 | static unsigned int fragmentation_score_zone_weighted(struct zone *zone) |
2115 | { |
2116 | unsigned long score; |
2117 | |
2118 | score = zone->present_pages * fragmentation_score_zone(zone); |
2119 | return div64_ul(score, zone->zone_pgdat->node_present_pages + 1); |
2120 | } |
2121 | |
2122 | /* |
2123 | * The per-node proactive (background) compaction process is started by its |
2124 | * corresponding kcompactd thread when the node's fragmentation score |
2125 | * exceeds the high threshold. The compaction process remains active till |
2126 | * the node's score falls below the low threshold, or one of the back-off |
2127 | * conditions is met. |
2128 | */ |
2129 | static unsigned int fragmentation_score_node(pg_data_t *pgdat) |
2130 | { |
2131 | unsigned int score = 0; |
2132 | int zoneid; |
2133 | |
2134 | for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
2135 | struct zone *zone; |
2136 | |
2137 | zone = &pgdat->node_zones[zoneid]; |
2138 | if (!populated_zone(zone)) |
2139 | continue; |
2140 | score += fragmentation_score_zone_weighted(zone); |
2141 | } |
2142 | |
2143 | return score; |
2144 | } |
2145 | |
2146 | static unsigned int fragmentation_score_wmark(bool low) |
2147 | { |
2148 | unsigned int wmark_low; |
2149 | |
2150 | /* |
2151 | * Cap the low watermark to avoid excessive compaction |
2152 | * activity in case a user sets the proactiveness tunable |
2153 | * close to 100 (maximum). |
2154 | */ |
2155 | wmark_low = max(100U - sysctl_compaction_proactiveness, 5U); |
2156 | return low ? wmark_low : min(wmark_low + 10, 100U); |
2157 | } |
2158 | |
2159 | static bool should_proactive_compact_node(pg_data_t *pgdat) |
2160 | { |
2161 | int wmark_high; |
2162 | |
2163 | if (!sysctl_compaction_proactiveness || kswapd_is_running(pgdat)) |
2164 | return false; |
2165 | |
2166 | wmark_high = fragmentation_score_wmark(low: false); |
2167 | return fragmentation_score_node(pgdat) > wmark_high; |
2168 | } |
2169 | |
2170 | static enum compact_result __compact_finished(struct compact_control *cc) |
2171 | { |
2172 | unsigned int order; |
2173 | const int migratetype = cc->migratetype; |
2174 | int ret; |
2175 | |
2176 | /* Compaction run completes if the migrate and free scanner meet */ |
2177 | if (compact_scanners_met(cc)) { |
2178 | /* Let the next compaction start anew. */ |
2179 | reset_cached_positions(zone: cc->zone); |
2180 | |
2181 | /* |
2182 | * Mark that the PG_migrate_skip information should be cleared |
2183 | * by kswapd when it goes to sleep. kcompactd does not set the |
2184 | * flag itself as the decision to be clear should be directly |
2185 | * based on an allocation request. |
2186 | */ |
2187 | if (cc->direct_compaction) |
2188 | cc->zone->compact_blockskip_flush = true; |
2189 | |
2190 | if (cc->whole_zone) |
2191 | return COMPACT_COMPLETE; |
2192 | else |
2193 | return COMPACT_PARTIAL_SKIPPED; |
2194 | } |
2195 | |
2196 | if (cc->proactive_compaction) { |
2197 | int score, wmark_low; |
2198 | pg_data_t *pgdat; |
2199 | |
2200 | pgdat = cc->zone->zone_pgdat; |
2201 | if (kswapd_is_running(pgdat)) |
2202 | return COMPACT_PARTIAL_SKIPPED; |
2203 | |
2204 | score = fragmentation_score_zone(zone: cc->zone); |
2205 | wmark_low = fragmentation_score_wmark(low: true); |
2206 | |
2207 | if (score > wmark_low) |
2208 | ret = COMPACT_CONTINUE; |
2209 | else |
2210 | ret = COMPACT_SUCCESS; |
2211 | |
2212 | goto out; |
2213 | } |
2214 | |
2215 | if (is_via_compact_memory(order: cc->order)) |
2216 | return COMPACT_CONTINUE; |
2217 | |
2218 | /* |
2219 | * Always finish scanning a pageblock to reduce the possibility of |
2220 | * fallbacks in the future. This is particularly important when |
2221 | * migration source is unmovable/reclaimable but it's not worth |
2222 | * special casing. |
2223 | */ |
2224 | if (!pageblock_aligned(cc->migrate_pfn)) |
2225 | return COMPACT_CONTINUE; |
2226 | |
2227 | /* Direct compactor: Is a suitable page free? */ |
2228 | ret = COMPACT_NO_SUITABLE_PAGE; |
2229 | for (order = cc->order; order <= MAX_ORDER; order++) { |
2230 | struct free_area *area = &cc->zone->free_area[order]; |
2231 | bool can_steal; |
2232 | |
2233 | /* Job done if page is free of the right migratetype */ |
2234 | if (!free_area_empty(area, migratetype)) |
2235 | return COMPACT_SUCCESS; |
2236 | |
2237 | #ifdef CONFIG_CMA |
2238 | /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */ |
2239 | if (migratetype == MIGRATE_MOVABLE && |
2240 | !free_area_empty(area, migratetype: MIGRATE_CMA)) |
2241 | return COMPACT_SUCCESS; |
2242 | #endif |
2243 | /* |
2244 | * Job done if allocation would steal freepages from |
2245 | * other migratetype buddy lists. |
2246 | */ |
2247 | if (find_suitable_fallback(area, order, migratetype, |
2248 | only_stealable: true, can_steal: &can_steal) != -1) |
2249 | /* |
2250 | * Movable pages are OK in any pageblock. If we are |
2251 | * stealing for a non-movable allocation, make sure |
2252 | * we finish compacting the current pageblock first |
2253 | * (which is assured by the above migrate_pfn align |
2254 | * check) so it is as free as possible and we won't |
2255 | * have to steal another one soon. |
2256 | */ |
2257 | return COMPACT_SUCCESS; |
2258 | } |
2259 | |
2260 | out: |
2261 | if (cc->contended || fatal_signal_pending(current)) |
2262 | ret = COMPACT_CONTENDED; |
2263 | |
2264 | return ret; |
2265 | } |
2266 | |
2267 | static enum compact_result compact_finished(struct compact_control *cc) |
2268 | { |
2269 | int ret; |
2270 | |
2271 | ret = __compact_finished(cc); |
2272 | trace_mm_compaction_finished(zone: cc->zone, order: cc->order, ret); |
2273 | if (ret == COMPACT_NO_SUITABLE_PAGE) |
2274 | ret = COMPACT_CONTINUE; |
2275 | |
2276 | return ret; |
2277 | } |
2278 | |
2279 | static bool __compaction_suitable(struct zone *zone, int order, |
2280 | int highest_zoneidx, |
2281 | unsigned long wmark_target) |
2282 | { |
2283 | unsigned long watermark; |
2284 | /* |
2285 | * Watermarks for order-0 must be met for compaction to be able to |
2286 | * isolate free pages for migration targets. This means that the |
2287 | * watermark and alloc_flags have to match, or be more pessimistic than |
2288 | * the check in __isolate_free_page(). We don't use the direct |
2289 | * compactor's alloc_flags, as they are not relevant for freepage |
2290 | * isolation. We however do use the direct compactor's highest_zoneidx |
2291 | * to skip over zones where lowmem reserves would prevent allocation |
2292 | * even if compaction succeeds. |
2293 | * For costly orders, we require low watermark instead of min for |
2294 | * compaction to proceed to increase its chances. |
2295 | * ALLOC_CMA is used, as pages in CMA pageblocks are considered |
2296 | * suitable migration targets |
2297 | */ |
2298 | watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ? |
2299 | low_wmark_pages(zone) : min_wmark_pages(zone); |
2300 | watermark += compact_gap(order); |
2301 | return __zone_watermark_ok(z: zone, order: 0, mark: watermark, highest_zoneidx, |
2302 | ALLOC_CMA, free_pages: wmark_target); |
2303 | } |
2304 | |
2305 | /* |
2306 | * compaction_suitable: Is this suitable to run compaction on this zone now? |
2307 | */ |
2308 | bool compaction_suitable(struct zone *zone, int order, int highest_zoneidx) |
2309 | { |
2310 | enum compact_result compact_result; |
2311 | bool suitable; |
2312 | |
2313 | suitable = __compaction_suitable(zone, order, highest_zoneidx, |
2314 | wmark_target: zone_page_state(zone, item: NR_FREE_PAGES)); |
2315 | /* |
2316 | * fragmentation index determines if allocation failures are due to |
2317 | * low memory or external fragmentation |
2318 | * |
2319 | * index of -1000 would imply allocations might succeed depending on |
2320 | * watermarks, but we already failed the high-order watermark check |
2321 | * index towards 0 implies failure is due to lack of memory |
2322 | * index towards 1000 implies failure is due to fragmentation |
2323 | * |
2324 | * Only compact if a failure would be due to fragmentation. Also |
2325 | * ignore fragindex for non-costly orders where the alternative to |
2326 | * a successful reclaim/compaction is OOM. Fragindex and the |
2327 | * vm.extfrag_threshold sysctl is meant as a heuristic to prevent |
2328 | * excessive compaction for costly orders, but it should not be at the |
2329 | * expense of system stability. |
2330 | */ |
2331 | if (suitable) { |
2332 | compact_result = COMPACT_CONTINUE; |
2333 | if (order > PAGE_ALLOC_COSTLY_ORDER) { |
2334 | int fragindex = fragmentation_index(zone, order); |
2335 | |
2336 | if (fragindex >= 0 && |
2337 | fragindex <= sysctl_extfrag_threshold) { |
2338 | suitable = false; |
2339 | compact_result = COMPACT_NOT_SUITABLE_ZONE; |
2340 | } |
2341 | } |
2342 | } else { |
2343 | compact_result = COMPACT_SKIPPED; |
2344 | } |
2345 | |
2346 | trace_mm_compaction_suitable(zone, order, ret: compact_result); |
2347 | |
2348 | return suitable; |
2349 | } |
2350 | |
2351 | bool compaction_zonelist_suitable(struct alloc_context *ac, int order, |
2352 | int alloc_flags) |
2353 | { |
2354 | struct zone *zone; |
2355 | struct zoneref *z; |
2356 | |
2357 | /* |
2358 | * Make sure at least one zone would pass __compaction_suitable if we continue |
2359 | * retrying the reclaim. |
2360 | */ |
2361 | for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, |
2362 | ac->highest_zoneidx, ac->nodemask) { |
2363 | unsigned long available; |
2364 | |
2365 | /* |
2366 | * Do not consider all the reclaimable memory because we do not |
2367 | * want to trash just for a single high order allocation which |
2368 | * is even not guaranteed to appear even if __compaction_suitable |
2369 | * is happy about the watermark check. |
2370 | */ |
2371 | available = zone_reclaimable_pages(zone) / order; |
2372 | available += zone_page_state_snapshot(zone, item: NR_FREE_PAGES); |
2373 | if (__compaction_suitable(zone, order, highest_zoneidx: ac->highest_zoneidx, |
2374 | wmark_target: available)) |
2375 | return true; |
2376 | } |
2377 | |
2378 | return false; |
2379 | } |
2380 | |
2381 | /* |
2382 | * Should we do compaction for target allocation order. |
2383 | * Return COMPACT_SUCCESS if allocation for target order can be already |
2384 | * satisfied |
2385 | * Return COMPACT_SKIPPED if compaction for target order is likely to fail |
2386 | * Return COMPACT_CONTINUE if compaction for target order should be ran |
2387 | */ |
2388 | static enum compact_result |
2389 | compaction_suit_allocation_order(struct zone *zone, unsigned int order, |
2390 | int highest_zoneidx, unsigned int alloc_flags) |
2391 | { |
2392 | unsigned long watermark; |
2393 | |
2394 | watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK); |
2395 | if (zone_watermark_ok(z: zone, order, mark: watermark, highest_zoneidx, |
2396 | alloc_flags)) |
2397 | return COMPACT_SUCCESS; |
2398 | |
2399 | if (!compaction_suitable(zone, order, highest_zoneidx)) |
2400 | return COMPACT_SKIPPED; |
2401 | |
2402 | return COMPACT_CONTINUE; |
2403 | } |
2404 | |
2405 | static enum compact_result |
2406 | compact_zone(struct compact_control *cc, struct capture_control *capc) |
2407 | { |
2408 | enum compact_result ret; |
2409 | unsigned long start_pfn = cc->zone->zone_start_pfn; |
2410 | unsigned long end_pfn = zone_end_pfn(zone: cc->zone); |
2411 | unsigned long last_migrated_pfn; |
2412 | const bool sync = cc->mode != MIGRATE_ASYNC; |
2413 | bool update_cached; |
2414 | unsigned int nr_succeeded = 0; |
2415 | |
2416 | /* |
2417 | * These counters track activities during zone compaction. Initialize |
2418 | * them before compacting a new zone. |
2419 | */ |
2420 | cc->total_migrate_scanned = 0; |
2421 | cc->total_free_scanned = 0; |
2422 | cc->nr_migratepages = 0; |
2423 | cc->nr_freepages = 0; |
2424 | INIT_LIST_HEAD(list: &cc->freepages); |
2425 | INIT_LIST_HEAD(list: &cc->migratepages); |
2426 | |
2427 | cc->migratetype = gfp_migratetype(gfp_flags: cc->gfp_mask); |
2428 | |
2429 | if (!is_via_compact_memory(order: cc->order)) { |
2430 | ret = compaction_suit_allocation_order(zone: cc->zone, order: cc->order, |
2431 | highest_zoneidx: cc->highest_zoneidx, |
2432 | alloc_flags: cc->alloc_flags); |
2433 | if (ret != COMPACT_CONTINUE) |
2434 | return ret; |
2435 | } |
2436 | |
2437 | /* |
2438 | * Clear pageblock skip if there were failures recently and compaction |
2439 | * is about to be retried after being deferred. |
2440 | */ |
2441 | if (compaction_restarting(zone: cc->zone, order: cc->order)) |
2442 | __reset_isolation_suitable(zone: cc->zone); |
2443 | |
2444 | /* |
2445 | * Setup to move all movable pages to the end of the zone. Used cached |
2446 | * information on where the scanners should start (unless we explicitly |
2447 | * want to compact the whole zone), but check that it is initialised |
2448 | * by ensuring the values are within zone boundaries. |
2449 | */ |
2450 | cc->fast_start_pfn = 0; |
2451 | if (cc->whole_zone) { |
2452 | cc->migrate_pfn = start_pfn; |
2453 | cc->free_pfn = pageblock_start_pfn(end_pfn - 1); |
2454 | } else { |
2455 | cc->migrate_pfn = cc->zone->compact_cached_migrate_pfn[sync]; |
2456 | cc->free_pfn = cc->zone->compact_cached_free_pfn; |
2457 | if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) { |
2458 | cc->free_pfn = pageblock_start_pfn(end_pfn - 1); |
2459 | cc->zone->compact_cached_free_pfn = cc->free_pfn; |
2460 | } |
2461 | if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) { |
2462 | cc->migrate_pfn = start_pfn; |
2463 | cc->zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn; |
2464 | cc->zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn; |
2465 | } |
2466 | |
2467 | if (cc->migrate_pfn <= cc->zone->compact_init_migrate_pfn) |
2468 | cc->whole_zone = true; |
2469 | } |
2470 | |
2471 | last_migrated_pfn = 0; |
2472 | |
2473 | /* |
2474 | * Migrate has separate cached PFNs for ASYNC and SYNC* migration on |
2475 | * the basis that some migrations will fail in ASYNC mode. However, |
2476 | * if the cached PFNs match and pageblocks are skipped due to having |
2477 | * no isolation candidates, then the sync state does not matter. |
2478 | * Until a pageblock with isolation candidates is found, keep the |
2479 | * cached PFNs in sync to avoid revisiting the same blocks. |
2480 | */ |
2481 | update_cached = !sync && |
2482 | cc->zone->compact_cached_migrate_pfn[0] == cc->zone->compact_cached_migrate_pfn[1]; |
2483 | |
2484 | trace_mm_compaction_begin(cc, zone_start: start_pfn, zone_end: end_pfn, sync); |
2485 | |
2486 | /* lru_add_drain_all could be expensive with involving other CPUs */ |
2487 | lru_add_drain(); |
2488 | |
2489 | while ((ret = compact_finished(cc)) == COMPACT_CONTINUE) { |
2490 | int err; |
2491 | unsigned long iteration_start_pfn = cc->migrate_pfn; |
2492 | |
2493 | /* |
2494 | * Avoid multiple rescans of the same pageblock which can |
2495 | * happen if a page cannot be isolated (dirty/writeback in |
2496 | * async mode) or if the migrated pages are being allocated |
2497 | * before the pageblock is cleared. The first rescan will |
2498 | * capture the entire pageblock for migration. If it fails, |
2499 | * it'll be marked skip and scanning will proceed as normal. |
2500 | */ |
2501 | cc->finish_pageblock = false; |
2502 | if (pageblock_start_pfn(last_migrated_pfn) == |
2503 | pageblock_start_pfn(iteration_start_pfn)) { |
2504 | cc->finish_pageblock = true; |
2505 | } |
2506 | |
2507 | rescan: |
2508 | switch (isolate_migratepages(cc)) { |
2509 | case ISOLATE_ABORT: |
2510 | ret = COMPACT_CONTENDED; |
2511 | putback_movable_pages(l: &cc->migratepages); |
2512 | cc->nr_migratepages = 0; |
2513 | goto out; |
2514 | case ISOLATE_NONE: |
2515 | if (update_cached) { |
2516 | cc->zone->compact_cached_migrate_pfn[1] = |
2517 | cc->zone->compact_cached_migrate_pfn[0]; |
2518 | } |
2519 | |
2520 | /* |
2521 | * We haven't isolated and migrated anything, but |
2522 | * there might still be unflushed migrations from |
2523 | * previous cc->order aligned block. |
2524 | */ |
2525 | goto check_drain; |
2526 | case ISOLATE_SUCCESS: |
2527 | update_cached = false; |
2528 | last_migrated_pfn = max(cc->zone->zone_start_pfn, |
2529 | pageblock_start_pfn(cc->migrate_pfn - 1)); |
2530 | } |
2531 | |
2532 | err = migrate_pages(l: &cc->migratepages, new: compaction_alloc, |
2533 | free: compaction_free, private: (unsigned long)cc, mode: cc->mode, |
2534 | reason: MR_COMPACTION, ret_succeeded: &nr_succeeded); |
2535 | |
2536 | trace_mm_compaction_migratepages(cc, nr_succeeded); |
2537 | |
2538 | /* All pages were either migrated or will be released */ |
2539 | cc->nr_migratepages = 0; |
2540 | if (err) { |
2541 | putback_movable_pages(l: &cc->migratepages); |
2542 | /* |
2543 | * migrate_pages() may return -ENOMEM when scanners meet |
2544 | * and we want compact_finished() to detect it |
2545 | */ |
2546 | if (err == -ENOMEM && !compact_scanners_met(cc)) { |
2547 | ret = COMPACT_CONTENDED; |
2548 | goto out; |
2549 | } |
2550 | /* |
2551 | * If an ASYNC or SYNC_LIGHT fails to migrate a page |
2552 | * within the pageblock_order-aligned block and |
2553 | * fast_find_migrateblock may be used then scan the |
2554 | * remainder of the pageblock. This will mark the |
2555 | * pageblock "skip" to avoid rescanning in the near |
2556 | * future. This will isolate more pages than necessary |
2557 | * for the request but avoid loops due to |
2558 | * fast_find_migrateblock revisiting blocks that were |
2559 | * recently partially scanned. |
2560 | */ |
2561 | if (!pageblock_aligned(cc->migrate_pfn) && |
2562 | !cc->ignore_skip_hint && !cc->finish_pageblock && |
2563 | (cc->mode < MIGRATE_SYNC)) { |
2564 | cc->finish_pageblock = true; |
2565 | |
2566 | /* |
2567 | * Draining pcplists does not help THP if |
2568 | * any page failed to migrate. Even after |
2569 | * drain, the pageblock will not be free. |
2570 | */ |
2571 | if (cc->order == COMPACTION_HPAGE_ORDER) |
2572 | last_migrated_pfn = 0; |
2573 | |
2574 | goto rescan; |
2575 | } |
2576 | } |
2577 | |
2578 | /* Stop if a page has been captured */ |
2579 | if (capc && capc->page) { |
2580 | ret = COMPACT_SUCCESS; |
2581 | break; |
2582 | } |
2583 | |
2584 | check_drain: |
2585 | /* |
2586 | * Has the migration scanner moved away from the previous |
2587 | * cc->order aligned block where we migrated from? If yes, |
2588 | * flush the pages that were freed, so that they can merge and |
2589 | * compact_finished() can detect immediately if allocation |
2590 | * would succeed. |
2591 | */ |
2592 | if (cc->order > 0 && last_migrated_pfn) { |
2593 | unsigned long current_block_start = |
2594 | block_start_pfn(cc->migrate_pfn, cc->order); |
2595 | |
2596 | if (last_migrated_pfn < current_block_start) { |
2597 | lru_add_drain_cpu_zone(zone: cc->zone); |
2598 | /* No more flushing until we migrate again */ |
2599 | last_migrated_pfn = 0; |
2600 | } |
2601 | } |
2602 | } |
2603 | |
2604 | out: |
2605 | /* |
2606 | * Release free pages and update where the free scanner should restart, |
2607 | * so we don't leave any returned pages behind in the next attempt. |
2608 | */ |
2609 | if (cc->nr_freepages > 0) { |
2610 | unsigned long free_pfn = release_freepages(freelist: &cc->freepages); |
2611 | |
2612 | cc->nr_freepages = 0; |
2613 | VM_BUG_ON(free_pfn == 0); |
2614 | /* The cached pfn is always the first in a pageblock */ |
2615 | free_pfn = pageblock_start_pfn(free_pfn); |
2616 | /* |
2617 | * Only go back, not forward. The cached pfn might have been |
2618 | * already reset to zone end in compact_finished() |
2619 | */ |
2620 | if (free_pfn > cc->zone->compact_cached_free_pfn) |
2621 | cc->zone->compact_cached_free_pfn = free_pfn; |
2622 | } |
2623 | |
2624 | count_compact_events(item: COMPACTMIGRATE_SCANNED, delta: cc->total_migrate_scanned); |
2625 | count_compact_events(item: COMPACTFREE_SCANNED, delta: cc->total_free_scanned); |
2626 | |
2627 | trace_mm_compaction_end(cc, zone_start: start_pfn, zone_end: end_pfn, sync, status: ret); |
2628 | |
2629 | VM_BUG_ON(!list_empty(&cc->freepages)); |
2630 | VM_BUG_ON(!list_empty(&cc->migratepages)); |
2631 | |
2632 | return ret; |
2633 | } |
2634 | |
2635 | static enum compact_result compact_zone_order(struct zone *zone, int order, |
2636 | gfp_t gfp_mask, enum compact_priority prio, |
2637 | unsigned int alloc_flags, int highest_zoneidx, |
2638 | struct page **capture) |
2639 | { |
2640 | enum compact_result ret; |
2641 | struct compact_control cc = { |
2642 | .order = order, |
2643 | .search_order = order, |
2644 | .gfp_mask = gfp_mask, |
2645 | .zone = zone, |
2646 | .mode = (prio == COMPACT_PRIO_ASYNC) ? |
2647 | MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT, |
2648 | .alloc_flags = alloc_flags, |
2649 | .highest_zoneidx = highest_zoneidx, |
2650 | .direct_compaction = true, |
2651 | .whole_zone = (prio == MIN_COMPACT_PRIORITY), |
2652 | .ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY), |
2653 | .ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY) |
2654 | }; |
2655 | struct capture_control capc = { |
2656 | .cc = &cc, |
2657 | .page = NULL, |
2658 | }; |
2659 | |
2660 | /* |
2661 | * Make sure the structs are really initialized before we expose the |
2662 | * capture control, in case we are interrupted and the interrupt handler |
2663 | * frees a page. |
2664 | */ |
2665 | barrier(); |
2666 | WRITE_ONCE(current->capture_control, &capc); |
2667 | |
2668 | ret = compact_zone(cc: &cc, capc: &capc); |
2669 | |
2670 | /* |
2671 | * Make sure we hide capture control first before we read the captured |
2672 | * page pointer, otherwise an interrupt could free and capture a page |
2673 | * and we would leak it. |
2674 | */ |
2675 | WRITE_ONCE(current->capture_control, NULL); |
2676 | *capture = READ_ONCE(capc.page); |
2677 | /* |
2678 | * Technically, it is also possible that compaction is skipped but |
2679 | * the page is still captured out of luck(IRQ came and freed the page). |
2680 | * Returning COMPACT_SUCCESS in such cases helps in properly accounting |
2681 | * the COMPACT[STALL|FAIL] when compaction is skipped. |
2682 | */ |
2683 | if (*capture) |
2684 | ret = COMPACT_SUCCESS; |
2685 | |
2686 | return ret; |
2687 | } |
2688 | |
2689 | /** |
2690 | * try_to_compact_pages - Direct compact to satisfy a high-order allocation |
2691 | * @gfp_mask: The GFP mask of the current allocation |
2692 | * @order: The order of the current allocation |
2693 | * @alloc_flags: The allocation flags of the current allocation |
2694 | * @ac: The context of current allocation |
2695 | * @prio: Determines how hard direct compaction should try to succeed |
2696 | * @capture: Pointer to free page created by compaction will be stored here |
2697 | * |
2698 | * This is the main entry point for direct page compaction. |
2699 | */ |
2700 | enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order, |
2701 | unsigned int alloc_flags, const struct alloc_context *ac, |
2702 | enum compact_priority prio, struct page **capture) |
2703 | { |
2704 | int may_perform_io = (__force int)(gfp_mask & __GFP_IO); |
2705 | struct zoneref *z; |
2706 | struct zone *zone; |
2707 | enum compact_result rc = COMPACT_SKIPPED; |
2708 | |
2709 | /* |
2710 | * Check if the GFP flags allow compaction - GFP_NOIO is really |
2711 | * tricky context because the migration might require IO |
2712 | */ |
2713 | if (!may_perform_io) |
2714 | return COMPACT_SKIPPED; |
2715 | |
2716 | trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio); |
2717 | |
2718 | /* Compact each zone in the list */ |
2719 | for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, |
2720 | ac->highest_zoneidx, ac->nodemask) { |
2721 | enum compact_result status; |
2722 | |
2723 | if (prio > MIN_COMPACT_PRIORITY |
2724 | && compaction_deferred(zone, order)) { |
2725 | rc = max_t(enum compact_result, COMPACT_DEFERRED, rc); |
2726 | continue; |
2727 | } |
2728 | |
2729 | status = compact_zone_order(zone, order, gfp_mask, prio, |
2730 | alloc_flags, highest_zoneidx: ac->highest_zoneidx, capture); |
2731 | rc = max(status, rc); |
2732 | |
2733 | /* The allocation should succeed, stop compacting */ |
2734 | if (status == COMPACT_SUCCESS) { |
2735 | /* |
2736 | * We think the allocation will succeed in this zone, |
2737 | * but it is not certain, hence the false. The caller |
2738 | * will repeat this with true if allocation indeed |
2739 | * succeeds in this zone. |
2740 | */ |
2741 | compaction_defer_reset(zone, order, alloc_success: false); |
2742 | |
2743 | break; |
2744 | } |
2745 | |
2746 | if (prio != COMPACT_PRIO_ASYNC && (status == COMPACT_COMPLETE || |
2747 | status == COMPACT_PARTIAL_SKIPPED)) |
2748 | /* |
2749 | * We think that allocation won't succeed in this zone |
2750 | * so we defer compaction there. If it ends up |
2751 | * succeeding after all, it will be reset. |
2752 | */ |
2753 | defer_compaction(zone, order); |
2754 | |
2755 | /* |
2756 | * We might have stopped compacting due to need_resched() in |
2757 | * async compaction, or due to a fatal signal detected. In that |
2758 | * case do not try further zones |
2759 | */ |
2760 | if ((prio == COMPACT_PRIO_ASYNC && need_resched()) |
2761 | || fatal_signal_pending(current)) |
2762 | break; |
2763 | } |
2764 | |
2765 | return rc; |
2766 | } |
2767 | |
2768 | /* |
2769 | * Compact all zones within a node till each zone's fragmentation score |
2770 | * reaches within proactive compaction thresholds (as determined by the |
2771 | * proactiveness tunable). |
2772 | * |
2773 | * It is possible that the function returns before reaching score targets |
2774 | * due to various back-off conditions, such as, contention on per-node or |
2775 | * per-zone locks. |
2776 | */ |
2777 | static void proactive_compact_node(pg_data_t *pgdat) |
2778 | { |
2779 | int zoneid; |
2780 | struct zone *zone; |
2781 | struct compact_control cc = { |
2782 | .order = -1, |
2783 | .mode = MIGRATE_SYNC_LIGHT, |
2784 | .ignore_skip_hint = true, |
2785 | .whole_zone = true, |
2786 | .gfp_mask = GFP_KERNEL, |
2787 | .proactive_compaction = true, |
2788 | }; |
2789 | |
2790 | for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
2791 | zone = &pgdat->node_zones[zoneid]; |
2792 | if (!populated_zone(zone)) |
2793 | continue; |
2794 | |
2795 | cc.zone = zone; |
2796 | |
2797 | compact_zone(cc: &cc, NULL); |
2798 | |
2799 | count_compact_events(item: KCOMPACTD_MIGRATE_SCANNED, |
2800 | delta: cc.total_migrate_scanned); |
2801 | count_compact_events(item: KCOMPACTD_FREE_SCANNED, |
2802 | delta: cc.total_free_scanned); |
2803 | } |
2804 | } |
2805 | |
2806 | /* Compact all zones within a node */ |
2807 | static void compact_node(int nid) |
2808 | { |
2809 | pg_data_t *pgdat = NODE_DATA(nid); |
2810 | int zoneid; |
2811 | struct zone *zone; |
2812 | struct compact_control cc = { |
2813 | .order = -1, |
2814 | .mode = MIGRATE_SYNC, |
2815 | .ignore_skip_hint = true, |
2816 | .whole_zone = true, |
2817 | .gfp_mask = GFP_KERNEL, |
2818 | }; |
2819 | |
2820 | |
2821 | for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
2822 | |
2823 | zone = &pgdat->node_zones[zoneid]; |
2824 | if (!populated_zone(zone)) |
2825 | continue; |
2826 | |
2827 | cc.zone = zone; |
2828 | |
2829 | compact_zone(cc: &cc, NULL); |
2830 | } |
2831 | } |
2832 | |
2833 | /* Compact all nodes in the system */ |
2834 | static void compact_nodes(void) |
2835 | { |
2836 | int nid; |
2837 | |
2838 | /* Flush pending updates to the LRU lists */ |
2839 | lru_add_drain_all(); |
2840 | |
2841 | for_each_online_node(nid) |
2842 | compact_node(nid); |
2843 | } |
2844 | |
2845 | static int compaction_proactiveness_sysctl_handler(struct ctl_table *table, int write, |
2846 | void *buffer, size_t *length, loff_t *ppos) |
2847 | { |
2848 | int rc, nid; |
2849 | |
2850 | rc = proc_dointvec_minmax(table, write, buffer, length, ppos); |
2851 | if (rc) |
2852 | return rc; |
2853 | |
2854 | if (write && sysctl_compaction_proactiveness) { |
2855 | for_each_online_node(nid) { |
2856 | pg_data_t *pgdat = NODE_DATA(nid); |
2857 | |
2858 | if (pgdat->proactive_compact_trigger) |
2859 | continue; |
2860 | |
2861 | pgdat->proactive_compact_trigger = true; |
2862 | trace_mm_compaction_wakeup_kcompactd(nid: pgdat->node_id, order: -1, |
2863 | highest_zoneidx: pgdat->nr_zones - 1); |
2864 | wake_up_interruptible(&pgdat->kcompactd_wait); |
2865 | } |
2866 | } |
2867 | |
2868 | return 0; |
2869 | } |
2870 | |
2871 | /* |
2872 | * This is the entry point for compacting all nodes via |
2873 | * /proc/sys/vm/compact_memory |
2874 | */ |
2875 | static int sysctl_compaction_handler(struct ctl_table *table, int write, |
2876 | void *buffer, size_t *length, loff_t *ppos) |
2877 | { |
2878 | int ret; |
2879 | |
2880 | ret = proc_dointvec(table, write, buffer, length, ppos); |
2881 | if (ret) |
2882 | return ret; |
2883 | |
2884 | if (sysctl_compact_memory != 1) |
2885 | return -EINVAL; |
2886 | |
2887 | if (write) |
2888 | compact_nodes(); |
2889 | |
2890 | return 0; |
2891 | } |
2892 | |
2893 | #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) |
2894 | static ssize_t compact_store(struct device *dev, |
2895 | struct device_attribute *attr, |
2896 | const char *buf, size_t count) |
2897 | { |
2898 | int nid = dev->id; |
2899 | |
2900 | if (nid >= 0 && nid < nr_node_ids && node_online(nid)) { |
2901 | /* Flush pending updates to the LRU lists */ |
2902 | lru_add_drain_all(); |
2903 | |
2904 | compact_node(nid); |
2905 | } |
2906 | |
2907 | return count; |
2908 | } |
2909 | static DEVICE_ATTR_WO(compact); |
2910 | |
2911 | int compaction_register_node(struct node *node) |
2912 | { |
2913 | return device_create_file(device: &node->dev, entry: &dev_attr_compact); |
2914 | } |
2915 | |
2916 | void compaction_unregister_node(struct node *node) |
2917 | { |
2918 | device_remove_file(dev: &node->dev, attr: &dev_attr_compact); |
2919 | } |
2920 | #endif /* CONFIG_SYSFS && CONFIG_NUMA */ |
2921 | |
2922 | static inline bool kcompactd_work_requested(pg_data_t *pgdat) |
2923 | { |
2924 | return pgdat->kcompactd_max_order > 0 || kthread_should_stop() || |
2925 | pgdat->proactive_compact_trigger; |
2926 | } |
2927 | |
2928 | static bool kcompactd_node_suitable(pg_data_t *pgdat) |
2929 | { |
2930 | int zoneid; |
2931 | struct zone *zone; |
2932 | enum zone_type highest_zoneidx = pgdat->kcompactd_highest_zoneidx; |
2933 | enum compact_result ret; |
2934 | |
2935 | for (zoneid = 0; zoneid <= highest_zoneidx; zoneid++) { |
2936 | zone = &pgdat->node_zones[zoneid]; |
2937 | |
2938 | if (!populated_zone(zone)) |
2939 | continue; |
2940 | |
2941 | ret = compaction_suit_allocation_order(zone, |
2942 | order: pgdat->kcompactd_max_order, |
2943 | highest_zoneidx, ALLOC_WMARK_MIN); |
2944 | if (ret == COMPACT_CONTINUE) |
2945 | return true; |
2946 | } |
2947 | |
2948 | return false; |
2949 | } |
2950 | |
2951 | static void kcompactd_do_work(pg_data_t *pgdat) |
2952 | { |
2953 | /* |
2954 | * With no special task, compact all zones so that a page of requested |
2955 | * order is allocatable. |
2956 | */ |
2957 | int zoneid; |
2958 | struct zone *zone; |
2959 | struct compact_control cc = { |
2960 | .order = pgdat->kcompactd_max_order, |
2961 | .search_order = pgdat->kcompactd_max_order, |
2962 | .highest_zoneidx = pgdat->kcompactd_highest_zoneidx, |
2963 | .mode = MIGRATE_SYNC_LIGHT, |
2964 | .ignore_skip_hint = false, |
2965 | .gfp_mask = GFP_KERNEL, |
2966 | }; |
2967 | enum compact_result ret; |
2968 | |
2969 | trace_mm_compaction_kcompactd_wake(nid: pgdat->node_id, order: cc.order, |
2970 | highest_zoneidx: cc.highest_zoneidx); |
2971 | count_compact_event(item: KCOMPACTD_WAKE); |
2972 | |
2973 | for (zoneid = 0; zoneid <= cc.highest_zoneidx; zoneid++) { |
2974 | int status; |
2975 | |
2976 | zone = &pgdat->node_zones[zoneid]; |
2977 | if (!populated_zone(zone)) |
2978 | continue; |
2979 | |
2980 | if (compaction_deferred(zone, order: cc.order)) |
2981 | continue; |
2982 | |
2983 | ret = compaction_suit_allocation_order(zone, |
2984 | order: cc.order, highest_zoneidx: zoneid, ALLOC_WMARK_MIN); |
2985 | if (ret != COMPACT_CONTINUE) |
2986 | continue; |
2987 | |
2988 | if (kthread_should_stop()) |
2989 | return; |
2990 | |
2991 | cc.zone = zone; |
2992 | status = compact_zone(cc: &cc, NULL); |
2993 | |
2994 | if (status == COMPACT_SUCCESS) { |
2995 | compaction_defer_reset(zone, order: cc.order, alloc_success: false); |
2996 | } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) { |
2997 | /* |
2998 | * Buddy pages may become stranded on pcps that could |
2999 | * otherwise coalesce on the zone's free area for |
3000 | * order >= cc.order. This is ratelimited by the |
3001 | * upcoming deferral. |
3002 | */ |
3003 | drain_all_pages(zone); |
3004 | |
3005 | /* |
3006 | * We use sync migration mode here, so we defer like |
3007 | * sync direct compaction does. |
3008 | */ |
3009 | defer_compaction(zone, order: cc.order); |
3010 | } |
3011 | |
3012 | count_compact_events(item: KCOMPACTD_MIGRATE_SCANNED, |
3013 | delta: cc.total_migrate_scanned); |
3014 | count_compact_events(item: KCOMPACTD_FREE_SCANNED, |
3015 | delta: cc.total_free_scanned); |
3016 | } |
3017 | |
3018 | /* |
3019 | * Regardless of success, we are done until woken up next. But remember |
3020 | * the requested order/highest_zoneidx in case it was higher/tighter |
3021 | * than our current ones |
3022 | */ |
3023 | if (pgdat->kcompactd_max_order <= cc.order) |
3024 | pgdat->kcompactd_max_order = 0; |
3025 | if (pgdat->kcompactd_highest_zoneidx >= cc.highest_zoneidx) |
3026 | pgdat->kcompactd_highest_zoneidx = pgdat->nr_zones - 1; |
3027 | } |
3028 | |
3029 | void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx) |
3030 | { |
3031 | if (!order) |
3032 | return; |
3033 | |
3034 | if (pgdat->kcompactd_max_order < order) |
3035 | pgdat->kcompactd_max_order = order; |
3036 | |
3037 | if (pgdat->kcompactd_highest_zoneidx > highest_zoneidx) |
3038 | pgdat->kcompactd_highest_zoneidx = highest_zoneidx; |
3039 | |
3040 | /* |
3041 | * Pairs with implicit barrier in wait_event_freezable() |
3042 | * such that wakeups are not missed. |
3043 | */ |
3044 | if (!wq_has_sleeper(wq_head: &pgdat->kcompactd_wait)) |
3045 | return; |
3046 | |
3047 | if (!kcompactd_node_suitable(pgdat)) |
3048 | return; |
3049 | |
3050 | trace_mm_compaction_wakeup_kcompactd(nid: pgdat->node_id, order, |
3051 | highest_zoneidx); |
3052 | wake_up_interruptible(&pgdat->kcompactd_wait); |
3053 | } |
3054 | |
3055 | /* |
3056 | * The background compaction daemon, started as a kernel thread |
3057 | * from the init process. |
3058 | */ |
3059 | static int kcompactd(void *p) |
3060 | { |
3061 | pg_data_t *pgdat = (pg_data_t *)p; |
3062 | struct task_struct *tsk = current; |
3063 | long default_timeout = msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC); |
3064 | long timeout = default_timeout; |
3065 | |
3066 | const struct cpumask *cpumask = cpumask_of_node(node: pgdat->node_id); |
3067 | |
3068 | if (!cpumask_empty(srcp: cpumask)) |
3069 | set_cpus_allowed_ptr(p: tsk, new_mask: cpumask); |
3070 | |
3071 | set_freezable(); |
3072 | |
3073 | pgdat->kcompactd_max_order = 0; |
3074 | pgdat->kcompactd_highest_zoneidx = pgdat->nr_zones - 1; |
3075 | |
3076 | while (!kthread_should_stop()) { |
3077 | unsigned long pflags; |
3078 | |
3079 | /* |
3080 | * Avoid the unnecessary wakeup for proactive compaction |
3081 | * when it is disabled. |
3082 | */ |
3083 | if (!sysctl_compaction_proactiveness) |
3084 | timeout = MAX_SCHEDULE_TIMEOUT; |
3085 | trace_mm_compaction_kcompactd_sleep(nid: pgdat->node_id); |
3086 | if (wait_event_freezable_timeout(pgdat->kcompactd_wait, |
3087 | kcompactd_work_requested(pgdat), timeout) && |
3088 | !pgdat->proactive_compact_trigger) { |
3089 | |
3090 | psi_memstall_enter(flags: &pflags); |
3091 | kcompactd_do_work(pgdat); |
3092 | psi_memstall_leave(flags: &pflags); |
3093 | /* |
3094 | * Reset the timeout value. The defer timeout from |
3095 | * proactive compaction is lost here but that is fine |
3096 | * as the condition of the zone changing substantionally |
3097 | * then carrying on with the previous defer interval is |
3098 | * not useful. |
3099 | */ |
3100 | timeout = default_timeout; |
3101 | continue; |
3102 | } |
3103 | |
3104 | /* |
3105 | * Start the proactive work with default timeout. Based |
3106 | * on the fragmentation score, this timeout is updated. |
3107 | */ |
3108 | timeout = default_timeout; |
3109 | if (should_proactive_compact_node(pgdat)) { |
3110 | unsigned int prev_score, score; |
3111 | |
3112 | prev_score = fragmentation_score_node(pgdat); |
3113 | proactive_compact_node(pgdat); |
3114 | score = fragmentation_score_node(pgdat); |
3115 | /* |
3116 | * Defer proactive compaction if the fragmentation |
3117 | * score did not go down i.e. no progress made. |
3118 | */ |
3119 | if (unlikely(score >= prev_score)) |
3120 | timeout = |
3121 | default_timeout << COMPACT_MAX_DEFER_SHIFT; |
3122 | } |
3123 | if (unlikely(pgdat->proactive_compact_trigger)) |
3124 | pgdat->proactive_compact_trigger = false; |
3125 | } |
3126 | |
3127 | return 0; |
3128 | } |
3129 | |
3130 | /* |
3131 | * This kcompactd start function will be called by init and node-hot-add. |
3132 | * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added. |
3133 | */ |
3134 | void __meminit kcompactd_run(int nid) |
3135 | { |
3136 | pg_data_t *pgdat = NODE_DATA(nid); |
3137 | |
3138 | if (pgdat->kcompactd) |
3139 | return; |
3140 | |
3141 | pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d" , nid); |
3142 | if (IS_ERR(ptr: pgdat->kcompactd)) { |
3143 | pr_err("Failed to start kcompactd on node %d\n" , nid); |
3144 | pgdat->kcompactd = NULL; |
3145 | } |
3146 | } |
3147 | |
3148 | /* |
3149 | * Called by memory hotplug when all memory in a node is offlined. Caller must |
3150 | * be holding mem_hotplug_begin/done(). |
3151 | */ |
3152 | void __meminit kcompactd_stop(int nid) |
3153 | { |
3154 | struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd; |
3155 | |
3156 | if (kcompactd) { |
3157 | kthread_stop(k: kcompactd); |
3158 | NODE_DATA(nid)->kcompactd = NULL; |
3159 | } |
3160 | } |
3161 | |
3162 | /* |
3163 | * It's optimal to keep kcompactd on the same CPUs as their memory, but |
3164 | * not required for correctness. So if the last cpu in a node goes |
3165 | * away, we get changed to run anywhere: as the first one comes back, |
3166 | * restore their cpu bindings. |
3167 | */ |
3168 | static int kcompactd_cpu_online(unsigned int cpu) |
3169 | { |
3170 | int nid; |
3171 | |
3172 | for_each_node_state(nid, N_MEMORY) { |
3173 | pg_data_t *pgdat = NODE_DATA(nid); |
3174 | const struct cpumask *mask; |
3175 | |
3176 | mask = cpumask_of_node(node: pgdat->node_id); |
3177 | |
3178 | if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) |
3179 | /* One of our CPUs online: restore mask */ |
3180 | if (pgdat->kcompactd) |
3181 | set_cpus_allowed_ptr(p: pgdat->kcompactd, new_mask: mask); |
3182 | } |
3183 | return 0; |
3184 | } |
3185 | |
3186 | static int proc_dointvec_minmax_warn_RT_change(struct ctl_table *table, |
3187 | int write, void *buffer, size_t *lenp, loff_t *ppos) |
3188 | { |
3189 | int ret, old; |
3190 | |
3191 | if (!IS_ENABLED(CONFIG_PREEMPT_RT) || !write) |
3192 | return proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
3193 | |
3194 | old = *(int *)table->data; |
3195 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
3196 | if (ret) |
3197 | return ret; |
3198 | if (old != *(int *)table->data) |
3199 | pr_warn_once("sysctl attribute %s changed by %s[%d]\n" , |
3200 | table->procname, current->comm, |
3201 | task_pid_nr(current)); |
3202 | return ret; |
3203 | } |
3204 | |
3205 | static struct ctl_table vm_compaction[] = { |
3206 | { |
3207 | .procname = "compact_memory" , |
3208 | .data = &sysctl_compact_memory, |
3209 | .maxlen = sizeof(int), |
3210 | .mode = 0200, |
3211 | .proc_handler = sysctl_compaction_handler, |
3212 | }, |
3213 | { |
3214 | .procname = "compaction_proactiveness" , |
3215 | .data = &sysctl_compaction_proactiveness, |
3216 | .maxlen = sizeof(sysctl_compaction_proactiveness), |
3217 | .mode = 0644, |
3218 | .proc_handler = compaction_proactiveness_sysctl_handler, |
3219 | .extra1 = SYSCTL_ZERO, |
3220 | .extra2 = SYSCTL_ONE_HUNDRED, |
3221 | }, |
3222 | { |
3223 | .procname = "extfrag_threshold" , |
3224 | .data = &sysctl_extfrag_threshold, |
3225 | .maxlen = sizeof(int), |
3226 | .mode = 0644, |
3227 | .proc_handler = proc_dointvec_minmax, |
3228 | .extra1 = SYSCTL_ZERO, |
3229 | .extra2 = SYSCTL_ONE_THOUSAND, |
3230 | }, |
3231 | { |
3232 | .procname = "compact_unevictable_allowed" , |
3233 | .data = &sysctl_compact_unevictable_allowed, |
3234 | .maxlen = sizeof(int), |
3235 | .mode = 0644, |
3236 | .proc_handler = proc_dointvec_minmax_warn_RT_change, |
3237 | .extra1 = SYSCTL_ZERO, |
3238 | .extra2 = SYSCTL_ONE, |
3239 | }, |
3240 | { } |
3241 | }; |
3242 | |
3243 | static int __init kcompactd_init(void) |
3244 | { |
3245 | int nid; |
3246 | int ret; |
3247 | |
3248 | ret = cpuhp_setup_state_nocalls(state: CPUHP_AP_ONLINE_DYN, |
3249 | name: "mm/compaction:online" , |
3250 | startup: kcompactd_cpu_online, NULL); |
3251 | if (ret < 0) { |
3252 | pr_err("kcompactd: failed to register hotplug callbacks.\n" ); |
3253 | return ret; |
3254 | } |
3255 | |
3256 | for_each_node_state(nid, N_MEMORY) |
3257 | kcompactd_run(nid); |
3258 | register_sysctl_init("vm" , vm_compaction); |
3259 | return 0; |
3260 | } |
3261 | subsys_initcall(kcompactd_init) |
3262 | |
3263 | #endif /* CONFIG_COMPACTION */ |
3264 | |