Line data Source code
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 0 : static inline void count_compact_event(enum vm_event_item item)
30 : {
31 0 : count_vm_event(item);
32 : }
33 :
34 0 : static inline void count_compact_events(enum vm_event_item item, long delta)
35 : {
36 0 : count_vm_events(item, delta);
37 0 : }
38 : #else
39 : #define count_compact_event(item) do { } while (0)
40 : #define count_compact_events(item, delta) do { } while (0)
41 : #endif
42 :
43 : #if defined CONFIG_COMPACTION || defined CONFIG_CMA
44 :
45 : #define CREATE_TRACE_POINTS
46 : #include <trace/events/compaction.h>
47 :
48 : #define block_start_pfn(pfn, order) round_down(pfn, 1UL << (order))
49 : #define block_end_pfn(pfn, order) ALIGN((pfn) + 1, 1UL << (order))
50 : #define pageblock_start_pfn(pfn) block_start_pfn(pfn, pageblock_order)
51 : #define pageblock_end_pfn(pfn) block_end_pfn(pfn, pageblock_order)
52 :
53 : /*
54 : * Fragmentation score check interval for proactive compaction purposes.
55 : */
56 : static const unsigned int HPAGE_FRAG_CHECK_INTERVAL_MSEC = 500;
57 :
58 : /*
59 : * Page order with-respect-to which proactive compaction
60 : * calculates external fragmentation, which is used as
61 : * the "fragmentation score" of a node/zone.
62 : */
63 : #if defined CONFIG_TRANSPARENT_HUGEPAGE
64 : #define COMPACTION_HPAGE_ORDER HPAGE_PMD_ORDER
65 : #elif defined CONFIG_HUGETLBFS
66 : #define COMPACTION_HPAGE_ORDER HUGETLB_PAGE_ORDER
67 : #else
68 : #define COMPACTION_HPAGE_ORDER (PMD_SHIFT - PAGE_SHIFT)
69 : #endif
70 :
71 0 : static unsigned long release_freepages(struct list_head *freelist)
72 : {
73 0 : struct page *page, *next;
74 0 : unsigned long high_pfn = 0;
75 :
76 0 : list_for_each_entry_safe(page, next, freelist, lru) {
77 0 : unsigned long pfn = page_to_pfn(page);
78 0 : list_del(&page->lru);
79 0 : __free_page(page);
80 0 : if (pfn > high_pfn)
81 : high_pfn = pfn;
82 : }
83 :
84 0 : return high_pfn;
85 : }
86 :
87 0 : static void split_map_pages(struct list_head *list)
88 : {
89 0 : unsigned int i, order, nr_pages;
90 0 : struct page *page, *next;
91 0 : LIST_HEAD(tmp_list);
92 :
93 0 : list_for_each_entry_safe(page, next, list, lru) {
94 0 : list_del(&page->lru);
95 :
96 0 : order = page_private(page);
97 0 : nr_pages = 1 << order;
98 :
99 0 : post_alloc_hook(page, order, __GFP_MOVABLE);
100 0 : if (order)
101 0 : split_page(page, order);
102 :
103 0 : for (i = 0; i < nr_pages; i++) {
104 0 : list_add(&page->lru, &tmp_list);
105 0 : page++;
106 : }
107 : }
108 :
109 0 : list_splice(&tmp_list, list);
110 0 : }
111 :
112 : #ifdef CONFIG_COMPACTION
113 :
114 0 : int PageMovable(struct page *page)
115 : {
116 0 : struct address_space *mapping;
117 :
118 0 : VM_BUG_ON_PAGE(!PageLocked(page), page);
119 0 : if (!__PageMovable(page))
120 : return 0;
121 :
122 0 : mapping = page_mapping(page);
123 0 : if (mapping && mapping->a_ops && mapping->a_ops->isolate_page)
124 0 : return 1;
125 :
126 : return 0;
127 : }
128 : EXPORT_SYMBOL(PageMovable);
129 :
130 0 : void __SetPageMovable(struct page *page, struct address_space *mapping)
131 : {
132 0 : VM_BUG_ON_PAGE(!PageLocked(page), page);
133 0 : VM_BUG_ON_PAGE((unsigned long)mapping & PAGE_MAPPING_MOVABLE, page);
134 0 : page->mapping = (void *)((unsigned long)mapping | PAGE_MAPPING_MOVABLE);
135 0 : }
136 : EXPORT_SYMBOL(__SetPageMovable);
137 :
138 0 : void __ClearPageMovable(struct page *page)
139 : {
140 0 : VM_BUG_ON_PAGE(!PageMovable(page), page);
141 : /*
142 : * Clear registered address_space val with keeping PAGE_MAPPING_MOVABLE
143 : * flag so that VM can catch up released page by driver after isolation.
144 : * With it, VM migration doesn't try to put it back.
145 : */
146 0 : page->mapping = (void *)((unsigned long)page->mapping &
147 : PAGE_MAPPING_MOVABLE);
148 0 : }
149 : EXPORT_SYMBOL(__ClearPageMovable);
150 :
151 : /* Do not skip compaction more than 64 times */
152 : #define COMPACT_MAX_DEFER_SHIFT 6
153 :
154 : /*
155 : * Compaction is deferred when compaction fails to result in a page
156 : * allocation success. 1 << compact_defer_shift, compactions are skipped up
157 : * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
158 : */
159 0 : static void defer_compaction(struct zone *zone, int order)
160 : {
161 0 : zone->compact_considered = 0;
162 0 : zone->compact_defer_shift++;
163 :
164 0 : if (order < zone->compact_order_failed)
165 0 : zone->compact_order_failed = order;
166 :
167 0 : if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
168 0 : zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
169 :
170 0 : trace_mm_compaction_defer_compaction(zone, order);
171 0 : }
172 :
173 : /* Returns true if compaction should be skipped this time */
174 0 : static bool compaction_deferred(struct zone *zone, int order)
175 : {
176 0 : unsigned long defer_limit = 1UL << zone->compact_defer_shift;
177 :
178 0 : if (order < zone->compact_order_failed)
179 : return false;
180 :
181 : /* Avoid possible overflow */
182 0 : if (++zone->compact_considered >= defer_limit) {
183 0 : zone->compact_considered = defer_limit;
184 0 : return false;
185 : }
186 :
187 0 : trace_mm_compaction_deferred(zone, order);
188 :
189 0 : return true;
190 : }
191 :
192 : /*
193 : * Update defer tracking counters after successful compaction of given order,
194 : * which means an allocation either succeeded (alloc_success == true) or is
195 : * expected to succeed.
196 : */
197 0 : void compaction_defer_reset(struct zone *zone, int order,
198 : bool alloc_success)
199 : {
200 0 : if (alloc_success) {
201 0 : zone->compact_considered = 0;
202 0 : zone->compact_defer_shift = 0;
203 : }
204 0 : if (order >= zone->compact_order_failed)
205 0 : zone->compact_order_failed = order + 1;
206 :
207 0 : trace_mm_compaction_defer_reset(zone, order);
208 0 : }
209 :
210 : /* Returns true if restarting compaction after many failures */
211 0 : static bool compaction_restarting(struct zone *zone, int order)
212 : {
213 0 : if (order < zone->compact_order_failed)
214 : return false;
215 :
216 0 : return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
217 0 : zone->compact_considered >= 1UL << zone->compact_defer_shift;
218 : }
219 :
220 : /* Returns true if the pageblock should be scanned for pages to isolate. */
221 0 : static inline bool isolation_suitable(struct compact_control *cc,
222 : struct page *page)
223 : {
224 0 : if (cc->ignore_skip_hint)
225 : return true;
226 :
227 0 : return !get_pageblock_skip(page);
228 : }
229 :
230 0 : static void reset_cached_positions(struct zone *zone)
231 : {
232 0 : zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn;
233 0 : zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn;
234 0 : zone->compact_cached_free_pfn =
235 0 : pageblock_start_pfn(zone_end_pfn(zone) - 1);
236 : }
237 :
238 : /*
239 : * Compound pages of >= pageblock_order should consistently be skipped until
240 : * released. It is always pointless to compact pages of such order (if they are
241 : * migratable), and the pageblocks they occupy cannot contain any free pages.
242 : */
243 0 : static bool pageblock_skip_persistent(struct page *page)
244 : {
245 0 : if (!PageCompound(page))
246 : return false;
247 :
248 0 : page = compound_head(page);
249 :
250 0 : if (compound_order(page) >= pageblock_order)
251 0 : return true;
252 :
253 : return false;
254 : }
255 :
256 : static bool
257 0 : __reset_isolation_pfn(struct zone *zone, unsigned long pfn, bool check_source,
258 : bool check_target)
259 : {
260 0 : struct page *page = pfn_to_online_page(pfn);
261 0 : struct page *block_page;
262 0 : struct page *end_page;
263 0 : unsigned long block_pfn;
264 :
265 0 : if (!page)
266 : return false;
267 0 : if (zone != page_zone(page))
268 : return false;
269 0 : if (pageblock_skip_persistent(page))
270 : return false;
271 :
272 : /*
273 : * If skip is already cleared do no further checking once the
274 : * restart points have been set.
275 : */
276 0 : if (check_source && check_target && !get_pageblock_skip(page))
277 : return true;
278 :
279 : /*
280 : * If clearing skip for the target scanner, do not select a
281 : * non-movable pageblock as the starting point.
282 : */
283 0 : if (!check_source && check_target &&
284 0 : get_pageblock_migratetype(page) != MIGRATE_MOVABLE)
285 : return false;
286 :
287 : /* Ensure the start of the pageblock or zone is online and valid */
288 0 : block_pfn = pageblock_start_pfn(pfn);
289 0 : block_pfn = max(block_pfn, zone->zone_start_pfn);
290 0 : block_page = pfn_to_online_page(block_pfn);
291 0 : if (block_page) {
292 0 : page = block_page;
293 0 : pfn = block_pfn;
294 : }
295 :
296 : /* Ensure the end of the pageblock or zone is online and valid */
297 0 : block_pfn = pageblock_end_pfn(pfn) - 1;
298 0 : block_pfn = min(block_pfn, zone_end_pfn(zone) - 1);
299 0 : end_page = pfn_to_online_page(block_pfn);
300 0 : if (!end_page)
301 : return false;
302 :
303 : /*
304 : * Only clear the hint if a sample indicates there is either a
305 : * free page or an LRU page in the block. One or other condition
306 : * is necessary for the block to be a migration source/target.
307 : */
308 0 : do {
309 0 : if (pfn_valid_within(pfn)) {
310 0 : if (check_source && PageLRU(page)) {
311 0 : clear_pageblock_skip(page);
312 0 : return true;
313 : }
314 :
315 0 : if (check_target && PageBuddy(page)) {
316 0 : clear_pageblock_skip(page);
317 0 : return true;
318 : }
319 : }
320 :
321 0 : page += (1 << PAGE_ALLOC_COSTLY_ORDER);
322 0 : pfn += (1 << PAGE_ALLOC_COSTLY_ORDER);
323 0 : } while (page <= end_page);
324 :
325 : return false;
326 : }
327 :
328 : /*
329 : * This function is called to clear all cached information on pageblocks that
330 : * should be skipped for page isolation when the migrate and free page scanner
331 : * meet.
332 : */
333 0 : static void __reset_isolation_suitable(struct zone *zone)
334 : {
335 0 : unsigned long migrate_pfn = zone->zone_start_pfn;
336 0 : unsigned long free_pfn = zone_end_pfn(zone) - 1;
337 0 : unsigned long reset_migrate = free_pfn;
338 0 : unsigned long reset_free = migrate_pfn;
339 0 : bool source_set = false;
340 0 : bool free_set = false;
341 :
342 0 : if (!zone->compact_blockskip_flush)
343 : return;
344 :
345 0 : zone->compact_blockskip_flush = false;
346 :
347 : /*
348 : * Walk the zone and update pageblock skip information. Source looks
349 : * for PageLRU while target looks for PageBuddy. When the scanner
350 : * is found, both PageBuddy and PageLRU are checked as the pageblock
351 : * is suitable as both source and target.
352 : */
353 0 : for (; migrate_pfn < free_pfn; migrate_pfn += pageblock_nr_pages,
354 0 : free_pfn -= pageblock_nr_pages) {
355 0 : cond_resched();
356 :
357 : /* Update the migrate PFN */
358 0 : if (__reset_isolation_pfn(zone, migrate_pfn, true, source_set) &&
359 : migrate_pfn < reset_migrate) {
360 0 : source_set = true;
361 0 : reset_migrate = migrate_pfn;
362 0 : zone->compact_init_migrate_pfn = reset_migrate;
363 0 : zone->compact_cached_migrate_pfn[0] = reset_migrate;
364 0 : zone->compact_cached_migrate_pfn[1] = reset_migrate;
365 : }
366 :
367 : /* Update the free PFN */
368 0 : if (__reset_isolation_pfn(zone, free_pfn, free_set, true) &&
369 : free_pfn > reset_free) {
370 0 : free_set = true;
371 0 : reset_free = free_pfn;
372 0 : zone->compact_init_free_pfn = reset_free;
373 0 : zone->compact_cached_free_pfn = reset_free;
374 : }
375 : }
376 :
377 : /* Leave no distance if no suitable block was reset */
378 0 : if (reset_migrate >= reset_free) {
379 0 : zone->compact_cached_migrate_pfn[0] = migrate_pfn;
380 0 : zone->compact_cached_migrate_pfn[1] = migrate_pfn;
381 0 : zone->compact_cached_free_pfn = free_pfn;
382 : }
383 : }
384 :
385 1 : void reset_isolation_suitable(pg_data_t *pgdat)
386 : {
387 1 : int zoneid;
388 :
389 4 : for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
390 3 : struct zone *zone = &pgdat->node_zones[zoneid];
391 3 : if (!populated_zone(zone))
392 2 : continue;
393 :
394 : /* Only flush if a full compaction finished recently */
395 1 : if (zone->compact_blockskip_flush)
396 0 : __reset_isolation_suitable(zone);
397 : }
398 1 : }
399 :
400 : /*
401 : * Sets the pageblock skip bit if it was clear. Note that this is a hint as
402 : * locks are not required for read/writers. Returns true if it was already set.
403 : */
404 0 : static bool test_and_set_skip(struct compact_control *cc, struct page *page,
405 : unsigned long pfn)
406 : {
407 0 : bool skip;
408 :
409 : /* Do no update if skip hint is being ignored */
410 0 : if (cc->ignore_skip_hint)
411 : return false;
412 :
413 0 : if (!IS_ALIGNED(pfn, pageblock_nr_pages))
414 : return false;
415 :
416 0 : skip = get_pageblock_skip(page);
417 0 : if (!skip && !cc->no_set_skip_hint)
418 0 : set_pageblock_skip(page);
419 :
420 : return skip;
421 : }
422 :
423 0 : static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
424 : {
425 0 : struct zone *zone = cc->zone;
426 :
427 0 : pfn = pageblock_end_pfn(pfn);
428 :
429 : /* Set for isolation rather than compaction */
430 0 : if (cc->no_set_skip_hint)
431 : return;
432 :
433 0 : if (pfn > zone->compact_cached_migrate_pfn[0])
434 0 : zone->compact_cached_migrate_pfn[0] = pfn;
435 0 : if (cc->mode != MIGRATE_ASYNC &&
436 0 : pfn > zone->compact_cached_migrate_pfn[1])
437 0 : zone->compact_cached_migrate_pfn[1] = pfn;
438 : }
439 :
440 : /*
441 : * If no pages were isolated then mark this pageblock to be skipped in the
442 : * future. The information is later cleared by __reset_isolation_suitable().
443 : */
444 0 : static void update_pageblock_skip(struct compact_control *cc,
445 : struct page *page, unsigned long pfn)
446 : {
447 0 : struct zone *zone = cc->zone;
448 :
449 0 : if (cc->no_set_skip_hint)
450 : return;
451 :
452 0 : if (!page)
453 : return;
454 :
455 0 : set_pageblock_skip(page);
456 :
457 : /* Update where async and sync compaction should restart */
458 0 : if (pfn < zone->compact_cached_free_pfn)
459 0 : zone->compact_cached_free_pfn = pfn;
460 : }
461 : #else
462 : static inline bool isolation_suitable(struct compact_control *cc,
463 : struct page *page)
464 : {
465 : return true;
466 : }
467 :
468 : static inline bool pageblock_skip_persistent(struct page *page)
469 : {
470 : return false;
471 : }
472 :
473 : static inline void update_pageblock_skip(struct compact_control *cc,
474 : struct page *page, unsigned long pfn)
475 : {
476 : }
477 :
478 : static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
479 : {
480 : }
481 :
482 : static bool test_and_set_skip(struct compact_control *cc, struct page *page,
483 : unsigned long pfn)
484 : {
485 : return false;
486 : }
487 : #endif /* CONFIG_COMPACTION */
488 :
489 : /*
490 : * Compaction requires the taking of some coarse locks that are potentially
491 : * very heavily contended. For async compaction, trylock and record if the
492 : * lock is contended. The lock will still be acquired but compaction will
493 : * abort when the current block is finished regardless of success rate.
494 : * Sync compaction acquires the lock.
495 : *
496 : * Always returns true which makes it easier to track lock state in callers.
497 : */
498 0 : static bool compact_lock_irqsave(spinlock_t *lock, unsigned long *flags,
499 : struct compact_control *cc)
500 : __acquires(lock)
501 : {
502 : /* Track if the lock is contended in async mode */
503 0 : if (cc->mode == MIGRATE_ASYNC && !cc->contended) {
504 0 : if (spin_trylock_irqsave(lock, *flags))
505 : return true;
506 :
507 0 : cc->contended = true;
508 : }
509 :
510 0 : spin_lock_irqsave(lock, *flags);
511 0 : return true;
512 : }
513 :
514 : /*
515 : * Compaction requires the taking of some coarse locks that are potentially
516 : * very heavily contended. The lock should be periodically unlocked to avoid
517 : * having disabled IRQs for a long time, even when there is nobody waiting on
518 : * the lock. It might also be that allowing the IRQs will result in
519 : * need_resched() becoming true. If scheduling is needed, async compaction
520 : * aborts. Sync compaction schedules.
521 : * Either compaction type will also abort if a fatal signal is pending.
522 : * In either case if the lock was locked, it is dropped and not regained.
523 : *
524 : * Returns true if compaction should abort due to fatal signal pending, or
525 : * async compaction due to need_resched()
526 : * Returns false when compaction can continue (sync compaction might have
527 : * scheduled)
528 : */
529 0 : static bool compact_unlock_should_abort(spinlock_t *lock,
530 : unsigned long flags, bool *locked, struct compact_control *cc)
531 : {
532 0 : if (*locked) {
533 0 : spin_unlock_irqrestore(lock, flags);
534 0 : *locked = false;
535 : }
536 :
537 0 : if (fatal_signal_pending(current)) {
538 0 : cc->contended = true;
539 0 : return true;
540 : }
541 :
542 0 : cond_resched();
543 :
544 0 : return false;
545 : }
546 :
547 : /*
548 : * Isolate free pages onto a private freelist. If @strict is true, will abort
549 : * returning 0 on any invalid PFNs or non-free pages inside of the pageblock
550 : * (even though it may still end up isolating some pages).
551 : */
552 0 : static unsigned long isolate_freepages_block(struct compact_control *cc,
553 : unsigned long *start_pfn,
554 : unsigned long end_pfn,
555 : struct list_head *freelist,
556 : unsigned int stride,
557 : bool strict)
558 : {
559 0 : int nr_scanned = 0, total_isolated = 0;
560 0 : struct page *cursor;
561 0 : unsigned long flags = 0;
562 0 : bool locked = false;
563 0 : unsigned long blockpfn = *start_pfn;
564 0 : unsigned int order;
565 :
566 : /* Strict mode is for isolation, speed is secondary */
567 0 : if (strict)
568 0 : stride = 1;
569 :
570 0 : cursor = pfn_to_page(blockpfn);
571 :
572 : /* Isolate free pages. */
573 0 : for (; blockpfn < end_pfn; blockpfn += stride, cursor += stride) {
574 0 : int isolated;
575 0 : struct page *page = cursor;
576 :
577 : /*
578 : * Periodically drop the lock (if held) regardless of its
579 : * contention, to give chance to IRQs. Abort if fatal signal
580 : * pending or async compaction detects need_resched()
581 : */
582 0 : if (!(blockpfn % SWAP_CLUSTER_MAX)
583 0 : && compact_unlock_should_abort(&cc->zone->lock, flags,
584 : &locked, cc))
585 : break;
586 :
587 0 : nr_scanned++;
588 0 : if (!pfn_valid_within(blockpfn))
589 : goto isolate_fail;
590 :
591 : /*
592 : * For compound pages such as THP and hugetlbfs, we can save
593 : * potentially a lot of iterations if we skip them at once.
594 : * The check is racy, but we can consider only valid values
595 : * and the only danger is skipping too much.
596 : */
597 0 : if (PageCompound(page)) {
598 0 : const unsigned int order = compound_order(page);
599 :
600 0 : if (likely(order < MAX_ORDER)) {
601 0 : blockpfn += (1UL << order) - 1;
602 0 : cursor += (1UL << order) - 1;
603 : }
604 0 : goto isolate_fail;
605 : }
606 :
607 0 : if (!PageBuddy(page))
608 0 : goto isolate_fail;
609 :
610 : /*
611 : * If we already hold the lock, we can skip some rechecking.
612 : * Note that if we hold the lock now, checked_pageblock was
613 : * already set in some previous iteration (or strict is true),
614 : * so it is correct to skip the suitable migration target
615 : * recheck as well.
616 : */
617 0 : if (!locked) {
618 0 : locked = compact_lock_irqsave(&cc->zone->lock,
619 : &flags, cc);
620 :
621 : /* Recheck this is a buddy page under lock */
622 0 : if (!PageBuddy(page))
623 0 : goto isolate_fail;
624 : }
625 :
626 : /* Found a free page, will break it into order-0 pages */
627 0 : order = buddy_order(page);
628 0 : isolated = __isolate_free_page(page, order);
629 0 : if (!isolated)
630 : break;
631 0 : set_page_private(page, order);
632 :
633 0 : total_isolated += isolated;
634 0 : cc->nr_freepages += isolated;
635 0 : list_add_tail(&page->lru, freelist);
636 :
637 0 : if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
638 0 : blockpfn += isolated;
639 0 : break;
640 : }
641 : /* Advance to the end of split page */
642 0 : blockpfn += isolated - 1;
643 0 : cursor += isolated - 1;
644 0 : continue;
645 :
646 0 : isolate_fail:
647 0 : if (strict)
648 : break;
649 : else
650 0 : continue;
651 :
652 : }
653 :
654 0 : if (locked)
655 0 : spin_unlock_irqrestore(&cc->zone->lock, flags);
656 :
657 : /*
658 : * There is a tiny chance that we have read bogus compound_order(),
659 : * so be careful to not go outside of the pageblock.
660 : */
661 0 : if (unlikely(blockpfn > end_pfn))
662 0 : blockpfn = end_pfn;
663 :
664 0 : trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn,
665 : nr_scanned, total_isolated);
666 :
667 : /* Record how far we have got within the block */
668 0 : *start_pfn = blockpfn;
669 :
670 : /*
671 : * If strict isolation is requested by CMA then check that all the
672 : * pages requested were isolated. If there were any failures, 0 is
673 : * returned and CMA will fail.
674 : */
675 0 : if (strict && blockpfn < end_pfn)
676 0 : total_isolated = 0;
677 :
678 0 : cc->total_free_scanned += nr_scanned;
679 0 : if (total_isolated)
680 0 : count_compact_events(COMPACTISOLATED, total_isolated);
681 0 : return total_isolated;
682 : }
683 :
684 : /**
685 : * isolate_freepages_range() - isolate free pages.
686 : * @cc: Compaction control structure.
687 : * @start_pfn: The first PFN to start isolating.
688 : * @end_pfn: The one-past-last PFN.
689 : *
690 : * Non-free pages, invalid PFNs, or zone boundaries within the
691 : * [start_pfn, end_pfn) range are considered errors, cause function to
692 : * undo its actions and return zero.
693 : *
694 : * Otherwise, function returns one-past-the-last PFN of isolated page
695 : * (which may be greater then end_pfn if end fell in a middle of
696 : * a free page).
697 : */
698 : unsigned long
699 0 : isolate_freepages_range(struct compact_control *cc,
700 : unsigned long start_pfn, unsigned long end_pfn)
701 : {
702 0 : unsigned long isolated, pfn, block_start_pfn, block_end_pfn;
703 0 : LIST_HEAD(freelist);
704 :
705 0 : pfn = start_pfn;
706 0 : block_start_pfn = pageblock_start_pfn(pfn);
707 0 : if (block_start_pfn < cc->zone->zone_start_pfn)
708 : block_start_pfn = cc->zone->zone_start_pfn;
709 0 : block_end_pfn = pageblock_end_pfn(pfn);
710 :
711 0 : for (; pfn < end_pfn; pfn += isolated,
712 0 : block_start_pfn = block_end_pfn,
713 0 : block_end_pfn += pageblock_nr_pages) {
714 : /* Protect pfn from changing by isolate_freepages_block */
715 0 : unsigned long isolate_start_pfn = pfn;
716 :
717 0 : block_end_pfn = min(block_end_pfn, end_pfn);
718 :
719 : /*
720 : * pfn could pass the block_end_pfn if isolated freepage
721 : * is more than pageblock order. In this case, we adjust
722 : * scanning range to right one.
723 : */
724 0 : if (pfn >= block_end_pfn) {
725 0 : block_start_pfn = pageblock_start_pfn(pfn);
726 0 : block_end_pfn = pageblock_end_pfn(pfn);
727 0 : block_end_pfn = min(block_end_pfn, end_pfn);
728 : }
729 :
730 0 : if (!pageblock_pfn_to_page(block_start_pfn,
731 : block_end_pfn, cc->zone))
732 : break;
733 :
734 0 : isolated = isolate_freepages_block(cc, &isolate_start_pfn,
735 : block_end_pfn, &freelist, 0, true);
736 :
737 : /*
738 : * In strict mode, isolate_freepages_block() returns 0 if
739 : * there are any holes in the block (ie. invalid PFNs or
740 : * non-free pages).
741 : */
742 0 : if (!isolated)
743 : break;
744 :
745 : /*
746 : * If we managed to isolate pages, it is always (1 << n) *
747 : * pageblock_nr_pages for some non-negative n. (Max order
748 : * page may span two pageblocks).
749 : */
750 : }
751 :
752 : /* __isolate_free_page() does not map the pages */
753 0 : split_map_pages(&freelist);
754 :
755 0 : if (pfn < end_pfn) {
756 : /* Loop terminated early, cleanup. */
757 0 : release_freepages(&freelist);
758 0 : return 0;
759 : }
760 :
761 : /* We don't use freelists for anything. */
762 : return pfn;
763 : }
764 :
765 : /* Similar to reclaim, but different enough that they don't share logic */
766 0 : static bool too_many_isolated(pg_data_t *pgdat)
767 : {
768 0 : unsigned long active, inactive, isolated;
769 :
770 0 : inactive = node_page_state(pgdat, NR_INACTIVE_FILE) +
771 0 : node_page_state(pgdat, NR_INACTIVE_ANON);
772 0 : active = node_page_state(pgdat, NR_ACTIVE_FILE) +
773 0 : node_page_state(pgdat, NR_ACTIVE_ANON);
774 0 : isolated = node_page_state(pgdat, NR_ISOLATED_FILE) +
775 0 : node_page_state(pgdat, NR_ISOLATED_ANON);
776 :
777 0 : return isolated > (inactive + active) / 2;
778 : }
779 :
780 : /**
781 : * isolate_migratepages_block() - isolate all migrate-able pages within
782 : * a single pageblock
783 : * @cc: Compaction control structure.
784 : * @low_pfn: The first PFN to isolate
785 : * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
786 : * @isolate_mode: Isolation mode to be used.
787 : *
788 : * Isolate all pages that can be migrated from the range specified by
789 : * [low_pfn, end_pfn). The range is expected to be within same pageblock.
790 : * Returns zero if there is a fatal signal pending, otherwise PFN of the
791 : * first page that was not scanned (which may be both less, equal to or more
792 : * than end_pfn).
793 : *
794 : * The pages are isolated on cc->migratepages list (not required to be empty),
795 : * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field
796 : * is neither read nor updated.
797 : */
798 : static unsigned long
799 0 : isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
800 : unsigned long end_pfn, isolate_mode_t isolate_mode)
801 : {
802 0 : pg_data_t *pgdat = cc->zone->zone_pgdat;
803 0 : unsigned long nr_scanned = 0, nr_isolated = 0;
804 0 : struct lruvec *lruvec;
805 0 : unsigned long flags = 0;
806 0 : struct lruvec *locked = NULL;
807 0 : struct page *page = NULL, *valid_page = NULL;
808 0 : unsigned long start_pfn = low_pfn;
809 0 : bool skip_on_failure = false;
810 0 : unsigned long next_skip_pfn = 0;
811 0 : bool skip_updated = false;
812 :
813 : /*
814 : * Ensure that there are not too many pages isolated from the LRU
815 : * list by either parallel reclaimers or compaction. If there are,
816 : * delay for some time until fewer pages are isolated
817 : */
818 0 : while (unlikely(too_many_isolated(pgdat))) {
819 : /* stop isolation if there are still pages not migrated */
820 0 : if (cc->nr_migratepages)
821 : return 0;
822 :
823 : /* async migration should just abort */
824 0 : if (cc->mode == MIGRATE_ASYNC)
825 : return 0;
826 :
827 0 : congestion_wait(BLK_RW_ASYNC, HZ/10);
828 :
829 0 : if (fatal_signal_pending(current))
830 : return 0;
831 : }
832 :
833 0 : cond_resched();
834 :
835 0 : if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) {
836 0 : skip_on_failure = true;
837 0 : next_skip_pfn = block_end_pfn(low_pfn, cc->order);
838 : }
839 :
840 : /* Time to isolate some pages for migration */
841 0 : for (; low_pfn < end_pfn; low_pfn++) {
842 :
843 0 : if (skip_on_failure && low_pfn >= next_skip_pfn) {
844 : /*
845 : * We have isolated all migration candidates in the
846 : * previous order-aligned block, and did not skip it due
847 : * to failure. We should migrate the pages now and
848 : * hopefully succeed compaction.
849 : */
850 0 : if (nr_isolated)
851 : break;
852 :
853 : /*
854 : * We failed to isolate in the previous order-aligned
855 : * block. Set the new boundary to the end of the
856 : * current block. Note we can't simply increase
857 : * next_skip_pfn by 1 << order, as low_pfn might have
858 : * been incremented by a higher number due to skipping
859 : * a compound or a high-order buddy page in the
860 : * previous loop iteration.
861 : */
862 0 : next_skip_pfn = block_end_pfn(low_pfn, cc->order);
863 : }
864 :
865 : /*
866 : * Periodically drop the lock (if held) regardless of its
867 : * contention, to give chance to IRQs. Abort completely if
868 : * a fatal signal is pending.
869 : */
870 0 : if (!(low_pfn % SWAP_CLUSTER_MAX)) {
871 0 : if (locked) {
872 0 : unlock_page_lruvec_irqrestore(locked, flags);
873 0 : locked = NULL;
874 : }
875 :
876 0 : if (fatal_signal_pending(current)) {
877 0 : cc->contended = true;
878 :
879 0 : low_pfn = 0;
880 0 : goto fatal_pending;
881 : }
882 :
883 0 : cond_resched();
884 : }
885 :
886 0 : if (!pfn_valid_within(low_pfn))
887 : goto isolate_fail;
888 0 : nr_scanned++;
889 :
890 0 : page = pfn_to_page(low_pfn);
891 :
892 : /*
893 : * Check if the pageblock has already been marked skipped.
894 : * Only the aligned PFN is checked as the caller isolates
895 : * COMPACT_CLUSTER_MAX at a time so the second call must
896 : * not falsely conclude that the block should be skipped.
897 : */
898 0 : if (!valid_page && IS_ALIGNED(low_pfn, pageblock_nr_pages)) {
899 0 : if (!cc->ignore_skip_hint && get_pageblock_skip(page)) {
900 0 : low_pfn = end_pfn;
901 0 : page = NULL;
902 0 : goto isolate_abort;
903 : }
904 : valid_page = page;
905 : }
906 :
907 : /*
908 : * Skip if free. We read page order here without zone lock
909 : * which is generally unsafe, but the race window is small and
910 : * the worst thing that can happen is that we skip some
911 : * potential isolation targets.
912 : */
913 0 : if (PageBuddy(page)) {
914 0 : unsigned long freepage_order = buddy_order_unsafe(page);
915 :
916 : /*
917 : * Without lock, we cannot be sure that what we got is
918 : * a valid page order. Consider only values in the
919 : * valid order range to prevent low_pfn overflow.
920 : */
921 0 : if (freepage_order > 0 && freepage_order < MAX_ORDER)
922 0 : low_pfn += (1UL << freepage_order) - 1;
923 0 : continue;
924 : }
925 :
926 : /*
927 : * Regardless of being on LRU, compound pages such as THP and
928 : * hugetlbfs are not to be compacted unless we are attempting
929 : * an allocation much larger than the huge page size (eg CMA).
930 : * We can potentially save a lot of iterations if we skip them
931 : * at once. The check is racy, but we can consider only valid
932 : * values and the only danger is skipping too much.
933 : */
934 0 : if (PageCompound(page) && !cc->alloc_contig) {
935 0 : const unsigned int order = compound_order(page);
936 :
937 0 : if (likely(order < MAX_ORDER))
938 0 : low_pfn += (1UL << order) - 1;
939 0 : goto isolate_fail;
940 : }
941 :
942 : /*
943 : * Check may be lockless but that's ok as we recheck later.
944 : * It's possible to migrate LRU and non-lru movable pages.
945 : * Skip any other type of page
946 : */
947 0 : if (!PageLRU(page)) {
948 : /*
949 : * __PageMovable can return false positive so we need
950 : * to verify it under page_lock.
951 : */
952 0 : if (unlikely(__PageMovable(page)) &&
953 0 : !PageIsolated(page)) {
954 0 : if (locked) {
955 0 : unlock_page_lruvec_irqrestore(locked, flags);
956 0 : locked = NULL;
957 : }
958 :
959 0 : if (!isolate_movable_page(page, isolate_mode))
960 0 : goto isolate_success;
961 : }
962 :
963 0 : goto isolate_fail;
964 : }
965 :
966 : /*
967 : * Migration will fail if an anonymous page is pinned in memory,
968 : * so avoid taking lru_lock and isolating it unnecessarily in an
969 : * admittedly racy check.
970 : */
971 0 : if (!page_mapping(page) &&
972 0 : page_count(page) > page_mapcount(page))
973 0 : goto isolate_fail;
974 :
975 : /*
976 : * Only allow to migrate anonymous pages in GFP_NOFS context
977 : * because those do not depend on fs locks.
978 : */
979 0 : if (!(cc->gfp_mask & __GFP_FS) && page_mapping(page))
980 0 : goto isolate_fail;
981 :
982 : /*
983 : * Be careful not to clear PageLRU until after we're
984 : * sure the page is not being freed elsewhere -- the
985 : * page release code relies on it.
986 : */
987 0 : if (unlikely(!get_page_unless_zero(page)))
988 0 : goto isolate_fail;
989 :
990 0 : if (!__isolate_lru_page_prepare(page, isolate_mode))
991 0 : goto isolate_fail_put;
992 :
993 : /* Try isolate the page */
994 0 : if (!TestClearPageLRU(page))
995 0 : goto isolate_fail_put;
996 :
997 0 : lruvec = mem_cgroup_page_lruvec(page, pgdat);
998 :
999 : /* If we already hold the lock, we can skip some rechecking */
1000 0 : if (lruvec != locked) {
1001 0 : if (locked)
1002 0 : unlock_page_lruvec_irqrestore(locked, flags);
1003 :
1004 0 : compact_lock_irqsave(&lruvec->lru_lock, &flags, cc);
1005 0 : locked = lruvec;
1006 :
1007 0 : lruvec_memcg_debug(lruvec, page);
1008 :
1009 : /* Try get exclusive access under lock */
1010 0 : if (!skip_updated) {
1011 0 : skip_updated = true;
1012 0 : if (test_and_set_skip(cc, page, low_pfn))
1013 0 : goto isolate_abort;
1014 : }
1015 :
1016 : /*
1017 : * Page become compound since the non-locked check,
1018 : * and it's on LRU. It can only be a THP so the order
1019 : * is safe to read and it's 0 for tail pages.
1020 : */
1021 0 : if (unlikely(PageCompound(page) && !cc->alloc_contig)) {
1022 0 : low_pfn += compound_nr(page) - 1;
1023 0 : SetPageLRU(page);
1024 0 : goto isolate_fail_put;
1025 : }
1026 : }
1027 :
1028 : /* The whole page is taken off the LRU; skip the tail pages. */
1029 0 : if (PageCompound(page))
1030 0 : low_pfn += compound_nr(page) - 1;
1031 :
1032 : /* Successfully isolated */
1033 0 : del_page_from_lru_list(page, lruvec);
1034 0 : mod_node_page_state(page_pgdat(page),
1035 0 : NR_ISOLATED_ANON + page_is_file_lru(page),
1036 0 : thp_nr_pages(page));
1037 :
1038 0 : isolate_success:
1039 0 : list_add(&page->lru, &cc->migratepages);
1040 0 : cc->nr_migratepages += compound_nr(page);
1041 0 : nr_isolated += compound_nr(page);
1042 :
1043 : /*
1044 : * Avoid isolating too much unless this block is being
1045 : * rescanned (e.g. dirty/writeback pages, parallel allocation)
1046 : * or a lock is contended. For contention, isolate quickly to
1047 : * potentially remove one source of contention.
1048 : */
1049 0 : if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX &&
1050 0 : !cc->rescan && !cc->contended) {
1051 0 : ++low_pfn;
1052 0 : break;
1053 : }
1054 :
1055 0 : continue;
1056 :
1057 0 : isolate_fail_put:
1058 : /* Avoid potential deadlock in freeing page under lru_lock */
1059 0 : if (locked) {
1060 0 : unlock_page_lruvec_irqrestore(locked, flags);
1061 0 : locked = NULL;
1062 : }
1063 0 : put_page(page);
1064 :
1065 0 : isolate_fail:
1066 0 : if (!skip_on_failure)
1067 0 : continue;
1068 :
1069 : /*
1070 : * We have isolated some pages, but then failed. Release them
1071 : * instead of migrating, as we cannot form the cc->order buddy
1072 : * page anyway.
1073 : */
1074 0 : if (nr_isolated) {
1075 0 : if (locked) {
1076 0 : unlock_page_lruvec_irqrestore(locked, flags);
1077 0 : locked = NULL;
1078 : }
1079 0 : putback_movable_pages(&cc->migratepages);
1080 0 : cc->nr_migratepages = 0;
1081 0 : nr_isolated = 0;
1082 : }
1083 :
1084 0 : if (low_pfn < next_skip_pfn) {
1085 0 : low_pfn = next_skip_pfn - 1;
1086 : /*
1087 : * The check near the loop beginning would have updated
1088 : * next_skip_pfn too, but this is a bit simpler.
1089 : */
1090 0 : next_skip_pfn += 1UL << cc->order;
1091 : }
1092 : }
1093 :
1094 : /*
1095 : * The PageBuddy() check could have potentially brought us outside
1096 : * the range to be scanned.
1097 : */
1098 0 : if (unlikely(low_pfn > end_pfn))
1099 0 : low_pfn = end_pfn;
1100 :
1101 : page = NULL;
1102 :
1103 0 : isolate_abort:
1104 0 : if (locked)
1105 0 : unlock_page_lruvec_irqrestore(locked, flags);
1106 0 : if (page) {
1107 0 : SetPageLRU(page);
1108 0 : put_page(page);
1109 : }
1110 :
1111 : /*
1112 : * Updated the cached scanner pfn once the pageblock has been scanned
1113 : * Pages will either be migrated in which case there is no point
1114 : * scanning in the near future or migration failed in which case the
1115 : * failure reason may persist. The block is marked for skipping if
1116 : * there were no pages isolated in the block or if the block is
1117 : * rescanned twice in a row.
1118 : */
1119 0 : if (low_pfn == end_pfn && (!nr_isolated || cc->rescan)) {
1120 0 : if (valid_page && !skip_updated)
1121 0 : set_pageblock_skip(valid_page);
1122 0 : update_cached_migrate(cc, low_pfn);
1123 : }
1124 :
1125 0 : trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn,
1126 : nr_scanned, nr_isolated);
1127 :
1128 0 : fatal_pending:
1129 0 : cc->total_migrate_scanned += nr_scanned;
1130 0 : if (nr_isolated)
1131 0 : count_compact_events(COMPACTISOLATED, nr_isolated);
1132 :
1133 : return low_pfn;
1134 : }
1135 :
1136 : /**
1137 : * isolate_migratepages_range() - isolate migrate-able pages in a PFN range
1138 : * @cc: Compaction control structure.
1139 : * @start_pfn: The first PFN to start isolating.
1140 : * @end_pfn: The one-past-last PFN.
1141 : *
1142 : * Returns zero if isolation fails fatally due to e.g. pending signal.
1143 : * Otherwise, function returns one-past-the-last PFN of isolated page
1144 : * (which may be greater than end_pfn if end fell in a middle of a THP page).
1145 : */
1146 : unsigned long
1147 0 : isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
1148 : unsigned long end_pfn)
1149 : {
1150 0 : unsigned long pfn, block_start_pfn, block_end_pfn;
1151 :
1152 : /* Scan block by block. First and last block may be incomplete */
1153 0 : pfn = start_pfn;
1154 0 : block_start_pfn = pageblock_start_pfn(pfn);
1155 0 : if (block_start_pfn < cc->zone->zone_start_pfn)
1156 : block_start_pfn = cc->zone->zone_start_pfn;
1157 0 : block_end_pfn = pageblock_end_pfn(pfn);
1158 :
1159 0 : for (; pfn < end_pfn; pfn = block_end_pfn,
1160 0 : block_start_pfn = block_end_pfn,
1161 0 : block_end_pfn += pageblock_nr_pages) {
1162 :
1163 0 : block_end_pfn = min(block_end_pfn, end_pfn);
1164 :
1165 0 : if (!pageblock_pfn_to_page(block_start_pfn,
1166 : block_end_pfn, cc->zone))
1167 0 : continue;
1168 :
1169 0 : pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
1170 : ISOLATE_UNEVICTABLE);
1171 :
1172 0 : if (!pfn)
1173 : break;
1174 :
1175 0 : if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX)
1176 : break;
1177 : }
1178 :
1179 0 : return pfn;
1180 : }
1181 :
1182 : #endif /* CONFIG_COMPACTION || CONFIG_CMA */
1183 : #ifdef CONFIG_COMPACTION
1184 :
1185 0 : static bool suitable_migration_source(struct compact_control *cc,
1186 : struct page *page)
1187 : {
1188 0 : int block_mt;
1189 :
1190 0 : if (pageblock_skip_persistent(page))
1191 : return false;
1192 :
1193 0 : if ((cc->mode != MIGRATE_ASYNC) || !cc->direct_compaction)
1194 : return true;
1195 :
1196 0 : block_mt = get_pageblock_migratetype(page);
1197 :
1198 0 : if (cc->migratetype == MIGRATE_MOVABLE)
1199 0 : return is_migrate_movable(block_mt);
1200 : else
1201 0 : return block_mt == cc->migratetype;
1202 : }
1203 :
1204 : /* Returns true if the page is within a block suitable for migration to */
1205 0 : static bool suitable_migration_target(struct compact_control *cc,
1206 : struct page *page)
1207 : {
1208 : /* If the page is a large free page, then disallow migration */
1209 0 : if (PageBuddy(page)) {
1210 : /*
1211 : * We are checking page_order without zone->lock taken. But
1212 : * the only small danger is that we skip a potentially suitable
1213 : * pageblock, so it's not worth to check order for valid range.
1214 : */
1215 0 : if (buddy_order_unsafe(page) >= pageblock_order)
1216 : return false;
1217 : }
1218 :
1219 0 : if (cc->ignore_block_suitable)
1220 : return true;
1221 :
1222 : /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
1223 0 : if (is_migrate_movable(get_pageblock_migratetype(page)))
1224 0 : return true;
1225 :
1226 : /* Otherwise skip the block */
1227 : return false;
1228 : }
1229 :
1230 : static inline unsigned int
1231 0 : freelist_scan_limit(struct compact_control *cc)
1232 : {
1233 0 : unsigned short shift = BITS_PER_LONG - 1;
1234 :
1235 0 : return (COMPACT_CLUSTER_MAX >> min(shift, cc->fast_search_fail)) + 1;
1236 : }
1237 :
1238 : /*
1239 : * Test whether the free scanner has reached the same or lower pageblock than
1240 : * the migration scanner, and compaction should thus terminate.
1241 : */
1242 0 : static inline bool compact_scanners_met(struct compact_control *cc)
1243 : {
1244 0 : return (cc->free_pfn >> pageblock_order)
1245 0 : <= (cc->migrate_pfn >> pageblock_order);
1246 : }
1247 :
1248 : /*
1249 : * Used when scanning for a suitable migration target which scans freelists
1250 : * in reverse. Reorders the list such as the unscanned pages are scanned
1251 : * first on the next iteration of the free scanner
1252 : */
1253 : static void
1254 0 : move_freelist_head(struct list_head *freelist, struct page *freepage)
1255 : {
1256 0 : LIST_HEAD(sublist);
1257 :
1258 0 : if (!list_is_last(freelist, &freepage->lru)) {
1259 0 : list_cut_before(&sublist, freelist, &freepage->lru);
1260 0 : if (!list_empty(&sublist))
1261 0 : list_splice_tail(&sublist, freelist);
1262 : }
1263 0 : }
1264 :
1265 : /*
1266 : * Similar to move_freelist_head except used by the migration scanner
1267 : * when scanning forward. It's possible for these list operations to
1268 : * move against each other if they search the free list exactly in
1269 : * lockstep.
1270 : */
1271 : static void
1272 0 : move_freelist_tail(struct list_head *freelist, struct page *freepage)
1273 : {
1274 0 : LIST_HEAD(sublist);
1275 :
1276 0 : if (!list_is_first(freelist, &freepage->lru)) {
1277 0 : list_cut_position(&sublist, freelist, &freepage->lru);
1278 0 : if (!list_empty(&sublist))
1279 0 : list_splice_tail(&sublist, freelist);
1280 : }
1281 0 : }
1282 :
1283 : static void
1284 0 : fast_isolate_around(struct compact_control *cc, unsigned long pfn, unsigned long nr_isolated)
1285 : {
1286 0 : unsigned long start_pfn, end_pfn;
1287 0 : struct page *page;
1288 :
1289 : /* Do not search around if there are enough pages already */
1290 0 : if (cc->nr_freepages >= cc->nr_migratepages)
1291 0 : return;
1292 :
1293 : /* Minimise scanning during async compaction */
1294 0 : if (cc->direct_compaction && cc->mode == MIGRATE_ASYNC)
1295 : return;
1296 :
1297 : /* Pageblock boundaries */
1298 0 : start_pfn = max(pageblock_start_pfn(pfn), cc->zone->zone_start_pfn);
1299 0 : end_pfn = min(pageblock_end_pfn(pfn), zone_end_pfn(cc->zone));
1300 :
1301 0 : page = pageblock_pfn_to_page(start_pfn, end_pfn, cc->zone);
1302 0 : if (!page)
1303 : return;
1304 :
1305 : /* Scan before */
1306 0 : if (start_pfn != pfn) {
1307 0 : isolate_freepages_block(cc, &start_pfn, pfn, &cc->freepages, 1, false);
1308 0 : if (cc->nr_freepages >= cc->nr_migratepages)
1309 : return;
1310 : }
1311 :
1312 : /* Scan after */
1313 0 : start_pfn = pfn + nr_isolated;
1314 0 : if (start_pfn < end_pfn)
1315 0 : isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false);
1316 :
1317 : /* Skip this pageblock in the future as it's full or nearly full */
1318 0 : if (cc->nr_freepages < cc->nr_migratepages)
1319 0 : set_pageblock_skip(page);
1320 : }
1321 :
1322 : /* Search orders in round-robin fashion */
1323 0 : static int next_search_order(struct compact_control *cc, int order)
1324 : {
1325 0 : order--;
1326 0 : if (order < 0)
1327 0 : order = cc->order - 1;
1328 :
1329 : /* Search wrapped around? */
1330 0 : if (order == cc->search_order) {
1331 0 : cc->search_order--;
1332 0 : if (cc->search_order < 0)
1333 0 : cc->search_order = cc->order - 1;
1334 0 : return -1;
1335 : }
1336 :
1337 : return order;
1338 : }
1339 :
1340 : static unsigned long
1341 0 : fast_isolate_freepages(struct compact_control *cc)
1342 : {
1343 0 : unsigned int limit = min(1U, freelist_scan_limit(cc) >> 1);
1344 0 : unsigned int nr_scanned = 0;
1345 0 : unsigned long low_pfn, min_pfn, highest = 0;
1346 0 : unsigned long nr_isolated = 0;
1347 0 : unsigned long distance;
1348 0 : struct page *page = NULL;
1349 0 : bool scan_start = false;
1350 0 : int order;
1351 :
1352 : /* Full compaction passes in a negative order */
1353 0 : if (cc->order <= 0)
1354 0 : return cc->free_pfn;
1355 :
1356 : /*
1357 : * If starting the scan, use a deeper search and use the highest
1358 : * PFN found if a suitable one is not found.
1359 : */
1360 0 : if (cc->free_pfn >= cc->zone->compact_init_free_pfn) {
1361 0 : limit = pageblock_nr_pages >> 1;
1362 0 : scan_start = true;
1363 : }
1364 :
1365 : /*
1366 : * Preferred point is in the top quarter of the scan space but take
1367 : * a pfn from the top half if the search is problematic.
1368 : */
1369 0 : distance = (cc->free_pfn - cc->migrate_pfn);
1370 0 : low_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 2));
1371 0 : min_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 1));
1372 :
1373 0 : if (WARN_ON_ONCE(min_pfn > low_pfn))
1374 0 : low_pfn = min_pfn;
1375 :
1376 : /*
1377 : * Search starts from the last successful isolation order or the next
1378 : * order to search after a previous failure
1379 : */
1380 0 : cc->search_order = min_t(unsigned int, cc->order - 1, cc->search_order);
1381 :
1382 0 : for (order = cc->search_order;
1383 0 : !page && order >= 0;
1384 0 : order = next_search_order(cc, order)) {
1385 0 : struct free_area *area = &cc->zone->free_area[order];
1386 0 : struct list_head *freelist;
1387 0 : struct page *freepage;
1388 0 : unsigned long flags;
1389 0 : unsigned int order_scanned = 0;
1390 0 : unsigned long high_pfn = 0;
1391 :
1392 0 : if (!area->nr_free)
1393 0 : continue;
1394 :
1395 0 : spin_lock_irqsave(&cc->zone->lock, flags);
1396 0 : freelist = &area->free_list[MIGRATE_MOVABLE];
1397 0 : list_for_each_entry_reverse(freepage, freelist, lru) {
1398 0 : unsigned long pfn;
1399 :
1400 0 : order_scanned++;
1401 0 : nr_scanned++;
1402 0 : pfn = page_to_pfn(freepage);
1403 :
1404 0 : if (pfn >= highest)
1405 0 : highest = max(pageblock_start_pfn(pfn),
1406 : cc->zone->zone_start_pfn);
1407 :
1408 0 : if (pfn >= low_pfn) {
1409 0 : cc->fast_search_fail = 0;
1410 0 : cc->search_order = order;
1411 0 : page = freepage;
1412 0 : break;
1413 : }
1414 :
1415 0 : if (pfn >= min_pfn && pfn > high_pfn) {
1416 0 : high_pfn = pfn;
1417 :
1418 : /* Shorten the scan if a candidate is found */
1419 0 : limit >>= 1;
1420 : }
1421 :
1422 0 : if (order_scanned >= limit)
1423 : break;
1424 : }
1425 :
1426 : /* Use a minimum pfn if a preferred one was not found */
1427 0 : if (!page && high_pfn) {
1428 0 : page = pfn_to_page(high_pfn);
1429 :
1430 : /* Update freepage for the list reorder below */
1431 0 : freepage = page;
1432 : }
1433 :
1434 : /* Reorder to so a future search skips recent pages */
1435 0 : move_freelist_head(freelist, freepage);
1436 :
1437 : /* Isolate the page if available */
1438 0 : if (page) {
1439 0 : if (__isolate_free_page(page, order)) {
1440 0 : set_page_private(page, order);
1441 0 : nr_isolated = 1 << order;
1442 0 : cc->nr_freepages += nr_isolated;
1443 0 : list_add_tail(&page->lru, &cc->freepages);
1444 0 : count_compact_events(COMPACTISOLATED, nr_isolated);
1445 : } else {
1446 : /* If isolation fails, abort the search */
1447 0 : order = cc->search_order + 1;
1448 0 : page = NULL;
1449 : }
1450 : }
1451 :
1452 0 : spin_unlock_irqrestore(&cc->zone->lock, flags);
1453 :
1454 : /*
1455 : * Smaller scan on next order so the total scan ig related
1456 : * to freelist_scan_limit.
1457 : */
1458 0 : if (order_scanned >= limit)
1459 0 : limit = min(1U, limit >> 1);
1460 : }
1461 :
1462 0 : if (!page) {
1463 0 : cc->fast_search_fail++;
1464 0 : if (scan_start) {
1465 : /*
1466 : * Use the highest PFN found above min. If one was
1467 : * not found, be pessimistic for direct compaction
1468 : * and use the min mark.
1469 : */
1470 0 : if (highest) {
1471 0 : page = pfn_to_page(highest);
1472 0 : cc->free_pfn = highest;
1473 : } else {
1474 0 : if (cc->direct_compaction && pfn_valid(min_pfn)) {
1475 0 : page = pageblock_pfn_to_page(min_pfn,
1476 0 : min(pageblock_end_pfn(min_pfn),
1477 : zone_end_pfn(cc->zone)),
1478 : cc->zone);
1479 0 : cc->free_pfn = min_pfn;
1480 : }
1481 : }
1482 : }
1483 : }
1484 :
1485 0 : if (highest && highest >= cc->zone->compact_cached_free_pfn) {
1486 0 : highest -= pageblock_nr_pages;
1487 0 : cc->zone->compact_cached_free_pfn = highest;
1488 : }
1489 :
1490 0 : cc->total_free_scanned += nr_scanned;
1491 0 : if (!page)
1492 0 : return cc->free_pfn;
1493 :
1494 0 : low_pfn = page_to_pfn(page);
1495 0 : fast_isolate_around(cc, low_pfn, nr_isolated);
1496 0 : return low_pfn;
1497 : }
1498 :
1499 : /*
1500 : * Based on information in the current compact_control, find blocks
1501 : * suitable for isolating free pages from and then isolate them.
1502 : */
1503 0 : static void isolate_freepages(struct compact_control *cc)
1504 : {
1505 0 : struct zone *zone = cc->zone;
1506 0 : struct page *page;
1507 0 : unsigned long block_start_pfn; /* start of current pageblock */
1508 0 : unsigned long isolate_start_pfn; /* exact pfn we start at */
1509 0 : unsigned long block_end_pfn; /* end of current pageblock */
1510 0 : unsigned long low_pfn; /* lowest pfn scanner is able to scan */
1511 0 : struct list_head *freelist = &cc->freepages;
1512 0 : unsigned int stride;
1513 :
1514 : /* Try a small search of the free lists for a candidate */
1515 0 : isolate_start_pfn = fast_isolate_freepages(cc);
1516 0 : if (cc->nr_freepages)
1517 0 : goto splitmap;
1518 :
1519 : /*
1520 : * Initialise the free scanner. The starting point is where we last
1521 : * successfully isolated from, zone-cached value, or the end of the
1522 : * zone when isolating for the first time. For looping we also need
1523 : * this pfn aligned down to the pageblock boundary, because we do
1524 : * block_start_pfn -= pageblock_nr_pages in the for loop.
1525 : * For ending point, take care when isolating in last pageblock of a
1526 : * zone which ends in the middle of a pageblock.
1527 : * The low boundary is the end of the pageblock the migration scanner
1528 : * is using.
1529 : */
1530 0 : isolate_start_pfn = cc->free_pfn;
1531 0 : block_start_pfn = pageblock_start_pfn(isolate_start_pfn);
1532 0 : block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
1533 : zone_end_pfn(zone));
1534 0 : low_pfn = pageblock_end_pfn(cc->migrate_pfn);
1535 0 : stride = cc->mode == MIGRATE_ASYNC ? COMPACT_CLUSTER_MAX : 1;
1536 :
1537 : /*
1538 : * Isolate free pages until enough are available to migrate the
1539 : * pages on cc->migratepages. We stop searching if the migrate
1540 : * and free page scanners meet or enough free pages are isolated.
1541 : */
1542 0 : for (; block_start_pfn >= low_pfn;
1543 0 : block_end_pfn = block_start_pfn,
1544 0 : block_start_pfn -= pageblock_nr_pages,
1545 0 : isolate_start_pfn = block_start_pfn) {
1546 0 : unsigned long nr_isolated;
1547 :
1548 : /*
1549 : * This can iterate a massively long zone without finding any
1550 : * suitable migration targets, so periodically check resched.
1551 : */
1552 0 : if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)))
1553 0 : cond_resched();
1554 :
1555 0 : page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
1556 : zone);
1557 0 : if (!page)
1558 0 : continue;
1559 :
1560 : /* Check the block is suitable for migration */
1561 0 : if (!suitable_migration_target(cc, page))
1562 0 : continue;
1563 :
1564 : /* If isolation recently failed, do not retry */
1565 0 : if (!isolation_suitable(cc, page))
1566 0 : continue;
1567 :
1568 : /* Found a block suitable for isolating free pages from. */
1569 0 : nr_isolated = isolate_freepages_block(cc, &isolate_start_pfn,
1570 : block_end_pfn, freelist, stride, false);
1571 :
1572 : /* Update the skip hint if the full pageblock was scanned */
1573 0 : if (isolate_start_pfn == block_end_pfn)
1574 0 : update_pageblock_skip(cc, page, block_start_pfn);
1575 :
1576 : /* Are enough freepages isolated? */
1577 0 : if (cc->nr_freepages >= cc->nr_migratepages) {
1578 0 : if (isolate_start_pfn >= block_end_pfn) {
1579 : /*
1580 : * Restart at previous pageblock if more
1581 : * freepages can be isolated next time.
1582 : */
1583 0 : isolate_start_pfn =
1584 0 : block_start_pfn - pageblock_nr_pages;
1585 : }
1586 : break;
1587 0 : } else if (isolate_start_pfn < block_end_pfn) {
1588 : /*
1589 : * If isolation failed early, do not continue
1590 : * needlessly.
1591 : */
1592 : break;
1593 : }
1594 :
1595 : /* Adjust stride depending on isolation */
1596 0 : if (nr_isolated) {
1597 0 : stride = 1;
1598 0 : continue;
1599 : }
1600 0 : stride = min_t(unsigned int, COMPACT_CLUSTER_MAX, stride << 1);
1601 : }
1602 :
1603 : /*
1604 : * Record where the free scanner will restart next time. Either we
1605 : * broke from the loop and set isolate_start_pfn based on the last
1606 : * call to isolate_freepages_block(), or we met the migration scanner
1607 : * and the loop terminated due to isolate_start_pfn < low_pfn
1608 : */
1609 0 : cc->free_pfn = isolate_start_pfn;
1610 :
1611 0 : splitmap:
1612 : /* __isolate_free_page() does not map the pages */
1613 0 : split_map_pages(freelist);
1614 0 : }
1615 :
1616 : /*
1617 : * This is a migrate-callback that "allocates" freepages by taking pages
1618 : * from the isolated freelists in the block we are migrating to.
1619 : */
1620 0 : static struct page *compaction_alloc(struct page *migratepage,
1621 : unsigned long data)
1622 : {
1623 0 : struct compact_control *cc = (struct compact_control *)data;
1624 0 : struct page *freepage;
1625 :
1626 0 : if (list_empty(&cc->freepages)) {
1627 0 : isolate_freepages(cc);
1628 :
1629 0 : if (list_empty(&cc->freepages))
1630 : return NULL;
1631 : }
1632 :
1633 0 : freepage = list_entry(cc->freepages.next, struct page, lru);
1634 0 : list_del(&freepage->lru);
1635 0 : cc->nr_freepages--;
1636 :
1637 0 : return freepage;
1638 : }
1639 :
1640 : /*
1641 : * This is a migrate-callback that "frees" freepages back to the isolated
1642 : * freelist. All pages on the freelist are from the same zone, so there is no
1643 : * special handling needed for NUMA.
1644 : */
1645 0 : static void compaction_free(struct page *page, unsigned long data)
1646 : {
1647 0 : struct compact_control *cc = (struct compact_control *)data;
1648 :
1649 0 : list_add(&page->lru, &cc->freepages);
1650 0 : cc->nr_freepages++;
1651 0 : }
1652 :
1653 : /* possible outcome of isolate_migratepages */
1654 : typedef enum {
1655 : ISOLATE_ABORT, /* Abort compaction now */
1656 : ISOLATE_NONE, /* No pages isolated, continue scanning */
1657 : ISOLATE_SUCCESS, /* Pages isolated, migrate */
1658 : } isolate_migrate_t;
1659 :
1660 : /*
1661 : * Allow userspace to control policy on scanning the unevictable LRU for
1662 : * compactable pages.
1663 : */
1664 : #ifdef CONFIG_PREEMPT_RT
1665 : int sysctl_compact_unevictable_allowed __read_mostly = 0;
1666 : #else
1667 : int sysctl_compact_unevictable_allowed __read_mostly = 1;
1668 : #endif
1669 :
1670 : static inline void
1671 0 : update_fast_start_pfn(struct compact_control *cc, unsigned long pfn)
1672 : {
1673 0 : if (cc->fast_start_pfn == ULONG_MAX)
1674 : return;
1675 :
1676 0 : if (!cc->fast_start_pfn)
1677 0 : cc->fast_start_pfn = pfn;
1678 :
1679 0 : cc->fast_start_pfn = min(cc->fast_start_pfn, pfn);
1680 : }
1681 :
1682 : static inline unsigned long
1683 0 : reinit_migrate_pfn(struct compact_control *cc)
1684 : {
1685 0 : if (!cc->fast_start_pfn || cc->fast_start_pfn == ULONG_MAX)
1686 0 : return cc->migrate_pfn;
1687 :
1688 0 : cc->migrate_pfn = cc->fast_start_pfn;
1689 0 : cc->fast_start_pfn = ULONG_MAX;
1690 :
1691 0 : return cc->migrate_pfn;
1692 : }
1693 :
1694 : /*
1695 : * Briefly search the free lists for a migration source that already has
1696 : * some free pages to reduce the number of pages that need migration
1697 : * before a pageblock is free.
1698 : */
1699 0 : static unsigned long fast_find_migrateblock(struct compact_control *cc)
1700 : {
1701 0 : unsigned int limit = freelist_scan_limit(cc);
1702 0 : unsigned int nr_scanned = 0;
1703 0 : unsigned long distance;
1704 0 : unsigned long pfn = cc->migrate_pfn;
1705 0 : unsigned long high_pfn;
1706 0 : int order;
1707 0 : bool found_block = false;
1708 :
1709 : /* Skip hints are relied on to avoid repeats on the fast search */
1710 0 : if (cc->ignore_skip_hint)
1711 : return pfn;
1712 :
1713 : /*
1714 : * If the migrate_pfn is not at the start of a zone or the start
1715 : * of a pageblock then assume this is a continuation of a previous
1716 : * scan restarted due to COMPACT_CLUSTER_MAX.
1717 : */
1718 0 : if (pfn != cc->zone->zone_start_pfn && pfn != pageblock_start_pfn(pfn))
1719 : return pfn;
1720 :
1721 : /*
1722 : * For smaller orders, just linearly scan as the number of pages
1723 : * to migrate should be relatively small and does not necessarily
1724 : * justify freeing up a large block for a small allocation.
1725 : */
1726 0 : if (cc->order <= PAGE_ALLOC_COSTLY_ORDER)
1727 : return pfn;
1728 :
1729 : /*
1730 : * Only allow kcompactd and direct requests for movable pages to
1731 : * quickly clear out a MOVABLE pageblock for allocation. This
1732 : * reduces the risk that a large movable pageblock is freed for
1733 : * an unmovable/reclaimable small allocation.
1734 : */
1735 0 : if (cc->direct_compaction && cc->migratetype != MIGRATE_MOVABLE)
1736 : return pfn;
1737 :
1738 : /*
1739 : * When starting the migration scanner, pick any pageblock within the
1740 : * first half of the search space. Otherwise try and pick a pageblock
1741 : * within the first eighth to reduce the chances that a migration
1742 : * target later becomes a source.
1743 : */
1744 0 : distance = (cc->free_pfn - cc->migrate_pfn) >> 1;
1745 0 : if (cc->migrate_pfn != cc->zone->zone_start_pfn)
1746 0 : distance >>= 2;
1747 0 : high_pfn = pageblock_start_pfn(cc->migrate_pfn + distance);
1748 :
1749 0 : for (order = cc->order - 1;
1750 0 : order >= PAGE_ALLOC_COSTLY_ORDER && !found_block && nr_scanned < limit;
1751 0 : order--) {
1752 0 : struct free_area *area = &cc->zone->free_area[order];
1753 0 : struct list_head *freelist;
1754 0 : unsigned long flags;
1755 0 : struct page *freepage;
1756 :
1757 0 : if (!area->nr_free)
1758 0 : continue;
1759 :
1760 0 : spin_lock_irqsave(&cc->zone->lock, flags);
1761 0 : freelist = &area->free_list[MIGRATE_MOVABLE];
1762 0 : list_for_each_entry(freepage, freelist, lru) {
1763 0 : unsigned long free_pfn;
1764 :
1765 0 : if (nr_scanned++ >= limit) {
1766 0 : move_freelist_tail(freelist, freepage);
1767 0 : break;
1768 : }
1769 :
1770 0 : free_pfn = page_to_pfn(freepage);
1771 0 : if (free_pfn < high_pfn) {
1772 : /*
1773 : * Avoid if skipped recently. Ideally it would
1774 : * move to the tail but even safe iteration of
1775 : * the list assumes an entry is deleted, not
1776 : * reordered.
1777 : */
1778 0 : if (get_pageblock_skip(freepage))
1779 0 : continue;
1780 :
1781 : /* Reorder to so a future search skips recent pages */
1782 0 : move_freelist_tail(freelist, freepage);
1783 :
1784 0 : update_fast_start_pfn(cc, free_pfn);
1785 0 : pfn = pageblock_start_pfn(free_pfn);
1786 0 : cc->fast_search_fail = 0;
1787 0 : found_block = true;
1788 0 : set_pageblock_skip(freepage);
1789 0 : break;
1790 : }
1791 : }
1792 0 : spin_unlock_irqrestore(&cc->zone->lock, flags);
1793 : }
1794 :
1795 0 : cc->total_migrate_scanned += nr_scanned;
1796 :
1797 : /*
1798 : * If fast scanning failed then use a cached entry for a page block
1799 : * that had free pages as the basis for starting a linear scan.
1800 : */
1801 0 : if (!found_block) {
1802 0 : cc->fast_search_fail++;
1803 0 : pfn = reinit_migrate_pfn(cc);
1804 : }
1805 : return pfn;
1806 : }
1807 :
1808 : /*
1809 : * Isolate all pages that can be migrated from the first suitable block,
1810 : * starting at the block pointed to by the migrate scanner pfn within
1811 : * compact_control.
1812 : */
1813 0 : static isolate_migrate_t isolate_migratepages(struct compact_control *cc)
1814 : {
1815 0 : unsigned long block_start_pfn;
1816 0 : unsigned long block_end_pfn;
1817 0 : unsigned long low_pfn;
1818 0 : struct page *page;
1819 0 : const isolate_mode_t isolate_mode =
1820 0 : (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
1821 0 : (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0);
1822 0 : bool fast_find_block;
1823 :
1824 : /*
1825 : * Start at where we last stopped, or beginning of the zone as
1826 : * initialized by compact_zone(). The first failure will use
1827 : * the lowest PFN as the starting point for linear scanning.
1828 : */
1829 0 : low_pfn = fast_find_migrateblock(cc);
1830 0 : block_start_pfn = pageblock_start_pfn(low_pfn);
1831 0 : if (block_start_pfn < cc->zone->zone_start_pfn)
1832 : block_start_pfn = cc->zone->zone_start_pfn;
1833 :
1834 : /*
1835 : * fast_find_migrateblock marks a pageblock skipped so to avoid
1836 : * the isolation_suitable check below, check whether the fast
1837 : * search was successful.
1838 : */
1839 0 : fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail;
1840 :
1841 : /* Only scan within a pageblock boundary */
1842 0 : block_end_pfn = pageblock_end_pfn(low_pfn);
1843 :
1844 : /*
1845 : * Iterate over whole pageblocks until we find the first suitable.
1846 : * Do not cross the free scanner.
1847 : */
1848 0 : for (; block_end_pfn <= cc->free_pfn;
1849 0 : fast_find_block = false,
1850 0 : low_pfn = block_end_pfn,
1851 0 : block_start_pfn = block_end_pfn,
1852 0 : block_end_pfn += pageblock_nr_pages) {
1853 :
1854 : /*
1855 : * This can potentially iterate a massively long zone with
1856 : * many pageblocks unsuitable, so periodically check if we
1857 : * need to schedule.
1858 : */
1859 0 : if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)))
1860 0 : cond_resched();
1861 :
1862 0 : page = pageblock_pfn_to_page(block_start_pfn,
1863 : block_end_pfn, cc->zone);
1864 0 : if (!page)
1865 0 : continue;
1866 :
1867 : /*
1868 : * If isolation recently failed, do not retry. Only check the
1869 : * pageblock once. COMPACT_CLUSTER_MAX causes a pageblock
1870 : * to be visited multiple times. Assume skip was checked
1871 : * before making it "skip" so other compaction instances do
1872 : * not scan the same block.
1873 : */
1874 0 : if (IS_ALIGNED(low_pfn, pageblock_nr_pages) &&
1875 0 : !fast_find_block && !isolation_suitable(cc, page))
1876 0 : continue;
1877 :
1878 : /*
1879 : * For async compaction, also only scan in MOVABLE blocks
1880 : * without huge pages. Async compaction is optimistic to see
1881 : * if the minimum amount of work satisfies the allocation.
1882 : * The cached PFN is updated as it's possible that all
1883 : * remaining blocks between source and target are unsuitable
1884 : * and the compaction scanners fail to meet.
1885 : */
1886 0 : if (!suitable_migration_source(cc, page)) {
1887 0 : update_cached_migrate(cc, block_end_pfn);
1888 0 : continue;
1889 : }
1890 :
1891 : /* Perform the isolation */
1892 0 : low_pfn = isolate_migratepages_block(cc, low_pfn,
1893 : block_end_pfn, isolate_mode);
1894 :
1895 0 : if (!low_pfn)
1896 : return ISOLATE_ABORT;
1897 :
1898 : /*
1899 : * Either we isolated something and proceed with migration. Or
1900 : * we failed and compact_zone should decide if we should
1901 : * continue or not.
1902 : */
1903 : break;
1904 : }
1905 :
1906 : /* Record where migration scanner will be restarted. */
1907 0 : cc->migrate_pfn = low_pfn;
1908 :
1909 0 : return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
1910 : }
1911 :
1912 : /*
1913 : * order == -1 is expected when compacting via
1914 : * /proc/sys/vm/compact_memory
1915 : */
1916 0 : static inline bool is_via_compact_memory(int order)
1917 : {
1918 0 : return order == -1;
1919 : }
1920 :
1921 79 : static bool kswapd_is_running(pg_data_t *pgdat)
1922 : {
1923 79 : return pgdat->kswapd && (pgdat->kswapd->state == TASK_RUNNING);
1924 : }
1925 :
1926 : /*
1927 : * A zone's fragmentation score is the external fragmentation wrt to the
1928 : * COMPACTION_HPAGE_ORDER. It returns a value in the range [0, 100].
1929 : */
1930 237 : static unsigned int fragmentation_score_zone(struct zone *zone)
1931 : {
1932 237 : return extfrag_for_order(zone, COMPACTION_HPAGE_ORDER);
1933 : }
1934 :
1935 : /*
1936 : * A weighted zone's fragmentation score is the external fragmentation
1937 : * wrt to the COMPACTION_HPAGE_ORDER scaled by the zone's size. It
1938 : * returns a value in the range [0, 100].
1939 : *
1940 : * The scaling factor ensures that proactive compaction focuses on larger
1941 : * zones like ZONE_NORMAL, rather than smaller, specialized zones like
1942 : * ZONE_DMA32. For smaller zones, the score value remains close to zero,
1943 : * and thus never exceeds the high threshold for proactive compaction.
1944 : */
1945 237 : static unsigned int fragmentation_score_zone_weighted(struct zone *zone)
1946 : {
1947 237 : unsigned long score;
1948 :
1949 237 : score = zone->present_pages * fragmentation_score_zone(zone);
1950 237 : return div64_ul(score, zone->zone_pgdat->node_present_pages + 1);
1951 : }
1952 :
1953 : /*
1954 : * The per-node proactive (background) compaction process is started by its
1955 : * corresponding kcompactd thread when the node's fragmentation score
1956 : * exceeds the high threshold. The compaction process remains active till
1957 : * the node's score falls below the low threshold, or one of the back-off
1958 : * conditions is met.
1959 : */
1960 79 : static unsigned int fragmentation_score_node(pg_data_t *pgdat)
1961 : {
1962 79 : unsigned int score = 0;
1963 79 : int zoneid;
1964 :
1965 316 : for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
1966 237 : struct zone *zone;
1967 :
1968 237 : zone = &pgdat->node_zones[zoneid];
1969 237 : score += fragmentation_score_zone_weighted(zone);
1970 : }
1971 :
1972 79 : return score;
1973 : }
1974 :
1975 79 : static unsigned int fragmentation_score_wmark(pg_data_t *pgdat, bool low)
1976 : {
1977 79 : unsigned int wmark_low;
1978 :
1979 : /*
1980 : * Cap the low watermak to avoid excessive compaction
1981 : * activity in case a user sets the proactivess tunable
1982 : * close to 100 (maximum).
1983 : */
1984 79 : wmark_low = max(100U - sysctl_compaction_proactiveness, 5U);
1985 79 : return low ? wmark_low : min(wmark_low + 10, 100U);
1986 : }
1987 :
1988 79 : static bool should_proactive_compact_node(pg_data_t *pgdat)
1989 : {
1990 79 : int wmark_high;
1991 :
1992 158 : if (!sysctl_compaction_proactiveness || kswapd_is_running(pgdat))
1993 : return false;
1994 :
1995 79 : wmark_high = fragmentation_score_wmark(pgdat, false);
1996 79 : return fragmentation_score_node(pgdat) > wmark_high;
1997 : }
1998 :
1999 0 : static enum compact_result __compact_finished(struct compact_control *cc)
2000 : {
2001 0 : unsigned int order;
2002 0 : const int migratetype = cc->migratetype;
2003 0 : int ret;
2004 :
2005 : /* Compaction run completes if the migrate and free scanner meet */
2006 0 : if (compact_scanners_met(cc)) {
2007 : /* Let the next compaction start anew. */
2008 0 : reset_cached_positions(cc->zone);
2009 :
2010 : /*
2011 : * Mark that the PG_migrate_skip information should be cleared
2012 : * by kswapd when it goes to sleep. kcompactd does not set the
2013 : * flag itself as the decision to be clear should be directly
2014 : * based on an allocation request.
2015 : */
2016 0 : if (cc->direct_compaction)
2017 0 : cc->zone->compact_blockskip_flush = true;
2018 :
2019 0 : if (cc->whole_zone)
2020 : return COMPACT_COMPLETE;
2021 : else
2022 0 : return COMPACT_PARTIAL_SKIPPED;
2023 : }
2024 :
2025 0 : if (cc->proactive_compaction) {
2026 0 : int score, wmark_low;
2027 0 : pg_data_t *pgdat;
2028 :
2029 0 : pgdat = cc->zone->zone_pgdat;
2030 0 : if (kswapd_is_running(pgdat))
2031 : return COMPACT_PARTIAL_SKIPPED;
2032 :
2033 0 : score = fragmentation_score_zone(cc->zone);
2034 0 : wmark_low = fragmentation_score_wmark(pgdat, true);
2035 :
2036 0 : if (score > wmark_low)
2037 : ret = COMPACT_CONTINUE;
2038 : else
2039 0 : ret = COMPACT_SUCCESS;
2040 :
2041 0 : goto out;
2042 : }
2043 :
2044 0 : if (is_via_compact_memory(cc->order))
2045 : return COMPACT_CONTINUE;
2046 :
2047 : /*
2048 : * Always finish scanning a pageblock to reduce the possibility of
2049 : * fallbacks in the future. This is particularly important when
2050 : * migration source is unmovable/reclaimable but it's not worth
2051 : * special casing.
2052 : */
2053 0 : if (!IS_ALIGNED(cc->migrate_pfn, pageblock_nr_pages))
2054 : return COMPACT_CONTINUE;
2055 :
2056 : /* Direct compactor: Is a suitable page free? */
2057 0 : ret = COMPACT_NO_SUITABLE_PAGE;
2058 0 : for (order = cc->order; order < MAX_ORDER; order++) {
2059 0 : struct free_area *area = &cc->zone->free_area[order];
2060 0 : bool can_steal;
2061 :
2062 : /* Job done if page is free of the right migratetype */
2063 0 : if (!free_area_empty(area, migratetype))
2064 0 : return COMPACT_SUCCESS;
2065 :
2066 : #ifdef CONFIG_CMA
2067 : /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
2068 : if (migratetype == MIGRATE_MOVABLE &&
2069 : !free_area_empty(area, MIGRATE_CMA))
2070 : return COMPACT_SUCCESS;
2071 : #endif
2072 : /*
2073 : * Job done if allocation would steal freepages from
2074 : * other migratetype buddy lists.
2075 : */
2076 0 : if (find_suitable_fallback(area, order, migratetype,
2077 : true, &can_steal) != -1) {
2078 :
2079 : /* movable pages are OK in any pageblock */
2080 0 : if (migratetype == MIGRATE_MOVABLE)
2081 : return COMPACT_SUCCESS;
2082 :
2083 : /*
2084 : * We are stealing for a non-movable allocation. Make
2085 : * sure we finish compacting the current pageblock
2086 : * first so it is as free as possible and we won't
2087 : * have to steal another one soon. This only applies
2088 : * to sync compaction, as async compaction operates
2089 : * on pageblocks of the same migratetype.
2090 : */
2091 0 : if (cc->mode == MIGRATE_ASYNC ||
2092 0 : IS_ALIGNED(cc->migrate_pfn,
2093 : pageblock_nr_pages)) {
2094 : return COMPACT_SUCCESS;
2095 : }
2096 :
2097 0 : ret = COMPACT_CONTINUE;
2098 0 : break;
2099 : }
2100 : }
2101 :
2102 0 : out:
2103 0 : if (cc->contended || fatal_signal_pending(current))
2104 : ret = COMPACT_CONTENDED;
2105 :
2106 0 : return ret;
2107 : }
2108 :
2109 0 : static enum compact_result compact_finished(struct compact_control *cc)
2110 : {
2111 0 : int ret;
2112 :
2113 0 : ret = __compact_finished(cc);
2114 0 : trace_mm_compaction_finished(cc->zone, cc->order, ret);
2115 0 : if (ret == COMPACT_NO_SUITABLE_PAGE)
2116 0 : ret = COMPACT_CONTINUE;
2117 :
2118 0 : return ret;
2119 : }
2120 :
2121 0 : static enum compact_result __compaction_suitable(struct zone *zone, int order,
2122 : unsigned int alloc_flags,
2123 : int highest_zoneidx,
2124 : unsigned long wmark_target)
2125 : {
2126 0 : unsigned long watermark;
2127 :
2128 0 : if (is_via_compact_memory(order))
2129 : return COMPACT_CONTINUE;
2130 :
2131 0 : watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
2132 : /*
2133 : * If watermarks for high-order allocation are already met, there
2134 : * should be no need for compaction at all.
2135 : */
2136 0 : if (zone_watermark_ok(zone, order, watermark, highest_zoneidx,
2137 : alloc_flags))
2138 : return COMPACT_SUCCESS;
2139 :
2140 : /*
2141 : * Watermarks for order-0 must be met for compaction to be able to
2142 : * isolate free pages for migration targets. This means that the
2143 : * watermark and alloc_flags have to match, or be more pessimistic than
2144 : * the check in __isolate_free_page(). We don't use the direct
2145 : * compactor's alloc_flags, as they are not relevant for freepage
2146 : * isolation. We however do use the direct compactor's highest_zoneidx
2147 : * to skip over zones where lowmem reserves would prevent allocation
2148 : * even if compaction succeeds.
2149 : * For costly orders, we require low watermark instead of min for
2150 : * compaction to proceed to increase its chances.
2151 : * ALLOC_CMA is used, as pages in CMA pageblocks are considered
2152 : * suitable migration targets
2153 : */
2154 0 : watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ?
2155 0 : low_wmark_pages(zone) : min_wmark_pages(zone);
2156 0 : watermark += compact_gap(order);
2157 0 : if (!__zone_watermark_ok(zone, 0, watermark, highest_zoneidx,
2158 : ALLOC_CMA, wmark_target))
2159 0 : return COMPACT_SKIPPED;
2160 :
2161 : return COMPACT_CONTINUE;
2162 : }
2163 :
2164 : /*
2165 : * compaction_suitable: Is this suitable to run compaction on this zone now?
2166 : * Returns
2167 : * COMPACT_SKIPPED - If there are too few free pages for compaction
2168 : * COMPACT_SUCCESS - If the allocation would succeed without compaction
2169 : * COMPACT_CONTINUE - If compaction should run now
2170 : */
2171 0 : enum compact_result compaction_suitable(struct zone *zone, int order,
2172 : unsigned int alloc_flags,
2173 : int highest_zoneidx)
2174 : {
2175 0 : enum compact_result ret;
2176 0 : int fragindex;
2177 :
2178 0 : ret = __compaction_suitable(zone, order, alloc_flags, highest_zoneidx,
2179 : zone_page_state(zone, NR_FREE_PAGES));
2180 : /*
2181 : * fragmentation index determines if allocation failures are due to
2182 : * low memory or external fragmentation
2183 : *
2184 : * index of -1000 would imply allocations might succeed depending on
2185 : * watermarks, but we already failed the high-order watermark check
2186 : * index towards 0 implies failure is due to lack of memory
2187 : * index towards 1000 implies failure is due to fragmentation
2188 : *
2189 : * Only compact if a failure would be due to fragmentation. Also
2190 : * ignore fragindex for non-costly orders where the alternative to
2191 : * a successful reclaim/compaction is OOM. Fragindex and the
2192 : * vm.extfrag_threshold sysctl is meant as a heuristic to prevent
2193 : * excessive compaction for costly orders, but it should not be at the
2194 : * expense of system stability.
2195 : */
2196 0 : if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) {
2197 0 : fragindex = fragmentation_index(zone, order);
2198 0 : if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
2199 0 : ret = COMPACT_NOT_SUITABLE_ZONE;
2200 : }
2201 :
2202 0 : trace_mm_compaction_suitable(zone, order, ret);
2203 0 : if (ret == COMPACT_NOT_SUITABLE_ZONE)
2204 : ret = COMPACT_SKIPPED;
2205 :
2206 0 : return ret;
2207 : }
2208 :
2209 0 : bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
2210 : int alloc_flags)
2211 : {
2212 0 : struct zone *zone;
2213 0 : struct zoneref *z;
2214 :
2215 : /*
2216 : * Make sure at least one zone would pass __compaction_suitable if we continue
2217 : * retrying the reclaim.
2218 : */
2219 0 : for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
2220 : ac->highest_zoneidx, ac->nodemask) {
2221 0 : unsigned long available;
2222 0 : enum compact_result compact_result;
2223 :
2224 : /*
2225 : * Do not consider all the reclaimable memory because we do not
2226 : * want to trash just for a single high order allocation which
2227 : * is even not guaranteed to appear even if __compaction_suitable
2228 : * is happy about the watermark check.
2229 : */
2230 0 : available = zone_reclaimable_pages(zone) / order;
2231 0 : available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
2232 0 : compact_result = __compaction_suitable(zone, order, alloc_flags,
2233 0 : ac->highest_zoneidx, available);
2234 0 : if (compact_result != COMPACT_SKIPPED)
2235 : return true;
2236 : }
2237 :
2238 : return false;
2239 : }
2240 :
2241 : static enum compact_result
2242 0 : compact_zone(struct compact_control *cc, struct capture_control *capc)
2243 : {
2244 0 : enum compact_result ret;
2245 0 : unsigned long start_pfn = cc->zone->zone_start_pfn;
2246 0 : unsigned long end_pfn = zone_end_pfn(cc->zone);
2247 0 : unsigned long last_migrated_pfn;
2248 0 : const bool sync = cc->mode != MIGRATE_ASYNC;
2249 0 : bool update_cached;
2250 :
2251 : /*
2252 : * These counters track activities during zone compaction. Initialize
2253 : * them before compacting a new zone.
2254 : */
2255 0 : cc->total_migrate_scanned = 0;
2256 0 : cc->total_free_scanned = 0;
2257 0 : cc->nr_migratepages = 0;
2258 0 : cc->nr_freepages = 0;
2259 0 : INIT_LIST_HEAD(&cc->freepages);
2260 0 : INIT_LIST_HEAD(&cc->migratepages);
2261 :
2262 0 : cc->migratetype = gfp_migratetype(cc->gfp_mask);
2263 0 : ret = compaction_suitable(cc->zone, cc->order, cc->alloc_flags,
2264 : cc->highest_zoneidx);
2265 : /* Compaction is likely to fail */
2266 0 : if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
2267 : return ret;
2268 :
2269 : /* huh, compaction_suitable is returning something unexpected */
2270 0 : VM_BUG_ON(ret != COMPACT_CONTINUE);
2271 :
2272 : /*
2273 : * Clear pageblock skip if there were failures recently and compaction
2274 : * is about to be retried after being deferred.
2275 : */
2276 0 : if (compaction_restarting(cc->zone, cc->order))
2277 0 : __reset_isolation_suitable(cc->zone);
2278 :
2279 : /*
2280 : * Setup to move all movable pages to the end of the zone. Used cached
2281 : * information on where the scanners should start (unless we explicitly
2282 : * want to compact the whole zone), but check that it is initialised
2283 : * by ensuring the values are within zone boundaries.
2284 : */
2285 0 : cc->fast_start_pfn = 0;
2286 0 : if (cc->whole_zone) {
2287 0 : cc->migrate_pfn = start_pfn;
2288 0 : cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
2289 : } else {
2290 0 : cc->migrate_pfn = cc->zone->compact_cached_migrate_pfn[sync];
2291 0 : cc->free_pfn = cc->zone->compact_cached_free_pfn;
2292 0 : if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) {
2293 0 : cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
2294 0 : cc->zone->compact_cached_free_pfn = cc->free_pfn;
2295 : }
2296 0 : if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) {
2297 0 : cc->migrate_pfn = start_pfn;
2298 0 : cc->zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
2299 0 : cc->zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
2300 : }
2301 :
2302 0 : if (cc->migrate_pfn <= cc->zone->compact_init_migrate_pfn)
2303 0 : cc->whole_zone = true;
2304 : }
2305 :
2306 0 : last_migrated_pfn = 0;
2307 :
2308 : /*
2309 : * Migrate has separate cached PFNs for ASYNC and SYNC* migration on
2310 : * the basis that some migrations will fail in ASYNC mode. However,
2311 : * if the cached PFNs match and pageblocks are skipped due to having
2312 : * no isolation candidates, then the sync state does not matter.
2313 : * Until a pageblock with isolation candidates is found, keep the
2314 : * cached PFNs in sync to avoid revisiting the same blocks.
2315 : */
2316 0 : update_cached = !sync &&
2317 0 : cc->zone->compact_cached_migrate_pfn[0] == cc->zone->compact_cached_migrate_pfn[1];
2318 :
2319 0 : trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
2320 : cc->free_pfn, end_pfn, sync);
2321 :
2322 0 : migrate_prep_local();
2323 :
2324 0 : while ((ret = compact_finished(cc)) == COMPACT_CONTINUE) {
2325 0 : int err;
2326 0 : unsigned long iteration_start_pfn = cc->migrate_pfn;
2327 :
2328 : /*
2329 : * Avoid multiple rescans which can happen if a page cannot be
2330 : * isolated (dirty/writeback in async mode) or if the migrated
2331 : * pages are being allocated before the pageblock is cleared.
2332 : * The first rescan will capture the entire pageblock for
2333 : * migration. If it fails, it'll be marked skip and scanning
2334 : * will proceed as normal.
2335 : */
2336 0 : cc->rescan = false;
2337 0 : if (pageblock_start_pfn(last_migrated_pfn) ==
2338 : pageblock_start_pfn(iteration_start_pfn)) {
2339 0 : cc->rescan = true;
2340 : }
2341 :
2342 0 : switch (isolate_migratepages(cc)) {
2343 0 : case ISOLATE_ABORT:
2344 0 : ret = COMPACT_CONTENDED;
2345 0 : putback_movable_pages(&cc->migratepages);
2346 0 : cc->nr_migratepages = 0;
2347 0 : goto out;
2348 0 : case ISOLATE_NONE:
2349 0 : if (update_cached) {
2350 0 : cc->zone->compact_cached_migrate_pfn[1] =
2351 0 : cc->zone->compact_cached_migrate_pfn[0];
2352 : }
2353 :
2354 : /*
2355 : * We haven't isolated and migrated anything, but
2356 : * there might still be unflushed migrations from
2357 : * previous cc->order aligned block.
2358 : */
2359 0 : goto check_drain;
2360 0 : case ISOLATE_SUCCESS:
2361 0 : update_cached = false;
2362 0 : last_migrated_pfn = iteration_start_pfn;
2363 : }
2364 :
2365 0 : err = migrate_pages(&cc->migratepages, compaction_alloc,
2366 : compaction_free, (unsigned long)cc, cc->mode,
2367 : MR_COMPACTION);
2368 :
2369 0 : trace_mm_compaction_migratepages(cc->nr_migratepages, err,
2370 : &cc->migratepages);
2371 :
2372 : /* All pages were either migrated or will be released */
2373 0 : cc->nr_migratepages = 0;
2374 0 : if (err) {
2375 0 : putback_movable_pages(&cc->migratepages);
2376 : /*
2377 : * migrate_pages() may return -ENOMEM when scanners meet
2378 : * and we want compact_finished() to detect it
2379 : */
2380 0 : if (err == -ENOMEM && !compact_scanners_met(cc)) {
2381 0 : ret = COMPACT_CONTENDED;
2382 0 : goto out;
2383 : }
2384 : /*
2385 : * We failed to migrate at least one page in the current
2386 : * order-aligned block, so skip the rest of it.
2387 : */
2388 0 : if (cc->direct_compaction &&
2389 0 : (cc->mode == MIGRATE_ASYNC)) {
2390 0 : cc->migrate_pfn = block_end_pfn(
2391 : cc->migrate_pfn - 1, cc->order);
2392 : /* Draining pcplists is useless in this case */
2393 0 : last_migrated_pfn = 0;
2394 : }
2395 : }
2396 :
2397 0 : check_drain:
2398 : /*
2399 : * Has the migration scanner moved away from the previous
2400 : * cc->order aligned block where we migrated from? If yes,
2401 : * flush the pages that were freed, so that they can merge and
2402 : * compact_finished() can detect immediately if allocation
2403 : * would succeed.
2404 : */
2405 0 : if (cc->order > 0 && last_migrated_pfn) {
2406 0 : unsigned long current_block_start =
2407 0 : block_start_pfn(cc->migrate_pfn, cc->order);
2408 :
2409 0 : if (last_migrated_pfn < current_block_start) {
2410 0 : lru_add_drain_cpu_zone(cc->zone);
2411 : /* No more flushing until we migrate again */
2412 0 : last_migrated_pfn = 0;
2413 : }
2414 : }
2415 :
2416 : /* Stop if a page has been captured */
2417 0 : if (capc && capc->page) {
2418 : ret = COMPACT_SUCCESS;
2419 : break;
2420 : }
2421 : }
2422 :
2423 0 : out:
2424 : /*
2425 : * Release free pages and update where the free scanner should restart,
2426 : * so we don't leave any returned pages behind in the next attempt.
2427 : */
2428 0 : if (cc->nr_freepages > 0) {
2429 0 : unsigned long free_pfn = release_freepages(&cc->freepages);
2430 :
2431 0 : cc->nr_freepages = 0;
2432 0 : VM_BUG_ON(free_pfn == 0);
2433 : /* The cached pfn is always the first in a pageblock */
2434 0 : free_pfn = pageblock_start_pfn(free_pfn);
2435 : /*
2436 : * Only go back, not forward. The cached pfn might have been
2437 : * already reset to zone end in compact_finished()
2438 : */
2439 0 : if (free_pfn > cc->zone->compact_cached_free_pfn)
2440 0 : cc->zone->compact_cached_free_pfn = free_pfn;
2441 : }
2442 :
2443 0 : count_compact_events(COMPACTMIGRATE_SCANNED, cc->total_migrate_scanned);
2444 0 : count_compact_events(COMPACTFREE_SCANNED, cc->total_free_scanned);
2445 :
2446 0 : trace_mm_compaction_end(start_pfn, cc->migrate_pfn,
2447 : cc->free_pfn, end_pfn, sync, ret);
2448 :
2449 0 : return ret;
2450 : }
2451 :
2452 0 : static enum compact_result compact_zone_order(struct zone *zone, int order,
2453 : gfp_t gfp_mask, enum compact_priority prio,
2454 : unsigned int alloc_flags, int highest_zoneidx,
2455 : struct page **capture)
2456 : {
2457 0 : enum compact_result ret;
2458 0 : struct compact_control cc = {
2459 : .order = order,
2460 : .search_order = order,
2461 : .gfp_mask = gfp_mask,
2462 : .zone = zone,
2463 : .mode = (prio == COMPACT_PRIO_ASYNC) ?
2464 0 : MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT,
2465 : .alloc_flags = alloc_flags,
2466 : .highest_zoneidx = highest_zoneidx,
2467 : .direct_compaction = true,
2468 : .whole_zone = (prio == MIN_COMPACT_PRIORITY),
2469 0 : .ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY),
2470 : .ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY)
2471 : };
2472 0 : struct capture_control capc = {
2473 : .cc = &cc,
2474 : .page = NULL,
2475 : };
2476 :
2477 : /*
2478 : * Make sure the structs are really initialized before we expose the
2479 : * capture control, in case we are interrupted and the interrupt handler
2480 : * frees a page.
2481 : */
2482 0 : barrier();
2483 0 : WRITE_ONCE(current->capture_control, &capc);
2484 :
2485 0 : ret = compact_zone(&cc, &capc);
2486 :
2487 0 : VM_BUG_ON(!list_empty(&cc.freepages));
2488 0 : VM_BUG_ON(!list_empty(&cc.migratepages));
2489 :
2490 : /*
2491 : * Make sure we hide capture control first before we read the captured
2492 : * page pointer, otherwise an interrupt could free and capture a page
2493 : * and we would leak it.
2494 : */
2495 0 : WRITE_ONCE(current->capture_control, NULL);
2496 0 : *capture = READ_ONCE(capc.page);
2497 :
2498 0 : return ret;
2499 : }
2500 :
2501 : int sysctl_extfrag_threshold = 500;
2502 :
2503 : /**
2504 : * try_to_compact_pages - Direct compact to satisfy a high-order allocation
2505 : * @gfp_mask: The GFP mask of the current allocation
2506 : * @order: The order of the current allocation
2507 : * @alloc_flags: The allocation flags of the current allocation
2508 : * @ac: The context of current allocation
2509 : * @prio: Determines how hard direct compaction should try to succeed
2510 : * @capture: Pointer to free page created by compaction will be stored here
2511 : *
2512 : * This is the main entry point for direct page compaction.
2513 : */
2514 0 : enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
2515 : unsigned int alloc_flags, const struct alloc_context *ac,
2516 : enum compact_priority prio, struct page **capture)
2517 : {
2518 0 : int may_perform_io = gfp_mask & __GFP_IO;
2519 0 : struct zoneref *z;
2520 0 : struct zone *zone;
2521 0 : enum compact_result rc = COMPACT_SKIPPED;
2522 :
2523 : /*
2524 : * Check if the GFP flags allow compaction - GFP_NOIO is really
2525 : * tricky context because the migration might require IO
2526 : */
2527 0 : if (!may_perform_io)
2528 : return COMPACT_SKIPPED;
2529 :
2530 0 : trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio);
2531 :
2532 : /* Compact each zone in the list */
2533 0 : for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
2534 : ac->highest_zoneidx, ac->nodemask) {
2535 0 : enum compact_result status;
2536 :
2537 0 : if (prio > MIN_COMPACT_PRIORITY
2538 0 : && compaction_deferred(zone, order)) {
2539 0 : rc = max_t(enum compact_result, COMPACT_DEFERRED, rc);
2540 0 : continue;
2541 : }
2542 :
2543 0 : status = compact_zone_order(zone, order, gfp_mask, prio,
2544 0 : alloc_flags, ac->highest_zoneidx, capture);
2545 0 : rc = max(status, rc);
2546 :
2547 : /* The allocation should succeed, stop compacting */
2548 0 : if (status == COMPACT_SUCCESS) {
2549 : /*
2550 : * We think the allocation will succeed in this zone,
2551 : * but it is not certain, hence the false. The caller
2552 : * will repeat this with true if allocation indeed
2553 : * succeeds in this zone.
2554 : */
2555 0 : compaction_defer_reset(zone, order, false);
2556 :
2557 0 : break;
2558 : }
2559 :
2560 0 : if (prio != COMPACT_PRIO_ASYNC && (status == COMPACT_COMPLETE ||
2561 : status == COMPACT_PARTIAL_SKIPPED))
2562 : /*
2563 : * We think that allocation won't succeed in this zone
2564 : * so we defer compaction there. If it ends up
2565 : * succeeding after all, it will be reset.
2566 : */
2567 0 : defer_compaction(zone, order);
2568 :
2569 : /*
2570 : * We might have stopped compacting due to need_resched() in
2571 : * async compaction, or due to a fatal signal detected. In that
2572 : * case do not try further zones
2573 : */
2574 0 : if ((prio == COMPACT_PRIO_ASYNC && need_resched())
2575 0 : || fatal_signal_pending(current))
2576 : break;
2577 : }
2578 :
2579 : return rc;
2580 : }
2581 :
2582 : /*
2583 : * Compact all zones within a node till each zone's fragmentation score
2584 : * reaches within proactive compaction thresholds (as determined by the
2585 : * proactiveness tunable).
2586 : *
2587 : * It is possible that the function returns before reaching score targets
2588 : * due to various back-off conditions, such as, contention on per-node or
2589 : * per-zone locks.
2590 : */
2591 0 : static void proactive_compact_node(pg_data_t *pgdat)
2592 : {
2593 0 : int zoneid;
2594 0 : struct zone *zone;
2595 0 : struct compact_control cc = {
2596 : .order = -1,
2597 : .mode = MIGRATE_SYNC_LIGHT,
2598 : .ignore_skip_hint = true,
2599 : .whole_zone = true,
2600 : .gfp_mask = GFP_KERNEL,
2601 : .proactive_compaction = true,
2602 : };
2603 :
2604 0 : for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
2605 0 : zone = &pgdat->node_zones[zoneid];
2606 0 : if (!populated_zone(zone))
2607 0 : continue;
2608 :
2609 0 : cc.zone = zone;
2610 :
2611 0 : compact_zone(&cc, NULL);
2612 :
2613 0 : VM_BUG_ON(!list_empty(&cc.freepages));
2614 0 : VM_BUG_ON(!list_empty(&cc.migratepages));
2615 : }
2616 0 : }
2617 :
2618 : /* Compact all zones within a node */
2619 0 : static void compact_node(int nid)
2620 : {
2621 0 : pg_data_t *pgdat = NODE_DATA(nid);
2622 0 : int zoneid;
2623 0 : struct zone *zone;
2624 0 : struct compact_control cc = {
2625 : .order = -1,
2626 : .mode = MIGRATE_SYNC,
2627 : .ignore_skip_hint = true,
2628 : .whole_zone = true,
2629 : .gfp_mask = GFP_KERNEL,
2630 : };
2631 :
2632 :
2633 0 : for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
2634 :
2635 0 : zone = &pgdat->node_zones[zoneid];
2636 0 : if (!populated_zone(zone))
2637 0 : continue;
2638 :
2639 0 : cc.zone = zone;
2640 :
2641 0 : compact_zone(&cc, NULL);
2642 :
2643 0 : VM_BUG_ON(!list_empty(&cc.freepages));
2644 0 : VM_BUG_ON(!list_empty(&cc.migratepages));
2645 : }
2646 0 : }
2647 :
2648 : /* Compact all nodes in the system */
2649 0 : static void compact_nodes(void)
2650 : {
2651 0 : int nid;
2652 :
2653 : /* Flush pending updates to the LRU lists */
2654 0 : lru_add_drain_all();
2655 :
2656 0 : for_each_online_node(nid)
2657 0 : compact_node(nid);
2658 0 : }
2659 :
2660 : /* The written value is actually unused, all memory is compacted */
2661 : int sysctl_compact_memory;
2662 :
2663 : /*
2664 : * Tunable for proactive compaction. It determines how
2665 : * aggressively the kernel should compact memory in the
2666 : * background. It takes values in the range [0, 100].
2667 : */
2668 : unsigned int __read_mostly sysctl_compaction_proactiveness = 20;
2669 :
2670 : /*
2671 : * This is the entry point for compacting all nodes via
2672 : * /proc/sys/vm/compact_memory
2673 : */
2674 0 : int sysctl_compaction_handler(struct ctl_table *table, int write,
2675 : void *buffer, size_t *length, loff_t *ppos)
2676 : {
2677 0 : if (write)
2678 0 : compact_nodes();
2679 :
2680 0 : return 0;
2681 : }
2682 :
2683 : #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
2684 0 : static ssize_t sysfs_compact_node(struct device *dev,
2685 : struct device_attribute *attr,
2686 : const char *buf, size_t count)
2687 : {
2688 0 : int nid = dev->id;
2689 :
2690 0 : if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
2691 : /* Flush pending updates to the LRU lists */
2692 0 : lru_add_drain_all();
2693 :
2694 0 : compact_node(nid);
2695 : }
2696 :
2697 0 : return count;
2698 : }
2699 : static DEVICE_ATTR(compact, 0200, NULL, sysfs_compact_node);
2700 :
2701 1 : int compaction_register_node(struct node *node)
2702 : {
2703 1 : return device_create_file(&node->dev, &dev_attr_compact);
2704 : }
2705 :
2706 0 : void compaction_unregister_node(struct node *node)
2707 : {
2708 0 : return device_remove_file(&node->dev, &dev_attr_compact);
2709 : }
2710 : #endif /* CONFIG_SYSFS && CONFIG_NUMA */
2711 :
2712 239 : static inline bool kcompactd_work_requested(pg_data_t *pgdat)
2713 : {
2714 239 : return pgdat->kcompactd_max_order > 0 || kthread_should_stop();
2715 : }
2716 :
2717 0 : static bool kcompactd_node_suitable(pg_data_t *pgdat)
2718 : {
2719 0 : int zoneid;
2720 0 : struct zone *zone;
2721 0 : enum zone_type highest_zoneidx = pgdat->kcompactd_highest_zoneidx;
2722 :
2723 0 : for (zoneid = 0; zoneid <= highest_zoneidx; zoneid++) {
2724 0 : zone = &pgdat->node_zones[zoneid];
2725 :
2726 0 : if (!populated_zone(zone))
2727 0 : continue;
2728 :
2729 0 : if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0,
2730 : highest_zoneidx) == COMPACT_CONTINUE)
2731 : return true;
2732 : }
2733 :
2734 : return false;
2735 : }
2736 :
2737 0 : static void kcompactd_do_work(pg_data_t *pgdat)
2738 : {
2739 : /*
2740 : * With no special task, compact all zones so that a page of requested
2741 : * order is allocatable.
2742 : */
2743 0 : int zoneid;
2744 0 : struct zone *zone;
2745 0 : struct compact_control cc = {
2746 : .order = pgdat->kcompactd_max_order,
2747 0 : .search_order = pgdat->kcompactd_max_order,
2748 0 : .highest_zoneidx = pgdat->kcompactd_highest_zoneidx,
2749 : .mode = MIGRATE_SYNC_LIGHT,
2750 : .ignore_skip_hint = false,
2751 : .gfp_mask = GFP_KERNEL,
2752 : };
2753 0 : trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order,
2754 : cc.highest_zoneidx);
2755 0 : count_compact_event(KCOMPACTD_WAKE);
2756 :
2757 0 : for (zoneid = 0; zoneid <= cc.highest_zoneidx; zoneid++) {
2758 0 : int status;
2759 :
2760 0 : zone = &pgdat->node_zones[zoneid];
2761 0 : if (!populated_zone(zone))
2762 0 : continue;
2763 :
2764 0 : if (compaction_deferred(zone, cc.order))
2765 0 : continue;
2766 :
2767 0 : if (compaction_suitable(zone, cc.order, 0, zoneid) !=
2768 : COMPACT_CONTINUE)
2769 0 : continue;
2770 :
2771 0 : if (kthread_should_stop())
2772 0 : return;
2773 :
2774 0 : cc.zone = zone;
2775 0 : status = compact_zone(&cc, NULL);
2776 :
2777 0 : if (status == COMPACT_SUCCESS) {
2778 0 : compaction_defer_reset(zone, cc.order, false);
2779 0 : } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) {
2780 : /*
2781 : * Buddy pages may become stranded on pcps that could
2782 : * otherwise coalesce on the zone's free area for
2783 : * order >= cc.order. This is ratelimited by the
2784 : * upcoming deferral.
2785 : */
2786 0 : drain_all_pages(zone);
2787 :
2788 : /*
2789 : * We use sync migration mode here, so we defer like
2790 : * sync direct compaction does.
2791 : */
2792 0 : defer_compaction(zone, cc.order);
2793 : }
2794 :
2795 0 : count_compact_events(KCOMPACTD_MIGRATE_SCANNED,
2796 0 : cc.total_migrate_scanned);
2797 0 : count_compact_events(KCOMPACTD_FREE_SCANNED,
2798 0 : cc.total_free_scanned);
2799 :
2800 0 : VM_BUG_ON(!list_empty(&cc.freepages));
2801 0 : VM_BUG_ON(!list_empty(&cc.migratepages));
2802 : }
2803 :
2804 : /*
2805 : * Regardless of success, we are done until woken up next. But remember
2806 : * the requested order/highest_zoneidx in case it was higher/tighter
2807 : * than our current ones
2808 : */
2809 0 : if (pgdat->kcompactd_max_order <= cc.order)
2810 0 : pgdat->kcompactd_max_order = 0;
2811 0 : if (pgdat->kcompactd_highest_zoneidx >= cc.highest_zoneidx)
2812 0 : pgdat->kcompactd_highest_zoneidx = pgdat->nr_zones - 1;
2813 : }
2814 :
2815 1 : void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx)
2816 : {
2817 1 : if (!order)
2818 : return;
2819 :
2820 0 : if (pgdat->kcompactd_max_order < order)
2821 0 : pgdat->kcompactd_max_order = order;
2822 :
2823 0 : if (pgdat->kcompactd_highest_zoneidx > highest_zoneidx)
2824 0 : pgdat->kcompactd_highest_zoneidx = highest_zoneidx;
2825 :
2826 : /*
2827 : * Pairs with implicit barrier in wait_event_freezable()
2828 : * such that wakeups are not missed.
2829 : */
2830 0 : if (!wq_has_sleeper(&pgdat->kcompactd_wait))
2831 : return;
2832 :
2833 0 : if (!kcompactd_node_suitable(pgdat))
2834 : return;
2835 :
2836 0 : trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order,
2837 : highest_zoneidx);
2838 0 : wake_up_interruptible(&pgdat->kcompactd_wait);
2839 : }
2840 :
2841 : /*
2842 : * The background compaction daemon, started as a kernel thread
2843 : * from the init process.
2844 : */
2845 1 : static int kcompactd(void *p)
2846 : {
2847 1 : pg_data_t *pgdat = (pg_data_t*)p;
2848 1 : struct task_struct *tsk = current;
2849 1 : unsigned int proactive_defer = 0;
2850 :
2851 1 : const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2852 :
2853 1 : if (!cpumask_empty(cpumask))
2854 1 : set_cpus_allowed_ptr(tsk, cpumask);
2855 :
2856 1 : set_freezable();
2857 :
2858 1 : pgdat->kcompactd_max_order = 0;
2859 1 : pgdat->kcompactd_highest_zoneidx = pgdat->nr_zones - 1;
2860 :
2861 81 : while (!kthread_should_stop()) {
2862 80 : unsigned long pflags;
2863 :
2864 80 : trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
2865 159 : if (wait_event_freezable_timeout(pgdat->kcompactd_wait,
2866 : kcompactd_work_requested(pgdat),
2867 : msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC))) {
2868 :
2869 0 : psi_memstall_enter(&pflags);
2870 0 : kcompactd_do_work(pgdat);
2871 0 : psi_memstall_leave(&pflags);
2872 80 : continue;
2873 : }
2874 :
2875 : /* kcompactd wait timeout */
2876 79 : if (should_proactive_compact_node(pgdat)) {
2877 0 : unsigned int prev_score, score;
2878 :
2879 0 : if (proactive_defer) {
2880 0 : proactive_defer--;
2881 0 : continue;
2882 : }
2883 0 : prev_score = fragmentation_score_node(pgdat);
2884 0 : proactive_compact_node(pgdat);
2885 0 : score = fragmentation_score_node(pgdat);
2886 : /*
2887 : * Defer proactive compaction if the fragmentation
2888 : * score did not go down i.e. no progress made.
2889 : */
2890 0 : proactive_defer = score < prev_score ?
2891 0 : 0 : 1 << COMPACT_MAX_DEFER_SHIFT;
2892 : }
2893 : }
2894 :
2895 0 : return 0;
2896 : }
2897 :
2898 : /*
2899 : * This kcompactd start function will be called by init and node-hot-add.
2900 : * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added.
2901 : */
2902 1 : int kcompactd_run(int nid)
2903 : {
2904 1 : pg_data_t *pgdat = NODE_DATA(nid);
2905 1 : int ret = 0;
2906 :
2907 1 : if (pgdat->kcompactd)
2908 : return 0;
2909 :
2910 1 : pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid);
2911 1 : if (IS_ERR(pgdat->kcompactd)) {
2912 0 : pr_err("Failed to start kcompactd on node %d\n", nid);
2913 0 : ret = PTR_ERR(pgdat->kcompactd);
2914 0 : pgdat->kcompactd = NULL;
2915 : }
2916 : return ret;
2917 : }
2918 :
2919 : /*
2920 : * Called by memory hotplug when all memory in a node is offlined. Caller must
2921 : * hold mem_hotplug_begin/end().
2922 : */
2923 0 : void kcompactd_stop(int nid)
2924 : {
2925 0 : struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd;
2926 :
2927 0 : if (kcompactd) {
2928 0 : kthread_stop(kcompactd);
2929 0 : NODE_DATA(nid)->kcompactd = NULL;
2930 : }
2931 0 : }
2932 :
2933 : /*
2934 : * It's optimal to keep kcompactd on the same CPUs as their memory, but
2935 : * not required for correctness. So if the last cpu in a node goes
2936 : * away, we get changed to run anywhere: as the first one comes back,
2937 : * restore their cpu bindings.
2938 : */
2939 0 : static int kcompactd_cpu_online(unsigned int cpu)
2940 : {
2941 0 : int nid;
2942 :
2943 0 : for_each_node_state(nid, N_MEMORY) {
2944 0 : pg_data_t *pgdat = NODE_DATA(nid);
2945 0 : const struct cpumask *mask;
2946 :
2947 0 : mask = cpumask_of_node(pgdat->node_id);
2948 :
2949 0 : if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2950 : /* One of our CPUs online: restore mask */
2951 0 : set_cpus_allowed_ptr(pgdat->kcompactd, mask);
2952 : }
2953 0 : return 0;
2954 : }
2955 :
2956 1 : static int __init kcompactd_init(void)
2957 : {
2958 1 : int nid;
2959 1 : int ret;
2960 :
2961 1 : ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
2962 : "mm/compaction:online",
2963 : kcompactd_cpu_online, NULL);
2964 1 : if (ret < 0) {
2965 0 : pr_err("kcompactd: failed to register hotplug callbacks.\n");
2966 0 : return ret;
2967 : }
2968 :
2969 2 : for_each_node_state(nid, N_MEMORY)
2970 1 : kcompactd_run(nid);
2971 : return 0;
2972 : }
2973 : subsys_initcall(kcompactd_init)
2974 :
2975 : #endif /* CONFIG_COMPACTION */
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