Branch data 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 : : }
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 : 0 : static unsigned long release_freepages(struct list_head *freelist)
54 : : {
55 : 0 : struct page *page, *next;
56 : 0 : unsigned long high_pfn = 0;
57 : :
58 [ # # ]: 0 : list_for_each_entry_safe(page, next, freelist, lru) {
59 : 0 : unsigned long pfn = page_to_pfn(page);
60 : 0 : list_del(&page->lru);
61 : 0 : __free_page(page);
62 : 0 : if (pfn > high_pfn)
63 : : high_pfn = pfn;
64 : : }
65 : :
66 : 0 : return high_pfn;
67 : : }
68 : :
69 : 0 : static void split_map_pages(struct list_head *list)
70 : : {
71 : 0 : unsigned int i, order, nr_pages;
72 : 0 : struct page *page, *next;
73 : 0 : LIST_HEAD(tmp_list);
74 : :
75 [ # # ]: 0 : list_for_each_entry_safe(page, next, list, lru) {
76 : 0 : list_del(&page->lru);
77 : :
78 : 0 : order = page_private(page);
79 : 0 : nr_pages = 1 << order;
80 : :
81 : 0 : post_alloc_hook(page, order, __GFP_MOVABLE);
82 [ # # ]: 0 : if (order)
83 : 0 : split_page(page, order);
84 : :
85 [ # # ]: 0 : for (i = 0; i < nr_pages; i++) {
86 : 0 : list_add(&page->lru, &tmp_list);
87 : 0 : page++;
88 : : }
89 : : }
90 : :
91 [ # # ]: 0 : list_splice(&tmp_list, list);
92 : 0 : }
93 : :
94 : : #ifdef CONFIG_COMPACTION
95 : :
96 : 0 : int PageMovable(struct page *page)
97 : : {
98 : 0 : struct address_space *mapping;
99 : :
100 : 0 : VM_BUG_ON_PAGE(!PageLocked(page), page);
101 [ # # ]: 0 : if (!__PageMovable(page))
102 : : return 0;
103 : :
104 : 0 : mapping = page_mapping(page);
105 [ # # # # : 0 : if (mapping && mapping->a_ops && mapping->a_ops->isolate_page)
# # ]
106 : 0 : return 1;
107 : :
108 : : return 0;
109 : : }
110 : : EXPORT_SYMBOL(PageMovable);
111 : :
112 : 0 : void __SetPageMovable(struct page *page, struct address_space *mapping)
113 : : {
114 : 0 : VM_BUG_ON_PAGE(!PageLocked(page), page);
115 : 0 : VM_BUG_ON_PAGE((unsigned long)mapping & PAGE_MAPPING_MOVABLE, page);
116 : 0 : page->mapping = (void *)((unsigned long)mapping | PAGE_MAPPING_MOVABLE);
117 : 0 : }
118 : : EXPORT_SYMBOL(__SetPageMovable);
119 : :
120 : 0 : void __ClearPageMovable(struct page *page)
121 : : {
122 : 0 : VM_BUG_ON_PAGE(!PageLocked(page), page);
123 : 0 : VM_BUG_ON_PAGE(!PageMovable(page), page);
124 : : /*
125 : : * Clear registered address_space val with keeping PAGE_MAPPING_MOVABLE
126 : : * flag so that VM can catch up released page by driver after isolation.
127 : : * With it, VM migration doesn't try to put it back.
128 : : */
129 : 0 : page->mapping = (void *)((unsigned long)page->mapping &
130 : : PAGE_MAPPING_MOVABLE);
131 : 0 : }
132 : : EXPORT_SYMBOL(__ClearPageMovable);
133 : :
134 : : /* Do not skip compaction more than 64 times */
135 : : #define COMPACT_MAX_DEFER_SHIFT 6
136 : :
137 : : /*
138 : : * Compaction is deferred when compaction fails to result in a page
139 : : * allocation success. 1 << compact_defer_limit compactions are skipped up
140 : : * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
141 : : */
142 : 0 : void defer_compaction(struct zone *zone, int order)
143 : : {
144 : 0 : zone->compact_considered = 0;
145 : 0 : zone->compact_defer_shift++;
146 : :
147 [ # # ]: 0 : if (order < zone->compact_order_failed)
148 : 0 : zone->compact_order_failed = order;
149 : :
150 [ # # ]: 0 : if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
151 : 0 : zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
152 : :
153 : 0 : trace_mm_compaction_defer_compaction(zone, order);
154 : 0 : }
155 : :
156 : : /* Returns true if compaction should be skipped this time */
157 : 0 : bool compaction_deferred(struct zone *zone, int order)
158 : : {
159 : 0 : unsigned long defer_limit = 1UL << zone->compact_defer_shift;
160 : :
161 [ # # ]: 0 : if (order < zone->compact_order_failed)
162 : : return false;
163 : :
164 : : /* Avoid possible overflow */
165 [ # # ]: 0 : if (++zone->compact_considered > defer_limit)
166 : 0 : zone->compact_considered = defer_limit;
167 : :
168 [ # # ]: 0 : if (zone->compact_considered >= defer_limit)
169 : : return false;
170 : :
171 : 0 : trace_mm_compaction_deferred(zone, order);
172 : :
173 : 0 : return true;
174 : : }
175 : :
176 : : /*
177 : : * Update defer tracking counters after successful compaction of given order,
178 : : * which means an allocation either succeeded (alloc_success == true) or is
179 : : * expected to succeed.
180 : : */
181 : 0 : void compaction_defer_reset(struct zone *zone, int order,
182 : : bool alloc_success)
183 : : {
184 [ # # ]: 0 : if (alloc_success) {
185 : 0 : zone->compact_considered = 0;
186 : 0 : zone->compact_defer_shift = 0;
187 : : }
188 [ # # ]: 0 : if (order >= zone->compact_order_failed)
189 : 0 : zone->compact_order_failed = order + 1;
190 : :
191 : 0 : trace_mm_compaction_defer_reset(zone, order);
192 : 0 : }
193 : :
194 : : /* Returns true if restarting compaction after many failures */
195 : 0 : bool compaction_restarting(struct zone *zone, int order)
196 : : {
197 [ # # ]: 0 : if (order < zone->compact_order_failed)
198 : : return false;
199 : :
200 [ # # # # ]: 0 : return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
201 [ # # # # ]: 0 : zone->compact_considered >= 1UL << zone->compact_defer_shift;
202 : : }
203 : :
204 : : /* Returns true if the pageblock should be scanned for pages to isolate. */
205 : : static inline bool isolation_suitable(struct compact_control *cc,
206 : : struct page *page)
207 : : {
208 : : if (cc->ignore_skip_hint)
209 : : return true;
210 : :
211 : : return !get_pageblock_skip(page);
212 : : }
213 : :
214 : 0 : static void reset_cached_positions(struct zone *zone)
215 : : {
216 : 0 : zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn;
217 : 0 : zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn;
218 : 0 : zone->compact_cached_free_pfn =
219 : 0 : pageblock_start_pfn(zone_end_pfn(zone) - 1);
220 : : }
221 : :
222 : : /*
223 : : * Compound pages of >= pageblock_order should consistenly be skipped until
224 : : * released. It is always pointless to compact pages of such order (if they are
225 : : * migratable), and the pageblocks they occupy cannot contain any free pages.
226 : : */
227 : 0 : static bool pageblock_skip_persistent(struct page *page)
228 : : {
229 [ # # ]: 0 : if (!PageCompound(page))
230 : : return false;
231 : :
232 [ # # ]: 0 : page = compound_head(page);
233 : :
234 [ # # ]: 0 : if (compound_order(page) >= pageblock_order)
235 : 0 : return true;
236 : :
237 : : return false;
238 : : }
239 : :
240 : : static bool
241 : 0 : __reset_isolation_pfn(struct zone *zone, unsigned long pfn, bool check_source,
242 : : bool check_target)
243 : : {
244 [ # # ]: 0 : struct page *page = pfn_to_online_page(pfn);
245 : 0 : struct page *block_page;
246 : 0 : struct page *end_page;
247 : 0 : unsigned long block_pfn;
248 : :
249 [ # # ]: 0 : if (!page)
250 : : return false;
251 [ # # ]: 0 : if (zone != page_zone(page))
252 : : return false;
253 [ # # ]: 0 : if (pageblock_skip_persistent(page))
254 : : return false;
255 : :
256 : : /*
257 : : * If skip is already cleared do no further checking once the
258 : : * restart points have been set.
259 : : */
260 [ # # # # ]: 0 : if (check_source && check_target && !get_pageblock_skip(page))
261 : : return true;
262 : :
263 : : /*
264 : : * If clearing skip for the target scanner, do not select a
265 : : * non-movable pageblock as the starting point.
266 : : */
267 [ # # # # ]: 0 : if (!check_source && check_target &&
268 : 0 : get_pageblock_migratetype(page) != MIGRATE_MOVABLE)
269 : : return false;
270 : :
271 : : /* Ensure the start of the pageblock or zone is online and valid */
272 : 0 : block_pfn = pageblock_start_pfn(pfn);
273 : 0 : block_pfn = max(block_pfn, zone->zone_start_pfn);
274 [ # # ]: 0 : block_page = pfn_to_online_page(block_pfn);
275 [ # # ]: 0 : if (block_page) {
276 : 0 : page = block_page;
277 : 0 : pfn = block_pfn;
278 : : }
279 : :
280 : : /* Ensure the end of the pageblock or zone is online and valid */
281 : 0 : block_pfn = pageblock_end_pfn(pfn) - 1;
282 : 0 : block_pfn = min(block_pfn, zone_end_pfn(zone) - 1);
283 [ # # ]: 0 : end_page = pfn_to_online_page(block_pfn);
284 [ # # ]: 0 : if (!end_page)
285 : : return false;
286 : :
287 : : /*
288 : : * Only clear the hint if a sample indicates there is either a
289 : : * free page or an LRU page in the block. One or other condition
290 : : * is necessary for the block to be a migration source/target.
291 : : */
292 : 0 : do {
293 : 0 : if (pfn_valid_within(pfn)) {
294 [ # # # # ]: 0 : if (check_source && PageLRU(page)) {
295 : 0 : clear_pageblock_skip(page);
296 : 0 : return true;
297 : : }
298 : :
299 [ # # # # ]: 0 : if (check_target && PageBuddy(page)) {
300 : 0 : clear_pageblock_skip(page);
301 : 0 : return true;
302 : : }
303 : : }
304 : :
305 : 0 : page += (1 << PAGE_ALLOC_COSTLY_ORDER);
306 : 0 : pfn += (1 << PAGE_ALLOC_COSTLY_ORDER);
307 [ # # ]: 0 : } while (page <= end_page);
308 : :
309 : : return false;
310 : : }
311 : :
312 : : /*
313 : : * This function is called to clear all cached information on pageblocks that
314 : : * should be skipped for page isolation when the migrate and free page scanner
315 : : * meet.
316 : : */
317 : 0 : static void __reset_isolation_suitable(struct zone *zone)
318 : : {
319 : 0 : unsigned long migrate_pfn = zone->zone_start_pfn;
320 [ # # ]: 0 : unsigned long free_pfn = zone_end_pfn(zone) - 1;
321 : 0 : unsigned long reset_migrate = free_pfn;
322 : 0 : unsigned long reset_free = migrate_pfn;
323 : 0 : bool source_set = false;
324 : 0 : bool free_set = false;
325 : :
326 [ # # ]: 0 : if (!zone->compact_blockskip_flush)
327 : : return;
328 : :
329 : 0 : zone->compact_blockskip_flush = false;
330 : :
331 : : /*
332 : : * Walk the zone and update pageblock skip information. Source looks
333 : : * for PageLRU while target looks for PageBuddy. When the scanner
334 : : * is found, both PageBuddy and PageLRU are checked as the pageblock
335 : : * is suitable as both source and target.
336 : : */
337 [ # # ]: 0 : for (; migrate_pfn < free_pfn; migrate_pfn += pageblock_nr_pages,
338 : 0 : free_pfn -= pageblock_nr_pages) {
339 : 0 : cond_resched();
340 : :
341 : : /* Update the migrate PFN */
342 [ # # # # ]: 0 : if (__reset_isolation_pfn(zone, migrate_pfn, true, source_set) &&
343 : : migrate_pfn < reset_migrate) {
344 : 0 : source_set = true;
345 : 0 : reset_migrate = migrate_pfn;
346 : 0 : zone->compact_init_migrate_pfn = reset_migrate;
347 : 0 : zone->compact_cached_migrate_pfn[0] = reset_migrate;
348 : 0 : zone->compact_cached_migrate_pfn[1] = reset_migrate;
349 : : }
350 : :
351 : : /* Update the free PFN */
352 [ # # # # ]: 0 : if (__reset_isolation_pfn(zone, free_pfn, free_set, true) &&
353 : : free_pfn > reset_free) {
354 : 0 : free_set = true;
355 : 0 : reset_free = free_pfn;
356 : 0 : zone->compact_init_free_pfn = reset_free;
357 : 0 : zone->compact_cached_free_pfn = reset_free;
358 : : }
359 : : }
360 : :
361 : : /* Leave no distance if no suitable block was reset */
362 [ # # ]: 0 : if (reset_migrate >= reset_free) {
363 : 0 : zone->compact_cached_migrate_pfn[0] = migrate_pfn;
364 : 0 : zone->compact_cached_migrate_pfn[1] = migrate_pfn;
365 : 0 : zone->compact_cached_free_pfn = free_pfn;
366 : : }
367 : : }
368 : :
369 : 21 : void reset_isolation_suitable(pg_data_t *pgdat)
370 : : {
371 : 21 : int zoneid;
372 : :
373 [ + + ]: 105 : for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
374 : 84 : struct zone *zone = &pgdat->node_zones[zoneid];
375 [ + + ]: 84 : if (!populated_zone(zone))
376 : 42 : continue;
377 : :
378 : : /* Only flush if a full compaction finished recently */
379 [ - + ]: 42 : if (zone->compact_blockskip_flush)
380 : 0 : __reset_isolation_suitable(zone);
381 : : }
382 : 21 : }
383 : :
384 : : /*
385 : : * Sets the pageblock skip bit if it was clear. Note that this is a hint as
386 : : * locks are not required for read/writers. Returns true if it was already set.
387 : : */
388 : : static bool test_and_set_skip(struct compact_control *cc, struct page *page,
389 : : unsigned long pfn)
390 : : {
391 : : bool skip;
392 : :
393 : : /* Do no update if skip hint is being ignored */
394 : : if (cc->ignore_skip_hint)
395 : : return false;
396 : :
397 : : if (!IS_ALIGNED(pfn, pageblock_nr_pages))
398 : : return false;
399 : :
400 : : skip = get_pageblock_skip(page);
401 : : if (!skip && !cc->no_set_skip_hint)
402 : : set_pageblock_skip(page);
403 : :
404 : : return skip;
405 : : }
406 : :
407 : 0 : static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
408 : : {
409 : 0 : struct zone *zone = cc->zone;
410 : :
411 : 0 : pfn = pageblock_end_pfn(pfn);
412 : :
413 : : /* Set for isolation rather than compaction */
414 : 0 : if (cc->no_set_skip_hint)
415 : : return;
416 : :
417 [ # # # # ]: 0 : if (pfn > zone->compact_cached_migrate_pfn[0])
418 : 0 : zone->compact_cached_migrate_pfn[0] = pfn;
419 [ # # # # ]: 0 : if (cc->mode != MIGRATE_ASYNC &&
420 [ # # # # ]: 0 : pfn > zone->compact_cached_migrate_pfn[1])
421 : 0 : zone->compact_cached_migrate_pfn[1] = pfn;
422 : : }
423 : :
424 : : /*
425 : : * If no pages were isolated then mark this pageblock to be skipped in the
426 : : * future. The information is later cleared by __reset_isolation_suitable().
427 : : */
428 : : static void update_pageblock_skip(struct compact_control *cc,
429 : : struct page *page, unsigned long pfn)
430 : : {
431 : : struct zone *zone = cc->zone;
432 : :
433 : : if (cc->no_set_skip_hint)
434 : : return;
435 : :
436 : : if (!page)
437 : : return;
438 : :
439 : : set_pageblock_skip(page);
440 : :
441 : : /* Update where async and sync compaction should restart */
442 : : if (pfn < zone->compact_cached_free_pfn)
443 : : zone->compact_cached_free_pfn = pfn;
444 : : }
445 : : #else
446 : : static inline bool isolation_suitable(struct compact_control *cc,
447 : : struct page *page)
448 : : {
449 : : return true;
450 : : }
451 : :
452 : : static inline bool pageblock_skip_persistent(struct page *page)
453 : : {
454 : : return false;
455 : : }
456 : :
457 : : static inline void update_pageblock_skip(struct compact_control *cc,
458 : : struct page *page, unsigned long pfn)
459 : : {
460 : : }
461 : :
462 : : static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
463 : : {
464 : : }
465 : :
466 : : static bool test_and_set_skip(struct compact_control *cc, struct page *page,
467 : : unsigned long pfn)
468 : : {
469 : : return false;
470 : : }
471 : : #endif /* CONFIG_COMPACTION */
472 : :
473 : : /*
474 : : * Compaction requires the taking of some coarse locks that are potentially
475 : : * very heavily contended. For async compaction, trylock and record if the
476 : : * lock is contended. The lock will still be acquired but compaction will
477 : : * abort when the current block is finished regardless of success rate.
478 : : * Sync compaction acquires the lock.
479 : : *
480 : : * Always returns true which makes it easier to track lock state in callers.
481 : : */
482 : : static bool compact_lock_irqsave(spinlock_t *lock, unsigned long *flags,
483 : : struct compact_control *cc)
484 : : {
485 : : /* Track if the lock is contended in async mode */
486 : : if (cc->mode == MIGRATE_ASYNC && !cc->contended) {
487 : : if (spin_trylock_irqsave(lock, *flags))
488 : : return true;
489 : :
490 : : cc->contended = true;
491 : : }
492 : :
493 : : spin_lock_irqsave(lock, *flags);
494 : : return true;
495 : : }
496 : :
497 : : /*
498 : : * Compaction requires the taking of some coarse locks that are potentially
499 : : * very heavily contended. The lock should be periodically unlocked to avoid
500 : : * having disabled IRQs for a long time, even when there is nobody waiting on
501 : : * the lock. It might also be that allowing the IRQs will result in
502 : : * need_resched() becoming true. If scheduling is needed, async compaction
503 : : * aborts. Sync compaction schedules.
504 : : * Either compaction type will also abort if a fatal signal is pending.
505 : : * In either case if the lock was locked, it is dropped and not regained.
506 : : *
507 : : * Returns true if compaction should abort due to fatal signal pending, or
508 : : * async compaction due to need_resched()
509 : : * Returns false when compaction can continue (sync compaction might have
510 : : * scheduled)
511 : : */
512 : : static bool compact_unlock_should_abort(spinlock_t *lock,
513 : : unsigned long flags, bool *locked, struct compact_control *cc)
514 : : {
515 : : if (*locked) {
516 : : spin_unlock_irqrestore(lock, flags);
517 : : *locked = false;
518 : : }
519 : :
520 : : if (fatal_signal_pending(current)) {
521 : : cc->contended = true;
522 : : return true;
523 : : }
524 : :
525 : : cond_resched();
526 : :
527 : : return false;
528 : : }
529 : :
530 : : /*
531 : : * Isolate free pages onto a private freelist. If @strict is true, will abort
532 : : * returning 0 on any invalid PFNs or non-free pages inside of the pageblock
533 : : * (even though it may still end up isolating some pages).
534 : : */
535 : 0 : static unsigned long isolate_freepages_block(struct compact_control *cc,
536 : : unsigned long *start_pfn,
537 : : unsigned long end_pfn,
538 : : struct list_head *freelist,
539 : : unsigned int stride,
540 : : bool strict)
541 : : {
542 : 0 : int nr_scanned = 0, total_isolated = 0;
543 : 0 : struct page *cursor;
544 : 0 : unsigned long flags = 0;
545 : 0 : bool locked = false;
546 : 0 : unsigned long blockpfn = *start_pfn;
547 : 0 : unsigned int order;
548 : :
549 : : /* Strict mode is for isolation, speed is secondary */
550 [ # # ]: 0 : if (strict)
551 : 0 : stride = 1;
552 : :
553 : 0 : cursor = pfn_to_page(blockpfn);
554 : :
555 : : /* Isolate free pages. */
556 [ # # ]: 0 : for (; blockpfn < end_pfn; blockpfn += stride, cursor += stride) {
557 : 0 : int isolated;
558 : 0 : struct page *page = cursor;
559 : :
560 : : /*
561 : : * Periodically drop the lock (if held) regardless of its
562 : : * contention, to give chance to IRQs. Abort if fatal signal
563 : : * pending or async compaction detects need_resched()
564 : : */
565 [ # # ]: 0 : if (!(blockpfn % SWAP_CLUSTER_MAX)
566 [ # # ]: 0 : && compact_unlock_should_abort(&cc->zone->lock, flags,
567 : : &locked, cc))
568 : : break;
569 : :
570 : 0 : nr_scanned++;
571 : 0 : if (!pfn_valid_within(blockpfn))
572 : : goto isolate_fail;
573 : :
574 : : /*
575 : : * For compound pages such as THP and hugetlbfs, we can save
576 : : * potentially a lot of iterations if we skip them at once.
577 : : * The check is racy, but we can consider only valid values
578 : : * and the only danger is skipping too much.
579 : : */
580 [ # # ]: 0 : if (PageCompound(page)) {
581 : 0 : const unsigned int order = compound_order(page);
582 : :
583 [ # # ]: 0 : if (likely(order < MAX_ORDER)) {
584 : 0 : blockpfn += (1UL << order) - 1;
585 : 0 : cursor += (1UL << order) - 1;
586 : : }
587 : 0 : goto isolate_fail;
588 : : }
589 : :
590 [ # # ]: 0 : if (!PageBuddy(page))
591 : 0 : goto isolate_fail;
592 : :
593 : : /*
594 : : * If we already hold the lock, we can skip some rechecking.
595 : : * Note that if we hold the lock now, checked_pageblock was
596 : : * already set in some previous iteration (or strict is true),
597 : : * so it is correct to skip the suitable migration target
598 : : * recheck as well.
599 : : */
600 [ # # ]: 0 : if (!locked) {
601 : 0 : locked = compact_lock_irqsave(&cc->zone->lock,
602 : : &flags, cc);
603 : :
604 : : /* Recheck this is a buddy page under lock */
605 [ # # ]: 0 : if (!PageBuddy(page))
606 : 0 : goto isolate_fail;
607 : : }
608 : :
609 : : /* Found a free page, will break it into order-0 pages */
610 : 0 : order = page_order(page);
611 : 0 : isolated = __isolate_free_page(page, order);
612 [ # # ]: 0 : if (!isolated)
613 : : break;
614 : 0 : set_page_private(page, order);
615 : :
616 : 0 : total_isolated += isolated;
617 : 0 : cc->nr_freepages += isolated;
618 [ # # ]: 0 : list_add_tail(&page->lru, freelist);
619 : :
620 [ # # # # ]: 0 : if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
621 : 0 : blockpfn += isolated;
622 : 0 : break;
623 : : }
624 : : /* Advance to the end of split page */
625 : 0 : blockpfn += isolated - 1;
626 : 0 : cursor += isolated - 1;
627 : 0 : continue;
628 : :
629 : 0 : isolate_fail:
630 [ # # ]: 0 : if (strict)
631 : : break;
632 : : else
633 : 0 : continue;
634 : :
635 : : }
636 : :
637 [ # # ]: 0 : if (locked)
638 : 0 : spin_unlock_irqrestore(&cc->zone->lock, flags);
639 : :
640 : : /*
641 : : * There is a tiny chance that we have read bogus compound_order(),
642 : : * so be careful to not go outside of the pageblock.
643 : : */
644 [ # # ]: 0 : if (unlikely(blockpfn > end_pfn))
645 : 0 : blockpfn = end_pfn;
646 : :
647 : 0 : trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn,
648 : : nr_scanned, total_isolated);
649 : :
650 : : /* Record how far we have got within the block */
651 : 0 : *start_pfn = blockpfn;
652 : :
653 : : /*
654 : : * If strict isolation is requested by CMA then check that all the
655 : : * pages requested were isolated. If there were any failures, 0 is
656 : : * returned and CMA will fail.
657 : : */
658 [ # # ]: 0 : if (strict && blockpfn < end_pfn)
659 : 0 : total_isolated = 0;
660 : :
661 : 0 : cc->total_free_scanned += nr_scanned;
662 [ # # ]: 0 : if (total_isolated)
663 [ # # ]: 0 : count_compact_events(COMPACTISOLATED, total_isolated);
664 : 0 : return total_isolated;
665 : : }
666 : :
667 : : /**
668 : : * isolate_freepages_range() - isolate free pages.
669 : : * @cc: Compaction control structure.
670 : : * @start_pfn: The first PFN to start isolating.
671 : : * @end_pfn: The one-past-last PFN.
672 : : *
673 : : * Non-free pages, invalid PFNs, or zone boundaries within the
674 : : * [start_pfn, end_pfn) range are considered errors, cause function to
675 : : * undo its actions and return zero.
676 : : *
677 : : * Otherwise, function returns one-past-the-last PFN of isolated page
678 : : * (which may be greater then end_pfn if end fell in a middle of
679 : : * a free page).
680 : : */
681 : : unsigned long
682 : 0 : isolate_freepages_range(struct compact_control *cc,
683 : : unsigned long start_pfn, unsigned long end_pfn)
684 : : {
685 : 0 : unsigned long isolated, pfn, block_start_pfn, block_end_pfn;
686 : 0 : LIST_HEAD(freelist);
687 : :
688 : 0 : pfn = start_pfn;
689 : 0 : block_start_pfn = pageblock_start_pfn(pfn);
690 : 0 : if (block_start_pfn < cc->zone->zone_start_pfn)
691 : : block_start_pfn = cc->zone->zone_start_pfn;
692 : 0 : block_end_pfn = pageblock_end_pfn(pfn);
693 : :
694 [ # # ]: 0 : for (; pfn < end_pfn; pfn += isolated,
695 : : block_start_pfn = block_end_pfn,
696 : 0 : block_end_pfn += pageblock_nr_pages) {
697 : : /* Protect pfn from changing by isolate_freepages_block */
698 : 0 : unsigned long isolate_start_pfn = pfn;
699 : :
700 : 0 : block_end_pfn = min(block_end_pfn, end_pfn);
701 : :
702 : : /*
703 : : * pfn could pass the block_end_pfn if isolated freepage
704 : : * is more than pageblock order. In this case, we adjust
705 : : * scanning range to right one.
706 : : */
707 [ # # ]: 0 : if (pfn >= block_end_pfn) {
708 : 0 : block_start_pfn = pageblock_start_pfn(pfn);
709 : 0 : block_end_pfn = pageblock_end_pfn(pfn);
710 : 0 : block_end_pfn = min(block_end_pfn, end_pfn);
711 : : }
712 : :
713 [ # # # # ]: 0 : if (!pageblock_pfn_to_page(block_start_pfn,
714 : : block_end_pfn, cc->zone))
715 : : break;
716 : :
717 : 0 : isolated = isolate_freepages_block(cc, &isolate_start_pfn,
718 : : block_end_pfn, &freelist, 0, true);
719 : :
720 : : /*
721 : : * In strict mode, isolate_freepages_block() returns 0 if
722 : : * there are any holes in the block (ie. invalid PFNs or
723 : : * non-free pages).
724 : : */
725 [ # # ]: 0 : if (!isolated)
726 : : break;
727 : :
728 : : /*
729 : : * If we managed to isolate pages, it is always (1 << n) *
730 : : * pageblock_nr_pages for some non-negative n. (Max order
731 : : * page may span two pageblocks).
732 : : */
733 : : }
734 : :
735 : : /* __isolate_free_page() does not map the pages */
736 : 0 : split_map_pages(&freelist);
737 : :
738 [ # # ]: 0 : if (pfn < end_pfn) {
739 : : /* Loop terminated early, cleanup. */
740 : 0 : release_freepages(&freelist);
741 : 0 : return 0;
742 : : }
743 : :
744 : : /* We don't use freelists for anything. */
745 : : return pfn;
746 : : }
747 : :
748 : : /* Similar to reclaim, but different enough that they don't share logic */
749 : 0 : static bool too_many_isolated(pg_data_t *pgdat)
750 : : {
751 : 0 : unsigned long active, inactive, isolated;
752 : :
753 : 0 : inactive = node_page_state(pgdat, NR_INACTIVE_FILE) +
754 : 0 : node_page_state(pgdat, NR_INACTIVE_ANON);
755 : 0 : active = node_page_state(pgdat, NR_ACTIVE_FILE) +
756 : 0 : node_page_state(pgdat, NR_ACTIVE_ANON);
757 : 0 : isolated = node_page_state(pgdat, NR_ISOLATED_FILE) +
758 : 0 : node_page_state(pgdat, NR_ISOLATED_ANON);
759 : :
760 : 0 : return isolated > (inactive + active) / 2;
761 : : }
762 : :
763 : : /**
764 : : * isolate_migratepages_block() - isolate all migrate-able pages within
765 : : * a single pageblock
766 : : * @cc: Compaction control structure.
767 : : * @low_pfn: The first PFN to isolate
768 : : * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
769 : : * @isolate_mode: Isolation mode to be used.
770 : : *
771 : : * Isolate all pages that can be migrated from the range specified by
772 : : * [low_pfn, end_pfn). The range is expected to be within same pageblock.
773 : : * Returns zero if there is a fatal signal pending, otherwise PFN of the
774 : : * first page that was not scanned (which may be both less, equal to or more
775 : : * than end_pfn).
776 : : *
777 : : * The pages are isolated on cc->migratepages list (not required to be empty),
778 : : * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field
779 : : * is neither read nor updated.
780 : : */
781 : : static unsigned long
782 : 0 : isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
783 : : unsigned long end_pfn, isolate_mode_t isolate_mode)
784 : : {
785 : 0 : pg_data_t *pgdat = cc->zone->zone_pgdat;
786 : 0 : unsigned long nr_scanned = 0, nr_isolated = 0;
787 : 0 : struct lruvec *lruvec;
788 : 0 : unsigned long flags = 0;
789 : 0 : bool locked = false;
790 : 0 : struct page *page = NULL, *valid_page = NULL;
791 : 0 : unsigned long start_pfn = low_pfn;
792 : 0 : bool skip_on_failure = false;
793 : 0 : unsigned long next_skip_pfn = 0;
794 : 0 : bool skip_updated = false;
795 : :
796 : : /*
797 : : * Ensure that there are not too many pages isolated from the LRU
798 : : * list by either parallel reclaimers or compaction. If there are,
799 : : * delay for some time until fewer pages are isolated
800 : : */
801 [ # # ]: 0 : while (unlikely(too_many_isolated(pgdat))) {
802 : : /* async migration should just abort */
803 [ # # ]: 0 : if (cc->mode == MIGRATE_ASYNC)
804 : : return 0;
805 : :
806 : 0 : congestion_wait(BLK_RW_ASYNC, HZ/10);
807 : :
808 [ # # ]: 0 : if (fatal_signal_pending(current))
809 : : return 0;
810 : : }
811 : :
812 : 0 : cond_resched();
813 : :
814 [ # # # # ]: 0 : if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) {
815 : 0 : skip_on_failure = true;
816 : 0 : next_skip_pfn = block_end_pfn(low_pfn, cc->order);
817 : : }
818 : :
819 : : /* Time to isolate some pages for migration */
820 [ # # ]: 0 : for (; low_pfn < end_pfn; low_pfn++) {
821 : :
822 [ # # ]: 0 : if (skip_on_failure && low_pfn >= next_skip_pfn) {
823 : : /*
824 : : * We have isolated all migration candidates in the
825 : : * previous order-aligned block, and did not skip it due
826 : : * to failure. We should migrate the pages now and
827 : : * hopefully succeed compaction.
828 : : */
829 [ # # ]: 0 : if (nr_isolated)
830 : : break;
831 : :
832 : : /*
833 : : * We failed to isolate in the previous order-aligned
834 : : * block. Set the new boundary to the end of the
835 : : * current block. Note we can't simply increase
836 : : * next_skip_pfn by 1 << order, as low_pfn might have
837 : : * been incremented by a higher number due to skipping
838 : : * a compound or a high-order buddy page in the
839 : : * previous loop iteration.
840 : : */
841 : 0 : next_skip_pfn = block_end_pfn(low_pfn, cc->order);
842 : : }
843 : :
844 : : /*
845 : : * Periodically drop the lock (if held) regardless of its
846 : : * contention, to give chance to IRQs. Abort completely if
847 : : * a fatal signal is pending.
848 : : */
849 [ # # ]: 0 : if (!(low_pfn % SWAP_CLUSTER_MAX)
850 [ # # ]: 0 : && compact_unlock_should_abort(&pgdat->lru_lock,
851 : : flags, &locked, cc)) {
852 : 0 : low_pfn = 0;
853 : 0 : goto fatal_pending;
854 : : }
855 : :
856 : 0 : if (!pfn_valid_within(low_pfn))
857 : : goto isolate_fail;
858 : 0 : nr_scanned++;
859 : :
860 : 0 : page = pfn_to_page(low_pfn);
861 : :
862 : : /*
863 : : * Check if the pageblock has already been marked skipped.
864 : : * Only the aligned PFN is checked as the caller isolates
865 : : * COMPACT_CLUSTER_MAX at a time so the second call must
866 : : * not falsely conclude that the block should be skipped.
867 : : */
868 [ # # # # ]: 0 : if (!valid_page && IS_ALIGNED(low_pfn, pageblock_nr_pages)) {
869 [ # # # # ]: 0 : if (!cc->ignore_skip_hint && get_pageblock_skip(page)) {
870 : 0 : low_pfn = end_pfn;
871 : 0 : goto isolate_abort;
872 : : }
873 : : valid_page = page;
874 : : }
875 : :
876 : : /*
877 : : * Skip if free. We read page order here without zone lock
878 : : * which is generally unsafe, but the race window is small and
879 : : * the worst thing that can happen is that we skip some
880 : : * potential isolation targets.
881 : : */
882 [ # # ]: 0 : if (PageBuddy(page)) {
883 [ # # ]: 0 : unsigned long freepage_order = page_order_unsafe(page);
884 : :
885 : : /*
886 : : * Without lock, we cannot be sure that what we got is
887 : : * a valid page order. Consider only values in the
888 : : * valid order range to prevent low_pfn overflow.
889 : : */
890 [ # # ]: 0 : if (freepage_order > 0 && freepage_order < MAX_ORDER)
891 : 0 : low_pfn += (1UL << freepage_order) - 1;
892 : 0 : continue;
893 : : }
894 : :
895 : : /*
896 : : * Regardless of being on LRU, compound pages such as THP and
897 : : * hugetlbfs are not to be compacted. We can potentially save
898 : : * a lot of iterations if we skip them at once. The check is
899 : : * racy, but we can consider only valid values and the only
900 : : * danger is skipping too much.
901 : : */
902 [ # # ]: 0 : if (PageCompound(page)) {
903 : 0 : const unsigned int order = compound_order(page);
904 : :
905 [ # # ]: 0 : if (likely(order < MAX_ORDER))
906 : 0 : low_pfn += (1UL << order) - 1;
907 : 0 : goto isolate_fail;
908 : : }
909 : :
910 : : /*
911 : : * Check may be lockless but that's ok as we recheck later.
912 : : * It's possible to migrate LRU and non-lru movable pages.
913 : : * Skip any other type of page
914 : : */
915 [ # # # # ]: 0 : if (!PageLRU(page)) {
916 : : /*
917 : : * __PageMovable can return false positive so we need
918 : : * to verify it under page_lock.
919 : : */
920 [ # # # # ]: 0 : if (unlikely(__PageMovable(page)) &&
921 : : !PageIsolated(page)) {
922 [ # # ]: 0 : if (locked) {
923 : 0 : spin_unlock_irqrestore(&pgdat->lru_lock,
924 : : flags);
925 : 0 : locked = false;
926 : : }
927 : :
928 [ # # ]: 0 : if (!isolate_movable_page(page, isolate_mode))
929 : 0 : goto isolate_success;
930 : : }
931 : :
932 : 0 : goto isolate_fail;
933 : : }
934 : :
935 : : /*
936 : : * Migration will fail if an anonymous page is pinned in memory,
937 : : * so avoid taking lru_lock and isolating it unnecessarily in an
938 : : * admittedly racy check.
939 : : */
940 [ # # # # ]: 0 : if (!page_mapping(page) &&
941 : 0 : page_count(page) > page_mapcount(page))
942 : 0 : goto isolate_fail;
943 : :
944 : : /*
945 : : * Only allow to migrate anonymous pages in GFP_NOFS context
946 : : * because those do not depend on fs locks.
947 : : */
948 [ # # # # ]: 0 : if (!(cc->gfp_mask & __GFP_FS) && page_mapping(page))
949 : 0 : goto isolate_fail;
950 : :
951 : : /* If we already hold the lock, we can skip some rechecking */
952 [ # # ]: 0 : if (!locked) {
953 : 0 : locked = compact_lock_irqsave(&pgdat->lru_lock,
954 : : &flags, cc);
955 : :
956 : : /* Try get exclusive access under lock */
957 [ # # ]: 0 : if (!skip_updated) {
958 : 0 : skip_updated = true;
959 [ # # ]: 0 : if (test_and_set_skip(cc, page, low_pfn))
960 : 0 : goto isolate_abort;
961 : : }
962 : :
963 : : /* Recheck PageLRU and PageCompound under lock */
964 [ # # # # ]: 0 : if (!PageLRU(page))
965 : 0 : goto isolate_fail;
966 : :
967 : : /*
968 : : * Page become compound since the non-locked check,
969 : : * and it's on LRU. It can only be a THP so the order
970 : : * is safe to read and it's 0 for tail pages.
971 : : */
972 [ # # ]: 0 : if (unlikely(PageCompound(page))) {
973 : 0 : low_pfn += compound_nr(page) - 1;
974 : 0 : goto isolate_fail;
975 : : }
976 : : }
977 : :
978 : 0 : lruvec = mem_cgroup_page_lruvec(page, pgdat);
979 : :
980 : : /* Try isolate the page */
981 [ # # ]: 0 : if (__isolate_lru_page(page, isolate_mode) != 0)
982 : 0 : goto isolate_fail;
983 : :
984 : 0 : VM_BUG_ON_PAGE(PageCompound(page), page);
985 : :
986 : : /* Successfully isolated */
987 [ # # ]: 0 : del_page_from_lru_list(page, lruvec, page_lru(page));
988 : 0 : inc_node_page_state(page,
989 : 0 : NR_ISOLATED_ANON + page_is_file_cache(page));
990 : :
991 : 0 : isolate_success:
992 [ # # ]: 0 : list_add(&page->lru, &cc->migratepages);
993 : 0 : cc->nr_migratepages++;
994 : 0 : nr_isolated++;
995 : :
996 : : /*
997 : : * Avoid isolating too much unless this block is being
998 : : * rescanned (e.g. dirty/writeback pages, parallel allocation)
999 : : * or a lock is contended. For contention, isolate quickly to
1000 : : * potentially remove one source of contention.
1001 : : */
1002 [ # # ]: 0 : if (cc->nr_migratepages == COMPACT_CLUSTER_MAX &&
1003 [ # # # # ]: 0 : !cc->rescan && !cc->contended) {
1004 : 0 : ++low_pfn;
1005 : 0 : break;
1006 : : }
1007 : :
1008 : 0 : continue;
1009 : 0 : isolate_fail:
1010 [ # # ]: 0 : if (!skip_on_failure)
1011 : 0 : continue;
1012 : :
1013 : : /*
1014 : : * We have isolated some pages, but then failed. Release them
1015 : : * instead of migrating, as we cannot form the cc->order buddy
1016 : : * page anyway.
1017 : : */
1018 [ # # ]: 0 : if (nr_isolated) {
1019 [ # # ]: 0 : if (locked) {
1020 : 0 : spin_unlock_irqrestore(&pgdat->lru_lock, flags);
1021 : 0 : locked = false;
1022 : : }
1023 : 0 : putback_movable_pages(&cc->migratepages);
1024 : 0 : cc->nr_migratepages = 0;
1025 : 0 : nr_isolated = 0;
1026 : : }
1027 : :
1028 [ # # ]: 0 : if (low_pfn < next_skip_pfn) {
1029 : 0 : low_pfn = next_skip_pfn - 1;
1030 : : /*
1031 : : * The check near the loop beginning would have updated
1032 : : * next_skip_pfn too, but this is a bit simpler.
1033 : : */
1034 : 0 : next_skip_pfn += 1UL << cc->order;
1035 : : }
1036 : : }
1037 : :
1038 : : /*
1039 : : * The PageBuddy() check could have potentially brought us outside
1040 : : * the range to be scanned.
1041 : : */
1042 [ # # ]: 0 : if (unlikely(low_pfn > end_pfn))
1043 : 0 : low_pfn = end_pfn;
1044 : :
1045 : 0 : isolate_abort:
1046 [ # # ]: 0 : if (locked)
1047 : 0 : spin_unlock_irqrestore(&pgdat->lru_lock, flags);
1048 : :
1049 : : /*
1050 : : * Updated the cached scanner pfn once the pageblock has been scanned
1051 : : * Pages will either be migrated in which case there is no point
1052 : : * scanning in the near future or migration failed in which case the
1053 : : * failure reason may persist. The block is marked for skipping if
1054 : : * there were no pages isolated in the block or if the block is
1055 : : * rescanned twice in a row.
1056 : : */
1057 [ # # # # : 0 : if (low_pfn == end_pfn && (!nr_isolated || cc->rescan)) {
# # ]
1058 [ # # ]: 0 : if (valid_page && !skip_updated)
1059 : 0 : set_pageblock_skip(valid_page);
1060 [ # # ]: 0 : update_cached_migrate(cc, low_pfn);
1061 : : }
1062 : :
1063 : 0 : trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn,
1064 : : nr_scanned, nr_isolated);
1065 : :
1066 : 0 : fatal_pending:
1067 : 0 : cc->total_migrate_scanned += nr_scanned;
1068 [ # # ]: 0 : if (nr_isolated)
1069 [ # # ]: 0 : count_compact_events(COMPACTISOLATED, nr_isolated);
1070 : :
1071 : : return low_pfn;
1072 : : }
1073 : :
1074 : : /**
1075 : : * isolate_migratepages_range() - isolate migrate-able pages in a PFN range
1076 : : * @cc: Compaction control structure.
1077 : : * @start_pfn: The first PFN to start isolating.
1078 : : * @end_pfn: The one-past-last PFN.
1079 : : *
1080 : : * Returns zero if isolation fails fatally due to e.g. pending signal.
1081 : : * Otherwise, function returns one-past-the-last PFN of isolated page
1082 : : * (which may be greater than end_pfn if end fell in a middle of a THP page).
1083 : : */
1084 : : unsigned long
1085 : 0 : isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
1086 : : unsigned long end_pfn)
1087 : : {
1088 : 0 : unsigned long pfn, block_start_pfn, block_end_pfn;
1089 : :
1090 : : /* Scan block by block. First and last block may be incomplete */
1091 : 0 : pfn = start_pfn;
1092 : 0 : block_start_pfn = pageblock_start_pfn(pfn);
1093 : 0 : if (block_start_pfn < cc->zone->zone_start_pfn)
1094 : : block_start_pfn = cc->zone->zone_start_pfn;
1095 : 0 : block_end_pfn = pageblock_end_pfn(pfn);
1096 : :
1097 [ # # ]: 0 : for (; pfn < end_pfn; pfn = block_end_pfn,
1098 : : block_start_pfn = block_end_pfn,
1099 : 0 : block_end_pfn += pageblock_nr_pages) {
1100 : :
1101 : 0 : block_end_pfn = min(block_end_pfn, end_pfn);
1102 : :
1103 [ # # # # ]: 0 : if (!pageblock_pfn_to_page(block_start_pfn,
1104 : : block_end_pfn, cc->zone))
1105 : 0 : continue;
1106 : :
1107 : 0 : pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
1108 : : ISOLATE_UNEVICTABLE);
1109 : :
1110 [ # # ]: 0 : if (!pfn)
1111 : : break;
1112 : :
1113 [ # # ]: 0 : if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
1114 : : break;
1115 : : }
1116 : :
1117 : 0 : return pfn;
1118 : : }
1119 : :
1120 : : #endif /* CONFIG_COMPACTION || CONFIG_CMA */
1121 : : #ifdef CONFIG_COMPACTION
1122 : :
1123 : 0 : static bool suitable_migration_source(struct compact_control *cc,
1124 : : struct page *page)
1125 : : {
1126 : 0 : int block_mt;
1127 : :
1128 [ # # ]: 0 : if (pageblock_skip_persistent(page))
1129 : : return false;
1130 : :
1131 [ # # # # ]: 0 : if ((cc->mode != MIGRATE_ASYNC) || !cc->direct_compaction)
1132 : : return true;
1133 : :
1134 : 0 : block_mt = get_pageblock_migratetype(page);
1135 : :
1136 [ # # ]: 0 : if (cc->migratetype == MIGRATE_MOVABLE)
1137 : 0 : return is_migrate_movable(block_mt);
1138 : : else
1139 : 0 : return block_mt == cc->migratetype;
1140 : : }
1141 : :
1142 : : /* Returns true if the page is within a block suitable for migration to */
1143 : : static bool suitable_migration_target(struct compact_control *cc,
1144 : : struct page *page)
1145 : : {
1146 : : /* If the page is a large free page, then disallow migration */
1147 : : if (PageBuddy(page)) {
1148 : : /*
1149 : : * We are checking page_order without zone->lock taken. But
1150 : : * the only small danger is that we skip a potentially suitable
1151 : : * pageblock, so it's not worth to check order for valid range.
1152 : : */
1153 : : if (page_order_unsafe(page) >= pageblock_order)
1154 : : return false;
1155 : : }
1156 : :
1157 : : if (cc->ignore_block_suitable)
1158 : : return true;
1159 : :
1160 : : /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
1161 : : if (is_migrate_movable(get_pageblock_migratetype(page)))
1162 : : return true;
1163 : :
1164 : : /* Otherwise skip the block */
1165 : : return false;
1166 : : }
1167 : :
1168 : : static inline unsigned int
1169 : 0 : freelist_scan_limit(struct compact_control *cc)
1170 : : {
1171 : 0 : unsigned short shift = BITS_PER_LONG - 1;
1172 : :
1173 : 0 : return (COMPACT_CLUSTER_MAX >> min(shift, cc->fast_search_fail)) + 1;
1174 : : }
1175 : :
1176 : : /*
1177 : : * Test whether the free scanner has reached the same or lower pageblock than
1178 : : * the migration scanner, and compaction should thus terminate.
1179 : : */
1180 : 0 : static inline bool compact_scanners_met(struct compact_control *cc)
1181 : : {
1182 : 0 : return (cc->free_pfn >> pageblock_order)
1183 : 0 : <= (cc->migrate_pfn >> pageblock_order);
1184 : : }
1185 : :
1186 : : /*
1187 : : * Used when scanning for a suitable migration target which scans freelists
1188 : : * in reverse. Reorders the list such as the unscanned pages are scanned
1189 : : * first on the next iteration of the free scanner
1190 : : */
1191 : : static void
1192 : 0 : move_freelist_head(struct list_head *freelist, struct page *freepage)
1193 : : {
1194 : 0 : LIST_HEAD(sublist);
1195 : :
1196 [ # # ]: 0 : if (!list_is_last(freelist, &freepage->lru)) {
1197 [ # # ]: 0 : list_cut_before(&sublist, freelist, &freepage->lru);
1198 [ # # ]: 0 : if (!list_empty(&sublist))
1199 [ # # ]: 0 : list_splice_tail(&sublist, freelist);
1200 : : }
1201 : 0 : }
1202 : :
1203 : : /*
1204 : : * Similar to move_freelist_head except used by the migration scanner
1205 : : * when scanning forward. It's possible for these list operations to
1206 : : * move against each other if they search the free list exactly in
1207 : : * lockstep.
1208 : : */
1209 : : static void
1210 : 0 : move_freelist_tail(struct list_head *freelist, struct page *freepage)
1211 : : {
1212 : 0 : LIST_HEAD(sublist);
1213 : :
1214 [ # # ]: 0 : if (!list_is_first(freelist, &freepage->lru)) {
1215 : 0 : list_cut_position(&sublist, freelist, &freepage->lru);
1216 [ # # ]: 0 : if (!list_empty(&sublist))
1217 [ # # ]: 0 : list_splice_tail(&sublist, freelist);
1218 : : }
1219 : 0 : }
1220 : :
1221 : : static void
1222 : 0 : fast_isolate_around(struct compact_control *cc, unsigned long pfn, unsigned long nr_isolated)
1223 : : {
1224 : 0 : unsigned long start_pfn, end_pfn;
1225 : 0 : struct page *page = pfn_to_page(pfn);
1226 : :
1227 : : /* Do not search around if there are enough pages already */
1228 [ # # ]: 0 : if (cc->nr_freepages >= cc->nr_migratepages)
1229 : 0 : return;
1230 : :
1231 : : /* Minimise scanning during async compaction */
1232 [ # # # # ]: 0 : if (cc->direct_compaction && cc->mode == MIGRATE_ASYNC)
1233 : : return;
1234 : :
1235 : : /* Pageblock boundaries */
1236 : 0 : start_pfn = pageblock_start_pfn(pfn);
1237 [ # # ]: 0 : end_pfn = min(pageblock_end_pfn(pfn), zone_end_pfn(cc->zone)) - 1;
1238 : :
1239 : : /* Scan before */
1240 [ # # ]: 0 : if (start_pfn != pfn) {
1241 : 0 : isolate_freepages_block(cc, &start_pfn, pfn, &cc->freepages, 1, false);
1242 [ # # ]: 0 : if (cc->nr_freepages >= cc->nr_migratepages)
1243 : : return;
1244 : : }
1245 : :
1246 : : /* Scan after */
1247 : 0 : start_pfn = pfn + nr_isolated;
1248 [ # # ]: 0 : if (start_pfn < end_pfn)
1249 : 0 : isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false);
1250 : :
1251 : : /* Skip this pageblock in the future as it's full or nearly full */
1252 [ # # ]: 0 : if (cc->nr_freepages < cc->nr_migratepages)
1253 : 0 : set_pageblock_skip(page);
1254 : : }
1255 : :
1256 : : /* Search orders in round-robin fashion */
1257 : 0 : static int next_search_order(struct compact_control *cc, int order)
1258 : : {
1259 : 0 : order--;
1260 : 0 : if (order < 0)
1261 : 0 : order = cc->order - 1;
1262 : :
1263 : : /* Search wrapped around? */
1264 [ # # ]: 0 : if (order == cc->search_order) {
1265 : 0 : cc->search_order--;
1266 [ # # ]: 0 : if (cc->search_order < 0)
1267 : 0 : cc->search_order = cc->order - 1;
1268 : : return -1;
1269 : : }
1270 : :
1271 : : return order;
1272 : : }
1273 : :
1274 : : static unsigned long
1275 : 0 : fast_isolate_freepages(struct compact_control *cc)
1276 : : {
1277 : 0 : unsigned int limit = min(1U, freelist_scan_limit(cc) >> 1);
1278 : 0 : unsigned int nr_scanned = 0;
1279 : 0 : unsigned long low_pfn, min_pfn, high_pfn = 0, highest = 0;
1280 : 0 : unsigned long nr_isolated = 0;
1281 : 0 : unsigned long distance;
1282 : 0 : struct page *page = NULL;
1283 : 0 : bool scan_start = false;
1284 : 0 : int order;
1285 : :
1286 : : /* Full compaction passes in a negative order */
1287 [ # # ]: 0 : if (cc->order <= 0)
1288 : 0 : return cc->free_pfn;
1289 : :
1290 : : /*
1291 : : * If starting the scan, use a deeper search and use the highest
1292 : : * PFN found if a suitable one is not found.
1293 : : */
1294 [ # # ]: 0 : if (cc->free_pfn >= cc->zone->compact_init_free_pfn) {
1295 : 0 : limit = pageblock_nr_pages >> 1;
1296 : 0 : scan_start = true;
1297 : : }
1298 : :
1299 : : /*
1300 : : * Preferred point is in the top quarter of the scan space but take
1301 : : * a pfn from the top half if the search is problematic.
1302 : : */
1303 : 0 : distance = (cc->free_pfn - cc->migrate_pfn);
1304 : 0 : low_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 2));
1305 : 0 : min_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 1));
1306 : :
1307 [ # # # # ]: 0 : if (WARN_ON_ONCE(min_pfn > low_pfn))
1308 : 0 : low_pfn = min_pfn;
1309 : :
1310 : : /*
1311 : : * Search starts from the last successful isolation order or the next
1312 : : * order to search after a previous failure
1313 : : */
1314 : 0 : cc->search_order = min_t(unsigned int, cc->order - 1, cc->search_order);
1315 : :
1316 : 0 : for (order = cc->search_order;
1317 [ # # ]: 0 : !page && order >= 0;
1318 [ # # ]: 0 : order = next_search_order(cc, order)) {
1319 : 0 : struct free_area *area = &cc->zone->free_area[order];
1320 : 0 : struct list_head *freelist;
1321 : 0 : struct page *freepage;
1322 : 0 : unsigned long flags;
1323 : 0 : unsigned int order_scanned = 0;
1324 : :
1325 [ # # ]: 0 : if (!area->nr_free)
1326 : 0 : continue;
1327 : :
1328 : 0 : spin_lock_irqsave(&cc->zone->lock, flags);
1329 : 0 : freelist = &area->free_list[MIGRATE_MOVABLE];
1330 [ # # ]: 0 : list_for_each_entry_reverse(freepage, freelist, lru) {
1331 : 0 : unsigned long pfn;
1332 : :
1333 : 0 : order_scanned++;
1334 : 0 : nr_scanned++;
1335 : 0 : pfn = page_to_pfn(freepage);
1336 : :
1337 [ # # ]: 0 : if (pfn >= highest)
1338 : 0 : highest = pageblock_start_pfn(pfn);
1339 : :
1340 [ # # ]: 0 : if (pfn >= low_pfn) {
1341 : 0 : cc->fast_search_fail = 0;
1342 : 0 : cc->search_order = order;
1343 : 0 : page = freepage;
1344 : 0 : break;
1345 : : }
1346 : :
1347 [ # # ]: 0 : if (pfn >= min_pfn && pfn > high_pfn) {
1348 : 0 : high_pfn = pfn;
1349 : :
1350 : : /* Shorten the scan if a candidate is found */
1351 : 0 : limit >>= 1;
1352 : : }
1353 : :
1354 [ # # ]: 0 : if (order_scanned >= limit)
1355 : : break;
1356 : : }
1357 : :
1358 : : /* Use a minimum pfn if a preferred one was not found */
1359 [ # # ]: 0 : if (!page && high_pfn) {
1360 : 0 : page = pfn_to_page(high_pfn);
1361 : :
1362 : : /* Update freepage for the list reorder below */
1363 : 0 : freepage = page;
1364 : : }
1365 : :
1366 : : /* Reorder to so a future search skips recent pages */
1367 : 0 : move_freelist_head(freelist, freepage);
1368 : :
1369 : : /* Isolate the page if available */
1370 [ # # ]: 0 : if (page) {
1371 [ # # ]: 0 : if (__isolate_free_page(page, order)) {
1372 : 0 : set_page_private(page, order);
1373 : 0 : nr_isolated = 1 << order;
1374 : 0 : cc->nr_freepages += nr_isolated;
1375 [ # # ]: 0 : list_add_tail(&page->lru, &cc->freepages);
1376 [ # # ]: 0 : count_compact_events(COMPACTISOLATED, nr_isolated);
1377 : : } else {
1378 : : /* If isolation fails, abort the search */
1379 : 0 : order = cc->search_order + 1;
1380 : 0 : page = NULL;
1381 : : }
1382 : : }
1383 : :
1384 : 0 : spin_unlock_irqrestore(&cc->zone->lock, flags);
1385 : :
1386 : : /*
1387 : : * Smaller scan on next order so the total scan ig related
1388 : : * to freelist_scan_limit.
1389 : : */
1390 [ # # ]: 0 : if (order_scanned >= limit)
1391 : 0 : limit = min(1U, limit >> 1);
1392 : : }
1393 : :
1394 [ # # ]: 0 : if (!page) {
1395 : 0 : cc->fast_search_fail++;
1396 [ # # ]: 0 : if (scan_start) {
1397 : : /*
1398 : : * Use the highest PFN found above min. If one was
1399 : : * not found, be pessemistic for direct compaction
1400 : : * and use the min mark.
1401 : : */
1402 [ # # ]: 0 : if (highest) {
1403 : 0 : page = pfn_to_page(highest);
1404 : 0 : cc->free_pfn = highest;
1405 : : } else {
1406 [ # # # # ]: 0 : if (cc->direct_compaction && pfn_valid(min_pfn)) {
1407 : 0 : page = pfn_to_page(min_pfn);
1408 : 0 : cc->free_pfn = min_pfn;
1409 : : }
1410 : : }
1411 : : }
1412 : : }
1413 : :
1414 [ # # # # ]: 0 : if (highest && highest >= cc->zone->compact_cached_free_pfn) {
1415 : 0 : highest -= pageblock_nr_pages;
1416 : 0 : cc->zone->compact_cached_free_pfn = highest;
1417 : : }
1418 : :
1419 : 0 : cc->total_free_scanned += nr_scanned;
1420 [ # # ]: 0 : if (!page)
1421 : 0 : return cc->free_pfn;
1422 : :
1423 : 0 : low_pfn = page_to_pfn(page);
1424 : 0 : fast_isolate_around(cc, low_pfn, nr_isolated);
1425 : 0 : return low_pfn;
1426 : : }
1427 : :
1428 : : /*
1429 : : * Based on information in the current compact_control, find blocks
1430 : : * suitable for isolating free pages from and then isolate them.
1431 : : */
1432 : 0 : static void isolate_freepages(struct compact_control *cc)
1433 : : {
1434 : 0 : struct zone *zone = cc->zone;
1435 : 0 : struct page *page;
1436 : 0 : unsigned long block_start_pfn; /* start of current pageblock */
1437 : 0 : unsigned long isolate_start_pfn; /* exact pfn we start at */
1438 : 0 : unsigned long block_end_pfn; /* end of current pageblock */
1439 : 0 : unsigned long low_pfn; /* lowest pfn scanner is able to scan */
1440 : 0 : struct list_head *freelist = &cc->freepages;
1441 : 0 : unsigned int stride;
1442 : :
1443 : : /* Try a small search of the free lists for a candidate */
1444 : 0 : isolate_start_pfn = fast_isolate_freepages(cc);
1445 [ # # ]: 0 : if (cc->nr_freepages)
1446 : 0 : goto splitmap;
1447 : :
1448 : : /*
1449 : : * Initialise the free scanner. The starting point is where we last
1450 : : * successfully isolated from, zone-cached value, or the end of the
1451 : : * zone when isolating for the first time. For looping we also need
1452 : : * this pfn aligned down to the pageblock boundary, because we do
1453 : : * block_start_pfn -= pageblock_nr_pages in the for loop.
1454 : : * For ending point, take care when isolating in last pageblock of a
1455 : : * a zone which ends in the middle of a pageblock.
1456 : : * The low boundary is the end of the pageblock the migration scanner
1457 : : * is using.
1458 : : */
1459 : 0 : isolate_start_pfn = cc->free_pfn;
1460 : 0 : block_start_pfn = pageblock_start_pfn(isolate_start_pfn);
1461 [ # # ]: 0 : block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
1462 : : zone_end_pfn(zone));
1463 : 0 : low_pfn = pageblock_end_pfn(cc->migrate_pfn);
1464 [ # # ]: 0 : stride = cc->mode == MIGRATE_ASYNC ? COMPACT_CLUSTER_MAX : 1;
1465 : :
1466 : : /*
1467 : : * Isolate free pages until enough are available to migrate the
1468 : : * pages on cc->migratepages. We stop searching if the migrate
1469 : : * and free page scanners meet or enough free pages are isolated.
1470 : : */
1471 [ # # ]: 0 : for (; block_start_pfn >= low_pfn;
1472 : 0 : block_end_pfn = block_start_pfn,
1473 : 0 : block_start_pfn -= pageblock_nr_pages,
1474 : 0 : isolate_start_pfn = block_start_pfn) {
1475 : 0 : unsigned long nr_isolated;
1476 : :
1477 : : /*
1478 : : * This can iterate a massively long zone without finding any
1479 : : * suitable migration targets, so periodically check resched.
1480 : : */
1481 [ # # ]: 0 : if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)))
1482 : 0 : cond_resched();
1483 : :
1484 [ # # ]: 0 : page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
1485 : : zone);
1486 [ # # ]: 0 : if (!page)
1487 : 0 : continue;
1488 : :
1489 : : /* Check the block is suitable for migration */
1490 [ # # ]: 0 : if (!suitable_migration_target(cc, page))
1491 : 0 : continue;
1492 : :
1493 : : /* If isolation recently failed, do not retry */
1494 [ # # ]: 0 : if (!isolation_suitable(cc, page))
1495 : 0 : continue;
1496 : :
1497 : : /* Found a block suitable for isolating free pages from. */
1498 : 0 : nr_isolated = isolate_freepages_block(cc, &isolate_start_pfn,
1499 : : block_end_pfn, freelist, stride, false);
1500 : :
1501 : : /* Update the skip hint if the full pageblock was scanned */
1502 [ # # ]: 0 : if (isolate_start_pfn == block_end_pfn)
1503 : 0 : update_pageblock_skip(cc, page, block_start_pfn);
1504 : :
1505 : : /* Are enough freepages isolated? */
1506 [ # # ]: 0 : if (cc->nr_freepages >= cc->nr_migratepages) {
1507 [ # # ]: 0 : if (isolate_start_pfn >= block_end_pfn) {
1508 : : /*
1509 : : * Restart at previous pageblock if more
1510 : : * freepages can be isolated next time.
1511 : : */
1512 : 0 : isolate_start_pfn =
1513 : 0 : block_start_pfn - pageblock_nr_pages;
1514 : : }
1515 : : break;
1516 [ # # ]: 0 : } else if (isolate_start_pfn < block_end_pfn) {
1517 : : /*
1518 : : * If isolation failed early, do not continue
1519 : : * needlessly.
1520 : : */
1521 : : break;
1522 : : }
1523 : :
1524 : : /* Adjust stride depending on isolation */
1525 [ # # ]: 0 : if (nr_isolated) {
1526 : 0 : stride = 1;
1527 : 0 : continue;
1528 : : }
1529 : 0 : stride = min_t(unsigned int, COMPACT_CLUSTER_MAX, stride << 1);
1530 : : }
1531 : :
1532 : : /*
1533 : : * Record where the free scanner will restart next time. Either we
1534 : : * broke from the loop and set isolate_start_pfn based on the last
1535 : : * call to isolate_freepages_block(), or we met the migration scanner
1536 : : * and the loop terminated due to isolate_start_pfn < low_pfn
1537 : : */
1538 : 0 : cc->free_pfn = isolate_start_pfn;
1539 : :
1540 : 0 : splitmap:
1541 : : /* __isolate_free_page() does not map the pages */
1542 : 0 : split_map_pages(freelist);
1543 : 0 : }
1544 : :
1545 : : /*
1546 : : * This is a migrate-callback that "allocates" freepages by taking pages
1547 : : * from the isolated freelists in the block we are migrating to.
1548 : : */
1549 : 0 : static struct page *compaction_alloc(struct page *migratepage,
1550 : : unsigned long data)
1551 : : {
1552 : 0 : struct compact_control *cc = (struct compact_control *)data;
1553 : 0 : struct page *freepage;
1554 : :
1555 [ # # ]: 0 : if (list_empty(&cc->freepages)) {
1556 : 0 : isolate_freepages(cc);
1557 : :
1558 [ # # ]: 0 : if (list_empty(&cc->freepages))
1559 : : return NULL;
1560 : : }
1561 : :
1562 : 0 : freepage = list_entry(cc->freepages.next, struct page, lru);
1563 : 0 : list_del(&freepage->lru);
1564 : 0 : cc->nr_freepages--;
1565 : :
1566 : 0 : return freepage;
1567 : : }
1568 : :
1569 : : /*
1570 : : * This is a migrate-callback that "frees" freepages back to the isolated
1571 : : * freelist. All pages on the freelist are from the same zone, so there is no
1572 : : * special handling needed for NUMA.
1573 : : */
1574 : 0 : static void compaction_free(struct page *page, unsigned long data)
1575 : : {
1576 : 0 : struct compact_control *cc = (struct compact_control *)data;
1577 : :
1578 : 0 : list_add(&page->lru, &cc->freepages);
1579 : 0 : cc->nr_freepages++;
1580 : 0 : }
1581 : :
1582 : : /* possible outcome of isolate_migratepages */
1583 : : typedef enum {
1584 : : ISOLATE_ABORT, /* Abort compaction now */
1585 : : ISOLATE_NONE, /* No pages isolated, continue scanning */
1586 : : ISOLATE_SUCCESS, /* Pages isolated, migrate */
1587 : : } isolate_migrate_t;
1588 : :
1589 : : /*
1590 : : * Allow userspace to control policy on scanning the unevictable LRU for
1591 : : * compactable pages.
1592 : : */
1593 : : int sysctl_compact_unevictable_allowed __read_mostly = 1;
1594 : :
1595 : : static inline void
1596 : 0 : update_fast_start_pfn(struct compact_control *cc, unsigned long pfn)
1597 : : {
1598 : 0 : if (cc->fast_start_pfn == ULONG_MAX)
1599 : : return;
1600 : :
1601 [ # # ]: 0 : if (!cc->fast_start_pfn)
1602 : 0 : cc->fast_start_pfn = pfn;
1603 : :
1604 : 0 : cc->fast_start_pfn = min(cc->fast_start_pfn, pfn);
1605 : : }
1606 : :
1607 : : static inline unsigned long
1608 : 0 : reinit_migrate_pfn(struct compact_control *cc)
1609 : : {
1610 : 0 : if (!cc->fast_start_pfn || cc->fast_start_pfn == ULONG_MAX)
1611 : : return cc->migrate_pfn;
1612 : :
1613 : 0 : cc->migrate_pfn = cc->fast_start_pfn;
1614 : 0 : cc->fast_start_pfn = ULONG_MAX;
1615 : :
1616 : 0 : return cc->migrate_pfn;
1617 : : }
1618 : :
1619 : : /*
1620 : : * Briefly search the free lists for a migration source that already has
1621 : : * some free pages to reduce the number of pages that need migration
1622 : : * before a pageblock is free.
1623 : : */
1624 : 0 : static unsigned long fast_find_migrateblock(struct compact_control *cc)
1625 : : {
1626 : 0 : unsigned int limit = freelist_scan_limit(cc);
1627 : 0 : unsigned int nr_scanned = 0;
1628 : 0 : unsigned long distance;
1629 : 0 : unsigned long pfn = cc->migrate_pfn;
1630 : 0 : unsigned long high_pfn;
1631 : 0 : int order;
1632 : :
1633 : : /* Skip hints are relied on to avoid repeats on the fast search */
1634 [ # # ]: 0 : if (cc->ignore_skip_hint)
1635 : : return pfn;
1636 : :
1637 : : /*
1638 : : * If the migrate_pfn is not at the start of a zone or the start
1639 : : * of a pageblock then assume this is a continuation of a previous
1640 : : * scan restarted due to COMPACT_CLUSTER_MAX.
1641 : : */
1642 [ # # # # ]: 0 : if (pfn != cc->zone->zone_start_pfn && pfn != pageblock_start_pfn(pfn))
1643 : : return pfn;
1644 : :
1645 : : /*
1646 : : * For smaller orders, just linearly scan as the number of pages
1647 : : * to migrate should be relatively small and does not necessarily
1648 : : * justify freeing up a large block for a small allocation.
1649 : : */
1650 [ # # ]: 0 : if (cc->order <= PAGE_ALLOC_COSTLY_ORDER)
1651 : : return pfn;
1652 : :
1653 : : /*
1654 : : * Only allow kcompactd and direct requests for movable pages to
1655 : : * quickly clear out a MOVABLE pageblock for allocation. This
1656 : : * reduces the risk that a large movable pageblock is freed for
1657 : : * an unmovable/reclaimable small allocation.
1658 : : */
1659 [ # # # # ]: 0 : if (cc->direct_compaction && cc->migratetype != MIGRATE_MOVABLE)
1660 : : return pfn;
1661 : :
1662 : : /*
1663 : : * When starting the migration scanner, pick any pageblock within the
1664 : : * first half of the search space. Otherwise try and pick a pageblock
1665 : : * within the first eighth to reduce the chances that a migration
1666 : : * target later becomes a source.
1667 : : */
1668 : 0 : distance = (cc->free_pfn - cc->migrate_pfn) >> 1;
1669 [ # # ]: 0 : if (cc->migrate_pfn != cc->zone->zone_start_pfn)
1670 : 0 : distance >>= 2;
1671 : 0 : high_pfn = pageblock_start_pfn(cc->migrate_pfn + distance);
1672 : :
1673 : 0 : for (order = cc->order - 1;
1674 [ # # # # : 0 : order >= PAGE_ALLOC_COSTLY_ORDER && pfn == cc->migrate_pfn && nr_scanned < limit;
# # ]
1675 : 0 : order--) {
1676 : 0 : struct free_area *area = &cc->zone->free_area[order];
1677 : 0 : struct list_head *freelist;
1678 : 0 : unsigned long flags;
1679 : 0 : struct page *freepage;
1680 : :
1681 [ # # ]: 0 : if (!area->nr_free)
1682 : 0 : continue;
1683 : :
1684 : 0 : spin_lock_irqsave(&cc->zone->lock, flags);
1685 : 0 : freelist = &area->free_list[MIGRATE_MOVABLE];
1686 [ # # ]: 0 : list_for_each_entry(freepage, freelist, lru) {
1687 : 0 : unsigned long free_pfn;
1688 : :
1689 : 0 : nr_scanned++;
1690 : 0 : free_pfn = page_to_pfn(freepage);
1691 [ # # ]: 0 : if (free_pfn < high_pfn) {
1692 : : /*
1693 : : * Avoid if skipped recently. Ideally it would
1694 : : * move to the tail but even safe iteration of
1695 : : * the list assumes an entry is deleted, not
1696 : : * reordered.
1697 : : */
1698 [ # # ]: 0 : if (get_pageblock_skip(freepage)) {
1699 [ # # ]: 0 : if (list_is_last(freelist, &freepage->lru))
1700 : : break;
1701 : :
1702 : 0 : continue;
1703 : : }
1704 : :
1705 : : /* Reorder to so a future search skips recent pages */
1706 : 0 : move_freelist_tail(freelist, freepage);
1707 : :
1708 [ # # ]: 0 : update_fast_start_pfn(cc, free_pfn);
1709 : 0 : pfn = pageblock_start_pfn(free_pfn);
1710 : 0 : cc->fast_search_fail = 0;
1711 : 0 : set_pageblock_skip(freepage);
1712 : 0 : break;
1713 : : }
1714 : :
1715 [ # # ]: 0 : if (nr_scanned >= limit) {
1716 : 0 : cc->fast_search_fail++;
1717 : 0 : move_freelist_tail(freelist, freepage);
1718 : 0 : break;
1719 : : }
1720 : : }
1721 : 0 : spin_unlock_irqrestore(&cc->zone->lock, flags);
1722 : : }
1723 : :
1724 : 0 : cc->total_migrate_scanned += nr_scanned;
1725 : :
1726 : : /*
1727 : : * If fast scanning failed then use a cached entry for a page block
1728 : : * that had free pages as the basis for starting a linear scan.
1729 : : */
1730 [ # # ]: 0 : if (pfn == cc->migrate_pfn)
1731 [ # # ]: 0 : pfn = reinit_migrate_pfn(cc);
1732 : :
1733 : : return pfn;
1734 : : }
1735 : :
1736 : : /*
1737 : : * Isolate all pages that can be migrated from the first suitable block,
1738 : : * starting at the block pointed to by the migrate scanner pfn within
1739 : : * compact_control.
1740 : : */
1741 : 0 : static isolate_migrate_t isolate_migratepages(struct compact_control *cc)
1742 : : {
1743 : 0 : unsigned long block_start_pfn;
1744 : 0 : unsigned long block_end_pfn;
1745 : 0 : unsigned long low_pfn;
1746 : 0 : struct page *page;
1747 : 0 : const isolate_mode_t isolate_mode =
1748 [ # # ]: 0 : (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
1749 [ # # ]: 0 : (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0);
1750 : 0 : bool fast_find_block;
1751 : :
1752 : : /*
1753 : : * Start at where we last stopped, or beginning of the zone as
1754 : : * initialized by compact_zone(). The first failure will use
1755 : : * the lowest PFN as the starting point for linear scanning.
1756 : : */
1757 : 0 : low_pfn = fast_find_migrateblock(cc);
1758 : 0 : block_start_pfn = pageblock_start_pfn(low_pfn);
1759 : 0 : if (block_start_pfn < cc->zone->zone_start_pfn)
1760 : : block_start_pfn = cc->zone->zone_start_pfn;
1761 : :
1762 : : /*
1763 : : * fast_find_migrateblock marks a pageblock skipped so to avoid
1764 : : * the isolation_suitable check below, check whether the fast
1765 : : * search was successful.
1766 : : */
1767 [ # # # # ]: 0 : fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail;
1768 : :
1769 : : /* Only scan within a pageblock boundary */
1770 : 0 : block_end_pfn = pageblock_end_pfn(low_pfn);
1771 : :
1772 : : /*
1773 : : * Iterate over whole pageblocks until we find the first suitable.
1774 : : * Do not cross the free scanner.
1775 : : */
1776 [ # # ]: 0 : for (; block_end_pfn <= cc->free_pfn;
1777 : 0 : fast_find_block = false,
1778 : : low_pfn = block_end_pfn,
1779 : : block_start_pfn = block_end_pfn,
1780 : 0 : block_end_pfn += pageblock_nr_pages) {
1781 : :
1782 : : /*
1783 : : * This can potentially iterate a massively long zone with
1784 : : * many pageblocks unsuitable, so periodically check if we
1785 : : * need to schedule.
1786 : : */
1787 [ # # ]: 0 : if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)))
1788 : 0 : cond_resched();
1789 : :
1790 [ # # ]: 0 : page = pageblock_pfn_to_page(block_start_pfn,
1791 : : block_end_pfn, cc->zone);
1792 [ # # ]: 0 : if (!page)
1793 : 0 : continue;
1794 : :
1795 : : /*
1796 : : * If isolation recently failed, do not retry. Only check the
1797 : : * pageblock once. COMPACT_CLUSTER_MAX causes a pageblock
1798 : : * to be visited multiple times. Assume skip was checked
1799 : : * before making it "skip" so other compaction instances do
1800 : : * not scan the same block.
1801 : : */
1802 [ # # # # ]: 0 : if (IS_ALIGNED(low_pfn, pageblock_nr_pages) &&
1803 [ # # ]: 0 : !fast_find_block && !isolation_suitable(cc, page))
1804 : 0 : continue;
1805 : :
1806 : : /*
1807 : : * For async compaction, also only scan in MOVABLE blocks
1808 : : * without huge pages. Async compaction is optimistic to see
1809 : : * if the minimum amount of work satisfies the allocation.
1810 : : * The cached PFN is updated as it's possible that all
1811 : : * remaining blocks between source and target are unsuitable
1812 : : * and the compaction scanners fail to meet.
1813 : : */
1814 [ # # ]: 0 : if (!suitable_migration_source(cc, page)) {
1815 [ # # ]: 0 : update_cached_migrate(cc, block_end_pfn);
1816 : 0 : continue;
1817 : : }
1818 : :
1819 : : /* Perform the isolation */
1820 : 0 : low_pfn = isolate_migratepages_block(cc, low_pfn,
1821 : : block_end_pfn, isolate_mode);
1822 : :
1823 [ # # ]: 0 : if (!low_pfn)
1824 : : return ISOLATE_ABORT;
1825 : :
1826 : : /*
1827 : : * Either we isolated something and proceed with migration. Or
1828 : : * we failed and compact_zone should decide if we should
1829 : : * continue or not.
1830 : : */
1831 : : break;
1832 : : }
1833 : :
1834 : : /* Record where migration scanner will be restarted. */
1835 : 0 : cc->migrate_pfn = low_pfn;
1836 : :
1837 [ # # ]: 0 : return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
1838 : : }
1839 : :
1840 : : /*
1841 : : * order == -1 is expected when compacting via
1842 : : * /proc/sys/vm/compact_memory
1843 : : */
1844 : 0 : static inline bool is_via_compact_memory(int order)
1845 : : {
1846 : 0 : return order == -1;
1847 : : }
1848 : :
1849 : 0 : static enum compact_result __compact_finished(struct compact_control *cc)
1850 : : {
1851 : 0 : unsigned int order;
1852 : 0 : const int migratetype = cc->migratetype;
1853 : 0 : int ret;
1854 : :
1855 : : /* Compaction run completes if the migrate and free scanner meet */
1856 [ # # ]: 0 : if (compact_scanners_met(cc)) {
1857 : : /* Let the next compaction start anew. */
1858 [ # # ]: 0 : reset_cached_positions(cc->zone);
1859 : :
1860 : : /*
1861 : : * Mark that the PG_migrate_skip information should be cleared
1862 : : * by kswapd when it goes to sleep. kcompactd does not set the
1863 : : * flag itself as the decision to be clear should be directly
1864 : : * based on an allocation request.
1865 : : */
1866 [ # # ]: 0 : if (cc->direct_compaction)
1867 : 0 : cc->zone->compact_blockskip_flush = true;
1868 : :
1869 [ # # ]: 0 : if (cc->whole_zone)
1870 : : return COMPACT_COMPLETE;
1871 : : else
1872 : 0 : return COMPACT_PARTIAL_SKIPPED;
1873 : : }
1874 : :
1875 [ # # ]: 0 : if (is_via_compact_memory(cc->order))
1876 : : return COMPACT_CONTINUE;
1877 : :
1878 : : /*
1879 : : * Always finish scanning a pageblock to reduce the possibility of
1880 : : * fallbacks in the future. This is particularly important when
1881 : : * migration source is unmovable/reclaimable but it's not worth
1882 : : * special casing.
1883 : : */
1884 [ # # ]: 0 : if (!IS_ALIGNED(cc->migrate_pfn, pageblock_nr_pages))
1885 : : return COMPACT_CONTINUE;
1886 : :
1887 : : /* Direct compactor: Is a suitable page free? */
1888 : 0 : ret = COMPACT_NO_SUITABLE_PAGE;
1889 [ # # ]: 0 : for (order = cc->order; order < MAX_ORDER; order++) {
1890 : 0 : struct free_area *area = &cc->zone->free_area[order];
1891 : 0 : bool can_steal;
1892 : :
1893 : : /* Job done if page is free of the right migratetype */
1894 [ # # ]: 0 : if (!free_area_empty(area, migratetype))
1895 : 0 : return COMPACT_SUCCESS;
1896 : :
1897 : : #ifdef CONFIG_CMA
1898 : : /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
1899 : : if (migratetype == MIGRATE_MOVABLE &&
1900 : : !free_area_empty(area, MIGRATE_CMA))
1901 : : return COMPACT_SUCCESS;
1902 : : #endif
1903 : : /*
1904 : : * Job done if allocation would steal freepages from
1905 : : * other migratetype buddy lists.
1906 : : */
1907 [ # # ]: 0 : if (find_suitable_fallback(area, order, migratetype,
1908 : : true, &can_steal) != -1) {
1909 : :
1910 : : /* movable pages are OK in any pageblock */
1911 [ # # ]: 0 : if (migratetype == MIGRATE_MOVABLE)
1912 : : return COMPACT_SUCCESS;
1913 : :
1914 : : /*
1915 : : * We are stealing for a non-movable allocation. Make
1916 : : * sure we finish compacting the current pageblock
1917 : : * first so it is as free as possible and we won't
1918 : : * have to steal another one soon. This only applies
1919 : : * to sync compaction, as async compaction operates
1920 : : * on pageblocks of the same migratetype.
1921 : : */
1922 [ # # ]: 0 : if (cc->mode == MIGRATE_ASYNC ||
1923 [ # # ]: 0 : IS_ALIGNED(cc->migrate_pfn,
1924 : : pageblock_nr_pages)) {
1925 : : return COMPACT_SUCCESS;
1926 : : }
1927 : :
1928 : 0 : ret = COMPACT_CONTINUE;
1929 : 0 : break;
1930 : : }
1931 : : }
1932 : :
1933 [ # # # # ]: 0 : if (cc->contended || fatal_signal_pending(current))
1934 : : ret = COMPACT_CONTENDED;
1935 : :
1936 : 0 : return ret;
1937 : : }
1938 : :
1939 : 0 : static enum compact_result compact_finished(struct compact_control *cc)
1940 : : {
1941 : 0 : int ret;
1942 : :
1943 : 0 : ret = __compact_finished(cc);
1944 : 0 : trace_mm_compaction_finished(cc->zone, cc->order, ret);
1945 [ # # ]: 0 : if (ret == COMPACT_NO_SUITABLE_PAGE)
1946 : 0 : ret = COMPACT_CONTINUE;
1947 : :
1948 : 0 : return ret;
1949 : : }
1950 : :
1951 : : /*
1952 : : * compaction_suitable: Is this suitable to run compaction on this zone now?
1953 : : * Returns
1954 : : * COMPACT_SKIPPED - If there are too few free pages for compaction
1955 : : * COMPACT_SUCCESS - If the allocation would succeed without compaction
1956 : : * COMPACT_CONTINUE - If compaction should run now
1957 : : */
1958 : 0 : static enum compact_result __compaction_suitable(struct zone *zone, int order,
1959 : : unsigned int alloc_flags,
1960 : : int classzone_idx,
1961 : : unsigned long wmark_target)
1962 : : {
1963 : 0 : unsigned long watermark;
1964 : :
1965 [ # # ]: 0 : if (is_via_compact_memory(order))
1966 : : return COMPACT_CONTINUE;
1967 : :
1968 : 0 : watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
1969 : : /*
1970 : : * If watermarks for high-order allocation are already met, there
1971 : : * should be no need for compaction at all.
1972 : : */
1973 [ # # ]: 0 : if (zone_watermark_ok(zone, order, watermark, classzone_idx,
1974 : : alloc_flags))
1975 : : return COMPACT_SUCCESS;
1976 : :
1977 : : /*
1978 : : * Watermarks for order-0 must be met for compaction to be able to
1979 : : * isolate free pages for migration targets. This means that the
1980 : : * watermark and alloc_flags have to match, or be more pessimistic than
1981 : : * the check in __isolate_free_page(). We don't use the direct
1982 : : * compactor's alloc_flags, as they are not relevant for freepage
1983 : : * isolation. We however do use the direct compactor's classzone_idx to
1984 : : * skip over zones where lowmem reserves would prevent allocation even
1985 : : * if compaction succeeds.
1986 : : * For costly orders, we require low watermark instead of min for
1987 : : * compaction to proceed to increase its chances.
1988 : : * ALLOC_CMA is used, as pages in CMA pageblocks are considered
1989 : : * suitable migration targets
1990 : : */
1991 : 0 : watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ?
1992 [ # # ]: 0 : low_wmark_pages(zone) : min_wmark_pages(zone);
1993 : 0 : watermark += compact_gap(order);
1994 [ # # ]: 0 : if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx,
1995 : : ALLOC_CMA, wmark_target))
1996 : 0 : return COMPACT_SKIPPED;
1997 : :
1998 : : return COMPACT_CONTINUE;
1999 : : }
2000 : :
2001 : 0 : enum compact_result compaction_suitable(struct zone *zone, int order,
2002 : : unsigned int alloc_flags,
2003 : : int classzone_idx)
2004 : : {
2005 : 0 : enum compact_result ret;
2006 : 0 : int fragindex;
2007 : :
2008 : 0 : ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx,
2009 : : zone_page_state(zone, NR_FREE_PAGES));
2010 : : /*
2011 : : * fragmentation index determines if allocation failures are due to
2012 : : * low memory or external fragmentation
2013 : : *
2014 : : * index of -1000 would imply allocations might succeed depending on
2015 : : * watermarks, but we already failed the high-order watermark check
2016 : : * index towards 0 implies failure is due to lack of memory
2017 : : * index towards 1000 implies failure is due to fragmentation
2018 : : *
2019 : : * Only compact if a failure would be due to fragmentation. Also
2020 : : * ignore fragindex for non-costly orders where the alternative to
2021 : : * a successful reclaim/compaction is OOM. Fragindex and the
2022 : : * vm.extfrag_threshold sysctl is meant as a heuristic to prevent
2023 : : * excessive compaction for costly orders, but it should not be at the
2024 : : * expense of system stability.
2025 : : */
2026 [ # # ]: 0 : if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) {
2027 : 0 : fragindex = fragmentation_index(zone, order);
2028 [ # # # # ]: 0 : if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
2029 : 0 : ret = COMPACT_NOT_SUITABLE_ZONE;
2030 : : }
2031 : :
2032 : 0 : trace_mm_compaction_suitable(zone, order, ret);
2033 : 0 : if (ret == COMPACT_NOT_SUITABLE_ZONE)
2034 : : ret = COMPACT_SKIPPED;
2035 : :
2036 : 0 : return ret;
2037 : : }
2038 : :
2039 : 0 : bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
2040 : : int alloc_flags)
2041 : : {
2042 : 0 : struct zone *zone;
2043 : 0 : struct zoneref *z;
2044 : :
2045 : : /*
2046 : : * Make sure at least one zone would pass __compaction_suitable if we continue
2047 : : * retrying the reclaim.
2048 : : */
2049 [ # # # # : 0 : for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
# # ]
2050 : : ac->nodemask) {
2051 : 0 : unsigned long available;
2052 : 0 : enum compact_result compact_result;
2053 : :
2054 : : /*
2055 : : * Do not consider all the reclaimable memory because we do not
2056 : : * want to trash just for a single high order allocation which
2057 : : * is even not guaranteed to appear even if __compaction_suitable
2058 : : * is happy about the watermark check.
2059 : : */
2060 : 0 : available = zone_reclaimable_pages(zone) / order;
2061 : 0 : available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
2062 : 0 : compact_result = __compaction_suitable(zone, order, alloc_flags,
2063 : : ac_classzone_idx(ac), available);
2064 [ # # ]: 0 : if (compact_result != COMPACT_SKIPPED)
2065 : : return true;
2066 : : }
2067 : :
2068 : : return false;
2069 : : }
2070 : :
2071 : : static enum compact_result
2072 : 0 : compact_zone(struct compact_control *cc, struct capture_control *capc)
2073 : : {
2074 : 0 : enum compact_result ret;
2075 : 0 : unsigned long start_pfn = cc->zone->zone_start_pfn;
2076 [ # # ]: 0 : unsigned long end_pfn = zone_end_pfn(cc->zone);
2077 : 0 : unsigned long last_migrated_pfn;
2078 : 0 : const bool sync = cc->mode != MIGRATE_ASYNC;
2079 : 0 : bool update_cached;
2080 : :
2081 : : /*
2082 : : * These counters track activities during zone compaction. Initialize
2083 : : * them before compacting a new zone.
2084 : : */
2085 : 0 : cc->total_migrate_scanned = 0;
2086 : 0 : cc->total_free_scanned = 0;
2087 : 0 : cc->nr_migratepages = 0;
2088 : 0 : cc->nr_freepages = 0;
2089 [ # # ]: 0 : INIT_LIST_HEAD(&cc->freepages);
2090 : 0 : INIT_LIST_HEAD(&cc->migratepages);
2091 : :
2092 [ # # ]: 0 : cc->migratetype = gfpflags_to_migratetype(cc->gfp_mask);
2093 : 0 : ret = compaction_suitable(cc->zone, cc->order, cc->alloc_flags,
2094 : : cc->classzone_idx);
2095 : : /* Compaction is likely to fail */
2096 [ # # ]: 0 : if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
2097 : : return ret;
2098 : :
2099 : : /* huh, compaction_suitable is returning something unexpected */
2100 : 0 : VM_BUG_ON(ret != COMPACT_CONTINUE);
2101 : :
2102 : : /*
2103 : : * Clear pageblock skip if there were failures recently and compaction
2104 : : * is about to be retried after being deferred.
2105 : : */
2106 [ # # # # ]: 0 : if (compaction_restarting(cc->zone, cc->order))
2107 : 0 : __reset_isolation_suitable(cc->zone);
2108 : :
2109 : : /*
2110 : : * Setup to move all movable pages to the end of the zone. Used cached
2111 : : * information on where the scanners should start (unless we explicitly
2112 : : * want to compact the whole zone), but check that it is initialised
2113 : : * by ensuring the values are within zone boundaries.
2114 : : */
2115 : 0 : cc->fast_start_pfn = 0;
2116 [ # # ]: 0 : if (cc->whole_zone) {
2117 : 0 : cc->migrate_pfn = start_pfn;
2118 : 0 : cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
2119 : : } else {
2120 : 0 : cc->migrate_pfn = cc->zone->compact_cached_migrate_pfn[sync];
2121 : 0 : cc->free_pfn = cc->zone->compact_cached_free_pfn;
2122 [ # # # # ]: 0 : if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) {
2123 : 0 : cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
2124 : 0 : cc->zone->compact_cached_free_pfn = cc->free_pfn;
2125 : : }
2126 [ # # # # ]: 0 : if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) {
2127 : 0 : cc->migrate_pfn = start_pfn;
2128 : 0 : cc->zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
2129 : 0 : cc->zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
2130 : : }
2131 : :
2132 [ # # ]: 0 : if (cc->migrate_pfn <= cc->zone->compact_init_migrate_pfn)
2133 : 0 : cc->whole_zone = true;
2134 : : }
2135 : :
2136 : 0 : last_migrated_pfn = 0;
2137 : :
2138 : : /*
2139 : : * Migrate has separate cached PFNs for ASYNC and SYNC* migration on
2140 : : * the basis that some migrations will fail in ASYNC mode. However,
2141 : : * if the cached PFNs match and pageblocks are skipped due to having
2142 : : * no isolation candidates, then the sync state does not matter.
2143 : : * Until a pageblock with isolation candidates is found, keep the
2144 : : * cached PFNs in sync to avoid revisiting the same blocks.
2145 : : */
2146 [ # # ]: 0 : update_cached = !sync &&
2147 [ # # ]: 0 : cc->zone->compact_cached_migrate_pfn[0] == cc->zone->compact_cached_migrate_pfn[1];
2148 : :
2149 : 0 : trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
2150 : : cc->free_pfn, end_pfn, sync);
2151 : :
2152 : 0 : migrate_prep_local();
2153 : :
2154 [ # # ]: 0 : while ((ret = compact_finished(cc)) == COMPACT_CONTINUE) {
2155 : 0 : int err;
2156 : 0 : unsigned long start_pfn = cc->migrate_pfn;
2157 : :
2158 : : /*
2159 : : * Avoid multiple rescans which can happen if a page cannot be
2160 : : * isolated (dirty/writeback in async mode) or if the migrated
2161 : : * pages are being allocated before the pageblock is cleared.
2162 : : * The first rescan will capture the entire pageblock for
2163 : : * migration. If it fails, it'll be marked skip and scanning
2164 : : * will proceed as normal.
2165 : : */
2166 : 0 : cc->rescan = false;
2167 [ # # ]: 0 : if (pageblock_start_pfn(last_migrated_pfn) ==
2168 : : pageblock_start_pfn(start_pfn)) {
2169 : 0 : cc->rescan = true;
2170 : : }
2171 : :
2172 [ # # # # ]: 0 : switch (isolate_migratepages(cc)) {
2173 : 0 : case ISOLATE_ABORT:
2174 : 0 : ret = COMPACT_CONTENDED;
2175 : 0 : putback_movable_pages(&cc->migratepages);
2176 : 0 : cc->nr_migratepages = 0;
2177 : 0 : last_migrated_pfn = 0;
2178 : 0 : goto out;
2179 : 0 : case ISOLATE_NONE:
2180 [ # # ]: 0 : if (update_cached) {
2181 : 0 : cc->zone->compact_cached_migrate_pfn[1] =
2182 : 0 : cc->zone->compact_cached_migrate_pfn[0];
2183 : : }
2184 : :
2185 : : /*
2186 : : * We haven't isolated and migrated anything, but
2187 : : * there might still be unflushed migrations from
2188 : : * previous cc->order aligned block.
2189 : : */
2190 : 0 : goto check_drain;
2191 : 0 : case ISOLATE_SUCCESS:
2192 : 0 : update_cached = false;
2193 : 0 : last_migrated_pfn = start_pfn;
2194 : 0 : ;
2195 : : }
2196 : :
2197 : 0 : err = migrate_pages(&cc->migratepages, compaction_alloc,
2198 : : compaction_free, (unsigned long)cc, cc->mode,
2199 : : MR_COMPACTION);
2200 : :
2201 : 0 : trace_mm_compaction_migratepages(cc->nr_migratepages, err,
2202 : : &cc->migratepages);
2203 : :
2204 : : /* All pages were either migrated or will be released */
2205 : 0 : cc->nr_migratepages = 0;
2206 [ # # ]: 0 : if (err) {
2207 : 0 : putback_movable_pages(&cc->migratepages);
2208 : : /*
2209 : : * migrate_pages() may return -ENOMEM when scanners meet
2210 : : * and we want compact_finished() to detect it
2211 : : */
2212 [ # # # # ]: 0 : if (err == -ENOMEM && !compact_scanners_met(cc)) {
2213 : 0 : ret = COMPACT_CONTENDED;
2214 : 0 : goto out;
2215 : : }
2216 : : /*
2217 : : * We failed to migrate at least one page in the current
2218 : : * order-aligned block, so skip the rest of it.
2219 : : */
2220 [ # # ]: 0 : if (cc->direct_compaction &&
2221 [ # # ]: 0 : (cc->mode == MIGRATE_ASYNC)) {
2222 : 0 : cc->migrate_pfn = block_end_pfn(
2223 : : cc->migrate_pfn - 1, cc->order);
2224 : : /* Draining pcplists is useless in this case */
2225 : 0 : last_migrated_pfn = 0;
2226 : : }
2227 : : }
2228 : :
2229 : 0 : check_drain:
2230 : : /*
2231 : : * Has the migration scanner moved away from the previous
2232 : : * cc->order aligned block where we migrated from? If yes,
2233 : : * flush the pages that were freed, so that they can merge and
2234 : : * compact_finished() can detect immediately if allocation
2235 : : * would succeed.
2236 : : */
2237 [ # # # # ]: 0 : if (cc->order > 0 && last_migrated_pfn) {
2238 : 0 : int cpu;
2239 : 0 : unsigned long current_block_start =
2240 : 0 : block_start_pfn(cc->migrate_pfn, cc->order);
2241 : :
2242 [ # # ]: 0 : if (last_migrated_pfn < current_block_start) {
2243 : 0 : cpu = get_cpu();
2244 : 0 : lru_add_drain_cpu(cpu);
2245 : 0 : drain_local_pages(cc->zone);
2246 : 0 : put_cpu();
2247 : : /* No more flushing until we migrate again */
2248 : 0 : last_migrated_pfn = 0;
2249 : : }
2250 : : }
2251 : :
2252 : : /* Stop if a page has been captured */
2253 [ # # # # ]: 0 : if (capc && capc->page) {
2254 : : ret = COMPACT_SUCCESS;
2255 : : break;
2256 : : }
2257 : : }
2258 : :
2259 : 0 : out:
2260 : : /*
2261 : : * Release free pages and update where the free scanner should restart,
2262 : : * so we don't leave any returned pages behind in the next attempt.
2263 : : */
2264 [ # # ]: 0 : if (cc->nr_freepages > 0) {
2265 : 0 : unsigned long free_pfn = release_freepages(&cc->freepages);
2266 : :
2267 : 0 : cc->nr_freepages = 0;
2268 : 0 : VM_BUG_ON(free_pfn == 0);
2269 : : /* The cached pfn is always the first in a pageblock */
2270 : 0 : free_pfn = pageblock_start_pfn(free_pfn);
2271 : : /*
2272 : : * Only go back, not forward. The cached pfn might have been
2273 : : * already reset to zone end in compact_finished()
2274 : : */
2275 [ # # ]: 0 : if (free_pfn > cc->zone->compact_cached_free_pfn)
2276 : 0 : cc->zone->compact_cached_free_pfn = free_pfn;
2277 : : }
2278 : :
2279 [ # # ]: 0 : count_compact_events(COMPACTMIGRATE_SCANNED, cc->total_migrate_scanned);
2280 [ # # ]: 0 : count_compact_events(COMPACTFREE_SCANNED, cc->total_free_scanned);
2281 : :
2282 : 0 : trace_mm_compaction_end(start_pfn, cc->migrate_pfn,
2283 : : cc->free_pfn, end_pfn, sync, ret);
2284 : :
2285 : 0 : return ret;
2286 : : }
2287 : :
2288 : 0 : static enum compact_result compact_zone_order(struct zone *zone, int order,
2289 : : gfp_t gfp_mask, enum compact_priority prio,
2290 : : unsigned int alloc_flags, int classzone_idx,
2291 : : struct page **capture)
2292 : : {
2293 : 0 : enum compact_result ret;
2294 : 0 : struct compact_control cc = {
2295 : : .order = order,
2296 : : .search_order = order,
2297 : : .gfp_mask = gfp_mask,
2298 : : .zone = zone,
2299 : : .mode = (prio == COMPACT_PRIO_ASYNC) ?
2300 : 0 : MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT,
2301 : : .alloc_flags = alloc_flags,
2302 : : .classzone_idx = classzone_idx,
2303 : : .direct_compaction = true,
2304 : : .whole_zone = (prio == MIN_COMPACT_PRIORITY),
2305 : 0 : .ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY),
2306 : : .ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY)
2307 : : };
2308 : 0 : struct capture_control capc = {
2309 : : .cc = &cc,
2310 : : .page = NULL,
2311 : : };
2312 : :
2313 [ # # ]: 0 : if (capture)
2314 : 0 : current->capture_control = &capc;
2315 : :
2316 : 0 : ret = compact_zone(&cc, &capc);
2317 : :
2318 : 0 : VM_BUG_ON(!list_empty(&cc.freepages));
2319 : 0 : VM_BUG_ON(!list_empty(&cc.migratepages));
2320 : :
2321 : 0 : *capture = capc.page;
2322 : 0 : current->capture_control = NULL;
2323 : :
2324 : 0 : return ret;
2325 : : }
2326 : :
2327 : : int sysctl_extfrag_threshold = 500;
2328 : :
2329 : : /**
2330 : : * try_to_compact_pages - Direct compact to satisfy a high-order allocation
2331 : : * @gfp_mask: The GFP mask of the current allocation
2332 : : * @order: The order of the current allocation
2333 : : * @alloc_flags: The allocation flags of the current allocation
2334 : : * @ac: The context of current allocation
2335 : : * @prio: Determines how hard direct compaction should try to succeed
2336 : : *
2337 : : * This is the main entry point for direct page compaction.
2338 : : */
2339 : 0 : enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
2340 : : unsigned int alloc_flags, const struct alloc_context *ac,
2341 : : enum compact_priority prio, struct page **capture)
2342 : : {
2343 : 0 : int may_perform_io = gfp_mask & __GFP_IO;
2344 : 0 : struct zoneref *z;
2345 : 0 : struct zone *zone;
2346 : 0 : enum compact_result rc = COMPACT_SKIPPED;
2347 : :
2348 : : /*
2349 : : * Check if the GFP flags allow compaction - GFP_NOIO is really
2350 : : * tricky context because the migration might require IO
2351 : : */
2352 [ # # ]: 0 : if (!may_perform_io)
2353 : : return COMPACT_SKIPPED;
2354 : :
2355 : 0 : trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio);
2356 : :
2357 : : /* Compact each zone in the list */
2358 [ # # # # : 0 : for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
# # ]
2359 : : ac->nodemask) {
2360 : 0 : enum compact_result status;
2361 : :
2362 [ # # ]: 0 : if (prio > MIN_COMPACT_PRIORITY
2363 [ # # ]: 0 : && compaction_deferred(zone, order)) {
2364 : 0 : rc = max_t(enum compact_result, COMPACT_DEFERRED, rc);
2365 : 0 : continue;
2366 : : }
2367 : :
2368 : 0 : status = compact_zone_order(zone, order, gfp_mask, prio,
2369 : : alloc_flags, ac_classzone_idx(ac), capture);
2370 : 0 : rc = max(status, rc);
2371 : :
2372 : : /* The allocation should succeed, stop compacting */
2373 [ # # ]: 0 : if (status == COMPACT_SUCCESS) {
2374 : : /*
2375 : : * We think the allocation will succeed in this zone,
2376 : : * but it is not certain, hence the false. The caller
2377 : : * will repeat this with true if allocation indeed
2378 : : * succeeds in this zone.
2379 : : */
2380 [ # # ]: 0 : compaction_defer_reset(zone, order, false);
2381 : :
2382 : : break;
2383 : : }
2384 : :
2385 [ # # # # ]: 0 : if (prio != COMPACT_PRIO_ASYNC && (status == COMPACT_COMPLETE ||
2386 : : status == COMPACT_PARTIAL_SKIPPED))
2387 : : /*
2388 : : * We think that allocation won't succeed in this zone
2389 : : * so we defer compaction there. If it ends up
2390 : : * succeeding after all, it will be reset.
2391 : : */
2392 : 0 : defer_compaction(zone, order);
2393 : :
2394 : : /*
2395 : : * We might have stopped compacting due to need_resched() in
2396 : : * async compaction, or due to a fatal signal detected. In that
2397 : : * case do not try further zones
2398 : : */
2399 [ # # # # ]: 0 : if ((prio == COMPACT_PRIO_ASYNC && need_resched())
2400 [ # # ]: 0 : || fatal_signal_pending(current))
2401 : : break;
2402 : : }
2403 : :
2404 : : return rc;
2405 : : }
2406 : :
2407 : :
2408 : : /* Compact all zones within a node */
2409 : 0 : static void compact_node(int nid)
2410 : : {
2411 : 0 : pg_data_t *pgdat = NODE_DATA(nid);
2412 : 0 : int zoneid;
2413 : 0 : struct zone *zone;
2414 : 0 : struct compact_control cc = {
2415 : : .order = -1,
2416 : : .mode = MIGRATE_SYNC,
2417 : : .ignore_skip_hint = true,
2418 : : .whole_zone = true,
2419 : : .gfp_mask = GFP_KERNEL,
2420 : : };
2421 : :
2422 : :
2423 [ # # ]: 0 : for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
2424 : :
2425 : 0 : zone = &pgdat->node_zones[zoneid];
2426 [ # # ]: 0 : if (!populated_zone(zone))
2427 : 0 : continue;
2428 : :
2429 : 0 : cc.zone = zone;
2430 : :
2431 : 0 : compact_zone(&cc, NULL);
2432 : :
2433 : 0 : VM_BUG_ON(!list_empty(&cc.freepages));
2434 : 0 : VM_BUG_ON(!list_empty(&cc.migratepages));
2435 : : }
2436 : 0 : }
2437 : :
2438 : : /* Compact all nodes in the system */
2439 : 0 : static void compact_nodes(void)
2440 : : {
2441 : 0 : int nid;
2442 : :
2443 : : /* Flush pending updates to the LRU lists */
2444 : 0 : lru_add_drain_all();
2445 : :
2446 [ # # ]: 0 : for_each_online_node(nid)
2447 : 0 : compact_node(nid);
2448 : 0 : }
2449 : :
2450 : : /* The written value is actually unused, all memory is compacted */
2451 : : int sysctl_compact_memory;
2452 : :
2453 : : /*
2454 : : * This is the entry point for compacting all nodes via
2455 : : * /proc/sys/vm/compact_memory
2456 : : */
2457 : 0 : int sysctl_compaction_handler(struct ctl_table *table, int write,
2458 : : void __user *buffer, size_t *length, loff_t *ppos)
2459 : : {
2460 [ # # ]: 0 : if (write)
2461 : 0 : compact_nodes();
2462 : :
2463 : 0 : return 0;
2464 : : }
2465 : :
2466 : : #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
2467 : 0 : static ssize_t sysfs_compact_node(struct device *dev,
2468 : : struct device_attribute *attr,
2469 : : const char *buf, size_t count)
2470 : : {
2471 : 0 : int nid = dev->id;
2472 : :
2473 [ # # # # : 0 : if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
# # ]
2474 : : /* Flush pending updates to the LRU lists */
2475 : 0 : lru_add_drain_all();
2476 : :
2477 : 0 : compact_node(nid);
2478 : : }
2479 : :
2480 : 0 : return count;
2481 : : }
2482 : : static DEVICE_ATTR(compact, 0200, NULL, sysfs_compact_node);
2483 : :
2484 : 21 : int compaction_register_node(struct node *node)
2485 : : {
2486 : 21 : return device_create_file(&node->dev, &dev_attr_compact);
2487 : : }
2488 : :
2489 : 0 : void compaction_unregister_node(struct node *node)
2490 : : {
2491 : 0 : return device_remove_file(&node->dev, &dev_attr_compact);
2492 : : }
2493 : : #endif /* CONFIG_SYSFS && CONFIG_NUMA */
2494 : :
2495 : 42 : static inline bool kcompactd_work_requested(pg_data_t *pgdat)
2496 : : {
2497 [ - + - + ]: 42 : return pgdat->kcompactd_max_order > 0 || kthread_should_stop();
2498 : : }
2499 : :
2500 : 0 : static bool kcompactd_node_suitable(pg_data_t *pgdat)
2501 : : {
2502 : 0 : int zoneid;
2503 : 0 : struct zone *zone;
2504 : 0 : enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx;
2505 : :
2506 [ # # ]: 0 : for (zoneid = 0; zoneid <= classzone_idx; zoneid++) {
2507 : 0 : zone = &pgdat->node_zones[zoneid];
2508 : :
2509 [ # # ]: 0 : if (!populated_zone(zone))
2510 : 0 : continue;
2511 : :
2512 [ # # ]: 0 : if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0,
2513 : : classzone_idx) == COMPACT_CONTINUE)
2514 : : return true;
2515 : : }
2516 : :
2517 : : return false;
2518 : : }
2519 : :
2520 : 0 : static void kcompactd_do_work(pg_data_t *pgdat)
2521 : : {
2522 : : /*
2523 : : * With no special task, compact all zones so that a page of requested
2524 : : * order is allocatable.
2525 : : */
2526 : 0 : int zoneid;
2527 : 0 : struct zone *zone;
2528 : 0 : struct compact_control cc = {
2529 : : .order = pgdat->kcompactd_max_order,
2530 : 0 : .search_order = pgdat->kcompactd_max_order,
2531 : 0 : .classzone_idx = pgdat->kcompactd_classzone_idx,
2532 : : .mode = MIGRATE_SYNC_LIGHT,
2533 : : .ignore_skip_hint = false,
2534 : : .gfp_mask = GFP_KERNEL,
2535 : : };
2536 : 0 : trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order,
2537 : : cc.classzone_idx);
2538 : 0 : count_compact_event(KCOMPACTD_WAKE);
2539 : :
2540 [ # # ]: 0 : for (zoneid = 0; zoneid <= cc.classzone_idx; zoneid++) {
2541 : 0 : int status;
2542 : :
2543 : 0 : zone = &pgdat->node_zones[zoneid];
2544 [ # # ]: 0 : if (!populated_zone(zone))
2545 : 0 : continue;
2546 : :
2547 [ # # ]: 0 : if (compaction_deferred(zone, cc.order))
2548 : 0 : continue;
2549 : :
2550 [ # # ]: 0 : if (compaction_suitable(zone, cc.order, 0, zoneid) !=
2551 : : COMPACT_CONTINUE)
2552 : 0 : continue;
2553 : :
2554 [ # # ]: 0 : if (kthread_should_stop())
2555 : 0 : return;
2556 : :
2557 : 0 : cc.zone = zone;
2558 : 0 : status = compact_zone(&cc, NULL);
2559 : :
2560 [ # # ]: 0 : if (status == COMPACT_SUCCESS) {
2561 [ # # ]: 0 : compaction_defer_reset(zone, cc.order, false);
2562 [ # # ]: 0 : } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) {
2563 : : /*
2564 : : * Buddy pages may become stranded on pcps that could
2565 : : * otherwise coalesce on the zone's free area for
2566 : : * order >= cc.order. This is ratelimited by the
2567 : : * upcoming deferral.
2568 : : */
2569 : 0 : drain_all_pages(zone);
2570 : :
2571 : : /*
2572 : : * We use sync migration mode here, so we defer like
2573 : : * sync direct compaction does.
2574 : : */
2575 : 0 : defer_compaction(zone, cc.order);
2576 : : }
2577 : :
2578 : 0 : count_compact_events(KCOMPACTD_MIGRATE_SCANNED,
2579 [ # # ]: 0 : cc.total_migrate_scanned);
2580 : 0 : count_compact_events(KCOMPACTD_FREE_SCANNED,
2581 [ # # ]: 0 : cc.total_free_scanned);
2582 : :
2583 : 0 : VM_BUG_ON(!list_empty(&cc.freepages));
2584 : 0 : VM_BUG_ON(!list_empty(&cc.migratepages));
2585 : : }
2586 : :
2587 : : /*
2588 : : * Regardless of success, we are done until woken up next. But remember
2589 : : * the requested order/classzone_idx in case it was higher/tighter than
2590 : : * our current ones
2591 : : */
2592 [ # # ]: 0 : if (pgdat->kcompactd_max_order <= cc.order)
2593 : 0 : pgdat->kcompactd_max_order = 0;
2594 [ # # ]: 0 : if (pgdat->kcompactd_classzone_idx >= cc.classzone_idx)
2595 : 0 : pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
2596 : : }
2597 : :
2598 : 21 : void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
2599 : : {
2600 [ - + ]: 21 : if (!order)
2601 : : return;
2602 : :
2603 [ # # ]: 0 : if (pgdat->kcompactd_max_order < order)
2604 : 0 : pgdat->kcompactd_max_order = order;
2605 : :
2606 [ # # ]: 0 : if (pgdat->kcompactd_classzone_idx > classzone_idx)
2607 : 0 : pgdat->kcompactd_classzone_idx = classzone_idx;
2608 : :
2609 : : /*
2610 : : * Pairs with implicit barrier in wait_event_freezable()
2611 : : * such that wakeups are not missed.
2612 : : */
2613 [ # # ]: 0 : if (!wq_has_sleeper(&pgdat->kcompactd_wait))
2614 : : return;
2615 : :
2616 [ # # ]: 0 : if (!kcompactd_node_suitable(pgdat))
2617 : : return;
2618 : :
2619 : 0 : trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order,
2620 : : classzone_idx);
2621 : 0 : wake_up_interruptible(&pgdat->kcompactd_wait);
2622 : : }
2623 : :
2624 : : /*
2625 : : * The background compaction daemon, started as a kernel thread
2626 : : * from the init process.
2627 : : */
2628 : 21 : static int kcompactd(void *p)
2629 : : {
2630 : 21 : pg_data_t *pgdat = (pg_data_t*)p;
2631 [ + - ]: 21 : struct task_struct *tsk = current;
2632 : :
2633 [ + - ]: 21 : const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2634 : :
2635 [ + - ]: 21 : if (!cpumask_empty(cpumask))
2636 : 21 : set_cpus_allowed_ptr(tsk, cpumask);
2637 : :
2638 : 21 : set_freezable();
2639 : :
2640 : 21 : pgdat->kcompactd_max_order = 0;
2641 : 21 : pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
2642 : :
2643 [ + - ]: 21 : while (!kthread_should_stop()) {
2644 : 21 : unsigned long pflags;
2645 : :
2646 : 21 : trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
2647 [ + - + - : 63 : wait_event_freezable(pgdat->kcompactd_wait,
+ - + - -
+ ]
2648 : : kcompactd_work_requested(pgdat));
2649 : :
2650 : 0 : psi_memstall_enter(&pflags);
2651 : 0 : kcompactd_do_work(pgdat);
2652 : 0 : psi_memstall_leave(&pflags);
2653 : : }
2654 : :
2655 : 0 : return 0;
2656 : : }
2657 : :
2658 : : /*
2659 : : * This kcompactd start function will be called by init and node-hot-add.
2660 : : * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added.
2661 : : */
2662 : 21 : int kcompactd_run(int nid)
2663 : : {
2664 : 21 : pg_data_t *pgdat = NODE_DATA(nid);
2665 : 21 : int ret = 0;
2666 : :
2667 [ + - ]: 21 : if (pgdat->kcompactd)
2668 : : return 0;
2669 : :
2670 [ + - ]: 21 : pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid);
2671 [ - + ]: 21 : if (IS_ERR(pgdat->kcompactd)) {
2672 : 0 : pr_err("Failed to start kcompactd on node %d\n", nid);
2673 : 0 : ret = PTR_ERR(pgdat->kcompactd);
2674 : 0 : pgdat->kcompactd = NULL;
2675 : : }
2676 : : return ret;
2677 : : }
2678 : :
2679 : : /*
2680 : : * Called by memory hotplug when all memory in a node is offlined. Caller must
2681 : : * hold mem_hotplug_begin/end().
2682 : : */
2683 : 0 : void kcompactd_stop(int nid)
2684 : : {
2685 : 0 : struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd;
2686 : :
2687 [ # # ]: 0 : if (kcompactd) {
2688 : 0 : kthread_stop(kcompactd);
2689 : 0 : NODE_DATA(nid)->kcompactd = NULL;
2690 : : }
2691 : 0 : }
2692 : :
2693 : : /*
2694 : : * It's optimal to keep kcompactd on the same CPUs as their memory, but
2695 : : * not required for correctness. So if the last cpu in a node goes
2696 : : * away, we get changed to run anywhere: as the first one comes back,
2697 : : * restore their cpu bindings.
2698 : : */
2699 : 0 : static int kcompactd_cpu_online(unsigned int cpu)
2700 : : {
2701 : 0 : int nid;
2702 : :
2703 [ # # ]: 0 : for_each_node_state(nid, N_MEMORY) {
2704 : 0 : pg_data_t *pgdat = NODE_DATA(nid);
2705 : 0 : const struct cpumask *mask;
2706 : :
2707 : 0 : mask = cpumask_of_node(pgdat->node_id);
2708 : :
2709 [ # # ]: 0 : if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2710 : : /* One of our CPUs online: restore mask */
2711 : 0 : set_cpus_allowed_ptr(pgdat->kcompactd, mask);
2712 : : }
2713 : 0 : return 0;
2714 : : }
2715 : :
2716 : 21 : static int __init kcompactd_init(void)
2717 : : {
2718 : 21 : int nid;
2719 : 21 : int ret;
2720 : :
2721 : 21 : ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
2722 : : "mm/compaction:online",
2723 : : kcompactd_cpu_online, NULL);
2724 [ - + ]: 21 : if (ret < 0) {
2725 : 0 : pr_err("kcompactd: failed to register hotplug callbacks.\n");
2726 : 0 : return ret;
2727 : : }
2728 : :
2729 [ + + ]: 84 : for_each_node_state(nid, N_MEMORY)
2730 : 21 : kcompactd_run(nid);
2731 : : return 0;
2732 : : }
2733 : : subsys_initcall(kcompactd_init)
2734 : :
2735 : : #endif /* CONFIG_COMPACTION */
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