1 /*
2 * linux/mm/vmscan.c
3 *
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 *
6 * Swap reorganised 29.12.95, Stephen Tweedie.
7 * kswapd added: 7.1.96 sct
8 * Removed kswapd_ctl limits, and swap out as many pages as needed
9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11 * Multiqueue VM started 5.8.00, Rik van Riel.
12 */
13
14 #include <linux/mm.h>
15 #include <linux/module.h>
16 #include <linux/slab.h>
17 #include <linux/kernel_stat.h>
18 #include <linux/swap.h>
19 #include <linux/pagemap.h>
20 #include <linux/init.h>
21 #include <linux/highmem.h>
22 #include <linux/vmstat.h>
23 #include <linux/file.h>
24 #include <linux/writeback.h>
25 #include <linux/blkdev.h>
26 #include <linux/interrupt.h>
27 #include <linux/buffer_head.h> /* for try_to_release_page(),
28 buffer_heads_over_limit */
29 #include <linux/mm_inline.h>
30 #include <linux/pagevec.h>
31 #include <linux/backing-dev.h>
32 #include <linux/rmap.h>
33 #include <linux/topology.h>
34 #include <linux/cpu.h>
35 #include <linux/cpuset.h>
36 #include <linux/notifier.h>
37 #include <linux/rwsem.h>
38 #include <linux/delay.h>
39 #include <linux/kthread.h>
40 #include <linux/freezer.h>
41 #include <linux/memcontrol.h>
42
43 #include <asm/tlbflush.h>
44 #include <asm/div64.h>
45
46 #include <linux/swapops.h>
47
48 #include "internal.h"
49
50 struct scan_control {
51 /* Incremented by the number of inactive pages that were scanned */
52 unsigned long nr_scanned;
53
54 /* This context's GFP mask */
55 gfp_t gfp_mask;
56
57 int may_writepage;
58
59 /* Can pages be swapped as part of reclaim? */
60 int may_swap;
61
62 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
63 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
64 * In this context, it doesn't matter that we scan the
65 * whole list at once. */
66 int swap_cluster_max;
67
68 int swappiness;
69
70 int all_unreclaimable;
71
72 int order;
73
74 /* Which cgroup do we reclaim from */
75 struct mem_cgroup *mem_cgroup;
76
77 /* Pluggable isolate pages callback */
78 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
79 unsigned long *scanned, int order, int mode,
80 struct zone *z, struct mem_cgroup *mem_cont,
81 int active);
82 };
83
84 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
85
86 #ifdef ARCH_HAS_PREFETCH
87 #define prefetch_prev_lru_page(_page, _base, _field) \
88 do { \
89 if ((_page)->lru.prev != _base) { \
90 struct page *prev; \
91 \
92 prev = lru_to_page(&(_page->lru)); \
93 prefetch(&prev->_field); \
94 } \
95 } while (0)
96 #else
97 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
98 #endif
99
100 #ifdef ARCH_HAS_PREFETCHW
101 #define prefetchw_prev_lru_page(_page, _base, _field) \
102 do { \
103 if ((_page)->lru.prev != _base) { \
104 struct page *prev; \
105 \
106 prev = lru_to_page(&(_page->lru)); \
107 prefetchw(&prev->_field); \
108 } \
109 } while (0)
110 #else
111 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
112 #endif
113
114 /*
115 * From 0 .. 100. Higher means more swappy.
116 */
117 int vm_swappiness = 60;
118 long vm_total_pages; /* The total number of pages which the VM controls */
119
120 static LIST_HEAD(shrinker_list);
121 static DECLARE_RWSEM(shrinker_rwsem);
122
123 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
124 #define scan_global_lru(sc) (!(sc)->mem_cgroup)
125 #else
126 #define scan_global_lru(sc) (1)
127 #endif
128
129 /*
130 * Add a shrinker callback to be called from the vm
131 */
132 void register_shrinker(struct shrinker *shrinker)
133 {
134 shrinker->nr = 0;
135 down_write(&shrinker_rwsem);
136 list_add_tail(&shrinker->list, &shrinker_list);
137 up_write(&shrinker_rwsem);
138 }
139 EXPORT_SYMBOL(register_shrinker);
140
141 /*
142 * Remove one
143 */
144 void unregister_shrinker(struct shrinker *shrinker)
145 {
146 down_write(&shrinker_rwsem);
147 list_del(&shrinker->list);
148 up_write(&shrinker_rwsem);
149 }
150 EXPORT_SYMBOL(unregister_shrinker);
151
152 #define SHRINK_BATCH 128
153 /*
154 * Call the shrink functions to age shrinkable caches
155 *
156 * Here we assume it costs one seek to replace a lru page and that it also
157 * takes a seek to recreate a cache object. With this in mind we age equal
158 * percentages of the lru and ageable caches. This should balance the seeks
159 * generated by these structures.
160 *
161 * If the vm encountered mapped pages on the LRU it increase the pressure on
162 * slab to avoid swapping.
163 *
164 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
165 *
166 * `lru_pages' represents the number of on-LRU pages in all the zones which
167 * are eligible for the caller's allocation attempt. It is used for balancing
168 * slab reclaim versus page reclaim.
169 *
170 * Returns the number of slab objects which we shrunk.
171 */
172 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
173 unsigned long lru_pages)
174 {
175 struct shrinker *shrinker;
176 unsigned long ret = 0;
177
178 if (scanned == 0)
179 scanned = SWAP_CLUSTER_MAX;
180
181 if (!down_read_trylock(&shrinker_rwsem))
182 return 1; /* Assume we'll be able to shrink next time */
183
184 list_for_each_entry(shrinker, &shrinker_list, list) {
185 unsigned long long delta;
186 unsigned long total_scan;
187 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
188
189 delta = (4 * scanned) / shrinker->seeks;
190 delta *= max_pass;
191 do_div(delta, lru_pages + 1);
192 shrinker->nr += delta;
193 if (shrinker->nr < 0) {
194 printk(KERN_ERR "%s: nr=%ld\n",
195 __FUNCTION__, shrinker->nr);
196 shrinker->nr = max_pass;
197 }
198
199 /*
200 * Avoid risking looping forever due to too large nr value:
201 * never try to free more than twice the estimate number of
202 * freeable entries.
203 */
204 if (shrinker->nr > max_pass * 2)
205 shrinker->nr = max_pass * 2;
206
207 total_scan = shrinker->nr;
208 shrinker->nr = 0;
209
210 while (total_scan >= SHRINK_BATCH) {
211 long this_scan = SHRINK_BATCH;
212 int shrink_ret;
213 int nr_before;
214
215 nr_before = (*shrinker->shrink)(0, gfp_mask);
216 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
217 if (shrink_ret == -1)
218 break;
219 if (shrink_ret < nr_before)
220 ret += nr_before - shrink_ret;
221 count_vm_events(SLABS_SCANNED, this_scan);
222 total_scan -= this_scan;
223
224 cond_resched();
225 }
226
227 shrinker->nr += total_scan;
228 }
229 up_read(&shrinker_rwsem);
230 return ret;
231 }
232
233 /* Called without lock on whether page is mapped, so answer is unstable */
234 static inline int page_mapping_inuse(struct page *page)
235 {
236 struct address_space *mapping;
237
238 /* Page is in somebody's page tables. */
239 if (page_mapped(page))
240 return 1;
241
242 /* Be more reluctant to reclaim swapcache than pagecache */
243 if (PageSwapCache(page))
244 return 1;
245
246 mapping = page_mapping(page);
247 if (!mapping)
248 return 0;
249
250 /* File is mmap'd by somebody? */
251 return mapping_mapped(mapping);
252 }
253
254 static inline int is_page_cache_freeable(struct page *page)
255 {
256 return page_count(page) - !!PagePrivate(page) == 2;
257 }
258
259 static int may_write_to_queue(struct backing_dev_info *bdi)
260 {
261 if (current->flags & PF_SWAPWRITE)
262 return 1;
263 if (!bdi_write_congested(bdi))
264 return 1;
265 if (bdi == current->backing_dev_info)
266 return 1;
267 return 0;
268 }
269
270 /*
271 * We detected a synchronous write error writing a page out. Probably
272 * -ENOSPC. We need to propagate that into the address_space for a subsequent
273 * fsync(), msync() or close().
274 *
275 * The tricky part is that after writepage we cannot touch the mapping: nothing
276 * prevents it from being freed up. But we have a ref on the page and once
277 * that page is locked, the mapping is pinned.
278 *
279 * We're allowed to run sleeping lock_page() here because we know the caller has
280 * __GFP_FS.
281 */
282 static void handle_write_error(struct address_space *mapping,
283 struct page *page, int error)
284 {
285 lock_page(page);
286 if (page_mapping(page) == mapping)
287 mapping_set_error(mapping, error);
288 unlock_page(page);
289 }
290
291 /* Request for sync pageout. */
292 enum pageout_io {
293 PAGEOUT_IO_ASYNC,
294 PAGEOUT_IO_SYNC,
295 };
296
297 /* possible outcome of pageout() */
298 typedef enum {
299 /* failed to write page out, page is locked */
300 PAGE_KEEP,
301 /* move page to the active list, page is locked */
302 PAGE_ACTIVATE,
303 /* page has been sent to the disk successfully, page is unlocked */
304 PAGE_SUCCESS,
305 /* page is clean and locked */
306 PAGE_CLEAN,
307 } pageout_t;
308
309 /*
310 * pageout is called by shrink_page_list() for each dirty page.
311 * Calls ->writepage().
312 */
313 static pageout_t pageout(struct page *page, struct address_space *mapping,
314 enum pageout_io sync_writeback)
315 {
316 /*
317 * If the page is dirty, only perform writeback if that write
318 * will be non-blocking. To prevent this allocation from being
319 * stalled by pagecache activity. But note that there may be
320 * stalls if we need to run get_block(). We could test
321 * PagePrivate for that.
322 *
323 * If this process is currently in generic_file_write() against
324 * this page's queue, we can perform writeback even if that
325 * will block.
326 *
327 * If the page is swapcache, write it back even if that would
328 * block, for some throttling. This happens by accident, because
329 * swap_backing_dev_info is bust: it doesn't reflect the
330 * congestion state of the swapdevs. Easy to fix, if needed.
331 * See swapfile.c:page_queue_congested().
332 */
333 if (!is_page_cache_freeable(page))
334 return PAGE_KEEP;
335 if (!mapping) {
336 /*
337 * Some data journaling orphaned pages can have
338 * page->mapping == NULL while being dirty with clean buffers.
339 */
340 if (PagePrivate(page)) {
341 if (try_to_free_buffers(page)) {
342 ClearPageDirty(page);
343 printk("%s: orphaned page\n", __FUNCTION__);
344 return PAGE_CLEAN;
345 }
346 }
347 return PAGE_KEEP;
348 }
349 if (mapping->a_ops->writepage == NULL)
350 return PAGE_ACTIVATE;
351 if (!may_write_to_queue(mapping->backing_dev_info))
352 return PAGE_KEEP;
353
354 if (clear_page_dirty_for_io(page)) {
355 int res;
356 struct writeback_control wbc = {
357 .sync_mode = WB_SYNC_NONE,
358 .nr_to_write = SWAP_CLUSTER_MAX,
359 .range_start = 0,
360 .range_end = LLONG_MAX,
361 .nonblocking = 1,
362 .for_reclaim = 1,
363 };
364
365 SetPageReclaim(page);
366 res = mapping->a_ops->writepage(page, &wbc);
367 if (res < 0)
368 handle_write_error(mapping, page, res);
369 if (res == AOP_WRITEPAGE_ACTIVATE) {
370 ClearPageReclaim(page);
371 return PAGE_ACTIVATE;
372 }
373
374 /*
375 * Wait on writeback if requested to. This happens when
376 * direct reclaiming a large contiguous area and the
377 * first attempt to free a range of pages fails.
378 */
379 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
380 wait_on_page_writeback(page);
381
382 if (!PageWriteback(page)) {
383 /* synchronous write or broken a_ops? */
384 ClearPageReclaim(page);
385 }
386 inc_zone_page_state(page, NR_VMSCAN_WRITE);
387 return PAGE_SUCCESS;
388 }
389
390 return PAGE_CLEAN;
391 }
392
393 /*
394 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
395 * someone else has a ref on the page, abort and return 0. If it was
396 * successfully detached, return 1. Assumes the caller has a single ref on
397 * this page.
398 */
399 int remove_mapping(struct address_space *mapping, struct page *page)
400 {
401 BUG_ON(!PageLocked(page));
402 BUG_ON(mapping != page_mapping(page));
403
404 lock_page_ref_irq(page);
405 /*
406 * The non racy check for a busy page.
407 *
408 * Must be careful with the order of the tests. When someone has
409 * a ref to the page, it may be possible that they dirty it then
410 * drop the reference. So if PageDirty is tested before page_count
411 * here, then the following race may occur:
412 *
413 * get_user_pages(&page);
414 * [user mapping goes away]
415 * write_to(page);
416 * !PageDirty(page) [good]
417 * SetPageDirty(page);
418 * put_page(page);
419 * !page_count(page) [good, discard it]
420 *
421 * [oops, our write_to data is lost]
422 *
423 * Reversing the order of the tests ensures such a situation cannot
424 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
425 * load is not satisfied before that of page->_count.
426 *
427 * Note that if SetPageDirty is always performed via set_page_dirty,
428 * and thus under tree_lock, then this ordering is not required.
429 */
430 if (unlikely(page_count(page) != 2))
431 goto cannot_free;
432 smp_rmb();
433 if (unlikely(PageDirty(page)))
434 goto cannot_free;
435
436 if (PageSwapCache(page)) {
437 swp_entry_t swap = { .val = page_private(page) };
438 __delete_from_swap_cache(page);
439 swap_free(swap);
440 goto free_it;
441 }
442
443 __remove_from_page_cache(page);
444
445 free_it:
446 unlock_page_ref_irq(page);
447 __put_page(page); /* The pagecache ref */
448 return 1;
449
450 cannot_free:
451 unlock_page_ref_irq(page);
452 return 0;
453 }
454
455 /*
456 * shrink_page_list() returns the number of reclaimed pages
457 */
458 static unsigned long shrink_page_list(struct list_head *page_list,
459 struct scan_control *sc,
460 enum pageout_io sync_writeback)
461 {
462 LIST_HEAD(ret_pages);
463 struct pagevec freed_pvec;
464 int pgactivate = 0;
465 unsigned long nr_reclaimed = 0;
466
467 cond_resched();
468
469 pagevec_init(&freed_pvec, 1);
470 while (!list_empty(page_list)) {
471 struct address_space *mapping;
472 struct page *page;
473 int may_enter_fs;
474 int referenced;
475
476 cond_resched();
477
478 page = lru_to_page(page_list);
479 list_del(&page->lru);
480
481 if (TestSetPageLocked(page))
482 goto keep;
483
484 VM_BUG_ON(PageActive(page));
485
486 sc->nr_scanned++;
487
488 if (!sc->may_swap && page_mapped(page))
489 goto keep_locked;
490
491 /* Double the slab pressure for mapped and swapcache pages */
492 if (page_mapped(page) || PageSwapCache(page))
493 sc->nr_scanned++;
494
495 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
496 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
497
498 if (PageWriteback(page)) {
499 /*
500 * Synchronous reclaim is performed in two passes,
501 * first an asynchronous pass over the list to
502 * start parallel writeback, and a second synchronous
503 * pass to wait for the IO to complete. Wait here
504 * for any page for which writeback has already
505 * started.
506 */
507 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
508 wait_on_page_writeback(page);
509 else
510 goto keep_locked;
511 }
512
513 referenced = page_referenced(page, 1, sc->mem_cgroup);
514 /* In active use or really unfreeable? Activate it. */
515 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
516 referenced && page_mapping_inuse(page))
517 goto activate_locked;
518
519 #ifdef CONFIG_SWAP
520 /*
521 * Anonymous process memory has backing store?
522 * Try to allocate it some swap space here.
523 */
524 if (PageAnon(page) && !PageSwapCache(page))
525 if (!add_to_swap(page, GFP_ATOMIC))
526 goto activate_locked;
527 #endif /* CONFIG_SWAP */
528
529 mapping = page_mapping(page);
530
531 /*
532 * The page is mapped into the page tables of one or more
533 * processes. Try to unmap it here.
534 */
535 if (page_mapped(page) && mapping) {
536 switch (try_to_unmap(page, 0)) {
537 case SWAP_FAIL:
538 goto activate_locked;
539 case SWAP_AGAIN:
540 goto keep_locked;
541 case SWAP_SUCCESS:
542 ; /* try to free the page below */
543 }
544 }
545
546 if (PageDirty(page)) {
547 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
548 goto keep_locked;
549 if (!may_enter_fs)
550 goto keep_locked;
551 if (!sc->may_writepage)
552 goto keep_locked;
553
554 /* Page is dirty, try to write it out here */
555 switch (pageout(page, mapping, sync_writeback)) {
556 case PAGE_KEEP:
557 goto keep_locked;
558 case PAGE_ACTIVATE:
559 goto activate_locked;
560 case PAGE_SUCCESS:
561 if (PageWriteback(page) || PageDirty(page))
562 goto keep;
563 /*
564 * A synchronous write - probably a ramdisk. Go
565 * ahead and try to reclaim the page.
566 */
567 if (TestSetPageLocked(page))
568 goto keep;
569 if (PageDirty(page) || PageWriteback(page))
570 goto keep_locked;
571 mapping = page_mapping(page);
572 case PAGE_CLEAN:
573 ; /* try to free the page below */
574 }
575 }
576
577 /*
578 * If the page has buffers, try to free the buffer mappings
579 * associated with this page. If we succeed we try to free
580 * the page as well.
581 *
582 * We do this even if the page is PageDirty().
583 * try_to_release_page() does not perform I/O, but it is
584 * possible for a page to have PageDirty set, but it is actually
585 * clean (all its buffers are clean). This happens if the
586 * buffers were written out directly, with submit_bh(). ext3
587 * will do this, as well as the blockdev mapping.
588 * try_to_release_page() will discover that cleanness and will
589 * drop the buffers and mark the page clean - it can be freed.
590 *
591 * Rarely, pages can have buffers and no ->mapping. These are
592 * the pages which were not successfully invalidated in
593 * truncate_complete_page(). We try to drop those buffers here
594 * and if that worked, and the page is no longer mapped into
595 * process address space (page_count == 1) it can be freed.
596 * Otherwise, leave the page on the LRU so it is swappable.
597 */
598 if (PagePrivate(page)) {
599 if (!try_to_release_page(page, sc->gfp_mask))
600 goto activate_locked;
601 if (!mapping && page_count(page) == 1)
602 goto free_it;
603 }
604
605 if (!mapping || !remove_mapping(mapping, page))
606 goto keep_locked;
607
608 free_it:
609 unlock_page(page);
610 nr_reclaimed++;
611 if (!pagevec_add(&freed_pvec, page))
612 __pagevec_release_nonlru(&freed_pvec);
613 continue;
614
615 activate_locked:
616 SetPageActive(page);
617 pgactivate++;
618 keep_locked:
619 unlock_page(page);
620 keep:
621 list_add(&page->lru, &ret_pages);
622 VM_BUG_ON(PageLRU(page));
623 }
624 list_splice(&ret_pages, page_list);
625 if (pagevec_count(&freed_pvec))
626 __pagevec_release_nonlru(&freed_pvec);
627 count_vm_events(PGACTIVATE, pgactivate);
628 return nr_reclaimed;
629 }
630
631 /* LRU Isolation modes. */
632 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
633 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
634 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
635
636 /*
637 * Attempt to remove the specified page from its LRU. Only take this page
638 * if it is of the appropriate PageActive status. Pages which are being
639 * freed elsewhere are also ignored.
640 *
641 * page: page to consider
642 * mode: one of the LRU isolation modes defined above
643 *
644 * returns 0 on success, -ve errno on failure.
645 */
646 int __isolate_lru_page(struct page *page, int mode)
647 {
648 int ret = -EINVAL;
649
650 /* Only take pages on the LRU. */
651 if (!PageLRU(page))
652 return ret;
653
654 /*
655 * When checking the active state, we need to be sure we are
656 * dealing with comparible boolean values. Take the logical not
657 * of each.
658 */
659 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
660 return ret;
661
662 ret = -EBUSY;
663 if (likely(get_page_unless_zero(page))) {
664 /*
665 * Be careful not to clear PageLRU until after we're
666 * sure the page is not being freed elsewhere -- the
667 * page release code relies on it.
668 */
669 ClearPageLRU(page);
670 ret = 0;
671 }
672
673 return ret;
674 }
675
676 /*
677 * zone->lru_lock is heavily contended. Some of the functions that
678 * shrink the lists perform better by taking out a batch of pages
679 * and working on them outside the LRU lock.
680 *
681 * For pagecache intensive workloads, this function is the hottest
682 * spot in the kernel (apart from copy_*_user functions).
683 *
684 * Appropriate locks must be held before calling this function.
685 *
686 * @nr_to_scan: The number of pages to look through on the list.
687 * @src: The LRU list to pull pages off.
688 * @dst: The temp list to put pages on to.
689 * @scanned: The number of pages that were scanned.
690 * @order: The caller's attempted allocation order
691 * @mode: One of the LRU isolation modes
692 *
693 * returns how many pages were moved onto *@dst.
694 */
695 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
696 struct list_head *src, struct list_head *dst,
697 unsigned long *scanned, int order, int mode)
698 {
699 unsigned long nr_taken = 0;
700 unsigned long scan;
701
702 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
703 struct page *page;
704 unsigned long pfn;
705 unsigned long end_pfn;
706 unsigned long page_pfn;
707 int zone_id;
708
709 page = lru_to_page(src);
710 prefetchw_prev_lru_page(page, src, flags);
711
712 VM_BUG_ON(!PageLRU(page));
713
714 switch (__isolate_lru_page(page, mode)) {
715 case 0:
716 list_move(&page->lru, dst);
717 nr_taken++;
718 break;
719
720 case -EBUSY:
721 /* else it is being freed elsewhere */
722 list_move(&page->lru, src);
723 continue;
724
725 default:
726 BUG();
727 }
728
729 if (!order)
730 continue;
731
732 /*
733 * Attempt to take all pages in the order aligned region
734 * surrounding the tag page. Only take those pages of
735 * the same active state as that tag page. We may safely
736 * round the target page pfn down to the requested order
737 * as the mem_map is guarenteed valid out to MAX_ORDER,
738 * where that page is in a different zone we will detect
739 * it from its zone id and abort this block scan.
740 */
741 zone_id = page_zone_id(page);
742 page_pfn = page_to_pfn(page);
743 pfn = page_pfn & ~((1 << order) - 1);
744 end_pfn = pfn + (1 << order);
745 for (; pfn < end_pfn; pfn++) {
746 struct page *cursor_page;
747
748 /* The target page is in the block, ignore it. */
749 if (unlikely(pfn == page_pfn))
750 continue;
751
752 /* Avoid holes within the zone. */
753 if (unlikely(!pfn_valid_within(pfn)))
754 break;
755
756 cursor_page = pfn_to_page(pfn);
757 /* Check that we have not crossed a zone boundary. */
758 if (unlikely(page_zone_id(cursor_page) != zone_id))
759 continue;
760 switch (__isolate_lru_page(cursor_page, mode)) {
761 case 0:
762 list_move(&cursor_page->lru, dst);
763 nr_taken++;
764 scan++;
765 break;
766
767 case -EBUSY:
768 /* else it is being freed elsewhere */
769 list_move(&cursor_page->lru, src);
770 default:
771 break;
772 }
773 }
774 }
775
776 *scanned = scan;
777 return nr_taken;
778 }
779
780 static unsigned long isolate_pages_global(unsigned long nr,
781 struct list_head *dst,
782 unsigned long *scanned, int order,
783 int mode, struct zone *z,
784 struct mem_cgroup *mem_cont,
785 int active)
786 {
787 if (active)
788 return isolate_lru_pages(nr, &z->active_list, dst,
789 scanned, order, mode);
790 else
791 return isolate_lru_pages(nr, &z->inactive_list, dst,
792 scanned, order, mode);
793 }
794
795 /*
796 * clear_active_flags() is a helper for shrink_active_list(), clearing
797 * any active bits from the pages in the list.
798 */
799 static unsigned long clear_active_flags(struct list_head *page_list)
800 {
801 int nr_active = 0;
802 struct page *page;
803
804 list_for_each_entry(page, page_list, lru)
805 if (PageActive(page)) {
806 ClearPageActive(page);
807 nr_active++;
808 }
809
810 return nr_active;
811 }
812
813 /*
814 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
815 * of reclaimed pages
816 */
817 static unsigned long shrink_inactive_list(unsigned long max_scan,
818 struct zone *zone, struct scan_control *sc)
819 {
820 LIST_HEAD(page_list);
821 struct pagevec pvec;
822 unsigned long nr_scanned = 0;
823 unsigned long nr_reclaimed = 0;
824
825 pagevec_init(&pvec, 1);
826
827 lru_add_drain();
828 spin_lock_irq(&zone->lru_lock);
829 do {
830 struct page *page;
831 unsigned long nr_taken;
832 unsigned long nr_scan;
833 unsigned long nr_freed;
834 unsigned long nr_active;
835
836 nr_taken = sc->isolate_pages(sc->swap_cluster_max,
837 &page_list, &nr_scan, sc->order,
838 (sc->order > PAGE_ALLOC_COSTLY_ORDER)?
839 ISOLATE_BOTH : ISOLATE_INACTIVE,
840 zone, sc->mem_cgroup, 0);
841 nr_active = clear_active_flags(&page_list);
842 __count_vm_events(PGDEACTIVATE, nr_active);
843
844 __mod_zone_page_state(zone, NR_ACTIVE, -nr_active);
845 __mod_zone_page_state(zone, NR_INACTIVE,
846 -(nr_taken - nr_active));
847 if (scan_global_lru(sc))
848 zone->pages_scanned += nr_scan;
849 spin_unlock_irq(&zone->lru_lock);
850
851 nr_scanned += nr_scan;
852 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
853
854 /*
855 * If we are direct reclaiming for contiguous pages and we do
856 * not reclaim everything in the list, try again and wait
857 * for IO to complete. This will stall high-order allocations
858 * but that should be acceptable to the caller
859 */
860 if (nr_freed < nr_taken && !current_is_kswapd() &&
861 sc->order > PAGE_ALLOC_COSTLY_ORDER) {
862 congestion_wait(WRITE, HZ/10);
863
864 /*
865 * The attempt at page out may have made some
866 * of the pages active, mark them inactive again.
867 */
868 nr_active = clear_active_flags(&page_list);
869 count_vm_events(PGDEACTIVATE, nr_active);
870
871 nr_freed += shrink_page_list(&page_list, sc,
872 PAGEOUT_IO_SYNC);
873 }
874
875 nr_reclaimed += nr_freed;
876 local_irq_disable_nort();
877 if (current_is_kswapd()) {
878 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
879 __count_vm_events(KSWAPD_STEAL, nr_freed);
880 } else if (scan_global_lru(sc))
881 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
882
883 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
884
885 if (nr_taken == 0)
886 goto done;
887
888 spin_lock(&zone->lru_lock);
889 /*
890 * Put back any unfreeable pages.
891 */
892 while (!list_empty(&page_list)) {
893 page = lru_to_page(&page_list);
894 VM_BUG_ON(PageLRU(page));
895 SetPageLRU(page);
896 list_del(&page->lru);
897 if (PageActive(page))
898 add_page_to_active_list(zone, page);
899 else
900 add_page_to_inactive_list(zone, page);
901 if (!pagevec_add(&pvec, page)) {
902 spin_unlock_irq(&zone->lru_lock);
903 __pagevec_release(&pvec);
904 spin_lock_irq(&zone->lru_lock);
905 }
906 }
907 } while (nr_scanned < max_scan);
908 /*
909 * Non-PREEMPT_RT relies on IRQs-off protecting the page_states
910 * per-CPU data. PREEMPT_RT has that data protected even in
911 * __mod_page_state(), so no need to keep IRQs disabled.
912 */
913 spin_unlock(&zone->lru_lock);
914 done:
915 local_irq_enable_nort();
916 pagevec_release(&pvec);
917 return nr_reclaimed;
918 }
919
920 /*
921 * We are about to scan this zone at a certain priority level. If that priority
922 * level is smaller (ie: more urgent) than the previous priority, then note
923 * that priority level within the zone. This is done so that when the next
924 * process comes in to scan this zone, it will immediately start out at this
925 * priority level rather than having to build up its own scanning priority.
926 * Here, this priority affects only the reclaim-mapped threshold.
927 */
928 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
929 {
930 if (priority < zone->prev_priority)
931 zone->prev_priority = priority;
932 }
933
934 static inline int zone_is_near_oom(struct zone *zone)
935 {
936 return zone->pages_scanned >= (zone_page_state(zone, NR_ACTIVE)
937 + zone_page_state(zone, NR_INACTIVE))*3;
938 }
939
940 /*
941 * Determine we should try to reclaim mapped pages.
942 * This is called only when sc->mem_cgroup is NULL.
943 */
944 static int calc_reclaim_mapped(struct scan_control *sc, struct zone *zone,
945 int priority)
946 {
947 long mapped_ratio;
948 long distress;
949 long swap_tendency;
950 long imbalance;
951 int reclaim_mapped = 0;
952 int prev_priority;
953
954 if (scan_global_lru(sc) && zone_is_near_oom(zone))
955 return 1;
956 /*
957 * `distress' is a measure of how much trouble we're having
958 * reclaiming pages. 0 -> no problems. 100 -> great trouble.
959 */
960 if (scan_global_lru(sc))
961 prev_priority = zone->prev_priority;
962 else
963 prev_priority = mem_cgroup_get_reclaim_priority(sc->mem_cgroup);
964
965 distress = 100 >> min(prev_priority, priority);
966
967 /*
968 * The point of this algorithm is to decide when to start
969 * reclaiming mapped memory instead of just pagecache. Work out
970 * how much memory
971 * is mapped.
972 */
973 if (scan_global_lru(sc))
974 mapped_ratio = ((global_page_state(NR_FILE_MAPPED) +
975 global_page_state(NR_ANON_PAGES)) * 100) /
976 vm_total_pages;
977 else
978 mapped_ratio = mem_cgroup_calc_mapped_ratio(sc->mem_cgroup);
979
980 /*
981 * Now decide how much we really want to unmap some pages. The
982 * mapped ratio is downgraded - just because there's a lot of
983 * mapped memory doesn't necessarily mean that page reclaim
984 * isn't succeeding.
985 *
986 * The distress ratio is important - we don't want to start
987 * going oom.
988 *
989 * A 100% value of vm_swappiness overrides this algorithm
990 * altogether.
991 */
992 swap_tendency = mapped_ratio / 2 + distress + sc->swappiness;
993
994 /*
995 * If there's huge imbalance between active and inactive
996 * (think active 100 times larger than inactive) we should
997 * become more permissive, or the system will take too much
998 * cpu before it start swapping during memory pressure.
999 * Distress is about avoiding early-oom, this is about
1000 * making swappiness graceful despite setting it to low
1001 * values.
1002 *
1003 * Avoid div by zero with nr_inactive+1, and max resulting
1004 * value is vm_total_pages.
1005 */
1006 if (scan_global_lru(sc)) {
1007 imbalance = zone_page_state(zone, NR_ACTIVE);
1008 imbalance /= zone_page_state(zone, NR_INACTIVE) + 1;
1009 } else
1010 imbalance = mem_cgroup_reclaim_imbalance(sc->mem_cgroup);
1011
1012 /*
1013 * Reduce the effect of imbalance if swappiness is low,
1014 * this means for a swappiness very low, the imbalance
1015 * must be much higher than 100 for this logic to make
1016 * the difference.
1017 *
1018 * Max temporary value is vm_total_pages*100.
1019 */
1020 imbalance *= (vm_swappiness + 1);
1021 imbalance /= 100;
1022
1023 /*
1024 * If not much of the ram is mapped, makes the imbalance
1025 * less relevant, it's high priority we refill the inactive
1026 * list with mapped pages only in presence of high ratio of
1027 * mapped pages.
1028 *
1029 * Max temporary value is vm_total_pages*100.
1030 */
1031 imbalance *= mapped_ratio;
1032 imbalance /= 100;
1033
1034 /* apply imbalance feedback to swap_tendency */
1035 swap_tendency += imbalance;
1036
1037 /*
1038 * Now use this metric to decide whether to start moving mapped
1039 * memory onto the inactive list.
1040 */
1041 if (swap_tendency >= 100)
1042 reclaim_mapped = 1;
1043
1044 return reclaim_mapped;
1045 }
1046
1047 /*
1048 * This moves pages from the active list to the inactive list.
1049 *
1050 * We move them the other way if the page is referenced by one or more
1051 * processes, from rmap.
1052 *
1053 * If the pages are mostly unmapped, the processing is fast and it is
1054 * appropriate to hold zone->lru_lock across the whole operation. But if
1055 * the pages are mapped, the processing is slow (page_referenced()) so we
1056 * should drop zone->lru_lock around each page. It's impossible to balance
1057 * this, so instead we remove the pages from the LRU while processing them.
1058 * It is safe to rely on PG_active against the non-LRU pages in here because
1059 * nobody will play with that bit on a non-LRU page.
1060 *
1061 * The downside is that we have to touch page->_count against each page.
1062 * But we had to alter page->flags anyway.
1063 */
1064
1065
1066 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1067 struct scan_control *sc, int priority)
1068 {
1069 unsigned long pgmoved;
1070 int pgdeactivate = 0;
1071 unsigned long pgscanned;
1072 LIST_HEAD(l_hold); /* The pages which were snipped off */
1073 LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */
1074 LIST_HEAD(l_active); /* Pages to go onto the active_list */
1075 struct page *page;
1076 struct pagevec pvec;
1077 int reclaim_mapped = 0;
1078
1079 if (sc->may_swap)
1080 reclaim_mapped = calc_reclaim_mapped(sc, zone, priority);
1081
1082 lru_add_drain();
1083 spin_lock_irq(&zone->lru_lock);
1084 pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1085 ISOLATE_ACTIVE, zone,
1086 sc->mem_cgroup, 1);
1087 /*
1088 * zone->pages_scanned is used for detect zone's oom
1089 * mem_cgroup remembers nr_scan by itself.
1090 */
1091 if (scan_global_lru(sc))
1092 zone->pages_scanned += pgscanned;
1093
1094 __mod_zone_page_state(zone, NR_ACTIVE, -pgmoved);
1095 spin_unlock_irq(&zone->lru_lock);
1096
1097 while (!list_empty(&l_hold)) {
1098 cond_resched();
1099 page = lru_to_page(&l_hold);
1100 list_del(&page->lru);
1101 if (page_mapped(page)) {
1102 if (!reclaim_mapped ||
1103 (total_swap_pages == 0 && PageAnon(page)) ||
1104 page_referenced(page, 0, sc->mem_cgroup)) {
1105 list_add(&page->lru, &l_active);
1106 continue;
1107 }
1108 }
1109 list_add(&page->lru, &l_inactive);
1110 }
1111
1112 pagevec_init(&pvec, 1);
1113 pgmoved = 0;
1114 spin_lock_irq(&zone->lru_lock);
1115 while (!list_empty(&l_inactive)) {
1116 page = lru_to_page(&l_inactive);
1117 prefetchw_prev_lru_page(page, &l_inactive, flags);
1118 VM_BUG_ON(PageLRU(page));
1119 SetPageLRU(page);
1120 VM_BUG_ON(!PageActive(page));
1121 ClearPageActive(page);
1122
1123 list_move(&page->lru, &zone->inactive_list);
1124 mem_cgroup_move_lists(page, false);
1125 pgmoved++;
1126 if (!pagevec_add(&pvec, page)) {
1127 __mod_zone_page_state(zone, NR_INACTIVE, pgmoved);
1128 spin_unlock_irq(&zone->lru_lock);
1129 pgdeactivate += pgmoved;
1130 pgmoved = 0;
1131 if (buffer_heads_over_limit)
1132 pagevec_strip(&pvec);
1133 __pagevec_release(&pvec);
1134 spin_lock_irq(&zone->lru_lock);
1135 }
1136 }
1137 __mod_zone_page_state(zone, NR_INACTIVE, pgmoved);
1138 pgdeactivate += pgmoved;
1139 if (buffer_heads_over_limit) {
1140 spin_unlock_irq(&zone->lru_lock);
1141 pagevec_strip(&pvec);
1142 spin_lock_irq(&zone->lru_lock);
1143 }
1144
1145 pgmoved = 0;
1146 while (!list_empty(&l_active)) {
1147 page = lru_to_page(&l_active);
1148 prefetchw_prev_lru_page(page, &l_active, flags);
1149 VM_BUG_ON(PageLRU(page));
1150 SetPageLRU(page);
1151 VM_BUG_ON(!PageActive(page));
1152
1153 list_move(&page->lru, &zone->active_list);
1154 mem_cgroup_move_lists(page, true);
1155 pgmoved++;
1156 if (!pagevec_add(&pvec, page)) {
1157 __mod_zone_page_state(zone, NR_ACTIVE, pgmoved);
1158 pgmoved = 0;
1159 spin_unlock_irq(&zone->lru_lock);
1160 __pagevec_release(&pvec);
1161 spin_lock_irq(&zone->lru_lock);
1162 }
1163 }
1164 __mod_zone_page_state(zone, NR_ACTIVE, pgmoved);
1165
1166 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1167 __count_vm_events(PGDEACTIVATE, pgdeactivate);
1168 spin_unlock_irq(&zone->lru_lock);
1169
1170 pagevec_release(&pvec);
1171 }
1172
1173 /*
1174 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1175 */
1176 static unsigned long shrink_zone(int priority, struct zone *zone,
1177 struct scan_control *sc)
1178 {
1179 unsigned long nr_active;
1180 unsigned long nr_inactive;
1181 unsigned long nr_to_scan;
1182 unsigned long nr_reclaimed = 0;
1183
1184 if (scan_global_lru(sc)) {
1185 /*
1186 * Add one to nr_to_scan just to make sure that the kernel
1187 * will slowly sift through the active list.
1188 */
1189 zone->nr_scan_active +=
1190 (zone_page_state(zone, NR_ACTIVE) >> priority) + 1;
1191 nr_active = zone->nr_scan_active;
1192 zone->nr_scan_inactive +=
1193 (zone_page_state(zone, NR_INACTIVE) >> priority) + 1;
1194 nr_inactive = zone->nr_scan_inactive;
1195 if (nr_inactive >= sc->swap_cluster_max)
1196 zone->nr_scan_inactive = 0;
1197 else
1198 nr_inactive = 0;
1199
1200 if (nr_active >= sc->swap_cluster_max)
1201 zone->nr_scan_active = 0;
1202 else
1203 nr_active = 0;
1204 } else {
1205 /*
1206 * This reclaim occurs not because zone memory shortage but
1207 * because memory controller hits its limit.
1208 * Then, don't modify zone reclaim related data.
1209 */
1210 nr_active = mem_cgroup_calc_reclaim_active(sc->mem_cgroup,
1211 zone, priority);
1212
1213 nr_inactive = mem_cgroup_calc_reclaim_inactive(sc->mem_cgroup,
1214 zone, priority);
1215 }
1216
1217
1218 while (nr_active || nr_inactive) {
1219 if (nr_active) {
1220 nr_to_scan = min(nr_active,
1221 (unsigned long)sc->swap_cluster_max);
1222 nr_active -= nr_to_scan;
1223 shrink_active_list(nr_to_scan, zone, sc, priority);
1224 }
1225
1226 if (nr_inactive) {
1227 nr_to_scan = min(nr_inactive,
1228 (unsigned long)sc->swap_cluster_max);
1229 nr_inactive -= nr_to_scan;
1230 nr_reclaimed += shrink_inactive_list(nr_to_scan, zone,
1231 sc);
1232 }
1233 }
1234
1235 throttle_vm_writeout(sc->gfp_mask);
1236 return nr_reclaimed;
1237 }
1238
1239 /*
1240 * This is the direct reclaim path, for page-allocating processes. We only
1241 * try to reclaim pages from zones which will satisfy the caller's allocation
1242 * request.
1243 *
1244 * We reclaim from a zone even if that zone is over pages_high. Because:
1245 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1246 * allocation or
1247 * b) The zones may be over pages_high but they must go *over* pages_high to
1248 * satisfy the `incremental min' zone defense algorithm.
1249 *
1250 * Returns the number of reclaimed pages.
1251 *
1252 * If a zone is deemed to be full of pinned pages then just give it a light
1253 * scan then give up on it.
1254 */
1255 static unsigned long shrink_zones(int priority, struct zone **zones,
1256 struct scan_control *sc)
1257 {
1258 unsigned long nr_reclaimed = 0;
1259 int i;
1260
1261
1262 sc->all_unreclaimable = 1;
1263 for (i = 0; zones[i] != NULL; i++) {
1264 struct zone *zone = zones[i];
1265
1266 if (!populated_zone(zone))
1267 continue;
1268 /*
1269 * Take care memory controller reclaiming has small influence
1270 * to global LRU.
1271 */
1272 if (scan_global_lru(sc)) {
1273 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1274 continue;
1275 note_zone_scanning_priority(zone, priority);
1276
1277 if (zone_is_all_unreclaimable(zone) &&
1278 priority != DEF_PRIORITY)
1279 continue; /* Let kswapd poll it */
1280 sc->all_unreclaimable = 0;
1281 } else {
1282 /*
1283 * Ignore cpuset limitation here. We just want to reduce
1284 * # of used pages by us regardless of memory shortage.
1285 */
1286 sc->all_unreclaimable = 0;
1287 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1288 priority);
1289 }
1290
1291 nr_reclaimed += shrink_zone(priority, zone, sc);
1292 }
1293
1294 return nr_reclaimed;
1295 }
1296
1297 /*
1298 * This is the main entry point to direct page reclaim.
1299 *
1300 * If a full scan of the inactive list fails to free enough memory then we
1301 * are "out of memory" and something needs to be killed.
1302 *
1303 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1304 * high - the zone may be full of dirty or under-writeback pages, which this
1305 * caller can't do much about. We kick pdflush and take explicit naps in the
1306 * hope that some of these pages can be written. But if the allocating task
1307 * holds filesystem locks which prevent writeout this might not work, and the
1308 * allocation attempt will fail.
1309 */
1310 static unsigned long do_try_to_free_pages(struct zone **zones, gfp_t gfp_mask,
1311 struct scan_control *sc)
1312 {
1313 int priority;
1314 int ret = 0;
1315 unsigned long total_scanned = 0;
1316 unsigned long nr_reclaimed = 0;
1317 struct reclaim_state *reclaim_state = current->reclaim_state;
1318 unsigned long lru_pages = 0;
1319 int i;
1320
1321 if (scan_global_lru(sc))
1322 count_vm_event(ALLOCSTALL);
1323 /*
1324 * mem_cgroup will not do shrink_slab.
1325 */
1326 if (scan_global_lru(sc)) {
1327 for (i = 0; zones[i] != NULL; i++) {
1328 struct zone *zone = zones[i];
1329
1330 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1331 continue;
1332
1333 lru_pages += zone_page_state(zone, NR_ACTIVE)
1334 + zone_page_state(zone, NR_INACTIVE);
1335 }
1336 }
1337
1338 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1339 sc->nr_scanned = 0;
1340 if (!priority)
1341 disable_swap_token();
1342 nr_reclaimed += shrink_zones(priority, zones, sc);
1343 /*
1344 * Don't shrink slabs when reclaiming memory from
1345 * over limit cgroups
1346 */
1347 if (scan_global_lru(sc)) {
1348 shrink_slab(sc->nr_scanned, gfp_mask, lru_pages);
1349 if (reclaim_state) {
1350 nr_reclaimed += reclaim_state->reclaimed_slab;
1351 reclaim_state->reclaimed_slab = 0;
1352 }
1353 }
1354 total_scanned += sc->nr_scanned;
1355 if (nr_reclaimed >= sc->swap_cluster_max) {
1356 ret = 1;
1357 goto out;
1358 }
1359
1360 /*
1361 * Try to write back as many pages as we just scanned. This
1362 * tends to cause slow streaming writers to write data to the
1363 * disk smoothly, at the dirtying rate, which is nice. But
1364 * that's undesirable in laptop mode, where we *want* lumpy
1365 * writeout. So in laptop mode, write out the whole world.
1366 */
1367 if (total_scanned > sc->swap_cluster_max +
1368 sc->swap_cluster_max / 2) {
1369 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1370 sc->may_writepage = 1;
1371 }
1372
1373 /* Take a nap, wait for some writeback to complete */
1374 if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1375 congestion_wait(WRITE, HZ/10);
1376 }
1377 /* top priority shrink_caches still had more to do? don't OOM, then */
1378 if (!sc->all_unreclaimable && scan_global_lru(sc))
1379 ret = 1;
1380 out:
1381 /*
1382 * Now that we've scanned all the zones at this priority level, note
1383 * that level within the zone so that the next thread which performs
1384 * scanning of this zone will immediately start out at this priority
1385 * level. This affects only the decision whether or not to bring
1386 * mapped pages onto the inactive list.
1387 */
1388 if (priority < 0)
1389 priority = 0;
1390
1391 if (scan_global_lru(sc)) {
1392 for (i = 0; zones[i] != NULL; i++) {
1393 struct zone *zone = zones[i];
1394
1395 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1396 continue;
1397
1398 zone->prev_priority = priority;
1399 }
1400 } else
1401 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1402
1403 return ret;
1404 }
1405
1406 unsigned long try_to_free_pages(struct zone **zones, int order, gfp_t gfp_mask)
1407 {
1408 struct scan_control sc = {
1409 .gfp_mask = gfp_mask,
1410 .may_writepage = !laptop_mode,
1411 .swap_cluster_max = SWAP_CLUSTER_MAX,
1412 .may_swap = 1,
1413 .swappiness = vm_swappiness,
1414 .order = order,
1415 .mem_cgroup = NULL,
1416 .isolate_pages = isolate_pages_global,
1417 };
1418
1419 return do_try_to_free_pages(zones, gfp_mask, &sc);
1420 }
1421
1422 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1423
1424 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1425 gfp_t gfp_mask)
1426 {
1427 struct scan_control sc = {
1428 .gfp_mask = gfp_mask,
1429 .may_writepage = !laptop_mode,
1430 .may_swap = 1,
1431 .swap_cluster_max = SWAP_CLUSTER_MAX,
1432 .swappiness = vm_swappiness,
1433 .order = 0,
1434 .mem_cgroup = mem_cont,
1435 .isolate_pages = mem_cgroup_isolate_pages,
1436 };
1437 struct zone **zones;
1438 int target_zone = gfp_zone(GFP_HIGHUSER_MOVABLE);
1439
1440 zones = NODE_DATA(numa_node_id())->node_zonelists[target_zone].zones;
1441 if (do_try_to_free_pages(zones, sc.gfp_mask, &sc))
1442 return 1;
1443 return 0;
1444 }
1445 #endif
1446
1447 /*
1448 * For kswapd, balance_pgdat() will work across all this node's zones until
1449 * they are all at pages_high.
1450 *
1451 * Returns the number of pages which were actually freed.
1452 *
1453 * There is special handling here for zones which are full of pinned pages.
1454 * This can happen if the pages are all mlocked, or if they are all used by
1455 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1456 * What we do is to detect the case where all pages in the zone have been
1457 * scanned twice and there has been zero successful reclaim. Mark the zone as
1458 * dead and from now on, only perform a short scan. Basically we're polling
1459 * the zone for when the problem goes away.
1460 *
1461 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1462 * zones which have free_pages > pages_high, but once a zone is found to have
1463 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1464 * of the number of free pages in the lower zones. This interoperates with
1465 * the page allocator fallback scheme to ensure that aging of pages is balanced
1466 * across the zones.
1467 */
1468 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1469 {
1470 int all_zones_ok;
1471 int priority;
1472 int i;
1473 unsigned long total_scanned;
1474 unsigned long nr_reclaimed;
1475 struct reclaim_state *reclaim_state = current->reclaim_state;
1476 struct scan_control sc = {
1477 .gfp_mask = GFP_KERNEL,
1478 .may_swap = 1,
1479 .swap_cluster_max = SWAP_CLUSTER_MAX,
1480 .swappiness = vm_swappiness,
1481 .order = order,
1482 .mem_cgroup = NULL,
1483 .isolate_pages = isolate_pages_global,
1484 };
1485 /*
1486 * temp_priority is used to remember the scanning priority at which
1487 * this zone was successfully refilled to free_pages == pages_high.
1488 */
1489 int temp_priority[MAX_NR_ZONES];
1490
1491 loop_again:
1492 total_scanned = 0;
1493 nr_reclaimed = 0;
1494 sc.may_writepage = !laptop_mode;
1495 count_vm_event(PAGEOUTRUN);
1496
1497 for (i = 0; i < pgdat->nr_zones; i++)
1498 temp_priority[i] = DEF_PRIORITY;
1499
1500 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1501 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1502 unsigned long lru_pages = 0;
1503
1504 /* The swap token gets in the way of swapout... */
1505 if (!priority)
1506 disable_swap_token();
1507
1508 all_zones_ok = 1;
1509
1510 /*
1511 * Scan in the highmem->dma direction for the highest
1512 * zone which needs scanning
1513 */
1514 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1515 struct zone *zone = pgdat->node_zones + i;
1516
1517 if (!populated_zone(zone))
1518 continue;
1519
1520 if (zone_is_all_unreclaimable(zone) &&
1521 priority != DEF_PRIORITY)
1522 continue;
1523
1524 if (!zone_watermark_ok(zone, order, zone->pages_high,
1525 0, 0)) {
1526 end_zone = i;
1527 break;
1528 }
1529 }
1530 if (i < 0)
1531 goto out;
1532
1533 for (i = 0; i <= end_zone; i++) {
1534 struct zone *zone = pgdat->node_zones + i;
1535
1536 lru_pages += zone_page_state(zone, NR_ACTIVE)
1537 + zone_page_state(zone, NR_INACTIVE);
1538 }
1539
1540 /*
1541 * Now scan the zone in the dma->highmem direction, stopping
1542 * at the last zone which needs scanning.
1543 *
1544 * We do this because the page allocator works in the opposite
1545 * direction. This prevents the page allocator from allocating
1546 * pages behind kswapd's direction of progress, which would
1547 * cause too much scanning of the lower zones.
1548 */
1549 for (i = 0; i <= end_zone; i++) {
1550 struct zone *zone = pgdat->node_zones + i;
1551 int nr_slab;
1552
1553 if (!populated_zone(zone))
1554 continue;
1555
1556 if (zone_is_all_unreclaimable(zone) &&
1557 priority != DEF_PRIORITY)
1558 continue;
1559
1560 if (!zone_watermark_ok(zone, order, zone->pages_high,
1561 end_zone, 0))
1562 all_zones_ok = 0;
1563 temp_priority[i] = priority;
1564 sc.nr_scanned = 0;
1565 note_zone_scanning_priority(zone, priority);
1566 /*
1567 * We put equal pressure on every zone, unless one
1568 * zone has way too many pages free already.
1569 */
1570 if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
1571 end_zone, 0))
1572 nr_reclaimed += shrink_zone(priority, zone, &sc);
1573 reclaim_state->reclaimed_slab = 0;
1574 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1575 lru_pages);
1576 nr_reclaimed += reclaim_state->reclaimed_slab;
1577 total_scanned += sc.nr_scanned;
1578 if (zone_is_all_unreclaimable(zone))
1579 continue;
1580 if (nr_slab == 0 && zone->pages_scanned >=
1581 (zone_page_state(zone, NR_ACTIVE)
1582 + zone_page_state(zone, NR_INACTIVE)) * 6)
1583 zone_set_flag(zone,
1584 ZONE_ALL_UNRECLAIMABLE);
1585 /*
1586 * If we've done a decent amount of scanning and
1587 * the reclaim ratio is low, start doing writepage
1588 * even in laptop mode
1589 */
1590 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1591 total_scanned > nr_reclaimed + nr_reclaimed / 2)
1592 sc.may_writepage = 1;
1593 }
1594 if (all_zones_ok)
1595 break; /* kswapd: all done */
1596 /*
1597 * OK, kswapd is getting into trouble. Take a nap, then take
1598 * another pass across the zones.
1599 */
1600 if (total_scanned && priority < DEF_PRIORITY - 2)
1601 congestion_wait(WRITE, HZ/10);
1602
1603 /*
1604 * We do this so kswapd doesn't build up large priorities for
1605 * example when it is freeing in parallel with allocators. It
1606 * matches the direct reclaim path behaviour in terms of impact
1607 * on zone->*_priority.
1608 */
1609 if (nr_reclaimed >= SWAP_CLUSTER_MAX)
1610 break;
1611 }
1612 out:
1613 /*
1614 * Note within each zone the priority level at which this zone was
1615 * brought into a happy state. So that the next thread which scans this
1616 * zone will start out at that priority level.
1617 */
1618 for (i = 0; i < pgdat->nr_zones; i++) {
1619 struct zone *zone = pgdat->node_zones + i;
1620
1621 zone->prev_priority = temp_priority[i];
1622 }
1623 if (!all_zones_ok) {
1624 cond_resched();
1625
1626 try_to_freeze();
1627
1628 goto loop_again;
1629 }
1630
1631 return nr_reclaimed;
1632 }
1633
1634 /*
1635 * The background pageout daemon, started as a kernel thread
1636 * from the init process.
1637 *
1638 * This basically trickles out pages so that we have _some_
1639 * free memory available even if there is no other activity
1640 * that frees anything up. This is needed for things like routing
1641 * etc, where we otherwise might have all activity going on in
1642 * asynchronous contexts that cannot page things out.
1643 *
1644 * If there are applications that are active memory-allocators
1645 * (most normal use), this basically shouldn't matter.
1646 */
1647 static int kswapd(void *p)
1648 {
1649 unsigned long order;
1650 pg_data_t *pgdat = (pg_data_t*)p;
1651 struct task_struct *tsk = current;
1652 DEFINE_WAIT(wait);
1653 struct reclaim_state reclaim_state = {
1654 .reclaimed_slab = 0,
1655 };
1656 cpumask_t cpumask;
1657
1658 cpumask = node_to_cpumask(pgdat->node_id);
1659 if (!cpus_empty(cpumask))
1660 set_cpus_allowed(tsk, cpumask);
1661 current->reclaim_state = &reclaim_state;
1662
1663 /*
1664 * Tell the memory management that we're a "memory allocator",
1665 * and that if we need more memory we should get access to it
1666 * regardless (see "__alloc_pages()"). "kswapd" should
1667 * never get caught in the normal page freeing logic.
1668 *
1669 * (Kswapd normally doesn't need memory anyway, but sometimes
1670 * you need a small amount of memory in order to be able to
1671 * page out something else, and this flag essentially protects
1672 * us from recursively trying to free more memory as we're
1673 * trying to free the first piece of memory in the first place).
1674 */
1675 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
1676 set_freezable();
1677
1678 order = 0;
1679 for ( ; ; ) {
1680 unsigned long new_order;
1681
1682 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
1683 new_order = pgdat->kswapd_max_order;
1684 pgdat->kswapd_max_order = 0;
1685 if (order < new_order) {
1686 /*
1687 * Don't sleep if someone wants a larger 'order'
1688 * allocation
1689 */
1690 order = new_order;
1691 } else {
1692 if (!freezing(current))
1693 schedule();
1694
1695 order = pgdat->kswapd_max_order;
1696 }
1697 finish_wait(&pgdat->kswapd_wait, &wait);
1698
1699 if (!try_to_freeze()) {
1700 /* We can speed up thawing tasks if we don't call
1701 * balance_pgdat after returning from the refrigerator
1702 */
1703 balance_pgdat(pgdat, order);
1704 }
1705 }
1706 return 0;
1707 }
1708
1709 /*
1710 * A zone is low on free memory, so wake its kswapd task to service it.
1711 */
1712 void wakeup_kswapd(struct zone *zone, int order)
1713 {
1714 pg_data_t *pgdat;
1715
1716 if (!populated_zone(zone))
1717 return;
1718
1719 pgdat = zone->zone_pgdat;
1720 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
1721 return;
1722 if (pgdat->kswapd_max_order < order)
1723 pgdat->kswapd_max_order = order;
1724 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1725 return;
1726 if (!waitqueue_active(&pgdat->kswapd_wait))
1727 return;
1728 wake_up_interruptible(&pgdat->kswapd_wait);
1729 }
1730
1731 #ifdef CONFIG_PM
1732 /*
1733 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
1734 * from LRU lists system-wide, for given pass and priority, and returns the
1735 * number of reclaimed pages
1736 *
1737 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
1738 */
1739 static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
1740 int pass, struct scan_control *sc)
1741 {
1742 struct zone *zone;
1743 unsigned long nr_to_scan, ret = 0;
1744
1745 for_each_zone(zone) {
1746
1747 if (!populated_zone(zone))
1748 continue;
1749
1750 if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
1751 continue;
1752
1753 /* For pass = 0 we don't shrink the active list */
1754 if (pass > 0) {
1755 zone->nr_scan_active +=
1756 (zone_page_state(zone, NR_ACTIVE) >> prio) + 1;
1757 if (zone->nr_scan_active >= nr_pages || pass > 3) {
1758 zone->nr_scan_active = 0;
1759 nr_to_scan = min(nr_pages,
1760 zone_page_state(zone, NR_ACTIVE));
1761 shrink_active_list(nr_to_scan, zone, sc, prio);
1762 }
1763 }
1764
1765 zone->nr_scan_inactive +=
1766 (zone_page_state(zone, NR_INACTIVE) >> prio) + 1;
1767 if (zone->nr_scan_inactive >= nr_pages || pass > 3) {
1768 zone->nr_scan_inactive = 0;
1769 nr_to_scan = min(nr_pages,
1770 zone_page_state(zone, NR_INACTIVE));
1771 ret += shrink_inactive_list(nr_to_scan, zone, sc);
1772 if (ret >= nr_pages)
1773 return ret;
1774 }
1775 }
1776
1777 return ret;
1778 }
1779
1780 static unsigned long count_lru_pages(void)
1781 {
1782 return global_page_state(NR_ACTIVE) + global_page_state(NR_INACTIVE);
1783 }
1784
1785 /*
1786 * Try to free `nr_pages' of memory, system-wide, and return the number of
1787 * freed pages.
1788 *
1789 * Rather than trying to age LRUs the aim is to preserve the overall
1790 * LRU order by reclaiming preferentially
1791 * inactive > active > active referenced > active mapped
1792 */
1793 unsigned long shrink_all_memory(unsigned long nr_pages)
1794 {
1795 unsigned long lru_pages, nr_slab;
1796 unsigned long ret = 0;
1797 int pass;
1798 struct reclaim_state reclaim_state;
1799 struct scan_control sc = {
1800 .gfp_mask = GFP_KERNEL,
1801 .may_swap = 0,
1802 .swap_cluster_max = nr_pages,
1803 .may_writepage = 1,
1804 .swappiness = vm_swappiness,
1805 .isolate_pages = isolate_pages_global,
1806 };
1807
1808 current->reclaim_state = &reclaim_state;
1809
1810 lru_pages = count_lru_pages();
1811 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
1812 /* If slab caches are huge, it's better to hit them first */
1813 while (nr_slab >= lru_pages) {
1814 reclaim_state.reclaimed_slab = 0;
1815 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
1816 if (!reclaim_state.reclaimed_slab)
1817 break;
1818
1819 ret += reclaim_state.reclaimed_slab;
1820 if (ret >= nr_pages)
1821 goto out;
1822
1823 nr_slab -= reclaim_state.reclaimed_slab;
1824 }
1825
1826 /*
1827 * We try to shrink LRUs in 5 passes:
1828 * 0 = Reclaim from inactive_list only
1829 * 1 = Reclaim from active list but don't reclaim mapped
1830 * 2 = 2nd pass of type 1
1831 * 3 = Reclaim mapped (normal reclaim)
1832 * 4 = 2nd pass of type 3
1833 */
1834 for (pass = 0; pass < 5; pass++) {
1835 int prio;
1836
1837 /* Force reclaiming mapped pages in the passes #3 and #4 */
1838 if (pass > 2) {
1839 sc.may_swap = 1;
1840 sc.swappiness = 100;
1841 }
1842
1843 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
1844 unsigned long nr_to_scan = nr_pages - ret;
1845
1846 sc.nr_scanned = 0;
1847 ret += shrink_all_zones(nr_to_scan, prio, pass, &sc);
1848 if (ret >= nr_pages)
1849 goto out;
1850
1851 reclaim_state.reclaimed_slab = 0;
1852 shrink_slab(sc.nr_scanned, sc.gfp_mask,
1853 count_lru_pages());
1854 ret += reclaim_state.reclaimed_slab;
1855 if (ret >= nr_pages)
1856 goto out;
1857
1858 if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
1859 congestion_wait(WRITE, HZ / 10);
1860 }
1861 }
1862
1863 /*
1864 * If ret = 0, we could not shrink LRUs, but there may be something
1865 * in slab caches
1866 */
1867 if (!ret) {
1868 do {
1869 reclaim_state.reclaimed_slab = 0;
1870 shrink_slab(nr_pages, sc.gfp_mask, count_lru_pages());
1871 ret += reclaim_state.reclaimed_slab;
1872 } while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
1873 }
1874
1875 out:
1876 current->reclaim_state = NULL;
1877
1878 return ret;
1879 }
1880 #endif
1881
1882 /* It's optimal to keep kswapds on the same CPUs as their memory, but
1883 not required for correctness. So if the last cpu in a node goes
1884 away, we get changed to run anywhere: as the first one comes back,
1885 restore their cpu bindings. */
1886 static int __devinit cpu_callback(struct notifier_block *nfb,
1887 unsigned long action, void *hcpu)
1888 {
1889 pg_data_t *pgdat;
1890 cpumask_t mask;
1891 int nid;
1892
1893 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
1894 for_each_node_state(nid, N_HIGH_MEMORY) {
1895 pgdat = NODE_DATA(nid);
1896 mask = node_to_cpumask(pgdat->node_id);
1897 if (any_online_cpu(mask) != NR_CPUS)
1898 /* One of our CPUs online: restore mask */
1899 set_cpus_allowed(pgdat->kswapd, mask);
1900 }
1901 }
1902 return NOTIFY_OK;
1903 }
1904
1905 /*
1906 * This kswapd start function will be called by init and node-hot-add.
1907 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
1908 */
1909 int kswapd_run(int nid)
1910 {
1911 pg_data_t *pgdat = NODE_DATA(nid);
1912 int ret = 0;
1913
1914 if (pgdat->kswapd)
1915 return 0;
1916
1917 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
1918 if (IS_ERR(pgdat->kswapd)) {
1919 /* failure at boot is fatal */
1920 BUG_ON(system_state == SYSTEM_BOOTING);
1921 printk("Failed to start kswapd on node %d\n",nid);
1922 ret = -1;
1923 }
1924 return ret;
1925 }
1926
1927 static int __init kswapd_init(void)
1928 {
1929 int nid;
1930
1931 swap_setup();
1932 for_each_node_state(nid, N_HIGH_MEMORY)
1933 kswapd_run(nid);
1934 hotcpu_notifier(cpu_callback, 0);
1935 return 0;
1936 }
1937
1938 module_init(kswapd_init)
1939
1940 #ifdef CONFIG_NUMA
1941 /*
1942 * Zone reclaim mode
1943 *
1944 * If non-zero call zone_reclaim when the number of free pages falls below
1945 * the watermarks.
1946 */
1947 int zone_reclaim_mode __read_mostly;
1948
1949 #define RECLAIM_OFF 0
1950 #define RECLAIM_ZONE (1<<0) /* Run shrink_cache on the zone */
1951 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
1952 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
1953
1954 /*
1955 * Priority for ZONE_RECLAIM. This determines the fraction of pages
1956 * of a node considered for each zone_reclaim. 4 scans 1/16th of
1957 * a zone.
1958 */
1959 #define ZONE_RECLAIM_PRIORITY 4
1960
1961 /*
1962 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
1963 * occur.
1964 */
1965 int sysctl_min_unmapped_ratio = 1;
1966
1967 /*
1968 * If the number of slab pages in a zone grows beyond this percentage then
1969 * slab reclaim needs to occur.
1970 */
1971 int sysctl_min_slab_ratio = 5;
1972
1973 /*
1974 * Try to free up some pages from this zone through reclaim.
1975 */
1976 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
1977 {
1978 /* Minimum pages needed in order to stay on node */
1979 const unsigned long nr_pages = 1 << order;
1980 struct task_struct *p = current;
1981 struct reclaim_state reclaim_state;
1982 int priority;
1983 unsigned long nr_reclaimed = 0;
1984 struct scan_control sc = {
1985 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
1986 .may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
1987 .swap_cluster_max = max_t(unsigned long, nr_pages,
1988 SWAP_CLUSTER_MAX),
1989 .gfp_mask = gfp_mask,
1990 .swappiness = vm_swappiness,
1991 .isolate_pages = isolate_pages_global,
1992 };
1993 unsigned long slab_reclaimable;
1994
1995 disable_swap_token();
1996 cond_resched();
1997 /*
1998 * We need to be able to allocate from the reserves for RECLAIM_SWAP
1999 * and we also need to be able to write out pages for RECLAIM_WRITE
2000 * and RECLAIM_SWAP.
2001 */
2002 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2003 reclaim_state.reclaimed_slab = 0;
2004 p->reclaim_state = &reclaim_state;
2005
2006 if (zone_page_state(zone, NR_FILE_PAGES) -
2007 zone_page_state(zone, NR_FILE_MAPPED) >
2008 zone->min_unmapped_pages) {
2009 /*
2010 * Free memory by calling shrink zone with increasing
2011 * priorities until we have enough memory freed.
2012 */
2013 priority = ZONE_RECLAIM_PRIORITY;
2014 do {
2015 note_zone_scanning_priority(zone, priority);
2016 nr_reclaimed += shrink_zone(priority, zone, &sc);
2017 priority--;
2018 } while (priority >= 0 && nr_reclaimed < nr_pages);
2019 }
2020
2021 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2022 if (slab_reclaimable > zone->min_slab_pages) {
2023 /*
2024 * shrink_slab() does not currently allow us to determine how
2025 * many pages were freed in this zone. So we take the current
2026 * number of slab pages and shake the slab until it is reduced
2027 * by the same nr_pages that we used for reclaiming unmapped
2028 * pages.
2029 *
2030 * Note that shrink_slab will free memory on all zones and may
2031 * take a long time.
2032 */
2033 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2034 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2035 slab_reclaimable - nr_pages)
2036 ;
2037
2038 /*
2039 * Update nr_reclaimed by the number of slab pages we
2040 * reclaimed from this zone.
2041 */
2042 nr_reclaimed += slab_reclaimable -
2043 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2044 }
2045
2046 p->reclaim_state = NULL;
2047 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2048 return nr_reclaimed >= nr_pages;
2049 }
2050
2051 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2052 {
2053 int node_id;
2054 int ret;
2055
2056 /*
2057 * Zone reclaim reclaims unmapped file backed pages and
2058 * slab pages if we are over the defined limits.
2059 *
2060 * A small portion of unmapped file backed pages is needed for
2061 * file I/O otherwise pages read by file I/O will be immediately
2062 * thrown out if the zone is overallocated. So we do not reclaim
2063 * if less than a specified percentage of the zone is used by
2064 * unmapped file backed pages.
2065 */
2066 if (zone_page_state(zone, NR_FILE_PAGES) -
2067 zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
2068 && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
2069 <= zone->min_slab_pages)
2070 return 0;
2071
2072 if (zone_is_all_unreclaimable(zone))
2073 return 0;
2074
2075 /*
2076 * Do not scan if the allocation should not be delayed.
2077 */
2078 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2079 return 0;
2080
2081 /*
2082 * Only run zone reclaim on the local zone or on zones that do not
2083 * have associated processors. This will favor the local processor
2084 * over remote processors and spread off node memory allocations
2085 * as wide as possible.
2086 */
2087 node_id = zone_to_nid(zone);
2088 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2089 return 0;
2090
2091 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2092 return 0;
2093 ret = __zone_reclaim(zone, gfp_mask, order);
2094 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2095
2096 return ret;
2097 }
2098 #endif
2099
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