4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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.
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/buffer_head.h> /* for try_to_release_page(),
27 buffer_heads_over_limit */
28 #include <linux/mm_inline.h>
29 #include <linux/pagevec.h>
30 #include <linux/backing-dev.h>
31 #include <linux/rmap.h>
32 #include <linux/topology.h>
33 #include <linux/cpu.h>
34 #include <linux/cpuset.h>
35 #include <linux/notifier.h>
36 #include <linux/rwsem.h>
37 #include <linux/delay.h>
38 #include <linux/kthread.h>
39 #include <linux/freezer.h>
40 #include <linux/memcontrol.h>
41 #include <linux/delayacct.h>
42 #include <linux/sysctl.h>
44 #include <asm/tlbflush.h>
45 #include <asm/div64.h>
47 #include <linux/swapops.h>
52 /* Incremented by the number of inactive pages that were scanned */
53 unsigned long nr_scanned;
55 /* Number of pages freed so far during a call to shrink_zones() */
56 unsigned long nr_reclaimed;
58 /* How many pages shrink_list() should reclaim */
59 unsigned long nr_to_reclaim;
61 unsigned long hibernation_mode;
63 /* This context's GFP mask */
68 /* Can mapped pages be reclaimed? */
71 /* Can pages be swapped as part of reclaim? */
76 int all_unreclaimable;
80 /* Which cgroup do we reclaim from */
81 struct mem_cgroup *mem_cgroup;
84 * Nodemask of nodes allowed by the caller. If NULL, all nodes
89 /* Pluggable isolate pages callback */
90 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
91 unsigned long *scanned, int order, int mode,
92 struct zone *z, struct mem_cgroup *mem_cont,
93 int active, int file);
96 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
98 #ifdef ARCH_HAS_PREFETCH
99 #define prefetch_prev_lru_page(_page, _base, _field) \
101 if ((_page)->lru.prev != _base) { \
104 prev = lru_to_page(&(_page->lru)); \
105 prefetch(&prev->_field); \
109 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
112 #ifdef ARCH_HAS_PREFETCHW
113 #define prefetchw_prev_lru_page(_page, _base, _field) \
115 if ((_page)->lru.prev != _base) { \
118 prev = lru_to_page(&(_page->lru)); \
119 prefetchw(&prev->_field); \
123 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
127 * From 0 .. 100. Higher means more swappy.
129 int vm_swappiness = 60;
130 long vm_total_pages; /* The total number of pages which the VM controls */
132 static LIST_HEAD(shrinker_list);
133 static DECLARE_RWSEM(shrinker_rwsem);
135 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
136 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
138 #define scanning_global_lru(sc) (1)
141 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
142 struct scan_control *sc)
144 if (!scanning_global_lru(sc))
145 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
147 return &zone->reclaim_stat;
150 static unsigned long zone_nr_lru_pages(struct zone *zone,
151 struct scan_control *sc, enum lru_list lru)
153 if (!scanning_global_lru(sc))
154 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);
156 return zone_page_state(zone, NR_LRU_BASE + lru);
161 * Add a shrinker callback to be called from the vm
163 void register_shrinker(struct shrinker *shrinker)
166 down_write(&shrinker_rwsem);
167 list_add_tail(&shrinker->list, &shrinker_list);
168 up_write(&shrinker_rwsem);
170 EXPORT_SYMBOL(register_shrinker);
175 void unregister_shrinker(struct shrinker *shrinker)
177 down_write(&shrinker_rwsem);
178 list_del(&shrinker->list);
179 up_write(&shrinker_rwsem);
181 EXPORT_SYMBOL(unregister_shrinker);
183 #define SHRINK_BATCH 128
185 * Call the shrink functions to age shrinkable caches
187 * Here we assume it costs one seek to replace a lru page and that it also
188 * takes a seek to recreate a cache object. With this in mind we age equal
189 * percentages of the lru and ageable caches. This should balance the seeks
190 * generated by these structures.
192 * If the vm encountered mapped pages on the LRU it increase the pressure on
193 * slab to avoid swapping.
195 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
197 * `lru_pages' represents the number of on-LRU pages in all the zones which
198 * are eligible for the caller's allocation attempt. It is used for balancing
199 * slab reclaim versus page reclaim.
201 * Returns the number of slab objects which we shrunk.
203 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
204 unsigned long lru_pages)
206 struct shrinker *shrinker;
207 unsigned long ret = 0;
210 scanned = SWAP_CLUSTER_MAX;
212 if (!down_read_trylock(&shrinker_rwsem))
213 return 1; /* Assume we'll be able to shrink next time */
215 list_for_each_entry(shrinker, &shrinker_list, list) {
216 unsigned long long delta;
217 unsigned long total_scan;
218 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
220 delta = (4 * scanned) / shrinker->seeks;
222 do_div(delta, lru_pages + 1);
223 shrinker->nr += delta;
224 if (shrinker->nr < 0) {
225 printk(KERN_ERR "shrink_slab: %pF negative objects to "
227 shrinker->shrink, shrinker->nr);
228 shrinker->nr = max_pass;
232 * Avoid risking looping forever due to too large nr value:
233 * never try to free more than twice the estimate number of
236 if (shrinker->nr > max_pass * 2)
237 shrinker->nr = max_pass * 2;
239 total_scan = shrinker->nr;
242 while (total_scan >= SHRINK_BATCH) {
243 long this_scan = SHRINK_BATCH;
247 nr_before = (*shrinker->shrink)(0, gfp_mask);
248 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
249 if (shrink_ret == -1)
251 if (shrink_ret < nr_before)
252 ret += nr_before - shrink_ret;
253 count_vm_events(SLABS_SCANNED, this_scan);
254 total_scan -= this_scan;
259 shrinker->nr += total_scan;
261 up_read(&shrinker_rwsem);
265 /* Called without lock on whether page is mapped, so answer is unstable */
266 static inline int page_mapping_inuse(struct page *page)
268 struct address_space *mapping;
270 /* Page is in somebody's page tables. */
271 if (page_mapped(page))
274 /* Be more reluctant to reclaim swapcache than pagecache */
275 if (PageSwapCache(page))
278 mapping = page_mapping(page);
282 /* File is mmap'd by somebody? */
283 return mapping_mapped(mapping);
286 static inline int is_page_cache_freeable(struct page *page)
289 * A freeable page cache page is referenced only by the caller
290 * that isolated the page, the page cache radix tree and
291 * optional buffer heads at page->private.
293 return page_count(page) - page_has_private(page) == 2;
296 static int may_write_to_queue(struct backing_dev_info *bdi)
298 if (current->flags & PF_SWAPWRITE)
300 if (!bdi_write_congested(bdi))
302 if (bdi == current->backing_dev_info)
308 * We detected a synchronous write error writing a page out. Probably
309 * -ENOSPC. We need to propagate that into the address_space for a subsequent
310 * fsync(), msync() or close().
312 * The tricky part is that after writepage we cannot touch the mapping: nothing
313 * prevents it from being freed up. But we have a ref on the page and once
314 * that page is locked, the mapping is pinned.
316 * We're allowed to run sleeping lock_page() here because we know the caller has
319 static void handle_write_error(struct address_space *mapping,
320 struct page *page, int error)
323 if (page_mapping(page) == mapping)
324 mapping_set_error(mapping, error);
328 /* Request for sync pageout. */
334 /* possible outcome of pageout() */
336 /* failed to write page out, page is locked */
338 /* move page to the active list, page is locked */
340 /* page has been sent to the disk successfully, page is unlocked */
342 /* page is clean and locked */
347 * pageout is called by shrink_page_list() for each dirty page.
348 * Calls ->writepage().
350 static pageout_t pageout(struct page *page, struct address_space *mapping,
351 enum pageout_io sync_writeback)
354 * If the page is dirty, only perform writeback if that write
355 * will be non-blocking. To prevent this allocation from being
356 * stalled by pagecache activity. But note that there may be
357 * stalls if we need to run get_block(). We could test
358 * PagePrivate for that.
360 * If this process is currently in __generic_file_aio_write() against
361 * this page's queue, we can perform writeback even if that
364 * If the page is swapcache, write it back even if that would
365 * block, for some throttling. This happens by accident, because
366 * swap_backing_dev_info is bust: it doesn't reflect the
367 * congestion state of the swapdevs. Easy to fix, if needed.
369 if (!is_page_cache_freeable(page))
373 * Some data journaling orphaned pages can have
374 * page->mapping == NULL while being dirty with clean buffers.
376 if (page_has_private(page)) {
377 if (try_to_free_buffers(page)) {
378 ClearPageDirty(page);
379 printk("%s: orphaned page\n", __func__);
385 if (mapping->a_ops->writepage == NULL)
386 return PAGE_ACTIVATE;
387 if (!may_write_to_queue(mapping->backing_dev_info))
390 if (clear_page_dirty_for_io(page)) {
392 struct writeback_control wbc = {
393 .sync_mode = WB_SYNC_NONE,
394 .nr_to_write = SWAP_CLUSTER_MAX,
396 .range_end = LLONG_MAX,
401 SetPageReclaim(page);
402 res = mapping->a_ops->writepage(page, &wbc);
404 handle_write_error(mapping, page, res);
405 if (res == AOP_WRITEPAGE_ACTIVATE) {
406 ClearPageReclaim(page);
407 return PAGE_ACTIVATE;
411 * Wait on writeback if requested to. This happens when
412 * direct reclaiming a large contiguous area and the
413 * first attempt to free a range of pages fails.
415 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
416 wait_on_page_writeback(page);
418 if (!PageWriteback(page)) {
419 /* synchronous write or broken a_ops? */
420 ClearPageReclaim(page);
422 inc_zone_page_state(page, NR_VMSCAN_WRITE);
430 * Same as remove_mapping, but if the page is removed from the mapping, it
431 * gets returned with a refcount of 0.
433 static int __remove_mapping(struct address_space *mapping, struct page *page)
435 BUG_ON(!PageLocked(page));
436 BUG_ON(mapping != page_mapping(page));
438 spin_lock_irq(&mapping->tree_lock);
440 * The non racy check for a busy page.
442 * Must be careful with the order of the tests. When someone has
443 * a ref to the page, it may be possible that they dirty it then
444 * drop the reference. So if PageDirty is tested before page_count
445 * here, then the following race may occur:
447 * get_user_pages(&page);
448 * [user mapping goes away]
450 * !PageDirty(page) [good]
451 * SetPageDirty(page);
453 * !page_count(page) [good, discard it]
455 * [oops, our write_to data is lost]
457 * Reversing the order of the tests ensures such a situation cannot
458 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
459 * load is not satisfied before that of page->_count.
461 * Note that if SetPageDirty is always performed via set_page_dirty,
462 * and thus under tree_lock, then this ordering is not required.
464 if (!page_freeze_refs(page, 2))
466 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
467 if (unlikely(PageDirty(page))) {
468 page_unfreeze_refs(page, 2);
472 if (PageSwapCache(page)) {
473 swp_entry_t swap = { .val = page_private(page) };
474 __delete_from_swap_cache(page);
475 spin_unlock_irq(&mapping->tree_lock);
476 swapcache_free(swap, page);
478 __remove_from_page_cache(page);
479 spin_unlock_irq(&mapping->tree_lock);
480 mem_cgroup_uncharge_cache_page(page);
486 spin_unlock_irq(&mapping->tree_lock);
491 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
492 * someone else has a ref on the page, abort and return 0. If it was
493 * successfully detached, return 1. Assumes the caller has a single ref on
496 int remove_mapping(struct address_space *mapping, struct page *page)
498 if (__remove_mapping(mapping, page)) {
500 * Unfreezing the refcount with 1 rather than 2 effectively
501 * drops the pagecache ref for us without requiring another
504 page_unfreeze_refs(page, 1);
511 * putback_lru_page - put previously isolated page onto appropriate LRU list
512 * @page: page to be put back to appropriate lru list
514 * Add previously isolated @page to appropriate LRU list.
515 * Page may still be unevictable for other reasons.
517 * lru_lock must not be held, interrupts must be enabled.
519 void putback_lru_page(struct page *page)
522 int active = !!TestClearPageActive(page);
523 int was_unevictable = PageUnevictable(page);
525 VM_BUG_ON(PageLRU(page));
528 ClearPageUnevictable(page);
530 if (page_evictable(page, NULL)) {
532 * For evictable pages, we can use the cache.
533 * In event of a race, worst case is we end up with an
534 * unevictable page on [in]active list.
535 * We know how to handle that.
537 lru = active + page_lru_base_type(page);
538 lru_cache_add_lru(page, lru);
541 * Put unevictable pages directly on zone's unevictable
544 lru = LRU_UNEVICTABLE;
545 add_page_to_unevictable_list(page);
547 * When racing with an mlock clearing (page is
548 * unlocked), make sure that if the other thread does
549 * not observe our setting of PG_lru and fails
550 * isolation, we see PG_mlocked cleared below and move
551 * the page back to the evictable list.
553 * The other side is TestClearPageMlocked().
559 * page's status can change while we move it among lru. If an evictable
560 * page is on unevictable list, it never be freed. To avoid that,
561 * check after we added it to the list, again.
563 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
564 if (!isolate_lru_page(page)) {
568 /* This means someone else dropped this page from LRU
569 * So, it will be freed or putback to LRU again. There is
570 * nothing to do here.
574 if (was_unevictable && lru != LRU_UNEVICTABLE)
575 count_vm_event(UNEVICTABLE_PGRESCUED);
576 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
577 count_vm_event(UNEVICTABLE_PGCULLED);
579 put_page(page); /* drop ref from isolate */
583 * shrink_page_list() returns the number of reclaimed pages
585 static unsigned long shrink_page_list(struct list_head *page_list,
586 struct scan_control *sc,
587 enum pageout_io sync_writeback)
589 LIST_HEAD(ret_pages);
590 struct pagevec freed_pvec;
592 unsigned long nr_reclaimed = 0;
593 unsigned long vm_flags;
597 pagevec_init(&freed_pvec, 1);
598 while (!list_empty(page_list)) {
599 struct address_space *mapping;
606 page = lru_to_page(page_list);
607 list_del(&page->lru);
609 if (!trylock_page(page))
612 VM_BUG_ON(PageActive(page));
616 if (unlikely(!page_evictable(page, NULL)))
619 if (!sc->may_unmap && page_mapped(page))
622 /* Double the slab pressure for mapped and swapcache pages */
623 if (page_mapped(page) || PageSwapCache(page))
626 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
627 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
629 if (PageWriteback(page)) {
631 * Synchronous reclaim is performed in two passes,
632 * first an asynchronous pass over the list to
633 * start parallel writeback, and a second synchronous
634 * pass to wait for the IO to complete. Wait here
635 * for any page for which writeback has already
638 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
639 wait_on_page_writeback(page);
644 referenced = page_referenced(page, 1,
645 sc->mem_cgroup, &vm_flags);
647 * In active use or really unfreeable? Activate it.
648 * If page which have PG_mlocked lost isoltation race,
649 * try_to_unmap moves it to unevictable list
651 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
652 referenced && page_mapping_inuse(page)
653 && !(vm_flags & VM_LOCKED))
654 goto activate_locked;
657 * Anonymous process memory has backing store?
658 * Try to allocate it some swap space here.
660 if (PageAnon(page) && !PageSwapCache(page)) {
661 if (!(sc->gfp_mask & __GFP_IO))
663 if (!add_to_swap(page))
664 goto activate_locked;
668 mapping = page_mapping(page);
671 * The page is mapped into the page tables of one or more
672 * processes. Try to unmap it here.
674 if (page_mapped(page) && mapping) {
675 switch (try_to_unmap(page, TTU_UNMAP)) {
677 goto activate_locked;
683 ; /* try to free the page below */
687 if (PageDirty(page)) {
688 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
692 if (!sc->may_writepage)
695 /* Page is dirty, try to write it out here */
696 switch (pageout(page, mapping, sync_writeback)) {
700 goto activate_locked;
702 if (PageWriteback(page) || PageDirty(page))
705 * A synchronous write - probably a ramdisk. Go
706 * ahead and try to reclaim the page.
708 if (!trylock_page(page))
710 if (PageDirty(page) || PageWriteback(page))
712 mapping = page_mapping(page);
714 ; /* try to free the page below */
719 * If the page has buffers, try to free the buffer mappings
720 * associated with this page. If we succeed we try to free
723 * We do this even if the page is PageDirty().
724 * try_to_release_page() does not perform I/O, but it is
725 * possible for a page to have PageDirty set, but it is actually
726 * clean (all its buffers are clean). This happens if the
727 * buffers were written out directly, with submit_bh(). ext3
728 * will do this, as well as the blockdev mapping.
729 * try_to_release_page() will discover that cleanness and will
730 * drop the buffers and mark the page clean - it can be freed.
732 * Rarely, pages can have buffers and no ->mapping. These are
733 * the pages which were not successfully invalidated in
734 * truncate_complete_page(). We try to drop those buffers here
735 * and if that worked, and the page is no longer mapped into
736 * process address space (page_count == 1) it can be freed.
737 * Otherwise, leave the page on the LRU so it is swappable.
739 if (page_has_private(page)) {
740 if (!try_to_release_page(page, sc->gfp_mask))
741 goto activate_locked;
742 if (!mapping && page_count(page) == 1) {
744 if (put_page_testzero(page))
748 * rare race with speculative reference.
749 * the speculative reference will free
750 * this page shortly, so we may
751 * increment nr_reclaimed here (and
752 * leave it off the LRU).
760 if (!mapping || !__remove_mapping(mapping, page))
764 * At this point, we have no other references and there is
765 * no way to pick any more up (removed from LRU, removed
766 * from pagecache). Can use non-atomic bitops now (and
767 * we obviously don't have to worry about waking up a process
768 * waiting on the page lock, because there are no references.
770 __clear_page_locked(page);
773 if (!pagevec_add(&freed_pvec, page)) {
774 __pagevec_free(&freed_pvec);
775 pagevec_reinit(&freed_pvec);
780 if (PageSwapCache(page))
781 try_to_free_swap(page);
783 putback_lru_page(page);
787 /* Not a candidate for swapping, so reclaim swap space. */
788 if (PageSwapCache(page) && vm_swap_full())
789 try_to_free_swap(page);
790 VM_BUG_ON(PageActive(page));
796 list_add(&page->lru, &ret_pages);
797 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
799 list_splice(&ret_pages, page_list);
800 if (pagevec_count(&freed_pvec))
801 __pagevec_free(&freed_pvec);
802 count_vm_events(PGACTIVATE, pgactivate);
806 /* LRU Isolation modes. */
807 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
808 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
809 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
812 * Attempt to remove the specified page from its LRU. Only take this page
813 * if it is of the appropriate PageActive status. Pages which are being
814 * freed elsewhere are also ignored.
816 * page: page to consider
817 * mode: one of the LRU isolation modes defined above
819 * returns 0 on success, -ve errno on failure.
821 int __isolate_lru_page(struct page *page, int mode, int file)
825 /* Only take pages on the LRU. */
830 * When checking the active state, we need to be sure we are
831 * dealing with comparible boolean values. Take the logical not
834 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
837 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
841 * When this function is being called for lumpy reclaim, we
842 * initially look into all LRU pages, active, inactive and
843 * unevictable; only give shrink_page_list evictable pages.
845 if (PageUnevictable(page))
850 if (likely(get_page_unless_zero(page))) {
852 * Be careful not to clear PageLRU until after we're
853 * sure the page is not being freed elsewhere -- the
854 * page release code relies on it.
864 * zone->lru_lock is heavily contended. Some of the functions that
865 * shrink the lists perform better by taking out a batch of pages
866 * and working on them outside the LRU lock.
868 * For pagecache intensive workloads, this function is the hottest
869 * spot in the kernel (apart from copy_*_user functions).
871 * Appropriate locks must be held before calling this function.
873 * @nr_to_scan: The number of pages to look through on the list.
874 * @src: The LRU list to pull pages off.
875 * @dst: The temp list to put pages on to.
876 * @scanned: The number of pages that were scanned.
877 * @order: The caller's attempted allocation order
878 * @mode: One of the LRU isolation modes
879 * @file: True [1] if isolating file [!anon] pages
881 * returns how many pages were moved onto *@dst.
883 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
884 struct list_head *src, struct list_head *dst,
885 unsigned long *scanned, int order, int mode, int file)
887 unsigned long nr_taken = 0;
890 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
893 unsigned long end_pfn;
894 unsigned long page_pfn;
897 page = lru_to_page(src);
898 prefetchw_prev_lru_page(page, src, flags);
900 VM_BUG_ON(!PageLRU(page));
902 switch (__isolate_lru_page(page, mode, file)) {
904 list_move(&page->lru, dst);
905 mem_cgroup_del_lru(page);
910 /* else it is being freed elsewhere */
911 list_move(&page->lru, src);
912 mem_cgroup_rotate_lru_list(page, page_lru(page));
923 * Attempt to take all pages in the order aligned region
924 * surrounding the tag page. Only take those pages of
925 * the same active state as that tag page. We may safely
926 * round the target page pfn down to the requested order
927 * as the mem_map is guarenteed valid out to MAX_ORDER,
928 * where that page is in a different zone we will detect
929 * it from its zone id and abort this block scan.
931 zone_id = page_zone_id(page);
932 page_pfn = page_to_pfn(page);
933 pfn = page_pfn & ~((1 << order) - 1);
934 end_pfn = pfn + (1 << order);
935 for (; pfn < end_pfn; pfn++) {
936 struct page *cursor_page;
938 /* The target page is in the block, ignore it. */
939 if (unlikely(pfn == page_pfn))
942 /* Avoid holes within the zone. */
943 if (unlikely(!pfn_valid_within(pfn)))
946 cursor_page = pfn_to_page(pfn);
948 /* Check that we have not crossed a zone boundary. */
949 if (unlikely(page_zone_id(cursor_page) != zone_id))
953 * If we don't have enough swap space, reclaiming of
954 * anon page which don't already have a swap slot is
957 if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
958 !PageSwapCache(cursor_page))
961 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
962 list_move(&cursor_page->lru, dst);
963 mem_cgroup_del_lru(cursor_page);
974 static unsigned long isolate_pages_global(unsigned long nr,
975 struct list_head *dst,
976 unsigned long *scanned, int order,
977 int mode, struct zone *z,
978 struct mem_cgroup *mem_cont,
979 int active, int file)
986 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
991 * clear_active_flags() is a helper for shrink_active_list(), clearing
992 * any active bits from the pages in the list.
994 static unsigned long clear_active_flags(struct list_head *page_list,
1001 list_for_each_entry(page, page_list, lru) {
1002 lru = page_lru_base_type(page);
1003 if (PageActive(page)) {
1005 ClearPageActive(page);
1015 * isolate_lru_page - tries to isolate a page from its LRU list
1016 * @page: page to isolate from its LRU list
1018 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1019 * vmstat statistic corresponding to whatever LRU list the page was on.
1021 * Returns 0 if the page was removed from an LRU list.
1022 * Returns -EBUSY if the page was not on an LRU list.
1024 * The returned page will have PageLRU() cleared. If it was found on
1025 * the active list, it will have PageActive set. If it was found on
1026 * the unevictable list, it will have the PageUnevictable bit set. That flag
1027 * may need to be cleared by the caller before letting the page go.
1029 * The vmstat statistic corresponding to the list on which the page was
1030 * found will be decremented.
1033 * (1) Must be called with an elevated refcount on the page. This is a
1034 * fundamentnal difference from isolate_lru_pages (which is called
1035 * without a stable reference).
1036 * (2) the lru_lock must not be held.
1037 * (3) interrupts must be enabled.
1039 int isolate_lru_page(struct page *page)
1043 if (PageLRU(page)) {
1044 struct zone *zone = page_zone(page);
1046 spin_lock_irq(&zone->lru_lock);
1047 if (PageLRU(page) && get_page_unless_zero(page)) {
1048 int lru = page_lru(page);
1052 del_page_from_lru_list(zone, page, lru);
1054 spin_unlock_irq(&zone->lru_lock);
1060 * Are there way too many processes in the direct reclaim path already?
1062 static int too_many_isolated(struct zone *zone, int file,
1063 struct scan_control *sc)
1065 unsigned long inactive, isolated;
1067 if (current_is_kswapd())
1070 if (!scanning_global_lru(sc))
1074 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1075 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1077 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1078 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1081 return isolated > inactive;
1085 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1086 * of reclaimed pages
1088 static unsigned long shrink_inactive_list(unsigned long max_scan,
1089 struct zone *zone, struct scan_control *sc,
1090 int priority, int file)
1092 LIST_HEAD(page_list);
1093 struct pagevec pvec;
1094 unsigned long nr_scanned = 0;
1095 unsigned long nr_reclaimed = 0;
1096 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1097 int lumpy_reclaim = 0;
1099 while (unlikely(too_many_isolated(zone, file, sc))) {
1100 congestion_wait(BLK_RW_ASYNC, HZ/10);
1102 /* We are about to die and free our memory. Return now. */
1103 if (fatal_signal_pending(current))
1104 return SWAP_CLUSTER_MAX;
1108 * If we need a large contiguous chunk of memory, or have
1109 * trouble getting a small set of contiguous pages, we
1110 * will reclaim both active and inactive pages.
1112 * We use the same threshold as pageout congestion_wait below.
1114 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1116 else if (sc->order && priority < DEF_PRIORITY - 2)
1119 pagevec_init(&pvec, 1);
1122 spin_lock_irq(&zone->lru_lock);
1125 unsigned long nr_taken;
1126 unsigned long nr_scan;
1127 unsigned long nr_freed;
1128 unsigned long nr_active;
1129 unsigned int count[NR_LRU_LISTS] = { 0, };
1130 int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE;
1131 unsigned long nr_anon;
1132 unsigned long nr_file;
1134 nr_taken = sc->isolate_pages(SWAP_CLUSTER_MAX,
1135 &page_list, &nr_scan, sc->order, mode,
1136 zone, sc->mem_cgroup, 0, file);
1138 if (scanning_global_lru(sc)) {
1139 zone->pages_scanned += nr_scan;
1140 if (current_is_kswapd())
1141 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1144 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1151 nr_active = clear_active_flags(&page_list, count);
1152 __count_vm_events(PGDEACTIVATE, nr_active);
1154 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1155 -count[LRU_ACTIVE_FILE]);
1156 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1157 -count[LRU_INACTIVE_FILE]);
1158 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1159 -count[LRU_ACTIVE_ANON]);
1160 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1161 -count[LRU_INACTIVE_ANON]);
1163 nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1164 nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1165 __mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
1166 __mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
1168 reclaim_stat->recent_scanned[0] += count[LRU_INACTIVE_ANON];
1169 reclaim_stat->recent_scanned[0] += count[LRU_ACTIVE_ANON];
1170 reclaim_stat->recent_scanned[1] += count[LRU_INACTIVE_FILE];
1171 reclaim_stat->recent_scanned[1] += count[LRU_ACTIVE_FILE];
1173 spin_unlock_irq(&zone->lru_lock);
1175 nr_scanned += nr_scan;
1176 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1179 * If we are direct reclaiming for contiguous pages and we do
1180 * not reclaim everything in the list, try again and wait
1181 * for IO to complete. This will stall high-order allocations
1182 * but that should be acceptable to the caller
1184 if (nr_freed < nr_taken && !current_is_kswapd() &&
1186 congestion_wait(BLK_RW_ASYNC, HZ/10);
1189 * The attempt at page out may have made some
1190 * of the pages active, mark them inactive again.
1192 nr_active = clear_active_flags(&page_list, count);
1193 count_vm_events(PGDEACTIVATE, nr_active);
1195 nr_freed += shrink_page_list(&page_list, sc,
1199 nr_reclaimed += nr_freed;
1201 local_irq_disable();
1202 if (current_is_kswapd())
1203 __count_vm_events(KSWAPD_STEAL, nr_freed);
1204 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
1206 spin_lock(&zone->lru_lock);
1208 * Put back any unfreeable pages.
1210 while (!list_empty(&page_list)) {
1212 page = lru_to_page(&page_list);
1213 VM_BUG_ON(PageLRU(page));
1214 list_del(&page->lru);
1215 if (unlikely(!page_evictable(page, NULL))) {
1216 spin_unlock_irq(&zone->lru_lock);
1217 putback_lru_page(page);
1218 spin_lock_irq(&zone->lru_lock);
1222 lru = page_lru(page);
1223 add_page_to_lru_list(zone, page, lru);
1224 if (is_active_lru(lru)) {
1225 int file = is_file_lru(lru);
1226 reclaim_stat->recent_rotated[file]++;
1228 if (!pagevec_add(&pvec, page)) {
1229 spin_unlock_irq(&zone->lru_lock);
1230 __pagevec_release(&pvec);
1231 spin_lock_irq(&zone->lru_lock);
1234 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1235 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1237 } while (nr_scanned < max_scan);
1240 spin_unlock_irq(&zone->lru_lock);
1241 pagevec_release(&pvec);
1242 return nr_reclaimed;
1246 * We are about to scan this zone at a certain priority level. If that priority
1247 * level is smaller (ie: more urgent) than the previous priority, then note
1248 * that priority level within the zone. This is done so that when the next
1249 * process comes in to scan this zone, it will immediately start out at this
1250 * priority level rather than having to build up its own scanning priority.
1251 * Here, this priority affects only the reclaim-mapped threshold.
1253 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1255 if (priority < zone->prev_priority)
1256 zone->prev_priority = priority;
1260 * This moves pages from the active list to the inactive list.
1262 * We move them the other way if the page is referenced by one or more
1263 * processes, from rmap.
1265 * If the pages are mostly unmapped, the processing is fast and it is
1266 * appropriate to hold zone->lru_lock across the whole operation. But if
1267 * the pages are mapped, the processing is slow (page_referenced()) so we
1268 * should drop zone->lru_lock around each page. It's impossible to balance
1269 * this, so instead we remove the pages from the LRU while processing them.
1270 * It is safe to rely on PG_active against the non-LRU pages in here because
1271 * nobody will play with that bit on a non-LRU page.
1273 * The downside is that we have to touch page->_count against each page.
1274 * But we had to alter page->flags anyway.
1277 static void move_active_pages_to_lru(struct zone *zone,
1278 struct list_head *list,
1281 unsigned long pgmoved = 0;
1282 struct pagevec pvec;
1285 pagevec_init(&pvec, 1);
1287 while (!list_empty(list)) {
1288 page = lru_to_page(list);
1290 VM_BUG_ON(PageLRU(page));
1293 list_move(&page->lru, &zone->lru[lru].list);
1294 mem_cgroup_add_lru_list(page, lru);
1297 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1298 spin_unlock_irq(&zone->lru_lock);
1299 if (buffer_heads_over_limit)
1300 pagevec_strip(&pvec);
1301 __pagevec_release(&pvec);
1302 spin_lock_irq(&zone->lru_lock);
1305 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1306 if (!is_active_lru(lru))
1307 __count_vm_events(PGDEACTIVATE, pgmoved);
1310 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1311 struct scan_control *sc, int priority, int file)
1313 unsigned long nr_taken;
1314 unsigned long pgscanned;
1315 unsigned long vm_flags;
1316 LIST_HEAD(l_hold); /* The pages which were snipped off */
1317 LIST_HEAD(l_active);
1318 LIST_HEAD(l_inactive);
1320 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1321 unsigned long nr_rotated = 0;
1324 spin_lock_irq(&zone->lru_lock);
1325 nr_taken = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1326 ISOLATE_ACTIVE, zone,
1327 sc->mem_cgroup, 1, file);
1329 * zone->pages_scanned is used for detect zone's oom
1330 * mem_cgroup remembers nr_scan by itself.
1332 if (scanning_global_lru(sc)) {
1333 zone->pages_scanned += pgscanned;
1335 reclaim_stat->recent_scanned[file] += nr_taken;
1337 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1339 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1341 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1342 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1343 spin_unlock_irq(&zone->lru_lock);
1345 while (!list_empty(&l_hold)) {
1347 page = lru_to_page(&l_hold);
1348 list_del(&page->lru);
1350 if (unlikely(!page_evictable(page, NULL))) {
1351 putback_lru_page(page);
1355 /* page_referenced clears PageReferenced */
1356 if (page_mapping_inuse(page) &&
1357 page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1360 * Identify referenced, file-backed active pages and
1361 * give them one more trip around the active list. So
1362 * that executable code get better chances to stay in
1363 * memory under moderate memory pressure. Anon pages
1364 * are not likely to be evicted by use-once streaming
1365 * IO, plus JVM can create lots of anon VM_EXEC pages,
1366 * so we ignore them here.
1368 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1369 list_add(&page->lru, &l_active);
1374 ClearPageActive(page); /* we are de-activating */
1375 list_add(&page->lru, &l_inactive);
1379 * Move pages back to the lru list.
1381 spin_lock_irq(&zone->lru_lock);
1383 * Count referenced pages from currently used mappings as rotated,
1384 * even though only some of them are actually re-activated. This
1385 * helps balance scan pressure between file and anonymous pages in
1388 reclaim_stat->recent_rotated[file] += nr_rotated;
1390 move_active_pages_to_lru(zone, &l_active,
1391 LRU_ACTIVE + file * LRU_FILE);
1392 move_active_pages_to_lru(zone, &l_inactive,
1393 LRU_BASE + file * LRU_FILE);
1394 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1395 spin_unlock_irq(&zone->lru_lock);
1398 static int inactive_anon_is_low_global(struct zone *zone)
1400 unsigned long active, inactive;
1402 active = zone_page_state(zone, NR_ACTIVE_ANON);
1403 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1405 if (inactive * zone->inactive_ratio < active)
1412 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1413 * @zone: zone to check
1414 * @sc: scan control of this context
1416 * Returns true if the zone does not have enough inactive anon pages,
1417 * meaning some active anon pages need to be deactivated.
1419 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1423 if (scanning_global_lru(sc))
1424 low = inactive_anon_is_low_global(zone);
1426 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1430 static int inactive_file_is_low_global(struct zone *zone)
1432 unsigned long active, inactive;
1434 active = zone_page_state(zone, NR_ACTIVE_FILE);
1435 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1437 return (active > inactive);
1441 * inactive_file_is_low - check if file pages need to be deactivated
1442 * @zone: zone to check
1443 * @sc: scan control of this context
1445 * When the system is doing streaming IO, memory pressure here
1446 * ensures that active file pages get deactivated, until more
1447 * than half of the file pages are on the inactive list.
1449 * Once we get to that situation, protect the system's working
1450 * set from being evicted by disabling active file page aging.
1452 * This uses a different ratio than the anonymous pages, because
1453 * the page cache uses a use-once replacement algorithm.
1455 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1459 if (scanning_global_lru(sc))
1460 low = inactive_file_is_low_global(zone);
1462 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1466 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1470 return inactive_file_is_low(zone, sc);
1472 return inactive_anon_is_low(zone, sc);
1475 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1476 struct zone *zone, struct scan_control *sc, int priority)
1478 int file = is_file_lru(lru);
1480 if (is_active_lru(lru)) {
1481 if (inactive_list_is_low(zone, sc, file))
1482 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1486 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1490 * Determine how aggressively the anon and file LRU lists should be
1491 * scanned. The relative value of each set of LRU lists is determined
1492 * by looking at the fraction of the pages scanned we did rotate back
1493 * onto the active list instead of evict.
1495 * percent[0] specifies how much pressure to put on ram/swap backed
1496 * memory, while percent[1] determines pressure on the file LRUs.
1498 static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
1499 unsigned long *percent)
1501 unsigned long anon, file, free;
1502 unsigned long anon_prio, file_prio;
1503 unsigned long ap, fp;
1504 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1506 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1507 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1508 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1509 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1511 if (scanning_global_lru(sc)) {
1512 free = zone_page_state(zone, NR_FREE_PAGES);
1513 /* If we have very few page cache pages,
1514 force-scan anon pages. */
1515 if (unlikely(file + free <= high_wmark_pages(zone))) {
1523 * OK, so we have swap space and a fair amount of page cache
1524 * pages. We use the recently rotated / recently scanned
1525 * ratios to determine how valuable each cache is.
1527 * Because workloads change over time (and to avoid overflow)
1528 * we keep these statistics as a floating average, which ends
1529 * up weighing recent references more than old ones.
1531 * anon in [0], file in [1]
1533 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1534 spin_lock_irq(&zone->lru_lock);
1535 reclaim_stat->recent_scanned[0] /= 2;
1536 reclaim_stat->recent_rotated[0] /= 2;
1537 spin_unlock_irq(&zone->lru_lock);
1540 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1541 spin_lock_irq(&zone->lru_lock);
1542 reclaim_stat->recent_scanned[1] /= 2;
1543 reclaim_stat->recent_rotated[1] /= 2;
1544 spin_unlock_irq(&zone->lru_lock);
1548 * With swappiness at 100, anonymous and file have the same priority.
1549 * This scanning priority is essentially the inverse of IO cost.
1551 anon_prio = sc->swappiness;
1552 file_prio = 200 - sc->swappiness;
1555 * The amount of pressure on anon vs file pages is inversely
1556 * proportional to the fraction of recently scanned pages on
1557 * each list that were recently referenced and in active use.
1559 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1560 ap /= reclaim_stat->recent_rotated[0] + 1;
1562 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1563 fp /= reclaim_stat->recent_rotated[1] + 1;
1565 /* Normalize to percentages */
1566 percent[0] = 100 * ap / (ap + fp + 1);
1567 percent[1] = 100 - percent[0];
1571 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1572 * until we collected @swap_cluster_max pages to scan.
1574 static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
1575 unsigned long *nr_saved_scan)
1579 *nr_saved_scan += nr_to_scan;
1580 nr = *nr_saved_scan;
1582 if (nr >= SWAP_CLUSTER_MAX)
1591 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1593 static void shrink_zone(int priority, struct zone *zone,
1594 struct scan_control *sc)
1596 unsigned long nr[NR_LRU_LISTS];
1597 unsigned long nr_to_scan;
1598 unsigned long percent[2]; /* anon @ 0; file @ 1 */
1600 unsigned long nr_reclaimed = sc->nr_reclaimed;
1601 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1602 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1605 /* If we have no swap space, do not bother scanning anon pages. */
1606 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1611 get_scan_ratio(zone, sc, percent);
1613 for_each_evictable_lru(l) {
1614 int file = is_file_lru(l);
1617 scan = zone_nr_lru_pages(zone, sc, l);
1618 if (priority || noswap) {
1620 scan = (scan * percent[file]) / 100;
1622 nr[l] = nr_scan_try_batch(scan,
1623 &reclaim_stat->nr_saved_scan[l]);
1626 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1627 nr[LRU_INACTIVE_FILE]) {
1628 for_each_evictable_lru(l) {
1630 nr_to_scan = min_t(unsigned long,
1631 nr[l], SWAP_CLUSTER_MAX);
1632 nr[l] -= nr_to_scan;
1634 nr_reclaimed += shrink_list(l, nr_to_scan,
1635 zone, sc, priority);
1639 * On large memory systems, scan >> priority can become
1640 * really large. This is fine for the starting priority;
1641 * we want to put equal scanning pressure on each zone.
1642 * However, if the VM has a harder time of freeing pages,
1643 * with multiple processes reclaiming pages, the total
1644 * freeing target can get unreasonably large.
1646 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
1650 sc->nr_reclaimed = nr_reclaimed;
1653 * Even if we did not try to evict anon pages at all, we want to
1654 * rebalance the anon lru active/inactive ratio.
1656 if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0)
1657 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1659 throttle_vm_writeout(sc->gfp_mask);
1663 * This is the direct reclaim path, for page-allocating processes. We only
1664 * try to reclaim pages from zones which will satisfy the caller's allocation
1667 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1669 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1671 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1672 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1673 * zone defense algorithm.
1675 * If a zone is deemed to be full of pinned pages then just give it a light
1676 * scan then give up on it.
1678 static void shrink_zones(int priority, struct zonelist *zonelist,
1679 struct scan_control *sc)
1681 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1685 sc->all_unreclaimable = 1;
1686 for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
1688 if (!populated_zone(zone))
1691 * Take care memory controller reclaiming has small influence
1694 if (scanning_global_lru(sc)) {
1695 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1697 note_zone_scanning_priority(zone, priority);
1699 if (zone_is_all_unreclaimable(zone) &&
1700 priority != DEF_PRIORITY)
1701 continue; /* Let kswapd poll it */
1702 sc->all_unreclaimable = 0;
1705 * Ignore cpuset limitation here. We just want to reduce
1706 * # of used pages by us regardless of memory shortage.
1708 sc->all_unreclaimable = 0;
1709 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1713 shrink_zone(priority, zone, sc);
1718 * This is the main entry point to direct page reclaim.
1720 * If a full scan of the inactive list fails to free enough memory then we
1721 * are "out of memory" and something needs to be killed.
1723 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1724 * high - the zone may be full of dirty or under-writeback pages, which this
1725 * caller can't do much about. We kick the writeback threads and take explicit
1726 * naps in the hope that some of these pages can be written. But if the
1727 * allocating task holds filesystem locks which prevent writeout this might not
1728 * work, and the allocation attempt will fail.
1730 * returns: 0, if no pages reclaimed
1731 * else, the number of pages reclaimed
1733 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1734 struct scan_control *sc)
1737 unsigned long ret = 0;
1738 unsigned long total_scanned = 0;
1739 struct reclaim_state *reclaim_state = current->reclaim_state;
1740 unsigned long lru_pages = 0;
1743 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1744 unsigned long writeback_threshold;
1746 delayacct_freepages_start();
1748 if (scanning_global_lru(sc))
1749 count_vm_event(ALLOCSTALL);
1751 * mem_cgroup will not do shrink_slab.
1753 if (scanning_global_lru(sc)) {
1754 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1756 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1759 lru_pages += zone_reclaimable_pages(zone);
1763 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1766 disable_swap_token();
1767 shrink_zones(priority, zonelist, sc);
1769 * Don't shrink slabs when reclaiming memory from
1770 * over limit cgroups
1772 if (scanning_global_lru(sc)) {
1773 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1774 if (reclaim_state) {
1775 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1776 reclaim_state->reclaimed_slab = 0;
1779 total_scanned += sc->nr_scanned;
1780 if (sc->nr_reclaimed >= sc->nr_to_reclaim) {
1781 ret = sc->nr_reclaimed;
1786 * Try to write back as many pages as we just scanned. This
1787 * tends to cause slow streaming writers to write data to the
1788 * disk smoothly, at the dirtying rate, which is nice. But
1789 * that's undesirable in laptop mode, where we *want* lumpy
1790 * writeout. So in laptop mode, write out the whole world.
1792 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
1793 if (total_scanned > writeback_threshold) {
1794 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
1795 sc->may_writepage = 1;
1798 /* Take a nap, wait for some writeback to complete */
1799 if (!sc->hibernation_mode && sc->nr_scanned &&
1800 priority < DEF_PRIORITY - 2)
1801 congestion_wait(BLK_RW_ASYNC, HZ/10);
1803 /* top priority shrink_zones still had more to do? don't OOM, then */
1804 if (!sc->all_unreclaimable && scanning_global_lru(sc))
1805 ret = sc->nr_reclaimed;
1808 * Now that we've scanned all the zones at this priority level, note
1809 * that level within the zone so that the next thread which performs
1810 * scanning of this zone will immediately start out at this priority
1811 * level. This affects only the decision whether or not to bring
1812 * mapped pages onto the inactive list.
1817 if (scanning_global_lru(sc)) {
1818 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1820 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1823 zone->prev_priority = priority;
1826 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1828 delayacct_freepages_end();
1833 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1834 gfp_t gfp_mask, nodemask_t *nodemask)
1836 struct scan_control sc = {
1837 .gfp_mask = gfp_mask,
1838 .may_writepage = !laptop_mode,
1839 .nr_to_reclaim = SWAP_CLUSTER_MAX,
1842 .swappiness = vm_swappiness,
1845 .isolate_pages = isolate_pages_global,
1846 .nodemask = nodemask,
1849 return do_try_to_free_pages(zonelist, &sc);
1852 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1854 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
1855 gfp_t gfp_mask, bool noswap,
1856 unsigned int swappiness,
1857 struct zone *zone, int nid)
1859 struct scan_control sc = {
1860 .may_writepage = !laptop_mode,
1862 .may_swap = !noswap,
1863 .swappiness = swappiness,
1866 .isolate_pages = mem_cgroup_isolate_pages,
1868 nodemask_t nm = nodemask_of_node(nid);
1870 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1871 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1873 sc.nr_reclaimed = 0;
1876 * NOTE: Although we can get the priority field, using it
1877 * here is not a good idea, since it limits the pages we can scan.
1878 * if we don't reclaim here, the shrink_zone from balance_pgdat
1879 * will pick up pages from other mem cgroup's as well. We hack
1880 * the priority and make it zero.
1882 shrink_zone(0, zone, &sc);
1883 return sc.nr_reclaimed;
1886 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1889 unsigned int swappiness)
1891 struct zonelist *zonelist;
1892 struct scan_control sc = {
1893 .may_writepage = !laptop_mode,
1895 .may_swap = !noswap,
1896 .nr_to_reclaim = SWAP_CLUSTER_MAX,
1897 .swappiness = swappiness,
1899 .mem_cgroup = mem_cont,
1900 .isolate_pages = mem_cgroup_isolate_pages,
1901 .nodemask = NULL, /* we don't care the placement */
1904 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1905 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1906 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1907 return do_try_to_free_pages(zonelist, &sc);
1911 /* is kswapd sleeping prematurely? */
1912 static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
1916 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
1920 /* If after HZ/10, a zone is below the high mark, it's premature */
1921 for (i = 0; i < pgdat->nr_zones; i++) {
1922 struct zone *zone = pgdat->node_zones + i;
1924 if (!populated_zone(zone))
1927 if (!zone_watermark_ok(zone, order, high_wmark_pages(zone),
1936 * For kswapd, balance_pgdat() will work across all this node's zones until
1937 * they are all at high_wmark_pages(zone).
1939 * Returns the number of pages which were actually freed.
1941 * There is special handling here for zones which are full of pinned pages.
1942 * This can happen if the pages are all mlocked, or if they are all used by
1943 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1944 * What we do is to detect the case where all pages in the zone have been
1945 * scanned twice and there has been zero successful reclaim. Mark the zone as
1946 * dead and from now on, only perform a short scan. Basically we're polling
1947 * the zone for when the problem goes away.
1949 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1950 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
1951 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
1952 * lower zones regardless of the number of free pages in the lower zones. This
1953 * interoperates with the page allocator fallback scheme to ensure that aging
1954 * of pages is balanced across the zones.
1956 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1961 unsigned long total_scanned;
1962 struct reclaim_state *reclaim_state = current->reclaim_state;
1963 struct scan_control sc = {
1964 .gfp_mask = GFP_KERNEL,
1968 * kswapd doesn't want to be bailed out while reclaim. because
1969 * we want to put equal scanning pressure on each zone.
1971 .nr_to_reclaim = ULONG_MAX,
1972 .swappiness = vm_swappiness,
1975 .isolate_pages = isolate_pages_global,
1978 * temp_priority is used to remember the scanning priority at which
1979 * this zone was successfully refilled to
1980 * free_pages == high_wmark_pages(zone).
1982 int temp_priority[MAX_NR_ZONES];
1986 sc.nr_reclaimed = 0;
1987 sc.may_writepage = !laptop_mode;
1988 count_vm_event(PAGEOUTRUN);
1990 for (i = 0; i < pgdat->nr_zones; i++)
1991 temp_priority[i] = DEF_PRIORITY;
1993 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1994 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1995 unsigned long lru_pages = 0;
1996 int has_under_min_watermark_zone = 0;
1998 /* The swap token gets in the way of swapout... */
2000 disable_swap_token();
2005 * Scan in the highmem->dma direction for the highest
2006 * zone which needs scanning
2008 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2009 struct zone *zone = pgdat->node_zones + i;
2011 if (!populated_zone(zone))
2014 if (zone_is_all_unreclaimable(zone) &&
2015 priority != DEF_PRIORITY)
2019 * Do some background aging of the anon list, to give
2020 * pages a chance to be referenced before reclaiming.
2022 if (inactive_anon_is_low(zone, &sc))
2023 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2026 if (!zone_watermark_ok(zone, order,
2027 high_wmark_pages(zone), 0, 0)) {
2035 for (i = 0; i <= end_zone; i++) {
2036 struct zone *zone = pgdat->node_zones + i;
2038 lru_pages += zone_reclaimable_pages(zone);
2042 * Now scan the zone in the dma->highmem direction, stopping
2043 * at the last zone which needs scanning.
2045 * We do this because the page allocator works in the opposite
2046 * direction. This prevents the page allocator from allocating
2047 * pages behind kswapd's direction of progress, which would
2048 * cause too much scanning of the lower zones.
2050 for (i = 0; i <= end_zone; i++) {
2051 struct zone *zone = pgdat->node_zones + i;
2055 if (!populated_zone(zone))
2058 if (zone_is_all_unreclaimable(zone) &&
2059 priority != DEF_PRIORITY)
2062 if (!zone_watermark_ok(zone, order,
2063 high_wmark_pages(zone), end_zone, 0))
2065 temp_priority[i] = priority;
2067 note_zone_scanning_priority(zone, priority);
2069 nid = pgdat->node_id;
2070 zid = zone_idx(zone);
2072 * Call soft limit reclaim before calling shrink_zone.
2073 * For now we ignore the return value
2075 mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask,
2078 * We put equal pressure on every zone, unless one
2079 * zone has way too many pages free already.
2081 if (!zone_watermark_ok(zone, order,
2082 8*high_wmark_pages(zone), end_zone, 0))
2083 shrink_zone(priority, zone, &sc);
2084 reclaim_state->reclaimed_slab = 0;
2085 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
2087 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2088 total_scanned += sc.nr_scanned;
2089 if (zone_is_all_unreclaimable(zone))
2091 if (nr_slab == 0 && zone->pages_scanned >=
2092 (zone_reclaimable_pages(zone) * 6))
2094 ZONE_ALL_UNRECLAIMABLE);
2096 * If we've done a decent amount of scanning and
2097 * the reclaim ratio is low, start doing writepage
2098 * even in laptop mode
2100 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2101 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2102 sc.may_writepage = 1;
2105 * We are still under min water mark. it mean we have
2106 * GFP_ATOMIC allocation failure risk. Hurry up!
2108 if (!zone_watermark_ok(zone, order, min_wmark_pages(zone),
2110 has_under_min_watermark_zone = 1;
2114 break; /* kswapd: all done */
2116 * OK, kswapd is getting into trouble. Take a nap, then take
2117 * another pass across the zones.
2119 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2120 if (has_under_min_watermark_zone)
2121 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2123 congestion_wait(BLK_RW_ASYNC, HZ/10);
2127 * We do this so kswapd doesn't build up large priorities for
2128 * example when it is freeing in parallel with allocators. It
2129 * matches the direct reclaim path behaviour in terms of impact
2130 * on zone->*_priority.
2132 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2137 * Note within each zone the priority level at which this zone was
2138 * brought into a happy state. So that the next thread which scans this
2139 * zone will start out at that priority level.
2141 for (i = 0; i < pgdat->nr_zones; i++) {
2142 struct zone *zone = pgdat->node_zones + i;
2144 zone->prev_priority = temp_priority[i];
2146 if (!all_zones_ok) {
2152 * Fragmentation may mean that the system cannot be
2153 * rebalanced for high-order allocations in all zones.
2154 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2155 * it means the zones have been fully scanned and are still
2156 * not balanced. For high-order allocations, there is
2157 * little point trying all over again as kswapd may
2160 * Instead, recheck all watermarks at order-0 as they
2161 * are the most important. If watermarks are ok, kswapd will go
2162 * back to sleep. High-order users can still perform direct
2163 * reclaim if they wish.
2165 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2166 order = sc.order = 0;
2171 return sc.nr_reclaimed;
2175 * The background pageout daemon, started as a kernel thread
2176 * from the init process.
2178 * This basically trickles out pages so that we have _some_
2179 * free memory available even if there is no other activity
2180 * that frees anything up. This is needed for things like routing
2181 * etc, where we otherwise might have all activity going on in
2182 * asynchronous contexts that cannot page things out.
2184 * If there are applications that are active memory-allocators
2185 * (most normal use), this basically shouldn't matter.
2187 static int kswapd(void *p)
2189 unsigned long order;
2190 pg_data_t *pgdat = (pg_data_t*)p;
2191 struct task_struct *tsk = current;
2193 struct reclaim_state reclaim_state = {
2194 .reclaimed_slab = 0,
2196 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2198 lockdep_set_current_reclaim_state(GFP_KERNEL);
2200 if (!cpumask_empty(cpumask))
2201 set_cpus_allowed_ptr(tsk, cpumask);
2202 current->reclaim_state = &reclaim_state;
2205 * Tell the memory management that we're a "memory allocator",
2206 * and that if we need more memory we should get access to it
2207 * regardless (see "__alloc_pages()"). "kswapd" should
2208 * never get caught in the normal page freeing logic.
2210 * (Kswapd normally doesn't need memory anyway, but sometimes
2211 * you need a small amount of memory in order to be able to
2212 * page out something else, and this flag essentially protects
2213 * us from recursively trying to free more memory as we're
2214 * trying to free the first piece of memory in the first place).
2216 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2221 unsigned long new_order;
2224 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2225 new_order = pgdat->kswapd_max_order;
2226 pgdat->kswapd_max_order = 0;
2227 if (order < new_order) {
2229 * Don't sleep if someone wants a larger 'order'
2234 if (!freezing(current) && !kthread_should_stop()) {
2237 /* Try to sleep for a short interval */
2238 if (!sleeping_prematurely(pgdat, order, remaining)) {
2239 remaining = schedule_timeout(HZ/10);
2240 finish_wait(&pgdat->kswapd_wait, &wait);
2241 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2245 * After a short sleep, check if it was a
2246 * premature sleep. If not, then go fully
2247 * to sleep until explicitly woken up
2249 if (!sleeping_prematurely(pgdat, order, remaining))
2253 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2255 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2259 order = pgdat->kswapd_max_order;
2261 finish_wait(&pgdat->kswapd_wait, &wait);
2263 ret = try_to_freeze();
2264 if (kthread_should_stop())
2268 * We can speed up thawing tasks if we don't call balance_pgdat
2269 * after returning from the refrigerator
2272 balance_pgdat(pgdat, order);
2278 * A zone is low on free memory, so wake its kswapd task to service it.
2280 void wakeup_kswapd(struct zone *zone, int order)
2284 if (!populated_zone(zone))
2287 pgdat = zone->zone_pgdat;
2288 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
2290 if (pgdat->kswapd_max_order < order)
2291 pgdat->kswapd_max_order = order;
2292 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2294 if (!waitqueue_active(&pgdat->kswapd_wait))
2296 wake_up_interruptible(&pgdat->kswapd_wait);
2300 * The reclaimable count would be mostly accurate.
2301 * The less reclaimable pages may be
2302 * - mlocked pages, which will be moved to unevictable list when encountered
2303 * - mapped pages, which may require several travels to be reclaimed
2304 * - dirty pages, which is not "instantly" reclaimable
2306 unsigned long global_reclaimable_pages(void)
2310 nr = global_page_state(NR_ACTIVE_FILE) +
2311 global_page_state(NR_INACTIVE_FILE);
2313 if (nr_swap_pages > 0)
2314 nr += global_page_state(NR_ACTIVE_ANON) +
2315 global_page_state(NR_INACTIVE_ANON);
2320 unsigned long zone_reclaimable_pages(struct zone *zone)
2324 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2325 zone_page_state(zone, NR_INACTIVE_FILE);
2327 if (nr_swap_pages > 0)
2328 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2329 zone_page_state(zone, NR_INACTIVE_ANON);
2334 #ifdef CONFIG_HIBERNATION
2336 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2339 * Rather than trying to age LRUs the aim is to preserve the overall
2340 * LRU order by reclaiming preferentially
2341 * inactive > active > active referenced > active mapped
2343 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2345 struct reclaim_state reclaim_state;
2346 struct scan_control sc = {
2347 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2351 .nr_to_reclaim = nr_to_reclaim,
2352 .hibernation_mode = 1,
2353 .swappiness = vm_swappiness,
2355 .isolate_pages = isolate_pages_global,
2357 struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2358 struct task_struct *p = current;
2359 unsigned long nr_reclaimed;
2361 p->flags |= PF_MEMALLOC;
2362 lockdep_set_current_reclaim_state(sc.gfp_mask);
2363 reclaim_state.reclaimed_slab = 0;
2364 p->reclaim_state = &reclaim_state;
2366 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
2368 p->reclaim_state = NULL;
2369 lockdep_clear_current_reclaim_state();
2370 p->flags &= ~PF_MEMALLOC;
2372 return nr_reclaimed;
2374 #endif /* CONFIG_HIBERNATION */
2376 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2377 not required for correctness. So if the last cpu in a node goes
2378 away, we get changed to run anywhere: as the first one comes back,
2379 restore their cpu bindings. */
2380 static int __devinit cpu_callback(struct notifier_block *nfb,
2381 unsigned long action, void *hcpu)
2385 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2386 for_each_node_state(nid, N_HIGH_MEMORY) {
2387 pg_data_t *pgdat = NODE_DATA(nid);
2388 const struct cpumask *mask;
2390 mask = cpumask_of_node(pgdat->node_id);
2392 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2393 /* One of our CPUs online: restore mask */
2394 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2401 * This kswapd start function will be called by init and node-hot-add.
2402 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2404 int kswapd_run(int nid)
2406 pg_data_t *pgdat = NODE_DATA(nid);
2412 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2413 if (IS_ERR(pgdat->kswapd)) {
2414 /* failure at boot is fatal */
2415 BUG_ON(system_state == SYSTEM_BOOTING);
2416 printk("Failed to start kswapd on node %d\n",nid);
2423 * Called by memory hotplug when all memory in a node is offlined.
2425 void kswapd_stop(int nid)
2427 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
2430 kthread_stop(kswapd);
2433 static int __init kswapd_init(void)
2438 for_each_node_state(nid, N_HIGH_MEMORY)
2440 hotcpu_notifier(cpu_callback, 0);
2444 module_init(kswapd_init)
2450 * If non-zero call zone_reclaim when the number of free pages falls below
2453 int zone_reclaim_mode __read_mostly;
2455 #define RECLAIM_OFF 0
2456 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2457 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2458 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2461 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2462 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2465 #define ZONE_RECLAIM_PRIORITY 4
2468 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2471 int sysctl_min_unmapped_ratio = 1;
2474 * If the number of slab pages in a zone grows beyond this percentage then
2475 * slab reclaim needs to occur.
2477 int sysctl_min_slab_ratio = 5;
2479 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
2481 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
2482 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
2483 zone_page_state(zone, NR_ACTIVE_FILE);
2486 * It's possible for there to be more file mapped pages than
2487 * accounted for by the pages on the file LRU lists because
2488 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2490 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
2493 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
2494 static long zone_pagecache_reclaimable(struct zone *zone)
2496 long nr_pagecache_reclaimable;
2500 * If RECLAIM_SWAP is set, then all file pages are considered
2501 * potentially reclaimable. Otherwise, we have to worry about
2502 * pages like swapcache and zone_unmapped_file_pages() provides
2505 if (zone_reclaim_mode & RECLAIM_SWAP)
2506 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
2508 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
2510 /* If we can't clean pages, remove dirty pages from consideration */
2511 if (!(zone_reclaim_mode & RECLAIM_WRITE))
2512 delta += zone_page_state(zone, NR_FILE_DIRTY);
2514 /* Watch for any possible underflows due to delta */
2515 if (unlikely(delta > nr_pagecache_reclaimable))
2516 delta = nr_pagecache_reclaimable;
2518 return nr_pagecache_reclaimable - delta;
2522 * Try to free up some pages from this zone through reclaim.
2524 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2526 /* Minimum pages needed in order to stay on node */
2527 const unsigned long nr_pages = 1 << order;
2528 struct task_struct *p = current;
2529 struct reclaim_state reclaim_state;
2531 struct scan_control sc = {
2532 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2533 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2535 .nr_to_reclaim = max_t(unsigned long, nr_pages,
2537 .gfp_mask = gfp_mask,
2538 .swappiness = vm_swappiness,
2540 .isolate_pages = isolate_pages_global,
2542 unsigned long slab_reclaimable;
2544 disable_swap_token();
2547 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2548 * and we also need to be able to write out pages for RECLAIM_WRITE
2551 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2552 reclaim_state.reclaimed_slab = 0;
2553 p->reclaim_state = &reclaim_state;
2555 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
2557 * Free memory by calling shrink zone with increasing
2558 * priorities until we have enough memory freed.
2560 priority = ZONE_RECLAIM_PRIORITY;
2562 note_zone_scanning_priority(zone, priority);
2563 shrink_zone(priority, zone, &sc);
2565 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2568 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2569 if (slab_reclaimable > zone->min_slab_pages) {
2571 * shrink_slab() does not currently allow us to determine how
2572 * many pages were freed in this zone. So we take the current
2573 * number of slab pages and shake the slab until it is reduced
2574 * by the same nr_pages that we used for reclaiming unmapped
2577 * Note that shrink_slab will free memory on all zones and may
2580 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2581 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2582 slab_reclaimable - nr_pages)
2586 * Update nr_reclaimed by the number of slab pages we
2587 * reclaimed from this zone.
2589 sc.nr_reclaimed += slab_reclaimable -
2590 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2593 p->reclaim_state = NULL;
2594 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2595 return sc.nr_reclaimed >= nr_pages;
2598 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2604 * Zone reclaim reclaims unmapped file backed pages and
2605 * slab pages if we are over the defined limits.
2607 * A small portion of unmapped file backed pages is needed for
2608 * file I/O otherwise pages read by file I/O will be immediately
2609 * thrown out if the zone is overallocated. So we do not reclaim
2610 * if less than a specified percentage of the zone is used by
2611 * unmapped file backed pages.
2613 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
2614 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
2615 return ZONE_RECLAIM_FULL;
2617 if (zone_is_all_unreclaimable(zone))
2618 return ZONE_RECLAIM_FULL;
2621 * Do not scan if the allocation should not be delayed.
2623 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2624 return ZONE_RECLAIM_NOSCAN;
2627 * Only run zone reclaim on the local zone or on zones that do not
2628 * have associated processors. This will favor the local processor
2629 * over remote processors and spread off node memory allocations
2630 * as wide as possible.
2632 node_id = zone_to_nid(zone);
2633 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2634 return ZONE_RECLAIM_NOSCAN;
2636 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2637 return ZONE_RECLAIM_NOSCAN;
2639 ret = __zone_reclaim(zone, gfp_mask, order);
2640 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2643 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
2650 * page_evictable - test whether a page is evictable
2651 * @page: the page to test
2652 * @vma: the VMA in which the page is or will be mapped, may be NULL
2654 * Test whether page is evictable--i.e., should be placed on active/inactive
2655 * lists vs unevictable list. The vma argument is !NULL when called from the
2656 * fault path to determine how to instantate a new page.
2658 * Reasons page might not be evictable:
2659 * (1) page's mapping marked unevictable
2660 * (2) page is part of an mlocked VMA
2663 int page_evictable(struct page *page, struct vm_area_struct *vma)
2666 if (mapping_unevictable(page_mapping(page)))
2669 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2676 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2677 * @page: page to check evictability and move to appropriate lru list
2678 * @zone: zone page is in
2680 * Checks a page for evictability and moves the page to the appropriate
2683 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2684 * have PageUnevictable set.
2686 static void check_move_unevictable_page(struct page *page, struct zone *zone)
2688 VM_BUG_ON(PageActive(page));
2691 ClearPageUnevictable(page);
2692 if (page_evictable(page, NULL)) {
2693 enum lru_list l = page_lru_base_type(page);
2695 __dec_zone_state(zone, NR_UNEVICTABLE);
2696 list_move(&page->lru, &zone->lru[l].list);
2697 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2698 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2699 __count_vm_event(UNEVICTABLE_PGRESCUED);
2702 * rotate unevictable list
2704 SetPageUnevictable(page);
2705 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2706 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
2707 if (page_evictable(page, NULL))
2713 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2714 * @mapping: struct address_space to scan for evictable pages
2716 * Scan all pages in mapping. Check unevictable pages for
2717 * evictability and move them to the appropriate zone lru list.
2719 void scan_mapping_unevictable_pages(struct address_space *mapping)
2722 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2725 struct pagevec pvec;
2727 if (mapping->nrpages == 0)
2730 pagevec_init(&pvec, 0);
2731 while (next < end &&
2732 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2738 for (i = 0; i < pagevec_count(&pvec); i++) {
2739 struct page *page = pvec.pages[i];
2740 pgoff_t page_index = page->index;
2741 struct zone *pagezone = page_zone(page);
2744 if (page_index > next)
2748 if (pagezone != zone) {
2750 spin_unlock_irq(&zone->lru_lock);
2752 spin_lock_irq(&zone->lru_lock);
2755 if (PageLRU(page) && PageUnevictable(page))
2756 check_move_unevictable_page(page, zone);
2759 spin_unlock_irq(&zone->lru_lock);
2760 pagevec_release(&pvec);
2762 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2768 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2769 * @zone - zone of which to scan the unevictable list
2771 * Scan @zone's unevictable LRU lists to check for pages that have become
2772 * evictable. Move those that have to @zone's inactive list where they
2773 * become candidates for reclaim, unless shrink_inactive_zone() decides
2774 * to reactivate them. Pages that are still unevictable are rotated
2775 * back onto @zone's unevictable list.
2777 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2778 static void scan_zone_unevictable_pages(struct zone *zone)
2780 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2782 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2784 while (nr_to_scan > 0) {
2785 unsigned long batch_size = min(nr_to_scan,
2786 SCAN_UNEVICTABLE_BATCH_SIZE);
2788 spin_lock_irq(&zone->lru_lock);
2789 for (scan = 0; scan < batch_size; scan++) {
2790 struct page *page = lru_to_page(l_unevictable);
2792 if (!trylock_page(page))
2795 prefetchw_prev_lru_page(page, l_unevictable, flags);
2797 if (likely(PageLRU(page) && PageUnevictable(page)))
2798 check_move_unevictable_page(page, zone);
2802 spin_unlock_irq(&zone->lru_lock);
2804 nr_to_scan -= batch_size;
2810 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2812 * A really big hammer: scan all zones' unevictable LRU lists to check for
2813 * pages that have become evictable. Move those back to the zones'
2814 * inactive list where they become candidates for reclaim.
2815 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2816 * and we add swap to the system. As such, it runs in the context of a task
2817 * that has possibly/probably made some previously unevictable pages
2820 static void scan_all_zones_unevictable_pages(void)
2824 for_each_zone(zone) {
2825 scan_zone_unevictable_pages(zone);
2830 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2831 * all nodes' unevictable lists for evictable pages
2833 unsigned long scan_unevictable_pages;
2835 int scan_unevictable_handler(struct ctl_table *table, int write,
2836 void __user *buffer,
2837 size_t *length, loff_t *ppos)
2839 proc_doulongvec_minmax(table, write, buffer, length, ppos);
2841 if (write && *(unsigned long *)table->data)
2842 scan_all_zones_unevictable_pages();
2844 scan_unevictable_pages = 0;
2849 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2850 * a specified node's per zone unevictable lists for evictable pages.
2853 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2854 struct sysdev_attribute *attr,
2857 return sprintf(buf, "0\n"); /* always zero; should fit... */
2860 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2861 struct sysdev_attribute *attr,
2862 const char *buf, size_t count)
2864 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2867 unsigned long req = strict_strtoul(buf, 10, &res);
2870 return 1; /* zero is no-op */
2872 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2873 if (!populated_zone(zone))
2875 scan_zone_unevictable_pages(zone);
2881 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2882 read_scan_unevictable_node,
2883 write_scan_unevictable_node);
2885 int scan_unevictable_register_node(struct node *node)
2887 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2890 void scan_unevictable_unregister_node(struct node *node)
2892 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);