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 /* This context's GFP mask */
63 /* Can mapped pages be reclaimed? */
66 /* Can pages be swapped as part of reclaim? */
69 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
70 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
71 * In this context, it doesn't matter that we scan the
72 * whole list at once. */
77 int all_unreclaimable;
81 /* Which cgroup do we reclaim from */
82 struct mem_cgroup *mem_cgroup;
85 * Nodemask of nodes allowed by the caller. If NULL, all nodes
90 /* Pluggable isolate pages callback */
91 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
92 unsigned long *scanned, int order, int mode,
93 struct zone *z, struct mem_cgroup *mem_cont,
94 int active, int file);
97 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
99 #ifdef ARCH_HAS_PREFETCH
100 #define prefetch_prev_lru_page(_page, _base, _field) \
102 if ((_page)->lru.prev != _base) { \
105 prev = lru_to_page(&(_page->lru)); \
106 prefetch(&prev->_field); \
110 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
113 #ifdef ARCH_HAS_PREFETCHW
114 #define prefetchw_prev_lru_page(_page, _base, _field) \
116 if ((_page)->lru.prev != _base) { \
119 prev = lru_to_page(&(_page->lru)); \
120 prefetchw(&prev->_field); \
124 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
128 * From 0 .. 100. Higher means more swappy.
130 int vm_swappiness = 60;
131 long vm_total_pages; /* The total number of pages which the VM controls */
133 static LIST_HEAD(shrinker_list);
134 static DECLARE_RWSEM(shrinker_rwsem);
136 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
137 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
139 #define scanning_global_lru(sc) (1)
142 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
143 struct scan_control *sc)
145 if (!scanning_global_lru(sc))
146 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
148 return &zone->reclaim_stat;
151 static unsigned long zone_nr_pages(struct zone *zone, struct scan_control *sc,
154 if (!scanning_global_lru(sc))
155 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);
157 return zone_page_state(zone, NR_LRU_BASE + lru);
162 * Add a shrinker callback to be called from the vm
164 void register_shrinker(struct shrinker *shrinker)
167 down_write(&shrinker_rwsem);
168 list_add_tail(&shrinker->list, &shrinker_list);
169 up_write(&shrinker_rwsem);
171 EXPORT_SYMBOL(register_shrinker);
176 void unregister_shrinker(struct shrinker *shrinker)
178 down_write(&shrinker_rwsem);
179 list_del(&shrinker->list);
180 up_write(&shrinker_rwsem);
182 EXPORT_SYMBOL(unregister_shrinker);
184 #define SHRINK_BATCH 128
186 * Call the shrink functions to age shrinkable caches
188 * Here we assume it costs one seek to replace a lru page and that it also
189 * takes a seek to recreate a cache object. With this in mind we age equal
190 * percentages of the lru and ageable caches. This should balance the seeks
191 * generated by these structures.
193 * If the vm encountered mapped pages on the LRU it increase the pressure on
194 * slab to avoid swapping.
196 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
198 * `lru_pages' represents the number of on-LRU pages in all the zones which
199 * are eligible for the caller's allocation attempt. It is used for balancing
200 * slab reclaim versus page reclaim.
202 * Returns the number of slab objects which we shrunk.
204 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
205 unsigned long lru_pages)
207 struct shrinker *shrinker;
208 unsigned long ret = 0;
211 scanned = SWAP_CLUSTER_MAX;
213 if (!down_read_trylock(&shrinker_rwsem))
214 return 1; /* Assume we'll be able to shrink next time */
216 list_for_each_entry(shrinker, &shrinker_list, list) {
217 unsigned long long delta;
218 unsigned long total_scan;
219 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
221 delta = (4 * scanned) / shrinker->seeks;
223 do_div(delta, lru_pages + 1);
224 shrinker->nr += delta;
225 if (shrinker->nr < 0) {
226 printk(KERN_ERR "shrink_slab: %pF negative objects to "
228 shrinker->shrink, shrinker->nr);
229 shrinker->nr = max_pass;
233 * Avoid risking looping forever due to too large nr value:
234 * never try to free more than twice the estimate number of
237 if (shrinker->nr > max_pass * 2)
238 shrinker->nr = max_pass * 2;
240 total_scan = shrinker->nr;
243 while (total_scan >= SHRINK_BATCH) {
244 long this_scan = SHRINK_BATCH;
248 nr_before = (*shrinker->shrink)(0, gfp_mask);
249 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
250 if (shrink_ret == -1)
252 if (shrink_ret < nr_before)
253 ret += nr_before - shrink_ret;
254 count_vm_events(SLABS_SCANNED, this_scan);
255 total_scan -= this_scan;
260 shrinker->nr += total_scan;
262 up_read(&shrinker_rwsem);
266 /* Called without lock on whether page is mapped, so answer is unstable */
267 static inline int page_mapping_inuse(struct page *page)
269 struct address_space *mapping;
271 /* Page is in somebody's page tables. */
272 if (page_mapped(page))
275 /* Be more reluctant to reclaim swapcache than pagecache */
276 if (PageSwapCache(page))
279 mapping = page_mapping(page);
283 /* File is mmap'd by somebody? */
284 return mapping_mapped(mapping);
287 static inline int is_page_cache_freeable(struct page *page)
289 return page_count(page) - !!page_has_private(page) == 2;
292 static int may_write_to_queue(struct backing_dev_info *bdi)
294 if (current->flags & PF_SWAPWRITE)
296 if (!bdi_write_congested(bdi))
298 if (bdi == current->backing_dev_info)
304 * We detected a synchronous write error writing a page out. Probably
305 * -ENOSPC. We need to propagate that into the address_space for a subsequent
306 * fsync(), msync() or close().
308 * The tricky part is that after writepage we cannot touch the mapping: nothing
309 * prevents it from being freed up. But we have a ref on the page and once
310 * that page is locked, the mapping is pinned.
312 * We're allowed to run sleeping lock_page() here because we know the caller has
315 static void handle_write_error(struct address_space *mapping,
316 struct page *page, int error)
319 if (page_mapping(page) == mapping)
320 mapping_set_error(mapping, error);
324 /* Request for sync pageout. */
330 /* possible outcome of pageout() */
332 /* failed to write page out, page is locked */
334 /* move page to the active list, page is locked */
336 /* page has been sent to the disk successfully, page is unlocked */
338 /* page is clean and locked */
343 * pageout is called by shrink_page_list() for each dirty page.
344 * Calls ->writepage().
346 static pageout_t pageout(struct page *page, struct address_space *mapping,
347 enum pageout_io sync_writeback)
350 * If the page is dirty, only perform writeback if that write
351 * will be non-blocking. To prevent this allocation from being
352 * stalled by pagecache activity. But note that there may be
353 * stalls if we need to run get_block(). We could test
354 * PagePrivate for that.
356 * If this process is currently in generic_file_write() against
357 * this page's queue, we can perform writeback even if that
360 * If the page is swapcache, write it back even if that would
361 * block, for some throttling. This happens by accident, because
362 * swap_backing_dev_info is bust: it doesn't reflect the
363 * congestion state of the swapdevs. Easy to fix, if needed.
364 * See swapfile.c:page_queue_congested().
366 if (!is_page_cache_freeable(page))
370 * Some data journaling orphaned pages can have
371 * page->mapping == NULL while being dirty with clean buffers.
373 if (page_has_private(page)) {
374 if (try_to_free_buffers(page)) {
375 ClearPageDirty(page);
376 printk("%s: orphaned page\n", __func__);
382 if (mapping->a_ops->writepage == NULL)
383 return PAGE_ACTIVATE;
384 if (!may_write_to_queue(mapping->backing_dev_info))
387 if (clear_page_dirty_for_io(page)) {
389 struct writeback_control wbc = {
390 .sync_mode = WB_SYNC_NONE,
391 .nr_to_write = SWAP_CLUSTER_MAX,
393 .range_end = LLONG_MAX,
398 SetPageReclaim(page);
399 res = mapping->a_ops->writepage(page, &wbc);
401 handle_write_error(mapping, page, res);
402 if (res == AOP_WRITEPAGE_ACTIVATE) {
403 ClearPageReclaim(page);
404 return PAGE_ACTIVATE;
408 * Wait on writeback if requested to. This happens when
409 * direct reclaiming a large contiguous area and the
410 * first attempt to free a range of pages fails.
412 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
413 wait_on_page_writeback(page);
415 if (!PageWriteback(page)) {
416 /* synchronous write or broken a_ops? */
417 ClearPageReclaim(page);
419 inc_zone_page_state(page, NR_VMSCAN_WRITE);
427 * Same as remove_mapping, but if the page is removed from the mapping, it
428 * gets returned with a refcount of 0.
430 static int __remove_mapping(struct address_space *mapping, struct page *page)
432 BUG_ON(!PageLocked(page));
433 BUG_ON(mapping != page_mapping(page));
435 spin_lock_irq(&mapping->tree_lock);
437 * The non racy check for a busy page.
439 * Must be careful with the order of the tests. When someone has
440 * a ref to the page, it may be possible that they dirty it then
441 * drop the reference. So if PageDirty is tested before page_count
442 * here, then the following race may occur:
444 * get_user_pages(&page);
445 * [user mapping goes away]
447 * !PageDirty(page) [good]
448 * SetPageDirty(page);
450 * !page_count(page) [good, discard it]
452 * [oops, our write_to data is lost]
454 * Reversing the order of the tests ensures such a situation cannot
455 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
456 * load is not satisfied before that of page->_count.
458 * Note that if SetPageDirty is always performed via set_page_dirty,
459 * and thus under tree_lock, then this ordering is not required.
461 if (!page_freeze_refs(page, 2))
463 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
464 if (unlikely(PageDirty(page))) {
465 page_unfreeze_refs(page, 2);
469 if (PageSwapCache(page)) {
470 swp_entry_t swap = { .val = page_private(page) };
471 __delete_from_swap_cache(page);
472 spin_unlock_irq(&mapping->tree_lock);
473 swapcache_free(swap, page);
475 __remove_from_page_cache(page);
476 spin_unlock_irq(&mapping->tree_lock);
477 mem_cgroup_uncharge_cache_page(page);
483 spin_unlock_irq(&mapping->tree_lock);
488 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
489 * someone else has a ref on the page, abort and return 0. If it was
490 * successfully detached, return 1. Assumes the caller has a single ref on
493 int remove_mapping(struct address_space *mapping, struct page *page)
495 if (__remove_mapping(mapping, page)) {
497 * Unfreezing the refcount with 1 rather than 2 effectively
498 * drops the pagecache ref for us without requiring another
501 page_unfreeze_refs(page, 1);
508 * putback_lru_page - put previously isolated page onto appropriate LRU list
509 * @page: page to be put back to appropriate lru list
511 * Add previously isolated @page to appropriate LRU list.
512 * Page may still be unevictable for other reasons.
514 * lru_lock must not be held, interrupts must be enabled.
516 void putback_lru_page(struct page *page)
519 int active = !!TestClearPageActive(page);
520 int was_unevictable = PageUnevictable(page);
522 VM_BUG_ON(PageLRU(page));
525 ClearPageUnevictable(page);
527 if (page_evictable(page, NULL)) {
529 * For evictable pages, we can use the cache.
530 * In event of a race, worst case is we end up with an
531 * unevictable page on [in]active list.
532 * We know how to handle that.
534 lru = active + page_is_file_cache(page);
535 lru_cache_add_lru(page, lru);
538 * Put unevictable pages directly on zone's unevictable
541 lru = LRU_UNEVICTABLE;
542 add_page_to_unevictable_list(page);
546 * page's status can change while we move it among lru. If an evictable
547 * page is on unevictable list, it never be freed. To avoid that,
548 * check after we added it to the list, again.
550 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
551 if (!isolate_lru_page(page)) {
555 /* This means someone else dropped this page from LRU
556 * So, it will be freed or putback to LRU again. There is
557 * nothing to do here.
561 if (was_unevictable && lru != LRU_UNEVICTABLE)
562 count_vm_event(UNEVICTABLE_PGRESCUED);
563 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
564 count_vm_event(UNEVICTABLE_PGCULLED);
566 put_page(page); /* drop ref from isolate */
570 * shrink_page_list() returns the number of reclaimed pages
572 static unsigned long shrink_page_list(struct list_head *page_list,
573 struct scan_control *sc,
574 enum pageout_io sync_writeback)
576 LIST_HEAD(ret_pages);
577 struct pagevec freed_pvec;
579 unsigned long nr_reclaimed = 0;
580 unsigned long vm_flags;
584 pagevec_init(&freed_pvec, 1);
585 while (!list_empty(page_list)) {
586 struct address_space *mapping;
593 page = lru_to_page(page_list);
594 list_del(&page->lru);
596 if (!trylock_page(page))
599 VM_BUG_ON(PageActive(page));
603 if (unlikely(!page_evictable(page, NULL)))
606 if (!sc->may_unmap && page_mapped(page))
609 /* Double the slab pressure for mapped and swapcache pages */
610 if (page_mapped(page) || PageSwapCache(page))
613 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
614 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
616 if (PageWriteback(page)) {
618 * Synchronous reclaim is performed in two passes,
619 * first an asynchronous pass over the list to
620 * start parallel writeback, and a second synchronous
621 * pass to wait for the IO to complete. Wait here
622 * for any page for which writeback has already
625 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
626 wait_on_page_writeback(page);
631 referenced = page_referenced(page, 1,
632 sc->mem_cgroup, &vm_flags);
633 /* In active use or really unfreeable? Activate it. */
634 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
635 referenced && page_mapping_inuse(page))
636 goto activate_locked;
639 * Anonymous process memory has backing store?
640 * Try to allocate it some swap space here.
642 if (PageAnon(page) && !PageSwapCache(page)) {
643 if (!(sc->gfp_mask & __GFP_IO))
645 if (!add_to_swap(page))
646 goto activate_locked;
650 mapping = page_mapping(page);
653 * The page is mapped into the page tables of one or more
654 * processes. Try to unmap it here.
656 if (page_mapped(page) && mapping) {
657 switch (try_to_unmap(page, 0)) {
659 goto activate_locked;
665 ; /* try to free the page below */
669 if (PageDirty(page)) {
670 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
674 if (!sc->may_writepage)
677 /* Page is dirty, try to write it out here */
678 switch (pageout(page, mapping, sync_writeback)) {
682 goto activate_locked;
684 if (PageWriteback(page) || PageDirty(page))
687 * A synchronous write - probably a ramdisk. Go
688 * ahead and try to reclaim the page.
690 if (!trylock_page(page))
692 if (PageDirty(page) || PageWriteback(page))
694 mapping = page_mapping(page);
696 ; /* try to free the page below */
701 * If the page has buffers, try to free the buffer mappings
702 * associated with this page. If we succeed we try to free
705 * We do this even if the page is PageDirty().
706 * try_to_release_page() does not perform I/O, but it is
707 * possible for a page to have PageDirty set, but it is actually
708 * clean (all its buffers are clean). This happens if the
709 * buffers were written out directly, with submit_bh(). ext3
710 * will do this, as well as the blockdev mapping.
711 * try_to_release_page() will discover that cleanness and will
712 * drop the buffers and mark the page clean - it can be freed.
714 * Rarely, pages can have buffers and no ->mapping. These are
715 * the pages which were not successfully invalidated in
716 * truncate_complete_page(). We try to drop those buffers here
717 * and if that worked, and the page is no longer mapped into
718 * process address space (page_count == 1) it can be freed.
719 * Otherwise, leave the page on the LRU so it is swappable.
721 if (page_has_private(page)) {
722 if (!try_to_release_page(page, sc->gfp_mask))
723 goto activate_locked;
724 if (!mapping && page_count(page) == 1) {
726 if (put_page_testzero(page))
730 * rare race with speculative reference.
731 * the speculative reference will free
732 * this page shortly, so we may
733 * increment nr_reclaimed here (and
734 * leave it off the LRU).
742 if (!mapping || !__remove_mapping(mapping, page))
746 * At this point, we have no other references and there is
747 * no way to pick any more up (removed from LRU, removed
748 * from pagecache). Can use non-atomic bitops now (and
749 * we obviously don't have to worry about waking up a process
750 * waiting on the page lock, because there are no references.
752 __clear_page_locked(page);
755 if (!pagevec_add(&freed_pvec, page)) {
756 __pagevec_free(&freed_pvec);
757 pagevec_reinit(&freed_pvec);
762 if (PageSwapCache(page))
763 try_to_free_swap(page);
765 putback_lru_page(page);
769 /* Not a candidate for swapping, so reclaim swap space. */
770 if (PageSwapCache(page) && vm_swap_full())
771 try_to_free_swap(page);
772 VM_BUG_ON(PageActive(page));
778 list_add(&page->lru, &ret_pages);
779 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
781 list_splice(&ret_pages, page_list);
782 if (pagevec_count(&freed_pvec))
783 __pagevec_free(&freed_pvec);
784 count_vm_events(PGACTIVATE, pgactivate);
788 /* LRU Isolation modes. */
789 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
790 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
791 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
794 * Attempt to remove the specified page from its LRU. Only take this page
795 * if it is of the appropriate PageActive status. Pages which are being
796 * freed elsewhere are also ignored.
798 * page: page to consider
799 * mode: one of the LRU isolation modes defined above
801 * returns 0 on success, -ve errno on failure.
803 int __isolate_lru_page(struct page *page, int mode, int file)
807 /* Only take pages on the LRU. */
812 * When checking the active state, we need to be sure we are
813 * dealing with comparible boolean values. Take the logical not
816 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
819 if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
823 * When this function is being called for lumpy reclaim, we
824 * initially look into all LRU pages, active, inactive and
825 * unevictable; only give shrink_page_list evictable pages.
827 if (PageUnevictable(page))
832 if (likely(get_page_unless_zero(page))) {
834 * Be careful not to clear PageLRU until after we're
835 * sure the page is not being freed elsewhere -- the
836 * page release code relies on it.
840 mem_cgroup_del_lru(page);
847 * zone->lru_lock is heavily contended. Some of the functions that
848 * shrink the lists perform better by taking out a batch of pages
849 * and working on them outside the LRU lock.
851 * For pagecache intensive workloads, this function is the hottest
852 * spot in the kernel (apart from copy_*_user functions).
854 * Appropriate locks must be held before calling this function.
856 * @nr_to_scan: The number of pages to look through on the list.
857 * @src: The LRU list to pull pages off.
858 * @dst: The temp list to put pages on to.
859 * @scanned: The number of pages that were scanned.
860 * @order: The caller's attempted allocation order
861 * @mode: One of the LRU isolation modes
862 * @file: True [1] if isolating file [!anon] pages
864 * returns how many pages were moved onto *@dst.
866 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
867 struct list_head *src, struct list_head *dst,
868 unsigned long *scanned, int order, int mode, int file)
870 unsigned long nr_taken = 0;
873 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
876 unsigned long end_pfn;
877 unsigned long page_pfn;
880 page = lru_to_page(src);
881 prefetchw_prev_lru_page(page, src, flags);
883 VM_BUG_ON(!PageLRU(page));
885 switch (__isolate_lru_page(page, mode, file)) {
887 list_move(&page->lru, dst);
892 /* else it is being freed elsewhere */
893 list_move(&page->lru, src);
904 * Attempt to take all pages in the order aligned region
905 * surrounding the tag page. Only take those pages of
906 * the same active state as that tag page. We may safely
907 * round the target page pfn down to the requested order
908 * as the mem_map is guarenteed valid out to MAX_ORDER,
909 * where that page is in a different zone we will detect
910 * it from its zone id and abort this block scan.
912 zone_id = page_zone_id(page);
913 page_pfn = page_to_pfn(page);
914 pfn = page_pfn & ~((1 << order) - 1);
915 end_pfn = pfn + (1 << order);
916 for (; pfn < end_pfn; pfn++) {
917 struct page *cursor_page;
919 /* The target page is in the block, ignore it. */
920 if (unlikely(pfn == page_pfn))
923 /* Avoid holes within the zone. */
924 if (unlikely(!pfn_valid_within(pfn)))
927 cursor_page = pfn_to_page(pfn);
929 /* Check that we have not crossed a zone boundary. */
930 if (unlikely(page_zone_id(cursor_page) != zone_id))
932 switch (__isolate_lru_page(cursor_page, mode, file)) {
934 list_move(&cursor_page->lru, dst);
940 /* else it is being freed elsewhere */
941 list_move(&cursor_page->lru, src);
943 break; /* ! on LRU or wrong list */
952 static unsigned long isolate_pages_global(unsigned long nr,
953 struct list_head *dst,
954 unsigned long *scanned, int order,
955 int mode, struct zone *z,
956 struct mem_cgroup *mem_cont,
957 int active, int file)
964 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
969 * clear_active_flags() is a helper for shrink_active_list(), clearing
970 * any active bits from the pages in the list.
972 static unsigned long clear_active_flags(struct list_head *page_list,
979 list_for_each_entry(page, page_list, lru) {
980 lru = page_is_file_cache(page);
981 if (PageActive(page)) {
983 ClearPageActive(page);
993 * isolate_lru_page - tries to isolate a page from its LRU list
994 * @page: page to isolate from its LRU list
996 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
997 * vmstat statistic corresponding to whatever LRU list the page was on.
999 * Returns 0 if the page was removed from an LRU list.
1000 * Returns -EBUSY if the page was not on an LRU list.
1002 * The returned page will have PageLRU() cleared. If it was found on
1003 * the active list, it will have PageActive set. If it was found on
1004 * the unevictable list, it will have the PageUnevictable bit set. That flag
1005 * may need to be cleared by the caller before letting the page go.
1007 * The vmstat statistic corresponding to the list on which the page was
1008 * found will be decremented.
1011 * (1) Must be called with an elevated refcount on the page. This is a
1012 * fundamentnal difference from isolate_lru_pages (which is called
1013 * without a stable reference).
1014 * (2) the lru_lock must not be held.
1015 * (3) interrupts must be enabled.
1017 int isolate_lru_page(struct page *page)
1021 if (PageLRU(page)) {
1022 struct zone *zone = page_zone(page);
1024 spin_lock_irq(&zone->lru_lock);
1025 if (PageLRU(page) && get_page_unless_zero(page)) {
1026 int lru = page_lru(page);
1030 del_page_from_lru_list(zone, page, lru);
1032 spin_unlock_irq(&zone->lru_lock);
1038 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1039 * of reclaimed pages
1041 static unsigned long shrink_inactive_list(unsigned long max_scan,
1042 struct zone *zone, struct scan_control *sc,
1043 int priority, int file)
1045 LIST_HEAD(page_list);
1046 struct pagevec pvec;
1047 unsigned long nr_scanned = 0;
1048 unsigned long nr_reclaimed = 0;
1049 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1050 int lumpy_reclaim = 0;
1053 * If we need a large contiguous chunk of memory, or have
1054 * trouble getting a small set of contiguous pages, we
1055 * will reclaim both active and inactive pages.
1057 * We use the same threshold as pageout congestion_wait below.
1059 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1061 else if (sc->order && priority < DEF_PRIORITY - 2)
1064 pagevec_init(&pvec, 1);
1067 spin_lock_irq(&zone->lru_lock);
1070 unsigned long nr_taken;
1071 unsigned long nr_scan;
1072 unsigned long nr_freed;
1073 unsigned long nr_active;
1074 unsigned int count[NR_LRU_LISTS] = { 0, };
1075 int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE;
1077 nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1078 &page_list, &nr_scan, sc->order, mode,
1079 zone, sc->mem_cgroup, 0, file);
1080 nr_active = clear_active_flags(&page_list, count);
1081 __count_vm_events(PGDEACTIVATE, nr_active);
1083 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1084 -count[LRU_ACTIVE_FILE]);
1085 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1086 -count[LRU_INACTIVE_FILE]);
1087 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1088 -count[LRU_ACTIVE_ANON]);
1089 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1090 -count[LRU_INACTIVE_ANON]);
1092 if (scanning_global_lru(sc))
1093 zone->pages_scanned += nr_scan;
1095 reclaim_stat->recent_scanned[0] += count[LRU_INACTIVE_ANON];
1096 reclaim_stat->recent_scanned[0] += count[LRU_ACTIVE_ANON];
1097 reclaim_stat->recent_scanned[1] += count[LRU_INACTIVE_FILE];
1098 reclaim_stat->recent_scanned[1] += count[LRU_ACTIVE_FILE];
1100 spin_unlock_irq(&zone->lru_lock);
1102 nr_scanned += nr_scan;
1103 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1106 * If we are direct reclaiming for contiguous pages and we do
1107 * not reclaim everything in the list, try again and wait
1108 * for IO to complete. This will stall high-order allocations
1109 * but that should be acceptable to the caller
1111 if (nr_freed < nr_taken && !current_is_kswapd() &&
1113 congestion_wait(WRITE, HZ/10);
1116 * The attempt at page out may have made some
1117 * of the pages active, mark them inactive again.
1119 nr_active = clear_active_flags(&page_list, count);
1120 count_vm_events(PGDEACTIVATE, nr_active);
1122 nr_freed += shrink_page_list(&page_list, sc,
1126 nr_reclaimed += nr_freed;
1127 local_irq_disable();
1128 if (current_is_kswapd()) {
1129 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
1130 __count_vm_events(KSWAPD_STEAL, nr_freed);
1131 } else if (scanning_global_lru(sc))
1132 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
1134 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
1139 spin_lock(&zone->lru_lock);
1141 * Put back any unfreeable pages.
1143 while (!list_empty(&page_list)) {
1145 page = lru_to_page(&page_list);
1146 VM_BUG_ON(PageLRU(page));
1147 list_del(&page->lru);
1148 if (unlikely(!page_evictable(page, NULL))) {
1149 spin_unlock_irq(&zone->lru_lock);
1150 putback_lru_page(page);
1151 spin_lock_irq(&zone->lru_lock);
1155 lru = page_lru(page);
1156 add_page_to_lru_list(zone, page, lru);
1157 if (PageActive(page)) {
1158 int file = !!page_is_file_cache(page);
1159 reclaim_stat->recent_rotated[file]++;
1161 if (!pagevec_add(&pvec, page)) {
1162 spin_unlock_irq(&zone->lru_lock);
1163 __pagevec_release(&pvec);
1164 spin_lock_irq(&zone->lru_lock);
1167 } while (nr_scanned < max_scan);
1168 spin_unlock(&zone->lru_lock);
1171 pagevec_release(&pvec);
1172 return nr_reclaimed;
1176 * We are about to scan this zone at a certain priority level. If that priority
1177 * level is smaller (ie: more urgent) than the previous priority, then note
1178 * that priority level within the zone. This is done so that when the next
1179 * process comes in to scan this zone, it will immediately start out at this
1180 * priority level rather than having to build up its own scanning priority.
1181 * Here, this priority affects only the reclaim-mapped threshold.
1183 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1185 if (priority < zone->prev_priority)
1186 zone->prev_priority = priority;
1190 * This moves pages from the active list to the inactive list.
1192 * We move them the other way if the page is referenced by one or more
1193 * processes, from rmap.
1195 * If the pages are mostly unmapped, the processing is fast and it is
1196 * appropriate to hold zone->lru_lock across the whole operation. But if
1197 * the pages are mapped, the processing is slow (page_referenced()) so we
1198 * should drop zone->lru_lock around each page. It's impossible to balance
1199 * this, so instead we remove the pages from the LRU while processing them.
1200 * It is safe to rely on PG_active against the non-LRU pages in here because
1201 * nobody will play with that bit on a non-LRU page.
1203 * The downside is that we have to touch page->_count against each page.
1204 * But we had to alter page->flags anyway.
1208 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1209 struct scan_control *sc, int priority, int file)
1211 unsigned long pgmoved;
1212 unsigned long pgscanned;
1213 unsigned long vm_flags;
1214 LIST_HEAD(l_hold); /* The pages which were snipped off */
1215 LIST_HEAD(l_inactive);
1217 struct pagevec pvec;
1219 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1222 spin_lock_irq(&zone->lru_lock);
1223 pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1224 ISOLATE_ACTIVE, zone,
1225 sc->mem_cgroup, 1, file);
1227 * zone->pages_scanned is used for detect zone's oom
1228 * mem_cgroup remembers nr_scan by itself.
1230 if (scanning_global_lru(sc)) {
1231 zone->pages_scanned += pgscanned;
1233 reclaim_stat->recent_scanned[!!file] += pgmoved;
1236 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
1238 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
1239 spin_unlock_irq(&zone->lru_lock);
1241 pgmoved = 0; /* count referenced (mapping) mapped pages */
1242 while (!list_empty(&l_hold)) {
1244 page = lru_to_page(&l_hold);
1245 list_del(&page->lru);
1247 if (unlikely(!page_evictable(page, NULL))) {
1248 putback_lru_page(page);
1252 /* page_referenced clears PageReferenced */
1253 if (page_mapping_inuse(page) &&
1254 page_referenced(page, 0, sc->mem_cgroup, &vm_flags))
1257 list_add(&page->lru, &l_inactive);
1261 * Move the pages to the [file or anon] inactive list.
1263 pagevec_init(&pvec, 1);
1264 lru = LRU_BASE + file * LRU_FILE;
1266 spin_lock_irq(&zone->lru_lock);
1268 * Count referenced pages from currently used mappings as
1269 * rotated, even though they are moved to the inactive list.
1270 * This helps balance scan pressure between file and anonymous
1271 * pages in get_scan_ratio.
1273 reclaim_stat->recent_rotated[!!file] += pgmoved;
1275 pgmoved = 0; /* count pages moved to inactive list */
1276 while (!list_empty(&l_inactive)) {
1277 page = lru_to_page(&l_inactive);
1278 prefetchw_prev_lru_page(page, &l_inactive, flags);
1279 VM_BUG_ON(PageLRU(page));
1281 VM_BUG_ON(!PageActive(page));
1282 ClearPageActive(page);
1284 list_move(&page->lru, &zone->lru[lru].list);
1285 mem_cgroup_add_lru_list(page, lru);
1287 if (!pagevec_add(&pvec, page)) {
1288 spin_unlock_irq(&zone->lru_lock);
1289 if (buffer_heads_over_limit)
1290 pagevec_strip(&pvec);
1291 __pagevec_release(&pvec);
1292 spin_lock_irq(&zone->lru_lock);
1295 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1296 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1297 __count_vm_events(PGDEACTIVATE, pgmoved);
1298 spin_unlock_irq(&zone->lru_lock);
1299 if (buffer_heads_over_limit)
1300 pagevec_strip(&pvec);
1301 pagevec_release(&pvec);
1304 static int inactive_anon_is_low_global(struct zone *zone)
1306 unsigned long active, inactive;
1308 active = zone_page_state(zone, NR_ACTIVE_ANON);
1309 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1311 if (inactive * zone->inactive_ratio < active)
1318 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1319 * @zone: zone to check
1320 * @sc: scan control of this context
1322 * Returns true if the zone does not have enough inactive anon pages,
1323 * meaning some active anon pages need to be deactivated.
1325 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1329 if (scanning_global_lru(sc))
1330 low = inactive_anon_is_low_global(zone);
1332 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1336 static int inactive_file_is_low_global(struct zone *zone)
1338 unsigned long active, inactive;
1340 active = zone_page_state(zone, NR_ACTIVE_FILE);
1341 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1343 return (active > inactive);
1347 * inactive_file_is_low - check if file pages need to be deactivated
1348 * @zone: zone to check
1349 * @sc: scan control of this context
1351 * When the system is doing streaming IO, memory pressure here
1352 * ensures that active file pages get deactivated, until more
1353 * than half of the file pages are on the inactive list.
1355 * Once we get to that situation, protect the system's working
1356 * set from being evicted by disabling active file page aging.
1358 * This uses a different ratio than the anonymous pages, because
1359 * the page cache uses a use-once replacement algorithm.
1361 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1365 if (scanning_global_lru(sc))
1366 low = inactive_file_is_low_global(zone);
1368 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1372 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1373 struct zone *zone, struct scan_control *sc, int priority)
1375 int file = is_file_lru(lru);
1377 if (lru == LRU_ACTIVE_FILE && inactive_file_is_low(zone, sc)) {
1378 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1382 if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) {
1383 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1386 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1390 * Determine how aggressively the anon and file LRU lists should be
1391 * scanned. The relative value of each set of LRU lists is determined
1392 * by looking at the fraction of the pages scanned we did rotate back
1393 * onto the active list instead of evict.
1395 * percent[0] specifies how much pressure to put on ram/swap backed
1396 * memory, while percent[1] determines pressure on the file LRUs.
1398 static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
1399 unsigned long *percent)
1401 unsigned long anon, file, free;
1402 unsigned long anon_prio, file_prio;
1403 unsigned long ap, fp;
1404 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1406 /* If we have no swap space, do not bother scanning anon pages. */
1407 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1413 anon = zone_nr_pages(zone, sc, LRU_ACTIVE_ANON) +
1414 zone_nr_pages(zone, sc, LRU_INACTIVE_ANON);
1415 file = zone_nr_pages(zone, sc, LRU_ACTIVE_FILE) +
1416 zone_nr_pages(zone, sc, LRU_INACTIVE_FILE);
1418 if (scanning_global_lru(sc)) {
1419 free = zone_page_state(zone, NR_FREE_PAGES);
1420 /* If we have very few page cache pages,
1421 force-scan anon pages. */
1422 if (unlikely(file + free <= high_wmark_pages(zone))) {
1430 * OK, so we have swap space and a fair amount of page cache
1431 * pages. We use the recently rotated / recently scanned
1432 * ratios to determine how valuable each cache is.
1434 * Because workloads change over time (and to avoid overflow)
1435 * we keep these statistics as a floating average, which ends
1436 * up weighing recent references more than old ones.
1438 * anon in [0], file in [1]
1440 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1441 spin_lock_irq(&zone->lru_lock);
1442 reclaim_stat->recent_scanned[0] /= 2;
1443 reclaim_stat->recent_rotated[0] /= 2;
1444 spin_unlock_irq(&zone->lru_lock);
1447 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1448 spin_lock_irq(&zone->lru_lock);
1449 reclaim_stat->recent_scanned[1] /= 2;
1450 reclaim_stat->recent_rotated[1] /= 2;
1451 spin_unlock_irq(&zone->lru_lock);
1455 * With swappiness at 100, anonymous and file have the same priority.
1456 * This scanning priority is essentially the inverse of IO cost.
1458 anon_prio = sc->swappiness;
1459 file_prio = 200 - sc->swappiness;
1462 * The amount of pressure on anon vs file pages is inversely
1463 * proportional to the fraction of recently scanned pages on
1464 * each list that were recently referenced and in active use.
1466 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1467 ap /= reclaim_stat->recent_rotated[0] + 1;
1469 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1470 fp /= reclaim_stat->recent_rotated[1] + 1;
1472 /* Normalize to percentages */
1473 percent[0] = 100 * ap / (ap + fp + 1);
1474 percent[1] = 100 - percent[0];
1478 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1479 * until we collected @swap_cluster_max pages to scan.
1481 static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
1482 unsigned long *nr_saved_scan,
1483 unsigned long swap_cluster_max)
1487 *nr_saved_scan += nr_to_scan;
1488 nr = *nr_saved_scan;
1490 if (nr >= swap_cluster_max)
1499 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1501 static void shrink_zone(int priority, struct zone *zone,
1502 struct scan_control *sc)
1504 unsigned long nr[NR_LRU_LISTS];
1505 unsigned long nr_to_scan;
1506 unsigned long percent[2]; /* anon @ 0; file @ 1 */
1508 unsigned long nr_reclaimed = sc->nr_reclaimed;
1509 unsigned long swap_cluster_max = sc->swap_cluster_max;
1511 get_scan_ratio(zone, sc, percent);
1513 for_each_evictable_lru(l) {
1514 int file = is_file_lru(l);
1517 scan = zone_nr_pages(zone, sc, l);
1520 scan = (scan * percent[file]) / 100;
1522 if (scanning_global_lru(sc))
1523 nr[l] = nr_scan_try_batch(scan,
1524 &zone->lru[l].nr_saved_scan,
1530 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1531 nr[LRU_INACTIVE_FILE]) {
1532 for_each_evictable_lru(l) {
1534 nr_to_scan = min(nr[l], swap_cluster_max);
1535 nr[l] -= nr_to_scan;
1537 nr_reclaimed += shrink_list(l, nr_to_scan,
1538 zone, sc, priority);
1542 * On large memory systems, scan >> priority can become
1543 * really large. This is fine for the starting priority;
1544 * we want to put equal scanning pressure on each zone.
1545 * However, if the VM has a harder time of freeing pages,
1546 * with multiple processes reclaiming pages, the total
1547 * freeing target can get unreasonably large.
1549 if (nr_reclaimed > swap_cluster_max &&
1550 priority < DEF_PRIORITY && !current_is_kswapd())
1554 sc->nr_reclaimed = nr_reclaimed;
1557 * Even if we did not try to evict anon pages at all, we want to
1558 * rebalance the anon lru active/inactive ratio.
1560 if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0)
1561 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1563 throttle_vm_writeout(sc->gfp_mask);
1567 * This is the direct reclaim path, for page-allocating processes. We only
1568 * try to reclaim pages from zones which will satisfy the caller's allocation
1571 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1573 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1575 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1576 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1577 * zone defense algorithm.
1579 * If a zone is deemed to be full of pinned pages then just give it a light
1580 * scan then give up on it.
1582 static void shrink_zones(int priority, struct zonelist *zonelist,
1583 struct scan_control *sc)
1585 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1589 sc->all_unreclaimable = 1;
1590 for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
1592 if (!populated_zone(zone))
1595 * Take care memory controller reclaiming has small influence
1598 if (scanning_global_lru(sc)) {
1599 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1601 note_zone_scanning_priority(zone, priority);
1603 if (zone_is_all_unreclaimable(zone) &&
1604 priority != DEF_PRIORITY)
1605 continue; /* Let kswapd poll it */
1606 sc->all_unreclaimable = 0;
1609 * Ignore cpuset limitation here. We just want to reduce
1610 * # of used pages by us regardless of memory shortage.
1612 sc->all_unreclaimable = 0;
1613 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1617 shrink_zone(priority, zone, sc);
1622 * This is the main entry point to direct page reclaim.
1624 * If a full scan of the inactive list fails to free enough memory then we
1625 * are "out of memory" and something needs to be killed.
1627 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1628 * high - the zone may be full of dirty or under-writeback pages, which this
1629 * caller can't do much about. We kick pdflush and take explicit naps in the
1630 * hope that some of these pages can be written. But if the allocating task
1631 * holds filesystem locks which prevent writeout this might not work, and the
1632 * allocation attempt will fail.
1634 * returns: 0, if no pages reclaimed
1635 * else, the number of pages reclaimed
1637 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1638 struct scan_control *sc)
1641 unsigned long ret = 0;
1642 unsigned long total_scanned = 0;
1643 struct reclaim_state *reclaim_state = current->reclaim_state;
1644 unsigned long lru_pages = 0;
1647 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1649 delayacct_freepages_start();
1651 if (scanning_global_lru(sc))
1652 count_vm_event(ALLOCSTALL);
1654 * mem_cgroup will not do shrink_slab.
1656 if (scanning_global_lru(sc)) {
1657 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1659 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1662 lru_pages += zone_lru_pages(zone);
1666 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1669 disable_swap_token();
1670 shrink_zones(priority, zonelist, sc);
1672 * Don't shrink slabs when reclaiming memory from
1673 * over limit cgroups
1675 if (scanning_global_lru(sc)) {
1676 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1677 if (reclaim_state) {
1678 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1679 reclaim_state->reclaimed_slab = 0;
1682 total_scanned += sc->nr_scanned;
1683 if (sc->nr_reclaimed >= sc->swap_cluster_max) {
1684 ret = sc->nr_reclaimed;
1689 * Try to write back as many pages as we just scanned. This
1690 * tends to cause slow streaming writers to write data to the
1691 * disk smoothly, at the dirtying rate, which is nice. But
1692 * that's undesirable in laptop mode, where we *want* lumpy
1693 * writeout. So in laptop mode, write out the whole world.
1695 if (total_scanned > sc->swap_cluster_max +
1696 sc->swap_cluster_max / 2) {
1697 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1698 sc->may_writepage = 1;
1701 /* Take a nap, wait for some writeback to complete */
1702 if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1703 congestion_wait(WRITE, HZ/10);
1705 /* top priority shrink_zones still had more to do? don't OOM, then */
1706 if (!sc->all_unreclaimable && scanning_global_lru(sc))
1707 ret = sc->nr_reclaimed;
1710 * Now that we've scanned all the zones at this priority level, note
1711 * that level within the zone so that the next thread which performs
1712 * scanning of this zone will immediately start out at this priority
1713 * level. This affects only the decision whether or not to bring
1714 * mapped pages onto the inactive list.
1719 if (scanning_global_lru(sc)) {
1720 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1722 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1725 zone->prev_priority = priority;
1728 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1730 delayacct_freepages_end();
1735 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1736 gfp_t gfp_mask, nodemask_t *nodemask)
1738 struct scan_control sc = {
1739 .gfp_mask = gfp_mask,
1740 .may_writepage = !laptop_mode,
1741 .swap_cluster_max = SWAP_CLUSTER_MAX,
1744 .swappiness = vm_swappiness,
1747 .isolate_pages = isolate_pages_global,
1748 .nodemask = nodemask,
1751 return do_try_to_free_pages(zonelist, &sc);
1754 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1756 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1759 unsigned int swappiness)
1761 struct scan_control sc = {
1762 .may_writepage = !laptop_mode,
1764 .may_swap = !noswap,
1765 .swap_cluster_max = SWAP_CLUSTER_MAX,
1766 .swappiness = swappiness,
1768 .mem_cgroup = mem_cont,
1769 .isolate_pages = mem_cgroup_isolate_pages,
1770 .nodemask = NULL, /* we don't care the placement */
1772 struct zonelist *zonelist;
1774 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1775 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1776 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1777 return do_try_to_free_pages(zonelist, &sc);
1782 * For kswapd, balance_pgdat() will work across all this node's zones until
1783 * they are all at high_wmark_pages(zone).
1785 * Returns the number of pages which were actually freed.
1787 * There is special handling here for zones which are full of pinned pages.
1788 * This can happen if the pages are all mlocked, or if they are all used by
1789 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1790 * What we do is to detect the case where all pages in the zone have been
1791 * scanned twice and there has been zero successful reclaim. Mark the zone as
1792 * dead and from now on, only perform a short scan. Basically we're polling
1793 * the zone for when the problem goes away.
1795 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1796 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
1797 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
1798 * lower zones regardless of the number of free pages in the lower zones. This
1799 * interoperates with the page allocator fallback scheme to ensure that aging
1800 * of pages is balanced across the zones.
1802 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1807 unsigned long total_scanned;
1808 struct reclaim_state *reclaim_state = current->reclaim_state;
1809 struct scan_control sc = {
1810 .gfp_mask = GFP_KERNEL,
1813 .swap_cluster_max = SWAP_CLUSTER_MAX,
1814 .swappiness = vm_swappiness,
1817 .isolate_pages = isolate_pages_global,
1820 * temp_priority is used to remember the scanning priority at which
1821 * this zone was successfully refilled to
1822 * free_pages == high_wmark_pages(zone).
1824 int temp_priority[MAX_NR_ZONES];
1828 sc.nr_reclaimed = 0;
1829 sc.may_writepage = !laptop_mode;
1830 count_vm_event(PAGEOUTRUN);
1832 for (i = 0; i < pgdat->nr_zones; i++)
1833 temp_priority[i] = DEF_PRIORITY;
1835 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1836 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1837 unsigned long lru_pages = 0;
1839 /* The swap token gets in the way of swapout... */
1841 disable_swap_token();
1846 * Scan in the highmem->dma direction for the highest
1847 * zone which needs scanning
1849 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1850 struct zone *zone = pgdat->node_zones + i;
1852 if (!populated_zone(zone))
1855 if (zone_is_all_unreclaimable(zone) &&
1856 priority != DEF_PRIORITY)
1860 * Do some background aging of the anon list, to give
1861 * pages a chance to be referenced before reclaiming.
1863 if (inactive_anon_is_low(zone, &sc))
1864 shrink_active_list(SWAP_CLUSTER_MAX, zone,
1867 if (!zone_watermark_ok(zone, order,
1868 high_wmark_pages(zone), 0, 0)) {
1876 for (i = 0; i <= end_zone; i++) {
1877 struct zone *zone = pgdat->node_zones + i;
1879 lru_pages += zone_lru_pages(zone);
1883 * Now scan the zone in the dma->highmem direction, stopping
1884 * at the last zone which needs scanning.
1886 * We do this because the page allocator works in the opposite
1887 * direction. This prevents the page allocator from allocating
1888 * pages behind kswapd's direction of progress, which would
1889 * cause too much scanning of the lower zones.
1891 for (i = 0; i <= end_zone; i++) {
1892 struct zone *zone = pgdat->node_zones + i;
1895 if (!populated_zone(zone))
1898 if (zone_is_all_unreclaimable(zone) &&
1899 priority != DEF_PRIORITY)
1902 if (!zone_watermark_ok(zone, order,
1903 high_wmark_pages(zone), end_zone, 0))
1905 temp_priority[i] = priority;
1907 note_zone_scanning_priority(zone, priority);
1909 * We put equal pressure on every zone, unless one
1910 * zone has way too many pages free already.
1912 if (!zone_watermark_ok(zone, order,
1913 8*high_wmark_pages(zone), end_zone, 0))
1914 shrink_zone(priority, zone, &sc);
1915 reclaim_state->reclaimed_slab = 0;
1916 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1918 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
1919 total_scanned += sc.nr_scanned;
1920 if (zone_is_all_unreclaimable(zone))
1922 if (nr_slab == 0 && zone->pages_scanned >=
1923 (zone_lru_pages(zone) * 6))
1925 ZONE_ALL_UNRECLAIMABLE);
1927 * If we've done a decent amount of scanning and
1928 * the reclaim ratio is low, start doing writepage
1929 * even in laptop mode
1931 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1932 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
1933 sc.may_writepage = 1;
1936 break; /* kswapd: all done */
1938 * OK, kswapd is getting into trouble. Take a nap, then take
1939 * another pass across the zones.
1941 if (total_scanned && priority < DEF_PRIORITY - 2)
1942 congestion_wait(WRITE, HZ/10);
1945 * We do this so kswapd doesn't build up large priorities for
1946 * example when it is freeing in parallel with allocators. It
1947 * matches the direct reclaim path behaviour in terms of impact
1948 * on zone->*_priority.
1950 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
1955 * Note within each zone the priority level at which this zone was
1956 * brought into a happy state. So that the next thread which scans this
1957 * zone will start out at that priority level.
1959 for (i = 0; i < pgdat->nr_zones; i++) {
1960 struct zone *zone = pgdat->node_zones + i;
1962 zone->prev_priority = temp_priority[i];
1964 if (!all_zones_ok) {
1970 * Fragmentation may mean that the system cannot be
1971 * rebalanced for high-order allocations in all zones.
1972 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
1973 * it means the zones have been fully scanned and are still
1974 * not balanced. For high-order allocations, there is
1975 * little point trying all over again as kswapd may
1978 * Instead, recheck all watermarks at order-0 as they
1979 * are the most important. If watermarks are ok, kswapd will go
1980 * back to sleep. High-order users can still perform direct
1981 * reclaim if they wish.
1983 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
1984 order = sc.order = 0;
1989 return sc.nr_reclaimed;
1993 * The background pageout daemon, started as a kernel thread
1994 * from the init process.
1996 * This basically trickles out pages so that we have _some_
1997 * free memory available even if there is no other activity
1998 * that frees anything up. This is needed for things like routing
1999 * etc, where we otherwise might have all activity going on in
2000 * asynchronous contexts that cannot page things out.
2002 * If there are applications that are active memory-allocators
2003 * (most normal use), this basically shouldn't matter.
2005 static int kswapd(void *p)
2007 unsigned long order;
2008 pg_data_t *pgdat = (pg_data_t*)p;
2009 struct task_struct *tsk = current;
2011 struct reclaim_state reclaim_state = {
2012 .reclaimed_slab = 0,
2014 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2016 lockdep_set_current_reclaim_state(GFP_KERNEL);
2018 if (!cpumask_empty(cpumask))
2019 set_cpus_allowed_ptr(tsk, cpumask);
2020 current->reclaim_state = &reclaim_state;
2023 * Tell the memory management that we're a "memory allocator",
2024 * and that if we need more memory we should get access to it
2025 * regardless (see "__alloc_pages()"). "kswapd" should
2026 * never get caught in the normal page freeing logic.
2028 * (Kswapd normally doesn't need memory anyway, but sometimes
2029 * you need a small amount of memory in order to be able to
2030 * page out something else, and this flag essentially protects
2031 * us from recursively trying to free more memory as we're
2032 * trying to free the first piece of memory in the first place).
2034 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2039 unsigned long new_order;
2041 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2042 new_order = pgdat->kswapd_max_order;
2043 pgdat->kswapd_max_order = 0;
2044 if (order < new_order) {
2046 * Don't sleep if someone wants a larger 'order'
2051 if (!freezing(current))
2054 order = pgdat->kswapd_max_order;
2056 finish_wait(&pgdat->kswapd_wait, &wait);
2058 if (!try_to_freeze()) {
2059 /* We can speed up thawing tasks if we don't call
2060 * balance_pgdat after returning from the refrigerator
2062 balance_pgdat(pgdat, order);
2069 * A zone is low on free memory, so wake its kswapd task to service it.
2071 void wakeup_kswapd(struct zone *zone, int order)
2075 if (!populated_zone(zone))
2078 pgdat = zone->zone_pgdat;
2079 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
2081 if (pgdat->kswapd_max_order < order)
2082 pgdat->kswapd_max_order = order;
2083 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2085 if (!waitqueue_active(&pgdat->kswapd_wait))
2087 wake_up_interruptible(&pgdat->kswapd_wait);
2090 unsigned long global_lru_pages(void)
2092 return global_page_state(NR_ACTIVE_ANON)
2093 + global_page_state(NR_ACTIVE_FILE)
2094 + global_page_state(NR_INACTIVE_ANON)
2095 + global_page_state(NR_INACTIVE_FILE);
2098 #ifdef CONFIG_HIBERNATION
2100 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
2101 * from LRU lists system-wide, for given pass and priority.
2103 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
2105 static void shrink_all_zones(unsigned long nr_pages, int prio,
2106 int pass, struct scan_control *sc)
2109 unsigned long nr_reclaimed = 0;
2111 for_each_populated_zone(zone) {
2114 if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
2117 for_each_evictable_lru(l) {
2118 enum zone_stat_item ls = NR_LRU_BASE + l;
2119 unsigned long lru_pages = zone_page_state(zone, ls);
2121 /* For pass = 0, we don't shrink the active list */
2122 if (pass == 0 && (l == LRU_ACTIVE_ANON ||
2123 l == LRU_ACTIVE_FILE))
2126 zone->lru[l].nr_saved_scan += (lru_pages >> prio) + 1;
2127 if (zone->lru[l].nr_saved_scan >= nr_pages || pass > 3) {
2128 unsigned long nr_to_scan;
2130 zone->lru[l].nr_saved_scan = 0;
2131 nr_to_scan = min(nr_pages, lru_pages);
2132 nr_reclaimed += shrink_list(l, nr_to_scan, zone,
2134 if (nr_reclaimed >= nr_pages) {
2135 sc->nr_reclaimed += nr_reclaimed;
2141 sc->nr_reclaimed += nr_reclaimed;
2145 * Try to free `nr_pages' of memory, system-wide, and return the number of
2148 * Rather than trying to age LRUs the aim is to preserve the overall
2149 * LRU order by reclaiming preferentially
2150 * inactive > active > active referenced > active mapped
2152 unsigned long shrink_all_memory(unsigned long nr_pages)
2154 unsigned long lru_pages, nr_slab;
2156 struct reclaim_state reclaim_state;
2157 struct scan_control sc = {
2158 .gfp_mask = GFP_KERNEL,
2161 .isolate_pages = isolate_pages_global,
2165 current->reclaim_state = &reclaim_state;
2167 lru_pages = global_lru_pages();
2168 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
2169 /* If slab caches are huge, it's better to hit them first */
2170 while (nr_slab >= lru_pages) {
2171 reclaim_state.reclaimed_slab = 0;
2172 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
2173 if (!reclaim_state.reclaimed_slab)
2176 sc.nr_reclaimed += reclaim_state.reclaimed_slab;
2177 if (sc.nr_reclaimed >= nr_pages)
2180 nr_slab -= reclaim_state.reclaimed_slab;
2184 * We try to shrink LRUs in 5 passes:
2185 * 0 = Reclaim from inactive_list only
2186 * 1 = Reclaim from active list but don't reclaim mapped
2187 * 2 = 2nd pass of type 1
2188 * 3 = Reclaim mapped (normal reclaim)
2189 * 4 = 2nd pass of type 3
2191 for (pass = 0; pass < 5; pass++) {
2194 /* Force reclaiming mapped pages in the passes #3 and #4 */
2198 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
2199 unsigned long nr_to_scan = nr_pages - sc.nr_reclaimed;
2202 sc.swap_cluster_max = nr_to_scan;
2203 shrink_all_zones(nr_to_scan, prio, pass, &sc);
2204 if (sc.nr_reclaimed >= nr_pages)
2207 reclaim_state.reclaimed_slab = 0;
2208 shrink_slab(sc.nr_scanned, sc.gfp_mask,
2209 global_lru_pages());
2210 sc.nr_reclaimed += reclaim_state.reclaimed_slab;
2211 if (sc.nr_reclaimed >= nr_pages)
2214 if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
2215 congestion_wait(WRITE, HZ / 10);
2220 * If sc.nr_reclaimed = 0, we could not shrink LRUs, but there may be
2221 * something in slab caches
2223 if (!sc.nr_reclaimed) {
2225 reclaim_state.reclaimed_slab = 0;
2226 shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
2227 sc.nr_reclaimed += reclaim_state.reclaimed_slab;
2228 } while (sc.nr_reclaimed < nr_pages &&
2229 reclaim_state.reclaimed_slab > 0);
2234 current->reclaim_state = NULL;
2236 return sc.nr_reclaimed;
2238 #endif /* CONFIG_HIBERNATION */
2240 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2241 not required for correctness. So if the last cpu in a node goes
2242 away, we get changed to run anywhere: as the first one comes back,
2243 restore their cpu bindings. */
2244 static int __devinit cpu_callback(struct notifier_block *nfb,
2245 unsigned long action, void *hcpu)
2249 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2250 for_each_node_state(nid, N_HIGH_MEMORY) {
2251 pg_data_t *pgdat = NODE_DATA(nid);
2252 const struct cpumask *mask;
2254 mask = cpumask_of_node(pgdat->node_id);
2256 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2257 /* One of our CPUs online: restore mask */
2258 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2265 * This kswapd start function will be called by init and node-hot-add.
2266 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2268 int kswapd_run(int nid)
2270 pg_data_t *pgdat = NODE_DATA(nid);
2276 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2277 if (IS_ERR(pgdat->kswapd)) {
2278 /* failure at boot is fatal */
2279 BUG_ON(system_state == SYSTEM_BOOTING);
2280 printk("Failed to start kswapd on node %d\n",nid);
2286 static int __init kswapd_init(void)
2291 for_each_node_state(nid, N_HIGH_MEMORY)
2293 hotcpu_notifier(cpu_callback, 0);
2297 module_init(kswapd_init)
2303 * If non-zero call zone_reclaim when the number of free pages falls below
2306 int zone_reclaim_mode __read_mostly;
2308 #define RECLAIM_OFF 0
2309 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2310 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2311 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2314 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2315 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2318 #define ZONE_RECLAIM_PRIORITY 4
2321 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2324 int sysctl_min_unmapped_ratio = 1;
2327 * If the number of slab pages in a zone grows beyond this percentage then
2328 * slab reclaim needs to occur.
2330 int sysctl_min_slab_ratio = 5;
2333 * Try to free up some pages from this zone through reclaim.
2335 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2337 /* Minimum pages needed in order to stay on node */
2338 const unsigned long nr_pages = 1 << order;
2339 struct task_struct *p = current;
2340 struct reclaim_state reclaim_state;
2342 struct scan_control sc = {
2343 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2344 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2346 .swap_cluster_max = max_t(unsigned long, nr_pages,
2348 .gfp_mask = gfp_mask,
2349 .swappiness = vm_swappiness,
2351 .isolate_pages = isolate_pages_global,
2353 unsigned long slab_reclaimable;
2355 disable_swap_token();
2358 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2359 * and we also need to be able to write out pages for RECLAIM_WRITE
2362 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2363 reclaim_state.reclaimed_slab = 0;
2364 p->reclaim_state = &reclaim_state;
2366 if (zone_page_state(zone, NR_FILE_PAGES) -
2367 zone_page_state(zone, NR_FILE_MAPPED) >
2368 zone->min_unmapped_pages) {
2370 * Free memory by calling shrink zone with increasing
2371 * priorities until we have enough memory freed.
2373 priority = ZONE_RECLAIM_PRIORITY;
2375 note_zone_scanning_priority(zone, priority);
2376 shrink_zone(priority, zone, &sc);
2378 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2381 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2382 if (slab_reclaimable > zone->min_slab_pages) {
2384 * shrink_slab() does not currently allow us to determine how
2385 * many pages were freed in this zone. So we take the current
2386 * number of slab pages and shake the slab until it is reduced
2387 * by the same nr_pages that we used for reclaiming unmapped
2390 * Note that shrink_slab will free memory on all zones and may
2393 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2394 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2395 slab_reclaimable - nr_pages)
2399 * Update nr_reclaimed by the number of slab pages we
2400 * reclaimed from this zone.
2402 sc.nr_reclaimed += slab_reclaimable -
2403 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2406 p->reclaim_state = NULL;
2407 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2408 return sc.nr_reclaimed >= nr_pages;
2411 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2417 * Zone reclaim reclaims unmapped file backed pages and
2418 * slab pages if we are over the defined limits.
2420 * A small portion of unmapped file backed pages is needed for
2421 * file I/O otherwise pages read by file I/O will be immediately
2422 * thrown out if the zone is overallocated. So we do not reclaim
2423 * if less than a specified percentage of the zone is used by
2424 * unmapped file backed pages.
2426 if (zone_page_state(zone, NR_FILE_PAGES) -
2427 zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
2428 && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
2429 <= zone->min_slab_pages)
2432 if (zone_is_all_unreclaimable(zone))
2436 * Do not scan if the allocation should not be delayed.
2438 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2442 * Only run zone reclaim on the local zone or on zones that do not
2443 * have associated processors. This will favor the local processor
2444 * over remote processors and spread off node memory allocations
2445 * as wide as possible.
2447 node_id = zone_to_nid(zone);
2448 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2451 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2453 ret = __zone_reclaim(zone, gfp_mask, order);
2454 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2461 * page_evictable - test whether a page is evictable
2462 * @page: the page to test
2463 * @vma: the VMA in which the page is or will be mapped, may be NULL
2465 * Test whether page is evictable--i.e., should be placed on active/inactive
2466 * lists vs unevictable list. The vma argument is !NULL when called from the
2467 * fault path to determine how to instantate a new page.
2469 * Reasons page might not be evictable:
2470 * (1) page's mapping marked unevictable
2471 * (2) page is part of an mlocked VMA
2474 int page_evictable(struct page *page, struct vm_area_struct *vma)
2477 if (mapping_unevictable(page_mapping(page)))
2480 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2487 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2488 * @page: page to check evictability and move to appropriate lru list
2489 * @zone: zone page is in
2491 * Checks a page for evictability and moves the page to the appropriate
2494 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2495 * have PageUnevictable set.
2497 static void check_move_unevictable_page(struct page *page, struct zone *zone)
2499 VM_BUG_ON(PageActive(page));
2502 ClearPageUnevictable(page);
2503 if (page_evictable(page, NULL)) {
2504 enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
2506 __dec_zone_state(zone, NR_UNEVICTABLE);
2507 list_move(&page->lru, &zone->lru[l].list);
2508 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2509 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2510 __count_vm_event(UNEVICTABLE_PGRESCUED);
2513 * rotate unevictable list
2515 SetPageUnevictable(page);
2516 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2517 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
2518 if (page_evictable(page, NULL))
2524 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2525 * @mapping: struct address_space to scan for evictable pages
2527 * Scan all pages in mapping. Check unevictable pages for
2528 * evictability and move them to the appropriate zone lru list.
2530 void scan_mapping_unevictable_pages(struct address_space *mapping)
2533 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2536 struct pagevec pvec;
2538 if (mapping->nrpages == 0)
2541 pagevec_init(&pvec, 0);
2542 while (next < end &&
2543 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2549 for (i = 0; i < pagevec_count(&pvec); i++) {
2550 struct page *page = pvec.pages[i];
2551 pgoff_t page_index = page->index;
2552 struct zone *pagezone = page_zone(page);
2555 if (page_index > next)
2559 if (pagezone != zone) {
2561 spin_unlock_irq(&zone->lru_lock);
2563 spin_lock_irq(&zone->lru_lock);
2566 if (PageLRU(page) && PageUnevictable(page))
2567 check_move_unevictable_page(page, zone);
2570 spin_unlock_irq(&zone->lru_lock);
2571 pagevec_release(&pvec);
2573 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2579 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2580 * @zone - zone of which to scan the unevictable list
2582 * Scan @zone's unevictable LRU lists to check for pages that have become
2583 * evictable. Move those that have to @zone's inactive list where they
2584 * become candidates for reclaim, unless shrink_inactive_zone() decides
2585 * to reactivate them. Pages that are still unevictable are rotated
2586 * back onto @zone's unevictable list.
2588 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2589 static void scan_zone_unevictable_pages(struct zone *zone)
2591 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2593 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2595 while (nr_to_scan > 0) {
2596 unsigned long batch_size = min(nr_to_scan,
2597 SCAN_UNEVICTABLE_BATCH_SIZE);
2599 spin_lock_irq(&zone->lru_lock);
2600 for (scan = 0; scan < batch_size; scan++) {
2601 struct page *page = lru_to_page(l_unevictable);
2603 if (!trylock_page(page))
2606 prefetchw_prev_lru_page(page, l_unevictable, flags);
2608 if (likely(PageLRU(page) && PageUnevictable(page)))
2609 check_move_unevictable_page(page, zone);
2613 spin_unlock_irq(&zone->lru_lock);
2615 nr_to_scan -= batch_size;
2621 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2623 * A really big hammer: scan all zones' unevictable LRU lists to check for
2624 * pages that have become evictable. Move those back to the zones'
2625 * inactive list where they become candidates for reclaim.
2626 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2627 * and we add swap to the system. As such, it runs in the context of a task
2628 * that has possibly/probably made some previously unevictable pages
2631 static void scan_all_zones_unevictable_pages(void)
2635 for_each_zone(zone) {
2636 scan_zone_unevictable_pages(zone);
2641 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2642 * all nodes' unevictable lists for evictable pages
2644 unsigned long scan_unevictable_pages;
2646 int scan_unevictable_handler(struct ctl_table *table, int write,
2647 struct file *file, void __user *buffer,
2648 size_t *length, loff_t *ppos)
2650 proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
2652 if (write && *(unsigned long *)table->data)
2653 scan_all_zones_unevictable_pages();
2655 scan_unevictable_pages = 0;
2660 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2661 * a specified node's per zone unevictable lists for evictable pages.
2664 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2665 struct sysdev_attribute *attr,
2668 return sprintf(buf, "0\n"); /* always zero; should fit... */
2671 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2672 struct sysdev_attribute *attr,
2673 const char *buf, size_t count)
2675 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2678 unsigned long req = strict_strtoul(buf, 10, &res);
2681 return 1; /* zero is no-op */
2683 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2684 if (!populated_zone(zone))
2686 scan_zone_unevictable_pages(zone);
2692 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2693 read_scan_unevictable_node,
2694 write_scan_unevictable_node);
2696 int scan_unevictable_register_node(struct node *node)
2698 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2701 void scan_unevictable_unregister_node(struct node *node)
2703 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);