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? */
74 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
75 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
76 * In this context, it doesn't matter that we scan the
77 * whole list at once. */
82 int all_unreclaimable;
86 /* Which cgroup do we reclaim from */
87 struct mem_cgroup *mem_cgroup;
90 * Nodemask of nodes allowed by the caller. If NULL, all nodes
95 /* Pluggable isolate pages callback */
96 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
97 unsigned long *scanned, int order, int mode,
98 struct zone *z, struct mem_cgroup *mem_cont,
99 int active, int file);
102 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
104 #ifdef ARCH_HAS_PREFETCH
105 #define prefetch_prev_lru_page(_page, _base, _field) \
107 if ((_page)->lru.prev != _base) { \
110 prev = lru_to_page(&(_page->lru)); \
111 prefetch(&prev->_field); \
115 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
118 #ifdef ARCH_HAS_PREFETCHW
119 #define prefetchw_prev_lru_page(_page, _base, _field) \
121 if ((_page)->lru.prev != _base) { \
124 prev = lru_to_page(&(_page->lru)); \
125 prefetchw(&prev->_field); \
129 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
133 * From 0 .. 100. Higher means more swappy.
135 int vm_swappiness = 60;
136 long vm_total_pages; /* The total number of pages which the VM controls */
138 static LIST_HEAD(shrinker_list);
139 static DECLARE_RWSEM(shrinker_rwsem);
141 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
142 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
144 #define scanning_global_lru(sc) (1)
147 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
148 struct scan_control *sc)
150 if (!scanning_global_lru(sc))
151 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
153 return &zone->reclaim_stat;
156 static unsigned long zone_nr_lru_pages(struct zone *zone,
157 struct scan_control *sc, enum lru_list lru)
159 if (!scanning_global_lru(sc))
160 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);
162 return zone_page_state(zone, NR_LRU_BASE + lru);
167 * Add a shrinker callback to be called from the vm
169 void register_shrinker(struct shrinker *shrinker)
172 down_write(&shrinker_rwsem);
173 list_add_tail(&shrinker->list, &shrinker_list);
174 up_write(&shrinker_rwsem);
176 EXPORT_SYMBOL(register_shrinker);
181 void unregister_shrinker(struct shrinker *shrinker)
183 down_write(&shrinker_rwsem);
184 list_del(&shrinker->list);
185 up_write(&shrinker_rwsem);
187 EXPORT_SYMBOL(unregister_shrinker);
189 #define SHRINK_BATCH 128
191 * Call the shrink functions to age shrinkable caches
193 * Here we assume it costs one seek to replace a lru page and that it also
194 * takes a seek to recreate a cache object. With this in mind we age equal
195 * percentages of the lru and ageable caches. This should balance the seeks
196 * generated by these structures.
198 * If the vm encountered mapped pages on the LRU it increase the pressure on
199 * slab to avoid swapping.
201 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
203 * `lru_pages' represents the number of on-LRU pages in all the zones which
204 * are eligible for the caller's allocation attempt. It is used for balancing
205 * slab reclaim versus page reclaim.
207 * Returns the number of slab objects which we shrunk.
209 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
210 unsigned long lru_pages)
212 struct shrinker *shrinker;
213 unsigned long ret = 0;
216 scanned = SWAP_CLUSTER_MAX;
218 if (!down_read_trylock(&shrinker_rwsem))
219 return 1; /* Assume we'll be able to shrink next time */
221 list_for_each_entry(shrinker, &shrinker_list, list) {
222 unsigned long long delta;
223 unsigned long total_scan;
224 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
226 delta = (4 * scanned) / shrinker->seeks;
228 do_div(delta, lru_pages + 1);
229 shrinker->nr += delta;
230 if (shrinker->nr < 0) {
231 printk(KERN_ERR "shrink_slab: %pF negative objects to "
233 shrinker->shrink, shrinker->nr);
234 shrinker->nr = max_pass;
238 * Avoid risking looping forever due to too large nr value:
239 * never try to free more than twice the estimate number of
242 if (shrinker->nr > max_pass * 2)
243 shrinker->nr = max_pass * 2;
245 total_scan = shrinker->nr;
248 while (total_scan >= SHRINK_BATCH) {
249 long this_scan = SHRINK_BATCH;
253 nr_before = (*shrinker->shrink)(0, gfp_mask);
254 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
255 if (shrink_ret == -1)
257 if (shrink_ret < nr_before)
258 ret += nr_before - shrink_ret;
259 count_vm_events(SLABS_SCANNED, this_scan);
260 total_scan -= this_scan;
265 shrinker->nr += total_scan;
267 up_read(&shrinker_rwsem);
271 /* Called without lock on whether page is mapped, so answer is unstable */
272 static inline int page_mapping_inuse(struct page *page)
274 struct address_space *mapping;
276 /* Page is in somebody's page tables. */
277 if (page_mapped(page))
280 /* Be more reluctant to reclaim swapcache than pagecache */
281 if (PageSwapCache(page))
284 mapping = page_mapping(page);
288 /* File is mmap'd by somebody? */
289 return mapping_mapped(mapping);
292 static inline int is_page_cache_freeable(struct page *page)
295 * A freeable page cache page is referenced only by the caller
296 * that isolated the page, the page cache radix tree and
297 * optional buffer heads at page->private.
299 return page_count(page) - page_has_private(page) == 2;
302 static int may_write_to_queue(struct backing_dev_info *bdi)
304 if (current->flags & PF_SWAPWRITE)
306 if (!bdi_write_congested(bdi))
308 if (bdi == current->backing_dev_info)
314 * We detected a synchronous write error writing a page out. Probably
315 * -ENOSPC. We need to propagate that into the address_space for a subsequent
316 * fsync(), msync() or close().
318 * The tricky part is that after writepage we cannot touch the mapping: nothing
319 * prevents it from being freed up. But we have a ref on the page and once
320 * that page is locked, the mapping is pinned.
322 * We're allowed to run sleeping lock_page() here because we know the caller has
325 static void handle_write_error(struct address_space *mapping,
326 struct page *page, int error)
329 if (page_mapping(page) == mapping)
330 mapping_set_error(mapping, error);
334 /* Request for sync pageout. */
340 /* possible outcome of pageout() */
342 /* failed to write page out, page is locked */
344 /* move page to the active list, page is locked */
346 /* page has been sent to the disk successfully, page is unlocked */
348 /* page is clean and locked */
353 * pageout is called by shrink_page_list() for each dirty page.
354 * Calls ->writepage().
356 static pageout_t pageout(struct page *page, struct address_space *mapping,
357 enum pageout_io sync_writeback)
360 * If the page is dirty, only perform writeback if that write
361 * will be non-blocking. To prevent this allocation from being
362 * stalled by pagecache activity. But note that there may be
363 * stalls if we need to run get_block(). We could test
364 * PagePrivate for that.
366 * If this process is currently in __generic_file_aio_write() against
367 * this page's queue, we can perform writeback even if that
370 * If the page is swapcache, write it back even if that would
371 * block, for some throttling. This happens by accident, because
372 * swap_backing_dev_info is bust: it doesn't reflect the
373 * congestion state of the swapdevs. Easy to fix, if needed.
375 if (!is_page_cache_freeable(page))
379 * Some data journaling orphaned pages can have
380 * page->mapping == NULL while being dirty with clean buffers.
382 if (page_has_private(page)) {
383 if (try_to_free_buffers(page)) {
384 ClearPageDirty(page);
385 printk("%s: orphaned page\n", __func__);
391 if (mapping->a_ops->writepage == NULL)
392 return PAGE_ACTIVATE;
393 if (!may_write_to_queue(mapping->backing_dev_info))
396 if (clear_page_dirty_for_io(page)) {
398 struct writeback_control wbc = {
399 .sync_mode = WB_SYNC_NONE,
400 .nr_to_write = SWAP_CLUSTER_MAX,
402 .range_end = LLONG_MAX,
407 SetPageReclaim(page);
408 res = mapping->a_ops->writepage(page, &wbc);
410 handle_write_error(mapping, page, res);
411 if (res == AOP_WRITEPAGE_ACTIVATE) {
412 ClearPageReclaim(page);
413 return PAGE_ACTIVATE;
417 * Wait on writeback if requested to. This happens when
418 * direct reclaiming a large contiguous area and the
419 * first attempt to free a range of pages fails.
421 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
422 wait_on_page_writeback(page);
424 if (!PageWriteback(page)) {
425 /* synchronous write or broken a_ops? */
426 ClearPageReclaim(page);
428 inc_zone_page_state(page, NR_VMSCAN_WRITE);
436 * Same as remove_mapping, but if the page is removed from the mapping, it
437 * gets returned with a refcount of 0.
439 static int __remove_mapping(struct address_space *mapping, struct page *page)
441 BUG_ON(!PageLocked(page));
442 BUG_ON(mapping != page_mapping(page));
444 spin_lock_irq(&mapping->tree_lock);
446 * The non racy check for a busy page.
448 * Must be careful with the order of the tests. When someone has
449 * a ref to the page, it may be possible that they dirty it then
450 * drop the reference. So if PageDirty is tested before page_count
451 * here, then the following race may occur:
453 * get_user_pages(&page);
454 * [user mapping goes away]
456 * !PageDirty(page) [good]
457 * SetPageDirty(page);
459 * !page_count(page) [good, discard it]
461 * [oops, our write_to data is lost]
463 * Reversing the order of the tests ensures such a situation cannot
464 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
465 * load is not satisfied before that of page->_count.
467 * Note that if SetPageDirty is always performed via set_page_dirty,
468 * and thus under tree_lock, then this ordering is not required.
470 if (!page_freeze_refs(page, 2))
472 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
473 if (unlikely(PageDirty(page))) {
474 page_unfreeze_refs(page, 2);
478 if (PageSwapCache(page)) {
479 swp_entry_t swap = { .val = page_private(page) };
480 __delete_from_swap_cache(page);
481 spin_unlock_irq(&mapping->tree_lock);
482 swapcache_free(swap, page);
484 __remove_from_page_cache(page);
485 spin_unlock_irq(&mapping->tree_lock);
486 mem_cgroup_uncharge_cache_page(page);
492 spin_unlock_irq(&mapping->tree_lock);
497 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
498 * someone else has a ref on the page, abort and return 0. If it was
499 * successfully detached, return 1. Assumes the caller has a single ref on
502 int remove_mapping(struct address_space *mapping, struct page *page)
504 if (__remove_mapping(mapping, page)) {
506 * Unfreezing the refcount with 1 rather than 2 effectively
507 * drops the pagecache ref for us without requiring another
510 page_unfreeze_refs(page, 1);
517 * putback_lru_page - put previously isolated page onto appropriate LRU list
518 * @page: page to be put back to appropriate lru list
520 * Add previously isolated @page to appropriate LRU list.
521 * Page may still be unevictable for other reasons.
523 * lru_lock must not be held, interrupts must be enabled.
525 void putback_lru_page(struct page *page)
528 int active = !!TestClearPageActive(page);
529 int was_unevictable = PageUnevictable(page);
531 VM_BUG_ON(PageLRU(page));
534 ClearPageUnevictable(page);
536 if (page_evictable(page, NULL)) {
538 * For evictable pages, we can use the cache.
539 * In event of a race, worst case is we end up with an
540 * unevictable page on [in]active list.
541 * We know how to handle that.
543 lru = active + page_lru_base_type(page);
544 lru_cache_add_lru(page, lru);
547 * Put unevictable pages directly on zone's unevictable
550 lru = LRU_UNEVICTABLE;
551 add_page_to_unevictable_list(page);
553 * When racing with an mlock clearing (page is
554 * unlocked), make sure that if the other thread does
555 * not observe our setting of PG_lru and fails
556 * isolation, we see PG_mlocked cleared below and move
557 * the page back to the evictable list.
559 * The other side is TestClearPageMlocked().
565 * page's status can change while we move it among lru. If an evictable
566 * page is on unevictable list, it never be freed. To avoid that,
567 * check after we added it to the list, again.
569 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
570 if (!isolate_lru_page(page)) {
574 /* This means someone else dropped this page from LRU
575 * So, it will be freed or putback to LRU again. There is
576 * nothing to do here.
580 if (was_unevictable && lru != LRU_UNEVICTABLE)
581 count_vm_event(UNEVICTABLE_PGRESCUED);
582 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
583 count_vm_event(UNEVICTABLE_PGCULLED);
585 put_page(page); /* drop ref from isolate */
589 * shrink_page_list() returns the number of reclaimed pages
591 static unsigned long shrink_page_list(struct list_head *page_list,
592 struct scan_control *sc,
593 enum pageout_io sync_writeback)
595 LIST_HEAD(ret_pages);
596 struct pagevec freed_pvec;
598 unsigned long nr_reclaimed = 0;
599 unsigned long vm_flags;
603 pagevec_init(&freed_pvec, 1);
604 while (!list_empty(page_list)) {
605 struct address_space *mapping;
612 page = lru_to_page(page_list);
613 list_del(&page->lru);
615 if (!trylock_page(page))
618 VM_BUG_ON(PageActive(page));
622 if (unlikely(!page_evictable(page, NULL)))
625 if (!sc->may_unmap && page_mapped(page))
628 /* Double the slab pressure for mapped and swapcache pages */
629 if (page_mapped(page) || PageSwapCache(page))
632 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
633 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
635 if (PageWriteback(page)) {
637 * Synchronous reclaim is performed in two passes,
638 * first an asynchronous pass over the list to
639 * start parallel writeback, and a second synchronous
640 * pass to wait for the IO to complete. Wait here
641 * for any page for which writeback has already
644 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
645 wait_on_page_writeback(page);
650 referenced = page_referenced(page, 1,
651 sc->mem_cgroup, &vm_flags);
653 * In active use or really unfreeable? Activate it.
654 * If page which have PG_mlocked lost isoltation race,
655 * try_to_unmap moves it to unevictable list
657 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
658 referenced && page_mapping_inuse(page)
659 && !(vm_flags & VM_LOCKED))
660 goto activate_locked;
663 * Anonymous process memory has backing store?
664 * Try to allocate it some swap space here.
666 if (PageAnon(page) && !PageSwapCache(page)) {
667 if (!(sc->gfp_mask & __GFP_IO))
669 if (!add_to_swap(page))
670 goto activate_locked;
674 mapping = page_mapping(page);
677 * The page is mapped into the page tables of one or more
678 * processes. Try to unmap it here.
680 if (page_mapped(page) && mapping) {
681 switch (try_to_unmap(page, TTU_UNMAP)) {
683 goto activate_locked;
689 ; /* try to free the page below */
693 if (PageDirty(page)) {
694 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
698 if (!sc->may_writepage)
701 /* Page is dirty, try to write it out here */
702 switch (pageout(page, mapping, sync_writeback)) {
706 goto activate_locked;
708 if (PageWriteback(page) || PageDirty(page))
711 * A synchronous write - probably a ramdisk. Go
712 * ahead and try to reclaim the page.
714 if (!trylock_page(page))
716 if (PageDirty(page) || PageWriteback(page))
718 mapping = page_mapping(page);
720 ; /* try to free the page below */
725 * If the page has buffers, try to free the buffer mappings
726 * associated with this page. If we succeed we try to free
729 * We do this even if the page is PageDirty().
730 * try_to_release_page() does not perform I/O, but it is
731 * possible for a page to have PageDirty set, but it is actually
732 * clean (all its buffers are clean). This happens if the
733 * buffers were written out directly, with submit_bh(). ext3
734 * will do this, as well as the blockdev mapping.
735 * try_to_release_page() will discover that cleanness and will
736 * drop the buffers and mark the page clean - it can be freed.
738 * Rarely, pages can have buffers and no ->mapping. These are
739 * the pages which were not successfully invalidated in
740 * truncate_complete_page(). We try to drop those buffers here
741 * and if that worked, and the page is no longer mapped into
742 * process address space (page_count == 1) it can be freed.
743 * Otherwise, leave the page on the LRU so it is swappable.
745 if (page_has_private(page)) {
746 if (!try_to_release_page(page, sc->gfp_mask))
747 goto activate_locked;
748 if (!mapping && page_count(page) == 1) {
750 if (put_page_testzero(page))
754 * rare race with speculative reference.
755 * the speculative reference will free
756 * this page shortly, so we may
757 * increment nr_reclaimed here (and
758 * leave it off the LRU).
766 if (!mapping || !__remove_mapping(mapping, page))
770 * At this point, we have no other references and there is
771 * no way to pick any more up (removed from LRU, removed
772 * from pagecache). Can use non-atomic bitops now (and
773 * we obviously don't have to worry about waking up a process
774 * waiting on the page lock, because there are no references.
776 __clear_page_locked(page);
779 if (!pagevec_add(&freed_pvec, page)) {
780 __pagevec_free(&freed_pvec);
781 pagevec_reinit(&freed_pvec);
786 if (PageSwapCache(page))
787 try_to_free_swap(page);
789 putback_lru_page(page);
793 /* Not a candidate for swapping, so reclaim swap space. */
794 if (PageSwapCache(page) && vm_swap_full())
795 try_to_free_swap(page);
796 VM_BUG_ON(PageActive(page));
802 list_add(&page->lru, &ret_pages);
803 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
805 list_splice(&ret_pages, page_list);
806 if (pagevec_count(&freed_pvec))
807 __pagevec_free(&freed_pvec);
808 count_vm_events(PGACTIVATE, pgactivate);
812 /* LRU Isolation modes. */
813 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
814 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
815 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
818 * Attempt to remove the specified page from its LRU. Only take this page
819 * if it is of the appropriate PageActive status. Pages which are being
820 * freed elsewhere are also ignored.
822 * page: page to consider
823 * mode: one of the LRU isolation modes defined above
825 * returns 0 on success, -ve errno on failure.
827 int __isolate_lru_page(struct page *page, int mode, int file)
831 /* Only take pages on the LRU. */
836 * When checking the active state, we need to be sure we are
837 * dealing with comparible boolean values. Take the logical not
840 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
843 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
847 * When this function is being called for lumpy reclaim, we
848 * initially look into all LRU pages, active, inactive and
849 * unevictable; only give shrink_page_list evictable pages.
851 if (PageUnevictable(page))
856 if (likely(get_page_unless_zero(page))) {
858 * Be careful not to clear PageLRU until after we're
859 * sure the page is not being freed elsewhere -- the
860 * page release code relies on it.
870 * zone->lru_lock is heavily contended. Some of the functions that
871 * shrink the lists perform better by taking out a batch of pages
872 * and working on them outside the LRU lock.
874 * For pagecache intensive workloads, this function is the hottest
875 * spot in the kernel (apart from copy_*_user functions).
877 * Appropriate locks must be held before calling this function.
879 * @nr_to_scan: The number of pages to look through on the list.
880 * @src: The LRU list to pull pages off.
881 * @dst: The temp list to put pages on to.
882 * @scanned: The number of pages that were scanned.
883 * @order: The caller's attempted allocation order
884 * @mode: One of the LRU isolation modes
885 * @file: True [1] if isolating file [!anon] pages
887 * returns how many pages were moved onto *@dst.
889 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
890 struct list_head *src, struct list_head *dst,
891 unsigned long *scanned, int order, int mode, int file)
893 unsigned long nr_taken = 0;
896 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
899 unsigned long end_pfn;
900 unsigned long page_pfn;
903 page = lru_to_page(src);
904 prefetchw_prev_lru_page(page, src, flags);
906 VM_BUG_ON(!PageLRU(page));
908 switch (__isolate_lru_page(page, mode, file)) {
910 list_move(&page->lru, dst);
911 mem_cgroup_del_lru(page);
916 /* else it is being freed elsewhere */
917 list_move(&page->lru, src);
918 mem_cgroup_rotate_lru_list(page, page_lru(page));
929 * Attempt to take all pages in the order aligned region
930 * surrounding the tag page. Only take those pages of
931 * the same active state as that tag page. We may safely
932 * round the target page pfn down to the requested order
933 * as the mem_map is guarenteed valid out to MAX_ORDER,
934 * where that page is in a different zone we will detect
935 * it from its zone id and abort this block scan.
937 zone_id = page_zone_id(page);
938 page_pfn = page_to_pfn(page);
939 pfn = page_pfn & ~((1 << order) - 1);
940 end_pfn = pfn + (1 << order);
941 for (; pfn < end_pfn; pfn++) {
942 struct page *cursor_page;
944 /* The target page is in the block, ignore it. */
945 if (unlikely(pfn == page_pfn))
948 /* Avoid holes within the zone. */
949 if (unlikely(!pfn_valid_within(pfn)))
952 cursor_page = pfn_to_page(pfn);
954 /* Check that we have not crossed a zone boundary. */
955 if (unlikely(page_zone_id(cursor_page) != zone_id))
959 * If we don't have enough swap space, reclaiming of
960 * anon page which don't already have a swap slot is
963 if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
964 !PageSwapCache(cursor_page))
967 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
968 list_move(&cursor_page->lru, dst);
969 mem_cgroup_del_lru(cursor_page);
980 static unsigned long isolate_pages_global(unsigned long nr,
981 struct list_head *dst,
982 unsigned long *scanned, int order,
983 int mode, struct zone *z,
984 struct mem_cgroup *mem_cont,
985 int active, int file)
992 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
997 * clear_active_flags() is a helper for shrink_active_list(), clearing
998 * any active bits from the pages in the list.
1000 static unsigned long clear_active_flags(struct list_head *page_list,
1001 unsigned int *count)
1007 list_for_each_entry(page, page_list, lru) {
1008 lru = page_lru_base_type(page);
1009 if (PageActive(page)) {
1011 ClearPageActive(page);
1021 * isolate_lru_page - tries to isolate a page from its LRU list
1022 * @page: page to isolate from its LRU list
1024 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1025 * vmstat statistic corresponding to whatever LRU list the page was on.
1027 * Returns 0 if the page was removed from an LRU list.
1028 * Returns -EBUSY if the page was not on an LRU list.
1030 * The returned page will have PageLRU() cleared. If it was found on
1031 * the active list, it will have PageActive set. If it was found on
1032 * the unevictable list, it will have the PageUnevictable bit set. That flag
1033 * may need to be cleared by the caller before letting the page go.
1035 * The vmstat statistic corresponding to the list on which the page was
1036 * found will be decremented.
1039 * (1) Must be called with an elevated refcount on the page. This is a
1040 * fundamentnal difference from isolate_lru_pages (which is called
1041 * without a stable reference).
1042 * (2) the lru_lock must not be held.
1043 * (3) interrupts must be enabled.
1045 int isolate_lru_page(struct page *page)
1049 if (PageLRU(page)) {
1050 struct zone *zone = page_zone(page);
1052 spin_lock_irq(&zone->lru_lock);
1053 if (PageLRU(page) && get_page_unless_zero(page)) {
1054 int lru = page_lru(page);
1058 del_page_from_lru_list(zone, page, lru);
1060 spin_unlock_irq(&zone->lru_lock);
1066 * Are there way too many processes in the direct reclaim path already?
1068 static int too_many_isolated(struct zone *zone, int file,
1069 struct scan_control *sc)
1071 unsigned long inactive, isolated;
1073 if (current_is_kswapd())
1076 if (!scanning_global_lru(sc))
1080 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1081 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1083 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1084 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1087 return isolated > inactive;
1091 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1092 * of reclaimed pages
1094 static unsigned long shrink_inactive_list(unsigned long max_scan,
1095 struct zone *zone, struct scan_control *sc,
1096 int priority, int file)
1098 LIST_HEAD(page_list);
1099 struct pagevec pvec;
1100 unsigned long nr_scanned = 0;
1101 unsigned long nr_reclaimed = 0;
1102 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1103 int lumpy_reclaim = 0;
1105 while (unlikely(too_many_isolated(zone, file, sc))) {
1106 congestion_wait(BLK_RW_ASYNC, HZ/10);
1108 /* We are about to die and free our memory. Return now. */
1109 if (fatal_signal_pending(current))
1110 return SWAP_CLUSTER_MAX;
1114 * If we need a large contiguous chunk of memory, or have
1115 * trouble getting a small set of contiguous pages, we
1116 * will reclaim both active and inactive pages.
1118 * We use the same threshold as pageout congestion_wait below.
1120 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1122 else if (sc->order && priority < DEF_PRIORITY - 2)
1125 pagevec_init(&pvec, 1);
1128 spin_lock_irq(&zone->lru_lock);
1131 unsigned long nr_taken;
1132 unsigned long nr_scan;
1133 unsigned long nr_freed;
1134 unsigned long nr_active;
1135 unsigned int count[NR_LRU_LISTS] = { 0, };
1136 int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE;
1137 unsigned long nr_anon;
1138 unsigned long nr_file;
1140 nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1141 &page_list, &nr_scan, sc->order, mode,
1142 zone, sc->mem_cgroup, 0, file);
1144 if (scanning_global_lru(sc)) {
1145 zone->pages_scanned += nr_scan;
1146 if (current_is_kswapd())
1147 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1150 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1157 nr_active = clear_active_flags(&page_list, count);
1158 __count_vm_events(PGDEACTIVATE, nr_active);
1160 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1161 -count[LRU_ACTIVE_FILE]);
1162 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1163 -count[LRU_INACTIVE_FILE]);
1164 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1165 -count[LRU_ACTIVE_ANON]);
1166 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1167 -count[LRU_INACTIVE_ANON]);
1169 nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1170 nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1171 __mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
1172 __mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
1174 reclaim_stat->recent_scanned[0] += count[LRU_INACTIVE_ANON];
1175 reclaim_stat->recent_scanned[0] += count[LRU_ACTIVE_ANON];
1176 reclaim_stat->recent_scanned[1] += count[LRU_INACTIVE_FILE];
1177 reclaim_stat->recent_scanned[1] += count[LRU_ACTIVE_FILE];
1179 spin_unlock_irq(&zone->lru_lock);
1181 nr_scanned += nr_scan;
1182 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1185 * If we are direct reclaiming for contiguous pages and we do
1186 * not reclaim everything in the list, try again and wait
1187 * for IO to complete. This will stall high-order allocations
1188 * but that should be acceptable to the caller
1190 if (nr_freed < nr_taken && !current_is_kswapd() &&
1192 congestion_wait(BLK_RW_ASYNC, HZ/10);
1195 * The attempt at page out may have made some
1196 * of the pages active, mark them inactive again.
1198 nr_active = clear_active_flags(&page_list, count);
1199 count_vm_events(PGDEACTIVATE, nr_active);
1201 nr_freed += shrink_page_list(&page_list, sc,
1205 nr_reclaimed += nr_freed;
1207 local_irq_disable();
1208 if (current_is_kswapd())
1209 __count_vm_events(KSWAPD_STEAL, nr_freed);
1210 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
1212 spin_lock(&zone->lru_lock);
1214 * Put back any unfreeable pages.
1216 while (!list_empty(&page_list)) {
1218 page = lru_to_page(&page_list);
1219 VM_BUG_ON(PageLRU(page));
1220 list_del(&page->lru);
1221 if (unlikely(!page_evictable(page, NULL))) {
1222 spin_unlock_irq(&zone->lru_lock);
1223 putback_lru_page(page);
1224 spin_lock_irq(&zone->lru_lock);
1228 lru = page_lru(page);
1229 add_page_to_lru_list(zone, page, lru);
1230 if (is_active_lru(lru)) {
1231 int file = is_file_lru(lru);
1232 reclaim_stat->recent_rotated[file]++;
1234 if (!pagevec_add(&pvec, page)) {
1235 spin_unlock_irq(&zone->lru_lock);
1236 __pagevec_release(&pvec);
1237 spin_lock_irq(&zone->lru_lock);
1240 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1241 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1243 } while (nr_scanned < max_scan);
1246 spin_unlock_irq(&zone->lru_lock);
1247 pagevec_release(&pvec);
1248 return nr_reclaimed;
1252 * We are about to scan this zone at a certain priority level. If that priority
1253 * level is smaller (ie: more urgent) than the previous priority, then note
1254 * that priority level within the zone. This is done so that when the next
1255 * process comes in to scan this zone, it will immediately start out at this
1256 * priority level rather than having to build up its own scanning priority.
1257 * Here, this priority affects only the reclaim-mapped threshold.
1259 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1261 if (priority < zone->prev_priority)
1262 zone->prev_priority = priority;
1266 * This moves pages from the active list to the inactive list.
1268 * We move them the other way if the page is referenced by one or more
1269 * processes, from rmap.
1271 * If the pages are mostly unmapped, the processing is fast and it is
1272 * appropriate to hold zone->lru_lock across the whole operation. But if
1273 * the pages are mapped, the processing is slow (page_referenced()) so we
1274 * should drop zone->lru_lock around each page. It's impossible to balance
1275 * this, so instead we remove the pages from the LRU while processing them.
1276 * It is safe to rely on PG_active against the non-LRU pages in here because
1277 * nobody will play with that bit on a non-LRU page.
1279 * The downside is that we have to touch page->_count against each page.
1280 * But we had to alter page->flags anyway.
1283 static void move_active_pages_to_lru(struct zone *zone,
1284 struct list_head *list,
1287 unsigned long pgmoved = 0;
1288 struct pagevec pvec;
1291 pagevec_init(&pvec, 1);
1293 while (!list_empty(list)) {
1294 page = lru_to_page(list);
1296 VM_BUG_ON(PageLRU(page));
1299 list_move(&page->lru, &zone->lru[lru].list);
1300 mem_cgroup_add_lru_list(page, lru);
1303 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1304 spin_unlock_irq(&zone->lru_lock);
1305 if (buffer_heads_over_limit)
1306 pagevec_strip(&pvec);
1307 __pagevec_release(&pvec);
1308 spin_lock_irq(&zone->lru_lock);
1311 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1312 if (!is_active_lru(lru))
1313 __count_vm_events(PGDEACTIVATE, pgmoved);
1316 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1317 struct scan_control *sc, int priority, int file)
1319 unsigned long nr_taken;
1320 unsigned long pgscanned;
1321 unsigned long vm_flags;
1322 LIST_HEAD(l_hold); /* The pages which were snipped off */
1323 LIST_HEAD(l_active);
1324 LIST_HEAD(l_inactive);
1326 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1327 unsigned long nr_rotated = 0;
1330 spin_lock_irq(&zone->lru_lock);
1331 nr_taken = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1332 ISOLATE_ACTIVE, zone,
1333 sc->mem_cgroup, 1, file);
1335 * zone->pages_scanned is used for detect zone's oom
1336 * mem_cgroup remembers nr_scan by itself.
1338 if (scanning_global_lru(sc)) {
1339 zone->pages_scanned += pgscanned;
1341 reclaim_stat->recent_scanned[file] += nr_taken;
1343 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1345 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1347 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1348 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1349 spin_unlock_irq(&zone->lru_lock);
1351 while (!list_empty(&l_hold)) {
1353 page = lru_to_page(&l_hold);
1354 list_del(&page->lru);
1356 if (unlikely(!page_evictable(page, NULL))) {
1357 putback_lru_page(page);
1361 /* page_referenced clears PageReferenced */
1362 if (page_mapping_inuse(page) &&
1363 page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1366 * Identify referenced, file-backed active pages and
1367 * give them one more trip around the active list. So
1368 * that executable code get better chances to stay in
1369 * memory under moderate memory pressure. Anon pages
1370 * are not likely to be evicted by use-once streaming
1371 * IO, plus JVM can create lots of anon VM_EXEC pages,
1372 * so we ignore them here.
1374 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1375 list_add(&page->lru, &l_active);
1380 ClearPageActive(page); /* we are de-activating */
1381 list_add(&page->lru, &l_inactive);
1385 * Move pages back to the lru list.
1387 spin_lock_irq(&zone->lru_lock);
1389 * Count referenced pages from currently used mappings as rotated,
1390 * even though only some of them are actually re-activated. This
1391 * helps balance scan pressure between file and anonymous pages in
1394 reclaim_stat->recent_rotated[file] += nr_rotated;
1396 move_active_pages_to_lru(zone, &l_active,
1397 LRU_ACTIVE + file * LRU_FILE);
1398 move_active_pages_to_lru(zone, &l_inactive,
1399 LRU_BASE + file * LRU_FILE);
1400 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1401 spin_unlock_irq(&zone->lru_lock);
1404 static int inactive_anon_is_low_global(struct zone *zone)
1406 unsigned long active, inactive;
1408 active = zone_page_state(zone, NR_ACTIVE_ANON);
1409 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1411 if (inactive * zone->inactive_ratio < active)
1418 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1419 * @zone: zone to check
1420 * @sc: scan control of this context
1422 * Returns true if the zone does not have enough inactive anon pages,
1423 * meaning some active anon pages need to be deactivated.
1425 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1429 if (scanning_global_lru(sc))
1430 low = inactive_anon_is_low_global(zone);
1432 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1436 static int inactive_file_is_low_global(struct zone *zone)
1438 unsigned long active, inactive;
1440 active = zone_page_state(zone, NR_ACTIVE_FILE);
1441 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1443 return (active > inactive);
1447 * inactive_file_is_low - check if file pages need to be deactivated
1448 * @zone: zone to check
1449 * @sc: scan control of this context
1451 * When the system is doing streaming IO, memory pressure here
1452 * ensures that active file pages get deactivated, until more
1453 * than half of the file pages are on the inactive list.
1455 * Once we get to that situation, protect the system's working
1456 * set from being evicted by disabling active file page aging.
1458 * This uses a different ratio than the anonymous pages, because
1459 * the page cache uses a use-once replacement algorithm.
1461 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1465 if (scanning_global_lru(sc))
1466 low = inactive_file_is_low_global(zone);
1468 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1472 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1473 struct zone *zone, struct scan_control *sc, int priority)
1475 int file = is_file_lru(lru);
1477 if (lru == LRU_ACTIVE_FILE && inactive_file_is_low(zone, sc)) {
1478 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1482 if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) {
1483 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,
1576 unsigned long swap_cluster_max)
1580 *nr_saved_scan += nr_to_scan;
1581 nr = *nr_saved_scan;
1583 if (nr >= swap_cluster_max)
1592 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1594 static void shrink_zone(int priority, struct zone *zone,
1595 struct scan_control *sc)
1597 unsigned long nr[NR_LRU_LISTS];
1598 unsigned long nr_to_scan;
1599 unsigned long percent[2]; /* anon @ 0; file @ 1 */
1601 unsigned long nr_reclaimed = sc->nr_reclaimed;
1602 unsigned long swap_cluster_max = sc->swap_cluster_max;
1603 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1604 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1607 /* If we have no swap space, do not bother scanning anon pages. */
1608 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1613 get_scan_ratio(zone, sc, percent);
1615 for_each_evictable_lru(l) {
1616 int file = is_file_lru(l);
1619 scan = zone_nr_lru_pages(zone, sc, l);
1620 if (priority || noswap) {
1622 scan = (scan * percent[file]) / 100;
1624 nr[l] = nr_scan_try_batch(scan,
1625 &reclaim_stat->nr_saved_scan[l],
1629 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1630 nr[LRU_INACTIVE_FILE]) {
1631 for_each_evictable_lru(l) {
1633 nr_to_scan = min(nr[l], swap_cluster_max);
1634 nr[l] -= nr_to_scan;
1636 nr_reclaimed += shrink_list(l, nr_to_scan,
1637 zone, sc, priority);
1641 * On large memory systems, scan >> priority can become
1642 * really large. This is fine for the starting priority;
1643 * we want to put equal scanning pressure on each zone.
1644 * However, if the VM has a harder time of freeing pages,
1645 * with multiple processes reclaiming pages, the total
1646 * freeing target can get unreasonably large.
1648 if (nr_reclaimed > nr_to_reclaim && priority < DEF_PRIORITY)
1652 sc->nr_reclaimed = nr_reclaimed;
1655 * Even if we did not try to evict anon pages at all, we want to
1656 * rebalance the anon lru active/inactive ratio.
1658 if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0)
1659 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1661 throttle_vm_writeout(sc->gfp_mask);
1665 * This is the direct reclaim path, for page-allocating processes. We only
1666 * try to reclaim pages from zones which will satisfy the caller's allocation
1669 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1671 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1673 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1674 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1675 * zone defense algorithm.
1677 * If a zone is deemed to be full of pinned pages then just give it a light
1678 * scan then give up on it.
1680 static void shrink_zones(int priority, struct zonelist *zonelist,
1681 struct scan_control *sc)
1683 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1687 sc->all_unreclaimable = 1;
1688 for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
1690 if (!populated_zone(zone))
1693 * Take care memory controller reclaiming has small influence
1696 if (scanning_global_lru(sc)) {
1697 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1699 note_zone_scanning_priority(zone, priority);
1701 if (zone_is_all_unreclaimable(zone) &&
1702 priority != DEF_PRIORITY)
1703 continue; /* Let kswapd poll it */
1704 sc->all_unreclaimable = 0;
1707 * Ignore cpuset limitation here. We just want to reduce
1708 * # of used pages by us regardless of memory shortage.
1710 sc->all_unreclaimable = 0;
1711 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1715 shrink_zone(priority, zone, sc);
1720 * This is the main entry point to direct page reclaim.
1722 * If a full scan of the inactive list fails to free enough memory then we
1723 * are "out of memory" and something needs to be killed.
1725 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1726 * high - the zone may be full of dirty or under-writeback pages, which this
1727 * caller can't do much about. We kick the writeback threads and take explicit
1728 * naps in the hope that some of these pages can be written. But if the
1729 * allocating task holds filesystem locks which prevent writeout this might not
1730 * work, and the allocation attempt will fail.
1732 * returns: 0, if no pages reclaimed
1733 * else, the number of pages reclaimed
1735 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1736 struct scan_control *sc)
1739 unsigned long ret = 0;
1740 unsigned long total_scanned = 0;
1741 struct reclaim_state *reclaim_state = current->reclaim_state;
1742 unsigned long lru_pages = 0;
1745 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1746 unsigned long writeback_threshold;
1748 delayacct_freepages_start();
1750 if (scanning_global_lru(sc))
1751 count_vm_event(ALLOCSTALL);
1753 * mem_cgroup will not do shrink_slab.
1755 if (scanning_global_lru(sc)) {
1756 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1758 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1761 lru_pages += zone_reclaimable_pages(zone);
1765 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1768 disable_swap_token();
1769 shrink_zones(priority, zonelist, sc);
1771 * Don't shrink slabs when reclaiming memory from
1772 * over limit cgroups
1774 if (scanning_global_lru(sc)) {
1775 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1776 if (reclaim_state) {
1777 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1778 reclaim_state->reclaimed_slab = 0;
1781 total_scanned += sc->nr_scanned;
1782 if (sc->nr_reclaimed >= sc->nr_to_reclaim) {
1783 ret = sc->nr_reclaimed;
1788 * Try to write back as many pages as we just scanned. This
1789 * tends to cause slow streaming writers to write data to the
1790 * disk smoothly, at the dirtying rate, which is nice. But
1791 * that's undesirable in laptop mode, where we *want* lumpy
1792 * writeout. So in laptop mode, write out the whole world.
1794 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
1795 if (total_scanned > writeback_threshold) {
1796 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
1797 sc->may_writepage = 1;
1800 /* Take a nap, wait for some writeback to complete */
1801 if (!sc->hibernation_mode && sc->nr_scanned &&
1802 priority < DEF_PRIORITY - 2)
1803 congestion_wait(BLK_RW_ASYNC, HZ/10);
1805 /* top priority shrink_zones still had more to do? don't OOM, then */
1806 if (!sc->all_unreclaimable && scanning_global_lru(sc))
1807 ret = sc->nr_reclaimed;
1810 * Now that we've scanned all the zones at this priority level, note
1811 * that level within the zone so that the next thread which performs
1812 * scanning of this zone will immediately start out at this priority
1813 * level. This affects only the decision whether or not to bring
1814 * mapped pages onto the inactive list.
1819 if (scanning_global_lru(sc)) {
1820 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1822 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1825 zone->prev_priority = priority;
1828 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1830 delayacct_freepages_end();
1835 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1836 gfp_t gfp_mask, nodemask_t *nodemask)
1838 struct scan_control sc = {
1839 .gfp_mask = gfp_mask,
1840 .may_writepage = !laptop_mode,
1841 .swap_cluster_max = SWAP_CLUSTER_MAX,
1842 .nr_to_reclaim = SWAP_CLUSTER_MAX,
1845 .swappiness = vm_swappiness,
1848 .isolate_pages = isolate_pages_global,
1849 .nodemask = nodemask,
1852 return do_try_to_free_pages(zonelist, &sc);
1855 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1857 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
1858 gfp_t gfp_mask, bool noswap,
1859 unsigned int swappiness,
1860 struct zone *zone, int nid)
1862 struct scan_control sc = {
1863 .may_writepage = !laptop_mode,
1865 .may_swap = !noswap,
1866 .swap_cluster_max = SWAP_CLUSTER_MAX,
1867 .swappiness = swappiness,
1870 .isolate_pages = mem_cgroup_isolate_pages,
1872 nodemask_t nm = nodemask_of_node(nid);
1874 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1875 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1877 sc.nr_reclaimed = 0;
1880 * NOTE: Although we can get the priority field, using it
1881 * here is not a good idea, since it limits the pages we can scan.
1882 * if we don't reclaim here, the shrink_zone from balance_pgdat
1883 * will pick up pages from other mem cgroup's as well. We hack
1884 * the priority and make it zero.
1886 shrink_zone(0, zone, &sc);
1887 return sc.nr_reclaimed;
1890 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1893 unsigned int swappiness)
1895 struct zonelist *zonelist;
1896 struct scan_control sc = {
1897 .may_writepage = !laptop_mode,
1899 .may_swap = !noswap,
1900 .swap_cluster_max = SWAP_CLUSTER_MAX,
1901 .nr_to_reclaim = SWAP_CLUSTER_MAX,
1902 .swappiness = swappiness,
1904 .mem_cgroup = mem_cont,
1905 .isolate_pages = mem_cgroup_isolate_pages,
1906 .nodemask = NULL, /* we don't care the placement */
1909 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1910 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1911 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1912 return do_try_to_free_pages(zonelist, &sc);
1916 /* is kswapd sleeping prematurely? */
1917 static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
1921 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
1925 /* If after HZ/10, a zone is below the high mark, it's premature */
1926 for (i = 0; i < pgdat->nr_zones; i++) {
1927 struct zone *zone = pgdat->node_zones + i;
1929 if (!populated_zone(zone))
1932 if (!zone_watermark_ok(zone, order, high_wmark_pages(zone),
1941 * For kswapd, balance_pgdat() will work across all this node's zones until
1942 * they are all at high_wmark_pages(zone).
1944 * Returns the number of pages which were actually freed.
1946 * There is special handling here for zones which are full of pinned pages.
1947 * This can happen if the pages are all mlocked, or if they are all used by
1948 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1949 * What we do is to detect the case where all pages in the zone have been
1950 * scanned twice and there has been zero successful reclaim. Mark the zone as
1951 * dead and from now on, only perform a short scan. Basically we're polling
1952 * the zone for when the problem goes away.
1954 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1955 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
1956 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
1957 * lower zones regardless of the number of free pages in the lower zones. This
1958 * interoperates with the page allocator fallback scheme to ensure that aging
1959 * of pages is balanced across the zones.
1961 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1966 unsigned long total_scanned;
1967 struct reclaim_state *reclaim_state = current->reclaim_state;
1968 struct scan_control sc = {
1969 .gfp_mask = GFP_KERNEL,
1972 .swap_cluster_max = SWAP_CLUSTER_MAX,
1974 * kswapd doesn't want to be bailed out while reclaim. because
1975 * we want to put equal scanning pressure on each zone.
1977 .nr_to_reclaim = ULONG_MAX,
1978 .swappiness = vm_swappiness,
1981 .isolate_pages = isolate_pages_global,
1984 * temp_priority is used to remember the scanning priority at which
1985 * this zone was successfully refilled to
1986 * free_pages == high_wmark_pages(zone).
1988 int temp_priority[MAX_NR_ZONES];
1992 sc.nr_reclaimed = 0;
1993 sc.may_writepage = !laptop_mode;
1994 count_vm_event(PAGEOUTRUN);
1996 for (i = 0; i < pgdat->nr_zones; i++)
1997 temp_priority[i] = DEF_PRIORITY;
1999 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2000 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2001 unsigned long lru_pages = 0;
2002 int has_under_min_watermark_zone = 0;
2004 /* The swap token gets in the way of swapout... */
2006 disable_swap_token();
2011 * Scan in the highmem->dma direction for the highest
2012 * zone which needs scanning
2014 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2015 struct zone *zone = pgdat->node_zones + i;
2017 if (!populated_zone(zone))
2020 if (zone_is_all_unreclaimable(zone) &&
2021 priority != DEF_PRIORITY)
2025 * Do some background aging of the anon list, to give
2026 * pages a chance to be referenced before reclaiming.
2028 if (inactive_anon_is_low(zone, &sc))
2029 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2032 if (!zone_watermark_ok(zone, order,
2033 high_wmark_pages(zone), 0, 0)) {
2041 for (i = 0; i <= end_zone; i++) {
2042 struct zone *zone = pgdat->node_zones + i;
2044 lru_pages += zone_reclaimable_pages(zone);
2048 * Now scan the zone in the dma->highmem direction, stopping
2049 * at the last zone which needs scanning.
2051 * We do this because the page allocator works in the opposite
2052 * direction. This prevents the page allocator from allocating
2053 * pages behind kswapd's direction of progress, which would
2054 * cause too much scanning of the lower zones.
2056 for (i = 0; i <= end_zone; i++) {
2057 struct zone *zone = pgdat->node_zones + i;
2061 if (!populated_zone(zone))
2064 if (zone_is_all_unreclaimable(zone) &&
2065 priority != DEF_PRIORITY)
2068 if (!zone_watermark_ok(zone, order,
2069 high_wmark_pages(zone), end_zone, 0))
2071 temp_priority[i] = priority;
2073 note_zone_scanning_priority(zone, priority);
2075 nid = pgdat->node_id;
2076 zid = zone_idx(zone);
2078 * Call soft limit reclaim before calling shrink_zone.
2079 * For now we ignore the return value
2081 mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask,
2084 * We put equal pressure on every zone, unless one
2085 * zone has way too many pages free already.
2087 if (!zone_watermark_ok(zone, order,
2088 8*high_wmark_pages(zone), end_zone, 0))
2089 shrink_zone(priority, zone, &sc);
2090 reclaim_state->reclaimed_slab = 0;
2091 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
2093 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2094 total_scanned += sc.nr_scanned;
2095 if (zone_is_all_unreclaimable(zone))
2097 if (nr_slab == 0 && zone->pages_scanned >=
2098 (zone_reclaimable_pages(zone) * 6))
2100 ZONE_ALL_UNRECLAIMABLE);
2102 * If we've done a decent amount of scanning and
2103 * the reclaim ratio is low, start doing writepage
2104 * even in laptop mode
2106 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2107 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2108 sc.may_writepage = 1;
2111 * We are still under min water mark. it mean we have
2112 * GFP_ATOMIC allocation failure risk. Hurry up!
2114 if (!zone_watermark_ok(zone, order, min_wmark_pages(zone),
2116 has_under_min_watermark_zone = 1;
2120 break; /* kswapd: all done */
2122 * OK, kswapd is getting into trouble. Take a nap, then take
2123 * another pass across the zones.
2125 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2126 if (has_under_min_watermark_zone)
2127 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2129 congestion_wait(BLK_RW_ASYNC, HZ/10);
2133 * We do this so kswapd doesn't build up large priorities for
2134 * example when it is freeing in parallel with allocators. It
2135 * matches the direct reclaim path behaviour in terms of impact
2136 * on zone->*_priority.
2138 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2143 * Note within each zone the priority level at which this zone was
2144 * brought into a happy state. So that the next thread which scans this
2145 * zone will start out at that priority level.
2147 for (i = 0; i < pgdat->nr_zones; i++) {
2148 struct zone *zone = pgdat->node_zones + i;
2150 zone->prev_priority = temp_priority[i];
2152 if (!all_zones_ok) {
2158 * Fragmentation may mean that the system cannot be
2159 * rebalanced for high-order allocations in all zones.
2160 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2161 * it means the zones have been fully scanned and are still
2162 * not balanced. For high-order allocations, there is
2163 * little point trying all over again as kswapd may
2166 * Instead, recheck all watermarks at order-0 as they
2167 * are the most important. If watermarks are ok, kswapd will go
2168 * back to sleep. High-order users can still perform direct
2169 * reclaim if they wish.
2171 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2172 order = sc.order = 0;
2177 return sc.nr_reclaimed;
2181 * The background pageout daemon, started as a kernel thread
2182 * from the init process.
2184 * This basically trickles out pages so that we have _some_
2185 * free memory available even if there is no other activity
2186 * that frees anything up. This is needed for things like routing
2187 * etc, where we otherwise might have all activity going on in
2188 * asynchronous contexts that cannot page things out.
2190 * If there are applications that are active memory-allocators
2191 * (most normal use), this basically shouldn't matter.
2193 static int kswapd(void *p)
2195 unsigned long order;
2196 pg_data_t *pgdat = (pg_data_t*)p;
2197 struct task_struct *tsk = current;
2199 struct reclaim_state reclaim_state = {
2200 .reclaimed_slab = 0,
2202 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2204 lockdep_set_current_reclaim_state(GFP_KERNEL);
2206 if (!cpumask_empty(cpumask))
2207 set_cpus_allowed_ptr(tsk, cpumask);
2208 current->reclaim_state = &reclaim_state;
2211 * Tell the memory management that we're a "memory allocator",
2212 * and that if we need more memory we should get access to it
2213 * regardless (see "__alloc_pages()"). "kswapd" should
2214 * never get caught in the normal page freeing logic.
2216 * (Kswapd normally doesn't need memory anyway, but sometimes
2217 * you need a small amount of memory in order to be able to
2218 * page out something else, and this flag essentially protects
2219 * us from recursively trying to free more memory as we're
2220 * trying to free the first piece of memory in the first place).
2222 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2227 unsigned long new_order;
2230 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2231 new_order = pgdat->kswapd_max_order;
2232 pgdat->kswapd_max_order = 0;
2233 if (order < new_order) {
2235 * Don't sleep if someone wants a larger 'order'
2240 if (!freezing(current) && !kthread_should_stop()) {
2243 /* Try to sleep for a short interval */
2244 if (!sleeping_prematurely(pgdat, order, remaining)) {
2245 remaining = schedule_timeout(HZ/10);
2246 finish_wait(&pgdat->kswapd_wait, &wait);
2247 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2251 * After a short sleep, check if it was a
2252 * premature sleep. If not, then go fully
2253 * to sleep until explicitly woken up
2255 if (!sleeping_prematurely(pgdat, order, remaining))
2259 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2261 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2265 order = pgdat->kswapd_max_order;
2267 finish_wait(&pgdat->kswapd_wait, &wait);
2269 ret = try_to_freeze();
2270 if (kthread_should_stop())
2274 * We can speed up thawing tasks if we don't call balance_pgdat
2275 * after returning from the refrigerator
2278 balance_pgdat(pgdat, order);
2284 * A zone is low on free memory, so wake its kswapd task to service it.
2286 void wakeup_kswapd(struct zone *zone, int order)
2290 if (!populated_zone(zone))
2293 pgdat = zone->zone_pgdat;
2294 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
2296 if (pgdat->kswapd_max_order < order)
2297 pgdat->kswapd_max_order = order;
2298 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2300 if (!waitqueue_active(&pgdat->kswapd_wait))
2302 wake_up_interruptible(&pgdat->kswapd_wait);
2306 * The reclaimable count would be mostly accurate.
2307 * The less reclaimable pages may be
2308 * - mlocked pages, which will be moved to unevictable list when encountered
2309 * - mapped pages, which may require several travels to be reclaimed
2310 * - dirty pages, which is not "instantly" reclaimable
2312 unsigned long global_reclaimable_pages(void)
2316 nr = global_page_state(NR_ACTIVE_FILE) +
2317 global_page_state(NR_INACTIVE_FILE);
2319 if (nr_swap_pages > 0)
2320 nr += global_page_state(NR_ACTIVE_ANON) +
2321 global_page_state(NR_INACTIVE_ANON);
2326 unsigned long zone_reclaimable_pages(struct zone *zone)
2330 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2331 zone_page_state(zone, NR_INACTIVE_FILE);
2333 if (nr_swap_pages > 0)
2334 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2335 zone_page_state(zone, NR_INACTIVE_ANON);
2340 #ifdef CONFIG_HIBERNATION
2342 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2345 * Rather than trying to age LRUs the aim is to preserve the overall
2346 * LRU order by reclaiming preferentially
2347 * inactive > active > active referenced > active mapped
2349 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2351 struct reclaim_state reclaim_state;
2352 struct scan_control sc = {
2353 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2357 .swap_cluster_max = SWAP_CLUSTER_MAX,
2358 .nr_to_reclaim = nr_to_reclaim,
2359 .hibernation_mode = 1,
2360 .swappiness = vm_swappiness,
2362 .isolate_pages = isolate_pages_global,
2364 struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2365 struct task_struct *p = current;
2366 unsigned long nr_reclaimed;
2368 p->flags |= PF_MEMALLOC;
2369 lockdep_set_current_reclaim_state(sc.gfp_mask);
2370 reclaim_state.reclaimed_slab = 0;
2371 p->reclaim_state = &reclaim_state;
2373 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
2375 p->reclaim_state = NULL;
2376 lockdep_clear_current_reclaim_state();
2377 p->flags &= ~PF_MEMALLOC;
2379 return nr_reclaimed;
2381 #endif /* CONFIG_HIBERNATION */
2383 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2384 not required for correctness. So if the last cpu in a node goes
2385 away, we get changed to run anywhere: as the first one comes back,
2386 restore their cpu bindings. */
2387 static int __devinit cpu_callback(struct notifier_block *nfb,
2388 unsigned long action, void *hcpu)
2392 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2393 for_each_node_state(nid, N_HIGH_MEMORY) {
2394 pg_data_t *pgdat = NODE_DATA(nid);
2395 const struct cpumask *mask;
2397 mask = cpumask_of_node(pgdat->node_id);
2399 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2400 /* One of our CPUs online: restore mask */
2401 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2408 * This kswapd start function will be called by init and node-hot-add.
2409 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2411 int kswapd_run(int nid)
2413 pg_data_t *pgdat = NODE_DATA(nid);
2419 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2420 if (IS_ERR(pgdat->kswapd)) {
2421 /* failure at boot is fatal */
2422 BUG_ON(system_state == SYSTEM_BOOTING);
2423 printk("Failed to start kswapd on node %d\n",nid);
2430 * Called by memory hotplug when all memory in a node is offlined.
2432 void kswapd_stop(int nid)
2434 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
2437 kthread_stop(kswapd);
2440 static int __init kswapd_init(void)
2445 for_each_node_state(nid, N_HIGH_MEMORY)
2447 hotcpu_notifier(cpu_callback, 0);
2451 module_init(kswapd_init)
2457 * If non-zero call zone_reclaim when the number of free pages falls below
2460 int zone_reclaim_mode __read_mostly;
2462 #define RECLAIM_OFF 0
2463 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2464 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2465 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2468 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2469 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2472 #define ZONE_RECLAIM_PRIORITY 4
2475 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2478 int sysctl_min_unmapped_ratio = 1;
2481 * If the number of slab pages in a zone grows beyond this percentage then
2482 * slab reclaim needs to occur.
2484 int sysctl_min_slab_ratio = 5;
2486 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
2488 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
2489 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
2490 zone_page_state(zone, NR_ACTIVE_FILE);
2493 * It's possible for there to be more file mapped pages than
2494 * accounted for by the pages on the file LRU lists because
2495 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2497 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
2500 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
2501 static long zone_pagecache_reclaimable(struct zone *zone)
2503 long nr_pagecache_reclaimable;
2507 * If RECLAIM_SWAP is set, then all file pages are considered
2508 * potentially reclaimable. Otherwise, we have to worry about
2509 * pages like swapcache and zone_unmapped_file_pages() provides
2512 if (zone_reclaim_mode & RECLAIM_SWAP)
2513 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
2515 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
2517 /* If we can't clean pages, remove dirty pages from consideration */
2518 if (!(zone_reclaim_mode & RECLAIM_WRITE))
2519 delta += zone_page_state(zone, NR_FILE_DIRTY);
2521 /* Watch for any possible underflows due to delta */
2522 if (unlikely(delta > nr_pagecache_reclaimable))
2523 delta = nr_pagecache_reclaimable;
2525 return nr_pagecache_reclaimable - delta;
2529 * Try to free up some pages from this zone through reclaim.
2531 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2533 /* Minimum pages needed in order to stay on node */
2534 const unsigned long nr_pages = 1 << order;
2535 struct task_struct *p = current;
2536 struct reclaim_state reclaim_state;
2538 struct scan_control sc = {
2539 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2540 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2542 .swap_cluster_max = max_t(unsigned long, nr_pages,
2544 .nr_to_reclaim = max_t(unsigned long, nr_pages,
2546 .gfp_mask = gfp_mask,
2547 .swappiness = vm_swappiness,
2549 .isolate_pages = isolate_pages_global,
2551 unsigned long slab_reclaimable;
2553 disable_swap_token();
2556 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2557 * and we also need to be able to write out pages for RECLAIM_WRITE
2560 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2561 reclaim_state.reclaimed_slab = 0;
2562 p->reclaim_state = &reclaim_state;
2564 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
2566 * Free memory by calling shrink zone with increasing
2567 * priorities until we have enough memory freed.
2569 priority = ZONE_RECLAIM_PRIORITY;
2571 note_zone_scanning_priority(zone, priority);
2572 shrink_zone(priority, zone, &sc);
2574 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2577 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2578 if (slab_reclaimable > zone->min_slab_pages) {
2580 * shrink_slab() does not currently allow us to determine how
2581 * many pages were freed in this zone. So we take the current
2582 * number of slab pages and shake the slab until it is reduced
2583 * by the same nr_pages that we used for reclaiming unmapped
2586 * Note that shrink_slab will free memory on all zones and may
2589 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2590 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2591 slab_reclaimable - nr_pages)
2595 * Update nr_reclaimed by the number of slab pages we
2596 * reclaimed from this zone.
2598 sc.nr_reclaimed += slab_reclaimable -
2599 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2602 p->reclaim_state = NULL;
2603 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2604 return sc.nr_reclaimed >= nr_pages;
2607 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2613 * Zone reclaim reclaims unmapped file backed pages and
2614 * slab pages if we are over the defined limits.
2616 * A small portion of unmapped file backed pages is needed for
2617 * file I/O otherwise pages read by file I/O will be immediately
2618 * thrown out if the zone is overallocated. So we do not reclaim
2619 * if less than a specified percentage of the zone is used by
2620 * unmapped file backed pages.
2622 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
2623 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
2624 return ZONE_RECLAIM_FULL;
2626 if (zone_is_all_unreclaimable(zone))
2627 return ZONE_RECLAIM_FULL;
2630 * Do not scan if the allocation should not be delayed.
2632 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2633 return ZONE_RECLAIM_NOSCAN;
2636 * Only run zone reclaim on the local zone or on zones that do not
2637 * have associated processors. This will favor the local processor
2638 * over remote processors and spread off node memory allocations
2639 * as wide as possible.
2641 node_id = zone_to_nid(zone);
2642 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2643 return ZONE_RECLAIM_NOSCAN;
2645 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2646 return ZONE_RECLAIM_NOSCAN;
2648 ret = __zone_reclaim(zone, gfp_mask, order);
2649 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2652 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
2659 * page_evictable - test whether a page is evictable
2660 * @page: the page to test
2661 * @vma: the VMA in which the page is or will be mapped, may be NULL
2663 * Test whether page is evictable--i.e., should be placed on active/inactive
2664 * lists vs unevictable list. The vma argument is !NULL when called from the
2665 * fault path to determine how to instantate a new page.
2667 * Reasons page might not be evictable:
2668 * (1) page's mapping marked unevictable
2669 * (2) page is part of an mlocked VMA
2672 int page_evictable(struct page *page, struct vm_area_struct *vma)
2675 if (mapping_unevictable(page_mapping(page)))
2678 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2685 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2686 * @page: page to check evictability and move to appropriate lru list
2687 * @zone: zone page is in
2689 * Checks a page for evictability and moves the page to the appropriate
2692 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2693 * have PageUnevictable set.
2695 static void check_move_unevictable_page(struct page *page, struct zone *zone)
2697 VM_BUG_ON(PageActive(page));
2700 ClearPageUnevictable(page);
2701 if (page_evictable(page, NULL)) {
2702 enum lru_list l = page_lru_base_type(page);
2704 __dec_zone_state(zone, NR_UNEVICTABLE);
2705 list_move(&page->lru, &zone->lru[l].list);
2706 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2707 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2708 __count_vm_event(UNEVICTABLE_PGRESCUED);
2711 * rotate unevictable list
2713 SetPageUnevictable(page);
2714 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2715 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
2716 if (page_evictable(page, NULL))
2722 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2723 * @mapping: struct address_space to scan for evictable pages
2725 * Scan all pages in mapping. Check unevictable pages for
2726 * evictability and move them to the appropriate zone lru list.
2728 void scan_mapping_unevictable_pages(struct address_space *mapping)
2731 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2734 struct pagevec pvec;
2736 if (mapping->nrpages == 0)
2739 pagevec_init(&pvec, 0);
2740 while (next < end &&
2741 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2747 for (i = 0; i < pagevec_count(&pvec); i++) {
2748 struct page *page = pvec.pages[i];
2749 pgoff_t page_index = page->index;
2750 struct zone *pagezone = page_zone(page);
2753 if (page_index > next)
2757 if (pagezone != zone) {
2759 spin_unlock_irq(&zone->lru_lock);
2761 spin_lock_irq(&zone->lru_lock);
2764 if (PageLRU(page) && PageUnevictable(page))
2765 check_move_unevictable_page(page, zone);
2768 spin_unlock_irq(&zone->lru_lock);
2769 pagevec_release(&pvec);
2771 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2777 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2778 * @zone - zone of which to scan the unevictable list
2780 * Scan @zone's unevictable LRU lists to check for pages that have become
2781 * evictable. Move those that have to @zone's inactive list where they
2782 * become candidates for reclaim, unless shrink_inactive_zone() decides
2783 * to reactivate them. Pages that are still unevictable are rotated
2784 * back onto @zone's unevictable list.
2786 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2787 static void scan_zone_unevictable_pages(struct zone *zone)
2789 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2791 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2793 while (nr_to_scan > 0) {
2794 unsigned long batch_size = min(nr_to_scan,
2795 SCAN_UNEVICTABLE_BATCH_SIZE);
2797 spin_lock_irq(&zone->lru_lock);
2798 for (scan = 0; scan < batch_size; scan++) {
2799 struct page *page = lru_to_page(l_unevictable);
2801 if (!trylock_page(page))
2804 prefetchw_prev_lru_page(page, l_unevictable, flags);
2806 if (likely(PageLRU(page) && PageUnevictable(page)))
2807 check_move_unevictable_page(page, zone);
2811 spin_unlock_irq(&zone->lru_lock);
2813 nr_to_scan -= batch_size;
2819 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2821 * A really big hammer: scan all zones' unevictable LRU lists to check for
2822 * pages that have become evictable. Move those back to the zones'
2823 * inactive list where they become candidates for reclaim.
2824 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2825 * and we add swap to the system. As such, it runs in the context of a task
2826 * that has possibly/probably made some previously unevictable pages
2829 static void scan_all_zones_unevictable_pages(void)
2833 for_each_zone(zone) {
2834 scan_zone_unevictable_pages(zone);
2839 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2840 * all nodes' unevictable lists for evictable pages
2842 unsigned long scan_unevictable_pages;
2844 int scan_unevictable_handler(struct ctl_table *table, int write,
2845 void __user *buffer,
2846 size_t *length, loff_t *ppos)
2848 proc_doulongvec_minmax(table, write, buffer, length, ppos);
2850 if (write && *(unsigned long *)table->data)
2851 scan_all_zones_unevictable_pages();
2853 scan_unevictable_pages = 0;
2858 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2859 * a specified node's per zone unevictable lists for evictable pages.
2862 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2863 struct sysdev_attribute *attr,
2866 return sprintf(buf, "0\n"); /* always zero; should fit... */
2869 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2870 struct sysdev_attribute *attr,
2871 const char *buf, size_t count)
2873 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2876 unsigned long req = strict_strtoul(buf, 10, &res);
2879 return 1; /* zero is no-op */
2881 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2882 if (!populated_zone(zone))
2884 scan_zone_unevictable_pages(zone);
2890 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2891 read_scan_unevictable_node,
2892 write_scan_unevictable_node);
2894 int scan_unevictable_register_node(struct node *node)
2896 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2899 void scan_unevictable_unregister_node(struct node *node)
2901 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);