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/gfp.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/backing-dev.h>
30 #include <linux/rmap.h>
31 #include <linux/topology.h>
32 #include <linux/cpu.h>
33 #include <linux/cpuset.h>
34 #include <linux/compaction.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>
43 #include <linux/oom.h>
44 #include <linux/prefetch.h>
46 #include <asm/tlbflush.h>
47 #include <asm/div64.h>
49 #include <linux/swapops.h>
53 #define CREATE_TRACE_POINTS
54 #include <trace/events/vmscan.h>
57 /* Incremented by the number of inactive pages that were scanned */
58 unsigned long nr_scanned;
60 /* Number of pages freed so far during a call to shrink_zones() */
61 unsigned long nr_reclaimed;
63 /* How many pages shrink_list() should reclaim */
64 unsigned long nr_to_reclaim;
66 unsigned long hibernation_mode;
68 /* This context's GFP mask */
73 /* Can mapped pages be reclaimed? */
76 /* Can pages be swapped as part of reclaim? */
81 /* Scan (total_size >> priority) pages at once */
85 * The memory cgroup that hit its limit and as a result is the
86 * primary target of this reclaim invocation.
88 struct mem_cgroup *target_mem_cgroup;
91 * Nodemask of nodes allowed by the caller. If NULL, all nodes
97 struct mem_cgroup_zone {
98 struct mem_cgroup *mem_cgroup;
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 static bool global_reclaim(struct scan_control *sc)
144 return !sc->target_mem_cgroup;
147 static bool global_reclaim(struct scan_control *sc)
153 static struct zone_reclaim_stat *get_reclaim_stat(struct mem_cgroup_zone *mz)
155 return &mem_cgroup_zone_lruvec(mz->zone, mz->mem_cgroup)->reclaim_stat;
158 static unsigned long get_lruvec_size(struct lruvec *lruvec, enum lru_list lru)
160 if (!mem_cgroup_disabled())
161 return mem_cgroup_get_lruvec_size(lruvec, lru);
163 return zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru);
167 * Add a shrinker callback to be called from the vm
169 void register_shrinker(struct shrinker *shrinker)
171 atomic_long_set(&shrinker->nr_in_batch, 0);
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 static inline int do_shrinker_shrink(struct shrinker *shrinker,
190 struct shrink_control *sc,
191 unsigned long nr_to_scan)
193 sc->nr_to_scan = nr_to_scan;
194 return (*shrinker->shrink)(shrinker, sc);
197 #define SHRINK_BATCH 128
199 * Call the shrink functions to age shrinkable caches
201 * Here we assume it costs one seek to replace a lru page and that it also
202 * takes a seek to recreate a cache object. With this in mind we age equal
203 * percentages of the lru and ageable caches. This should balance the seeks
204 * generated by these structures.
206 * If the vm encountered mapped pages on the LRU it increase the pressure on
207 * slab to avoid swapping.
209 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
211 * `lru_pages' represents the number of on-LRU pages in all the zones which
212 * are eligible for the caller's allocation attempt. It is used for balancing
213 * slab reclaim versus page reclaim.
215 * Returns the number of slab objects which we shrunk.
217 unsigned long shrink_slab(struct shrink_control *shrink,
218 unsigned long nr_pages_scanned,
219 unsigned long lru_pages)
221 struct shrinker *shrinker;
222 unsigned long ret = 0;
224 if (nr_pages_scanned == 0)
225 nr_pages_scanned = SWAP_CLUSTER_MAX;
227 if (!down_read_trylock(&shrinker_rwsem)) {
228 /* Assume we'll be able to shrink next time */
233 list_for_each_entry(shrinker, &shrinker_list, list) {
234 unsigned long long delta;
240 long batch_size = shrinker->batch ? shrinker->batch
243 max_pass = do_shrinker_shrink(shrinker, shrink, 0);
248 * copy the current shrinker scan count into a local variable
249 * and zero it so that other concurrent shrinker invocations
250 * don't also do this scanning work.
252 nr = atomic_long_xchg(&shrinker->nr_in_batch, 0);
255 delta = (4 * nr_pages_scanned) / shrinker->seeks;
257 do_div(delta, lru_pages + 1);
259 if (total_scan < 0) {
260 printk(KERN_ERR "shrink_slab: %pF negative objects to "
262 shrinker->shrink, total_scan);
263 total_scan = max_pass;
267 * We need to avoid excessive windup on filesystem shrinkers
268 * due to large numbers of GFP_NOFS allocations causing the
269 * shrinkers to return -1 all the time. This results in a large
270 * nr being built up so when a shrink that can do some work
271 * comes along it empties the entire cache due to nr >>>
272 * max_pass. This is bad for sustaining a working set in
275 * Hence only allow the shrinker to scan the entire cache when
276 * a large delta change is calculated directly.
278 if (delta < max_pass / 4)
279 total_scan = min(total_scan, max_pass / 2);
282 * Avoid risking looping forever due to too large nr value:
283 * never try to free more than twice the estimate number of
286 if (total_scan > max_pass * 2)
287 total_scan = max_pass * 2;
289 trace_mm_shrink_slab_start(shrinker, shrink, nr,
290 nr_pages_scanned, lru_pages,
291 max_pass, delta, total_scan);
293 while (total_scan >= batch_size) {
296 nr_before = do_shrinker_shrink(shrinker, shrink, 0);
297 shrink_ret = do_shrinker_shrink(shrinker, shrink,
299 if (shrink_ret == -1)
301 if (shrink_ret < nr_before)
302 ret += nr_before - shrink_ret;
303 count_vm_events(SLABS_SCANNED, batch_size);
304 total_scan -= batch_size;
310 * move the unused scan count back into the shrinker in a
311 * manner that handles concurrent updates. If we exhausted the
312 * scan, there is no need to do an update.
315 new_nr = atomic_long_add_return(total_scan,
316 &shrinker->nr_in_batch);
318 new_nr = atomic_long_read(&shrinker->nr_in_batch);
320 trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr);
322 up_read(&shrinker_rwsem);
328 static inline int is_page_cache_freeable(struct page *page)
331 * A freeable page cache page is referenced only by the caller
332 * that isolated the page, the page cache radix tree and
333 * optional buffer heads at page->private.
335 return page_count(page) - page_has_private(page) == 2;
338 static int may_write_to_queue(struct backing_dev_info *bdi,
339 struct scan_control *sc)
341 if (current->flags & PF_SWAPWRITE)
343 if (!bdi_write_congested(bdi))
345 if (bdi == current->backing_dev_info)
351 * We detected a synchronous write error writing a page out. Probably
352 * -ENOSPC. We need to propagate that into the address_space for a subsequent
353 * fsync(), msync() or close().
355 * The tricky part is that after writepage we cannot touch the mapping: nothing
356 * prevents it from being freed up. But we have a ref on the page and once
357 * that page is locked, the mapping is pinned.
359 * We're allowed to run sleeping lock_page() here because we know the caller has
362 static void handle_write_error(struct address_space *mapping,
363 struct page *page, int error)
366 if (page_mapping(page) == mapping)
367 mapping_set_error(mapping, error);
371 /* possible outcome of pageout() */
373 /* failed to write page out, page is locked */
375 /* move page to the active list, page is locked */
377 /* page has been sent to the disk successfully, page is unlocked */
379 /* page is clean and locked */
384 * pageout is called by shrink_page_list() for each dirty page.
385 * Calls ->writepage().
387 static pageout_t pageout(struct page *page, struct address_space *mapping,
388 struct scan_control *sc)
391 * If the page is dirty, only perform writeback if that write
392 * will be non-blocking. To prevent this allocation from being
393 * stalled by pagecache activity. But note that there may be
394 * stalls if we need to run get_block(). We could test
395 * PagePrivate for that.
397 * If this process is currently in __generic_file_aio_write() against
398 * this page's queue, we can perform writeback even if that
401 * If the page is swapcache, write it back even if that would
402 * block, for some throttling. This happens by accident, because
403 * swap_backing_dev_info is bust: it doesn't reflect the
404 * congestion state of the swapdevs. Easy to fix, if needed.
406 if (!is_page_cache_freeable(page))
410 * Some data journaling orphaned pages can have
411 * page->mapping == NULL while being dirty with clean buffers.
413 if (page_has_private(page)) {
414 if (try_to_free_buffers(page)) {
415 ClearPageDirty(page);
416 printk("%s: orphaned page\n", __func__);
422 if (mapping->a_ops->writepage == NULL)
423 return PAGE_ACTIVATE;
424 if (!may_write_to_queue(mapping->backing_dev_info, sc))
427 if (clear_page_dirty_for_io(page)) {
429 struct writeback_control wbc = {
430 .sync_mode = WB_SYNC_NONE,
431 .nr_to_write = SWAP_CLUSTER_MAX,
433 .range_end = LLONG_MAX,
437 SetPageReclaim(page);
438 res = mapping->a_ops->writepage(page, &wbc);
440 handle_write_error(mapping, page, res);
441 if (res == AOP_WRITEPAGE_ACTIVATE) {
442 ClearPageReclaim(page);
443 return PAGE_ACTIVATE;
446 if (!PageWriteback(page)) {
447 /* synchronous write or broken a_ops? */
448 ClearPageReclaim(page);
450 trace_mm_vmscan_writepage(page, trace_reclaim_flags(page));
451 inc_zone_page_state(page, NR_VMSCAN_WRITE);
459 * Same as remove_mapping, but if the page is removed from the mapping, it
460 * gets returned with a refcount of 0.
462 static int __remove_mapping(struct address_space *mapping, struct page *page)
464 BUG_ON(!PageLocked(page));
465 BUG_ON(mapping != page_mapping(page));
467 spin_lock_irq(&mapping->tree_lock);
469 * The non racy check for a busy page.
471 * Must be careful with the order of the tests. When someone has
472 * a ref to the page, it may be possible that they dirty it then
473 * drop the reference. So if PageDirty is tested before page_count
474 * here, then the following race may occur:
476 * get_user_pages(&page);
477 * [user mapping goes away]
479 * !PageDirty(page) [good]
480 * SetPageDirty(page);
482 * !page_count(page) [good, discard it]
484 * [oops, our write_to data is lost]
486 * Reversing the order of the tests ensures such a situation cannot
487 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
488 * load is not satisfied before that of page->_count.
490 * Note that if SetPageDirty is always performed via set_page_dirty,
491 * and thus under tree_lock, then this ordering is not required.
493 if (!page_freeze_refs(page, 2))
495 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
496 if (unlikely(PageDirty(page))) {
497 page_unfreeze_refs(page, 2);
501 if (PageSwapCache(page)) {
502 swp_entry_t swap = { .val = page_private(page) };
503 __delete_from_swap_cache(page);
504 spin_unlock_irq(&mapping->tree_lock);
505 swapcache_free(swap, page);
507 void (*freepage)(struct page *);
509 freepage = mapping->a_ops->freepage;
511 __delete_from_page_cache(page);
512 spin_unlock_irq(&mapping->tree_lock);
513 mem_cgroup_uncharge_cache_page(page);
515 if (freepage != NULL)
522 spin_unlock_irq(&mapping->tree_lock);
527 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
528 * someone else has a ref on the page, abort and return 0. If it was
529 * successfully detached, return 1. Assumes the caller has a single ref on
532 int remove_mapping(struct address_space *mapping, struct page *page)
534 if (__remove_mapping(mapping, page)) {
536 * Unfreezing the refcount with 1 rather than 2 effectively
537 * drops the pagecache ref for us without requiring another
540 page_unfreeze_refs(page, 1);
547 * putback_lru_page - put previously isolated page onto appropriate LRU list
548 * @page: page to be put back to appropriate lru list
550 * Add previously isolated @page to appropriate LRU list.
551 * Page may still be unevictable for other reasons.
553 * lru_lock must not be held, interrupts must be enabled.
555 void putback_lru_page(struct page *page)
558 int active = !!TestClearPageActive(page);
559 int was_unevictable = PageUnevictable(page);
561 VM_BUG_ON(PageLRU(page));
564 ClearPageUnevictable(page);
566 if (page_evictable(page, NULL)) {
568 * For evictable pages, we can use the cache.
569 * In event of a race, worst case is we end up with an
570 * unevictable page on [in]active list.
571 * We know how to handle that.
573 lru = active + page_lru_base_type(page);
574 lru_cache_add_lru(page, lru);
577 * Put unevictable pages directly on zone's unevictable
580 lru = LRU_UNEVICTABLE;
581 add_page_to_unevictable_list(page);
583 * When racing with an mlock or AS_UNEVICTABLE clearing
584 * (page is unlocked) make sure that if the other thread
585 * does not observe our setting of PG_lru and fails
586 * isolation/check_move_unevictable_pages,
587 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
588 * the page back to the evictable list.
590 * The other side is TestClearPageMlocked() or shmem_lock().
596 * page's status can change while we move it among lru. If an evictable
597 * page is on unevictable list, it never be freed. To avoid that,
598 * check after we added it to the list, again.
600 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
601 if (!isolate_lru_page(page)) {
605 /* This means someone else dropped this page from LRU
606 * So, it will be freed or putback to LRU again. There is
607 * nothing to do here.
611 if (was_unevictable && lru != LRU_UNEVICTABLE)
612 count_vm_event(UNEVICTABLE_PGRESCUED);
613 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
614 count_vm_event(UNEVICTABLE_PGCULLED);
616 put_page(page); /* drop ref from isolate */
619 enum page_references {
621 PAGEREF_RECLAIM_CLEAN,
626 static enum page_references page_check_references(struct page *page,
627 struct scan_control *sc)
629 int referenced_ptes, referenced_page;
630 unsigned long vm_flags;
632 referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup,
634 referenced_page = TestClearPageReferenced(page);
637 * Mlock lost the isolation race with us. Let try_to_unmap()
638 * move the page to the unevictable list.
640 if (vm_flags & VM_LOCKED)
641 return PAGEREF_RECLAIM;
643 if (referenced_ptes) {
644 if (PageSwapBacked(page))
645 return PAGEREF_ACTIVATE;
647 * All mapped pages start out with page table
648 * references from the instantiating fault, so we need
649 * to look twice if a mapped file page is used more
652 * Mark it and spare it for another trip around the
653 * inactive list. Another page table reference will
654 * lead to its activation.
656 * Note: the mark is set for activated pages as well
657 * so that recently deactivated but used pages are
660 SetPageReferenced(page);
662 if (referenced_page || referenced_ptes > 1)
663 return PAGEREF_ACTIVATE;
666 * Activate file-backed executable pages after first usage.
668 if (vm_flags & VM_EXEC)
669 return PAGEREF_ACTIVATE;
674 /* Reclaim if clean, defer dirty pages to writeback */
675 if (referenced_page && !PageSwapBacked(page))
676 return PAGEREF_RECLAIM_CLEAN;
678 return PAGEREF_RECLAIM;
682 * shrink_page_list() returns the number of reclaimed pages
684 static unsigned long shrink_page_list(struct list_head *page_list,
686 struct scan_control *sc,
687 unsigned long *ret_nr_dirty,
688 unsigned long *ret_nr_writeback)
690 LIST_HEAD(ret_pages);
691 LIST_HEAD(free_pages);
693 unsigned long nr_dirty = 0;
694 unsigned long nr_congested = 0;
695 unsigned long nr_reclaimed = 0;
696 unsigned long nr_writeback = 0;
700 while (!list_empty(page_list)) {
701 enum page_references references;
702 struct address_space *mapping;
708 page = lru_to_page(page_list);
709 list_del(&page->lru);
711 if (!trylock_page(page))
714 VM_BUG_ON(PageActive(page));
715 VM_BUG_ON(page_zone(page) != zone);
719 if (unlikely(!page_evictable(page, NULL)))
722 if (!sc->may_unmap && page_mapped(page))
725 /* Double the slab pressure for mapped and swapcache pages */
726 if (page_mapped(page) || PageSwapCache(page))
729 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
730 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
732 if (PageWriteback(page)) {
738 references = page_check_references(page, sc);
739 switch (references) {
740 case PAGEREF_ACTIVATE:
741 goto activate_locked;
744 case PAGEREF_RECLAIM:
745 case PAGEREF_RECLAIM_CLEAN:
746 ; /* try to reclaim the page below */
750 * Anonymous process memory has backing store?
751 * Try to allocate it some swap space here.
753 if (PageAnon(page) && !PageSwapCache(page)) {
754 if (!(sc->gfp_mask & __GFP_IO))
756 if (!add_to_swap(page))
757 goto activate_locked;
761 mapping = page_mapping(page);
764 * The page is mapped into the page tables of one or more
765 * processes. Try to unmap it here.
767 if (page_mapped(page) && mapping) {
768 switch (try_to_unmap(page, TTU_UNMAP)) {
770 goto activate_locked;
776 ; /* try to free the page below */
780 if (PageDirty(page)) {
784 * Only kswapd can writeback filesystem pages to
785 * avoid risk of stack overflow but do not writeback
786 * unless under significant pressure.
788 if (page_is_file_cache(page) &&
789 (!current_is_kswapd() ||
790 sc->priority >= DEF_PRIORITY - 2)) {
792 * Immediately reclaim when written back.
793 * Similar in principal to deactivate_page()
794 * except we already have the page isolated
795 * and know it's dirty
797 inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
798 SetPageReclaim(page);
803 if (references == PAGEREF_RECLAIM_CLEAN)
807 if (!sc->may_writepage)
810 /* Page is dirty, try to write it out here */
811 switch (pageout(page, mapping, sc)) {
816 goto activate_locked;
818 if (PageWriteback(page))
824 * A synchronous write - probably a ramdisk. Go
825 * ahead and try to reclaim the page.
827 if (!trylock_page(page))
829 if (PageDirty(page) || PageWriteback(page))
831 mapping = page_mapping(page);
833 ; /* try to free the page below */
838 * If the page has buffers, try to free the buffer mappings
839 * associated with this page. If we succeed we try to free
842 * We do this even if the page is PageDirty().
843 * try_to_release_page() does not perform I/O, but it is
844 * possible for a page to have PageDirty set, but it is actually
845 * clean (all its buffers are clean). This happens if the
846 * buffers were written out directly, with submit_bh(). ext3
847 * will do this, as well as the blockdev mapping.
848 * try_to_release_page() will discover that cleanness and will
849 * drop the buffers and mark the page clean - it can be freed.
851 * Rarely, pages can have buffers and no ->mapping. These are
852 * the pages which were not successfully invalidated in
853 * truncate_complete_page(). We try to drop those buffers here
854 * and if that worked, and the page is no longer mapped into
855 * process address space (page_count == 1) it can be freed.
856 * Otherwise, leave the page on the LRU so it is swappable.
858 if (page_has_private(page)) {
859 if (!try_to_release_page(page, sc->gfp_mask))
860 goto activate_locked;
861 if (!mapping && page_count(page) == 1) {
863 if (put_page_testzero(page))
867 * rare race with speculative reference.
868 * the speculative reference will free
869 * this page shortly, so we may
870 * increment nr_reclaimed here (and
871 * leave it off the LRU).
879 if (!mapping || !__remove_mapping(mapping, page))
883 * At this point, we have no other references and there is
884 * no way to pick any more up (removed from LRU, removed
885 * from pagecache). Can use non-atomic bitops now (and
886 * we obviously don't have to worry about waking up a process
887 * waiting on the page lock, because there are no references.
889 __clear_page_locked(page);
894 * Is there need to periodically free_page_list? It would
895 * appear not as the counts should be low
897 list_add(&page->lru, &free_pages);
901 if (PageSwapCache(page))
902 try_to_free_swap(page);
904 putback_lru_page(page);
908 /* Not a candidate for swapping, so reclaim swap space. */
909 if (PageSwapCache(page) && vm_swap_full())
910 try_to_free_swap(page);
911 VM_BUG_ON(PageActive(page));
917 list_add(&page->lru, &ret_pages);
918 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
922 * Tag a zone as congested if all the dirty pages encountered were
923 * backed by a congested BDI. In this case, reclaimers should just
924 * back off and wait for congestion to clear because further reclaim
925 * will encounter the same problem
927 if (nr_dirty && nr_dirty == nr_congested && global_reclaim(sc))
928 zone_set_flag(zone, ZONE_CONGESTED);
930 free_hot_cold_page_list(&free_pages, 1);
932 list_splice(&ret_pages, page_list);
933 count_vm_events(PGACTIVATE, pgactivate);
934 *ret_nr_dirty += nr_dirty;
935 *ret_nr_writeback += nr_writeback;
940 * Attempt to remove the specified page from its LRU. Only take this page
941 * if it is of the appropriate PageActive status. Pages which are being
942 * freed elsewhere are also ignored.
944 * page: page to consider
945 * mode: one of the LRU isolation modes defined above
947 * returns 0 on success, -ve errno on failure.
949 int __isolate_lru_page(struct page *page, isolate_mode_t mode)
953 /* Only take pages on the LRU. */
957 /* Do not give back unevictable pages for compaction */
958 if (PageUnevictable(page))
964 * To minimise LRU disruption, the caller can indicate that it only
965 * wants to isolate pages it will be able to operate on without
966 * blocking - clean pages for the most part.
968 * ISOLATE_CLEAN means that only clean pages should be isolated. This
969 * is used by reclaim when it is cannot write to backing storage
971 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
972 * that it is possible to migrate without blocking
974 if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
975 /* All the caller can do on PageWriteback is block */
976 if (PageWriteback(page))
979 if (PageDirty(page)) {
980 struct address_space *mapping;
982 /* ISOLATE_CLEAN means only clean pages */
983 if (mode & ISOLATE_CLEAN)
987 * Only pages without mappings or that have a
988 * ->migratepage callback are possible to migrate
991 mapping = page_mapping(page);
992 if (mapping && !mapping->a_ops->migratepage)
997 if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
1000 if (likely(get_page_unless_zero(page))) {
1002 * Be careful not to clear PageLRU until after we're
1003 * sure the page is not being freed elsewhere -- the
1004 * page release code relies on it.
1014 * zone->lru_lock is heavily contended. Some of the functions that
1015 * shrink the lists perform better by taking out a batch of pages
1016 * and working on them outside the LRU lock.
1018 * For pagecache intensive workloads, this function is the hottest
1019 * spot in the kernel (apart from copy_*_user functions).
1021 * Appropriate locks must be held before calling this function.
1023 * @nr_to_scan: The number of pages to look through on the list.
1024 * @lruvec: The LRU vector to pull pages from.
1025 * @dst: The temp list to put pages on to.
1026 * @nr_scanned: The number of pages that were scanned.
1027 * @sc: The scan_control struct for this reclaim session
1028 * @mode: One of the LRU isolation modes
1029 * @lru: LRU list id for isolating
1031 * returns how many pages were moved onto *@dst.
1033 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1034 struct lruvec *lruvec, struct list_head *dst,
1035 unsigned long *nr_scanned, struct scan_control *sc,
1036 isolate_mode_t mode, enum lru_list lru)
1038 struct list_head *src;
1039 unsigned long nr_taken = 0;
1041 int file = is_file_lru(lru);
1043 src = &lruvec->lists[lru];
1045 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
1048 page = lru_to_page(src);
1049 prefetchw_prev_lru_page(page, src, flags);
1051 VM_BUG_ON(!PageLRU(page));
1053 switch (__isolate_lru_page(page, mode)) {
1055 mem_cgroup_lru_del_list(page, lru);
1056 list_move(&page->lru, dst);
1057 nr_taken += hpage_nr_pages(page);
1061 /* else it is being freed elsewhere */
1062 list_move(&page->lru, src);
1072 trace_mm_vmscan_lru_isolate(sc->order,
1080 * isolate_lru_page - tries to isolate a page from its LRU list
1081 * @page: page to isolate from its LRU list
1083 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1084 * vmstat statistic corresponding to whatever LRU list the page was on.
1086 * Returns 0 if the page was removed from an LRU list.
1087 * Returns -EBUSY if the page was not on an LRU list.
1089 * The returned page will have PageLRU() cleared. If it was found on
1090 * the active list, it will have PageActive set. If it was found on
1091 * the unevictable list, it will have the PageUnevictable bit set. That flag
1092 * may need to be cleared by the caller before letting the page go.
1094 * The vmstat statistic corresponding to the list on which the page was
1095 * found will be decremented.
1098 * (1) Must be called with an elevated refcount on the page. This is a
1099 * fundamentnal difference from isolate_lru_pages (which is called
1100 * without a stable reference).
1101 * (2) the lru_lock must not be held.
1102 * (3) interrupts must be enabled.
1104 int isolate_lru_page(struct page *page)
1108 VM_BUG_ON(!page_count(page));
1110 if (PageLRU(page)) {
1111 struct zone *zone = page_zone(page);
1113 spin_lock_irq(&zone->lru_lock);
1114 if (PageLRU(page)) {
1115 int lru = page_lru(page);
1120 del_page_from_lru_list(zone, page, lru);
1122 spin_unlock_irq(&zone->lru_lock);
1128 * Are there way too many processes in the direct reclaim path already?
1130 static int too_many_isolated(struct zone *zone, int file,
1131 struct scan_control *sc)
1133 unsigned long inactive, isolated;
1135 if (current_is_kswapd())
1138 if (!global_reclaim(sc))
1142 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1143 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1145 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1146 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1149 return isolated > inactive;
1152 static noinline_for_stack void
1153 putback_inactive_pages(struct lruvec *lruvec,
1154 struct list_head *page_list)
1156 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
1157 struct zone *zone = lruvec_zone(lruvec);
1158 LIST_HEAD(pages_to_free);
1161 * Put back any unfreeable pages.
1163 while (!list_empty(page_list)) {
1164 struct page *page = lru_to_page(page_list);
1167 VM_BUG_ON(PageLRU(page));
1168 list_del(&page->lru);
1169 if (unlikely(!page_evictable(page, NULL))) {
1170 spin_unlock_irq(&zone->lru_lock);
1171 putback_lru_page(page);
1172 spin_lock_irq(&zone->lru_lock);
1176 lru = page_lru(page);
1177 add_page_to_lru_list(zone, page, lru);
1178 if (is_active_lru(lru)) {
1179 int file = is_file_lru(lru);
1180 int numpages = hpage_nr_pages(page);
1181 reclaim_stat->recent_rotated[file] += numpages;
1183 if (put_page_testzero(page)) {
1184 __ClearPageLRU(page);
1185 __ClearPageActive(page);
1186 del_page_from_lru_list(zone, page, lru);
1188 if (unlikely(PageCompound(page))) {
1189 spin_unlock_irq(&zone->lru_lock);
1190 (*get_compound_page_dtor(page))(page);
1191 spin_lock_irq(&zone->lru_lock);
1193 list_add(&page->lru, &pages_to_free);
1198 * To save our caller's stack, now use input list for pages to free.
1200 list_splice(&pages_to_free, page_list);
1204 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1205 * of reclaimed pages
1207 static noinline_for_stack unsigned long
1208 shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz,
1209 struct scan_control *sc, enum lru_list lru)
1211 LIST_HEAD(page_list);
1212 unsigned long nr_scanned;
1213 unsigned long nr_reclaimed = 0;
1214 unsigned long nr_taken;
1215 unsigned long nr_dirty = 0;
1216 unsigned long nr_writeback = 0;
1217 isolate_mode_t isolate_mode = 0;
1218 int file = is_file_lru(lru);
1219 struct zone *zone = mz->zone;
1220 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1221 struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, mz->mem_cgroup);
1223 while (unlikely(too_many_isolated(zone, file, sc))) {
1224 congestion_wait(BLK_RW_ASYNC, HZ/10);
1226 /* We are about to die and free our memory. Return now. */
1227 if (fatal_signal_pending(current))
1228 return SWAP_CLUSTER_MAX;
1234 isolate_mode |= ISOLATE_UNMAPPED;
1235 if (!sc->may_writepage)
1236 isolate_mode |= ISOLATE_CLEAN;
1238 spin_lock_irq(&zone->lru_lock);
1240 nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list,
1241 &nr_scanned, sc, isolate_mode, lru);
1243 __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
1244 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1246 if (global_reclaim(sc)) {
1247 zone->pages_scanned += nr_scanned;
1248 if (current_is_kswapd())
1249 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1252 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1255 spin_unlock_irq(&zone->lru_lock);
1260 nr_reclaimed = shrink_page_list(&page_list, zone, sc,
1261 &nr_dirty, &nr_writeback);
1263 spin_lock_irq(&zone->lru_lock);
1265 reclaim_stat->recent_scanned[file] += nr_taken;
1267 if (global_reclaim(sc)) {
1268 if (current_is_kswapd())
1269 __count_zone_vm_events(PGSTEAL_KSWAPD, zone,
1272 __count_zone_vm_events(PGSTEAL_DIRECT, zone,
1276 putback_inactive_pages(lruvec, &page_list);
1278 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1280 spin_unlock_irq(&zone->lru_lock);
1282 free_hot_cold_page_list(&page_list, 1);
1285 * If reclaim is isolating dirty pages under writeback, it implies
1286 * that the long-lived page allocation rate is exceeding the page
1287 * laundering rate. Either the global limits are not being effective
1288 * at throttling processes due to the page distribution throughout
1289 * zones or there is heavy usage of a slow backing device. The
1290 * only option is to throttle from reclaim context which is not ideal
1291 * as there is no guarantee the dirtying process is throttled in the
1292 * same way balance_dirty_pages() manages.
1294 * This scales the number of dirty pages that must be under writeback
1295 * before throttling depending on priority. It is a simple backoff
1296 * function that has the most effect in the range DEF_PRIORITY to
1297 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
1298 * in trouble and reclaim is considered to be in trouble.
1300 * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle
1301 * DEF_PRIORITY-1 50% must be PageWriteback
1302 * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble
1304 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
1305 * isolated page is PageWriteback
1307 if (nr_writeback && nr_writeback >=
1308 (nr_taken >> (DEF_PRIORITY - sc->priority)))
1309 wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
1311 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1313 nr_scanned, nr_reclaimed,
1315 trace_shrink_flags(file));
1316 return nr_reclaimed;
1320 * This moves pages from the active list to the inactive list.
1322 * We move them the other way if the page is referenced by one or more
1323 * processes, from rmap.
1325 * If the pages are mostly unmapped, the processing is fast and it is
1326 * appropriate to hold zone->lru_lock across the whole operation. But if
1327 * the pages are mapped, the processing is slow (page_referenced()) so we
1328 * should drop zone->lru_lock around each page. It's impossible to balance
1329 * this, so instead we remove the pages from the LRU while processing them.
1330 * It is safe to rely on PG_active against the non-LRU pages in here because
1331 * nobody will play with that bit on a non-LRU page.
1333 * The downside is that we have to touch page->_count against each page.
1334 * But we had to alter page->flags anyway.
1337 static void move_active_pages_to_lru(struct zone *zone,
1338 struct list_head *list,
1339 struct list_head *pages_to_free,
1342 unsigned long pgmoved = 0;
1345 while (!list_empty(list)) {
1346 struct lruvec *lruvec;
1348 page = lru_to_page(list);
1350 VM_BUG_ON(PageLRU(page));
1353 lruvec = mem_cgroup_lru_add_list(zone, page, lru);
1354 list_move(&page->lru, &lruvec->lists[lru]);
1355 pgmoved += hpage_nr_pages(page);
1357 if (put_page_testzero(page)) {
1358 __ClearPageLRU(page);
1359 __ClearPageActive(page);
1360 del_page_from_lru_list(zone, page, lru);
1362 if (unlikely(PageCompound(page))) {
1363 spin_unlock_irq(&zone->lru_lock);
1364 (*get_compound_page_dtor(page))(page);
1365 spin_lock_irq(&zone->lru_lock);
1367 list_add(&page->lru, pages_to_free);
1370 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1371 if (!is_active_lru(lru))
1372 __count_vm_events(PGDEACTIVATE, pgmoved);
1375 static void shrink_active_list(unsigned long nr_to_scan,
1376 struct mem_cgroup_zone *mz,
1377 struct scan_control *sc,
1380 unsigned long nr_taken;
1381 unsigned long nr_scanned;
1382 unsigned long vm_flags;
1383 LIST_HEAD(l_hold); /* The pages which were snipped off */
1384 LIST_HEAD(l_active);
1385 LIST_HEAD(l_inactive);
1387 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1388 unsigned long nr_rotated = 0;
1389 isolate_mode_t isolate_mode = 0;
1390 int file = is_file_lru(lru);
1391 struct zone *zone = mz->zone;
1392 struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, mz->mem_cgroup);
1397 isolate_mode |= ISOLATE_UNMAPPED;
1398 if (!sc->may_writepage)
1399 isolate_mode |= ISOLATE_CLEAN;
1401 spin_lock_irq(&zone->lru_lock);
1403 nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold,
1404 &nr_scanned, sc, isolate_mode, lru);
1405 if (global_reclaim(sc))
1406 zone->pages_scanned += nr_scanned;
1408 reclaim_stat->recent_scanned[file] += nr_taken;
1410 __count_zone_vm_events(PGREFILL, zone, nr_scanned);
1411 __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
1412 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1413 spin_unlock_irq(&zone->lru_lock);
1415 while (!list_empty(&l_hold)) {
1417 page = lru_to_page(&l_hold);
1418 list_del(&page->lru);
1420 if (unlikely(!page_evictable(page, NULL))) {
1421 putback_lru_page(page);
1425 if (unlikely(buffer_heads_over_limit)) {
1426 if (page_has_private(page) && trylock_page(page)) {
1427 if (page_has_private(page))
1428 try_to_release_page(page, 0);
1433 if (page_referenced(page, 0, sc->target_mem_cgroup,
1435 nr_rotated += hpage_nr_pages(page);
1437 * Identify referenced, file-backed active pages and
1438 * give them one more trip around the active list. So
1439 * that executable code get better chances to stay in
1440 * memory under moderate memory pressure. Anon pages
1441 * are not likely to be evicted by use-once streaming
1442 * IO, plus JVM can create lots of anon VM_EXEC pages,
1443 * so we ignore them here.
1445 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1446 list_add(&page->lru, &l_active);
1451 ClearPageActive(page); /* we are de-activating */
1452 list_add(&page->lru, &l_inactive);
1456 * Move pages back to the lru list.
1458 spin_lock_irq(&zone->lru_lock);
1460 * Count referenced pages from currently used mappings as rotated,
1461 * even though only some of them are actually re-activated. This
1462 * helps balance scan pressure between file and anonymous pages in
1465 reclaim_stat->recent_rotated[file] += nr_rotated;
1467 move_active_pages_to_lru(zone, &l_active, &l_hold, lru);
1468 move_active_pages_to_lru(zone, &l_inactive, &l_hold, lru - LRU_ACTIVE);
1469 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1470 spin_unlock_irq(&zone->lru_lock);
1472 free_hot_cold_page_list(&l_hold, 1);
1476 static int inactive_anon_is_low_global(struct zone *zone)
1478 unsigned long active, inactive;
1480 active = zone_page_state(zone, NR_ACTIVE_ANON);
1481 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1483 if (inactive * zone->inactive_ratio < active)
1490 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1491 * @zone: zone to check
1492 * @sc: scan control of this context
1494 * Returns true if the zone does not have enough inactive anon pages,
1495 * meaning some active anon pages need to be deactivated.
1497 static int inactive_anon_is_low(struct mem_cgroup_zone *mz)
1500 * If we don't have swap space, anonymous page deactivation
1503 if (!total_swap_pages)
1506 if (!mem_cgroup_disabled())
1507 return mem_cgroup_inactive_anon_is_low(mz->mem_cgroup,
1510 return inactive_anon_is_low_global(mz->zone);
1513 static inline int inactive_anon_is_low(struct mem_cgroup_zone *mz)
1519 static int inactive_file_is_low_global(struct zone *zone)
1521 unsigned long active, inactive;
1523 active = zone_page_state(zone, NR_ACTIVE_FILE);
1524 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1526 return (active > inactive);
1530 * inactive_file_is_low - check if file pages need to be deactivated
1531 * @mz: memory cgroup and zone to check
1533 * When the system is doing streaming IO, memory pressure here
1534 * ensures that active file pages get deactivated, until more
1535 * than half of the file pages are on the inactive list.
1537 * Once we get to that situation, protect the system's working
1538 * set from being evicted by disabling active file page aging.
1540 * This uses a different ratio than the anonymous pages, because
1541 * the page cache uses a use-once replacement algorithm.
1543 static int inactive_file_is_low(struct mem_cgroup_zone *mz)
1545 if (!mem_cgroup_disabled())
1546 return mem_cgroup_inactive_file_is_low(mz->mem_cgroup,
1549 return inactive_file_is_low_global(mz->zone);
1552 static int inactive_list_is_low(struct mem_cgroup_zone *mz, int file)
1555 return inactive_file_is_low(mz);
1557 return inactive_anon_is_low(mz);
1560 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1561 struct mem_cgroup_zone *mz,
1562 struct scan_control *sc)
1564 int file = is_file_lru(lru);
1566 if (is_active_lru(lru)) {
1567 if (inactive_list_is_low(mz, file))
1568 shrink_active_list(nr_to_scan, mz, sc, lru);
1572 return shrink_inactive_list(nr_to_scan, mz, sc, lru);
1575 static int vmscan_swappiness(struct scan_control *sc)
1577 if (global_reclaim(sc))
1578 return vm_swappiness;
1579 return mem_cgroup_swappiness(sc->target_mem_cgroup);
1583 * Determine how aggressively the anon and file LRU lists should be
1584 * scanned. The relative value of each set of LRU lists is determined
1585 * by looking at the fraction of the pages scanned we did rotate back
1586 * onto the active list instead of evict.
1588 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1590 static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
1593 unsigned long anon, file, free;
1594 unsigned long anon_prio, file_prio;
1595 unsigned long ap, fp;
1596 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1597 u64 fraction[2], denominator;
1600 bool force_scan = false;
1601 struct lruvec *lruvec;
1603 lruvec = mem_cgroup_zone_lruvec(mz->zone, mz->mem_cgroup);
1606 * If the zone or memcg is small, nr[l] can be 0. This
1607 * results in no scanning on this priority and a potential
1608 * priority drop. Global direct reclaim can go to the next
1609 * zone and tends to have no problems. Global kswapd is for
1610 * zone balancing and it needs to scan a minimum amount. When
1611 * reclaiming for a memcg, a priority drop can cause high
1612 * latencies, so it's better to scan a minimum amount there as
1615 if (current_is_kswapd() && mz->zone->all_unreclaimable)
1617 if (!global_reclaim(sc))
1620 /* If we have no swap space, do not bother scanning anon pages. */
1621 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1629 anon = get_lruvec_size(lruvec, LRU_ACTIVE_ANON) +
1630 get_lruvec_size(lruvec, LRU_INACTIVE_ANON);
1631 file = get_lruvec_size(lruvec, LRU_ACTIVE_FILE) +
1632 get_lruvec_size(lruvec, LRU_INACTIVE_FILE);
1634 if (global_reclaim(sc)) {
1635 free = zone_page_state(mz->zone, NR_FREE_PAGES);
1636 /* If we have very few page cache pages,
1637 force-scan anon pages. */
1638 if (unlikely(file + free <= high_wmark_pages(mz->zone))) {
1647 * With swappiness at 100, anonymous and file have the same priority.
1648 * This scanning priority is essentially the inverse of IO cost.
1650 anon_prio = vmscan_swappiness(sc);
1651 file_prio = 200 - vmscan_swappiness(sc);
1654 * OK, so we have swap space and a fair amount of page cache
1655 * pages. We use the recently rotated / recently scanned
1656 * ratios to determine how valuable each cache is.
1658 * Because workloads change over time (and to avoid overflow)
1659 * we keep these statistics as a floating average, which ends
1660 * up weighing recent references more than old ones.
1662 * anon in [0], file in [1]
1664 spin_lock_irq(&mz->zone->lru_lock);
1665 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1666 reclaim_stat->recent_scanned[0] /= 2;
1667 reclaim_stat->recent_rotated[0] /= 2;
1670 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1671 reclaim_stat->recent_scanned[1] /= 2;
1672 reclaim_stat->recent_rotated[1] /= 2;
1676 * The amount of pressure on anon vs file pages is inversely
1677 * proportional to the fraction of recently scanned pages on
1678 * each list that were recently referenced and in active use.
1680 ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
1681 ap /= reclaim_stat->recent_rotated[0] + 1;
1683 fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
1684 fp /= reclaim_stat->recent_rotated[1] + 1;
1685 spin_unlock_irq(&mz->zone->lru_lock);
1689 denominator = ap + fp + 1;
1691 for_each_evictable_lru(lru) {
1692 int file = is_file_lru(lru);
1695 scan = get_lruvec_size(lruvec, lru);
1696 if (sc->priority || noswap || !vmscan_swappiness(sc)) {
1697 scan >>= sc->priority;
1698 if (!scan && force_scan)
1699 scan = SWAP_CLUSTER_MAX;
1700 scan = div64_u64(scan * fraction[file], denominator);
1706 /* Use reclaim/compaction for costly allocs or under memory pressure */
1707 static bool in_reclaim_compaction(struct scan_control *sc)
1709 if (COMPACTION_BUILD && sc->order &&
1710 (sc->order > PAGE_ALLOC_COSTLY_ORDER ||
1711 sc->priority < DEF_PRIORITY - 2))
1718 * Reclaim/compaction is used for high-order allocation requests. It reclaims
1719 * order-0 pages before compacting the zone. should_continue_reclaim() returns
1720 * true if more pages should be reclaimed such that when the page allocator
1721 * calls try_to_compact_zone() that it will have enough free pages to succeed.
1722 * It will give up earlier than that if there is difficulty reclaiming pages.
1724 static inline bool should_continue_reclaim(struct mem_cgroup_zone *mz,
1725 unsigned long nr_reclaimed,
1726 unsigned long nr_scanned,
1727 struct scan_control *sc)
1729 unsigned long pages_for_compaction;
1730 unsigned long inactive_lru_pages;
1731 struct lruvec *lruvec;
1733 /* If not in reclaim/compaction mode, stop */
1734 if (!in_reclaim_compaction(sc))
1737 /* Consider stopping depending on scan and reclaim activity */
1738 if (sc->gfp_mask & __GFP_REPEAT) {
1740 * For __GFP_REPEAT allocations, stop reclaiming if the
1741 * full LRU list has been scanned and we are still failing
1742 * to reclaim pages. This full LRU scan is potentially
1743 * expensive but a __GFP_REPEAT caller really wants to succeed
1745 if (!nr_reclaimed && !nr_scanned)
1749 * For non-__GFP_REPEAT allocations which can presumably
1750 * fail without consequence, stop if we failed to reclaim
1751 * any pages from the last SWAP_CLUSTER_MAX number of
1752 * pages that were scanned. This will return to the
1753 * caller faster at the risk reclaim/compaction and
1754 * the resulting allocation attempt fails
1761 * If we have not reclaimed enough pages for compaction and the
1762 * inactive lists are large enough, continue reclaiming
1764 lruvec = mem_cgroup_zone_lruvec(mz->zone, mz->mem_cgroup);
1765 pages_for_compaction = (2UL << sc->order);
1766 inactive_lru_pages = get_lruvec_size(lruvec, LRU_INACTIVE_FILE);
1767 if (nr_swap_pages > 0)
1768 inactive_lru_pages += get_lruvec_size(lruvec,
1770 if (sc->nr_reclaimed < pages_for_compaction &&
1771 inactive_lru_pages > pages_for_compaction)
1774 /* If compaction would go ahead or the allocation would succeed, stop */
1775 switch (compaction_suitable(mz->zone, sc->order)) {
1776 case COMPACT_PARTIAL:
1777 case COMPACT_CONTINUE:
1785 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1787 static void shrink_mem_cgroup_zone(struct mem_cgroup_zone *mz,
1788 struct scan_control *sc)
1790 unsigned long nr[NR_LRU_LISTS];
1791 unsigned long nr_to_scan;
1793 unsigned long nr_reclaimed, nr_scanned;
1794 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1795 struct blk_plug plug;
1799 nr_scanned = sc->nr_scanned;
1800 get_scan_count(mz, sc, nr);
1802 blk_start_plug(&plug);
1803 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1804 nr[LRU_INACTIVE_FILE]) {
1805 for_each_evictable_lru(lru) {
1807 nr_to_scan = min_t(unsigned long,
1808 nr[lru], SWAP_CLUSTER_MAX);
1809 nr[lru] -= nr_to_scan;
1811 nr_reclaimed += shrink_list(lru, nr_to_scan,
1816 * On large memory systems, scan >> priority can become
1817 * really large. This is fine for the starting priority;
1818 * we want to put equal scanning pressure on each zone.
1819 * However, if the VM has a harder time of freeing pages,
1820 * with multiple processes reclaiming pages, the total
1821 * freeing target can get unreasonably large.
1823 if (nr_reclaimed >= nr_to_reclaim &&
1824 sc->priority < DEF_PRIORITY)
1827 blk_finish_plug(&plug);
1828 sc->nr_reclaimed += nr_reclaimed;
1831 * Even if we did not try to evict anon pages at all, we want to
1832 * rebalance the anon lru active/inactive ratio.
1834 if (inactive_anon_is_low(mz))
1835 shrink_active_list(SWAP_CLUSTER_MAX, mz,
1836 sc, LRU_ACTIVE_ANON);
1838 /* reclaim/compaction might need reclaim to continue */
1839 if (should_continue_reclaim(mz, nr_reclaimed,
1840 sc->nr_scanned - nr_scanned, sc))
1843 throttle_vm_writeout(sc->gfp_mask);
1846 static void shrink_zone(struct zone *zone, struct scan_control *sc)
1848 struct mem_cgroup *root = sc->target_mem_cgroup;
1849 struct mem_cgroup_reclaim_cookie reclaim = {
1851 .priority = sc->priority,
1853 struct mem_cgroup *memcg;
1855 memcg = mem_cgroup_iter(root, NULL, &reclaim);
1857 struct mem_cgroup_zone mz = {
1858 .mem_cgroup = memcg,
1862 shrink_mem_cgroup_zone(&mz, sc);
1864 * Limit reclaim has historically picked one memcg and
1865 * scanned it with decreasing priority levels until
1866 * nr_to_reclaim had been reclaimed. This priority
1867 * cycle is thus over after a single memcg.
1869 * Direct reclaim and kswapd, on the other hand, have
1870 * to scan all memory cgroups to fulfill the overall
1871 * scan target for the zone.
1873 if (!global_reclaim(sc)) {
1874 mem_cgroup_iter_break(root, memcg);
1877 memcg = mem_cgroup_iter(root, memcg, &reclaim);
1881 /* Returns true if compaction should go ahead for a high-order request */
1882 static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
1884 unsigned long balance_gap, watermark;
1887 /* Do not consider compaction for orders reclaim is meant to satisfy */
1888 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER)
1892 * Compaction takes time to run and there are potentially other
1893 * callers using the pages just freed. Continue reclaiming until
1894 * there is a buffer of free pages available to give compaction
1895 * a reasonable chance of completing and allocating the page
1897 balance_gap = min(low_wmark_pages(zone),
1898 (zone->present_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
1899 KSWAPD_ZONE_BALANCE_GAP_RATIO);
1900 watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order);
1901 watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0);
1904 * If compaction is deferred, reclaim up to a point where
1905 * compaction will have a chance of success when re-enabled
1907 if (compaction_deferred(zone, sc->order))
1908 return watermark_ok;
1910 /* If compaction is not ready to start, keep reclaiming */
1911 if (!compaction_suitable(zone, sc->order))
1914 return watermark_ok;
1918 * This is the direct reclaim path, for page-allocating processes. We only
1919 * try to reclaim pages from zones which will satisfy the caller's allocation
1922 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1924 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1926 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1927 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1928 * zone defense algorithm.
1930 * If a zone is deemed to be full of pinned pages then just give it a light
1931 * scan then give up on it.
1933 * This function returns true if a zone is being reclaimed for a costly
1934 * high-order allocation and compaction is ready to begin. This indicates to
1935 * the caller that it should consider retrying the allocation instead of
1938 static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
1942 unsigned long nr_soft_reclaimed;
1943 unsigned long nr_soft_scanned;
1944 bool aborted_reclaim = false;
1947 * If the number of buffer_heads in the machine exceeds the maximum
1948 * allowed level, force direct reclaim to scan the highmem zone as
1949 * highmem pages could be pinning lowmem pages storing buffer_heads
1951 if (buffer_heads_over_limit)
1952 sc->gfp_mask |= __GFP_HIGHMEM;
1954 for_each_zone_zonelist_nodemask(zone, z, zonelist,
1955 gfp_zone(sc->gfp_mask), sc->nodemask) {
1956 if (!populated_zone(zone))
1959 * Take care memory controller reclaiming has small influence
1962 if (global_reclaim(sc)) {
1963 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1965 if (zone->all_unreclaimable &&
1966 sc->priority != DEF_PRIORITY)
1967 continue; /* Let kswapd poll it */
1968 if (COMPACTION_BUILD) {
1970 * If we already have plenty of memory free for
1971 * compaction in this zone, don't free any more.
1972 * Even though compaction is invoked for any
1973 * non-zero order, only frequent costly order
1974 * reclamation is disruptive enough to become a
1975 * noticeable problem, like transparent huge
1978 if (compaction_ready(zone, sc)) {
1979 aborted_reclaim = true;
1984 * This steals pages from memory cgroups over softlimit
1985 * and returns the number of reclaimed pages and
1986 * scanned pages. This works for global memory pressure
1987 * and balancing, not for a memcg's limit.
1989 nr_soft_scanned = 0;
1990 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
1991 sc->order, sc->gfp_mask,
1993 sc->nr_reclaimed += nr_soft_reclaimed;
1994 sc->nr_scanned += nr_soft_scanned;
1995 /* need some check for avoid more shrink_zone() */
1998 shrink_zone(zone, sc);
2001 return aborted_reclaim;
2004 static bool zone_reclaimable(struct zone *zone)
2006 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
2009 /* All zones in zonelist are unreclaimable? */
2010 static bool all_unreclaimable(struct zonelist *zonelist,
2011 struct scan_control *sc)
2016 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2017 gfp_zone(sc->gfp_mask), sc->nodemask) {
2018 if (!populated_zone(zone))
2020 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2022 if (!zone->all_unreclaimable)
2030 * This is the main entry point to direct page reclaim.
2032 * If a full scan of the inactive list fails to free enough memory then we
2033 * are "out of memory" and something needs to be killed.
2035 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2036 * high - the zone may be full of dirty or under-writeback pages, which this
2037 * caller can't do much about. We kick the writeback threads and take explicit
2038 * naps in the hope that some of these pages can be written. But if the
2039 * allocating task holds filesystem locks which prevent writeout this might not
2040 * work, and the allocation attempt will fail.
2042 * returns: 0, if no pages reclaimed
2043 * else, the number of pages reclaimed
2045 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2046 struct scan_control *sc,
2047 struct shrink_control *shrink)
2049 unsigned long total_scanned = 0;
2050 struct reclaim_state *reclaim_state = current->reclaim_state;
2053 unsigned long writeback_threshold;
2054 bool aborted_reclaim;
2056 delayacct_freepages_start();
2058 if (global_reclaim(sc))
2059 count_vm_event(ALLOCSTALL);
2063 aborted_reclaim = shrink_zones(zonelist, sc);
2066 * Don't shrink slabs when reclaiming memory from
2067 * over limit cgroups
2069 if (global_reclaim(sc)) {
2070 unsigned long lru_pages = 0;
2071 for_each_zone_zonelist(zone, z, zonelist,
2072 gfp_zone(sc->gfp_mask)) {
2073 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2076 lru_pages += zone_reclaimable_pages(zone);
2079 shrink_slab(shrink, sc->nr_scanned, lru_pages);
2080 if (reclaim_state) {
2081 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2082 reclaim_state->reclaimed_slab = 0;
2085 total_scanned += sc->nr_scanned;
2086 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
2090 * Try to write back as many pages as we just scanned. This
2091 * tends to cause slow streaming writers to write data to the
2092 * disk smoothly, at the dirtying rate, which is nice. But
2093 * that's undesirable in laptop mode, where we *want* lumpy
2094 * writeout. So in laptop mode, write out the whole world.
2096 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2097 if (total_scanned > writeback_threshold) {
2098 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
2099 WB_REASON_TRY_TO_FREE_PAGES);
2100 sc->may_writepage = 1;
2103 /* Take a nap, wait for some writeback to complete */
2104 if (!sc->hibernation_mode && sc->nr_scanned &&
2105 sc->priority < DEF_PRIORITY - 2) {
2106 struct zone *preferred_zone;
2108 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2109 &cpuset_current_mems_allowed,
2111 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
2113 } while (--sc->priority >= 0);
2116 delayacct_freepages_end();
2118 if (sc->nr_reclaimed)
2119 return sc->nr_reclaimed;
2122 * As hibernation is going on, kswapd is freezed so that it can't mark
2123 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2126 if (oom_killer_disabled)
2129 /* Aborted reclaim to try compaction? don't OOM, then */
2130 if (aborted_reclaim)
2133 /* top priority shrink_zones still had more to do? don't OOM, then */
2134 if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc))
2140 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2141 gfp_t gfp_mask, nodemask_t *nodemask)
2143 unsigned long nr_reclaimed;
2144 struct scan_control sc = {
2145 .gfp_mask = gfp_mask,
2146 .may_writepage = !laptop_mode,
2147 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2151 .priority = DEF_PRIORITY,
2152 .target_mem_cgroup = NULL,
2153 .nodemask = nodemask,
2155 struct shrink_control shrink = {
2156 .gfp_mask = sc.gfp_mask,
2159 trace_mm_vmscan_direct_reclaim_begin(order,
2163 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2165 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2167 return nr_reclaimed;
2170 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2172 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
2173 gfp_t gfp_mask, bool noswap,
2175 unsigned long *nr_scanned)
2177 struct scan_control sc = {
2179 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2180 .may_writepage = !laptop_mode,
2182 .may_swap = !noswap,
2185 .target_mem_cgroup = memcg,
2187 struct mem_cgroup_zone mz = {
2188 .mem_cgroup = memcg,
2192 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2193 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2195 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
2200 * NOTE: Although we can get the priority field, using it
2201 * here is not a good idea, since it limits the pages we can scan.
2202 * if we don't reclaim here, the shrink_zone from balance_pgdat
2203 * will pick up pages from other mem cgroup's as well. We hack
2204 * the priority and make it zero.
2206 shrink_mem_cgroup_zone(&mz, &sc);
2208 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2210 *nr_scanned = sc.nr_scanned;
2211 return sc.nr_reclaimed;
2214 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
2218 struct zonelist *zonelist;
2219 unsigned long nr_reclaimed;
2221 struct scan_control sc = {
2222 .may_writepage = !laptop_mode,
2224 .may_swap = !noswap,
2225 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2227 .priority = DEF_PRIORITY,
2228 .target_mem_cgroup = memcg,
2229 .nodemask = NULL, /* we don't care the placement */
2230 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2231 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2233 struct shrink_control shrink = {
2234 .gfp_mask = sc.gfp_mask,
2238 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2239 * take care of from where we get pages. So the node where we start the
2240 * scan does not need to be the current node.
2242 nid = mem_cgroup_select_victim_node(memcg);
2244 zonelist = NODE_DATA(nid)->node_zonelists;
2246 trace_mm_vmscan_memcg_reclaim_begin(0,
2250 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2252 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2254 return nr_reclaimed;
2258 static void age_active_anon(struct zone *zone, struct scan_control *sc)
2260 struct mem_cgroup *memcg;
2262 if (!total_swap_pages)
2265 memcg = mem_cgroup_iter(NULL, NULL, NULL);
2267 struct mem_cgroup_zone mz = {
2268 .mem_cgroup = memcg,
2272 if (inactive_anon_is_low(&mz))
2273 shrink_active_list(SWAP_CLUSTER_MAX, &mz,
2274 sc, LRU_ACTIVE_ANON);
2276 memcg = mem_cgroup_iter(NULL, memcg, NULL);
2281 * pgdat_balanced is used when checking if a node is balanced for high-order
2282 * allocations. Only zones that meet watermarks and are in a zone allowed
2283 * by the callers classzone_idx are added to balanced_pages. The total of
2284 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2285 * for the node to be considered balanced. Forcing all zones to be balanced
2286 * for high orders can cause excessive reclaim when there are imbalanced zones.
2287 * The choice of 25% is due to
2288 * o a 16M DMA zone that is balanced will not balance a zone on any
2289 * reasonable sized machine
2290 * o On all other machines, the top zone must be at least a reasonable
2291 * percentage of the middle zones. For example, on 32-bit x86, highmem
2292 * would need to be at least 256M for it to be balance a whole node.
2293 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2294 * to balance a node on its own. These seemed like reasonable ratios.
2296 static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
2299 unsigned long present_pages = 0;
2302 for (i = 0; i <= classzone_idx; i++)
2303 present_pages += pgdat->node_zones[i].present_pages;
2305 /* A special case here: if zone has no page, we think it's balanced */
2306 return balanced_pages >= (present_pages >> 2);
2309 /* is kswapd sleeping prematurely? */
2310 static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
2314 unsigned long balanced = 0;
2315 bool all_zones_ok = true;
2317 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2321 /* Check the watermark levels */
2322 for (i = 0; i <= classzone_idx; i++) {
2323 struct zone *zone = pgdat->node_zones + i;
2325 if (!populated_zone(zone))
2329 * balance_pgdat() skips over all_unreclaimable after
2330 * DEF_PRIORITY. Effectively, it considers them balanced so
2331 * they must be considered balanced here as well if kswapd
2334 if (zone->all_unreclaimable) {
2335 balanced += zone->present_pages;
2339 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2341 all_zones_ok = false;
2343 balanced += zone->present_pages;
2347 * For high-order requests, the balanced zones must contain at least
2348 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2352 return !pgdat_balanced(pgdat, balanced, classzone_idx);
2354 return !all_zones_ok;
2358 * For kswapd, balance_pgdat() will work across all this node's zones until
2359 * they are all at high_wmark_pages(zone).
2361 * Returns the final order kswapd was reclaiming at
2363 * There is special handling here for zones which are full of pinned pages.
2364 * This can happen if the pages are all mlocked, or if they are all used by
2365 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2366 * What we do is to detect the case where all pages in the zone have been
2367 * scanned twice and there has been zero successful reclaim. Mark the zone as
2368 * dead and from now on, only perform a short scan. Basically we're polling
2369 * the zone for when the problem goes away.
2371 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2372 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2373 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2374 * lower zones regardless of the number of free pages in the lower zones. This
2375 * interoperates with the page allocator fallback scheme to ensure that aging
2376 * of pages is balanced across the zones.
2378 static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2382 unsigned long balanced;
2384 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2385 unsigned long total_scanned;
2386 struct reclaim_state *reclaim_state = current->reclaim_state;
2387 unsigned long nr_soft_reclaimed;
2388 unsigned long nr_soft_scanned;
2389 struct scan_control sc = {
2390 .gfp_mask = GFP_KERNEL,
2394 * kswapd doesn't want to be bailed out while reclaim. because
2395 * we want to put equal scanning pressure on each zone.
2397 .nr_to_reclaim = ULONG_MAX,
2399 .target_mem_cgroup = NULL,
2401 struct shrink_control shrink = {
2402 .gfp_mask = sc.gfp_mask,
2406 sc.priority = DEF_PRIORITY;
2407 sc.nr_reclaimed = 0;
2408 sc.may_writepage = !laptop_mode;
2409 count_vm_event(PAGEOUTRUN);
2412 unsigned long lru_pages = 0;
2413 int has_under_min_watermark_zone = 0;
2419 * Scan in the highmem->dma direction for the highest
2420 * zone which needs scanning
2422 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2423 struct zone *zone = pgdat->node_zones + i;
2425 if (!populated_zone(zone))
2428 if (zone->all_unreclaimable &&
2429 sc.priority != DEF_PRIORITY)
2433 * Do some background aging of the anon list, to give
2434 * pages a chance to be referenced before reclaiming.
2436 age_active_anon(zone, &sc);
2439 * If the number of buffer_heads in the machine
2440 * exceeds the maximum allowed level and this node
2441 * has a highmem zone, force kswapd to reclaim from
2442 * it to relieve lowmem pressure.
2444 if (buffer_heads_over_limit && is_highmem_idx(i)) {
2449 if (!zone_watermark_ok_safe(zone, order,
2450 high_wmark_pages(zone), 0, 0)) {
2454 /* If balanced, clear the congested flag */
2455 zone_clear_flag(zone, ZONE_CONGESTED);
2461 for (i = 0; i <= end_zone; i++) {
2462 struct zone *zone = pgdat->node_zones + i;
2464 lru_pages += zone_reclaimable_pages(zone);
2468 * Now scan the zone in the dma->highmem direction, stopping
2469 * at the last zone which needs scanning.
2471 * We do this because the page allocator works in the opposite
2472 * direction. This prevents the page allocator from allocating
2473 * pages behind kswapd's direction of progress, which would
2474 * cause too much scanning of the lower zones.
2476 for (i = 0; i <= end_zone; i++) {
2477 struct zone *zone = pgdat->node_zones + i;
2478 int nr_slab, testorder;
2479 unsigned long balance_gap;
2481 if (!populated_zone(zone))
2484 if (zone->all_unreclaimable &&
2485 sc.priority != DEF_PRIORITY)
2490 nr_soft_scanned = 0;
2492 * Call soft limit reclaim before calling shrink_zone.
2494 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2497 sc.nr_reclaimed += nr_soft_reclaimed;
2498 total_scanned += nr_soft_scanned;
2501 * We put equal pressure on every zone, unless
2502 * one zone has way too many pages free
2503 * already. The "too many pages" is defined
2504 * as the high wmark plus a "gap" where the
2505 * gap is either the low watermark or 1%
2506 * of the zone, whichever is smaller.
2508 balance_gap = min(low_wmark_pages(zone),
2509 (zone->present_pages +
2510 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2511 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2513 * Kswapd reclaims only single pages with compaction
2514 * enabled. Trying too hard to reclaim until contiguous
2515 * free pages have become available can hurt performance
2516 * by evicting too much useful data from memory.
2517 * Do not reclaim more than needed for compaction.
2520 if (COMPACTION_BUILD && order &&
2521 compaction_suitable(zone, order) !=
2525 if ((buffer_heads_over_limit && is_highmem_idx(i)) ||
2526 !zone_watermark_ok_safe(zone, testorder,
2527 high_wmark_pages(zone) + balance_gap,
2529 shrink_zone(zone, &sc);
2531 reclaim_state->reclaimed_slab = 0;
2532 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
2533 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2534 total_scanned += sc.nr_scanned;
2536 if (nr_slab == 0 && !zone_reclaimable(zone))
2537 zone->all_unreclaimable = 1;
2541 * If we've done a decent amount of scanning and
2542 * the reclaim ratio is low, start doing writepage
2543 * even in laptop mode
2545 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2546 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2547 sc.may_writepage = 1;
2549 if (zone->all_unreclaimable) {
2550 if (end_zone && end_zone == i)
2555 if (!zone_watermark_ok_safe(zone, testorder,
2556 high_wmark_pages(zone), end_zone, 0)) {
2559 * We are still under min water mark. This
2560 * means that we have a GFP_ATOMIC allocation
2561 * failure risk. Hurry up!
2563 if (!zone_watermark_ok_safe(zone, order,
2564 min_wmark_pages(zone), end_zone, 0))
2565 has_under_min_watermark_zone = 1;
2568 * If a zone reaches its high watermark,
2569 * consider it to be no longer congested. It's
2570 * possible there are dirty pages backed by
2571 * congested BDIs but as pressure is relieved,
2572 * spectulatively avoid congestion waits
2574 zone_clear_flag(zone, ZONE_CONGESTED);
2575 if (i <= *classzone_idx)
2576 balanced += zone->present_pages;
2580 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
2581 break; /* kswapd: all done */
2583 * OK, kswapd is getting into trouble. Take a nap, then take
2584 * another pass across the zones.
2586 if (total_scanned && (sc.priority < DEF_PRIORITY - 2)) {
2587 if (has_under_min_watermark_zone)
2588 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2590 congestion_wait(BLK_RW_ASYNC, HZ/10);
2594 * We do this so kswapd doesn't build up large priorities for
2595 * example when it is freeing in parallel with allocators. It
2596 * matches the direct reclaim path behaviour in terms of impact
2597 * on zone->*_priority.
2599 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2601 } while (--sc.priority >= 0);
2605 * order-0: All zones must meet high watermark for a balanced node
2606 * high-order: Balanced zones must make up at least 25% of the node
2607 * for the node to be balanced
2609 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
2615 * Fragmentation may mean that the system cannot be
2616 * rebalanced for high-order allocations in all zones.
2617 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2618 * it means the zones have been fully scanned and are still
2619 * not balanced. For high-order allocations, there is
2620 * little point trying all over again as kswapd may
2623 * Instead, recheck all watermarks at order-0 as they
2624 * are the most important. If watermarks are ok, kswapd will go
2625 * back to sleep. High-order users can still perform direct
2626 * reclaim if they wish.
2628 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2629 order = sc.order = 0;
2635 * If kswapd was reclaiming at a higher order, it has the option of
2636 * sleeping without all zones being balanced. Before it does, it must
2637 * ensure that the watermarks for order-0 on *all* zones are met and
2638 * that the congestion flags are cleared. The congestion flag must
2639 * be cleared as kswapd is the only mechanism that clears the flag
2640 * and it is potentially going to sleep here.
2643 int zones_need_compaction = 1;
2645 for (i = 0; i <= end_zone; i++) {
2646 struct zone *zone = pgdat->node_zones + i;
2648 if (!populated_zone(zone))
2651 if (zone->all_unreclaimable &&
2652 sc.priority != DEF_PRIORITY)
2655 /* Would compaction fail due to lack of free memory? */
2656 if (COMPACTION_BUILD &&
2657 compaction_suitable(zone, order) == COMPACT_SKIPPED)
2660 /* Confirm the zone is balanced for order-0 */
2661 if (!zone_watermark_ok(zone, 0,
2662 high_wmark_pages(zone), 0, 0)) {
2663 order = sc.order = 0;
2667 /* Check if the memory needs to be defragmented. */
2668 if (zone_watermark_ok(zone, order,
2669 low_wmark_pages(zone), *classzone_idx, 0))
2670 zones_need_compaction = 0;
2672 /* If balanced, clear the congested flag */
2673 zone_clear_flag(zone, ZONE_CONGESTED);
2676 if (zones_need_compaction)
2677 compact_pgdat(pgdat, order);
2681 * Return the order we were reclaiming at so sleeping_prematurely()
2682 * makes a decision on the order we were last reclaiming at. However,
2683 * if another caller entered the allocator slow path while kswapd
2684 * was awake, order will remain at the higher level
2686 *classzone_idx = end_zone;
2690 static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2695 if (freezing(current) || kthread_should_stop())
2698 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2700 /* Try to sleep for a short interval */
2701 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2702 remaining = schedule_timeout(HZ/10);
2703 finish_wait(&pgdat->kswapd_wait, &wait);
2704 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2708 * After a short sleep, check if it was a premature sleep. If not, then
2709 * go fully to sleep until explicitly woken up.
2711 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2712 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2715 * vmstat counters are not perfectly accurate and the estimated
2716 * value for counters such as NR_FREE_PAGES can deviate from the
2717 * true value by nr_online_cpus * threshold. To avoid the zone
2718 * watermarks being breached while under pressure, we reduce the
2719 * per-cpu vmstat threshold while kswapd is awake and restore
2720 * them before going back to sleep.
2722 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
2724 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
2727 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2729 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2731 finish_wait(&pgdat->kswapd_wait, &wait);
2735 * The background pageout daemon, started as a kernel thread
2736 * from the init process.
2738 * This basically trickles out pages so that we have _some_
2739 * free memory available even if there is no other activity
2740 * that frees anything up. This is needed for things like routing
2741 * etc, where we otherwise might have all activity going on in
2742 * asynchronous contexts that cannot page things out.
2744 * If there are applications that are active memory-allocators
2745 * (most normal use), this basically shouldn't matter.
2747 static int kswapd(void *p)
2749 unsigned long order, new_order;
2750 unsigned balanced_order;
2751 int classzone_idx, new_classzone_idx;
2752 int balanced_classzone_idx;
2753 pg_data_t *pgdat = (pg_data_t*)p;
2754 struct task_struct *tsk = current;
2756 struct reclaim_state reclaim_state = {
2757 .reclaimed_slab = 0,
2759 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2761 lockdep_set_current_reclaim_state(GFP_KERNEL);
2763 if (!cpumask_empty(cpumask))
2764 set_cpus_allowed_ptr(tsk, cpumask);
2765 current->reclaim_state = &reclaim_state;
2768 * Tell the memory management that we're a "memory allocator",
2769 * and that if we need more memory we should get access to it
2770 * regardless (see "__alloc_pages()"). "kswapd" should
2771 * never get caught in the normal page freeing logic.
2773 * (Kswapd normally doesn't need memory anyway, but sometimes
2774 * you need a small amount of memory in order to be able to
2775 * page out something else, and this flag essentially protects
2776 * us from recursively trying to free more memory as we're
2777 * trying to free the first piece of memory in the first place).
2779 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2782 order = new_order = 0;
2784 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
2785 balanced_classzone_idx = classzone_idx;
2790 * If the last balance_pgdat was unsuccessful it's unlikely a
2791 * new request of a similar or harder type will succeed soon
2792 * so consider going to sleep on the basis we reclaimed at
2794 if (balanced_classzone_idx >= new_classzone_idx &&
2795 balanced_order == new_order) {
2796 new_order = pgdat->kswapd_max_order;
2797 new_classzone_idx = pgdat->classzone_idx;
2798 pgdat->kswapd_max_order = 0;
2799 pgdat->classzone_idx = pgdat->nr_zones - 1;
2802 if (order < new_order || classzone_idx > new_classzone_idx) {
2804 * Don't sleep if someone wants a larger 'order'
2805 * allocation or has tigher zone constraints
2808 classzone_idx = new_classzone_idx;
2810 kswapd_try_to_sleep(pgdat, balanced_order,
2811 balanced_classzone_idx);
2812 order = pgdat->kswapd_max_order;
2813 classzone_idx = pgdat->classzone_idx;
2815 new_classzone_idx = classzone_idx;
2816 pgdat->kswapd_max_order = 0;
2817 pgdat->classzone_idx = pgdat->nr_zones - 1;
2820 ret = try_to_freeze();
2821 if (kthread_should_stop())
2825 * We can speed up thawing tasks if we don't call balance_pgdat
2826 * after returning from the refrigerator
2829 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2830 balanced_classzone_idx = classzone_idx;
2831 balanced_order = balance_pgdat(pgdat, order,
2832 &balanced_classzone_idx);
2839 * A zone is low on free memory, so wake its kswapd task to service it.
2841 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
2845 if (!populated_zone(zone))
2848 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2850 pgdat = zone->zone_pgdat;
2851 if (pgdat->kswapd_max_order < order) {
2852 pgdat->kswapd_max_order = order;
2853 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
2855 if (!waitqueue_active(&pgdat->kswapd_wait))
2857 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
2860 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2861 wake_up_interruptible(&pgdat->kswapd_wait);
2865 * The reclaimable count would be mostly accurate.
2866 * The less reclaimable pages may be
2867 * - mlocked pages, which will be moved to unevictable list when encountered
2868 * - mapped pages, which may require several travels to be reclaimed
2869 * - dirty pages, which is not "instantly" reclaimable
2871 unsigned long global_reclaimable_pages(void)
2875 nr = global_page_state(NR_ACTIVE_FILE) +
2876 global_page_state(NR_INACTIVE_FILE);
2878 if (nr_swap_pages > 0)
2879 nr += global_page_state(NR_ACTIVE_ANON) +
2880 global_page_state(NR_INACTIVE_ANON);
2885 unsigned long zone_reclaimable_pages(struct zone *zone)
2889 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2890 zone_page_state(zone, NR_INACTIVE_FILE);
2892 if (nr_swap_pages > 0)
2893 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2894 zone_page_state(zone, NR_INACTIVE_ANON);
2899 #ifdef CONFIG_HIBERNATION
2901 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2904 * Rather than trying to age LRUs the aim is to preserve the overall
2905 * LRU order by reclaiming preferentially
2906 * inactive > active > active referenced > active mapped
2908 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2910 struct reclaim_state reclaim_state;
2911 struct scan_control sc = {
2912 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2916 .nr_to_reclaim = nr_to_reclaim,
2917 .hibernation_mode = 1,
2919 .priority = DEF_PRIORITY,
2921 struct shrink_control shrink = {
2922 .gfp_mask = sc.gfp_mask,
2924 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2925 struct task_struct *p = current;
2926 unsigned long nr_reclaimed;
2928 p->flags |= PF_MEMALLOC;
2929 lockdep_set_current_reclaim_state(sc.gfp_mask);
2930 reclaim_state.reclaimed_slab = 0;
2931 p->reclaim_state = &reclaim_state;
2933 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2935 p->reclaim_state = NULL;
2936 lockdep_clear_current_reclaim_state();
2937 p->flags &= ~PF_MEMALLOC;
2939 return nr_reclaimed;
2941 #endif /* CONFIG_HIBERNATION */
2943 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2944 not required for correctness. So if the last cpu in a node goes
2945 away, we get changed to run anywhere: as the first one comes back,
2946 restore their cpu bindings. */
2947 static int __devinit cpu_callback(struct notifier_block *nfb,
2948 unsigned long action, void *hcpu)
2952 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2953 for_each_node_state(nid, N_HIGH_MEMORY) {
2954 pg_data_t *pgdat = NODE_DATA(nid);
2955 const struct cpumask *mask;
2957 mask = cpumask_of_node(pgdat->node_id);
2959 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2960 /* One of our CPUs online: restore mask */
2961 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2968 * This kswapd start function will be called by init and node-hot-add.
2969 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2971 int kswapd_run(int nid)
2973 pg_data_t *pgdat = NODE_DATA(nid);
2979 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2980 if (IS_ERR(pgdat->kswapd)) {
2981 /* failure at boot is fatal */
2982 BUG_ON(system_state == SYSTEM_BOOTING);
2983 printk("Failed to start kswapd on node %d\n",nid);
2990 * Called by memory hotplug when all memory in a node is offlined.
2992 void kswapd_stop(int nid)
2994 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
2997 kthread_stop(kswapd);
3000 static int __init kswapd_init(void)
3005 for_each_node_state(nid, N_HIGH_MEMORY)
3007 hotcpu_notifier(cpu_callback, 0);
3011 module_init(kswapd_init)
3017 * If non-zero call zone_reclaim when the number of free pages falls below
3020 int zone_reclaim_mode __read_mostly;
3022 #define RECLAIM_OFF 0
3023 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3024 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3025 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3028 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3029 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3032 #define ZONE_RECLAIM_PRIORITY 4
3035 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3038 int sysctl_min_unmapped_ratio = 1;
3041 * If the number of slab pages in a zone grows beyond this percentage then
3042 * slab reclaim needs to occur.
3044 int sysctl_min_slab_ratio = 5;
3046 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
3048 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
3049 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
3050 zone_page_state(zone, NR_ACTIVE_FILE);
3053 * It's possible for there to be more file mapped pages than
3054 * accounted for by the pages on the file LRU lists because
3055 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3057 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
3060 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3061 static long zone_pagecache_reclaimable(struct zone *zone)
3063 long nr_pagecache_reclaimable;
3067 * If RECLAIM_SWAP is set, then all file pages are considered
3068 * potentially reclaimable. Otherwise, we have to worry about
3069 * pages like swapcache and zone_unmapped_file_pages() provides
3072 if (zone_reclaim_mode & RECLAIM_SWAP)
3073 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
3075 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
3077 /* If we can't clean pages, remove dirty pages from consideration */
3078 if (!(zone_reclaim_mode & RECLAIM_WRITE))
3079 delta += zone_page_state(zone, NR_FILE_DIRTY);
3081 /* Watch for any possible underflows due to delta */
3082 if (unlikely(delta > nr_pagecache_reclaimable))
3083 delta = nr_pagecache_reclaimable;
3085 return nr_pagecache_reclaimable - delta;
3089 * Try to free up some pages from this zone through reclaim.
3091 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3093 /* Minimum pages needed in order to stay on node */
3094 const unsigned long nr_pages = 1 << order;
3095 struct task_struct *p = current;
3096 struct reclaim_state reclaim_state;
3097 struct scan_control sc = {
3098 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3099 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3101 .nr_to_reclaim = max_t(unsigned long, nr_pages,
3103 .gfp_mask = gfp_mask,
3105 .priority = ZONE_RECLAIM_PRIORITY,
3107 struct shrink_control shrink = {
3108 .gfp_mask = sc.gfp_mask,
3110 unsigned long nr_slab_pages0, nr_slab_pages1;
3114 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3115 * and we also need to be able to write out pages for RECLAIM_WRITE
3118 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
3119 lockdep_set_current_reclaim_state(gfp_mask);
3120 reclaim_state.reclaimed_slab = 0;
3121 p->reclaim_state = &reclaim_state;
3123 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3125 * Free memory by calling shrink zone with increasing
3126 * priorities until we have enough memory freed.
3129 shrink_zone(zone, &sc);
3130 } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
3133 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3134 if (nr_slab_pages0 > zone->min_slab_pages) {
3136 * shrink_slab() does not currently allow us to determine how
3137 * many pages were freed in this zone. So we take the current
3138 * number of slab pages and shake the slab until it is reduced
3139 * by the same nr_pages that we used for reclaiming unmapped
3142 * Note that shrink_slab will free memory on all zones and may
3146 unsigned long lru_pages = zone_reclaimable_pages(zone);
3148 /* No reclaimable slab or very low memory pressure */
3149 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3152 /* Freed enough memory */
3153 nr_slab_pages1 = zone_page_state(zone,
3154 NR_SLAB_RECLAIMABLE);
3155 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
3160 * Update nr_reclaimed by the number of slab pages we
3161 * reclaimed from this zone.
3163 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3164 if (nr_slab_pages1 < nr_slab_pages0)
3165 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3168 p->reclaim_state = NULL;
3169 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3170 lockdep_clear_current_reclaim_state();
3171 return sc.nr_reclaimed >= nr_pages;
3174 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3180 * Zone reclaim reclaims unmapped file backed pages and
3181 * slab pages if we are over the defined limits.
3183 * A small portion of unmapped file backed pages is needed for
3184 * file I/O otherwise pages read by file I/O will be immediately
3185 * thrown out if the zone is overallocated. So we do not reclaim
3186 * if less than a specified percentage of the zone is used by
3187 * unmapped file backed pages.
3189 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3190 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3191 return ZONE_RECLAIM_FULL;
3193 if (zone->all_unreclaimable)
3194 return ZONE_RECLAIM_FULL;
3197 * Do not scan if the allocation should not be delayed.
3199 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3200 return ZONE_RECLAIM_NOSCAN;
3203 * Only run zone reclaim on the local zone or on zones that do not
3204 * have associated processors. This will favor the local processor
3205 * over remote processors and spread off node memory allocations
3206 * as wide as possible.
3208 node_id = zone_to_nid(zone);
3209 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3210 return ZONE_RECLAIM_NOSCAN;
3212 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3213 return ZONE_RECLAIM_NOSCAN;
3215 ret = __zone_reclaim(zone, gfp_mask, order);
3216 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
3219 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3226 * page_evictable - test whether a page is evictable
3227 * @page: the page to test
3228 * @vma: the VMA in which the page is or will be mapped, may be NULL
3230 * Test whether page is evictable--i.e., should be placed on active/inactive
3231 * lists vs unevictable list. The vma argument is !NULL when called from the
3232 * fault path to determine how to instantate a new page.
3234 * Reasons page might not be evictable:
3235 * (1) page's mapping marked unevictable
3236 * (2) page is part of an mlocked VMA
3239 int page_evictable(struct page *page, struct vm_area_struct *vma)
3242 if (mapping_unevictable(page_mapping(page)))
3245 if (PageMlocked(page) || (vma && mlocked_vma_newpage(vma, page)))
3253 * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
3254 * @pages: array of pages to check
3255 * @nr_pages: number of pages to check
3257 * Checks pages for evictability and moves them to the appropriate lru list.
3259 * This function is only used for SysV IPC SHM_UNLOCK.
3261 void check_move_unevictable_pages(struct page **pages, int nr_pages)
3263 struct lruvec *lruvec;
3264 struct zone *zone = NULL;
3269 for (i = 0; i < nr_pages; i++) {
3270 struct page *page = pages[i];
3271 struct zone *pagezone;
3274 pagezone = page_zone(page);
3275 if (pagezone != zone) {
3277 spin_unlock_irq(&zone->lru_lock);
3279 spin_lock_irq(&zone->lru_lock);
3282 if (!PageLRU(page) || !PageUnevictable(page))
3285 if (page_evictable(page, NULL)) {
3286 enum lru_list lru = page_lru_base_type(page);
3288 VM_BUG_ON(PageActive(page));
3289 ClearPageUnevictable(page);
3290 __dec_zone_state(zone, NR_UNEVICTABLE);
3291 lruvec = mem_cgroup_lru_move_lists(zone, page,
3292 LRU_UNEVICTABLE, lru);
3293 list_move(&page->lru, &lruvec->lists[lru]);
3294 __inc_zone_state(zone, NR_INACTIVE_ANON + lru);
3300 __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
3301 __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
3302 spin_unlock_irq(&zone->lru_lock);
3305 #endif /* CONFIG_SHMEM */
3307 static void warn_scan_unevictable_pages(void)
3309 printk_once(KERN_WARNING
3310 "%s: The scan_unevictable_pages sysctl/node-interface has been "
3311 "disabled for lack of a legitimate use case. If you have "
3312 "one, please send an email to linux-mm@kvack.org.\n",
3317 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3318 * all nodes' unevictable lists for evictable pages
3320 unsigned long scan_unevictable_pages;
3322 int scan_unevictable_handler(struct ctl_table *table, int write,
3323 void __user *buffer,
3324 size_t *length, loff_t *ppos)
3326 warn_scan_unevictable_pages();
3327 proc_doulongvec_minmax(table, write, buffer, length, ppos);
3328 scan_unevictable_pages = 0;
3334 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3335 * a specified node's per zone unevictable lists for evictable pages.
3338 static ssize_t read_scan_unevictable_node(struct device *dev,
3339 struct device_attribute *attr,
3342 warn_scan_unevictable_pages();
3343 return sprintf(buf, "0\n"); /* always zero; should fit... */
3346 static ssize_t write_scan_unevictable_node(struct device *dev,
3347 struct device_attribute *attr,
3348 const char *buf, size_t count)
3350 warn_scan_unevictable_pages();
3355 static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3356 read_scan_unevictable_node,
3357 write_scan_unevictable_node);
3359 int scan_unevictable_register_node(struct node *node)
3361 return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages);
3364 void scan_unevictable_unregister_node(struct node *node)
3366 device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages);