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? */
82 * The memory cgroup that hit its limit and as a result is the
83 * primary target of this reclaim invocation.
85 struct mem_cgroup *target_mem_cgroup;
88 * Nodemask of nodes allowed by the caller. If NULL, all nodes
94 struct mem_cgroup_zone {
95 struct mem_cgroup *mem_cgroup;
99 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
101 #ifdef ARCH_HAS_PREFETCH
102 #define prefetch_prev_lru_page(_page, _base, _field) \
104 if ((_page)->lru.prev != _base) { \
107 prev = lru_to_page(&(_page->lru)); \
108 prefetch(&prev->_field); \
112 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
115 #ifdef ARCH_HAS_PREFETCHW
116 #define prefetchw_prev_lru_page(_page, _base, _field) \
118 if ((_page)->lru.prev != _base) { \
121 prev = lru_to_page(&(_page->lru)); \
122 prefetchw(&prev->_field); \
126 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
130 * From 0 .. 100. Higher means more swappy.
132 int vm_swappiness = 60;
133 long vm_total_pages; /* The total number of pages which the VM controls */
135 static LIST_HEAD(shrinker_list);
136 static DECLARE_RWSEM(shrinker_rwsem);
138 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
139 static bool global_reclaim(struct scan_control *sc)
141 return !sc->target_mem_cgroup;
144 static bool global_reclaim(struct scan_control *sc)
150 static struct zone_reclaim_stat *get_reclaim_stat(struct mem_cgroup_zone *mz)
152 return &mem_cgroup_zone_lruvec(mz->zone, mz->mem_cgroup)->reclaim_stat;
155 static unsigned long zone_nr_lru_pages(struct mem_cgroup_zone *mz,
158 if (!mem_cgroup_disabled())
159 return mem_cgroup_zone_nr_lru_pages(mz->mem_cgroup,
160 zone_to_nid(mz->zone),
164 return zone_page_state(mz->zone, NR_LRU_BASE + lru);
169 * Add a shrinker callback to be called from the vm
171 void register_shrinker(struct shrinker *shrinker)
173 atomic_long_set(&shrinker->nr_in_batch, 0);
174 down_write(&shrinker_rwsem);
175 list_add_tail(&shrinker->list, &shrinker_list);
176 up_write(&shrinker_rwsem);
178 EXPORT_SYMBOL(register_shrinker);
183 void unregister_shrinker(struct shrinker *shrinker)
185 down_write(&shrinker_rwsem);
186 list_del(&shrinker->list);
187 up_write(&shrinker_rwsem);
189 EXPORT_SYMBOL(unregister_shrinker);
191 static inline int do_shrinker_shrink(struct shrinker *shrinker,
192 struct shrink_control *sc,
193 unsigned long nr_to_scan)
195 sc->nr_to_scan = nr_to_scan;
196 return (*shrinker->shrink)(shrinker, sc);
199 #define SHRINK_BATCH 128
201 * Call the shrink functions to age shrinkable caches
203 * Here we assume it costs one seek to replace a lru page and that it also
204 * takes a seek to recreate a cache object. With this in mind we age equal
205 * percentages of the lru and ageable caches. This should balance the seeks
206 * generated by these structures.
208 * If the vm encountered mapped pages on the LRU it increase the pressure on
209 * slab to avoid swapping.
211 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
213 * `lru_pages' represents the number of on-LRU pages in all the zones which
214 * are eligible for the caller's allocation attempt. It is used for balancing
215 * slab reclaim versus page reclaim.
217 * Returns the number of slab objects which we shrunk.
219 unsigned long shrink_slab(struct shrink_control *shrink,
220 unsigned long nr_pages_scanned,
221 unsigned long lru_pages)
223 struct shrinker *shrinker;
224 unsigned long ret = 0;
226 if (nr_pages_scanned == 0)
227 nr_pages_scanned = SWAP_CLUSTER_MAX;
229 if (!down_read_trylock(&shrinker_rwsem)) {
230 /* Assume we'll be able to shrink next time */
235 list_for_each_entry(shrinker, &shrinker_list, list) {
236 unsigned long long delta;
242 long batch_size = shrinker->batch ? shrinker->batch
245 max_pass = do_shrinker_shrink(shrinker, shrink, 0);
250 * copy the current shrinker scan count into a local variable
251 * and zero it so that other concurrent shrinker invocations
252 * don't also do this scanning work.
254 nr = atomic_long_xchg(&shrinker->nr_in_batch, 0);
257 delta = (4 * nr_pages_scanned) / shrinker->seeks;
259 do_div(delta, lru_pages + 1);
261 if (total_scan < 0) {
262 printk(KERN_ERR "shrink_slab: %pF negative objects to "
264 shrinker->shrink, total_scan);
265 total_scan = max_pass;
269 * We need to avoid excessive windup on filesystem shrinkers
270 * due to large numbers of GFP_NOFS allocations causing the
271 * shrinkers to return -1 all the time. This results in a large
272 * nr being built up so when a shrink that can do some work
273 * comes along it empties the entire cache due to nr >>>
274 * max_pass. This is bad for sustaining a working set in
277 * Hence only allow the shrinker to scan the entire cache when
278 * a large delta change is calculated directly.
280 if (delta < max_pass / 4)
281 total_scan = min(total_scan, max_pass / 2);
284 * Avoid risking looping forever due to too large nr value:
285 * never try to free more than twice the estimate number of
288 if (total_scan > max_pass * 2)
289 total_scan = max_pass * 2;
291 trace_mm_shrink_slab_start(shrinker, shrink, nr,
292 nr_pages_scanned, lru_pages,
293 max_pass, delta, total_scan);
295 while (total_scan >= batch_size) {
298 nr_before = do_shrinker_shrink(shrinker, shrink, 0);
299 shrink_ret = do_shrinker_shrink(shrinker, shrink,
301 if (shrink_ret == -1)
303 if (shrink_ret < nr_before)
304 ret += nr_before - shrink_ret;
305 count_vm_events(SLABS_SCANNED, batch_size);
306 total_scan -= batch_size;
312 * move the unused scan count back into the shrinker in a
313 * manner that handles concurrent updates. If we exhausted the
314 * scan, there is no need to do an update.
317 new_nr = atomic_long_add_return(total_scan,
318 &shrinker->nr_in_batch);
320 new_nr = atomic_long_read(&shrinker->nr_in_batch);
322 trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr);
324 up_read(&shrinker_rwsem);
330 static inline int is_page_cache_freeable(struct page *page)
333 * A freeable page cache page is referenced only by the caller
334 * that isolated the page, the page cache radix tree and
335 * optional buffer heads at page->private.
337 return page_count(page) - page_has_private(page) == 2;
340 static int may_write_to_queue(struct backing_dev_info *bdi,
341 struct scan_control *sc)
343 if (current->flags & PF_SWAPWRITE)
345 if (!bdi_write_congested(bdi))
347 if (bdi == current->backing_dev_info)
353 * We detected a synchronous write error writing a page out. Probably
354 * -ENOSPC. We need to propagate that into the address_space for a subsequent
355 * fsync(), msync() or close().
357 * The tricky part is that after writepage we cannot touch the mapping: nothing
358 * prevents it from being freed up. But we have a ref on the page and once
359 * that page is locked, the mapping is pinned.
361 * We're allowed to run sleeping lock_page() here because we know the caller has
364 static void handle_write_error(struct address_space *mapping,
365 struct page *page, int error)
368 if (page_mapping(page) == mapping)
369 mapping_set_error(mapping, error);
373 /* possible outcome of pageout() */
375 /* failed to write page out, page is locked */
377 /* move page to the active list, page is locked */
379 /* page has been sent to the disk successfully, page is unlocked */
381 /* page is clean and locked */
386 * pageout is called by shrink_page_list() for each dirty page.
387 * Calls ->writepage().
389 static pageout_t pageout(struct page *page, struct address_space *mapping,
390 struct scan_control *sc)
393 * If the page is dirty, only perform writeback if that write
394 * will be non-blocking. To prevent this allocation from being
395 * stalled by pagecache activity. But note that there may be
396 * stalls if we need to run get_block(). We could test
397 * PagePrivate for that.
399 * If this process is currently in __generic_file_aio_write() against
400 * this page's queue, we can perform writeback even if that
403 * If the page is swapcache, write it back even if that would
404 * block, for some throttling. This happens by accident, because
405 * swap_backing_dev_info is bust: it doesn't reflect the
406 * congestion state of the swapdevs. Easy to fix, if needed.
408 if (!is_page_cache_freeable(page))
412 * Some data journaling orphaned pages can have
413 * page->mapping == NULL while being dirty with clean buffers.
415 if (page_has_private(page)) {
416 if (try_to_free_buffers(page)) {
417 ClearPageDirty(page);
418 printk("%s: orphaned page\n", __func__);
424 if (mapping->a_ops->writepage == NULL)
425 return PAGE_ACTIVATE;
426 if (!may_write_to_queue(mapping->backing_dev_info, sc))
429 if (clear_page_dirty_for_io(page)) {
431 struct writeback_control wbc = {
432 .sync_mode = WB_SYNC_NONE,
433 .nr_to_write = SWAP_CLUSTER_MAX,
435 .range_end = LLONG_MAX,
439 SetPageReclaim(page);
440 res = mapping->a_ops->writepage(page, &wbc);
442 handle_write_error(mapping, page, res);
443 if (res == AOP_WRITEPAGE_ACTIVATE) {
444 ClearPageReclaim(page);
445 return PAGE_ACTIVATE;
448 if (!PageWriteback(page)) {
449 /* synchronous write or broken a_ops? */
450 ClearPageReclaim(page);
452 trace_mm_vmscan_writepage(page, trace_reclaim_flags(page));
453 inc_zone_page_state(page, NR_VMSCAN_WRITE);
461 * Same as remove_mapping, but if the page is removed from the mapping, it
462 * gets returned with a refcount of 0.
464 static int __remove_mapping(struct address_space *mapping, struct page *page)
466 BUG_ON(!PageLocked(page));
467 BUG_ON(mapping != page_mapping(page));
469 spin_lock_irq(&mapping->tree_lock);
471 * The non racy check for a busy page.
473 * Must be careful with the order of the tests. When someone has
474 * a ref to the page, it may be possible that they dirty it then
475 * drop the reference. So if PageDirty is tested before page_count
476 * here, then the following race may occur:
478 * get_user_pages(&page);
479 * [user mapping goes away]
481 * !PageDirty(page) [good]
482 * SetPageDirty(page);
484 * !page_count(page) [good, discard it]
486 * [oops, our write_to data is lost]
488 * Reversing the order of the tests ensures such a situation cannot
489 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
490 * load is not satisfied before that of page->_count.
492 * Note that if SetPageDirty is always performed via set_page_dirty,
493 * and thus under tree_lock, then this ordering is not required.
495 if (!page_freeze_refs(page, 2))
497 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
498 if (unlikely(PageDirty(page))) {
499 page_unfreeze_refs(page, 2);
503 if (PageSwapCache(page)) {
504 swp_entry_t swap = { .val = page_private(page) };
505 __delete_from_swap_cache(page);
506 spin_unlock_irq(&mapping->tree_lock);
507 swapcache_free(swap, page);
509 void (*freepage)(struct page *);
511 freepage = mapping->a_ops->freepage;
513 __delete_from_page_cache(page);
514 spin_unlock_irq(&mapping->tree_lock);
515 mem_cgroup_uncharge_cache_page(page);
517 if (freepage != NULL)
524 spin_unlock_irq(&mapping->tree_lock);
529 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
530 * someone else has a ref on the page, abort and return 0. If it was
531 * successfully detached, return 1. Assumes the caller has a single ref on
534 int remove_mapping(struct address_space *mapping, struct page *page)
536 if (__remove_mapping(mapping, page)) {
538 * Unfreezing the refcount with 1 rather than 2 effectively
539 * drops the pagecache ref for us without requiring another
542 page_unfreeze_refs(page, 1);
549 * putback_lru_page - put previously isolated page onto appropriate LRU list
550 * @page: page to be put back to appropriate lru list
552 * Add previously isolated @page to appropriate LRU list.
553 * Page may still be unevictable for other reasons.
555 * lru_lock must not be held, interrupts must be enabled.
557 void putback_lru_page(struct page *page)
560 int active = !!TestClearPageActive(page);
561 int was_unevictable = PageUnevictable(page);
563 VM_BUG_ON(PageLRU(page));
566 ClearPageUnevictable(page);
568 if (page_evictable(page, NULL)) {
570 * For evictable pages, we can use the cache.
571 * In event of a race, worst case is we end up with an
572 * unevictable page on [in]active list.
573 * We know how to handle that.
575 lru = active + page_lru_base_type(page);
576 lru_cache_add_lru(page, lru);
579 * Put unevictable pages directly on zone's unevictable
582 lru = LRU_UNEVICTABLE;
583 add_page_to_unevictable_list(page);
585 * When racing with an mlock or AS_UNEVICTABLE clearing
586 * (page is unlocked) make sure that if the other thread
587 * does not observe our setting of PG_lru and fails
588 * isolation/check_move_unevictable_pages,
589 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
590 * the page back to the evictable list.
592 * The other side is TestClearPageMlocked() or shmem_lock().
598 * page's status can change while we move it among lru. If an evictable
599 * page is on unevictable list, it never be freed. To avoid that,
600 * check after we added it to the list, again.
602 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
603 if (!isolate_lru_page(page)) {
607 /* This means someone else dropped this page from LRU
608 * So, it will be freed or putback to LRU again. There is
609 * nothing to do here.
613 if (was_unevictable && lru != LRU_UNEVICTABLE)
614 count_vm_event(UNEVICTABLE_PGRESCUED);
615 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
616 count_vm_event(UNEVICTABLE_PGCULLED);
618 put_page(page); /* drop ref from isolate */
621 enum page_references {
623 PAGEREF_RECLAIM_CLEAN,
628 static enum page_references page_check_references(struct page *page,
629 struct mem_cgroup_zone *mz,
630 struct scan_control *sc)
632 int referenced_ptes, referenced_page;
633 unsigned long vm_flags;
635 referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup,
637 referenced_page = TestClearPageReferenced(page);
640 * Mlock lost the isolation race with us. Let try_to_unmap()
641 * move the page to the unevictable list.
643 if (vm_flags & VM_LOCKED)
644 return PAGEREF_RECLAIM;
646 if (referenced_ptes) {
647 if (PageSwapBacked(page))
648 return PAGEREF_ACTIVATE;
650 * All mapped pages start out with page table
651 * references from the instantiating fault, so we need
652 * to look twice if a mapped file page is used more
655 * Mark it and spare it for another trip around the
656 * inactive list. Another page table reference will
657 * lead to its activation.
659 * Note: the mark is set for activated pages as well
660 * so that recently deactivated but used pages are
663 SetPageReferenced(page);
665 if (referenced_page || referenced_ptes > 1)
666 return PAGEREF_ACTIVATE;
669 * Activate file-backed executable pages after first usage.
671 if (vm_flags & VM_EXEC)
672 return PAGEREF_ACTIVATE;
677 /* Reclaim if clean, defer dirty pages to writeback */
678 if (referenced_page && !PageSwapBacked(page))
679 return PAGEREF_RECLAIM_CLEAN;
681 return PAGEREF_RECLAIM;
685 * shrink_page_list() returns the number of reclaimed pages
687 static unsigned long shrink_page_list(struct list_head *page_list,
688 struct mem_cgroup_zone *mz,
689 struct scan_control *sc,
691 unsigned long *ret_nr_dirty,
692 unsigned long *ret_nr_writeback)
694 LIST_HEAD(ret_pages);
695 LIST_HEAD(free_pages);
697 unsigned long nr_dirty = 0;
698 unsigned long nr_congested = 0;
699 unsigned long nr_reclaimed = 0;
700 unsigned long nr_writeback = 0;
704 while (!list_empty(page_list)) {
705 enum page_references references;
706 struct address_space *mapping;
712 page = lru_to_page(page_list);
713 list_del(&page->lru);
715 if (!trylock_page(page))
718 VM_BUG_ON(PageActive(page));
719 VM_BUG_ON(page_zone(page) != mz->zone);
723 if (unlikely(!page_evictable(page, NULL)))
726 if (!sc->may_unmap && page_mapped(page))
729 /* Double the slab pressure for mapped and swapcache pages */
730 if (page_mapped(page) || PageSwapCache(page))
733 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
734 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
736 if (PageWriteback(page)) {
742 references = page_check_references(page, mz, sc);
743 switch (references) {
744 case PAGEREF_ACTIVATE:
745 goto activate_locked;
748 case PAGEREF_RECLAIM:
749 case PAGEREF_RECLAIM_CLEAN:
750 ; /* try to reclaim the page below */
754 * Anonymous process memory has backing store?
755 * Try to allocate it some swap space here.
757 if (PageAnon(page) && !PageSwapCache(page)) {
758 if (!(sc->gfp_mask & __GFP_IO))
760 if (!add_to_swap(page))
761 goto activate_locked;
765 mapping = page_mapping(page);
768 * The page is mapped into the page tables of one or more
769 * processes. Try to unmap it here.
771 if (page_mapped(page) && mapping) {
772 switch (try_to_unmap(page, TTU_UNMAP)) {
774 goto activate_locked;
780 ; /* try to free the page below */
784 if (PageDirty(page)) {
788 * Only kswapd can writeback filesystem pages to
789 * avoid risk of stack overflow but do not writeback
790 * unless under significant pressure.
792 if (page_is_file_cache(page) &&
793 (!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) {
795 * Immediately reclaim when written back.
796 * Similar in principal to deactivate_page()
797 * except we already have the page isolated
798 * and know it's dirty
800 inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
801 SetPageReclaim(page);
806 if (references == PAGEREF_RECLAIM_CLEAN)
810 if (!sc->may_writepage)
813 /* Page is dirty, try to write it out here */
814 switch (pageout(page, mapping, sc)) {
819 goto activate_locked;
821 if (PageWriteback(page))
827 * A synchronous write - probably a ramdisk. Go
828 * ahead and try to reclaim the page.
830 if (!trylock_page(page))
832 if (PageDirty(page) || PageWriteback(page))
834 mapping = page_mapping(page);
836 ; /* try to free the page below */
841 * If the page has buffers, try to free the buffer mappings
842 * associated with this page. If we succeed we try to free
845 * We do this even if the page is PageDirty().
846 * try_to_release_page() does not perform I/O, but it is
847 * possible for a page to have PageDirty set, but it is actually
848 * clean (all its buffers are clean). This happens if the
849 * buffers were written out directly, with submit_bh(). ext3
850 * will do this, as well as the blockdev mapping.
851 * try_to_release_page() will discover that cleanness and will
852 * drop the buffers and mark the page clean - it can be freed.
854 * Rarely, pages can have buffers and no ->mapping. These are
855 * the pages which were not successfully invalidated in
856 * truncate_complete_page(). We try to drop those buffers here
857 * and if that worked, and the page is no longer mapped into
858 * process address space (page_count == 1) it can be freed.
859 * Otherwise, leave the page on the LRU so it is swappable.
861 if (page_has_private(page)) {
862 if (!try_to_release_page(page, sc->gfp_mask))
863 goto activate_locked;
864 if (!mapping && page_count(page) == 1) {
866 if (put_page_testzero(page))
870 * rare race with speculative reference.
871 * the speculative reference will free
872 * this page shortly, so we may
873 * increment nr_reclaimed here (and
874 * leave it off the LRU).
882 if (!mapping || !__remove_mapping(mapping, page))
886 * At this point, we have no other references and there is
887 * no way to pick any more up (removed from LRU, removed
888 * from pagecache). Can use non-atomic bitops now (and
889 * we obviously don't have to worry about waking up a process
890 * waiting on the page lock, because there are no references.
892 __clear_page_locked(page);
897 * Is there need to periodically free_page_list? It would
898 * appear not as the counts should be low
900 list_add(&page->lru, &free_pages);
904 if (PageSwapCache(page))
905 try_to_free_swap(page);
907 putback_lru_page(page);
911 /* Not a candidate for swapping, so reclaim swap space. */
912 if (PageSwapCache(page) && vm_swap_full())
913 try_to_free_swap(page);
914 VM_BUG_ON(PageActive(page));
920 list_add(&page->lru, &ret_pages);
921 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
925 * Tag a zone as congested if all the dirty pages encountered were
926 * backed by a congested BDI. In this case, reclaimers should just
927 * back off and wait for congestion to clear because further reclaim
928 * will encounter the same problem
930 if (nr_dirty && nr_dirty == nr_congested && global_reclaim(sc))
931 zone_set_flag(mz->zone, ZONE_CONGESTED);
933 free_hot_cold_page_list(&free_pages, 1);
935 list_splice(&ret_pages, page_list);
936 count_vm_events(PGACTIVATE, pgactivate);
937 *ret_nr_dirty += nr_dirty;
938 *ret_nr_writeback += nr_writeback;
943 * Attempt to remove the specified page from its LRU. Only take this page
944 * if it is of the appropriate PageActive status. Pages which are being
945 * freed elsewhere are also ignored.
947 * page: page to consider
948 * mode: one of the LRU isolation modes defined above
950 * returns 0 on success, -ve errno on failure.
952 int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
957 /* Only take pages on the LRU. */
961 all_lru_mode = (mode & (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) ==
962 (ISOLATE_ACTIVE|ISOLATE_INACTIVE);
965 * When checking the active state, we need to be sure we are
966 * dealing with comparible boolean values. Take the logical not
969 if (!all_lru_mode && !PageActive(page) != !(mode & ISOLATE_ACTIVE))
972 if (!all_lru_mode && !!page_is_file_cache(page) != file)
975 /* Do not give back unevictable pages for compaction */
976 if (PageUnevictable(page))
982 * To minimise LRU disruption, the caller can indicate that it only
983 * wants to isolate pages it will be able to operate on without
984 * blocking - clean pages for the most part.
986 * ISOLATE_CLEAN means that only clean pages should be isolated. This
987 * is used by reclaim when it is cannot write to backing storage
989 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
990 * that it is possible to migrate without blocking
992 if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
993 /* All the caller can do on PageWriteback is block */
994 if (PageWriteback(page))
997 if (PageDirty(page)) {
998 struct address_space *mapping;
1000 /* ISOLATE_CLEAN means only clean pages */
1001 if (mode & ISOLATE_CLEAN)
1005 * Only pages without mappings or that have a
1006 * ->migratepage callback are possible to migrate
1009 mapping = page_mapping(page);
1010 if (mapping && !mapping->a_ops->migratepage)
1015 if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
1018 if (likely(get_page_unless_zero(page))) {
1020 * Be careful not to clear PageLRU until after we're
1021 * sure the page is not being freed elsewhere -- the
1022 * page release code relies on it.
1032 * zone->lru_lock is heavily contended. Some of the functions that
1033 * shrink the lists perform better by taking out a batch of pages
1034 * and working on them outside the LRU lock.
1036 * For pagecache intensive workloads, this function is the hottest
1037 * spot in the kernel (apart from copy_*_user functions).
1039 * Appropriate locks must be held before calling this function.
1041 * @nr_to_scan: The number of pages to look through on the list.
1042 * @mz: The mem_cgroup_zone to pull pages from.
1043 * @dst: The temp list to put pages on to.
1044 * @nr_scanned: The number of pages that were scanned.
1045 * @sc: The scan_control struct for this reclaim session
1046 * @mode: One of the LRU isolation modes
1047 * @active: True [1] if isolating active pages
1048 * @file: True [1] if isolating file [!anon] pages
1050 * returns how many pages were moved onto *@dst.
1052 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1053 struct mem_cgroup_zone *mz, struct list_head *dst,
1054 unsigned long *nr_scanned, struct scan_control *sc,
1055 isolate_mode_t mode, int active, int file)
1057 struct lruvec *lruvec;
1058 struct list_head *src;
1059 unsigned long nr_taken = 0;
1063 lruvec = mem_cgroup_zone_lruvec(mz->zone, mz->mem_cgroup);
1068 src = &lruvec->lists[lru];
1070 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
1073 page = lru_to_page(src);
1074 prefetchw_prev_lru_page(page, src, flags);
1076 VM_BUG_ON(!PageLRU(page));
1078 switch (__isolate_lru_page(page, mode, file)) {
1080 mem_cgroup_lru_del(page);
1081 list_move(&page->lru, dst);
1082 nr_taken += hpage_nr_pages(page);
1086 /* else it is being freed elsewhere */
1087 list_move(&page->lru, src);
1097 trace_mm_vmscan_lru_isolate(sc->order,
1105 * isolate_lru_page - tries to isolate a page from its LRU list
1106 * @page: page to isolate from its LRU list
1108 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1109 * vmstat statistic corresponding to whatever LRU list the page was on.
1111 * Returns 0 if the page was removed from an LRU list.
1112 * Returns -EBUSY if the page was not on an LRU list.
1114 * The returned page will have PageLRU() cleared. If it was found on
1115 * the active list, it will have PageActive set. If it was found on
1116 * the unevictable list, it will have the PageUnevictable bit set. That flag
1117 * may need to be cleared by the caller before letting the page go.
1119 * The vmstat statistic corresponding to the list on which the page was
1120 * found will be decremented.
1123 * (1) Must be called with an elevated refcount on the page. This is a
1124 * fundamentnal difference from isolate_lru_pages (which is called
1125 * without a stable reference).
1126 * (2) the lru_lock must not be held.
1127 * (3) interrupts must be enabled.
1129 int isolate_lru_page(struct page *page)
1133 VM_BUG_ON(!page_count(page));
1135 if (PageLRU(page)) {
1136 struct zone *zone = page_zone(page);
1138 spin_lock_irq(&zone->lru_lock);
1139 if (PageLRU(page)) {
1140 int lru = page_lru(page);
1145 del_page_from_lru_list(zone, page, lru);
1147 spin_unlock_irq(&zone->lru_lock);
1153 * Are there way too many processes in the direct reclaim path already?
1155 static int too_many_isolated(struct zone *zone, int file,
1156 struct scan_control *sc)
1158 unsigned long inactive, isolated;
1160 if (current_is_kswapd())
1163 if (!global_reclaim(sc))
1167 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1168 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1170 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1171 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1174 return isolated > inactive;
1177 static noinline_for_stack void
1178 putback_inactive_pages(struct mem_cgroup_zone *mz,
1179 struct list_head *page_list)
1181 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1182 struct zone *zone = mz->zone;
1183 LIST_HEAD(pages_to_free);
1186 * Put back any unfreeable pages.
1188 while (!list_empty(page_list)) {
1189 struct page *page = lru_to_page(page_list);
1192 VM_BUG_ON(PageLRU(page));
1193 list_del(&page->lru);
1194 if (unlikely(!page_evictable(page, NULL))) {
1195 spin_unlock_irq(&zone->lru_lock);
1196 putback_lru_page(page);
1197 spin_lock_irq(&zone->lru_lock);
1201 lru = page_lru(page);
1202 add_page_to_lru_list(zone, page, lru);
1203 if (is_active_lru(lru)) {
1204 int file = is_file_lru(lru);
1205 int numpages = hpage_nr_pages(page);
1206 reclaim_stat->recent_rotated[file] += numpages;
1208 if (put_page_testzero(page)) {
1209 __ClearPageLRU(page);
1210 __ClearPageActive(page);
1211 del_page_from_lru_list(zone, page, lru);
1213 if (unlikely(PageCompound(page))) {
1214 spin_unlock_irq(&zone->lru_lock);
1215 (*get_compound_page_dtor(page))(page);
1216 spin_lock_irq(&zone->lru_lock);
1218 list_add(&page->lru, &pages_to_free);
1223 * To save our caller's stack, now use input list for pages to free.
1225 list_splice(&pages_to_free, page_list);
1228 static noinline_for_stack void
1229 update_isolated_counts(struct mem_cgroup_zone *mz,
1230 struct list_head *page_list,
1231 unsigned long *nr_anon,
1232 unsigned long *nr_file)
1234 struct zone *zone = mz->zone;
1235 unsigned int count[NR_LRU_LISTS] = { 0, };
1236 unsigned long nr_active = 0;
1241 * Count pages and clear active flags
1243 list_for_each_entry(page, page_list, lru) {
1244 int numpages = hpage_nr_pages(page);
1245 lru = page_lru_base_type(page);
1246 if (PageActive(page)) {
1248 ClearPageActive(page);
1249 nr_active += numpages;
1251 count[lru] += numpages;
1255 __count_vm_events(PGDEACTIVATE, nr_active);
1257 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1258 -count[LRU_ACTIVE_FILE]);
1259 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1260 -count[LRU_INACTIVE_FILE]);
1261 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1262 -count[LRU_ACTIVE_ANON]);
1263 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1264 -count[LRU_INACTIVE_ANON]);
1266 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1267 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1269 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
1270 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
1275 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1276 * of reclaimed pages
1278 static noinline_for_stack unsigned long
1279 shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz,
1280 struct scan_control *sc, int priority, int file)
1282 LIST_HEAD(page_list);
1283 unsigned long nr_scanned;
1284 unsigned long nr_reclaimed = 0;
1285 unsigned long nr_taken;
1286 unsigned long nr_anon;
1287 unsigned long nr_file;
1288 unsigned long nr_dirty = 0;
1289 unsigned long nr_writeback = 0;
1290 isolate_mode_t isolate_mode = ISOLATE_INACTIVE;
1291 struct zone *zone = mz->zone;
1292 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1294 while (unlikely(too_many_isolated(zone, file, sc))) {
1295 congestion_wait(BLK_RW_ASYNC, HZ/10);
1297 /* We are about to die and free our memory. Return now. */
1298 if (fatal_signal_pending(current))
1299 return SWAP_CLUSTER_MAX;
1305 isolate_mode |= ISOLATE_UNMAPPED;
1306 if (!sc->may_writepage)
1307 isolate_mode |= ISOLATE_CLEAN;
1309 spin_lock_irq(&zone->lru_lock);
1311 nr_taken = isolate_lru_pages(nr_to_scan, mz, &page_list, &nr_scanned,
1312 sc, isolate_mode, 0, file);
1313 if (global_reclaim(sc)) {
1314 zone->pages_scanned += nr_scanned;
1315 if (current_is_kswapd())
1316 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1319 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1322 spin_unlock_irq(&zone->lru_lock);
1327 update_isolated_counts(mz, &page_list, &nr_anon, &nr_file);
1329 nr_reclaimed = shrink_page_list(&page_list, mz, sc, priority,
1330 &nr_dirty, &nr_writeback);
1332 spin_lock_irq(&zone->lru_lock);
1334 reclaim_stat->recent_scanned[0] += nr_anon;
1335 reclaim_stat->recent_scanned[1] += nr_file;
1337 if (global_reclaim(sc)) {
1338 if (current_is_kswapd())
1339 __count_zone_vm_events(PGSTEAL_KSWAPD, zone,
1342 __count_zone_vm_events(PGSTEAL_DIRECT, zone,
1346 putback_inactive_pages(mz, &page_list);
1348 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1349 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1351 spin_unlock_irq(&zone->lru_lock);
1353 free_hot_cold_page_list(&page_list, 1);
1356 * If reclaim is isolating dirty pages under writeback, it implies
1357 * that the long-lived page allocation rate is exceeding the page
1358 * laundering rate. Either the global limits are not being effective
1359 * at throttling processes due to the page distribution throughout
1360 * zones or there is heavy usage of a slow backing device. The
1361 * only option is to throttle from reclaim context which is not ideal
1362 * as there is no guarantee the dirtying process is throttled in the
1363 * same way balance_dirty_pages() manages.
1365 * This scales the number of dirty pages that must be under writeback
1366 * before throttling depending on priority. It is a simple backoff
1367 * function that has the most effect in the range DEF_PRIORITY to
1368 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
1369 * in trouble and reclaim is considered to be in trouble.
1371 * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle
1372 * DEF_PRIORITY-1 50% must be PageWriteback
1373 * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble
1375 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
1376 * isolated page is PageWriteback
1378 if (nr_writeback && nr_writeback >= (nr_taken >> (DEF_PRIORITY-priority)))
1379 wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
1381 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1383 nr_scanned, nr_reclaimed,
1385 trace_shrink_flags(file));
1386 return nr_reclaimed;
1390 * This moves pages from the active list to the inactive list.
1392 * We move them the other way if the page is referenced by one or more
1393 * processes, from rmap.
1395 * If the pages are mostly unmapped, the processing is fast and it is
1396 * appropriate to hold zone->lru_lock across the whole operation. But if
1397 * the pages are mapped, the processing is slow (page_referenced()) so we
1398 * should drop zone->lru_lock around each page. It's impossible to balance
1399 * this, so instead we remove the pages from the LRU while processing them.
1400 * It is safe to rely on PG_active against the non-LRU pages in here because
1401 * nobody will play with that bit on a non-LRU page.
1403 * The downside is that we have to touch page->_count against each page.
1404 * But we had to alter page->flags anyway.
1407 static void move_active_pages_to_lru(struct zone *zone,
1408 struct list_head *list,
1409 struct list_head *pages_to_free,
1412 unsigned long pgmoved = 0;
1415 while (!list_empty(list)) {
1416 struct lruvec *lruvec;
1418 page = lru_to_page(list);
1420 VM_BUG_ON(PageLRU(page));
1423 lruvec = mem_cgroup_lru_add_list(zone, page, lru);
1424 list_move(&page->lru, &lruvec->lists[lru]);
1425 pgmoved += hpage_nr_pages(page);
1427 if (put_page_testzero(page)) {
1428 __ClearPageLRU(page);
1429 __ClearPageActive(page);
1430 del_page_from_lru_list(zone, page, lru);
1432 if (unlikely(PageCompound(page))) {
1433 spin_unlock_irq(&zone->lru_lock);
1434 (*get_compound_page_dtor(page))(page);
1435 spin_lock_irq(&zone->lru_lock);
1437 list_add(&page->lru, pages_to_free);
1440 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1441 if (!is_active_lru(lru))
1442 __count_vm_events(PGDEACTIVATE, pgmoved);
1445 static void shrink_active_list(unsigned long nr_to_scan,
1446 struct mem_cgroup_zone *mz,
1447 struct scan_control *sc,
1448 int priority, int file)
1450 unsigned long nr_taken;
1451 unsigned long nr_scanned;
1452 unsigned long vm_flags;
1453 LIST_HEAD(l_hold); /* The pages which were snipped off */
1454 LIST_HEAD(l_active);
1455 LIST_HEAD(l_inactive);
1457 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1458 unsigned long nr_rotated = 0;
1459 isolate_mode_t isolate_mode = ISOLATE_ACTIVE;
1460 struct zone *zone = mz->zone;
1465 isolate_mode |= ISOLATE_UNMAPPED;
1466 if (!sc->may_writepage)
1467 isolate_mode |= ISOLATE_CLEAN;
1469 spin_lock_irq(&zone->lru_lock);
1471 nr_taken = isolate_lru_pages(nr_to_scan, mz, &l_hold, &nr_scanned, sc,
1472 isolate_mode, 1, file);
1473 if (global_reclaim(sc))
1474 zone->pages_scanned += nr_scanned;
1476 reclaim_stat->recent_scanned[file] += nr_taken;
1478 __count_zone_vm_events(PGREFILL, zone, nr_scanned);
1480 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1482 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1483 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1484 spin_unlock_irq(&zone->lru_lock);
1486 while (!list_empty(&l_hold)) {
1488 page = lru_to_page(&l_hold);
1489 list_del(&page->lru);
1491 if (unlikely(!page_evictable(page, NULL))) {
1492 putback_lru_page(page);
1496 if (unlikely(buffer_heads_over_limit)) {
1497 if (page_has_private(page) && trylock_page(page)) {
1498 if (page_has_private(page))
1499 try_to_release_page(page, 0);
1504 if (page_referenced(page, 0, sc->target_mem_cgroup,
1506 nr_rotated += hpage_nr_pages(page);
1508 * Identify referenced, file-backed active pages and
1509 * give them one more trip around the active list. So
1510 * that executable code get better chances to stay in
1511 * memory under moderate memory pressure. Anon pages
1512 * are not likely to be evicted by use-once streaming
1513 * IO, plus JVM can create lots of anon VM_EXEC pages,
1514 * so we ignore them here.
1516 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1517 list_add(&page->lru, &l_active);
1522 ClearPageActive(page); /* we are de-activating */
1523 list_add(&page->lru, &l_inactive);
1527 * Move pages back to the lru list.
1529 spin_lock_irq(&zone->lru_lock);
1531 * Count referenced pages from currently used mappings as rotated,
1532 * even though only some of them are actually re-activated. This
1533 * helps balance scan pressure between file and anonymous pages in
1536 reclaim_stat->recent_rotated[file] += nr_rotated;
1538 move_active_pages_to_lru(zone, &l_active, &l_hold,
1539 LRU_ACTIVE + file * LRU_FILE);
1540 move_active_pages_to_lru(zone, &l_inactive, &l_hold,
1541 LRU_BASE + file * LRU_FILE);
1542 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1543 spin_unlock_irq(&zone->lru_lock);
1545 free_hot_cold_page_list(&l_hold, 1);
1549 static int inactive_anon_is_low_global(struct zone *zone)
1551 unsigned long active, inactive;
1553 active = zone_page_state(zone, NR_ACTIVE_ANON);
1554 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1556 if (inactive * zone->inactive_ratio < active)
1563 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1564 * @zone: zone to check
1565 * @sc: scan control of this context
1567 * Returns true if the zone does not have enough inactive anon pages,
1568 * meaning some active anon pages need to be deactivated.
1570 static int inactive_anon_is_low(struct mem_cgroup_zone *mz)
1573 * If we don't have swap space, anonymous page deactivation
1576 if (!total_swap_pages)
1579 if (!mem_cgroup_disabled())
1580 return mem_cgroup_inactive_anon_is_low(mz->mem_cgroup,
1583 return inactive_anon_is_low_global(mz->zone);
1586 static inline int inactive_anon_is_low(struct mem_cgroup_zone *mz)
1592 static int inactive_file_is_low_global(struct zone *zone)
1594 unsigned long active, inactive;
1596 active = zone_page_state(zone, NR_ACTIVE_FILE);
1597 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1599 return (active > inactive);
1603 * inactive_file_is_low - check if file pages need to be deactivated
1604 * @mz: memory cgroup and zone to check
1606 * When the system is doing streaming IO, memory pressure here
1607 * ensures that active file pages get deactivated, until more
1608 * than half of the file pages are on the inactive list.
1610 * Once we get to that situation, protect the system's working
1611 * set from being evicted by disabling active file page aging.
1613 * This uses a different ratio than the anonymous pages, because
1614 * the page cache uses a use-once replacement algorithm.
1616 static int inactive_file_is_low(struct mem_cgroup_zone *mz)
1618 if (!mem_cgroup_disabled())
1619 return mem_cgroup_inactive_file_is_low(mz->mem_cgroup,
1622 return inactive_file_is_low_global(mz->zone);
1625 static int inactive_list_is_low(struct mem_cgroup_zone *mz, int file)
1628 return inactive_file_is_low(mz);
1630 return inactive_anon_is_low(mz);
1633 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1634 struct mem_cgroup_zone *mz,
1635 struct scan_control *sc, int priority)
1637 int file = is_file_lru(lru);
1639 if (is_active_lru(lru)) {
1640 if (inactive_list_is_low(mz, file))
1641 shrink_active_list(nr_to_scan, mz, sc, priority, file);
1645 return shrink_inactive_list(nr_to_scan, mz, sc, priority, file);
1648 static int vmscan_swappiness(struct mem_cgroup_zone *mz,
1649 struct scan_control *sc)
1651 if (global_reclaim(sc))
1652 return vm_swappiness;
1653 return mem_cgroup_swappiness(mz->mem_cgroup);
1657 * Determine how aggressively the anon and file LRU lists should be
1658 * scanned. The relative value of each set of LRU lists is determined
1659 * by looking at the fraction of the pages scanned we did rotate back
1660 * onto the active list instead of evict.
1662 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
1663 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
1665 static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
1666 unsigned long *nr, int priority)
1668 unsigned long anon, file, free;
1669 unsigned long anon_prio, file_prio;
1670 unsigned long ap, fp;
1671 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1672 u64 fraction[2], denominator;
1675 bool force_scan = false;
1678 * If the zone or memcg is small, nr[l] can be 0. This
1679 * results in no scanning on this priority and a potential
1680 * priority drop. Global direct reclaim can go to the next
1681 * zone and tends to have no problems. Global kswapd is for
1682 * zone balancing and it needs to scan a minimum amount. When
1683 * reclaiming for a memcg, a priority drop can cause high
1684 * latencies, so it's better to scan a minimum amount there as
1687 if (current_is_kswapd() && mz->zone->all_unreclaimable)
1689 if (!global_reclaim(sc))
1692 /* If we have no swap space, do not bother scanning anon pages. */
1693 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1701 anon = zone_nr_lru_pages(mz, LRU_ACTIVE_ANON) +
1702 zone_nr_lru_pages(mz, LRU_INACTIVE_ANON);
1703 file = zone_nr_lru_pages(mz, LRU_ACTIVE_FILE) +
1704 zone_nr_lru_pages(mz, LRU_INACTIVE_FILE);
1706 if (global_reclaim(sc)) {
1707 free = zone_page_state(mz->zone, NR_FREE_PAGES);
1708 /* If we have very few page cache pages,
1709 force-scan anon pages. */
1710 if (unlikely(file + free <= high_wmark_pages(mz->zone))) {
1719 * With swappiness at 100, anonymous and file have the same priority.
1720 * This scanning priority is essentially the inverse of IO cost.
1722 anon_prio = vmscan_swappiness(mz, sc);
1723 file_prio = 200 - vmscan_swappiness(mz, sc);
1726 * OK, so we have swap space and a fair amount of page cache
1727 * pages. We use the recently rotated / recently scanned
1728 * ratios to determine how valuable each cache is.
1730 * Because workloads change over time (and to avoid overflow)
1731 * we keep these statistics as a floating average, which ends
1732 * up weighing recent references more than old ones.
1734 * anon in [0], file in [1]
1736 spin_lock_irq(&mz->zone->lru_lock);
1737 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1738 reclaim_stat->recent_scanned[0] /= 2;
1739 reclaim_stat->recent_rotated[0] /= 2;
1742 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1743 reclaim_stat->recent_scanned[1] /= 2;
1744 reclaim_stat->recent_rotated[1] /= 2;
1748 * The amount of pressure on anon vs file pages is inversely
1749 * proportional to the fraction of recently scanned pages on
1750 * each list that were recently referenced and in active use.
1752 ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
1753 ap /= reclaim_stat->recent_rotated[0] + 1;
1755 fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
1756 fp /= reclaim_stat->recent_rotated[1] + 1;
1757 spin_unlock_irq(&mz->zone->lru_lock);
1761 denominator = ap + fp + 1;
1763 for_each_evictable_lru(lru) {
1764 int file = is_file_lru(lru);
1767 scan = zone_nr_lru_pages(mz, lru);
1768 if (priority || noswap || !vmscan_swappiness(mz, sc)) {
1770 if (!scan && force_scan)
1771 scan = SWAP_CLUSTER_MAX;
1772 scan = div64_u64(scan * fraction[file], denominator);
1778 /* Use reclaim/compaction for costly allocs or under memory pressure */
1779 static bool in_reclaim_compaction(int priority, struct scan_control *sc)
1781 if (COMPACTION_BUILD && sc->order &&
1782 (sc->order > PAGE_ALLOC_COSTLY_ORDER ||
1783 priority < DEF_PRIORITY - 2))
1790 * Reclaim/compaction is used for high-order allocation requests. It reclaims
1791 * order-0 pages before compacting the zone. should_continue_reclaim() returns
1792 * true if more pages should be reclaimed such that when the page allocator
1793 * calls try_to_compact_zone() that it will have enough free pages to succeed.
1794 * It will give up earlier than that if there is difficulty reclaiming pages.
1796 static inline bool should_continue_reclaim(struct mem_cgroup_zone *mz,
1797 unsigned long nr_reclaimed,
1798 unsigned long nr_scanned,
1800 struct scan_control *sc)
1802 unsigned long pages_for_compaction;
1803 unsigned long inactive_lru_pages;
1805 /* If not in reclaim/compaction mode, stop */
1806 if (!in_reclaim_compaction(priority, sc))
1809 /* Consider stopping depending on scan and reclaim activity */
1810 if (sc->gfp_mask & __GFP_REPEAT) {
1812 * For __GFP_REPEAT allocations, stop reclaiming if the
1813 * full LRU list has been scanned and we are still failing
1814 * to reclaim pages. This full LRU scan is potentially
1815 * expensive but a __GFP_REPEAT caller really wants to succeed
1817 if (!nr_reclaimed && !nr_scanned)
1821 * For non-__GFP_REPEAT allocations which can presumably
1822 * fail without consequence, stop if we failed to reclaim
1823 * any pages from the last SWAP_CLUSTER_MAX number of
1824 * pages that were scanned. This will return to the
1825 * caller faster at the risk reclaim/compaction and
1826 * the resulting allocation attempt fails
1833 * If we have not reclaimed enough pages for compaction and the
1834 * inactive lists are large enough, continue reclaiming
1836 pages_for_compaction = (2UL << sc->order);
1837 inactive_lru_pages = zone_nr_lru_pages(mz, LRU_INACTIVE_FILE);
1838 if (nr_swap_pages > 0)
1839 inactive_lru_pages += zone_nr_lru_pages(mz, LRU_INACTIVE_ANON);
1840 if (sc->nr_reclaimed < pages_for_compaction &&
1841 inactive_lru_pages > pages_for_compaction)
1844 /* If compaction would go ahead or the allocation would succeed, stop */
1845 switch (compaction_suitable(mz->zone, sc->order)) {
1846 case COMPACT_PARTIAL:
1847 case COMPACT_CONTINUE:
1855 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1857 static void shrink_mem_cgroup_zone(int priority, struct mem_cgroup_zone *mz,
1858 struct scan_control *sc)
1860 unsigned long nr[NR_LRU_LISTS];
1861 unsigned long nr_to_scan;
1863 unsigned long nr_reclaimed, nr_scanned;
1864 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1865 struct blk_plug plug;
1869 nr_scanned = sc->nr_scanned;
1870 get_scan_count(mz, sc, nr, priority);
1872 blk_start_plug(&plug);
1873 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1874 nr[LRU_INACTIVE_FILE]) {
1875 for_each_evictable_lru(lru) {
1877 nr_to_scan = min_t(unsigned long,
1878 nr[lru], SWAP_CLUSTER_MAX);
1879 nr[lru] -= nr_to_scan;
1881 nr_reclaimed += shrink_list(lru, nr_to_scan,
1886 * On large memory systems, scan >> priority can become
1887 * really large. This is fine for the starting priority;
1888 * we want to put equal scanning pressure on each zone.
1889 * However, if the VM has a harder time of freeing pages,
1890 * with multiple processes reclaiming pages, the total
1891 * freeing target can get unreasonably large.
1893 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
1896 blk_finish_plug(&plug);
1897 sc->nr_reclaimed += nr_reclaimed;
1900 * Even if we did not try to evict anon pages at all, we want to
1901 * rebalance the anon lru active/inactive ratio.
1903 if (inactive_anon_is_low(mz))
1904 shrink_active_list(SWAP_CLUSTER_MAX, mz, sc, priority, 0);
1906 /* reclaim/compaction might need reclaim to continue */
1907 if (should_continue_reclaim(mz, nr_reclaimed,
1908 sc->nr_scanned - nr_scanned,
1912 throttle_vm_writeout(sc->gfp_mask);
1915 static void shrink_zone(int priority, struct zone *zone,
1916 struct scan_control *sc)
1918 struct mem_cgroup *root = sc->target_mem_cgroup;
1919 struct mem_cgroup_reclaim_cookie reclaim = {
1921 .priority = priority,
1923 struct mem_cgroup *memcg;
1925 memcg = mem_cgroup_iter(root, NULL, &reclaim);
1927 struct mem_cgroup_zone mz = {
1928 .mem_cgroup = memcg,
1932 shrink_mem_cgroup_zone(priority, &mz, sc);
1934 * Limit reclaim has historically picked one memcg and
1935 * scanned it with decreasing priority levels until
1936 * nr_to_reclaim had been reclaimed. This priority
1937 * cycle is thus over after a single memcg.
1939 * Direct reclaim and kswapd, on the other hand, have
1940 * to scan all memory cgroups to fulfill the overall
1941 * scan target for the zone.
1943 if (!global_reclaim(sc)) {
1944 mem_cgroup_iter_break(root, memcg);
1947 memcg = mem_cgroup_iter(root, memcg, &reclaim);
1951 /* Returns true if compaction should go ahead for a high-order request */
1952 static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
1954 unsigned long balance_gap, watermark;
1957 /* Do not consider compaction for orders reclaim is meant to satisfy */
1958 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER)
1962 * Compaction takes time to run and there are potentially other
1963 * callers using the pages just freed. Continue reclaiming until
1964 * there is a buffer of free pages available to give compaction
1965 * a reasonable chance of completing and allocating the page
1967 balance_gap = min(low_wmark_pages(zone),
1968 (zone->present_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
1969 KSWAPD_ZONE_BALANCE_GAP_RATIO);
1970 watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order);
1971 watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0);
1974 * If compaction is deferred, reclaim up to a point where
1975 * compaction will have a chance of success when re-enabled
1977 if (compaction_deferred(zone, sc->order))
1978 return watermark_ok;
1980 /* If compaction is not ready to start, keep reclaiming */
1981 if (!compaction_suitable(zone, sc->order))
1984 return watermark_ok;
1988 * This is the direct reclaim path, for page-allocating processes. We only
1989 * try to reclaim pages from zones which will satisfy the caller's allocation
1992 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1994 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1996 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1997 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1998 * zone defense algorithm.
2000 * If a zone is deemed to be full of pinned pages then just give it a light
2001 * scan then give up on it.
2003 * This function returns true if a zone is being reclaimed for a costly
2004 * high-order allocation and compaction is ready to begin. This indicates to
2005 * the caller that it should consider retrying the allocation instead of
2008 static bool shrink_zones(int priority, struct zonelist *zonelist,
2009 struct scan_control *sc)
2013 unsigned long nr_soft_reclaimed;
2014 unsigned long nr_soft_scanned;
2015 bool aborted_reclaim = false;
2018 * If the number of buffer_heads in the machine exceeds the maximum
2019 * allowed level, force direct reclaim to scan the highmem zone as
2020 * highmem pages could be pinning lowmem pages storing buffer_heads
2022 if (buffer_heads_over_limit)
2023 sc->gfp_mask |= __GFP_HIGHMEM;
2025 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2026 gfp_zone(sc->gfp_mask), sc->nodemask) {
2027 if (!populated_zone(zone))
2030 * Take care memory controller reclaiming has small influence
2033 if (global_reclaim(sc)) {
2034 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2036 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2037 continue; /* Let kswapd poll it */
2038 if (COMPACTION_BUILD) {
2040 * If we already have plenty of memory free for
2041 * compaction in this zone, don't free any more.
2042 * Even though compaction is invoked for any
2043 * non-zero order, only frequent costly order
2044 * reclamation is disruptive enough to become a
2045 * noticeable problem, like transparent huge
2048 if (compaction_ready(zone, sc)) {
2049 aborted_reclaim = true;
2054 * This steals pages from memory cgroups over softlimit
2055 * and returns the number of reclaimed pages and
2056 * scanned pages. This works for global memory pressure
2057 * and balancing, not for a memcg's limit.
2059 nr_soft_scanned = 0;
2060 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2061 sc->order, sc->gfp_mask,
2063 sc->nr_reclaimed += nr_soft_reclaimed;
2064 sc->nr_scanned += nr_soft_scanned;
2065 /* need some check for avoid more shrink_zone() */
2068 shrink_zone(priority, zone, sc);
2071 return aborted_reclaim;
2074 static bool zone_reclaimable(struct zone *zone)
2076 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
2079 /* All zones in zonelist are unreclaimable? */
2080 static bool all_unreclaimable(struct zonelist *zonelist,
2081 struct scan_control *sc)
2086 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2087 gfp_zone(sc->gfp_mask), sc->nodemask) {
2088 if (!populated_zone(zone))
2090 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2092 if (!zone->all_unreclaimable)
2100 * This is the main entry point to direct page reclaim.
2102 * If a full scan of the inactive list fails to free enough memory then we
2103 * are "out of memory" and something needs to be killed.
2105 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2106 * high - the zone may be full of dirty or under-writeback pages, which this
2107 * caller can't do much about. We kick the writeback threads and take explicit
2108 * naps in the hope that some of these pages can be written. But if the
2109 * allocating task holds filesystem locks which prevent writeout this might not
2110 * work, and the allocation attempt will fail.
2112 * returns: 0, if no pages reclaimed
2113 * else, the number of pages reclaimed
2115 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2116 struct scan_control *sc,
2117 struct shrink_control *shrink)
2120 unsigned long total_scanned = 0;
2121 struct reclaim_state *reclaim_state = current->reclaim_state;
2124 unsigned long writeback_threshold;
2125 bool aborted_reclaim;
2127 delayacct_freepages_start();
2129 if (global_reclaim(sc))
2130 count_vm_event(ALLOCSTALL);
2132 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2134 aborted_reclaim = shrink_zones(priority, zonelist, sc);
2137 * Don't shrink slabs when reclaiming memory from
2138 * over limit cgroups
2140 if (global_reclaim(sc)) {
2141 unsigned long lru_pages = 0;
2142 for_each_zone_zonelist(zone, z, zonelist,
2143 gfp_zone(sc->gfp_mask)) {
2144 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2147 lru_pages += zone_reclaimable_pages(zone);
2150 shrink_slab(shrink, sc->nr_scanned, lru_pages);
2151 if (reclaim_state) {
2152 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2153 reclaim_state->reclaimed_slab = 0;
2156 total_scanned += sc->nr_scanned;
2157 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
2161 * Try to write back as many pages as we just scanned. This
2162 * tends to cause slow streaming writers to write data to the
2163 * disk smoothly, at the dirtying rate, which is nice. But
2164 * that's undesirable in laptop mode, where we *want* lumpy
2165 * writeout. So in laptop mode, write out the whole world.
2167 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2168 if (total_scanned > writeback_threshold) {
2169 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
2170 WB_REASON_TRY_TO_FREE_PAGES);
2171 sc->may_writepage = 1;
2174 /* Take a nap, wait for some writeback to complete */
2175 if (!sc->hibernation_mode && sc->nr_scanned &&
2176 priority < DEF_PRIORITY - 2) {
2177 struct zone *preferred_zone;
2179 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2180 &cpuset_current_mems_allowed,
2182 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
2187 delayacct_freepages_end();
2189 if (sc->nr_reclaimed)
2190 return sc->nr_reclaimed;
2193 * As hibernation is going on, kswapd is freezed so that it can't mark
2194 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2197 if (oom_killer_disabled)
2200 /* Aborted reclaim to try compaction? don't OOM, then */
2201 if (aborted_reclaim)
2204 /* top priority shrink_zones still had more to do? don't OOM, then */
2205 if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc))
2211 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2212 gfp_t gfp_mask, nodemask_t *nodemask)
2214 unsigned long nr_reclaimed;
2215 struct scan_control sc = {
2216 .gfp_mask = gfp_mask,
2217 .may_writepage = !laptop_mode,
2218 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2222 .target_mem_cgroup = NULL,
2223 .nodemask = nodemask,
2225 struct shrink_control shrink = {
2226 .gfp_mask = sc.gfp_mask,
2229 trace_mm_vmscan_direct_reclaim_begin(order,
2233 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2235 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2237 return nr_reclaimed;
2240 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2242 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
2243 gfp_t gfp_mask, bool noswap,
2245 unsigned long *nr_scanned)
2247 struct scan_control sc = {
2249 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2250 .may_writepage = !laptop_mode,
2252 .may_swap = !noswap,
2254 .target_mem_cgroup = memcg,
2256 struct mem_cgroup_zone mz = {
2257 .mem_cgroup = memcg,
2261 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2262 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2264 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2269 * NOTE: Although we can get the priority field, using it
2270 * here is not a good idea, since it limits the pages we can scan.
2271 * if we don't reclaim here, the shrink_zone from balance_pgdat
2272 * will pick up pages from other mem cgroup's as well. We hack
2273 * the priority and make it zero.
2275 shrink_mem_cgroup_zone(0, &mz, &sc);
2277 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2279 *nr_scanned = sc.nr_scanned;
2280 return sc.nr_reclaimed;
2283 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
2287 struct zonelist *zonelist;
2288 unsigned long nr_reclaimed;
2290 struct scan_control sc = {
2291 .may_writepage = !laptop_mode,
2293 .may_swap = !noswap,
2294 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2296 .target_mem_cgroup = memcg,
2297 .nodemask = NULL, /* we don't care the placement */
2298 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2299 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2301 struct shrink_control shrink = {
2302 .gfp_mask = sc.gfp_mask,
2306 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2307 * take care of from where we get pages. So the node where we start the
2308 * scan does not need to be the current node.
2310 nid = mem_cgroup_select_victim_node(memcg);
2312 zonelist = NODE_DATA(nid)->node_zonelists;
2314 trace_mm_vmscan_memcg_reclaim_begin(0,
2318 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2320 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2322 return nr_reclaimed;
2326 static void age_active_anon(struct zone *zone, struct scan_control *sc,
2329 struct mem_cgroup *memcg;
2331 if (!total_swap_pages)
2334 memcg = mem_cgroup_iter(NULL, NULL, NULL);
2336 struct mem_cgroup_zone mz = {
2337 .mem_cgroup = memcg,
2341 if (inactive_anon_is_low(&mz))
2342 shrink_active_list(SWAP_CLUSTER_MAX, &mz,
2345 memcg = mem_cgroup_iter(NULL, memcg, NULL);
2350 * pgdat_balanced is used when checking if a node is balanced for high-order
2351 * allocations. Only zones that meet watermarks and are in a zone allowed
2352 * by the callers classzone_idx are added to balanced_pages. The total of
2353 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2354 * for the node to be considered balanced. Forcing all zones to be balanced
2355 * for high orders can cause excessive reclaim when there are imbalanced zones.
2356 * The choice of 25% is due to
2357 * o a 16M DMA zone that is balanced will not balance a zone on any
2358 * reasonable sized machine
2359 * o On all other machines, the top zone must be at least a reasonable
2360 * percentage of the middle zones. For example, on 32-bit x86, highmem
2361 * would need to be at least 256M for it to be balance a whole node.
2362 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2363 * to balance a node on its own. These seemed like reasonable ratios.
2365 static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
2368 unsigned long present_pages = 0;
2371 for (i = 0; i <= classzone_idx; i++)
2372 present_pages += pgdat->node_zones[i].present_pages;
2374 /* A special case here: if zone has no page, we think it's balanced */
2375 return balanced_pages >= (present_pages >> 2);
2378 /* is kswapd sleeping prematurely? */
2379 static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
2383 unsigned long balanced = 0;
2384 bool all_zones_ok = true;
2386 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2390 /* Check the watermark levels */
2391 for (i = 0; i <= classzone_idx; i++) {
2392 struct zone *zone = pgdat->node_zones + i;
2394 if (!populated_zone(zone))
2398 * balance_pgdat() skips over all_unreclaimable after
2399 * DEF_PRIORITY. Effectively, it considers them balanced so
2400 * they must be considered balanced here as well if kswapd
2403 if (zone->all_unreclaimable) {
2404 balanced += zone->present_pages;
2408 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2410 all_zones_ok = false;
2412 balanced += zone->present_pages;
2416 * For high-order requests, the balanced zones must contain at least
2417 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2421 return !pgdat_balanced(pgdat, balanced, classzone_idx);
2423 return !all_zones_ok;
2427 * For kswapd, balance_pgdat() will work across all this node's zones until
2428 * they are all at high_wmark_pages(zone).
2430 * Returns the final order kswapd was reclaiming at
2432 * There is special handling here for zones which are full of pinned pages.
2433 * This can happen if the pages are all mlocked, or if they are all used by
2434 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2435 * What we do is to detect the case where all pages in the zone have been
2436 * scanned twice and there has been zero successful reclaim. Mark the zone as
2437 * dead and from now on, only perform a short scan. Basically we're polling
2438 * the zone for when the problem goes away.
2440 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2441 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2442 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2443 * lower zones regardless of the number of free pages in the lower zones. This
2444 * interoperates with the page allocator fallback scheme to ensure that aging
2445 * of pages is balanced across the zones.
2447 static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2451 unsigned long balanced;
2454 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2455 unsigned long total_scanned;
2456 struct reclaim_state *reclaim_state = current->reclaim_state;
2457 unsigned long nr_soft_reclaimed;
2458 unsigned long nr_soft_scanned;
2459 struct scan_control sc = {
2460 .gfp_mask = GFP_KERNEL,
2464 * kswapd doesn't want to be bailed out while reclaim. because
2465 * we want to put equal scanning pressure on each zone.
2467 .nr_to_reclaim = ULONG_MAX,
2469 .target_mem_cgroup = NULL,
2471 struct shrink_control shrink = {
2472 .gfp_mask = sc.gfp_mask,
2476 sc.nr_reclaimed = 0;
2477 sc.may_writepage = !laptop_mode;
2478 count_vm_event(PAGEOUTRUN);
2480 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2481 unsigned long lru_pages = 0;
2482 int has_under_min_watermark_zone = 0;
2488 * Scan in the highmem->dma direction for the highest
2489 * zone which needs scanning
2491 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2492 struct zone *zone = pgdat->node_zones + i;
2494 if (!populated_zone(zone))
2497 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2501 * Do some background aging of the anon list, to give
2502 * pages a chance to be referenced before reclaiming.
2504 age_active_anon(zone, &sc, priority);
2507 * If the number of buffer_heads in the machine
2508 * exceeds the maximum allowed level and this node
2509 * has a highmem zone, force kswapd to reclaim from
2510 * it to relieve lowmem pressure.
2512 if (buffer_heads_over_limit && is_highmem_idx(i)) {
2517 if (!zone_watermark_ok_safe(zone, order,
2518 high_wmark_pages(zone), 0, 0)) {
2522 /* If balanced, clear the congested flag */
2523 zone_clear_flag(zone, ZONE_CONGESTED);
2529 for (i = 0; i <= end_zone; i++) {
2530 struct zone *zone = pgdat->node_zones + i;
2532 lru_pages += zone_reclaimable_pages(zone);
2536 * Now scan the zone in the dma->highmem direction, stopping
2537 * at the last zone which needs scanning.
2539 * We do this because the page allocator works in the opposite
2540 * direction. This prevents the page allocator from allocating
2541 * pages behind kswapd's direction of progress, which would
2542 * cause too much scanning of the lower zones.
2544 for (i = 0; i <= end_zone; i++) {
2545 struct zone *zone = pgdat->node_zones + i;
2546 int nr_slab, testorder;
2547 unsigned long balance_gap;
2549 if (!populated_zone(zone))
2552 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2557 nr_soft_scanned = 0;
2559 * Call soft limit reclaim before calling shrink_zone.
2561 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2564 sc.nr_reclaimed += nr_soft_reclaimed;
2565 total_scanned += nr_soft_scanned;
2568 * We put equal pressure on every zone, unless
2569 * one zone has way too many pages free
2570 * already. The "too many pages" is defined
2571 * as the high wmark plus a "gap" where the
2572 * gap is either the low watermark or 1%
2573 * of the zone, whichever is smaller.
2575 balance_gap = min(low_wmark_pages(zone),
2576 (zone->present_pages +
2577 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2578 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2580 * Kswapd reclaims only single pages with compaction
2581 * enabled. Trying too hard to reclaim until contiguous
2582 * free pages have become available can hurt performance
2583 * by evicting too much useful data from memory.
2584 * Do not reclaim more than needed for compaction.
2587 if (COMPACTION_BUILD && order &&
2588 compaction_suitable(zone, order) !=
2592 if ((buffer_heads_over_limit && is_highmem_idx(i)) ||
2593 !zone_watermark_ok_safe(zone, testorder,
2594 high_wmark_pages(zone) + balance_gap,
2596 shrink_zone(priority, zone, &sc);
2598 reclaim_state->reclaimed_slab = 0;
2599 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
2600 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2601 total_scanned += sc.nr_scanned;
2603 if (nr_slab == 0 && !zone_reclaimable(zone))
2604 zone->all_unreclaimable = 1;
2608 * If we've done a decent amount of scanning and
2609 * the reclaim ratio is low, start doing writepage
2610 * even in laptop mode
2612 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2613 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2614 sc.may_writepage = 1;
2616 if (zone->all_unreclaimable) {
2617 if (end_zone && end_zone == i)
2622 if (!zone_watermark_ok_safe(zone, testorder,
2623 high_wmark_pages(zone), end_zone, 0)) {
2626 * We are still under min water mark. This
2627 * means that we have a GFP_ATOMIC allocation
2628 * failure risk. Hurry up!
2630 if (!zone_watermark_ok_safe(zone, order,
2631 min_wmark_pages(zone), end_zone, 0))
2632 has_under_min_watermark_zone = 1;
2635 * If a zone reaches its high watermark,
2636 * consider it to be no longer congested. It's
2637 * possible there are dirty pages backed by
2638 * congested BDIs but as pressure is relieved,
2639 * speculatively avoid congestion waits
2641 zone_clear_flag(zone, ZONE_CONGESTED);
2642 if (i <= *classzone_idx)
2643 balanced += zone->present_pages;
2647 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
2648 break; /* kswapd: all done */
2650 * OK, kswapd is getting into trouble. Take a nap, then take
2651 * another pass across the zones.
2653 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2654 if (has_under_min_watermark_zone)
2655 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2657 congestion_wait(BLK_RW_ASYNC, HZ/10);
2661 * We do this so kswapd doesn't build up large priorities for
2662 * example when it is freeing in parallel with allocators. It
2663 * matches the direct reclaim path behaviour in terms of impact
2664 * on zone->*_priority.
2666 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2672 * order-0: All zones must meet high watermark for a balanced node
2673 * high-order: Balanced zones must make up at least 25% of the node
2674 * for the node to be balanced
2676 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
2682 * Fragmentation may mean that the system cannot be
2683 * rebalanced for high-order allocations in all zones.
2684 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2685 * it means the zones have been fully scanned and are still
2686 * not balanced. For high-order allocations, there is
2687 * little point trying all over again as kswapd may
2690 * Instead, recheck all watermarks at order-0 as they
2691 * are the most important. If watermarks are ok, kswapd will go
2692 * back to sleep. High-order users can still perform direct
2693 * reclaim if they wish.
2695 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2696 order = sc.order = 0;
2702 * If kswapd was reclaiming at a higher order, it has the option of
2703 * sleeping without all zones being balanced. Before it does, it must
2704 * ensure that the watermarks for order-0 on *all* zones are met and
2705 * that the congestion flags are cleared. The congestion flag must
2706 * be cleared as kswapd is the only mechanism that clears the flag
2707 * and it is potentially going to sleep here.
2710 int zones_need_compaction = 1;
2712 for (i = 0; i <= end_zone; i++) {
2713 struct zone *zone = pgdat->node_zones + i;
2715 if (!populated_zone(zone))
2718 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2721 /* Would compaction fail due to lack of free memory? */
2722 if (COMPACTION_BUILD &&
2723 compaction_suitable(zone, order) == COMPACT_SKIPPED)
2726 /* Confirm the zone is balanced for order-0 */
2727 if (!zone_watermark_ok(zone, 0,
2728 high_wmark_pages(zone), 0, 0)) {
2729 order = sc.order = 0;
2733 /* Check if the memory needs to be defragmented. */
2734 if (zone_watermark_ok(zone, order,
2735 low_wmark_pages(zone), *classzone_idx, 0))
2736 zones_need_compaction = 0;
2738 /* If balanced, clear the congested flag */
2739 zone_clear_flag(zone, ZONE_CONGESTED);
2742 if (zones_need_compaction)
2743 compact_pgdat(pgdat, order);
2747 * Return the order we were reclaiming at so sleeping_prematurely()
2748 * makes a decision on the order we were last reclaiming at. However,
2749 * if another caller entered the allocator slow path while kswapd
2750 * was awake, order will remain at the higher level
2752 *classzone_idx = end_zone;
2756 static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2761 if (freezing(current) || kthread_should_stop())
2764 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2766 /* Try to sleep for a short interval */
2767 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2768 remaining = schedule_timeout(HZ/10);
2769 finish_wait(&pgdat->kswapd_wait, &wait);
2770 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2774 * After a short sleep, check if it was a premature sleep. If not, then
2775 * go fully to sleep until explicitly woken up.
2777 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2778 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2781 * vmstat counters are not perfectly accurate and the estimated
2782 * value for counters such as NR_FREE_PAGES can deviate from the
2783 * true value by nr_online_cpus * threshold. To avoid the zone
2784 * watermarks being breached while under pressure, we reduce the
2785 * per-cpu vmstat threshold while kswapd is awake and restore
2786 * them before going back to sleep.
2788 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
2790 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
2793 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2795 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2797 finish_wait(&pgdat->kswapd_wait, &wait);
2801 * The background pageout daemon, started as a kernel thread
2802 * from the init process.
2804 * This basically trickles out pages so that we have _some_
2805 * free memory available even if there is no other activity
2806 * that frees anything up. This is needed for things like routing
2807 * etc, where we otherwise might have all activity going on in
2808 * asynchronous contexts that cannot page things out.
2810 * If there are applications that are active memory-allocators
2811 * (most normal use), this basically shouldn't matter.
2813 static int kswapd(void *p)
2815 unsigned long order, new_order;
2816 unsigned balanced_order;
2817 int classzone_idx, new_classzone_idx;
2818 int balanced_classzone_idx;
2819 pg_data_t *pgdat = (pg_data_t*)p;
2820 struct task_struct *tsk = current;
2822 struct reclaim_state reclaim_state = {
2823 .reclaimed_slab = 0,
2825 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2827 lockdep_set_current_reclaim_state(GFP_KERNEL);
2829 if (!cpumask_empty(cpumask))
2830 set_cpus_allowed_ptr(tsk, cpumask);
2831 current->reclaim_state = &reclaim_state;
2834 * Tell the memory management that we're a "memory allocator",
2835 * and that if we need more memory we should get access to it
2836 * regardless (see "__alloc_pages()"). "kswapd" should
2837 * never get caught in the normal page freeing logic.
2839 * (Kswapd normally doesn't need memory anyway, but sometimes
2840 * you need a small amount of memory in order to be able to
2841 * page out something else, and this flag essentially protects
2842 * us from recursively trying to free more memory as we're
2843 * trying to free the first piece of memory in the first place).
2845 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2848 order = new_order = 0;
2850 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
2851 balanced_classzone_idx = classzone_idx;
2856 * If the last balance_pgdat was unsuccessful it's unlikely a
2857 * new request of a similar or harder type will succeed soon
2858 * so consider going to sleep on the basis we reclaimed at
2860 if (balanced_classzone_idx >= new_classzone_idx &&
2861 balanced_order == new_order) {
2862 new_order = pgdat->kswapd_max_order;
2863 new_classzone_idx = pgdat->classzone_idx;
2864 pgdat->kswapd_max_order = 0;
2865 pgdat->classzone_idx = pgdat->nr_zones - 1;
2868 if (order < new_order || classzone_idx > new_classzone_idx) {
2870 * Don't sleep if someone wants a larger 'order'
2871 * allocation or has tigher zone constraints
2874 classzone_idx = new_classzone_idx;
2876 kswapd_try_to_sleep(pgdat, balanced_order,
2877 balanced_classzone_idx);
2878 order = pgdat->kswapd_max_order;
2879 classzone_idx = pgdat->classzone_idx;
2881 new_classzone_idx = classzone_idx;
2882 pgdat->kswapd_max_order = 0;
2883 pgdat->classzone_idx = pgdat->nr_zones - 1;
2886 ret = try_to_freeze();
2887 if (kthread_should_stop())
2891 * We can speed up thawing tasks if we don't call balance_pgdat
2892 * after returning from the refrigerator
2895 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2896 balanced_classzone_idx = classzone_idx;
2897 balanced_order = balance_pgdat(pgdat, order,
2898 &balanced_classzone_idx);
2905 * A zone is low on free memory, so wake its kswapd task to service it.
2907 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
2911 if (!populated_zone(zone))
2914 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2916 pgdat = zone->zone_pgdat;
2917 if (pgdat->kswapd_max_order < order) {
2918 pgdat->kswapd_max_order = order;
2919 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
2921 if (!waitqueue_active(&pgdat->kswapd_wait))
2923 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
2926 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2927 wake_up_interruptible(&pgdat->kswapd_wait);
2931 * The reclaimable count would be mostly accurate.
2932 * The less reclaimable pages may be
2933 * - mlocked pages, which will be moved to unevictable list when encountered
2934 * - mapped pages, which may require several travels to be reclaimed
2935 * - dirty pages, which is not "instantly" reclaimable
2937 unsigned long global_reclaimable_pages(void)
2941 nr = global_page_state(NR_ACTIVE_FILE) +
2942 global_page_state(NR_INACTIVE_FILE);
2944 if (nr_swap_pages > 0)
2945 nr += global_page_state(NR_ACTIVE_ANON) +
2946 global_page_state(NR_INACTIVE_ANON);
2951 unsigned long zone_reclaimable_pages(struct zone *zone)
2955 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2956 zone_page_state(zone, NR_INACTIVE_FILE);
2958 if (nr_swap_pages > 0)
2959 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2960 zone_page_state(zone, NR_INACTIVE_ANON);
2965 #ifdef CONFIG_HIBERNATION
2967 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2970 * Rather than trying to age LRUs the aim is to preserve the overall
2971 * LRU order by reclaiming preferentially
2972 * inactive > active > active referenced > active mapped
2974 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2976 struct reclaim_state reclaim_state;
2977 struct scan_control sc = {
2978 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2982 .nr_to_reclaim = nr_to_reclaim,
2983 .hibernation_mode = 1,
2986 struct shrink_control shrink = {
2987 .gfp_mask = sc.gfp_mask,
2989 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2990 struct task_struct *p = current;
2991 unsigned long nr_reclaimed;
2993 p->flags |= PF_MEMALLOC;
2994 lockdep_set_current_reclaim_state(sc.gfp_mask);
2995 reclaim_state.reclaimed_slab = 0;
2996 p->reclaim_state = &reclaim_state;
2998 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
3000 p->reclaim_state = NULL;
3001 lockdep_clear_current_reclaim_state();
3002 p->flags &= ~PF_MEMALLOC;
3004 return nr_reclaimed;
3006 #endif /* CONFIG_HIBERNATION */
3008 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3009 not required for correctness. So if the last cpu in a node goes
3010 away, we get changed to run anywhere: as the first one comes back,
3011 restore their cpu bindings. */
3012 static int __devinit cpu_callback(struct notifier_block *nfb,
3013 unsigned long action, void *hcpu)
3017 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
3018 for_each_node_state(nid, N_HIGH_MEMORY) {
3019 pg_data_t *pgdat = NODE_DATA(nid);
3020 const struct cpumask *mask;
3022 mask = cpumask_of_node(pgdat->node_id);
3024 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
3025 /* One of our CPUs online: restore mask */
3026 set_cpus_allowed_ptr(pgdat->kswapd, mask);
3033 * This kswapd start function will be called by init and node-hot-add.
3034 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3036 int kswapd_run(int nid)
3038 pg_data_t *pgdat = NODE_DATA(nid);
3044 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
3045 if (IS_ERR(pgdat->kswapd)) {
3046 /* failure at boot is fatal */
3047 BUG_ON(system_state == SYSTEM_BOOTING);
3048 printk("Failed to start kswapd on node %d\n",nid);
3055 * Called by memory hotplug when all memory in a node is offlined.
3057 void kswapd_stop(int nid)
3059 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
3062 kthread_stop(kswapd);
3065 static int __init kswapd_init(void)
3070 for_each_node_state(nid, N_HIGH_MEMORY)
3072 hotcpu_notifier(cpu_callback, 0);
3076 module_init(kswapd_init)
3082 * If non-zero call zone_reclaim when the number of free pages falls below
3085 int zone_reclaim_mode __read_mostly;
3087 #define RECLAIM_OFF 0
3088 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3089 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3090 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3093 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3094 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3097 #define ZONE_RECLAIM_PRIORITY 4
3100 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3103 int sysctl_min_unmapped_ratio = 1;
3106 * If the number of slab pages in a zone grows beyond this percentage then
3107 * slab reclaim needs to occur.
3109 int sysctl_min_slab_ratio = 5;
3111 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
3113 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
3114 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
3115 zone_page_state(zone, NR_ACTIVE_FILE);
3118 * It's possible for there to be more file mapped pages than
3119 * accounted for by the pages on the file LRU lists because
3120 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3122 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
3125 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3126 static long zone_pagecache_reclaimable(struct zone *zone)
3128 long nr_pagecache_reclaimable;
3132 * If RECLAIM_SWAP is set, then all file pages are considered
3133 * potentially reclaimable. Otherwise, we have to worry about
3134 * pages like swapcache and zone_unmapped_file_pages() provides
3137 if (zone_reclaim_mode & RECLAIM_SWAP)
3138 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
3140 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
3142 /* If we can't clean pages, remove dirty pages from consideration */
3143 if (!(zone_reclaim_mode & RECLAIM_WRITE))
3144 delta += zone_page_state(zone, NR_FILE_DIRTY);
3146 /* Watch for any possible underflows due to delta */
3147 if (unlikely(delta > nr_pagecache_reclaimable))
3148 delta = nr_pagecache_reclaimable;
3150 return nr_pagecache_reclaimable - delta;
3154 * Try to free up some pages from this zone through reclaim.
3156 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3158 /* Minimum pages needed in order to stay on node */
3159 const unsigned long nr_pages = 1 << order;
3160 struct task_struct *p = current;
3161 struct reclaim_state reclaim_state;
3163 struct scan_control sc = {
3164 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3165 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3167 .nr_to_reclaim = max_t(unsigned long, nr_pages,
3169 .gfp_mask = gfp_mask,
3172 struct shrink_control shrink = {
3173 .gfp_mask = sc.gfp_mask,
3175 unsigned long nr_slab_pages0, nr_slab_pages1;
3179 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3180 * and we also need to be able to write out pages for RECLAIM_WRITE
3183 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
3184 lockdep_set_current_reclaim_state(gfp_mask);
3185 reclaim_state.reclaimed_slab = 0;
3186 p->reclaim_state = &reclaim_state;
3188 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3190 * Free memory by calling shrink zone with increasing
3191 * priorities until we have enough memory freed.
3193 priority = ZONE_RECLAIM_PRIORITY;
3195 shrink_zone(priority, zone, &sc);
3197 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3200 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3201 if (nr_slab_pages0 > zone->min_slab_pages) {
3203 * shrink_slab() does not currently allow us to determine how
3204 * many pages were freed in this zone. So we take the current
3205 * number of slab pages and shake the slab until it is reduced
3206 * by the same nr_pages that we used for reclaiming unmapped
3209 * Note that shrink_slab will free memory on all zones and may
3213 unsigned long lru_pages = zone_reclaimable_pages(zone);
3215 /* No reclaimable slab or very low memory pressure */
3216 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3219 /* Freed enough memory */
3220 nr_slab_pages1 = zone_page_state(zone,
3221 NR_SLAB_RECLAIMABLE);
3222 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
3227 * Update nr_reclaimed by the number of slab pages we
3228 * reclaimed from this zone.
3230 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3231 if (nr_slab_pages1 < nr_slab_pages0)
3232 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3235 p->reclaim_state = NULL;
3236 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3237 lockdep_clear_current_reclaim_state();
3238 return sc.nr_reclaimed >= nr_pages;
3241 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3247 * Zone reclaim reclaims unmapped file backed pages and
3248 * slab pages if we are over the defined limits.
3250 * A small portion of unmapped file backed pages is needed for
3251 * file I/O otherwise pages read by file I/O will be immediately
3252 * thrown out if the zone is overallocated. So we do not reclaim
3253 * if less than a specified percentage of the zone is used by
3254 * unmapped file backed pages.
3256 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3257 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3258 return ZONE_RECLAIM_FULL;
3260 if (zone->all_unreclaimable)
3261 return ZONE_RECLAIM_FULL;
3264 * Do not scan if the allocation should not be delayed.
3266 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3267 return ZONE_RECLAIM_NOSCAN;
3270 * Only run zone reclaim on the local zone or on zones that do not
3271 * have associated processors. This will favor the local processor
3272 * over remote processors and spread off node memory allocations
3273 * as wide as possible.
3275 node_id = zone_to_nid(zone);
3276 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3277 return ZONE_RECLAIM_NOSCAN;
3279 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3280 return ZONE_RECLAIM_NOSCAN;
3282 ret = __zone_reclaim(zone, gfp_mask, order);
3283 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
3286 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3293 * page_evictable - test whether a page is evictable
3294 * @page: the page to test
3295 * @vma: the VMA in which the page is or will be mapped, may be NULL
3297 * Test whether page is evictable--i.e., should be placed on active/inactive
3298 * lists vs unevictable list. The vma argument is !NULL when called from the
3299 * fault path to determine how to instantate a new page.
3301 * Reasons page might not be evictable:
3302 * (1) page's mapping marked unevictable
3303 * (2) page is part of an mlocked VMA
3306 int page_evictable(struct page *page, struct vm_area_struct *vma)
3309 if (mapping_unevictable(page_mapping(page)))
3312 if (PageMlocked(page) || (vma && mlocked_vma_newpage(vma, page)))
3320 * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
3321 * @pages: array of pages to check
3322 * @nr_pages: number of pages to check
3324 * Checks pages for evictability and moves them to the appropriate lru list.
3326 * This function is only used for SysV IPC SHM_UNLOCK.
3328 void check_move_unevictable_pages(struct page **pages, int nr_pages)
3330 struct lruvec *lruvec;
3331 struct zone *zone = NULL;
3336 for (i = 0; i < nr_pages; i++) {
3337 struct page *page = pages[i];
3338 struct zone *pagezone;
3341 pagezone = page_zone(page);
3342 if (pagezone != zone) {
3344 spin_unlock_irq(&zone->lru_lock);
3346 spin_lock_irq(&zone->lru_lock);
3349 if (!PageLRU(page) || !PageUnevictable(page))
3352 if (page_evictable(page, NULL)) {
3353 enum lru_list lru = page_lru_base_type(page);
3355 VM_BUG_ON(PageActive(page));
3356 ClearPageUnevictable(page);
3357 __dec_zone_state(zone, NR_UNEVICTABLE);
3358 lruvec = mem_cgroup_lru_move_lists(zone, page,
3359 LRU_UNEVICTABLE, lru);
3360 list_move(&page->lru, &lruvec->lists[lru]);
3361 __inc_zone_state(zone, NR_INACTIVE_ANON + lru);
3367 __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
3368 __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
3369 spin_unlock_irq(&zone->lru_lock);
3372 #endif /* CONFIG_SHMEM */
3374 static void warn_scan_unevictable_pages(void)
3376 printk_once(KERN_WARNING
3377 "%s: The scan_unevictable_pages sysctl/node-interface has been "
3378 "disabled for lack of a legitimate use case. If you have "
3379 "one, please send an email to linux-mm@kvack.org.\n",
3384 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3385 * all nodes' unevictable lists for evictable pages
3387 unsigned long scan_unevictable_pages;
3389 int scan_unevictable_handler(struct ctl_table *table, int write,
3390 void __user *buffer,
3391 size_t *length, loff_t *ppos)
3393 warn_scan_unevictable_pages();
3394 proc_doulongvec_minmax(table, write, buffer, length, ppos);
3395 scan_unevictable_pages = 0;
3401 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3402 * a specified node's per zone unevictable lists for evictable pages.
3405 static ssize_t read_scan_unevictable_node(struct device *dev,
3406 struct device_attribute *attr,
3409 warn_scan_unevictable_pages();
3410 return sprintf(buf, "0\n"); /* always zero; should fit... */
3413 static ssize_t write_scan_unevictable_node(struct device *dev,
3414 struct device_attribute *attr,
3415 const char *buf, size_t count)
3417 warn_scan_unevictable_pages();
3422 static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3423 read_scan_unevictable_node,
3424 write_scan_unevictable_node);
3426 int scan_unevictable_register_node(struct node *node)
3428 return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages);
3431 void scan_unevictable_unregister_node(struct node *node)
3433 device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages);