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/pagevec.h>
30 #include <linux/backing-dev.h>
31 #include <linux/rmap.h>
32 #include <linux/topology.h>
33 #include <linux/cpu.h>
34 #include <linux/cpuset.h>
35 #include <linux/notifier.h>
36 #include <linux/rwsem.h>
37 #include <linux/delay.h>
38 #include <linux/kthread.h>
39 #include <linux/freezer.h>
40 #include <linux/memcontrol.h>
41 #include <linux/delayacct.h>
42 #include <linux/sysctl.h>
44 #include <asm/tlbflush.h>
45 #include <asm/div64.h>
47 #include <linux/swapops.h>
51 #define CREATE_TRACE_POINTS
52 #include <trace/events/vmscan.h>
55 /* Incremented by the number of inactive pages that were scanned */
56 unsigned long nr_scanned;
58 /* Number of pages freed so far during a call to shrink_zones() */
59 unsigned long nr_reclaimed;
61 /* How many pages shrink_list() should reclaim */
62 unsigned long nr_to_reclaim;
64 unsigned long hibernation_mode;
66 /* This context's GFP mask */
71 /* Can mapped pages be reclaimed? */
74 /* Can pages be swapped as part of reclaim? */
82 * Intend to reclaim enough contenious memory rather than to reclaim
83 * enough amount memory. I.e, it's the mode for high order allocation.
85 bool lumpy_reclaim_mode;
87 /* Which cgroup do we reclaim from */
88 struct mem_cgroup *mem_cgroup;
91 * Nodemask of nodes allowed by the caller. If NULL, all nodes
97 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
99 #ifdef ARCH_HAS_PREFETCH
100 #define prefetch_prev_lru_page(_page, _base, _field) \
102 if ((_page)->lru.prev != _base) { \
105 prev = lru_to_page(&(_page->lru)); \
106 prefetch(&prev->_field); \
110 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
113 #ifdef ARCH_HAS_PREFETCHW
114 #define prefetchw_prev_lru_page(_page, _base, _field) \
116 if ((_page)->lru.prev != _base) { \
119 prev = lru_to_page(&(_page->lru)); \
120 prefetchw(&prev->_field); \
124 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
128 * From 0 .. 100. Higher means more swappy.
130 int vm_swappiness = 60;
131 long vm_total_pages; /* The total number of pages which the VM controls */
133 static LIST_HEAD(shrinker_list);
134 static DECLARE_RWSEM(shrinker_rwsem);
136 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
137 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
139 #define scanning_global_lru(sc) (1)
142 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
143 struct scan_control *sc)
145 if (!scanning_global_lru(sc))
146 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
148 return &zone->reclaim_stat;
151 static unsigned long zone_nr_lru_pages(struct zone *zone,
152 struct scan_control *sc, enum lru_list lru)
154 if (!scanning_global_lru(sc))
155 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);
157 return zone_page_state(zone, NR_LRU_BASE + lru);
162 * Add a shrinker callback to be called from the vm
164 void register_shrinker(struct shrinker *shrinker)
167 down_write(&shrinker_rwsem);
168 list_add_tail(&shrinker->list, &shrinker_list);
169 up_write(&shrinker_rwsem);
171 EXPORT_SYMBOL(register_shrinker);
176 void unregister_shrinker(struct shrinker *shrinker)
178 down_write(&shrinker_rwsem);
179 list_del(&shrinker->list);
180 up_write(&shrinker_rwsem);
182 EXPORT_SYMBOL(unregister_shrinker);
184 #define SHRINK_BATCH 128
186 * Call the shrink functions to age shrinkable caches
188 * Here we assume it costs one seek to replace a lru page and that it also
189 * takes a seek to recreate a cache object. With this in mind we age equal
190 * percentages of the lru and ageable caches. This should balance the seeks
191 * generated by these structures.
193 * If the vm encountered mapped pages on the LRU it increase the pressure on
194 * slab to avoid swapping.
196 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
198 * `lru_pages' represents the number of on-LRU pages in all the zones which
199 * are eligible for the caller's allocation attempt. It is used for balancing
200 * slab reclaim versus page reclaim.
202 * Returns the number of slab objects which we shrunk.
204 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
205 unsigned long lru_pages)
207 struct shrinker *shrinker;
208 unsigned long ret = 0;
211 scanned = SWAP_CLUSTER_MAX;
213 if (!down_read_trylock(&shrinker_rwsem))
214 return 1; /* Assume we'll be able to shrink next time */
216 list_for_each_entry(shrinker, &shrinker_list, list) {
217 unsigned long long delta;
218 unsigned long total_scan;
219 unsigned long max_pass;
221 max_pass = (*shrinker->shrink)(shrinker, 0, gfp_mask);
222 delta = (4 * scanned) / shrinker->seeks;
224 do_div(delta, lru_pages + 1);
225 shrinker->nr += delta;
226 if (shrinker->nr < 0) {
227 printk(KERN_ERR "shrink_slab: %pF negative objects to "
229 shrinker->shrink, shrinker->nr);
230 shrinker->nr = max_pass;
234 * Avoid risking looping forever due to too large nr value:
235 * never try to free more than twice the estimate number of
238 if (shrinker->nr > max_pass * 2)
239 shrinker->nr = max_pass * 2;
241 total_scan = shrinker->nr;
244 while (total_scan >= SHRINK_BATCH) {
245 long this_scan = SHRINK_BATCH;
249 nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask);
250 shrink_ret = (*shrinker->shrink)(shrinker, this_scan,
252 if (shrink_ret == -1)
254 if (shrink_ret < nr_before)
255 ret += nr_before - shrink_ret;
256 count_vm_events(SLABS_SCANNED, this_scan);
257 total_scan -= this_scan;
262 shrinker->nr += total_scan;
264 up_read(&shrinker_rwsem);
268 static inline int is_page_cache_freeable(struct page *page)
271 * A freeable page cache page is referenced only by the caller
272 * that isolated the page, the page cache radix tree and
273 * optional buffer heads at page->private.
275 return page_count(page) - page_has_private(page) == 2;
278 static int may_write_to_queue(struct backing_dev_info *bdi)
280 if (current->flags & PF_SWAPWRITE)
282 if (!bdi_write_congested(bdi))
284 if (bdi == current->backing_dev_info)
290 * We detected a synchronous write error writing a page out. Probably
291 * -ENOSPC. We need to propagate that into the address_space for a subsequent
292 * fsync(), msync() or close().
294 * The tricky part is that after writepage we cannot touch the mapping: nothing
295 * prevents it from being freed up. But we have a ref on the page and once
296 * that page is locked, the mapping is pinned.
298 * We're allowed to run sleeping lock_page() here because we know the caller has
301 static void handle_write_error(struct address_space *mapping,
302 struct page *page, int error)
304 lock_page_nosync(page);
305 if (page_mapping(page) == mapping)
306 mapping_set_error(mapping, error);
310 /* Request for sync pageout. */
316 /* possible outcome of pageout() */
318 /* failed to write page out, page is locked */
320 /* move page to the active list, page is locked */
322 /* page has been sent to the disk successfully, page is unlocked */
324 /* page is clean and locked */
329 * pageout is called by shrink_page_list() for each dirty page.
330 * Calls ->writepage().
332 static pageout_t pageout(struct page *page, struct address_space *mapping,
333 enum pageout_io sync_writeback)
336 * If the page is dirty, only perform writeback if that write
337 * will be non-blocking. To prevent this allocation from being
338 * stalled by pagecache activity. But note that there may be
339 * stalls if we need to run get_block(). We could test
340 * PagePrivate for that.
342 * If this process is currently in __generic_file_aio_write() against
343 * this page's queue, we can perform writeback even if that
346 * If the page is swapcache, write it back even if that would
347 * block, for some throttling. This happens by accident, because
348 * swap_backing_dev_info is bust: it doesn't reflect the
349 * congestion state of the swapdevs. Easy to fix, if needed.
351 if (!is_page_cache_freeable(page))
355 * Some data journaling orphaned pages can have
356 * page->mapping == NULL while being dirty with clean buffers.
358 if (page_has_private(page)) {
359 if (try_to_free_buffers(page)) {
360 ClearPageDirty(page);
361 printk("%s: orphaned page\n", __func__);
367 if (mapping->a_ops->writepage == NULL)
368 return PAGE_ACTIVATE;
369 if (!may_write_to_queue(mapping->backing_dev_info))
372 if (clear_page_dirty_for_io(page)) {
374 struct writeback_control wbc = {
375 .sync_mode = WB_SYNC_NONE,
376 .nr_to_write = SWAP_CLUSTER_MAX,
378 .range_end = LLONG_MAX,
383 SetPageReclaim(page);
384 res = mapping->a_ops->writepage(page, &wbc);
386 handle_write_error(mapping, page, res);
387 if (res == AOP_WRITEPAGE_ACTIVATE) {
388 ClearPageReclaim(page);
389 return PAGE_ACTIVATE;
393 * Wait on writeback if requested to. This happens when
394 * direct reclaiming a large contiguous area and the
395 * first attempt to free a range of pages fails.
397 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
398 wait_on_page_writeback(page);
400 if (!PageWriteback(page)) {
401 /* synchronous write or broken a_ops? */
402 ClearPageReclaim(page);
404 inc_zone_page_state(page, NR_VMSCAN_WRITE);
412 * Same as remove_mapping, but if the page is removed from the mapping, it
413 * gets returned with a refcount of 0.
415 static int __remove_mapping(struct address_space *mapping, struct page *page)
417 BUG_ON(!PageLocked(page));
418 BUG_ON(mapping != page_mapping(page));
420 spin_lock_irq(&mapping->tree_lock);
422 * The non racy check for a busy page.
424 * Must be careful with the order of the tests. When someone has
425 * a ref to the page, it may be possible that they dirty it then
426 * drop the reference. So if PageDirty is tested before page_count
427 * here, then the following race may occur:
429 * get_user_pages(&page);
430 * [user mapping goes away]
432 * !PageDirty(page) [good]
433 * SetPageDirty(page);
435 * !page_count(page) [good, discard it]
437 * [oops, our write_to data is lost]
439 * Reversing the order of the tests ensures such a situation cannot
440 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
441 * load is not satisfied before that of page->_count.
443 * Note that if SetPageDirty is always performed via set_page_dirty,
444 * and thus under tree_lock, then this ordering is not required.
446 if (!page_freeze_refs(page, 2))
448 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
449 if (unlikely(PageDirty(page))) {
450 page_unfreeze_refs(page, 2);
454 if (PageSwapCache(page)) {
455 swp_entry_t swap = { .val = page_private(page) };
456 __delete_from_swap_cache(page);
457 spin_unlock_irq(&mapping->tree_lock);
458 swapcache_free(swap, page);
460 __remove_from_page_cache(page);
461 spin_unlock_irq(&mapping->tree_lock);
462 mem_cgroup_uncharge_cache_page(page);
468 spin_unlock_irq(&mapping->tree_lock);
473 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
474 * someone else has a ref on the page, abort and return 0. If it was
475 * successfully detached, return 1. Assumes the caller has a single ref on
478 int remove_mapping(struct address_space *mapping, struct page *page)
480 if (__remove_mapping(mapping, page)) {
482 * Unfreezing the refcount with 1 rather than 2 effectively
483 * drops the pagecache ref for us without requiring another
486 page_unfreeze_refs(page, 1);
493 * putback_lru_page - put previously isolated page onto appropriate LRU list
494 * @page: page to be put back to appropriate lru list
496 * Add previously isolated @page to appropriate LRU list.
497 * Page may still be unevictable for other reasons.
499 * lru_lock must not be held, interrupts must be enabled.
501 void putback_lru_page(struct page *page)
504 int active = !!TestClearPageActive(page);
505 int was_unevictable = PageUnevictable(page);
507 VM_BUG_ON(PageLRU(page));
510 ClearPageUnevictable(page);
512 if (page_evictable(page, NULL)) {
514 * For evictable pages, we can use the cache.
515 * In event of a race, worst case is we end up with an
516 * unevictable page on [in]active list.
517 * We know how to handle that.
519 lru = active + page_lru_base_type(page);
520 lru_cache_add_lru(page, lru);
523 * Put unevictable pages directly on zone's unevictable
526 lru = LRU_UNEVICTABLE;
527 add_page_to_unevictable_list(page);
529 * When racing with an mlock clearing (page is
530 * unlocked), make sure that if the other thread does
531 * not observe our setting of PG_lru and fails
532 * isolation, we see PG_mlocked cleared below and move
533 * the page back to the evictable list.
535 * The other side is TestClearPageMlocked().
541 * page's status can change while we move it among lru. If an evictable
542 * page is on unevictable list, it never be freed. To avoid that,
543 * check after we added it to the list, again.
545 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
546 if (!isolate_lru_page(page)) {
550 /* This means someone else dropped this page from LRU
551 * So, it will be freed or putback to LRU again. There is
552 * nothing to do here.
556 if (was_unevictable && lru != LRU_UNEVICTABLE)
557 count_vm_event(UNEVICTABLE_PGRESCUED);
558 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
559 count_vm_event(UNEVICTABLE_PGCULLED);
561 put_page(page); /* drop ref from isolate */
564 enum page_references {
566 PAGEREF_RECLAIM_CLEAN,
571 static enum page_references page_check_references(struct page *page,
572 struct scan_control *sc)
574 int referenced_ptes, referenced_page;
575 unsigned long vm_flags;
577 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
578 referenced_page = TestClearPageReferenced(page);
580 /* Lumpy reclaim - ignore references */
581 if (sc->lumpy_reclaim_mode)
582 return PAGEREF_RECLAIM;
585 * Mlock lost the isolation race with us. Let try_to_unmap()
586 * move the page to the unevictable list.
588 if (vm_flags & VM_LOCKED)
589 return PAGEREF_RECLAIM;
591 if (referenced_ptes) {
593 return PAGEREF_ACTIVATE;
595 * All mapped pages start out with page table
596 * references from the instantiating fault, so we need
597 * to look twice if a mapped file page is used more
600 * Mark it and spare it for another trip around the
601 * inactive list. Another page table reference will
602 * lead to its activation.
604 * Note: the mark is set for activated pages as well
605 * so that recently deactivated but used pages are
608 SetPageReferenced(page);
611 return PAGEREF_ACTIVATE;
616 /* Reclaim if clean, defer dirty pages to writeback */
618 return PAGEREF_RECLAIM_CLEAN;
620 return PAGEREF_RECLAIM;
624 * shrink_page_list() returns the number of reclaimed pages
626 static unsigned long shrink_page_list(struct list_head *page_list,
627 struct scan_control *sc,
628 enum pageout_io sync_writeback)
630 LIST_HEAD(ret_pages);
631 struct pagevec freed_pvec;
633 unsigned long nr_reclaimed = 0;
637 pagevec_init(&freed_pvec, 1);
638 while (!list_empty(page_list)) {
639 enum page_references references;
640 struct address_space *mapping;
646 page = lru_to_page(page_list);
647 list_del(&page->lru);
649 if (!trylock_page(page))
652 VM_BUG_ON(PageActive(page));
656 if (unlikely(!page_evictable(page, NULL)))
659 if (!sc->may_unmap && page_mapped(page))
662 /* Double the slab pressure for mapped and swapcache pages */
663 if (page_mapped(page) || PageSwapCache(page))
666 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
667 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
669 if (PageWriteback(page)) {
671 * Synchronous reclaim is performed in two passes,
672 * first an asynchronous pass over the list to
673 * start parallel writeback, and a second synchronous
674 * pass to wait for the IO to complete. Wait here
675 * for any page for which writeback has already
678 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
679 wait_on_page_writeback(page);
684 references = page_check_references(page, sc);
685 switch (references) {
686 case PAGEREF_ACTIVATE:
687 goto activate_locked;
690 case PAGEREF_RECLAIM:
691 case PAGEREF_RECLAIM_CLEAN:
692 ; /* try to reclaim the page below */
696 * Anonymous process memory has backing store?
697 * Try to allocate it some swap space here.
699 if (PageAnon(page) && !PageSwapCache(page)) {
700 if (!(sc->gfp_mask & __GFP_IO))
702 if (!add_to_swap(page))
703 goto activate_locked;
707 mapping = page_mapping(page);
710 * The page is mapped into the page tables of one or more
711 * processes. Try to unmap it here.
713 if (page_mapped(page) && mapping) {
714 switch (try_to_unmap(page, TTU_UNMAP)) {
716 goto activate_locked;
722 ; /* try to free the page below */
726 if (PageDirty(page)) {
727 if (references == PAGEREF_RECLAIM_CLEAN)
731 if (!sc->may_writepage)
734 /* Page is dirty, try to write it out here */
735 switch (pageout(page, mapping, sync_writeback)) {
739 goto activate_locked;
741 if (PageWriteback(page) || PageDirty(page))
744 * A synchronous write - probably a ramdisk. Go
745 * ahead and try to reclaim the page.
747 if (!trylock_page(page))
749 if (PageDirty(page) || PageWriteback(page))
751 mapping = page_mapping(page);
753 ; /* try to free the page below */
758 * If the page has buffers, try to free the buffer mappings
759 * associated with this page. If we succeed we try to free
762 * We do this even if the page is PageDirty().
763 * try_to_release_page() does not perform I/O, but it is
764 * possible for a page to have PageDirty set, but it is actually
765 * clean (all its buffers are clean). This happens if the
766 * buffers were written out directly, with submit_bh(). ext3
767 * will do this, as well as the blockdev mapping.
768 * try_to_release_page() will discover that cleanness and will
769 * drop the buffers and mark the page clean - it can be freed.
771 * Rarely, pages can have buffers and no ->mapping. These are
772 * the pages which were not successfully invalidated in
773 * truncate_complete_page(). We try to drop those buffers here
774 * and if that worked, and the page is no longer mapped into
775 * process address space (page_count == 1) it can be freed.
776 * Otherwise, leave the page on the LRU so it is swappable.
778 if (page_has_private(page)) {
779 if (!try_to_release_page(page, sc->gfp_mask))
780 goto activate_locked;
781 if (!mapping && page_count(page) == 1) {
783 if (put_page_testzero(page))
787 * rare race with speculative reference.
788 * the speculative reference will free
789 * this page shortly, so we may
790 * increment nr_reclaimed here (and
791 * leave it off the LRU).
799 if (!mapping || !__remove_mapping(mapping, page))
803 * At this point, we have no other references and there is
804 * no way to pick any more up (removed from LRU, removed
805 * from pagecache). Can use non-atomic bitops now (and
806 * we obviously don't have to worry about waking up a process
807 * waiting on the page lock, because there are no references.
809 __clear_page_locked(page);
812 if (!pagevec_add(&freed_pvec, page)) {
813 __pagevec_free(&freed_pvec);
814 pagevec_reinit(&freed_pvec);
819 if (PageSwapCache(page))
820 try_to_free_swap(page);
822 putback_lru_page(page);
826 /* Not a candidate for swapping, so reclaim swap space. */
827 if (PageSwapCache(page) && vm_swap_full())
828 try_to_free_swap(page);
829 VM_BUG_ON(PageActive(page));
835 list_add(&page->lru, &ret_pages);
836 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
838 list_splice(&ret_pages, page_list);
839 if (pagevec_count(&freed_pvec))
840 __pagevec_free(&freed_pvec);
841 count_vm_events(PGACTIVATE, pgactivate);
846 * Attempt to remove the specified page from its LRU. Only take this page
847 * if it is of the appropriate PageActive status. Pages which are being
848 * freed elsewhere are also ignored.
850 * page: page to consider
851 * mode: one of the LRU isolation modes defined above
853 * returns 0 on success, -ve errno on failure.
855 int __isolate_lru_page(struct page *page, int mode, int file)
859 /* Only take pages on the LRU. */
864 * When checking the active state, we need to be sure we are
865 * dealing with comparible boolean values. Take the logical not
868 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
871 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
875 * When this function is being called for lumpy reclaim, we
876 * initially look into all LRU pages, active, inactive and
877 * unevictable; only give shrink_page_list evictable pages.
879 if (PageUnevictable(page))
884 if (likely(get_page_unless_zero(page))) {
886 * Be careful not to clear PageLRU until after we're
887 * sure the page is not being freed elsewhere -- the
888 * page release code relies on it.
898 * zone->lru_lock is heavily contended. Some of the functions that
899 * shrink the lists perform better by taking out a batch of pages
900 * and working on them outside the LRU lock.
902 * For pagecache intensive workloads, this function is the hottest
903 * spot in the kernel (apart from copy_*_user functions).
905 * Appropriate locks must be held before calling this function.
907 * @nr_to_scan: The number of pages to look through on the list.
908 * @src: The LRU list to pull pages off.
909 * @dst: The temp list to put pages on to.
910 * @scanned: The number of pages that were scanned.
911 * @order: The caller's attempted allocation order
912 * @mode: One of the LRU isolation modes
913 * @file: True [1] if isolating file [!anon] pages
915 * returns how many pages were moved onto *@dst.
917 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
918 struct list_head *src, struct list_head *dst,
919 unsigned long *scanned, int order, int mode, int file)
921 unsigned long nr_taken = 0;
922 unsigned long nr_lumpy_taken = 0;
923 unsigned long nr_lumpy_dirty = 0;
924 unsigned long nr_lumpy_failed = 0;
927 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
930 unsigned long end_pfn;
931 unsigned long page_pfn;
934 page = lru_to_page(src);
935 prefetchw_prev_lru_page(page, src, flags);
937 VM_BUG_ON(!PageLRU(page));
939 switch (__isolate_lru_page(page, mode, file)) {
941 list_move(&page->lru, dst);
942 mem_cgroup_del_lru(page);
947 /* else it is being freed elsewhere */
948 list_move(&page->lru, src);
949 mem_cgroup_rotate_lru_list(page, page_lru(page));
960 * Attempt to take all pages in the order aligned region
961 * surrounding the tag page. Only take those pages of
962 * the same active state as that tag page. We may safely
963 * round the target page pfn down to the requested order
964 * as the mem_map is guarenteed valid out to MAX_ORDER,
965 * where that page is in a different zone we will detect
966 * it from its zone id and abort this block scan.
968 zone_id = page_zone_id(page);
969 page_pfn = page_to_pfn(page);
970 pfn = page_pfn & ~((1 << order) - 1);
971 end_pfn = pfn + (1 << order);
972 for (; pfn < end_pfn; pfn++) {
973 struct page *cursor_page;
975 /* The target page is in the block, ignore it. */
976 if (unlikely(pfn == page_pfn))
979 /* Avoid holes within the zone. */
980 if (unlikely(!pfn_valid_within(pfn)))
983 cursor_page = pfn_to_page(pfn);
985 /* Check that we have not crossed a zone boundary. */
986 if (unlikely(page_zone_id(cursor_page) != zone_id))
990 * If we don't have enough swap space, reclaiming of
991 * anon page which don't already have a swap slot is
994 if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
995 !PageSwapCache(cursor_page))
998 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
999 list_move(&cursor_page->lru, dst);
1000 mem_cgroup_del_lru(cursor_page);
1003 if (PageDirty(cursor_page))
1007 if (mode == ISOLATE_BOTH &&
1008 page_count(cursor_page))
1016 trace_mm_vmscan_lru_isolate(order,
1019 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
1024 static unsigned long isolate_pages_global(unsigned long nr,
1025 struct list_head *dst,
1026 unsigned long *scanned, int order,
1027 int mode, struct zone *z,
1028 int active, int file)
1035 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1040 * clear_active_flags() is a helper for shrink_active_list(), clearing
1041 * any active bits from the pages in the list.
1043 static unsigned long clear_active_flags(struct list_head *page_list,
1044 unsigned int *count)
1050 list_for_each_entry(page, page_list, lru) {
1051 lru = page_lru_base_type(page);
1052 if (PageActive(page)) {
1054 ClearPageActive(page);
1064 * isolate_lru_page - tries to isolate a page from its LRU list
1065 * @page: page to isolate from its LRU list
1067 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1068 * vmstat statistic corresponding to whatever LRU list the page was on.
1070 * Returns 0 if the page was removed from an LRU list.
1071 * Returns -EBUSY if the page was not on an LRU list.
1073 * The returned page will have PageLRU() cleared. If it was found on
1074 * the active list, it will have PageActive set. If it was found on
1075 * the unevictable list, it will have the PageUnevictable bit set. That flag
1076 * may need to be cleared by the caller before letting the page go.
1078 * The vmstat statistic corresponding to the list on which the page was
1079 * found will be decremented.
1082 * (1) Must be called with an elevated refcount on the page. This is a
1083 * fundamentnal difference from isolate_lru_pages (which is called
1084 * without a stable reference).
1085 * (2) the lru_lock must not be held.
1086 * (3) interrupts must be enabled.
1088 int isolate_lru_page(struct page *page)
1092 if (PageLRU(page)) {
1093 struct zone *zone = page_zone(page);
1095 spin_lock_irq(&zone->lru_lock);
1096 if (PageLRU(page) && get_page_unless_zero(page)) {
1097 int lru = page_lru(page);
1101 del_page_from_lru_list(zone, page, lru);
1103 spin_unlock_irq(&zone->lru_lock);
1109 * Are there way too many processes in the direct reclaim path already?
1111 static int too_many_isolated(struct zone *zone, int file,
1112 struct scan_control *sc)
1114 unsigned long inactive, isolated;
1116 if (current_is_kswapd())
1119 if (!scanning_global_lru(sc))
1123 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1124 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1126 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1127 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1130 return isolated > inactive;
1134 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1135 * of reclaimed pages
1137 static unsigned long shrink_inactive_list(unsigned long max_scan,
1138 struct zone *zone, struct scan_control *sc,
1139 int priority, int file)
1141 LIST_HEAD(page_list);
1142 struct pagevec pvec;
1143 unsigned long nr_scanned = 0;
1144 unsigned long nr_reclaimed = 0;
1145 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1147 while (unlikely(too_many_isolated(zone, file, sc))) {
1148 congestion_wait(BLK_RW_ASYNC, HZ/10);
1150 /* We are about to die and free our memory. Return now. */
1151 if (fatal_signal_pending(current))
1152 return SWAP_CLUSTER_MAX;
1156 pagevec_init(&pvec, 1);
1159 spin_lock_irq(&zone->lru_lock);
1162 unsigned long nr_taken;
1163 unsigned long nr_scan;
1164 unsigned long nr_freed;
1165 unsigned long nr_active;
1166 unsigned int count[NR_LRU_LISTS] = { 0, };
1167 int mode = sc->lumpy_reclaim_mode ? ISOLATE_BOTH : ISOLATE_INACTIVE;
1168 unsigned long nr_anon;
1169 unsigned long nr_file;
1171 if (scanning_global_lru(sc)) {
1172 nr_taken = isolate_pages_global(SWAP_CLUSTER_MAX,
1173 &page_list, &nr_scan,
1176 zone->pages_scanned += nr_scan;
1177 if (current_is_kswapd())
1178 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1181 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1184 nr_taken = mem_cgroup_isolate_pages(SWAP_CLUSTER_MAX,
1185 &page_list, &nr_scan,
1187 zone, sc->mem_cgroup,
1190 * mem_cgroup_isolate_pages() keeps track of
1191 * scanned pages on its own.
1198 nr_active = clear_active_flags(&page_list, count);
1199 __count_vm_events(PGDEACTIVATE, nr_active);
1201 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1202 -count[LRU_ACTIVE_FILE]);
1203 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1204 -count[LRU_INACTIVE_FILE]);
1205 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1206 -count[LRU_ACTIVE_ANON]);
1207 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1208 -count[LRU_INACTIVE_ANON]);
1210 nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1211 nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1212 __mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
1213 __mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
1215 reclaim_stat->recent_scanned[0] += nr_anon;
1216 reclaim_stat->recent_scanned[1] += nr_file;
1218 spin_unlock_irq(&zone->lru_lock);
1220 nr_scanned += nr_scan;
1221 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1224 * If we are direct reclaiming for contiguous pages and we do
1225 * not reclaim everything in the list, try again and wait
1226 * for IO to complete. This will stall high-order allocations
1227 * but that should be acceptable to the caller
1229 if (nr_freed < nr_taken && !current_is_kswapd() &&
1230 sc->lumpy_reclaim_mode) {
1231 congestion_wait(BLK_RW_ASYNC, HZ/10);
1234 * The attempt at page out may have made some
1235 * of the pages active, mark them inactive again.
1237 nr_active = clear_active_flags(&page_list, count);
1238 count_vm_events(PGDEACTIVATE, nr_active);
1240 nr_freed += shrink_page_list(&page_list, sc,
1244 nr_reclaimed += nr_freed;
1246 local_irq_disable();
1247 if (current_is_kswapd())
1248 __count_vm_events(KSWAPD_STEAL, nr_freed);
1249 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
1251 spin_lock(&zone->lru_lock);
1253 * Put back any unfreeable pages.
1255 while (!list_empty(&page_list)) {
1257 page = lru_to_page(&page_list);
1258 VM_BUG_ON(PageLRU(page));
1259 list_del(&page->lru);
1260 if (unlikely(!page_evictable(page, NULL))) {
1261 spin_unlock_irq(&zone->lru_lock);
1262 putback_lru_page(page);
1263 spin_lock_irq(&zone->lru_lock);
1267 lru = page_lru(page);
1268 add_page_to_lru_list(zone, page, lru);
1269 if (is_active_lru(lru)) {
1270 int file = is_file_lru(lru);
1271 reclaim_stat->recent_rotated[file]++;
1273 if (!pagevec_add(&pvec, page)) {
1274 spin_unlock_irq(&zone->lru_lock);
1275 __pagevec_release(&pvec);
1276 spin_lock_irq(&zone->lru_lock);
1279 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1280 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1282 } while (nr_scanned < max_scan);
1285 spin_unlock_irq(&zone->lru_lock);
1286 pagevec_release(&pvec);
1287 return nr_reclaimed;
1291 * We are about to scan this zone at a certain priority level. If that priority
1292 * level is smaller (ie: more urgent) than the previous priority, then note
1293 * that priority level within the zone. This is done so that when the next
1294 * process comes in to scan this zone, it will immediately start out at this
1295 * priority level rather than having to build up its own scanning priority.
1296 * Here, this priority affects only the reclaim-mapped threshold.
1298 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1300 if (priority < zone->prev_priority)
1301 zone->prev_priority = priority;
1305 * This moves pages from the active list to the inactive list.
1307 * We move them the other way if the page is referenced by one or more
1308 * processes, from rmap.
1310 * If the pages are mostly unmapped, the processing is fast and it is
1311 * appropriate to hold zone->lru_lock across the whole operation. But if
1312 * the pages are mapped, the processing is slow (page_referenced()) so we
1313 * should drop zone->lru_lock around each page. It's impossible to balance
1314 * this, so instead we remove the pages from the LRU while processing them.
1315 * It is safe to rely on PG_active against the non-LRU pages in here because
1316 * nobody will play with that bit on a non-LRU page.
1318 * The downside is that we have to touch page->_count against each page.
1319 * But we had to alter page->flags anyway.
1322 static void move_active_pages_to_lru(struct zone *zone,
1323 struct list_head *list,
1326 unsigned long pgmoved = 0;
1327 struct pagevec pvec;
1330 pagevec_init(&pvec, 1);
1332 while (!list_empty(list)) {
1333 page = lru_to_page(list);
1335 VM_BUG_ON(PageLRU(page));
1338 list_move(&page->lru, &zone->lru[lru].list);
1339 mem_cgroup_add_lru_list(page, lru);
1342 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1343 spin_unlock_irq(&zone->lru_lock);
1344 if (buffer_heads_over_limit)
1345 pagevec_strip(&pvec);
1346 __pagevec_release(&pvec);
1347 spin_lock_irq(&zone->lru_lock);
1350 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1351 if (!is_active_lru(lru))
1352 __count_vm_events(PGDEACTIVATE, pgmoved);
1355 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1356 struct scan_control *sc, int priority, int file)
1358 unsigned long nr_taken;
1359 unsigned long pgscanned;
1360 unsigned long vm_flags;
1361 LIST_HEAD(l_hold); /* The pages which were snipped off */
1362 LIST_HEAD(l_active);
1363 LIST_HEAD(l_inactive);
1365 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1366 unsigned long nr_rotated = 0;
1369 spin_lock_irq(&zone->lru_lock);
1370 if (scanning_global_lru(sc)) {
1371 nr_taken = isolate_pages_global(nr_pages, &l_hold,
1372 &pgscanned, sc->order,
1373 ISOLATE_ACTIVE, zone,
1375 zone->pages_scanned += pgscanned;
1377 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
1378 &pgscanned, sc->order,
1379 ISOLATE_ACTIVE, zone,
1380 sc->mem_cgroup, 1, file);
1382 * mem_cgroup_isolate_pages() keeps track of
1383 * scanned pages on its own.
1387 reclaim_stat->recent_scanned[file] += nr_taken;
1389 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1391 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1393 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1394 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1395 spin_unlock_irq(&zone->lru_lock);
1397 while (!list_empty(&l_hold)) {
1399 page = lru_to_page(&l_hold);
1400 list_del(&page->lru);
1402 if (unlikely(!page_evictable(page, NULL))) {
1403 putback_lru_page(page);
1407 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1410 * Identify referenced, file-backed active pages and
1411 * give them one more trip around the active list. So
1412 * that executable code get better chances to stay in
1413 * memory under moderate memory pressure. Anon pages
1414 * are not likely to be evicted by use-once streaming
1415 * IO, plus JVM can create lots of anon VM_EXEC pages,
1416 * so we ignore them here.
1418 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1419 list_add(&page->lru, &l_active);
1424 ClearPageActive(page); /* we are de-activating */
1425 list_add(&page->lru, &l_inactive);
1429 * Move pages back to the lru list.
1431 spin_lock_irq(&zone->lru_lock);
1433 * Count referenced pages from currently used mappings as rotated,
1434 * even though only some of them are actually re-activated. This
1435 * helps balance scan pressure between file and anonymous pages in
1438 reclaim_stat->recent_rotated[file] += nr_rotated;
1440 move_active_pages_to_lru(zone, &l_active,
1441 LRU_ACTIVE + file * LRU_FILE);
1442 move_active_pages_to_lru(zone, &l_inactive,
1443 LRU_BASE + file * LRU_FILE);
1444 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1445 spin_unlock_irq(&zone->lru_lock);
1448 static int inactive_anon_is_low_global(struct zone *zone)
1450 unsigned long active, inactive;
1452 active = zone_page_state(zone, NR_ACTIVE_ANON);
1453 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1455 if (inactive * zone->inactive_ratio < active)
1462 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1463 * @zone: zone to check
1464 * @sc: scan control of this context
1466 * Returns true if the zone does not have enough inactive anon pages,
1467 * meaning some active anon pages need to be deactivated.
1469 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1473 if (scanning_global_lru(sc))
1474 low = inactive_anon_is_low_global(zone);
1476 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1480 static int inactive_file_is_low_global(struct zone *zone)
1482 unsigned long active, inactive;
1484 active = zone_page_state(zone, NR_ACTIVE_FILE);
1485 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1487 return (active > inactive);
1491 * inactive_file_is_low - check if file pages need to be deactivated
1492 * @zone: zone to check
1493 * @sc: scan control of this context
1495 * When the system is doing streaming IO, memory pressure here
1496 * ensures that active file pages get deactivated, until more
1497 * than half of the file pages are on the inactive list.
1499 * Once we get to that situation, protect the system's working
1500 * set from being evicted by disabling active file page aging.
1502 * This uses a different ratio than the anonymous pages, because
1503 * the page cache uses a use-once replacement algorithm.
1505 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1509 if (scanning_global_lru(sc))
1510 low = inactive_file_is_low_global(zone);
1512 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1516 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1520 return inactive_file_is_low(zone, sc);
1522 return inactive_anon_is_low(zone, sc);
1525 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1526 struct zone *zone, struct scan_control *sc, int priority)
1528 int file = is_file_lru(lru);
1530 if (is_active_lru(lru)) {
1531 if (inactive_list_is_low(zone, sc, file))
1532 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1536 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1540 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1541 * until we collected @swap_cluster_max pages to scan.
1543 static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
1544 unsigned long *nr_saved_scan)
1548 *nr_saved_scan += nr_to_scan;
1549 nr = *nr_saved_scan;
1551 if (nr >= SWAP_CLUSTER_MAX)
1560 * Determine how aggressively the anon and file LRU lists should be
1561 * scanned. The relative value of each set of LRU lists is determined
1562 * by looking at the fraction of the pages scanned we did rotate back
1563 * onto the active list instead of evict.
1565 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1567 static void get_scan_count(struct zone *zone, struct scan_control *sc,
1568 unsigned long *nr, int priority)
1570 unsigned long anon, file, free;
1571 unsigned long anon_prio, file_prio;
1572 unsigned long ap, fp;
1573 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1574 u64 fraction[2], denominator;
1578 /* If we have no swap space, do not bother scanning anon pages. */
1579 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1587 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1588 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1589 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1590 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1592 if (scanning_global_lru(sc)) {
1593 free = zone_page_state(zone, NR_FREE_PAGES);
1594 /* If we have very few page cache pages,
1595 force-scan anon pages. */
1596 if (unlikely(file + free <= high_wmark_pages(zone))) {
1605 * OK, so we have swap space and a fair amount of page cache
1606 * pages. We use the recently rotated / recently scanned
1607 * ratios to determine how valuable each cache is.
1609 * Because workloads change over time (and to avoid overflow)
1610 * we keep these statistics as a floating average, which ends
1611 * up weighing recent references more than old ones.
1613 * anon in [0], file in [1]
1615 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1616 spin_lock_irq(&zone->lru_lock);
1617 reclaim_stat->recent_scanned[0] /= 2;
1618 reclaim_stat->recent_rotated[0] /= 2;
1619 spin_unlock_irq(&zone->lru_lock);
1622 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1623 spin_lock_irq(&zone->lru_lock);
1624 reclaim_stat->recent_scanned[1] /= 2;
1625 reclaim_stat->recent_rotated[1] /= 2;
1626 spin_unlock_irq(&zone->lru_lock);
1630 * With swappiness at 100, anonymous and file have the same priority.
1631 * This scanning priority is essentially the inverse of IO cost.
1633 anon_prio = sc->swappiness;
1634 file_prio = 200 - sc->swappiness;
1637 * The amount of pressure on anon vs file pages is inversely
1638 * proportional to the fraction of recently scanned pages on
1639 * each list that were recently referenced and in active use.
1641 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1642 ap /= reclaim_stat->recent_rotated[0] + 1;
1644 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1645 fp /= reclaim_stat->recent_rotated[1] + 1;
1649 denominator = ap + fp + 1;
1651 for_each_evictable_lru(l) {
1652 int file = is_file_lru(l);
1655 scan = zone_nr_lru_pages(zone, sc, l);
1656 if (priority || noswap) {
1658 scan = div64_u64(scan * fraction[file], denominator);
1660 nr[l] = nr_scan_try_batch(scan,
1661 &reclaim_stat->nr_saved_scan[l]);
1665 static void set_lumpy_reclaim_mode(int priority, struct scan_control *sc)
1668 * If we need a large contiguous chunk of memory, or have
1669 * trouble getting a small set of contiguous pages, we
1670 * will reclaim both active and inactive pages.
1672 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1673 sc->lumpy_reclaim_mode = 1;
1674 else if (sc->order && priority < DEF_PRIORITY - 2)
1675 sc->lumpy_reclaim_mode = 1;
1677 sc->lumpy_reclaim_mode = 0;
1681 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1683 static void shrink_zone(int priority, struct zone *zone,
1684 struct scan_control *sc)
1686 unsigned long nr[NR_LRU_LISTS];
1687 unsigned long nr_to_scan;
1689 unsigned long nr_reclaimed = sc->nr_reclaimed;
1690 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1692 get_scan_count(zone, sc, nr, priority);
1694 set_lumpy_reclaim_mode(priority, sc);
1696 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1697 nr[LRU_INACTIVE_FILE]) {
1698 for_each_evictable_lru(l) {
1700 nr_to_scan = min_t(unsigned long,
1701 nr[l], SWAP_CLUSTER_MAX);
1702 nr[l] -= nr_to_scan;
1704 nr_reclaimed += shrink_list(l, nr_to_scan,
1705 zone, sc, priority);
1709 * On large memory systems, scan >> priority can become
1710 * really large. This is fine for the starting priority;
1711 * we want to put equal scanning pressure on each zone.
1712 * However, if the VM has a harder time of freeing pages,
1713 * with multiple processes reclaiming pages, the total
1714 * freeing target can get unreasonably large.
1716 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
1720 sc->nr_reclaimed = nr_reclaimed;
1723 * Even if we did not try to evict anon pages at all, we want to
1724 * rebalance the anon lru active/inactive ratio.
1726 if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0)
1727 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1729 throttle_vm_writeout(sc->gfp_mask);
1733 * This is the direct reclaim path, for page-allocating processes. We only
1734 * try to reclaim pages from zones which will satisfy the caller's allocation
1737 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1739 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1741 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1742 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1743 * zone defense algorithm.
1745 * If a zone is deemed to be full of pinned pages then just give it a light
1746 * scan then give up on it.
1748 static bool shrink_zones(int priority, struct zonelist *zonelist,
1749 struct scan_control *sc)
1751 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1754 bool all_unreclaimable = true;
1756 for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
1758 if (!populated_zone(zone))
1761 * Take care memory controller reclaiming has small influence
1764 if (scanning_global_lru(sc)) {
1765 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1767 note_zone_scanning_priority(zone, priority);
1769 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1770 continue; /* Let kswapd poll it */
1773 * Ignore cpuset limitation here. We just want to reduce
1774 * # of used pages by us regardless of memory shortage.
1776 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1780 shrink_zone(priority, zone, sc);
1781 all_unreclaimable = false;
1783 return all_unreclaimable;
1787 * This is the main entry point to direct page reclaim.
1789 * If a full scan of the inactive list fails to free enough memory then we
1790 * are "out of memory" and something needs to be killed.
1792 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1793 * high - the zone may be full of dirty or under-writeback pages, which this
1794 * caller can't do much about. We kick the writeback threads and take explicit
1795 * naps in the hope that some of these pages can be written. But if the
1796 * allocating task holds filesystem locks which prevent writeout this might not
1797 * work, and the allocation attempt will fail.
1799 * returns: 0, if no pages reclaimed
1800 * else, the number of pages reclaimed
1802 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1803 struct scan_control *sc)
1806 bool all_unreclaimable;
1807 unsigned long total_scanned = 0;
1808 struct reclaim_state *reclaim_state = current->reclaim_state;
1811 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1812 unsigned long writeback_threshold;
1815 delayacct_freepages_start();
1817 if (scanning_global_lru(sc))
1818 count_vm_event(ALLOCSTALL);
1820 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1823 disable_swap_token();
1824 all_unreclaimable = shrink_zones(priority, zonelist, sc);
1826 * Don't shrink slabs when reclaiming memory from
1827 * over limit cgroups
1829 if (scanning_global_lru(sc)) {
1830 unsigned long lru_pages = 0;
1831 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1832 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1835 lru_pages += zone_reclaimable_pages(zone);
1838 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1839 if (reclaim_state) {
1840 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1841 reclaim_state->reclaimed_slab = 0;
1844 total_scanned += sc->nr_scanned;
1845 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
1849 * Try to write back as many pages as we just scanned. This
1850 * tends to cause slow streaming writers to write data to the
1851 * disk smoothly, at the dirtying rate, which is nice. But
1852 * that's undesirable in laptop mode, where we *want* lumpy
1853 * writeout. So in laptop mode, write out the whole world.
1855 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
1856 if (total_scanned > writeback_threshold) {
1857 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
1858 sc->may_writepage = 1;
1861 /* Take a nap, wait for some writeback to complete */
1862 if (!sc->hibernation_mode && sc->nr_scanned &&
1863 priority < DEF_PRIORITY - 2)
1864 congestion_wait(BLK_RW_ASYNC, HZ/10);
1869 * Now that we've scanned all the zones at this priority level, note
1870 * that level within the zone so that the next thread which performs
1871 * scanning of this zone will immediately start out at this priority
1872 * level. This affects only the decision whether or not to bring
1873 * mapped pages onto the inactive list.
1878 if (scanning_global_lru(sc)) {
1879 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1881 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1884 zone->prev_priority = priority;
1887 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1889 delayacct_freepages_end();
1892 if (sc->nr_reclaimed)
1893 return sc->nr_reclaimed;
1895 /* top priority shrink_zones still had more to do? don't OOM, then */
1896 if (scanning_global_lru(sc) && !all_unreclaimable)
1902 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1903 gfp_t gfp_mask, nodemask_t *nodemask)
1905 unsigned long nr_reclaimed;
1906 struct scan_control sc = {
1907 .gfp_mask = gfp_mask,
1908 .may_writepage = !laptop_mode,
1909 .nr_to_reclaim = SWAP_CLUSTER_MAX,
1912 .swappiness = vm_swappiness,
1915 .nodemask = nodemask,
1918 trace_mm_vmscan_direct_reclaim_begin(order,
1922 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
1924 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
1926 return nr_reclaimed;
1929 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1931 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
1932 gfp_t gfp_mask, bool noswap,
1933 unsigned int swappiness,
1934 struct zone *zone, int nid)
1936 struct scan_control sc = {
1937 .may_writepage = !laptop_mode,
1939 .may_swap = !noswap,
1940 .swappiness = swappiness,
1944 nodemask_t nm = nodemask_of_node(nid);
1946 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1947 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1949 sc.nr_reclaimed = 0;
1952 * NOTE: Although we can get the priority field, using it
1953 * here is not a good idea, since it limits the pages we can scan.
1954 * if we don't reclaim here, the shrink_zone from balance_pgdat
1955 * will pick up pages from other mem cgroup's as well. We hack
1956 * the priority and make it zero.
1958 shrink_zone(0, zone, &sc);
1959 return sc.nr_reclaimed;
1962 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1965 unsigned int swappiness)
1967 struct zonelist *zonelist;
1968 struct scan_control sc = {
1969 .may_writepage = !laptop_mode,
1971 .may_swap = !noswap,
1972 .nr_to_reclaim = SWAP_CLUSTER_MAX,
1973 .swappiness = swappiness,
1975 .mem_cgroup = mem_cont,
1976 .nodemask = NULL, /* we don't care the placement */
1979 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1980 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1981 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1982 return do_try_to_free_pages(zonelist, &sc);
1986 /* is kswapd sleeping prematurely? */
1987 static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
1991 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
1995 /* If after HZ/10, a zone is below the high mark, it's premature */
1996 for (i = 0; i < pgdat->nr_zones; i++) {
1997 struct zone *zone = pgdat->node_zones + i;
1999 if (!populated_zone(zone))
2002 if (zone->all_unreclaimable)
2005 if (!zone_watermark_ok(zone, order, high_wmark_pages(zone),
2014 * For kswapd, balance_pgdat() will work across all this node's zones until
2015 * they are all at high_wmark_pages(zone).
2017 * Returns the number of pages which were actually freed.
2019 * There is special handling here for zones which are full of pinned pages.
2020 * This can happen if the pages are all mlocked, or if they are all used by
2021 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2022 * What we do is to detect the case where all pages in the zone have been
2023 * scanned twice and there has been zero successful reclaim. Mark the zone as
2024 * dead and from now on, only perform a short scan. Basically we're polling
2025 * the zone for when the problem goes away.
2027 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2028 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2029 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2030 * lower zones regardless of the number of free pages in the lower zones. This
2031 * interoperates with the page allocator fallback scheme to ensure that aging
2032 * of pages is balanced across the zones.
2034 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
2039 unsigned long total_scanned;
2040 struct reclaim_state *reclaim_state = current->reclaim_state;
2041 struct scan_control sc = {
2042 .gfp_mask = GFP_KERNEL,
2046 * kswapd doesn't want to be bailed out while reclaim. because
2047 * we want to put equal scanning pressure on each zone.
2049 .nr_to_reclaim = ULONG_MAX,
2050 .swappiness = vm_swappiness,
2055 * temp_priority is used to remember the scanning priority at which
2056 * this zone was successfully refilled to
2057 * free_pages == high_wmark_pages(zone).
2059 int temp_priority[MAX_NR_ZONES];
2063 sc.nr_reclaimed = 0;
2064 sc.may_writepage = !laptop_mode;
2065 count_vm_event(PAGEOUTRUN);
2067 for (i = 0; i < pgdat->nr_zones; i++)
2068 temp_priority[i] = DEF_PRIORITY;
2070 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2071 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2072 unsigned long lru_pages = 0;
2073 int has_under_min_watermark_zone = 0;
2075 /* The swap token gets in the way of swapout... */
2077 disable_swap_token();
2082 * Scan in the highmem->dma direction for the highest
2083 * zone which needs scanning
2085 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2086 struct zone *zone = pgdat->node_zones + i;
2088 if (!populated_zone(zone))
2091 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2095 * Do some background aging of the anon list, to give
2096 * pages a chance to be referenced before reclaiming.
2098 if (inactive_anon_is_low(zone, &sc))
2099 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2102 if (!zone_watermark_ok(zone, order,
2103 high_wmark_pages(zone), 0, 0)) {
2111 for (i = 0; i <= end_zone; i++) {
2112 struct zone *zone = pgdat->node_zones + i;
2114 lru_pages += zone_reclaimable_pages(zone);
2118 * Now scan the zone in the dma->highmem direction, stopping
2119 * at the last zone which needs scanning.
2121 * We do this because the page allocator works in the opposite
2122 * direction. This prevents the page allocator from allocating
2123 * pages behind kswapd's direction of progress, which would
2124 * cause too much scanning of the lower zones.
2126 for (i = 0; i <= end_zone; i++) {
2127 struct zone *zone = pgdat->node_zones + i;
2131 if (!populated_zone(zone))
2134 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2137 temp_priority[i] = priority;
2139 note_zone_scanning_priority(zone, priority);
2141 nid = pgdat->node_id;
2142 zid = zone_idx(zone);
2144 * Call soft limit reclaim before calling shrink_zone.
2145 * For now we ignore the return value
2147 mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask,
2150 * We put equal pressure on every zone, unless one
2151 * zone has way too many pages free already.
2153 if (!zone_watermark_ok(zone, order,
2154 8*high_wmark_pages(zone), end_zone, 0))
2155 shrink_zone(priority, zone, &sc);
2156 reclaim_state->reclaimed_slab = 0;
2157 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
2159 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2160 total_scanned += sc.nr_scanned;
2161 if (zone->all_unreclaimable)
2164 zone->pages_scanned >= (zone_reclaimable_pages(zone) * 6))
2165 zone->all_unreclaimable = 1;
2167 * If we've done a decent amount of scanning and
2168 * the reclaim ratio is low, start doing writepage
2169 * even in laptop mode
2171 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2172 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2173 sc.may_writepage = 1;
2175 if (!zone_watermark_ok(zone, order,
2176 high_wmark_pages(zone), end_zone, 0)) {
2179 * We are still under min water mark. This
2180 * means that we have a GFP_ATOMIC allocation
2181 * failure risk. Hurry up!
2183 if (!zone_watermark_ok(zone, order,
2184 min_wmark_pages(zone), end_zone, 0))
2185 has_under_min_watermark_zone = 1;
2190 break; /* kswapd: all done */
2192 * OK, kswapd is getting into trouble. Take a nap, then take
2193 * another pass across the zones.
2195 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2196 if (has_under_min_watermark_zone)
2197 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2199 congestion_wait(BLK_RW_ASYNC, HZ/10);
2203 * We do this so kswapd doesn't build up large priorities for
2204 * example when it is freeing in parallel with allocators. It
2205 * matches the direct reclaim path behaviour in terms of impact
2206 * on zone->*_priority.
2208 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2213 * Note within each zone the priority level at which this zone was
2214 * brought into a happy state. So that the next thread which scans this
2215 * zone will start out at that priority level.
2217 for (i = 0; i < pgdat->nr_zones; i++) {
2218 struct zone *zone = pgdat->node_zones + i;
2220 zone->prev_priority = temp_priority[i];
2222 if (!all_zones_ok) {
2228 * Fragmentation may mean that the system cannot be
2229 * rebalanced for high-order allocations in all zones.
2230 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2231 * it means the zones have been fully scanned and are still
2232 * not balanced. For high-order allocations, there is
2233 * little point trying all over again as kswapd may
2236 * Instead, recheck all watermarks at order-0 as they
2237 * are the most important. If watermarks are ok, kswapd will go
2238 * back to sleep. High-order users can still perform direct
2239 * reclaim if they wish.
2241 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2242 order = sc.order = 0;
2247 return sc.nr_reclaimed;
2251 * The background pageout daemon, started as a kernel thread
2252 * from the init process.
2254 * This basically trickles out pages so that we have _some_
2255 * free memory available even if there is no other activity
2256 * that frees anything up. This is needed for things like routing
2257 * etc, where we otherwise might have all activity going on in
2258 * asynchronous contexts that cannot page things out.
2260 * If there are applications that are active memory-allocators
2261 * (most normal use), this basically shouldn't matter.
2263 static int kswapd(void *p)
2265 unsigned long order;
2266 pg_data_t *pgdat = (pg_data_t*)p;
2267 struct task_struct *tsk = current;
2269 struct reclaim_state reclaim_state = {
2270 .reclaimed_slab = 0,
2272 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2274 lockdep_set_current_reclaim_state(GFP_KERNEL);
2276 if (!cpumask_empty(cpumask))
2277 set_cpus_allowed_ptr(tsk, cpumask);
2278 current->reclaim_state = &reclaim_state;
2281 * Tell the memory management that we're a "memory allocator",
2282 * and that if we need more memory we should get access to it
2283 * regardless (see "__alloc_pages()"). "kswapd" should
2284 * never get caught in the normal page freeing logic.
2286 * (Kswapd normally doesn't need memory anyway, but sometimes
2287 * you need a small amount of memory in order to be able to
2288 * page out something else, and this flag essentially protects
2289 * us from recursively trying to free more memory as we're
2290 * trying to free the first piece of memory in the first place).
2292 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2297 unsigned long new_order;
2300 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2301 new_order = pgdat->kswapd_max_order;
2302 pgdat->kswapd_max_order = 0;
2303 if (order < new_order) {
2305 * Don't sleep if someone wants a larger 'order'
2310 if (!freezing(current) && !kthread_should_stop()) {
2313 /* Try to sleep for a short interval */
2314 if (!sleeping_prematurely(pgdat, order, remaining)) {
2315 remaining = schedule_timeout(HZ/10);
2316 finish_wait(&pgdat->kswapd_wait, &wait);
2317 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2321 * After a short sleep, check if it was a
2322 * premature sleep. If not, then go fully
2323 * to sleep until explicitly woken up
2325 if (!sleeping_prematurely(pgdat, order, remaining)) {
2326 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2330 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2332 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2336 order = pgdat->kswapd_max_order;
2338 finish_wait(&pgdat->kswapd_wait, &wait);
2340 ret = try_to_freeze();
2341 if (kthread_should_stop())
2345 * We can speed up thawing tasks if we don't call balance_pgdat
2346 * after returning from the refrigerator
2349 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2350 balance_pgdat(pgdat, order);
2357 * A zone is low on free memory, so wake its kswapd task to service it.
2359 void wakeup_kswapd(struct zone *zone, int order)
2363 if (!populated_zone(zone))
2366 pgdat = zone->zone_pgdat;
2367 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
2369 if (pgdat->kswapd_max_order < order)
2370 pgdat->kswapd_max_order = order;
2371 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2372 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2374 if (!waitqueue_active(&pgdat->kswapd_wait))
2376 wake_up_interruptible(&pgdat->kswapd_wait);
2380 * The reclaimable count would be mostly accurate.
2381 * The less reclaimable pages may be
2382 * - mlocked pages, which will be moved to unevictable list when encountered
2383 * - mapped pages, which may require several travels to be reclaimed
2384 * - dirty pages, which is not "instantly" reclaimable
2386 unsigned long global_reclaimable_pages(void)
2390 nr = global_page_state(NR_ACTIVE_FILE) +
2391 global_page_state(NR_INACTIVE_FILE);
2393 if (nr_swap_pages > 0)
2394 nr += global_page_state(NR_ACTIVE_ANON) +
2395 global_page_state(NR_INACTIVE_ANON);
2400 unsigned long zone_reclaimable_pages(struct zone *zone)
2404 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2405 zone_page_state(zone, NR_INACTIVE_FILE);
2407 if (nr_swap_pages > 0)
2408 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2409 zone_page_state(zone, NR_INACTIVE_ANON);
2414 #ifdef CONFIG_HIBERNATION
2416 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2419 * Rather than trying to age LRUs the aim is to preserve the overall
2420 * LRU order by reclaiming preferentially
2421 * inactive > active > active referenced > active mapped
2423 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2425 struct reclaim_state reclaim_state;
2426 struct scan_control sc = {
2427 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2431 .nr_to_reclaim = nr_to_reclaim,
2432 .hibernation_mode = 1,
2433 .swappiness = vm_swappiness,
2436 struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2437 struct task_struct *p = current;
2438 unsigned long nr_reclaimed;
2440 p->flags |= PF_MEMALLOC;
2441 lockdep_set_current_reclaim_state(sc.gfp_mask);
2442 reclaim_state.reclaimed_slab = 0;
2443 p->reclaim_state = &reclaim_state;
2445 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
2447 p->reclaim_state = NULL;
2448 lockdep_clear_current_reclaim_state();
2449 p->flags &= ~PF_MEMALLOC;
2451 return nr_reclaimed;
2453 #endif /* CONFIG_HIBERNATION */
2455 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2456 not required for correctness. So if the last cpu in a node goes
2457 away, we get changed to run anywhere: as the first one comes back,
2458 restore their cpu bindings. */
2459 static int __devinit cpu_callback(struct notifier_block *nfb,
2460 unsigned long action, void *hcpu)
2464 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2465 for_each_node_state(nid, N_HIGH_MEMORY) {
2466 pg_data_t *pgdat = NODE_DATA(nid);
2467 const struct cpumask *mask;
2469 mask = cpumask_of_node(pgdat->node_id);
2471 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2472 /* One of our CPUs online: restore mask */
2473 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2480 * This kswapd start function will be called by init and node-hot-add.
2481 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2483 int kswapd_run(int nid)
2485 pg_data_t *pgdat = NODE_DATA(nid);
2491 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2492 if (IS_ERR(pgdat->kswapd)) {
2493 /* failure at boot is fatal */
2494 BUG_ON(system_state == SYSTEM_BOOTING);
2495 printk("Failed to start kswapd on node %d\n",nid);
2502 * Called by memory hotplug when all memory in a node is offlined.
2504 void kswapd_stop(int nid)
2506 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
2509 kthread_stop(kswapd);
2512 static int __init kswapd_init(void)
2517 for_each_node_state(nid, N_HIGH_MEMORY)
2519 hotcpu_notifier(cpu_callback, 0);
2523 module_init(kswapd_init)
2529 * If non-zero call zone_reclaim when the number of free pages falls below
2532 int zone_reclaim_mode __read_mostly;
2534 #define RECLAIM_OFF 0
2535 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2536 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2537 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2540 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2541 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2544 #define ZONE_RECLAIM_PRIORITY 4
2547 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2550 int sysctl_min_unmapped_ratio = 1;
2553 * If the number of slab pages in a zone grows beyond this percentage then
2554 * slab reclaim needs to occur.
2556 int sysctl_min_slab_ratio = 5;
2558 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
2560 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
2561 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
2562 zone_page_state(zone, NR_ACTIVE_FILE);
2565 * It's possible for there to be more file mapped pages than
2566 * accounted for by the pages on the file LRU lists because
2567 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2569 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
2572 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
2573 static long zone_pagecache_reclaimable(struct zone *zone)
2575 long nr_pagecache_reclaimable;
2579 * If RECLAIM_SWAP is set, then all file pages are considered
2580 * potentially reclaimable. Otherwise, we have to worry about
2581 * pages like swapcache and zone_unmapped_file_pages() provides
2584 if (zone_reclaim_mode & RECLAIM_SWAP)
2585 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
2587 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
2589 /* If we can't clean pages, remove dirty pages from consideration */
2590 if (!(zone_reclaim_mode & RECLAIM_WRITE))
2591 delta += zone_page_state(zone, NR_FILE_DIRTY);
2593 /* Watch for any possible underflows due to delta */
2594 if (unlikely(delta > nr_pagecache_reclaimable))
2595 delta = nr_pagecache_reclaimable;
2597 return nr_pagecache_reclaimable - delta;
2601 * Try to free up some pages from this zone through reclaim.
2603 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2605 /* Minimum pages needed in order to stay on node */
2606 const unsigned long nr_pages = 1 << order;
2607 struct task_struct *p = current;
2608 struct reclaim_state reclaim_state;
2610 struct scan_control sc = {
2611 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2612 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2614 .nr_to_reclaim = max_t(unsigned long, nr_pages,
2616 .gfp_mask = gfp_mask,
2617 .swappiness = vm_swappiness,
2620 unsigned long slab_reclaimable;
2624 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2625 * and we also need to be able to write out pages for RECLAIM_WRITE
2628 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2629 lockdep_set_current_reclaim_state(gfp_mask);
2630 reclaim_state.reclaimed_slab = 0;
2631 p->reclaim_state = &reclaim_state;
2633 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
2635 * Free memory by calling shrink zone with increasing
2636 * priorities until we have enough memory freed.
2638 priority = ZONE_RECLAIM_PRIORITY;
2640 note_zone_scanning_priority(zone, priority);
2641 shrink_zone(priority, zone, &sc);
2643 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2646 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2647 if (slab_reclaimable > zone->min_slab_pages) {
2649 * shrink_slab() does not currently allow us to determine how
2650 * many pages were freed in this zone. So we take the current
2651 * number of slab pages and shake the slab until it is reduced
2652 * by the same nr_pages that we used for reclaiming unmapped
2655 * Note that shrink_slab will free memory on all zones and may
2658 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2659 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2660 slab_reclaimable - nr_pages)
2664 * Update nr_reclaimed by the number of slab pages we
2665 * reclaimed from this zone.
2667 sc.nr_reclaimed += slab_reclaimable -
2668 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2671 p->reclaim_state = NULL;
2672 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2673 lockdep_clear_current_reclaim_state();
2674 return sc.nr_reclaimed >= nr_pages;
2677 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2683 * Zone reclaim reclaims unmapped file backed pages and
2684 * slab pages if we are over the defined limits.
2686 * A small portion of unmapped file backed pages is needed for
2687 * file I/O otherwise pages read by file I/O will be immediately
2688 * thrown out if the zone is overallocated. So we do not reclaim
2689 * if less than a specified percentage of the zone is used by
2690 * unmapped file backed pages.
2692 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
2693 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
2694 return ZONE_RECLAIM_FULL;
2696 if (zone->all_unreclaimable)
2697 return ZONE_RECLAIM_FULL;
2700 * Do not scan if the allocation should not be delayed.
2702 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2703 return ZONE_RECLAIM_NOSCAN;
2706 * Only run zone reclaim on the local zone or on zones that do not
2707 * have associated processors. This will favor the local processor
2708 * over remote processors and spread off node memory allocations
2709 * as wide as possible.
2711 node_id = zone_to_nid(zone);
2712 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2713 return ZONE_RECLAIM_NOSCAN;
2715 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2716 return ZONE_RECLAIM_NOSCAN;
2718 ret = __zone_reclaim(zone, gfp_mask, order);
2719 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2722 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
2729 * page_evictable - test whether a page is evictable
2730 * @page: the page to test
2731 * @vma: the VMA in which the page is or will be mapped, may be NULL
2733 * Test whether page is evictable--i.e., should be placed on active/inactive
2734 * lists vs unevictable list. The vma argument is !NULL when called from the
2735 * fault path to determine how to instantate a new page.
2737 * Reasons page might not be evictable:
2738 * (1) page's mapping marked unevictable
2739 * (2) page is part of an mlocked VMA
2742 int page_evictable(struct page *page, struct vm_area_struct *vma)
2745 if (mapping_unevictable(page_mapping(page)))
2748 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2755 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2756 * @page: page to check evictability and move to appropriate lru list
2757 * @zone: zone page is in
2759 * Checks a page for evictability and moves the page to the appropriate
2762 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2763 * have PageUnevictable set.
2765 static void check_move_unevictable_page(struct page *page, struct zone *zone)
2767 VM_BUG_ON(PageActive(page));
2770 ClearPageUnevictable(page);
2771 if (page_evictable(page, NULL)) {
2772 enum lru_list l = page_lru_base_type(page);
2774 __dec_zone_state(zone, NR_UNEVICTABLE);
2775 list_move(&page->lru, &zone->lru[l].list);
2776 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2777 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2778 __count_vm_event(UNEVICTABLE_PGRESCUED);
2781 * rotate unevictable list
2783 SetPageUnevictable(page);
2784 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2785 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
2786 if (page_evictable(page, NULL))
2792 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2793 * @mapping: struct address_space to scan for evictable pages
2795 * Scan all pages in mapping. Check unevictable pages for
2796 * evictability and move them to the appropriate zone lru list.
2798 void scan_mapping_unevictable_pages(struct address_space *mapping)
2801 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2804 struct pagevec pvec;
2806 if (mapping->nrpages == 0)
2809 pagevec_init(&pvec, 0);
2810 while (next < end &&
2811 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2817 for (i = 0; i < pagevec_count(&pvec); i++) {
2818 struct page *page = pvec.pages[i];
2819 pgoff_t page_index = page->index;
2820 struct zone *pagezone = page_zone(page);
2823 if (page_index > next)
2827 if (pagezone != zone) {
2829 spin_unlock_irq(&zone->lru_lock);
2831 spin_lock_irq(&zone->lru_lock);
2834 if (PageLRU(page) && PageUnevictable(page))
2835 check_move_unevictable_page(page, zone);
2838 spin_unlock_irq(&zone->lru_lock);
2839 pagevec_release(&pvec);
2841 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2847 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2848 * @zone - zone of which to scan the unevictable list
2850 * Scan @zone's unevictable LRU lists to check for pages that have become
2851 * evictable. Move those that have to @zone's inactive list where they
2852 * become candidates for reclaim, unless shrink_inactive_zone() decides
2853 * to reactivate them. Pages that are still unevictable are rotated
2854 * back onto @zone's unevictable list.
2856 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2857 static void scan_zone_unevictable_pages(struct zone *zone)
2859 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2861 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2863 while (nr_to_scan > 0) {
2864 unsigned long batch_size = min(nr_to_scan,
2865 SCAN_UNEVICTABLE_BATCH_SIZE);
2867 spin_lock_irq(&zone->lru_lock);
2868 for (scan = 0; scan < batch_size; scan++) {
2869 struct page *page = lru_to_page(l_unevictable);
2871 if (!trylock_page(page))
2874 prefetchw_prev_lru_page(page, l_unevictable, flags);
2876 if (likely(PageLRU(page) && PageUnevictable(page)))
2877 check_move_unevictable_page(page, zone);
2881 spin_unlock_irq(&zone->lru_lock);
2883 nr_to_scan -= batch_size;
2889 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2891 * A really big hammer: scan all zones' unevictable LRU lists to check for
2892 * pages that have become evictable. Move those back to the zones'
2893 * inactive list where they become candidates for reclaim.
2894 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2895 * and we add swap to the system. As such, it runs in the context of a task
2896 * that has possibly/probably made some previously unevictable pages
2899 static void scan_all_zones_unevictable_pages(void)
2903 for_each_zone(zone) {
2904 scan_zone_unevictable_pages(zone);
2909 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2910 * all nodes' unevictable lists for evictable pages
2912 unsigned long scan_unevictable_pages;
2914 int scan_unevictable_handler(struct ctl_table *table, int write,
2915 void __user *buffer,
2916 size_t *length, loff_t *ppos)
2918 proc_doulongvec_minmax(table, write, buffer, length, ppos);
2920 if (write && *(unsigned long *)table->data)
2921 scan_all_zones_unevictable_pages();
2923 scan_unevictable_pages = 0;
2928 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2929 * a specified node's per zone unevictable lists for evictable pages.
2932 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2933 struct sysdev_attribute *attr,
2936 return sprintf(buf, "0\n"); /* always zero; should fit... */
2939 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2940 struct sysdev_attribute *attr,
2941 const char *buf, size_t count)
2943 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2946 unsigned long req = strict_strtoul(buf, 10, &res);
2949 return 1; /* zero is no-op */
2951 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2952 if (!populated_zone(zone))
2954 scan_zone_unevictable_pages(zone);
2960 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2961 read_scan_unevictable_node,
2962 write_scan_unevictable_node);
2964 int scan_unevictable_register_node(struct node *node)
2966 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2969 void scan_unevictable_unregister_node(struct node *node)
2971 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);