4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 * Swap reorganised 29.12.95, Stephen Tweedie.
7 * kswapd added: 7.1.96 sct
8 * Removed kswapd_ctl limits, and swap out as many pages as needed
9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11 * Multiqueue VM started 5.8.00, Rik van Riel.
15 #include <linux/module.h>
16 #include <linux/slab.h>
17 #include <linux/kernel_stat.h>
18 #include <linux/swap.h>
19 #include <linux/pagemap.h>
20 #include <linux/init.h>
21 #include <linux/highmem.h>
22 #include <linux/vmstat.h>
23 #include <linux/file.h>
24 #include <linux/writeback.h>
25 #include <linux/blkdev.h>
26 #include <linux/buffer_head.h> /* for try_to_release_page(),
27 buffer_heads_over_limit */
28 #include <linux/mm_inline.h>
29 #include <linux/pagevec.h>
30 #include <linux/backing-dev.h>
31 #include <linux/rmap.h>
32 #include <linux/topology.h>
33 #include <linux/cpu.h>
34 #include <linux/cpuset.h>
35 #include <linux/notifier.h>
36 #include <linux/rwsem.h>
37 #include <linux/delay.h>
38 #include <linux/kthread.h>
39 #include <linux/freezer.h>
40 #include <linux/memcontrol.h>
41 #include <linux/delayacct.h>
42 #include <linux/sysctl.h>
44 #include <asm/tlbflush.h>
45 #include <asm/div64.h>
47 #include <linux/swapops.h>
52 /* Incremented by the number of inactive pages that were scanned */
53 unsigned long nr_scanned
;
55 /* Number of pages freed so far during a call to shrink_zones() */
56 unsigned long nr_reclaimed
;
58 /* How many pages shrink_list() should reclaim */
59 unsigned long nr_to_reclaim
;
61 unsigned long hibernation_mode
;
63 /* This context's GFP mask */
68 /* Can mapped pages be reclaimed? */
71 /* Can pages be swapped as part of reclaim? */
76 int all_unreclaimable
;
80 /* Which cgroup do we reclaim from */
81 struct mem_cgroup
*mem_cgroup
;
84 * Nodemask of nodes allowed by the caller. If NULL, all nodes
89 /* Pluggable isolate pages callback */
90 unsigned long (*isolate_pages
)(unsigned long nr
, struct list_head
*dst
,
91 unsigned long *scanned
, int order
, int mode
,
92 struct zone
*z
, struct mem_cgroup
*mem_cont
,
93 int active
, int file
);
96 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
98 #ifdef ARCH_HAS_PREFETCH
99 #define prefetch_prev_lru_page(_page, _base, _field) \
101 if ((_page)->lru.prev != _base) { \
104 prev = lru_to_page(&(_page->lru)); \
105 prefetch(&prev->_field); \
109 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
112 #ifdef ARCH_HAS_PREFETCHW
113 #define prefetchw_prev_lru_page(_page, _base, _field) \
115 if ((_page)->lru.prev != _base) { \
118 prev = lru_to_page(&(_page->lru)); \
119 prefetchw(&prev->_field); \
123 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
127 * From 0 .. 100. Higher means more swappy.
129 int vm_swappiness
= 60;
130 long vm_total_pages
; /* The total number of pages which the VM controls */
132 static LIST_HEAD(shrinker_list
);
133 static DECLARE_RWSEM(shrinker_rwsem
);
135 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
136 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
138 #define scanning_global_lru(sc) (1)
141 static struct zone_reclaim_stat
*get_reclaim_stat(struct zone
*zone
,
142 struct scan_control
*sc
)
144 if (!scanning_global_lru(sc
))
145 return mem_cgroup_get_reclaim_stat(sc
->mem_cgroup
, zone
);
147 return &zone
->reclaim_stat
;
150 static unsigned long zone_nr_lru_pages(struct zone
*zone
,
151 struct scan_control
*sc
, enum lru_list lru
)
153 if (!scanning_global_lru(sc
))
154 return mem_cgroup_zone_nr_pages(sc
->mem_cgroup
, zone
, lru
);
156 return zone_page_state(zone
, NR_LRU_BASE
+ lru
);
161 * Add a shrinker callback to be called from the vm
163 void register_shrinker(struct shrinker
*shrinker
)
166 down_write(&shrinker_rwsem
);
167 list_add_tail(&shrinker
->list
, &shrinker_list
);
168 up_write(&shrinker_rwsem
);
170 EXPORT_SYMBOL(register_shrinker
);
175 void unregister_shrinker(struct shrinker
*shrinker
)
177 down_write(&shrinker_rwsem
);
178 list_del(&shrinker
->list
);
179 up_write(&shrinker_rwsem
);
181 EXPORT_SYMBOL(unregister_shrinker
);
183 #define SHRINK_BATCH 128
185 * Call the shrink functions to age shrinkable caches
187 * Here we assume it costs one seek to replace a lru page and that it also
188 * takes a seek to recreate a cache object. With this in mind we age equal
189 * percentages of the lru and ageable caches. This should balance the seeks
190 * generated by these structures.
192 * If the vm encountered mapped pages on the LRU it increase the pressure on
193 * slab to avoid swapping.
195 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
197 * `lru_pages' represents the number of on-LRU pages in all the zones which
198 * are eligible for the caller's allocation attempt. It is used for balancing
199 * slab reclaim versus page reclaim.
201 * Returns the number of slab objects which we shrunk.
203 unsigned long shrink_slab(unsigned long scanned
, gfp_t gfp_mask
,
204 unsigned long lru_pages
)
206 struct shrinker
*shrinker
;
207 unsigned long ret
= 0;
210 scanned
= SWAP_CLUSTER_MAX
;
212 if (!down_read_trylock(&shrinker_rwsem
))
213 return 1; /* Assume we'll be able to shrink next time */
215 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
216 unsigned long long delta
;
217 unsigned long total_scan
;
218 unsigned long max_pass
= (*shrinker
->shrink
)(0, gfp_mask
);
220 delta
= (4 * scanned
) / shrinker
->seeks
;
222 do_div(delta
, lru_pages
+ 1);
223 shrinker
->nr
+= delta
;
224 if (shrinker
->nr
< 0) {
225 printk(KERN_ERR
"shrink_slab: %pF negative objects to "
227 shrinker
->shrink
, shrinker
->nr
);
228 shrinker
->nr
= max_pass
;
232 * Avoid risking looping forever due to too large nr value:
233 * never try to free more than twice the estimate number of
236 if (shrinker
->nr
> max_pass
* 2)
237 shrinker
->nr
= max_pass
* 2;
239 total_scan
= shrinker
->nr
;
242 while (total_scan
>= SHRINK_BATCH
) {
243 long this_scan
= SHRINK_BATCH
;
247 nr_before
= (*shrinker
->shrink
)(0, gfp_mask
);
248 shrink_ret
= (*shrinker
->shrink
)(this_scan
, gfp_mask
);
249 if (shrink_ret
== -1)
251 if (shrink_ret
< nr_before
)
252 ret
+= nr_before
- shrink_ret
;
253 count_vm_events(SLABS_SCANNED
, this_scan
);
254 total_scan
-= this_scan
;
259 shrinker
->nr
+= total_scan
;
261 up_read(&shrinker_rwsem
);
265 /* Called without lock on whether page is mapped, so answer is unstable */
266 static inline int page_mapping_inuse(struct page
*page
)
268 struct address_space
*mapping
;
270 /* Page is in somebody's page tables. */
271 if (page_mapped(page
))
274 /* Be more reluctant to reclaim swapcache than pagecache */
275 if (PageSwapCache(page
))
278 mapping
= page_mapping(page
);
282 /* File is mmap'd by somebody? */
283 return mapping_mapped(mapping
);
286 static inline int is_page_cache_freeable(struct page
*page
)
289 * A freeable page cache page is referenced only by the caller
290 * that isolated the page, the page cache radix tree and
291 * optional buffer heads at page->private.
293 return page_count(page
) - page_has_private(page
) == 2;
296 static int may_write_to_queue(struct backing_dev_info
*bdi
)
298 if (current
->flags
& PF_SWAPWRITE
)
300 if (!bdi_write_congested(bdi
))
302 if (bdi
== current
->backing_dev_info
)
308 * We detected a synchronous write error writing a page out. Probably
309 * -ENOSPC. We need to propagate that into the address_space for a subsequent
310 * fsync(), msync() or close().
312 * The tricky part is that after writepage we cannot touch the mapping: nothing
313 * prevents it from being freed up. But we have a ref on the page and once
314 * that page is locked, the mapping is pinned.
316 * We're allowed to run sleeping lock_page() here because we know the caller has
319 static void handle_write_error(struct address_space
*mapping
,
320 struct page
*page
, int error
)
323 if (page_mapping(page
) == mapping
)
324 mapping_set_error(mapping
, error
);
328 /* Request for sync pageout. */
334 /* possible outcome of pageout() */
336 /* failed to write page out, page is locked */
338 /* move page to the active list, page is locked */
340 /* page has been sent to the disk successfully, page is unlocked */
342 /* page is clean and locked */
347 * pageout is called by shrink_page_list() for each dirty page.
348 * Calls ->writepage().
350 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
351 enum pageout_io sync_writeback
)
354 * If the page is dirty, only perform writeback if that write
355 * will be non-blocking. To prevent this allocation from being
356 * stalled by pagecache activity. But note that there may be
357 * stalls if we need to run get_block(). We could test
358 * PagePrivate for that.
360 * If this process is currently in __generic_file_aio_write() against
361 * this page's queue, we can perform writeback even if that
364 * If the page is swapcache, write it back even if that would
365 * block, for some throttling. This happens by accident, because
366 * swap_backing_dev_info is bust: it doesn't reflect the
367 * congestion state of the swapdevs. Easy to fix, if needed.
369 if (!is_page_cache_freeable(page
))
373 * Some data journaling orphaned pages can have
374 * page->mapping == NULL while being dirty with clean buffers.
376 if (page_has_private(page
)) {
377 if (try_to_free_buffers(page
)) {
378 ClearPageDirty(page
);
379 printk("%s: orphaned page\n", __func__
);
385 if (mapping
->a_ops
->writepage
== NULL
)
386 return PAGE_ACTIVATE
;
387 if (!may_write_to_queue(mapping
->backing_dev_info
))
390 if (clear_page_dirty_for_io(page
)) {
392 struct writeback_control wbc
= {
393 .sync_mode
= WB_SYNC_NONE
,
394 .nr_to_write
= SWAP_CLUSTER_MAX
,
396 .range_end
= LLONG_MAX
,
401 SetPageReclaim(page
);
402 res
= mapping
->a_ops
->writepage(page
, &wbc
);
404 handle_write_error(mapping
, page
, res
);
405 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
406 ClearPageReclaim(page
);
407 return PAGE_ACTIVATE
;
411 * Wait on writeback if requested to. This happens when
412 * direct reclaiming a large contiguous area and the
413 * first attempt to free a range of pages fails.
415 if (PageWriteback(page
) && sync_writeback
== PAGEOUT_IO_SYNC
)
416 wait_on_page_writeback(page
);
418 if (!PageWriteback(page
)) {
419 /* synchronous write or broken a_ops? */
420 ClearPageReclaim(page
);
422 inc_zone_page_state(page
, NR_VMSCAN_WRITE
);
430 * Same as remove_mapping, but if the page is removed from the mapping, it
431 * gets returned with a refcount of 0.
433 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
)
435 BUG_ON(!PageLocked(page
));
436 BUG_ON(mapping
!= page_mapping(page
));
438 spin_lock_irq(&mapping
->tree_lock
);
440 * The non racy check for a busy page.
442 * Must be careful with the order of the tests. When someone has
443 * a ref to the page, it may be possible that they dirty it then
444 * drop the reference. So if PageDirty is tested before page_count
445 * here, then the following race may occur:
447 * get_user_pages(&page);
448 * [user mapping goes away]
450 * !PageDirty(page) [good]
451 * SetPageDirty(page);
453 * !page_count(page) [good, discard it]
455 * [oops, our write_to data is lost]
457 * Reversing the order of the tests ensures such a situation cannot
458 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
459 * load is not satisfied before that of page->_count.
461 * Note that if SetPageDirty is always performed via set_page_dirty,
462 * and thus under tree_lock, then this ordering is not required.
464 if (!page_freeze_refs(page
, 2))
466 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
467 if (unlikely(PageDirty(page
))) {
468 page_unfreeze_refs(page
, 2);
472 if (PageSwapCache(page
)) {
473 swp_entry_t swap
= { .val
= page_private(page
) };
474 __delete_from_swap_cache(page
);
475 spin_unlock_irq(&mapping
->tree_lock
);
476 swapcache_free(swap
, page
);
478 __remove_from_page_cache(page
);
479 spin_unlock_irq(&mapping
->tree_lock
);
480 mem_cgroup_uncharge_cache_page(page
);
486 spin_unlock_irq(&mapping
->tree_lock
);
491 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
492 * someone else has a ref on the page, abort and return 0. If it was
493 * successfully detached, return 1. Assumes the caller has a single ref on
496 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
498 if (__remove_mapping(mapping
, page
)) {
500 * Unfreezing the refcount with 1 rather than 2 effectively
501 * drops the pagecache ref for us without requiring another
504 page_unfreeze_refs(page
, 1);
511 * putback_lru_page - put previously isolated page onto appropriate LRU list
512 * @page: page to be put back to appropriate lru list
514 * Add previously isolated @page to appropriate LRU list.
515 * Page may still be unevictable for other reasons.
517 * lru_lock must not be held, interrupts must be enabled.
519 void putback_lru_page(struct page
*page
)
522 int active
= !!TestClearPageActive(page
);
523 int was_unevictable
= PageUnevictable(page
);
525 VM_BUG_ON(PageLRU(page
));
528 ClearPageUnevictable(page
);
530 if (page_evictable(page
, NULL
)) {
532 * For evictable pages, we can use the cache.
533 * In event of a race, worst case is we end up with an
534 * unevictable page on [in]active list.
535 * We know how to handle that.
537 lru
= active
+ page_lru_base_type(page
);
538 lru_cache_add_lru(page
, lru
);
541 * Put unevictable pages directly on zone's unevictable
544 lru
= LRU_UNEVICTABLE
;
545 add_page_to_unevictable_list(page
);
547 * When racing with an mlock clearing (page is
548 * unlocked), make sure that if the other thread does
549 * not observe our setting of PG_lru and fails
550 * isolation, we see PG_mlocked cleared below and move
551 * the page back to the evictable list.
553 * The other side is TestClearPageMlocked().
559 * page's status can change while we move it among lru. If an evictable
560 * page is on unevictable list, it never be freed. To avoid that,
561 * check after we added it to the list, again.
563 if (lru
== LRU_UNEVICTABLE
&& page_evictable(page
, NULL
)) {
564 if (!isolate_lru_page(page
)) {
568 /* This means someone else dropped this page from LRU
569 * So, it will be freed or putback to LRU again. There is
570 * nothing to do here.
574 if (was_unevictable
&& lru
!= LRU_UNEVICTABLE
)
575 count_vm_event(UNEVICTABLE_PGRESCUED
);
576 else if (!was_unevictable
&& lru
== LRU_UNEVICTABLE
)
577 count_vm_event(UNEVICTABLE_PGCULLED
);
579 put_page(page
); /* drop ref from isolate */
583 * shrink_page_list() returns the number of reclaimed pages
585 static unsigned long shrink_page_list(struct list_head
*page_list
,
586 struct scan_control
*sc
,
587 enum pageout_io sync_writeback
)
589 LIST_HEAD(ret_pages
);
590 struct pagevec freed_pvec
;
592 unsigned long nr_reclaimed
= 0;
593 unsigned long vm_flags
;
597 pagevec_init(&freed_pvec
, 1);
598 while (!list_empty(page_list
)) {
599 struct address_space
*mapping
;
606 page
= lru_to_page(page_list
);
607 list_del(&page
->lru
);
609 if (!trylock_page(page
))
612 VM_BUG_ON(PageActive(page
));
616 if (unlikely(!page_evictable(page
, NULL
)))
619 if (!sc
->may_unmap
&& page_mapped(page
))
622 /* Double the slab pressure for mapped and swapcache pages */
623 if (page_mapped(page
) || PageSwapCache(page
))
626 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
627 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
629 if (PageWriteback(page
)) {
631 * Synchronous reclaim is performed in two passes,
632 * first an asynchronous pass over the list to
633 * start parallel writeback, and a second synchronous
634 * pass to wait for the IO to complete. Wait here
635 * for any page for which writeback has already
638 if (sync_writeback
== PAGEOUT_IO_SYNC
&& may_enter_fs
)
639 wait_on_page_writeback(page
);
644 referenced
= page_referenced(page
, 1,
645 sc
->mem_cgroup
, &vm_flags
);
647 * In active use or really unfreeable? Activate it.
648 * If page which have PG_mlocked lost isoltation race,
649 * try_to_unmap moves it to unevictable list
651 if (sc
->order
<= PAGE_ALLOC_COSTLY_ORDER
&&
652 referenced
&& page_mapping_inuse(page
)
653 && !(vm_flags
& VM_LOCKED
))
654 goto activate_locked
;
657 * Anonymous process memory has backing store?
658 * Try to allocate it some swap space here.
660 if (PageAnon(page
) && !PageSwapCache(page
)) {
661 if (!(sc
->gfp_mask
& __GFP_IO
))
663 if (!add_to_swap(page
))
664 goto activate_locked
;
668 mapping
= page_mapping(page
);
671 * The page is mapped into the page tables of one or more
672 * processes. Try to unmap it here.
674 if (page_mapped(page
) && mapping
) {
675 switch (try_to_unmap(page
, TTU_UNMAP
)) {
677 goto activate_locked
;
683 ; /* try to free the page below */
687 if (PageDirty(page
)) {
688 if (sc
->order
<= PAGE_ALLOC_COSTLY_ORDER
&& referenced
)
692 if (!sc
->may_writepage
)
695 /* Page is dirty, try to write it out here */
696 switch (pageout(page
, mapping
, sync_writeback
)) {
700 goto activate_locked
;
702 if (PageWriteback(page
) || PageDirty(page
))
705 * A synchronous write - probably a ramdisk. Go
706 * ahead and try to reclaim the page.
708 if (!trylock_page(page
))
710 if (PageDirty(page
) || PageWriteback(page
))
712 mapping
= page_mapping(page
);
714 ; /* try to free the page below */
719 * If the page has buffers, try to free the buffer mappings
720 * associated with this page. If we succeed we try to free
723 * We do this even if the page is PageDirty().
724 * try_to_release_page() does not perform I/O, but it is
725 * possible for a page to have PageDirty set, but it is actually
726 * clean (all its buffers are clean). This happens if the
727 * buffers were written out directly, with submit_bh(). ext3
728 * will do this, as well as the blockdev mapping.
729 * try_to_release_page() will discover that cleanness and will
730 * drop the buffers and mark the page clean - it can be freed.
732 * Rarely, pages can have buffers and no ->mapping. These are
733 * the pages which were not successfully invalidated in
734 * truncate_complete_page(). We try to drop those buffers here
735 * and if that worked, and the page is no longer mapped into
736 * process address space (page_count == 1) it can be freed.
737 * Otherwise, leave the page on the LRU so it is swappable.
739 if (page_has_private(page
)) {
740 if (!try_to_release_page(page
, sc
->gfp_mask
))
741 goto activate_locked
;
742 if (!mapping
&& page_count(page
) == 1) {
744 if (put_page_testzero(page
))
748 * rare race with speculative reference.
749 * the speculative reference will free
750 * this page shortly, so we may
751 * increment nr_reclaimed here (and
752 * leave it off the LRU).
760 if (!mapping
|| !__remove_mapping(mapping
, page
))
764 * At this point, we have no other references and there is
765 * no way to pick any more up (removed from LRU, removed
766 * from pagecache). Can use non-atomic bitops now (and
767 * we obviously don't have to worry about waking up a process
768 * waiting on the page lock, because there are no references.
770 __clear_page_locked(page
);
773 if (!pagevec_add(&freed_pvec
, page
)) {
774 __pagevec_free(&freed_pvec
);
775 pagevec_reinit(&freed_pvec
);
780 if (PageSwapCache(page
))
781 try_to_free_swap(page
);
783 putback_lru_page(page
);
787 /* Not a candidate for swapping, so reclaim swap space. */
788 if (PageSwapCache(page
) && vm_swap_full())
789 try_to_free_swap(page
);
790 VM_BUG_ON(PageActive(page
));
796 list_add(&page
->lru
, &ret_pages
);
797 VM_BUG_ON(PageLRU(page
) || PageUnevictable(page
));
799 list_splice(&ret_pages
, page_list
);
800 if (pagevec_count(&freed_pvec
))
801 __pagevec_free(&freed_pvec
);
802 count_vm_events(PGACTIVATE
, pgactivate
);
806 /* LRU Isolation modes. */
807 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
808 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
809 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
812 * Attempt to remove the specified page from its LRU. Only take this page
813 * if it is of the appropriate PageActive status. Pages which are being
814 * freed elsewhere are also ignored.
816 * page: page to consider
817 * mode: one of the LRU isolation modes defined above
819 * returns 0 on success, -ve errno on failure.
821 int __isolate_lru_page(struct page
*page
, int mode
, int file
)
825 /* Only take pages on the LRU. */
830 * When checking the active state, we need to be sure we are
831 * dealing with comparible boolean values. Take the logical not
834 if (mode
!= ISOLATE_BOTH
&& (!PageActive(page
) != !mode
))
837 if (mode
!= ISOLATE_BOTH
&& page_is_file_cache(page
) != file
)
841 * When this function is being called for lumpy reclaim, we
842 * initially look into all LRU pages, active, inactive and
843 * unevictable; only give shrink_page_list evictable pages.
845 if (PageUnevictable(page
))
850 if (likely(get_page_unless_zero(page
))) {
852 * Be careful not to clear PageLRU until after we're
853 * sure the page is not being freed elsewhere -- the
854 * page release code relies on it.
864 * zone->lru_lock is heavily contended. Some of the functions that
865 * shrink the lists perform better by taking out a batch of pages
866 * and working on them outside the LRU lock.
868 * For pagecache intensive workloads, this function is the hottest
869 * spot in the kernel (apart from copy_*_user functions).
871 * Appropriate locks must be held before calling this function.
873 * @nr_to_scan: The number of pages to look through on the list.
874 * @src: The LRU list to pull pages off.
875 * @dst: The temp list to put pages on to.
876 * @scanned: The number of pages that were scanned.
877 * @order: The caller's attempted allocation order
878 * @mode: One of the LRU isolation modes
879 * @file: True [1] if isolating file [!anon] pages
881 * returns how many pages were moved onto *@dst.
883 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
884 struct list_head
*src
, struct list_head
*dst
,
885 unsigned long *scanned
, int order
, int mode
, int file
)
887 unsigned long nr_taken
= 0;
890 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
893 unsigned long end_pfn
;
894 unsigned long page_pfn
;
897 page
= lru_to_page(src
);
898 prefetchw_prev_lru_page(page
, src
, flags
);
900 VM_BUG_ON(!PageLRU(page
));
902 switch (__isolate_lru_page(page
, mode
, file
)) {
904 list_move(&page
->lru
, dst
);
905 mem_cgroup_del_lru(page
);
910 /* else it is being freed elsewhere */
911 list_move(&page
->lru
, src
);
912 mem_cgroup_rotate_lru_list(page
, page_lru(page
));
923 * Attempt to take all pages in the order aligned region
924 * surrounding the tag page. Only take those pages of
925 * the same active state as that tag page. We may safely
926 * round the target page pfn down to the requested order
927 * as the mem_map is guarenteed valid out to MAX_ORDER,
928 * where that page is in a different zone we will detect
929 * it from its zone id and abort this block scan.
931 zone_id
= page_zone_id(page
);
932 page_pfn
= page_to_pfn(page
);
933 pfn
= page_pfn
& ~((1 << order
) - 1);
934 end_pfn
= pfn
+ (1 << order
);
935 for (; pfn
< end_pfn
; pfn
++) {
936 struct page
*cursor_page
;
938 /* The target page is in the block, ignore it. */
939 if (unlikely(pfn
== page_pfn
))
942 /* Avoid holes within the zone. */
943 if (unlikely(!pfn_valid_within(pfn
)))
946 cursor_page
= pfn_to_page(pfn
);
948 /* Check that we have not crossed a zone boundary. */
949 if (unlikely(page_zone_id(cursor_page
) != zone_id
))
953 * If we don't have enough swap space, reclaiming of
954 * anon page which don't already have a swap slot is
957 if (nr_swap_pages
<= 0 && PageAnon(cursor_page
) &&
958 !PageSwapCache(cursor_page
))
961 if (__isolate_lru_page(cursor_page
, mode
, file
) == 0) {
962 list_move(&cursor_page
->lru
, dst
);
963 mem_cgroup_del_lru(cursor_page
);
974 static unsigned long isolate_pages_global(unsigned long nr
,
975 struct list_head
*dst
,
976 unsigned long *scanned
, int order
,
977 int mode
, struct zone
*z
,
978 struct mem_cgroup
*mem_cont
,
979 int active
, int file
)
986 return isolate_lru_pages(nr
, &z
->lru
[lru
].list
, dst
, scanned
, order
,
991 * clear_active_flags() is a helper for shrink_active_list(), clearing
992 * any active bits from the pages in the list.
994 static unsigned long clear_active_flags(struct list_head
*page_list
,
1001 list_for_each_entry(page
, page_list
, lru
) {
1002 lru
= page_lru_base_type(page
);
1003 if (PageActive(page
)) {
1005 ClearPageActive(page
);
1015 * isolate_lru_page - tries to isolate a page from its LRU list
1016 * @page: page to isolate from its LRU list
1018 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1019 * vmstat statistic corresponding to whatever LRU list the page was on.
1021 * Returns 0 if the page was removed from an LRU list.
1022 * Returns -EBUSY if the page was not on an LRU list.
1024 * The returned page will have PageLRU() cleared. If it was found on
1025 * the active list, it will have PageActive set. If it was found on
1026 * the unevictable list, it will have the PageUnevictable bit set. That flag
1027 * may need to be cleared by the caller before letting the page go.
1029 * The vmstat statistic corresponding to the list on which the page was
1030 * found will be decremented.
1033 * (1) Must be called with an elevated refcount on the page. This is a
1034 * fundamentnal difference from isolate_lru_pages (which is called
1035 * without a stable reference).
1036 * (2) the lru_lock must not be held.
1037 * (3) interrupts must be enabled.
1039 int isolate_lru_page(struct page
*page
)
1043 if (PageLRU(page
)) {
1044 struct zone
*zone
= page_zone(page
);
1046 spin_lock_irq(&zone
->lru_lock
);
1047 if (PageLRU(page
) && get_page_unless_zero(page
)) {
1048 int lru
= page_lru(page
);
1052 del_page_from_lru_list(zone
, page
, lru
);
1054 spin_unlock_irq(&zone
->lru_lock
);
1060 * Are there way too many processes in the direct reclaim path already?
1062 static int too_many_isolated(struct zone
*zone
, int file
,
1063 struct scan_control
*sc
)
1065 unsigned long inactive
, isolated
;
1067 if (current_is_kswapd())
1070 if (!scanning_global_lru(sc
))
1074 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1075 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
);
1077 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1078 isolated
= zone_page_state(zone
, NR_ISOLATED_ANON
);
1081 return isolated
> inactive
;
1085 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1086 * of reclaimed pages
1088 static unsigned long shrink_inactive_list(unsigned long max_scan
,
1089 struct zone
*zone
, struct scan_control
*sc
,
1090 int priority
, int file
)
1092 LIST_HEAD(page_list
);
1093 struct pagevec pvec
;
1094 unsigned long nr_scanned
= 0;
1095 unsigned long nr_reclaimed
= 0;
1096 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1097 int lumpy_reclaim
= 0;
1099 while (unlikely(too_many_isolated(zone
, file
, sc
))) {
1100 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1102 /* We are about to die and free our memory. Return now. */
1103 if (fatal_signal_pending(current
))
1104 return SWAP_CLUSTER_MAX
;
1108 * If we need a large contiguous chunk of memory, or have
1109 * trouble getting a small set of contiguous pages, we
1110 * will reclaim both active and inactive pages.
1112 * We use the same threshold as pageout congestion_wait below.
1114 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
1116 else if (sc
->order
&& priority
< DEF_PRIORITY
- 2)
1119 pagevec_init(&pvec
, 1);
1122 spin_lock_irq(&zone
->lru_lock
);
1125 unsigned long nr_taken
;
1126 unsigned long nr_scan
;
1127 unsigned long nr_freed
;
1128 unsigned long nr_active
;
1129 unsigned int count
[NR_LRU_LISTS
] = { 0, };
1130 int mode
= lumpy_reclaim
? ISOLATE_BOTH
: ISOLATE_INACTIVE
;
1131 unsigned long nr_anon
;
1132 unsigned long nr_file
;
1134 nr_taken
= sc
->isolate_pages(SWAP_CLUSTER_MAX
,
1135 &page_list
, &nr_scan
, sc
->order
, mode
,
1136 zone
, sc
->mem_cgroup
, 0, file
);
1138 if (scanning_global_lru(sc
)) {
1139 zone
->pages_scanned
+= nr_scan
;
1140 if (current_is_kswapd())
1141 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
,
1144 __count_zone_vm_events(PGSCAN_DIRECT
, zone
,
1151 nr_active
= clear_active_flags(&page_list
, count
);
1152 __count_vm_events(PGDEACTIVATE
, nr_active
);
1154 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
,
1155 -count
[LRU_ACTIVE_FILE
]);
1156 __mod_zone_page_state(zone
, NR_INACTIVE_FILE
,
1157 -count
[LRU_INACTIVE_FILE
]);
1158 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
,
1159 -count
[LRU_ACTIVE_ANON
]);
1160 __mod_zone_page_state(zone
, NR_INACTIVE_ANON
,
1161 -count
[LRU_INACTIVE_ANON
]);
1163 nr_anon
= count
[LRU_ACTIVE_ANON
] + count
[LRU_INACTIVE_ANON
];
1164 nr_file
= count
[LRU_ACTIVE_FILE
] + count
[LRU_INACTIVE_FILE
];
1165 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, nr_anon
);
1166 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, nr_file
);
1168 reclaim_stat
->recent_scanned
[0] += nr_anon
;
1169 reclaim_stat
->recent_scanned
[1] += nr_file
;
1171 spin_unlock_irq(&zone
->lru_lock
);
1173 nr_scanned
+= nr_scan
;
1174 nr_freed
= shrink_page_list(&page_list
, sc
, PAGEOUT_IO_ASYNC
);
1177 * If we are direct reclaiming for contiguous pages and we do
1178 * not reclaim everything in the list, try again and wait
1179 * for IO to complete. This will stall high-order allocations
1180 * but that should be acceptable to the caller
1182 if (nr_freed
< nr_taken
&& !current_is_kswapd() &&
1184 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1187 * The attempt at page out may have made some
1188 * of the pages active, mark them inactive again.
1190 nr_active
= clear_active_flags(&page_list
, count
);
1191 count_vm_events(PGDEACTIVATE
, nr_active
);
1193 nr_freed
+= shrink_page_list(&page_list
, sc
,
1197 nr_reclaimed
+= nr_freed
;
1199 local_irq_disable();
1200 if (current_is_kswapd())
1201 __count_vm_events(KSWAPD_STEAL
, nr_freed
);
1202 __count_zone_vm_events(PGSTEAL
, zone
, nr_freed
);
1204 spin_lock(&zone
->lru_lock
);
1206 * Put back any unfreeable pages.
1208 while (!list_empty(&page_list
)) {
1210 page
= lru_to_page(&page_list
);
1211 VM_BUG_ON(PageLRU(page
));
1212 list_del(&page
->lru
);
1213 if (unlikely(!page_evictable(page
, NULL
))) {
1214 spin_unlock_irq(&zone
->lru_lock
);
1215 putback_lru_page(page
);
1216 spin_lock_irq(&zone
->lru_lock
);
1220 lru
= page_lru(page
);
1221 add_page_to_lru_list(zone
, page
, lru
);
1222 if (is_active_lru(lru
)) {
1223 int file
= is_file_lru(lru
);
1224 reclaim_stat
->recent_rotated
[file
]++;
1226 if (!pagevec_add(&pvec
, page
)) {
1227 spin_unlock_irq(&zone
->lru_lock
);
1228 __pagevec_release(&pvec
);
1229 spin_lock_irq(&zone
->lru_lock
);
1232 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, -nr_anon
);
1233 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, -nr_file
);
1235 } while (nr_scanned
< max_scan
);
1238 spin_unlock_irq(&zone
->lru_lock
);
1239 pagevec_release(&pvec
);
1240 return nr_reclaimed
;
1244 * We are about to scan this zone at a certain priority level. If that priority
1245 * level is smaller (ie: more urgent) than the previous priority, then note
1246 * that priority level within the zone. This is done so that when the next
1247 * process comes in to scan this zone, it will immediately start out at this
1248 * priority level rather than having to build up its own scanning priority.
1249 * Here, this priority affects only the reclaim-mapped threshold.
1251 static inline void note_zone_scanning_priority(struct zone
*zone
, int priority
)
1253 if (priority
< zone
->prev_priority
)
1254 zone
->prev_priority
= priority
;
1258 * This moves pages from the active list to the inactive list.
1260 * We move them the other way if the page is referenced by one or more
1261 * processes, from rmap.
1263 * If the pages are mostly unmapped, the processing is fast and it is
1264 * appropriate to hold zone->lru_lock across the whole operation. But if
1265 * the pages are mapped, the processing is slow (page_referenced()) so we
1266 * should drop zone->lru_lock around each page. It's impossible to balance
1267 * this, so instead we remove the pages from the LRU while processing them.
1268 * It is safe to rely on PG_active against the non-LRU pages in here because
1269 * nobody will play with that bit on a non-LRU page.
1271 * The downside is that we have to touch page->_count against each page.
1272 * But we had to alter page->flags anyway.
1275 static void move_active_pages_to_lru(struct zone
*zone
,
1276 struct list_head
*list
,
1279 unsigned long pgmoved
= 0;
1280 struct pagevec pvec
;
1283 pagevec_init(&pvec
, 1);
1285 while (!list_empty(list
)) {
1286 page
= lru_to_page(list
);
1288 VM_BUG_ON(PageLRU(page
));
1291 list_move(&page
->lru
, &zone
->lru
[lru
].list
);
1292 mem_cgroup_add_lru_list(page
, lru
);
1295 if (!pagevec_add(&pvec
, page
) || list_empty(list
)) {
1296 spin_unlock_irq(&zone
->lru_lock
);
1297 if (buffer_heads_over_limit
)
1298 pagevec_strip(&pvec
);
1299 __pagevec_release(&pvec
);
1300 spin_lock_irq(&zone
->lru_lock
);
1303 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1304 if (!is_active_lru(lru
))
1305 __count_vm_events(PGDEACTIVATE
, pgmoved
);
1308 static void shrink_active_list(unsigned long nr_pages
, struct zone
*zone
,
1309 struct scan_control
*sc
, int priority
, int file
)
1311 unsigned long nr_taken
;
1312 unsigned long pgscanned
;
1313 unsigned long vm_flags
;
1314 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1315 LIST_HEAD(l_active
);
1316 LIST_HEAD(l_inactive
);
1318 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1319 unsigned long nr_rotated
= 0;
1322 spin_lock_irq(&zone
->lru_lock
);
1323 nr_taken
= sc
->isolate_pages(nr_pages
, &l_hold
, &pgscanned
, sc
->order
,
1324 ISOLATE_ACTIVE
, zone
,
1325 sc
->mem_cgroup
, 1, file
);
1327 * zone->pages_scanned is used for detect zone's oom
1328 * mem_cgroup remembers nr_scan by itself.
1330 if (scanning_global_lru(sc
)) {
1331 zone
->pages_scanned
+= pgscanned
;
1333 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1335 __count_zone_vm_events(PGREFILL
, zone
, pgscanned
);
1337 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
, -nr_taken
);
1339 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
, -nr_taken
);
1340 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1341 spin_unlock_irq(&zone
->lru_lock
);
1343 while (!list_empty(&l_hold
)) {
1345 page
= lru_to_page(&l_hold
);
1346 list_del(&page
->lru
);
1348 if (unlikely(!page_evictable(page
, NULL
))) {
1349 putback_lru_page(page
);
1353 /* page_referenced clears PageReferenced */
1354 if (page_mapping_inuse(page
) &&
1355 page_referenced(page
, 0, sc
->mem_cgroup
, &vm_flags
)) {
1358 * Identify referenced, file-backed active pages and
1359 * give them one more trip around the active list. So
1360 * that executable code get better chances to stay in
1361 * memory under moderate memory pressure. Anon pages
1362 * are not likely to be evicted by use-once streaming
1363 * IO, plus JVM can create lots of anon VM_EXEC pages,
1364 * so we ignore them here.
1366 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1367 list_add(&page
->lru
, &l_active
);
1372 ClearPageActive(page
); /* we are de-activating */
1373 list_add(&page
->lru
, &l_inactive
);
1377 * Move pages back to the lru list.
1379 spin_lock_irq(&zone
->lru_lock
);
1381 * Count referenced pages from currently used mappings as rotated,
1382 * even though only some of them are actually re-activated. This
1383 * helps balance scan pressure between file and anonymous pages in
1386 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1388 move_active_pages_to_lru(zone
, &l_active
,
1389 LRU_ACTIVE
+ file
* LRU_FILE
);
1390 move_active_pages_to_lru(zone
, &l_inactive
,
1391 LRU_BASE
+ file
* LRU_FILE
);
1392 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1393 spin_unlock_irq(&zone
->lru_lock
);
1396 static int inactive_anon_is_low_global(struct zone
*zone
)
1398 unsigned long active
, inactive
;
1400 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1401 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1403 if (inactive
* zone
->inactive_ratio
< active
)
1410 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1411 * @zone: zone to check
1412 * @sc: scan control of this context
1414 * Returns true if the zone does not have enough inactive anon pages,
1415 * meaning some active anon pages need to be deactivated.
1417 static int inactive_anon_is_low(struct zone
*zone
, struct scan_control
*sc
)
1421 if (scanning_global_lru(sc
))
1422 low
= inactive_anon_is_low_global(zone
);
1424 low
= mem_cgroup_inactive_anon_is_low(sc
->mem_cgroup
);
1428 static int inactive_file_is_low_global(struct zone
*zone
)
1430 unsigned long active
, inactive
;
1432 active
= zone_page_state(zone
, NR_ACTIVE_FILE
);
1433 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1435 return (active
> inactive
);
1439 * inactive_file_is_low - check if file pages need to be deactivated
1440 * @zone: zone to check
1441 * @sc: scan control of this context
1443 * When the system is doing streaming IO, memory pressure here
1444 * ensures that active file pages get deactivated, until more
1445 * than half of the file pages are on the inactive list.
1447 * Once we get to that situation, protect the system's working
1448 * set from being evicted by disabling active file page aging.
1450 * This uses a different ratio than the anonymous pages, because
1451 * the page cache uses a use-once replacement algorithm.
1453 static int inactive_file_is_low(struct zone
*zone
, struct scan_control
*sc
)
1457 if (scanning_global_lru(sc
))
1458 low
= inactive_file_is_low_global(zone
);
1460 low
= mem_cgroup_inactive_file_is_low(sc
->mem_cgroup
);
1464 static int inactive_list_is_low(struct zone
*zone
, struct scan_control
*sc
,
1468 return inactive_file_is_low(zone
, sc
);
1470 return inactive_anon_is_low(zone
, sc
);
1473 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1474 struct zone
*zone
, struct scan_control
*sc
, int priority
)
1476 int file
= is_file_lru(lru
);
1478 if (is_active_lru(lru
)) {
1479 if (inactive_list_is_low(zone
, sc
, file
))
1480 shrink_active_list(nr_to_scan
, zone
, sc
, priority
, file
);
1484 return shrink_inactive_list(nr_to_scan
, zone
, sc
, priority
, file
);
1488 * Determine how aggressively the anon and file LRU lists should be
1489 * scanned. The relative value of each set of LRU lists is determined
1490 * by looking at the fraction of the pages scanned we did rotate back
1491 * onto the active list instead of evict.
1493 * percent[0] specifies how much pressure to put on ram/swap backed
1494 * memory, while percent[1] determines pressure on the file LRUs.
1496 static void get_scan_ratio(struct zone
*zone
, struct scan_control
*sc
,
1497 unsigned long *percent
)
1499 unsigned long anon
, file
, free
;
1500 unsigned long anon_prio
, file_prio
;
1501 unsigned long ap
, fp
;
1502 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1504 anon
= zone_nr_lru_pages(zone
, sc
, LRU_ACTIVE_ANON
) +
1505 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_ANON
);
1506 file
= zone_nr_lru_pages(zone
, sc
, LRU_ACTIVE_FILE
) +
1507 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_FILE
);
1509 if (scanning_global_lru(sc
)) {
1510 free
= zone_page_state(zone
, NR_FREE_PAGES
);
1511 /* If we have very few page cache pages,
1512 force-scan anon pages. */
1513 if (unlikely(file
+ free
<= high_wmark_pages(zone
))) {
1521 * OK, so we have swap space and a fair amount of page cache
1522 * pages. We use the recently rotated / recently scanned
1523 * ratios to determine how valuable each cache is.
1525 * Because workloads change over time (and to avoid overflow)
1526 * we keep these statistics as a floating average, which ends
1527 * up weighing recent references more than old ones.
1529 * anon in [0], file in [1]
1531 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
1532 spin_lock_irq(&zone
->lru_lock
);
1533 reclaim_stat
->recent_scanned
[0] /= 2;
1534 reclaim_stat
->recent_rotated
[0] /= 2;
1535 spin_unlock_irq(&zone
->lru_lock
);
1538 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
1539 spin_lock_irq(&zone
->lru_lock
);
1540 reclaim_stat
->recent_scanned
[1] /= 2;
1541 reclaim_stat
->recent_rotated
[1] /= 2;
1542 spin_unlock_irq(&zone
->lru_lock
);
1546 * With swappiness at 100, anonymous and file have the same priority.
1547 * This scanning priority is essentially the inverse of IO cost.
1549 anon_prio
= sc
->swappiness
;
1550 file_prio
= 200 - sc
->swappiness
;
1553 * The amount of pressure on anon vs file pages is inversely
1554 * proportional to the fraction of recently scanned pages on
1555 * each list that were recently referenced and in active use.
1557 ap
= (anon_prio
+ 1) * (reclaim_stat
->recent_scanned
[0] + 1);
1558 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
1560 fp
= (file_prio
+ 1) * (reclaim_stat
->recent_scanned
[1] + 1);
1561 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
1563 /* Normalize to percentages */
1564 percent
[0] = 100 * ap
/ (ap
+ fp
+ 1);
1565 percent
[1] = 100 - percent
[0];
1569 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1570 * until we collected @swap_cluster_max pages to scan.
1572 static unsigned long nr_scan_try_batch(unsigned long nr_to_scan
,
1573 unsigned long *nr_saved_scan
)
1577 *nr_saved_scan
+= nr_to_scan
;
1578 nr
= *nr_saved_scan
;
1580 if (nr
>= SWAP_CLUSTER_MAX
)
1589 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1591 static void shrink_zone(int priority
, struct zone
*zone
,
1592 struct scan_control
*sc
)
1594 unsigned long nr
[NR_LRU_LISTS
];
1595 unsigned long nr_to_scan
;
1596 unsigned long percent
[2]; /* anon @ 0; file @ 1 */
1598 unsigned long nr_reclaimed
= sc
->nr_reclaimed
;
1599 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
1600 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1603 /* If we have no swap space, do not bother scanning anon pages. */
1604 if (!sc
->may_swap
|| (nr_swap_pages
<= 0)) {
1609 get_scan_ratio(zone
, sc
, percent
);
1611 for_each_evictable_lru(l
) {
1612 int file
= is_file_lru(l
);
1615 scan
= zone_nr_lru_pages(zone
, sc
, l
);
1616 if (priority
|| noswap
) {
1618 scan
= (scan
* percent
[file
]) / 100;
1620 nr
[l
] = nr_scan_try_batch(scan
,
1621 &reclaim_stat
->nr_saved_scan
[l
]);
1624 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
1625 nr
[LRU_INACTIVE_FILE
]) {
1626 for_each_evictable_lru(l
) {
1628 nr_to_scan
= min_t(unsigned long,
1629 nr
[l
], SWAP_CLUSTER_MAX
);
1630 nr
[l
] -= nr_to_scan
;
1632 nr_reclaimed
+= shrink_list(l
, nr_to_scan
,
1633 zone
, sc
, priority
);
1637 * On large memory systems, scan >> priority can become
1638 * really large. This is fine for the starting priority;
1639 * we want to put equal scanning pressure on each zone.
1640 * However, if the VM has a harder time of freeing pages,
1641 * with multiple processes reclaiming pages, the total
1642 * freeing target can get unreasonably large.
1644 if (nr_reclaimed
>= nr_to_reclaim
&& priority
< DEF_PRIORITY
)
1648 sc
->nr_reclaimed
= nr_reclaimed
;
1651 * Even if we did not try to evict anon pages at all, we want to
1652 * rebalance the anon lru active/inactive ratio.
1654 if (inactive_anon_is_low(zone
, sc
) && nr_swap_pages
> 0)
1655 shrink_active_list(SWAP_CLUSTER_MAX
, zone
, sc
, priority
, 0);
1657 throttle_vm_writeout(sc
->gfp_mask
);
1661 * This is the direct reclaim path, for page-allocating processes. We only
1662 * try to reclaim pages from zones which will satisfy the caller's allocation
1665 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1667 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1669 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1670 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1671 * zone defense algorithm.
1673 * If a zone is deemed to be full of pinned pages then just give it a light
1674 * scan then give up on it.
1676 static void shrink_zones(int priority
, struct zonelist
*zonelist
,
1677 struct scan_control
*sc
)
1679 enum zone_type high_zoneidx
= gfp_zone(sc
->gfp_mask
);
1683 sc
->all_unreclaimable
= 1;
1684 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
, high_zoneidx
,
1686 if (!populated_zone(zone
))
1689 * Take care memory controller reclaiming has small influence
1692 if (scanning_global_lru(sc
)) {
1693 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1695 note_zone_scanning_priority(zone
, priority
);
1697 if (zone_is_all_unreclaimable(zone
) &&
1698 priority
!= DEF_PRIORITY
)
1699 continue; /* Let kswapd poll it */
1700 sc
->all_unreclaimable
= 0;
1703 * Ignore cpuset limitation here. We just want to reduce
1704 * # of used pages by us regardless of memory shortage.
1706 sc
->all_unreclaimable
= 0;
1707 mem_cgroup_note_reclaim_priority(sc
->mem_cgroup
,
1711 shrink_zone(priority
, zone
, sc
);
1716 * This is the main entry point to direct page reclaim.
1718 * If a full scan of the inactive list fails to free enough memory then we
1719 * are "out of memory" and something needs to be killed.
1721 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1722 * high - the zone may be full of dirty or under-writeback pages, which this
1723 * caller can't do much about. We kick the writeback threads and take explicit
1724 * naps in the hope that some of these pages can be written. But if the
1725 * allocating task holds filesystem locks which prevent writeout this might not
1726 * work, and the allocation attempt will fail.
1728 * returns: 0, if no pages reclaimed
1729 * else, the number of pages reclaimed
1731 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
1732 struct scan_control
*sc
)
1735 unsigned long ret
= 0;
1736 unsigned long total_scanned
= 0;
1737 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
1738 unsigned long lru_pages
= 0;
1741 enum zone_type high_zoneidx
= gfp_zone(sc
->gfp_mask
);
1742 unsigned long writeback_threshold
;
1744 delayacct_freepages_start();
1746 if (scanning_global_lru(sc
))
1747 count_vm_event(ALLOCSTALL
);
1749 * mem_cgroup will not do shrink_slab.
1751 if (scanning_global_lru(sc
)) {
1752 for_each_zone_zonelist(zone
, z
, zonelist
, high_zoneidx
) {
1754 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1757 lru_pages
+= zone_reclaimable_pages(zone
);
1761 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
1764 disable_swap_token();
1765 shrink_zones(priority
, zonelist
, sc
);
1767 * Don't shrink slabs when reclaiming memory from
1768 * over limit cgroups
1770 if (scanning_global_lru(sc
)) {
1771 shrink_slab(sc
->nr_scanned
, sc
->gfp_mask
, lru_pages
);
1772 if (reclaim_state
) {
1773 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
1774 reclaim_state
->reclaimed_slab
= 0;
1777 total_scanned
+= sc
->nr_scanned
;
1778 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
) {
1779 ret
= sc
->nr_reclaimed
;
1784 * Try to write back as many pages as we just scanned. This
1785 * tends to cause slow streaming writers to write data to the
1786 * disk smoothly, at the dirtying rate, which is nice. But
1787 * that's undesirable in laptop mode, where we *want* lumpy
1788 * writeout. So in laptop mode, write out the whole world.
1790 writeback_threshold
= sc
->nr_to_reclaim
+ sc
->nr_to_reclaim
/ 2;
1791 if (total_scanned
> writeback_threshold
) {
1792 wakeup_flusher_threads(laptop_mode
? 0 : total_scanned
);
1793 sc
->may_writepage
= 1;
1796 /* Take a nap, wait for some writeback to complete */
1797 if (!sc
->hibernation_mode
&& sc
->nr_scanned
&&
1798 priority
< DEF_PRIORITY
- 2)
1799 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1801 /* top priority shrink_zones still had more to do? don't OOM, then */
1802 if (!sc
->all_unreclaimable
&& scanning_global_lru(sc
))
1803 ret
= sc
->nr_reclaimed
;
1806 * Now that we've scanned all the zones at this priority level, note
1807 * that level within the zone so that the next thread which performs
1808 * scanning of this zone will immediately start out at this priority
1809 * level. This affects only the decision whether or not to bring
1810 * mapped pages onto the inactive list.
1815 if (scanning_global_lru(sc
)) {
1816 for_each_zone_zonelist(zone
, z
, zonelist
, high_zoneidx
) {
1818 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1821 zone
->prev_priority
= priority
;
1824 mem_cgroup_record_reclaim_priority(sc
->mem_cgroup
, priority
);
1826 delayacct_freepages_end();
1831 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
1832 gfp_t gfp_mask
, nodemask_t
*nodemask
)
1834 struct scan_control sc
= {
1835 .gfp_mask
= gfp_mask
,
1836 .may_writepage
= !laptop_mode
,
1837 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
1840 .swappiness
= vm_swappiness
,
1843 .isolate_pages
= isolate_pages_global
,
1844 .nodemask
= nodemask
,
1847 return do_try_to_free_pages(zonelist
, &sc
);
1850 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1852 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup
*mem
,
1853 gfp_t gfp_mask
, bool noswap
,
1854 unsigned int swappiness
,
1855 struct zone
*zone
, int nid
)
1857 struct scan_control sc
= {
1858 .may_writepage
= !laptop_mode
,
1860 .may_swap
= !noswap
,
1861 .swappiness
= swappiness
,
1864 .isolate_pages
= mem_cgroup_isolate_pages
,
1866 nodemask_t nm
= nodemask_of_node(nid
);
1868 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
1869 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
1871 sc
.nr_reclaimed
= 0;
1874 * NOTE: Although we can get the priority field, using it
1875 * here is not a good idea, since it limits the pages we can scan.
1876 * if we don't reclaim here, the shrink_zone from balance_pgdat
1877 * will pick up pages from other mem cgroup's as well. We hack
1878 * the priority and make it zero.
1880 shrink_zone(0, zone
, &sc
);
1881 return sc
.nr_reclaimed
;
1884 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*mem_cont
,
1887 unsigned int swappiness
)
1889 struct zonelist
*zonelist
;
1890 struct scan_control sc
= {
1891 .may_writepage
= !laptop_mode
,
1893 .may_swap
= !noswap
,
1894 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
1895 .swappiness
= swappiness
,
1897 .mem_cgroup
= mem_cont
,
1898 .isolate_pages
= mem_cgroup_isolate_pages
,
1899 .nodemask
= NULL
, /* we don't care the placement */
1902 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
1903 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
1904 zonelist
= NODE_DATA(numa_node_id())->node_zonelists
;
1905 return do_try_to_free_pages(zonelist
, &sc
);
1909 /* is kswapd sleeping prematurely? */
1910 static int sleeping_prematurely(pg_data_t
*pgdat
, int order
, long remaining
)
1914 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
1918 /* If after HZ/10, a zone is below the high mark, it's premature */
1919 for (i
= 0; i
< pgdat
->nr_zones
; i
++) {
1920 struct zone
*zone
= pgdat
->node_zones
+ i
;
1922 if (!populated_zone(zone
))
1925 if (zone_is_all_unreclaimable(zone
))
1928 if (!zone_watermark_ok(zone
, order
, high_wmark_pages(zone
),
1937 * For kswapd, balance_pgdat() will work across all this node's zones until
1938 * they are all at high_wmark_pages(zone).
1940 * Returns the number of pages which were actually freed.
1942 * There is special handling here for zones which are full of pinned pages.
1943 * This can happen if the pages are all mlocked, or if they are all used by
1944 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1945 * What we do is to detect the case where all pages in the zone have been
1946 * scanned twice and there has been zero successful reclaim. Mark the zone as
1947 * dead and from now on, only perform a short scan. Basically we're polling
1948 * the zone for when the problem goes away.
1950 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1951 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
1952 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
1953 * lower zones regardless of the number of free pages in the lower zones. This
1954 * interoperates with the page allocator fallback scheme to ensure that aging
1955 * of pages is balanced across the zones.
1957 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
)
1962 unsigned long total_scanned
;
1963 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
1964 struct scan_control sc
= {
1965 .gfp_mask
= GFP_KERNEL
,
1969 * kswapd doesn't want to be bailed out while reclaim. because
1970 * we want to put equal scanning pressure on each zone.
1972 .nr_to_reclaim
= ULONG_MAX
,
1973 .swappiness
= vm_swappiness
,
1976 .isolate_pages
= isolate_pages_global
,
1979 * temp_priority is used to remember the scanning priority at which
1980 * this zone was successfully refilled to
1981 * free_pages == high_wmark_pages(zone).
1983 int temp_priority
[MAX_NR_ZONES
];
1987 sc
.nr_reclaimed
= 0;
1988 sc
.may_writepage
= !laptop_mode
;
1989 count_vm_event(PAGEOUTRUN
);
1991 for (i
= 0; i
< pgdat
->nr_zones
; i
++)
1992 temp_priority
[i
] = DEF_PRIORITY
;
1994 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
1995 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
1996 unsigned long lru_pages
= 0;
1997 int has_under_min_watermark_zone
= 0;
1999 /* The swap token gets in the way of swapout... */
2001 disable_swap_token();
2006 * Scan in the highmem->dma direction for the highest
2007 * zone which needs scanning
2009 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
2010 struct zone
*zone
= pgdat
->node_zones
+ i
;
2012 if (!populated_zone(zone
))
2015 if (zone_is_all_unreclaimable(zone
) &&
2016 priority
!= DEF_PRIORITY
)
2020 * Do some background aging of the anon list, to give
2021 * pages a chance to be referenced before reclaiming.
2023 if (inactive_anon_is_low(zone
, &sc
))
2024 shrink_active_list(SWAP_CLUSTER_MAX
, zone
,
2027 if (!zone_watermark_ok(zone
, order
,
2028 high_wmark_pages(zone
), 0, 0)) {
2036 for (i
= 0; i
<= end_zone
; i
++) {
2037 struct zone
*zone
= pgdat
->node_zones
+ i
;
2039 lru_pages
+= zone_reclaimable_pages(zone
);
2043 * Now scan the zone in the dma->highmem direction, stopping
2044 * at the last zone which needs scanning.
2046 * We do this because the page allocator works in the opposite
2047 * direction. This prevents the page allocator from allocating
2048 * pages behind kswapd's direction of progress, which would
2049 * cause too much scanning of the lower zones.
2051 for (i
= 0; i
<= end_zone
; i
++) {
2052 struct zone
*zone
= pgdat
->node_zones
+ i
;
2056 if (!populated_zone(zone
))
2059 if (zone_is_all_unreclaimable(zone
) &&
2060 priority
!= DEF_PRIORITY
)
2063 if (!zone_watermark_ok(zone
, order
,
2064 high_wmark_pages(zone
), end_zone
, 0))
2066 temp_priority
[i
] = priority
;
2068 note_zone_scanning_priority(zone
, priority
);
2070 nid
= pgdat
->node_id
;
2071 zid
= zone_idx(zone
);
2073 * Call soft limit reclaim before calling shrink_zone.
2074 * For now we ignore the return value
2076 mem_cgroup_soft_limit_reclaim(zone
, order
, sc
.gfp_mask
,
2079 * We put equal pressure on every zone, unless one
2080 * zone has way too many pages free already.
2082 if (!zone_watermark_ok(zone
, order
,
2083 8*high_wmark_pages(zone
), end_zone
, 0))
2084 shrink_zone(priority
, zone
, &sc
);
2085 reclaim_state
->reclaimed_slab
= 0;
2086 nr_slab
= shrink_slab(sc
.nr_scanned
, GFP_KERNEL
,
2088 sc
.nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2089 total_scanned
+= sc
.nr_scanned
;
2090 if (zone_is_all_unreclaimable(zone
))
2092 if (nr_slab
== 0 && zone
->pages_scanned
>=
2093 (zone_reclaimable_pages(zone
) * 6))
2095 ZONE_ALL_UNRECLAIMABLE
);
2097 * If we've done a decent amount of scanning and
2098 * the reclaim ratio is low, start doing writepage
2099 * even in laptop mode
2101 if (total_scanned
> SWAP_CLUSTER_MAX
* 2 &&
2102 total_scanned
> sc
.nr_reclaimed
+ sc
.nr_reclaimed
/ 2)
2103 sc
.may_writepage
= 1;
2106 * We are still under min water mark. it mean we have
2107 * GFP_ATOMIC allocation failure risk. Hurry up!
2109 if (!zone_watermark_ok(zone
, order
, min_wmark_pages(zone
),
2111 has_under_min_watermark_zone
= 1;
2115 break; /* kswapd: all done */
2117 * OK, kswapd is getting into trouble. Take a nap, then take
2118 * another pass across the zones.
2120 if (total_scanned
&& (priority
< DEF_PRIORITY
- 2)) {
2121 if (has_under_min_watermark_zone
)
2122 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT
);
2124 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
2128 * We do this so kswapd doesn't build up large priorities for
2129 * example when it is freeing in parallel with allocators. It
2130 * matches the direct reclaim path behaviour in terms of impact
2131 * on zone->*_priority.
2133 if (sc
.nr_reclaimed
>= SWAP_CLUSTER_MAX
)
2138 * Note within each zone the priority level at which this zone was
2139 * brought into a happy state. So that the next thread which scans this
2140 * zone will start out at that priority level.
2142 for (i
= 0; i
< pgdat
->nr_zones
; i
++) {
2143 struct zone
*zone
= pgdat
->node_zones
+ i
;
2145 zone
->prev_priority
= temp_priority
[i
];
2147 if (!all_zones_ok
) {
2153 * Fragmentation may mean that the system cannot be
2154 * rebalanced for high-order allocations in all zones.
2155 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2156 * it means the zones have been fully scanned and are still
2157 * not balanced. For high-order allocations, there is
2158 * little point trying all over again as kswapd may
2161 * Instead, recheck all watermarks at order-0 as they
2162 * are the most important. If watermarks are ok, kswapd will go
2163 * back to sleep. High-order users can still perform direct
2164 * reclaim if they wish.
2166 if (sc
.nr_reclaimed
< SWAP_CLUSTER_MAX
)
2167 order
= sc
.order
= 0;
2172 return sc
.nr_reclaimed
;
2176 * The background pageout daemon, started as a kernel thread
2177 * from the init process.
2179 * This basically trickles out pages so that we have _some_
2180 * free memory available even if there is no other activity
2181 * that frees anything up. This is needed for things like routing
2182 * etc, where we otherwise might have all activity going on in
2183 * asynchronous contexts that cannot page things out.
2185 * If there are applications that are active memory-allocators
2186 * (most normal use), this basically shouldn't matter.
2188 static int kswapd(void *p
)
2190 unsigned long order
;
2191 pg_data_t
*pgdat
= (pg_data_t
*)p
;
2192 struct task_struct
*tsk
= current
;
2194 struct reclaim_state reclaim_state
= {
2195 .reclaimed_slab
= 0,
2197 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
2199 lockdep_set_current_reclaim_state(GFP_KERNEL
);
2201 if (!cpumask_empty(cpumask
))
2202 set_cpus_allowed_ptr(tsk
, cpumask
);
2203 current
->reclaim_state
= &reclaim_state
;
2206 * Tell the memory management that we're a "memory allocator",
2207 * and that if we need more memory we should get access to it
2208 * regardless (see "__alloc_pages()"). "kswapd" should
2209 * never get caught in the normal page freeing logic.
2211 * (Kswapd normally doesn't need memory anyway, but sometimes
2212 * you need a small amount of memory in order to be able to
2213 * page out something else, and this flag essentially protects
2214 * us from recursively trying to free more memory as we're
2215 * trying to free the first piece of memory in the first place).
2217 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
2222 unsigned long new_order
;
2225 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2226 new_order
= pgdat
->kswapd_max_order
;
2227 pgdat
->kswapd_max_order
= 0;
2228 if (order
< new_order
) {
2230 * Don't sleep if someone wants a larger 'order'
2235 if (!freezing(current
) && !kthread_should_stop()) {
2238 /* Try to sleep for a short interval */
2239 if (!sleeping_prematurely(pgdat
, order
, remaining
)) {
2240 remaining
= schedule_timeout(HZ
/10);
2241 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2242 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2246 * After a short sleep, check if it was a
2247 * premature sleep. If not, then go fully
2248 * to sleep until explicitly woken up
2250 if (!sleeping_prematurely(pgdat
, order
, remaining
))
2254 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
2256 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
2260 order
= pgdat
->kswapd_max_order
;
2262 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2264 ret
= try_to_freeze();
2265 if (kthread_should_stop())
2269 * We can speed up thawing tasks if we don't call balance_pgdat
2270 * after returning from the refrigerator
2273 balance_pgdat(pgdat
, order
);
2279 * A zone is low on free memory, so wake its kswapd task to service it.
2281 void wakeup_kswapd(struct zone
*zone
, int order
)
2285 if (!populated_zone(zone
))
2288 pgdat
= zone
->zone_pgdat
;
2289 if (zone_watermark_ok(zone
, order
, low_wmark_pages(zone
), 0, 0))
2291 if (pgdat
->kswapd_max_order
< order
)
2292 pgdat
->kswapd_max_order
= order
;
2293 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2295 if (!waitqueue_active(&pgdat
->kswapd_wait
))
2297 wake_up_interruptible(&pgdat
->kswapd_wait
);
2301 * The reclaimable count would be mostly accurate.
2302 * The less reclaimable pages may be
2303 * - mlocked pages, which will be moved to unevictable list when encountered
2304 * - mapped pages, which may require several travels to be reclaimed
2305 * - dirty pages, which is not "instantly" reclaimable
2307 unsigned long global_reclaimable_pages(void)
2311 nr
= global_page_state(NR_ACTIVE_FILE
) +
2312 global_page_state(NR_INACTIVE_FILE
);
2314 if (nr_swap_pages
> 0)
2315 nr
+= global_page_state(NR_ACTIVE_ANON
) +
2316 global_page_state(NR_INACTIVE_ANON
);
2321 unsigned long zone_reclaimable_pages(struct zone
*zone
)
2325 nr
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
2326 zone_page_state(zone
, NR_INACTIVE_FILE
);
2328 if (nr_swap_pages
> 0)
2329 nr
+= zone_page_state(zone
, NR_ACTIVE_ANON
) +
2330 zone_page_state(zone
, NR_INACTIVE_ANON
);
2335 #ifdef CONFIG_HIBERNATION
2337 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2340 * Rather than trying to age LRUs the aim is to preserve the overall
2341 * LRU order by reclaiming preferentially
2342 * inactive > active > active referenced > active mapped
2344 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
2346 struct reclaim_state reclaim_state
;
2347 struct scan_control sc
= {
2348 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
2352 .nr_to_reclaim
= nr_to_reclaim
,
2353 .hibernation_mode
= 1,
2354 .swappiness
= vm_swappiness
,
2356 .isolate_pages
= isolate_pages_global
,
2358 struct zonelist
* zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
2359 struct task_struct
*p
= current
;
2360 unsigned long nr_reclaimed
;
2362 p
->flags
|= PF_MEMALLOC
;
2363 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
2364 reclaim_state
.reclaimed_slab
= 0;
2365 p
->reclaim_state
= &reclaim_state
;
2367 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2369 p
->reclaim_state
= NULL
;
2370 lockdep_clear_current_reclaim_state();
2371 p
->flags
&= ~PF_MEMALLOC
;
2373 return nr_reclaimed
;
2375 #endif /* CONFIG_HIBERNATION */
2377 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2378 not required for correctness. So if the last cpu in a node goes
2379 away, we get changed to run anywhere: as the first one comes back,
2380 restore their cpu bindings. */
2381 static int __devinit
cpu_callback(struct notifier_block
*nfb
,
2382 unsigned long action
, void *hcpu
)
2386 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
2387 for_each_node_state(nid
, N_HIGH_MEMORY
) {
2388 pg_data_t
*pgdat
= NODE_DATA(nid
);
2389 const struct cpumask
*mask
;
2391 mask
= cpumask_of_node(pgdat
->node_id
);
2393 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
2394 /* One of our CPUs online: restore mask */
2395 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
2402 * This kswapd start function will be called by init and node-hot-add.
2403 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2405 int kswapd_run(int nid
)
2407 pg_data_t
*pgdat
= NODE_DATA(nid
);
2413 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
2414 if (IS_ERR(pgdat
->kswapd
)) {
2415 /* failure at boot is fatal */
2416 BUG_ON(system_state
== SYSTEM_BOOTING
);
2417 printk("Failed to start kswapd on node %d\n",nid
);
2424 * Called by memory hotplug when all memory in a node is offlined.
2426 void kswapd_stop(int nid
)
2428 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
2431 kthread_stop(kswapd
);
2434 static int __init
kswapd_init(void)
2439 for_each_node_state(nid
, N_HIGH_MEMORY
)
2441 hotcpu_notifier(cpu_callback
, 0);
2445 module_init(kswapd_init
)
2451 * If non-zero call zone_reclaim when the number of free pages falls below
2454 int zone_reclaim_mode __read_mostly
;
2456 #define RECLAIM_OFF 0
2457 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2458 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2459 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2462 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2463 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2466 #define ZONE_RECLAIM_PRIORITY 4
2469 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2472 int sysctl_min_unmapped_ratio
= 1;
2475 * If the number of slab pages in a zone grows beyond this percentage then
2476 * slab reclaim needs to occur.
2478 int sysctl_min_slab_ratio
= 5;
2480 static inline unsigned long zone_unmapped_file_pages(struct zone
*zone
)
2482 unsigned long file_mapped
= zone_page_state(zone
, NR_FILE_MAPPED
);
2483 unsigned long file_lru
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
2484 zone_page_state(zone
, NR_ACTIVE_FILE
);
2487 * It's possible for there to be more file mapped pages than
2488 * accounted for by the pages on the file LRU lists because
2489 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2491 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
2494 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
2495 static long zone_pagecache_reclaimable(struct zone
*zone
)
2497 long nr_pagecache_reclaimable
;
2501 * If RECLAIM_SWAP is set, then all file pages are considered
2502 * potentially reclaimable. Otherwise, we have to worry about
2503 * pages like swapcache and zone_unmapped_file_pages() provides
2506 if (zone_reclaim_mode
& RECLAIM_SWAP
)
2507 nr_pagecache_reclaimable
= zone_page_state(zone
, NR_FILE_PAGES
);
2509 nr_pagecache_reclaimable
= zone_unmapped_file_pages(zone
);
2511 /* If we can't clean pages, remove dirty pages from consideration */
2512 if (!(zone_reclaim_mode
& RECLAIM_WRITE
))
2513 delta
+= zone_page_state(zone
, NR_FILE_DIRTY
);
2515 /* Watch for any possible underflows due to delta */
2516 if (unlikely(delta
> nr_pagecache_reclaimable
))
2517 delta
= nr_pagecache_reclaimable
;
2519 return nr_pagecache_reclaimable
- delta
;
2523 * Try to free up some pages from this zone through reclaim.
2525 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
2527 /* Minimum pages needed in order to stay on node */
2528 const unsigned long nr_pages
= 1 << order
;
2529 struct task_struct
*p
= current
;
2530 struct reclaim_state reclaim_state
;
2532 struct scan_control sc
= {
2533 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
2534 .may_unmap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
2536 .nr_to_reclaim
= max_t(unsigned long, nr_pages
,
2538 .gfp_mask
= gfp_mask
,
2539 .swappiness
= vm_swappiness
,
2541 .isolate_pages
= isolate_pages_global
,
2543 unsigned long slab_reclaimable
;
2545 disable_swap_token();
2548 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2549 * and we also need to be able to write out pages for RECLAIM_WRITE
2552 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
2553 reclaim_state
.reclaimed_slab
= 0;
2554 p
->reclaim_state
= &reclaim_state
;
2556 if (zone_pagecache_reclaimable(zone
) > zone
->min_unmapped_pages
) {
2558 * Free memory by calling shrink zone with increasing
2559 * priorities until we have enough memory freed.
2561 priority
= ZONE_RECLAIM_PRIORITY
;
2563 note_zone_scanning_priority(zone
, priority
);
2564 shrink_zone(priority
, zone
, &sc
);
2566 } while (priority
>= 0 && sc
.nr_reclaimed
< nr_pages
);
2569 slab_reclaimable
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
2570 if (slab_reclaimable
> zone
->min_slab_pages
) {
2572 * shrink_slab() does not currently allow us to determine how
2573 * many pages were freed in this zone. So we take the current
2574 * number of slab pages and shake the slab until it is reduced
2575 * by the same nr_pages that we used for reclaiming unmapped
2578 * Note that shrink_slab will free memory on all zones and may
2581 while (shrink_slab(sc
.nr_scanned
, gfp_mask
, order
) &&
2582 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) >
2583 slab_reclaimable
- nr_pages
)
2587 * Update nr_reclaimed by the number of slab pages we
2588 * reclaimed from this zone.
2590 sc
.nr_reclaimed
+= slab_reclaimable
-
2591 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
2594 p
->reclaim_state
= NULL
;
2595 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
2596 return sc
.nr_reclaimed
>= nr_pages
;
2599 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
2605 * Zone reclaim reclaims unmapped file backed pages and
2606 * slab pages if we are over the defined limits.
2608 * A small portion of unmapped file backed pages is needed for
2609 * file I/O otherwise pages read by file I/O will be immediately
2610 * thrown out if the zone is overallocated. So we do not reclaim
2611 * if less than a specified percentage of the zone is used by
2612 * unmapped file backed pages.
2614 if (zone_pagecache_reclaimable(zone
) <= zone
->min_unmapped_pages
&&
2615 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) <= zone
->min_slab_pages
)
2616 return ZONE_RECLAIM_FULL
;
2618 if (zone_is_all_unreclaimable(zone
))
2619 return ZONE_RECLAIM_FULL
;
2622 * Do not scan if the allocation should not be delayed.
2624 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
2625 return ZONE_RECLAIM_NOSCAN
;
2628 * Only run zone reclaim on the local zone or on zones that do not
2629 * have associated processors. This will favor the local processor
2630 * over remote processors and spread off node memory allocations
2631 * as wide as possible.
2633 node_id
= zone_to_nid(zone
);
2634 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
2635 return ZONE_RECLAIM_NOSCAN
;
2637 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
2638 return ZONE_RECLAIM_NOSCAN
;
2640 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
2641 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);
2644 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
2651 * page_evictable - test whether a page is evictable
2652 * @page: the page to test
2653 * @vma: the VMA in which the page is or will be mapped, may be NULL
2655 * Test whether page is evictable--i.e., should be placed on active/inactive
2656 * lists vs unevictable list. The vma argument is !NULL when called from the
2657 * fault path to determine how to instantate a new page.
2659 * Reasons page might not be evictable:
2660 * (1) page's mapping marked unevictable
2661 * (2) page is part of an mlocked VMA
2664 int page_evictable(struct page
*page
, struct vm_area_struct
*vma
)
2667 if (mapping_unevictable(page_mapping(page
)))
2670 if (PageMlocked(page
) || (vma
&& is_mlocked_vma(vma
, page
)))
2677 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2678 * @page: page to check evictability and move to appropriate lru list
2679 * @zone: zone page is in
2681 * Checks a page for evictability and moves the page to the appropriate
2684 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2685 * have PageUnevictable set.
2687 static void check_move_unevictable_page(struct page
*page
, struct zone
*zone
)
2689 VM_BUG_ON(PageActive(page
));
2692 ClearPageUnevictable(page
);
2693 if (page_evictable(page
, NULL
)) {
2694 enum lru_list l
= page_lru_base_type(page
);
2696 __dec_zone_state(zone
, NR_UNEVICTABLE
);
2697 list_move(&page
->lru
, &zone
->lru
[l
].list
);
2698 mem_cgroup_move_lists(page
, LRU_UNEVICTABLE
, l
);
2699 __inc_zone_state(zone
, NR_INACTIVE_ANON
+ l
);
2700 __count_vm_event(UNEVICTABLE_PGRESCUED
);
2703 * rotate unevictable list
2705 SetPageUnevictable(page
);
2706 list_move(&page
->lru
, &zone
->lru
[LRU_UNEVICTABLE
].list
);
2707 mem_cgroup_rotate_lru_list(page
, LRU_UNEVICTABLE
);
2708 if (page_evictable(page
, NULL
))
2714 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2715 * @mapping: struct address_space to scan for evictable pages
2717 * Scan all pages in mapping. Check unevictable pages for
2718 * evictability and move them to the appropriate zone lru list.
2720 void scan_mapping_unevictable_pages(struct address_space
*mapping
)
2723 pgoff_t end
= (i_size_read(mapping
->host
) + PAGE_CACHE_SIZE
- 1) >>
2726 struct pagevec pvec
;
2728 if (mapping
->nrpages
== 0)
2731 pagevec_init(&pvec
, 0);
2732 while (next
< end
&&
2733 pagevec_lookup(&pvec
, mapping
, next
, PAGEVEC_SIZE
)) {
2739 for (i
= 0; i
< pagevec_count(&pvec
); i
++) {
2740 struct page
*page
= pvec
.pages
[i
];
2741 pgoff_t page_index
= page
->index
;
2742 struct zone
*pagezone
= page_zone(page
);
2745 if (page_index
> next
)
2749 if (pagezone
!= zone
) {
2751 spin_unlock_irq(&zone
->lru_lock
);
2753 spin_lock_irq(&zone
->lru_lock
);
2756 if (PageLRU(page
) && PageUnevictable(page
))
2757 check_move_unevictable_page(page
, zone
);
2760 spin_unlock_irq(&zone
->lru_lock
);
2761 pagevec_release(&pvec
);
2763 count_vm_events(UNEVICTABLE_PGSCANNED
, pg_scanned
);
2769 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2770 * @zone - zone of which to scan the unevictable list
2772 * Scan @zone's unevictable LRU lists to check for pages that have become
2773 * evictable. Move those that have to @zone's inactive list where they
2774 * become candidates for reclaim, unless shrink_inactive_zone() decides
2775 * to reactivate them. Pages that are still unevictable are rotated
2776 * back onto @zone's unevictable list.
2778 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2779 static void scan_zone_unevictable_pages(struct zone
*zone
)
2781 struct list_head
*l_unevictable
= &zone
->lru
[LRU_UNEVICTABLE
].list
;
2783 unsigned long nr_to_scan
= zone_page_state(zone
, NR_UNEVICTABLE
);
2785 while (nr_to_scan
> 0) {
2786 unsigned long batch_size
= min(nr_to_scan
,
2787 SCAN_UNEVICTABLE_BATCH_SIZE
);
2789 spin_lock_irq(&zone
->lru_lock
);
2790 for (scan
= 0; scan
< batch_size
; scan
++) {
2791 struct page
*page
= lru_to_page(l_unevictable
);
2793 if (!trylock_page(page
))
2796 prefetchw_prev_lru_page(page
, l_unevictable
, flags
);
2798 if (likely(PageLRU(page
) && PageUnevictable(page
)))
2799 check_move_unevictable_page(page
, zone
);
2803 spin_unlock_irq(&zone
->lru_lock
);
2805 nr_to_scan
-= batch_size
;
2811 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2813 * A really big hammer: scan all zones' unevictable LRU lists to check for
2814 * pages that have become evictable. Move those back to the zones'
2815 * inactive list where they become candidates for reclaim.
2816 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2817 * and we add swap to the system. As such, it runs in the context of a task
2818 * that has possibly/probably made some previously unevictable pages
2821 static void scan_all_zones_unevictable_pages(void)
2825 for_each_zone(zone
) {
2826 scan_zone_unevictable_pages(zone
);
2831 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2832 * all nodes' unevictable lists for evictable pages
2834 unsigned long scan_unevictable_pages
;
2836 int scan_unevictable_handler(struct ctl_table
*table
, int write
,
2837 void __user
*buffer
,
2838 size_t *length
, loff_t
*ppos
)
2840 proc_doulongvec_minmax(table
, write
, buffer
, length
, ppos
);
2842 if (write
&& *(unsigned long *)table
->data
)
2843 scan_all_zones_unevictable_pages();
2845 scan_unevictable_pages
= 0;
2850 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2851 * a specified node's per zone unevictable lists for evictable pages.
2854 static ssize_t
read_scan_unevictable_node(struct sys_device
*dev
,
2855 struct sysdev_attribute
*attr
,
2858 return sprintf(buf
, "0\n"); /* always zero; should fit... */
2861 static ssize_t
write_scan_unevictable_node(struct sys_device
*dev
,
2862 struct sysdev_attribute
*attr
,
2863 const char *buf
, size_t count
)
2865 struct zone
*node_zones
= NODE_DATA(dev
->id
)->node_zones
;
2868 unsigned long req
= strict_strtoul(buf
, 10, &res
);
2871 return 1; /* zero is no-op */
2873 for (zone
= node_zones
; zone
- node_zones
< MAX_NR_ZONES
; ++zone
) {
2874 if (!populated_zone(zone
))
2876 scan_zone_unevictable_pages(zone
);
2882 static SYSDEV_ATTR(scan_unevictable_pages
, S_IRUGO
| S_IWUSR
,
2883 read_scan_unevictable_node
,
2884 write_scan_unevictable_node
);
2886 int scan_unevictable_register_node(struct node
*node
)
2888 return sysdev_create_file(&node
->sysdev
, &attr_scan_unevictable_pages
);
2891 void scan_unevictable_unregister_node(struct node
*node
)
2893 sysdev_remove_file(&node
->sysdev
, &attr_scan_unevictable_pages
);