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/compaction.h>
36 #include <linux/notifier.h>
37 #include <linux/rwsem.h>
38 #include <linux/delay.h>
39 #include <linux/kthread.h>
40 #include <linux/freezer.h>
41 #include <linux/memcontrol.h>
42 #include <linux/delayacct.h>
43 #include <linux/sysctl.h>
44 #include <linux/oom.h>
46 #include <asm/tlbflush.h>
47 #include <asm/div64.h>
49 #include <linux/swapops.h>
53 #define CREATE_TRACE_POINTS
54 #include <trace/events/vmscan.h>
57 * reclaim_mode determines how the inactive list is shrunk
58 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages
59 * RECLAIM_MODE_ASYNC: Do not block
60 * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback
61 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference
62 * page from the LRU and reclaim all pages within a
63 * naturally aligned range
64 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of
65 * order-0 pages and then compact the zone
67 typedef unsigned __bitwise__ reclaim_mode_t
;
68 #define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u)
69 #define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u)
70 #define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u)
71 #define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u)
72 #define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u)
75 /* Incremented by the number of inactive pages that were scanned */
76 unsigned long nr_scanned
;
78 /* Number of pages freed so far during a call to shrink_zones() */
79 unsigned long nr_reclaimed
;
81 /* How many pages shrink_list() should reclaim */
82 unsigned long nr_to_reclaim
;
84 unsigned long hibernation_mode
;
86 /* This context's GFP mask */
91 /* Can mapped pages be reclaimed? */
94 /* Can pages be swapped as part of reclaim? */
102 * Intend to reclaim enough continuous memory rather than reclaim
103 * enough amount of memory. i.e, mode for high order allocation.
105 reclaim_mode_t reclaim_mode
;
107 /* Which cgroup do we reclaim from */
108 struct mem_cgroup
*mem_cgroup
;
111 * Nodemask of nodes allowed by the caller. If NULL, all nodes
114 nodemask_t
*nodemask
;
117 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
119 #ifdef ARCH_HAS_PREFETCH
120 #define prefetch_prev_lru_page(_page, _base, _field) \
122 if ((_page)->lru.prev != _base) { \
125 prev = lru_to_page(&(_page->lru)); \
126 prefetch(&prev->_field); \
130 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
133 #ifdef ARCH_HAS_PREFETCHW
134 #define prefetchw_prev_lru_page(_page, _base, _field) \
136 if ((_page)->lru.prev != _base) { \
139 prev = lru_to_page(&(_page->lru)); \
140 prefetchw(&prev->_field); \
144 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
148 * From 0 .. 100. Higher means more swappy.
150 int vm_swappiness
= 60;
151 long vm_total_pages
; /* The total number of pages which the VM controls */
153 static LIST_HEAD(shrinker_list
);
154 static DECLARE_RWSEM(shrinker_rwsem
);
156 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
157 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
159 #define scanning_global_lru(sc) (1)
162 static struct zone_reclaim_stat
*get_reclaim_stat(struct zone
*zone
,
163 struct scan_control
*sc
)
165 if (!scanning_global_lru(sc
))
166 return mem_cgroup_get_reclaim_stat(sc
->mem_cgroup
, zone
);
168 return &zone
->reclaim_stat
;
171 static unsigned long zone_nr_lru_pages(struct zone
*zone
,
172 struct scan_control
*sc
, enum lru_list lru
)
174 if (!scanning_global_lru(sc
))
175 return mem_cgroup_zone_nr_pages(sc
->mem_cgroup
, zone
, lru
);
177 return zone_page_state(zone
, NR_LRU_BASE
+ lru
);
182 * Add a shrinker callback to be called from the vm
184 void register_shrinker(struct shrinker
*shrinker
)
187 down_write(&shrinker_rwsem
);
188 list_add_tail(&shrinker
->list
, &shrinker_list
);
189 up_write(&shrinker_rwsem
);
191 EXPORT_SYMBOL(register_shrinker
);
196 void unregister_shrinker(struct shrinker
*shrinker
)
198 down_write(&shrinker_rwsem
);
199 list_del(&shrinker
->list
);
200 up_write(&shrinker_rwsem
);
202 EXPORT_SYMBOL(unregister_shrinker
);
204 #define SHRINK_BATCH 128
206 * Call the shrink functions to age shrinkable caches
208 * Here we assume it costs one seek to replace a lru page and that it also
209 * takes a seek to recreate a cache object. With this in mind we age equal
210 * percentages of the lru and ageable caches. This should balance the seeks
211 * generated by these structures.
213 * If the vm encountered mapped pages on the LRU it increase the pressure on
214 * slab to avoid swapping.
216 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
218 * `lru_pages' represents the number of on-LRU pages in all the zones which
219 * are eligible for the caller's allocation attempt. It is used for balancing
220 * slab reclaim versus page reclaim.
222 * Returns the number of slab objects which we shrunk.
224 unsigned long shrink_slab(unsigned long scanned
, gfp_t gfp_mask
,
225 unsigned long lru_pages
)
227 struct shrinker
*shrinker
;
228 unsigned long ret
= 0;
231 scanned
= SWAP_CLUSTER_MAX
;
233 if (!down_read_trylock(&shrinker_rwsem
)) {
234 /* Assume we'll be able to shrink next time */
239 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
240 unsigned long long delta
;
241 unsigned long total_scan
;
242 unsigned long max_pass
;
244 max_pass
= (*shrinker
->shrink
)(shrinker
, 0, gfp_mask
);
245 delta
= (4 * scanned
) / shrinker
->seeks
;
247 do_div(delta
, lru_pages
+ 1);
248 shrinker
->nr
+= delta
;
249 if (shrinker
->nr
< 0) {
250 printk(KERN_ERR
"shrink_slab: %pF negative objects to "
252 shrinker
->shrink
, shrinker
->nr
);
253 shrinker
->nr
= max_pass
;
257 * Avoid risking looping forever due to too large nr value:
258 * never try to free more than twice the estimate number of
261 if (shrinker
->nr
> max_pass
* 2)
262 shrinker
->nr
= max_pass
* 2;
264 total_scan
= shrinker
->nr
;
267 while (total_scan
>= SHRINK_BATCH
) {
268 long this_scan
= SHRINK_BATCH
;
272 nr_before
= (*shrinker
->shrink
)(shrinker
, 0, gfp_mask
);
273 shrink_ret
= (*shrinker
->shrink
)(shrinker
, this_scan
,
275 if (shrink_ret
== -1)
277 if (shrink_ret
< nr_before
)
278 ret
+= nr_before
- shrink_ret
;
279 count_vm_events(SLABS_SCANNED
, this_scan
);
280 total_scan
-= this_scan
;
285 shrinker
->nr
+= total_scan
;
287 up_read(&shrinker_rwsem
);
293 static void set_reclaim_mode(int priority
, struct scan_control
*sc
,
296 reclaim_mode_t syncmode
= sync
? RECLAIM_MODE_SYNC
: RECLAIM_MODE_ASYNC
;
299 * Initially assume we are entering either lumpy reclaim or
300 * reclaim/compaction.Depending on the order, we will either set the
301 * sync mode or just reclaim order-0 pages later.
303 if (COMPACTION_BUILD
)
304 sc
->reclaim_mode
= RECLAIM_MODE_COMPACTION
;
306 sc
->reclaim_mode
= RECLAIM_MODE_LUMPYRECLAIM
;
309 * Avoid using lumpy reclaim or reclaim/compaction if possible by
310 * restricting when its set to either costly allocations or when
311 * under memory pressure
313 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
314 sc
->reclaim_mode
|= syncmode
;
315 else if (sc
->order
&& priority
< DEF_PRIORITY
- 2)
316 sc
->reclaim_mode
|= syncmode
;
318 sc
->reclaim_mode
= RECLAIM_MODE_SINGLE
| RECLAIM_MODE_ASYNC
;
321 static void reset_reclaim_mode(struct scan_control
*sc
)
323 sc
->reclaim_mode
= RECLAIM_MODE_SINGLE
| RECLAIM_MODE_ASYNC
;
326 static inline int is_page_cache_freeable(struct page
*page
)
329 * A freeable page cache page is referenced only by the caller
330 * that isolated the page, the page cache radix tree and
331 * optional buffer heads at page->private.
333 return page_count(page
) - page_has_private(page
) == 2;
336 static int may_write_to_queue(struct backing_dev_info
*bdi
,
337 struct scan_control
*sc
)
339 if (current
->flags
& PF_SWAPWRITE
)
341 if (!bdi_write_congested(bdi
))
343 if (bdi
== current
->backing_dev_info
)
346 /* lumpy reclaim for hugepage often need a lot of write */
347 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
353 * We detected a synchronous write error writing a page out. Probably
354 * -ENOSPC. We need to propagate that into the address_space for a subsequent
355 * fsync(), msync() or close().
357 * The tricky part is that after writepage we cannot touch the mapping: nothing
358 * prevents it from being freed up. But we have a ref on the page and once
359 * that page is locked, the mapping is pinned.
361 * We're allowed to run sleeping lock_page() here because we know the caller has
364 static void handle_write_error(struct address_space
*mapping
,
365 struct page
*page
, int error
)
368 if (page_mapping(page
) == mapping
)
369 mapping_set_error(mapping
, error
);
373 /* possible outcome of pageout() */
375 /* failed to write page out, page is locked */
377 /* move page to the active list, page is locked */
379 /* page has been sent to the disk successfully, page is unlocked */
381 /* page is clean and locked */
386 * pageout is called by shrink_page_list() for each dirty page.
387 * Calls ->writepage().
389 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
390 struct scan_control
*sc
)
393 * If the page is dirty, only perform writeback if that write
394 * will be non-blocking. To prevent this allocation from being
395 * stalled by pagecache activity. But note that there may be
396 * stalls if we need to run get_block(). We could test
397 * PagePrivate for that.
399 * If this process is currently in __generic_file_aio_write() against
400 * this page's queue, we can perform writeback even if that
403 * If the page is swapcache, write it back even if that would
404 * block, for some throttling. This happens by accident, because
405 * swap_backing_dev_info is bust: it doesn't reflect the
406 * congestion state of the swapdevs. Easy to fix, if needed.
408 if (!is_page_cache_freeable(page
))
412 * Some data journaling orphaned pages can have
413 * page->mapping == NULL while being dirty with clean buffers.
415 if (page_has_private(page
)) {
416 if (try_to_free_buffers(page
)) {
417 ClearPageDirty(page
);
418 printk("%s: orphaned page\n", __func__
);
424 if (mapping
->a_ops
->writepage
== NULL
)
425 return PAGE_ACTIVATE
;
426 if (!may_write_to_queue(mapping
->backing_dev_info
, sc
))
429 if (clear_page_dirty_for_io(page
)) {
431 struct writeback_control wbc
= {
432 .sync_mode
= WB_SYNC_NONE
,
433 .nr_to_write
= SWAP_CLUSTER_MAX
,
435 .range_end
= LLONG_MAX
,
439 SetPageReclaim(page
);
440 res
= mapping
->a_ops
->writepage(page
, &wbc
);
442 handle_write_error(mapping
, page
, res
);
443 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
444 ClearPageReclaim(page
);
445 return PAGE_ACTIVATE
;
449 * Wait on writeback if requested to. This happens when
450 * direct reclaiming a large contiguous area and the
451 * first attempt to free a range of pages fails.
453 if (PageWriteback(page
) &&
454 (sc
->reclaim_mode
& RECLAIM_MODE_SYNC
))
455 wait_on_page_writeback(page
);
457 if (!PageWriteback(page
)) {
458 /* synchronous write or broken a_ops? */
459 ClearPageReclaim(page
);
461 trace_mm_vmscan_writepage(page
,
462 trace_reclaim_flags(page
, sc
->reclaim_mode
));
463 inc_zone_page_state(page
, NR_VMSCAN_WRITE
);
471 * Same as remove_mapping, but if the page is removed from the mapping, it
472 * gets returned with a refcount of 0.
474 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
)
476 BUG_ON(!PageLocked(page
));
477 BUG_ON(mapping
!= page_mapping(page
));
479 spin_lock_irq(&mapping
->tree_lock
);
481 * The non racy check for a busy page.
483 * Must be careful with the order of the tests. When someone has
484 * a ref to the page, it may be possible that they dirty it then
485 * drop the reference. So if PageDirty is tested before page_count
486 * here, then the following race may occur:
488 * get_user_pages(&page);
489 * [user mapping goes away]
491 * !PageDirty(page) [good]
492 * SetPageDirty(page);
494 * !page_count(page) [good, discard it]
496 * [oops, our write_to data is lost]
498 * Reversing the order of the tests ensures such a situation cannot
499 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
500 * load is not satisfied before that of page->_count.
502 * Note that if SetPageDirty is always performed via set_page_dirty,
503 * and thus under tree_lock, then this ordering is not required.
505 if (!page_freeze_refs(page
, 2))
507 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
508 if (unlikely(PageDirty(page
))) {
509 page_unfreeze_refs(page
, 2);
513 if (PageSwapCache(page
)) {
514 swp_entry_t swap
= { .val
= page_private(page
) };
515 __delete_from_swap_cache(page
);
516 spin_unlock_irq(&mapping
->tree_lock
);
517 swapcache_free(swap
, page
);
519 void (*freepage
)(struct page
*);
521 freepage
= mapping
->a_ops
->freepage
;
523 __delete_from_page_cache(page
);
524 spin_unlock_irq(&mapping
->tree_lock
);
525 mem_cgroup_uncharge_cache_page(page
);
527 if (freepage
!= NULL
)
534 spin_unlock_irq(&mapping
->tree_lock
);
539 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
540 * someone else has a ref on the page, abort and return 0. If it was
541 * successfully detached, return 1. Assumes the caller has a single ref on
544 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
546 if (__remove_mapping(mapping
, page
)) {
548 * Unfreezing the refcount with 1 rather than 2 effectively
549 * drops the pagecache ref for us without requiring another
552 page_unfreeze_refs(page
, 1);
559 * putback_lru_page - put previously isolated page onto appropriate LRU list
560 * @page: page to be put back to appropriate lru list
562 * Add previously isolated @page to appropriate LRU list.
563 * Page may still be unevictable for other reasons.
565 * lru_lock must not be held, interrupts must be enabled.
567 void putback_lru_page(struct page
*page
)
570 int active
= !!TestClearPageActive(page
);
571 int was_unevictable
= PageUnevictable(page
);
573 VM_BUG_ON(PageLRU(page
));
576 ClearPageUnevictable(page
);
578 if (page_evictable(page
, NULL
)) {
580 * For evictable pages, we can use the cache.
581 * In event of a race, worst case is we end up with an
582 * unevictable page on [in]active list.
583 * We know how to handle that.
585 lru
= active
+ page_lru_base_type(page
);
586 lru_cache_add_lru(page
, lru
);
589 * Put unevictable pages directly on zone's unevictable
592 lru
= LRU_UNEVICTABLE
;
593 add_page_to_unevictable_list(page
);
595 * When racing with an mlock clearing (page is
596 * unlocked), make sure that if the other thread does
597 * not observe our setting of PG_lru and fails
598 * isolation, we see PG_mlocked cleared below and move
599 * the page back to the evictable list.
601 * The other side is TestClearPageMlocked().
607 * page's status can change while we move it among lru. If an evictable
608 * page is on unevictable list, it never be freed. To avoid that,
609 * check after we added it to the list, again.
611 if (lru
== LRU_UNEVICTABLE
&& page_evictable(page
, NULL
)) {
612 if (!isolate_lru_page(page
)) {
616 /* This means someone else dropped this page from LRU
617 * So, it will be freed or putback to LRU again. There is
618 * nothing to do here.
622 if (was_unevictable
&& lru
!= LRU_UNEVICTABLE
)
623 count_vm_event(UNEVICTABLE_PGRESCUED
);
624 else if (!was_unevictable
&& lru
== LRU_UNEVICTABLE
)
625 count_vm_event(UNEVICTABLE_PGCULLED
);
627 put_page(page
); /* drop ref from isolate */
630 enum page_references
{
632 PAGEREF_RECLAIM_CLEAN
,
637 static enum page_references
page_check_references(struct page
*page
,
638 struct scan_control
*sc
)
640 int referenced_ptes
, referenced_page
;
641 unsigned long vm_flags
;
643 referenced_ptes
= page_referenced(page
, 1, sc
->mem_cgroup
, &vm_flags
);
644 referenced_page
= TestClearPageReferenced(page
);
646 /* Lumpy reclaim - ignore references */
647 if (sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
)
648 return PAGEREF_RECLAIM
;
651 * Mlock lost the isolation race with us. Let try_to_unmap()
652 * move the page to the unevictable list.
654 if (vm_flags
& VM_LOCKED
)
655 return PAGEREF_RECLAIM
;
657 if (referenced_ptes
) {
659 return PAGEREF_ACTIVATE
;
661 * All mapped pages start out with page table
662 * references from the instantiating fault, so we need
663 * to look twice if a mapped file page is used more
666 * Mark it and spare it for another trip around the
667 * inactive list. Another page table reference will
668 * lead to its activation.
670 * Note: the mark is set for activated pages as well
671 * so that recently deactivated but used pages are
674 SetPageReferenced(page
);
677 return PAGEREF_ACTIVATE
;
682 /* Reclaim if clean, defer dirty pages to writeback */
683 if (referenced_page
&& !PageSwapBacked(page
))
684 return PAGEREF_RECLAIM_CLEAN
;
686 return PAGEREF_RECLAIM
;
689 static noinline_for_stack
void free_page_list(struct list_head
*free_pages
)
691 struct pagevec freed_pvec
;
692 struct page
*page
, *tmp
;
694 pagevec_init(&freed_pvec
, 1);
696 list_for_each_entry_safe(page
, tmp
, free_pages
, lru
) {
697 list_del(&page
->lru
);
698 if (!pagevec_add(&freed_pvec
, page
)) {
699 __pagevec_free(&freed_pvec
);
700 pagevec_reinit(&freed_pvec
);
704 pagevec_free(&freed_pvec
);
708 * shrink_page_list() returns the number of reclaimed pages
710 static unsigned long shrink_page_list(struct list_head
*page_list
,
712 struct scan_control
*sc
)
714 LIST_HEAD(ret_pages
);
715 LIST_HEAD(free_pages
);
717 unsigned long nr_dirty
= 0;
718 unsigned long nr_congested
= 0;
719 unsigned long nr_reclaimed
= 0;
723 while (!list_empty(page_list
)) {
724 enum page_references references
;
725 struct address_space
*mapping
;
731 page
= lru_to_page(page_list
);
732 list_del(&page
->lru
);
734 if (!trylock_page(page
))
737 VM_BUG_ON(PageActive(page
));
738 VM_BUG_ON(page_zone(page
) != zone
);
742 if (unlikely(!page_evictable(page
, NULL
)))
745 if (!sc
->may_unmap
&& page_mapped(page
))
748 /* Double the slab pressure for mapped and swapcache pages */
749 if (page_mapped(page
) || PageSwapCache(page
))
752 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
753 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
755 if (PageWriteback(page
)) {
757 * Synchronous reclaim is performed in two passes,
758 * first an asynchronous pass over the list to
759 * start parallel writeback, and a second synchronous
760 * pass to wait for the IO to complete. Wait here
761 * for any page for which writeback has already
764 if ((sc
->reclaim_mode
& RECLAIM_MODE_SYNC
) &&
766 wait_on_page_writeback(page
);
773 references
= page_check_references(page
, sc
);
774 switch (references
) {
775 case PAGEREF_ACTIVATE
:
776 goto activate_locked
;
779 case PAGEREF_RECLAIM
:
780 case PAGEREF_RECLAIM_CLEAN
:
781 ; /* try to reclaim the page below */
785 * Anonymous process memory has backing store?
786 * Try to allocate it some swap space here.
788 if (PageAnon(page
) && !PageSwapCache(page
)) {
789 if (!(sc
->gfp_mask
& __GFP_IO
))
791 if (!add_to_swap(page
))
792 goto activate_locked
;
796 mapping
= page_mapping(page
);
799 * The page is mapped into the page tables of one or more
800 * processes. Try to unmap it here.
802 if (page_mapped(page
) && mapping
) {
803 switch (try_to_unmap(page
, TTU_UNMAP
)) {
805 goto activate_locked
;
811 ; /* try to free the page below */
815 if (PageDirty(page
)) {
818 if (references
== PAGEREF_RECLAIM_CLEAN
)
822 if (!sc
->may_writepage
)
825 /* Page is dirty, try to write it out here */
826 switch (pageout(page
, mapping
, sc
)) {
831 goto activate_locked
;
833 if (PageWriteback(page
))
839 * A synchronous write - probably a ramdisk. Go
840 * ahead and try to reclaim the page.
842 if (!trylock_page(page
))
844 if (PageDirty(page
) || PageWriteback(page
))
846 mapping
= page_mapping(page
);
848 ; /* try to free the page below */
853 * If the page has buffers, try to free the buffer mappings
854 * associated with this page. If we succeed we try to free
857 * We do this even if the page is PageDirty().
858 * try_to_release_page() does not perform I/O, but it is
859 * possible for a page to have PageDirty set, but it is actually
860 * clean (all its buffers are clean). This happens if the
861 * buffers were written out directly, with submit_bh(). ext3
862 * will do this, as well as the blockdev mapping.
863 * try_to_release_page() will discover that cleanness and will
864 * drop the buffers and mark the page clean - it can be freed.
866 * Rarely, pages can have buffers and no ->mapping. These are
867 * the pages which were not successfully invalidated in
868 * truncate_complete_page(). We try to drop those buffers here
869 * and if that worked, and the page is no longer mapped into
870 * process address space (page_count == 1) it can be freed.
871 * Otherwise, leave the page on the LRU so it is swappable.
873 if (page_has_private(page
)) {
874 if (!try_to_release_page(page
, sc
->gfp_mask
))
875 goto activate_locked
;
876 if (!mapping
&& page_count(page
) == 1) {
878 if (put_page_testzero(page
))
882 * rare race with speculative reference.
883 * the speculative reference will free
884 * this page shortly, so we may
885 * increment nr_reclaimed here (and
886 * leave it off the LRU).
894 if (!mapping
|| !__remove_mapping(mapping
, page
))
898 * At this point, we have no other references and there is
899 * no way to pick any more up (removed from LRU, removed
900 * from pagecache). Can use non-atomic bitops now (and
901 * we obviously don't have to worry about waking up a process
902 * waiting on the page lock, because there are no references.
904 __clear_page_locked(page
);
909 * Is there need to periodically free_page_list? It would
910 * appear not as the counts should be low
912 list_add(&page
->lru
, &free_pages
);
916 if (PageSwapCache(page
))
917 try_to_free_swap(page
);
919 putback_lru_page(page
);
920 reset_reclaim_mode(sc
);
924 /* Not a candidate for swapping, so reclaim swap space. */
925 if (PageSwapCache(page
) && vm_swap_full())
926 try_to_free_swap(page
);
927 VM_BUG_ON(PageActive(page
));
933 reset_reclaim_mode(sc
);
935 list_add(&page
->lru
, &ret_pages
);
936 VM_BUG_ON(PageLRU(page
) || PageUnevictable(page
));
940 * Tag a zone as congested if all the dirty pages encountered were
941 * backed by a congested BDI. In this case, reclaimers should just
942 * back off and wait for congestion to clear because further reclaim
943 * will encounter the same problem
945 if (nr_dirty
&& nr_dirty
== nr_congested
&& scanning_global_lru(sc
))
946 zone_set_flag(zone
, ZONE_CONGESTED
);
948 free_page_list(&free_pages
);
950 list_splice(&ret_pages
, page_list
);
951 count_vm_events(PGACTIVATE
, pgactivate
);
956 * Attempt to remove the specified page from its LRU. Only take this page
957 * if it is of the appropriate PageActive status. Pages which are being
958 * freed elsewhere are also ignored.
960 * page: page to consider
961 * mode: one of the LRU isolation modes defined above
963 * returns 0 on success, -ve errno on failure.
965 int __isolate_lru_page(struct page
*page
, int mode
, int file
)
969 /* Only take pages on the LRU. */
974 * When checking the active state, we need to be sure we are
975 * dealing with comparible boolean values. Take the logical not
978 if (mode
!= ISOLATE_BOTH
&& (!PageActive(page
) != !mode
))
981 if (mode
!= ISOLATE_BOTH
&& page_is_file_cache(page
) != file
)
985 * When this function is being called for lumpy reclaim, we
986 * initially look into all LRU pages, active, inactive and
987 * unevictable; only give shrink_page_list evictable pages.
989 if (PageUnevictable(page
))
994 if (likely(get_page_unless_zero(page
))) {
996 * Be careful not to clear PageLRU until after we're
997 * sure the page is not being freed elsewhere -- the
998 * page release code relies on it.
1008 * zone->lru_lock is heavily contended. Some of the functions that
1009 * shrink the lists perform better by taking out a batch of pages
1010 * and working on them outside the LRU lock.
1012 * For pagecache intensive workloads, this function is the hottest
1013 * spot in the kernel (apart from copy_*_user functions).
1015 * Appropriate locks must be held before calling this function.
1017 * @nr_to_scan: The number of pages to look through on the list.
1018 * @src: The LRU list to pull pages off.
1019 * @dst: The temp list to put pages on to.
1020 * @scanned: The number of pages that were scanned.
1021 * @order: The caller's attempted allocation order
1022 * @mode: One of the LRU isolation modes
1023 * @file: True [1] if isolating file [!anon] pages
1025 * returns how many pages were moved onto *@dst.
1027 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1028 struct list_head
*src
, struct list_head
*dst
,
1029 unsigned long *scanned
, int order
, int mode
, int file
)
1031 unsigned long nr_taken
= 0;
1032 unsigned long nr_lumpy_taken
= 0;
1033 unsigned long nr_lumpy_dirty
= 0;
1034 unsigned long nr_lumpy_failed
= 0;
1037 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
1040 unsigned long end_pfn
;
1041 unsigned long page_pfn
;
1044 page
= lru_to_page(src
);
1045 prefetchw_prev_lru_page(page
, src
, flags
);
1047 VM_BUG_ON(!PageLRU(page
));
1049 switch (__isolate_lru_page(page
, mode
, file
)) {
1051 list_move(&page
->lru
, dst
);
1052 mem_cgroup_del_lru(page
);
1053 nr_taken
+= hpage_nr_pages(page
);
1057 /* else it is being freed elsewhere */
1058 list_move(&page
->lru
, src
);
1059 mem_cgroup_rotate_lru_list(page
, page_lru(page
));
1070 * Attempt to take all pages in the order aligned region
1071 * surrounding the tag page. Only take those pages of
1072 * the same active state as that tag page. We may safely
1073 * round the target page pfn down to the requested order
1074 * as the mem_map is guaranteed valid out to MAX_ORDER,
1075 * where that page is in a different zone we will detect
1076 * it from its zone id and abort this block scan.
1078 zone_id
= page_zone_id(page
);
1079 page_pfn
= page_to_pfn(page
);
1080 pfn
= page_pfn
& ~((1 << order
) - 1);
1081 end_pfn
= pfn
+ (1 << order
);
1082 for (; pfn
< end_pfn
; pfn
++) {
1083 struct page
*cursor_page
;
1085 /* The target page is in the block, ignore it. */
1086 if (unlikely(pfn
== page_pfn
))
1089 /* Avoid holes within the zone. */
1090 if (unlikely(!pfn_valid_within(pfn
)))
1093 cursor_page
= pfn_to_page(pfn
);
1095 /* Check that we have not crossed a zone boundary. */
1096 if (unlikely(page_zone_id(cursor_page
) != zone_id
))
1100 * If we don't have enough swap space, reclaiming of
1101 * anon page which don't already have a swap slot is
1104 if (nr_swap_pages
<= 0 && PageAnon(cursor_page
) &&
1105 !PageSwapCache(cursor_page
))
1108 if (__isolate_lru_page(cursor_page
, mode
, file
) == 0) {
1109 list_move(&cursor_page
->lru
, dst
);
1110 mem_cgroup_del_lru(cursor_page
);
1111 nr_taken
+= hpage_nr_pages(page
);
1113 if (PageDirty(cursor_page
))
1118 * Check if the page is freed already.
1120 * We can't use page_count() as that
1121 * requires compound_head and we don't
1122 * have a pin on the page here. If a
1123 * page is tail, we may or may not
1124 * have isolated the head, so assume
1125 * it's not free, it'd be tricky to
1126 * track the head status without a
1129 if (!PageTail(cursor_page
) &&
1130 !atomic_read(&cursor_page
->_count
))
1136 /* If we break out of the loop above, lumpy reclaim failed */
1143 trace_mm_vmscan_lru_isolate(order
,
1146 nr_lumpy_taken
, nr_lumpy_dirty
, nr_lumpy_failed
,
1151 static unsigned long isolate_pages_global(unsigned long nr
,
1152 struct list_head
*dst
,
1153 unsigned long *scanned
, int order
,
1154 int mode
, struct zone
*z
,
1155 int active
, int file
)
1162 return isolate_lru_pages(nr
, &z
->lru
[lru
].list
, dst
, scanned
, order
,
1167 * clear_active_flags() is a helper for shrink_active_list(), clearing
1168 * any active bits from the pages in the list.
1170 static unsigned long clear_active_flags(struct list_head
*page_list
,
1171 unsigned int *count
)
1177 list_for_each_entry(page
, page_list
, lru
) {
1178 int numpages
= hpage_nr_pages(page
);
1179 lru
= page_lru_base_type(page
);
1180 if (PageActive(page
)) {
1182 ClearPageActive(page
);
1183 nr_active
+= numpages
;
1186 count
[lru
] += numpages
;
1193 * isolate_lru_page - tries to isolate a page from its LRU list
1194 * @page: page to isolate from its LRU list
1196 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1197 * vmstat statistic corresponding to whatever LRU list the page was on.
1199 * Returns 0 if the page was removed from an LRU list.
1200 * Returns -EBUSY if the page was not on an LRU list.
1202 * The returned page will have PageLRU() cleared. If it was found on
1203 * the active list, it will have PageActive set. If it was found on
1204 * the unevictable list, it will have the PageUnevictable bit set. That flag
1205 * may need to be cleared by the caller before letting the page go.
1207 * The vmstat statistic corresponding to the list on which the page was
1208 * found will be decremented.
1211 * (1) Must be called with an elevated refcount on the page. This is a
1212 * fundamentnal difference from isolate_lru_pages (which is called
1213 * without a stable reference).
1214 * (2) the lru_lock must not be held.
1215 * (3) interrupts must be enabled.
1217 int isolate_lru_page(struct page
*page
)
1221 if (PageLRU(page
)) {
1222 struct zone
*zone
= page_zone(page
);
1224 spin_lock_irq(&zone
->lru_lock
);
1225 if (PageLRU(page
) && get_page_unless_zero(page
)) {
1226 int lru
= page_lru(page
);
1230 del_page_from_lru_list(zone
, page
, lru
);
1232 spin_unlock_irq(&zone
->lru_lock
);
1238 * Are there way too many processes in the direct reclaim path already?
1240 static int too_many_isolated(struct zone
*zone
, int file
,
1241 struct scan_control
*sc
)
1243 unsigned long inactive
, isolated
;
1245 if (current_is_kswapd())
1248 if (!scanning_global_lru(sc
))
1252 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1253 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
);
1255 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1256 isolated
= zone_page_state(zone
, NR_ISOLATED_ANON
);
1259 return isolated
> inactive
;
1263 * TODO: Try merging with migrations version of putback_lru_pages
1265 static noinline_for_stack
void
1266 putback_lru_pages(struct zone
*zone
, struct scan_control
*sc
,
1267 unsigned long nr_anon
, unsigned long nr_file
,
1268 struct list_head
*page_list
)
1271 struct pagevec pvec
;
1272 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1274 pagevec_init(&pvec
, 1);
1277 * Put back any unfreeable pages.
1279 spin_lock(&zone
->lru_lock
);
1280 while (!list_empty(page_list
)) {
1282 page
= lru_to_page(page_list
);
1283 VM_BUG_ON(PageLRU(page
));
1284 list_del(&page
->lru
);
1285 if (unlikely(!page_evictable(page
, NULL
))) {
1286 spin_unlock_irq(&zone
->lru_lock
);
1287 putback_lru_page(page
);
1288 spin_lock_irq(&zone
->lru_lock
);
1292 lru
= page_lru(page
);
1293 add_page_to_lru_list(zone
, page
, lru
);
1294 if (is_active_lru(lru
)) {
1295 int file
= is_file_lru(lru
);
1296 int numpages
= hpage_nr_pages(page
);
1297 reclaim_stat
->recent_rotated
[file
] += numpages
;
1299 if (!pagevec_add(&pvec
, page
)) {
1300 spin_unlock_irq(&zone
->lru_lock
);
1301 __pagevec_release(&pvec
);
1302 spin_lock_irq(&zone
->lru_lock
);
1305 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, -nr_anon
);
1306 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, -nr_file
);
1308 spin_unlock_irq(&zone
->lru_lock
);
1309 pagevec_release(&pvec
);
1312 static noinline_for_stack
void update_isolated_counts(struct zone
*zone
,
1313 struct scan_control
*sc
,
1314 unsigned long *nr_anon
,
1315 unsigned long *nr_file
,
1316 struct list_head
*isolated_list
)
1318 unsigned long nr_active
;
1319 unsigned int count
[NR_LRU_LISTS
] = { 0, };
1320 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1322 nr_active
= clear_active_flags(isolated_list
, count
);
1323 __count_vm_events(PGDEACTIVATE
, nr_active
);
1325 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
,
1326 -count
[LRU_ACTIVE_FILE
]);
1327 __mod_zone_page_state(zone
, NR_INACTIVE_FILE
,
1328 -count
[LRU_INACTIVE_FILE
]);
1329 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
,
1330 -count
[LRU_ACTIVE_ANON
]);
1331 __mod_zone_page_state(zone
, NR_INACTIVE_ANON
,
1332 -count
[LRU_INACTIVE_ANON
]);
1334 *nr_anon
= count
[LRU_ACTIVE_ANON
] + count
[LRU_INACTIVE_ANON
];
1335 *nr_file
= count
[LRU_ACTIVE_FILE
] + count
[LRU_INACTIVE_FILE
];
1336 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, *nr_anon
);
1337 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, *nr_file
);
1339 reclaim_stat
->recent_scanned
[0] += *nr_anon
;
1340 reclaim_stat
->recent_scanned
[1] += *nr_file
;
1344 * Returns true if the caller should wait to clean dirty/writeback pages.
1346 * If we are direct reclaiming for contiguous pages and we do not reclaim
1347 * everything in the list, try again and wait for writeback IO to complete.
1348 * This will stall high-order allocations noticeably. Only do that when really
1349 * need to free the pages under high memory pressure.
1351 static inline bool should_reclaim_stall(unsigned long nr_taken
,
1352 unsigned long nr_freed
,
1354 struct scan_control
*sc
)
1356 int lumpy_stall_priority
;
1358 /* kswapd should not stall on sync IO */
1359 if (current_is_kswapd())
1362 /* Only stall on lumpy reclaim */
1363 if (sc
->reclaim_mode
& RECLAIM_MODE_SINGLE
)
1366 /* If we have relaimed everything on the isolated list, no stall */
1367 if (nr_freed
== nr_taken
)
1371 * For high-order allocations, there are two stall thresholds.
1372 * High-cost allocations stall immediately where as lower
1373 * order allocations such as stacks require the scanning
1374 * priority to be much higher before stalling.
1376 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
1377 lumpy_stall_priority
= DEF_PRIORITY
;
1379 lumpy_stall_priority
= DEF_PRIORITY
/ 3;
1381 return priority
<= lumpy_stall_priority
;
1385 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1386 * of reclaimed pages
1388 static noinline_for_stack
unsigned long
1389 shrink_inactive_list(unsigned long nr_to_scan
, struct zone
*zone
,
1390 struct scan_control
*sc
, int priority
, int file
)
1392 LIST_HEAD(page_list
);
1393 unsigned long nr_scanned
;
1394 unsigned long nr_reclaimed
= 0;
1395 unsigned long nr_taken
;
1396 unsigned long nr_anon
;
1397 unsigned long nr_file
;
1399 while (unlikely(too_many_isolated(zone
, file
, sc
))) {
1400 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1402 /* We are about to die and free our memory. Return now. */
1403 if (fatal_signal_pending(current
))
1404 return SWAP_CLUSTER_MAX
;
1407 set_reclaim_mode(priority
, sc
, false);
1409 spin_lock_irq(&zone
->lru_lock
);
1411 if (scanning_global_lru(sc
)) {
1412 nr_taken
= isolate_pages_global(nr_to_scan
,
1413 &page_list
, &nr_scanned
, sc
->order
,
1414 sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
?
1415 ISOLATE_BOTH
: ISOLATE_INACTIVE
,
1417 zone
->pages_scanned
+= nr_scanned
;
1418 if (current_is_kswapd())
1419 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
,
1422 __count_zone_vm_events(PGSCAN_DIRECT
, zone
,
1425 nr_taken
= mem_cgroup_isolate_pages(nr_to_scan
,
1426 &page_list
, &nr_scanned
, sc
->order
,
1427 sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
?
1428 ISOLATE_BOTH
: ISOLATE_INACTIVE
,
1429 zone
, sc
->mem_cgroup
,
1432 * mem_cgroup_isolate_pages() keeps track of
1433 * scanned pages on its own.
1437 if (nr_taken
== 0) {
1438 spin_unlock_irq(&zone
->lru_lock
);
1442 update_isolated_counts(zone
, sc
, &nr_anon
, &nr_file
, &page_list
);
1444 spin_unlock_irq(&zone
->lru_lock
);
1446 nr_reclaimed
= shrink_page_list(&page_list
, zone
, sc
);
1448 /* Check if we should syncronously wait for writeback */
1449 if (should_reclaim_stall(nr_taken
, nr_reclaimed
, priority
, sc
)) {
1450 set_reclaim_mode(priority
, sc
, true);
1451 nr_reclaimed
+= shrink_page_list(&page_list
, zone
, sc
);
1454 local_irq_disable();
1455 if (current_is_kswapd())
1456 __count_vm_events(KSWAPD_STEAL
, nr_reclaimed
);
1457 __count_zone_vm_events(PGSTEAL
, zone
, nr_reclaimed
);
1459 putback_lru_pages(zone
, sc
, nr_anon
, nr_file
, &page_list
);
1461 trace_mm_vmscan_lru_shrink_inactive(zone
->zone_pgdat
->node_id
,
1463 nr_scanned
, nr_reclaimed
,
1465 trace_shrink_flags(file
, sc
->reclaim_mode
));
1466 return nr_reclaimed
;
1470 * This moves pages from the active list to the inactive list.
1472 * We move them the other way if the page is referenced by one or more
1473 * processes, from rmap.
1475 * If the pages are mostly unmapped, the processing is fast and it is
1476 * appropriate to hold zone->lru_lock across the whole operation. But if
1477 * the pages are mapped, the processing is slow (page_referenced()) so we
1478 * should drop zone->lru_lock around each page. It's impossible to balance
1479 * this, so instead we remove the pages from the LRU while processing them.
1480 * It is safe to rely on PG_active against the non-LRU pages in here because
1481 * nobody will play with that bit on a non-LRU page.
1483 * The downside is that we have to touch page->_count against each page.
1484 * But we had to alter page->flags anyway.
1487 static void move_active_pages_to_lru(struct zone
*zone
,
1488 struct list_head
*list
,
1491 unsigned long pgmoved
= 0;
1492 struct pagevec pvec
;
1495 pagevec_init(&pvec
, 1);
1497 while (!list_empty(list
)) {
1498 page
= lru_to_page(list
);
1500 VM_BUG_ON(PageLRU(page
));
1503 list_move(&page
->lru
, &zone
->lru
[lru
].list
);
1504 mem_cgroup_add_lru_list(page
, lru
);
1505 pgmoved
+= hpage_nr_pages(page
);
1507 if (!pagevec_add(&pvec
, page
) || list_empty(list
)) {
1508 spin_unlock_irq(&zone
->lru_lock
);
1509 if (buffer_heads_over_limit
)
1510 pagevec_strip(&pvec
);
1511 __pagevec_release(&pvec
);
1512 spin_lock_irq(&zone
->lru_lock
);
1515 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1516 if (!is_active_lru(lru
))
1517 __count_vm_events(PGDEACTIVATE
, pgmoved
);
1520 static void shrink_active_list(unsigned long nr_pages
, struct zone
*zone
,
1521 struct scan_control
*sc
, int priority
, int file
)
1523 unsigned long nr_taken
;
1524 unsigned long pgscanned
;
1525 unsigned long vm_flags
;
1526 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1527 LIST_HEAD(l_active
);
1528 LIST_HEAD(l_inactive
);
1530 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1531 unsigned long nr_rotated
= 0;
1534 spin_lock_irq(&zone
->lru_lock
);
1535 if (scanning_global_lru(sc
)) {
1536 nr_taken
= isolate_pages_global(nr_pages
, &l_hold
,
1537 &pgscanned
, sc
->order
,
1538 ISOLATE_ACTIVE
, zone
,
1540 zone
->pages_scanned
+= pgscanned
;
1542 nr_taken
= mem_cgroup_isolate_pages(nr_pages
, &l_hold
,
1543 &pgscanned
, sc
->order
,
1544 ISOLATE_ACTIVE
, zone
,
1545 sc
->mem_cgroup
, 1, file
);
1547 * mem_cgroup_isolate_pages() keeps track of
1548 * scanned pages on its own.
1552 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1554 __count_zone_vm_events(PGREFILL
, zone
, pgscanned
);
1556 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
, -nr_taken
);
1558 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
, -nr_taken
);
1559 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1560 spin_unlock_irq(&zone
->lru_lock
);
1562 while (!list_empty(&l_hold
)) {
1564 page
= lru_to_page(&l_hold
);
1565 list_del(&page
->lru
);
1567 if (unlikely(!page_evictable(page
, NULL
))) {
1568 putback_lru_page(page
);
1572 if (page_referenced(page
, 0, sc
->mem_cgroup
, &vm_flags
)) {
1573 nr_rotated
+= hpage_nr_pages(page
);
1575 * Identify referenced, file-backed active pages and
1576 * give them one more trip around the active list. So
1577 * that executable code get better chances to stay in
1578 * memory under moderate memory pressure. Anon pages
1579 * are not likely to be evicted by use-once streaming
1580 * IO, plus JVM can create lots of anon VM_EXEC pages,
1581 * so we ignore them here.
1583 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1584 list_add(&page
->lru
, &l_active
);
1589 ClearPageActive(page
); /* we are de-activating */
1590 list_add(&page
->lru
, &l_inactive
);
1594 * Move pages back to the lru list.
1596 spin_lock_irq(&zone
->lru_lock
);
1598 * Count referenced pages from currently used mappings as rotated,
1599 * even though only some of them are actually re-activated. This
1600 * helps balance scan pressure between file and anonymous pages in
1603 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1605 move_active_pages_to_lru(zone
, &l_active
,
1606 LRU_ACTIVE
+ file
* LRU_FILE
);
1607 move_active_pages_to_lru(zone
, &l_inactive
,
1608 LRU_BASE
+ file
* LRU_FILE
);
1609 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1610 spin_unlock_irq(&zone
->lru_lock
);
1614 static int inactive_anon_is_low_global(struct zone
*zone
)
1616 unsigned long active
, inactive
;
1618 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1619 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1621 if (inactive
* zone
->inactive_ratio
< active
)
1628 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1629 * @zone: zone to check
1630 * @sc: scan control of this context
1632 * Returns true if the zone does not have enough inactive anon pages,
1633 * meaning some active anon pages need to be deactivated.
1635 static int inactive_anon_is_low(struct zone
*zone
, struct scan_control
*sc
)
1640 * If we don't have swap space, anonymous page deactivation
1643 if (!total_swap_pages
)
1646 if (scanning_global_lru(sc
))
1647 low
= inactive_anon_is_low_global(zone
);
1649 low
= mem_cgroup_inactive_anon_is_low(sc
->mem_cgroup
);
1653 static inline int inactive_anon_is_low(struct zone
*zone
,
1654 struct scan_control
*sc
)
1660 static int inactive_file_is_low_global(struct zone
*zone
)
1662 unsigned long active
, inactive
;
1664 active
= zone_page_state(zone
, NR_ACTIVE_FILE
);
1665 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1667 return (active
> inactive
);
1671 * inactive_file_is_low - check if file pages need to be deactivated
1672 * @zone: zone to check
1673 * @sc: scan control of this context
1675 * When the system is doing streaming IO, memory pressure here
1676 * ensures that active file pages get deactivated, until more
1677 * than half of the file pages are on the inactive list.
1679 * Once we get to that situation, protect the system's working
1680 * set from being evicted by disabling active file page aging.
1682 * This uses a different ratio than the anonymous pages, because
1683 * the page cache uses a use-once replacement algorithm.
1685 static int inactive_file_is_low(struct zone
*zone
, struct scan_control
*sc
)
1689 if (scanning_global_lru(sc
))
1690 low
= inactive_file_is_low_global(zone
);
1692 low
= mem_cgroup_inactive_file_is_low(sc
->mem_cgroup
);
1696 static int inactive_list_is_low(struct zone
*zone
, struct scan_control
*sc
,
1700 return inactive_file_is_low(zone
, sc
);
1702 return inactive_anon_is_low(zone
, sc
);
1705 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1706 struct zone
*zone
, struct scan_control
*sc
, int priority
)
1708 int file
= is_file_lru(lru
);
1710 if (is_active_lru(lru
)) {
1711 if (inactive_list_is_low(zone
, sc
, file
))
1712 shrink_active_list(nr_to_scan
, zone
, sc
, priority
, file
);
1716 return shrink_inactive_list(nr_to_scan
, zone
, sc
, priority
, file
);
1720 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1721 * until we collected @swap_cluster_max pages to scan.
1723 static unsigned long nr_scan_try_batch(unsigned long nr_to_scan
,
1724 unsigned long *nr_saved_scan
)
1728 *nr_saved_scan
+= nr_to_scan
;
1729 nr
= *nr_saved_scan
;
1731 if (nr
>= SWAP_CLUSTER_MAX
)
1740 * Determine how aggressively the anon and file LRU lists should be
1741 * scanned. The relative value of each set of LRU lists is determined
1742 * by looking at the fraction of the pages scanned we did rotate back
1743 * onto the active list instead of evict.
1745 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1747 static void get_scan_count(struct zone
*zone
, struct scan_control
*sc
,
1748 unsigned long *nr
, int priority
)
1750 unsigned long anon
, file
, free
;
1751 unsigned long anon_prio
, file_prio
;
1752 unsigned long ap
, fp
;
1753 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1754 u64 fraction
[2], denominator
;
1758 /* If we have no swap space, do not bother scanning anon pages. */
1759 if (!sc
->may_swap
|| (nr_swap_pages
<= 0)) {
1767 anon
= zone_nr_lru_pages(zone
, sc
, LRU_ACTIVE_ANON
) +
1768 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_ANON
);
1769 file
= zone_nr_lru_pages(zone
, sc
, LRU_ACTIVE_FILE
) +
1770 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_FILE
);
1772 if (scanning_global_lru(sc
)) {
1773 free
= zone_page_state(zone
, NR_FREE_PAGES
);
1774 /* If we have very few page cache pages,
1775 force-scan anon pages. */
1776 if (unlikely(file
+ free
<= high_wmark_pages(zone
))) {
1785 * With swappiness at 100, anonymous and file have the same priority.
1786 * This scanning priority is essentially the inverse of IO cost.
1788 anon_prio
= sc
->swappiness
;
1789 file_prio
= 200 - sc
->swappiness
;
1792 * OK, so we have swap space and a fair amount of page cache
1793 * pages. We use the recently rotated / recently scanned
1794 * ratios to determine how valuable each cache is.
1796 * Because workloads change over time (and to avoid overflow)
1797 * we keep these statistics as a floating average, which ends
1798 * up weighing recent references more than old ones.
1800 * anon in [0], file in [1]
1802 spin_lock_irq(&zone
->lru_lock
);
1803 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
1804 reclaim_stat
->recent_scanned
[0] /= 2;
1805 reclaim_stat
->recent_rotated
[0] /= 2;
1808 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
1809 reclaim_stat
->recent_scanned
[1] /= 2;
1810 reclaim_stat
->recent_rotated
[1] /= 2;
1814 * The amount of pressure on anon vs file pages is inversely
1815 * proportional to the fraction of recently scanned pages on
1816 * each list that were recently referenced and in active use.
1818 ap
= (anon_prio
+ 1) * (reclaim_stat
->recent_scanned
[0] + 1);
1819 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
1821 fp
= (file_prio
+ 1) * (reclaim_stat
->recent_scanned
[1] + 1);
1822 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
1823 spin_unlock_irq(&zone
->lru_lock
);
1827 denominator
= ap
+ fp
+ 1;
1829 for_each_evictable_lru(l
) {
1830 int file
= is_file_lru(l
);
1833 scan
= zone_nr_lru_pages(zone
, sc
, l
);
1834 if (priority
|| noswap
) {
1836 scan
= div64_u64(scan
* fraction
[file
], denominator
);
1838 nr
[l
] = nr_scan_try_batch(scan
,
1839 &reclaim_stat
->nr_saved_scan
[l
]);
1844 * Reclaim/compaction depends on a number of pages being freed. To avoid
1845 * disruption to the system, a small number of order-0 pages continue to be
1846 * rotated and reclaimed in the normal fashion. However, by the time we get
1847 * back to the allocator and call try_to_compact_zone(), we ensure that
1848 * there are enough free pages for it to be likely successful
1850 static inline bool should_continue_reclaim(struct zone
*zone
,
1851 unsigned long nr_reclaimed
,
1852 unsigned long nr_scanned
,
1853 struct scan_control
*sc
)
1855 unsigned long pages_for_compaction
;
1856 unsigned long inactive_lru_pages
;
1858 /* If not in reclaim/compaction mode, stop */
1859 if (!(sc
->reclaim_mode
& RECLAIM_MODE_COMPACTION
))
1862 /* Consider stopping depending on scan and reclaim activity */
1863 if (sc
->gfp_mask
& __GFP_REPEAT
) {
1865 * For __GFP_REPEAT allocations, stop reclaiming if the
1866 * full LRU list has been scanned and we are still failing
1867 * to reclaim pages. This full LRU scan is potentially
1868 * expensive but a __GFP_REPEAT caller really wants to succeed
1870 if (!nr_reclaimed
&& !nr_scanned
)
1874 * For non-__GFP_REPEAT allocations which can presumably
1875 * fail without consequence, stop if we failed to reclaim
1876 * any pages from the last SWAP_CLUSTER_MAX number of
1877 * pages that were scanned. This will return to the
1878 * caller faster at the risk reclaim/compaction and
1879 * the resulting allocation attempt fails
1886 * If we have not reclaimed enough pages for compaction and the
1887 * inactive lists are large enough, continue reclaiming
1889 pages_for_compaction
= (2UL << sc
->order
);
1890 inactive_lru_pages
= zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_ANON
) +
1891 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_FILE
);
1892 if (sc
->nr_reclaimed
< pages_for_compaction
&&
1893 inactive_lru_pages
> pages_for_compaction
)
1896 /* If compaction would go ahead or the allocation would succeed, stop */
1897 switch (compaction_suitable(zone
, sc
->order
)) {
1898 case COMPACT_PARTIAL
:
1899 case COMPACT_CONTINUE
:
1907 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1909 static void shrink_zone(int priority
, struct zone
*zone
,
1910 struct scan_control
*sc
)
1912 unsigned long nr
[NR_LRU_LISTS
];
1913 unsigned long nr_to_scan
;
1915 unsigned long nr_reclaimed
, nr_scanned
;
1916 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
1920 nr_scanned
= sc
->nr_scanned
;
1921 get_scan_count(zone
, sc
, nr
, priority
);
1923 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
1924 nr
[LRU_INACTIVE_FILE
]) {
1925 for_each_evictable_lru(l
) {
1927 nr_to_scan
= min_t(unsigned long,
1928 nr
[l
], SWAP_CLUSTER_MAX
);
1929 nr
[l
] -= nr_to_scan
;
1931 nr_reclaimed
+= shrink_list(l
, nr_to_scan
,
1932 zone
, sc
, priority
);
1936 * On large memory systems, scan >> priority can become
1937 * really large. This is fine for the starting priority;
1938 * we want to put equal scanning pressure on each zone.
1939 * However, if the VM has a harder time of freeing pages,
1940 * with multiple processes reclaiming pages, the total
1941 * freeing target can get unreasonably large.
1943 if (nr_reclaimed
>= nr_to_reclaim
&& priority
< DEF_PRIORITY
)
1946 sc
->nr_reclaimed
+= nr_reclaimed
;
1949 * Even if we did not try to evict anon pages at all, we want to
1950 * rebalance the anon lru active/inactive ratio.
1952 if (inactive_anon_is_low(zone
, sc
))
1953 shrink_active_list(SWAP_CLUSTER_MAX
, zone
, sc
, priority
, 0);
1955 /* reclaim/compaction might need reclaim to continue */
1956 if (should_continue_reclaim(zone
, nr_reclaimed
,
1957 sc
->nr_scanned
- nr_scanned
, sc
))
1960 throttle_vm_writeout(sc
->gfp_mask
);
1964 * This is the direct reclaim path, for page-allocating processes. We only
1965 * try to reclaim pages from zones which will satisfy the caller's allocation
1968 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1970 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1972 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1973 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1974 * zone defense algorithm.
1976 * If a zone is deemed to be full of pinned pages then just give it a light
1977 * scan then give up on it.
1979 static void shrink_zones(int priority
, struct zonelist
*zonelist
,
1980 struct scan_control
*sc
)
1985 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
1986 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
1987 if (!populated_zone(zone
))
1990 * Take care memory controller reclaiming has small influence
1993 if (scanning_global_lru(sc
)) {
1994 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1996 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
1997 continue; /* Let kswapd poll it */
2000 shrink_zone(priority
, zone
, sc
);
2004 static bool zone_reclaimable(struct zone
*zone
)
2006 return zone
->pages_scanned
< zone_reclaimable_pages(zone
) * 6;
2009 /* All zones in zonelist are unreclaimable? */
2010 static bool all_unreclaimable(struct zonelist
*zonelist
,
2011 struct scan_control
*sc
)
2016 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2017 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2018 if (!populated_zone(zone
))
2020 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2022 if (!zone
->all_unreclaimable
)
2030 * This is the main entry point to direct page reclaim.
2032 * If a full scan of the inactive list fails to free enough memory then we
2033 * are "out of memory" and something needs to be killed.
2035 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2036 * high - the zone may be full of dirty or under-writeback pages, which this
2037 * caller can't do much about. We kick the writeback threads and take explicit
2038 * naps in the hope that some of these pages can be written. But if the
2039 * allocating task holds filesystem locks which prevent writeout this might not
2040 * work, and the allocation attempt will fail.
2042 * returns: 0, if no pages reclaimed
2043 * else, the number of pages reclaimed
2045 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2046 struct scan_control
*sc
)
2049 unsigned long total_scanned
= 0;
2050 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2053 unsigned long writeback_threshold
;
2056 delayacct_freepages_start();
2058 if (scanning_global_lru(sc
))
2059 count_vm_event(ALLOCSTALL
);
2061 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2064 disable_swap_token();
2065 shrink_zones(priority
, zonelist
, sc
);
2067 * Don't shrink slabs when reclaiming memory from
2068 * over limit cgroups
2070 if (scanning_global_lru(sc
)) {
2071 unsigned long lru_pages
= 0;
2072 for_each_zone_zonelist(zone
, z
, zonelist
,
2073 gfp_zone(sc
->gfp_mask
)) {
2074 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2077 lru_pages
+= zone_reclaimable_pages(zone
);
2080 shrink_slab(sc
->nr_scanned
, sc
->gfp_mask
, lru_pages
);
2081 if (reclaim_state
) {
2082 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2083 reclaim_state
->reclaimed_slab
= 0;
2086 total_scanned
+= sc
->nr_scanned
;
2087 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
2091 * Try to write back as many pages as we just scanned. This
2092 * tends to cause slow streaming writers to write data to the
2093 * disk smoothly, at the dirtying rate, which is nice. But
2094 * that's undesirable in laptop mode, where we *want* lumpy
2095 * writeout. So in laptop mode, write out the whole world.
2097 writeback_threshold
= sc
->nr_to_reclaim
+ sc
->nr_to_reclaim
/ 2;
2098 if (total_scanned
> writeback_threshold
) {
2099 wakeup_flusher_threads(laptop_mode
? 0 : total_scanned
);
2100 sc
->may_writepage
= 1;
2103 /* Take a nap, wait for some writeback to complete */
2104 if (!sc
->hibernation_mode
&& sc
->nr_scanned
&&
2105 priority
< DEF_PRIORITY
- 2) {
2106 struct zone
*preferred_zone
;
2108 first_zones_zonelist(zonelist
, gfp_zone(sc
->gfp_mask
),
2109 &cpuset_current_mems_allowed
,
2111 wait_iff_congested(preferred_zone
, BLK_RW_ASYNC
, HZ
/10);
2116 delayacct_freepages_end();
2119 if (sc
->nr_reclaimed
)
2120 return sc
->nr_reclaimed
;
2123 * As hibernation is going on, kswapd is freezed so that it can't mark
2124 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2127 if (oom_killer_disabled
)
2130 /* top priority shrink_zones still had more to do? don't OOM, then */
2131 if (scanning_global_lru(sc
) && !all_unreclaimable(zonelist
, sc
))
2137 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
2138 gfp_t gfp_mask
, nodemask_t
*nodemask
)
2140 unsigned long nr_reclaimed
;
2141 struct scan_control sc
= {
2142 .gfp_mask
= gfp_mask
,
2143 .may_writepage
= !laptop_mode
,
2144 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2147 .swappiness
= vm_swappiness
,
2150 .nodemask
= nodemask
,
2153 trace_mm_vmscan_direct_reclaim_begin(order
,
2157 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2159 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
2161 return nr_reclaimed
;
2164 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2166 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup
*mem
,
2167 gfp_t gfp_mask
, bool noswap
,
2168 unsigned int swappiness
,
2171 struct scan_control sc
= {
2172 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2173 .may_writepage
= !laptop_mode
,
2175 .may_swap
= !noswap
,
2176 .swappiness
= swappiness
,
2180 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2181 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2183 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2188 * NOTE: Although we can get the priority field, using it
2189 * here is not a good idea, since it limits the pages we can scan.
2190 * if we don't reclaim here, the shrink_zone from balance_pgdat
2191 * will pick up pages from other mem cgroup's as well. We hack
2192 * the priority and make it zero.
2194 shrink_zone(0, zone
, &sc
);
2196 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
2198 return sc
.nr_reclaimed
;
2201 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*mem_cont
,
2204 unsigned int swappiness
)
2206 struct zonelist
*zonelist
;
2207 unsigned long nr_reclaimed
;
2208 struct scan_control sc
= {
2209 .may_writepage
= !laptop_mode
,
2211 .may_swap
= !noswap
,
2212 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2213 .swappiness
= swappiness
,
2215 .mem_cgroup
= mem_cont
,
2216 .nodemask
= NULL
, /* we don't care the placement */
2219 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2220 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2221 zonelist
= NODE_DATA(numa_node_id())->node_zonelists
;
2223 trace_mm_vmscan_memcg_reclaim_begin(0,
2227 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2229 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
2231 return nr_reclaimed
;
2236 * pgdat_balanced is used when checking if a node is balanced for high-order
2237 * allocations. Only zones that meet watermarks and are in a zone allowed
2238 * by the callers classzone_idx are added to balanced_pages. The total of
2239 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2240 * for the node to be considered balanced. Forcing all zones to be balanced
2241 * for high orders can cause excessive reclaim when there are imbalanced zones.
2242 * The choice of 25% is due to
2243 * o a 16M DMA zone that is balanced will not balance a zone on any
2244 * reasonable sized machine
2245 * o On all other machines, the top zone must be at least a reasonable
2246 * percentage of the middle zones. For example, on 32-bit x86, highmem
2247 * would need to be at least 256M for it to be balance a whole node.
2248 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2249 * to balance a node on its own. These seemed like reasonable ratios.
2251 static bool pgdat_balanced(pg_data_t
*pgdat
, unsigned long balanced_pages
,
2254 unsigned long present_pages
= 0;
2257 for (i
= 0; i
<= classzone_idx
; i
++)
2258 present_pages
+= pgdat
->node_zones
[i
].present_pages
;
2260 /* A special case here: if zone has no page, we think it's balanced */
2261 return balanced_pages
>= (present_pages
>> 2);
2264 /* is kswapd sleeping prematurely? */
2265 static bool sleeping_prematurely(pg_data_t
*pgdat
, int order
, long remaining
,
2269 unsigned long balanced
= 0;
2270 bool all_zones_ok
= true;
2272 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2276 /* Check the watermark levels */
2277 for (i
= 0; i
<= classzone_idx
; i
++) {
2278 struct zone
*zone
= pgdat
->node_zones
+ i
;
2280 if (!populated_zone(zone
))
2284 * balance_pgdat() skips over all_unreclaimable after
2285 * DEF_PRIORITY. Effectively, it considers them balanced so
2286 * they must be considered balanced here as well if kswapd
2289 if (zone
->all_unreclaimable
) {
2290 balanced
+= zone
->present_pages
;
2294 if (!zone_watermark_ok_safe(zone
, order
, high_wmark_pages(zone
),
2296 all_zones_ok
= false;
2298 balanced
+= zone
->present_pages
;
2302 * For high-order requests, the balanced zones must contain at least
2303 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2307 return !pgdat_balanced(pgdat
, balanced
, classzone_idx
);
2309 return !all_zones_ok
;
2313 * For kswapd, balance_pgdat() will work across all this node's zones until
2314 * they are all at high_wmark_pages(zone).
2316 * Returns the final order kswapd was reclaiming at
2318 * There is special handling here for zones which are full of pinned pages.
2319 * This can happen if the pages are all mlocked, or if they are all used by
2320 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2321 * What we do is to detect the case where all pages in the zone have been
2322 * scanned twice and there has been zero successful reclaim. Mark the zone as
2323 * dead and from now on, only perform a short scan. Basically we're polling
2324 * the zone for when the problem goes away.
2326 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2327 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2328 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2329 * lower zones regardless of the number of free pages in the lower zones. This
2330 * interoperates with the page allocator fallback scheme to ensure that aging
2331 * of pages is balanced across the zones.
2333 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
,
2337 unsigned long balanced
;
2340 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
2341 unsigned long total_scanned
;
2342 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2343 struct scan_control sc
= {
2344 .gfp_mask
= GFP_KERNEL
,
2348 * kswapd doesn't want to be bailed out while reclaim. because
2349 * we want to put equal scanning pressure on each zone.
2351 .nr_to_reclaim
= ULONG_MAX
,
2352 .swappiness
= vm_swappiness
,
2358 sc
.nr_reclaimed
= 0;
2359 sc
.may_writepage
= !laptop_mode
;
2360 count_vm_event(PAGEOUTRUN
);
2362 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2363 unsigned long lru_pages
= 0;
2364 int has_under_min_watermark_zone
= 0;
2366 /* The swap token gets in the way of swapout... */
2368 disable_swap_token();
2374 * Scan in the highmem->dma direction for the highest
2375 * zone which needs scanning
2377 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
2378 struct zone
*zone
= pgdat
->node_zones
+ i
;
2380 if (!populated_zone(zone
))
2383 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2387 * Do some background aging of the anon list, to give
2388 * pages a chance to be referenced before reclaiming.
2390 if (inactive_anon_is_low(zone
, &sc
))
2391 shrink_active_list(SWAP_CLUSTER_MAX
, zone
,
2394 if (!zone_watermark_ok_safe(zone
, order
,
2395 high_wmark_pages(zone
), 0, 0)) {
2404 for (i
= 0; i
<= end_zone
; i
++) {
2405 struct zone
*zone
= pgdat
->node_zones
+ i
;
2407 lru_pages
+= zone_reclaimable_pages(zone
);
2411 * Now scan the zone in the dma->highmem direction, stopping
2412 * at the last zone which needs scanning.
2414 * We do this because the page allocator works in the opposite
2415 * direction. This prevents the page allocator from allocating
2416 * pages behind kswapd's direction of progress, which would
2417 * cause too much scanning of the lower zones.
2419 for (i
= 0; i
<= end_zone
; i
++) {
2420 struct zone
*zone
= pgdat
->node_zones
+ i
;
2422 unsigned long balance_gap
;
2424 if (!populated_zone(zone
))
2427 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2433 * Call soft limit reclaim before calling shrink_zone.
2434 * For now we ignore the return value
2436 mem_cgroup_soft_limit_reclaim(zone
, order
, sc
.gfp_mask
);
2439 * We put equal pressure on every zone, unless
2440 * one zone has way too many pages free
2441 * already. The "too many pages" is defined
2442 * as the high wmark plus a "gap" where the
2443 * gap is either the low watermark or 1%
2444 * of the zone, whichever is smaller.
2446 balance_gap
= min(low_wmark_pages(zone
),
2447 (zone
->present_pages
+
2448 KSWAPD_ZONE_BALANCE_GAP_RATIO
-1) /
2449 KSWAPD_ZONE_BALANCE_GAP_RATIO
);
2450 if (!zone_watermark_ok_safe(zone
, order
,
2451 high_wmark_pages(zone
) + balance_gap
,
2453 shrink_zone(priority
, zone
, &sc
);
2455 reclaim_state
->reclaimed_slab
= 0;
2456 nr_slab
= shrink_slab(sc
.nr_scanned
, GFP_KERNEL
,
2458 sc
.nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2459 total_scanned
+= sc
.nr_scanned
;
2461 if (nr_slab
== 0 && !zone_reclaimable(zone
))
2462 zone
->all_unreclaimable
= 1;
2466 * If we've done a decent amount of scanning and
2467 * the reclaim ratio is low, start doing writepage
2468 * even in laptop mode
2470 if (total_scanned
> SWAP_CLUSTER_MAX
* 2 &&
2471 total_scanned
> sc
.nr_reclaimed
+ sc
.nr_reclaimed
/ 2)
2472 sc
.may_writepage
= 1;
2474 if (zone
->all_unreclaimable
)
2477 if (!zone_watermark_ok_safe(zone
, order
,
2478 high_wmark_pages(zone
), end_zone
, 0)) {
2481 * We are still under min water mark. This
2482 * means that we have a GFP_ATOMIC allocation
2483 * failure risk. Hurry up!
2485 if (!zone_watermark_ok_safe(zone
, order
,
2486 min_wmark_pages(zone
), end_zone
, 0))
2487 has_under_min_watermark_zone
= 1;
2490 * If a zone reaches its high watermark,
2491 * consider it to be no longer congested. It's
2492 * possible there are dirty pages backed by
2493 * congested BDIs but as pressure is relieved,
2494 * spectulatively avoid congestion waits
2496 zone_clear_flag(zone
, ZONE_CONGESTED
);
2497 if (i
<= *classzone_idx
)
2498 balanced
+= zone
->present_pages
;
2502 if (all_zones_ok
|| (order
&& pgdat_balanced(pgdat
, balanced
, *classzone_idx
)))
2503 break; /* kswapd: all done */
2505 * OK, kswapd is getting into trouble. Take a nap, then take
2506 * another pass across the zones.
2508 if (total_scanned
&& (priority
< DEF_PRIORITY
- 2)) {
2509 if (has_under_min_watermark_zone
)
2510 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT
);
2512 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
2516 * We do this so kswapd doesn't build up large priorities for
2517 * example when it is freeing in parallel with allocators. It
2518 * matches the direct reclaim path behaviour in terms of impact
2519 * on zone->*_priority.
2521 if (sc
.nr_reclaimed
>= SWAP_CLUSTER_MAX
)
2527 * order-0: All zones must meet high watermark for a balanced node
2528 * high-order: Balanced zones must make up at least 25% of the node
2529 * for the node to be balanced
2531 if (!(all_zones_ok
|| (order
&& pgdat_balanced(pgdat
, balanced
, *classzone_idx
)))) {
2537 * Fragmentation may mean that the system cannot be
2538 * rebalanced for high-order allocations in all zones.
2539 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2540 * it means the zones have been fully scanned and are still
2541 * not balanced. For high-order allocations, there is
2542 * little point trying all over again as kswapd may
2545 * Instead, recheck all watermarks at order-0 as they
2546 * are the most important. If watermarks are ok, kswapd will go
2547 * back to sleep. High-order users can still perform direct
2548 * reclaim if they wish.
2550 if (sc
.nr_reclaimed
< SWAP_CLUSTER_MAX
)
2551 order
= sc
.order
= 0;
2557 * If kswapd was reclaiming at a higher order, it has the option of
2558 * sleeping without all zones being balanced. Before it does, it must
2559 * ensure that the watermarks for order-0 on *all* zones are met and
2560 * that the congestion flags are cleared. The congestion flag must
2561 * be cleared as kswapd is the only mechanism that clears the flag
2562 * and it is potentially going to sleep here.
2565 for (i
= 0; i
<= end_zone
; i
++) {
2566 struct zone
*zone
= pgdat
->node_zones
+ i
;
2568 if (!populated_zone(zone
))
2571 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2574 /* Confirm the zone is balanced for order-0 */
2575 if (!zone_watermark_ok(zone
, 0,
2576 high_wmark_pages(zone
), 0, 0)) {
2577 order
= sc
.order
= 0;
2581 /* If balanced, clear the congested flag */
2582 zone_clear_flag(zone
, ZONE_CONGESTED
);
2587 * Return the order we were reclaiming at so sleeping_prematurely()
2588 * makes a decision on the order we were last reclaiming at. However,
2589 * if another caller entered the allocator slow path while kswapd
2590 * was awake, order will remain at the higher level
2592 *classzone_idx
= end_zone
;
2596 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
2601 if (freezing(current
) || kthread_should_stop())
2604 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2606 /* Try to sleep for a short interval */
2607 if (!sleeping_prematurely(pgdat
, order
, remaining
, classzone_idx
)) {
2608 remaining
= schedule_timeout(HZ
/10);
2609 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2610 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2614 * After a short sleep, check if it was a premature sleep. If not, then
2615 * go fully to sleep until explicitly woken up.
2617 if (!sleeping_prematurely(pgdat
, order
, remaining
, classzone_idx
)) {
2618 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
2621 * vmstat counters are not perfectly accurate and the estimated
2622 * value for counters such as NR_FREE_PAGES can deviate from the
2623 * true value by nr_online_cpus * threshold. To avoid the zone
2624 * watermarks being breached while under pressure, we reduce the
2625 * per-cpu vmstat threshold while kswapd is awake and restore
2626 * them before going back to sleep.
2628 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
2630 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
2633 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
2635 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
2637 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2641 * The background pageout daemon, started as a kernel thread
2642 * from the init process.
2644 * This basically trickles out pages so that we have _some_
2645 * free memory available even if there is no other activity
2646 * that frees anything up. This is needed for things like routing
2647 * etc, where we otherwise might have all activity going on in
2648 * asynchronous contexts that cannot page things out.
2650 * If there are applications that are active memory-allocators
2651 * (most normal use), this basically shouldn't matter.
2653 static int kswapd(void *p
)
2655 unsigned long order
;
2657 pg_data_t
*pgdat
= (pg_data_t
*)p
;
2658 struct task_struct
*tsk
= current
;
2660 struct reclaim_state reclaim_state
= {
2661 .reclaimed_slab
= 0,
2663 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
2665 lockdep_set_current_reclaim_state(GFP_KERNEL
);
2667 if (!cpumask_empty(cpumask
))
2668 set_cpus_allowed_ptr(tsk
, cpumask
);
2669 current
->reclaim_state
= &reclaim_state
;
2672 * Tell the memory management that we're a "memory allocator",
2673 * and that if we need more memory we should get access to it
2674 * regardless (see "__alloc_pages()"). "kswapd" should
2675 * never get caught in the normal page freeing logic.
2677 * (Kswapd normally doesn't need memory anyway, but sometimes
2678 * you need a small amount of memory in order to be able to
2679 * page out something else, and this flag essentially protects
2680 * us from recursively trying to free more memory as we're
2681 * trying to free the first piece of memory in the first place).
2683 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
2687 classzone_idx
= MAX_NR_ZONES
- 1;
2689 unsigned long new_order
;
2690 int new_classzone_idx
;
2693 new_order
= pgdat
->kswapd_max_order
;
2694 new_classzone_idx
= pgdat
->classzone_idx
;
2695 pgdat
->kswapd_max_order
= 0;
2696 pgdat
->classzone_idx
= MAX_NR_ZONES
- 1;
2697 if (order
< new_order
|| classzone_idx
> new_classzone_idx
) {
2699 * Don't sleep if someone wants a larger 'order'
2700 * allocation or has tigher zone constraints
2703 classzone_idx
= new_classzone_idx
;
2705 kswapd_try_to_sleep(pgdat
, order
, classzone_idx
);
2706 order
= pgdat
->kswapd_max_order
;
2707 classzone_idx
= pgdat
->classzone_idx
;
2708 pgdat
->kswapd_max_order
= 0;
2709 pgdat
->classzone_idx
= MAX_NR_ZONES
- 1;
2712 ret
= try_to_freeze();
2713 if (kthread_should_stop())
2717 * We can speed up thawing tasks if we don't call balance_pgdat
2718 * after returning from the refrigerator
2721 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, order
);
2722 order
= balance_pgdat(pgdat
, order
, &classzone_idx
);
2729 * A zone is low on free memory, so wake its kswapd task to service it.
2731 void wakeup_kswapd(struct zone
*zone
, int order
, enum zone_type classzone_idx
)
2735 if (!populated_zone(zone
))
2738 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2740 pgdat
= zone
->zone_pgdat
;
2741 if (pgdat
->kswapd_max_order
< order
) {
2742 pgdat
->kswapd_max_order
= order
;
2743 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
, classzone_idx
);
2745 if (!waitqueue_active(&pgdat
->kswapd_wait
))
2747 if (zone_watermark_ok_safe(zone
, order
, low_wmark_pages(zone
), 0, 0))
2750 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, zone_idx(zone
), order
);
2751 wake_up_interruptible(&pgdat
->kswapd_wait
);
2755 * The reclaimable count would be mostly accurate.
2756 * The less reclaimable pages may be
2757 * - mlocked pages, which will be moved to unevictable list when encountered
2758 * - mapped pages, which may require several travels to be reclaimed
2759 * - dirty pages, which is not "instantly" reclaimable
2761 unsigned long global_reclaimable_pages(void)
2765 nr
= global_page_state(NR_ACTIVE_FILE
) +
2766 global_page_state(NR_INACTIVE_FILE
);
2768 if (nr_swap_pages
> 0)
2769 nr
+= global_page_state(NR_ACTIVE_ANON
) +
2770 global_page_state(NR_INACTIVE_ANON
);
2775 unsigned long zone_reclaimable_pages(struct zone
*zone
)
2779 nr
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
2780 zone_page_state(zone
, NR_INACTIVE_FILE
);
2782 if (nr_swap_pages
> 0)
2783 nr
+= zone_page_state(zone
, NR_ACTIVE_ANON
) +
2784 zone_page_state(zone
, NR_INACTIVE_ANON
);
2789 #ifdef CONFIG_HIBERNATION
2791 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2794 * Rather than trying to age LRUs the aim is to preserve the overall
2795 * LRU order by reclaiming preferentially
2796 * inactive > active > active referenced > active mapped
2798 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
2800 struct reclaim_state reclaim_state
;
2801 struct scan_control sc
= {
2802 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
2806 .nr_to_reclaim
= nr_to_reclaim
,
2807 .hibernation_mode
= 1,
2808 .swappiness
= vm_swappiness
,
2811 struct zonelist
* zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
2812 struct task_struct
*p
= current
;
2813 unsigned long nr_reclaimed
;
2815 p
->flags
|= PF_MEMALLOC
;
2816 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
2817 reclaim_state
.reclaimed_slab
= 0;
2818 p
->reclaim_state
= &reclaim_state
;
2820 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2822 p
->reclaim_state
= NULL
;
2823 lockdep_clear_current_reclaim_state();
2824 p
->flags
&= ~PF_MEMALLOC
;
2826 return nr_reclaimed
;
2828 #endif /* CONFIG_HIBERNATION */
2830 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2831 not required for correctness. So if the last cpu in a node goes
2832 away, we get changed to run anywhere: as the first one comes back,
2833 restore their cpu bindings. */
2834 static int __devinit
cpu_callback(struct notifier_block
*nfb
,
2835 unsigned long action
, void *hcpu
)
2839 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
2840 for_each_node_state(nid
, N_HIGH_MEMORY
) {
2841 pg_data_t
*pgdat
= NODE_DATA(nid
);
2842 const struct cpumask
*mask
;
2844 mask
= cpumask_of_node(pgdat
->node_id
);
2846 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
2847 /* One of our CPUs online: restore mask */
2848 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
2855 * This kswapd start function will be called by init and node-hot-add.
2856 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2858 int kswapd_run(int nid
)
2860 pg_data_t
*pgdat
= NODE_DATA(nid
);
2866 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
2867 if (IS_ERR(pgdat
->kswapd
)) {
2868 /* failure at boot is fatal */
2869 BUG_ON(system_state
== SYSTEM_BOOTING
);
2870 printk("Failed to start kswapd on node %d\n",nid
);
2877 * Called by memory hotplug when all memory in a node is offlined.
2879 void kswapd_stop(int nid
)
2881 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
2884 kthread_stop(kswapd
);
2887 static int __init
kswapd_init(void)
2892 for_each_node_state(nid
, N_HIGH_MEMORY
)
2894 hotcpu_notifier(cpu_callback
, 0);
2898 module_init(kswapd_init
)
2904 * If non-zero call zone_reclaim when the number of free pages falls below
2907 int zone_reclaim_mode __read_mostly
;
2909 #define RECLAIM_OFF 0
2910 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2911 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2912 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2915 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2916 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2919 #define ZONE_RECLAIM_PRIORITY 4
2922 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2925 int sysctl_min_unmapped_ratio
= 1;
2928 * If the number of slab pages in a zone grows beyond this percentage then
2929 * slab reclaim needs to occur.
2931 int sysctl_min_slab_ratio
= 5;
2933 static inline unsigned long zone_unmapped_file_pages(struct zone
*zone
)
2935 unsigned long file_mapped
= zone_page_state(zone
, NR_FILE_MAPPED
);
2936 unsigned long file_lru
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
2937 zone_page_state(zone
, NR_ACTIVE_FILE
);
2940 * It's possible for there to be more file mapped pages than
2941 * accounted for by the pages on the file LRU lists because
2942 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2944 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
2947 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
2948 static long zone_pagecache_reclaimable(struct zone
*zone
)
2950 long nr_pagecache_reclaimable
;
2954 * If RECLAIM_SWAP is set, then all file pages are considered
2955 * potentially reclaimable. Otherwise, we have to worry about
2956 * pages like swapcache and zone_unmapped_file_pages() provides
2959 if (zone_reclaim_mode
& RECLAIM_SWAP
)
2960 nr_pagecache_reclaimable
= zone_page_state(zone
, NR_FILE_PAGES
);
2962 nr_pagecache_reclaimable
= zone_unmapped_file_pages(zone
);
2964 /* If we can't clean pages, remove dirty pages from consideration */
2965 if (!(zone_reclaim_mode
& RECLAIM_WRITE
))
2966 delta
+= zone_page_state(zone
, NR_FILE_DIRTY
);
2968 /* Watch for any possible underflows due to delta */
2969 if (unlikely(delta
> nr_pagecache_reclaimable
))
2970 delta
= nr_pagecache_reclaimable
;
2972 return nr_pagecache_reclaimable
- delta
;
2976 * Try to free up some pages from this zone through reclaim.
2978 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
2980 /* Minimum pages needed in order to stay on node */
2981 const unsigned long nr_pages
= 1 << order
;
2982 struct task_struct
*p
= current
;
2983 struct reclaim_state reclaim_state
;
2985 struct scan_control sc
= {
2986 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
2987 .may_unmap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
2989 .nr_to_reclaim
= max_t(unsigned long, nr_pages
,
2991 .gfp_mask
= gfp_mask
,
2992 .swappiness
= vm_swappiness
,
2995 unsigned long nr_slab_pages0
, nr_slab_pages1
;
2999 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3000 * and we also need to be able to write out pages for RECLAIM_WRITE
3003 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
3004 lockdep_set_current_reclaim_state(gfp_mask
);
3005 reclaim_state
.reclaimed_slab
= 0;
3006 p
->reclaim_state
= &reclaim_state
;
3008 if (zone_pagecache_reclaimable(zone
) > zone
->min_unmapped_pages
) {
3010 * Free memory by calling shrink zone with increasing
3011 * priorities until we have enough memory freed.
3013 priority
= ZONE_RECLAIM_PRIORITY
;
3015 shrink_zone(priority
, zone
, &sc
);
3017 } while (priority
>= 0 && sc
.nr_reclaimed
< nr_pages
);
3020 nr_slab_pages0
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3021 if (nr_slab_pages0
> zone
->min_slab_pages
) {
3023 * shrink_slab() does not currently allow us to determine how
3024 * many pages were freed in this zone. So we take the current
3025 * number of slab pages and shake the slab until it is reduced
3026 * by the same nr_pages that we used for reclaiming unmapped
3029 * Note that shrink_slab will free memory on all zones and may
3033 unsigned long lru_pages
= zone_reclaimable_pages(zone
);
3035 /* No reclaimable slab or very low memory pressure */
3036 if (!shrink_slab(sc
.nr_scanned
, gfp_mask
, lru_pages
))
3039 /* Freed enough memory */
3040 nr_slab_pages1
= zone_page_state(zone
,
3041 NR_SLAB_RECLAIMABLE
);
3042 if (nr_slab_pages1
+ nr_pages
<= nr_slab_pages0
)
3047 * Update nr_reclaimed by the number of slab pages we
3048 * reclaimed from this zone.
3050 nr_slab_pages1
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3051 if (nr_slab_pages1
< nr_slab_pages0
)
3052 sc
.nr_reclaimed
+= nr_slab_pages0
- nr_slab_pages1
;
3055 p
->reclaim_state
= NULL
;
3056 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
3057 lockdep_clear_current_reclaim_state();
3058 return sc
.nr_reclaimed
>= nr_pages
;
3061 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3067 * Zone reclaim reclaims unmapped file backed pages and
3068 * slab pages if we are over the defined limits.
3070 * A small portion of unmapped file backed pages is needed for
3071 * file I/O otherwise pages read by file I/O will be immediately
3072 * thrown out if the zone is overallocated. So we do not reclaim
3073 * if less than a specified percentage of the zone is used by
3074 * unmapped file backed pages.
3076 if (zone_pagecache_reclaimable(zone
) <= zone
->min_unmapped_pages
&&
3077 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) <= zone
->min_slab_pages
)
3078 return ZONE_RECLAIM_FULL
;
3080 if (zone
->all_unreclaimable
)
3081 return ZONE_RECLAIM_FULL
;
3084 * Do not scan if the allocation should not be delayed.
3086 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
3087 return ZONE_RECLAIM_NOSCAN
;
3090 * Only run zone reclaim on the local zone or on zones that do not
3091 * have associated processors. This will favor the local processor
3092 * over remote processors and spread off node memory allocations
3093 * as wide as possible.
3095 node_id
= zone_to_nid(zone
);
3096 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
3097 return ZONE_RECLAIM_NOSCAN
;
3099 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
3100 return ZONE_RECLAIM_NOSCAN
;
3102 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
3103 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);
3106 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
3113 * page_evictable - test whether a page is evictable
3114 * @page: the page to test
3115 * @vma: the VMA in which the page is or will be mapped, may be NULL
3117 * Test whether page is evictable--i.e., should be placed on active/inactive
3118 * lists vs unevictable list. The vma argument is !NULL when called from the
3119 * fault path to determine how to instantate a new page.
3121 * Reasons page might not be evictable:
3122 * (1) page's mapping marked unevictable
3123 * (2) page is part of an mlocked VMA
3126 int page_evictable(struct page
*page
, struct vm_area_struct
*vma
)
3129 if (mapping_unevictable(page_mapping(page
)))
3132 if (PageMlocked(page
) || (vma
&& is_mlocked_vma(vma
, page
)))
3139 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3140 * @page: page to check evictability and move to appropriate lru list
3141 * @zone: zone page is in
3143 * Checks a page for evictability and moves the page to the appropriate
3146 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3147 * have PageUnevictable set.
3149 static void check_move_unevictable_page(struct page
*page
, struct zone
*zone
)
3151 VM_BUG_ON(PageActive(page
));
3154 ClearPageUnevictable(page
);
3155 if (page_evictable(page
, NULL
)) {
3156 enum lru_list l
= page_lru_base_type(page
);
3158 __dec_zone_state(zone
, NR_UNEVICTABLE
);
3159 list_move(&page
->lru
, &zone
->lru
[l
].list
);
3160 mem_cgroup_move_lists(page
, LRU_UNEVICTABLE
, l
);
3161 __inc_zone_state(zone
, NR_INACTIVE_ANON
+ l
);
3162 __count_vm_event(UNEVICTABLE_PGRESCUED
);
3165 * rotate unevictable list
3167 SetPageUnevictable(page
);
3168 list_move(&page
->lru
, &zone
->lru
[LRU_UNEVICTABLE
].list
);
3169 mem_cgroup_rotate_lru_list(page
, LRU_UNEVICTABLE
);
3170 if (page_evictable(page
, NULL
))
3176 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3177 * @mapping: struct address_space to scan for evictable pages
3179 * Scan all pages in mapping. Check unevictable pages for
3180 * evictability and move them to the appropriate zone lru list.
3182 void scan_mapping_unevictable_pages(struct address_space
*mapping
)
3185 pgoff_t end
= (i_size_read(mapping
->host
) + PAGE_CACHE_SIZE
- 1) >>
3188 struct pagevec pvec
;
3190 if (mapping
->nrpages
== 0)
3193 pagevec_init(&pvec
, 0);
3194 while (next
< end
&&
3195 pagevec_lookup(&pvec
, mapping
, next
, PAGEVEC_SIZE
)) {
3201 for (i
= 0; i
< pagevec_count(&pvec
); i
++) {
3202 struct page
*page
= pvec
.pages
[i
];
3203 pgoff_t page_index
= page
->index
;
3204 struct zone
*pagezone
= page_zone(page
);
3207 if (page_index
> next
)
3211 if (pagezone
!= zone
) {
3213 spin_unlock_irq(&zone
->lru_lock
);
3215 spin_lock_irq(&zone
->lru_lock
);
3218 if (PageLRU(page
) && PageUnevictable(page
))
3219 check_move_unevictable_page(page
, zone
);
3222 spin_unlock_irq(&zone
->lru_lock
);
3223 pagevec_release(&pvec
);
3225 count_vm_events(UNEVICTABLE_PGSCANNED
, pg_scanned
);
3231 * scan_zone_unevictable_pages - check unevictable list for evictable pages
3232 * @zone - zone of which to scan the unevictable list
3234 * Scan @zone's unevictable LRU lists to check for pages that have become
3235 * evictable. Move those that have to @zone's inactive list where they
3236 * become candidates for reclaim, unless shrink_inactive_zone() decides
3237 * to reactivate them. Pages that are still unevictable are rotated
3238 * back onto @zone's unevictable list.
3240 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
3241 static void scan_zone_unevictable_pages(struct zone
*zone
)
3243 struct list_head
*l_unevictable
= &zone
->lru
[LRU_UNEVICTABLE
].list
;
3245 unsigned long nr_to_scan
= zone_page_state(zone
, NR_UNEVICTABLE
);
3247 while (nr_to_scan
> 0) {
3248 unsigned long batch_size
= min(nr_to_scan
,
3249 SCAN_UNEVICTABLE_BATCH_SIZE
);
3251 spin_lock_irq(&zone
->lru_lock
);
3252 for (scan
= 0; scan
< batch_size
; scan
++) {
3253 struct page
*page
= lru_to_page(l_unevictable
);
3255 if (!trylock_page(page
))
3258 prefetchw_prev_lru_page(page
, l_unevictable
, flags
);
3260 if (likely(PageLRU(page
) && PageUnevictable(page
)))
3261 check_move_unevictable_page(page
, zone
);
3265 spin_unlock_irq(&zone
->lru_lock
);
3267 nr_to_scan
-= batch_size
;
3273 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
3275 * A really big hammer: scan all zones' unevictable LRU lists to check for
3276 * pages that have become evictable. Move those back to the zones'
3277 * inactive list where they become candidates for reclaim.
3278 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
3279 * and we add swap to the system. As such, it runs in the context of a task
3280 * that has possibly/probably made some previously unevictable pages
3283 static void scan_all_zones_unevictable_pages(void)
3287 for_each_zone(zone
) {
3288 scan_zone_unevictable_pages(zone
);
3293 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3294 * all nodes' unevictable lists for evictable pages
3296 unsigned long scan_unevictable_pages
;
3298 int scan_unevictable_handler(struct ctl_table
*table
, int write
,
3299 void __user
*buffer
,
3300 size_t *length
, loff_t
*ppos
)
3302 proc_doulongvec_minmax(table
, write
, buffer
, length
, ppos
);
3304 if (write
&& *(unsigned long *)table
->data
)
3305 scan_all_zones_unevictable_pages();
3307 scan_unevictable_pages
= 0;
3313 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3314 * a specified node's per zone unevictable lists for evictable pages.
3317 static ssize_t
read_scan_unevictable_node(struct sys_device
*dev
,
3318 struct sysdev_attribute
*attr
,
3321 return sprintf(buf
, "0\n"); /* always zero; should fit... */
3324 static ssize_t
write_scan_unevictable_node(struct sys_device
*dev
,
3325 struct sysdev_attribute
*attr
,
3326 const char *buf
, size_t count
)
3328 struct zone
*node_zones
= NODE_DATA(dev
->id
)->node_zones
;
3331 unsigned long req
= strict_strtoul(buf
, 10, &res
);
3334 return 1; /* zero is no-op */
3336 for (zone
= node_zones
; zone
- node_zones
< MAX_NR_ZONES
; ++zone
) {
3337 if (!populated_zone(zone
))
3339 scan_zone_unevictable_pages(zone
);
3345 static SYSDEV_ATTR(scan_unevictable_pages
, S_IRUGO
| S_IWUSR
,
3346 read_scan_unevictable_node
,
3347 write_scan_unevictable_node
);
3349 int scan_unevictable_register_node(struct node
*node
)
3351 return sysdev_create_file(&node
->sysdev
, &attr_scan_unevictable_pages
);
3354 void scan_unevictable_unregister_node(struct node
*node
)
3356 sysdev_remove_file(&node
->sysdev
, &attr_scan_unevictable_pages
);