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>
45 #include <linux/prefetch.h>
47 #include <asm/tlbflush.h>
48 #include <asm/div64.h>
50 #include <linux/swapops.h>
54 #define CREATE_TRACE_POINTS
55 #include <trace/events/vmscan.h>
58 * reclaim_mode determines how the inactive list is shrunk
59 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages
60 * RECLAIM_MODE_ASYNC: Do not block
61 * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback
62 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference
63 * page from the LRU and reclaim all pages within a
64 * naturally aligned range
65 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of
66 * order-0 pages and then compact the zone
68 typedef unsigned __bitwise__ reclaim_mode_t
;
69 #define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u)
70 #define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u)
71 #define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u)
72 #define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u)
73 #define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u)
76 /* Incremented by the number of inactive pages that were scanned */
77 unsigned long nr_scanned
;
79 /* Number of pages freed so far during a call to shrink_zones() */
80 unsigned long nr_reclaimed
;
82 /* How many pages shrink_list() should reclaim */
83 unsigned long nr_to_reclaim
;
85 unsigned long hibernation_mode
;
87 /* This context's GFP mask */
92 /* Can mapped pages be reclaimed? */
95 /* Can pages be swapped as part of reclaim? */
101 * Intend to reclaim enough continuous memory rather than reclaim
102 * enough amount of memory. i.e, mode for high order allocation.
104 reclaim_mode_t reclaim_mode
;
106 /* Which cgroup do we reclaim from */
107 struct mem_cgroup
*mem_cgroup
;
110 * Nodemask of nodes allowed by the caller. If NULL, all nodes
113 nodemask_t
*nodemask
;
116 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
118 #ifdef ARCH_HAS_PREFETCH
119 #define prefetch_prev_lru_page(_page, _base, _field) \
121 if ((_page)->lru.prev != _base) { \
124 prev = lru_to_page(&(_page->lru)); \
125 prefetch(&prev->_field); \
129 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
132 #ifdef ARCH_HAS_PREFETCHW
133 #define prefetchw_prev_lru_page(_page, _base, _field) \
135 if ((_page)->lru.prev != _base) { \
138 prev = lru_to_page(&(_page->lru)); \
139 prefetchw(&prev->_field); \
143 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
147 * From 0 .. 100. Higher means more swappy.
149 int vm_swappiness
= 60;
150 long vm_total_pages
; /* The total number of pages which the VM controls */
152 static LIST_HEAD(shrinker_list
);
153 static DECLARE_RWSEM(shrinker_rwsem
);
155 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
156 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
158 #define scanning_global_lru(sc) (1)
161 static struct zone_reclaim_stat
*get_reclaim_stat(struct zone
*zone
,
162 struct scan_control
*sc
)
164 if (!scanning_global_lru(sc
))
165 return mem_cgroup_get_reclaim_stat(sc
->mem_cgroup
, zone
);
167 return &zone
->reclaim_stat
;
170 static unsigned long zone_nr_lru_pages(struct zone
*zone
,
171 struct scan_control
*sc
, enum lru_list lru
)
173 if (!scanning_global_lru(sc
))
174 return mem_cgroup_zone_nr_lru_pages(sc
->mem_cgroup
,
175 zone_to_nid(zone
), zone_idx(zone
), BIT(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 static inline int do_shrinker_shrink(struct shrinker
*shrinker
,
205 struct shrink_control
*sc
,
206 unsigned long nr_to_scan
)
208 sc
->nr_to_scan
= nr_to_scan
;
209 return (*shrinker
->shrink
)(shrinker
, sc
);
212 #define SHRINK_BATCH 128
214 * Call the shrink functions to age shrinkable caches
216 * Here we assume it costs one seek to replace a lru page and that it also
217 * takes a seek to recreate a cache object. With this in mind we age equal
218 * percentages of the lru and ageable caches. This should balance the seeks
219 * generated by these structures.
221 * If the vm encountered mapped pages on the LRU it increase the pressure on
222 * slab to avoid swapping.
224 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
226 * `lru_pages' represents the number of on-LRU pages in all the zones which
227 * are eligible for the caller's allocation attempt. It is used for balancing
228 * slab reclaim versus page reclaim.
230 * Returns the number of slab objects which we shrunk.
232 unsigned long shrink_slab(struct shrink_control
*shrink
,
233 unsigned long nr_pages_scanned
,
234 unsigned long lru_pages
)
236 struct shrinker
*shrinker
;
237 unsigned long ret
= 0;
239 if (nr_pages_scanned
== 0)
240 nr_pages_scanned
= SWAP_CLUSTER_MAX
;
242 if (!down_read_trylock(&shrinker_rwsem
)) {
243 /* Assume we'll be able to shrink next time */
248 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
249 unsigned long long delta
;
250 unsigned long total_scan
;
251 unsigned long max_pass
;
255 long batch_size
= shrinker
->batch
? shrinker
->batch
259 * copy the current shrinker scan count into a local variable
260 * and zero it so that other concurrent shrinker invocations
261 * don't also do this scanning work.
265 } while (cmpxchg(&shrinker
->nr
, nr
, 0) != nr
);
268 max_pass
= do_shrinker_shrink(shrinker
, shrink
, 0);
269 delta
= (4 * nr_pages_scanned
) / shrinker
->seeks
;
271 do_div(delta
, lru_pages
+ 1);
273 if (total_scan
< 0) {
274 printk(KERN_ERR
"shrink_slab: %pF negative objects to "
276 shrinker
->shrink
, total_scan
);
277 total_scan
= max_pass
;
281 * We need to avoid excessive windup on filesystem shrinkers
282 * due to large numbers of GFP_NOFS allocations causing the
283 * shrinkers to return -1 all the time. This results in a large
284 * nr being built up so when a shrink that can do some work
285 * comes along it empties the entire cache due to nr >>>
286 * max_pass. This is bad for sustaining a working set in
289 * Hence only allow the shrinker to scan the entire cache when
290 * a large delta change is calculated directly.
292 if (delta
< max_pass
/ 4)
293 total_scan
= min(total_scan
, max_pass
/ 2);
296 * Avoid risking looping forever due to too large nr value:
297 * never try to free more than twice the estimate number of
300 if (total_scan
> max_pass
* 2)
301 total_scan
= max_pass
* 2;
303 trace_mm_shrink_slab_start(shrinker
, shrink
, nr
,
304 nr_pages_scanned
, lru_pages
,
305 max_pass
, delta
, total_scan
);
307 while (total_scan
>= batch_size
) {
310 nr_before
= do_shrinker_shrink(shrinker
, shrink
, 0);
311 shrink_ret
= do_shrinker_shrink(shrinker
, shrink
,
313 if (shrink_ret
== -1)
315 if (shrink_ret
< nr_before
)
316 ret
+= nr_before
- shrink_ret
;
317 count_vm_events(SLABS_SCANNED
, batch_size
);
318 total_scan
-= batch_size
;
324 * move the unused scan count back into the shrinker in a
325 * manner that handles concurrent updates. If we exhausted the
326 * scan, there is no need to do an update.
330 new_nr
= total_scan
+ nr
;
333 } while (cmpxchg(&shrinker
->nr
, nr
, new_nr
) != nr
);
335 trace_mm_shrink_slab_end(shrinker
, shrink_ret
, nr
, new_nr
);
337 up_read(&shrinker_rwsem
);
343 static void set_reclaim_mode(int priority
, struct scan_control
*sc
,
346 reclaim_mode_t syncmode
= sync
? RECLAIM_MODE_SYNC
: RECLAIM_MODE_ASYNC
;
349 * Initially assume we are entering either lumpy reclaim or
350 * reclaim/compaction.Depending on the order, we will either set the
351 * sync mode or just reclaim order-0 pages later.
353 if (COMPACTION_BUILD
)
354 sc
->reclaim_mode
= RECLAIM_MODE_COMPACTION
;
356 sc
->reclaim_mode
= RECLAIM_MODE_LUMPYRECLAIM
;
359 * Avoid using lumpy reclaim or reclaim/compaction if possible by
360 * restricting when its set to either costly allocations or when
361 * under memory pressure
363 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
364 sc
->reclaim_mode
|= syncmode
;
365 else if (sc
->order
&& priority
< DEF_PRIORITY
- 2)
366 sc
->reclaim_mode
|= syncmode
;
368 sc
->reclaim_mode
= RECLAIM_MODE_SINGLE
| RECLAIM_MODE_ASYNC
;
371 static void reset_reclaim_mode(struct scan_control
*sc
)
373 sc
->reclaim_mode
= RECLAIM_MODE_SINGLE
| RECLAIM_MODE_ASYNC
;
376 static inline int is_page_cache_freeable(struct page
*page
)
379 * A freeable page cache page is referenced only by the caller
380 * that isolated the page, the page cache radix tree and
381 * optional buffer heads at page->private.
383 return page_count(page
) - page_has_private(page
) == 2;
386 static int may_write_to_queue(struct backing_dev_info
*bdi
,
387 struct scan_control
*sc
)
389 if (current
->flags
& PF_SWAPWRITE
)
391 if (!bdi_write_congested(bdi
))
393 if (bdi
== current
->backing_dev_info
)
396 /* lumpy reclaim for hugepage often need a lot of write */
397 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
403 * We detected a synchronous write error writing a page out. Probably
404 * -ENOSPC. We need to propagate that into the address_space for a subsequent
405 * fsync(), msync() or close().
407 * The tricky part is that after writepage we cannot touch the mapping: nothing
408 * prevents it from being freed up. But we have a ref on the page and once
409 * that page is locked, the mapping is pinned.
411 * We're allowed to run sleeping lock_page() here because we know the caller has
414 static void handle_write_error(struct address_space
*mapping
,
415 struct page
*page
, int error
)
418 if (page_mapping(page
) == mapping
)
419 mapping_set_error(mapping
, error
);
423 /* possible outcome of pageout() */
425 /* failed to write page out, page is locked */
427 /* move page to the active list, page is locked */
429 /* page has been sent to the disk successfully, page is unlocked */
431 /* page is clean and locked */
436 * pageout is called by shrink_page_list() for each dirty page.
437 * Calls ->writepage().
439 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
440 struct scan_control
*sc
)
443 * If the page is dirty, only perform writeback if that write
444 * will be non-blocking. To prevent this allocation from being
445 * stalled by pagecache activity. But note that there may be
446 * stalls if we need to run get_block(). We could test
447 * PagePrivate for that.
449 * If this process is currently in __generic_file_aio_write() against
450 * this page's queue, we can perform writeback even if that
453 * If the page is swapcache, write it back even if that would
454 * block, for some throttling. This happens by accident, because
455 * swap_backing_dev_info is bust: it doesn't reflect the
456 * congestion state of the swapdevs. Easy to fix, if needed.
458 if (!is_page_cache_freeable(page
))
462 * Some data journaling orphaned pages can have
463 * page->mapping == NULL while being dirty with clean buffers.
465 if (page_has_private(page
)) {
466 if (try_to_free_buffers(page
)) {
467 ClearPageDirty(page
);
468 printk("%s: orphaned page\n", __func__
);
474 if (mapping
->a_ops
->writepage
== NULL
)
475 return PAGE_ACTIVATE
;
476 if (!may_write_to_queue(mapping
->backing_dev_info
, sc
))
479 if (clear_page_dirty_for_io(page
)) {
481 struct writeback_control wbc
= {
482 .sync_mode
= WB_SYNC_NONE
,
483 .nr_to_write
= SWAP_CLUSTER_MAX
,
485 .range_end
= LLONG_MAX
,
489 SetPageReclaim(page
);
490 res
= mapping
->a_ops
->writepage(page
, &wbc
);
492 handle_write_error(mapping
, page
, res
);
493 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
494 ClearPageReclaim(page
);
495 return PAGE_ACTIVATE
;
498 if (!PageWriteback(page
)) {
499 /* synchronous write or broken a_ops? */
500 ClearPageReclaim(page
);
502 trace_mm_vmscan_writepage(page
,
503 trace_reclaim_flags(page
, sc
->reclaim_mode
));
504 inc_zone_page_state(page
, NR_VMSCAN_WRITE
);
512 * Same as remove_mapping, but if the page is removed from the mapping, it
513 * gets returned with a refcount of 0.
515 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
)
517 BUG_ON(!PageLocked(page
));
518 BUG_ON(mapping
!= page_mapping(page
));
520 spin_lock_irq(&mapping
->tree_lock
);
522 * The non racy check for a busy page.
524 * Must be careful with the order of the tests. When someone has
525 * a ref to the page, it may be possible that they dirty it then
526 * drop the reference. So if PageDirty is tested before page_count
527 * here, then the following race may occur:
529 * get_user_pages(&page);
530 * [user mapping goes away]
532 * !PageDirty(page) [good]
533 * SetPageDirty(page);
535 * !page_count(page) [good, discard it]
537 * [oops, our write_to data is lost]
539 * Reversing the order of the tests ensures such a situation cannot
540 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
541 * load is not satisfied before that of page->_count.
543 * Note that if SetPageDirty is always performed via set_page_dirty,
544 * and thus under tree_lock, then this ordering is not required.
546 if (!page_freeze_refs(page
, 2))
548 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
549 if (unlikely(PageDirty(page
))) {
550 page_unfreeze_refs(page
, 2);
554 if (PageSwapCache(page
)) {
555 swp_entry_t swap
= { .val
= page_private(page
) };
556 __delete_from_swap_cache(page
);
557 spin_unlock_irq(&mapping
->tree_lock
);
558 swapcache_free(swap
, page
);
560 void (*freepage
)(struct page
*);
562 freepage
= mapping
->a_ops
->freepage
;
564 __delete_from_page_cache(page
);
565 spin_unlock_irq(&mapping
->tree_lock
);
566 mem_cgroup_uncharge_cache_page(page
);
568 if (freepage
!= NULL
)
575 spin_unlock_irq(&mapping
->tree_lock
);
580 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
581 * someone else has a ref on the page, abort and return 0. If it was
582 * successfully detached, return 1. Assumes the caller has a single ref on
585 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
587 if (__remove_mapping(mapping
, page
)) {
589 * Unfreezing the refcount with 1 rather than 2 effectively
590 * drops the pagecache ref for us without requiring another
593 page_unfreeze_refs(page
, 1);
600 * putback_lru_page - put previously isolated page onto appropriate LRU list
601 * @page: page to be put back to appropriate lru list
603 * Add previously isolated @page to appropriate LRU list.
604 * Page may still be unevictable for other reasons.
606 * lru_lock must not be held, interrupts must be enabled.
608 void putback_lru_page(struct page
*page
)
611 int active
= !!TestClearPageActive(page
);
612 int was_unevictable
= PageUnevictable(page
);
614 VM_BUG_ON(PageLRU(page
));
617 ClearPageUnevictable(page
);
619 if (page_evictable(page
, NULL
)) {
621 * For evictable pages, we can use the cache.
622 * In event of a race, worst case is we end up with an
623 * unevictable page on [in]active list.
624 * We know how to handle that.
626 lru
= active
+ page_lru_base_type(page
);
627 lru_cache_add_lru(page
, lru
);
630 * Put unevictable pages directly on zone's unevictable
633 lru
= LRU_UNEVICTABLE
;
634 add_page_to_unevictable_list(page
);
636 * When racing with an mlock clearing (page is
637 * unlocked), make sure that if the other thread does
638 * not observe our setting of PG_lru and fails
639 * isolation, we see PG_mlocked cleared below and move
640 * the page back to the evictable list.
642 * The other side is TestClearPageMlocked().
648 * page's status can change while we move it among lru. If an evictable
649 * page is on unevictable list, it never be freed. To avoid that,
650 * check after we added it to the list, again.
652 if (lru
== LRU_UNEVICTABLE
&& page_evictable(page
, NULL
)) {
653 if (!isolate_lru_page(page
)) {
657 /* This means someone else dropped this page from LRU
658 * So, it will be freed or putback to LRU again. There is
659 * nothing to do here.
663 if (was_unevictable
&& lru
!= LRU_UNEVICTABLE
)
664 count_vm_event(UNEVICTABLE_PGRESCUED
);
665 else if (!was_unevictable
&& lru
== LRU_UNEVICTABLE
)
666 count_vm_event(UNEVICTABLE_PGCULLED
);
668 put_page(page
); /* drop ref from isolate */
671 enum page_references
{
673 PAGEREF_RECLAIM_CLEAN
,
678 static enum page_references
page_check_references(struct page
*page
,
679 struct scan_control
*sc
)
681 int referenced_ptes
, referenced_page
;
682 unsigned long vm_flags
;
684 referenced_ptes
= page_referenced(page
, 1, sc
->mem_cgroup
, &vm_flags
);
685 referenced_page
= TestClearPageReferenced(page
);
687 /* Lumpy reclaim - ignore references */
688 if (sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
)
689 return PAGEREF_RECLAIM
;
692 * Mlock lost the isolation race with us. Let try_to_unmap()
693 * move the page to the unevictable list.
695 if (vm_flags
& VM_LOCKED
)
696 return PAGEREF_RECLAIM
;
698 if (referenced_ptes
) {
700 return PAGEREF_ACTIVATE
;
702 * All mapped pages start out with page table
703 * references from the instantiating fault, so we need
704 * to look twice if a mapped file page is used more
707 * Mark it and spare it for another trip around the
708 * inactive list. Another page table reference will
709 * lead to its activation.
711 * Note: the mark is set for activated pages as well
712 * so that recently deactivated but used pages are
715 SetPageReferenced(page
);
718 return PAGEREF_ACTIVATE
;
723 /* Reclaim if clean, defer dirty pages to writeback */
724 if (referenced_page
&& !PageSwapBacked(page
))
725 return PAGEREF_RECLAIM_CLEAN
;
727 return PAGEREF_RECLAIM
;
730 static noinline_for_stack
void free_page_list(struct list_head
*free_pages
)
732 struct pagevec freed_pvec
;
733 struct page
*page
, *tmp
;
735 pagevec_init(&freed_pvec
, 1);
737 list_for_each_entry_safe(page
, tmp
, free_pages
, lru
) {
738 list_del(&page
->lru
);
739 if (!pagevec_add(&freed_pvec
, page
)) {
740 __pagevec_free(&freed_pvec
);
741 pagevec_reinit(&freed_pvec
);
745 pagevec_free(&freed_pvec
);
749 * shrink_page_list() returns the number of reclaimed pages
751 static unsigned long shrink_page_list(struct list_head
*page_list
,
753 struct scan_control
*sc
,
755 unsigned long *ret_nr_dirty
,
756 unsigned long *ret_nr_writeback
)
758 LIST_HEAD(ret_pages
);
759 LIST_HEAD(free_pages
);
761 unsigned long nr_dirty
= 0;
762 unsigned long nr_congested
= 0;
763 unsigned long nr_reclaimed
= 0;
764 unsigned long nr_writeback
= 0;
768 while (!list_empty(page_list
)) {
769 enum page_references references
;
770 struct address_space
*mapping
;
776 page
= lru_to_page(page_list
);
777 list_del(&page
->lru
);
779 if (!trylock_page(page
))
782 VM_BUG_ON(PageActive(page
));
783 VM_BUG_ON(page_zone(page
) != zone
);
787 if (unlikely(!page_evictable(page
, NULL
)))
790 if (!sc
->may_unmap
&& page_mapped(page
))
793 /* Double the slab pressure for mapped and swapcache pages */
794 if (page_mapped(page
) || PageSwapCache(page
))
797 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
798 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
800 if (PageWriteback(page
)) {
803 * Synchronous reclaim cannot queue pages for
804 * writeback due to the possibility of stack overflow
805 * but if it encounters a page under writeback, wait
806 * for the IO to complete.
808 if ((sc
->reclaim_mode
& RECLAIM_MODE_SYNC
) &&
810 wait_on_page_writeback(page
);
817 references
= page_check_references(page
, sc
);
818 switch (references
) {
819 case PAGEREF_ACTIVATE
:
820 goto activate_locked
;
823 case PAGEREF_RECLAIM
:
824 case PAGEREF_RECLAIM_CLEAN
:
825 ; /* try to reclaim the page below */
829 * Anonymous process memory has backing store?
830 * Try to allocate it some swap space here.
832 if (PageAnon(page
) && !PageSwapCache(page
)) {
833 if (!(sc
->gfp_mask
& __GFP_IO
))
835 if (!add_to_swap(page
))
836 goto activate_locked
;
840 mapping
= page_mapping(page
);
843 * The page is mapped into the page tables of one or more
844 * processes. Try to unmap it here.
846 if (page_mapped(page
) && mapping
) {
847 switch (try_to_unmap(page
, TTU_UNMAP
)) {
849 goto activate_locked
;
855 ; /* try to free the page below */
859 if (PageDirty(page
)) {
863 * Only kswapd can writeback filesystem pages to
864 * avoid risk of stack overflow but do not writeback
865 * unless under significant pressure.
867 if (page_is_file_cache(page
) &&
868 (!current_is_kswapd() || priority
>= DEF_PRIORITY
- 2)) {
870 * Immediately reclaim when written back.
871 * Similar in principal to deactivate_page()
872 * except we already have the page isolated
873 * and know it's dirty
875 inc_zone_page_state(page
, NR_VMSCAN_IMMEDIATE
);
876 SetPageReclaim(page
);
881 if (references
== PAGEREF_RECLAIM_CLEAN
)
885 if (!sc
->may_writepage
)
888 /* Page is dirty, try to write it out here */
889 switch (pageout(page
, mapping
, sc
)) {
894 goto activate_locked
;
896 if (PageWriteback(page
))
902 * A synchronous write - probably a ramdisk. Go
903 * ahead and try to reclaim the page.
905 if (!trylock_page(page
))
907 if (PageDirty(page
) || PageWriteback(page
))
909 mapping
= page_mapping(page
);
911 ; /* try to free the page below */
916 * If the page has buffers, try to free the buffer mappings
917 * associated with this page. If we succeed we try to free
920 * We do this even if the page is PageDirty().
921 * try_to_release_page() does not perform I/O, but it is
922 * possible for a page to have PageDirty set, but it is actually
923 * clean (all its buffers are clean). This happens if the
924 * buffers were written out directly, with submit_bh(). ext3
925 * will do this, as well as the blockdev mapping.
926 * try_to_release_page() will discover that cleanness and will
927 * drop the buffers and mark the page clean - it can be freed.
929 * Rarely, pages can have buffers and no ->mapping. These are
930 * the pages which were not successfully invalidated in
931 * truncate_complete_page(). We try to drop those buffers here
932 * and if that worked, and the page is no longer mapped into
933 * process address space (page_count == 1) it can be freed.
934 * Otherwise, leave the page on the LRU so it is swappable.
936 if (page_has_private(page
)) {
937 if (!try_to_release_page(page
, sc
->gfp_mask
))
938 goto activate_locked
;
939 if (!mapping
&& page_count(page
) == 1) {
941 if (put_page_testzero(page
))
945 * rare race with speculative reference.
946 * the speculative reference will free
947 * this page shortly, so we may
948 * increment nr_reclaimed here (and
949 * leave it off the LRU).
957 if (!mapping
|| !__remove_mapping(mapping
, page
))
961 * At this point, we have no other references and there is
962 * no way to pick any more up (removed from LRU, removed
963 * from pagecache). Can use non-atomic bitops now (and
964 * we obviously don't have to worry about waking up a process
965 * waiting on the page lock, because there are no references.
967 __clear_page_locked(page
);
972 * Is there need to periodically free_page_list? It would
973 * appear not as the counts should be low
975 list_add(&page
->lru
, &free_pages
);
979 if (PageSwapCache(page
))
980 try_to_free_swap(page
);
982 putback_lru_page(page
);
983 reset_reclaim_mode(sc
);
987 /* Not a candidate for swapping, so reclaim swap space. */
988 if (PageSwapCache(page
) && vm_swap_full())
989 try_to_free_swap(page
);
990 VM_BUG_ON(PageActive(page
));
996 reset_reclaim_mode(sc
);
998 list_add(&page
->lru
, &ret_pages
);
999 VM_BUG_ON(PageLRU(page
) || PageUnevictable(page
));
1003 * Tag a zone as congested if all the dirty pages encountered were
1004 * backed by a congested BDI. In this case, reclaimers should just
1005 * back off and wait for congestion to clear because further reclaim
1006 * will encounter the same problem
1008 if (nr_dirty
&& nr_dirty
== nr_congested
&& scanning_global_lru(sc
))
1009 zone_set_flag(zone
, ZONE_CONGESTED
);
1011 free_page_list(&free_pages
);
1013 list_splice(&ret_pages
, page_list
);
1014 count_vm_events(PGACTIVATE
, pgactivate
);
1015 *ret_nr_dirty
+= nr_dirty
;
1016 *ret_nr_writeback
+= nr_writeback
;
1017 return nr_reclaimed
;
1021 * Attempt to remove the specified page from its LRU. Only take this page
1022 * if it is of the appropriate PageActive status. Pages which are being
1023 * freed elsewhere are also ignored.
1025 * page: page to consider
1026 * mode: one of the LRU isolation modes defined above
1028 * returns 0 on success, -ve errno on failure.
1030 int __isolate_lru_page(struct page
*page
, isolate_mode_t mode
, int file
)
1035 /* Only take pages on the LRU. */
1039 all_lru_mode
= (mode
& (ISOLATE_ACTIVE
|ISOLATE_INACTIVE
)) ==
1040 (ISOLATE_ACTIVE
|ISOLATE_INACTIVE
);
1043 * When checking the active state, we need to be sure we are
1044 * dealing with comparible boolean values. Take the logical not
1047 if (!all_lru_mode
&& !PageActive(page
) != !(mode
& ISOLATE_ACTIVE
))
1050 if (!all_lru_mode
&& !!page_is_file_cache(page
) != file
)
1054 * When this function is being called for lumpy reclaim, we
1055 * initially look into all LRU pages, active, inactive and
1056 * unevictable; only give shrink_page_list evictable pages.
1058 if (PageUnevictable(page
))
1063 if ((mode
& ISOLATE_CLEAN
) && (PageDirty(page
) || PageWriteback(page
)))
1066 if ((mode
& ISOLATE_UNMAPPED
) && page_mapped(page
))
1069 if (likely(get_page_unless_zero(page
))) {
1071 * Be careful not to clear PageLRU until after we're
1072 * sure the page is not being freed elsewhere -- the
1073 * page release code relies on it.
1083 * zone->lru_lock is heavily contended. Some of the functions that
1084 * shrink the lists perform better by taking out a batch of pages
1085 * and working on them outside the LRU lock.
1087 * For pagecache intensive workloads, this function is the hottest
1088 * spot in the kernel (apart from copy_*_user functions).
1090 * Appropriate locks must be held before calling this function.
1092 * @nr_to_scan: The number of pages to look through on the list.
1093 * @src: The LRU list to pull pages off.
1094 * @dst: The temp list to put pages on to.
1095 * @scanned: The number of pages that were scanned.
1096 * @order: The caller's attempted allocation order
1097 * @mode: One of the LRU isolation modes
1098 * @file: True [1] if isolating file [!anon] pages
1100 * returns how many pages were moved onto *@dst.
1102 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1103 struct list_head
*src
, struct list_head
*dst
,
1104 unsigned long *scanned
, int order
, isolate_mode_t mode
,
1107 unsigned long nr_taken
= 0;
1108 unsigned long nr_lumpy_taken
= 0;
1109 unsigned long nr_lumpy_dirty
= 0;
1110 unsigned long nr_lumpy_failed
= 0;
1113 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
1116 unsigned long end_pfn
;
1117 unsigned long page_pfn
;
1120 page
= lru_to_page(src
);
1121 prefetchw_prev_lru_page(page
, src
, flags
);
1123 VM_BUG_ON(!PageLRU(page
));
1125 switch (__isolate_lru_page(page
, mode
, file
)) {
1127 list_move(&page
->lru
, dst
);
1128 mem_cgroup_del_lru(page
);
1129 nr_taken
+= hpage_nr_pages(page
);
1133 /* else it is being freed elsewhere */
1134 list_move(&page
->lru
, src
);
1135 mem_cgroup_rotate_lru_list(page
, page_lru(page
));
1146 * Attempt to take all pages in the order aligned region
1147 * surrounding the tag page. Only take those pages of
1148 * the same active state as that tag page. We may safely
1149 * round the target page pfn down to the requested order
1150 * as the mem_map is guaranteed valid out to MAX_ORDER,
1151 * where that page is in a different zone we will detect
1152 * it from its zone id and abort this block scan.
1154 zone_id
= page_zone_id(page
);
1155 page_pfn
= page_to_pfn(page
);
1156 pfn
= page_pfn
& ~((1 << order
) - 1);
1157 end_pfn
= pfn
+ (1 << order
);
1158 for (; pfn
< end_pfn
; pfn
++) {
1159 struct page
*cursor_page
;
1161 /* The target page is in the block, ignore it. */
1162 if (unlikely(pfn
== page_pfn
))
1165 /* Avoid holes within the zone. */
1166 if (unlikely(!pfn_valid_within(pfn
)))
1169 cursor_page
= pfn_to_page(pfn
);
1171 /* Check that we have not crossed a zone boundary. */
1172 if (unlikely(page_zone_id(cursor_page
) != zone_id
))
1176 * If we don't have enough swap space, reclaiming of
1177 * anon page which don't already have a swap slot is
1180 if (nr_swap_pages
<= 0 && PageAnon(cursor_page
) &&
1181 !PageSwapCache(cursor_page
))
1184 if (__isolate_lru_page(cursor_page
, mode
, file
) == 0) {
1185 list_move(&cursor_page
->lru
, dst
);
1186 mem_cgroup_del_lru(cursor_page
);
1187 nr_taken
+= hpage_nr_pages(page
);
1189 if (PageDirty(cursor_page
))
1194 * Check if the page is freed already.
1196 * We can't use page_count() as that
1197 * requires compound_head and we don't
1198 * have a pin on the page here. If a
1199 * page is tail, we may or may not
1200 * have isolated the head, so assume
1201 * it's not free, it'd be tricky to
1202 * track the head status without a
1205 if (!PageTail(cursor_page
) &&
1206 !atomic_read(&cursor_page
->_count
))
1212 /* If we break out of the loop above, lumpy reclaim failed */
1219 trace_mm_vmscan_lru_isolate(order
,
1222 nr_lumpy_taken
, nr_lumpy_dirty
, nr_lumpy_failed
,
1227 static unsigned long isolate_pages_global(unsigned long nr
,
1228 struct list_head
*dst
,
1229 unsigned long *scanned
, int order
,
1230 isolate_mode_t mode
,
1231 struct zone
*z
, int active
, int file
)
1238 return isolate_lru_pages(nr
, &z
->lru
[lru
].list
, dst
, scanned
, order
,
1243 * clear_active_flags() is a helper for shrink_active_list(), clearing
1244 * any active bits from the pages in the list.
1246 static unsigned long clear_active_flags(struct list_head
*page_list
,
1247 unsigned int *count
)
1253 list_for_each_entry(page
, page_list
, lru
) {
1254 int numpages
= hpage_nr_pages(page
);
1255 lru
= page_lru_base_type(page
);
1256 if (PageActive(page
)) {
1258 ClearPageActive(page
);
1259 nr_active
+= numpages
;
1262 count
[lru
] += numpages
;
1269 * isolate_lru_page - tries to isolate a page from its LRU list
1270 * @page: page to isolate from its LRU list
1272 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1273 * vmstat statistic corresponding to whatever LRU list the page was on.
1275 * Returns 0 if the page was removed from an LRU list.
1276 * Returns -EBUSY if the page was not on an LRU list.
1278 * The returned page will have PageLRU() cleared. If it was found on
1279 * the active list, it will have PageActive set. If it was found on
1280 * the unevictable list, it will have the PageUnevictable bit set. That flag
1281 * may need to be cleared by the caller before letting the page go.
1283 * The vmstat statistic corresponding to the list on which the page was
1284 * found will be decremented.
1287 * (1) Must be called with an elevated refcount on the page. This is a
1288 * fundamentnal difference from isolate_lru_pages (which is called
1289 * without a stable reference).
1290 * (2) the lru_lock must not be held.
1291 * (3) interrupts must be enabled.
1293 int isolate_lru_page(struct page
*page
)
1297 VM_BUG_ON(!page_count(page
));
1299 if (PageLRU(page
)) {
1300 struct zone
*zone
= page_zone(page
);
1302 spin_lock_irq(&zone
->lru_lock
);
1303 if (PageLRU(page
)) {
1304 int lru
= page_lru(page
);
1309 del_page_from_lru_list(zone
, page
, lru
);
1311 spin_unlock_irq(&zone
->lru_lock
);
1317 * Are there way too many processes in the direct reclaim path already?
1319 static int too_many_isolated(struct zone
*zone
, int file
,
1320 struct scan_control
*sc
)
1322 unsigned long inactive
, isolated
;
1324 if (current_is_kswapd())
1327 if (!scanning_global_lru(sc
))
1331 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1332 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
);
1334 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1335 isolated
= zone_page_state(zone
, NR_ISOLATED_ANON
);
1338 return isolated
> inactive
;
1342 * TODO: Try merging with migrations version of putback_lru_pages
1344 static noinline_for_stack
void
1345 putback_lru_pages(struct zone
*zone
, struct scan_control
*sc
,
1346 unsigned long nr_anon
, unsigned long nr_file
,
1347 struct list_head
*page_list
)
1350 struct pagevec pvec
;
1351 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1353 pagevec_init(&pvec
, 1);
1356 * Put back any unfreeable pages.
1358 spin_lock(&zone
->lru_lock
);
1359 while (!list_empty(page_list
)) {
1361 page
= lru_to_page(page_list
);
1362 VM_BUG_ON(PageLRU(page
));
1363 list_del(&page
->lru
);
1364 if (unlikely(!page_evictable(page
, NULL
))) {
1365 spin_unlock_irq(&zone
->lru_lock
);
1366 putback_lru_page(page
);
1367 spin_lock_irq(&zone
->lru_lock
);
1371 lru
= page_lru(page
);
1372 add_page_to_lru_list(zone
, page
, lru
);
1373 if (is_active_lru(lru
)) {
1374 int file
= is_file_lru(lru
);
1375 int numpages
= hpage_nr_pages(page
);
1376 reclaim_stat
->recent_rotated
[file
] += numpages
;
1378 if (!pagevec_add(&pvec
, page
)) {
1379 spin_unlock_irq(&zone
->lru_lock
);
1380 __pagevec_release(&pvec
);
1381 spin_lock_irq(&zone
->lru_lock
);
1384 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, -nr_anon
);
1385 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, -nr_file
);
1387 spin_unlock_irq(&zone
->lru_lock
);
1388 pagevec_release(&pvec
);
1391 static noinline_for_stack
void update_isolated_counts(struct zone
*zone
,
1392 struct scan_control
*sc
,
1393 unsigned long *nr_anon
,
1394 unsigned long *nr_file
,
1395 struct list_head
*isolated_list
)
1397 unsigned long nr_active
;
1398 unsigned int count
[NR_LRU_LISTS
] = { 0, };
1399 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1401 nr_active
= clear_active_flags(isolated_list
, count
);
1402 __count_vm_events(PGDEACTIVATE
, nr_active
);
1404 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
,
1405 -count
[LRU_ACTIVE_FILE
]);
1406 __mod_zone_page_state(zone
, NR_INACTIVE_FILE
,
1407 -count
[LRU_INACTIVE_FILE
]);
1408 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
,
1409 -count
[LRU_ACTIVE_ANON
]);
1410 __mod_zone_page_state(zone
, NR_INACTIVE_ANON
,
1411 -count
[LRU_INACTIVE_ANON
]);
1413 *nr_anon
= count
[LRU_ACTIVE_ANON
] + count
[LRU_INACTIVE_ANON
];
1414 *nr_file
= count
[LRU_ACTIVE_FILE
] + count
[LRU_INACTIVE_FILE
];
1415 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, *nr_anon
);
1416 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, *nr_file
);
1418 reclaim_stat
->recent_scanned
[0] += *nr_anon
;
1419 reclaim_stat
->recent_scanned
[1] += *nr_file
;
1423 * Returns true if a direct reclaim should wait on pages under writeback.
1425 * If we are direct reclaiming for contiguous pages and we do not reclaim
1426 * everything in the list, try again and wait for writeback IO to complete.
1427 * This will stall high-order allocations noticeably. Only do that when really
1428 * need to free the pages under high memory pressure.
1430 static inline bool should_reclaim_stall(unsigned long nr_taken
,
1431 unsigned long nr_freed
,
1433 struct scan_control
*sc
)
1435 int lumpy_stall_priority
;
1437 /* kswapd should not stall on sync IO */
1438 if (current_is_kswapd())
1441 /* Only stall on lumpy reclaim */
1442 if (sc
->reclaim_mode
& RECLAIM_MODE_SINGLE
)
1445 /* If we have reclaimed everything on the isolated list, no stall */
1446 if (nr_freed
== nr_taken
)
1450 * For high-order allocations, there are two stall thresholds.
1451 * High-cost allocations stall immediately where as lower
1452 * order allocations such as stacks require the scanning
1453 * priority to be much higher before stalling.
1455 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
1456 lumpy_stall_priority
= DEF_PRIORITY
;
1458 lumpy_stall_priority
= DEF_PRIORITY
/ 3;
1460 return priority
<= lumpy_stall_priority
;
1464 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1465 * of reclaimed pages
1467 static noinline_for_stack
unsigned long
1468 shrink_inactive_list(unsigned long nr_to_scan
, struct zone
*zone
,
1469 struct scan_control
*sc
, int priority
, int file
)
1471 LIST_HEAD(page_list
);
1472 unsigned long nr_scanned
;
1473 unsigned long nr_reclaimed
= 0;
1474 unsigned long nr_taken
;
1475 unsigned long nr_anon
;
1476 unsigned long nr_file
;
1477 unsigned long nr_dirty
= 0;
1478 unsigned long nr_writeback
= 0;
1479 isolate_mode_t reclaim_mode
= ISOLATE_INACTIVE
;
1481 while (unlikely(too_many_isolated(zone
, file
, sc
))) {
1482 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1484 /* We are about to die and free our memory. Return now. */
1485 if (fatal_signal_pending(current
))
1486 return SWAP_CLUSTER_MAX
;
1489 set_reclaim_mode(priority
, sc
, false);
1490 if (sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
)
1491 reclaim_mode
|= ISOLATE_ACTIVE
;
1496 reclaim_mode
|= ISOLATE_UNMAPPED
;
1497 if (!sc
->may_writepage
)
1498 reclaim_mode
|= ISOLATE_CLEAN
;
1500 spin_lock_irq(&zone
->lru_lock
);
1502 if (scanning_global_lru(sc
)) {
1503 nr_taken
= isolate_pages_global(nr_to_scan
, &page_list
,
1504 &nr_scanned
, sc
->order
, reclaim_mode
, zone
, 0, file
);
1505 zone
->pages_scanned
+= nr_scanned
;
1506 if (current_is_kswapd())
1507 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
,
1510 __count_zone_vm_events(PGSCAN_DIRECT
, zone
,
1513 nr_taken
= mem_cgroup_isolate_pages(nr_to_scan
, &page_list
,
1514 &nr_scanned
, sc
->order
, reclaim_mode
, zone
,
1515 sc
->mem_cgroup
, 0, file
);
1517 * mem_cgroup_isolate_pages() keeps track of
1518 * scanned pages on its own.
1522 if (nr_taken
== 0) {
1523 spin_unlock_irq(&zone
->lru_lock
);
1527 update_isolated_counts(zone
, sc
, &nr_anon
, &nr_file
, &page_list
);
1529 spin_unlock_irq(&zone
->lru_lock
);
1531 nr_reclaimed
= shrink_page_list(&page_list
, zone
, sc
, priority
,
1532 &nr_dirty
, &nr_writeback
);
1534 /* Check if we should syncronously wait for writeback */
1535 if (should_reclaim_stall(nr_taken
, nr_reclaimed
, priority
, sc
)) {
1536 set_reclaim_mode(priority
, sc
, true);
1537 nr_reclaimed
+= shrink_page_list(&page_list
, zone
, sc
,
1538 priority
, &nr_dirty
, &nr_writeback
);
1541 local_irq_disable();
1542 if (current_is_kswapd())
1543 __count_vm_events(KSWAPD_STEAL
, nr_reclaimed
);
1544 __count_zone_vm_events(PGSTEAL
, zone
, nr_reclaimed
);
1546 putback_lru_pages(zone
, sc
, nr_anon
, nr_file
, &page_list
);
1549 * If reclaim is isolating dirty pages under writeback, it implies
1550 * that the long-lived page allocation rate is exceeding the page
1551 * laundering rate. Either the global limits are not being effective
1552 * at throttling processes due to the page distribution throughout
1553 * zones or there is heavy usage of a slow backing device. The
1554 * only option is to throttle from reclaim context which is not ideal
1555 * as there is no guarantee the dirtying process is throttled in the
1556 * same way balance_dirty_pages() manages.
1558 * This scales the number of dirty pages that must be under writeback
1559 * before throttling depending on priority. It is a simple backoff
1560 * function that has the most effect in the range DEF_PRIORITY to
1561 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
1562 * in trouble and reclaim is considered to be in trouble.
1564 * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle
1565 * DEF_PRIORITY-1 50% must be PageWriteback
1566 * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble
1568 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
1569 * isolated page is PageWriteback
1571 if (nr_writeback
&& nr_writeback
>= (nr_taken
>> (DEF_PRIORITY
-priority
)))
1572 wait_iff_congested(zone
, BLK_RW_ASYNC
, HZ
/10);
1574 trace_mm_vmscan_lru_shrink_inactive(zone
->zone_pgdat
->node_id
,
1576 nr_scanned
, nr_reclaimed
,
1578 trace_shrink_flags(file
, sc
->reclaim_mode
));
1579 return nr_reclaimed
;
1583 * This moves pages from the active list to the inactive list.
1585 * We move them the other way if the page is referenced by one or more
1586 * processes, from rmap.
1588 * If the pages are mostly unmapped, the processing is fast and it is
1589 * appropriate to hold zone->lru_lock across the whole operation. But if
1590 * the pages are mapped, the processing is slow (page_referenced()) so we
1591 * should drop zone->lru_lock around each page. It's impossible to balance
1592 * this, so instead we remove the pages from the LRU while processing them.
1593 * It is safe to rely on PG_active against the non-LRU pages in here because
1594 * nobody will play with that bit on a non-LRU page.
1596 * The downside is that we have to touch page->_count against each page.
1597 * But we had to alter page->flags anyway.
1600 static void move_active_pages_to_lru(struct zone
*zone
,
1601 struct list_head
*list
,
1604 unsigned long pgmoved
= 0;
1605 struct pagevec pvec
;
1608 pagevec_init(&pvec
, 1);
1610 while (!list_empty(list
)) {
1611 page
= lru_to_page(list
);
1613 VM_BUG_ON(PageLRU(page
));
1616 list_move(&page
->lru
, &zone
->lru
[lru
].list
);
1617 mem_cgroup_add_lru_list(page
, lru
);
1618 pgmoved
+= hpage_nr_pages(page
);
1620 if (!pagevec_add(&pvec
, page
) || list_empty(list
)) {
1621 spin_unlock_irq(&zone
->lru_lock
);
1622 if (buffer_heads_over_limit
)
1623 pagevec_strip(&pvec
);
1624 __pagevec_release(&pvec
);
1625 spin_lock_irq(&zone
->lru_lock
);
1628 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1629 if (!is_active_lru(lru
))
1630 __count_vm_events(PGDEACTIVATE
, pgmoved
);
1633 static void shrink_active_list(unsigned long nr_pages
, struct zone
*zone
,
1634 struct scan_control
*sc
, int priority
, int file
)
1636 unsigned long nr_taken
;
1637 unsigned long pgscanned
;
1638 unsigned long vm_flags
;
1639 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1640 LIST_HEAD(l_active
);
1641 LIST_HEAD(l_inactive
);
1643 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1644 unsigned long nr_rotated
= 0;
1645 isolate_mode_t reclaim_mode
= ISOLATE_ACTIVE
;
1650 reclaim_mode
|= ISOLATE_UNMAPPED
;
1651 if (!sc
->may_writepage
)
1652 reclaim_mode
|= ISOLATE_CLEAN
;
1654 spin_lock_irq(&zone
->lru_lock
);
1655 if (scanning_global_lru(sc
)) {
1656 nr_taken
= isolate_pages_global(nr_pages
, &l_hold
,
1657 &pgscanned
, sc
->order
,
1660 zone
->pages_scanned
+= pgscanned
;
1662 nr_taken
= mem_cgroup_isolate_pages(nr_pages
, &l_hold
,
1663 &pgscanned
, sc
->order
,
1665 sc
->mem_cgroup
, 1, file
);
1667 * mem_cgroup_isolate_pages() keeps track of
1668 * scanned pages on its own.
1672 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1674 __count_zone_vm_events(PGREFILL
, zone
, pgscanned
);
1676 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
, -nr_taken
);
1678 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
, -nr_taken
);
1679 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1680 spin_unlock_irq(&zone
->lru_lock
);
1682 while (!list_empty(&l_hold
)) {
1684 page
= lru_to_page(&l_hold
);
1685 list_del(&page
->lru
);
1687 if (unlikely(!page_evictable(page
, NULL
))) {
1688 putback_lru_page(page
);
1692 if (page_referenced(page
, 0, sc
->mem_cgroup
, &vm_flags
)) {
1693 nr_rotated
+= hpage_nr_pages(page
);
1695 * Identify referenced, file-backed active pages and
1696 * give them one more trip around the active list. So
1697 * that executable code get better chances to stay in
1698 * memory under moderate memory pressure. Anon pages
1699 * are not likely to be evicted by use-once streaming
1700 * IO, plus JVM can create lots of anon VM_EXEC pages,
1701 * so we ignore them here.
1703 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1704 list_add(&page
->lru
, &l_active
);
1709 ClearPageActive(page
); /* we are de-activating */
1710 list_add(&page
->lru
, &l_inactive
);
1714 * Move pages back to the lru list.
1716 spin_lock_irq(&zone
->lru_lock
);
1718 * Count referenced pages from currently used mappings as rotated,
1719 * even though only some of them are actually re-activated. This
1720 * helps balance scan pressure between file and anonymous pages in
1723 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1725 move_active_pages_to_lru(zone
, &l_active
,
1726 LRU_ACTIVE
+ file
* LRU_FILE
);
1727 move_active_pages_to_lru(zone
, &l_inactive
,
1728 LRU_BASE
+ file
* LRU_FILE
);
1729 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1730 spin_unlock_irq(&zone
->lru_lock
);
1734 static int inactive_anon_is_low_global(struct zone
*zone
)
1736 unsigned long active
, inactive
;
1738 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1739 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1741 if (inactive
* zone
->inactive_ratio
< active
)
1748 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1749 * @zone: zone to check
1750 * @sc: scan control of this context
1752 * Returns true if the zone does not have enough inactive anon pages,
1753 * meaning some active anon pages need to be deactivated.
1755 static int inactive_anon_is_low(struct zone
*zone
, struct scan_control
*sc
)
1760 * If we don't have swap space, anonymous page deactivation
1763 if (!total_swap_pages
)
1766 if (scanning_global_lru(sc
))
1767 low
= inactive_anon_is_low_global(zone
);
1769 low
= mem_cgroup_inactive_anon_is_low(sc
->mem_cgroup
);
1773 static inline int inactive_anon_is_low(struct zone
*zone
,
1774 struct scan_control
*sc
)
1780 static int inactive_file_is_low_global(struct zone
*zone
)
1782 unsigned long active
, inactive
;
1784 active
= zone_page_state(zone
, NR_ACTIVE_FILE
);
1785 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1787 return (active
> inactive
);
1791 * inactive_file_is_low - check if file pages need to be deactivated
1792 * @zone: zone to check
1793 * @sc: scan control of this context
1795 * When the system is doing streaming IO, memory pressure here
1796 * ensures that active file pages get deactivated, until more
1797 * than half of the file pages are on the inactive list.
1799 * Once we get to that situation, protect the system's working
1800 * set from being evicted by disabling active file page aging.
1802 * This uses a different ratio than the anonymous pages, because
1803 * the page cache uses a use-once replacement algorithm.
1805 static int inactive_file_is_low(struct zone
*zone
, struct scan_control
*sc
)
1809 if (scanning_global_lru(sc
))
1810 low
= inactive_file_is_low_global(zone
);
1812 low
= mem_cgroup_inactive_file_is_low(sc
->mem_cgroup
);
1816 static int inactive_list_is_low(struct zone
*zone
, struct scan_control
*sc
,
1820 return inactive_file_is_low(zone
, sc
);
1822 return inactive_anon_is_low(zone
, sc
);
1825 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1826 struct zone
*zone
, struct scan_control
*sc
, int priority
)
1828 int file
= is_file_lru(lru
);
1830 if (is_active_lru(lru
)) {
1831 if (inactive_list_is_low(zone
, sc
, file
))
1832 shrink_active_list(nr_to_scan
, zone
, sc
, priority
, file
);
1836 return shrink_inactive_list(nr_to_scan
, zone
, sc
, priority
, file
);
1839 static int vmscan_swappiness(struct scan_control
*sc
)
1841 if (scanning_global_lru(sc
))
1842 return vm_swappiness
;
1843 return mem_cgroup_swappiness(sc
->mem_cgroup
);
1847 * Determine how aggressively the anon and file LRU lists should be
1848 * scanned. The relative value of each set of LRU lists is determined
1849 * by looking at the fraction of the pages scanned we did rotate back
1850 * onto the active list instead of evict.
1852 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1854 static void get_scan_count(struct zone
*zone
, struct scan_control
*sc
,
1855 unsigned long *nr
, int priority
)
1857 unsigned long anon
, file
, free
;
1858 unsigned long anon_prio
, file_prio
;
1859 unsigned long ap
, fp
;
1860 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1861 u64 fraction
[2], denominator
;
1864 bool force_scan
= false;
1867 * If the zone or memcg is small, nr[l] can be 0. This
1868 * results in no scanning on this priority and a potential
1869 * priority drop. Global direct reclaim can go to the next
1870 * zone and tends to have no problems. Global kswapd is for
1871 * zone balancing and it needs to scan a minimum amount. When
1872 * reclaiming for a memcg, a priority drop can cause high
1873 * latencies, so it's better to scan a minimum amount there as
1876 if (scanning_global_lru(sc
) && current_is_kswapd())
1878 if (!scanning_global_lru(sc
))
1881 /* If we have no swap space, do not bother scanning anon pages. */
1882 if (!sc
->may_swap
|| (nr_swap_pages
<= 0)) {
1890 anon
= zone_nr_lru_pages(zone
, sc
, LRU_ACTIVE_ANON
) +
1891 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_ANON
);
1892 file
= zone_nr_lru_pages(zone
, sc
, LRU_ACTIVE_FILE
) +
1893 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_FILE
);
1895 if (scanning_global_lru(sc
)) {
1896 free
= zone_page_state(zone
, NR_FREE_PAGES
);
1897 /* If we have very few page cache pages,
1898 force-scan anon pages. */
1899 if (unlikely(file
+ free
<= high_wmark_pages(zone
))) {
1908 * With swappiness at 100, anonymous and file have the same priority.
1909 * This scanning priority is essentially the inverse of IO cost.
1911 anon_prio
= vmscan_swappiness(sc
);
1912 file_prio
= 200 - vmscan_swappiness(sc
);
1915 * OK, so we have swap space and a fair amount of page cache
1916 * pages. We use the recently rotated / recently scanned
1917 * ratios to determine how valuable each cache is.
1919 * Because workloads change over time (and to avoid overflow)
1920 * we keep these statistics as a floating average, which ends
1921 * up weighing recent references more than old ones.
1923 * anon in [0], file in [1]
1925 spin_lock_irq(&zone
->lru_lock
);
1926 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
1927 reclaim_stat
->recent_scanned
[0] /= 2;
1928 reclaim_stat
->recent_rotated
[0] /= 2;
1931 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
1932 reclaim_stat
->recent_scanned
[1] /= 2;
1933 reclaim_stat
->recent_rotated
[1] /= 2;
1937 * The amount of pressure on anon vs file pages is inversely
1938 * proportional to the fraction of recently scanned pages on
1939 * each list that were recently referenced and in active use.
1941 ap
= (anon_prio
+ 1) * (reclaim_stat
->recent_scanned
[0] + 1);
1942 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
1944 fp
= (file_prio
+ 1) * (reclaim_stat
->recent_scanned
[1] + 1);
1945 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
1946 spin_unlock_irq(&zone
->lru_lock
);
1950 denominator
= ap
+ fp
+ 1;
1952 for_each_evictable_lru(l
) {
1953 int file
= is_file_lru(l
);
1956 scan
= zone_nr_lru_pages(zone
, sc
, l
);
1957 if (priority
|| noswap
) {
1959 if (!scan
&& force_scan
)
1960 scan
= SWAP_CLUSTER_MAX
;
1961 scan
= div64_u64(scan
* fraction
[file
], denominator
);
1968 * Reclaim/compaction depends on a number of pages being freed. To avoid
1969 * disruption to the system, a small number of order-0 pages continue to be
1970 * rotated and reclaimed in the normal fashion. However, by the time we get
1971 * back to the allocator and call try_to_compact_zone(), we ensure that
1972 * there are enough free pages for it to be likely successful
1974 static inline bool should_continue_reclaim(struct zone
*zone
,
1975 unsigned long nr_reclaimed
,
1976 unsigned long nr_scanned
,
1977 struct scan_control
*sc
)
1979 unsigned long pages_for_compaction
;
1980 unsigned long inactive_lru_pages
;
1982 /* If not in reclaim/compaction mode, stop */
1983 if (!(sc
->reclaim_mode
& RECLAIM_MODE_COMPACTION
))
1986 /* Consider stopping depending on scan and reclaim activity */
1987 if (sc
->gfp_mask
& __GFP_REPEAT
) {
1989 * For __GFP_REPEAT allocations, stop reclaiming if the
1990 * full LRU list has been scanned and we are still failing
1991 * to reclaim pages. This full LRU scan is potentially
1992 * expensive but a __GFP_REPEAT caller really wants to succeed
1994 if (!nr_reclaimed
&& !nr_scanned
)
1998 * For non-__GFP_REPEAT allocations which can presumably
1999 * fail without consequence, stop if we failed to reclaim
2000 * any pages from the last SWAP_CLUSTER_MAX number of
2001 * pages that were scanned. This will return to the
2002 * caller faster at the risk reclaim/compaction and
2003 * the resulting allocation attempt fails
2010 * If we have not reclaimed enough pages for compaction and the
2011 * inactive lists are large enough, continue reclaiming
2013 pages_for_compaction
= (2UL << sc
->order
);
2014 inactive_lru_pages
= zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_ANON
) +
2015 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_FILE
);
2016 if (sc
->nr_reclaimed
< pages_for_compaction
&&
2017 inactive_lru_pages
> pages_for_compaction
)
2020 /* If compaction would go ahead or the allocation would succeed, stop */
2021 switch (compaction_suitable(zone
, sc
->order
)) {
2022 case COMPACT_PARTIAL
:
2023 case COMPACT_CONTINUE
:
2031 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
2033 static void shrink_zone(int priority
, struct zone
*zone
,
2034 struct scan_control
*sc
)
2036 unsigned long nr
[NR_LRU_LISTS
];
2037 unsigned long nr_to_scan
;
2039 unsigned long nr_reclaimed
, nr_scanned
;
2040 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
2041 struct blk_plug plug
;
2045 nr_scanned
= sc
->nr_scanned
;
2046 get_scan_count(zone
, sc
, nr
, priority
);
2048 blk_start_plug(&plug
);
2049 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
2050 nr
[LRU_INACTIVE_FILE
]) {
2051 for_each_evictable_lru(l
) {
2053 nr_to_scan
= min_t(unsigned long,
2054 nr
[l
], SWAP_CLUSTER_MAX
);
2055 nr
[l
] -= nr_to_scan
;
2057 nr_reclaimed
+= shrink_list(l
, nr_to_scan
,
2058 zone
, sc
, priority
);
2062 * On large memory systems, scan >> priority can become
2063 * really large. This is fine for the starting priority;
2064 * we want to put equal scanning pressure on each zone.
2065 * However, if the VM has a harder time of freeing pages,
2066 * with multiple processes reclaiming pages, the total
2067 * freeing target can get unreasonably large.
2069 if (nr_reclaimed
>= nr_to_reclaim
&& priority
< DEF_PRIORITY
)
2072 blk_finish_plug(&plug
);
2073 sc
->nr_reclaimed
+= nr_reclaimed
;
2076 * Even if we did not try to evict anon pages at all, we want to
2077 * rebalance the anon lru active/inactive ratio.
2079 if (inactive_anon_is_low(zone
, sc
))
2080 shrink_active_list(SWAP_CLUSTER_MAX
, zone
, sc
, priority
, 0);
2082 /* reclaim/compaction might need reclaim to continue */
2083 if (should_continue_reclaim(zone
, nr_reclaimed
,
2084 sc
->nr_scanned
- nr_scanned
, sc
))
2087 throttle_vm_writeout(sc
->gfp_mask
);
2091 * This is the direct reclaim path, for page-allocating processes. We only
2092 * try to reclaim pages from zones which will satisfy the caller's allocation
2095 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2097 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2099 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2100 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2101 * zone defense algorithm.
2103 * If a zone is deemed to be full of pinned pages then just give it a light
2104 * scan then give up on it.
2106 static void shrink_zones(int priority
, struct zonelist
*zonelist
,
2107 struct scan_control
*sc
)
2111 unsigned long nr_soft_reclaimed
;
2112 unsigned long nr_soft_scanned
;
2114 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2115 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2116 if (!populated_zone(zone
))
2119 * Take care memory controller reclaiming has small influence
2122 if (scanning_global_lru(sc
)) {
2123 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2125 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2126 continue; /* Let kswapd poll it */
2128 * This steals pages from memory cgroups over softlimit
2129 * and returns the number of reclaimed pages and
2130 * scanned pages. This works for global memory pressure
2131 * and balancing, not for a memcg's limit.
2133 nr_soft_scanned
= 0;
2134 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2135 sc
->order
, sc
->gfp_mask
,
2137 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
2138 sc
->nr_scanned
+= nr_soft_scanned
;
2139 /* need some check for avoid more shrink_zone() */
2142 shrink_zone(priority
, zone
, sc
);
2146 static bool zone_reclaimable(struct zone
*zone
)
2148 return zone
->pages_scanned
< zone_reclaimable_pages(zone
) * 6;
2151 /* All zones in zonelist are unreclaimable? */
2152 static bool all_unreclaimable(struct zonelist
*zonelist
,
2153 struct scan_control
*sc
)
2158 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2159 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2160 if (!populated_zone(zone
))
2162 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2164 if (!zone
->all_unreclaimable
)
2172 * This is the main entry point to direct page reclaim.
2174 * If a full scan of the inactive list fails to free enough memory then we
2175 * are "out of memory" and something needs to be killed.
2177 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2178 * high - the zone may be full of dirty or under-writeback pages, which this
2179 * caller can't do much about. We kick the writeback threads and take explicit
2180 * naps in the hope that some of these pages can be written. But if the
2181 * allocating task holds filesystem locks which prevent writeout this might not
2182 * work, and the allocation attempt will fail.
2184 * returns: 0, if no pages reclaimed
2185 * else, the number of pages reclaimed
2187 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2188 struct scan_control
*sc
,
2189 struct shrink_control
*shrink
)
2192 unsigned long total_scanned
= 0;
2193 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2196 unsigned long writeback_threshold
;
2199 delayacct_freepages_start();
2201 if (scanning_global_lru(sc
))
2202 count_vm_event(ALLOCSTALL
);
2204 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2207 disable_swap_token(sc
->mem_cgroup
);
2208 shrink_zones(priority
, zonelist
, sc
);
2210 * Don't shrink slabs when reclaiming memory from
2211 * over limit cgroups
2213 if (scanning_global_lru(sc
)) {
2214 unsigned long lru_pages
= 0;
2215 for_each_zone_zonelist(zone
, z
, zonelist
,
2216 gfp_zone(sc
->gfp_mask
)) {
2217 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2220 lru_pages
+= zone_reclaimable_pages(zone
);
2223 shrink_slab(shrink
, sc
->nr_scanned
, lru_pages
);
2224 if (reclaim_state
) {
2225 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2226 reclaim_state
->reclaimed_slab
= 0;
2229 total_scanned
+= sc
->nr_scanned
;
2230 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
2234 * Try to write back as many pages as we just scanned. This
2235 * tends to cause slow streaming writers to write data to the
2236 * disk smoothly, at the dirtying rate, which is nice. But
2237 * that's undesirable in laptop mode, where we *want* lumpy
2238 * writeout. So in laptop mode, write out the whole world.
2240 writeback_threshold
= sc
->nr_to_reclaim
+ sc
->nr_to_reclaim
/ 2;
2241 if (total_scanned
> writeback_threshold
) {
2242 wakeup_flusher_threads(laptop_mode
? 0 : total_scanned
);
2243 sc
->may_writepage
= 1;
2246 /* Take a nap, wait for some writeback to complete */
2247 if (!sc
->hibernation_mode
&& sc
->nr_scanned
&&
2248 priority
< DEF_PRIORITY
- 2) {
2249 struct zone
*preferred_zone
;
2251 first_zones_zonelist(zonelist
, gfp_zone(sc
->gfp_mask
),
2252 &cpuset_current_mems_allowed
,
2254 wait_iff_congested(preferred_zone
, BLK_RW_ASYNC
, HZ
/10);
2259 delayacct_freepages_end();
2262 if (sc
->nr_reclaimed
)
2263 return sc
->nr_reclaimed
;
2266 * As hibernation is going on, kswapd is freezed so that it can't mark
2267 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2270 if (oom_killer_disabled
)
2273 /* top priority shrink_zones still had more to do? don't OOM, then */
2274 if (scanning_global_lru(sc
) && !all_unreclaimable(zonelist
, sc
))
2280 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
2281 gfp_t gfp_mask
, nodemask_t
*nodemask
)
2283 unsigned long nr_reclaimed
;
2284 struct scan_control sc
= {
2285 .gfp_mask
= gfp_mask
,
2286 .may_writepage
= !laptop_mode
,
2287 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2292 .nodemask
= nodemask
,
2294 struct shrink_control shrink
= {
2295 .gfp_mask
= sc
.gfp_mask
,
2298 trace_mm_vmscan_direct_reclaim_begin(order
,
2302 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
2304 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
2306 return nr_reclaimed
;
2309 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2311 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup
*mem
,
2312 gfp_t gfp_mask
, bool noswap
,
2314 unsigned long *nr_scanned
)
2316 struct scan_control sc
= {
2318 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2319 .may_writepage
= !laptop_mode
,
2321 .may_swap
= !noswap
,
2326 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2327 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2329 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2334 * NOTE: Although we can get the priority field, using it
2335 * here is not a good idea, since it limits the pages we can scan.
2336 * if we don't reclaim here, the shrink_zone from balance_pgdat
2337 * will pick up pages from other mem cgroup's as well. We hack
2338 * the priority and make it zero.
2340 shrink_zone(0, zone
, &sc
);
2342 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
2344 *nr_scanned
= sc
.nr_scanned
;
2345 return sc
.nr_reclaimed
;
2348 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*mem_cont
,
2352 struct zonelist
*zonelist
;
2353 unsigned long nr_reclaimed
;
2355 struct scan_control sc
= {
2356 .may_writepage
= !laptop_mode
,
2358 .may_swap
= !noswap
,
2359 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2361 .mem_cgroup
= mem_cont
,
2362 .nodemask
= NULL
, /* we don't care the placement */
2363 .gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2364 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
2366 struct shrink_control shrink
= {
2367 .gfp_mask
= sc
.gfp_mask
,
2371 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2372 * take care of from where we get pages. So the node where we start the
2373 * scan does not need to be the current node.
2375 nid
= mem_cgroup_select_victim_node(mem_cont
);
2377 zonelist
= NODE_DATA(nid
)->node_zonelists
;
2379 trace_mm_vmscan_memcg_reclaim_begin(0,
2383 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
2385 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
2387 return nr_reclaimed
;
2392 * pgdat_balanced is used when checking if a node is balanced for high-order
2393 * allocations. Only zones that meet watermarks and are in a zone allowed
2394 * by the callers classzone_idx are added to balanced_pages. The total of
2395 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2396 * for the node to be considered balanced. Forcing all zones to be balanced
2397 * for high orders can cause excessive reclaim when there are imbalanced zones.
2398 * The choice of 25% is due to
2399 * o a 16M DMA zone that is balanced will not balance a zone on any
2400 * reasonable sized machine
2401 * o On all other machines, the top zone must be at least a reasonable
2402 * percentage of the middle zones. For example, on 32-bit x86, highmem
2403 * would need to be at least 256M for it to be balance a whole node.
2404 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2405 * to balance a node on its own. These seemed like reasonable ratios.
2407 static bool pgdat_balanced(pg_data_t
*pgdat
, unsigned long balanced_pages
,
2410 unsigned long present_pages
= 0;
2413 for (i
= 0; i
<= classzone_idx
; i
++)
2414 present_pages
+= pgdat
->node_zones
[i
].present_pages
;
2416 /* A special case here: if zone has no page, we think it's balanced */
2417 return balanced_pages
>= (present_pages
>> 2);
2420 /* is kswapd sleeping prematurely? */
2421 static bool sleeping_prematurely(pg_data_t
*pgdat
, int order
, long remaining
,
2425 unsigned long balanced
= 0;
2426 bool all_zones_ok
= true;
2428 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2432 /* Check the watermark levels */
2433 for (i
= 0; i
<= classzone_idx
; i
++) {
2434 struct zone
*zone
= pgdat
->node_zones
+ i
;
2436 if (!populated_zone(zone
))
2440 * balance_pgdat() skips over all_unreclaimable after
2441 * DEF_PRIORITY. Effectively, it considers them balanced so
2442 * they must be considered balanced here as well if kswapd
2445 if (zone
->all_unreclaimable
) {
2446 balanced
+= zone
->present_pages
;
2450 if (!zone_watermark_ok_safe(zone
, order
, high_wmark_pages(zone
),
2452 all_zones_ok
= false;
2454 balanced
+= zone
->present_pages
;
2458 * For high-order requests, the balanced zones must contain at least
2459 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2463 return !pgdat_balanced(pgdat
, balanced
, classzone_idx
);
2465 return !all_zones_ok
;
2469 * For kswapd, balance_pgdat() will work across all this node's zones until
2470 * they are all at high_wmark_pages(zone).
2472 * Returns the final order kswapd was reclaiming at
2474 * There is special handling here for zones which are full of pinned pages.
2475 * This can happen if the pages are all mlocked, or if they are all used by
2476 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2477 * What we do is to detect the case where all pages in the zone have been
2478 * scanned twice and there has been zero successful reclaim. Mark the zone as
2479 * dead and from now on, only perform a short scan. Basically we're polling
2480 * the zone for when the problem goes away.
2482 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2483 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2484 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2485 * lower zones regardless of the number of free pages in the lower zones. This
2486 * interoperates with the page allocator fallback scheme to ensure that aging
2487 * of pages is balanced across the zones.
2489 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
,
2493 unsigned long balanced
;
2496 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
2497 unsigned long total_scanned
;
2498 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2499 unsigned long nr_soft_reclaimed
;
2500 unsigned long nr_soft_scanned
;
2501 struct scan_control sc
= {
2502 .gfp_mask
= GFP_KERNEL
,
2506 * kswapd doesn't want to be bailed out while reclaim. because
2507 * we want to put equal scanning pressure on each zone.
2509 .nr_to_reclaim
= ULONG_MAX
,
2513 struct shrink_control shrink
= {
2514 .gfp_mask
= sc
.gfp_mask
,
2518 sc
.nr_reclaimed
= 0;
2519 sc
.may_writepage
= !laptop_mode
;
2520 count_vm_event(PAGEOUTRUN
);
2522 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2523 unsigned long lru_pages
= 0;
2524 int has_under_min_watermark_zone
= 0;
2526 /* The swap token gets in the way of swapout... */
2528 disable_swap_token(NULL
);
2534 * Scan in the highmem->dma direction for the highest
2535 * zone which needs scanning
2537 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
2538 struct zone
*zone
= pgdat
->node_zones
+ i
;
2540 if (!populated_zone(zone
))
2543 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2547 * Do some background aging of the anon list, to give
2548 * pages a chance to be referenced before reclaiming.
2550 if (inactive_anon_is_low(zone
, &sc
))
2551 shrink_active_list(SWAP_CLUSTER_MAX
, zone
,
2554 if (!zone_watermark_ok_safe(zone
, order
,
2555 high_wmark_pages(zone
), 0, 0)) {
2559 /* If balanced, clear the congested flag */
2560 zone_clear_flag(zone
, ZONE_CONGESTED
);
2566 for (i
= 0; i
<= end_zone
; i
++) {
2567 struct zone
*zone
= pgdat
->node_zones
+ i
;
2569 lru_pages
+= zone_reclaimable_pages(zone
);
2573 * Now scan the zone in the dma->highmem direction, stopping
2574 * at the last zone which needs scanning.
2576 * We do this because the page allocator works in the opposite
2577 * direction. This prevents the page allocator from allocating
2578 * pages behind kswapd's direction of progress, which would
2579 * cause too much scanning of the lower zones.
2581 for (i
= 0; i
<= end_zone
; i
++) {
2582 struct zone
*zone
= pgdat
->node_zones
+ i
;
2584 unsigned long balance_gap
;
2586 if (!populated_zone(zone
))
2589 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2594 nr_soft_scanned
= 0;
2596 * Call soft limit reclaim before calling shrink_zone.
2598 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2601 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
2602 total_scanned
+= nr_soft_scanned
;
2605 * We put equal pressure on every zone, unless
2606 * one zone has way too many pages free
2607 * already. The "too many pages" is defined
2608 * as the high wmark plus a "gap" where the
2609 * gap is either the low watermark or 1%
2610 * of the zone, whichever is smaller.
2612 balance_gap
= min(low_wmark_pages(zone
),
2613 (zone
->present_pages
+
2614 KSWAPD_ZONE_BALANCE_GAP_RATIO
-1) /
2615 KSWAPD_ZONE_BALANCE_GAP_RATIO
);
2616 if (!zone_watermark_ok_safe(zone
, order
,
2617 high_wmark_pages(zone
) + balance_gap
,
2619 shrink_zone(priority
, zone
, &sc
);
2621 reclaim_state
->reclaimed_slab
= 0;
2622 nr_slab
= shrink_slab(&shrink
, sc
.nr_scanned
, lru_pages
);
2623 sc
.nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2624 total_scanned
+= sc
.nr_scanned
;
2626 if (nr_slab
== 0 && !zone_reclaimable(zone
))
2627 zone
->all_unreclaimable
= 1;
2631 * If we've done a decent amount of scanning and
2632 * the reclaim ratio is low, start doing writepage
2633 * even in laptop mode
2635 if (total_scanned
> SWAP_CLUSTER_MAX
* 2 &&
2636 total_scanned
> sc
.nr_reclaimed
+ sc
.nr_reclaimed
/ 2)
2637 sc
.may_writepage
= 1;
2639 if (zone
->all_unreclaimable
) {
2640 if (end_zone
&& end_zone
== i
)
2645 if (!zone_watermark_ok_safe(zone
, order
,
2646 high_wmark_pages(zone
), end_zone
, 0)) {
2649 * We are still under min water mark. This
2650 * means that we have a GFP_ATOMIC allocation
2651 * failure risk. Hurry up!
2653 if (!zone_watermark_ok_safe(zone
, order
,
2654 min_wmark_pages(zone
), end_zone
, 0))
2655 has_under_min_watermark_zone
= 1;
2658 * If a zone reaches its high watermark,
2659 * consider it to be no longer congested. It's
2660 * possible there are dirty pages backed by
2661 * congested BDIs but as pressure is relieved,
2662 * spectulatively avoid congestion waits
2664 zone_clear_flag(zone
, ZONE_CONGESTED
);
2665 if (i
<= *classzone_idx
)
2666 balanced
+= zone
->present_pages
;
2670 if (all_zones_ok
|| (order
&& pgdat_balanced(pgdat
, balanced
, *classzone_idx
)))
2671 break; /* kswapd: all done */
2673 * OK, kswapd is getting into trouble. Take a nap, then take
2674 * another pass across the zones.
2676 if (total_scanned
&& (priority
< DEF_PRIORITY
- 2)) {
2677 if (has_under_min_watermark_zone
)
2678 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT
);
2680 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
2684 * We do this so kswapd doesn't build up large priorities for
2685 * example when it is freeing in parallel with allocators. It
2686 * matches the direct reclaim path behaviour in terms of impact
2687 * on zone->*_priority.
2689 if (sc
.nr_reclaimed
>= SWAP_CLUSTER_MAX
)
2695 * order-0: All zones must meet high watermark for a balanced node
2696 * high-order: Balanced zones must make up at least 25% of the node
2697 * for the node to be balanced
2699 if (!(all_zones_ok
|| (order
&& pgdat_balanced(pgdat
, balanced
, *classzone_idx
)))) {
2705 * Fragmentation may mean that the system cannot be
2706 * rebalanced for high-order allocations in all zones.
2707 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2708 * it means the zones have been fully scanned and are still
2709 * not balanced. For high-order allocations, there is
2710 * little point trying all over again as kswapd may
2713 * Instead, recheck all watermarks at order-0 as they
2714 * are the most important. If watermarks are ok, kswapd will go
2715 * back to sleep. High-order users can still perform direct
2716 * reclaim if they wish.
2718 if (sc
.nr_reclaimed
< SWAP_CLUSTER_MAX
)
2719 order
= sc
.order
= 0;
2725 * If kswapd was reclaiming at a higher order, it has the option of
2726 * sleeping without all zones being balanced. Before it does, it must
2727 * ensure that the watermarks for order-0 on *all* zones are met and
2728 * that the congestion flags are cleared. The congestion flag must
2729 * be cleared as kswapd is the only mechanism that clears the flag
2730 * and it is potentially going to sleep here.
2733 for (i
= 0; i
<= end_zone
; i
++) {
2734 struct zone
*zone
= pgdat
->node_zones
+ i
;
2736 if (!populated_zone(zone
))
2739 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2742 /* Confirm the zone is balanced for order-0 */
2743 if (!zone_watermark_ok(zone
, 0,
2744 high_wmark_pages(zone
), 0, 0)) {
2745 order
= sc
.order
= 0;
2749 /* If balanced, clear the congested flag */
2750 zone_clear_flag(zone
, ZONE_CONGESTED
);
2751 if (i
<= *classzone_idx
)
2752 balanced
+= zone
->present_pages
;
2757 * Return the order we were reclaiming at so sleeping_prematurely()
2758 * makes a decision on the order we were last reclaiming at. However,
2759 * if another caller entered the allocator slow path while kswapd
2760 * was awake, order will remain at the higher level
2762 *classzone_idx
= end_zone
;
2766 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
2771 if (freezing(current
) || kthread_should_stop())
2774 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2776 /* Try to sleep for a short interval */
2777 if (!sleeping_prematurely(pgdat
, order
, remaining
, classzone_idx
)) {
2778 remaining
= schedule_timeout(HZ
/10);
2779 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2780 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2784 * After a short sleep, check if it was a premature sleep. If not, then
2785 * go fully to sleep until explicitly woken up.
2787 if (!sleeping_prematurely(pgdat
, order
, remaining
, classzone_idx
)) {
2788 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
2791 * vmstat counters are not perfectly accurate and the estimated
2792 * value for counters such as NR_FREE_PAGES can deviate from the
2793 * true value by nr_online_cpus * threshold. To avoid the zone
2794 * watermarks being breached while under pressure, we reduce the
2795 * per-cpu vmstat threshold while kswapd is awake and restore
2796 * them before going back to sleep.
2798 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
2800 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
2803 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
2805 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
2807 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2811 * The background pageout daemon, started as a kernel thread
2812 * from the init process.
2814 * This basically trickles out pages so that we have _some_
2815 * free memory available even if there is no other activity
2816 * that frees anything up. This is needed for things like routing
2817 * etc, where we otherwise might have all activity going on in
2818 * asynchronous contexts that cannot page things out.
2820 * If there are applications that are active memory-allocators
2821 * (most normal use), this basically shouldn't matter.
2823 static int kswapd(void *p
)
2825 unsigned long order
, new_order
;
2826 unsigned balanced_order
;
2827 int classzone_idx
, new_classzone_idx
;
2828 int balanced_classzone_idx
;
2829 pg_data_t
*pgdat
= (pg_data_t
*)p
;
2830 struct task_struct
*tsk
= current
;
2832 struct reclaim_state reclaim_state
= {
2833 .reclaimed_slab
= 0,
2835 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
2837 lockdep_set_current_reclaim_state(GFP_KERNEL
);
2839 if (!cpumask_empty(cpumask
))
2840 set_cpus_allowed_ptr(tsk
, cpumask
);
2841 current
->reclaim_state
= &reclaim_state
;
2844 * Tell the memory management that we're a "memory allocator",
2845 * and that if we need more memory we should get access to it
2846 * regardless (see "__alloc_pages()"). "kswapd" should
2847 * never get caught in the normal page freeing logic.
2849 * (Kswapd normally doesn't need memory anyway, but sometimes
2850 * you need a small amount of memory in order to be able to
2851 * page out something else, and this flag essentially protects
2852 * us from recursively trying to free more memory as we're
2853 * trying to free the first piece of memory in the first place).
2855 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
2858 order
= new_order
= 0;
2860 classzone_idx
= new_classzone_idx
= pgdat
->nr_zones
- 1;
2861 balanced_classzone_idx
= classzone_idx
;
2866 * If the last balance_pgdat was unsuccessful it's unlikely a
2867 * new request of a similar or harder type will succeed soon
2868 * so consider going to sleep on the basis we reclaimed at
2870 if (balanced_classzone_idx
>= new_classzone_idx
&&
2871 balanced_order
== new_order
) {
2872 new_order
= pgdat
->kswapd_max_order
;
2873 new_classzone_idx
= pgdat
->classzone_idx
;
2874 pgdat
->kswapd_max_order
= 0;
2875 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
2878 if (order
< new_order
|| classzone_idx
> new_classzone_idx
) {
2880 * Don't sleep if someone wants a larger 'order'
2881 * allocation or has tigher zone constraints
2884 classzone_idx
= new_classzone_idx
;
2886 kswapd_try_to_sleep(pgdat
, balanced_order
,
2887 balanced_classzone_idx
);
2888 order
= pgdat
->kswapd_max_order
;
2889 classzone_idx
= pgdat
->classzone_idx
;
2890 pgdat
->kswapd_max_order
= 0;
2891 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
2894 ret
= try_to_freeze();
2895 if (kthread_should_stop())
2899 * We can speed up thawing tasks if we don't call balance_pgdat
2900 * after returning from the refrigerator
2903 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, order
);
2904 balanced_classzone_idx
= classzone_idx
;
2905 balanced_order
= balance_pgdat(pgdat
, order
,
2906 &balanced_classzone_idx
);
2913 * A zone is low on free memory, so wake its kswapd task to service it.
2915 void wakeup_kswapd(struct zone
*zone
, int order
, enum zone_type classzone_idx
)
2919 if (!populated_zone(zone
))
2922 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2924 pgdat
= zone
->zone_pgdat
;
2925 if (pgdat
->kswapd_max_order
< order
) {
2926 pgdat
->kswapd_max_order
= order
;
2927 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
, classzone_idx
);
2929 if (!waitqueue_active(&pgdat
->kswapd_wait
))
2931 if (zone_watermark_ok_safe(zone
, order
, low_wmark_pages(zone
), 0, 0))
2934 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, zone_idx(zone
), order
);
2935 wake_up_interruptible(&pgdat
->kswapd_wait
);
2939 * The reclaimable count would be mostly accurate.
2940 * The less reclaimable pages may be
2941 * - mlocked pages, which will be moved to unevictable list when encountered
2942 * - mapped pages, which may require several travels to be reclaimed
2943 * - dirty pages, which is not "instantly" reclaimable
2945 unsigned long global_reclaimable_pages(void)
2949 nr
= global_page_state(NR_ACTIVE_FILE
) +
2950 global_page_state(NR_INACTIVE_FILE
);
2952 if (nr_swap_pages
> 0)
2953 nr
+= global_page_state(NR_ACTIVE_ANON
) +
2954 global_page_state(NR_INACTIVE_ANON
);
2959 unsigned long zone_reclaimable_pages(struct zone
*zone
)
2963 nr
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
2964 zone_page_state(zone
, NR_INACTIVE_FILE
);
2966 if (nr_swap_pages
> 0)
2967 nr
+= zone_page_state(zone
, NR_ACTIVE_ANON
) +
2968 zone_page_state(zone
, NR_INACTIVE_ANON
);
2973 #ifdef CONFIG_HIBERNATION
2975 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2978 * Rather than trying to age LRUs the aim is to preserve the overall
2979 * LRU order by reclaiming preferentially
2980 * inactive > active > active referenced > active mapped
2982 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
2984 struct reclaim_state reclaim_state
;
2985 struct scan_control sc
= {
2986 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
2990 .nr_to_reclaim
= nr_to_reclaim
,
2991 .hibernation_mode
= 1,
2994 struct shrink_control shrink
= {
2995 .gfp_mask
= sc
.gfp_mask
,
2997 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
2998 struct task_struct
*p
= current
;
2999 unsigned long nr_reclaimed
;
3001 p
->flags
|= PF_MEMALLOC
;
3002 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
3003 reclaim_state
.reclaimed_slab
= 0;
3004 p
->reclaim_state
= &reclaim_state
;
3006 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
3008 p
->reclaim_state
= NULL
;
3009 lockdep_clear_current_reclaim_state();
3010 p
->flags
&= ~PF_MEMALLOC
;
3012 return nr_reclaimed
;
3014 #endif /* CONFIG_HIBERNATION */
3016 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3017 not required for correctness. So if the last cpu in a node goes
3018 away, we get changed to run anywhere: as the first one comes back,
3019 restore their cpu bindings. */
3020 static int __devinit
cpu_callback(struct notifier_block
*nfb
,
3021 unsigned long action
, void *hcpu
)
3025 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
3026 for_each_node_state(nid
, N_HIGH_MEMORY
) {
3027 pg_data_t
*pgdat
= NODE_DATA(nid
);
3028 const struct cpumask
*mask
;
3030 mask
= cpumask_of_node(pgdat
->node_id
);
3032 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
3033 /* One of our CPUs online: restore mask */
3034 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
3041 * This kswapd start function will be called by init and node-hot-add.
3042 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3044 int kswapd_run(int nid
)
3046 pg_data_t
*pgdat
= NODE_DATA(nid
);
3052 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
3053 if (IS_ERR(pgdat
->kswapd
)) {
3054 /* failure at boot is fatal */
3055 BUG_ON(system_state
== SYSTEM_BOOTING
);
3056 printk("Failed to start kswapd on node %d\n",nid
);
3063 * Called by memory hotplug when all memory in a node is offlined.
3065 void kswapd_stop(int nid
)
3067 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
3070 kthread_stop(kswapd
);
3073 static int __init
kswapd_init(void)
3078 for_each_node_state(nid
, N_HIGH_MEMORY
)
3080 hotcpu_notifier(cpu_callback
, 0);
3084 module_init(kswapd_init
)
3090 * If non-zero call zone_reclaim when the number of free pages falls below
3093 int zone_reclaim_mode __read_mostly
;
3095 #define RECLAIM_OFF 0
3096 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3097 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3098 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3101 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3102 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3105 #define ZONE_RECLAIM_PRIORITY 4
3108 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3111 int sysctl_min_unmapped_ratio
= 1;
3114 * If the number of slab pages in a zone grows beyond this percentage then
3115 * slab reclaim needs to occur.
3117 int sysctl_min_slab_ratio
= 5;
3119 static inline unsigned long zone_unmapped_file_pages(struct zone
*zone
)
3121 unsigned long file_mapped
= zone_page_state(zone
, NR_FILE_MAPPED
);
3122 unsigned long file_lru
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
3123 zone_page_state(zone
, NR_ACTIVE_FILE
);
3126 * It's possible for there to be more file mapped pages than
3127 * accounted for by the pages on the file LRU lists because
3128 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3130 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
3133 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3134 static long zone_pagecache_reclaimable(struct zone
*zone
)
3136 long nr_pagecache_reclaimable
;
3140 * If RECLAIM_SWAP is set, then all file pages are considered
3141 * potentially reclaimable. Otherwise, we have to worry about
3142 * pages like swapcache and zone_unmapped_file_pages() provides
3145 if (zone_reclaim_mode
& RECLAIM_SWAP
)
3146 nr_pagecache_reclaimable
= zone_page_state(zone
, NR_FILE_PAGES
);
3148 nr_pagecache_reclaimable
= zone_unmapped_file_pages(zone
);
3150 /* If we can't clean pages, remove dirty pages from consideration */
3151 if (!(zone_reclaim_mode
& RECLAIM_WRITE
))
3152 delta
+= zone_page_state(zone
, NR_FILE_DIRTY
);
3154 /* Watch for any possible underflows due to delta */
3155 if (unlikely(delta
> nr_pagecache_reclaimable
))
3156 delta
= nr_pagecache_reclaimable
;
3158 return nr_pagecache_reclaimable
- delta
;
3162 * Try to free up some pages from this zone through reclaim.
3164 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3166 /* Minimum pages needed in order to stay on node */
3167 const unsigned long nr_pages
= 1 << order
;
3168 struct task_struct
*p
= current
;
3169 struct reclaim_state reclaim_state
;
3171 struct scan_control sc
= {
3172 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
3173 .may_unmap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
3175 .nr_to_reclaim
= max_t(unsigned long, nr_pages
,
3177 .gfp_mask
= gfp_mask
,
3180 struct shrink_control shrink
= {
3181 .gfp_mask
= sc
.gfp_mask
,
3183 unsigned long nr_slab_pages0
, nr_slab_pages1
;
3187 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3188 * and we also need to be able to write out pages for RECLAIM_WRITE
3191 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
3192 lockdep_set_current_reclaim_state(gfp_mask
);
3193 reclaim_state
.reclaimed_slab
= 0;
3194 p
->reclaim_state
= &reclaim_state
;
3196 if (zone_pagecache_reclaimable(zone
) > zone
->min_unmapped_pages
) {
3198 * Free memory by calling shrink zone with increasing
3199 * priorities until we have enough memory freed.
3201 priority
= ZONE_RECLAIM_PRIORITY
;
3203 shrink_zone(priority
, zone
, &sc
);
3205 } while (priority
>= 0 && sc
.nr_reclaimed
< nr_pages
);
3208 nr_slab_pages0
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3209 if (nr_slab_pages0
> zone
->min_slab_pages
) {
3211 * shrink_slab() does not currently allow us to determine how
3212 * many pages were freed in this zone. So we take the current
3213 * number of slab pages and shake the slab until it is reduced
3214 * by the same nr_pages that we used for reclaiming unmapped
3217 * Note that shrink_slab will free memory on all zones and may
3221 unsigned long lru_pages
= zone_reclaimable_pages(zone
);
3223 /* No reclaimable slab or very low memory pressure */
3224 if (!shrink_slab(&shrink
, sc
.nr_scanned
, lru_pages
))
3227 /* Freed enough memory */
3228 nr_slab_pages1
= zone_page_state(zone
,
3229 NR_SLAB_RECLAIMABLE
);
3230 if (nr_slab_pages1
+ nr_pages
<= nr_slab_pages0
)
3235 * Update nr_reclaimed by the number of slab pages we
3236 * reclaimed from this zone.
3238 nr_slab_pages1
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3239 if (nr_slab_pages1
< nr_slab_pages0
)
3240 sc
.nr_reclaimed
+= nr_slab_pages0
- nr_slab_pages1
;
3243 p
->reclaim_state
= NULL
;
3244 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
3245 lockdep_clear_current_reclaim_state();
3246 return sc
.nr_reclaimed
>= nr_pages
;
3249 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3255 * Zone reclaim reclaims unmapped file backed pages and
3256 * slab pages if we are over the defined limits.
3258 * A small portion of unmapped file backed pages is needed for
3259 * file I/O otherwise pages read by file I/O will be immediately
3260 * thrown out if the zone is overallocated. So we do not reclaim
3261 * if less than a specified percentage of the zone is used by
3262 * unmapped file backed pages.
3264 if (zone_pagecache_reclaimable(zone
) <= zone
->min_unmapped_pages
&&
3265 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) <= zone
->min_slab_pages
)
3266 return ZONE_RECLAIM_FULL
;
3268 if (zone
->all_unreclaimable
)
3269 return ZONE_RECLAIM_FULL
;
3272 * Do not scan if the allocation should not be delayed.
3274 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
3275 return ZONE_RECLAIM_NOSCAN
;
3278 * Only run zone reclaim on the local zone or on zones that do not
3279 * have associated processors. This will favor the local processor
3280 * over remote processors and spread off node memory allocations
3281 * as wide as possible.
3283 node_id
= zone_to_nid(zone
);
3284 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
3285 return ZONE_RECLAIM_NOSCAN
;
3287 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
3288 return ZONE_RECLAIM_NOSCAN
;
3290 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
3291 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);
3294 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
3301 * page_evictable - test whether a page is evictable
3302 * @page: the page to test
3303 * @vma: the VMA in which the page is or will be mapped, may be NULL
3305 * Test whether page is evictable--i.e., should be placed on active/inactive
3306 * lists vs unevictable list. The vma argument is !NULL when called from the
3307 * fault path to determine how to instantate a new page.
3309 * Reasons page might not be evictable:
3310 * (1) page's mapping marked unevictable
3311 * (2) page is part of an mlocked VMA
3314 int page_evictable(struct page
*page
, struct vm_area_struct
*vma
)
3317 if (mapping_unevictable(page_mapping(page
)))
3320 if (PageMlocked(page
) || (vma
&& is_mlocked_vma(vma
, page
)))
3327 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3328 * @page: page to check evictability and move to appropriate lru list
3329 * @zone: zone page is in
3331 * Checks a page for evictability and moves the page to the appropriate
3334 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3335 * have PageUnevictable set.
3337 static void check_move_unevictable_page(struct page
*page
, struct zone
*zone
)
3339 VM_BUG_ON(PageActive(page
));
3342 ClearPageUnevictable(page
);
3343 if (page_evictable(page
, NULL
)) {
3344 enum lru_list l
= page_lru_base_type(page
);
3346 __dec_zone_state(zone
, NR_UNEVICTABLE
);
3347 list_move(&page
->lru
, &zone
->lru
[l
].list
);
3348 mem_cgroup_move_lists(page
, LRU_UNEVICTABLE
, l
);
3349 __inc_zone_state(zone
, NR_INACTIVE_ANON
+ l
);
3350 __count_vm_event(UNEVICTABLE_PGRESCUED
);
3353 * rotate unevictable list
3355 SetPageUnevictable(page
);
3356 list_move(&page
->lru
, &zone
->lru
[LRU_UNEVICTABLE
].list
);
3357 mem_cgroup_rotate_lru_list(page
, LRU_UNEVICTABLE
);
3358 if (page_evictable(page
, NULL
))
3364 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3365 * @mapping: struct address_space to scan for evictable pages
3367 * Scan all pages in mapping. Check unevictable pages for
3368 * evictability and move them to the appropriate zone lru list.
3370 void scan_mapping_unevictable_pages(struct address_space
*mapping
)
3373 pgoff_t end
= (i_size_read(mapping
->host
) + PAGE_CACHE_SIZE
- 1) >>
3376 struct pagevec pvec
;
3378 if (mapping
->nrpages
== 0)
3381 pagevec_init(&pvec
, 0);
3382 while (next
< end
&&
3383 pagevec_lookup(&pvec
, mapping
, next
, PAGEVEC_SIZE
)) {
3389 for (i
= 0; i
< pagevec_count(&pvec
); i
++) {
3390 struct page
*page
= pvec
.pages
[i
];
3391 pgoff_t page_index
= page
->index
;
3392 struct zone
*pagezone
= page_zone(page
);
3395 if (page_index
> next
)
3399 if (pagezone
!= zone
) {
3401 spin_unlock_irq(&zone
->lru_lock
);
3403 spin_lock_irq(&zone
->lru_lock
);
3406 if (PageLRU(page
) && PageUnevictable(page
))
3407 check_move_unevictable_page(page
, zone
);
3410 spin_unlock_irq(&zone
->lru_lock
);
3411 pagevec_release(&pvec
);
3413 count_vm_events(UNEVICTABLE_PGSCANNED
, pg_scanned
);
3419 * scan_zone_unevictable_pages - check unevictable list for evictable pages
3420 * @zone - zone of which to scan the unevictable list
3422 * Scan @zone's unevictable LRU lists to check for pages that have become
3423 * evictable. Move those that have to @zone's inactive list where they
3424 * become candidates for reclaim, unless shrink_inactive_zone() decides
3425 * to reactivate them. Pages that are still unevictable are rotated
3426 * back onto @zone's unevictable list.
3428 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
3429 static void scan_zone_unevictable_pages(struct zone
*zone
)
3431 struct list_head
*l_unevictable
= &zone
->lru
[LRU_UNEVICTABLE
].list
;
3433 unsigned long nr_to_scan
= zone_page_state(zone
, NR_UNEVICTABLE
);
3435 while (nr_to_scan
> 0) {
3436 unsigned long batch_size
= min(nr_to_scan
,
3437 SCAN_UNEVICTABLE_BATCH_SIZE
);
3439 spin_lock_irq(&zone
->lru_lock
);
3440 for (scan
= 0; scan
< batch_size
; scan
++) {
3441 struct page
*page
= lru_to_page(l_unevictable
);
3443 if (!trylock_page(page
))
3446 prefetchw_prev_lru_page(page
, l_unevictable
, flags
);
3448 if (likely(PageLRU(page
) && PageUnevictable(page
)))
3449 check_move_unevictable_page(page
, zone
);
3453 spin_unlock_irq(&zone
->lru_lock
);
3455 nr_to_scan
-= batch_size
;
3461 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
3463 * A really big hammer: scan all zones' unevictable LRU lists to check for
3464 * pages that have become evictable. Move those back to the zones'
3465 * inactive list where they become candidates for reclaim.
3466 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
3467 * and we add swap to the system. As such, it runs in the context of a task
3468 * that has possibly/probably made some previously unevictable pages
3471 static void scan_all_zones_unevictable_pages(void)
3475 for_each_zone(zone
) {
3476 scan_zone_unevictable_pages(zone
);
3481 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3482 * all nodes' unevictable lists for evictable pages
3484 unsigned long scan_unevictable_pages
;
3486 int scan_unevictable_handler(struct ctl_table
*table
, int write
,
3487 void __user
*buffer
,
3488 size_t *length
, loff_t
*ppos
)
3490 proc_doulongvec_minmax(table
, write
, buffer
, length
, ppos
);
3492 if (write
&& *(unsigned long *)table
->data
)
3493 scan_all_zones_unevictable_pages();
3495 scan_unevictable_pages
= 0;
3501 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3502 * a specified node's per zone unevictable lists for evictable pages.
3505 static ssize_t
read_scan_unevictable_node(struct sys_device
*dev
,
3506 struct sysdev_attribute
*attr
,
3509 return sprintf(buf
, "0\n"); /* always zero; should fit... */
3512 static ssize_t
write_scan_unevictable_node(struct sys_device
*dev
,
3513 struct sysdev_attribute
*attr
,
3514 const char *buf
, size_t count
)
3516 struct zone
*node_zones
= NODE_DATA(dev
->id
)->node_zones
;
3519 unsigned long req
= strict_strtoul(buf
, 10, &res
);
3522 return 1; /* zero is no-op */
3524 for (zone
= node_zones
; zone
- node_zones
< MAX_NR_ZONES
; ++zone
) {
3525 if (!populated_zone(zone
))
3527 scan_zone_unevictable_pages(zone
);
3533 static SYSDEV_ATTR(scan_unevictable_pages
, S_IRUGO
| S_IWUSR
,
3534 read_scan_unevictable_node
,
3535 write_scan_unevictable_node
);
3537 int scan_unevictable_register_node(struct node
*node
)
3539 return sysdev_create_file(&node
->sysdev
, &attr_scan_unevictable_pages
);
3542 void scan_unevictable_unregister_node(struct node
*node
)
3544 sysdev_remove_file(&node
->sysdev
, &attr_scan_unevictable_pages
);