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.
14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17 #include <linux/module.h>
18 #include <linux/gfp.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/swap.h>
21 #include <linux/pagemap.h>
22 #include <linux/init.h>
23 #include <linux/highmem.h>
24 #include <linux/vmpressure.h>
25 #include <linux/vmstat.h>
26 #include <linux/file.h>
27 #include <linux/writeback.h>
28 #include <linux/blkdev.h>
29 #include <linux/buffer_head.h> /* for try_to_release_page(),
30 buffer_heads_over_limit */
31 #include <linux/mm_inline.h>
32 #include <linux/backing-dev.h>
33 #include <linux/rmap.h>
34 #include <linux/topology.h>
35 #include <linux/cpu.h>
36 #include <linux/cpuset.h>
37 #include <linux/compaction.h>
38 #include <linux/notifier.h>
39 #include <linux/rwsem.h>
40 #include <linux/delay.h>
41 #include <linux/kthread.h>
42 #include <linux/freezer.h>
43 #include <linux/memcontrol.h>
44 #include <linux/delayacct.h>
45 #include <linux/sysctl.h>
46 #include <linux/oom.h>
47 #include <linux/prefetch.h>
48 #include <linux/printk.h>
50 #include <asm/tlbflush.h>
51 #include <asm/div64.h>
53 #include <linux/swapops.h>
54 #include <linux/balloon_compaction.h>
58 #define CREATE_TRACE_POINTS
59 #include <trace/events/vmscan.h>
62 /* How many pages shrink_list() should reclaim */
63 unsigned long nr_to_reclaim
;
65 /* This context's GFP mask */
68 /* Allocation order */
72 * Nodemask of nodes allowed by the caller. If NULL, all nodes
78 * The memory cgroup that hit its limit and as a result is the
79 * primary target of this reclaim invocation.
81 struct mem_cgroup
*target_mem_cgroup
;
83 /* Scan (total_size >> priority) pages at once */
86 unsigned int may_writepage
:1;
88 /* Can mapped pages be reclaimed? */
89 unsigned int may_unmap
:1;
91 /* Can pages be swapped as part of reclaim? */
92 unsigned int may_swap
:1;
94 /* Can cgroups be reclaimed below their normal consumption range? */
95 unsigned int may_thrash
:1;
97 unsigned int hibernation_mode
:1;
99 /* One of the zones is ready for compaction */
100 unsigned int compaction_ready
:1;
102 /* Incremented by the number of inactive pages that were scanned */
103 unsigned long nr_scanned
;
105 /* Number of pages freed so far during a call to shrink_zones() */
106 unsigned long nr_reclaimed
;
109 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
111 #ifdef ARCH_HAS_PREFETCH
112 #define prefetch_prev_lru_page(_page, _base, _field) \
114 if ((_page)->lru.prev != _base) { \
117 prev = lru_to_page(&(_page->lru)); \
118 prefetch(&prev->_field); \
122 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
125 #ifdef ARCH_HAS_PREFETCHW
126 #define prefetchw_prev_lru_page(_page, _base, _field) \
128 if ((_page)->lru.prev != _base) { \
131 prev = lru_to_page(&(_page->lru)); \
132 prefetchw(&prev->_field); \
136 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
140 * From 0 .. 100. Higher means more swappy.
142 int vm_swappiness
= 60;
144 * The total number of pages which are beyond the high watermark within all
147 unsigned long vm_total_pages
;
149 static LIST_HEAD(shrinker_list
);
150 static DECLARE_RWSEM(shrinker_rwsem
);
153 static bool global_reclaim(struct scan_control
*sc
)
155 return !sc
->target_mem_cgroup
;
158 static bool global_reclaim(struct scan_control
*sc
)
164 static unsigned long zone_reclaimable_pages(struct zone
*zone
)
168 nr
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
169 zone_page_state(zone
, NR_INACTIVE_FILE
);
171 if (get_nr_swap_pages() > 0)
172 nr
+= zone_page_state(zone
, NR_ACTIVE_ANON
) +
173 zone_page_state(zone
, NR_INACTIVE_ANON
);
178 bool zone_reclaimable(struct zone
*zone
)
180 return zone_page_state(zone
, NR_PAGES_SCANNED
) <
181 zone_reclaimable_pages(zone
) * 6;
184 static unsigned long get_lru_size(struct lruvec
*lruvec
, enum lru_list lru
)
186 if (!mem_cgroup_disabled())
187 return mem_cgroup_get_lru_size(lruvec
, lru
);
189 return zone_page_state(lruvec_zone(lruvec
), NR_LRU_BASE
+ lru
);
193 * Add a shrinker callback to be called from the vm.
195 int register_shrinker(struct shrinker
*shrinker
)
197 size_t size
= sizeof(*shrinker
->nr_deferred
);
200 * If we only have one possible node in the system anyway, save
201 * ourselves the trouble and disable NUMA aware behavior. This way we
202 * will save memory and some small loop time later.
204 if (nr_node_ids
== 1)
205 shrinker
->flags
&= ~SHRINKER_NUMA_AWARE
;
207 if (shrinker
->flags
& SHRINKER_NUMA_AWARE
)
210 shrinker
->nr_deferred
= kzalloc(size
, GFP_KERNEL
);
211 if (!shrinker
->nr_deferred
)
214 down_write(&shrinker_rwsem
);
215 list_add_tail(&shrinker
->list
, &shrinker_list
);
216 up_write(&shrinker_rwsem
);
219 EXPORT_SYMBOL(register_shrinker
);
224 void unregister_shrinker(struct shrinker
*shrinker
)
226 down_write(&shrinker_rwsem
);
227 list_del(&shrinker
->list
);
228 up_write(&shrinker_rwsem
);
229 kfree(shrinker
->nr_deferred
);
231 EXPORT_SYMBOL(unregister_shrinker
);
233 #define SHRINK_BATCH 128
235 static unsigned long do_shrink_slab(struct shrink_control
*shrinkctl
,
236 struct shrinker
*shrinker
,
237 unsigned long nr_scanned
,
238 unsigned long nr_eligible
)
240 unsigned long freed
= 0;
241 unsigned long long delta
;
246 int nid
= shrinkctl
->nid
;
247 long batch_size
= shrinker
->batch
? shrinker
->batch
250 freeable
= shrinker
->count_objects(shrinker
, shrinkctl
);
255 * copy the current shrinker scan count into a local variable
256 * and zero it so that other concurrent shrinker invocations
257 * don't also do this scanning work.
259 nr
= atomic_long_xchg(&shrinker
->nr_deferred
[nid
], 0);
262 delta
= (4 * nr_scanned
) / shrinker
->seeks
;
264 do_div(delta
, nr_eligible
+ 1);
266 if (total_scan
< 0) {
267 pr_err("shrink_slab: %pF negative objects to delete nr=%ld\n",
268 shrinker
->scan_objects
, total_scan
);
269 total_scan
= freeable
;
273 * We need to avoid excessive windup on filesystem shrinkers
274 * due to large numbers of GFP_NOFS allocations causing the
275 * shrinkers to return -1 all the time. This results in a large
276 * nr being built up so when a shrink that can do some work
277 * comes along it empties the entire cache due to nr >>>
278 * freeable. This is bad for sustaining a working set in
281 * Hence only allow the shrinker to scan the entire cache when
282 * a large delta change is calculated directly.
284 if (delta
< freeable
/ 4)
285 total_scan
= min(total_scan
, freeable
/ 2);
288 * Avoid risking looping forever due to too large nr value:
289 * never try to free more than twice the estimate number of
292 if (total_scan
> freeable
* 2)
293 total_scan
= freeable
* 2;
295 trace_mm_shrink_slab_start(shrinker
, shrinkctl
, nr
,
296 nr_scanned
, nr_eligible
,
297 freeable
, delta
, total_scan
);
300 * Normally, we should not scan less than batch_size objects in one
301 * pass to avoid too frequent shrinker calls, but if the slab has less
302 * than batch_size objects in total and we are really tight on memory,
303 * we will try to reclaim all available objects, otherwise we can end
304 * up failing allocations although there are plenty of reclaimable
305 * objects spread over several slabs with usage less than the
308 * We detect the "tight on memory" situations by looking at the total
309 * number of objects we want to scan (total_scan). If it is greater
310 * than the total number of objects on slab (freeable), we must be
311 * scanning at high prio and therefore should try to reclaim as much as
314 while (total_scan
>= batch_size
||
315 total_scan
>= freeable
) {
317 unsigned long nr_to_scan
= min(batch_size
, total_scan
);
319 shrinkctl
->nr_to_scan
= nr_to_scan
;
320 ret
= shrinker
->scan_objects(shrinker
, shrinkctl
);
321 if (ret
== SHRINK_STOP
)
325 count_vm_events(SLABS_SCANNED
, nr_to_scan
);
326 total_scan
-= nr_to_scan
;
332 * move the unused scan count back into the shrinker in a
333 * manner that handles concurrent updates. If we exhausted the
334 * scan, there is no need to do an update.
337 new_nr
= atomic_long_add_return(total_scan
,
338 &shrinker
->nr_deferred
[nid
]);
340 new_nr
= atomic_long_read(&shrinker
->nr_deferred
[nid
]);
342 trace_mm_shrink_slab_end(shrinker
, nid
, freed
, nr
, new_nr
, total_scan
);
347 * shrink_slab - shrink slab caches
348 * @gfp_mask: allocation context
349 * @nid: node whose slab caches to target
350 * @memcg: memory cgroup whose slab caches to target
351 * @nr_scanned: pressure numerator
352 * @nr_eligible: pressure denominator
354 * Call the shrink functions to age shrinkable caches.
356 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
357 * unaware shrinkers will receive a node id of 0 instead.
359 * @memcg specifies the memory cgroup to target. If it is not NULL,
360 * only shrinkers with SHRINKER_MEMCG_AWARE set will be called to scan
361 * objects from the memory cgroup specified. Otherwise all shrinkers
362 * are called, and memcg aware shrinkers are supposed to scan the
365 * @nr_scanned and @nr_eligible form a ratio that indicate how much of
366 * the available objects should be scanned. Page reclaim for example
367 * passes the number of pages scanned and the number of pages on the
368 * LRU lists that it considered on @nid, plus a bias in @nr_scanned
369 * when it encountered mapped pages. The ratio is further biased by
370 * the ->seeks setting of the shrink function, which indicates the
371 * cost to recreate an object relative to that of an LRU page.
373 * Returns the number of reclaimed slab objects.
375 static unsigned long shrink_slab(gfp_t gfp_mask
, int nid
,
376 struct mem_cgroup
*memcg
,
377 unsigned long nr_scanned
,
378 unsigned long nr_eligible
)
380 struct shrinker
*shrinker
;
381 unsigned long freed
= 0;
383 if (memcg
&& !memcg_kmem_is_active(memcg
))
387 nr_scanned
= SWAP_CLUSTER_MAX
;
389 if (!down_read_trylock(&shrinker_rwsem
)) {
391 * If we would return 0, our callers would understand that we
392 * have nothing else to shrink and give up trying. By returning
393 * 1 we keep it going and assume we'll be able to shrink next
400 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
401 struct shrink_control sc
= {
402 .gfp_mask
= gfp_mask
,
407 if (memcg
&& !(shrinker
->flags
& SHRINKER_MEMCG_AWARE
))
410 if (!(shrinker
->flags
& SHRINKER_NUMA_AWARE
))
413 freed
+= do_shrink_slab(&sc
, shrinker
, nr_scanned
, nr_eligible
);
416 up_read(&shrinker_rwsem
);
422 void drop_slab_node(int nid
)
427 struct mem_cgroup
*memcg
= NULL
;
431 freed
+= shrink_slab(GFP_KERNEL
, nid
, memcg
,
433 } while ((memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
)) != NULL
);
434 } while (freed
> 10);
441 for_each_online_node(nid
)
445 static inline int is_page_cache_freeable(struct page
*page
)
448 * A freeable page cache page is referenced only by the caller
449 * that isolated the page, the page cache radix tree and
450 * optional buffer heads at page->private.
452 return page_count(page
) - page_has_private(page
) == 2;
455 static int may_write_to_queue(struct backing_dev_info
*bdi
,
456 struct scan_control
*sc
)
458 if (current
->flags
& PF_SWAPWRITE
)
460 if (!bdi_write_congested(bdi
))
462 if (bdi
== current
->backing_dev_info
)
468 * We detected a synchronous write error writing a page out. Probably
469 * -ENOSPC. We need to propagate that into the address_space for a subsequent
470 * fsync(), msync() or close().
472 * The tricky part is that after writepage we cannot touch the mapping: nothing
473 * prevents it from being freed up. But we have a ref on the page and once
474 * that page is locked, the mapping is pinned.
476 * We're allowed to run sleeping lock_page() here because we know the caller has
479 static void handle_write_error(struct address_space
*mapping
,
480 struct page
*page
, int error
)
483 if (page_mapping(page
) == mapping
)
484 mapping_set_error(mapping
, error
);
488 /* possible outcome of pageout() */
490 /* failed to write page out, page is locked */
492 /* move page to the active list, page is locked */
494 /* page has been sent to the disk successfully, page is unlocked */
496 /* page is clean and locked */
501 * pageout is called by shrink_page_list() for each dirty page.
502 * Calls ->writepage().
504 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
505 struct scan_control
*sc
)
508 * If the page is dirty, only perform writeback if that write
509 * will be non-blocking. To prevent this allocation from being
510 * stalled by pagecache activity. But note that there may be
511 * stalls if we need to run get_block(). We could test
512 * PagePrivate for that.
514 * If this process is currently in __generic_file_write_iter() against
515 * this page's queue, we can perform writeback even if that
518 * If the page is swapcache, write it back even if that would
519 * block, for some throttling. This happens by accident, because
520 * swap_backing_dev_info is bust: it doesn't reflect the
521 * congestion state of the swapdevs. Easy to fix, if needed.
523 if (!is_page_cache_freeable(page
))
527 * Some data journaling orphaned pages can have
528 * page->mapping == NULL while being dirty with clean buffers.
530 if (page_has_private(page
)) {
531 if (try_to_free_buffers(page
)) {
532 ClearPageDirty(page
);
533 pr_info("%s: orphaned page\n", __func__
);
539 if (mapping
->a_ops
->writepage
== NULL
)
540 return PAGE_ACTIVATE
;
541 if (!may_write_to_queue(inode_to_bdi(mapping
->host
), sc
))
544 if (clear_page_dirty_for_io(page
)) {
546 struct writeback_control wbc
= {
547 .sync_mode
= WB_SYNC_NONE
,
548 .nr_to_write
= SWAP_CLUSTER_MAX
,
550 .range_end
= LLONG_MAX
,
554 SetPageReclaim(page
);
555 res
= mapping
->a_ops
->writepage(page
, &wbc
);
557 handle_write_error(mapping
, page
, res
);
558 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
559 ClearPageReclaim(page
);
560 return PAGE_ACTIVATE
;
563 if (!PageWriteback(page
)) {
564 /* synchronous write or broken a_ops? */
565 ClearPageReclaim(page
);
567 trace_mm_vmscan_writepage(page
, trace_reclaim_flags(page
));
568 inc_zone_page_state(page
, NR_VMSCAN_WRITE
);
576 * Same as remove_mapping, but if the page is removed from the mapping, it
577 * gets returned with a refcount of 0.
579 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
,
582 BUG_ON(!PageLocked(page
));
583 BUG_ON(mapping
!= page_mapping(page
));
585 spin_lock_irq(&mapping
->tree_lock
);
587 * The non racy check for a busy page.
589 * Must be careful with the order of the tests. When someone has
590 * a ref to the page, it may be possible that they dirty it then
591 * drop the reference. So if PageDirty is tested before page_count
592 * here, then the following race may occur:
594 * get_user_pages(&page);
595 * [user mapping goes away]
597 * !PageDirty(page) [good]
598 * SetPageDirty(page);
600 * !page_count(page) [good, discard it]
602 * [oops, our write_to data is lost]
604 * Reversing the order of the tests ensures such a situation cannot
605 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
606 * load is not satisfied before that of page->_count.
608 * Note that if SetPageDirty is always performed via set_page_dirty,
609 * and thus under tree_lock, then this ordering is not required.
611 if (!page_freeze_refs(page
, 2))
613 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
614 if (unlikely(PageDirty(page
))) {
615 page_unfreeze_refs(page
, 2);
619 if (PageSwapCache(page
)) {
620 swp_entry_t swap
= { .val
= page_private(page
) };
621 mem_cgroup_swapout(page
, swap
);
622 __delete_from_swap_cache(page
);
623 spin_unlock_irq(&mapping
->tree_lock
);
624 swapcache_free(swap
);
626 void (*freepage
)(struct page
*);
629 freepage
= mapping
->a_ops
->freepage
;
631 * Remember a shadow entry for reclaimed file cache in
632 * order to detect refaults, thus thrashing, later on.
634 * But don't store shadows in an address space that is
635 * already exiting. This is not just an optizimation,
636 * inode reclaim needs to empty out the radix tree or
637 * the nodes are lost. Don't plant shadows behind its
640 if (reclaimed
&& page_is_file_cache(page
) &&
641 !mapping_exiting(mapping
))
642 shadow
= workingset_eviction(mapping
, page
);
643 __delete_from_page_cache(page
, shadow
);
644 spin_unlock_irq(&mapping
->tree_lock
);
646 if (freepage
!= NULL
)
653 spin_unlock_irq(&mapping
->tree_lock
);
658 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
659 * someone else has a ref on the page, abort and return 0. If it was
660 * successfully detached, return 1. Assumes the caller has a single ref on
663 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
665 if (__remove_mapping(mapping
, page
, false)) {
667 * Unfreezing the refcount with 1 rather than 2 effectively
668 * drops the pagecache ref for us without requiring another
671 page_unfreeze_refs(page
, 1);
678 * putback_lru_page - put previously isolated page onto appropriate LRU list
679 * @page: page to be put back to appropriate lru list
681 * Add previously isolated @page to appropriate LRU list.
682 * Page may still be unevictable for other reasons.
684 * lru_lock must not be held, interrupts must be enabled.
686 void putback_lru_page(struct page
*page
)
689 int was_unevictable
= PageUnevictable(page
);
691 VM_BUG_ON_PAGE(PageLRU(page
), page
);
694 ClearPageUnevictable(page
);
696 if (page_evictable(page
)) {
698 * For evictable pages, we can use the cache.
699 * In event of a race, worst case is we end up with an
700 * unevictable page on [in]active list.
701 * We know how to handle that.
703 is_unevictable
= false;
707 * Put unevictable pages directly on zone's unevictable
710 is_unevictable
= true;
711 add_page_to_unevictable_list(page
);
713 * When racing with an mlock or AS_UNEVICTABLE clearing
714 * (page is unlocked) make sure that if the other thread
715 * does not observe our setting of PG_lru and fails
716 * isolation/check_move_unevictable_pages,
717 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
718 * the page back to the evictable list.
720 * The other side is TestClearPageMlocked() or shmem_lock().
726 * page's status can change while we move it among lru. If an evictable
727 * page is on unevictable list, it never be freed. To avoid that,
728 * check after we added it to the list, again.
730 if (is_unevictable
&& page_evictable(page
)) {
731 if (!isolate_lru_page(page
)) {
735 /* This means someone else dropped this page from LRU
736 * So, it will be freed or putback to LRU again. There is
737 * nothing to do here.
741 if (was_unevictable
&& !is_unevictable
)
742 count_vm_event(UNEVICTABLE_PGRESCUED
);
743 else if (!was_unevictable
&& is_unevictable
)
744 count_vm_event(UNEVICTABLE_PGCULLED
);
746 put_page(page
); /* drop ref from isolate */
749 enum page_references
{
751 PAGEREF_RECLAIM_CLEAN
,
756 static enum page_references
page_check_references(struct page
*page
,
757 struct scan_control
*sc
)
759 int referenced_ptes
, referenced_page
;
760 unsigned long vm_flags
;
762 referenced_ptes
= page_referenced(page
, 1, sc
->target_mem_cgroup
,
764 referenced_page
= TestClearPageReferenced(page
);
767 * Mlock lost the isolation race with us. Let try_to_unmap()
768 * move the page to the unevictable list.
770 if (vm_flags
& VM_LOCKED
)
771 return PAGEREF_RECLAIM
;
773 if (referenced_ptes
) {
774 if (PageSwapBacked(page
))
775 return PAGEREF_ACTIVATE
;
777 * All mapped pages start out with page table
778 * references from the instantiating fault, so we need
779 * to look twice if a mapped file page is used more
782 * Mark it and spare it for another trip around the
783 * inactive list. Another page table reference will
784 * lead to its activation.
786 * Note: the mark is set for activated pages as well
787 * so that recently deactivated but used pages are
790 SetPageReferenced(page
);
792 if (referenced_page
|| referenced_ptes
> 1)
793 return PAGEREF_ACTIVATE
;
796 * Activate file-backed executable pages after first usage.
798 if (vm_flags
& VM_EXEC
)
799 return PAGEREF_ACTIVATE
;
804 /* Reclaim if clean, defer dirty pages to writeback */
805 if (referenced_page
&& !PageSwapBacked(page
))
806 return PAGEREF_RECLAIM_CLEAN
;
808 return PAGEREF_RECLAIM
;
811 /* Check if a page is dirty or under writeback */
812 static void page_check_dirty_writeback(struct page
*page
,
813 bool *dirty
, bool *writeback
)
815 struct address_space
*mapping
;
818 * Anonymous pages are not handled by flushers and must be written
819 * from reclaim context. Do not stall reclaim based on them
821 if (!page_is_file_cache(page
)) {
827 /* By default assume that the page flags are accurate */
828 *dirty
= PageDirty(page
);
829 *writeback
= PageWriteback(page
);
831 /* Verify dirty/writeback state if the filesystem supports it */
832 if (!page_has_private(page
))
835 mapping
= page_mapping(page
);
836 if (mapping
&& mapping
->a_ops
->is_dirty_writeback
)
837 mapping
->a_ops
->is_dirty_writeback(page
, dirty
, writeback
);
841 * shrink_page_list() returns the number of reclaimed pages
843 static unsigned long shrink_page_list(struct list_head
*page_list
,
845 struct scan_control
*sc
,
846 enum ttu_flags ttu_flags
,
847 unsigned long *ret_nr_dirty
,
848 unsigned long *ret_nr_unqueued_dirty
,
849 unsigned long *ret_nr_congested
,
850 unsigned long *ret_nr_writeback
,
851 unsigned long *ret_nr_immediate
,
854 LIST_HEAD(ret_pages
);
855 LIST_HEAD(free_pages
);
857 unsigned long nr_unqueued_dirty
= 0;
858 unsigned long nr_dirty
= 0;
859 unsigned long nr_congested
= 0;
860 unsigned long nr_reclaimed
= 0;
861 unsigned long nr_writeback
= 0;
862 unsigned long nr_immediate
= 0;
866 while (!list_empty(page_list
)) {
867 struct address_space
*mapping
;
870 enum page_references references
= PAGEREF_RECLAIM_CLEAN
;
871 bool dirty
, writeback
;
875 page
= lru_to_page(page_list
);
876 list_del(&page
->lru
);
878 if (!trylock_page(page
))
881 VM_BUG_ON_PAGE(PageActive(page
), page
);
882 VM_BUG_ON_PAGE(page_zone(page
) != zone
, page
);
886 if (unlikely(!page_evictable(page
)))
889 if (!sc
->may_unmap
&& page_mapped(page
))
892 /* Double the slab pressure for mapped and swapcache pages */
893 if (page_mapped(page
) || PageSwapCache(page
))
896 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
897 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
900 * The number of dirty pages determines if a zone is marked
901 * reclaim_congested which affects wait_iff_congested. kswapd
902 * will stall and start writing pages if the tail of the LRU
903 * is all dirty unqueued pages.
905 page_check_dirty_writeback(page
, &dirty
, &writeback
);
906 if (dirty
|| writeback
)
909 if (dirty
&& !writeback
)
913 * Treat this page as congested if the underlying BDI is or if
914 * pages are cycling through the LRU so quickly that the
915 * pages marked for immediate reclaim are making it to the
916 * end of the LRU a second time.
918 mapping
= page_mapping(page
);
919 if (((dirty
|| writeback
) && mapping
&&
920 bdi_write_congested(inode_to_bdi(mapping
->host
))) ||
921 (writeback
&& PageReclaim(page
)))
925 * If a page at the tail of the LRU is under writeback, there
926 * are three cases to consider.
928 * 1) If reclaim is encountering an excessive number of pages
929 * under writeback and this page is both under writeback and
930 * PageReclaim then it indicates that pages are being queued
931 * for IO but are being recycled through the LRU before the
932 * IO can complete. Waiting on the page itself risks an
933 * indefinite stall if it is impossible to writeback the
934 * page due to IO error or disconnected storage so instead
935 * note that the LRU is being scanned too quickly and the
936 * caller can stall after page list has been processed.
938 * 2) Global reclaim encounters a page, memcg encounters a
939 * page that is not marked for immediate reclaim or
940 * the caller does not have __GFP_IO. In this case mark
941 * the page for immediate reclaim and continue scanning.
943 * __GFP_IO is checked because a loop driver thread might
944 * enter reclaim, and deadlock if it waits on a page for
945 * which it is needed to do the write (loop masks off
946 * __GFP_IO|__GFP_FS for this reason); but more thought
947 * would probably show more reasons.
949 * Don't require __GFP_FS, since we're not going into the
950 * FS, just waiting on its writeback completion. Worryingly,
951 * ext4 gfs2 and xfs allocate pages with
952 * grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so testing
953 * may_enter_fs here is liable to OOM on them.
955 * 3) memcg encounters a page that is not already marked
956 * PageReclaim. memcg does not have any dirty pages
957 * throttling so we could easily OOM just because too many
958 * pages are in writeback and there is nothing else to
959 * reclaim. Wait for the writeback to complete.
961 if (PageWriteback(page
)) {
963 if (current_is_kswapd() &&
965 test_bit(ZONE_WRITEBACK
, &zone
->flags
)) {
970 } else if (global_reclaim(sc
) ||
971 !PageReclaim(page
) || !(sc
->gfp_mask
& __GFP_IO
)) {
973 * This is slightly racy - end_page_writeback()
974 * might have just cleared PageReclaim, then
975 * setting PageReclaim here end up interpreted
976 * as PageReadahead - but that does not matter
977 * enough to care. What we do want is for this
978 * page to have PageReclaim set next time memcg
979 * reclaim reaches the tests above, so it will
980 * then wait_on_page_writeback() to avoid OOM;
981 * and it's also appropriate in global reclaim.
983 SetPageReclaim(page
);
990 wait_on_page_writeback(page
);
995 references
= page_check_references(page
, sc
);
997 switch (references
) {
998 case PAGEREF_ACTIVATE
:
999 goto activate_locked
;
1002 case PAGEREF_RECLAIM
:
1003 case PAGEREF_RECLAIM_CLEAN
:
1004 ; /* try to reclaim the page below */
1008 * Anonymous process memory has backing store?
1009 * Try to allocate it some swap space here.
1011 if (PageAnon(page
) && !PageSwapCache(page
)) {
1012 if (!(sc
->gfp_mask
& __GFP_IO
))
1014 if (!add_to_swap(page
, page_list
))
1015 goto activate_locked
;
1018 /* Adding to swap updated mapping */
1019 mapping
= page_mapping(page
);
1023 * The page is mapped into the page tables of one or more
1024 * processes. Try to unmap it here.
1026 if (page_mapped(page
) && mapping
) {
1027 switch (try_to_unmap(page
, ttu_flags
)) {
1029 goto activate_locked
;
1035 ; /* try to free the page below */
1039 if (PageDirty(page
)) {
1041 * Only kswapd can writeback filesystem pages to
1042 * avoid risk of stack overflow but only writeback
1043 * if many dirty pages have been encountered.
1045 if (page_is_file_cache(page
) &&
1046 (!current_is_kswapd() ||
1047 !test_bit(ZONE_DIRTY
, &zone
->flags
))) {
1049 * Immediately reclaim when written back.
1050 * Similar in principal to deactivate_page()
1051 * except we already have the page isolated
1052 * and know it's dirty
1054 inc_zone_page_state(page
, NR_VMSCAN_IMMEDIATE
);
1055 SetPageReclaim(page
);
1060 if (references
== PAGEREF_RECLAIM_CLEAN
)
1064 if (!sc
->may_writepage
)
1067 /* Page is dirty, try to write it out here */
1068 switch (pageout(page
, mapping
, sc
)) {
1072 goto activate_locked
;
1074 if (PageWriteback(page
))
1076 if (PageDirty(page
))
1080 * A synchronous write - probably a ramdisk. Go
1081 * ahead and try to reclaim the page.
1083 if (!trylock_page(page
))
1085 if (PageDirty(page
) || PageWriteback(page
))
1087 mapping
= page_mapping(page
);
1089 ; /* try to free the page below */
1094 * If the page has buffers, try to free the buffer mappings
1095 * associated with this page. If we succeed we try to free
1098 * We do this even if the page is PageDirty().
1099 * try_to_release_page() does not perform I/O, but it is
1100 * possible for a page to have PageDirty set, but it is actually
1101 * clean (all its buffers are clean). This happens if the
1102 * buffers were written out directly, with submit_bh(). ext3
1103 * will do this, as well as the blockdev mapping.
1104 * try_to_release_page() will discover that cleanness and will
1105 * drop the buffers and mark the page clean - it can be freed.
1107 * Rarely, pages can have buffers and no ->mapping. These are
1108 * the pages which were not successfully invalidated in
1109 * truncate_complete_page(). We try to drop those buffers here
1110 * and if that worked, and the page is no longer mapped into
1111 * process address space (page_count == 1) it can be freed.
1112 * Otherwise, leave the page on the LRU so it is swappable.
1114 if (page_has_private(page
)) {
1115 if (!try_to_release_page(page
, sc
->gfp_mask
))
1116 goto activate_locked
;
1117 if (!mapping
&& page_count(page
) == 1) {
1119 if (put_page_testzero(page
))
1123 * rare race with speculative reference.
1124 * the speculative reference will free
1125 * this page shortly, so we may
1126 * increment nr_reclaimed here (and
1127 * leave it off the LRU).
1135 if (!mapping
|| !__remove_mapping(mapping
, page
, true))
1139 * At this point, we have no other references and there is
1140 * no way to pick any more up (removed from LRU, removed
1141 * from pagecache). Can use non-atomic bitops now (and
1142 * we obviously don't have to worry about waking up a process
1143 * waiting on the page lock, because there are no references.
1145 __clear_page_locked(page
);
1150 * Is there need to periodically free_page_list? It would
1151 * appear not as the counts should be low
1153 list_add(&page
->lru
, &free_pages
);
1157 if (PageSwapCache(page
))
1158 try_to_free_swap(page
);
1160 putback_lru_page(page
);
1164 /* Not a candidate for swapping, so reclaim swap space. */
1165 if (PageSwapCache(page
) && vm_swap_full())
1166 try_to_free_swap(page
);
1167 VM_BUG_ON_PAGE(PageActive(page
), page
);
1168 SetPageActive(page
);
1173 list_add(&page
->lru
, &ret_pages
);
1174 VM_BUG_ON_PAGE(PageLRU(page
) || PageUnevictable(page
), page
);
1177 mem_cgroup_uncharge_list(&free_pages
);
1178 free_hot_cold_page_list(&free_pages
, true);
1180 list_splice(&ret_pages
, page_list
);
1181 count_vm_events(PGACTIVATE
, pgactivate
);
1183 *ret_nr_dirty
+= nr_dirty
;
1184 *ret_nr_congested
+= nr_congested
;
1185 *ret_nr_unqueued_dirty
+= nr_unqueued_dirty
;
1186 *ret_nr_writeback
+= nr_writeback
;
1187 *ret_nr_immediate
+= nr_immediate
;
1188 return nr_reclaimed
;
1191 unsigned long reclaim_clean_pages_from_list(struct zone
*zone
,
1192 struct list_head
*page_list
)
1194 struct scan_control sc
= {
1195 .gfp_mask
= GFP_KERNEL
,
1196 .priority
= DEF_PRIORITY
,
1199 unsigned long ret
, dummy1
, dummy2
, dummy3
, dummy4
, dummy5
;
1200 struct page
*page
, *next
;
1201 LIST_HEAD(clean_pages
);
1203 list_for_each_entry_safe(page
, next
, page_list
, lru
) {
1204 if (page_is_file_cache(page
) && !PageDirty(page
) &&
1205 !isolated_balloon_page(page
)) {
1206 ClearPageActive(page
);
1207 list_move(&page
->lru
, &clean_pages
);
1211 ret
= shrink_page_list(&clean_pages
, zone
, &sc
,
1212 TTU_UNMAP
|TTU_IGNORE_ACCESS
,
1213 &dummy1
, &dummy2
, &dummy3
, &dummy4
, &dummy5
, true);
1214 list_splice(&clean_pages
, page_list
);
1215 mod_zone_page_state(zone
, NR_ISOLATED_FILE
, -ret
);
1220 * Attempt to remove the specified page from its LRU. Only take this page
1221 * if it is of the appropriate PageActive status. Pages which are being
1222 * freed elsewhere are also ignored.
1224 * page: page to consider
1225 * mode: one of the LRU isolation modes defined above
1227 * returns 0 on success, -ve errno on failure.
1229 int __isolate_lru_page(struct page
*page
, isolate_mode_t mode
)
1233 /* Only take pages on the LRU. */
1237 /* Compaction should not handle unevictable pages but CMA can do so */
1238 if (PageUnevictable(page
) && !(mode
& ISOLATE_UNEVICTABLE
))
1244 * To minimise LRU disruption, the caller can indicate that it only
1245 * wants to isolate pages it will be able to operate on without
1246 * blocking - clean pages for the most part.
1248 * ISOLATE_CLEAN means that only clean pages should be isolated. This
1249 * is used by reclaim when it is cannot write to backing storage
1251 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1252 * that it is possible to migrate without blocking
1254 if (mode
& (ISOLATE_CLEAN
|ISOLATE_ASYNC_MIGRATE
)) {
1255 /* All the caller can do on PageWriteback is block */
1256 if (PageWriteback(page
))
1259 if (PageDirty(page
)) {
1260 struct address_space
*mapping
;
1262 /* ISOLATE_CLEAN means only clean pages */
1263 if (mode
& ISOLATE_CLEAN
)
1267 * Only pages without mappings or that have a
1268 * ->migratepage callback are possible to migrate
1271 mapping
= page_mapping(page
);
1272 if (mapping
&& !mapping
->a_ops
->migratepage
)
1277 if ((mode
& ISOLATE_UNMAPPED
) && page_mapped(page
))
1280 if (likely(get_page_unless_zero(page
))) {
1282 * Be careful not to clear PageLRU until after we're
1283 * sure the page is not being freed elsewhere -- the
1284 * page release code relies on it.
1294 * zone->lru_lock is heavily contended. Some of the functions that
1295 * shrink the lists perform better by taking out a batch of pages
1296 * and working on them outside the LRU lock.
1298 * For pagecache intensive workloads, this function is the hottest
1299 * spot in the kernel (apart from copy_*_user functions).
1301 * Appropriate locks must be held before calling this function.
1303 * @nr_to_scan: The number of pages to look through on the list.
1304 * @lruvec: The LRU vector to pull pages from.
1305 * @dst: The temp list to put pages on to.
1306 * @nr_scanned: The number of pages that were scanned.
1307 * @sc: The scan_control struct for this reclaim session
1308 * @mode: One of the LRU isolation modes
1309 * @lru: LRU list id for isolating
1311 * returns how many pages were moved onto *@dst.
1313 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1314 struct lruvec
*lruvec
, struct list_head
*dst
,
1315 unsigned long *nr_scanned
, struct scan_control
*sc
,
1316 isolate_mode_t mode
, enum lru_list lru
)
1318 struct list_head
*src
= &lruvec
->lists
[lru
];
1319 unsigned long nr_taken
= 0;
1322 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
1326 page
= lru_to_page(src
);
1327 prefetchw_prev_lru_page(page
, src
, flags
);
1329 VM_BUG_ON_PAGE(!PageLRU(page
), page
);
1331 switch (__isolate_lru_page(page
, mode
)) {
1333 nr_pages
= hpage_nr_pages(page
);
1334 mem_cgroup_update_lru_size(lruvec
, lru
, -nr_pages
);
1335 list_move(&page
->lru
, dst
);
1336 nr_taken
+= nr_pages
;
1340 /* else it is being freed elsewhere */
1341 list_move(&page
->lru
, src
);
1350 trace_mm_vmscan_lru_isolate(sc
->order
, nr_to_scan
, scan
,
1351 nr_taken
, mode
, is_file_lru(lru
));
1356 * isolate_lru_page - tries to isolate a page from its LRU list
1357 * @page: page to isolate from its LRU list
1359 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1360 * vmstat statistic corresponding to whatever LRU list the page was on.
1362 * Returns 0 if the page was removed from an LRU list.
1363 * Returns -EBUSY if the page was not on an LRU list.
1365 * The returned page will have PageLRU() cleared. If it was found on
1366 * the active list, it will have PageActive set. If it was found on
1367 * the unevictable list, it will have the PageUnevictable bit set. That flag
1368 * may need to be cleared by the caller before letting the page go.
1370 * The vmstat statistic corresponding to the list on which the page was
1371 * found will be decremented.
1374 * (1) Must be called with an elevated refcount on the page. This is a
1375 * fundamentnal difference from isolate_lru_pages (which is called
1376 * without a stable reference).
1377 * (2) the lru_lock must not be held.
1378 * (3) interrupts must be enabled.
1380 int isolate_lru_page(struct page
*page
)
1384 VM_BUG_ON_PAGE(!page_count(page
), page
);
1386 if (PageLRU(page
)) {
1387 struct zone
*zone
= page_zone(page
);
1388 struct lruvec
*lruvec
;
1390 spin_lock_irq(&zone
->lru_lock
);
1391 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1392 if (PageLRU(page
)) {
1393 int lru
= page_lru(page
);
1396 del_page_from_lru_list(page
, lruvec
, lru
);
1399 spin_unlock_irq(&zone
->lru_lock
);
1405 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1406 * then get resheduled. When there are massive number of tasks doing page
1407 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1408 * the LRU list will go small and be scanned faster than necessary, leading to
1409 * unnecessary swapping, thrashing and OOM.
1411 static int too_many_isolated(struct zone
*zone
, int file
,
1412 struct scan_control
*sc
)
1414 unsigned long inactive
, isolated
;
1416 if (current_is_kswapd())
1419 if (!global_reclaim(sc
))
1423 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1424 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
);
1426 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1427 isolated
= zone_page_state(zone
, NR_ISOLATED_ANON
);
1431 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1432 * won't get blocked by normal direct-reclaimers, forming a circular
1435 if ((sc
->gfp_mask
& GFP_IOFS
) == GFP_IOFS
)
1438 return isolated
> inactive
;
1441 static noinline_for_stack
void
1442 putback_inactive_pages(struct lruvec
*lruvec
, struct list_head
*page_list
)
1444 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1445 struct zone
*zone
= lruvec_zone(lruvec
);
1446 LIST_HEAD(pages_to_free
);
1449 * Put back any unfreeable pages.
1451 while (!list_empty(page_list
)) {
1452 struct page
*page
= lru_to_page(page_list
);
1455 VM_BUG_ON_PAGE(PageLRU(page
), page
);
1456 list_del(&page
->lru
);
1457 if (unlikely(!page_evictable(page
))) {
1458 spin_unlock_irq(&zone
->lru_lock
);
1459 putback_lru_page(page
);
1460 spin_lock_irq(&zone
->lru_lock
);
1464 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1467 lru
= page_lru(page
);
1468 add_page_to_lru_list(page
, lruvec
, lru
);
1470 if (is_active_lru(lru
)) {
1471 int file
= is_file_lru(lru
);
1472 int numpages
= hpage_nr_pages(page
);
1473 reclaim_stat
->recent_rotated
[file
] += numpages
;
1475 if (put_page_testzero(page
)) {
1476 __ClearPageLRU(page
);
1477 __ClearPageActive(page
);
1478 del_page_from_lru_list(page
, lruvec
, lru
);
1480 if (unlikely(PageCompound(page
))) {
1481 spin_unlock_irq(&zone
->lru_lock
);
1482 mem_cgroup_uncharge(page
);
1483 (*get_compound_page_dtor(page
))(page
);
1484 spin_lock_irq(&zone
->lru_lock
);
1486 list_add(&page
->lru
, &pages_to_free
);
1491 * To save our caller's stack, now use input list for pages to free.
1493 list_splice(&pages_to_free
, page_list
);
1497 * If a kernel thread (such as nfsd for loop-back mounts) services
1498 * a backing device by writing to the page cache it sets PF_LESS_THROTTLE.
1499 * In that case we should only throttle if the backing device it is
1500 * writing to is congested. In other cases it is safe to throttle.
1502 static int current_may_throttle(void)
1504 return !(current
->flags
& PF_LESS_THROTTLE
) ||
1505 current
->backing_dev_info
== NULL
||
1506 bdi_write_congested(current
->backing_dev_info
);
1510 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1511 * of reclaimed pages
1513 static noinline_for_stack
unsigned long
1514 shrink_inactive_list(unsigned long nr_to_scan
, struct lruvec
*lruvec
,
1515 struct scan_control
*sc
, enum lru_list lru
)
1517 LIST_HEAD(page_list
);
1518 unsigned long nr_scanned
;
1519 unsigned long nr_reclaimed
= 0;
1520 unsigned long nr_taken
;
1521 unsigned long nr_dirty
= 0;
1522 unsigned long nr_congested
= 0;
1523 unsigned long nr_unqueued_dirty
= 0;
1524 unsigned long nr_writeback
= 0;
1525 unsigned long nr_immediate
= 0;
1526 isolate_mode_t isolate_mode
= 0;
1527 int file
= is_file_lru(lru
);
1528 struct zone
*zone
= lruvec_zone(lruvec
);
1529 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1531 while (unlikely(too_many_isolated(zone
, file
, sc
))) {
1532 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1534 /* We are about to die and free our memory. Return now. */
1535 if (fatal_signal_pending(current
))
1536 return SWAP_CLUSTER_MAX
;
1542 isolate_mode
|= ISOLATE_UNMAPPED
;
1543 if (!sc
->may_writepage
)
1544 isolate_mode
|= ISOLATE_CLEAN
;
1546 spin_lock_irq(&zone
->lru_lock
);
1548 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &page_list
,
1549 &nr_scanned
, sc
, isolate_mode
, lru
);
1551 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, -nr_taken
);
1552 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1554 if (global_reclaim(sc
)) {
1555 __mod_zone_page_state(zone
, NR_PAGES_SCANNED
, nr_scanned
);
1556 if (current_is_kswapd())
1557 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
, nr_scanned
);
1559 __count_zone_vm_events(PGSCAN_DIRECT
, zone
, nr_scanned
);
1561 spin_unlock_irq(&zone
->lru_lock
);
1566 nr_reclaimed
= shrink_page_list(&page_list
, zone
, sc
, TTU_UNMAP
,
1567 &nr_dirty
, &nr_unqueued_dirty
, &nr_congested
,
1568 &nr_writeback
, &nr_immediate
,
1571 spin_lock_irq(&zone
->lru_lock
);
1573 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1575 if (global_reclaim(sc
)) {
1576 if (current_is_kswapd())
1577 __count_zone_vm_events(PGSTEAL_KSWAPD
, zone
,
1580 __count_zone_vm_events(PGSTEAL_DIRECT
, zone
,
1584 putback_inactive_pages(lruvec
, &page_list
);
1586 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1588 spin_unlock_irq(&zone
->lru_lock
);
1590 mem_cgroup_uncharge_list(&page_list
);
1591 free_hot_cold_page_list(&page_list
, true);
1594 * If reclaim is isolating dirty pages under writeback, it implies
1595 * that the long-lived page allocation rate is exceeding the page
1596 * laundering rate. Either the global limits are not being effective
1597 * at throttling processes due to the page distribution throughout
1598 * zones or there is heavy usage of a slow backing device. The
1599 * only option is to throttle from reclaim context which is not ideal
1600 * as there is no guarantee the dirtying process is throttled in the
1601 * same way balance_dirty_pages() manages.
1603 * Once a zone is flagged ZONE_WRITEBACK, kswapd will count the number
1604 * of pages under pages flagged for immediate reclaim and stall if any
1605 * are encountered in the nr_immediate check below.
1607 if (nr_writeback
&& nr_writeback
== nr_taken
)
1608 set_bit(ZONE_WRITEBACK
, &zone
->flags
);
1611 * memcg will stall in page writeback so only consider forcibly
1612 * stalling for global reclaim
1614 if (global_reclaim(sc
)) {
1616 * Tag a zone as congested if all the dirty pages scanned were
1617 * backed by a congested BDI and wait_iff_congested will stall.
1619 if (nr_dirty
&& nr_dirty
== nr_congested
)
1620 set_bit(ZONE_CONGESTED
, &zone
->flags
);
1623 * If dirty pages are scanned that are not queued for IO, it
1624 * implies that flushers are not keeping up. In this case, flag
1625 * the zone ZONE_DIRTY and kswapd will start writing pages from
1628 if (nr_unqueued_dirty
== nr_taken
)
1629 set_bit(ZONE_DIRTY
, &zone
->flags
);
1632 * If kswapd scans pages marked marked for immediate
1633 * reclaim and under writeback (nr_immediate), it implies
1634 * that pages are cycling through the LRU faster than
1635 * they are written so also forcibly stall.
1637 if (nr_immediate
&& current_may_throttle())
1638 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1642 * Stall direct reclaim for IO completions if underlying BDIs or zone
1643 * is congested. Allow kswapd to continue until it starts encountering
1644 * unqueued dirty pages or cycling through the LRU too quickly.
1646 if (!sc
->hibernation_mode
&& !current_is_kswapd() &&
1647 current_may_throttle())
1648 wait_iff_congested(zone
, BLK_RW_ASYNC
, HZ
/10);
1650 trace_mm_vmscan_lru_shrink_inactive(zone
->zone_pgdat
->node_id
,
1652 nr_scanned
, nr_reclaimed
,
1654 trace_shrink_flags(file
));
1655 return nr_reclaimed
;
1659 * This moves pages from the active list to the inactive list.
1661 * We move them the other way if the page is referenced by one or more
1662 * processes, from rmap.
1664 * If the pages are mostly unmapped, the processing is fast and it is
1665 * appropriate to hold zone->lru_lock across the whole operation. But if
1666 * the pages are mapped, the processing is slow (page_referenced()) so we
1667 * should drop zone->lru_lock around each page. It's impossible to balance
1668 * this, so instead we remove the pages from the LRU while processing them.
1669 * It is safe to rely on PG_active against the non-LRU pages in here because
1670 * nobody will play with that bit on a non-LRU page.
1672 * The downside is that we have to touch page->_count against each page.
1673 * But we had to alter page->flags anyway.
1676 static void move_active_pages_to_lru(struct lruvec
*lruvec
,
1677 struct list_head
*list
,
1678 struct list_head
*pages_to_free
,
1681 struct zone
*zone
= lruvec_zone(lruvec
);
1682 unsigned long pgmoved
= 0;
1686 while (!list_empty(list
)) {
1687 page
= lru_to_page(list
);
1688 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1690 VM_BUG_ON_PAGE(PageLRU(page
), page
);
1693 nr_pages
= hpage_nr_pages(page
);
1694 mem_cgroup_update_lru_size(lruvec
, lru
, nr_pages
);
1695 list_move(&page
->lru
, &lruvec
->lists
[lru
]);
1696 pgmoved
+= nr_pages
;
1698 if (put_page_testzero(page
)) {
1699 __ClearPageLRU(page
);
1700 __ClearPageActive(page
);
1701 del_page_from_lru_list(page
, lruvec
, lru
);
1703 if (unlikely(PageCompound(page
))) {
1704 spin_unlock_irq(&zone
->lru_lock
);
1705 mem_cgroup_uncharge(page
);
1706 (*get_compound_page_dtor(page
))(page
);
1707 spin_lock_irq(&zone
->lru_lock
);
1709 list_add(&page
->lru
, pages_to_free
);
1712 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1713 if (!is_active_lru(lru
))
1714 __count_vm_events(PGDEACTIVATE
, pgmoved
);
1717 static void shrink_active_list(unsigned long nr_to_scan
,
1718 struct lruvec
*lruvec
,
1719 struct scan_control
*sc
,
1722 unsigned long nr_taken
;
1723 unsigned long nr_scanned
;
1724 unsigned long vm_flags
;
1725 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1726 LIST_HEAD(l_active
);
1727 LIST_HEAD(l_inactive
);
1729 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1730 unsigned long nr_rotated
= 0;
1731 isolate_mode_t isolate_mode
= 0;
1732 int file
= is_file_lru(lru
);
1733 struct zone
*zone
= lruvec_zone(lruvec
);
1738 isolate_mode
|= ISOLATE_UNMAPPED
;
1739 if (!sc
->may_writepage
)
1740 isolate_mode
|= ISOLATE_CLEAN
;
1742 spin_lock_irq(&zone
->lru_lock
);
1744 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &l_hold
,
1745 &nr_scanned
, sc
, isolate_mode
, lru
);
1746 if (global_reclaim(sc
))
1747 __mod_zone_page_state(zone
, NR_PAGES_SCANNED
, nr_scanned
);
1749 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1751 __count_zone_vm_events(PGREFILL
, zone
, nr_scanned
);
1752 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, -nr_taken
);
1753 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1754 spin_unlock_irq(&zone
->lru_lock
);
1756 while (!list_empty(&l_hold
)) {
1758 page
= lru_to_page(&l_hold
);
1759 list_del(&page
->lru
);
1761 if (unlikely(!page_evictable(page
))) {
1762 putback_lru_page(page
);
1766 if (unlikely(buffer_heads_over_limit
)) {
1767 if (page_has_private(page
) && trylock_page(page
)) {
1768 if (page_has_private(page
))
1769 try_to_release_page(page
, 0);
1774 if (page_referenced(page
, 0, sc
->target_mem_cgroup
,
1776 nr_rotated
+= hpage_nr_pages(page
);
1778 * Identify referenced, file-backed active pages and
1779 * give them one more trip around the active list. So
1780 * that executable code get better chances to stay in
1781 * memory under moderate memory pressure. Anon pages
1782 * are not likely to be evicted by use-once streaming
1783 * IO, plus JVM can create lots of anon VM_EXEC pages,
1784 * so we ignore them here.
1786 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1787 list_add(&page
->lru
, &l_active
);
1792 ClearPageActive(page
); /* we are de-activating */
1793 list_add(&page
->lru
, &l_inactive
);
1797 * Move pages back to the lru list.
1799 spin_lock_irq(&zone
->lru_lock
);
1801 * Count referenced pages from currently used mappings as rotated,
1802 * even though only some of them are actually re-activated. This
1803 * helps balance scan pressure between file and anonymous pages in
1806 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1808 move_active_pages_to_lru(lruvec
, &l_active
, &l_hold
, lru
);
1809 move_active_pages_to_lru(lruvec
, &l_inactive
, &l_hold
, lru
- LRU_ACTIVE
);
1810 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1811 spin_unlock_irq(&zone
->lru_lock
);
1813 mem_cgroup_uncharge_list(&l_hold
);
1814 free_hot_cold_page_list(&l_hold
, true);
1818 static int inactive_anon_is_low_global(struct zone
*zone
)
1820 unsigned long active
, inactive
;
1822 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1823 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1825 if (inactive
* zone
->inactive_ratio
< active
)
1832 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1833 * @lruvec: LRU vector to check
1835 * Returns true if the zone does not have enough inactive anon pages,
1836 * meaning some active anon pages need to be deactivated.
1838 static int inactive_anon_is_low(struct lruvec
*lruvec
)
1841 * If we don't have swap space, anonymous page deactivation
1844 if (!total_swap_pages
)
1847 if (!mem_cgroup_disabled())
1848 return mem_cgroup_inactive_anon_is_low(lruvec
);
1850 return inactive_anon_is_low_global(lruvec_zone(lruvec
));
1853 static inline int inactive_anon_is_low(struct lruvec
*lruvec
)
1860 * inactive_file_is_low - check if file pages need to be deactivated
1861 * @lruvec: LRU vector to check
1863 * When the system is doing streaming IO, memory pressure here
1864 * ensures that active file pages get deactivated, until more
1865 * than half of the file pages are on the inactive list.
1867 * Once we get to that situation, protect the system's working
1868 * set from being evicted by disabling active file page aging.
1870 * This uses a different ratio than the anonymous pages, because
1871 * the page cache uses a use-once replacement algorithm.
1873 static int inactive_file_is_low(struct lruvec
*lruvec
)
1875 unsigned long inactive
;
1876 unsigned long active
;
1878 inactive
= get_lru_size(lruvec
, LRU_INACTIVE_FILE
);
1879 active
= get_lru_size(lruvec
, LRU_ACTIVE_FILE
);
1881 return active
> inactive
;
1884 static int inactive_list_is_low(struct lruvec
*lruvec
, enum lru_list lru
)
1886 if (is_file_lru(lru
))
1887 return inactive_file_is_low(lruvec
);
1889 return inactive_anon_is_low(lruvec
);
1892 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1893 struct lruvec
*lruvec
, struct scan_control
*sc
)
1895 if (is_active_lru(lru
)) {
1896 if (inactive_list_is_low(lruvec
, lru
))
1897 shrink_active_list(nr_to_scan
, lruvec
, sc
, lru
);
1901 return shrink_inactive_list(nr_to_scan
, lruvec
, sc
, lru
);
1912 * Determine how aggressively the anon and file LRU lists should be
1913 * scanned. The relative value of each set of LRU lists is determined
1914 * by looking at the fraction of the pages scanned we did rotate back
1915 * onto the active list instead of evict.
1917 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
1918 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
1920 static void get_scan_count(struct lruvec
*lruvec
, int swappiness
,
1921 struct scan_control
*sc
, unsigned long *nr
,
1922 unsigned long *lru_pages
)
1924 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1926 u64 denominator
= 0; /* gcc */
1927 struct zone
*zone
= lruvec_zone(lruvec
);
1928 unsigned long anon_prio
, file_prio
;
1929 enum scan_balance scan_balance
;
1930 unsigned long anon
, file
;
1931 bool force_scan
= false;
1932 unsigned long ap
, fp
;
1938 * If the zone or memcg is small, nr[l] can be 0. This
1939 * results in no scanning on this priority and a potential
1940 * priority drop. Global direct reclaim can go to the next
1941 * zone and tends to have no problems. Global kswapd is for
1942 * zone balancing and it needs to scan a minimum amount. When
1943 * reclaiming for a memcg, a priority drop can cause high
1944 * latencies, so it's better to scan a minimum amount there as
1947 if (current_is_kswapd()) {
1948 if (!zone_reclaimable(zone
))
1950 if (!mem_cgroup_lruvec_online(lruvec
))
1953 if (!global_reclaim(sc
))
1956 /* If we have no swap space, do not bother scanning anon pages. */
1957 if (!sc
->may_swap
|| (get_nr_swap_pages() <= 0)) {
1958 scan_balance
= SCAN_FILE
;
1963 * Global reclaim will swap to prevent OOM even with no
1964 * swappiness, but memcg users want to use this knob to
1965 * disable swapping for individual groups completely when
1966 * using the memory controller's swap limit feature would be
1969 if (!global_reclaim(sc
) && !swappiness
) {
1970 scan_balance
= SCAN_FILE
;
1975 * Do not apply any pressure balancing cleverness when the
1976 * system is close to OOM, scan both anon and file equally
1977 * (unless the swappiness setting disagrees with swapping).
1979 if (!sc
->priority
&& swappiness
) {
1980 scan_balance
= SCAN_EQUAL
;
1985 * Prevent the reclaimer from falling into the cache trap: as
1986 * cache pages start out inactive, every cache fault will tip
1987 * the scan balance towards the file LRU. And as the file LRU
1988 * shrinks, so does the window for rotation from references.
1989 * This means we have a runaway feedback loop where a tiny
1990 * thrashing file LRU becomes infinitely more attractive than
1991 * anon pages. Try to detect this based on file LRU size.
1993 if (global_reclaim(sc
)) {
1994 unsigned long zonefile
;
1995 unsigned long zonefree
;
1997 zonefree
= zone_page_state(zone
, NR_FREE_PAGES
);
1998 zonefile
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
1999 zone_page_state(zone
, NR_INACTIVE_FILE
);
2001 if (unlikely(zonefile
+ zonefree
<= high_wmark_pages(zone
))) {
2002 scan_balance
= SCAN_ANON
;
2008 * There is enough inactive page cache, do not reclaim
2009 * anything from the anonymous working set right now.
2011 if (!inactive_file_is_low(lruvec
)) {
2012 scan_balance
= SCAN_FILE
;
2016 scan_balance
= SCAN_FRACT
;
2019 * With swappiness at 100, anonymous and file have the same priority.
2020 * This scanning priority is essentially the inverse of IO cost.
2022 anon_prio
= swappiness
;
2023 file_prio
= 200 - anon_prio
;
2026 * OK, so we have swap space and a fair amount of page cache
2027 * pages. We use the recently rotated / recently scanned
2028 * ratios to determine how valuable each cache is.
2030 * Because workloads change over time (and to avoid overflow)
2031 * we keep these statistics as a floating average, which ends
2032 * up weighing recent references more than old ones.
2034 * anon in [0], file in [1]
2037 anon
= get_lru_size(lruvec
, LRU_ACTIVE_ANON
) +
2038 get_lru_size(lruvec
, LRU_INACTIVE_ANON
);
2039 file
= get_lru_size(lruvec
, LRU_ACTIVE_FILE
) +
2040 get_lru_size(lruvec
, LRU_INACTIVE_FILE
);
2042 spin_lock_irq(&zone
->lru_lock
);
2043 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
2044 reclaim_stat
->recent_scanned
[0] /= 2;
2045 reclaim_stat
->recent_rotated
[0] /= 2;
2048 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
2049 reclaim_stat
->recent_scanned
[1] /= 2;
2050 reclaim_stat
->recent_rotated
[1] /= 2;
2054 * The amount of pressure on anon vs file pages is inversely
2055 * proportional to the fraction of recently scanned pages on
2056 * each list that were recently referenced and in active use.
2058 ap
= anon_prio
* (reclaim_stat
->recent_scanned
[0] + 1);
2059 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
2061 fp
= file_prio
* (reclaim_stat
->recent_scanned
[1] + 1);
2062 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
2063 spin_unlock_irq(&zone
->lru_lock
);
2067 denominator
= ap
+ fp
+ 1;
2069 some_scanned
= false;
2070 /* Only use force_scan on second pass. */
2071 for (pass
= 0; !some_scanned
&& pass
< 2; pass
++) {
2073 for_each_evictable_lru(lru
) {
2074 int file
= is_file_lru(lru
);
2078 size
= get_lru_size(lruvec
, lru
);
2079 scan
= size
>> sc
->priority
;
2081 if (!scan
&& pass
&& force_scan
)
2082 scan
= min(size
, SWAP_CLUSTER_MAX
);
2084 switch (scan_balance
) {
2086 /* Scan lists relative to size */
2090 * Scan types proportional to swappiness and
2091 * their relative recent reclaim efficiency.
2093 scan
= div64_u64(scan
* fraction
[file
],
2098 /* Scan one type exclusively */
2099 if ((scan_balance
== SCAN_FILE
) != file
) {
2105 /* Look ma, no brain */
2113 * Skip the second pass and don't force_scan,
2114 * if we found something to scan.
2116 some_scanned
|= !!scan
;
2122 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
2124 static void shrink_lruvec(struct lruvec
*lruvec
, int swappiness
,
2125 struct scan_control
*sc
, unsigned long *lru_pages
)
2127 unsigned long nr
[NR_LRU_LISTS
];
2128 unsigned long targets
[NR_LRU_LISTS
];
2129 unsigned long nr_to_scan
;
2131 unsigned long nr_reclaimed
= 0;
2132 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
2133 struct blk_plug plug
;
2136 get_scan_count(lruvec
, swappiness
, sc
, nr
, lru_pages
);
2138 /* Record the original scan target for proportional adjustments later */
2139 memcpy(targets
, nr
, sizeof(nr
));
2142 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
2143 * event that can occur when there is little memory pressure e.g.
2144 * multiple streaming readers/writers. Hence, we do not abort scanning
2145 * when the requested number of pages are reclaimed when scanning at
2146 * DEF_PRIORITY on the assumption that the fact we are direct
2147 * reclaiming implies that kswapd is not keeping up and it is best to
2148 * do a batch of work at once. For memcg reclaim one check is made to
2149 * abort proportional reclaim if either the file or anon lru has already
2150 * dropped to zero at the first pass.
2152 scan_adjusted
= (global_reclaim(sc
) && !current_is_kswapd() &&
2153 sc
->priority
== DEF_PRIORITY
);
2155 blk_start_plug(&plug
);
2156 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
2157 nr
[LRU_INACTIVE_FILE
]) {
2158 unsigned long nr_anon
, nr_file
, percentage
;
2159 unsigned long nr_scanned
;
2161 for_each_evictable_lru(lru
) {
2163 nr_to_scan
= min(nr
[lru
], SWAP_CLUSTER_MAX
);
2164 nr
[lru
] -= nr_to_scan
;
2166 nr_reclaimed
+= shrink_list(lru
, nr_to_scan
,
2171 if (nr_reclaimed
< nr_to_reclaim
|| scan_adjusted
)
2175 * For kswapd and memcg, reclaim at least the number of pages
2176 * requested. Ensure that the anon and file LRUs are scanned
2177 * proportionally what was requested by get_scan_count(). We
2178 * stop reclaiming one LRU and reduce the amount scanning
2179 * proportional to the original scan target.
2181 nr_file
= nr
[LRU_INACTIVE_FILE
] + nr
[LRU_ACTIVE_FILE
];
2182 nr_anon
= nr
[LRU_INACTIVE_ANON
] + nr
[LRU_ACTIVE_ANON
];
2185 * It's just vindictive to attack the larger once the smaller
2186 * has gone to zero. And given the way we stop scanning the
2187 * smaller below, this makes sure that we only make one nudge
2188 * towards proportionality once we've got nr_to_reclaim.
2190 if (!nr_file
|| !nr_anon
)
2193 if (nr_file
> nr_anon
) {
2194 unsigned long scan_target
= targets
[LRU_INACTIVE_ANON
] +
2195 targets
[LRU_ACTIVE_ANON
] + 1;
2197 percentage
= nr_anon
* 100 / scan_target
;
2199 unsigned long scan_target
= targets
[LRU_INACTIVE_FILE
] +
2200 targets
[LRU_ACTIVE_FILE
] + 1;
2202 percentage
= nr_file
* 100 / scan_target
;
2205 /* Stop scanning the smaller of the LRU */
2207 nr
[lru
+ LRU_ACTIVE
] = 0;
2210 * Recalculate the other LRU scan count based on its original
2211 * scan target and the percentage scanning already complete
2213 lru
= (lru
== LRU_FILE
) ? LRU_BASE
: LRU_FILE
;
2214 nr_scanned
= targets
[lru
] - nr
[lru
];
2215 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2216 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2219 nr_scanned
= targets
[lru
] - nr
[lru
];
2220 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2221 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2223 scan_adjusted
= true;
2225 blk_finish_plug(&plug
);
2226 sc
->nr_reclaimed
+= nr_reclaimed
;
2229 * Even if we did not try to evict anon pages at all, we want to
2230 * rebalance the anon lru active/inactive ratio.
2232 if (inactive_anon_is_low(lruvec
))
2233 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
2234 sc
, LRU_ACTIVE_ANON
);
2236 throttle_vm_writeout(sc
->gfp_mask
);
2239 /* Use reclaim/compaction for costly allocs or under memory pressure */
2240 static bool in_reclaim_compaction(struct scan_control
*sc
)
2242 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
2243 (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
||
2244 sc
->priority
< DEF_PRIORITY
- 2))
2251 * Reclaim/compaction is used for high-order allocation requests. It reclaims
2252 * order-0 pages before compacting the zone. should_continue_reclaim() returns
2253 * true if more pages should be reclaimed such that when the page allocator
2254 * calls try_to_compact_zone() that it will have enough free pages to succeed.
2255 * It will give up earlier than that if there is difficulty reclaiming pages.
2257 static inline bool should_continue_reclaim(struct zone
*zone
,
2258 unsigned long nr_reclaimed
,
2259 unsigned long nr_scanned
,
2260 struct scan_control
*sc
)
2262 unsigned long pages_for_compaction
;
2263 unsigned long inactive_lru_pages
;
2265 /* If not in reclaim/compaction mode, stop */
2266 if (!in_reclaim_compaction(sc
))
2269 /* Consider stopping depending on scan and reclaim activity */
2270 if (sc
->gfp_mask
& __GFP_REPEAT
) {
2272 * For __GFP_REPEAT allocations, stop reclaiming if the
2273 * full LRU list has been scanned and we are still failing
2274 * to reclaim pages. This full LRU scan is potentially
2275 * expensive but a __GFP_REPEAT caller really wants to succeed
2277 if (!nr_reclaimed
&& !nr_scanned
)
2281 * For non-__GFP_REPEAT allocations which can presumably
2282 * fail without consequence, stop if we failed to reclaim
2283 * any pages from the last SWAP_CLUSTER_MAX number of
2284 * pages that were scanned. This will return to the
2285 * caller faster at the risk reclaim/compaction and
2286 * the resulting allocation attempt fails
2293 * If we have not reclaimed enough pages for compaction and the
2294 * inactive lists are large enough, continue reclaiming
2296 pages_for_compaction
= (2UL << sc
->order
);
2297 inactive_lru_pages
= zone_page_state(zone
, NR_INACTIVE_FILE
);
2298 if (get_nr_swap_pages() > 0)
2299 inactive_lru_pages
+= zone_page_state(zone
, NR_INACTIVE_ANON
);
2300 if (sc
->nr_reclaimed
< pages_for_compaction
&&
2301 inactive_lru_pages
> pages_for_compaction
)
2304 /* If compaction would go ahead or the allocation would succeed, stop */
2305 switch (compaction_suitable(zone
, sc
->order
, 0, 0)) {
2306 case COMPACT_PARTIAL
:
2307 case COMPACT_CONTINUE
:
2314 static bool shrink_zone(struct zone
*zone
, struct scan_control
*sc
,
2317 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2318 unsigned long nr_reclaimed
, nr_scanned
;
2319 bool reclaimable
= false;
2322 struct mem_cgroup
*root
= sc
->target_mem_cgroup
;
2323 struct mem_cgroup_reclaim_cookie reclaim
= {
2325 .priority
= sc
->priority
,
2327 unsigned long zone_lru_pages
= 0;
2328 struct mem_cgroup
*memcg
;
2330 nr_reclaimed
= sc
->nr_reclaimed
;
2331 nr_scanned
= sc
->nr_scanned
;
2333 memcg
= mem_cgroup_iter(root
, NULL
, &reclaim
);
2335 unsigned long lru_pages
;
2336 unsigned long scanned
;
2337 struct lruvec
*lruvec
;
2340 if (mem_cgroup_low(root
, memcg
)) {
2341 if (!sc
->may_thrash
)
2343 mem_cgroup_events(memcg
, MEMCG_LOW
, 1);
2346 lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
2347 swappiness
= mem_cgroup_swappiness(memcg
);
2348 scanned
= sc
->nr_scanned
;
2350 shrink_lruvec(lruvec
, swappiness
, sc
, &lru_pages
);
2351 zone_lru_pages
+= lru_pages
;
2353 if (memcg
&& is_classzone
)
2354 shrink_slab(sc
->gfp_mask
, zone_to_nid(zone
),
2355 memcg
, sc
->nr_scanned
- scanned
,
2359 * Direct reclaim and kswapd have to scan all memory
2360 * cgroups to fulfill the overall scan target for the
2363 * Limit reclaim, on the other hand, only cares about
2364 * nr_to_reclaim pages to be reclaimed and it will
2365 * retry with decreasing priority if one round over the
2366 * whole hierarchy is not sufficient.
2368 if (!global_reclaim(sc
) &&
2369 sc
->nr_reclaimed
>= sc
->nr_to_reclaim
) {
2370 mem_cgroup_iter_break(root
, memcg
);
2373 } while ((memcg
= mem_cgroup_iter(root
, memcg
, &reclaim
)));
2376 * Shrink the slab caches in the same proportion that
2377 * the eligible LRU pages were scanned.
2379 if (global_reclaim(sc
) && is_classzone
)
2380 shrink_slab(sc
->gfp_mask
, zone_to_nid(zone
), NULL
,
2381 sc
->nr_scanned
- nr_scanned
,
2384 if (reclaim_state
) {
2385 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2386 reclaim_state
->reclaimed_slab
= 0;
2389 vmpressure(sc
->gfp_mask
, sc
->target_mem_cgroup
,
2390 sc
->nr_scanned
- nr_scanned
,
2391 sc
->nr_reclaimed
- nr_reclaimed
);
2393 if (sc
->nr_reclaimed
- nr_reclaimed
)
2396 } while (should_continue_reclaim(zone
, sc
->nr_reclaimed
- nr_reclaimed
,
2397 sc
->nr_scanned
- nr_scanned
, sc
));
2403 * Returns true if compaction should go ahead for a high-order request, or
2404 * the high-order allocation would succeed without compaction.
2406 static inline bool compaction_ready(struct zone
*zone
, int order
)
2408 unsigned long balance_gap
, watermark
;
2412 * Compaction takes time to run and there are potentially other
2413 * callers using the pages just freed. Continue reclaiming until
2414 * there is a buffer of free pages available to give compaction
2415 * a reasonable chance of completing and allocating the page
2417 balance_gap
= min(low_wmark_pages(zone
), DIV_ROUND_UP(
2418 zone
->managed_pages
, KSWAPD_ZONE_BALANCE_GAP_RATIO
));
2419 watermark
= high_wmark_pages(zone
) + balance_gap
+ (2UL << order
);
2420 watermark_ok
= zone_watermark_ok_safe(zone
, 0, watermark
, 0, 0);
2423 * If compaction is deferred, reclaim up to a point where
2424 * compaction will have a chance of success when re-enabled
2426 if (compaction_deferred(zone
, order
))
2427 return watermark_ok
;
2430 * If compaction is not ready to start and allocation is not likely
2431 * to succeed without it, then keep reclaiming.
2433 if (compaction_suitable(zone
, order
, 0, 0) == COMPACT_SKIPPED
)
2436 return watermark_ok
;
2440 * This is the direct reclaim path, for page-allocating processes. We only
2441 * try to reclaim pages from zones which will satisfy the caller's allocation
2444 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2446 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2448 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2449 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2450 * zone defense algorithm.
2452 * If a zone is deemed to be full of pinned pages then just give it a light
2453 * scan then give up on it.
2455 * Returns true if a zone was reclaimable.
2457 static bool shrink_zones(struct zonelist
*zonelist
, struct scan_control
*sc
)
2461 unsigned long nr_soft_reclaimed
;
2462 unsigned long nr_soft_scanned
;
2464 enum zone_type requested_highidx
= gfp_zone(sc
->gfp_mask
);
2465 bool reclaimable
= false;
2468 * If the number of buffer_heads in the machine exceeds the maximum
2469 * allowed level, force direct reclaim to scan the highmem zone as
2470 * highmem pages could be pinning lowmem pages storing buffer_heads
2472 orig_mask
= sc
->gfp_mask
;
2473 if (buffer_heads_over_limit
)
2474 sc
->gfp_mask
|= __GFP_HIGHMEM
;
2476 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2477 requested_highidx
, sc
->nodemask
) {
2478 enum zone_type classzone_idx
;
2480 if (!populated_zone(zone
))
2483 classzone_idx
= requested_highidx
;
2484 while (!populated_zone(zone
->zone_pgdat
->node_zones
+
2489 * Take care memory controller reclaiming has small influence
2492 if (global_reclaim(sc
)) {
2493 if (!cpuset_zone_allowed(zone
,
2494 GFP_KERNEL
| __GFP_HARDWALL
))
2497 if (sc
->priority
!= DEF_PRIORITY
&&
2498 !zone_reclaimable(zone
))
2499 continue; /* Let kswapd poll it */
2502 * If we already have plenty of memory free for
2503 * compaction in this zone, don't free any more.
2504 * Even though compaction is invoked for any
2505 * non-zero order, only frequent costly order
2506 * reclamation is disruptive enough to become a
2507 * noticeable problem, like transparent huge
2510 if (IS_ENABLED(CONFIG_COMPACTION
) &&
2511 sc
->order
> PAGE_ALLOC_COSTLY_ORDER
&&
2512 zonelist_zone_idx(z
) <= requested_highidx
&&
2513 compaction_ready(zone
, sc
->order
)) {
2514 sc
->compaction_ready
= true;
2519 * This steals pages from memory cgroups over softlimit
2520 * and returns the number of reclaimed pages and
2521 * scanned pages. This works for global memory pressure
2522 * and balancing, not for a memcg's limit.
2524 nr_soft_scanned
= 0;
2525 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2526 sc
->order
, sc
->gfp_mask
,
2528 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
2529 sc
->nr_scanned
+= nr_soft_scanned
;
2530 if (nr_soft_reclaimed
)
2532 /* need some check for avoid more shrink_zone() */
2535 if (shrink_zone(zone
, sc
, zone_idx(zone
) == classzone_idx
))
2538 if (global_reclaim(sc
) &&
2539 !reclaimable
&& zone_reclaimable(zone
))
2544 * Restore to original mask to avoid the impact on the caller if we
2545 * promoted it to __GFP_HIGHMEM.
2547 sc
->gfp_mask
= orig_mask
;
2553 * This is the main entry point to direct page reclaim.
2555 * If a full scan of the inactive list fails to free enough memory then we
2556 * are "out of memory" and something needs to be killed.
2558 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2559 * high - the zone may be full of dirty or under-writeback pages, which this
2560 * caller can't do much about. We kick the writeback threads and take explicit
2561 * naps in the hope that some of these pages can be written. But if the
2562 * allocating task holds filesystem locks which prevent writeout this might not
2563 * work, and the allocation attempt will fail.
2565 * returns: 0, if no pages reclaimed
2566 * else, the number of pages reclaimed
2568 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2569 struct scan_control
*sc
)
2571 int initial_priority
= sc
->priority
;
2572 unsigned long total_scanned
= 0;
2573 unsigned long writeback_threshold
;
2574 bool zones_reclaimable
;
2576 delayacct_freepages_start();
2578 if (global_reclaim(sc
))
2579 count_vm_event(ALLOCSTALL
);
2582 vmpressure_prio(sc
->gfp_mask
, sc
->target_mem_cgroup
,
2585 zones_reclaimable
= shrink_zones(zonelist
, sc
);
2587 total_scanned
+= sc
->nr_scanned
;
2588 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
2591 if (sc
->compaction_ready
)
2595 * If we're getting trouble reclaiming, start doing
2596 * writepage even in laptop mode.
2598 if (sc
->priority
< DEF_PRIORITY
- 2)
2599 sc
->may_writepage
= 1;
2602 * Try to write back as many pages as we just scanned. This
2603 * tends to cause slow streaming writers to write data to the
2604 * disk smoothly, at the dirtying rate, which is nice. But
2605 * that's undesirable in laptop mode, where we *want* lumpy
2606 * writeout. So in laptop mode, write out the whole world.
2608 writeback_threshold
= sc
->nr_to_reclaim
+ sc
->nr_to_reclaim
/ 2;
2609 if (total_scanned
> writeback_threshold
) {
2610 wakeup_flusher_threads(laptop_mode
? 0 : total_scanned
,
2611 WB_REASON_TRY_TO_FREE_PAGES
);
2612 sc
->may_writepage
= 1;
2614 } while (--sc
->priority
>= 0);
2616 delayacct_freepages_end();
2618 if (sc
->nr_reclaimed
)
2619 return sc
->nr_reclaimed
;
2621 /* Aborted reclaim to try compaction? don't OOM, then */
2622 if (sc
->compaction_ready
)
2625 /* Untapped cgroup reserves? Don't OOM, retry. */
2626 if (!sc
->may_thrash
) {
2627 sc
->priority
= initial_priority
;
2632 /* Any of the zones still reclaimable? Don't OOM. */
2633 if (zones_reclaimable
)
2639 static bool pfmemalloc_watermark_ok(pg_data_t
*pgdat
)
2642 unsigned long pfmemalloc_reserve
= 0;
2643 unsigned long free_pages
= 0;
2647 for (i
= 0; i
<= ZONE_NORMAL
; i
++) {
2648 zone
= &pgdat
->node_zones
[i
];
2649 if (!populated_zone(zone
) ||
2650 zone_reclaimable_pages(zone
) == 0)
2653 pfmemalloc_reserve
+= min_wmark_pages(zone
);
2654 free_pages
+= zone_page_state(zone
, NR_FREE_PAGES
);
2657 /* If there are no reserves (unexpected config) then do not throttle */
2658 if (!pfmemalloc_reserve
)
2661 wmark_ok
= free_pages
> pfmemalloc_reserve
/ 2;
2663 /* kswapd must be awake if processes are being throttled */
2664 if (!wmark_ok
&& waitqueue_active(&pgdat
->kswapd_wait
)) {
2665 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
,
2666 (enum zone_type
)ZONE_NORMAL
);
2667 wake_up_interruptible(&pgdat
->kswapd_wait
);
2674 * Throttle direct reclaimers if backing storage is backed by the network
2675 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
2676 * depleted. kswapd will continue to make progress and wake the processes
2677 * when the low watermark is reached.
2679 * Returns true if a fatal signal was delivered during throttling. If this
2680 * happens, the page allocator should not consider triggering the OOM killer.
2682 static bool throttle_direct_reclaim(gfp_t gfp_mask
, struct zonelist
*zonelist
,
2683 nodemask_t
*nodemask
)
2687 pg_data_t
*pgdat
= NULL
;
2690 * Kernel threads should not be throttled as they may be indirectly
2691 * responsible for cleaning pages necessary for reclaim to make forward
2692 * progress. kjournald for example may enter direct reclaim while
2693 * committing a transaction where throttling it could forcing other
2694 * processes to block on log_wait_commit().
2696 if (current
->flags
& PF_KTHREAD
)
2700 * If a fatal signal is pending, this process should not throttle.
2701 * It should return quickly so it can exit and free its memory
2703 if (fatal_signal_pending(current
))
2707 * Check if the pfmemalloc reserves are ok by finding the first node
2708 * with a usable ZONE_NORMAL or lower zone. The expectation is that
2709 * GFP_KERNEL will be required for allocating network buffers when
2710 * swapping over the network so ZONE_HIGHMEM is unusable.
2712 * Throttling is based on the first usable node and throttled processes
2713 * wait on a queue until kswapd makes progress and wakes them. There
2714 * is an affinity then between processes waking up and where reclaim
2715 * progress has been made assuming the process wakes on the same node.
2716 * More importantly, processes running on remote nodes will not compete
2717 * for remote pfmemalloc reserves and processes on different nodes
2718 * should make reasonable progress.
2720 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2721 gfp_zone(gfp_mask
), nodemask
) {
2722 if (zone_idx(zone
) > ZONE_NORMAL
)
2725 /* Throttle based on the first usable node */
2726 pgdat
= zone
->zone_pgdat
;
2727 if (pfmemalloc_watermark_ok(pgdat
))
2732 /* If no zone was usable by the allocation flags then do not throttle */
2736 /* Account for the throttling */
2737 count_vm_event(PGSCAN_DIRECT_THROTTLE
);
2740 * If the caller cannot enter the filesystem, it's possible that it
2741 * is due to the caller holding an FS lock or performing a journal
2742 * transaction in the case of a filesystem like ext[3|4]. In this case,
2743 * it is not safe to block on pfmemalloc_wait as kswapd could be
2744 * blocked waiting on the same lock. Instead, throttle for up to a
2745 * second before continuing.
2747 if (!(gfp_mask
& __GFP_FS
)) {
2748 wait_event_interruptible_timeout(pgdat
->pfmemalloc_wait
,
2749 pfmemalloc_watermark_ok(pgdat
), HZ
);
2754 /* Throttle until kswapd wakes the process */
2755 wait_event_killable(zone
->zone_pgdat
->pfmemalloc_wait
,
2756 pfmemalloc_watermark_ok(pgdat
));
2759 if (fatal_signal_pending(current
))
2766 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
2767 gfp_t gfp_mask
, nodemask_t
*nodemask
)
2769 unsigned long nr_reclaimed
;
2770 struct scan_control sc
= {
2771 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2772 .gfp_mask
= (gfp_mask
= memalloc_noio_flags(gfp_mask
)),
2774 .nodemask
= nodemask
,
2775 .priority
= DEF_PRIORITY
,
2776 .may_writepage
= !laptop_mode
,
2782 * Do not enter reclaim if fatal signal was delivered while throttled.
2783 * 1 is returned so that the page allocator does not OOM kill at this
2786 if (throttle_direct_reclaim(gfp_mask
, zonelist
, nodemask
))
2789 trace_mm_vmscan_direct_reclaim_begin(order
,
2793 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2795 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
2797 return nr_reclaimed
;
2802 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup
*memcg
,
2803 gfp_t gfp_mask
, bool noswap
,
2805 unsigned long *nr_scanned
)
2807 struct scan_control sc
= {
2808 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2809 .target_mem_cgroup
= memcg
,
2810 .may_writepage
= !laptop_mode
,
2812 .may_swap
= !noswap
,
2814 struct lruvec
*lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
2815 int swappiness
= mem_cgroup_swappiness(memcg
);
2816 unsigned long lru_pages
;
2818 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2819 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2821 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc
.order
,
2826 * NOTE: Although we can get the priority field, using it
2827 * here is not a good idea, since it limits the pages we can scan.
2828 * if we don't reclaim here, the shrink_zone from balance_pgdat
2829 * will pick up pages from other mem cgroup's as well. We hack
2830 * the priority and make it zero.
2832 shrink_lruvec(lruvec
, swappiness
, &sc
, &lru_pages
);
2834 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
2836 *nr_scanned
= sc
.nr_scanned
;
2837 return sc
.nr_reclaimed
;
2840 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*memcg
,
2841 unsigned long nr_pages
,
2845 struct zonelist
*zonelist
;
2846 unsigned long nr_reclaimed
;
2848 struct scan_control sc
= {
2849 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
2850 .gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2851 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
2852 .target_mem_cgroup
= memcg
,
2853 .priority
= DEF_PRIORITY
,
2854 .may_writepage
= !laptop_mode
,
2856 .may_swap
= may_swap
,
2860 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2861 * take care of from where we get pages. So the node where we start the
2862 * scan does not need to be the current node.
2864 nid
= mem_cgroup_select_victim_node(memcg
);
2866 zonelist
= NODE_DATA(nid
)->node_zonelists
;
2868 trace_mm_vmscan_memcg_reclaim_begin(0,
2872 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2874 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
2876 return nr_reclaimed
;
2880 static void age_active_anon(struct zone
*zone
, struct scan_control
*sc
)
2882 struct mem_cgroup
*memcg
;
2884 if (!total_swap_pages
)
2887 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
2889 struct lruvec
*lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
2891 if (inactive_anon_is_low(lruvec
))
2892 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
2893 sc
, LRU_ACTIVE_ANON
);
2895 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
2899 static bool zone_balanced(struct zone
*zone
, int order
,
2900 unsigned long balance_gap
, int classzone_idx
)
2902 if (!zone_watermark_ok_safe(zone
, order
, high_wmark_pages(zone
) +
2903 balance_gap
, classzone_idx
, 0))
2906 if (IS_ENABLED(CONFIG_COMPACTION
) && order
&& compaction_suitable(zone
,
2907 order
, 0, classzone_idx
) == COMPACT_SKIPPED
)
2914 * pgdat_balanced() is used when checking if a node is balanced.
2916 * For order-0, all zones must be balanced!
2918 * For high-order allocations only zones that meet watermarks and are in a
2919 * zone allowed by the callers classzone_idx are added to balanced_pages. The
2920 * total of balanced pages must be at least 25% of the zones allowed by
2921 * classzone_idx for the node to be considered balanced. Forcing all zones to
2922 * be balanced for high orders can cause excessive reclaim when there are
2924 * The choice of 25% is due to
2925 * o a 16M DMA zone that is balanced will not balance a zone on any
2926 * reasonable sized machine
2927 * o On all other machines, the top zone must be at least a reasonable
2928 * percentage of the middle zones. For example, on 32-bit x86, highmem
2929 * would need to be at least 256M for it to be balance a whole node.
2930 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2931 * to balance a node on its own. These seemed like reasonable ratios.
2933 static bool pgdat_balanced(pg_data_t
*pgdat
, int order
, int classzone_idx
)
2935 unsigned long managed_pages
= 0;
2936 unsigned long balanced_pages
= 0;
2939 /* Check the watermark levels */
2940 for (i
= 0; i
<= classzone_idx
; i
++) {
2941 struct zone
*zone
= pgdat
->node_zones
+ i
;
2943 if (!populated_zone(zone
))
2946 managed_pages
+= zone
->managed_pages
;
2949 * A special case here:
2951 * balance_pgdat() skips over all_unreclaimable after
2952 * DEF_PRIORITY. Effectively, it considers them balanced so
2953 * they must be considered balanced here as well!
2955 if (!zone_reclaimable(zone
)) {
2956 balanced_pages
+= zone
->managed_pages
;
2960 if (zone_balanced(zone
, order
, 0, i
))
2961 balanced_pages
+= zone
->managed_pages
;
2967 return balanced_pages
>= (managed_pages
>> 2);
2973 * Prepare kswapd for sleeping. This verifies that there are no processes
2974 * waiting in throttle_direct_reclaim() and that watermarks have been met.
2976 * Returns true if kswapd is ready to sleep
2978 static bool prepare_kswapd_sleep(pg_data_t
*pgdat
, int order
, long remaining
,
2981 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2986 * The throttled processes are normally woken up in balance_pgdat() as
2987 * soon as pfmemalloc_watermark_ok() is true. But there is a potential
2988 * race between when kswapd checks the watermarks and a process gets
2989 * throttled. There is also a potential race if processes get
2990 * throttled, kswapd wakes, a large process exits thereby balancing the
2991 * zones, which causes kswapd to exit balance_pgdat() before reaching
2992 * the wake up checks. If kswapd is going to sleep, no process should
2993 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
2994 * the wake up is premature, processes will wake kswapd and get
2995 * throttled again. The difference from wake ups in balance_pgdat() is
2996 * that here we are under prepare_to_wait().
2998 if (waitqueue_active(&pgdat
->pfmemalloc_wait
))
2999 wake_up_all(&pgdat
->pfmemalloc_wait
);
3001 return pgdat_balanced(pgdat
, order
, classzone_idx
);
3005 * kswapd shrinks the zone by the number of pages required to reach
3006 * the high watermark.
3008 * Returns true if kswapd scanned at least the requested number of pages to
3009 * reclaim or if the lack of progress was due to pages under writeback.
3010 * This is used to determine if the scanning priority needs to be raised.
3012 static bool kswapd_shrink_zone(struct zone
*zone
,
3014 struct scan_control
*sc
,
3015 unsigned long *nr_attempted
)
3017 int testorder
= sc
->order
;
3018 unsigned long balance_gap
;
3019 bool lowmem_pressure
;
3021 /* Reclaim above the high watermark. */
3022 sc
->nr_to_reclaim
= max(SWAP_CLUSTER_MAX
, high_wmark_pages(zone
));
3025 * Kswapd reclaims only single pages with compaction enabled. Trying
3026 * too hard to reclaim until contiguous free pages have become
3027 * available can hurt performance by evicting too much useful data
3028 * from memory. Do not reclaim more than needed for compaction.
3030 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
3031 compaction_suitable(zone
, sc
->order
, 0, classzone_idx
)
3036 * We put equal pressure on every zone, unless one zone has way too
3037 * many pages free already. The "too many pages" is defined as the
3038 * high wmark plus a "gap" where the gap is either the low
3039 * watermark or 1% of the zone, whichever is smaller.
3041 balance_gap
= min(low_wmark_pages(zone
), DIV_ROUND_UP(
3042 zone
->managed_pages
, KSWAPD_ZONE_BALANCE_GAP_RATIO
));
3045 * If there is no low memory pressure or the zone is balanced then no
3046 * reclaim is necessary
3048 lowmem_pressure
= (buffer_heads_over_limit
&& is_highmem(zone
));
3049 if (!lowmem_pressure
&& zone_balanced(zone
, testorder
,
3050 balance_gap
, classzone_idx
))
3053 shrink_zone(zone
, sc
, zone_idx(zone
) == classzone_idx
);
3055 /* Account for the number of pages attempted to reclaim */
3056 *nr_attempted
+= sc
->nr_to_reclaim
;
3058 clear_bit(ZONE_WRITEBACK
, &zone
->flags
);
3061 * If a zone reaches its high watermark, consider it to be no longer
3062 * congested. It's possible there are dirty pages backed by congested
3063 * BDIs but as pressure is relieved, speculatively avoid congestion
3066 if (zone_reclaimable(zone
) &&
3067 zone_balanced(zone
, testorder
, 0, classzone_idx
)) {
3068 clear_bit(ZONE_CONGESTED
, &zone
->flags
);
3069 clear_bit(ZONE_DIRTY
, &zone
->flags
);
3072 return sc
->nr_scanned
>= sc
->nr_to_reclaim
;
3076 * For kswapd, balance_pgdat() will work across all this node's zones until
3077 * they are all at high_wmark_pages(zone).
3079 * Returns the final order kswapd was reclaiming at
3081 * There is special handling here for zones which are full of pinned pages.
3082 * This can happen if the pages are all mlocked, or if they are all used by
3083 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
3084 * What we do is to detect the case where all pages in the zone have been
3085 * scanned twice and there has been zero successful reclaim. Mark the zone as
3086 * dead and from now on, only perform a short scan. Basically we're polling
3087 * the zone for when the problem goes away.
3089 * kswapd scans the zones in the highmem->normal->dma direction. It skips
3090 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
3091 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
3092 * lower zones regardless of the number of free pages in the lower zones. This
3093 * interoperates with the page allocator fallback scheme to ensure that aging
3094 * of pages is balanced across the zones.
3096 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
,
3100 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
3101 unsigned long nr_soft_reclaimed
;
3102 unsigned long nr_soft_scanned
;
3103 struct scan_control sc
= {
3104 .gfp_mask
= GFP_KERNEL
,
3106 .priority
= DEF_PRIORITY
,
3107 .may_writepage
= !laptop_mode
,
3111 count_vm_event(PAGEOUTRUN
);
3114 unsigned long nr_attempted
= 0;
3115 bool raise_priority
= true;
3116 bool pgdat_needs_compaction
= (order
> 0);
3118 sc
.nr_reclaimed
= 0;
3121 * Scan in the highmem->dma direction for the highest
3122 * zone which needs scanning
3124 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
3125 struct zone
*zone
= pgdat
->node_zones
+ i
;
3127 if (!populated_zone(zone
))
3130 if (sc
.priority
!= DEF_PRIORITY
&&
3131 !zone_reclaimable(zone
))
3135 * Do some background aging of the anon list, to give
3136 * pages a chance to be referenced before reclaiming.
3138 age_active_anon(zone
, &sc
);
3141 * If the number of buffer_heads in the machine
3142 * exceeds the maximum allowed level and this node
3143 * has a highmem zone, force kswapd to reclaim from
3144 * it to relieve lowmem pressure.
3146 if (buffer_heads_over_limit
&& is_highmem_idx(i
)) {
3151 if (!zone_balanced(zone
, order
, 0, 0)) {
3156 * If balanced, clear the dirty and congested
3159 clear_bit(ZONE_CONGESTED
, &zone
->flags
);
3160 clear_bit(ZONE_DIRTY
, &zone
->flags
);
3167 for (i
= 0; i
<= end_zone
; i
++) {
3168 struct zone
*zone
= pgdat
->node_zones
+ i
;
3170 if (!populated_zone(zone
))
3174 * If any zone is currently balanced then kswapd will
3175 * not call compaction as it is expected that the
3176 * necessary pages are already available.
3178 if (pgdat_needs_compaction
&&
3179 zone_watermark_ok(zone
, order
,
3180 low_wmark_pages(zone
),
3182 pgdat_needs_compaction
= false;
3186 * If we're getting trouble reclaiming, start doing writepage
3187 * even in laptop mode.
3189 if (sc
.priority
< DEF_PRIORITY
- 2)
3190 sc
.may_writepage
= 1;
3193 * Now scan the zone in the dma->highmem direction, stopping
3194 * at the last zone which needs scanning.
3196 * We do this because the page allocator works in the opposite
3197 * direction. This prevents the page allocator from allocating
3198 * pages behind kswapd's direction of progress, which would
3199 * cause too much scanning of the lower zones.
3201 for (i
= 0; i
<= end_zone
; i
++) {
3202 struct zone
*zone
= pgdat
->node_zones
+ i
;
3204 if (!populated_zone(zone
))
3207 if (sc
.priority
!= DEF_PRIORITY
&&
3208 !zone_reclaimable(zone
))
3213 nr_soft_scanned
= 0;
3215 * Call soft limit reclaim before calling shrink_zone.
3217 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
3220 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
3223 * There should be no need to raise the scanning
3224 * priority if enough pages are already being scanned
3225 * that that high watermark would be met at 100%
3228 if (kswapd_shrink_zone(zone
, end_zone
,
3229 &sc
, &nr_attempted
))
3230 raise_priority
= false;
3234 * If the low watermark is met there is no need for processes
3235 * to be throttled on pfmemalloc_wait as they should not be
3236 * able to safely make forward progress. Wake them
3238 if (waitqueue_active(&pgdat
->pfmemalloc_wait
) &&
3239 pfmemalloc_watermark_ok(pgdat
))
3240 wake_up_all(&pgdat
->pfmemalloc_wait
);
3243 * Fragmentation may mean that the system cannot be rebalanced
3244 * for high-order allocations in all zones. If twice the
3245 * allocation size has been reclaimed and the zones are still
3246 * not balanced then recheck the watermarks at order-0 to
3247 * prevent kswapd reclaiming excessively. Assume that a
3248 * process requested a high-order can direct reclaim/compact.
3250 if (order
&& sc
.nr_reclaimed
>= 2UL << order
)
3251 order
= sc
.order
= 0;
3253 /* Check if kswapd should be suspending */
3254 if (try_to_freeze() || kthread_should_stop())
3258 * Compact if necessary and kswapd is reclaiming at least the
3259 * high watermark number of pages as requsted
3261 if (pgdat_needs_compaction
&& sc
.nr_reclaimed
> nr_attempted
)
3262 compact_pgdat(pgdat
, order
);
3265 * Raise priority if scanning rate is too low or there was no
3266 * progress in reclaiming pages
3268 if (raise_priority
|| !sc
.nr_reclaimed
)
3270 } while (sc
.priority
>= 1 &&
3271 !pgdat_balanced(pgdat
, order
, *classzone_idx
));
3275 * Return the order we were reclaiming at so prepare_kswapd_sleep()
3276 * makes a decision on the order we were last reclaiming at. However,
3277 * if another caller entered the allocator slow path while kswapd
3278 * was awake, order will remain at the higher level
3280 *classzone_idx
= end_zone
;
3284 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
3289 if (freezing(current
) || kthread_should_stop())
3292 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
3294 /* Try to sleep for a short interval */
3295 if (prepare_kswapd_sleep(pgdat
, order
, remaining
, classzone_idx
)) {
3296 remaining
= schedule_timeout(HZ
/10);
3297 finish_wait(&pgdat
->kswapd_wait
, &wait
);
3298 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
3302 * After a short sleep, check if it was a premature sleep. If not, then
3303 * go fully to sleep until explicitly woken up.
3305 if (prepare_kswapd_sleep(pgdat
, order
, remaining
, classzone_idx
)) {
3306 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
3309 * vmstat counters are not perfectly accurate and the estimated
3310 * value for counters such as NR_FREE_PAGES can deviate from the
3311 * true value by nr_online_cpus * threshold. To avoid the zone
3312 * watermarks being breached while under pressure, we reduce the
3313 * per-cpu vmstat threshold while kswapd is awake and restore
3314 * them before going back to sleep.
3316 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
3319 * Compaction records what page blocks it recently failed to
3320 * isolate pages from and skips them in the future scanning.
3321 * When kswapd is going to sleep, it is reasonable to assume
3322 * that pages and compaction may succeed so reset the cache.
3324 reset_isolation_suitable(pgdat
);
3326 if (!kthread_should_stop())
3329 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
3332 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
3334 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
3336 finish_wait(&pgdat
->kswapd_wait
, &wait
);
3340 * The background pageout daemon, started as a kernel thread
3341 * from the init process.
3343 * This basically trickles out pages so that we have _some_
3344 * free memory available even if there is no other activity
3345 * that frees anything up. This is needed for things like routing
3346 * etc, where we otherwise might have all activity going on in
3347 * asynchronous contexts that cannot page things out.
3349 * If there are applications that are active memory-allocators
3350 * (most normal use), this basically shouldn't matter.
3352 static int kswapd(void *p
)
3354 unsigned long order
, new_order
;
3355 unsigned balanced_order
;
3356 int classzone_idx
, new_classzone_idx
;
3357 int balanced_classzone_idx
;
3358 pg_data_t
*pgdat
= (pg_data_t
*)p
;
3359 struct task_struct
*tsk
= current
;
3361 struct reclaim_state reclaim_state
= {
3362 .reclaimed_slab
= 0,
3364 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
3366 lockdep_set_current_reclaim_state(GFP_KERNEL
);
3368 if (!cpumask_empty(cpumask
))
3369 set_cpus_allowed_ptr(tsk
, cpumask
);
3370 current
->reclaim_state
= &reclaim_state
;
3373 * Tell the memory management that we're a "memory allocator",
3374 * and that if we need more memory we should get access to it
3375 * regardless (see "__alloc_pages()"). "kswapd" should
3376 * never get caught in the normal page freeing logic.
3378 * (Kswapd normally doesn't need memory anyway, but sometimes
3379 * you need a small amount of memory in order to be able to
3380 * page out something else, and this flag essentially protects
3381 * us from recursively trying to free more memory as we're
3382 * trying to free the first piece of memory in the first place).
3384 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
3387 order
= new_order
= 0;
3389 classzone_idx
= new_classzone_idx
= pgdat
->nr_zones
- 1;
3390 balanced_classzone_idx
= classzone_idx
;
3395 * If the last balance_pgdat was unsuccessful it's unlikely a
3396 * new request of a similar or harder type will succeed soon
3397 * so consider going to sleep on the basis we reclaimed at
3399 if (balanced_classzone_idx
>= new_classzone_idx
&&
3400 balanced_order
== new_order
) {
3401 new_order
= pgdat
->kswapd_max_order
;
3402 new_classzone_idx
= pgdat
->classzone_idx
;
3403 pgdat
->kswapd_max_order
= 0;
3404 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
3407 if (order
< new_order
|| classzone_idx
> new_classzone_idx
) {
3409 * Don't sleep if someone wants a larger 'order'
3410 * allocation or has tigher zone constraints
3413 classzone_idx
= new_classzone_idx
;
3415 kswapd_try_to_sleep(pgdat
, balanced_order
,
3416 balanced_classzone_idx
);
3417 order
= pgdat
->kswapd_max_order
;
3418 classzone_idx
= pgdat
->classzone_idx
;
3420 new_classzone_idx
= classzone_idx
;
3421 pgdat
->kswapd_max_order
= 0;
3422 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
3425 ret
= try_to_freeze();
3426 if (kthread_should_stop())
3430 * We can speed up thawing tasks if we don't call balance_pgdat
3431 * after returning from the refrigerator
3434 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, order
);
3435 balanced_classzone_idx
= classzone_idx
;
3436 balanced_order
= balance_pgdat(pgdat
, order
,
3437 &balanced_classzone_idx
);
3441 tsk
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
);
3442 current
->reclaim_state
= NULL
;
3443 lockdep_clear_current_reclaim_state();
3449 * A zone is low on free memory, so wake its kswapd task to service it.
3451 void wakeup_kswapd(struct zone
*zone
, int order
, enum zone_type classzone_idx
)
3455 if (!populated_zone(zone
))
3458 if (!cpuset_zone_allowed(zone
, GFP_KERNEL
| __GFP_HARDWALL
))
3460 pgdat
= zone
->zone_pgdat
;
3461 if (pgdat
->kswapd_max_order
< order
) {
3462 pgdat
->kswapd_max_order
= order
;
3463 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
, classzone_idx
);
3465 if (!waitqueue_active(&pgdat
->kswapd_wait
))
3467 if (zone_balanced(zone
, order
, 0, 0))
3470 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, zone_idx(zone
), order
);
3471 wake_up_interruptible(&pgdat
->kswapd_wait
);
3474 #ifdef CONFIG_HIBERNATION
3476 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3479 * Rather than trying to age LRUs the aim is to preserve the overall
3480 * LRU order by reclaiming preferentially
3481 * inactive > active > active referenced > active mapped
3483 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
3485 struct reclaim_state reclaim_state
;
3486 struct scan_control sc
= {
3487 .nr_to_reclaim
= nr_to_reclaim
,
3488 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
3489 .priority
= DEF_PRIORITY
,
3493 .hibernation_mode
= 1,
3495 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
3496 struct task_struct
*p
= current
;
3497 unsigned long nr_reclaimed
;
3499 p
->flags
|= PF_MEMALLOC
;
3500 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
3501 reclaim_state
.reclaimed_slab
= 0;
3502 p
->reclaim_state
= &reclaim_state
;
3504 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3506 p
->reclaim_state
= NULL
;
3507 lockdep_clear_current_reclaim_state();
3508 p
->flags
&= ~PF_MEMALLOC
;
3510 return nr_reclaimed
;
3512 #endif /* CONFIG_HIBERNATION */
3514 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3515 not required for correctness. So if the last cpu in a node goes
3516 away, we get changed to run anywhere: as the first one comes back,
3517 restore their cpu bindings. */
3518 static int cpu_callback(struct notifier_block
*nfb
, unsigned long action
,
3523 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
3524 for_each_node_state(nid
, N_MEMORY
) {
3525 pg_data_t
*pgdat
= NODE_DATA(nid
);
3526 const struct cpumask
*mask
;
3528 mask
= cpumask_of_node(pgdat
->node_id
);
3530 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
3531 /* One of our CPUs online: restore mask */
3532 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
3539 * This kswapd start function will be called by init and node-hot-add.
3540 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3542 int kswapd_run(int nid
)
3544 pg_data_t
*pgdat
= NODE_DATA(nid
);
3550 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
3551 if (IS_ERR(pgdat
->kswapd
)) {
3552 /* failure at boot is fatal */
3553 BUG_ON(system_state
== SYSTEM_BOOTING
);
3554 pr_err("Failed to start kswapd on node %d\n", nid
);
3555 ret
= PTR_ERR(pgdat
->kswapd
);
3556 pgdat
->kswapd
= NULL
;
3562 * Called by memory hotplug when all memory in a node is offlined. Caller must
3563 * hold mem_hotplug_begin/end().
3565 void kswapd_stop(int nid
)
3567 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
3570 kthread_stop(kswapd
);
3571 NODE_DATA(nid
)->kswapd
= NULL
;
3575 static int __init
kswapd_init(void)
3580 for_each_node_state(nid
, N_MEMORY
)
3582 hotcpu_notifier(cpu_callback
, 0);
3586 module_init(kswapd_init
)
3592 * If non-zero call zone_reclaim when the number of free pages falls below
3595 int zone_reclaim_mode __read_mostly
;
3597 #define RECLAIM_OFF 0
3598 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3599 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3600 #define RECLAIM_UNMAP (1<<2) /* Unmap pages during reclaim */
3603 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3604 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3607 #define ZONE_RECLAIM_PRIORITY 4
3610 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3613 int sysctl_min_unmapped_ratio
= 1;
3616 * If the number of slab pages in a zone grows beyond this percentage then
3617 * slab reclaim needs to occur.
3619 int sysctl_min_slab_ratio
= 5;
3621 static inline unsigned long zone_unmapped_file_pages(struct zone
*zone
)
3623 unsigned long file_mapped
= zone_page_state(zone
, NR_FILE_MAPPED
);
3624 unsigned long file_lru
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
3625 zone_page_state(zone
, NR_ACTIVE_FILE
);
3628 * It's possible for there to be more file mapped pages than
3629 * accounted for by the pages on the file LRU lists because
3630 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3632 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
3635 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3636 static long zone_pagecache_reclaimable(struct zone
*zone
)
3638 long nr_pagecache_reclaimable
;
3642 * If RECLAIM_UNMAP is set, then all file pages are considered
3643 * potentially reclaimable. Otherwise, we have to worry about
3644 * pages like swapcache and zone_unmapped_file_pages() provides
3647 if (zone_reclaim_mode
& RECLAIM_UNMAP
)
3648 nr_pagecache_reclaimable
= zone_page_state(zone
, NR_FILE_PAGES
);
3650 nr_pagecache_reclaimable
= zone_unmapped_file_pages(zone
);
3652 /* If we can't clean pages, remove dirty pages from consideration */
3653 if (!(zone_reclaim_mode
& RECLAIM_WRITE
))
3654 delta
+= zone_page_state(zone
, NR_FILE_DIRTY
);
3656 /* Watch for any possible underflows due to delta */
3657 if (unlikely(delta
> nr_pagecache_reclaimable
))
3658 delta
= nr_pagecache_reclaimable
;
3660 return nr_pagecache_reclaimable
- delta
;
3664 * Try to free up some pages from this zone through reclaim.
3666 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3668 /* Minimum pages needed in order to stay on node */
3669 const unsigned long nr_pages
= 1 << order
;
3670 struct task_struct
*p
= current
;
3671 struct reclaim_state reclaim_state
;
3672 struct scan_control sc
= {
3673 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
3674 .gfp_mask
= (gfp_mask
= memalloc_noio_flags(gfp_mask
)),
3676 .priority
= ZONE_RECLAIM_PRIORITY
,
3677 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
3678 .may_unmap
= !!(zone_reclaim_mode
& RECLAIM_UNMAP
),
3684 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
3685 * and we also need to be able to write out pages for RECLAIM_WRITE
3686 * and RECLAIM_UNMAP.
3688 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
3689 lockdep_set_current_reclaim_state(gfp_mask
);
3690 reclaim_state
.reclaimed_slab
= 0;
3691 p
->reclaim_state
= &reclaim_state
;
3693 if (zone_pagecache_reclaimable(zone
) > zone
->min_unmapped_pages
) {
3695 * Free memory by calling shrink zone with increasing
3696 * priorities until we have enough memory freed.
3699 shrink_zone(zone
, &sc
, true);
3700 } while (sc
.nr_reclaimed
< nr_pages
&& --sc
.priority
>= 0);
3703 p
->reclaim_state
= NULL
;
3704 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
3705 lockdep_clear_current_reclaim_state();
3706 return sc
.nr_reclaimed
>= nr_pages
;
3709 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3715 * Zone reclaim reclaims unmapped file backed pages and
3716 * slab pages if we are over the defined limits.
3718 * A small portion of unmapped file backed pages is needed for
3719 * file I/O otherwise pages read by file I/O will be immediately
3720 * thrown out if the zone is overallocated. So we do not reclaim
3721 * if less than a specified percentage of the zone is used by
3722 * unmapped file backed pages.
3724 if (zone_pagecache_reclaimable(zone
) <= zone
->min_unmapped_pages
&&
3725 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) <= zone
->min_slab_pages
)
3726 return ZONE_RECLAIM_FULL
;
3728 if (!zone_reclaimable(zone
))
3729 return ZONE_RECLAIM_FULL
;
3732 * Do not scan if the allocation should not be delayed.
3734 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
3735 return ZONE_RECLAIM_NOSCAN
;
3738 * Only run zone reclaim on the local zone or on zones that do not
3739 * have associated processors. This will favor the local processor
3740 * over remote processors and spread off node memory allocations
3741 * as wide as possible.
3743 node_id
= zone_to_nid(zone
);
3744 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
3745 return ZONE_RECLAIM_NOSCAN
;
3747 if (test_and_set_bit(ZONE_RECLAIM_LOCKED
, &zone
->flags
))
3748 return ZONE_RECLAIM_NOSCAN
;
3750 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
3751 clear_bit(ZONE_RECLAIM_LOCKED
, &zone
->flags
);
3754 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
3761 * page_evictable - test whether a page is evictable
3762 * @page: the page to test
3764 * Test whether page is evictable--i.e., should be placed on active/inactive
3765 * lists vs unevictable list.
3767 * Reasons page might not be evictable:
3768 * (1) page's mapping marked unevictable
3769 * (2) page is part of an mlocked VMA
3772 int page_evictable(struct page
*page
)
3774 return !mapping_unevictable(page_mapping(page
)) && !PageMlocked(page
);
3779 * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
3780 * @pages: array of pages to check
3781 * @nr_pages: number of pages to check
3783 * Checks pages for evictability and moves them to the appropriate lru list.
3785 * This function is only used for SysV IPC SHM_UNLOCK.
3787 void check_move_unevictable_pages(struct page
**pages
, int nr_pages
)
3789 struct lruvec
*lruvec
;
3790 struct zone
*zone
= NULL
;
3795 for (i
= 0; i
< nr_pages
; i
++) {
3796 struct page
*page
= pages
[i
];
3797 struct zone
*pagezone
;
3800 pagezone
= page_zone(page
);
3801 if (pagezone
!= zone
) {
3803 spin_unlock_irq(&zone
->lru_lock
);
3805 spin_lock_irq(&zone
->lru_lock
);
3807 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
3809 if (!PageLRU(page
) || !PageUnevictable(page
))
3812 if (page_evictable(page
)) {
3813 enum lru_list lru
= page_lru_base_type(page
);
3815 VM_BUG_ON_PAGE(PageActive(page
), page
);
3816 ClearPageUnevictable(page
);
3817 del_page_from_lru_list(page
, lruvec
, LRU_UNEVICTABLE
);
3818 add_page_to_lru_list(page
, lruvec
, lru
);
3824 __count_vm_events(UNEVICTABLE_PGRESCUED
, pgrescued
);
3825 __count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
3826 spin_unlock_irq(&zone
->lru_lock
);
3829 #endif /* CONFIG_SHMEM */