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
;
159 * sane_reclaim - is the usual dirty throttling mechanism operational?
160 * @sc: scan_control in question
162 * The normal page dirty throttling mechanism in balance_dirty_pages() is
163 * completely broken with the legacy memcg and direct stalling in
164 * shrink_page_list() is used for throttling instead, which lacks all the
165 * niceties such as fairness, adaptive pausing, bandwidth proportional
166 * allocation and configurability.
168 * This function tests whether the vmscan currently in progress can assume
169 * that the normal dirty throttling mechanism is operational.
171 static bool sane_reclaim(struct scan_control
*sc
)
173 struct mem_cgroup
*memcg
= sc
->target_mem_cgroup
;
177 #ifdef CONFIG_CGROUP_WRITEBACK
178 if (cgroup_on_dfl(mem_cgroup_css(memcg
)->cgroup
))
184 static bool global_reclaim(struct scan_control
*sc
)
189 static bool sane_reclaim(struct scan_control
*sc
)
195 static unsigned long zone_reclaimable_pages(struct zone
*zone
)
199 nr
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
200 zone_page_state(zone
, NR_INACTIVE_FILE
);
202 if (get_nr_swap_pages() > 0)
203 nr
+= zone_page_state(zone
, NR_ACTIVE_ANON
) +
204 zone_page_state(zone
, NR_INACTIVE_ANON
);
209 bool zone_reclaimable(struct zone
*zone
)
211 return zone_page_state(zone
, NR_PAGES_SCANNED
) <
212 zone_reclaimable_pages(zone
) * 6;
215 static unsigned long get_lru_size(struct lruvec
*lruvec
, enum lru_list lru
)
217 if (!mem_cgroup_disabled())
218 return mem_cgroup_get_lru_size(lruvec
, lru
);
220 return zone_page_state(lruvec_zone(lruvec
), NR_LRU_BASE
+ lru
);
224 * Add a shrinker callback to be called from the vm.
226 int register_shrinker(struct shrinker
*shrinker
)
228 size_t size
= sizeof(*shrinker
->nr_deferred
);
231 * If we only have one possible node in the system anyway, save
232 * ourselves the trouble and disable NUMA aware behavior. This way we
233 * will save memory and some small loop time later.
235 if (nr_node_ids
== 1)
236 shrinker
->flags
&= ~SHRINKER_NUMA_AWARE
;
238 if (shrinker
->flags
& SHRINKER_NUMA_AWARE
)
241 shrinker
->nr_deferred
= kzalloc(size
, GFP_KERNEL
);
242 if (!shrinker
->nr_deferred
)
245 down_write(&shrinker_rwsem
);
246 list_add_tail(&shrinker
->list
, &shrinker_list
);
247 up_write(&shrinker_rwsem
);
250 EXPORT_SYMBOL(register_shrinker
);
255 void unregister_shrinker(struct shrinker
*shrinker
)
257 down_write(&shrinker_rwsem
);
258 list_del(&shrinker
->list
);
259 up_write(&shrinker_rwsem
);
260 kfree(shrinker
->nr_deferred
);
262 EXPORT_SYMBOL(unregister_shrinker
);
264 #define SHRINK_BATCH 128
266 static unsigned long do_shrink_slab(struct shrink_control
*shrinkctl
,
267 struct shrinker
*shrinker
,
268 unsigned long nr_scanned
,
269 unsigned long nr_eligible
)
271 unsigned long freed
= 0;
272 unsigned long long delta
;
277 int nid
= shrinkctl
->nid
;
278 long batch_size
= shrinker
->batch
? shrinker
->batch
281 freeable
= shrinker
->count_objects(shrinker
, shrinkctl
);
286 * copy the current shrinker scan count into a local variable
287 * and zero it so that other concurrent shrinker invocations
288 * don't also do this scanning work.
290 nr
= atomic_long_xchg(&shrinker
->nr_deferred
[nid
], 0);
293 delta
= (4 * nr_scanned
) / shrinker
->seeks
;
295 do_div(delta
, nr_eligible
+ 1);
297 if (total_scan
< 0) {
298 pr_err("shrink_slab: %pF negative objects to delete nr=%ld\n",
299 shrinker
->scan_objects
, total_scan
);
300 total_scan
= freeable
;
304 * We need to avoid excessive windup on filesystem shrinkers
305 * due to large numbers of GFP_NOFS allocations causing the
306 * shrinkers to return -1 all the time. This results in a large
307 * nr being built up so when a shrink that can do some work
308 * comes along it empties the entire cache due to nr >>>
309 * freeable. This is bad for sustaining a working set in
312 * Hence only allow the shrinker to scan the entire cache when
313 * a large delta change is calculated directly.
315 if (delta
< freeable
/ 4)
316 total_scan
= min(total_scan
, freeable
/ 2);
319 * Avoid risking looping forever due to too large nr value:
320 * never try to free more than twice the estimate number of
323 if (total_scan
> freeable
* 2)
324 total_scan
= freeable
* 2;
326 trace_mm_shrink_slab_start(shrinker
, shrinkctl
, nr
,
327 nr_scanned
, nr_eligible
,
328 freeable
, delta
, total_scan
);
331 * Normally, we should not scan less than batch_size objects in one
332 * pass to avoid too frequent shrinker calls, but if the slab has less
333 * than batch_size objects in total and we are really tight on memory,
334 * we will try to reclaim all available objects, otherwise we can end
335 * up failing allocations although there are plenty of reclaimable
336 * objects spread over several slabs with usage less than the
339 * We detect the "tight on memory" situations by looking at the total
340 * number of objects we want to scan (total_scan). If it is greater
341 * than the total number of objects on slab (freeable), we must be
342 * scanning at high prio and therefore should try to reclaim as much as
345 while (total_scan
>= batch_size
||
346 total_scan
>= freeable
) {
348 unsigned long nr_to_scan
= min(batch_size
, total_scan
);
350 shrinkctl
->nr_to_scan
= nr_to_scan
;
351 ret
= shrinker
->scan_objects(shrinker
, shrinkctl
);
352 if (ret
== SHRINK_STOP
)
356 count_vm_events(SLABS_SCANNED
, nr_to_scan
);
357 total_scan
-= nr_to_scan
;
363 * move the unused scan count back into the shrinker in a
364 * manner that handles concurrent updates. If we exhausted the
365 * scan, there is no need to do an update.
368 new_nr
= atomic_long_add_return(total_scan
,
369 &shrinker
->nr_deferred
[nid
]);
371 new_nr
= atomic_long_read(&shrinker
->nr_deferred
[nid
]);
373 trace_mm_shrink_slab_end(shrinker
, nid
, freed
, nr
, new_nr
, total_scan
);
378 * shrink_slab - shrink slab caches
379 * @gfp_mask: allocation context
380 * @nid: node whose slab caches to target
381 * @memcg: memory cgroup whose slab caches to target
382 * @nr_scanned: pressure numerator
383 * @nr_eligible: pressure denominator
385 * Call the shrink functions to age shrinkable caches.
387 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
388 * unaware shrinkers will receive a node id of 0 instead.
390 * @memcg specifies the memory cgroup to target. If it is not NULL,
391 * only shrinkers with SHRINKER_MEMCG_AWARE set will be called to scan
392 * objects from the memory cgroup specified. Otherwise all shrinkers
393 * are called, and memcg aware shrinkers are supposed to scan the
396 * @nr_scanned and @nr_eligible form a ratio that indicate how much of
397 * the available objects should be scanned. Page reclaim for example
398 * passes the number of pages scanned and the number of pages on the
399 * LRU lists that it considered on @nid, plus a bias in @nr_scanned
400 * when it encountered mapped pages. The ratio is further biased by
401 * the ->seeks setting of the shrink function, which indicates the
402 * cost to recreate an object relative to that of an LRU page.
404 * Returns the number of reclaimed slab objects.
406 static unsigned long shrink_slab(gfp_t gfp_mask
, int nid
,
407 struct mem_cgroup
*memcg
,
408 unsigned long nr_scanned
,
409 unsigned long nr_eligible
)
411 struct shrinker
*shrinker
;
412 unsigned long freed
= 0;
414 if (memcg
&& !memcg_kmem_is_active(memcg
))
418 nr_scanned
= SWAP_CLUSTER_MAX
;
420 if (!down_read_trylock(&shrinker_rwsem
)) {
422 * If we would return 0, our callers would understand that we
423 * have nothing else to shrink and give up trying. By returning
424 * 1 we keep it going and assume we'll be able to shrink next
431 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
432 struct shrink_control sc
= {
433 .gfp_mask
= gfp_mask
,
438 if (memcg
&& !(shrinker
->flags
& SHRINKER_MEMCG_AWARE
))
441 if (!(shrinker
->flags
& SHRINKER_NUMA_AWARE
))
444 freed
+= do_shrink_slab(&sc
, shrinker
, nr_scanned
, nr_eligible
);
447 up_read(&shrinker_rwsem
);
453 void drop_slab_node(int nid
)
458 struct mem_cgroup
*memcg
= NULL
;
462 freed
+= shrink_slab(GFP_KERNEL
, nid
, memcg
,
464 } while ((memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
)) != NULL
);
465 } while (freed
> 10);
472 for_each_online_node(nid
)
476 static inline int is_page_cache_freeable(struct page
*page
)
479 * A freeable page cache page is referenced only by the caller
480 * that isolated the page, the page cache radix tree and
481 * optional buffer heads at page->private.
483 return page_count(page
) - page_has_private(page
) == 2;
486 static int may_write_to_inode(struct inode
*inode
, struct scan_control
*sc
)
488 if (current
->flags
& PF_SWAPWRITE
)
490 if (!inode_write_congested(inode
))
492 if (inode_to_bdi(inode
) == current
->backing_dev_info
)
498 * We detected a synchronous write error writing a page out. Probably
499 * -ENOSPC. We need to propagate that into the address_space for a subsequent
500 * fsync(), msync() or close().
502 * The tricky part is that after writepage we cannot touch the mapping: nothing
503 * prevents it from being freed up. But we have a ref on the page and once
504 * that page is locked, the mapping is pinned.
506 * We're allowed to run sleeping lock_page() here because we know the caller has
509 static void handle_write_error(struct address_space
*mapping
,
510 struct page
*page
, int error
)
513 if (page_mapping(page
) == mapping
)
514 mapping_set_error(mapping
, error
);
518 /* possible outcome of pageout() */
520 /* failed to write page out, page is locked */
522 /* move page to the active list, page is locked */
524 /* page has been sent to the disk successfully, page is unlocked */
526 /* page is clean and locked */
531 * pageout is called by shrink_page_list() for each dirty page.
532 * Calls ->writepage().
534 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
535 struct scan_control
*sc
)
538 * If the page is dirty, only perform writeback if that write
539 * will be non-blocking. To prevent this allocation from being
540 * stalled by pagecache activity. But note that there may be
541 * stalls if we need to run get_block(). We could test
542 * PagePrivate for that.
544 * If this process is currently in __generic_file_write_iter() against
545 * this page's queue, we can perform writeback even if that
548 * If the page is swapcache, write it back even if that would
549 * block, for some throttling. This happens by accident, because
550 * swap_backing_dev_info is bust: it doesn't reflect the
551 * congestion state of the swapdevs. Easy to fix, if needed.
553 if (!is_page_cache_freeable(page
))
557 * Some data journaling orphaned pages can have
558 * page->mapping == NULL while being dirty with clean buffers.
560 if (page_has_private(page
)) {
561 if (try_to_free_buffers(page
)) {
562 ClearPageDirty(page
);
563 pr_info("%s: orphaned page\n", __func__
);
569 if (mapping
->a_ops
->writepage
== NULL
)
570 return PAGE_ACTIVATE
;
571 if (!may_write_to_inode(mapping
->host
, sc
))
574 if (clear_page_dirty_for_io(page
)) {
576 struct writeback_control wbc
= {
577 .sync_mode
= WB_SYNC_NONE
,
578 .nr_to_write
= SWAP_CLUSTER_MAX
,
580 .range_end
= LLONG_MAX
,
584 SetPageReclaim(page
);
585 res
= mapping
->a_ops
->writepage(page
, &wbc
);
587 handle_write_error(mapping
, page
, res
);
588 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
589 ClearPageReclaim(page
);
590 return PAGE_ACTIVATE
;
593 if (!PageWriteback(page
)) {
594 /* synchronous write or broken a_ops? */
595 ClearPageReclaim(page
);
597 trace_mm_vmscan_writepage(page
, trace_reclaim_flags(page
));
598 inc_zone_page_state(page
, NR_VMSCAN_WRITE
);
606 * Same as remove_mapping, but if the page is removed from the mapping, it
607 * gets returned with a refcount of 0.
609 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
,
613 struct mem_cgroup
*memcg
;
615 BUG_ON(!PageLocked(page
));
616 BUG_ON(mapping
!= page_mapping(page
));
618 memcg
= mem_cgroup_begin_page_stat(page
);
619 spin_lock_irqsave(&mapping
->tree_lock
, flags
);
621 * The non racy check for a busy page.
623 * Must be careful with the order of the tests. When someone has
624 * a ref to the page, it may be possible that they dirty it then
625 * drop the reference. So if PageDirty is tested before page_count
626 * here, then the following race may occur:
628 * get_user_pages(&page);
629 * [user mapping goes away]
631 * !PageDirty(page) [good]
632 * SetPageDirty(page);
634 * !page_count(page) [good, discard it]
636 * [oops, our write_to data is lost]
638 * Reversing the order of the tests ensures such a situation cannot
639 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
640 * load is not satisfied before that of page->_count.
642 * Note that if SetPageDirty is always performed via set_page_dirty,
643 * and thus under tree_lock, then this ordering is not required.
645 if (!page_freeze_refs(page
, 2))
647 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
648 if (unlikely(PageDirty(page
))) {
649 page_unfreeze_refs(page
, 2);
653 if (PageSwapCache(page
)) {
654 swp_entry_t swap
= { .val
= page_private(page
) };
655 mem_cgroup_swapout(page
, swap
);
656 __delete_from_swap_cache(page
);
657 spin_unlock_irqrestore(&mapping
->tree_lock
, flags
);
658 mem_cgroup_end_page_stat(memcg
);
659 swapcache_free(swap
);
661 void (*freepage
)(struct page
*);
664 freepage
= mapping
->a_ops
->freepage
;
666 * Remember a shadow entry for reclaimed file cache in
667 * order to detect refaults, thus thrashing, later on.
669 * But don't store shadows in an address space that is
670 * already exiting. This is not just an optizimation,
671 * inode reclaim needs to empty out the radix tree or
672 * the nodes are lost. Don't plant shadows behind its
675 if (reclaimed
&& page_is_file_cache(page
) &&
676 !mapping_exiting(mapping
))
677 shadow
= workingset_eviction(mapping
, page
);
678 __delete_from_page_cache(page
, shadow
, memcg
);
679 spin_unlock_irqrestore(&mapping
->tree_lock
, flags
);
680 mem_cgroup_end_page_stat(memcg
);
682 if (freepage
!= NULL
)
689 spin_unlock_irqrestore(&mapping
->tree_lock
, flags
);
690 mem_cgroup_end_page_stat(memcg
);
695 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
696 * someone else has a ref on the page, abort and return 0. If it was
697 * successfully detached, return 1. Assumes the caller has a single ref on
700 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
702 if (__remove_mapping(mapping
, page
, false)) {
704 * Unfreezing the refcount with 1 rather than 2 effectively
705 * drops the pagecache ref for us without requiring another
708 page_unfreeze_refs(page
, 1);
715 * putback_lru_page - put previously isolated page onto appropriate LRU list
716 * @page: page to be put back to appropriate lru list
718 * Add previously isolated @page to appropriate LRU list.
719 * Page may still be unevictable for other reasons.
721 * lru_lock must not be held, interrupts must be enabled.
723 void putback_lru_page(struct page
*page
)
726 int was_unevictable
= PageUnevictable(page
);
728 VM_BUG_ON_PAGE(PageLRU(page
), page
);
731 ClearPageUnevictable(page
);
733 if (page_evictable(page
)) {
735 * For evictable pages, we can use the cache.
736 * In event of a race, worst case is we end up with an
737 * unevictable page on [in]active list.
738 * We know how to handle that.
740 is_unevictable
= false;
744 * Put unevictable pages directly on zone's unevictable
747 is_unevictable
= true;
748 add_page_to_unevictable_list(page
);
750 * When racing with an mlock or AS_UNEVICTABLE clearing
751 * (page is unlocked) make sure that if the other thread
752 * does not observe our setting of PG_lru and fails
753 * isolation/check_move_unevictable_pages,
754 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
755 * the page back to the evictable list.
757 * The other side is TestClearPageMlocked() or shmem_lock().
763 * page's status can change while we move it among lru. If an evictable
764 * page is on unevictable list, it never be freed. To avoid that,
765 * check after we added it to the list, again.
767 if (is_unevictable
&& page_evictable(page
)) {
768 if (!isolate_lru_page(page
)) {
772 /* This means someone else dropped this page from LRU
773 * So, it will be freed or putback to LRU again. There is
774 * nothing to do here.
778 if (was_unevictable
&& !is_unevictable
)
779 count_vm_event(UNEVICTABLE_PGRESCUED
);
780 else if (!was_unevictable
&& is_unevictable
)
781 count_vm_event(UNEVICTABLE_PGCULLED
);
783 put_page(page
); /* drop ref from isolate */
786 enum page_references
{
788 PAGEREF_RECLAIM_CLEAN
,
793 static enum page_references
page_check_references(struct page
*page
,
794 struct scan_control
*sc
)
796 int referenced_ptes
, referenced_page
;
797 unsigned long vm_flags
;
799 referenced_ptes
= page_referenced(page
, 1, sc
->target_mem_cgroup
,
801 referenced_page
= TestClearPageReferenced(page
);
804 * Mlock lost the isolation race with us. Let try_to_unmap()
805 * move the page to the unevictable list.
807 if (vm_flags
& VM_LOCKED
)
808 return PAGEREF_RECLAIM
;
810 if (referenced_ptes
) {
811 if (PageSwapBacked(page
))
812 return PAGEREF_ACTIVATE
;
814 * All mapped pages start out with page table
815 * references from the instantiating fault, so we need
816 * to look twice if a mapped file page is used more
819 * Mark it and spare it for another trip around the
820 * inactive list. Another page table reference will
821 * lead to its activation.
823 * Note: the mark is set for activated pages as well
824 * so that recently deactivated but used pages are
827 SetPageReferenced(page
);
829 if (referenced_page
|| referenced_ptes
> 1)
830 return PAGEREF_ACTIVATE
;
833 * Activate file-backed executable pages after first usage.
835 if (vm_flags
& VM_EXEC
)
836 return PAGEREF_ACTIVATE
;
841 /* Reclaim if clean, defer dirty pages to writeback */
842 if (referenced_page
&& !PageSwapBacked(page
))
843 return PAGEREF_RECLAIM_CLEAN
;
845 return PAGEREF_RECLAIM
;
848 /* Check if a page is dirty or under writeback */
849 static void page_check_dirty_writeback(struct page
*page
,
850 bool *dirty
, bool *writeback
)
852 struct address_space
*mapping
;
855 * Anonymous pages are not handled by flushers and must be written
856 * from reclaim context. Do not stall reclaim based on them
858 if (!page_is_file_cache(page
)) {
864 /* By default assume that the page flags are accurate */
865 *dirty
= PageDirty(page
);
866 *writeback
= PageWriteback(page
);
868 /* Verify dirty/writeback state if the filesystem supports it */
869 if (!page_has_private(page
))
872 mapping
= page_mapping(page
);
873 if (mapping
&& mapping
->a_ops
->is_dirty_writeback
)
874 mapping
->a_ops
->is_dirty_writeback(page
, dirty
, writeback
);
878 * shrink_page_list() returns the number of reclaimed pages
880 static unsigned long shrink_page_list(struct list_head
*page_list
,
882 struct scan_control
*sc
,
883 enum ttu_flags ttu_flags
,
884 unsigned long *ret_nr_dirty
,
885 unsigned long *ret_nr_unqueued_dirty
,
886 unsigned long *ret_nr_congested
,
887 unsigned long *ret_nr_writeback
,
888 unsigned long *ret_nr_immediate
,
891 LIST_HEAD(ret_pages
);
892 LIST_HEAD(free_pages
);
894 unsigned long nr_unqueued_dirty
= 0;
895 unsigned long nr_dirty
= 0;
896 unsigned long nr_congested
= 0;
897 unsigned long nr_reclaimed
= 0;
898 unsigned long nr_writeback
= 0;
899 unsigned long nr_immediate
= 0;
903 while (!list_empty(page_list
)) {
904 struct address_space
*mapping
;
907 enum page_references references
= PAGEREF_RECLAIM_CLEAN
;
908 bool dirty
, writeback
;
912 page
= lru_to_page(page_list
);
913 list_del(&page
->lru
);
915 if (!trylock_page(page
))
918 VM_BUG_ON_PAGE(PageActive(page
), page
);
919 VM_BUG_ON_PAGE(page_zone(page
) != zone
, page
);
923 if (unlikely(!page_evictable(page
)))
926 if (!sc
->may_unmap
&& page_mapped(page
))
929 /* Double the slab pressure for mapped and swapcache pages */
930 if (page_mapped(page
) || PageSwapCache(page
))
933 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
934 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
937 * The number of dirty pages determines if a zone is marked
938 * reclaim_congested which affects wait_iff_congested. kswapd
939 * will stall and start writing pages if the tail of the LRU
940 * is all dirty unqueued pages.
942 page_check_dirty_writeback(page
, &dirty
, &writeback
);
943 if (dirty
|| writeback
)
946 if (dirty
&& !writeback
)
950 * Treat this page as congested if the underlying BDI is or if
951 * pages are cycling through the LRU so quickly that the
952 * pages marked for immediate reclaim are making it to the
953 * end of the LRU a second time.
955 mapping
= page_mapping(page
);
956 if (((dirty
|| writeback
) && mapping
&&
957 inode_write_congested(mapping
->host
)) ||
958 (writeback
&& PageReclaim(page
)))
962 * If a page at the tail of the LRU is under writeback, there
963 * are three cases to consider.
965 * 1) If reclaim is encountering an excessive number of pages
966 * under writeback and this page is both under writeback and
967 * PageReclaim then it indicates that pages are being queued
968 * for IO but are being recycled through the LRU before the
969 * IO can complete. Waiting on the page itself risks an
970 * indefinite stall if it is impossible to writeback the
971 * page due to IO error or disconnected storage so instead
972 * note that the LRU is being scanned too quickly and the
973 * caller can stall after page list has been processed.
975 * 2) Global or new memcg reclaim encounters a page that is
976 * not marked for immediate reclaim or the caller does not
977 * have __GFP_IO. In this case mark the page for immediate
978 * reclaim and continue scanning.
980 * __GFP_IO is checked because a loop driver thread might
981 * enter reclaim, and deadlock if it waits on a page for
982 * which it is needed to do the write (loop masks off
983 * __GFP_IO|__GFP_FS for this reason); but more thought
984 * would probably show more reasons.
986 * Don't require __GFP_FS, since we're not going into the
987 * FS, just waiting on its writeback completion. Worryingly,
988 * ext4 gfs2 and xfs allocate pages with
989 * grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so testing
990 * may_enter_fs here is liable to OOM on them.
992 * 3) Legacy memcg encounters a page that is not already marked
993 * PageReclaim. memcg does not have any dirty pages
994 * throttling so we could easily OOM just because too many
995 * pages are in writeback and there is nothing else to
996 * reclaim. Wait for the writeback to complete.
998 if (PageWriteback(page
)) {
1000 if (current_is_kswapd() &&
1001 PageReclaim(page
) &&
1002 test_bit(ZONE_WRITEBACK
, &zone
->flags
)) {
1007 } else if (sane_reclaim(sc
) ||
1008 !PageReclaim(page
) || !(sc
->gfp_mask
& __GFP_IO
)) {
1010 * This is slightly racy - end_page_writeback()
1011 * might have just cleared PageReclaim, then
1012 * setting PageReclaim here end up interpreted
1013 * as PageReadahead - but that does not matter
1014 * enough to care. What we do want is for this
1015 * page to have PageReclaim set next time memcg
1016 * reclaim reaches the tests above, so it will
1017 * then wait_on_page_writeback() to avoid OOM;
1018 * and it's also appropriate in global reclaim.
1020 SetPageReclaim(page
);
1027 wait_on_page_writeback(page
);
1032 references
= page_check_references(page
, sc
);
1034 switch (references
) {
1035 case PAGEREF_ACTIVATE
:
1036 goto activate_locked
;
1039 case PAGEREF_RECLAIM
:
1040 case PAGEREF_RECLAIM_CLEAN
:
1041 ; /* try to reclaim the page below */
1045 * Anonymous process memory has backing store?
1046 * Try to allocate it some swap space here.
1048 if (PageAnon(page
) && !PageSwapCache(page
)) {
1049 if (!(sc
->gfp_mask
& __GFP_IO
))
1051 if (!add_to_swap(page
, page_list
))
1052 goto activate_locked
;
1055 /* Adding to swap updated mapping */
1056 mapping
= page_mapping(page
);
1060 * The page is mapped into the page tables of one or more
1061 * processes. Try to unmap it here.
1063 if (page_mapped(page
) && mapping
) {
1064 switch (try_to_unmap(page
, ttu_flags
)) {
1066 goto activate_locked
;
1072 ; /* try to free the page below */
1076 if (PageDirty(page
)) {
1078 * Only kswapd can writeback filesystem pages to
1079 * avoid risk of stack overflow but only writeback
1080 * if many dirty pages have been encountered.
1082 if (page_is_file_cache(page
) &&
1083 (!current_is_kswapd() ||
1084 !test_bit(ZONE_DIRTY
, &zone
->flags
))) {
1086 * Immediately reclaim when written back.
1087 * Similar in principal to deactivate_page()
1088 * except we already have the page isolated
1089 * and know it's dirty
1091 inc_zone_page_state(page
, NR_VMSCAN_IMMEDIATE
);
1092 SetPageReclaim(page
);
1097 if (references
== PAGEREF_RECLAIM_CLEAN
)
1101 if (!sc
->may_writepage
)
1104 /* Page is dirty, try to write it out here */
1105 switch (pageout(page
, mapping
, sc
)) {
1109 goto activate_locked
;
1111 if (PageWriteback(page
))
1113 if (PageDirty(page
))
1117 * A synchronous write - probably a ramdisk. Go
1118 * ahead and try to reclaim the page.
1120 if (!trylock_page(page
))
1122 if (PageDirty(page
) || PageWriteback(page
))
1124 mapping
= page_mapping(page
);
1126 ; /* try to free the page below */
1131 * If the page has buffers, try to free the buffer mappings
1132 * associated with this page. If we succeed we try to free
1135 * We do this even if the page is PageDirty().
1136 * try_to_release_page() does not perform I/O, but it is
1137 * possible for a page to have PageDirty set, but it is actually
1138 * clean (all its buffers are clean). This happens if the
1139 * buffers were written out directly, with submit_bh(). ext3
1140 * will do this, as well as the blockdev mapping.
1141 * try_to_release_page() will discover that cleanness and will
1142 * drop the buffers and mark the page clean - it can be freed.
1144 * Rarely, pages can have buffers and no ->mapping. These are
1145 * the pages which were not successfully invalidated in
1146 * truncate_complete_page(). We try to drop those buffers here
1147 * and if that worked, and the page is no longer mapped into
1148 * process address space (page_count == 1) it can be freed.
1149 * Otherwise, leave the page on the LRU so it is swappable.
1151 if (page_has_private(page
)) {
1152 if (!try_to_release_page(page
, sc
->gfp_mask
))
1153 goto activate_locked
;
1154 if (!mapping
&& page_count(page
) == 1) {
1156 if (put_page_testzero(page
))
1160 * rare race with speculative reference.
1161 * the speculative reference will free
1162 * this page shortly, so we may
1163 * increment nr_reclaimed here (and
1164 * leave it off the LRU).
1172 if (!mapping
|| !__remove_mapping(mapping
, page
, true))
1176 * At this point, we have no other references and there is
1177 * no way to pick any more up (removed from LRU, removed
1178 * from pagecache). Can use non-atomic bitops now (and
1179 * we obviously don't have to worry about waking up a process
1180 * waiting on the page lock, because there are no references.
1182 __clear_page_locked(page
);
1187 * Is there need to periodically free_page_list? It would
1188 * appear not as the counts should be low
1190 list_add(&page
->lru
, &free_pages
);
1194 if (PageSwapCache(page
))
1195 try_to_free_swap(page
);
1197 putback_lru_page(page
);
1201 /* Not a candidate for swapping, so reclaim swap space. */
1202 if (PageSwapCache(page
) && vm_swap_full())
1203 try_to_free_swap(page
);
1204 VM_BUG_ON_PAGE(PageActive(page
), page
);
1205 SetPageActive(page
);
1210 list_add(&page
->lru
, &ret_pages
);
1211 VM_BUG_ON_PAGE(PageLRU(page
) || PageUnevictable(page
), page
);
1214 mem_cgroup_uncharge_list(&free_pages
);
1215 free_hot_cold_page_list(&free_pages
, true);
1217 list_splice(&ret_pages
, page_list
);
1218 count_vm_events(PGACTIVATE
, pgactivate
);
1220 *ret_nr_dirty
+= nr_dirty
;
1221 *ret_nr_congested
+= nr_congested
;
1222 *ret_nr_unqueued_dirty
+= nr_unqueued_dirty
;
1223 *ret_nr_writeback
+= nr_writeback
;
1224 *ret_nr_immediate
+= nr_immediate
;
1225 return nr_reclaimed
;
1228 unsigned long reclaim_clean_pages_from_list(struct zone
*zone
,
1229 struct list_head
*page_list
)
1231 struct scan_control sc
= {
1232 .gfp_mask
= GFP_KERNEL
,
1233 .priority
= DEF_PRIORITY
,
1236 unsigned long ret
, dummy1
, dummy2
, dummy3
, dummy4
, dummy5
;
1237 struct page
*page
, *next
;
1238 LIST_HEAD(clean_pages
);
1240 list_for_each_entry_safe(page
, next
, page_list
, lru
) {
1241 if (page_is_file_cache(page
) && !PageDirty(page
) &&
1242 !isolated_balloon_page(page
)) {
1243 ClearPageActive(page
);
1244 list_move(&page
->lru
, &clean_pages
);
1248 ret
= shrink_page_list(&clean_pages
, zone
, &sc
,
1249 TTU_UNMAP
|TTU_IGNORE_ACCESS
,
1250 &dummy1
, &dummy2
, &dummy3
, &dummy4
, &dummy5
, true);
1251 list_splice(&clean_pages
, page_list
);
1252 mod_zone_page_state(zone
, NR_ISOLATED_FILE
, -ret
);
1257 * Attempt to remove the specified page from its LRU. Only take this page
1258 * if it is of the appropriate PageActive status. Pages which are being
1259 * freed elsewhere are also ignored.
1261 * page: page to consider
1262 * mode: one of the LRU isolation modes defined above
1264 * returns 0 on success, -ve errno on failure.
1266 int __isolate_lru_page(struct page
*page
, isolate_mode_t mode
)
1270 /* Only take pages on the LRU. */
1274 /* Compaction should not handle unevictable pages but CMA can do so */
1275 if (PageUnevictable(page
) && !(mode
& ISOLATE_UNEVICTABLE
))
1281 * To minimise LRU disruption, the caller can indicate that it only
1282 * wants to isolate pages it will be able to operate on without
1283 * blocking - clean pages for the most part.
1285 * ISOLATE_CLEAN means that only clean pages should be isolated. This
1286 * is used by reclaim when it is cannot write to backing storage
1288 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1289 * that it is possible to migrate without blocking
1291 if (mode
& (ISOLATE_CLEAN
|ISOLATE_ASYNC_MIGRATE
)) {
1292 /* All the caller can do on PageWriteback is block */
1293 if (PageWriteback(page
))
1296 if (PageDirty(page
)) {
1297 struct address_space
*mapping
;
1299 /* ISOLATE_CLEAN means only clean pages */
1300 if (mode
& ISOLATE_CLEAN
)
1304 * Only pages without mappings or that have a
1305 * ->migratepage callback are possible to migrate
1308 mapping
= page_mapping(page
);
1309 if (mapping
&& !mapping
->a_ops
->migratepage
)
1314 if ((mode
& ISOLATE_UNMAPPED
) && page_mapped(page
))
1317 if (likely(get_page_unless_zero(page
))) {
1319 * Be careful not to clear PageLRU until after we're
1320 * sure the page is not being freed elsewhere -- the
1321 * page release code relies on it.
1331 * zone->lru_lock is heavily contended. Some of the functions that
1332 * shrink the lists perform better by taking out a batch of pages
1333 * and working on them outside the LRU lock.
1335 * For pagecache intensive workloads, this function is the hottest
1336 * spot in the kernel (apart from copy_*_user functions).
1338 * Appropriate locks must be held before calling this function.
1340 * @nr_to_scan: The number of pages to look through on the list.
1341 * @lruvec: The LRU vector to pull pages from.
1342 * @dst: The temp list to put pages on to.
1343 * @nr_scanned: The number of pages that were scanned.
1344 * @sc: The scan_control struct for this reclaim session
1345 * @mode: One of the LRU isolation modes
1346 * @lru: LRU list id for isolating
1348 * returns how many pages were moved onto *@dst.
1350 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1351 struct lruvec
*lruvec
, struct list_head
*dst
,
1352 unsigned long *nr_scanned
, struct scan_control
*sc
,
1353 isolate_mode_t mode
, enum lru_list lru
)
1355 struct list_head
*src
= &lruvec
->lists
[lru
];
1356 unsigned long nr_taken
= 0;
1359 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
1363 page
= lru_to_page(src
);
1364 prefetchw_prev_lru_page(page
, src
, flags
);
1366 VM_BUG_ON_PAGE(!PageLRU(page
), page
);
1368 switch (__isolate_lru_page(page
, mode
)) {
1370 nr_pages
= hpage_nr_pages(page
);
1371 mem_cgroup_update_lru_size(lruvec
, lru
, -nr_pages
);
1372 list_move(&page
->lru
, dst
);
1373 nr_taken
+= nr_pages
;
1377 /* else it is being freed elsewhere */
1378 list_move(&page
->lru
, src
);
1387 trace_mm_vmscan_lru_isolate(sc
->order
, nr_to_scan
, scan
,
1388 nr_taken
, mode
, is_file_lru(lru
));
1393 * isolate_lru_page - tries to isolate a page from its LRU list
1394 * @page: page to isolate from its LRU list
1396 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1397 * vmstat statistic corresponding to whatever LRU list the page was on.
1399 * Returns 0 if the page was removed from an LRU list.
1400 * Returns -EBUSY if the page was not on an LRU list.
1402 * The returned page will have PageLRU() cleared. If it was found on
1403 * the active list, it will have PageActive set. If it was found on
1404 * the unevictable list, it will have the PageUnevictable bit set. That flag
1405 * may need to be cleared by the caller before letting the page go.
1407 * The vmstat statistic corresponding to the list on which the page was
1408 * found will be decremented.
1411 * (1) Must be called with an elevated refcount on the page. This is a
1412 * fundamentnal difference from isolate_lru_pages (which is called
1413 * without a stable reference).
1414 * (2) the lru_lock must not be held.
1415 * (3) interrupts must be enabled.
1417 int isolate_lru_page(struct page
*page
)
1421 VM_BUG_ON_PAGE(!page_count(page
), page
);
1423 if (PageLRU(page
)) {
1424 struct zone
*zone
= page_zone(page
);
1425 struct lruvec
*lruvec
;
1427 spin_lock_irq(&zone
->lru_lock
);
1428 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1429 if (PageLRU(page
)) {
1430 int lru
= page_lru(page
);
1433 del_page_from_lru_list(page
, lruvec
, lru
);
1436 spin_unlock_irq(&zone
->lru_lock
);
1442 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1443 * then get resheduled. When there are massive number of tasks doing page
1444 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1445 * the LRU list will go small and be scanned faster than necessary, leading to
1446 * unnecessary swapping, thrashing and OOM.
1448 static int too_many_isolated(struct zone
*zone
, int file
,
1449 struct scan_control
*sc
)
1451 unsigned long inactive
, isolated
;
1453 if (current_is_kswapd())
1456 if (!sane_reclaim(sc
))
1460 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1461 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
);
1463 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1464 isolated
= zone_page_state(zone
, NR_ISOLATED_ANON
);
1468 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1469 * won't get blocked by normal direct-reclaimers, forming a circular
1472 if ((sc
->gfp_mask
& GFP_IOFS
) == GFP_IOFS
)
1475 return isolated
> inactive
;
1478 static noinline_for_stack
void
1479 putback_inactive_pages(struct lruvec
*lruvec
, struct list_head
*page_list
)
1481 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1482 struct zone
*zone
= lruvec_zone(lruvec
);
1483 LIST_HEAD(pages_to_free
);
1486 * Put back any unfreeable pages.
1488 while (!list_empty(page_list
)) {
1489 struct page
*page
= lru_to_page(page_list
);
1492 VM_BUG_ON_PAGE(PageLRU(page
), page
);
1493 list_del(&page
->lru
);
1494 if (unlikely(!page_evictable(page
))) {
1495 spin_unlock_irq(&zone
->lru_lock
);
1496 putback_lru_page(page
);
1497 spin_lock_irq(&zone
->lru_lock
);
1501 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1504 lru
= page_lru(page
);
1505 add_page_to_lru_list(page
, lruvec
, lru
);
1507 if (is_active_lru(lru
)) {
1508 int file
= is_file_lru(lru
);
1509 int numpages
= hpage_nr_pages(page
);
1510 reclaim_stat
->recent_rotated
[file
] += numpages
;
1512 if (put_page_testzero(page
)) {
1513 __ClearPageLRU(page
);
1514 __ClearPageActive(page
);
1515 del_page_from_lru_list(page
, lruvec
, lru
);
1517 if (unlikely(PageCompound(page
))) {
1518 spin_unlock_irq(&zone
->lru_lock
);
1519 mem_cgroup_uncharge(page
);
1520 (*get_compound_page_dtor(page
))(page
);
1521 spin_lock_irq(&zone
->lru_lock
);
1523 list_add(&page
->lru
, &pages_to_free
);
1528 * To save our caller's stack, now use input list for pages to free.
1530 list_splice(&pages_to_free
, page_list
);
1534 * If a kernel thread (such as nfsd for loop-back mounts) services
1535 * a backing device by writing to the page cache it sets PF_LESS_THROTTLE.
1536 * In that case we should only throttle if the backing device it is
1537 * writing to is congested. In other cases it is safe to throttle.
1539 static int current_may_throttle(void)
1541 return !(current
->flags
& PF_LESS_THROTTLE
) ||
1542 current
->backing_dev_info
== NULL
||
1543 bdi_write_congested(current
->backing_dev_info
);
1547 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1548 * of reclaimed pages
1550 static noinline_for_stack
unsigned long
1551 shrink_inactive_list(unsigned long nr_to_scan
, struct lruvec
*lruvec
,
1552 struct scan_control
*sc
, enum lru_list lru
)
1554 LIST_HEAD(page_list
);
1555 unsigned long nr_scanned
;
1556 unsigned long nr_reclaimed
= 0;
1557 unsigned long nr_taken
;
1558 unsigned long nr_dirty
= 0;
1559 unsigned long nr_congested
= 0;
1560 unsigned long nr_unqueued_dirty
= 0;
1561 unsigned long nr_writeback
= 0;
1562 unsigned long nr_immediate
= 0;
1563 isolate_mode_t isolate_mode
= 0;
1564 int file
= is_file_lru(lru
);
1565 struct zone
*zone
= lruvec_zone(lruvec
);
1566 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1568 while (unlikely(too_many_isolated(zone
, file
, sc
))) {
1569 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1571 /* We are about to die and free our memory. Return now. */
1572 if (fatal_signal_pending(current
))
1573 return SWAP_CLUSTER_MAX
;
1579 isolate_mode
|= ISOLATE_UNMAPPED
;
1580 if (!sc
->may_writepage
)
1581 isolate_mode
|= ISOLATE_CLEAN
;
1583 spin_lock_irq(&zone
->lru_lock
);
1585 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &page_list
,
1586 &nr_scanned
, sc
, isolate_mode
, lru
);
1588 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, -nr_taken
);
1589 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1591 if (global_reclaim(sc
)) {
1592 __mod_zone_page_state(zone
, NR_PAGES_SCANNED
, nr_scanned
);
1593 if (current_is_kswapd())
1594 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
, nr_scanned
);
1596 __count_zone_vm_events(PGSCAN_DIRECT
, zone
, nr_scanned
);
1598 spin_unlock_irq(&zone
->lru_lock
);
1603 nr_reclaimed
= shrink_page_list(&page_list
, zone
, sc
, TTU_UNMAP
,
1604 &nr_dirty
, &nr_unqueued_dirty
, &nr_congested
,
1605 &nr_writeback
, &nr_immediate
,
1608 spin_lock_irq(&zone
->lru_lock
);
1610 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1612 if (global_reclaim(sc
)) {
1613 if (current_is_kswapd())
1614 __count_zone_vm_events(PGSTEAL_KSWAPD
, zone
,
1617 __count_zone_vm_events(PGSTEAL_DIRECT
, zone
,
1621 putback_inactive_pages(lruvec
, &page_list
);
1623 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1625 spin_unlock_irq(&zone
->lru_lock
);
1627 mem_cgroup_uncharge_list(&page_list
);
1628 free_hot_cold_page_list(&page_list
, true);
1631 * If reclaim is isolating dirty pages under writeback, it implies
1632 * that the long-lived page allocation rate is exceeding the page
1633 * laundering rate. Either the global limits are not being effective
1634 * at throttling processes due to the page distribution throughout
1635 * zones or there is heavy usage of a slow backing device. The
1636 * only option is to throttle from reclaim context which is not ideal
1637 * as there is no guarantee the dirtying process is throttled in the
1638 * same way balance_dirty_pages() manages.
1640 * Once a zone is flagged ZONE_WRITEBACK, kswapd will count the number
1641 * of pages under pages flagged for immediate reclaim and stall if any
1642 * are encountered in the nr_immediate check below.
1644 if (nr_writeback
&& nr_writeback
== nr_taken
)
1645 set_bit(ZONE_WRITEBACK
, &zone
->flags
);
1648 * Legacy memcg will stall in page writeback so avoid forcibly
1651 if (sane_reclaim(sc
)) {
1653 * Tag a zone as congested if all the dirty pages scanned were
1654 * backed by a congested BDI and wait_iff_congested will stall.
1656 if (nr_dirty
&& nr_dirty
== nr_congested
)
1657 set_bit(ZONE_CONGESTED
, &zone
->flags
);
1660 * If dirty pages are scanned that are not queued for IO, it
1661 * implies that flushers are not keeping up. In this case, flag
1662 * the zone ZONE_DIRTY and kswapd will start writing pages from
1665 if (nr_unqueued_dirty
== nr_taken
)
1666 set_bit(ZONE_DIRTY
, &zone
->flags
);
1669 * If kswapd scans pages marked marked for immediate
1670 * reclaim and under writeback (nr_immediate), it implies
1671 * that pages are cycling through the LRU faster than
1672 * they are written so also forcibly stall.
1674 if (nr_immediate
&& current_may_throttle())
1675 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1679 * Stall direct reclaim for IO completions if underlying BDIs or zone
1680 * is congested. Allow kswapd to continue until it starts encountering
1681 * unqueued dirty pages or cycling through the LRU too quickly.
1683 if (!sc
->hibernation_mode
&& !current_is_kswapd() &&
1684 current_may_throttle())
1685 wait_iff_congested(zone
, BLK_RW_ASYNC
, HZ
/10);
1687 trace_mm_vmscan_lru_shrink_inactive(zone
->zone_pgdat
->node_id
,
1689 nr_scanned
, nr_reclaimed
,
1691 trace_shrink_flags(file
));
1692 return nr_reclaimed
;
1696 * This moves pages from the active list to the inactive list.
1698 * We move them the other way if the page is referenced by one or more
1699 * processes, from rmap.
1701 * If the pages are mostly unmapped, the processing is fast and it is
1702 * appropriate to hold zone->lru_lock across the whole operation. But if
1703 * the pages are mapped, the processing is slow (page_referenced()) so we
1704 * should drop zone->lru_lock around each page. It's impossible to balance
1705 * this, so instead we remove the pages from the LRU while processing them.
1706 * It is safe to rely on PG_active against the non-LRU pages in here because
1707 * nobody will play with that bit on a non-LRU page.
1709 * The downside is that we have to touch page->_count against each page.
1710 * But we had to alter page->flags anyway.
1713 static void move_active_pages_to_lru(struct lruvec
*lruvec
,
1714 struct list_head
*list
,
1715 struct list_head
*pages_to_free
,
1718 struct zone
*zone
= lruvec_zone(lruvec
);
1719 unsigned long pgmoved
= 0;
1723 while (!list_empty(list
)) {
1724 page
= lru_to_page(list
);
1725 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1727 VM_BUG_ON_PAGE(PageLRU(page
), page
);
1730 nr_pages
= hpage_nr_pages(page
);
1731 mem_cgroup_update_lru_size(lruvec
, lru
, nr_pages
);
1732 list_move(&page
->lru
, &lruvec
->lists
[lru
]);
1733 pgmoved
+= nr_pages
;
1735 if (put_page_testzero(page
)) {
1736 __ClearPageLRU(page
);
1737 __ClearPageActive(page
);
1738 del_page_from_lru_list(page
, lruvec
, lru
);
1740 if (unlikely(PageCompound(page
))) {
1741 spin_unlock_irq(&zone
->lru_lock
);
1742 mem_cgroup_uncharge(page
);
1743 (*get_compound_page_dtor(page
))(page
);
1744 spin_lock_irq(&zone
->lru_lock
);
1746 list_add(&page
->lru
, pages_to_free
);
1749 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1750 if (!is_active_lru(lru
))
1751 __count_vm_events(PGDEACTIVATE
, pgmoved
);
1754 static void shrink_active_list(unsigned long nr_to_scan
,
1755 struct lruvec
*lruvec
,
1756 struct scan_control
*sc
,
1759 unsigned long nr_taken
;
1760 unsigned long nr_scanned
;
1761 unsigned long vm_flags
;
1762 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1763 LIST_HEAD(l_active
);
1764 LIST_HEAD(l_inactive
);
1766 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1767 unsigned long nr_rotated
= 0;
1768 isolate_mode_t isolate_mode
= 0;
1769 int file
= is_file_lru(lru
);
1770 struct zone
*zone
= lruvec_zone(lruvec
);
1775 isolate_mode
|= ISOLATE_UNMAPPED
;
1776 if (!sc
->may_writepage
)
1777 isolate_mode
|= ISOLATE_CLEAN
;
1779 spin_lock_irq(&zone
->lru_lock
);
1781 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &l_hold
,
1782 &nr_scanned
, sc
, isolate_mode
, lru
);
1783 if (global_reclaim(sc
))
1784 __mod_zone_page_state(zone
, NR_PAGES_SCANNED
, nr_scanned
);
1786 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1788 __count_zone_vm_events(PGREFILL
, zone
, nr_scanned
);
1789 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, -nr_taken
);
1790 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1791 spin_unlock_irq(&zone
->lru_lock
);
1793 while (!list_empty(&l_hold
)) {
1795 page
= lru_to_page(&l_hold
);
1796 list_del(&page
->lru
);
1798 if (unlikely(!page_evictable(page
))) {
1799 putback_lru_page(page
);
1803 if (unlikely(buffer_heads_over_limit
)) {
1804 if (page_has_private(page
) && trylock_page(page
)) {
1805 if (page_has_private(page
))
1806 try_to_release_page(page
, 0);
1811 if (page_referenced(page
, 0, sc
->target_mem_cgroup
,
1813 nr_rotated
+= hpage_nr_pages(page
);
1815 * Identify referenced, file-backed active pages and
1816 * give them one more trip around the active list. So
1817 * that executable code get better chances to stay in
1818 * memory under moderate memory pressure. Anon pages
1819 * are not likely to be evicted by use-once streaming
1820 * IO, plus JVM can create lots of anon VM_EXEC pages,
1821 * so we ignore them here.
1823 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1824 list_add(&page
->lru
, &l_active
);
1829 ClearPageActive(page
); /* we are de-activating */
1830 list_add(&page
->lru
, &l_inactive
);
1834 * Move pages back to the lru list.
1836 spin_lock_irq(&zone
->lru_lock
);
1838 * Count referenced pages from currently used mappings as rotated,
1839 * even though only some of them are actually re-activated. This
1840 * helps balance scan pressure between file and anonymous pages in
1843 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1845 move_active_pages_to_lru(lruvec
, &l_active
, &l_hold
, lru
);
1846 move_active_pages_to_lru(lruvec
, &l_inactive
, &l_hold
, lru
- LRU_ACTIVE
);
1847 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1848 spin_unlock_irq(&zone
->lru_lock
);
1850 mem_cgroup_uncharge_list(&l_hold
);
1851 free_hot_cold_page_list(&l_hold
, true);
1855 static int inactive_anon_is_low_global(struct zone
*zone
)
1857 unsigned long active
, inactive
;
1859 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1860 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1862 if (inactive
* zone
->inactive_ratio
< active
)
1869 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1870 * @lruvec: LRU vector to check
1872 * Returns true if the zone does not have enough inactive anon pages,
1873 * meaning some active anon pages need to be deactivated.
1875 static int inactive_anon_is_low(struct lruvec
*lruvec
)
1878 * If we don't have swap space, anonymous page deactivation
1881 if (!total_swap_pages
)
1884 if (!mem_cgroup_disabled())
1885 return mem_cgroup_inactive_anon_is_low(lruvec
);
1887 return inactive_anon_is_low_global(lruvec_zone(lruvec
));
1890 static inline int inactive_anon_is_low(struct lruvec
*lruvec
)
1897 * inactive_file_is_low - check if file pages need to be deactivated
1898 * @lruvec: LRU vector to check
1900 * When the system is doing streaming IO, memory pressure here
1901 * ensures that active file pages get deactivated, until more
1902 * than half of the file pages are on the inactive list.
1904 * Once we get to that situation, protect the system's working
1905 * set from being evicted by disabling active file page aging.
1907 * This uses a different ratio than the anonymous pages, because
1908 * the page cache uses a use-once replacement algorithm.
1910 static int inactive_file_is_low(struct lruvec
*lruvec
)
1912 unsigned long inactive
;
1913 unsigned long active
;
1915 inactive
= get_lru_size(lruvec
, LRU_INACTIVE_FILE
);
1916 active
= get_lru_size(lruvec
, LRU_ACTIVE_FILE
);
1918 return active
> inactive
;
1921 static int inactive_list_is_low(struct lruvec
*lruvec
, enum lru_list lru
)
1923 if (is_file_lru(lru
))
1924 return inactive_file_is_low(lruvec
);
1926 return inactive_anon_is_low(lruvec
);
1929 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1930 struct lruvec
*lruvec
, struct scan_control
*sc
)
1932 if (is_active_lru(lru
)) {
1933 if (inactive_list_is_low(lruvec
, lru
))
1934 shrink_active_list(nr_to_scan
, lruvec
, sc
, lru
);
1938 return shrink_inactive_list(nr_to_scan
, lruvec
, sc
, lru
);
1949 * Determine how aggressively the anon and file LRU lists should be
1950 * scanned. The relative value of each set of LRU lists is determined
1951 * by looking at the fraction of the pages scanned we did rotate back
1952 * onto the active list instead of evict.
1954 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
1955 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
1957 static void get_scan_count(struct lruvec
*lruvec
, int swappiness
,
1958 struct scan_control
*sc
, unsigned long *nr
,
1959 unsigned long *lru_pages
)
1961 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1963 u64 denominator
= 0; /* gcc */
1964 struct zone
*zone
= lruvec_zone(lruvec
);
1965 unsigned long anon_prio
, file_prio
;
1966 enum scan_balance scan_balance
;
1967 unsigned long anon
, file
;
1968 bool force_scan
= false;
1969 unsigned long ap
, fp
;
1975 * If the zone or memcg is small, nr[l] can be 0. This
1976 * results in no scanning on this priority and a potential
1977 * priority drop. Global direct reclaim can go to the next
1978 * zone and tends to have no problems. Global kswapd is for
1979 * zone balancing and it needs to scan a minimum amount. When
1980 * reclaiming for a memcg, a priority drop can cause high
1981 * latencies, so it's better to scan a minimum amount there as
1984 if (current_is_kswapd()) {
1985 if (!zone_reclaimable(zone
))
1987 if (!mem_cgroup_lruvec_online(lruvec
))
1990 if (!global_reclaim(sc
))
1993 /* If we have no swap space, do not bother scanning anon pages. */
1994 if (!sc
->may_swap
|| (get_nr_swap_pages() <= 0)) {
1995 scan_balance
= SCAN_FILE
;
2000 * Global reclaim will swap to prevent OOM even with no
2001 * swappiness, but memcg users want to use this knob to
2002 * disable swapping for individual groups completely when
2003 * using the memory controller's swap limit feature would be
2006 if (!global_reclaim(sc
) && !swappiness
) {
2007 scan_balance
= SCAN_FILE
;
2012 * Do not apply any pressure balancing cleverness when the
2013 * system is close to OOM, scan both anon and file equally
2014 * (unless the swappiness setting disagrees with swapping).
2016 if (!sc
->priority
&& swappiness
) {
2017 scan_balance
= SCAN_EQUAL
;
2022 * Prevent the reclaimer from falling into the cache trap: as
2023 * cache pages start out inactive, every cache fault will tip
2024 * the scan balance towards the file LRU. And as the file LRU
2025 * shrinks, so does the window for rotation from references.
2026 * This means we have a runaway feedback loop where a tiny
2027 * thrashing file LRU becomes infinitely more attractive than
2028 * anon pages. Try to detect this based on file LRU size.
2030 if (global_reclaim(sc
)) {
2031 unsigned long zonefile
;
2032 unsigned long zonefree
;
2034 zonefree
= zone_page_state(zone
, NR_FREE_PAGES
);
2035 zonefile
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
2036 zone_page_state(zone
, NR_INACTIVE_FILE
);
2038 if (unlikely(zonefile
+ zonefree
<= high_wmark_pages(zone
))) {
2039 scan_balance
= SCAN_ANON
;
2045 * There is enough inactive page cache, do not reclaim
2046 * anything from the anonymous working set right now.
2048 if (!inactive_file_is_low(lruvec
)) {
2049 scan_balance
= SCAN_FILE
;
2053 scan_balance
= SCAN_FRACT
;
2056 * With swappiness at 100, anonymous and file have the same priority.
2057 * This scanning priority is essentially the inverse of IO cost.
2059 anon_prio
= swappiness
;
2060 file_prio
= 200 - anon_prio
;
2063 * OK, so we have swap space and a fair amount of page cache
2064 * pages. We use the recently rotated / recently scanned
2065 * ratios to determine how valuable each cache is.
2067 * Because workloads change over time (and to avoid overflow)
2068 * we keep these statistics as a floating average, which ends
2069 * up weighing recent references more than old ones.
2071 * anon in [0], file in [1]
2074 anon
= get_lru_size(lruvec
, LRU_ACTIVE_ANON
) +
2075 get_lru_size(lruvec
, LRU_INACTIVE_ANON
);
2076 file
= get_lru_size(lruvec
, LRU_ACTIVE_FILE
) +
2077 get_lru_size(lruvec
, LRU_INACTIVE_FILE
);
2079 spin_lock_irq(&zone
->lru_lock
);
2080 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
2081 reclaim_stat
->recent_scanned
[0] /= 2;
2082 reclaim_stat
->recent_rotated
[0] /= 2;
2085 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
2086 reclaim_stat
->recent_scanned
[1] /= 2;
2087 reclaim_stat
->recent_rotated
[1] /= 2;
2091 * The amount of pressure on anon vs file pages is inversely
2092 * proportional to the fraction of recently scanned pages on
2093 * each list that were recently referenced and in active use.
2095 ap
= anon_prio
* (reclaim_stat
->recent_scanned
[0] + 1);
2096 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
2098 fp
= file_prio
* (reclaim_stat
->recent_scanned
[1] + 1);
2099 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
2100 spin_unlock_irq(&zone
->lru_lock
);
2104 denominator
= ap
+ fp
+ 1;
2106 some_scanned
= false;
2107 /* Only use force_scan on second pass. */
2108 for (pass
= 0; !some_scanned
&& pass
< 2; pass
++) {
2110 for_each_evictable_lru(lru
) {
2111 int file
= is_file_lru(lru
);
2115 size
= get_lru_size(lruvec
, lru
);
2116 scan
= size
>> sc
->priority
;
2118 if (!scan
&& pass
&& force_scan
)
2119 scan
= min(size
, SWAP_CLUSTER_MAX
);
2121 switch (scan_balance
) {
2123 /* Scan lists relative to size */
2127 * Scan types proportional to swappiness and
2128 * their relative recent reclaim efficiency.
2130 scan
= div64_u64(scan
* fraction
[file
],
2135 /* Scan one type exclusively */
2136 if ((scan_balance
== SCAN_FILE
) != file
) {
2142 /* Look ma, no brain */
2150 * Skip the second pass and don't force_scan,
2151 * if we found something to scan.
2153 some_scanned
|= !!scan
;
2159 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
2161 static void shrink_lruvec(struct lruvec
*lruvec
, int swappiness
,
2162 struct scan_control
*sc
, unsigned long *lru_pages
)
2164 unsigned long nr
[NR_LRU_LISTS
];
2165 unsigned long targets
[NR_LRU_LISTS
];
2166 unsigned long nr_to_scan
;
2168 unsigned long nr_reclaimed
= 0;
2169 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
2170 struct blk_plug plug
;
2173 get_scan_count(lruvec
, swappiness
, sc
, nr
, lru_pages
);
2175 /* Record the original scan target for proportional adjustments later */
2176 memcpy(targets
, nr
, sizeof(nr
));
2179 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
2180 * event that can occur when there is little memory pressure e.g.
2181 * multiple streaming readers/writers. Hence, we do not abort scanning
2182 * when the requested number of pages are reclaimed when scanning at
2183 * DEF_PRIORITY on the assumption that the fact we are direct
2184 * reclaiming implies that kswapd is not keeping up and it is best to
2185 * do a batch of work at once. For memcg reclaim one check is made to
2186 * abort proportional reclaim if either the file or anon lru has already
2187 * dropped to zero at the first pass.
2189 scan_adjusted
= (global_reclaim(sc
) && !current_is_kswapd() &&
2190 sc
->priority
== DEF_PRIORITY
);
2192 blk_start_plug(&plug
);
2193 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
2194 nr
[LRU_INACTIVE_FILE
]) {
2195 unsigned long nr_anon
, nr_file
, percentage
;
2196 unsigned long nr_scanned
;
2198 for_each_evictable_lru(lru
) {
2200 nr_to_scan
= min(nr
[lru
], SWAP_CLUSTER_MAX
);
2201 nr
[lru
] -= nr_to_scan
;
2203 nr_reclaimed
+= shrink_list(lru
, nr_to_scan
,
2208 if (nr_reclaimed
< nr_to_reclaim
|| scan_adjusted
)
2212 * For kswapd and memcg, reclaim at least the number of pages
2213 * requested. Ensure that the anon and file LRUs are scanned
2214 * proportionally what was requested by get_scan_count(). We
2215 * stop reclaiming one LRU and reduce the amount scanning
2216 * proportional to the original scan target.
2218 nr_file
= nr
[LRU_INACTIVE_FILE
] + nr
[LRU_ACTIVE_FILE
];
2219 nr_anon
= nr
[LRU_INACTIVE_ANON
] + nr
[LRU_ACTIVE_ANON
];
2222 * It's just vindictive to attack the larger once the smaller
2223 * has gone to zero. And given the way we stop scanning the
2224 * smaller below, this makes sure that we only make one nudge
2225 * towards proportionality once we've got nr_to_reclaim.
2227 if (!nr_file
|| !nr_anon
)
2230 if (nr_file
> nr_anon
) {
2231 unsigned long scan_target
= targets
[LRU_INACTIVE_ANON
] +
2232 targets
[LRU_ACTIVE_ANON
] + 1;
2234 percentage
= nr_anon
* 100 / scan_target
;
2236 unsigned long scan_target
= targets
[LRU_INACTIVE_FILE
] +
2237 targets
[LRU_ACTIVE_FILE
] + 1;
2239 percentage
= nr_file
* 100 / scan_target
;
2242 /* Stop scanning the smaller of the LRU */
2244 nr
[lru
+ LRU_ACTIVE
] = 0;
2247 * Recalculate the other LRU scan count based on its original
2248 * scan target and the percentage scanning already complete
2250 lru
= (lru
== LRU_FILE
) ? LRU_BASE
: LRU_FILE
;
2251 nr_scanned
= targets
[lru
] - nr
[lru
];
2252 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2253 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2256 nr_scanned
= targets
[lru
] - nr
[lru
];
2257 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2258 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2260 scan_adjusted
= true;
2262 blk_finish_plug(&plug
);
2263 sc
->nr_reclaimed
+= nr_reclaimed
;
2266 * Even if we did not try to evict anon pages at all, we want to
2267 * rebalance the anon lru active/inactive ratio.
2269 if (inactive_anon_is_low(lruvec
))
2270 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
2271 sc
, LRU_ACTIVE_ANON
);
2273 throttle_vm_writeout(sc
->gfp_mask
);
2276 /* Use reclaim/compaction for costly allocs or under memory pressure */
2277 static bool in_reclaim_compaction(struct scan_control
*sc
)
2279 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
2280 (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
||
2281 sc
->priority
< DEF_PRIORITY
- 2))
2288 * Reclaim/compaction is used for high-order allocation requests. It reclaims
2289 * order-0 pages before compacting the zone. should_continue_reclaim() returns
2290 * true if more pages should be reclaimed such that when the page allocator
2291 * calls try_to_compact_zone() that it will have enough free pages to succeed.
2292 * It will give up earlier than that if there is difficulty reclaiming pages.
2294 static inline bool should_continue_reclaim(struct zone
*zone
,
2295 unsigned long nr_reclaimed
,
2296 unsigned long nr_scanned
,
2297 struct scan_control
*sc
)
2299 unsigned long pages_for_compaction
;
2300 unsigned long inactive_lru_pages
;
2302 /* If not in reclaim/compaction mode, stop */
2303 if (!in_reclaim_compaction(sc
))
2306 /* Consider stopping depending on scan and reclaim activity */
2307 if (sc
->gfp_mask
& __GFP_REPEAT
) {
2309 * For __GFP_REPEAT allocations, stop reclaiming if the
2310 * full LRU list has been scanned and we are still failing
2311 * to reclaim pages. This full LRU scan is potentially
2312 * expensive but a __GFP_REPEAT caller really wants to succeed
2314 if (!nr_reclaimed
&& !nr_scanned
)
2318 * For non-__GFP_REPEAT allocations which can presumably
2319 * fail without consequence, stop if we failed to reclaim
2320 * any pages from the last SWAP_CLUSTER_MAX number of
2321 * pages that were scanned. This will return to the
2322 * caller faster at the risk reclaim/compaction and
2323 * the resulting allocation attempt fails
2330 * If we have not reclaimed enough pages for compaction and the
2331 * inactive lists are large enough, continue reclaiming
2333 pages_for_compaction
= (2UL << sc
->order
);
2334 inactive_lru_pages
= zone_page_state(zone
, NR_INACTIVE_FILE
);
2335 if (get_nr_swap_pages() > 0)
2336 inactive_lru_pages
+= zone_page_state(zone
, NR_INACTIVE_ANON
);
2337 if (sc
->nr_reclaimed
< pages_for_compaction
&&
2338 inactive_lru_pages
> pages_for_compaction
)
2341 /* If compaction would go ahead or the allocation would succeed, stop */
2342 switch (compaction_suitable(zone
, sc
->order
, 0, 0)) {
2343 case COMPACT_PARTIAL
:
2344 case COMPACT_CONTINUE
:
2351 static bool shrink_zone(struct zone
*zone
, struct scan_control
*sc
,
2354 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2355 unsigned long nr_reclaimed
, nr_scanned
;
2356 bool reclaimable
= false;
2359 struct mem_cgroup
*root
= sc
->target_mem_cgroup
;
2360 struct mem_cgroup_reclaim_cookie reclaim
= {
2362 .priority
= sc
->priority
,
2364 unsigned long zone_lru_pages
= 0;
2365 struct mem_cgroup
*memcg
;
2367 nr_reclaimed
= sc
->nr_reclaimed
;
2368 nr_scanned
= sc
->nr_scanned
;
2370 memcg
= mem_cgroup_iter(root
, NULL
, &reclaim
);
2372 unsigned long lru_pages
;
2373 unsigned long scanned
;
2374 struct lruvec
*lruvec
;
2377 if (mem_cgroup_low(root
, memcg
)) {
2378 if (!sc
->may_thrash
)
2380 mem_cgroup_events(memcg
, MEMCG_LOW
, 1);
2383 lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
2384 swappiness
= mem_cgroup_swappiness(memcg
);
2385 scanned
= sc
->nr_scanned
;
2387 shrink_lruvec(lruvec
, swappiness
, sc
, &lru_pages
);
2388 zone_lru_pages
+= lru_pages
;
2390 if (memcg
&& is_classzone
)
2391 shrink_slab(sc
->gfp_mask
, zone_to_nid(zone
),
2392 memcg
, sc
->nr_scanned
- scanned
,
2396 * Direct reclaim and kswapd have to scan all memory
2397 * cgroups to fulfill the overall scan target for the
2400 * Limit reclaim, on the other hand, only cares about
2401 * nr_to_reclaim pages to be reclaimed and it will
2402 * retry with decreasing priority if one round over the
2403 * whole hierarchy is not sufficient.
2405 if (!global_reclaim(sc
) &&
2406 sc
->nr_reclaimed
>= sc
->nr_to_reclaim
) {
2407 mem_cgroup_iter_break(root
, memcg
);
2410 } while ((memcg
= mem_cgroup_iter(root
, memcg
, &reclaim
)));
2413 * Shrink the slab caches in the same proportion that
2414 * the eligible LRU pages were scanned.
2416 if (global_reclaim(sc
) && is_classzone
)
2417 shrink_slab(sc
->gfp_mask
, zone_to_nid(zone
), NULL
,
2418 sc
->nr_scanned
- nr_scanned
,
2421 if (reclaim_state
) {
2422 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2423 reclaim_state
->reclaimed_slab
= 0;
2426 vmpressure(sc
->gfp_mask
, sc
->target_mem_cgroup
,
2427 sc
->nr_scanned
- nr_scanned
,
2428 sc
->nr_reclaimed
- nr_reclaimed
);
2430 if (sc
->nr_reclaimed
- nr_reclaimed
)
2433 } while (should_continue_reclaim(zone
, sc
->nr_reclaimed
- nr_reclaimed
,
2434 sc
->nr_scanned
- nr_scanned
, sc
));
2440 * Returns true if compaction should go ahead for a high-order request, or
2441 * the high-order allocation would succeed without compaction.
2443 static inline bool compaction_ready(struct zone
*zone
, int order
)
2445 unsigned long balance_gap
, watermark
;
2449 * Compaction takes time to run and there are potentially other
2450 * callers using the pages just freed. Continue reclaiming until
2451 * there is a buffer of free pages available to give compaction
2452 * a reasonable chance of completing and allocating the page
2454 balance_gap
= min(low_wmark_pages(zone
), DIV_ROUND_UP(
2455 zone
->managed_pages
, KSWAPD_ZONE_BALANCE_GAP_RATIO
));
2456 watermark
= high_wmark_pages(zone
) + balance_gap
+ (2UL << order
);
2457 watermark_ok
= zone_watermark_ok_safe(zone
, 0, watermark
, 0, 0);
2460 * If compaction is deferred, reclaim up to a point where
2461 * compaction will have a chance of success when re-enabled
2463 if (compaction_deferred(zone
, order
))
2464 return watermark_ok
;
2467 * If compaction is not ready to start and allocation is not likely
2468 * to succeed without it, then keep reclaiming.
2470 if (compaction_suitable(zone
, order
, 0, 0) == COMPACT_SKIPPED
)
2473 return watermark_ok
;
2477 * This is the direct reclaim path, for page-allocating processes. We only
2478 * try to reclaim pages from zones which will satisfy the caller's allocation
2481 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2483 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2485 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2486 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2487 * zone defense algorithm.
2489 * If a zone is deemed to be full of pinned pages then just give it a light
2490 * scan then give up on it.
2492 * Returns true if a zone was reclaimable.
2494 static bool shrink_zones(struct zonelist
*zonelist
, struct scan_control
*sc
)
2498 unsigned long nr_soft_reclaimed
;
2499 unsigned long nr_soft_scanned
;
2501 enum zone_type requested_highidx
= gfp_zone(sc
->gfp_mask
);
2502 bool reclaimable
= false;
2505 * If the number of buffer_heads in the machine exceeds the maximum
2506 * allowed level, force direct reclaim to scan the highmem zone as
2507 * highmem pages could be pinning lowmem pages storing buffer_heads
2509 orig_mask
= sc
->gfp_mask
;
2510 if (buffer_heads_over_limit
)
2511 sc
->gfp_mask
|= __GFP_HIGHMEM
;
2513 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2514 requested_highidx
, sc
->nodemask
) {
2515 enum zone_type classzone_idx
;
2517 if (!populated_zone(zone
))
2520 classzone_idx
= requested_highidx
;
2521 while (!populated_zone(zone
->zone_pgdat
->node_zones
+
2526 * Take care memory controller reclaiming has small influence
2529 if (global_reclaim(sc
)) {
2530 if (!cpuset_zone_allowed(zone
,
2531 GFP_KERNEL
| __GFP_HARDWALL
))
2534 if (sc
->priority
!= DEF_PRIORITY
&&
2535 !zone_reclaimable(zone
))
2536 continue; /* Let kswapd poll it */
2539 * If we already have plenty of memory free for
2540 * compaction in this zone, don't free any more.
2541 * Even though compaction is invoked for any
2542 * non-zero order, only frequent costly order
2543 * reclamation is disruptive enough to become a
2544 * noticeable problem, like transparent huge
2547 if (IS_ENABLED(CONFIG_COMPACTION
) &&
2548 sc
->order
> PAGE_ALLOC_COSTLY_ORDER
&&
2549 zonelist_zone_idx(z
) <= requested_highidx
&&
2550 compaction_ready(zone
, sc
->order
)) {
2551 sc
->compaction_ready
= true;
2556 * This steals pages from memory cgroups over softlimit
2557 * and returns the number of reclaimed pages and
2558 * scanned pages. This works for global memory pressure
2559 * and balancing, not for a memcg's limit.
2561 nr_soft_scanned
= 0;
2562 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2563 sc
->order
, sc
->gfp_mask
,
2565 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
2566 sc
->nr_scanned
+= nr_soft_scanned
;
2567 if (nr_soft_reclaimed
)
2569 /* need some check for avoid more shrink_zone() */
2572 if (shrink_zone(zone
, sc
, zone_idx(zone
) == classzone_idx
))
2575 if (global_reclaim(sc
) &&
2576 !reclaimable
&& zone_reclaimable(zone
))
2581 * Restore to original mask to avoid the impact on the caller if we
2582 * promoted it to __GFP_HIGHMEM.
2584 sc
->gfp_mask
= orig_mask
;
2590 * This is the main entry point to direct page reclaim.
2592 * If a full scan of the inactive list fails to free enough memory then we
2593 * are "out of memory" and something needs to be killed.
2595 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2596 * high - the zone may be full of dirty or under-writeback pages, which this
2597 * caller can't do much about. We kick the writeback threads and take explicit
2598 * naps in the hope that some of these pages can be written. But if the
2599 * allocating task holds filesystem locks which prevent writeout this might not
2600 * work, and the allocation attempt will fail.
2602 * returns: 0, if no pages reclaimed
2603 * else, the number of pages reclaimed
2605 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2606 struct scan_control
*sc
)
2608 int initial_priority
= sc
->priority
;
2609 unsigned long total_scanned
= 0;
2610 unsigned long writeback_threshold
;
2611 bool zones_reclaimable
;
2613 delayacct_freepages_start();
2615 if (global_reclaim(sc
))
2616 count_vm_event(ALLOCSTALL
);
2619 vmpressure_prio(sc
->gfp_mask
, sc
->target_mem_cgroup
,
2622 zones_reclaimable
= shrink_zones(zonelist
, sc
);
2624 total_scanned
+= sc
->nr_scanned
;
2625 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
2628 if (sc
->compaction_ready
)
2632 * If we're getting trouble reclaiming, start doing
2633 * writepage even in laptop mode.
2635 if (sc
->priority
< DEF_PRIORITY
- 2)
2636 sc
->may_writepage
= 1;
2639 * Try to write back as many pages as we just scanned. This
2640 * tends to cause slow streaming writers to write data to the
2641 * disk smoothly, at the dirtying rate, which is nice. But
2642 * that's undesirable in laptop mode, where we *want* lumpy
2643 * writeout. So in laptop mode, write out the whole world.
2645 writeback_threshold
= sc
->nr_to_reclaim
+ sc
->nr_to_reclaim
/ 2;
2646 if (total_scanned
> writeback_threshold
) {
2647 wakeup_flusher_threads(laptop_mode
? 0 : total_scanned
,
2648 WB_REASON_TRY_TO_FREE_PAGES
);
2649 sc
->may_writepage
= 1;
2651 } while (--sc
->priority
>= 0);
2653 delayacct_freepages_end();
2655 if (sc
->nr_reclaimed
)
2656 return sc
->nr_reclaimed
;
2658 /* Aborted reclaim to try compaction? don't OOM, then */
2659 if (sc
->compaction_ready
)
2662 /* Untapped cgroup reserves? Don't OOM, retry. */
2663 if (!sc
->may_thrash
) {
2664 sc
->priority
= initial_priority
;
2669 /* Any of the zones still reclaimable? Don't OOM. */
2670 if (zones_reclaimable
)
2676 static bool pfmemalloc_watermark_ok(pg_data_t
*pgdat
)
2679 unsigned long pfmemalloc_reserve
= 0;
2680 unsigned long free_pages
= 0;
2684 for (i
= 0; i
<= ZONE_NORMAL
; i
++) {
2685 zone
= &pgdat
->node_zones
[i
];
2686 if (!populated_zone(zone
) ||
2687 zone_reclaimable_pages(zone
) == 0)
2690 pfmemalloc_reserve
+= min_wmark_pages(zone
);
2691 free_pages
+= zone_page_state(zone
, NR_FREE_PAGES
);
2694 /* If there are no reserves (unexpected config) then do not throttle */
2695 if (!pfmemalloc_reserve
)
2698 wmark_ok
= free_pages
> pfmemalloc_reserve
/ 2;
2700 /* kswapd must be awake if processes are being throttled */
2701 if (!wmark_ok
&& waitqueue_active(&pgdat
->kswapd_wait
)) {
2702 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
,
2703 (enum zone_type
)ZONE_NORMAL
);
2704 wake_up_interruptible(&pgdat
->kswapd_wait
);
2711 * Throttle direct reclaimers if backing storage is backed by the network
2712 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
2713 * depleted. kswapd will continue to make progress and wake the processes
2714 * when the low watermark is reached.
2716 * Returns true if a fatal signal was delivered during throttling. If this
2717 * happens, the page allocator should not consider triggering the OOM killer.
2719 static bool throttle_direct_reclaim(gfp_t gfp_mask
, struct zonelist
*zonelist
,
2720 nodemask_t
*nodemask
)
2724 pg_data_t
*pgdat
= NULL
;
2727 * Kernel threads should not be throttled as they may be indirectly
2728 * responsible for cleaning pages necessary for reclaim to make forward
2729 * progress. kjournald for example may enter direct reclaim while
2730 * committing a transaction where throttling it could forcing other
2731 * processes to block on log_wait_commit().
2733 if (current
->flags
& PF_KTHREAD
)
2737 * If a fatal signal is pending, this process should not throttle.
2738 * It should return quickly so it can exit and free its memory
2740 if (fatal_signal_pending(current
))
2744 * Check if the pfmemalloc reserves are ok by finding the first node
2745 * with a usable ZONE_NORMAL or lower zone. The expectation is that
2746 * GFP_KERNEL will be required for allocating network buffers when
2747 * swapping over the network so ZONE_HIGHMEM is unusable.
2749 * Throttling is based on the first usable node and throttled processes
2750 * wait on a queue until kswapd makes progress and wakes them. There
2751 * is an affinity then between processes waking up and where reclaim
2752 * progress has been made assuming the process wakes on the same node.
2753 * More importantly, processes running on remote nodes will not compete
2754 * for remote pfmemalloc reserves and processes on different nodes
2755 * should make reasonable progress.
2757 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2758 gfp_zone(gfp_mask
), nodemask
) {
2759 if (zone_idx(zone
) > ZONE_NORMAL
)
2762 /* Throttle based on the first usable node */
2763 pgdat
= zone
->zone_pgdat
;
2764 if (pfmemalloc_watermark_ok(pgdat
))
2769 /* If no zone was usable by the allocation flags then do not throttle */
2773 /* Account for the throttling */
2774 count_vm_event(PGSCAN_DIRECT_THROTTLE
);
2777 * If the caller cannot enter the filesystem, it's possible that it
2778 * is due to the caller holding an FS lock or performing a journal
2779 * transaction in the case of a filesystem like ext[3|4]. In this case,
2780 * it is not safe to block on pfmemalloc_wait as kswapd could be
2781 * blocked waiting on the same lock. Instead, throttle for up to a
2782 * second before continuing.
2784 if (!(gfp_mask
& __GFP_FS
)) {
2785 wait_event_interruptible_timeout(pgdat
->pfmemalloc_wait
,
2786 pfmemalloc_watermark_ok(pgdat
), HZ
);
2791 /* Throttle until kswapd wakes the process */
2792 wait_event_killable(zone
->zone_pgdat
->pfmemalloc_wait
,
2793 pfmemalloc_watermark_ok(pgdat
));
2796 if (fatal_signal_pending(current
))
2803 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
2804 gfp_t gfp_mask
, nodemask_t
*nodemask
)
2806 unsigned long nr_reclaimed
;
2807 struct scan_control sc
= {
2808 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2809 .gfp_mask
= (gfp_mask
= memalloc_noio_flags(gfp_mask
)),
2811 .nodemask
= nodemask
,
2812 .priority
= DEF_PRIORITY
,
2813 .may_writepage
= !laptop_mode
,
2819 * Do not enter reclaim if fatal signal was delivered while throttled.
2820 * 1 is returned so that the page allocator does not OOM kill at this
2823 if (throttle_direct_reclaim(gfp_mask
, zonelist
, nodemask
))
2826 trace_mm_vmscan_direct_reclaim_begin(order
,
2830 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2832 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
2834 return nr_reclaimed
;
2839 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup
*memcg
,
2840 gfp_t gfp_mask
, bool noswap
,
2842 unsigned long *nr_scanned
)
2844 struct scan_control sc
= {
2845 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2846 .target_mem_cgroup
= memcg
,
2847 .may_writepage
= !laptop_mode
,
2849 .may_swap
= !noswap
,
2851 struct lruvec
*lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
2852 int swappiness
= mem_cgroup_swappiness(memcg
);
2853 unsigned long lru_pages
;
2855 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2856 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2858 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc
.order
,
2863 * NOTE: Although we can get the priority field, using it
2864 * here is not a good idea, since it limits the pages we can scan.
2865 * if we don't reclaim here, the shrink_zone from balance_pgdat
2866 * will pick up pages from other mem cgroup's as well. We hack
2867 * the priority and make it zero.
2869 shrink_lruvec(lruvec
, swappiness
, &sc
, &lru_pages
);
2871 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
2873 *nr_scanned
= sc
.nr_scanned
;
2874 return sc
.nr_reclaimed
;
2877 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*memcg
,
2878 unsigned long nr_pages
,
2882 struct zonelist
*zonelist
;
2883 unsigned long nr_reclaimed
;
2885 struct scan_control sc
= {
2886 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
2887 .gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2888 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
2889 .target_mem_cgroup
= memcg
,
2890 .priority
= DEF_PRIORITY
,
2891 .may_writepage
= !laptop_mode
,
2893 .may_swap
= may_swap
,
2897 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2898 * take care of from where we get pages. So the node where we start the
2899 * scan does not need to be the current node.
2901 nid
= mem_cgroup_select_victim_node(memcg
);
2903 zonelist
= NODE_DATA(nid
)->node_zonelists
;
2905 trace_mm_vmscan_memcg_reclaim_begin(0,
2909 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2911 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
2913 return nr_reclaimed
;
2917 static void age_active_anon(struct zone
*zone
, struct scan_control
*sc
)
2919 struct mem_cgroup
*memcg
;
2921 if (!total_swap_pages
)
2924 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
2926 struct lruvec
*lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
2928 if (inactive_anon_is_low(lruvec
))
2929 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
2930 sc
, LRU_ACTIVE_ANON
);
2932 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
2936 static bool zone_balanced(struct zone
*zone
, int order
,
2937 unsigned long balance_gap
, int classzone_idx
)
2939 if (!zone_watermark_ok_safe(zone
, order
, high_wmark_pages(zone
) +
2940 balance_gap
, classzone_idx
, 0))
2943 if (IS_ENABLED(CONFIG_COMPACTION
) && order
&& compaction_suitable(zone
,
2944 order
, 0, classzone_idx
) == COMPACT_SKIPPED
)
2951 * pgdat_balanced() is used when checking if a node is balanced.
2953 * For order-0, all zones must be balanced!
2955 * For high-order allocations only zones that meet watermarks and are in a
2956 * zone allowed by the callers classzone_idx are added to balanced_pages. The
2957 * total of balanced pages must be at least 25% of the zones allowed by
2958 * classzone_idx for the node to be considered balanced. Forcing all zones to
2959 * be balanced for high orders can cause excessive reclaim when there are
2961 * The choice of 25% is due to
2962 * o a 16M DMA zone that is balanced will not balance a zone on any
2963 * reasonable sized machine
2964 * o On all other machines, the top zone must be at least a reasonable
2965 * percentage of the middle zones. For example, on 32-bit x86, highmem
2966 * would need to be at least 256M for it to be balance a whole node.
2967 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2968 * to balance a node on its own. These seemed like reasonable ratios.
2970 static bool pgdat_balanced(pg_data_t
*pgdat
, int order
, int classzone_idx
)
2972 unsigned long managed_pages
= 0;
2973 unsigned long balanced_pages
= 0;
2976 /* Check the watermark levels */
2977 for (i
= 0; i
<= classzone_idx
; i
++) {
2978 struct zone
*zone
= pgdat
->node_zones
+ i
;
2980 if (!populated_zone(zone
))
2983 managed_pages
+= zone
->managed_pages
;
2986 * A special case here:
2988 * balance_pgdat() skips over all_unreclaimable after
2989 * DEF_PRIORITY. Effectively, it considers them balanced so
2990 * they must be considered balanced here as well!
2992 if (!zone_reclaimable(zone
)) {
2993 balanced_pages
+= zone
->managed_pages
;
2997 if (zone_balanced(zone
, order
, 0, i
))
2998 balanced_pages
+= zone
->managed_pages
;
3004 return balanced_pages
>= (managed_pages
>> 2);
3010 * Prepare kswapd for sleeping. This verifies that there are no processes
3011 * waiting in throttle_direct_reclaim() and that watermarks have been met.
3013 * Returns true if kswapd is ready to sleep
3015 static bool prepare_kswapd_sleep(pg_data_t
*pgdat
, int order
, long remaining
,
3018 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
3023 * The throttled processes are normally woken up in balance_pgdat() as
3024 * soon as pfmemalloc_watermark_ok() is true. But there is a potential
3025 * race between when kswapd checks the watermarks and a process gets
3026 * throttled. There is also a potential race if processes get
3027 * throttled, kswapd wakes, a large process exits thereby balancing the
3028 * zones, which causes kswapd to exit balance_pgdat() before reaching
3029 * the wake up checks. If kswapd is going to sleep, no process should
3030 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
3031 * the wake up is premature, processes will wake kswapd and get
3032 * throttled again. The difference from wake ups in balance_pgdat() is
3033 * that here we are under prepare_to_wait().
3035 if (waitqueue_active(&pgdat
->pfmemalloc_wait
))
3036 wake_up_all(&pgdat
->pfmemalloc_wait
);
3038 return pgdat_balanced(pgdat
, order
, classzone_idx
);
3042 * kswapd shrinks the zone by the number of pages required to reach
3043 * the high watermark.
3045 * Returns true if kswapd scanned at least the requested number of pages to
3046 * reclaim or if the lack of progress was due to pages under writeback.
3047 * This is used to determine if the scanning priority needs to be raised.
3049 static bool kswapd_shrink_zone(struct zone
*zone
,
3051 struct scan_control
*sc
,
3052 unsigned long *nr_attempted
)
3054 int testorder
= sc
->order
;
3055 unsigned long balance_gap
;
3056 bool lowmem_pressure
;
3058 /* Reclaim above the high watermark. */
3059 sc
->nr_to_reclaim
= max(SWAP_CLUSTER_MAX
, high_wmark_pages(zone
));
3062 * Kswapd reclaims only single pages with compaction enabled. Trying
3063 * too hard to reclaim until contiguous free pages have become
3064 * available can hurt performance by evicting too much useful data
3065 * from memory. Do not reclaim more than needed for compaction.
3067 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
3068 compaction_suitable(zone
, sc
->order
, 0, classzone_idx
)
3073 * We put equal pressure on every zone, unless one zone has way too
3074 * many pages free already. The "too many pages" is defined as the
3075 * high wmark plus a "gap" where the gap is either the low
3076 * watermark or 1% of the zone, whichever is smaller.
3078 balance_gap
= min(low_wmark_pages(zone
), DIV_ROUND_UP(
3079 zone
->managed_pages
, KSWAPD_ZONE_BALANCE_GAP_RATIO
));
3082 * If there is no low memory pressure or the zone is balanced then no
3083 * reclaim is necessary
3085 lowmem_pressure
= (buffer_heads_over_limit
&& is_highmem(zone
));
3086 if (!lowmem_pressure
&& zone_balanced(zone
, testorder
,
3087 balance_gap
, classzone_idx
))
3090 shrink_zone(zone
, sc
, zone_idx(zone
) == classzone_idx
);
3092 /* Account for the number of pages attempted to reclaim */
3093 *nr_attempted
+= sc
->nr_to_reclaim
;
3095 clear_bit(ZONE_WRITEBACK
, &zone
->flags
);
3098 * If a zone reaches its high watermark, consider it to be no longer
3099 * congested. It's possible there are dirty pages backed by congested
3100 * BDIs but as pressure is relieved, speculatively avoid congestion
3103 if (zone_reclaimable(zone
) &&
3104 zone_balanced(zone
, testorder
, 0, classzone_idx
)) {
3105 clear_bit(ZONE_CONGESTED
, &zone
->flags
);
3106 clear_bit(ZONE_DIRTY
, &zone
->flags
);
3109 return sc
->nr_scanned
>= sc
->nr_to_reclaim
;
3113 * For kswapd, balance_pgdat() will work across all this node's zones until
3114 * they are all at high_wmark_pages(zone).
3116 * Returns the final order kswapd was reclaiming at
3118 * There is special handling here for zones which are full of pinned pages.
3119 * This can happen if the pages are all mlocked, or if they are all used by
3120 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
3121 * What we do is to detect the case where all pages in the zone have been
3122 * scanned twice and there has been zero successful reclaim. Mark the zone as
3123 * dead and from now on, only perform a short scan. Basically we're polling
3124 * the zone for when the problem goes away.
3126 * kswapd scans the zones in the highmem->normal->dma direction. It skips
3127 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
3128 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
3129 * lower zones regardless of the number of free pages in the lower zones. This
3130 * interoperates with the page allocator fallback scheme to ensure that aging
3131 * of pages is balanced across the zones.
3133 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
,
3137 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
3138 unsigned long nr_soft_reclaimed
;
3139 unsigned long nr_soft_scanned
;
3140 struct scan_control sc
= {
3141 .gfp_mask
= GFP_KERNEL
,
3143 .priority
= DEF_PRIORITY
,
3144 .may_writepage
= !laptop_mode
,
3148 count_vm_event(PAGEOUTRUN
);
3151 unsigned long nr_attempted
= 0;
3152 bool raise_priority
= true;
3153 bool pgdat_needs_compaction
= (order
> 0);
3155 sc
.nr_reclaimed
= 0;
3158 * Scan in the highmem->dma direction for the highest
3159 * zone which needs scanning
3161 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
3162 struct zone
*zone
= pgdat
->node_zones
+ i
;
3164 if (!populated_zone(zone
))
3167 if (sc
.priority
!= DEF_PRIORITY
&&
3168 !zone_reclaimable(zone
))
3172 * Do some background aging of the anon list, to give
3173 * pages a chance to be referenced before reclaiming.
3175 age_active_anon(zone
, &sc
);
3178 * If the number of buffer_heads in the machine
3179 * exceeds the maximum allowed level and this node
3180 * has a highmem zone, force kswapd to reclaim from
3181 * it to relieve lowmem pressure.
3183 if (buffer_heads_over_limit
&& is_highmem_idx(i
)) {
3188 if (!zone_balanced(zone
, order
, 0, 0)) {
3193 * If balanced, clear the dirty and congested
3196 clear_bit(ZONE_CONGESTED
, &zone
->flags
);
3197 clear_bit(ZONE_DIRTY
, &zone
->flags
);
3204 for (i
= 0; i
<= end_zone
; i
++) {
3205 struct zone
*zone
= pgdat
->node_zones
+ i
;
3207 if (!populated_zone(zone
))
3211 * If any zone is currently balanced then kswapd will
3212 * not call compaction as it is expected that the
3213 * necessary pages are already available.
3215 if (pgdat_needs_compaction
&&
3216 zone_watermark_ok(zone
, order
,
3217 low_wmark_pages(zone
),
3219 pgdat_needs_compaction
= false;
3223 * If we're getting trouble reclaiming, start doing writepage
3224 * even in laptop mode.
3226 if (sc
.priority
< DEF_PRIORITY
- 2)
3227 sc
.may_writepage
= 1;
3230 * Now scan the zone in the dma->highmem direction, stopping
3231 * at the last zone which needs scanning.
3233 * We do this because the page allocator works in the opposite
3234 * direction. This prevents the page allocator from allocating
3235 * pages behind kswapd's direction of progress, which would
3236 * cause too much scanning of the lower zones.
3238 for (i
= 0; i
<= end_zone
; i
++) {
3239 struct zone
*zone
= pgdat
->node_zones
+ i
;
3241 if (!populated_zone(zone
))
3244 if (sc
.priority
!= DEF_PRIORITY
&&
3245 !zone_reclaimable(zone
))
3250 nr_soft_scanned
= 0;
3252 * Call soft limit reclaim before calling shrink_zone.
3254 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
3257 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
3260 * There should be no need to raise the scanning
3261 * priority if enough pages are already being scanned
3262 * that that high watermark would be met at 100%
3265 if (kswapd_shrink_zone(zone
, end_zone
,
3266 &sc
, &nr_attempted
))
3267 raise_priority
= false;
3271 * If the low watermark is met there is no need for processes
3272 * to be throttled on pfmemalloc_wait as they should not be
3273 * able to safely make forward progress. Wake them
3275 if (waitqueue_active(&pgdat
->pfmemalloc_wait
) &&
3276 pfmemalloc_watermark_ok(pgdat
))
3277 wake_up_all(&pgdat
->pfmemalloc_wait
);
3280 * Fragmentation may mean that the system cannot be rebalanced
3281 * for high-order allocations in all zones. If twice the
3282 * allocation size has been reclaimed and the zones are still
3283 * not balanced then recheck the watermarks at order-0 to
3284 * prevent kswapd reclaiming excessively. Assume that a
3285 * process requested a high-order can direct reclaim/compact.
3287 if (order
&& sc
.nr_reclaimed
>= 2UL << order
)
3288 order
= sc
.order
= 0;
3290 /* Check if kswapd should be suspending */
3291 if (try_to_freeze() || kthread_should_stop())
3295 * Compact if necessary and kswapd is reclaiming at least the
3296 * high watermark number of pages as requsted
3298 if (pgdat_needs_compaction
&& sc
.nr_reclaimed
> nr_attempted
)
3299 compact_pgdat(pgdat
, order
);
3302 * Raise priority if scanning rate is too low or there was no
3303 * progress in reclaiming pages
3305 if (raise_priority
|| !sc
.nr_reclaimed
)
3307 } while (sc
.priority
>= 1 &&
3308 !pgdat_balanced(pgdat
, order
, *classzone_idx
));
3312 * Return the order we were reclaiming at so prepare_kswapd_sleep()
3313 * makes a decision on the order we were last reclaiming at. However,
3314 * if another caller entered the allocator slow path while kswapd
3315 * was awake, order will remain at the higher level
3317 *classzone_idx
= end_zone
;
3321 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
3326 if (freezing(current
) || kthread_should_stop())
3329 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
3331 /* Try to sleep for a short interval */
3332 if (prepare_kswapd_sleep(pgdat
, order
, remaining
, classzone_idx
)) {
3333 remaining
= schedule_timeout(HZ
/10);
3334 finish_wait(&pgdat
->kswapd_wait
, &wait
);
3335 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
3339 * After a short sleep, check if it was a premature sleep. If not, then
3340 * go fully to sleep until explicitly woken up.
3342 if (prepare_kswapd_sleep(pgdat
, order
, remaining
, classzone_idx
)) {
3343 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
3346 * vmstat counters are not perfectly accurate and the estimated
3347 * value for counters such as NR_FREE_PAGES can deviate from the
3348 * true value by nr_online_cpus * threshold. To avoid the zone
3349 * watermarks being breached while under pressure, we reduce the
3350 * per-cpu vmstat threshold while kswapd is awake and restore
3351 * them before going back to sleep.
3353 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
3356 * Compaction records what page blocks it recently failed to
3357 * isolate pages from and skips them in the future scanning.
3358 * When kswapd is going to sleep, it is reasonable to assume
3359 * that pages and compaction may succeed so reset the cache.
3361 reset_isolation_suitable(pgdat
);
3363 if (!kthread_should_stop())
3366 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
3369 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
3371 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
3373 finish_wait(&pgdat
->kswapd_wait
, &wait
);
3377 * The background pageout daemon, started as a kernel thread
3378 * from the init process.
3380 * This basically trickles out pages so that we have _some_
3381 * free memory available even if there is no other activity
3382 * that frees anything up. This is needed for things like routing
3383 * etc, where we otherwise might have all activity going on in
3384 * asynchronous contexts that cannot page things out.
3386 * If there are applications that are active memory-allocators
3387 * (most normal use), this basically shouldn't matter.
3389 static int kswapd(void *p
)
3391 unsigned long order
, new_order
;
3392 unsigned balanced_order
;
3393 int classzone_idx
, new_classzone_idx
;
3394 int balanced_classzone_idx
;
3395 pg_data_t
*pgdat
= (pg_data_t
*)p
;
3396 struct task_struct
*tsk
= current
;
3398 struct reclaim_state reclaim_state
= {
3399 .reclaimed_slab
= 0,
3401 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
3403 lockdep_set_current_reclaim_state(GFP_KERNEL
);
3405 if (!cpumask_empty(cpumask
))
3406 set_cpus_allowed_ptr(tsk
, cpumask
);
3407 current
->reclaim_state
= &reclaim_state
;
3410 * Tell the memory management that we're a "memory allocator",
3411 * and that if we need more memory we should get access to it
3412 * regardless (see "__alloc_pages()"). "kswapd" should
3413 * never get caught in the normal page freeing logic.
3415 * (Kswapd normally doesn't need memory anyway, but sometimes
3416 * you need a small amount of memory in order to be able to
3417 * page out something else, and this flag essentially protects
3418 * us from recursively trying to free more memory as we're
3419 * trying to free the first piece of memory in the first place).
3421 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
3424 order
= new_order
= 0;
3426 classzone_idx
= new_classzone_idx
= pgdat
->nr_zones
- 1;
3427 balanced_classzone_idx
= classzone_idx
;
3432 * If the last balance_pgdat was unsuccessful it's unlikely a
3433 * new request of a similar or harder type will succeed soon
3434 * so consider going to sleep on the basis we reclaimed at
3436 if (balanced_classzone_idx
>= new_classzone_idx
&&
3437 balanced_order
== new_order
) {
3438 new_order
= pgdat
->kswapd_max_order
;
3439 new_classzone_idx
= pgdat
->classzone_idx
;
3440 pgdat
->kswapd_max_order
= 0;
3441 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
3444 if (order
< new_order
|| classzone_idx
> new_classzone_idx
) {
3446 * Don't sleep if someone wants a larger 'order'
3447 * allocation or has tigher zone constraints
3450 classzone_idx
= new_classzone_idx
;
3452 kswapd_try_to_sleep(pgdat
, balanced_order
,
3453 balanced_classzone_idx
);
3454 order
= pgdat
->kswapd_max_order
;
3455 classzone_idx
= pgdat
->classzone_idx
;
3457 new_classzone_idx
= classzone_idx
;
3458 pgdat
->kswapd_max_order
= 0;
3459 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
3462 ret
= try_to_freeze();
3463 if (kthread_should_stop())
3467 * We can speed up thawing tasks if we don't call balance_pgdat
3468 * after returning from the refrigerator
3471 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, order
);
3472 balanced_classzone_idx
= classzone_idx
;
3473 balanced_order
= balance_pgdat(pgdat
, order
,
3474 &balanced_classzone_idx
);
3478 tsk
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
);
3479 current
->reclaim_state
= NULL
;
3480 lockdep_clear_current_reclaim_state();
3486 * A zone is low on free memory, so wake its kswapd task to service it.
3488 void wakeup_kswapd(struct zone
*zone
, int order
, enum zone_type classzone_idx
)
3492 if (!populated_zone(zone
))
3495 if (!cpuset_zone_allowed(zone
, GFP_KERNEL
| __GFP_HARDWALL
))
3497 pgdat
= zone
->zone_pgdat
;
3498 if (pgdat
->kswapd_max_order
< order
) {
3499 pgdat
->kswapd_max_order
= order
;
3500 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
, classzone_idx
);
3502 if (!waitqueue_active(&pgdat
->kswapd_wait
))
3504 if (zone_balanced(zone
, order
, 0, 0))
3507 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, zone_idx(zone
), order
);
3508 wake_up_interruptible(&pgdat
->kswapd_wait
);
3511 #ifdef CONFIG_HIBERNATION
3513 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3516 * Rather than trying to age LRUs the aim is to preserve the overall
3517 * LRU order by reclaiming preferentially
3518 * inactive > active > active referenced > active mapped
3520 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
3522 struct reclaim_state reclaim_state
;
3523 struct scan_control sc
= {
3524 .nr_to_reclaim
= nr_to_reclaim
,
3525 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
3526 .priority
= DEF_PRIORITY
,
3530 .hibernation_mode
= 1,
3532 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
3533 struct task_struct
*p
= current
;
3534 unsigned long nr_reclaimed
;
3536 p
->flags
|= PF_MEMALLOC
;
3537 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
3538 reclaim_state
.reclaimed_slab
= 0;
3539 p
->reclaim_state
= &reclaim_state
;
3541 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3543 p
->reclaim_state
= NULL
;
3544 lockdep_clear_current_reclaim_state();
3545 p
->flags
&= ~PF_MEMALLOC
;
3547 return nr_reclaimed
;
3549 #endif /* CONFIG_HIBERNATION */
3551 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3552 not required for correctness. So if the last cpu in a node goes
3553 away, we get changed to run anywhere: as the first one comes back,
3554 restore their cpu bindings. */
3555 static int cpu_callback(struct notifier_block
*nfb
, unsigned long action
,
3560 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
3561 for_each_node_state(nid
, N_MEMORY
) {
3562 pg_data_t
*pgdat
= NODE_DATA(nid
);
3563 const struct cpumask
*mask
;
3565 mask
= cpumask_of_node(pgdat
->node_id
);
3567 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
3568 /* One of our CPUs online: restore mask */
3569 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
3576 * This kswapd start function will be called by init and node-hot-add.
3577 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3579 int kswapd_run(int nid
)
3581 pg_data_t
*pgdat
= NODE_DATA(nid
);
3587 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
3588 if (IS_ERR(pgdat
->kswapd
)) {
3589 /* failure at boot is fatal */
3590 BUG_ON(system_state
== SYSTEM_BOOTING
);
3591 pr_err("Failed to start kswapd on node %d\n", nid
);
3592 ret
= PTR_ERR(pgdat
->kswapd
);
3593 pgdat
->kswapd
= NULL
;
3599 * Called by memory hotplug when all memory in a node is offlined. Caller must
3600 * hold mem_hotplug_begin/end().
3602 void kswapd_stop(int nid
)
3604 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
3607 kthread_stop(kswapd
);
3608 NODE_DATA(nid
)->kswapd
= NULL
;
3612 static int __init
kswapd_init(void)
3617 for_each_node_state(nid
, N_MEMORY
)
3619 hotcpu_notifier(cpu_callback
, 0);
3623 module_init(kswapd_init
)
3629 * If non-zero call zone_reclaim when the number of free pages falls below
3632 int zone_reclaim_mode __read_mostly
;
3634 #define RECLAIM_OFF 0
3635 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3636 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3637 #define RECLAIM_UNMAP (1<<2) /* Unmap pages during reclaim */
3640 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3641 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3644 #define ZONE_RECLAIM_PRIORITY 4
3647 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3650 int sysctl_min_unmapped_ratio
= 1;
3653 * If the number of slab pages in a zone grows beyond this percentage then
3654 * slab reclaim needs to occur.
3656 int sysctl_min_slab_ratio
= 5;
3658 static inline unsigned long zone_unmapped_file_pages(struct zone
*zone
)
3660 unsigned long file_mapped
= zone_page_state(zone
, NR_FILE_MAPPED
);
3661 unsigned long file_lru
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
3662 zone_page_state(zone
, NR_ACTIVE_FILE
);
3665 * It's possible for there to be more file mapped pages than
3666 * accounted for by the pages on the file LRU lists because
3667 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3669 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
3672 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3673 static long zone_pagecache_reclaimable(struct zone
*zone
)
3675 long nr_pagecache_reclaimable
;
3679 * If RECLAIM_UNMAP is set, then all file pages are considered
3680 * potentially reclaimable. Otherwise, we have to worry about
3681 * pages like swapcache and zone_unmapped_file_pages() provides
3684 if (zone_reclaim_mode
& RECLAIM_UNMAP
)
3685 nr_pagecache_reclaimable
= zone_page_state(zone
, NR_FILE_PAGES
);
3687 nr_pagecache_reclaimable
= zone_unmapped_file_pages(zone
);
3689 /* If we can't clean pages, remove dirty pages from consideration */
3690 if (!(zone_reclaim_mode
& RECLAIM_WRITE
))
3691 delta
+= zone_page_state(zone
, NR_FILE_DIRTY
);
3693 /* Watch for any possible underflows due to delta */
3694 if (unlikely(delta
> nr_pagecache_reclaimable
))
3695 delta
= nr_pagecache_reclaimable
;
3697 return nr_pagecache_reclaimable
- delta
;
3701 * Try to free up some pages from this zone through reclaim.
3703 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3705 /* Minimum pages needed in order to stay on node */
3706 const unsigned long nr_pages
= 1 << order
;
3707 struct task_struct
*p
= current
;
3708 struct reclaim_state reclaim_state
;
3709 struct scan_control sc
= {
3710 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
3711 .gfp_mask
= (gfp_mask
= memalloc_noio_flags(gfp_mask
)),
3713 .priority
= ZONE_RECLAIM_PRIORITY
,
3714 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
3715 .may_unmap
= !!(zone_reclaim_mode
& RECLAIM_UNMAP
),
3721 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
3722 * and we also need to be able to write out pages for RECLAIM_WRITE
3723 * and RECLAIM_UNMAP.
3725 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
3726 lockdep_set_current_reclaim_state(gfp_mask
);
3727 reclaim_state
.reclaimed_slab
= 0;
3728 p
->reclaim_state
= &reclaim_state
;
3730 if (zone_pagecache_reclaimable(zone
) > zone
->min_unmapped_pages
) {
3732 * Free memory by calling shrink zone with increasing
3733 * priorities until we have enough memory freed.
3736 shrink_zone(zone
, &sc
, true);
3737 } while (sc
.nr_reclaimed
< nr_pages
&& --sc
.priority
>= 0);
3740 p
->reclaim_state
= NULL
;
3741 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
3742 lockdep_clear_current_reclaim_state();
3743 return sc
.nr_reclaimed
>= nr_pages
;
3746 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3752 * Zone reclaim reclaims unmapped file backed pages and
3753 * slab pages if we are over the defined limits.
3755 * A small portion of unmapped file backed pages is needed for
3756 * file I/O otherwise pages read by file I/O will be immediately
3757 * thrown out if the zone is overallocated. So we do not reclaim
3758 * if less than a specified percentage of the zone is used by
3759 * unmapped file backed pages.
3761 if (zone_pagecache_reclaimable(zone
) <= zone
->min_unmapped_pages
&&
3762 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) <= zone
->min_slab_pages
)
3763 return ZONE_RECLAIM_FULL
;
3765 if (!zone_reclaimable(zone
))
3766 return ZONE_RECLAIM_FULL
;
3769 * Do not scan if the allocation should not be delayed.
3771 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
3772 return ZONE_RECLAIM_NOSCAN
;
3775 * Only run zone reclaim on the local zone or on zones that do not
3776 * have associated processors. This will favor the local processor
3777 * over remote processors and spread off node memory allocations
3778 * as wide as possible.
3780 node_id
= zone_to_nid(zone
);
3781 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
3782 return ZONE_RECLAIM_NOSCAN
;
3784 if (test_and_set_bit(ZONE_RECLAIM_LOCKED
, &zone
->flags
))
3785 return ZONE_RECLAIM_NOSCAN
;
3787 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
3788 clear_bit(ZONE_RECLAIM_LOCKED
, &zone
->flags
);
3791 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
3798 * page_evictable - test whether a page is evictable
3799 * @page: the page to test
3801 * Test whether page is evictable--i.e., should be placed on active/inactive
3802 * lists vs unevictable list.
3804 * Reasons page might not be evictable:
3805 * (1) page's mapping marked unevictable
3806 * (2) page is part of an mlocked VMA
3809 int page_evictable(struct page
*page
)
3811 return !mapping_unevictable(page_mapping(page
)) && !PageMlocked(page
);
3816 * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
3817 * @pages: array of pages to check
3818 * @nr_pages: number of pages to check
3820 * Checks pages for evictability and moves them to the appropriate lru list.
3822 * This function is only used for SysV IPC SHM_UNLOCK.
3824 void check_move_unevictable_pages(struct page
**pages
, int nr_pages
)
3826 struct lruvec
*lruvec
;
3827 struct zone
*zone
= NULL
;
3832 for (i
= 0; i
< nr_pages
; i
++) {
3833 struct page
*page
= pages
[i
];
3834 struct zone
*pagezone
;
3837 pagezone
= page_zone(page
);
3838 if (pagezone
!= zone
) {
3840 spin_unlock_irq(&zone
->lru_lock
);
3842 spin_lock_irq(&zone
->lru_lock
);
3844 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
3846 if (!PageLRU(page
) || !PageUnevictable(page
))
3849 if (page_evictable(page
)) {
3850 enum lru_list lru
= page_lru_base_type(page
);
3852 VM_BUG_ON_PAGE(PageActive(page
), page
);
3853 ClearPageUnevictable(page
);
3854 del_page_from_lru_list(page
, lruvec
, LRU_UNEVICTABLE
);
3855 add_page_to_lru_list(page
, lruvec
, lru
);
3861 __count_vm_events(UNEVICTABLE_PGRESCUED
, pgrescued
);
3862 __count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
3863 spin_unlock_irq(&zone
->lru_lock
);
3866 #endif /* CONFIG_SHMEM */