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 /* Incremented by the number of inactive pages that were scanned */
63 unsigned long nr_scanned
;
65 /* Number of pages freed so far during a call to shrink_zones() */
66 unsigned long nr_reclaimed
;
68 /* One of the zones is ready for compaction */
71 /* How many pages shrink_list() should reclaim */
72 unsigned long nr_to_reclaim
;
74 unsigned long hibernation_mode
;
76 /* This context's GFP mask */
81 /* Can mapped pages be reclaimed? */
84 /* Can pages be swapped as part of reclaim? */
89 /* Scan (total_size >> priority) pages at once */
92 /* anon vs. file LRUs scanning "ratio" */
96 * The memory cgroup that hit its limit and as a result is the
97 * primary target of this reclaim invocation.
99 struct mem_cgroup
*target_mem_cgroup
;
102 * Nodemask of nodes allowed by the caller. If NULL, all nodes
105 nodemask_t
*nodemask
;
108 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
110 #ifdef ARCH_HAS_PREFETCH
111 #define prefetch_prev_lru_page(_page, _base, _field) \
113 if ((_page)->lru.prev != _base) { \
116 prev = lru_to_page(&(_page->lru)); \
117 prefetch(&prev->_field); \
121 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
124 #ifdef ARCH_HAS_PREFETCHW
125 #define prefetchw_prev_lru_page(_page, _base, _field) \
127 if ((_page)->lru.prev != _base) { \
130 prev = lru_to_page(&(_page->lru)); \
131 prefetchw(&prev->_field); \
135 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
139 * From 0 .. 100. Higher means more swappy.
141 int vm_swappiness
= 60;
142 unsigned long vm_total_pages
; /* The total number of pages which the VM controls */
144 static LIST_HEAD(shrinker_list
);
145 static DECLARE_RWSEM(shrinker_rwsem
);
148 static bool global_reclaim(struct scan_control
*sc
)
150 return !sc
->target_mem_cgroup
;
153 static bool global_reclaim(struct scan_control
*sc
)
159 static unsigned long zone_reclaimable_pages(struct zone
*zone
)
163 nr
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
164 zone_page_state(zone
, NR_INACTIVE_FILE
);
166 if (get_nr_swap_pages() > 0)
167 nr
+= zone_page_state(zone
, NR_ACTIVE_ANON
) +
168 zone_page_state(zone
, NR_INACTIVE_ANON
);
173 bool zone_reclaimable(struct zone
*zone
)
175 return zone
->pages_scanned
< zone_reclaimable_pages(zone
) * 6;
178 static unsigned long get_lru_size(struct lruvec
*lruvec
, enum lru_list lru
)
180 if (!mem_cgroup_disabled())
181 return mem_cgroup_get_lru_size(lruvec
, lru
);
183 return zone_page_state(lruvec_zone(lruvec
), NR_LRU_BASE
+ lru
);
187 * Add a shrinker callback to be called from the vm.
189 int register_shrinker(struct shrinker
*shrinker
)
191 size_t size
= sizeof(*shrinker
->nr_deferred
);
194 * If we only have one possible node in the system anyway, save
195 * ourselves the trouble and disable NUMA aware behavior. This way we
196 * will save memory and some small loop time later.
198 if (nr_node_ids
== 1)
199 shrinker
->flags
&= ~SHRINKER_NUMA_AWARE
;
201 if (shrinker
->flags
& SHRINKER_NUMA_AWARE
)
204 shrinker
->nr_deferred
= kzalloc(size
, GFP_KERNEL
);
205 if (!shrinker
->nr_deferred
)
208 down_write(&shrinker_rwsem
);
209 list_add_tail(&shrinker
->list
, &shrinker_list
);
210 up_write(&shrinker_rwsem
);
213 EXPORT_SYMBOL(register_shrinker
);
218 void unregister_shrinker(struct shrinker
*shrinker
)
220 down_write(&shrinker_rwsem
);
221 list_del(&shrinker
->list
);
222 up_write(&shrinker_rwsem
);
223 kfree(shrinker
->nr_deferred
);
225 EXPORT_SYMBOL(unregister_shrinker
);
227 #define SHRINK_BATCH 128
230 shrink_slab_node(struct shrink_control
*shrinkctl
, struct shrinker
*shrinker
,
231 unsigned long nr_pages_scanned
, unsigned long lru_pages
)
233 unsigned long freed
= 0;
234 unsigned long long delta
;
239 int nid
= shrinkctl
->nid
;
240 long batch_size
= shrinker
->batch
? shrinker
->batch
243 freeable
= shrinker
->count_objects(shrinker
, shrinkctl
);
248 * copy the current shrinker scan count into a local variable
249 * and zero it so that other concurrent shrinker invocations
250 * don't also do this scanning work.
252 nr
= atomic_long_xchg(&shrinker
->nr_deferred
[nid
], 0);
255 delta
= (4 * nr_pages_scanned
) / shrinker
->seeks
;
257 do_div(delta
, lru_pages
+ 1);
259 if (total_scan
< 0) {
261 "shrink_slab: %pF negative objects to delete nr=%ld\n",
262 shrinker
->scan_objects
, total_scan
);
263 total_scan
= freeable
;
267 * We need to avoid excessive windup on filesystem shrinkers
268 * due to large numbers of GFP_NOFS allocations causing the
269 * shrinkers to return -1 all the time. This results in a large
270 * nr being built up so when a shrink that can do some work
271 * comes along it empties the entire cache due to nr >>>
272 * freeable. This is bad for sustaining a working set in
275 * Hence only allow the shrinker to scan the entire cache when
276 * a large delta change is calculated directly.
278 if (delta
< freeable
/ 4)
279 total_scan
= min(total_scan
, freeable
/ 2);
282 * Avoid risking looping forever due to too large nr value:
283 * never try to free more than twice the estimate number of
286 if (total_scan
> freeable
* 2)
287 total_scan
= freeable
* 2;
289 trace_mm_shrink_slab_start(shrinker
, shrinkctl
, nr
,
290 nr_pages_scanned
, lru_pages
,
291 freeable
, delta
, total_scan
);
294 * Normally, we should not scan less than batch_size objects in one
295 * pass to avoid too frequent shrinker calls, but if the slab has less
296 * than batch_size objects in total and we are really tight on memory,
297 * we will try to reclaim all available objects, otherwise we can end
298 * up failing allocations although there are plenty of reclaimable
299 * objects spread over several slabs with usage less than the
302 * We detect the "tight on memory" situations by looking at the total
303 * number of objects we want to scan (total_scan). If it is greater
304 * than the total number of objects on slab (freeable), we must be
305 * scanning at high prio and therefore should try to reclaim as much as
308 while (total_scan
>= batch_size
||
309 total_scan
>= freeable
) {
311 unsigned long nr_to_scan
= min(batch_size
, total_scan
);
313 shrinkctl
->nr_to_scan
= nr_to_scan
;
314 ret
= shrinker
->scan_objects(shrinker
, shrinkctl
);
315 if (ret
== SHRINK_STOP
)
319 count_vm_events(SLABS_SCANNED
, nr_to_scan
);
320 total_scan
-= nr_to_scan
;
326 * move the unused scan count back into the shrinker in a
327 * manner that handles concurrent updates. If we exhausted the
328 * scan, there is no need to do an update.
331 new_nr
= atomic_long_add_return(total_scan
,
332 &shrinker
->nr_deferred
[nid
]);
334 new_nr
= atomic_long_read(&shrinker
->nr_deferred
[nid
]);
336 trace_mm_shrink_slab_end(shrinker
, nid
, freed
, nr
, new_nr
, total_scan
);
341 * Call the shrink functions to age shrinkable caches
343 * Here we assume it costs one seek to replace a lru page and that it also
344 * takes a seek to recreate a cache object. With this in mind we age equal
345 * percentages of the lru and ageable caches. This should balance the seeks
346 * generated by these structures.
348 * If the vm encountered mapped pages on the LRU it increase the pressure on
349 * slab to avoid swapping.
351 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
353 * `lru_pages' represents the number of on-LRU pages in all the zones which
354 * are eligible for the caller's allocation attempt. It is used for balancing
355 * slab reclaim versus page reclaim.
357 * Returns the number of slab objects which we shrunk.
359 unsigned long shrink_slab(struct shrink_control
*shrinkctl
,
360 unsigned long nr_pages_scanned
,
361 unsigned long lru_pages
)
363 struct shrinker
*shrinker
;
364 unsigned long freed
= 0;
366 if (nr_pages_scanned
== 0)
367 nr_pages_scanned
= SWAP_CLUSTER_MAX
;
369 if (!down_read_trylock(&shrinker_rwsem
)) {
371 * If we would return 0, our callers would understand that we
372 * have nothing else to shrink and give up trying. By returning
373 * 1 we keep it going and assume we'll be able to shrink next
380 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
381 if (!(shrinker
->flags
& SHRINKER_NUMA_AWARE
)) {
383 freed
+= shrink_slab_node(shrinkctl
, shrinker
,
384 nr_pages_scanned
, lru_pages
);
388 for_each_node_mask(shrinkctl
->nid
, shrinkctl
->nodes_to_scan
) {
389 if (node_online(shrinkctl
->nid
))
390 freed
+= shrink_slab_node(shrinkctl
, shrinker
,
391 nr_pages_scanned
, lru_pages
);
395 up_read(&shrinker_rwsem
);
401 static inline int is_page_cache_freeable(struct page
*page
)
404 * A freeable page cache page is referenced only by the caller
405 * that isolated the page, the page cache radix tree and
406 * optional buffer heads at page->private.
408 return page_count(page
) - page_has_private(page
) == 2;
411 static int may_write_to_queue(struct backing_dev_info
*bdi
,
412 struct scan_control
*sc
)
414 if (current
->flags
& PF_SWAPWRITE
)
416 if (!bdi_write_congested(bdi
))
418 if (bdi
== current
->backing_dev_info
)
424 * We detected a synchronous write error writing a page out. Probably
425 * -ENOSPC. We need to propagate that into the address_space for a subsequent
426 * fsync(), msync() or close().
428 * The tricky part is that after writepage we cannot touch the mapping: nothing
429 * prevents it from being freed up. But we have a ref on the page and once
430 * that page is locked, the mapping is pinned.
432 * We're allowed to run sleeping lock_page() here because we know the caller has
435 static void handle_write_error(struct address_space
*mapping
,
436 struct page
*page
, int error
)
439 if (page_mapping(page
) == mapping
)
440 mapping_set_error(mapping
, error
);
444 /* possible outcome of pageout() */
446 /* failed to write page out, page is locked */
448 /* move page to the active list, page is locked */
450 /* page has been sent to the disk successfully, page is unlocked */
452 /* page is clean and locked */
457 * pageout is called by shrink_page_list() for each dirty page.
458 * Calls ->writepage().
460 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
461 struct scan_control
*sc
)
464 * If the page is dirty, only perform writeback if that write
465 * will be non-blocking. To prevent this allocation from being
466 * stalled by pagecache activity. But note that there may be
467 * stalls if we need to run get_block(). We could test
468 * PagePrivate for that.
470 * If this process is currently in __generic_file_write_iter() against
471 * this page's queue, we can perform writeback even if that
474 * If the page is swapcache, write it back even if that would
475 * block, for some throttling. This happens by accident, because
476 * swap_backing_dev_info is bust: it doesn't reflect the
477 * congestion state of the swapdevs. Easy to fix, if needed.
479 if (!is_page_cache_freeable(page
))
483 * Some data journaling orphaned pages can have
484 * page->mapping == NULL while being dirty with clean buffers.
486 if (page_has_private(page
)) {
487 if (try_to_free_buffers(page
)) {
488 ClearPageDirty(page
);
489 pr_info("%s: orphaned page\n", __func__
);
495 if (mapping
->a_ops
->writepage
== NULL
)
496 return PAGE_ACTIVATE
;
497 if (!may_write_to_queue(mapping
->backing_dev_info
, sc
))
500 if (clear_page_dirty_for_io(page
)) {
502 struct writeback_control wbc
= {
503 .sync_mode
= WB_SYNC_NONE
,
504 .nr_to_write
= SWAP_CLUSTER_MAX
,
506 .range_end
= LLONG_MAX
,
510 SetPageReclaim(page
);
511 res
= mapping
->a_ops
->writepage(page
, &wbc
);
513 handle_write_error(mapping
, page
, res
);
514 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
515 ClearPageReclaim(page
);
516 return PAGE_ACTIVATE
;
519 if (!PageWriteback(page
)) {
520 /* synchronous write or broken a_ops? */
521 ClearPageReclaim(page
);
523 trace_mm_vmscan_writepage(page
, trace_reclaim_flags(page
));
524 inc_zone_page_state(page
, NR_VMSCAN_WRITE
);
532 * Same as remove_mapping, but if the page is removed from the mapping, it
533 * gets returned with a refcount of 0.
535 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
,
538 BUG_ON(!PageLocked(page
));
539 BUG_ON(mapping
!= page_mapping(page
));
541 spin_lock_irq(&mapping
->tree_lock
);
543 * The non racy check for a busy page.
545 * Must be careful with the order of the tests. When someone has
546 * a ref to the page, it may be possible that they dirty it then
547 * drop the reference. So if PageDirty is tested before page_count
548 * here, then the following race may occur:
550 * get_user_pages(&page);
551 * [user mapping goes away]
553 * !PageDirty(page) [good]
554 * SetPageDirty(page);
556 * !page_count(page) [good, discard it]
558 * [oops, our write_to data is lost]
560 * Reversing the order of the tests ensures such a situation cannot
561 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
562 * load is not satisfied before that of page->_count.
564 * Note that if SetPageDirty is always performed via set_page_dirty,
565 * and thus under tree_lock, then this ordering is not required.
567 if (!page_freeze_refs(page
, 2))
569 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
570 if (unlikely(PageDirty(page
))) {
571 page_unfreeze_refs(page
, 2);
575 if (PageSwapCache(page
)) {
576 swp_entry_t swap
= { .val
= page_private(page
) };
577 __delete_from_swap_cache(page
);
578 spin_unlock_irq(&mapping
->tree_lock
);
579 swapcache_free(swap
, page
);
581 void (*freepage
)(struct page
*);
584 freepage
= mapping
->a_ops
->freepage
;
586 * Remember a shadow entry for reclaimed file cache in
587 * order to detect refaults, thus thrashing, later on.
589 * But don't store shadows in an address space that is
590 * already exiting. This is not just an optizimation,
591 * inode reclaim needs to empty out the radix tree or
592 * the nodes are lost. Don't plant shadows behind its
595 if (reclaimed
&& page_is_file_cache(page
) &&
596 !mapping_exiting(mapping
))
597 shadow
= workingset_eviction(mapping
, page
);
598 __delete_from_page_cache(page
, shadow
);
599 spin_unlock_irq(&mapping
->tree_lock
);
600 mem_cgroup_uncharge_cache_page(page
);
602 if (freepage
!= NULL
)
609 spin_unlock_irq(&mapping
->tree_lock
);
614 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
615 * someone else has a ref on the page, abort and return 0. If it was
616 * successfully detached, return 1. Assumes the caller has a single ref on
619 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
621 if (__remove_mapping(mapping
, page
, false)) {
623 * Unfreezing the refcount with 1 rather than 2 effectively
624 * drops the pagecache ref for us without requiring another
627 page_unfreeze_refs(page
, 1);
634 * putback_lru_page - put previously isolated page onto appropriate LRU list
635 * @page: page to be put back to appropriate lru list
637 * Add previously isolated @page to appropriate LRU list.
638 * Page may still be unevictable for other reasons.
640 * lru_lock must not be held, interrupts must be enabled.
642 void putback_lru_page(struct page
*page
)
645 int was_unevictable
= PageUnevictable(page
);
647 VM_BUG_ON_PAGE(PageLRU(page
), page
);
650 ClearPageUnevictable(page
);
652 if (page_evictable(page
)) {
654 * For evictable pages, we can use the cache.
655 * In event of a race, worst case is we end up with an
656 * unevictable page on [in]active list.
657 * We know how to handle that.
659 is_unevictable
= false;
663 * Put unevictable pages directly on zone's unevictable
666 is_unevictable
= true;
667 add_page_to_unevictable_list(page
);
669 * When racing with an mlock or AS_UNEVICTABLE clearing
670 * (page is unlocked) make sure that if the other thread
671 * does not observe our setting of PG_lru and fails
672 * isolation/check_move_unevictable_pages,
673 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
674 * the page back to the evictable list.
676 * The other side is TestClearPageMlocked() or shmem_lock().
682 * page's status can change while we move it among lru. If an evictable
683 * page is on unevictable list, it never be freed. To avoid that,
684 * check after we added it to the list, again.
686 if (is_unevictable
&& page_evictable(page
)) {
687 if (!isolate_lru_page(page
)) {
691 /* This means someone else dropped this page from LRU
692 * So, it will be freed or putback to LRU again. There is
693 * nothing to do here.
697 if (was_unevictable
&& !is_unevictable
)
698 count_vm_event(UNEVICTABLE_PGRESCUED
);
699 else if (!was_unevictable
&& is_unevictable
)
700 count_vm_event(UNEVICTABLE_PGCULLED
);
702 put_page(page
); /* drop ref from isolate */
705 enum page_references
{
707 PAGEREF_RECLAIM_CLEAN
,
712 static enum page_references
page_check_references(struct page
*page
,
713 struct scan_control
*sc
)
715 int referenced_ptes
, referenced_page
;
716 unsigned long vm_flags
;
718 referenced_ptes
= page_referenced(page
, 1, sc
->target_mem_cgroup
,
720 referenced_page
= TestClearPageReferenced(page
);
723 * Mlock lost the isolation race with us. Let try_to_unmap()
724 * move the page to the unevictable list.
726 if (vm_flags
& VM_LOCKED
)
727 return PAGEREF_RECLAIM
;
729 if (referenced_ptes
) {
730 if (PageSwapBacked(page
))
731 return PAGEREF_ACTIVATE
;
733 * All mapped pages start out with page table
734 * references from the instantiating fault, so we need
735 * to look twice if a mapped file page is used more
738 * Mark it and spare it for another trip around the
739 * inactive list. Another page table reference will
740 * lead to its activation.
742 * Note: the mark is set for activated pages as well
743 * so that recently deactivated but used pages are
746 SetPageReferenced(page
);
748 if (referenced_page
|| referenced_ptes
> 1)
749 return PAGEREF_ACTIVATE
;
752 * Activate file-backed executable pages after first usage.
754 if (vm_flags
& VM_EXEC
)
755 return PAGEREF_ACTIVATE
;
760 /* Reclaim if clean, defer dirty pages to writeback */
761 if (referenced_page
&& !PageSwapBacked(page
))
762 return PAGEREF_RECLAIM_CLEAN
;
764 return PAGEREF_RECLAIM
;
767 /* Check if a page is dirty or under writeback */
768 static void page_check_dirty_writeback(struct page
*page
,
769 bool *dirty
, bool *writeback
)
771 struct address_space
*mapping
;
774 * Anonymous pages are not handled by flushers and must be written
775 * from reclaim context. Do not stall reclaim based on them
777 if (!page_is_file_cache(page
)) {
783 /* By default assume that the page flags are accurate */
784 *dirty
= PageDirty(page
);
785 *writeback
= PageWriteback(page
);
787 /* Verify dirty/writeback state if the filesystem supports it */
788 if (!page_has_private(page
))
791 mapping
= page_mapping(page
);
792 if (mapping
&& mapping
->a_ops
->is_dirty_writeback
)
793 mapping
->a_ops
->is_dirty_writeback(page
, dirty
, writeback
);
797 * shrink_page_list() returns the number of reclaimed pages
799 static unsigned long shrink_page_list(struct list_head
*page_list
,
801 struct scan_control
*sc
,
802 enum ttu_flags ttu_flags
,
803 unsigned long *ret_nr_dirty
,
804 unsigned long *ret_nr_unqueued_dirty
,
805 unsigned long *ret_nr_congested
,
806 unsigned long *ret_nr_writeback
,
807 unsigned long *ret_nr_immediate
,
810 LIST_HEAD(ret_pages
);
811 LIST_HEAD(free_pages
);
813 unsigned long nr_unqueued_dirty
= 0;
814 unsigned long nr_dirty
= 0;
815 unsigned long nr_congested
= 0;
816 unsigned long nr_reclaimed
= 0;
817 unsigned long nr_writeback
= 0;
818 unsigned long nr_immediate
= 0;
822 mem_cgroup_uncharge_start();
823 while (!list_empty(page_list
)) {
824 struct address_space
*mapping
;
827 enum page_references references
= PAGEREF_RECLAIM_CLEAN
;
828 bool dirty
, writeback
;
832 page
= lru_to_page(page_list
);
833 list_del(&page
->lru
);
835 if (!trylock_page(page
))
838 VM_BUG_ON_PAGE(PageActive(page
), page
);
839 VM_BUG_ON_PAGE(page_zone(page
) != zone
, page
);
843 if (unlikely(!page_evictable(page
)))
846 if (!sc
->may_unmap
&& page_mapped(page
))
849 /* Double the slab pressure for mapped and swapcache pages */
850 if (page_mapped(page
) || PageSwapCache(page
))
853 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
854 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
857 * The number of dirty pages determines if a zone is marked
858 * reclaim_congested which affects wait_iff_congested. kswapd
859 * will stall and start writing pages if the tail of the LRU
860 * is all dirty unqueued pages.
862 page_check_dirty_writeback(page
, &dirty
, &writeback
);
863 if (dirty
|| writeback
)
866 if (dirty
&& !writeback
)
870 * Treat this page as congested if the underlying BDI is or if
871 * pages are cycling through the LRU so quickly that the
872 * pages marked for immediate reclaim are making it to the
873 * end of the LRU a second time.
875 mapping
= page_mapping(page
);
876 if ((mapping
&& bdi_write_congested(mapping
->backing_dev_info
)) ||
877 (writeback
&& PageReclaim(page
)))
881 * If a page at the tail of the LRU is under writeback, there
882 * are three cases to consider.
884 * 1) If reclaim is encountering an excessive number of pages
885 * under writeback and this page is both under writeback and
886 * PageReclaim then it indicates that pages are being queued
887 * for IO but are being recycled through the LRU before the
888 * IO can complete. Waiting on the page itself risks an
889 * indefinite stall if it is impossible to writeback the
890 * page due to IO error or disconnected storage so instead
891 * note that the LRU is being scanned too quickly and the
892 * caller can stall after page list has been processed.
894 * 2) Global reclaim encounters a page, memcg encounters a
895 * page that is not marked for immediate reclaim or
896 * the caller does not have __GFP_IO. In this case mark
897 * the page for immediate reclaim and continue scanning.
899 * __GFP_IO is checked because a loop driver thread might
900 * enter reclaim, and deadlock if it waits on a page for
901 * which it is needed to do the write (loop masks off
902 * __GFP_IO|__GFP_FS for this reason); but more thought
903 * would probably show more reasons.
905 * Don't require __GFP_FS, since we're not going into the
906 * FS, just waiting on its writeback completion. Worryingly,
907 * ext4 gfs2 and xfs allocate pages with
908 * grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so testing
909 * may_enter_fs here is liable to OOM on them.
911 * 3) memcg encounters a page that is not already marked
912 * PageReclaim. memcg does not have any dirty pages
913 * throttling so we could easily OOM just because too many
914 * pages are in writeback and there is nothing else to
915 * reclaim. Wait for the writeback to complete.
917 if (PageWriteback(page
)) {
919 if (current_is_kswapd() &&
921 zone_is_reclaim_writeback(zone
)) {
926 } else if (global_reclaim(sc
) ||
927 !PageReclaim(page
) || !(sc
->gfp_mask
& __GFP_IO
)) {
929 * This is slightly racy - end_page_writeback()
930 * might have just cleared PageReclaim, then
931 * setting PageReclaim here end up interpreted
932 * as PageReadahead - but that does not matter
933 * enough to care. What we do want is for this
934 * page to have PageReclaim set next time memcg
935 * reclaim reaches the tests above, so it will
936 * then wait_on_page_writeback() to avoid OOM;
937 * and it's also appropriate in global reclaim.
939 SetPageReclaim(page
);
946 wait_on_page_writeback(page
);
951 references
= page_check_references(page
, sc
);
953 switch (references
) {
954 case PAGEREF_ACTIVATE
:
955 goto activate_locked
;
958 case PAGEREF_RECLAIM
:
959 case PAGEREF_RECLAIM_CLEAN
:
960 ; /* try to reclaim the page below */
964 * Anonymous process memory has backing store?
965 * Try to allocate it some swap space here.
967 if (PageAnon(page
) && !PageSwapCache(page
)) {
968 if (!(sc
->gfp_mask
& __GFP_IO
))
970 if (!add_to_swap(page
, page_list
))
971 goto activate_locked
;
974 /* Adding to swap updated mapping */
975 mapping
= page_mapping(page
);
979 * The page is mapped into the page tables of one or more
980 * processes. Try to unmap it here.
982 if (page_mapped(page
) && mapping
) {
983 switch (try_to_unmap(page
, ttu_flags
)) {
985 goto activate_locked
;
991 ; /* try to free the page below */
995 if (PageDirty(page
)) {
997 * Only kswapd can writeback filesystem pages to
998 * avoid risk of stack overflow but only writeback
999 * if many dirty pages have been encountered.
1001 if (page_is_file_cache(page
) &&
1002 (!current_is_kswapd() ||
1003 !zone_is_reclaim_dirty(zone
))) {
1005 * Immediately reclaim when written back.
1006 * Similar in principal to deactivate_page()
1007 * except we already have the page isolated
1008 * and know it's dirty
1010 inc_zone_page_state(page
, NR_VMSCAN_IMMEDIATE
);
1011 SetPageReclaim(page
);
1016 if (references
== PAGEREF_RECLAIM_CLEAN
)
1020 if (!sc
->may_writepage
)
1023 /* Page is dirty, try to write it out here */
1024 switch (pageout(page
, mapping
, sc
)) {
1028 goto activate_locked
;
1030 if (PageWriteback(page
))
1032 if (PageDirty(page
))
1036 * A synchronous write - probably a ramdisk. Go
1037 * ahead and try to reclaim the page.
1039 if (!trylock_page(page
))
1041 if (PageDirty(page
) || PageWriteback(page
))
1043 mapping
= page_mapping(page
);
1045 ; /* try to free the page below */
1050 * If the page has buffers, try to free the buffer mappings
1051 * associated with this page. If we succeed we try to free
1054 * We do this even if the page is PageDirty().
1055 * try_to_release_page() does not perform I/O, but it is
1056 * possible for a page to have PageDirty set, but it is actually
1057 * clean (all its buffers are clean). This happens if the
1058 * buffers were written out directly, with submit_bh(). ext3
1059 * will do this, as well as the blockdev mapping.
1060 * try_to_release_page() will discover that cleanness and will
1061 * drop the buffers and mark the page clean - it can be freed.
1063 * Rarely, pages can have buffers and no ->mapping. These are
1064 * the pages which were not successfully invalidated in
1065 * truncate_complete_page(). We try to drop those buffers here
1066 * and if that worked, and the page is no longer mapped into
1067 * process address space (page_count == 1) it can be freed.
1068 * Otherwise, leave the page on the LRU so it is swappable.
1070 if (page_has_private(page
)) {
1071 if (!try_to_release_page(page
, sc
->gfp_mask
))
1072 goto activate_locked
;
1073 if (!mapping
&& page_count(page
) == 1) {
1075 if (put_page_testzero(page
))
1079 * rare race with speculative reference.
1080 * the speculative reference will free
1081 * this page shortly, so we may
1082 * increment nr_reclaimed here (and
1083 * leave it off the LRU).
1091 if (!mapping
|| !__remove_mapping(mapping
, page
, true))
1095 * At this point, we have no other references and there is
1096 * no way to pick any more up (removed from LRU, removed
1097 * from pagecache). Can use non-atomic bitops now (and
1098 * we obviously don't have to worry about waking up a process
1099 * waiting on the page lock, because there are no references.
1101 __clear_page_locked(page
);
1106 * Is there need to periodically free_page_list? It would
1107 * appear not as the counts should be low
1109 list_add(&page
->lru
, &free_pages
);
1113 if (PageSwapCache(page
))
1114 try_to_free_swap(page
);
1116 putback_lru_page(page
);
1120 /* Not a candidate for swapping, so reclaim swap space. */
1121 if (PageSwapCache(page
) && vm_swap_full())
1122 try_to_free_swap(page
);
1123 VM_BUG_ON_PAGE(PageActive(page
), page
);
1124 SetPageActive(page
);
1129 list_add(&page
->lru
, &ret_pages
);
1130 VM_BUG_ON_PAGE(PageLRU(page
) || PageUnevictable(page
), page
);
1133 free_hot_cold_page_list(&free_pages
, true);
1135 list_splice(&ret_pages
, page_list
);
1136 count_vm_events(PGACTIVATE
, pgactivate
);
1137 mem_cgroup_uncharge_end();
1138 *ret_nr_dirty
+= nr_dirty
;
1139 *ret_nr_congested
+= nr_congested
;
1140 *ret_nr_unqueued_dirty
+= nr_unqueued_dirty
;
1141 *ret_nr_writeback
+= nr_writeback
;
1142 *ret_nr_immediate
+= nr_immediate
;
1143 return nr_reclaimed
;
1146 unsigned long reclaim_clean_pages_from_list(struct zone
*zone
,
1147 struct list_head
*page_list
)
1149 struct scan_control sc
= {
1150 .gfp_mask
= GFP_KERNEL
,
1151 .priority
= DEF_PRIORITY
,
1154 unsigned long ret
, dummy1
, dummy2
, dummy3
, dummy4
, dummy5
;
1155 struct page
*page
, *next
;
1156 LIST_HEAD(clean_pages
);
1158 list_for_each_entry_safe(page
, next
, page_list
, lru
) {
1159 if (page_is_file_cache(page
) && !PageDirty(page
) &&
1160 !isolated_balloon_page(page
)) {
1161 ClearPageActive(page
);
1162 list_move(&page
->lru
, &clean_pages
);
1166 ret
= shrink_page_list(&clean_pages
, zone
, &sc
,
1167 TTU_UNMAP
|TTU_IGNORE_ACCESS
,
1168 &dummy1
, &dummy2
, &dummy3
, &dummy4
, &dummy5
, true);
1169 list_splice(&clean_pages
, page_list
);
1170 mod_zone_page_state(zone
, NR_ISOLATED_FILE
, -ret
);
1175 * Attempt to remove the specified page from its LRU. Only take this page
1176 * if it is of the appropriate PageActive status. Pages which are being
1177 * freed elsewhere are also ignored.
1179 * page: page to consider
1180 * mode: one of the LRU isolation modes defined above
1182 * returns 0 on success, -ve errno on failure.
1184 int __isolate_lru_page(struct page
*page
, isolate_mode_t mode
)
1188 /* Only take pages on the LRU. */
1192 /* Compaction should not handle unevictable pages but CMA can do so */
1193 if (PageUnevictable(page
) && !(mode
& ISOLATE_UNEVICTABLE
))
1199 * To minimise LRU disruption, the caller can indicate that it only
1200 * wants to isolate pages it will be able to operate on without
1201 * blocking - clean pages for the most part.
1203 * ISOLATE_CLEAN means that only clean pages should be isolated. This
1204 * is used by reclaim when it is cannot write to backing storage
1206 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1207 * that it is possible to migrate without blocking
1209 if (mode
& (ISOLATE_CLEAN
|ISOLATE_ASYNC_MIGRATE
)) {
1210 /* All the caller can do on PageWriteback is block */
1211 if (PageWriteback(page
))
1214 if (PageDirty(page
)) {
1215 struct address_space
*mapping
;
1217 /* ISOLATE_CLEAN means only clean pages */
1218 if (mode
& ISOLATE_CLEAN
)
1222 * Only pages without mappings or that have a
1223 * ->migratepage callback are possible to migrate
1226 mapping
= page_mapping(page
);
1227 if (mapping
&& !mapping
->a_ops
->migratepage
)
1232 if ((mode
& ISOLATE_UNMAPPED
) && page_mapped(page
))
1235 if (likely(get_page_unless_zero(page
))) {
1237 * Be careful not to clear PageLRU until after we're
1238 * sure the page is not being freed elsewhere -- the
1239 * page release code relies on it.
1249 * zone->lru_lock is heavily contended. Some of the functions that
1250 * shrink the lists perform better by taking out a batch of pages
1251 * and working on them outside the LRU lock.
1253 * For pagecache intensive workloads, this function is the hottest
1254 * spot in the kernel (apart from copy_*_user functions).
1256 * Appropriate locks must be held before calling this function.
1258 * @nr_to_scan: The number of pages to look through on the list.
1259 * @lruvec: The LRU vector to pull pages from.
1260 * @dst: The temp list to put pages on to.
1261 * @nr_scanned: The number of pages that were scanned.
1262 * @sc: The scan_control struct for this reclaim session
1263 * @mode: One of the LRU isolation modes
1264 * @lru: LRU list id for isolating
1266 * returns how many pages were moved onto *@dst.
1268 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1269 struct lruvec
*lruvec
, struct list_head
*dst
,
1270 unsigned long *nr_scanned
, struct scan_control
*sc
,
1271 isolate_mode_t mode
, enum lru_list lru
)
1273 struct list_head
*src
= &lruvec
->lists
[lru
];
1274 unsigned long nr_taken
= 0;
1277 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
1281 page
= lru_to_page(src
);
1282 prefetchw_prev_lru_page(page
, src
, flags
);
1284 VM_BUG_ON_PAGE(!PageLRU(page
), page
);
1286 switch (__isolate_lru_page(page
, mode
)) {
1288 nr_pages
= hpage_nr_pages(page
);
1289 mem_cgroup_update_lru_size(lruvec
, lru
, -nr_pages
);
1290 list_move(&page
->lru
, dst
);
1291 nr_taken
+= nr_pages
;
1295 /* else it is being freed elsewhere */
1296 list_move(&page
->lru
, src
);
1305 trace_mm_vmscan_lru_isolate(sc
->order
, nr_to_scan
, scan
,
1306 nr_taken
, mode
, is_file_lru(lru
));
1311 * isolate_lru_page - tries to isolate a page from its LRU list
1312 * @page: page to isolate from its LRU list
1314 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1315 * vmstat statistic corresponding to whatever LRU list the page was on.
1317 * Returns 0 if the page was removed from an LRU list.
1318 * Returns -EBUSY if the page was not on an LRU list.
1320 * The returned page will have PageLRU() cleared. If it was found on
1321 * the active list, it will have PageActive set. If it was found on
1322 * the unevictable list, it will have the PageUnevictable bit set. That flag
1323 * may need to be cleared by the caller before letting the page go.
1325 * The vmstat statistic corresponding to the list on which the page was
1326 * found will be decremented.
1329 * (1) Must be called with an elevated refcount on the page. This is a
1330 * fundamentnal difference from isolate_lru_pages (which is called
1331 * without a stable reference).
1332 * (2) the lru_lock must not be held.
1333 * (3) interrupts must be enabled.
1335 int isolate_lru_page(struct page
*page
)
1339 VM_BUG_ON_PAGE(!page_count(page
), page
);
1341 if (PageLRU(page
)) {
1342 struct zone
*zone
= page_zone(page
);
1343 struct lruvec
*lruvec
;
1345 spin_lock_irq(&zone
->lru_lock
);
1346 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1347 if (PageLRU(page
)) {
1348 int lru
= page_lru(page
);
1351 del_page_from_lru_list(page
, lruvec
, lru
);
1354 spin_unlock_irq(&zone
->lru_lock
);
1360 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1361 * then get resheduled. When there are massive number of tasks doing page
1362 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1363 * the LRU list will go small and be scanned faster than necessary, leading to
1364 * unnecessary swapping, thrashing and OOM.
1366 static int too_many_isolated(struct zone
*zone
, int file
,
1367 struct scan_control
*sc
)
1369 unsigned long inactive
, isolated
;
1371 if (current_is_kswapd())
1374 if (!global_reclaim(sc
))
1378 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1379 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
);
1381 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1382 isolated
= zone_page_state(zone
, NR_ISOLATED_ANON
);
1386 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1387 * won't get blocked by normal direct-reclaimers, forming a circular
1390 if ((sc
->gfp_mask
& GFP_IOFS
) == GFP_IOFS
)
1393 return isolated
> inactive
;
1396 static noinline_for_stack
void
1397 putback_inactive_pages(struct lruvec
*lruvec
, struct list_head
*page_list
)
1399 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1400 struct zone
*zone
= lruvec_zone(lruvec
);
1401 LIST_HEAD(pages_to_free
);
1404 * Put back any unfreeable pages.
1406 while (!list_empty(page_list
)) {
1407 struct page
*page
= lru_to_page(page_list
);
1410 VM_BUG_ON_PAGE(PageLRU(page
), page
);
1411 list_del(&page
->lru
);
1412 if (unlikely(!page_evictable(page
))) {
1413 spin_unlock_irq(&zone
->lru_lock
);
1414 putback_lru_page(page
);
1415 spin_lock_irq(&zone
->lru_lock
);
1419 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1422 lru
= page_lru(page
);
1423 add_page_to_lru_list(page
, lruvec
, lru
);
1425 if (is_active_lru(lru
)) {
1426 int file
= is_file_lru(lru
);
1427 int numpages
= hpage_nr_pages(page
);
1428 reclaim_stat
->recent_rotated
[file
] += numpages
;
1430 if (put_page_testzero(page
)) {
1431 __ClearPageLRU(page
);
1432 __ClearPageActive(page
);
1433 del_page_from_lru_list(page
, lruvec
, lru
);
1435 if (unlikely(PageCompound(page
))) {
1436 spin_unlock_irq(&zone
->lru_lock
);
1437 (*get_compound_page_dtor(page
))(page
);
1438 spin_lock_irq(&zone
->lru_lock
);
1440 list_add(&page
->lru
, &pages_to_free
);
1445 * To save our caller's stack, now use input list for pages to free.
1447 list_splice(&pages_to_free
, page_list
);
1451 * If a kernel thread (such as nfsd for loop-back mounts) services
1452 * a backing device by writing to the page cache it sets PF_LESS_THROTTLE.
1453 * In that case we should only throttle if the backing device it is
1454 * writing to is congested. In other cases it is safe to throttle.
1456 static int current_may_throttle(void)
1458 return !(current
->flags
& PF_LESS_THROTTLE
) ||
1459 current
->backing_dev_info
== NULL
||
1460 bdi_write_congested(current
->backing_dev_info
);
1464 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1465 * of reclaimed pages
1467 static noinline_for_stack
unsigned long
1468 shrink_inactive_list(unsigned long nr_to_scan
, struct lruvec
*lruvec
,
1469 struct scan_control
*sc
, enum lru_list lru
)
1471 LIST_HEAD(page_list
);
1472 unsigned long nr_scanned
;
1473 unsigned long nr_reclaimed
= 0;
1474 unsigned long nr_taken
;
1475 unsigned long nr_dirty
= 0;
1476 unsigned long nr_congested
= 0;
1477 unsigned long nr_unqueued_dirty
= 0;
1478 unsigned long nr_writeback
= 0;
1479 unsigned long nr_immediate
= 0;
1480 isolate_mode_t isolate_mode
= 0;
1481 int file
= is_file_lru(lru
);
1482 struct zone
*zone
= lruvec_zone(lruvec
);
1483 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1485 while (unlikely(too_many_isolated(zone
, file
, sc
))) {
1486 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1488 /* We are about to die and free our memory. Return now. */
1489 if (fatal_signal_pending(current
))
1490 return SWAP_CLUSTER_MAX
;
1496 isolate_mode
|= ISOLATE_UNMAPPED
;
1497 if (!sc
->may_writepage
)
1498 isolate_mode
|= ISOLATE_CLEAN
;
1500 spin_lock_irq(&zone
->lru_lock
);
1502 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &page_list
,
1503 &nr_scanned
, sc
, isolate_mode
, lru
);
1505 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, -nr_taken
);
1506 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1508 if (global_reclaim(sc
)) {
1509 zone
->pages_scanned
+= nr_scanned
;
1510 if (current_is_kswapd())
1511 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
, nr_scanned
);
1513 __count_zone_vm_events(PGSCAN_DIRECT
, zone
, nr_scanned
);
1515 spin_unlock_irq(&zone
->lru_lock
);
1520 nr_reclaimed
= shrink_page_list(&page_list
, zone
, sc
, TTU_UNMAP
,
1521 &nr_dirty
, &nr_unqueued_dirty
, &nr_congested
,
1522 &nr_writeback
, &nr_immediate
,
1525 spin_lock_irq(&zone
->lru_lock
);
1527 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1529 if (global_reclaim(sc
)) {
1530 if (current_is_kswapd())
1531 __count_zone_vm_events(PGSTEAL_KSWAPD
, zone
,
1534 __count_zone_vm_events(PGSTEAL_DIRECT
, zone
,
1538 putback_inactive_pages(lruvec
, &page_list
);
1540 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1542 spin_unlock_irq(&zone
->lru_lock
);
1544 free_hot_cold_page_list(&page_list
, true);
1547 * If reclaim is isolating dirty pages under writeback, it implies
1548 * that the long-lived page allocation rate is exceeding the page
1549 * laundering rate. Either the global limits are not being effective
1550 * at throttling processes due to the page distribution throughout
1551 * zones or there is heavy usage of a slow backing device. The
1552 * only option is to throttle from reclaim context which is not ideal
1553 * as there is no guarantee the dirtying process is throttled in the
1554 * same way balance_dirty_pages() manages.
1556 * Once a zone is flagged ZONE_WRITEBACK, kswapd will count the number
1557 * of pages under pages flagged for immediate reclaim and stall if any
1558 * are encountered in the nr_immediate check below.
1560 if (nr_writeback
&& nr_writeback
== nr_taken
)
1561 zone_set_flag(zone
, ZONE_WRITEBACK
);
1564 * memcg will stall in page writeback so only consider forcibly
1565 * stalling for global reclaim
1567 if (global_reclaim(sc
)) {
1569 * Tag a zone as congested if all the dirty pages scanned were
1570 * backed by a congested BDI and wait_iff_congested will stall.
1572 if (nr_dirty
&& nr_dirty
== nr_congested
)
1573 zone_set_flag(zone
, ZONE_CONGESTED
);
1576 * If dirty pages are scanned that are not queued for IO, it
1577 * implies that flushers are not keeping up. In this case, flag
1578 * the zone ZONE_TAIL_LRU_DIRTY and kswapd will start writing
1579 * pages from reclaim context.
1581 if (nr_unqueued_dirty
== nr_taken
)
1582 zone_set_flag(zone
, ZONE_TAIL_LRU_DIRTY
);
1585 * If kswapd scans pages marked marked for immediate
1586 * reclaim and under writeback (nr_immediate), it implies
1587 * that pages are cycling through the LRU faster than
1588 * they are written so also forcibly stall.
1590 if (nr_immediate
&& current_may_throttle())
1591 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1595 * Stall direct reclaim for IO completions if underlying BDIs or zone
1596 * is congested. Allow kswapd to continue until it starts encountering
1597 * unqueued dirty pages or cycling through the LRU too quickly.
1599 if (!sc
->hibernation_mode
&& !current_is_kswapd() &&
1600 current_may_throttle())
1601 wait_iff_congested(zone
, BLK_RW_ASYNC
, HZ
/10);
1603 trace_mm_vmscan_lru_shrink_inactive(zone
->zone_pgdat
->node_id
,
1605 nr_scanned
, nr_reclaimed
,
1607 trace_shrink_flags(file
));
1608 return nr_reclaimed
;
1612 * This moves pages from the active list to the inactive list.
1614 * We move them the other way if the page is referenced by one or more
1615 * processes, from rmap.
1617 * If the pages are mostly unmapped, the processing is fast and it is
1618 * appropriate to hold zone->lru_lock across the whole operation. But if
1619 * the pages are mapped, the processing is slow (page_referenced()) so we
1620 * should drop zone->lru_lock around each page. It's impossible to balance
1621 * this, so instead we remove the pages from the LRU while processing them.
1622 * It is safe to rely on PG_active against the non-LRU pages in here because
1623 * nobody will play with that bit on a non-LRU page.
1625 * The downside is that we have to touch page->_count against each page.
1626 * But we had to alter page->flags anyway.
1629 static void move_active_pages_to_lru(struct lruvec
*lruvec
,
1630 struct list_head
*list
,
1631 struct list_head
*pages_to_free
,
1634 struct zone
*zone
= lruvec_zone(lruvec
);
1635 unsigned long pgmoved
= 0;
1639 while (!list_empty(list
)) {
1640 page
= lru_to_page(list
);
1641 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1643 VM_BUG_ON_PAGE(PageLRU(page
), page
);
1646 nr_pages
= hpage_nr_pages(page
);
1647 mem_cgroup_update_lru_size(lruvec
, lru
, nr_pages
);
1648 list_move(&page
->lru
, &lruvec
->lists
[lru
]);
1649 pgmoved
+= nr_pages
;
1651 if (put_page_testzero(page
)) {
1652 __ClearPageLRU(page
);
1653 __ClearPageActive(page
);
1654 del_page_from_lru_list(page
, lruvec
, lru
);
1656 if (unlikely(PageCompound(page
))) {
1657 spin_unlock_irq(&zone
->lru_lock
);
1658 (*get_compound_page_dtor(page
))(page
);
1659 spin_lock_irq(&zone
->lru_lock
);
1661 list_add(&page
->lru
, pages_to_free
);
1664 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1665 if (!is_active_lru(lru
))
1666 __count_vm_events(PGDEACTIVATE
, pgmoved
);
1669 static void shrink_active_list(unsigned long nr_to_scan
,
1670 struct lruvec
*lruvec
,
1671 struct scan_control
*sc
,
1674 unsigned long nr_taken
;
1675 unsigned long nr_scanned
;
1676 unsigned long vm_flags
;
1677 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1678 LIST_HEAD(l_active
);
1679 LIST_HEAD(l_inactive
);
1681 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1682 unsigned long nr_rotated
= 0;
1683 isolate_mode_t isolate_mode
= 0;
1684 int file
= is_file_lru(lru
);
1685 struct zone
*zone
= lruvec_zone(lruvec
);
1690 isolate_mode
|= ISOLATE_UNMAPPED
;
1691 if (!sc
->may_writepage
)
1692 isolate_mode
|= ISOLATE_CLEAN
;
1694 spin_lock_irq(&zone
->lru_lock
);
1696 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &l_hold
,
1697 &nr_scanned
, sc
, isolate_mode
, lru
);
1698 if (global_reclaim(sc
))
1699 zone
->pages_scanned
+= nr_scanned
;
1701 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1703 __count_zone_vm_events(PGREFILL
, zone
, nr_scanned
);
1704 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, -nr_taken
);
1705 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1706 spin_unlock_irq(&zone
->lru_lock
);
1708 while (!list_empty(&l_hold
)) {
1710 page
= lru_to_page(&l_hold
);
1711 list_del(&page
->lru
);
1713 if (unlikely(!page_evictable(page
))) {
1714 putback_lru_page(page
);
1718 if (unlikely(buffer_heads_over_limit
)) {
1719 if (page_has_private(page
) && trylock_page(page
)) {
1720 if (page_has_private(page
))
1721 try_to_release_page(page
, 0);
1726 if (page_referenced(page
, 0, sc
->target_mem_cgroup
,
1728 nr_rotated
+= hpage_nr_pages(page
);
1730 * Identify referenced, file-backed active pages and
1731 * give them one more trip around the active list. So
1732 * that executable code get better chances to stay in
1733 * memory under moderate memory pressure. Anon pages
1734 * are not likely to be evicted by use-once streaming
1735 * IO, plus JVM can create lots of anon VM_EXEC pages,
1736 * so we ignore them here.
1738 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1739 list_add(&page
->lru
, &l_active
);
1744 ClearPageActive(page
); /* we are de-activating */
1745 list_add(&page
->lru
, &l_inactive
);
1749 * Move pages back to the lru list.
1751 spin_lock_irq(&zone
->lru_lock
);
1753 * Count referenced pages from currently used mappings as rotated,
1754 * even though only some of them are actually re-activated. This
1755 * helps balance scan pressure between file and anonymous pages in
1758 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1760 move_active_pages_to_lru(lruvec
, &l_active
, &l_hold
, lru
);
1761 move_active_pages_to_lru(lruvec
, &l_inactive
, &l_hold
, lru
- LRU_ACTIVE
);
1762 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1763 spin_unlock_irq(&zone
->lru_lock
);
1765 free_hot_cold_page_list(&l_hold
, true);
1769 static int inactive_anon_is_low_global(struct zone
*zone
)
1771 unsigned long active
, inactive
;
1773 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1774 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1776 if (inactive
* zone
->inactive_ratio
< active
)
1783 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1784 * @lruvec: LRU vector to check
1786 * Returns true if the zone does not have enough inactive anon pages,
1787 * meaning some active anon pages need to be deactivated.
1789 static int inactive_anon_is_low(struct lruvec
*lruvec
)
1792 * If we don't have swap space, anonymous page deactivation
1795 if (!total_swap_pages
)
1798 if (!mem_cgroup_disabled())
1799 return mem_cgroup_inactive_anon_is_low(lruvec
);
1801 return inactive_anon_is_low_global(lruvec_zone(lruvec
));
1804 static inline int inactive_anon_is_low(struct lruvec
*lruvec
)
1811 * inactive_file_is_low - check if file pages need to be deactivated
1812 * @lruvec: LRU vector to check
1814 * When the system is doing streaming IO, memory pressure here
1815 * ensures that active file pages get deactivated, until more
1816 * than half of the file pages are on the inactive list.
1818 * Once we get to that situation, protect the system's working
1819 * set from being evicted by disabling active file page aging.
1821 * This uses a different ratio than the anonymous pages, because
1822 * the page cache uses a use-once replacement algorithm.
1824 static int inactive_file_is_low(struct lruvec
*lruvec
)
1826 unsigned long inactive
;
1827 unsigned long active
;
1829 inactive
= get_lru_size(lruvec
, LRU_INACTIVE_FILE
);
1830 active
= get_lru_size(lruvec
, LRU_ACTIVE_FILE
);
1832 return active
> inactive
;
1835 static int inactive_list_is_low(struct lruvec
*lruvec
, enum lru_list lru
)
1837 if (is_file_lru(lru
))
1838 return inactive_file_is_low(lruvec
);
1840 return inactive_anon_is_low(lruvec
);
1843 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1844 struct lruvec
*lruvec
, struct scan_control
*sc
)
1846 if (is_active_lru(lru
)) {
1847 if (inactive_list_is_low(lruvec
, lru
))
1848 shrink_active_list(nr_to_scan
, lruvec
, sc
, lru
);
1852 return shrink_inactive_list(nr_to_scan
, lruvec
, sc
, lru
);
1863 * Determine how aggressively the anon and file LRU lists should be
1864 * scanned. The relative value of each set of LRU lists is determined
1865 * by looking at the fraction of the pages scanned we did rotate back
1866 * onto the active list instead of evict.
1868 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
1869 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
1871 static void get_scan_count(struct lruvec
*lruvec
, struct scan_control
*sc
,
1874 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1876 u64 denominator
= 0; /* gcc */
1877 struct zone
*zone
= lruvec_zone(lruvec
);
1878 unsigned long anon_prio
, file_prio
;
1879 enum scan_balance scan_balance
;
1880 unsigned long anon
, file
;
1881 bool force_scan
= false;
1882 unsigned long ap
, fp
;
1888 * If the zone or memcg is small, nr[l] can be 0. This
1889 * results in no scanning on this priority and a potential
1890 * priority drop. Global direct reclaim can go to the next
1891 * zone and tends to have no problems. Global kswapd is for
1892 * zone balancing and it needs to scan a minimum amount. When
1893 * reclaiming for a memcg, a priority drop can cause high
1894 * latencies, so it's better to scan a minimum amount there as
1897 if (current_is_kswapd() && !zone_reclaimable(zone
))
1899 if (!global_reclaim(sc
))
1902 /* If we have no swap space, do not bother scanning anon pages. */
1903 if (!sc
->may_swap
|| (get_nr_swap_pages() <= 0)) {
1904 scan_balance
= SCAN_FILE
;
1909 * Global reclaim will swap to prevent OOM even with no
1910 * swappiness, but memcg users want to use this knob to
1911 * disable swapping for individual groups completely when
1912 * using the memory controller's swap limit feature would be
1915 if (!global_reclaim(sc
) && !sc
->swappiness
) {
1916 scan_balance
= SCAN_FILE
;
1921 * Do not apply any pressure balancing cleverness when the
1922 * system is close to OOM, scan both anon and file equally
1923 * (unless the swappiness setting disagrees with swapping).
1925 if (!sc
->priority
&& sc
->swappiness
) {
1926 scan_balance
= SCAN_EQUAL
;
1930 anon
= get_lru_size(lruvec
, LRU_ACTIVE_ANON
) +
1931 get_lru_size(lruvec
, LRU_INACTIVE_ANON
);
1932 file
= get_lru_size(lruvec
, LRU_ACTIVE_FILE
) +
1933 get_lru_size(lruvec
, LRU_INACTIVE_FILE
);
1936 * Prevent the reclaimer from falling into the cache trap: as
1937 * cache pages start out inactive, every cache fault will tip
1938 * the scan balance towards the file LRU. And as the file LRU
1939 * shrinks, so does the window for rotation from references.
1940 * This means we have a runaway feedback loop where a tiny
1941 * thrashing file LRU becomes infinitely more attractive than
1942 * anon pages. Try to detect this based on file LRU size.
1944 if (global_reclaim(sc
)) {
1945 unsigned long free
= zone_page_state(zone
, NR_FREE_PAGES
);
1947 if (unlikely(file
+ free
<= high_wmark_pages(zone
))) {
1948 scan_balance
= SCAN_ANON
;
1954 * There is enough inactive page cache, do not reclaim
1955 * anything from the anonymous working set right now.
1957 if (!inactive_file_is_low(lruvec
)) {
1958 scan_balance
= SCAN_FILE
;
1962 scan_balance
= SCAN_FRACT
;
1965 * With swappiness at 100, anonymous and file have the same priority.
1966 * This scanning priority is essentially the inverse of IO cost.
1968 anon_prio
= sc
->swappiness
;
1969 file_prio
= 200 - anon_prio
;
1972 * OK, so we have swap space and a fair amount of page cache
1973 * pages. We use the recently rotated / recently scanned
1974 * ratios to determine how valuable each cache is.
1976 * Because workloads change over time (and to avoid overflow)
1977 * we keep these statistics as a floating average, which ends
1978 * up weighing recent references more than old ones.
1980 * anon in [0], file in [1]
1982 spin_lock_irq(&zone
->lru_lock
);
1983 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
1984 reclaim_stat
->recent_scanned
[0] /= 2;
1985 reclaim_stat
->recent_rotated
[0] /= 2;
1988 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
1989 reclaim_stat
->recent_scanned
[1] /= 2;
1990 reclaim_stat
->recent_rotated
[1] /= 2;
1994 * The amount of pressure on anon vs file pages is inversely
1995 * proportional to the fraction of recently scanned pages on
1996 * each list that were recently referenced and in active use.
1998 ap
= anon_prio
* (reclaim_stat
->recent_scanned
[0] + 1);
1999 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
2001 fp
= file_prio
* (reclaim_stat
->recent_scanned
[1] + 1);
2002 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
2003 spin_unlock_irq(&zone
->lru_lock
);
2007 denominator
= ap
+ fp
+ 1;
2009 some_scanned
= false;
2010 /* Only use force_scan on second pass. */
2011 for (pass
= 0; !some_scanned
&& pass
< 2; pass
++) {
2012 for_each_evictable_lru(lru
) {
2013 int file
= is_file_lru(lru
);
2017 size
= get_lru_size(lruvec
, lru
);
2018 scan
= size
>> sc
->priority
;
2020 if (!scan
&& pass
&& force_scan
)
2021 scan
= min(size
, SWAP_CLUSTER_MAX
);
2023 switch (scan_balance
) {
2025 /* Scan lists relative to size */
2029 * Scan types proportional to swappiness and
2030 * their relative recent reclaim efficiency.
2032 scan
= div64_u64(scan
* fraction
[file
],
2037 /* Scan one type exclusively */
2038 if ((scan_balance
== SCAN_FILE
) != file
)
2042 /* Look ma, no brain */
2047 * Skip the second pass and don't force_scan,
2048 * if we found something to scan.
2050 some_scanned
|= !!scan
;
2056 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
2058 static void shrink_lruvec(struct lruvec
*lruvec
, struct scan_control
*sc
)
2060 unsigned long nr
[NR_LRU_LISTS
];
2061 unsigned long targets
[NR_LRU_LISTS
];
2062 unsigned long nr_to_scan
;
2064 unsigned long nr_reclaimed
= 0;
2065 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
2066 struct blk_plug plug
;
2069 get_scan_count(lruvec
, sc
, nr
);
2071 /* Record the original scan target for proportional adjustments later */
2072 memcpy(targets
, nr
, sizeof(nr
));
2075 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
2076 * event that can occur when there is little memory pressure e.g.
2077 * multiple streaming readers/writers. Hence, we do not abort scanning
2078 * when the requested number of pages are reclaimed when scanning at
2079 * DEF_PRIORITY on the assumption that the fact we are direct
2080 * reclaiming implies that kswapd is not keeping up and it is best to
2081 * do a batch of work at once. For memcg reclaim one check is made to
2082 * abort proportional reclaim if either the file or anon lru has already
2083 * dropped to zero at the first pass.
2085 scan_adjusted
= (global_reclaim(sc
) && !current_is_kswapd() &&
2086 sc
->priority
== DEF_PRIORITY
);
2088 blk_start_plug(&plug
);
2089 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
2090 nr
[LRU_INACTIVE_FILE
]) {
2091 unsigned long nr_anon
, nr_file
, percentage
;
2092 unsigned long nr_scanned
;
2094 for_each_evictable_lru(lru
) {
2096 nr_to_scan
= min(nr
[lru
], SWAP_CLUSTER_MAX
);
2097 nr
[lru
] -= nr_to_scan
;
2099 nr_reclaimed
+= shrink_list(lru
, nr_to_scan
,
2104 if (nr_reclaimed
< nr_to_reclaim
|| scan_adjusted
)
2108 * For kswapd and memcg, reclaim at least the number of pages
2109 * requested. Ensure that the anon and file LRUs are scanned
2110 * proportionally what was requested by get_scan_count(). We
2111 * stop reclaiming one LRU and reduce the amount scanning
2112 * proportional to the original scan target.
2114 nr_file
= nr
[LRU_INACTIVE_FILE
] + nr
[LRU_ACTIVE_FILE
];
2115 nr_anon
= nr
[LRU_INACTIVE_ANON
] + nr
[LRU_ACTIVE_ANON
];
2118 * It's just vindictive to attack the larger once the smaller
2119 * has gone to zero. And given the way we stop scanning the
2120 * smaller below, this makes sure that we only make one nudge
2121 * towards proportionality once we've got nr_to_reclaim.
2123 if (!nr_file
|| !nr_anon
)
2126 if (nr_file
> nr_anon
) {
2127 unsigned long scan_target
= targets
[LRU_INACTIVE_ANON
] +
2128 targets
[LRU_ACTIVE_ANON
] + 1;
2130 percentage
= nr_anon
* 100 / scan_target
;
2132 unsigned long scan_target
= targets
[LRU_INACTIVE_FILE
] +
2133 targets
[LRU_ACTIVE_FILE
] + 1;
2135 percentage
= nr_file
* 100 / scan_target
;
2138 /* Stop scanning the smaller of the LRU */
2140 nr
[lru
+ LRU_ACTIVE
] = 0;
2143 * Recalculate the other LRU scan count based on its original
2144 * scan target and the percentage scanning already complete
2146 lru
= (lru
== LRU_FILE
) ? LRU_BASE
: LRU_FILE
;
2147 nr_scanned
= targets
[lru
] - nr
[lru
];
2148 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2149 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2152 nr_scanned
= targets
[lru
] - nr
[lru
];
2153 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2154 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2156 scan_adjusted
= true;
2158 blk_finish_plug(&plug
);
2159 sc
->nr_reclaimed
+= nr_reclaimed
;
2162 * Even if we did not try to evict anon pages at all, we want to
2163 * rebalance the anon lru active/inactive ratio.
2165 if (inactive_anon_is_low(lruvec
))
2166 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
2167 sc
, LRU_ACTIVE_ANON
);
2169 throttle_vm_writeout(sc
->gfp_mask
);
2172 /* Use reclaim/compaction for costly allocs or under memory pressure */
2173 static bool in_reclaim_compaction(struct scan_control
*sc
)
2175 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
2176 (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
||
2177 sc
->priority
< DEF_PRIORITY
- 2))
2184 * Reclaim/compaction is used for high-order allocation requests. It reclaims
2185 * order-0 pages before compacting the zone. should_continue_reclaim() returns
2186 * true if more pages should be reclaimed such that when the page allocator
2187 * calls try_to_compact_zone() that it will have enough free pages to succeed.
2188 * It will give up earlier than that if there is difficulty reclaiming pages.
2190 static inline bool should_continue_reclaim(struct zone
*zone
,
2191 unsigned long nr_reclaimed
,
2192 unsigned long nr_scanned
,
2193 struct scan_control
*sc
)
2195 unsigned long pages_for_compaction
;
2196 unsigned long inactive_lru_pages
;
2198 /* If not in reclaim/compaction mode, stop */
2199 if (!in_reclaim_compaction(sc
))
2202 /* Consider stopping depending on scan and reclaim activity */
2203 if (sc
->gfp_mask
& __GFP_REPEAT
) {
2205 * For __GFP_REPEAT allocations, stop reclaiming if the
2206 * full LRU list has been scanned and we are still failing
2207 * to reclaim pages. This full LRU scan is potentially
2208 * expensive but a __GFP_REPEAT caller really wants to succeed
2210 if (!nr_reclaimed
&& !nr_scanned
)
2214 * For non-__GFP_REPEAT allocations which can presumably
2215 * fail without consequence, stop if we failed to reclaim
2216 * any pages from the last SWAP_CLUSTER_MAX number of
2217 * pages that were scanned. This will return to the
2218 * caller faster at the risk reclaim/compaction and
2219 * the resulting allocation attempt fails
2226 * If we have not reclaimed enough pages for compaction and the
2227 * inactive lists are large enough, continue reclaiming
2229 pages_for_compaction
= (2UL << sc
->order
);
2230 inactive_lru_pages
= zone_page_state(zone
, NR_INACTIVE_FILE
);
2231 if (get_nr_swap_pages() > 0)
2232 inactive_lru_pages
+= zone_page_state(zone
, NR_INACTIVE_ANON
);
2233 if (sc
->nr_reclaimed
< pages_for_compaction
&&
2234 inactive_lru_pages
> pages_for_compaction
)
2237 /* If compaction would go ahead or the allocation would succeed, stop */
2238 switch (compaction_suitable(zone
, sc
->order
)) {
2239 case COMPACT_PARTIAL
:
2240 case COMPACT_CONTINUE
:
2247 static bool shrink_zone(struct zone
*zone
, struct scan_control
*sc
)
2249 unsigned long nr_reclaimed
, nr_scanned
;
2250 bool reclaimable
= false;
2253 struct mem_cgroup
*root
= sc
->target_mem_cgroup
;
2254 struct mem_cgroup_reclaim_cookie reclaim
= {
2256 .priority
= sc
->priority
,
2258 struct mem_cgroup
*memcg
;
2260 nr_reclaimed
= sc
->nr_reclaimed
;
2261 nr_scanned
= sc
->nr_scanned
;
2263 memcg
= mem_cgroup_iter(root
, NULL
, &reclaim
);
2265 struct lruvec
*lruvec
;
2267 lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
2269 sc
->swappiness
= mem_cgroup_swappiness(memcg
);
2270 shrink_lruvec(lruvec
, sc
);
2273 * Direct reclaim and kswapd have to scan all memory
2274 * cgroups to fulfill the overall scan target for the
2277 * Limit reclaim, on the other hand, only cares about
2278 * nr_to_reclaim pages to be reclaimed and it will
2279 * retry with decreasing priority if one round over the
2280 * whole hierarchy is not sufficient.
2282 if (!global_reclaim(sc
) &&
2283 sc
->nr_reclaimed
>= sc
->nr_to_reclaim
) {
2284 mem_cgroup_iter_break(root
, memcg
);
2287 memcg
= mem_cgroup_iter(root
, memcg
, &reclaim
);
2290 vmpressure(sc
->gfp_mask
, sc
->target_mem_cgroup
,
2291 sc
->nr_scanned
- nr_scanned
,
2292 sc
->nr_reclaimed
- nr_reclaimed
);
2294 if (sc
->nr_reclaimed
- nr_reclaimed
)
2297 } while (should_continue_reclaim(zone
, sc
->nr_reclaimed
- nr_reclaimed
,
2298 sc
->nr_scanned
- nr_scanned
, sc
));
2303 /* Returns true if compaction should go ahead for a high-order request */
2304 static inline bool compaction_ready(struct zone
*zone
, int order
)
2306 unsigned long balance_gap
, watermark
;
2310 * Compaction takes time to run and there are potentially other
2311 * callers using the pages just freed. Continue reclaiming until
2312 * there is a buffer of free pages available to give compaction
2313 * a reasonable chance of completing and allocating the page
2315 balance_gap
= min(low_wmark_pages(zone
), DIV_ROUND_UP(
2316 zone
->managed_pages
, KSWAPD_ZONE_BALANCE_GAP_RATIO
));
2317 watermark
= high_wmark_pages(zone
) + balance_gap
+ (2UL << order
);
2318 watermark_ok
= zone_watermark_ok_safe(zone
, 0, watermark
, 0, 0);
2321 * If compaction is deferred, reclaim up to a point where
2322 * compaction will have a chance of success when re-enabled
2324 if (compaction_deferred(zone
, order
))
2325 return watermark_ok
;
2327 /* If compaction is not ready to start, keep reclaiming */
2328 if (!compaction_suitable(zone
, order
))
2331 return watermark_ok
;
2335 * This is the direct reclaim path, for page-allocating processes. We only
2336 * try to reclaim pages from zones which will satisfy the caller's allocation
2339 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2341 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2343 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2344 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2345 * zone defense algorithm.
2347 * If a zone is deemed to be full of pinned pages then just give it a light
2348 * scan then give up on it.
2350 * Returns true if a zone was reclaimable.
2352 static bool shrink_zones(struct zonelist
*zonelist
, struct scan_control
*sc
)
2356 unsigned long nr_soft_reclaimed
;
2357 unsigned long nr_soft_scanned
;
2358 unsigned long lru_pages
= 0;
2359 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2361 struct shrink_control shrink
= {
2362 .gfp_mask
= sc
->gfp_mask
,
2364 enum zone_type requested_highidx
= gfp_zone(sc
->gfp_mask
);
2365 bool reclaimable
= false;
2368 * If the number of buffer_heads in the machine exceeds the maximum
2369 * allowed level, force direct reclaim to scan the highmem zone as
2370 * highmem pages could be pinning lowmem pages storing buffer_heads
2372 orig_mask
= sc
->gfp_mask
;
2373 if (buffer_heads_over_limit
)
2374 sc
->gfp_mask
|= __GFP_HIGHMEM
;
2376 nodes_clear(shrink
.nodes_to_scan
);
2378 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2379 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2380 if (!populated_zone(zone
))
2383 * Take care memory controller reclaiming has small influence
2386 if (global_reclaim(sc
)) {
2387 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2390 lru_pages
+= zone_reclaimable_pages(zone
);
2391 node_set(zone_to_nid(zone
), shrink
.nodes_to_scan
);
2393 if (sc
->priority
!= DEF_PRIORITY
&&
2394 !zone_reclaimable(zone
))
2395 continue; /* Let kswapd poll it */
2398 * If we already have plenty of memory free for
2399 * compaction in this zone, don't free any more.
2400 * Even though compaction is invoked for any
2401 * non-zero order, only frequent costly order
2402 * reclamation is disruptive enough to become a
2403 * noticeable problem, like transparent huge
2406 if (IS_ENABLED(CONFIG_COMPACTION
) &&
2407 sc
->order
> PAGE_ALLOC_COSTLY_ORDER
&&
2408 zonelist_zone_idx(z
) <= requested_highidx
&&
2409 compaction_ready(zone
, sc
->order
)) {
2410 sc
->compaction_ready
= true;
2415 * This steals pages from memory cgroups over softlimit
2416 * and returns the number of reclaimed pages and
2417 * scanned pages. This works for global memory pressure
2418 * and balancing, not for a memcg's limit.
2420 nr_soft_scanned
= 0;
2421 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2422 sc
->order
, sc
->gfp_mask
,
2424 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
2425 sc
->nr_scanned
+= nr_soft_scanned
;
2426 if (nr_soft_reclaimed
)
2428 /* need some check for avoid more shrink_zone() */
2431 if (shrink_zone(zone
, sc
))
2434 if (global_reclaim(sc
) &&
2435 !reclaimable
&& zone_reclaimable(zone
))
2440 * Don't shrink slabs when reclaiming memory from over limit cgroups
2441 * but do shrink slab at least once when aborting reclaim for
2442 * compaction to avoid unevenly scanning file/anon LRU pages over slab
2445 if (global_reclaim(sc
)) {
2446 shrink_slab(&shrink
, sc
->nr_scanned
, lru_pages
);
2447 if (reclaim_state
) {
2448 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2449 reclaim_state
->reclaimed_slab
= 0;
2454 * Restore to original mask to avoid the impact on the caller if we
2455 * promoted it to __GFP_HIGHMEM.
2457 sc
->gfp_mask
= orig_mask
;
2463 * This is the main entry point to direct page reclaim.
2465 * If a full scan of the inactive list fails to free enough memory then we
2466 * are "out of memory" and something needs to be killed.
2468 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2469 * high - the zone may be full of dirty or under-writeback pages, which this
2470 * caller can't do much about. We kick the writeback threads and take explicit
2471 * naps in the hope that some of these pages can be written. But if the
2472 * allocating task holds filesystem locks which prevent writeout this might not
2473 * work, and the allocation attempt will fail.
2475 * returns: 0, if no pages reclaimed
2476 * else, the number of pages reclaimed
2478 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2479 struct scan_control
*sc
)
2481 unsigned long total_scanned
= 0;
2482 unsigned long writeback_threshold
;
2483 bool zones_reclaimable
;
2485 delayacct_freepages_start();
2487 if (global_reclaim(sc
))
2488 count_vm_event(ALLOCSTALL
);
2491 vmpressure_prio(sc
->gfp_mask
, sc
->target_mem_cgroup
,
2494 zones_reclaimable
= shrink_zones(zonelist
, sc
);
2496 total_scanned
+= sc
->nr_scanned
;
2497 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
2500 if (sc
->compaction_ready
)
2504 * If we're getting trouble reclaiming, start doing
2505 * writepage even in laptop mode.
2507 if (sc
->priority
< DEF_PRIORITY
- 2)
2508 sc
->may_writepage
= 1;
2511 * Try to write back as many pages as we just scanned. This
2512 * tends to cause slow streaming writers to write data to the
2513 * disk smoothly, at the dirtying rate, which is nice. But
2514 * that's undesirable in laptop mode, where we *want* lumpy
2515 * writeout. So in laptop mode, write out the whole world.
2517 writeback_threshold
= sc
->nr_to_reclaim
+ sc
->nr_to_reclaim
/ 2;
2518 if (total_scanned
> writeback_threshold
) {
2519 wakeup_flusher_threads(laptop_mode
? 0 : total_scanned
,
2520 WB_REASON_TRY_TO_FREE_PAGES
);
2521 sc
->may_writepage
= 1;
2523 } while (--sc
->priority
>= 0);
2525 delayacct_freepages_end();
2527 if (sc
->nr_reclaimed
)
2528 return sc
->nr_reclaimed
;
2530 /* Aborted reclaim to try compaction? don't OOM, then */
2531 if (sc
->compaction_ready
)
2534 /* Any of the zones still reclaimable? Don't OOM. */
2535 if (zones_reclaimable
)
2541 static bool pfmemalloc_watermark_ok(pg_data_t
*pgdat
)
2544 unsigned long pfmemalloc_reserve
= 0;
2545 unsigned long free_pages
= 0;
2549 for (i
= 0; i
<= ZONE_NORMAL
; i
++) {
2550 zone
= &pgdat
->node_zones
[i
];
2551 if (!populated_zone(zone
))
2554 pfmemalloc_reserve
+= min_wmark_pages(zone
);
2555 free_pages
+= zone_page_state(zone
, NR_FREE_PAGES
);
2558 /* If there are no reserves (unexpected config) then do not throttle */
2559 if (!pfmemalloc_reserve
)
2562 wmark_ok
= free_pages
> pfmemalloc_reserve
/ 2;
2564 /* kswapd must be awake if processes are being throttled */
2565 if (!wmark_ok
&& waitqueue_active(&pgdat
->kswapd_wait
)) {
2566 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
,
2567 (enum zone_type
)ZONE_NORMAL
);
2568 wake_up_interruptible(&pgdat
->kswapd_wait
);
2575 * Throttle direct reclaimers if backing storage is backed by the network
2576 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
2577 * depleted. kswapd will continue to make progress and wake the processes
2578 * when the low watermark is reached.
2580 * Returns true if a fatal signal was delivered during throttling. If this
2581 * happens, the page allocator should not consider triggering the OOM killer.
2583 static bool throttle_direct_reclaim(gfp_t gfp_mask
, struct zonelist
*zonelist
,
2584 nodemask_t
*nodemask
)
2588 pg_data_t
*pgdat
= NULL
;
2591 * Kernel threads should not be throttled as they may be indirectly
2592 * responsible for cleaning pages necessary for reclaim to make forward
2593 * progress. kjournald for example may enter direct reclaim while
2594 * committing a transaction where throttling it could forcing other
2595 * processes to block on log_wait_commit().
2597 if (current
->flags
& PF_KTHREAD
)
2601 * If a fatal signal is pending, this process should not throttle.
2602 * It should return quickly so it can exit and free its memory
2604 if (fatal_signal_pending(current
))
2608 * Check if the pfmemalloc reserves are ok by finding the first node
2609 * with a usable ZONE_NORMAL or lower zone. The expectation is that
2610 * GFP_KERNEL will be required for allocating network buffers when
2611 * swapping over the network so ZONE_HIGHMEM is unusable.
2613 * Throttling is based on the first usable node and throttled processes
2614 * wait on a queue until kswapd makes progress and wakes them. There
2615 * is an affinity then between processes waking up and where reclaim
2616 * progress has been made assuming the process wakes on the same node.
2617 * More importantly, processes running on remote nodes will not compete
2618 * for remote pfmemalloc reserves and processes on different nodes
2619 * should make reasonable progress.
2621 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2622 gfp_mask
, nodemask
) {
2623 if (zone_idx(zone
) > ZONE_NORMAL
)
2626 /* Throttle based on the first usable node */
2627 pgdat
= zone
->zone_pgdat
;
2628 if (pfmemalloc_watermark_ok(pgdat
))
2633 /* If no zone was usable by the allocation flags then do not throttle */
2637 /* Account for the throttling */
2638 count_vm_event(PGSCAN_DIRECT_THROTTLE
);
2641 * If the caller cannot enter the filesystem, it's possible that it
2642 * is due to the caller holding an FS lock or performing a journal
2643 * transaction in the case of a filesystem like ext[3|4]. In this case,
2644 * it is not safe to block on pfmemalloc_wait as kswapd could be
2645 * blocked waiting on the same lock. Instead, throttle for up to a
2646 * second before continuing.
2648 if (!(gfp_mask
& __GFP_FS
)) {
2649 wait_event_interruptible_timeout(pgdat
->pfmemalloc_wait
,
2650 pfmemalloc_watermark_ok(pgdat
), HZ
);
2655 /* Throttle until kswapd wakes the process */
2656 wait_event_killable(zone
->zone_pgdat
->pfmemalloc_wait
,
2657 pfmemalloc_watermark_ok(pgdat
));
2660 if (fatal_signal_pending(current
))
2667 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
2668 gfp_t gfp_mask
, nodemask_t
*nodemask
)
2670 unsigned long nr_reclaimed
;
2671 struct scan_control sc
= {
2672 .gfp_mask
= (gfp_mask
= memalloc_noio_flags(gfp_mask
)),
2673 .may_writepage
= !laptop_mode
,
2674 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2678 .priority
= DEF_PRIORITY
,
2679 .target_mem_cgroup
= NULL
,
2680 .nodemask
= nodemask
,
2684 * Do not enter reclaim if fatal signal was delivered while throttled.
2685 * 1 is returned so that the page allocator does not OOM kill at this
2688 if (throttle_direct_reclaim(gfp_mask
, zonelist
, nodemask
))
2691 trace_mm_vmscan_direct_reclaim_begin(order
,
2695 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2697 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
2699 return nr_reclaimed
;
2704 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup
*memcg
,
2705 gfp_t gfp_mask
, bool noswap
,
2707 unsigned long *nr_scanned
)
2709 struct scan_control sc
= {
2711 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2712 .may_writepage
= !laptop_mode
,
2714 .may_swap
= !noswap
,
2717 .swappiness
= mem_cgroup_swappiness(memcg
),
2718 .target_mem_cgroup
= memcg
,
2720 struct lruvec
*lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
2722 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2723 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2725 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc
.order
,
2730 * NOTE: Although we can get the priority field, using it
2731 * here is not a good idea, since it limits the pages we can scan.
2732 * if we don't reclaim here, the shrink_zone from balance_pgdat
2733 * will pick up pages from other mem cgroup's as well. We hack
2734 * the priority and make it zero.
2736 shrink_lruvec(lruvec
, &sc
);
2738 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
2740 *nr_scanned
= sc
.nr_scanned
;
2741 return sc
.nr_reclaimed
;
2744 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*memcg
,
2748 struct zonelist
*zonelist
;
2749 unsigned long nr_reclaimed
;
2751 struct scan_control sc
= {
2752 .may_writepage
= !laptop_mode
,
2754 .may_swap
= !noswap
,
2755 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2757 .priority
= DEF_PRIORITY
,
2758 .target_mem_cgroup
= memcg
,
2759 .nodemask
= NULL
, /* we don't care the placement */
2760 .gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2761 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
2765 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2766 * take care of from where we get pages. So the node where we start the
2767 * scan does not need to be the current node.
2769 nid
= mem_cgroup_select_victim_node(memcg
);
2771 zonelist
= NODE_DATA(nid
)->node_zonelists
;
2773 trace_mm_vmscan_memcg_reclaim_begin(0,
2777 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2779 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
2781 return nr_reclaimed
;
2785 static void age_active_anon(struct zone
*zone
, struct scan_control
*sc
)
2787 struct mem_cgroup
*memcg
;
2789 if (!total_swap_pages
)
2792 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
2794 struct lruvec
*lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
2796 if (inactive_anon_is_low(lruvec
))
2797 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
2798 sc
, LRU_ACTIVE_ANON
);
2800 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
2804 static bool zone_balanced(struct zone
*zone
, int order
,
2805 unsigned long balance_gap
, int classzone_idx
)
2807 if (!zone_watermark_ok_safe(zone
, order
, high_wmark_pages(zone
) +
2808 balance_gap
, classzone_idx
, 0))
2811 if (IS_ENABLED(CONFIG_COMPACTION
) && order
&&
2812 !compaction_suitable(zone
, order
))
2819 * pgdat_balanced() is used when checking if a node is balanced.
2821 * For order-0, all zones must be balanced!
2823 * For high-order allocations only zones that meet watermarks and are in a
2824 * zone allowed by the callers classzone_idx are added to balanced_pages. The
2825 * total of balanced pages must be at least 25% of the zones allowed by
2826 * classzone_idx for the node to be considered balanced. Forcing all zones to
2827 * be balanced for high orders can cause excessive reclaim when there are
2829 * The choice of 25% is due to
2830 * o a 16M DMA zone that is balanced will not balance a zone on any
2831 * reasonable sized machine
2832 * o On all other machines, the top zone must be at least a reasonable
2833 * percentage of the middle zones. For example, on 32-bit x86, highmem
2834 * would need to be at least 256M for it to be balance a whole node.
2835 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2836 * to balance a node on its own. These seemed like reasonable ratios.
2838 static bool pgdat_balanced(pg_data_t
*pgdat
, int order
, int classzone_idx
)
2840 unsigned long managed_pages
= 0;
2841 unsigned long balanced_pages
= 0;
2844 /* Check the watermark levels */
2845 for (i
= 0; i
<= classzone_idx
; i
++) {
2846 struct zone
*zone
= pgdat
->node_zones
+ i
;
2848 if (!populated_zone(zone
))
2851 managed_pages
+= zone
->managed_pages
;
2854 * A special case here:
2856 * balance_pgdat() skips over all_unreclaimable after
2857 * DEF_PRIORITY. Effectively, it considers them balanced so
2858 * they must be considered balanced here as well!
2860 if (!zone_reclaimable(zone
)) {
2861 balanced_pages
+= zone
->managed_pages
;
2865 if (zone_balanced(zone
, order
, 0, i
))
2866 balanced_pages
+= zone
->managed_pages
;
2872 return balanced_pages
>= (managed_pages
>> 2);
2878 * Prepare kswapd for sleeping. This verifies that there are no processes
2879 * waiting in throttle_direct_reclaim() and that watermarks have been met.
2881 * Returns true if kswapd is ready to sleep
2883 static bool prepare_kswapd_sleep(pg_data_t
*pgdat
, int order
, long remaining
,
2886 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2891 * There is a potential race between when kswapd checks its watermarks
2892 * and a process gets throttled. There is also a potential race if
2893 * processes get throttled, kswapd wakes, a large process exits therby
2894 * balancing the zones that causes kswapd to miss a wakeup. If kswapd
2895 * is going to sleep, no process should be sleeping on pfmemalloc_wait
2896 * so wake them now if necessary. If necessary, processes will wake
2897 * kswapd and get throttled again
2899 if (waitqueue_active(&pgdat
->pfmemalloc_wait
)) {
2900 wake_up(&pgdat
->pfmemalloc_wait
);
2904 return pgdat_balanced(pgdat
, order
, classzone_idx
);
2908 * kswapd shrinks the zone by the number of pages required to reach
2909 * the high watermark.
2911 * Returns true if kswapd scanned at least the requested number of pages to
2912 * reclaim or if the lack of progress was due to pages under writeback.
2913 * This is used to determine if the scanning priority needs to be raised.
2915 static bool kswapd_shrink_zone(struct zone
*zone
,
2917 struct scan_control
*sc
,
2918 unsigned long lru_pages
,
2919 unsigned long *nr_attempted
)
2921 int testorder
= sc
->order
;
2922 unsigned long balance_gap
;
2923 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2924 struct shrink_control shrink
= {
2925 .gfp_mask
= sc
->gfp_mask
,
2927 bool lowmem_pressure
;
2929 /* Reclaim above the high watermark. */
2930 sc
->nr_to_reclaim
= max(SWAP_CLUSTER_MAX
, high_wmark_pages(zone
));
2933 * Kswapd reclaims only single pages with compaction enabled. Trying
2934 * too hard to reclaim until contiguous free pages have become
2935 * available can hurt performance by evicting too much useful data
2936 * from memory. Do not reclaim more than needed for compaction.
2938 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
2939 compaction_suitable(zone
, sc
->order
) !=
2944 * We put equal pressure on every zone, unless one zone has way too
2945 * many pages free already. The "too many pages" is defined as the
2946 * high wmark plus a "gap" where the gap is either the low
2947 * watermark or 1% of the zone, whichever is smaller.
2949 balance_gap
= min(low_wmark_pages(zone
), DIV_ROUND_UP(
2950 zone
->managed_pages
, KSWAPD_ZONE_BALANCE_GAP_RATIO
));
2953 * If there is no low memory pressure or the zone is balanced then no
2954 * reclaim is necessary
2956 lowmem_pressure
= (buffer_heads_over_limit
&& is_highmem(zone
));
2957 if (!lowmem_pressure
&& zone_balanced(zone
, testorder
,
2958 balance_gap
, classzone_idx
))
2961 shrink_zone(zone
, sc
);
2962 nodes_clear(shrink
.nodes_to_scan
);
2963 node_set(zone_to_nid(zone
), shrink
.nodes_to_scan
);
2965 reclaim_state
->reclaimed_slab
= 0;
2966 shrink_slab(&shrink
, sc
->nr_scanned
, lru_pages
);
2967 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2969 /* Account for the number of pages attempted to reclaim */
2970 *nr_attempted
+= sc
->nr_to_reclaim
;
2972 zone_clear_flag(zone
, ZONE_WRITEBACK
);
2975 * If a zone reaches its high watermark, consider it to be no longer
2976 * congested. It's possible there are dirty pages backed by congested
2977 * BDIs but as pressure is relieved, speculatively avoid congestion
2980 if (zone_reclaimable(zone
) &&
2981 zone_balanced(zone
, testorder
, 0, classzone_idx
)) {
2982 zone_clear_flag(zone
, ZONE_CONGESTED
);
2983 zone_clear_flag(zone
, ZONE_TAIL_LRU_DIRTY
);
2986 return sc
->nr_scanned
>= sc
->nr_to_reclaim
;
2990 * For kswapd, balance_pgdat() will work across all this node's zones until
2991 * they are all at high_wmark_pages(zone).
2993 * Returns the final order kswapd was reclaiming at
2995 * There is special handling here for zones which are full of pinned pages.
2996 * This can happen if the pages are all mlocked, or if they are all used by
2997 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2998 * What we do is to detect the case where all pages in the zone have been
2999 * scanned twice and there has been zero successful reclaim. Mark the zone as
3000 * dead and from now on, only perform a short scan. Basically we're polling
3001 * the zone for when the problem goes away.
3003 * kswapd scans the zones in the highmem->normal->dma direction. It skips
3004 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
3005 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
3006 * lower zones regardless of the number of free pages in the lower zones. This
3007 * interoperates with the page allocator fallback scheme to ensure that aging
3008 * of pages is balanced across the zones.
3010 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
,
3014 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
3015 unsigned long nr_soft_reclaimed
;
3016 unsigned long nr_soft_scanned
;
3017 struct scan_control sc
= {
3018 .gfp_mask
= GFP_KERNEL
,
3019 .priority
= DEF_PRIORITY
,
3022 .may_writepage
= !laptop_mode
,
3024 .target_mem_cgroup
= NULL
,
3026 count_vm_event(PAGEOUTRUN
);
3029 unsigned long lru_pages
= 0;
3030 unsigned long nr_attempted
= 0;
3031 bool raise_priority
= true;
3032 bool pgdat_needs_compaction
= (order
> 0);
3034 sc
.nr_reclaimed
= 0;
3037 * Scan in the highmem->dma direction for the highest
3038 * zone which needs scanning
3040 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
3041 struct zone
*zone
= pgdat
->node_zones
+ i
;
3043 if (!populated_zone(zone
))
3046 if (sc
.priority
!= DEF_PRIORITY
&&
3047 !zone_reclaimable(zone
))
3051 * Do some background aging of the anon list, to give
3052 * pages a chance to be referenced before reclaiming.
3054 age_active_anon(zone
, &sc
);
3057 * If the number of buffer_heads in the machine
3058 * exceeds the maximum allowed level and this node
3059 * has a highmem zone, force kswapd to reclaim from
3060 * it to relieve lowmem pressure.
3062 if (buffer_heads_over_limit
&& is_highmem_idx(i
)) {
3067 if (!zone_balanced(zone
, order
, 0, 0)) {
3072 * If balanced, clear the dirty and congested
3075 zone_clear_flag(zone
, ZONE_CONGESTED
);
3076 zone_clear_flag(zone
, ZONE_TAIL_LRU_DIRTY
);
3083 for (i
= 0; i
<= end_zone
; i
++) {
3084 struct zone
*zone
= pgdat
->node_zones
+ i
;
3086 if (!populated_zone(zone
))
3089 lru_pages
+= zone_reclaimable_pages(zone
);
3092 * If any zone is currently balanced then kswapd will
3093 * not call compaction as it is expected that the
3094 * necessary pages are already available.
3096 if (pgdat_needs_compaction
&&
3097 zone_watermark_ok(zone
, order
,
3098 low_wmark_pages(zone
),
3100 pgdat_needs_compaction
= false;
3104 * If we're getting trouble reclaiming, start doing writepage
3105 * even in laptop mode.
3107 if (sc
.priority
< DEF_PRIORITY
- 2)
3108 sc
.may_writepage
= 1;
3111 * Now scan the zone in the dma->highmem direction, stopping
3112 * at the last zone which needs scanning.
3114 * We do this because the page allocator works in the opposite
3115 * direction. This prevents the page allocator from allocating
3116 * pages behind kswapd's direction of progress, which would
3117 * cause too much scanning of the lower zones.
3119 for (i
= 0; i
<= end_zone
; i
++) {
3120 struct zone
*zone
= pgdat
->node_zones
+ i
;
3122 if (!populated_zone(zone
))
3125 if (sc
.priority
!= DEF_PRIORITY
&&
3126 !zone_reclaimable(zone
))
3131 nr_soft_scanned
= 0;
3133 * Call soft limit reclaim before calling shrink_zone.
3135 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
3138 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
3141 * There should be no need to raise the scanning
3142 * priority if enough pages are already being scanned
3143 * that that high watermark would be met at 100%
3146 if (kswapd_shrink_zone(zone
, end_zone
, &sc
,
3147 lru_pages
, &nr_attempted
))
3148 raise_priority
= false;
3152 * If the low watermark is met there is no need for processes
3153 * to be throttled on pfmemalloc_wait as they should not be
3154 * able to safely make forward progress. Wake them
3156 if (waitqueue_active(&pgdat
->pfmemalloc_wait
) &&
3157 pfmemalloc_watermark_ok(pgdat
))
3158 wake_up(&pgdat
->pfmemalloc_wait
);
3161 * Fragmentation may mean that the system cannot be rebalanced
3162 * for high-order allocations in all zones. If twice the
3163 * allocation size has been reclaimed and the zones are still
3164 * not balanced then recheck the watermarks at order-0 to
3165 * prevent kswapd reclaiming excessively. Assume that a
3166 * process requested a high-order can direct reclaim/compact.
3168 if (order
&& sc
.nr_reclaimed
>= 2UL << order
)
3169 order
= sc
.order
= 0;
3171 /* Check if kswapd should be suspending */
3172 if (try_to_freeze() || kthread_should_stop())
3176 * Compact if necessary and kswapd is reclaiming at least the
3177 * high watermark number of pages as requsted
3179 if (pgdat_needs_compaction
&& sc
.nr_reclaimed
> nr_attempted
)
3180 compact_pgdat(pgdat
, order
);
3183 * Raise priority if scanning rate is too low or there was no
3184 * progress in reclaiming pages
3186 if (raise_priority
|| !sc
.nr_reclaimed
)
3188 } while (sc
.priority
>= 1 &&
3189 !pgdat_balanced(pgdat
, order
, *classzone_idx
));
3193 * Return the order we were reclaiming at so prepare_kswapd_sleep()
3194 * makes a decision on the order we were last reclaiming at. However,
3195 * if another caller entered the allocator slow path while kswapd
3196 * was awake, order will remain at the higher level
3198 *classzone_idx
= end_zone
;
3202 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
3207 if (freezing(current
) || kthread_should_stop())
3210 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
3212 /* Try to sleep for a short interval */
3213 if (prepare_kswapd_sleep(pgdat
, order
, remaining
, classzone_idx
)) {
3214 remaining
= schedule_timeout(HZ
/10);
3215 finish_wait(&pgdat
->kswapd_wait
, &wait
);
3216 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
3220 * After a short sleep, check if it was a premature sleep. If not, then
3221 * go fully to sleep until explicitly woken up.
3223 if (prepare_kswapd_sleep(pgdat
, order
, remaining
, classzone_idx
)) {
3224 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
3227 * vmstat counters are not perfectly accurate and the estimated
3228 * value for counters such as NR_FREE_PAGES can deviate from the
3229 * true value by nr_online_cpus * threshold. To avoid the zone
3230 * watermarks being breached while under pressure, we reduce the
3231 * per-cpu vmstat threshold while kswapd is awake and restore
3232 * them before going back to sleep.
3234 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
3237 * Compaction records what page blocks it recently failed to
3238 * isolate pages from and skips them in the future scanning.
3239 * When kswapd is going to sleep, it is reasonable to assume
3240 * that pages and compaction may succeed so reset the cache.
3242 reset_isolation_suitable(pgdat
);
3244 if (!kthread_should_stop())
3247 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
3250 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
3252 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
3254 finish_wait(&pgdat
->kswapd_wait
, &wait
);
3258 * The background pageout daemon, started as a kernel thread
3259 * from the init process.
3261 * This basically trickles out pages so that we have _some_
3262 * free memory available even if there is no other activity
3263 * that frees anything up. This is needed for things like routing
3264 * etc, where we otherwise might have all activity going on in
3265 * asynchronous contexts that cannot page things out.
3267 * If there are applications that are active memory-allocators
3268 * (most normal use), this basically shouldn't matter.
3270 static int kswapd(void *p
)
3272 unsigned long order
, new_order
;
3273 unsigned balanced_order
;
3274 int classzone_idx
, new_classzone_idx
;
3275 int balanced_classzone_idx
;
3276 pg_data_t
*pgdat
= (pg_data_t
*)p
;
3277 struct task_struct
*tsk
= current
;
3279 struct reclaim_state reclaim_state
= {
3280 .reclaimed_slab
= 0,
3282 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
3284 lockdep_set_current_reclaim_state(GFP_KERNEL
);
3286 if (!cpumask_empty(cpumask
))
3287 set_cpus_allowed_ptr(tsk
, cpumask
);
3288 current
->reclaim_state
= &reclaim_state
;
3291 * Tell the memory management that we're a "memory allocator",
3292 * and that if we need more memory we should get access to it
3293 * regardless (see "__alloc_pages()"). "kswapd" should
3294 * never get caught in the normal page freeing logic.
3296 * (Kswapd normally doesn't need memory anyway, but sometimes
3297 * you need a small amount of memory in order to be able to
3298 * page out something else, and this flag essentially protects
3299 * us from recursively trying to free more memory as we're
3300 * trying to free the first piece of memory in the first place).
3302 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
3305 order
= new_order
= 0;
3307 classzone_idx
= new_classzone_idx
= pgdat
->nr_zones
- 1;
3308 balanced_classzone_idx
= classzone_idx
;
3313 * If the last balance_pgdat was unsuccessful it's unlikely a
3314 * new request of a similar or harder type will succeed soon
3315 * so consider going to sleep on the basis we reclaimed at
3317 if (balanced_classzone_idx
>= new_classzone_idx
&&
3318 balanced_order
== new_order
) {
3319 new_order
= pgdat
->kswapd_max_order
;
3320 new_classzone_idx
= pgdat
->classzone_idx
;
3321 pgdat
->kswapd_max_order
= 0;
3322 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
3325 if (order
< new_order
|| classzone_idx
> new_classzone_idx
) {
3327 * Don't sleep if someone wants a larger 'order'
3328 * allocation or has tigher zone constraints
3331 classzone_idx
= new_classzone_idx
;
3333 kswapd_try_to_sleep(pgdat
, balanced_order
,
3334 balanced_classzone_idx
);
3335 order
= pgdat
->kswapd_max_order
;
3336 classzone_idx
= pgdat
->classzone_idx
;
3338 new_classzone_idx
= classzone_idx
;
3339 pgdat
->kswapd_max_order
= 0;
3340 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
3343 ret
= try_to_freeze();
3344 if (kthread_should_stop())
3348 * We can speed up thawing tasks if we don't call balance_pgdat
3349 * after returning from the refrigerator
3352 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, order
);
3353 balanced_classzone_idx
= classzone_idx
;
3354 balanced_order
= balance_pgdat(pgdat
, order
,
3355 &balanced_classzone_idx
);
3359 tsk
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
);
3360 current
->reclaim_state
= NULL
;
3361 lockdep_clear_current_reclaim_state();
3367 * A zone is low on free memory, so wake its kswapd task to service it.
3369 void wakeup_kswapd(struct zone
*zone
, int order
, enum zone_type classzone_idx
)
3373 if (!populated_zone(zone
))
3376 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
3378 pgdat
= zone
->zone_pgdat
;
3379 if (pgdat
->kswapd_max_order
< order
) {
3380 pgdat
->kswapd_max_order
= order
;
3381 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
, classzone_idx
);
3383 if (!waitqueue_active(&pgdat
->kswapd_wait
))
3385 if (zone_balanced(zone
, order
, 0, 0))
3388 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, zone_idx(zone
), order
);
3389 wake_up_interruptible(&pgdat
->kswapd_wait
);
3392 #ifdef CONFIG_HIBERNATION
3394 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3397 * Rather than trying to age LRUs the aim is to preserve the overall
3398 * LRU order by reclaiming preferentially
3399 * inactive > active > active referenced > active mapped
3401 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
3403 struct reclaim_state reclaim_state
;
3404 struct scan_control sc
= {
3405 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
3409 .nr_to_reclaim
= nr_to_reclaim
,
3410 .hibernation_mode
= 1,
3412 .priority
= DEF_PRIORITY
,
3414 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
3415 struct task_struct
*p
= current
;
3416 unsigned long nr_reclaimed
;
3418 p
->flags
|= PF_MEMALLOC
;
3419 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
3420 reclaim_state
.reclaimed_slab
= 0;
3421 p
->reclaim_state
= &reclaim_state
;
3423 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3425 p
->reclaim_state
= NULL
;
3426 lockdep_clear_current_reclaim_state();
3427 p
->flags
&= ~PF_MEMALLOC
;
3429 return nr_reclaimed
;
3431 #endif /* CONFIG_HIBERNATION */
3433 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3434 not required for correctness. So if the last cpu in a node goes
3435 away, we get changed to run anywhere: as the first one comes back,
3436 restore their cpu bindings. */
3437 static int cpu_callback(struct notifier_block
*nfb
, unsigned long action
,
3442 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
3443 for_each_node_state(nid
, N_MEMORY
) {
3444 pg_data_t
*pgdat
= NODE_DATA(nid
);
3445 const struct cpumask
*mask
;
3447 mask
= cpumask_of_node(pgdat
->node_id
);
3449 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
3450 /* One of our CPUs online: restore mask */
3451 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
3458 * This kswapd start function will be called by init and node-hot-add.
3459 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3461 int kswapd_run(int nid
)
3463 pg_data_t
*pgdat
= NODE_DATA(nid
);
3469 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
3470 if (IS_ERR(pgdat
->kswapd
)) {
3471 /* failure at boot is fatal */
3472 BUG_ON(system_state
== SYSTEM_BOOTING
);
3473 pr_err("Failed to start kswapd on node %d\n", nid
);
3474 ret
= PTR_ERR(pgdat
->kswapd
);
3475 pgdat
->kswapd
= NULL
;
3481 * Called by memory hotplug when all memory in a node is offlined. Caller must
3482 * hold mem_hotplug_begin/end().
3484 void kswapd_stop(int nid
)
3486 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
3489 kthread_stop(kswapd
);
3490 NODE_DATA(nid
)->kswapd
= NULL
;
3494 static int __init
kswapd_init(void)
3499 for_each_node_state(nid
, N_MEMORY
)
3501 hotcpu_notifier(cpu_callback
, 0);
3505 module_init(kswapd_init
)
3511 * If non-zero call zone_reclaim when the number of free pages falls below
3514 int zone_reclaim_mode __read_mostly
;
3516 #define RECLAIM_OFF 0
3517 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3518 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3519 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3522 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3523 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3526 #define ZONE_RECLAIM_PRIORITY 4
3529 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3532 int sysctl_min_unmapped_ratio
= 1;
3535 * If the number of slab pages in a zone grows beyond this percentage then
3536 * slab reclaim needs to occur.
3538 int sysctl_min_slab_ratio
= 5;
3540 static inline unsigned long zone_unmapped_file_pages(struct zone
*zone
)
3542 unsigned long file_mapped
= zone_page_state(zone
, NR_FILE_MAPPED
);
3543 unsigned long file_lru
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
3544 zone_page_state(zone
, NR_ACTIVE_FILE
);
3547 * It's possible for there to be more file mapped pages than
3548 * accounted for by the pages on the file LRU lists because
3549 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3551 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
3554 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3555 static long zone_pagecache_reclaimable(struct zone
*zone
)
3557 long nr_pagecache_reclaimable
;
3561 * If RECLAIM_SWAP is set, then all file pages are considered
3562 * potentially reclaimable. Otherwise, we have to worry about
3563 * pages like swapcache and zone_unmapped_file_pages() provides
3566 if (zone_reclaim_mode
& RECLAIM_SWAP
)
3567 nr_pagecache_reclaimable
= zone_page_state(zone
, NR_FILE_PAGES
);
3569 nr_pagecache_reclaimable
= zone_unmapped_file_pages(zone
);
3571 /* If we can't clean pages, remove dirty pages from consideration */
3572 if (!(zone_reclaim_mode
& RECLAIM_WRITE
))
3573 delta
+= zone_page_state(zone
, NR_FILE_DIRTY
);
3575 /* Watch for any possible underflows due to delta */
3576 if (unlikely(delta
> nr_pagecache_reclaimable
))
3577 delta
= nr_pagecache_reclaimable
;
3579 return nr_pagecache_reclaimable
- delta
;
3583 * Try to free up some pages from this zone through reclaim.
3585 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3587 /* Minimum pages needed in order to stay on node */
3588 const unsigned long nr_pages
= 1 << order
;
3589 struct task_struct
*p
= current
;
3590 struct reclaim_state reclaim_state
;
3591 struct scan_control sc
= {
3592 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
3593 .may_unmap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
3595 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
3596 .gfp_mask
= (gfp_mask
= memalloc_noio_flags(gfp_mask
)),
3598 .priority
= ZONE_RECLAIM_PRIORITY
,
3600 struct shrink_control shrink
= {
3601 .gfp_mask
= sc
.gfp_mask
,
3603 unsigned long nr_slab_pages0
, nr_slab_pages1
;
3607 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3608 * and we also need to be able to write out pages for RECLAIM_WRITE
3611 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
3612 lockdep_set_current_reclaim_state(gfp_mask
);
3613 reclaim_state
.reclaimed_slab
= 0;
3614 p
->reclaim_state
= &reclaim_state
;
3616 if (zone_pagecache_reclaimable(zone
) > zone
->min_unmapped_pages
) {
3618 * Free memory by calling shrink zone with increasing
3619 * priorities until we have enough memory freed.
3622 shrink_zone(zone
, &sc
);
3623 } while (sc
.nr_reclaimed
< nr_pages
&& --sc
.priority
>= 0);
3626 nr_slab_pages0
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3627 if (nr_slab_pages0
> zone
->min_slab_pages
) {
3629 * shrink_slab() does not currently allow us to determine how
3630 * many pages were freed in this zone. So we take the current
3631 * number of slab pages and shake the slab until it is reduced
3632 * by the same nr_pages that we used for reclaiming unmapped
3635 nodes_clear(shrink
.nodes_to_scan
);
3636 node_set(zone_to_nid(zone
), shrink
.nodes_to_scan
);
3638 unsigned long lru_pages
= zone_reclaimable_pages(zone
);
3640 /* No reclaimable slab or very low memory pressure */
3641 if (!shrink_slab(&shrink
, sc
.nr_scanned
, lru_pages
))
3644 /* Freed enough memory */
3645 nr_slab_pages1
= zone_page_state(zone
,
3646 NR_SLAB_RECLAIMABLE
);
3647 if (nr_slab_pages1
+ nr_pages
<= nr_slab_pages0
)
3652 * Update nr_reclaimed by the number of slab pages we
3653 * reclaimed from this zone.
3655 nr_slab_pages1
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3656 if (nr_slab_pages1
< nr_slab_pages0
)
3657 sc
.nr_reclaimed
+= nr_slab_pages0
- nr_slab_pages1
;
3660 p
->reclaim_state
= NULL
;
3661 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
3662 lockdep_clear_current_reclaim_state();
3663 return sc
.nr_reclaimed
>= nr_pages
;
3666 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3672 * Zone reclaim reclaims unmapped file backed pages and
3673 * slab pages if we are over the defined limits.
3675 * A small portion of unmapped file backed pages is needed for
3676 * file I/O otherwise pages read by file I/O will be immediately
3677 * thrown out if the zone is overallocated. So we do not reclaim
3678 * if less than a specified percentage of the zone is used by
3679 * unmapped file backed pages.
3681 if (zone_pagecache_reclaimable(zone
) <= zone
->min_unmapped_pages
&&
3682 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) <= zone
->min_slab_pages
)
3683 return ZONE_RECLAIM_FULL
;
3685 if (!zone_reclaimable(zone
))
3686 return ZONE_RECLAIM_FULL
;
3689 * Do not scan if the allocation should not be delayed.
3691 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
3692 return ZONE_RECLAIM_NOSCAN
;
3695 * Only run zone reclaim on the local zone or on zones that do not
3696 * have associated processors. This will favor the local processor
3697 * over remote processors and spread off node memory allocations
3698 * as wide as possible.
3700 node_id
= zone_to_nid(zone
);
3701 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
3702 return ZONE_RECLAIM_NOSCAN
;
3704 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
3705 return ZONE_RECLAIM_NOSCAN
;
3707 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
3708 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);
3711 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
3718 * page_evictable - test whether a page is evictable
3719 * @page: the page to test
3721 * Test whether page is evictable--i.e., should be placed on active/inactive
3722 * lists vs unevictable list.
3724 * Reasons page might not be evictable:
3725 * (1) page's mapping marked unevictable
3726 * (2) page is part of an mlocked VMA
3729 int page_evictable(struct page
*page
)
3731 return !mapping_unevictable(page_mapping(page
)) && !PageMlocked(page
);
3736 * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
3737 * @pages: array of pages to check
3738 * @nr_pages: number of pages to check
3740 * Checks pages for evictability and moves them to the appropriate lru list.
3742 * This function is only used for SysV IPC SHM_UNLOCK.
3744 void check_move_unevictable_pages(struct page
**pages
, int nr_pages
)
3746 struct lruvec
*lruvec
;
3747 struct zone
*zone
= NULL
;
3752 for (i
= 0; i
< nr_pages
; i
++) {
3753 struct page
*page
= pages
[i
];
3754 struct zone
*pagezone
;
3757 pagezone
= page_zone(page
);
3758 if (pagezone
!= zone
) {
3760 spin_unlock_irq(&zone
->lru_lock
);
3762 spin_lock_irq(&zone
->lru_lock
);
3764 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
3766 if (!PageLRU(page
) || !PageUnevictable(page
))
3769 if (page_evictable(page
)) {
3770 enum lru_list lru
= page_lru_base_type(page
);
3772 VM_BUG_ON_PAGE(PageActive(page
), page
);
3773 ClearPageUnevictable(page
);
3774 del_page_from_lru_list(page
, lruvec
, LRU_UNEVICTABLE
);
3775 add_page_to_lru_list(page
, lruvec
, lru
);
3781 __count_vm_events(UNEVICTABLE_PGRESCUED
, pgrescued
);
3782 __count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
3783 spin_unlock_irq(&zone
->lru_lock
);
3786 #endif /* CONFIG_SHMEM */
3788 static void warn_scan_unevictable_pages(void)
3790 printk_once(KERN_WARNING
3791 "%s: The scan_unevictable_pages sysctl/node-interface has been "
3792 "disabled for lack of a legitimate use case. If you have "
3793 "one, please send an email to linux-mm@kvack.org.\n",
3798 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3799 * all nodes' unevictable lists for evictable pages
3801 unsigned long scan_unevictable_pages
;
3803 int scan_unevictable_handler(struct ctl_table
*table
, int write
,
3804 void __user
*buffer
,
3805 size_t *length
, loff_t
*ppos
)
3807 warn_scan_unevictable_pages();
3808 proc_doulongvec_minmax(table
, write
, buffer
, length
, ppos
);
3809 scan_unevictable_pages
= 0;
3815 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3816 * a specified node's per zone unevictable lists for evictable pages.
3819 static ssize_t
read_scan_unevictable_node(struct device
*dev
,
3820 struct device_attribute
*attr
,
3823 warn_scan_unevictable_pages();
3824 return sprintf(buf
, "0\n"); /* always zero; should fit... */
3827 static ssize_t
write_scan_unevictable_node(struct device
*dev
,
3828 struct device_attribute
*attr
,
3829 const char *buf
, size_t count
)
3831 warn_scan_unevictable_pages();
3836 static DEVICE_ATTR(scan_unevictable_pages
, S_IRUGO
| S_IWUSR
,
3837 read_scan_unevictable_node
,
3838 write_scan_unevictable_node
);
3840 int scan_unevictable_register_node(struct node
*node
)
3842 return device_create_file(&node
->dev
, &dev_attr_scan_unevictable_pages
);
3845 void scan_unevictable_unregister_node(struct node
*node
)
3847 device_remove_file(&node
->dev
, &dev_attr_scan_unevictable_pages
);