1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
7 * Swap reorganised 29.12.95, Stephen Tweedie.
8 * kswapd added: 7.1.96 sct
9 * Removed kswapd_ctl limits, and swap out as many pages as needed
10 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
11 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
12 * Multiqueue VM started 5.8.00, Rik van Riel.
15 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18 #include <linux/sched/mm.h>
19 #include <linux/module.h>
20 #include <linux/gfp.h>
21 #include <linux/kernel_stat.h>
22 #include <linux/swap.h>
23 #include <linux/pagemap.h>
24 #include <linux/init.h>
25 #include <linux/highmem.h>
26 #include <linux/vmpressure.h>
27 #include <linux/vmstat.h>
28 #include <linux/file.h>
29 #include <linux/writeback.h>
30 #include <linux/blkdev.h>
31 #include <linux/buffer_head.h> /* for try_to_release_page(),
32 buffer_heads_over_limit */
33 #include <linux/mm_inline.h>
34 #include <linux/backing-dev.h>
35 #include <linux/rmap.h>
36 #include <linux/topology.h>
37 #include <linux/cpu.h>
38 #include <linux/cpuset.h>
39 #include <linux/compaction.h>
40 #include <linux/notifier.h>
41 #include <linux/rwsem.h>
42 #include <linux/delay.h>
43 #include <linux/kthread.h>
44 #include <linux/freezer.h>
45 #include <linux/memcontrol.h>
46 #include <linux/delayacct.h>
47 #include <linux/sysctl.h>
48 #include <linux/oom.h>
49 #include <linux/pagevec.h>
50 #include <linux/prefetch.h>
51 #include <linux/printk.h>
52 #include <linux/dax.h>
53 #include <linux/psi.h>
55 #include <asm/tlbflush.h>
56 #include <asm/div64.h>
58 #include <linux/swapops.h>
59 #include <linux/balloon_compaction.h>
63 #define CREATE_TRACE_POINTS
64 #include <trace/events/vmscan.h>
67 /* How many pages shrink_list() should reclaim */
68 unsigned long nr_to_reclaim
;
71 * Nodemask of nodes allowed by the caller. If NULL, all nodes
77 * The memory cgroup that hit its limit and as a result is the
78 * primary target of this reclaim invocation.
80 struct mem_cgroup
*target_mem_cgroup
;
82 /* Writepage batching in laptop mode; RECLAIM_WRITE */
83 unsigned int may_writepage
:1;
85 /* Can mapped pages be reclaimed? */
86 unsigned int may_unmap
:1;
88 /* Can pages be swapped as part of reclaim? */
89 unsigned int may_swap
:1;
92 * Cgroups are not reclaimed below their configured memory.low,
93 * unless we threaten to OOM. If any cgroups are skipped due to
94 * memory.low and nothing was reclaimed, go back for memory.low.
96 unsigned int memcg_low_reclaim
:1;
97 unsigned int memcg_low_skipped
:1;
99 unsigned int hibernation_mode
:1;
101 /* One of the zones is ready for compaction */
102 unsigned int compaction_ready
:1;
104 /* Allocation order */
107 /* Scan (total_size >> priority) pages at once */
110 /* The highest zone to isolate pages for reclaim from */
113 /* This context's GFP mask */
116 /* Incremented by the number of inactive pages that were scanned */
117 unsigned long nr_scanned
;
119 /* Number of pages freed so far during a call to shrink_zones() */
120 unsigned long nr_reclaimed
;
124 unsigned int unqueued_dirty
;
125 unsigned int congested
;
126 unsigned int writeback
;
127 unsigned int immediate
;
128 unsigned int file_taken
;
132 /* for recording the reclaimed slab by now */
133 struct reclaim_state reclaim_state
;
136 #ifdef ARCH_HAS_PREFETCH
137 #define prefetch_prev_lru_page(_page, _base, _field) \
139 if ((_page)->lru.prev != _base) { \
142 prev = lru_to_page(&(_page->lru)); \
143 prefetch(&prev->_field); \
147 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
150 #ifdef ARCH_HAS_PREFETCHW
151 #define prefetchw_prev_lru_page(_page, _base, _field) \
153 if ((_page)->lru.prev != _base) { \
156 prev = lru_to_page(&(_page->lru)); \
157 prefetchw(&prev->_field); \
161 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
165 * From 0 .. 100. Higher means more swappy.
167 int vm_swappiness
= 60;
169 * The total number of pages which are beyond the high watermark within all
172 unsigned long vm_total_pages
;
174 static LIST_HEAD(shrinker_list
);
175 static DECLARE_RWSEM(shrinker_rwsem
);
177 #ifdef CONFIG_MEMCG_KMEM
180 * We allow subsystems to populate their shrinker-related
181 * LRU lists before register_shrinker_prepared() is called
182 * for the shrinker, since we don't want to impose
183 * restrictions on their internal registration order.
184 * In this case shrink_slab_memcg() may find corresponding
185 * bit is set in the shrinkers map.
187 * This value is used by the function to detect registering
188 * shrinkers and to skip do_shrink_slab() calls for them.
190 #define SHRINKER_REGISTERING ((struct shrinker *)~0UL)
192 static DEFINE_IDR(shrinker_idr
);
193 static int shrinker_nr_max
;
195 static int prealloc_memcg_shrinker(struct shrinker
*shrinker
)
197 int id
, ret
= -ENOMEM
;
199 down_write(&shrinker_rwsem
);
200 /* This may call shrinker, so it must use down_read_trylock() */
201 id
= idr_alloc(&shrinker_idr
, SHRINKER_REGISTERING
, 0, 0, GFP_KERNEL
);
205 if (id
>= shrinker_nr_max
) {
206 if (memcg_expand_shrinker_maps(id
)) {
207 idr_remove(&shrinker_idr
, id
);
211 shrinker_nr_max
= id
+ 1;
216 up_write(&shrinker_rwsem
);
220 static void unregister_memcg_shrinker(struct shrinker
*shrinker
)
222 int id
= shrinker
->id
;
226 down_write(&shrinker_rwsem
);
227 idr_remove(&shrinker_idr
, id
);
228 up_write(&shrinker_rwsem
);
230 #else /* CONFIG_MEMCG_KMEM */
231 static int prealloc_memcg_shrinker(struct shrinker
*shrinker
)
236 static void unregister_memcg_shrinker(struct shrinker
*shrinker
)
239 #endif /* CONFIG_MEMCG_KMEM */
241 static void set_task_reclaim_state(struct task_struct
*task
,
242 struct reclaim_state
*rs
)
244 /* Check for an overwrite */
245 WARN_ON_ONCE(rs
&& task
->reclaim_state
);
247 /* Check for the nulling of an already-nulled member */
248 WARN_ON_ONCE(!rs
&& !task
->reclaim_state
);
250 task
->reclaim_state
= rs
;
254 static bool global_reclaim(struct scan_control
*sc
)
256 return !sc
->target_mem_cgroup
;
260 * sane_reclaim - is the usual dirty throttling mechanism operational?
261 * @sc: scan_control in question
263 * The normal page dirty throttling mechanism in balance_dirty_pages() is
264 * completely broken with the legacy memcg and direct stalling in
265 * shrink_page_list() is used for throttling instead, which lacks all the
266 * niceties such as fairness, adaptive pausing, bandwidth proportional
267 * allocation and configurability.
269 * This function tests whether the vmscan currently in progress can assume
270 * that the normal dirty throttling mechanism is operational.
272 static bool sane_reclaim(struct scan_control
*sc
)
274 struct mem_cgroup
*memcg
= sc
->target_mem_cgroup
;
278 #ifdef CONFIG_CGROUP_WRITEBACK
279 if (cgroup_subsys_on_dfl(memory_cgrp_subsys
))
285 static void set_memcg_congestion(pg_data_t
*pgdat
,
286 struct mem_cgroup
*memcg
,
289 struct mem_cgroup_per_node
*mn
;
294 mn
= mem_cgroup_nodeinfo(memcg
, pgdat
->node_id
);
295 WRITE_ONCE(mn
->congested
, congested
);
298 static bool memcg_congested(pg_data_t
*pgdat
,
299 struct mem_cgroup
*memcg
)
301 struct mem_cgroup_per_node
*mn
;
303 mn
= mem_cgroup_nodeinfo(memcg
, pgdat
->node_id
);
304 return READ_ONCE(mn
->congested
);
308 static bool global_reclaim(struct scan_control
*sc
)
313 static bool sane_reclaim(struct scan_control
*sc
)
318 static inline void set_memcg_congestion(struct pglist_data
*pgdat
,
319 struct mem_cgroup
*memcg
, bool congested
)
323 static inline bool memcg_congested(struct pglist_data
*pgdat
,
324 struct mem_cgroup
*memcg
)
332 * This misses isolated pages which are not accounted for to save counters.
333 * As the data only determines if reclaim or compaction continues, it is
334 * not expected that isolated pages will be a dominating factor.
336 unsigned long zone_reclaimable_pages(struct zone
*zone
)
340 nr
= zone_page_state_snapshot(zone
, NR_ZONE_INACTIVE_FILE
) +
341 zone_page_state_snapshot(zone
, NR_ZONE_ACTIVE_FILE
);
342 if (get_nr_swap_pages() > 0)
343 nr
+= zone_page_state_snapshot(zone
, NR_ZONE_INACTIVE_ANON
) +
344 zone_page_state_snapshot(zone
, NR_ZONE_ACTIVE_ANON
);
350 * lruvec_lru_size - Returns the number of pages on the given LRU list.
351 * @lruvec: lru vector
353 * @zone_idx: zones to consider (use MAX_NR_ZONES for the whole LRU list)
355 unsigned long lruvec_lru_size(struct lruvec
*lruvec
, enum lru_list lru
, int zone_idx
)
357 unsigned long lru_size
= 0;
360 if (!mem_cgroup_disabled()) {
361 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++)
362 lru_size
+= mem_cgroup_get_zone_lru_size(lruvec
, lru
, zid
);
364 lru_size
= node_page_state(lruvec_pgdat(lruvec
), NR_LRU_BASE
+ lru
);
366 for (zid
= zone_idx
+ 1; zid
< MAX_NR_ZONES
; zid
++) {
367 struct zone
*zone
= &lruvec_pgdat(lruvec
)->node_zones
[zid
];
370 if (!managed_zone(zone
))
373 if (!mem_cgroup_disabled())
374 size
= mem_cgroup_get_zone_lru_size(lruvec
, lru
, zid
);
376 size
= zone_page_state(&lruvec_pgdat(lruvec
)->node_zones
[zid
],
377 NR_ZONE_LRU_BASE
+ lru
);
378 lru_size
-= min(size
, lru_size
);
386 * Add a shrinker callback to be called from the vm.
388 int prealloc_shrinker(struct shrinker
*shrinker
)
390 unsigned int size
= sizeof(*shrinker
->nr_deferred
);
392 if (shrinker
->flags
& SHRINKER_NUMA_AWARE
)
395 shrinker
->nr_deferred
= kzalloc(size
, GFP_KERNEL
);
396 if (!shrinker
->nr_deferred
)
399 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
) {
400 if (prealloc_memcg_shrinker(shrinker
))
407 kfree(shrinker
->nr_deferred
);
408 shrinker
->nr_deferred
= NULL
;
412 void free_prealloced_shrinker(struct shrinker
*shrinker
)
414 if (!shrinker
->nr_deferred
)
417 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
)
418 unregister_memcg_shrinker(shrinker
);
420 kfree(shrinker
->nr_deferred
);
421 shrinker
->nr_deferred
= NULL
;
424 void register_shrinker_prepared(struct shrinker
*shrinker
)
426 down_write(&shrinker_rwsem
);
427 list_add_tail(&shrinker
->list
, &shrinker_list
);
428 #ifdef CONFIG_MEMCG_KMEM
429 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
)
430 idr_replace(&shrinker_idr
, shrinker
, shrinker
->id
);
432 up_write(&shrinker_rwsem
);
435 int register_shrinker(struct shrinker
*shrinker
)
437 int err
= prealloc_shrinker(shrinker
);
441 register_shrinker_prepared(shrinker
);
444 EXPORT_SYMBOL(register_shrinker
);
449 void unregister_shrinker(struct shrinker
*shrinker
)
451 if (!shrinker
->nr_deferred
)
453 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
)
454 unregister_memcg_shrinker(shrinker
);
455 down_write(&shrinker_rwsem
);
456 list_del(&shrinker
->list
);
457 up_write(&shrinker_rwsem
);
458 kfree(shrinker
->nr_deferred
);
459 shrinker
->nr_deferred
= NULL
;
461 EXPORT_SYMBOL(unregister_shrinker
);
463 #define SHRINK_BATCH 128
465 static unsigned long do_shrink_slab(struct shrink_control
*shrinkctl
,
466 struct shrinker
*shrinker
, int priority
)
468 unsigned long freed
= 0;
469 unsigned long long delta
;
474 int nid
= shrinkctl
->nid
;
475 long batch_size
= shrinker
->batch
? shrinker
->batch
477 long scanned
= 0, next_deferred
;
479 if (!(shrinker
->flags
& SHRINKER_NUMA_AWARE
))
482 freeable
= shrinker
->count_objects(shrinker
, shrinkctl
);
483 if (freeable
== 0 || freeable
== SHRINK_EMPTY
)
487 * copy the current shrinker scan count into a local variable
488 * and zero it so that other concurrent shrinker invocations
489 * don't also do this scanning work.
491 nr
= atomic_long_xchg(&shrinker
->nr_deferred
[nid
], 0);
494 if (shrinker
->seeks
) {
495 delta
= freeable
>> priority
;
497 do_div(delta
, shrinker
->seeks
);
500 * These objects don't require any IO to create. Trim
501 * them aggressively under memory pressure to keep
502 * them from causing refetches in the IO caches.
504 delta
= freeable
/ 2;
508 if (total_scan
< 0) {
509 pr_err("shrink_slab: %pS negative objects to delete nr=%ld\n",
510 shrinker
->scan_objects
, total_scan
);
511 total_scan
= freeable
;
514 next_deferred
= total_scan
;
517 * We need to avoid excessive windup on filesystem shrinkers
518 * due to large numbers of GFP_NOFS allocations causing the
519 * shrinkers to return -1 all the time. This results in a large
520 * nr being built up so when a shrink that can do some work
521 * comes along it empties the entire cache due to nr >>>
522 * freeable. This is bad for sustaining a working set in
525 * Hence only allow the shrinker to scan the entire cache when
526 * a large delta change is calculated directly.
528 if (delta
< freeable
/ 4)
529 total_scan
= min(total_scan
, freeable
/ 2);
532 * Avoid risking looping forever due to too large nr value:
533 * never try to free more than twice the estimate number of
536 if (total_scan
> freeable
* 2)
537 total_scan
= freeable
* 2;
539 trace_mm_shrink_slab_start(shrinker
, shrinkctl
, nr
,
540 freeable
, delta
, total_scan
, priority
);
543 * Normally, we should not scan less than batch_size objects in one
544 * pass to avoid too frequent shrinker calls, but if the slab has less
545 * than batch_size objects in total and we are really tight on memory,
546 * we will try to reclaim all available objects, otherwise we can end
547 * up failing allocations although there are plenty of reclaimable
548 * objects spread over several slabs with usage less than the
551 * We detect the "tight on memory" situations by looking at the total
552 * number of objects we want to scan (total_scan). If it is greater
553 * than the total number of objects on slab (freeable), we must be
554 * scanning at high prio and therefore should try to reclaim as much as
557 while (total_scan
>= batch_size
||
558 total_scan
>= freeable
) {
560 unsigned long nr_to_scan
= min(batch_size
, total_scan
);
562 shrinkctl
->nr_to_scan
= nr_to_scan
;
563 shrinkctl
->nr_scanned
= nr_to_scan
;
564 ret
= shrinker
->scan_objects(shrinker
, shrinkctl
);
565 if (ret
== SHRINK_STOP
)
569 count_vm_events(SLABS_SCANNED
, shrinkctl
->nr_scanned
);
570 total_scan
-= shrinkctl
->nr_scanned
;
571 scanned
+= shrinkctl
->nr_scanned
;
576 if (next_deferred
>= scanned
)
577 next_deferred
-= scanned
;
581 * move the unused scan count back into the shrinker in a
582 * manner that handles concurrent updates. If we exhausted the
583 * scan, there is no need to do an update.
585 if (next_deferred
> 0)
586 new_nr
= atomic_long_add_return(next_deferred
,
587 &shrinker
->nr_deferred
[nid
]);
589 new_nr
= atomic_long_read(&shrinker
->nr_deferred
[nid
]);
591 trace_mm_shrink_slab_end(shrinker
, nid
, freed
, nr
, new_nr
, total_scan
);
595 #ifdef CONFIG_MEMCG_KMEM
596 static unsigned long shrink_slab_memcg(gfp_t gfp_mask
, int nid
,
597 struct mem_cgroup
*memcg
, int priority
)
599 struct memcg_shrinker_map
*map
;
600 unsigned long ret
, freed
= 0;
603 if (!memcg_kmem_enabled() || !mem_cgroup_online(memcg
))
606 if (!down_read_trylock(&shrinker_rwsem
))
609 map
= rcu_dereference_protected(memcg
->nodeinfo
[nid
]->shrinker_map
,
614 for_each_set_bit(i
, map
->map
, shrinker_nr_max
) {
615 struct shrink_control sc
= {
616 .gfp_mask
= gfp_mask
,
620 struct shrinker
*shrinker
;
622 shrinker
= idr_find(&shrinker_idr
, i
);
623 if (unlikely(!shrinker
|| shrinker
== SHRINKER_REGISTERING
)) {
625 clear_bit(i
, map
->map
);
629 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
630 if (ret
== SHRINK_EMPTY
) {
631 clear_bit(i
, map
->map
);
633 * After the shrinker reported that it had no objects to
634 * free, but before we cleared the corresponding bit in
635 * the memcg shrinker map, a new object might have been
636 * added. To make sure, we have the bit set in this
637 * case, we invoke the shrinker one more time and reset
638 * the bit if it reports that it is not empty anymore.
639 * The memory barrier here pairs with the barrier in
640 * memcg_set_shrinker_bit():
642 * list_lru_add() shrink_slab_memcg()
643 * list_add_tail() clear_bit()
645 * set_bit() do_shrink_slab()
647 smp_mb__after_atomic();
648 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
649 if (ret
== SHRINK_EMPTY
)
652 memcg_set_shrinker_bit(memcg
, nid
, i
);
656 if (rwsem_is_contended(&shrinker_rwsem
)) {
662 up_read(&shrinker_rwsem
);
665 #else /* CONFIG_MEMCG_KMEM */
666 static unsigned long shrink_slab_memcg(gfp_t gfp_mask
, int nid
,
667 struct mem_cgroup
*memcg
, int priority
)
671 #endif /* CONFIG_MEMCG_KMEM */
674 * shrink_slab - shrink slab caches
675 * @gfp_mask: allocation context
676 * @nid: node whose slab caches to target
677 * @memcg: memory cgroup whose slab caches to target
678 * @priority: the reclaim priority
680 * Call the shrink functions to age shrinkable caches.
682 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
683 * unaware shrinkers will receive a node id of 0 instead.
685 * @memcg specifies the memory cgroup to target. Unaware shrinkers
686 * are called only if it is the root cgroup.
688 * @priority is sc->priority, we take the number of objects and >> by priority
689 * in order to get the scan target.
691 * Returns the number of reclaimed slab objects.
693 static unsigned long shrink_slab(gfp_t gfp_mask
, int nid
,
694 struct mem_cgroup
*memcg
,
697 unsigned long ret
, freed
= 0;
698 struct shrinker
*shrinker
;
701 * The root memcg might be allocated even though memcg is disabled
702 * via "cgroup_disable=memory" boot parameter. This could make
703 * mem_cgroup_is_root() return false, then just run memcg slab
704 * shrink, but skip global shrink. This may result in premature
707 if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg
))
708 return shrink_slab_memcg(gfp_mask
, nid
, memcg
, priority
);
710 if (!down_read_trylock(&shrinker_rwsem
))
713 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
714 struct shrink_control sc
= {
715 .gfp_mask
= gfp_mask
,
720 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
721 if (ret
== SHRINK_EMPTY
)
725 * Bail out if someone want to register a new shrinker to
726 * prevent the regsitration from being stalled for long periods
727 * by parallel ongoing shrinking.
729 if (rwsem_is_contended(&shrinker_rwsem
)) {
735 up_read(&shrinker_rwsem
);
741 void drop_slab_node(int nid
)
746 struct mem_cgroup
*memcg
= NULL
;
749 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
751 freed
+= shrink_slab(GFP_KERNEL
, nid
, memcg
, 0);
752 } while ((memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
)) != NULL
);
753 } while (freed
> 10);
760 for_each_online_node(nid
)
764 static inline int is_page_cache_freeable(struct page
*page
)
767 * A freeable page cache page is referenced only by the caller
768 * that isolated the page, the page cache and optional buffer
769 * heads at page->private.
771 int page_cache_pins
= PageTransHuge(page
) && PageSwapCache(page
) ?
773 return page_count(page
) - page_has_private(page
) == 1 + page_cache_pins
;
776 static int may_write_to_inode(struct inode
*inode
, struct scan_control
*sc
)
778 if (current
->flags
& PF_SWAPWRITE
)
780 if (!inode_write_congested(inode
))
782 if (inode_to_bdi(inode
) == current
->backing_dev_info
)
788 * We detected a synchronous write error writing a page out. Probably
789 * -ENOSPC. We need to propagate that into the address_space for a subsequent
790 * fsync(), msync() or close().
792 * The tricky part is that after writepage we cannot touch the mapping: nothing
793 * prevents it from being freed up. But we have a ref on the page and once
794 * that page is locked, the mapping is pinned.
796 * We're allowed to run sleeping lock_page() here because we know the caller has
799 static void handle_write_error(struct address_space
*mapping
,
800 struct page
*page
, int error
)
803 if (page_mapping(page
) == mapping
)
804 mapping_set_error(mapping
, error
);
808 /* possible outcome of pageout() */
810 /* failed to write page out, page is locked */
812 /* move page to the active list, page is locked */
814 /* page has been sent to the disk successfully, page is unlocked */
816 /* page is clean and locked */
821 * pageout is called by shrink_page_list() for each dirty page.
822 * Calls ->writepage().
824 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
825 struct scan_control
*sc
)
828 * If the page is dirty, only perform writeback if that write
829 * will be non-blocking. To prevent this allocation from being
830 * stalled by pagecache activity. But note that there may be
831 * stalls if we need to run get_block(). We could test
832 * PagePrivate for that.
834 * If this process is currently in __generic_file_write_iter() against
835 * this page's queue, we can perform writeback even if that
838 * If the page is swapcache, write it back even if that would
839 * block, for some throttling. This happens by accident, because
840 * swap_backing_dev_info is bust: it doesn't reflect the
841 * congestion state of the swapdevs. Easy to fix, if needed.
843 if (!is_page_cache_freeable(page
))
847 * Some data journaling orphaned pages can have
848 * page->mapping == NULL while being dirty with clean buffers.
850 if (page_has_private(page
)) {
851 if (try_to_free_buffers(page
)) {
852 ClearPageDirty(page
);
853 pr_info("%s: orphaned page\n", __func__
);
859 if (mapping
->a_ops
->writepage
== NULL
)
860 return PAGE_ACTIVATE
;
861 if (!may_write_to_inode(mapping
->host
, sc
))
864 if (clear_page_dirty_for_io(page
)) {
866 struct writeback_control wbc
= {
867 .sync_mode
= WB_SYNC_NONE
,
868 .nr_to_write
= SWAP_CLUSTER_MAX
,
870 .range_end
= LLONG_MAX
,
874 SetPageReclaim(page
);
875 res
= mapping
->a_ops
->writepage(page
, &wbc
);
877 handle_write_error(mapping
, page
, res
);
878 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
879 ClearPageReclaim(page
);
880 return PAGE_ACTIVATE
;
883 if (!PageWriteback(page
)) {
884 /* synchronous write or broken a_ops? */
885 ClearPageReclaim(page
);
887 trace_mm_vmscan_writepage(page
);
888 inc_node_page_state(page
, NR_VMSCAN_WRITE
);
896 * Same as remove_mapping, but if the page is removed from the mapping, it
897 * gets returned with a refcount of 0.
899 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
,
905 BUG_ON(!PageLocked(page
));
906 BUG_ON(mapping
!= page_mapping(page
));
908 xa_lock_irqsave(&mapping
->i_pages
, flags
);
910 * The non racy check for a busy page.
912 * Must be careful with the order of the tests. When someone has
913 * a ref to the page, it may be possible that they dirty it then
914 * drop the reference. So if PageDirty is tested before page_count
915 * here, then the following race may occur:
917 * get_user_pages(&page);
918 * [user mapping goes away]
920 * !PageDirty(page) [good]
921 * SetPageDirty(page);
923 * !page_count(page) [good, discard it]
925 * [oops, our write_to data is lost]
927 * Reversing the order of the tests ensures such a situation cannot
928 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
929 * load is not satisfied before that of page->_refcount.
931 * Note that if SetPageDirty is always performed via set_page_dirty,
932 * and thus under the i_pages lock, then this ordering is not required.
934 if (unlikely(PageTransHuge(page
)) && PageSwapCache(page
))
935 refcount
= 1 + HPAGE_PMD_NR
;
938 if (!page_ref_freeze(page
, refcount
))
940 /* note: atomic_cmpxchg in page_ref_freeze provides the smp_rmb */
941 if (unlikely(PageDirty(page
))) {
942 page_ref_unfreeze(page
, refcount
);
946 if (PageSwapCache(page
)) {
947 swp_entry_t swap
= { .val
= page_private(page
) };
948 mem_cgroup_swapout(page
, swap
);
949 __delete_from_swap_cache(page
, swap
);
950 xa_unlock_irqrestore(&mapping
->i_pages
, flags
);
951 put_swap_page(page
, swap
);
953 void (*freepage
)(struct page
*);
956 freepage
= mapping
->a_ops
->freepage
;
958 * Remember a shadow entry for reclaimed file cache in
959 * order to detect refaults, thus thrashing, later on.
961 * But don't store shadows in an address space that is
962 * already exiting. This is not just an optizimation,
963 * inode reclaim needs to empty out the radix tree or
964 * the nodes are lost. Don't plant shadows behind its
967 * We also don't store shadows for DAX mappings because the
968 * only page cache pages found in these are zero pages
969 * covering holes, and because we don't want to mix DAX
970 * exceptional entries and shadow exceptional entries in the
971 * same address_space.
973 if (reclaimed
&& page_is_file_cache(page
) &&
974 !mapping_exiting(mapping
) && !dax_mapping(mapping
))
975 shadow
= workingset_eviction(page
);
976 __delete_from_page_cache(page
, shadow
);
977 xa_unlock_irqrestore(&mapping
->i_pages
, flags
);
979 if (freepage
!= NULL
)
986 xa_unlock_irqrestore(&mapping
->i_pages
, flags
);
991 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
992 * someone else has a ref on the page, abort and return 0. If it was
993 * successfully detached, return 1. Assumes the caller has a single ref on
996 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
998 if (__remove_mapping(mapping
, page
, false)) {
1000 * Unfreezing the refcount with 1 rather than 2 effectively
1001 * drops the pagecache ref for us without requiring another
1004 page_ref_unfreeze(page
, 1);
1011 * putback_lru_page - put previously isolated page onto appropriate LRU list
1012 * @page: page to be put back to appropriate lru list
1014 * Add previously isolated @page to appropriate LRU list.
1015 * Page may still be unevictable for other reasons.
1017 * lru_lock must not be held, interrupts must be enabled.
1019 void putback_lru_page(struct page
*page
)
1021 lru_cache_add(page
);
1022 put_page(page
); /* drop ref from isolate */
1025 enum page_references
{
1027 PAGEREF_RECLAIM_CLEAN
,
1032 static enum page_references
page_check_references(struct page
*page
,
1033 struct scan_control
*sc
)
1035 int referenced_ptes
, referenced_page
;
1036 unsigned long vm_flags
;
1038 referenced_ptes
= page_referenced(page
, 1, sc
->target_mem_cgroup
,
1040 referenced_page
= TestClearPageReferenced(page
);
1043 * Mlock lost the isolation race with us. Let try_to_unmap()
1044 * move the page to the unevictable list.
1046 if (vm_flags
& VM_LOCKED
)
1047 return PAGEREF_RECLAIM
;
1049 if (referenced_ptes
) {
1050 if (PageSwapBacked(page
))
1051 return PAGEREF_ACTIVATE
;
1053 * All mapped pages start out with page table
1054 * references from the instantiating fault, so we need
1055 * to look twice if a mapped file page is used more
1058 * Mark it and spare it for another trip around the
1059 * inactive list. Another page table reference will
1060 * lead to its activation.
1062 * Note: the mark is set for activated pages as well
1063 * so that recently deactivated but used pages are
1064 * quickly recovered.
1066 SetPageReferenced(page
);
1068 if (referenced_page
|| referenced_ptes
> 1)
1069 return PAGEREF_ACTIVATE
;
1072 * Activate file-backed executable pages after first usage.
1074 if (vm_flags
& VM_EXEC
)
1075 return PAGEREF_ACTIVATE
;
1077 return PAGEREF_KEEP
;
1080 /* Reclaim if clean, defer dirty pages to writeback */
1081 if (referenced_page
&& !PageSwapBacked(page
))
1082 return PAGEREF_RECLAIM_CLEAN
;
1084 return PAGEREF_RECLAIM
;
1087 /* Check if a page is dirty or under writeback */
1088 static void page_check_dirty_writeback(struct page
*page
,
1089 bool *dirty
, bool *writeback
)
1091 struct address_space
*mapping
;
1094 * Anonymous pages are not handled by flushers and must be written
1095 * from reclaim context. Do not stall reclaim based on them
1097 if (!page_is_file_cache(page
) ||
1098 (PageAnon(page
) && !PageSwapBacked(page
))) {
1104 /* By default assume that the page flags are accurate */
1105 *dirty
= PageDirty(page
);
1106 *writeback
= PageWriteback(page
);
1108 /* Verify dirty/writeback state if the filesystem supports it */
1109 if (!page_has_private(page
))
1112 mapping
= page_mapping(page
);
1113 if (mapping
&& mapping
->a_ops
->is_dirty_writeback
)
1114 mapping
->a_ops
->is_dirty_writeback(page
, dirty
, writeback
);
1118 * shrink_page_list() returns the number of reclaimed pages
1120 static unsigned long shrink_page_list(struct list_head
*page_list
,
1121 struct pglist_data
*pgdat
,
1122 struct scan_control
*sc
,
1123 enum ttu_flags ttu_flags
,
1124 struct reclaim_stat
*stat
,
1127 LIST_HEAD(ret_pages
);
1128 LIST_HEAD(free_pages
);
1129 unsigned nr_reclaimed
= 0;
1130 unsigned pgactivate
= 0;
1132 memset(stat
, 0, sizeof(*stat
));
1135 while (!list_empty(page_list
)) {
1136 struct address_space
*mapping
;
1139 enum page_references references
= PAGEREF_RECLAIM_CLEAN
;
1140 bool dirty
, writeback
;
1141 unsigned int nr_pages
;
1145 page
= lru_to_page(page_list
);
1146 list_del(&page
->lru
);
1148 if (!trylock_page(page
))
1151 VM_BUG_ON_PAGE(PageActive(page
), page
);
1153 nr_pages
= 1 << compound_order(page
);
1155 /* Account the number of base pages even though THP */
1156 sc
->nr_scanned
+= nr_pages
;
1158 if (unlikely(!page_evictable(page
)))
1159 goto activate_locked
;
1161 if (!sc
->may_unmap
&& page_mapped(page
))
1164 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
1165 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
1168 * The number of dirty pages determines if a node is marked
1169 * reclaim_congested which affects wait_iff_congested. kswapd
1170 * will stall and start writing pages if the tail of the LRU
1171 * is all dirty unqueued pages.
1173 page_check_dirty_writeback(page
, &dirty
, &writeback
);
1174 if (dirty
|| writeback
)
1177 if (dirty
&& !writeback
)
1178 stat
->nr_unqueued_dirty
++;
1181 * Treat this page as congested if the underlying BDI is or if
1182 * pages are cycling through the LRU so quickly that the
1183 * pages marked for immediate reclaim are making it to the
1184 * end of the LRU a second time.
1186 mapping
= page_mapping(page
);
1187 if (((dirty
|| writeback
) && mapping
&&
1188 inode_write_congested(mapping
->host
)) ||
1189 (writeback
&& PageReclaim(page
)))
1190 stat
->nr_congested
++;
1193 * If a page at the tail of the LRU is under writeback, there
1194 * are three cases to consider.
1196 * 1) If reclaim is encountering an excessive number of pages
1197 * under writeback and this page is both under writeback and
1198 * PageReclaim then it indicates that pages are being queued
1199 * for IO but are being recycled through the LRU before the
1200 * IO can complete. Waiting on the page itself risks an
1201 * indefinite stall if it is impossible to writeback the
1202 * page due to IO error or disconnected storage so instead
1203 * note that the LRU is being scanned too quickly and the
1204 * caller can stall after page list has been processed.
1206 * 2) Global or new memcg reclaim encounters a page that is
1207 * not marked for immediate reclaim, or the caller does not
1208 * have __GFP_FS (or __GFP_IO if it's simply going to swap,
1209 * not to fs). In this case mark the page for immediate
1210 * reclaim and continue scanning.
1212 * Require may_enter_fs because we would wait on fs, which
1213 * may not have submitted IO yet. And the loop driver might
1214 * enter reclaim, and deadlock if it waits on a page for
1215 * which it is needed to do the write (loop masks off
1216 * __GFP_IO|__GFP_FS for this reason); but more thought
1217 * would probably show more reasons.
1219 * 3) Legacy memcg encounters a page that is already marked
1220 * PageReclaim. memcg does not have any dirty pages
1221 * throttling so we could easily OOM just because too many
1222 * pages are in writeback and there is nothing else to
1223 * reclaim. Wait for the writeback to complete.
1225 * In cases 1) and 2) we activate the pages to get them out of
1226 * the way while we continue scanning for clean pages on the
1227 * inactive list and refilling from the active list. The
1228 * observation here is that waiting for disk writes is more
1229 * expensive than potentially causing reloads down the line.
1230 * Since they're marked for immediate reclaim, they won't put
1231 * memory pressure on the cache working set any longer than it
1232 * takes to write them to disk.
1234 if (PageWriteback(page
)) {
1236 if (current_is_kswapd() &&
1237 PageReclaim(page
) &&
1238 test_bit(PGDAT_WRITEBACK
, &pgdat
->flags
)) {
1239 stat
->nr_immediate
++;
1240 goto activate_locked
;
1243 } else if (sane_reclaim(sc
) ||
1244 !PageReclaim(page
) || !may_enter_fs
) {
1246 * This is slightly racy - end_page_writeback()
1247 * might have just cleared PageReclaim, then
1248 * setting PageReclaim here end up interpreted
1249 * as PageReadahead - but that does not matter
1250 * enough to care. What we do want is for this
1251 * page to have PageReclaim set next time memcg
1252 * reclaim reaches the tests above, so it will
1253 * then wait_on_page_writeback() to avoid OOM;
1254 * and it's also appropriate in global reclaim.
1256 SetPageReclaim(page
);
1257 stat
->nr_writeback
++;
1258 goto activate_locked
;
1263 wait_on_page_writeback(page
);
1264 /* then go back and try same page again */
1265 list_add_tail(&page
->lru
, page_list
);
1271 references
= page_check_references(page
, sc
);
1273 switch (references
) {
1274 case PAGEREF_ACTIVATE
:
1275 goto activate_locked
;
1277 stat
->nr_ref_keep
+= nr_pages
;
1279 case PAGEREF_RECLAIM
:
1280 case PAGEREF_RECLAIM_CLEAN
:
1281 ; /* try to reclaim the page below */
1285 * Anonymous process memory has backing store?
1286 * Try to allocate it some swap space here.
1287 * Lazyfree page could be freed directly
1289 if (PageAnon(page
) && PageSwapBacked(page
)) {
1290 if (!PageSwapCache(page
)) {
1291 if (!(sc
->gfp_mask
& __GFP_IO
))
1293 if (PageTransHuge(page
)) {
1294 /* cannot split THP, skip it */
1295 if (!can_split_huge_page(page
, NULL
))
1296 goto activate_locked
;
1298 * Split pages without a PMD map right
1299 * away. Chances are some or all of the
1300 * tail pages can be freed without IO.
1302 if (!compound_mapcount(page
) &&
1303 split_huge_page_to_list(page
,
1305 goto activate_locked
;
1307 if (!add_to_swap(page
)) {
1308 if (!PageTransHuge(page
))
1309 goto activate_locked_split
;
1310 /* Fallback to swap normal pages */
1311 if (split_huge_page_to_list(page
,
1313 goto activate_locked
;
1314 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
1315 count_vm_event(THP_SWPOUT_FALLBACK
);
1317 if (!add_to_swap(page
))
1318 goto activate_locked_split
;
1323 /* Adding to swap updated mapping */
1324 mapping
= page_mapping(page
);
1326 } else if (unlikely(PageTransHuge(page
))) {
1327 /* Split file THP */
1328 if (split_huge_page_to_list(page
, page_list
))
1333 * THP may get split above, need minus tail pages and update
1334 * nr_pages to avoid accounting tail pages twice.
1336 * The tail pages that are added into swap cache successfully
1339 if ((nr_pages
> 1) && !PageTransHuge(page
)) {
1340 sc
->nr_scanned
-= (nr_pages
- 1);
1345 * The page is mapped into the page tables of one or more
1346 * processes. Try to unmap it here.
1348 if (page_mapped(page
)) {
1349 enum ttu_flags flags
= ttu_flags
| TTU_BATCH_FLUSH
;
1351 if (unlikely(PageTransHuge(page
)))
1352 flags
|= TTU_SPLIT_HUGE_PMD
;
1353 if (!try_to_unmap(page
, flags
)) {
1354 stat
->nr_unmap_fail
+= nr_pages
;
1355 goto activate_locked
;
1359 if (PageDirty(page
)) {
1361 * Only kswapd can writeback filesystem pages
1362 * to avoid risk of stack overflow. But avoid
1363 * injecting inefficient single-page IO into
1364 * flusher writeback as much as possible: only
1365 * write pages when we've encountered many
1366 * dirty pages, and when we've already scanned
1367 * the rest of the LRU for clean pages and see
1368 * the same dirty pages again (PageReclaim).
1370 if (page_is_file_cache(page
) &&
1371 (!current_is_kswapd() || !PageReclaim(page
) ||
1372 !test_bit(PGDAT_DIRTY
, &pgdat
->flags
))) {
1374 * Immediately reclaim when written back.
1375 * Similar in principal to deactivate_page()
1376 * except we already have the page isolated
1377 * and know it's dirty
1379 inc_node_page_state(page
, NR_VMSCAN_IMMEDIATE
);
1380 SetPageReclaim(page
);
1382 goto activate_locked
;
1385 if (references
== PAGEREF_RECLAIM_CLEAN
)
1389 if (!sc
->may_writepage
)
1393 * Page is dirty. Flush the TLB if a writable entry
1394 * potentially exists to avoid CPU writes after IO
1395 * starts and then write it out here.
1397 try_to_unmap_flush_dirty();
1398 switch (pageout(page
, mapping
, sc
)) {
1402 goto activate_locked
;
1404 if (PageWriteback(page
))
1406 if (PageDirty(page
))
1410 * A synchronous write - probably a ramdisk. Go
1411 * ahead and try to reclaim the page.
1413 if (!trylock_page(page
))
1415 if (PageDirty(page
) || PageWriteback(page
))
1417 mapping
= page_mapping(page
);
1419 ; /* try to free the page below */
1424 * If the page has buffers, try to free the buffer mappings
1425 * associated with this page. If we succeed we try to free
1428 * We do this even if the page is PageDirty().
1429 * try_to_release_page() does not perform I/O, but it is
1430 * possible for a page to have PageDirty set, but it is actually
1431 * clean (all its buffers are clean). This happens if the
1432 * buffers were written out directly, with submit_bh(). ext3
1433 * will do this, as well as the blockdev mapping.
1434 * try_to_release_page() will discover that cleanness and will
1435 * drop the buffers and mark the page clean - it can be freed.
1437 * Rarely, pages can have buffers and no ->mapping. These are
1438 * the pages which were not successfully invalidated in
1439 * truncate_complete_page(). We try to drop those buffers here
1440 * and if that worked, and the page is no longer mapped into
1441 * process address space (page_count == 1) it can be freed.
1442 * Otherwise, leave the page on the LRU so it is swappable.
1444 if (page_has_private(page
)) {
1445 if (!try_to_release_page(page
, sc
->gfp_mask
))
1446 goto activate_locked
;
1447 if (!mapping
&& page_count(page
) == 1) {
1449 if (put_page_testzero(page
))
1453 * rare race with speculative reference.
1454 * the speculative reference will free
1455 * this page shortly, so we may
1456 * increment nr_reclaimed here (and
1457 * leave it off the LRU).
1465 if (PageAnon(page
) && !PageSwapBacked(page
)) {
1466 /* follow __remove_mapping for reference */
1467 if (!page_ref_freeze(page
, 1))
1469 if (PageDirty(page
)) {
1470 page_ref_unfreeze(page
, 1);
1474 count_vm_event(PGLAZYFREED
);
1475 count_memcg_page_event(page
, PGLAZYFREED
);
1476 } else if (!mapping
|| !__remove_mapping(mapping
, page
, true))
1482 * THP may get swapped out in a whole, need account
1485 nr_reclaimed
+= nr_pages
;
1488 * Is there need to periodically free_page_list? It would
1489 * appear not as the counts should be low
1491 if (unlikely(PageTransHuge(page
))) {
1492 mem_cgroup_uncharge(page
);
1493 (*get_compound_page_dtor(page
))(page
);
1495 list_add(&page
->lru
, &free_pages
);
1498 activate_locked_split
:
1500 * The tail pages that are failed to add into swap cache
1501 * reach here. Fixup nr_scanned and nr_pages.
1504 sc
->nr_scanned
-= (nr_pages
- 1);
1508 /* Not a candidate for swapping, so reclaim swap space. */
1509 if (PageSwapCache(page
) && (mem_cgroup_swap_full(page
) ||
1511 try_to_free_swap(page
);
1512 VM_BUG_ON_PAGE(PageActive(page
), page
);
1513 if (!PageMlocked(page
)) {
1514 int type
= page_is_file_cache(page
);
1515 SetPageActive(page
);
1516 stat
->nr_activate
[type
] += nr_pages
;
1517 count_memcg_page_event(page
, PGACTIVATE
);
1522 list_add(&page
->lru
, &ret_pages
);
1523 VM_BUG_ON_PAGE(PageLRU(page
) || PageUnevictable(page
), page
);
1526 pgactivate
= stat
->nr_activate
[0] + stat
->nr_activate
[1];
1528 mem_cgroup_uncharge_list(&free_pages
);
1529 try_to_unmap_flush();
1530 free_unref_page_list(&free_pages
);
1532 list_splice(&ret_pages
, page_list
);
1533 count_vm_events(PGACTIVATE
, pgactivate
);
1535 return nr_reclaimed
;
1538 unsigned long reclaim_clean_pages_from_list(struct zone
*zone
,
1539 struct list_head
*page_list
)
1541 struct scan_control sc
= {
1542 .gfp_mask
= GFP_KERNEL
,
1543 .priority
= DEF_PRIORITY
,
1546 struct reclaim_stat dummy_stat
;
1548 struct page
*page
, *next
;
1549 LIST_HEAD(clean_pages
);
1551 list_for_each_entry_safe(page
, next
, page_list
, lru
) {
1552 if (page_is_file_cache(page
) && !PageDirty(page
) &&
1553 !__PageMovable(page
) && !PageUnevictable(page
)) {
1554 ClearPageActive(page
);
1555 list_move(&page
->lru
, &clean_pages
);
1559 ret
= shrink_page_list(&clean_pages
, zone
->zone_pgdat
, &sc
,
1560 TTU_IGNORE_ACCESS
, &dummy_stat
, true);
1561 list_splice(&clean_pages
, page_list
);
1562 mod_node_page_state(zone
->zone_pgdat
, NR_ISOLATED_FILE
, -ret
);
1567 * Attempt to remove the specified page from its LRU. Only take this page
1568 * if it is of the appropriate PageActive status. Pages which are being
1569 * freed elsewhere are also ignored.
1571 * page: page to consider
1572 * mode: one of the LRU isolation modes defined above
1574 * returns 0 on success, -ve errno on failure.
1576 int __isolate_lru_page(struct page
*page
, isolate_mode_t mode
)
1580 /* Only take pages on the LRU. */
1584 /* Compaction should not handle unevictable pages but CMA can do so */
1585 if (PageUnevictable(page
) && !(mode
& ISOLATE_UNEVICTABLE
))
1591 * To minimise LRU disruption, the caller can indicate that it only
1592 * wants to isolate pages it will be able to operate on without
1593 * blocking - clean pages for the most part.
1595 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1596 * that it is possible to migrate without blocking
1598 if (mode
& ISOLATE_ASYNC_MIGRATE
) {
1599 /* All the caller can do on PageWriteback is block */
1600 if (PageWriteback(page
))
1603 if (PageDirty(page
)) {
1604 struct address_space
*mapping
;
1608 * Only pages without mappings or that have a
1609 * ->migratepage callback are possible to migrate
1610 * without blocking. However, we can be racing with
1611 * truncation so it's necessary to lock the page
1612 * to stabilise the mapping as truncation holds
1613 * the page lock until after the page is removed
1614 * from the page cache.
1616 if (!trylock_page(page
))
1619 mapping
= page_mapping(page
);
1620 migrate_dirty
= !mapping
|| mapping
->a_ops
->migratepage
;
1627 if ((mode
& ISOLATE_UNMAPPED
) && page_mapped(page
))
1630 if (likely(get_page_unless_zero(page
))) {
1632 * Be careful not to clear PageLRU until after we're
1633 * sure the page is not being freed elsewhere -- the
1634 * page release code relies on it.
1645 * Update LRU sizes after isolating pages. The LRU size updates must
1646 * be complete before mem_cgroup_update_lru_size due to a santity check.
1648 static __always_inline
void update_lru_sizes(struct lruvec
*lruvec
,
1649 enum lru_list lru
, unsigned long *nr_zone_taken
)
1653 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++) {
1654 if (!nr_zone_taken
[zid
])
1657 __update_lru_size(lruvec
, lru
, zid
, -nr_zone_taken
[zid
]);
1659 mem_cgroup_update_lru_size(lruvec
, lru
, zid
, -nr_zone_taken
[zid
]);
1666 * pgdat->lru_lock is heavily contended. Some of the functions that
1667 * shrink the lists perform better by taking out a batch of pages
1668 * and working on them outside the LRU lock.
1670 * For pagecache intensive workloads, this function is the hottest
1671 * spot in the kernel (apart from copy_*_user functions).
1673 * Appropriate locks must be held before calling this function.
1675 * @nr_to_scan: The number of eligible pages to look through on the list.
1676 * @lruvec: The LRU vector to pull pages from.
1677 * @dst: The temp list to put pages on to.
1678 * @nr_scanned: The number of pages that were scanned.
1679 * @sc: The scan_control struct for this reclaim session
1680 * @mode: One of the LRU isolation modes
1681 * @lru: LRU list id for isolating
1683 * returns how many pages were moved onto *@dst.
1685 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1686 struct lruvec
*lruvec
, struct list_head
*dst
,
1687 unsigned long *nr_scanned
, struct scan_control
*sc
,
1690 struct list_head
*src
= &lruvec
->lists
[lru
];
1691 unsigned long nr_taken
= 0;
1692 unsigned long nr_zone_taken
[MAX_NR_ZONES
] = { 0 };
1693 unsigned long nr_skipped
[MAX_NR_ZONES
] = { 0, };
1694 unsigned long skipped
= 0;
1695 unsigned long scan
, total_scan
, nr_pages
;
1696 LIST_HEAD(pages_skipped
);
1697 isolate_mode_t mode
= (sc
->may_unmap
? 0 : ISOLATE_UNMAPPED
);
1701 while (scan
< nr_to_scan
&& !list_empty(src
)) {
1704 page
= lru_to_page(src
);
1705 prefetchw_prev_lru_page(page
, src
, flags
);
1707 VM_BUG_ON_PAGE(!PageLRU(page
), page
);
1709 nr_pages
= 1 << compound_order(page
);
1710 total_scan
+= nr_pages
;
1712 if (page_zonenum(page
) > sc
->reclaim_idx
) {
1713 list_move(&page
->lru
, &pages_skipped
);
1714 nr_skipped
[page_zonenum(page
)] += nr_pages
;
1719 * Do not count skipped pages because that makes the function
1720 * return with no isolated pages if the LRU mostly contains
1721 * ineligible pages. This causes the VM to not reclaim any
1722 * pages, triggering a premature OOM.
1724 * Account all tail pages of THP. This would not cause
1725 * premature OOM since __isolate_lru_page() returns -EBUSY
1726 * only when the page is being freed somewhere else.
1729 switch (__isolate_lru_page(page
, mode
)) {
1731 nr_taken
+= nr_pages
;
1732 nr_zone_taken
[page_zonenum(page
)] += nr_pages
;
1733 list_move(&page
->lru
, dst
);
1737 /* else it is being freed elsewhere */
1738 list_move(&page
->lru
, src
);
1747 * Splice any skipped pages to the start of the LRU list. Note that
1748 * this disrupts the LRU order when reclaiming for lower zones but
1749 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
1750 * scanning would soon rescan the same pages to skip and put the
1751 * system at risk of premature OOM.
1753 if (!list_empty(&pages_skipped
)) {
1756 list_splice(&pages_skipped
, src
);
1757 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++) {
1758 if (!nr_skipped
[zid
])
1761 __count_zid_vm_events(PGSCAN_SKIP
, zid
, nr_skipped
[zid
]);
1762 skipped
+= nr_skipped
[zid
];
1765 *nr_scanned
= total_scan
;
1766 trace_mm_vmscan_lru_isolate(sc
->reclaim_idx
, sc
->order
, nr_to_scan
,
1767 total_scan
, skipped
, nr_taken
, mode
, lru
);
1768 update_lru_sizes(lruvec
, lru
, nr_zone_taken
);
1773 * isolate_lru_page - tries to isolate a page from its LRU list
1774 * @page: page to isolate from its LRU list
1776 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1777 * vmstat statistic corresponding to whatever LRU list the page was on.
1779 * Returns 0 if the page was removed from an LRU list.
1780 * Returns -EBUSY if the page was not on an LRU list.
1782 * The returned page will have PageLRU() cleared. If it was found on
1783 * the active list, it will have PageActive set. If it was found on
1784 * the unevictable list, it will have the PageUnevictable bit set. That flag
1785 * may need to be cleared by the caller before letting the page go.
1787 * The vmstat statistic corresponding to the list on which the page was
1788 * found will be decremented.
1792 * (1) Must be called with an elevated refcount on the page. This is a
1793 * fundamentnal difference from isolate_lru_pages (which is called
1794 * without a stable reference).
1795 * (2) the lru_lock must not be held.
1796 * (3) interrupts must be enabled.
1798 int isolate_lru_page(struct page
*page
)
1802 VM_BUG_ON_PAGE(!page_count(page
), page
);
1803 WARN_RATELIMIT(PageTail(page
), "trying to isolate tail page");
1805 if (PageLRU(page
)) {
1806 pg_data_t
*pgdat
= page_pgdat(page
);
1807 struct lruvec
*lruvec
;
1809 spin_lock_irq(&pgdat
->lru_lock
);
1810 lruvec
= mem_cgroup_page_lruvec(page
, pgdat
);
1811 if (PageLRU(page
)) {
1812 int lru
= page_lru(page
);
1815 del_page_from_lru_list(page
, lruvec
, lru
);
1818 spin_unlock_irq(&pgdat
->lru_lock
);
1824 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1825 * then get resheduled. When there are massive number of tasks doing page
1826 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1827 * the LRU list will go small and be scanned faster than necessary, leading to
1828 * unnecessary swapping, thrashing and OOM.
1830 static int too_many_isolated(struct pglist_data
*pgdat
, int file
,
1831 struct scan_control
*sc
)
1833 unsigned long inactive
, isolated
;
1835 if (current_is_kswapd())
1838 if (!sane_reclaim(sc
))
1842 inactive
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
1843 isolated
= node_page_state(pgdat
, NR_ISOLATED_FILE
);
1845 inactive
= node_page_state(pgdat
, NR_INACTIVE_ANON
);
1846 isolated
= node_page_state(pgdat
, NR_ISOLATED_ANON
);
1850 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1851 * won't get blocked by normal direct-reclaimers, forming a circular
1854 if ((sc
->gfp_mask
& (__GFP_IO
| __GFP_FS
)) == (__GFP_IO
| __GFP_FS
))
1857 return isolated
> inactive
;
1861 * This moves pages from @list to corresponding LRU list.
1863 * We move them the other way if the page is referenced by one or more
1864 * processes, from rmap.
1866 * If the pages are mostly unmapped, the processing is fast and it is
1867 * appropriate to hold zone_lru_lock across the whole operation. But if
1868 * the pages are mapped, the processing is slow (page_referenced()) so we
1869 * should drop zone_lru_lock around each page. It's impossible to balance
1870 * this, so instead we remove the pages from the LRU while processing them.
1871 * It is safe to rely on PG_active against the non-LRU pages in here because
1872 * nobody will play with that bit on a non-LRU page.
1874 * The downside is that we have to touch page->_refcount against each page.
1875 * But we had to alter page->flags anyway.
1877 * Returns the number of pages moved to the given lruvec.
1880 static unsigned noinline_for_stack
move_pages_to_lru(struct lruvec
*lruvec
,
1881 struct list_head
*list
)
1883 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
1884 int nr_pages
, nr_moved
= 0;
1885 LIST_HEAD(pages_to_free
);
1889 while (!list_empty(list
)) {
1890 page
= lru_to_page(list
);
1891 VM_BUG_ON_PAGE(PageLRU(page
), page
);
1892 if (unlikely(!page_evictable(page
))) {
1893 list_del(&page
->lru
);
1894 spin_unlock_irq(&pgdat
->lru_lock
);
1895 putback_lru_page(page
);
1896 spin_lock_irq(&pgdat
->lru_lock
);
1899 lruvec
= mem_cgroup_page_lruvec(page
, pgdat
);
1902 lru
= page_lru(page
);
1904 nr_pages
= hpage_nr_pages(page
);
1905 update_lru_size(lruvec
, lru
, page_zonenum(page
), nr_pages
);
1906 list_move(&page
->lru
, &lruvec
->lists
[lru
]);
1908 if (put_page_testzero(page
)) {
1909 __ClearPageLRU(page
);
1910 __ClearPageActive(page
);
1911 del_page_from_lru_list(page
, lruvec
, lru
);
1913 if (unlikely(PageCompound(page
))) {
1914 spin_unlock_irq(&pgdat
->lru_lock
);
1915 mem_cgroup_uncharge(page
);
1916 (*get_compound_page_dtor(page
))(page
);
1917 spin_lock_irq(&pgdat
->lru_lock
);
1919 list_add(&page
->lru
, &pages_to_free
);
1921 nr_moved
+= nr_pages
;
1926 * To save our caller's stack, now use input list for pages to free.
1928 list_splice(&pages_to_free
, list
);
1934 * If a kernel thread (such as nfsd for loop-back mounts) services
1935 * a backing device by writing to the page cache it sets PF_LESS_THROTTLE.
1936 * In that case we should only throttle if the backing device it is
1937 * writing to is congested. In other cases it is safe to throttle.
1939 static int current_may_throttle(void)
1941 return !(current
->flags
& PF_LESS_THROTTLE
) ||
1942 current
->backing_dev_info
== NULL
||
1943 bdi_write_congested(current
->backing_dev_info
);
1947 * shrink_inactive_list() is a helper for shrink_node(). It returns the number
1948 * of reclaimed pages
1950 static noinline_for_stack
unsigned long
1951 shrink_inactive_list(unsigned long nr_to_scan
, struct lruvec
*lruvec
,
1952 struct scan_control
*sc
, enum lru_list lru
)
1954 LIST_HEAD(page_list
);
1955 unsigned long nr_scanned
;
1956 unsigned long nr_reclaimed
= 0;
1957 unsigned long nr_taken
;
1958 struct reclaim_stat stat
;
1959 int file
= is_file_lru(lru
);
1960 enum vm_event_item item
;
1961 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
1962 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1963 bool stalled
= false;
1965 while (unlikely(too_many_isolated(pgdat
, file
, sc
))) {
1969 /* wait a bit for the reclaimer. */
1973 /* We are about to die and free our memory. Return now. */
1974 if (fatal_signal_pending(current
))
1975 return SWAP_CLUSTER_MAX
;
1980 spin_lock_irq(&pgdat
->lru_lock
);
1982 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &page_list
,
1983 &nr_scanned
, sc
, lru
);
1985 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1986 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1988 item
= current_is_kswapd() ? PGSCAN_KSWAPD
: PGSCAN_DIRECT
;
1989 if (global_reclaim(sc
))
1990 __count_vm_events(item
, nr_scanned
);
1991 __count_memcg_events(lruvec_memcg(lruvec
), item
, nr_scanned
);
1992 spin_unlock_irq(&pgdat
->lru_lock
);
1997 nr_reclaimed
= shrink_page_list(&page_list
, pgdat
, sc
, 0,
2000 spin_lock_irq(&pgdat
->lru_lock
);
2002 item
= current_is_kswapd() ? PGSTEAL_KSWAPD
: PGSTEAL_DIRECT
;
2003 if (global_reclaim(sc
))
2004 __count_vm_events(item
, nr_reclaimed
);
2005 __count_memcg_events(lruvec_memcg(lruvec
), item
, nr_reclaimed
);
2006 reclaim_stat
->recent_rotated
[0] += stat
.nr_activate
[0];
2007 reclaim_stat
->recent_rotated
[1] += stat
.nr_activate
[1];
2009 move_pages_to_lru(lruvec
, &page_list
);
2011 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
2013 spin_unlock_irq(&pgdat
->lru_lock
);
2015 mem_cgroup_uncharge_list(&page_list
);
2016 free_unref_page_list(&page_list
);
2019 * If dirty pages are scanned that are not queued for IO, it
2020 * implies that flushers are not doing their job. This can
2021 * happen when memory pressure pushes dirty pages to the end of
2022 * the LRU before the dirty limits are breached and the dirty
2023 * data has expired. It can also happen when the proportion of
2024 * dirty pages grows not through writes but through memory
2025 * pressure reclaiming all the clean cache. And in some cases,
2026 * the flushers simply cannot keep up with the allocation
2027 * rate. Nudge the flusher threads in case they are asleep.
2029 if (stat
.nr_unqueued_dirty
== nr_taken
)
2030 wakeup_flusher_threads(WB_REASON_VMSCAN
);
2032 sc
->nr
.dirty
+= stat
.nr_dirty
;
2033 sc
->nr
.congested
+= stat
.nr_congested
;
2034 sc
->nr
.unqueued_dirty
+= stat
.nr_unqueued_dirty
;
2035 sc
->nr
.writeback
+= stat
.nr_writeback
;
2036 sc
->nr
.immediate
+= stat
.nr_immediate
;
2037 sc
->nr
.taken
+= nr_taken
;
2039 sc
->nr
.file_taken
+= nr_taken
;
2041 trace_mm_vmscan_lru_shrink_inactive(pgdat
->node_id
,
2042 nr_scanned
, nr_reclaimed
, &stat
, sc
->priority
, file
);
2043 return nr_reclaimed
;
2046 static void shrink_active_list(unsigned long nr_to_scan
,
2047 struct lruvec
*lruvec
,
2048 struct scan_control
*sc
,
2051 unsigned long nr_taken
;
2052 unsigned long nr_scanned
;
2053 unsigned long vm_flags
;
2054 LIST_HEAD(l_hold
); /* The pages which were snipped off */
2055 LIST_HEAD(l_active
);
2056 LIST_HEAD(l_inactive
);
2058 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
2059 unsigned nr_deactivate
, nr_activate
;
2060 unsigned nr_rotated
= 0;
2061 int file
= is_file_lru(lru
);
2062 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2066 spin_lock_irq(&pgdat
->lru_lock
);
2068 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &l_hold
,
2069 &nr_scanned
, sc
, lru
);
2071 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, nr_taken
);
2072 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
2074 __count_vm_events(PGREFILL
, nr_scanned
);
2075 __count_memcg_events(lruvec_memcg(lruvec
), PGREFILL
, nr_scanned
);
2077 spin_unlock_irq(&pgdat
->lru_lock
);
2079 while (!list_empty(&l_hold
)) {
2081 page
= lru_to_page(&l_hold
);
2082 list_del(&page
->lru
);
2084 if (unlikely(!page_evictable(page
))) {
2085 putback_lru_page(page
);
2089 if (unlikely(buffer_heads_over_limit
)) {
2090 if (page_has_private(page
) && trylock_page(page
)) {
2091 if (page_has_private(page
))
2092 try_to_release_page(page
, 0);
2097 if (page_referenced(page
, 0, sc
->target_mem_cgroup
,
2099 nr_rotated
+= hpage_nr_pages(page
);
2101 * Identify referenced, file-backed active pages and
2102 * give them one more trip around the active list. So
2103 * that executable code get better chances to stay in
2104 * memory under moderate memory pressure. Anon pages
2105 * are not likely to be evicted by use-once streaming
2106 * IO, plus JVM can create lots of anon VM_EXEC pages,
2107 * so we ignore them here.
2109 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
2110 list_add(&page
->lru
, &l_active
);
2115 ClearPageActive(page
); /* we are de-activating */
2116 SetPageWorkingset(page
);
2117 list_add(&page
->lru
, &l_inactive
);
2121 * Move pages back to the lru list.
2123 spin_lock_irq(&pgdat
->lru_lock
);
2125 * Count referenced pages from currently used mappings as rotated,
2126 * even though only some of them are actually re-activated. This
2127 * helps balance scan pressure between file and anonymous pages in
2130 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
2132 nr_activate
= move_pages_to_lru(lruvec
, &l_active
);
2133 nr_deactivate
= move_pages_to_lru(lruvec
, &l_inactive
);
2134 /* Keep all free pages in l_active list */
2135 list_splice(&l_inactive
, &l_active
);
2137 __count_vm_events(PGDEACTIVATE
, nr_deactivate
);
2138 __count_memcg_events(lruvec_memcg(lruvec
), PGDEACTIVATE
, nr_deactivate
);
2140 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
2141 spin_unlock_irq(&pgdat
->lru_lock
);
2143 mem_cgroup_uncharge_list(&l_active
);
2144 free_unref_page_list(&l_active
);
2145 trace_mm_vmscan_lru_shrink_active(pgdat
->node_id
, nr_taken
, nr_activate
,
2146 nr_deactivate
, nr_rotated
, sc
->priority
, file
);
2150 * The inactive anon list should be small enough that the VM never has
2151 * to do too much work.
2153 * The inactive file list should be small enough to leave most memory
2154 * to the established workingset on the scan-resistant active list,
2155 * but large enough to avoid thrashing the aggregate readahead window.
2157 * Both inactive lists should also be large enough that each inactive
2158 * page has a chance to be referenced again before it is reclaimed.
2160 * If that fails and refaulting is observed, the inactive list grows.
2162 * The inactive_ratio is the target ratio of ACTIVE to INACTIVE pages
2163 * on this LRU, maintained by the pageout code. An inactive_ratio
2164 * of 3 means 3:1 or 25% of the pages are kept on the inactive list.
2167 * memory ratio inactive
2168 * -------------------------------------
2177 static bool inactive_list_is_low(struct lruvec
*lruvec
, bool file
,
2178 struct scan_control
*sc
, bool trace
)
2180 enum lru_list active_lru
= file
* LRU_FILE
+ LRU_ACTIVE
;
2181 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2182 enum lru_list inactive_lru
= file
* LRU_FILE
;
2183 unsigned long inactive
, active
;
2184 unsigned long inactive_ratio
;
2185 unsigned long refaults
;
2189 * If we don't have swap space, anonymous page deactivation
2192 if (!file
&& !total_swap_pages
)
2195 inactive
= lruvec_lru_size(lruvec
, inactive_lru
, sc
->reclaim_idx
);
2196 active
= lruvec_lru_size(lruvec
, active_lru
, sc
->reclaim_idx
);
2199 * When refaults are being observed, it means a new workingset
2200 * is being established. Disable active list protection to get
2201 * rid of the stale workingset quickly.
2203 refaults
= lruvec_page_state_local(lruvec
, WORKINGSET_ACTIVATE
);
2204 if (file
&& lruvec
->refaults
!= refaults
) {
2207 gb
= (inactive
+ active
) >> (30 - PAGE_SHIFT
);
2209 inactive_ratio
= int_sqrt(10 * gb
);
2215 trace_mm_vmscan_inactive_list_is_low(pgdat
->node_id
, sc
->reclaim_idx
,
2216 lruvec_lru_size(lruvec
, inactive_lru
, MAX_NR_ZONES
), inactive
,
2217 lruvec_lru_size(lruvec
, active_lru
, MAX_NR_ZONES
), active
,
2218 inactive_ratio
, file
);
2220 return inactive
* inactive_ratio
< active
;
2223 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
2224 struct lruvec
*lruvec
, struct scan_control
*sc
)
2226 if (is_active_lru(lru
)) {
2227 if (inactive_list_is_low(lruvec
, is_file_lru(lru
), sc
, true))
2228 shrink_active_list(nr_to_scan
, lruvec
, sc
, lru
);
2232 return shrink_inactive_list(nr_to_scan
, lruvec
, sc
, lru
);
2243 * Determine how aggressively the anon and file LRU lists should be
2244 * scanned. The relative value of each set of LRU lists is determined
2245 * by looking at the fraction of the pages scanned we did rotate back
2246 * onto the active list instead of evict.
2248 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
2249 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
2251 static void get_scan_count(struct lruvec
*lruvec
, struct mem_cgroup
*memcg
,
2252 struct scan_control
*sc
, unsigned long *nr
,
2253 unsigned long *lru_pages
)
2255 int swappiness
= mem_cgroup_swappiness(memcg
);
2256 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
2258 u64 denominator
= 0; /* gcc */
2259 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2260 unsigned long anon_prio
, file_prio
;
2261 enum scan_balance scan_balance
;
2262 unsigned long anon
, file
;
2263 unsigned long ap
, fp
;
2266 /* If we have no swap space, do not bother scanning anon pages. */
2267 if (!sc
->may_swap
|| mem_cgroup_get_nr_swap_pages(memcg
) <= 0) {
2268 scan_balance
= SCAN_FILE
;
2273 * Global reclaim will swap to prevent OOM even with no
2274 * swappiness, but memcg users want to use this knob to
2275 * disable swapping for individual groups completely when
2276 * using the memory controller's swap limit feature would be
2279 if (!global_reclaim(sc
) && !swappiness
) {
2280 scan_balance
= SCAN_FILE
;
2285 * Do not apply any pressure balancing cleverness when the
2286 * system is close to OOM, scan both anon and file equally
2287 * (unless the swappiness setting disagrees with swapping).
2289 if (!sc
->priority
&& swappiness
) {
2290 scan_balance
= SCAN_EQUAL
;
2295 * Prevent the reclaimer from falling into the cache trap: as
2296 * cache pages start out inactive, every cache fault will tip
2297 * the scan balance towards the file LRU. And as the file LRU
2298 * shrinks, so does the window for rotation from references.
2299 * This means we have a runaway feedback loop where a tiny
2300 * thrashing file LRU becomes infinitely more attractive than
2301 * anon pages. Try to detect this based on file LRU size.
2303 if (global_reclaim(sc
)) {
2304 unsigned long pgdatfile
;
2305 unsigned long pgdatfree
;
2307 unsigned long total_high_wmark
= 0;
2309 pgdatfree
= sum_zone_node_page_state(pgdat
->node_id
, NR_FREE_PAGES
);
2310 pgdatfile
= node_page_state(pgdat
, NR_ACTIVE_FILE
) +
2311 node_page_state(pgdat
, NR_INACTIVE_FILE
);
2313 for (z
= 0; z
< MAX_NR_ZONES
; z
++) {
2314 struct zone
*zone
= &pgdat
->node_zones
[z
];
2315 if (!managed_zone(zone
))
2318 total_high_wmark
+= high_wmark_pages(zone
);
2321 if (unlikely(pgdatfile
+ pgdatfree
<= total_high_wmark
)) {
2323 * Force SCAN_ANON if there are enough inactive
2324 * anonymous pages on the LRU in eligible zones.
2325 * Otherwise, the small LRU gets thrashed.
2327 if (!inactive_list_is_low(lruvec
, false, sc
, false) &&
2328 lruvec_lru_size(lruvec
, LRU_INACTIVE_ANON
, sc
->reclaim_idx
)
2330 scan_balance
= SCAN_ANON
;
2337 * If there is enough inactive page cache, i.e. if the size of the
2338 * inactive list is greater than that of the active list *and* the
2339 * inactive list actually has some pages to scan on this priority, we
2340 * do not reclaim anything from the anonymous working set right now.
2341 * Without the second condition we could end up never scanning an
2342 * lruvec even if it has plenty of old anonymous pages unless the
2343 * system is under heavy pressure.
2345 if (!inactive_list_is_low(lruvec
, true, sc
, false) &&
2346 lruvec_lru_size(lruvec
, LRU_INACTIVE_FILE
, sc
->reclaim_idx
) >> sc
->priority
) {
2347 scan_balance
= SCAN_FILE
;
2351 scan_balance
= SCAN_FRACT
;
2354 * With swappiness at 100, anonymous and file have the same priority.
2355 * This scanning priority is essentially the inverse of IO cost.
2357 anon_prio
= swappiness
;
2358 file_prio
= 200 - anon_prio
;
2361 * OK, so we have swap space and a fair amount of page cache
2362 * pages. We use the recently rotated / recently scanned
2363 * ratios to determine how valuable each cache is.
2365 * Because workloads change over time (and to avoid overflow)
2366 * we keep these statistics as a floating average, which ends
2367 * up weighing recent references more than old ones.
2369 * anon in [0], file in [1]
2372 anon
= lruvec_lru_size(lruvec
, LRU_ACTIVE_ANON
, MAX_NR_ZONES
) +
2373 lruvec_lru_size(lruvec
, LRU_INACTIVE_ANON
, MAX_NR_ZONES
);
2374 file
= lruvec_lru_size(lruvec
, LRU_ACTIVE_FILE
, MAX_NR_ZONES
) +
2375 lruvec_lru_size(lruvec
, LRU_INACTIVE_FILE
, MAX_NR_ZONES
);
2377 spin_lock_irq(&pgdat
->lru_lock
);
2378 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
2379 reclaim_stat
->recent_scanned
[0] /= 2;
2380 reclaim_stat
->recent_rotated
[0] /= 2;
2383 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
2384 reclaim_stat
->recent_scanned
[1] /= 2;
2385 reclaim_stat
->recent_rotated
[1] /= 2;
2389 * The amount of pressure on anon vs file pages is inversely
2390 * proportional to the fraction of recently scanned pages on
2391 * each list that were recently referenced and in active use.
2393 ap
= anon_prio
* (reclaim_stat
->recent_scanned
[0] + 1);
2394 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
2396 fp
= file_prio
* (reclaim_stat
->recent_scanned
[1] + 1);
2397 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
2398 spin_unlock_irq(&pgdat
->lru_lock
);
2402 denominator
= ap
+ fp
+ 1;
2405 for_each_evictable_lru(lru
) {
2406 int file
= is_file_lru(lru
);
2410 size
= lruvec_lru_size(lruvec
, lru
, sc
->reclaim_idx
);
2411 scan
= size
>> sc
->priority
;
2413 * If the cgroup's already been deleted, make sure to
2414 * scrape out the remaining cache.
2416 if (!scan
&& !mem_cgroup_online(memcg
))
2417 scan
= min(size
, SWAP_CLUSTER_MAX
);
2419 switch (scan_balance
) {
2421 /* Scan lists relative to size */
2425 * Scan types proportional to swappiness and
2426 * their relative recent reclaim efficiency.
2427 * Make sure we don't miss the last page
2428 * because of a round-off error.
2430 scan
= DIV64_U64_ROUND_UP(scan
* fraction
[file
],
2435 /* Scan one type exclusively */
2436 if ((scan_balance
== SCAN_FILE
) != file
) {
2442 /* Look ma, no brain */
2452 * This is a basic per-node page freer. Used by both kswapd and direct reclaim.
2454 static void shrink_node_memcg(struct pglist_data
*pgdat
, struct mem_cgroup
*memcg
,
2455 struct scan_control
*sc
, unsigned long *lru_pages
)
2457 struct lruvec
*lruvec
= mem_cgroup_lruvec(pgdat
, memcg
);
2458 unsigned long nr
[NR_LRU_LISTS
];
2459 unsigned long targets
[NR_LRU_LISTS
];
2460 unsigned long nr_to_scan
;
2462 unsigned long nr_reclaimed
= 0;
2463 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
2464 struct blk_plug plug
;
2467 get_scan_count(lruvec
, memcg
, sc
, nr
, lru_pages
);
2469 /* Record the original scan target for proportional adjustments later */
2470 memcpy(targets
, nr
, sizeof(nr
));
2473 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
2474 * event that can occur when there is little memory pressure e.g.
2475 * multiple streaming readers/writers. Hence, we do not abort scanning
2476 * when the requested number of pages are reclaimed when scanning at
2477 * DEF_PRIORITY on the assumption that the fact we are direct
2478 * reclaiming implies that kswapd is not keeping up and it is best to
2479 * do a batch of work at once. For memcg reclaim one check is made to
2480 * abort proportional reclaim if either the file or anon lru has already
2481 * dropped to zero at the first pass.
2483 scan_adjusted
= (global_reclaim(sc
) && !current_is_kswapd() &&
2484 sc
->priority
== DEF_PRIORITY
);
2486 blk_start_plug(&plug
);
2487 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
2488 nr
[LRU_INACTIVE_FILE
]) {
2489 unsigned long nr_anon
, nr_file
, percentage
;
2490 unsigned long nr_scanned
;
2492 for_each_evictable_lru(lru
) {
2494 nr_to_scan
= min(nr
[lru
], SWAP_CLUSTER_MAX
);
2495 nr
[lru
] -= nr_to_scan
;
2497 nr_reclaimed
+= shrink_list(lru
, nr_to_scan
,
2504 if (nr_reclaimed
< nr_to_reclaim
|| scan_adjusted
)
2508 * For kswapd and memcg, reclaim at least the number of pages
2509 * requested. Ensure that the anon and file LRUs are scanned
2510 * proportionally what was requested by get_scan_count(). We
2511 * stop reclaiming one LRU and reduce the amount scanning
2512 * proportional to the original scan target.
2514 nr_file
= nr
[LRU_INACTIVE_FILE
] + nr
[LRU_ACTIVE_FILE
];
2515 nr_anon
= nr
[LRU_INACTIVE_ANON
] + nr
[LRU_ACTIVE_ANON
];
2518 * It's just vindictive to attack the larger once the smaller
2519 * has gone to zero. And given the way we stop scanning the
2520 * smaller below, this makes sure that we only make one nudge
2521 * towards proportionality once we've got nr_to_reclaim.
2523 if (!nr_file
|| !nr_anon
)
2526 if (nr_file
> nr_anon
) {
2527 unsigned long scan_target
= targets
[LRU_INACTIVE_ANON
] +
2528 targets
[LRU_ACTIVE_ANON
] + 1;
2530 percentage
= nr_anon
* 100 / scan_target
;
2532 unsigned long scan_target
= targets
[LRU_INACTIVE_FILE
] +
2533 targets
[LRU_ACTIVE_FILE
] + 1;
2535 percentage
= nr_file
* 100 / scan_target
;
2538 /* Stop scanning the smaller of the LRU */
2540 nr
[lru
+ LRU_ACTIVE
] = 0;
2543 * Recalculate the other LRU scan count based on its original
2544 * scan target and the percentage scanning already complete
2546 lru
= (lru
== LRU_FILE
) ? LRU_BASE
: LRU_FILE
;
2547 nr_scanned
= targets
[lru
] - nr
[lru
];
2548 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2549 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2552 nr_scanned
= targets
[lru
] - nr
[lru
];
2553 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2554 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2556 scan_adjusted
= true;
2558 blk_finish_plug(&plug
);
2559 sc
->nr_reclaimed
+= nr_reclaimed
;
2562 * Even if we did not try to evict anon pages at all, we want to
2563 * rebalance the anon lru active/inactive ratio.
2565 if (inactive_list_is_low(lruvec
, false, sc
, true))
2566 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
2567 sc
, LRU_ACTIVE_ANON
);
2570 /* Use reclaim/compaction for costly allocs or under memory pressure */
2571 static bool in_reclaim_compaction(struct scan_control
*sc
)
2573 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
2574 (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
||
2575 sc
->priority
< DEF_PRIORITY
- 2))
2582 * Reclaim/compaction is used for high-order allocation requests. It reclaims
2583 * order-0 pages before compacting the zone. should_continue_reclaim() returns
2584 * true if more pages should be reclaimed such that when the page allocator
2585 * calls try_to_compact_zone() that it will have enough free pages to succeed.
2586 * It will give up earlier than that if there is difficulty reclaiming pages.
2588 static inline bool should_continue_reclaim(struct pglist_data
*pgdat
,
2589 unsigned long nr_reclaimed
,
2590 unsigned long nr_scanned
,
2591 struct scan_control
*sc
)
2593 unsigned long pages_for_compaction
;
2594 unsigned long inactive_lru_pages
;
2597 /* If not in reclaim/compaction mode, stop */
2598 if (!in_reclaim_compaction(sc
))
2601 /* Consider stopping depending on scan and reclaim activity */
2602 if (sc
->gfp_mask
& __GFP_RETRY_MAYFAIL
) {
2604 * For __GFP_RETRY_MAYFAIL allocations, stop reclaiming if the
2605 * full LRU list has been scanned and we are still failing
2606 * to reclaim pages. This full LRU scan is potentially
2607 * expensive but a __GFP_RETRY_MAYFAIL caller really wants to succeed
2609 if (!nr_reclaimed
&& !nr_scanned
)
2613 * For non-__GFP_RETRY_MAYFAIL allocations which can presumably
2614 * fail without consequence, stop if we failed to reclaim
2615 * any pages from the last SWAP_CLUSTER_MAX number of
2616 * pages that were scanned. This will return to the
2617 * caller faster at the risk reclaim/compaction and
2618 * the resulting allocation attempt fails
2625 * If we have not reclaimed enough pages for compaction and the
2626 * inactive lists are large enough, continue reclaiming
2628 pages_for_compaction
= compact_gap(sc
->order
);
2629 inactive_lru_pages
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
2630 if (get_nr_swap_pages() > 0)
2631 inactive_lru_pages
+= node_page_state(pgdat
, NR_INACTIVE_ANON
);
2632 if (sc
->nr_reclaimed
< pages_for_compaction
&&
2633 inactive_lru_pages
> pages_for_compaction
)
2636 /* If compaction would go ahead or the allocation would succeed, stop */
2637 for (z
= 0; z
<= sc
->reclaim_idx
; z
++) {
2638 struct zone
*zone
= &pgdat
->node_zones
[z
];
2639 if (!managed_zone(zone
))
2642 switch (compaction_suitable(zone
, sc
->order
, 0, sc
->reclaim_idx
)) {
2643 case COMPACT_SUCCESS
:
2644 case COMPACT_CONTINUE
:
2647 /* check next zone */
2654 static bool pgdat_memcg_congested(pg_data_t
*pgdat
, struct mem_cgroup
*memcg
)
2656 return test_bit(PGDAT_CONGESTED
, &pgdat
->flags
) ||
2657 (memcg
&& memcg_congested(pgdat
, memcg
));
2660 static bool shrink_node(pg_data_t
*pgdat
, struct scan_control
*sc
)
2662 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2663 unsigned long nr_reclaimed
, nr_scanned
;
2664 bool reclaimable
= false;
2667 struct mem_cgroup
*root
= sc
->target_mem_cgroup
;
2668 struct mem_cgroup_reclaim_cookie reclaim
= {
2670 .priority
= sc
->priority
,
2672 unsigned long node_lru_pages
= 0;
2673 struct mem_cgroup
*memcg
;
2675 memset(&sc
->nr
, 0, sizeof(sc
->nr
));
2677 nr_reclaimed
= sc
->nr_reclaimed
;
2678 nr_scanned
= sc
->nr_scanned
;
2680 memcg
= mem_cgroup_iter(root
, NULL
, &reclaim
);
2682 unsigned long lru_pages
;
2683 unsigned long reclaimed
;
2684 unsigned long scanned
;
2686 switch (mem_cgroup_protected(root
, memcg
)) {
2687 case MEMCG_PROT_MIN
:
2690 * If there is no reclaimable memory, OOM.
2693 case MEMCG_PROT_LOW
:
2696 * Respect the protection only as long as
2697 * there is an unprotected supply
2698 * of reclaimable memory from other cgroups.
2700 if (!sc
->memcg_low_reclaim
) {
2701 sc
->memcg_low_skipped
= 1;
2704 memcg_memory_event(memcg
, MEMCG_LOW
);
2706 case MEMCG_PROT_NONE
:
2710 reclaimed
= sc
->nr_reclaimed
;
2711 scanned
= sc
->nr_scanned
;
2712 shrink_node_memcg(pgdat
, memcg
, sc
, &lru_pages
);
2713 node_lru_pages
+= lru_pages
;
2715 shrink_slab(sc
->gfp_mask
, pgdat
->node_id
, memcg
,
2718 /* Record the group's reclaim efficiency */
2719 vmpressure(sc
->gfp_mask
, memcg
, false,
2720 sc
->nr_scanned
- scanned
,
2721 sc
->nr_reclaimed
- reclaimed
);
2724 * Kswapd have to scan all memory cgroups to fulfill
2725 * the overall scan target for the node.
2727 * Limit reclaim, on the other hand, only cares about
2728 * nr_to_reclaim pages to be reclaimed and it will
2729 * retry with decreasing priority if one round over the
2730 * whole hierarchy is not sufficient.
2732 if (!current_is_kswapd() &&
2733 sc
->nr_reclaimed
>= sc
->nr_to_reclaim
) {
2734 mem_cgroup_iter_break(root
, memcg
);
2737 } while ((memcg
= mem_cgroup_iter(root
, memcg
, &reclaim
)));
2739 if (reclaim_state
) {
2740 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2741 reclaim_state
->reclaimed_slab
= 0;
2744 /* Record the subtree's reclaim efficiency */
2745 vmpressure(sc
->gfp_mask
, sc
->target_mem_cgroup
, true,
2746 sc
->nr_scanned
- nr_scanned
,
2747 sc
->nr_reclaimed
- nr_reclaimed
);
2749 if (sc
->nr_reclaimed
- nr_reclaimed
)
2752 if (current_is_kswapd()) {
2754 * If reclaim is isolating dirty pages under writeback,
2755 * it implies that the long-lived page allocation rate
2756 * is exceeding the page laundering rate. Either the
2757 * global limits are not being effective at throttling
2758 * processes due to the page distribution throughout
2759 * zones or there is heavy usage of a slow backing
2760 * device. The only option is to throttle from reclaim
2761 * context which is not ideal as there is no guarantee
2762 * the dirtying process is throttled in the same way
2763 * balance_dirty_pages() manages.
2765 * Once a node is flagged PGDAT_WRITEBACK, kswapd will
2766 * count the number of pages under pages flagged for
2767 * immediate reclaim and stall if any are encountered
2768 * in the nr_immediate check below.
2770 if (sc
->nr
.writeback
&& sc
->nr
.writeback
== sc
->nr
.taken
)
2771 set_bit(PGDAT_WRITEBACK
, &pgdat
->flags
);
2774 * Tag a node as congested if all the dirty pages
2775 * scanned were backed by a congested BDI and
2776 * wait_iff_congested will stall.
2778 if (sc
->nr
.dirty
&& sc
->nr
.dirty
== sc
->nr
.congested
)
2779 set_bit(PGDAT_CONGESTED
, &pgdat
->flags
);
2781 /* Allow kswapd to start writing pages during reclaim.*/
2782 if (sc
->nr
.unqueued_dirty
== sc
->nr
.file_taken
)
2783 set_bit(PGDAT_DIRTY
, &pgdat
->flags
);
2786 * If kswapd scans pages marked marked for immediate
2787 * reclaim and under writeback (nr_immediate), it
2788 * implies that pages are cycling through the LRU
2789 * faster than they are written so also forcibly stall.
2791 if (sc
->nr
.immediate
)
2792 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
2796 * Legacy memcg will stall in page writeback so avoid forcibly
2797 * stalling in wait_iff_congested().
2799 if (!global_reclaim(sc
) && sane_reclaim(sc
) &&
2800 sc
->nr
.dirty
&& sc
->nr
.dirty
== sc
->nr
.congested
)
2801 set_memcg_congestion(pgdat
, root
, true);
2804 * Stall direct reclaim for IO completions if underlying BDIs
2805 * and node is congested. Allow kswapd to continue until it
2806 * starts encountering unqueued dirty pages or cycling through
2807 * the LRU too quickly.
2809 if (!sc
->hibernation_mode
&& !current_is_kswapd() &&
2810 current_may_throttle() && pgdat_memcg_congested(pgdat
, root
))
2811 wait_iff_congested(BLK_RW_ASYNC
, HZ
/10);
2813 } while (should_continue_reclaim(pgdat
, sc
->nr_reclaimed
- nr_reclaimed
,
2814 sc
->nr_scanned
- nr_scanned
, sc
));
2817 * Kswapd gives up on balancing particular nodes after too
2818 * many failures to reclaim anything from them and goes to
2819 * sleep. On reclaim progress, reset the failure counter. A
2820 * successful direct reclaim run will revive a dormant kswapd.
2823 pgdat
->kswapd_failures
= 0;
2829 * Returns true if compaction should go ahead for a costly-order request, or
2830 * the allocation would already succeed without compaction. Return false if we
2831 * should reclaim first.
2833 static inline bool compaction_ready(struct zone
*zone
, struct scan_control
*sc
)
2835 unsigned long watermark
;
2836 enum compact_result suitable
;
2838 suitable
= compaction_suitable(zone
, sc
->order
, 0, sc
->reclaim_idx
);
2839 if (suitable
== COMPACT_SUCCESS
)
2840 /* Allocation should succeed already. Don't reclaim. */
2842 if (suitable
== COMPACT_SKIPPED
)
2843 /* Compaction cannot yet proceed. Do reclaim. */
2847 * Compaction is already possible, but it takes time to run and there
2848 * are potentially other callers using the pages just freed. So proceed
2849 * with reclaim to make a buffer of free pages available to give
2850 * compaction a reasonable chance of completing and allocating the page.
2851 * Note that we won't actually reclaim the whole buffer in one attempt
2852 * as the target watermark in should_continue_reclaim() is lower. But if
2853 * we are already above the high+gap watermark, don't reclaim at all.
2855 watermark
= high_wmark_pages(zone
) + compact_gap(sc
->order
);
2857 return zone_watermark_ok_safe(zone
, 0, watermark
, sc
->reclaim_idx
);
2861 * This is the direct reclaim path, for page-allocating processes. We only
2862 * try to reclaim pages from zones which will satisfy the caller's allocation
2865 * If a zone is deemed to be full of pinned pages then just give it a light
2866 * scan then give up on it.
2868 static void shrink_zones(struct zonelist
*zonelist
, struct scan_control
*sc
)
2872 unsigned long nr_soft_reclaimed
;
2873 unsigned long nr_soft_scanned
;
2875 pg_data_t
*last_pgdat
= NULL
;
2878 * If the number of buffer_heads in the machine exceeds the maximum
2879 * allowed level, force direct reclaim to scan the highmem zone as
2880 * highmem pages could be pinning lowmem pages storing buffer_heads
2882 orig_mask
= sc
->gfp_mask
;
2883 if (buffer_heads_over_limit
) {
2884 sc
->gfp_mask
|= __GFP_HIGHMEM
;
2885 sc
->reclaim_idx
= gfp_zone(sc
->gfp_mask
);
2888 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2889 sc
->reclaim_idx
, sc
->nodemask
) {
2891 * Take care memory controller reclaiming has small influence
2894 if (global_reclaim(sc
)) {
2895 if (!cpuset_zone_allowed(zone
,
2896 GFP_KERNEL
| __GFP_HARDWALL
))
2900 * If we already have plenty of memory free for
2901 * compaction in this zone, don't free any more.
2902 * Even though compaction is invoked for any
2903 * non-zero order, only frequent costly order
2904 * reclamation is disruptive enough to become a
2905 * noticeable problem, like transparent huge
2908 if (IS_ENABLED(CONFIG_COMPACTION
) &&
2909 sc
->order
> PAGE_ALLOC_COSTLY_ORDER
&&
2910 compaction_ready(zone
, sc
)) {
2911 sc
->compaction_ready
= true;
2916 * Shrink each node in the zonelist once. If the
2917 * zonelist is ordered by zone (not the default) then a
2918 * node may be shrunk multiple times but in that case
2919 * the user prefers lower zones being preserved.
2921 if (zone
->zone_pgdat
== last_pgdat
)
2925 * This steals pages from memory cgroups over softlimit
2926 * and returns the number of reclaimed pages and
2927 * scanned pages. This works for global memory pressure
2928 * and balancing, not for a memcg's limit.
2930 nr_soft_scanned
= 0;
2931 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
->zone_pgdat
,
2932 sc
->order
, sc
->gfp_mask
,
2934 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
2935 sc
->nr_scanned
+= nr_soft_scanned
;
2936 /* need some check for avoid more shrink_zone() */
2939 /* See comment about same check for global reclaim above */
2940 if (zone
->zone_pgdat
== last_pgdat
)
2942 last_pgdat
= zone
->zone_pgdat
;
2943 shrink_node(zone
->zone_pgdat
, sc
);
2947 * Restore to original mask to avoid the impact on the caller if we
2948 * promoted it to __GFP_HIGHMEM.
2950 sc
->gfp_mask
= orig_mask
;
2953 static void snapshot_refaults(struct mem_cgroup
*root_memcg
, pg_data_t
*pgdat
)
2955 struct mem_cgroup
*memcg
;
2957 memcg
= mem_cgroup_iter(root_memcg
, NULL
, NULL
);
2959 unsigned long refaults
;
2960 struct lruvec
*lruvec
;
2962 lruvec
= mem_cgroup_lruvec(pgdat
, memcg
);
2963 refaults
= lruvec_page_state_local(lruvec
, WORKINGSET_ACTIVATE
);
2964 lruvec
->refaults
= refaults
;
2965 } while ((memcg
= mem_cgroup_iter(root_memcg
, memcg
, NULL
)));
2969 * This is the main entry point to direct page reclaim.
2971 * If a full scan of the inactive list fails to free enough memory then we
2972 * are "out of memory" and something needs to be killed.
2974 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2975 * high - the zone may be full of dirty or under-writeback pages, which this
2976 * caller can't do much about. We kick the writeback threads and take explicit
2977 * naps in the hope that some of these pages can be written. But if the
2978 * allocating task holds filesystem locks which prevent writeout this might not
2979 * work, and the allocation attempt will fail.
2981 * returns: 0, if no pages reclaimed
2982 * else, the number of pages reclaimed
2984 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2985 struct scan_control
*sc
)
2987 int initial_priority
= sc
->priority
;
2988 pg_data_t
*last_pgdat
;
2992 delayacct_freepages_start();
2994 if (global_reclaim(sc
))
2995 __count_zid_vm_events(ALLOCSTALL
, sc
->reclaim_idx
, 1);
2998 vmpressure_prio(sc
->gfp_mask
, sc
->target_mem_cgroup
,
3001 shrink_zones(zonelist
, sc
);
3003 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
3006 if (sc
->compaction_ready
)
3010 * If we're getting trouble reclaiming, start doing
3011 * writepage even in laptop mode.
3013 if (sc
->priority
< DEF_PRIORITY
- 2)
3014 sc
->may_writepage
= 1;
3015 } while (--sc
->priority
>= 0);
3018 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
, sc
->reclaim_idx
,
3020 if (zone
->zone_pgdat
== last_pgdat
)
3022 last_pgdat
= zone
->zone_pgdat
;
3023 snapshot_refaults(sc
->target_mem_cgroup
, zone
->zone_pgdat
);
3024 set_memcg_congestion(last_pgdat
, sc
->target_mem_cgroup
, false);
3027 delayacct_freepages_end();
3029 if (sc
->nr_reclaimed
)
3030 return sc
->nr_reclaimed
;
3032 /* Aborted reclaim to try compaction? don't OOM, then */
3033 if (sc
->compaction_ready
)
3036 /* Untapped cgroup reserves? Don't OOM, retry. */
3037 if (sc
->memcg_low_skipped
) {
3038 sc
->priority
= initial_priority
;
3039 sc
->memcg_low_reclaim
= 1;
3040 sc
->memcg_low_skipped
= 0;
3047 static bool allow_direct_reclaim(pg_data_t
*pgdat
)
3050 unsigned long pfmemalloc_reserve
= 0;
3051 unsigned long free_pages
= 0;
3055 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
3058 for (i
= 0; i
<= ZONE_NORMAL
; i
++) {
3059 zone
= &pgdat
->node_zones
[i
];
3060 if (!managed_zone(zone
))
3063 if (!zone_reclaimable_pages(zone
))
3066 pfmemalloc_reserve
+= min_wmark_pages(zone
);
3067 free_pages
+= zone_page_state(zone
, NR_FREE_PAGES
);
3070 /* If there are no reserves (unexpected config) then do not throttle */
3071 if (!pfmemalloc_reserve
)
3074 wmark_ok
= free_pages
> pfmemalloc_reserve
/ 2;
3076 /* kswapd must be awake if processes are being throttled */
3077 if (!wmark_ok
&& waitqueue_active(&pgdat
->kswapd_wait
)) {
3078 pgdat
->kswapd_classzone_idx
= min(pgdat
->kswapd_classzone_idx
,
3079 (enum zone_type
)ZONE_NORMAL
);
3080 wake_up_interruptible(&pgdat
->kswapd_wait
);
3087 * Throttle direct reclaimers if backing storage is backed by the network
3088 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
3089 * depleted. kswapd will continue to make progress and wake the processes
3090 * when the low watermark is reached.
3092 * Returns true if a fatal signal was delivered during throttling. If this
3093 * happens, the page allocator should not consider triggering the OOM killer.
3095 static bool throttle_direct_reclaim(gfp_t gfp_mask
, struct zonelist
*zonelist
,
3096 nodemask_t
*nodemask
)
3100 pg_data_t
*pgdat
= NULL
;
3103 * Kernel threads should not be throttled as they may be indirectly
3104 * responsible for cleaning pages necessary for reclaim to make forward
3105 * progress. kjournald for example may enter direct reclaim while
3106 * committing a transaction where throttling it could forcing other
3107 * processes to block on log_wait_commit().
3109 if (current
->flags
& PF_KTHREAD
)
3113 * If a fatal signal is pending, this process should not throttle.
3114 * It should return quickly so it can exit and free its memory
3116 if (fatal_signal_pending(current
))
3120 * Check if the pfmemalloc reserves are ok by finding the first node
3121 * with a usable ZONE_NORMAL or lower zone. The expectation is that
3122 * GFP_KERNEL will be required for allocating network buffers when
3123 * swapping over the network so ZONE_HIGHMEM is unusable.
3125 * Throttling is based on the first usable node and throttled processes
3126 * wait on a queue until kswapd makes progress and wakes them. There
3127 * is an affinity then between processes waking up and where reclaim
3128 * progress has been made assuming the process wakes on the same node.
3129 * More importantly, processes running on remote nodes will not compete
3130 * for remote pfmemalloc reserves and processes on different nodes
3131 * should make reasonable progress.
3133 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
3134 gfp_zone(gfp_mask
), nodemask
) {
3135 if (zone_idx(zone
) > ZONE_NORMAL
)
3138 /* Throttle based on the first usable node */
3139 pgdat
= zone
->zone_pgdat
;
3140 if (allow_direct_reclaim(pgdat
))
3145 /* If no zone was usable by the allocation flags then do not throttle */
3149 /* Account for the throttling */
3150 count_vm_event(PGSCAN_DIRECT_THROTTLE
);
3153 * If the caller cannot enter the filesystem, it's possible that it
3154 * is due to the caller holding an FS lock or performing a journal
3155 * transaction in the case of a filesystem like ext[3|4]. In this case,
3156 * it is not safe to block on pfmemalloc_wait as kswapd could be
3157 * blocked waiting on the same lock. Instead, throttle for up to a
3158 * second before continuing.
3160 if (!(gfp_mask
& __GFP_FS
)) {
3161 wait_event_interruptible_timeout(pgdat
->pfmemalloc_wait
,
3162 allow_direct_reclaim(pgdat
), HZ
);
3167 /* Throttle until kswapd wakes the process */
3168 wait_event_killable(zone
->zone_pgdat
->pfmemalloc_wait
,
3169 allow_direct_reclaim(pgdat
));
3172 if (fatal_signal_pending(current
))
3179 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
3180 gfp_t gfp_mask
, nodemask_t
*nodemask
)
3182 unsigned long nr_reclaimed
;
3183 struct scan_control sc
= {
3184 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
3185 .gfp_mask
= current_gfp_context(gfp_mask
),
3186 .reclaim_idx
= gfp_zone(gfp_mask
),
3188 .nodemask
= nodemask
,
3189 .priority
= DEF_PRIORITY
,
3190 .may_writepage
= !laptop_mode
,
3196 * scan_control uses s8 fields for order, priority, and reclaim_idx.
3197 * Confirm they are large enough for max values.
3199 BUILD_BUG_ON(MAX_ORDER
> S8_MAX
);
3200 BUILD_BUG_ON(DEF_PRIORITY
> S8_MAX
);
3201 BUILD_BUG_ON(MAX_NR_ZONES
> S8_MAX
);
3204 * Do not enter reclaim if fatal signal was delivered while throttled.
3205 * 1 is returned so that the page allocator does not OOM kill at this
3208 if (throttle_direct_reclaim(sc
.gfp_mask
, zonelist
, nodemask
))
3211 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3212 trace_mm_vmscan_direct_reclaim_begin(order
, sc
.gfp_mask
);
3214 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3216 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
3217 set_task_reclaim_state(current
, NULL
);
3219 return nr_reclaimed
;
3224 /* Only used by soft limit reclaim. Do not reuse for anything else. */
3225 unsigned long mem_cgroup_shrink_node(struct mem_cgroup
*memcg
,
3226 gfp_t gfp_mask
, bool noswap
,
3228 unsigned long *nr_scanned
)
3230 struct scan_control sc
= {
3231 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
3232 .target_mem_cgroup
= memcg
,
3233 .may_writepage
= !laptop_mode
,
3235 .reclaim_idx
= MAX_NR_ZONES
- 1,
3236 .may_swap
= !noswap
,
3238 unsigned long lru_pages
;
3240 WARN_ON_ONCE(!current
->reclaim_state
);
3242 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
3243 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
3245 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc
.order
,
3249 * NOTE: Although we can get the priority field, using it
3250 * here is not a good idea, since it limits the pages we can scan.
3251 * if we don't reclaim here, the shrink_node from balance_pgdat
3252 * will pick up pages from other mem cgroup's as well. We hack
3253 * the priority and make it zero.
3255 shrink_node_memcg(pgdat
, memcg
, &sc
, &lru_pages
);
3257 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
3259 *nr_scanned
= sc
.nr_scanned
;
3261 return sc
.nr_reclaimed
;
3264 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*memcg
,
3265 unsigned long nr_pages
,
3269 struct zonelist
*zonelist
;
3270 unsigned long nr_reclaimed
;
3271 unsigned long pflags
;
3273 unsigned int noreclaim_flag
;
3274 struct scan_control sc
= {
3275 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
3276 .gfp_mask
= (current_gfp_context(gfp_mask
) & GFP_RECLAIM_MASK
) |
3277 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
3278 .reclaim_idx
= MAX_NR_ZONES
- 1,
3279 .target_mem_cgroup
= memcg
,
3280 .priority
= DEF_PRIORITY
,
3281 .may_writepage
= !laptop_mode
,
3283 .may_swap
= may_swap
,
3286 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3288 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
3289 * take care of from where we get pages. So the node where we start the
3290 * scan does not need to be the current node.
3292 nid
= mem_cgroup_select_victim_node(memcg
);
3294 zonelist
= &NODE_DATA(nid
)->node_zonelists
[ZONELIST_FALLBACK
];
3296 trace_mm_vmscan_memcg_reclaim_begin(0, sc
.gfp_mask
);
3298 psi_memstall_enter(&pflags
);
3299 noreclaim_flag
= memalloc_noreclaim_save();
3301 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3303 memalloc_noreclaim_restore(noreclaim_flag
);
3304 psi_memstall_leave(&pflags
);
3306 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
3307 set_task_reclaim_state(current
, NULL
);
3309 return nr_reclaimed
;
3313 static void age_active_anon(struct pglist_data
*pgdat
,
3314 struct scan_control
*sc
)
3316 struct mem_cgroup
*memcg
;
3318 if (!total_swap_pages
)
3321 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
3323 struct lruvec
*lruvec
= mem_cgroup_lruvec(pgdat
, memcg
);
3325 if (inactive_list_is_low(lruvec
, false, sc
, true))
3326 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
3327 sc
, LRU_ACTIVE_ANON
);
3329 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
3333 static bool pgdat_watermark_boosted(pg_data_t
*pgdat
, int classzone_idx
)
3339 * Check for watermark boosts top-down as the higher zones
3340 * are more likely to be boosted. Both watermarks and boosts
3341 * should not be checked at the time time as reclaim would
3342 * start prematurely when there is no boosting and a lower
3345 for (i
= classzone_idx
; i
>= 0; i
--) {
3346 zone
= pgdat
->node_zones
+ i
;
3347 if (!managed_zone(zone
))
3350 if (zone
->watermark_boost
)
3358 * Returns true if there is an eligible zone balanced for the request order
3361 static bool pgdat_balanced(pg_data_t
*pgdat
, int order
, int classzone_idx
)
3364 unsigned long mark
= -1;
3368 * Check watermarks bottom-up as lower zones are more likely to
3371 for (i
= 0; i
<= classzone_idx
; i
++) {
3372 zone
= pgdat
->node_zones
+ i
;
3374 if (!managed_zone(zone
))
3377 mark
= high_wmark_pages(zone
);
3378 if (zone_watermark_ok_safe(zone
, order
, mark
, classzone_idx
))
3383 * If a node has no populated zone within classzone_idx, it does not
3384 * need balancing by definition. This can happen if a zone-restricted
3385 * allocation tries to wake a remote kswapd.
3393 /* Clear pgdat state for congested, dirty or under writeback. */
3394 static void clear_pgdat_congested(pg_data_t
*pgdat
)
3396 clear_bit(PGDAT_CONGESTED
, &pgdat
->flags
);
3397 clear_bit(PGDAT_DIRTY
, &pgdat
->flags
);
3398 clear_bit(PGDAT_WRITEBACK
, &pgdat
->flags
);
3402 * Prepare kswapd for sleeping. This verifies that there are no processes
3403 * waiting in throttle_direct_reclaim() and that watermarks have been met.
3405 * Returns true if kswapd is ready to sleep
3407 static bool prepare_kswapd_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
3410 * The throttled processes are normally woken up in balance_pgdat() as
3411 * soon as allow_direct_reclaim() is true. But there is a potential
3412 * race between when kswapd checks the watermarks and a process gets
3413 * throttled. There is also a potential race if processes get
3414 * throttled, kswapd wakes, a large process exits thereby balancing the
3415 * zones, which causes kswapd to exit balance_pgdat() before reaching
3416 * the wake up checks. If kswapd is going to sleep, no process should
3417 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
3418 * the wake up is premature, processes will wake kswapd and get
3419 * throttled again. The difference from wake ups in balance_pgdat() is
3420 * that here we are under prepare_to_wait().
3422 if (waitqueue_active(&pgdat
->pfmemalloc_wait
))
3423 wake_up_all(&pgdat
->pfmemalloc_wait
);
3425 /* Hopeless node, leave it to direct reclaim */
3426 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
3429 if (pgdat_balanced(pgdat
, order
, classzone_idx
)) {
3430 clear_pgdat_congested(pgdat
);
3438 * kswapd shrinks a node of pages that are at or below the highest usable
3439 * zone that is currently unbalanced.
3441 * Returns true if kswapd scanned at least the requested number of pages to
3442 * reclaim or if the lack of progress was due to pages under writeback.
3443 * This is used to determine if the scanning priority needs to be raised.
3445 static bool kswapd_shrink_node(pg_data_t
*pgdat
,
3446 struct scan_control
*sc
)
3451 /* Reclaim a number of pages proportional to the number of zones */
3452 sc
->nr_to_reclaim
= 0;
3453 for (z
= 0; z
<= sc
->reclaim_idx
; z
++) {
3454 zone
= pgdat
->node_zones
+ z
;
3455 if (!managed_zone(zone
))
3458 sc
->nr_to_reclaim
+= max(high_wmark_pages(zone
), SWAP_CLUSTER_MAX
);
3462 * Historically care was taken to put equal pressure on all zones but
3463 * now pressure is applied based on node LRU order.
3465 shrink_node(pgdat
, sc
);
3468 * Fragmentation may mean that the system cannot be rebalanced for
3469 * high-order allocations. If twice the allocation size has been
3470 * reclaimed then recheck watermarks only at order-0 to prevent
3471 * excessive reclaim. Assume that a process requested a high-order
3472 * can direct reclaim/compact.
3474 if (sc
->order
&& sc
->nr_reclaimed
>= compact_gap(sc
->order
))
3477 return sc
->nr_scanned
>= sc
->nr_to_reclaim
;
3481 * For kswapd, balance_pgdat() will reclaim pages across a node from zones
3482 * that are eligible for use by the caller until at least one zone is
3485 * Returns the order kswapd finished reclaiming at.
3487 * kswapd scans the zones in the highmem->normal->dma direction. It skips
3488 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
3489 * found to have free_pages <= high_wmark_pages(zone), any page in that zone
3490 * or lower is eligible for reclaim until at least one usable zone is
3493 static int balance_pgdat(pg_data_t
*pgdat
, int order
, int classzone_idx
)
3496 unsigned long nr_soft_reclaimed
;
3497 unsigned long nr_soft_scanned
;
3498 unsigned long pflags
;
3499 unsigned long nr_boost_reclaim
;
3500 unsigned long zone_boosts
[MAX_NR_ZONES
] = { 0, };
3503 struct scan_control sc
= {
3504 .gfp_mask
= GFP_KERNEL
,
3509 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3510 psi_memstall_enter(&pflags
);
3511 __fs_reclaim_acquire();
3513 count_vm_event(PAGEOUTRUN
);
3516 * Account for the reclaim boost. Note that the zone boost is left in
3517 * place so that parallel allocations that are near the watermark will
3518 * stall or direct reclaim until kswapd is finished.
3520 nr_boost_reclaim
= 0;
3521 for (i
= 0; i
<= classzone_idx
; i
++) {
3522 zone
= pgdat
->node_zones
+ i
;
3523 if (!managed_zone(zone
))
3526 nr_boost_reclaim
+= zone
->watermark_boost
;
3527 zone_boosts
[i
] = zone
->watermark_boost
;
3529 boosted
= nr_boost_reclaim
;
3532 sc
.priority
= DEF_PRIORITY
;
3534 unsigned long nr_reclaimed
= sc
.nr_reclaimed
;
3535 bool raise_priority
= true;
3539 sc
.reclaim_idx
= classzone_idx
;
3542 * If the number of buffer_heads exceeds the maximum allowed
3543 * then consider reclaiming from all zones. This has a dual
3544 * purpose -- on 64-bit systems it is expected that
3545 * buffer_heads are stripped during active rotation. On 32-bit
3546 * systems, highmem pages can pin lowmem memory and shrinking
3547 * buffers can relieve lowmem pressure. Reclaim may still not
3548 * go ahead if all eligible zones for the original allocation
3549 * request are balanced to avoid excessive reclaim from kswapd.
3551 if (buffer_heads_over_limit
) {
3552 for (i
= MAX_NR_ZONES
- 1; i
>= 0; i
--) {
3553 zone
= pgdat
->node_zones
+ i
;
3554 if (!managed_zone(zone
))
3563 * If the pgdat is imbalanced then ignore boosting and preserve
3564 * the watermarks for a later time and restart. Note that the
3565 * zone watermarks will be still reset at the end of balancing
3566 * on the grounds that the normal reclaim should be enough to
3567 * re-evaluate if boosting is required when kswapd next wakes.
3569 balanced
= pgdat_balanced(pgdat
, sc
.order
, classzone_idx
);
3570 if (!balanced
&& nr_boost_reclaim
) {
3571 nr_boost_reclaim
= 0;
3576 * If boosting is not active then only reclaim if there are no
3577 * eligible zones. Note that sc.reclaim_idx is not used as
3578 * buffer_heads_over_limit may have adjusted it.
3580 if (!nr_boost_reclaim
&& balanced
)
3583 /* Limit the priority of boosting to avoid reclaim writeback */
3584 if (nr_boost_reclaim
&& sc
.priority
== DEF_PRIORITY
- 2)
3585 raise_priority
= false;
3588 * Do not writeback or swap pages for boosted reclaim. The
3589 * intent is to relieve pressure not issue sub-optimal IO
3590 * from reclaim context. If no pages are reclaimed, the
3591 * reclaim will be aborted.
3593 sc
.may_writepage
= !laptop_mode
&& !nr_boost_reclaim
;
3594 sc
.may_swap
= !nr_boost_reclaim
;
3597 * Do some background aging of the anon list, to give
3598 * pages a chance to be referenced before reclaiming. All
3599 * pages are rotated regardless of classzone as this is
3600 * about consistent aging.
3602 age_active_anon(pgdat
, &sc
);
3605 * If we're getting trouble reclaiming, start doing writepage
3606 * even in laptop mode.
3608 if (sc
.priority
< DEF_PRIORITY
- 2)
3609 sc
.may_writepage
= 1;
3611 /* Call soft limit reclaim before calling shrink_node. */
3613 nr_soft_scanned
= 0;
3614 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(pgdat
, sc
.order
,
3615 sc
.gfp_mask
, &nr_soft_scanned
);
3616 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
3619 * There should be no need to raise the scanning priority if
3620 * enough pages are already being scanned that that high
3621 * watermark would be met at 100% efficiency.
3623 if (kswapd_shrink_node(pgdat
, &sc
))
3624 raise_priority
= false;
3627 * If the low watermark is met there is no need for processes
3628 * to be throttled on pfmemalloc_wait as they should not be
3629 * able to safely make forward progress. Wake them
3631 if (waitqueue_active(&pgdat
->pfmemalloc_wait
) &&
3632 allow_direct_reclaim(pgdat
))
3633 wake_up_all(&pgdat
->pfmemalloc_wait
);
3635 /* Check if kswapd should be suspending */
3636 __fs_reclaim_release();
3637 ret
= try_to_freeze();
3638 __fs_reclaim_acquire();
3639 if (ret
|| kthread_should_stop())
3643 * Raise priority if scanning rate is too low or there was no
3644 * progress in reclaiming pages
3646 nr_reclaimed
= sc
.nr_reclaimed
- nr_reclaimed
;
3647 nr_boost_reclaim
-= min(nr_boost_reclaim
, nr_reclaimed
);
3650 * If reclaim made no progress for a boost, stop reclaim as
3651 * IO cannot be queued and it could be an infinite loop in
3652 * extreme circumstances.
3654 if (nr_boost_reclaim
&& !nr_reclaimed
)
3657 if (raise_priority
|| !nr_reclaimed
)
3659 } while (sc
.priority
>= 1);
3661 if (!sc
.nr_reclaimed
)
3662 pgdat
->kswapd_failures
++;
3665 /* If reclaim was boosted, account for the reclaim done in this pass */
3667 unsigned long flags
;
3669 for (i
= 0; i
<= classzone_idx
; i
++) {
3670 if (!zone_boosts
[i
])
3673 /* Increments are under the zone lock */
3674 zone
= pgdat
->node_zones
+ i
;
3675 spin_lock_irqsave(&zone
->lock
, flags
);
3676 zone
->watermark_boost
-= min(zone
->watermark_boost
, zone_boosts
[i
]);
3677 spin_unlock_irqrestore(&zone
->lock
, flags
);
3681 * As there is now likely space, wakeup kcompact to defragment
3684 wakeup_kcompactd(pgdat
, pageblock_order
, classzone_idx
);
3687 snapshot_refaults(NULL
, pgdat
);
3688 __fs_reclaim_release();
3689 psi_memstall_leave(&pflags
);
3690 set_task_reclaim_state(current
, NULL
);
3693 * Return the order kswapd stopped reclaiming at as
3694 * prepare_kswapd_sleep() takes it into account. If another caller
3695 * entered the allocator slow path while kswapd was awake, order will
3696 * remain at the higher level.
3702 * The pgdat->kswapd_classzone_idx is used to pass the highest zone index to be
3703 * reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is not
3704 * a valid index then either kswapd runs for first time or kswapd couldn't sleep
3705 * after previous reclaim attempt (node is still unbalanced). In that case
3706 * return the zone index of the previous kswapd reclaim cycle.
3708 static enum zone_type
kswapd_classzone_idx(pg_data_t
*pgdat
,
3709 enum zone_type prev_classzone_idx
)
3711 if (pgdat
->kswapd_classzone_idx
== MAX_NR_ZONES
)
3712 return prev_classzone_idx
;
3713 return pgdat
->kswapd_classzone_idx
;
3716 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int alloc_order
, int reclaim_order
,
3717 unsigned int classzone_idx
)
3722 if (freezing(current
) || kthread_should_stop())
3725 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
3728 * Try to sleep for a short interval. Note that kcompactd will only be
3729 * woken if it is possible to sleep for a short interval. This is
3730 * deliberate on the assumption that if reclaim cannot keep an
3731 * eligible zone balanced that it's also unlikely that compaction will
3734 if (prepare_kswapd_sleep(pgdat
, reclaim_order
, classzone_idx
)) {
3736 * Compaction records what page blocks it recently failed to
3737 * isolate pages from and skips them in the future scanning.
3738 * When kswapd is going to sleep, it is reasonable to assume
3739 * that pages and compaction may succeed so reset the cache.
3741 reset_isolation_suitable(pgdat
);
3744 * We have freed the memory, now we should compact it to make
3745 * allocation of the requested order possible.
3747 wakeup_kcompactd(pgdat
, alloc_order
, classzone_idx
);
3749 remaining
= schedule_timeout(HZ
/10);
3752 * If woken prematurely then reset kswapd_classzone_idx and
3753 * order. The values will either be from a wakeup request or
3754 * the previous request that slept prematurely.
3757 pgdat
->kswapd_classzone_idx
= kswapd_classzone_idx(pgdat
, classzone_idx
);
3758 pgdat
->kswapd_order
= max(pgdat
->kswapd_order
, reclaim_order
);
3761 finish_wait(&pgdat
->kswapd_wait
, &wait
);
3762 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
3766 * After a short sleep, check if it was a premature sleep. If not, then
3767 * go fully to sleep until explicitly woken up.
3770 prepare_kswapd_sleep(pgdat
, reclaim_order
, classzone_idx
)) {
3771 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
3774 * vmstat counters are not perfectly accurate and the estimated
3775 * value for counters such as NR_FREE_PAGES can deviate from the
3776 * true value by nr_online_cpus * threshold. To avoid the zone
3777 * watermarks being breached while under pressure, we reduce the
3778 * per-cpu vmstat threshold while kswapd is awake and restore
3779 * them before going back to sleep.
3781 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
3783 if (!kthread_should_stop())
3786 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
3789 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
3791 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
3793 finish_wait(&pgdat
->kswapd_wait
, &wait
);
3797 * The background pageout daemon, started as a kernel thread
3798 * from the init process.
3800 * This basically trickles out pages so that we have _some_
3801 * free memory available even if there is no other activity
3802 * that frees anything up. This is needed for things like routing
3803 * etc, where we otherwise might have all activity going on in
3804 * asynchronous contexts that cannot page things out.
3806 * If there are applications that are active memory-allocators
3807 * (most normal use), this basically shouldn't matter.
3809 static int kswapd(void *p
)
3811 unsigned int alloc_order
, reclaim_order
;
3812 unsigned int classzone_idx
= MAX_NR_ZONES
- 1;
3813 pg_data_t
*pgdat
= (pg_data_t
*)p
;
3814 struct task_struct
*tsk
= current
;
3815 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
3817 if (!cpumask_empty(cpumask
))
3818 set_cpus_allowed_ptr(tsk
, cpumask
);
3821 * Tell the memory management that we're a "memory allocator",
3822 * and that if we need more memory we should get access to it
3823 * regardless (see "__alloc_pages()"). "kswapd" should
3824 * never get caught in the normal page freeing logic.
3826 * (Kswapd normally doesn't need memory anyway, but sometimes
3827 * you need a small amount of memory in order to be able to
3828 * page out something else, and this flag essentially protects
3829 * us from recursively trying to free more memory as we're
3830 * trying to free the first piece of memory in the first place).
3832 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
3835 pgdat
->kswapd_order
= 0;
3836 pgdat
->kswapd_classzone_idx
= MAX_NR_ZONES
;
3840 alloc_order
= reclaim_order
= pgdat
->kswapd_order
;
3841 classzone_idx
= kswapd_classzone_idx(pgdat
, classzone_idx
);
3844 kswapd_try_to_sleep(pgdat
, alloc_order
, reclaim_order
,
3847 /* Read the new order and classzone_idx */
3848 alloc_order
= reclaim_order
= pgdat
->kswapd_order
;
3849 classzone_idx
= kswapd_classzone_idx(pgdat
, classzone_idx
);
3850 pgdat
->kswapd_order
= 0;
3851 pgdat
->kswapd_classzone_idx
= MAX_NR_ZONES
;
3853 ret
= try_to_freeze();
3854 if (kthread_should_stop())
3858 * We can speed up thawing tasks if we don't call balance_pgdat
3859 * after returning from the refrigerator
3865 * Reclaim begins at the requested order but if a high-order
3866 * reclaim fails then kswapd falls back to reclaiming for
3867 * order-0. If that happens, kswapd will consider sleeping
3868 * for the order it finished reclaiming at (reclaim_order)
3869 * but kcompactd is woken to compact for the original
3870 * request (alloc_order).
3872 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, classzone_idx
,
3874 reclaim_order
= balance_pgdat(pgdat
, alloc_order
, classzone_idx
);
3875 if (reclaim_order
< alloc_order
)
3876 goto kswapd_try_sleep
;
3879 tsk
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
);
3885 * A zone is low on free memory or too fragmented for high-order memory. If
3886 * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
3887 * pgdat. It will wake up kcompactd after reclaiming memory. If kswapd reclaim
3888 * has failed or is not needed, still wake up kcompactd if only compaction is
3891 void wakeup_kswapd(struct zone
*zone
, gfp_t gfp_flags
, int order
,
3892 enum zone_type classzone_idx
)
3896 if (!managed_zone(zone
))
3899 if (!cpuset_zone_allowed(zone
, gfp_flags
))
3901 pgdat
= zone
->zone_pgdat
;
3903 if (pgdat
->kswapd_classzone_idx
== MAX_NR_ZONES
)
3904 pgdat
->kswapd_classzone_idx
= classzone_idx
;
3906 pgdat
->kswapd_classzone_idx
= max(pgdat
->kswapd_classzone_idx
,
3908 pgdat
->kswapd_order
= max(pgdat
->kswapd_order
, order
);
3909 if (!waitqueue_active(&pgdat
->kswapd_wait
))
3912 /* Hopeless node, leave it to direct reclaim if possible */
3913 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
||
3914 (pgdat_balanced(pgdat
, order
, classzone_idx
) &&
3915 !pgdat_watermark_boosted(pgdat
, classzone_idx
))) {
3917 * There may be plenty of free memory available, but it's too
3918 * fragmented for high-order allocations. Wake up kcompactd
3919 * and rely on compaction_suitable() to determine if it's
3920 * needed. If it fails, it will defer subsequent attempts to
3921 * ratelimit its work.
3923 if (!(gfp_flags
& __GFP_DIRECT_RECLAIM
))
3924 wakeup_kcompactd(pgdat
, order
, classzone_idx
);
3928 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, classzone_idx
, order
,
3930 wake_up_interruptible(&pgdat
->kswapd_wait
);
3933 #ifdef CONFIG_HIBERNATION
3935 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3938 * Rather than trying to age LRUs the aim is to preserve the overall
3939 * LRU order by reclaiming preferentially
3940 * inactive > active > active referenced > active mapped
3942 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
3944 struct scan_control sc
= {
3945 .nr_to_reclaim
= nr_to_reclaim
,
3946 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
3947 .reclaim_idx
= MAX_NR_ZONES
- 1,
3948 .priority
= DEF_PRIORITY
,
3952 .hibernation_mode
= 1,
3954 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
3955 unsigned long nr_reclaimed
;
3956 unsigned int noreclaim_flag
;
3958 fs_reclaim_acquire(sc
.gfp_mask
);
3959 noreclaim_flag
= memalloc_noreclaim_save();
3960 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3962 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3964 set_task_reclaim_state(current
, NULL
);
3965 memalloc_noreclaim_restore(noreclaim_flag
);
3966 fs_reclaim_release(sc
.gfp_mask
);
3968 return nr_reclaimed
;
3970 #endif /* CONFIG_HIBERNATION */
3972 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3973 not required for correctness. So if the last cpu in a node goes
3974 away, we get changed to run anywhere: as the first one comes back,
3975 restore their cpu bindings. */
3976 static int kswapd_cpu_online(unsigned int cpu
)
3980 for_each_node_state(nid
, N_MEMORY
) {
3981 pg_data_t
*pgdat
= NODE_DATA(nid
);
3982 const struct cpumask
*mask
;
3984 mask
= cpumask_of_node(pgdat
->node_id
);
3986 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
3987 /* One of our CPUs online: restore mask */
3988 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
3994 * This kswapd start function will be called by init and node-hot-add.
3995 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3997 int kswapd_run(int nid
)
3999 pg_data_t
*pgdat
= NODE_DATA(nid
);
4005 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
4006 if (IS_ERR(pgdat
->kswapd
)) {
4007 /* failure at boot is fatal */
4008 BUG_ON(system_state
< SYSTEM_RUNNING
);
4009 pr_err("Failed to start kswapd on node %d\n", nid
);
4010 ret
= PTR_ERR(pgdat
->kswapd
);
4011 pgdat
->kswapd
= NULL
;
4017 * Called by memory hotplug when all memory in a node is offlined. Caller must
4018 * hold mem_hotplug_begin/end().
4020 void kswapd_stop(int nid
)
4022 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
4025 kthread_stop(kswapd
);
4026 NODE_DATA(nid
)->kswapd
= NULL
;
4030 static int __init
kswapd_init(void)
4035 for_each_node_state(nid
, N_MEMORY
)
4037 ret
= cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN
,
4038 "mm/vmscan:online", kswapd_cpu_online
,
4044 module_init(kswapd_init
)
4050 * If non-zero call node_reclaim when the number of free pages falls below
4053 int node_reclaim_mode __read_mostly
;
4055 #define RECLAIM_OFF 0
4056 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
4057 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
4058 #define RECLAIM_UNMAP (1<<2) /* Unmap pages during reclaim */
4061 * Priority for NODE_RECLAIM. This determines the fraction of pages
4062 * of a node considered for each zone_reclaim. 4 scans 1/16th of
4065 #define NODE_RECLAIM_PRIORITY 4
4068 * Percentage of pages in a zone that must be unmapped for node_reclaim to
4071 int sysctl_min_unmapped_ratio
= 1;
4074 * If the number of slab pages in a zone grows beyond this percentage then
4075 * slab reclaim needs to occur.
4077 int sysctl_min_slab_ratio
= 5;
4079 static inline unsigned long node_unmapped_file_pages(struct pglist_data
*pgdat
)
4081 unsigned long file_mapped
= node_page_state(pgdat
, NR_FILE_MAPPED
);
4082 unsigned long file_lru
= node_page_state(pgdat
, NR_INACTIVE_FILE
) +
4083 node_page_state(pgdat
, NR_ACTIVE_FILE
);
4086 * It's possible for there to be more file mapped pages than
4087 * accounted for by the pages on the file LRU lists because
4088 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
4090 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
4093 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
4094 static unsigned long node_pagecache_reclaimable(struct pglist_data
*pgdat
)
4096 unsigned long nr_pagecache_reclaimable
;
4097 unsigned long delta
= 0;
4100 * If RECLAIM_UNMAP is set, then all file pages are considered
4101 * potentially reclaimable. Otherwise, we have to worry about
4102 * pages like swapcache and node_unmapped_file_pages() provides
4105 if (node_reclaim_mode
& RECLAIM_UNMAP
)
4106 nr_pagecache_reclaimable
= node_page_state(pgdat
, NR_FILE_PAGES
);
4108 nr_pagecache_reclaimable
= node_unmapped_file_pages(pgdat
);
4110 /* If we can't clean pages, remove dirty pages from consideration */
4111 if (!(node_reclaim_mode
& RECLAIM_WRITE
))
4112 delta
+= node_page_state(pgdat
, NR_FILE_DIRTY
);
4114 /* Watch for any possible underflows due to delta */
4115 if (unlikely(delta
> nr_pagecache_reclaimable
))
4116 delta
= nr_pagecache_reclaimable
;
4118 return nr_pagecache_reclaimable
- delta
;
4122 * Try to free up some pages from this node through reclaim.
4124 static int __node_reclaim(struct pglist_data
*pgdat
, gfp_t gfp_mask
, unsigned int order
)
4126 /* Minimum pages needed in order to stay on node */
4127 const unsigned long nr_pages
= 1 << order
;
4128 struct task_struct
*p
= current
;
4129 unsigned int noreclaim_flag
;
4130 struct scan_control sc
= {
4131 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
4132 .gfp_mask
= current_gfp_context(gfp_mask
),
4134 .priority
= NODE_RECLAIM_PRIORITY
,
4135 .may_writepage
= !!(node_reclaim_mode
& RECLAIM_WRITE
),
4136 .may_unmap
= !!(node_reclaim_mode
& RECLAIM_UNMAP
),
4138 .reclaim_idx
= gfp_zone(gfp_mask
),
4141 trace_mm_vmscan_node_reclaim_begin(pgdat
->node_id
, order
,
4145 fs_reclaim_acquire(sc
.gfp_mask
);
4147 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
4148 * and we also need to be able to write out pages for RECLAIM_WRITE
4149 * and RECLAIM_UNMAP.
4151 noreclaim_flag
= memalloc_noreclaim_save();
4152 p
->flags
|= PF_SWAPWRITE
;
4153 set_task_reclaim_state(p
, &sc
.reclaim_state
);
4155 if (node_pagecache_reclaimable(pgdat
) > pgdat
->min_unmapped_pages
) {
4157 * Free memory by calling shrink node with increasing
4158 * priorities until we have enough memory freed.
4161 shrink_node(pgdat
, &sc
);
4162 } while (sc
.nr_reclaimed
< nr_pages
&& --sc
.priority
>= 0);
4165 set_task_reclaim_state(p
, NULL
);
4166 current
->flags
&= ~PF_SWAPWRITE
;
4167 memalloc_noreclaim_restore(noreclaim_flag
);
4168 fs_reclaim_release(sc
.gfp_mask
);
4170 trace_mm_vmscan_node_reclaim_end(sc
.nr_reclaimed
);
4172 return sc
.nr_reclaimed
>= nr_pages
;
4175 int node_reclaim(struct pglist_data
*pgdat
, gfp_t gfp_mask
, unsigned int order
)
4180 * Node reclaim reclaims unmapped file backed pages and
4181 * slab pages if we are over the defined limits.
4183 * A small portion of unmapped file backed pages is needed for
4184 * file I/O otherwise pages read by file I/O will be immediately
4185 * thrown out if the node is overallocated. So we do not reclaim
4186 * if less than a specified percentage of the node is used by
4187 * unmapped file backed pages.
4189 if (node_pagecache_reclaimable(pgdat
) <= pgdat
->min_unmapped_pages
&&
4190 node_page_state(pgdat
, NR_SLAB_RECLAIMABLE
) <= pgdat
->min_slab_pages
)
4191 return NODE_RECLAIM_FULL
;
4194 * Do not scan if the allocation should not be delayed.
4196 if (!gfpflags_allow_blocking(gfp_mask
) || (current
->flags
& PF_MEMALLOC
))
4197 return NODE_RECLAIM_NOSCAN
;
4200 * Only run node reclaim on the local node or on nodes that do not
4201 * have associated processors. This will favor the local processor
4202 * over remote processors and spread off node memory allocations
4203 * as wide as possible.
4205 if (node_state(pgdat
->node_id
, N_CPU
) && pgdat
->node_id
!= numa_node_id())
4206 return NODE_RECLAIM_NOSCAN
;
4208 if (test_and_set_bit(PGDAT_RECLAIM_LOCKED
, &pgdat
->flags
))
4209 return NODE_RECLAIM_NOSCAN
;
4211 ret
= __node_reclaim(pgdat
, gfp_mask
, order
);
4212 clear_bit(PGDAT_RECLAIM_LOCKED
, &pgdat
->flags
);
4215 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
4222 * page_evictable - test whether a page is evictable
4223 * @page: the page to test
4225 * Test whether page is evictable--i.e., should be placed on active/inactive
4226 * lists vs unevictable list.
4228 * Reasons page might not be evictable:
4229 * (1) page's mapping marked unevictable
4230 * (2) page is part of an mlocked VMA
4233 int page_evictable(struct page
*page
)
4237 /* Prevent address_space of inode and swap cache from being freed */
4239 ret
= !mapping_unevictable(page_mapping(page
)) && !PageMlocked(page
);
4245 * check_move_unevictable_pages - check pages for evictability and move to
4246 * appropriate zone lru list
4247 * @pvec: pagevec with lru pages to check
4249 * Checks pages for evictability, if an evictable page is in the unevictable
4250 * lru list, moves it to the appropriate evictable lru list. This function
4251 * should be only used for lru pages.
4253 void check_move_unevictable_pages(struct pagevec
*pvec
)
4255 struct lruvec
*lruvec
;
4256 struct pglist_data
*pgdat
= NULL
;
4261 for (i
= 0; i
< pvec
->nr
; i
++) {
4262 struct page
*page
= pvec
->pages
[i
];
4263 struct pglist_data
*pagepgdat
= page_pgdat(page
);
4266 if (pagepgdat
!= pgdat
) {
4268 spin_unlock_irq(&pgdat
->lru_lock
);
4270 spin_lock_irq(&pgdat
->lru_lock
);
4272 lruvec
= mem_cgroup_page_lruvec(page
, pgdat
);
4274 if (!PageLRU(page
) || !PageUnevictable(page
))
4277 if (page_evictable(page
)) {
4278 enum lru_list lru
= page_lru_base_type(page
);
4280 VM_BUG_ON_PAGE(PageActive(page
), page
);
4281 ClearPageUnevictable(page
);
4282 del_page_from_lru_list(page
, lruvec
, LRU_UNEVICTABLE
);
4283 add_page_to_lru_list(page
, lruvec
, lru
);
4289 __count_vm_events(UNEVICTABLE_PGRESCUED
, pgrescued
);
4290 __count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
4291 spin_unlock_irq(&pgdat
->lru_lock
);
4294 EXPORT_SYMBOL_GPL(check_move_unevictable_pages
);