1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 * Swap reorganised 29.12.95, Stephen Tweedie.
6 * kswapd added: 7.1.96 sct
7 * Removed kswapd_ctl limits, and swap out as many pages as needed
8 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
9 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
10 * Multiqueue VM started 5.8.00, Rik van Riel.
13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
16 #include <linux/sched/mm.h>
17 #include <linux/module.h>
18 #include <linux/gfp.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/swap.h>
21 #include <linux/pagemap.h>
22 #include <linux/init.h>
23 #include <linux/highmem.h>
24 #include <linux/vmpressure.h>
25 #include <linux/vmstat.h>
26 #include <linux/file.h>
27 #include <linux/writeback.h>
28 #include <linux/blkdev.h>
29 #include <linux/buffer_head.h> /* for try_to_release_page(),
30 buffer_heads_over_limit */
31 #include <linux/mm_inline.h>
32 #include <linux/backing-dev.h>
33 #include <linux/rmap.h>
34 #include <linux/topology.h>
35 #include <linux/cpu.h>
36 #include <linux/cpuset.h>
37 #include <linux/compaction.h>
38 #include <linux/notifier.h>
39 #include <linux/rwsem.h>
40 #include <linux/delay.h>
41 #include <linux/kthread.h>
42 #include <linux/freezer.h>
43 #include <linux/memcontrol.h>
44 #include <linux/migrate.h>
45 #include <linux/delayacct.h>
46 #include <linux/sysctl.h>
47 #include <linux/oom.h>
48 #include <linux/pagevec.h>
49 #include <linux/prefetch.h>
50 #include <linux/printk.h>
51 #include <linux/dax.h>
52 #include <linux/psi.h>
54 #include <asm/tlbflush.h>
55 #include <asm/div64.h>
57 #include <linux/swapops.h>
58 #include <linux/balloon_compaction.h>
62 #define CREATE_TRACE_POINTS
63 #include <trace/events/vmscan.h>
66 /* How many pages shrink_list() should reclaim */
67 unsigned long nr_to_reclaim
;
70 * Nodemask of nodes allowed by the caller. If NULL, all nodes
76 * The memory cgroup that hit its limit and as a result is the
77 * primary target of this reclaim invocation.
79 struct mem_cgroup
*target_mem_cgroup
;
82 * Scan pressure balancing between anon and file LRUs
84 unsigned long anon_cost
;
85 unsigned long file_cost
;
87 /* Can active pages be deactivated as part of reclaim? */
88 #define DEACTIVATE_ANON 1
89 #define DEACTIVATE_FILE 2
90 unsigned int may_deactivate
:2;
91 unsigned int force_deactivate
:1;
92 unsigned int skipped_deactivate
:1;
94 /* Writepage batching in laptop mode; RECLAIM_WRITE */
95 unsigned int may_writepage
:1;
97 /* Can mapped pages be reclaimed? */
98 unsigned int may_unmap
:1;
100 /* Can pages be swapped as part of reclaim? */
101 unsigned int may_swap
:1;
104 * Cgroup memory below memory.low is protected as long as we
105 * don't threaten to OOM. If any cgroup is reclaimed at
106 * reduced force or passed over entirely due to its memory.low
107 * setting (memcg_low_skipped), and nothing is reclaimed as a
108 * result, then go back for one more cycle that reclaims the protected
109 * memory (memcg_low_reclaim) to avert OOM.
111 unsigned int memcg_low_reclaim
:1;
112 unsigned int memcg_low_skipped
:1;
114 unsigned int hibernation_mode
:1;
116 /* One of the zones is ready for compaction */
117 unsigned int compaction_ready
:1;
119 /* There is easily reclaimable cold cache in the current node */
120 unsigned int cache_trim_mode
:1;
122 /* The file pages on the current node are dangerously low */
123 unsigned int file_is_tiny
:1;
125 /* Always discard instead of demoting to lower tier memory */
126 unsigned int no_demotion
:1;
128 /* Allocation order */
131 /* Scan (total_size >> priority) pages at once */
134 /* The highest zone to isolate pages for reclaim from */
137 /* This context's GFP mask */
140 /* Incremented by the number of inactive pages that were scanned */
141 unsigned long nr_scanned
;
143 /* Number of pages freed so far during a call to shrink_zones() */
144 unsigned long nr_reclaimed
;
148 unsigned int unqueued_dirty
;
149 unsigned int congested
;
150 unsigned int writeback
;
151 unsigned int immediate
;
152 unsigned int file_taken
;
156 /* for recording the reclaimed slab by now */
157 struct reclaim_state reclaim_state
;
160 #ifdef ARCH_HAS_PREFETCHW
161 #define prefetchw_prev_lru_page(_page, _base, _field) \
163 if ((_page)->lru.prev != _base) { \
166 prev = lru_to_page(&(_page->lru)); \
167 prefetchw(&prev->_field); \
171 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
175 * From 0 .. 200. Higher means more swappy.
177 int vm_swappiness
= 60;
179 static void set_task_reclaim_state(struct task_struct
*task
,
180 struct reclaim_state
*rs
)
182 /* Check for an overwrite */
183 WARN_ON_ONCE(rs
&& task
->reclaim_state
);
185 /* Check for the nulling of an already-nulled member */
186 WARN_ON_ONCE(!rs
&& !task
->reclaim_state
);
188 task
->reclaim_state
= rs
;
191 static LIST_HEAD(shrinker_list
);
192 static DECLARE_RWSEM(shrinker_rwsem
);
195 static int shrinker_nr_max
;
197 /* The shrinker_info is expanded in a batch of BITS_PER_LONG */
198 static inline int shrinker_map_size(int nr_items
)
200 return (DIV_ROUND_UP(nr_items
, BITS_PER_LONG
) * sizeof(unsigned long));
203 static inline int shrinker_defer_size(int nr_items
)
205 return (round_up(nr_items
, BITS_PER_LONG
) * sizeof(atomic_long_t
));
208 static struct shrinker_info
*shrinker_info_protected(struct mem_cgroup
*memcg
,
211 return rcu_dereference_protected(memcg
->nodeinfo
[nid
]->shrinker_info
,
212 lockdep_is_held(&shrinker_rwsem
));
215 static int expand_one_shrinker_info(struct mem_cgroup
*memcg
,
216 int map_size
, int defer_size
,
217 int old_map_size
, int old_defer_size
)
219 struct shrinker_info
*new, *old
;
220 struct mem_cgroup_per_node
*pn
;
222 int size
= map_size
+ defer_size
;
225 pn
= memcg
->nodeinfo
[nid
];
226 old
= shrinker_info_protected(memcg
, nid
);
227 /* Not yet online memcg */
231 new = kvmalloc_node(sizeof(*new) + size
, GFP_KERNEL
, nid
);
235 new->nr_deferred
= (atomic_long_t
*)(new + 1);
236 new->map
= (void *)new->nr_deferred
+ defer_size
;
238 /* map: set all old bits, clear all new bits */
239 memset(new->map
, (int)0xff, old_map_size
);
240 memset((void *)new->map
+ old_map_size
, 0, map_size
- old_map_size
);
241 /* nr_deferred: copy old values, clear all new values */
242 memcpy(new->nr_deferred
, old
->nr_deferred
, old_defer_size
);
243 memset((void *)new->nr_deferred
+ old_defer_size
, 0,
244 defer_size
- old_defer_size
);
246 rcu_assign_pointer(pn
->shrinker_info
, new);
247 kvfree_rcu(old
, rcu
);
253 void free_shrinker_info(struct mem_cgroup
*memcg
)
255 struct mem_cgroup_per_node
*pn
;
256 struct shrinker_info
*info
;
260 pn
= memcg
->nodeinfo
[nid
];
261 info
= rcu_dereference_protected(pn
->shrinker_info
, true);
263 rcu_assign_pointer(pn
->shrinker_info
, NULL
);
267 int alloc_shrinker_info(struct mem_cgroup
*memcg
)
269 struct shrinker_info
*info
;
270 int nid
, size
, ret
= 0;
271 int map_size
, defer_size
= 0;
273 down_write(&shrinker_rwsem
);
274 map_size
= shrinker_map_size(shrinker_nr_max
);
275 defer_size
= shrinker_defer_size(shrinker_nr_max
);
276 size
= map_size
+ defer_size
;
278 info
= kvzalloc_node(sizeof(*info
) + size
, GFP_KERNEL
, nid
);
280 free_shrinker_info(memcg
);
284 info
->nr_deferred
= (atomic_long_t
*)(info
+ 1);
285 info
->map
= (void *)info
->nr_deferred
+ defer_size
;
286 rcu_assign_pointer(memcg
->nodeinfo
[nid
]->shrinker_info
, info
);
288 up_write(&shrinker_rwsem
);
293 static inline bool need_expand(int nr_max
)
295 return round_up(nr_max
, BITS_PER_LONG
) >
296 round_up(shrinker_nr_max
, BITS_PER_LONG
);
299 static int expand_shrinker_info(int new_id
)
302 int new_nr_max
= new_id
+ 1;
303 int map_size
, defer_size
= 0;
304 int old_map_size
, old_defer_size
= 0;
305 struct mem_cgroup
*memcg
;
307 if (!need_expand(new_nr_max
))
310 if (!root_mem_cgroup
)
313 lockdep_assert_held(&shrinker_rwsem
);
315 map_size
= shrinker_map_size(new_nr_max
);
316 defer_size
= shrinker_defer_size(new_nr_max
);
317 old_map_size
= shrinker_map_size(shrinker_nr_max
);
318 old_defer_size
= shrinker_defer_size(shrinker_nr_max
);
320 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
322 ret
= expand_one_shrinker_info(memcg
, map_size
, defer_size
,
323 old_map_size
, old_defer_size
);
325 mem_cgroup_iter_break(NULL
, memcg
);
328 } while ((memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
)) != NULL
);
331 shrinker_nr_max
= new_nr_max
;
336 void set_shrinker_bit(struct mem_cgroup
*memcg
, int nid
, int shrinker_id
)
338 if (shrinker_id
>= 0 && memcg
&& !mem_cgroup_is_root(memcg
)) {
339 struct shrinker_info
*info
;
342 info
= rcu_dereference(memcg
->nodeinfo
[nid
]->shrinker_info
);
343 /* Pairs with smp mb in shrink_slab() */
344 smp_mb__before_atomic();
345 set_bit(shrinker_id
, info
->map
);
350 static DEFINE_IDR(shrinker_idr
);
352 static int prealloc_memcg_shrinker(struct shrinker
*shrinker
)
354 int id
, ret
= -ENOMEM
;
356 if (mem_cgroup_disabled())
359 down_write(&shrinker_rwsem
);
360 /* This may call shrinker, so it must use down_read_trylock() */
361 id
= idr_alloc(&shrinker_idr
, shrinker
, 0, 0, GFP_KERNEL
);
365 if (id
>= shrinker_nr_max
) {
366 if (expand_shrinker_info(id
)) {
367 idr_remove(&shrinker_idr
, id
);
374 up_write(&shrinker_rwsem
);
378 static void unregister_memcg_shrinker(struct shrinker
*shrinker
)
380 int id
= shrinker
->id
;
384 lockdep_assert_held(&shrinker_rwsem
);
386 idr_remove(&shrinker_idr
, id
);
389 static long xchg_nr_deferred_memcg(int nid
, struct shrinker
*shrinker
,
390 struct mem_cgroup
*memcg
)
392 struct shrinker_info
*info
;
394 info
= shrinker_info_protected(memcg
, nid
);
395 return atomic_long_xchg(&info
->nr_deferred
[shrinker
->id
], 0);
398 static long add_nr_deferred_memcg(long nr
, int nid
, struct shrinker
*shrinker
,
399 struct mem_cgroup
*memcg
)
401 struct shrinker_info
*info
;
403 info
= shrinker_info_protected(memcg
, nid
);
404 return atomic_long_add_return(nr
, &info
->nr_deferred
[shrinker
->id
]);
407 void reparent_shrinker_deferred(struct mem_cgroup
*memcg
)
411 struct mem_cgroup
*parent
;
412 struct shrinker_info
*child_info
, *parent_info
;
414 parent
= parent_mem_cgroup(memcg
);
416 parent
= root_mem_cgroup
;
418 /* Prevent from concurrent shrinker_info expand */
419 down_read(&shrinker_rwsem
);
421 child_info
= shrinker_info_protected(memcg
, nid
);
422 parent_info
= shrinker_info_protected(parent
, nid
);
423 for (i
= 0; i
< shrinker_nr_max
; i
++) {
424 nr
= atomic_long_read(&child_info
->nr_deferred
[i
]);
425 atomic_long_add(nr
, &parent_info
->nr_deferred
[i
]);
428 up_read(&shrinker_rwsem
);
431 static bool cgroup_reclaim(struct scan_control
*sc
)
433 return sc
->target_mem_cgroup
;
437 * writeback_throttling_sane - is the usual dirty throttling mechanism available?
438 * @sc: scan_control in question
440 * The normal page dirty throttling mechanism in balance_dirty_pages() is
441 * completely broken with the legacy memcg and direct stalling in
442 * shrink_page_list() is used for throttling instead, which lacks all the
443 * niceties such as fairness, adaptive pausing, bandwidth proportional
444 * allocation and configurability.
446 * This function tests whether the vmscan currently in progress can assume
447 * that the normal dirty throttling mechanism is operational.
449 static bool writeback_throttling_sane(struct scan_control
*sc
)
451 if (!cgroup_reclaim(sc
))
453 #ifdef CONFIG_CGROUP_WRITEBACK
454 if (cgroup_subsys_on_dfl(memory_cgrp_subsys
))
460 static int prealloc_memcg_shrinker(struct shrinker
*shrinker
)
465 static void unregister_memcg_shrinker(struct shrinker
*shrinker
)
469 static long xchg_nr_deferred_memcg(int nid
, struct shrinker
*shrinker
,
470 struct mem_cgroup
*memcg
)
475 static long add_nr_deferred_memcg(long nr
, int nid
, struct shrinker
*shrinker
,
476 struct mem_cgroup
*memcg
)
481 static bool cgroup_reclaim(struct scan_control
*sc
)
486 static bool writeback_throttling_sane(struct scan_control
*sc
)
492 static long xchg_nr_deferred(struct shrinker
*shrinker
,
493 struct shrink_control
*sc
)
497 if (!(shrinker
->flags
& SHRINKER_NUMA_AWARE
))
501 (shrinker
->flags
& SHRINKER_MEMCG_AWARE
))
502 return xchg_nr_deferred_memcg(nid
, shrinker
,
505 return atomic_long_xchg(&shrinker
->nr_deferred
[nid
], 0);
509 static long add_nr_deferred(long nr
, struct shrinker
*shrinker
,
510 struct shrink_control
*sc
)
514 if (!(shrinker
->flags
& SHRINKER_NUMA_AWARE
))
518 (shrinker
->flags
& SHRINKER_MEMCG_AWARE
))
519 return add_nr_deferred_memcg(nr
, nid
, shrinker
,
522 return atomic_long_add_return(nr
, &shrinker
->nr_deferred
[nid
]);
525 static bool can_demote(int nid
, struct scan_control
*sc
)
527 if (!numa_demotion_enabled
)
532 /* It is pointless to do demotion in memcg reclaim */
533 if (cgroup_reclaim(sc
))
536 if (next_demotion_node(nid
) == NUMA_NO_NODE
)
542 static inline bool can_reclaim_anon_pages(struct mem_cgroup
*memcg
,
544 struct scan_control
*sc
)
548 * For non-memcg reclaim, is there
549 * space in any swap device?
551 if (get_nr_swap_pages() > 0)
554 /* Is the memcg below its swap limit? */
555 if (mem_cgroup_get_nr_swap_pages(memcg
) > 0)
560 * The page can not be swapped.
562 * Can it be reclaimed from this node via demotion?
564 return can_demote(nid
, sc
);
568 * This misses isolated pages which are not accounted for to save counters.
569 * As the data only determines if reclaim or compaction continues, it is
570 * not expected that isolated pages will be a dominating factor.
572 unsigned long zone_reclaimable_pages(struct zone
*zone
)
576 nr
= zone_page_state_snapshot(zone
, NR_ZONE_INACTIVE_FILE
) +
577 zone_page_state_snapshot(zone
, NR_ZONE_ACTIVE_FILE
);
578 if (can_reclaim_anon_pages(NULL
, zone_to_nid(zone
), NULL
))
579 nr
+= zone_page_state_snapshot(zone
, NR_ZONE_INACTIVE_ANON
) +
580 zone_page_state_snapshot(zone
, NR_ZONE_ACTIVE_ANON
);
586 * lruvec_lru_size - Returns the number of pages on the given LRU list.
587 * @lruvec: lru vector
589 * @zone_idx: zones to consider (use MAX_NR_ZONES for the whole LRU list)
591 static unsigned long lruvec_lru_size(struct lruvec
*lruvec
, enum lru_list lru
,
594 unsigned long size
= 0;
597 for (zid
= 0; zid
<= zone_idx
&& zid
< MAX_NR_ZONES
; zid
++) {
598 struct zone
*zone
= &lruvec_pgdat(lruvec
)->node_zones
[zid
];
600 if (!managed_zone(zone
))
603 if (!mem_cgroup_disabled())
604 size
+= mem_cgroup_get_zone_lru_size(lruvec
, lru
, zid
);
606 size
+= zone_page_state(zone
, NR_ZONE_LRU_BASE
+ lru
);
612 * Add a shrinker callback to be called from the vm.
614 int prealloc_shrinker(struct shrinker
*shrinker
)
619 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
) {
620 err
= prealloc_memcg_shrinker(shrinker
);
624 shrinker
->flags
&= ~SHRINKER_MEMCG_AWARE
;
627 size
= sizeof(*shrinker
->nr_deferred
);
628 if (shrinker
->flags
& SHRINKER_NUMA_AWARE
)
631 shrinker
->nr_deferred
= kzalloc(size
, GFP_KERNEL
);
632 if (!shrinker
->nr_deferred
)
638 void free_prealloced_shrinker(struct shrinker
*shrinker
)
640 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
) {
641 down_write(&shrinker_rwsem
);
642 unregister_memcg_shrinker(shrinker
);
643 up_write(&shrinker_rwsem
);
647 kfree(shrinker
->nr_deferred
);
648 shrinker
->nr_deferred
= NULL
;
651 void register_shrinker_prepared(struct shrinker
*shrinker
)
653 down_write(&shrinker_rwsem
);
654 list_add_tail(&shrinker
->list
, &shrinker_list
);
655 shrinker
->flags
|= SHRINKER_REGISTERED
;
656 up_write(&shrinker_rwsem
);
659 int register_shrinker(struct shrinker
*shrinker
)
661 int err
= prealloc_shrinker(shrinker
);
665 register_shrinker_prepared(shrinker
);
668 EXPORT_SYMBOL(register_shrinker
);
673 void unregister_shrinker(struct shrinker
*shrinker
)
675 if (!(shrinker
->flags
& SHRINKER_REGISTERED
))
678 down_write(&shrinker_rwsem
);
679 list_del(&shrinker
->list
);
680 shrinker
->flags
&= ~SHRINKER_REGISTERED
;
681 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
)
682 unregister_memcg_shrinker(shrinker
);
683 up_write(&shrinker_rwsem
);
685 kfree(shrinker
->nr_deferred
);
686 shrinker
->nr_deferred
= NULL
;
688 EXPORT_SYMBOL(unregister_shrinker
);
690 #define SHRINK_BATCH 128
692 static unsigned long do_shrink_slab(struct shrink_control
*shrinkctl
,
693 struct shrinker
*shrinker
, int priority
)
695 unsigned long freed
= 0;
696 unsigned long long delta
;
701 long batch_size
= shrinker
->batch
? shrinker
->batch
703 long scanned
= 0, next_deferred
;
705 freeable
= shrinker
->count_objects(shrinker
, shrinkctl
);
706 if (freeable
== 0 || freeable
== SHRINK_EMPTY
)
710 * copy the current shrinker scan count into a local variable
711 * and zero it so that other concurrent shrinker invocations
712 * don't also do this scanning work.
714 nr
= xchg_nr_deferred(shrinker
, shrinkctl
);
716 if (shrinker
->seeks
) {
717 delta
= freeable
>> priority
;
719 do_div(delta
, shrinker
->seeks
);
722 * These objects don't require any IO to create. Trim
723 * them aggressively under memory pressure to keep
724 * them from causing refetches in the IO caches.
726 delta
= freeable
/ 2;
729 total_scan
= nr
>> priority
;
731 total_scan
= min(total_scan
, (2 * freeable
));
733 trace_mm_shrink_slab_start(shrinker
, shrinkctl
, nr
,
734 freeable
, delta
, total_scan
, priority
);
737 * Normally, we should not scan less than batch_size objects in one
738 * pass to avoid too frequent shrinker calls, but if the slab has less
739 * than batch_size objects in total and we are really tight on memory,
740 * we will try to reclaim all available objects, otherwise we can end
741 * up failing allocations although there are plenty of reclaimable
742 * objects spread over several slabs with usage less than the
745 * We detect the "tight on memory" situations by looking at the total
746 * number of objects we want to scan (total_scan). If it is greater
747 * than the total number of objects on slab (freeable), we must be
748 * scanning at high prio and therefore should try to reclaim as much as
751 while (total_scan
>= batch_size
||
752 total_scan
>= freeable
) {
754 unsigned long nr_to_scan
= min(batch_size
, total_scan
);
756 shrinkctl
->nr_to_scan
= nr_to_scan
;
757 shrinkctl
->nr_scanned
= nr_to_scan
;
758 ret
= shrinker
->scan_objects(shrinker
, shrinkctl
);
759 if (ret
== SHRINK_STOP
)
763 count_vm_events(SLABS_SCANNED
, shrinkctl
->nr_scanned
);
764 total_scan
-= shrinkctl
->nr_scanned
;
765 scanned
+= shrinkctl
->nr_scanned
;
771 * The deferred work is increased by any new work (delta) that wasn't
772 * done, decreased by old deferred work that was done now.
774 * And it is capped to two times of the freeable items.
776 next_deferred
= max_t(long, (nr
+ delta
- scanned
), 0);
777 next_deferred
= min(next_deferred
, (2 * freeable
));
780 * move the unused scan count back into the shrinker in a
781 * manner that handles concurrent updates.
783 new_nr
= add_nr_deferred(next_deferred
, shrinker
, shrinkctl
);
785 trace_mm_shrink_slab_end(shrinker
, shrinkctl
->nid
, freed
, nr
, new_nr
, total_scan
);
790 static unsigned long shrink_slab_memcg(gfp_t gfp_mask
, int nid
,
791 struct mem_cgroup
*memcg
, int priority
)
793 struct shrinker_info
*info
;
794 unsigned long ret
, freed
= 0;
797 if (!mem_cgroup_online(memcg
))
800 if (!down_read_trylock(&shrinker_rwsem
))
803 info
= shrinker_info_protected(memcg
, nid
);
807 for_each_set_bit(i
, info
->map
, shrinker_nr_max
) {
808 struct shrink_control sc
= {
809 .gfp_mask
= gfp_mask
,
813 struct shrinker
*shrinker
;
815 shrinker
= idr_find(&shrinker_idr
, i
);
816 if (unlikely(!shrinker
|| !(shrinker
->flags
& SHRINKER_REGISTERED
))) {
818 clear_bit(i
, info
->map
);
822 /* Call non-slab shrinkers even though kmem is disabled */
823 if (!memcg_kmem_enabled() &&
824 !(shrinker
->flags
& SHRINKER_NONSLAB
))
827 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
828 if (ret
== SHRINK_EMPTY
) {
829 clear_bit(i
, info
->map
);
831 * After the shrinker reported that it had no objects to
832 * free, but before we cleared the corresponding bit in
833 * the memcg shrinker map, a new object might have been
834 * added. To make sure, we have the bit set in this
835 * case, we invoke the shrinker one more time and reset
836 * the bit if it reports that it is not empty anymore.
837 * The memory barrier here pairs with the barrier in
838 * set_shrinker_bit():
840 * list_lru_add() shrink_slab_memcg()
841 * list_add_tail() clear_bit()
843 * set_bit() do_shrink_slab()
845 smp_mb__after_atomic();
846 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
847 if (ret
== SHRINK_EMPTY
)
850 set_shrinker_bit(memcg
, nid
, i
);
854 if (rwsem_is_contended(&shrinker_rwsem
)) {
860 up_read(&shrinker_rwsem
);
863 #else /* CONFIG_MEMCG */
864 static unsigned long shrink_slab_memcg(gfp_t gfp_mask
, int nid
,
865 struct mem_cgroup
*memcg
, int priority
)
869 #endif /* CONFIG_MEMCG */
872 * shrink_slab - shrink slab caches
873 * @gfp_mask: allocation context
874 * @nid: node whose slab caches to target
875 * @memcg: memory cgroup whose slab caches to target
876 * @priority: the reclaim priority
878 * Call the shrink functions to age shrinkable caches.
880 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
881 * unaware shrinkers will receive a node id of 0 instead.
883 * @memcg specifies the memory cgroup to target. Unaware shrinkers
884 * are called only if it is the root cgroup.
886 * @priority is sc->priority, we take the number of objects and >> by priority
887 * in order to get the scan target.
889 * Returns the number of reclaimed slab objects.
891 static unsigned long shrink_slab(gfp_t gfp_mask
, int nid
,
892 struct mem_cgroup
*memcg
,
895 unsigned long ret
, freed
= 0;
896 struct shrinker
*shrinker
;
899 * The root memcg might be allocated even though memcg is disabled
900 * via "cgroup_disable=memory" boot parameter. This could make
901 * mem_cgroup_is_root() return false, then just run memcg slab
902 * shrink, but skip global shrink. This may result in premature
905 if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg
))
906 return shrink_slab_memcg(gfp_mask
, nid
, memcg
, priority
);
908 if (!down_read_trylock(&shrinker_rwsem
))
911 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
912 struct shrink_control sc
= {
913 .gfp_mask
= gfp_mask
,
918 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
919 if (ret
== SHRINK_EMPTY
)
923 * Bail out if someone want to register a new shrinker to
924 * prevent the registration from being stalled for long periods
925 * by parallel ongoing shrinking.
927 if (rwsem_is_contended(&shrinker_rwsem
)) {
933 up_read(&shrinker_rwsem
);
939 void drop_slab_node(int nid
)
945 struct mem_cgroup
*memcg
= NULL
;
947 if (fatal_signal_pending(current
))
951 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
953 freed
+= shrink_slab(GFP_KERNEL
, nid
, memcg
, 0);
954 } while ((memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
)) != NULL
);
955 } while ((freed
>> shift
++) > 1);
962 for_each_online_node(nid
)
966 static inline int is_page_cache_freeable(struct page
*page
)
969 * A freeable page cache page is referenced only by the caller
970 * that isolated the page, the page cache and optional buffer
971 * heads at page->private.
973 int page_cache_pins
= thp_nr_pages(page
);
974 return page_count(page
) - page_has_private(page
) == 1 + page_cache_pins
;
977 static int may_write_to_inode(struct inode
*inode
)
979 if (current
->flags
& PF_SWAPWRITE
)
981 if (!inode_write_congested(inode
))
983 if (inode_to_bdi(inode
) == current
->backing_dev_info
)
989 * We detected a synchronous write error writing a page out. Probably
990 * -ENOSPC. We need to propagate that into the address_space for a subsequent
991 * fsync(), msync() or close().
993 * The tricky part is that after writepage we cannot touch the mapping: nothing
994 * prevents it from being freed up. But we have a ref on the page and once
995 * that page is locked, the mapping is pinned.
997 * We're allowed to run sleeping lock_page() here because we know the caller has
1000 static void handle_write_error(struct address_space
*mapping
,
1001 struct page
*page
, int error
)
1004 if (page_mapping(page
) == mapping
)
1005 mapping_set_error(mapping
, error
);
1009 /* possible outcome of pageout() */
1011 /* failed to write page out, page is locked */
1013 /* move page to the active list, page is locked */
1015 /* page has been sent to the disk successfully, page is unlocked */
1017 /* page is clean and locked */
1022 * pageout is called by shrink_page_list() for each dirty page.
1023 * Calls ->writepage().
1025 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
)
1028 * If the page is dirty, only perform writeback if that write
1029 * will be non-blocking. To prevent this allocation from being
1030 * stalled by pagecache activity. But note that there may be
1031 * stalls if we need to run get_block(). We could test
1032 * PagePrivate for that.
1034 * If this process is currently in __generic_file_write_iter() against
1035 * this page's queue, we can perform writeback even if that
1038 * If the page is swapcache, write it back even if that would
1039 * block, for some throttling. This happens by accident, because
1040 * swap_backing_dev_info is bust: it doesn't reflect the
1041 * congestion state of the swapdevs. Easy to fix, if needed.
1043 if (!is_page_cache_freeable(page
))
1047 * Some data journaling orphaned pages can have
1048 * page->mapping == NULL while being dirty with clean buffers.
1050 if (page_has_private(page
)) {
1051 if (try_to_free_buffers(page
)) {
1052 ClearPageDirty(page
);
1053 pr_info("%s: orphaned page\n", __func__
);
1059 if (mapping
->a_ops
->writepage
== NULL
)
1060 return PAGE_ACTIVATE
;
1061 if (!may_write_to_inode(mapping
->host
))
1064 if (clear_page_dirty_for_io(page
)) {
1066 struct writeback_control wbc
= {
1067 .sync_mode
= WB_SYNC_NONE
,
1068 .nr_to_write
= SWAP_CLUSTER_MAX
,
1070 .range_end
= LLONG_MAX
,
1074 SetPageReclaim(page
);
1075 res
= mapping
->a_ops
->writepage(page
, &wbc
);
1077 handle_write_error(mapping
, page
, res
);
1078 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
1079 ClearPageReclaim(page
);
1080 return PAGE_ACTIVATE
;
1083 if (!PageWriteback(page
)) {
1084 /* synchronous write or broken a_ops? */
1085 ClearPageReclaim(page
);
1087 trace_mm_vmscan_writepage(page
);
1088 inc_node_page_state(page
, NR_VMSCAN_WRITE
);
1089 return PAGE_SUCCESS
;
1096 * Same as remove_mapping, but if the page is removed from the mapping, it
1097 * gets returned with a refcount of 0.
1099 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
,
1100 bool reclaimed
, struct mem_cgroup
*target_memcg
)
1103 void *shadow
= NULL
;
1105 BUG_ON(!PageLocked(page
));
1106 BUG_ON(mapping
!= page_mapping(page
));
1108 xa_lock_irq(&mapping
->i_pages
);
1110 * The non racy check for a busy page.
1112 * Must be careful with the order of the tests. When someone has
1113 * a ref to the page, it may be possible that they dirty it then
1114 * drop the reference. So if PageDirty is tested before page_count
1115 * here, then the following race may occur:
1117 * get_user_pages(&page);
1118 * [user mapping goes away]
1120 * !PageDirty(page) [good]
1121 * SetPageDirty(page);
1123 * !page_count(page) [good, discard it]
1125 * [oops, our write_to data is lost]
1127 * Reversing the order of the tests ensures such a situation cannot
1128 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
1129 * load is not satisfied before that of page->_refcount.
1131 * Note that if SetPageDirty is always performed via set_page_dirty,
1132 * and thus under the i_pages lock, then this ordering is not required.
1134 refcount
= 1 + compound_nr(page
);
1135 if (!page_ref_freeze(page
, refcount
))
1137 /* note: atomic_cmpxchg in page_ref_freeze provides the smp_rmb */
1138 if (unlikely(PageDirty(page
))) {
1139 page_ref_unfreeze(page
, refcount
);
1143 if (PageSwapCache(page
)) {
1144 swp_entry_t swap
= { .val
= page_private(page
) };
1145 mem_cgroup_swapout(page
, swap
);
1146 if (reclaimed
&& !mapping_exiting(mapping
))
1147 shadow
= workingset_eviction(page
, target_memcg
);
1148 __delete_from_swap_cache(page
, swap
, shadow
);
1149 xa_unlock_irq(&mapping
->i_pages
);
1150 put_swap_page(page
, swap
);
1152 void (*freepage
)(struct page
*);
1154 freepage
= mapping
->a_ops
->freepage
;
1156 * Remember a shadow entry for reclaimed file cache in
1157 * order to detect refaults, thus thrashing, later on.
1159 * But don't store shadows in an address space that is
1160 * already exiting. This is not just an optimization,
1161 * inode reclaim needs to empty out the radix tree or
1162 * the nodes are lost. Don't plant shadows behind its
1165 * We also don't store shadows for DAX mappings because the
1166 * only page cache pages found in these are zero pages
1167 * covering holes, and because we don't want to mix DAX
1168 * exceptional entries and shadow exceptional entries in the
1169 * same address_space.
1171 if (reclaimed
&& page_is_file_lru(page
) &&
1172 !mapping_exiting(mapping
) && !dax_mapping(mapping
))
1173 shadow
= workingset_eviction(page
, target_memcg
);
1174 __delete_from_page_cache(page
, shadow
);
1175 xa_unlock_irq(&mapping
->i_pages
);
1177 if (freepage
!= NULL
)
1184 xa_unlock_irq(&mapping
->i_pages
);
1189 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
1190 * someone else has a ref on the page, abort and return 0. If it was
1191 * successfully detached, return 1. Assumes the caller has a single ref on
1194 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
1196 if (__remove_mapping(mapping
, page
, false, NULL
)) {
1198 * Unfreezing the refcount with 1 rather than 2 effectively
1199 * drops the pagecache ref for us without requiring another
1202 page_ref_unfreeze(page
, 1);
1209 * putback_lru_page - put previously isolated page onto appropriate LRU list
1210 * @page: page to be put back to appropriate lru list
1212 * Add previously isolated @page to appropriate LRU list.
1213 * Page may still be unevictable for other reasons.
1215 * lru_lock must not be held, interrupts must be enabled.
1217 void putback_lru_page(struct page
*page
)
1219 lru_cache_add(page
);
1220 put_page(page
); /* drop ref from isolate */
1223 enum page_references
{
1225 PAGEREF_RECLAIM_CLEAN
,
1230 static enum page_references
page_check_references(struct page
*page
,
1231 struct scan_control
*sc
)
1233 int referenced_ptes
, referenced_page
;
1234 unsigned long vm_flags
;
1236 referenced_ptes
= page_referenced(page
, 1, sc
->target_mem_cgroup
,
1238 referenced_page
= TestClearPageReferenced(page
);
1241 * Mlock lost the isolation race with us. Let try_to_unmap()
1242 * move the page to the unevictable list.
1244 if (vm_flags
& VM_LOCKED
)
1245 return PAGEREF_RECLAIM
;
1247 if (referenced_ptes
) {
1249 * All mapped pages start out with page table
1250 * references from the instantiating fault, so we need
1251 * to look twice if a mapped file page is used more
1254 * Mark it and spare it for another trip around the
1255 * inactive list. Another page table reference will
1256 * lead to its activation.
1258 * Note: the mark is set for activated pages as well
1259 * so that recently deactivated but used pages are
1260 * quickly recovered.
1262 SetPageReferenced(page
);
1264 if (referenced_page
|| referenced_ptes
> 1)
1265 return PAGEREF_ACTIVATE
;
1268 * Activate file-backed executable pages after first usage.
1270 if ((vm_flags
& VM_EXEC
) && !PageSwapBacked(page
))
1271 return PAGEREF_ACTIVATE
;
1273 return PAGEREF_KEEP
;
1276 /* Reclaim if clean, defer dirty pages to writeback */
1277 if (referenced_page
&& !PageSwapBacked(page
))
1278 return PAGEREF_RECLAIM_CLEAN
;
1280 return PAGEREF_RECLAIM
;
1283 /* Check if a page is dirty or under writeback */
1284 static void page_check_dirty_writeback(struct page
*page
,
1285 bool *dirty
, bool *writeback
)
1287 struct address_space
*mapping
;
1290 * Anonymous pages are not handled by flushers and must be written
1291 * from reclaim context. Do not stall reclaim based on them
1293 if (!page_is_file_lru(page
) ||
1294 (PageAnon(page
) && !PageSwapBacked(page
))) {
1300 /* By default assume that the page flags are accurate */
1301 *dirty
= PageDirty(page
);
1302 *writeback
= PageWriteback(page
);
1304 /* Verify dirty/writeback state if the filesystem supports it */
1305 if (!page_has_private(page
))
1308 mapping
= page_mapping(page
);
1309 if (mapping
&& mapping
->a_ops
->is_dirty_writeback
)
1310 mapping
->a_ops
->is_dirty_writeback(page
, dirty
, writeback
);
1313 static struct page
*alloc_demote_page(struct page
*page
, unsigned long node
)
1315 struct migration_target_control mtc
= {
1317 * Allocate from 'node', or fail quickly and quietly.
1318 * When this happens, 'page' will likely just be discarded
1319 * instead of migrated.
1321 .gfp_mask
= (GFP_HIGHUSER_MOVABLE
& ~__GFP_RECLAIM
) |
1322 __GFP_THISNODE
| __GFP_NOWARN
|
1323 __GFP_NOMEMALLOC
| GFP_NOWAIT
,
1327 return alloc_migration_target(page
, (unsigned long)&mtc
);
1331 * Take pages on @demote_list and attempt to demote them to
1332 * another node. Pages which are not demoted are left on
1335 static unsigned int demote_page_list(struct list_head
*demote_pages
,
1336 struct pglist_data
*pgdat
)
1338 int target_nid
= next_demotion_node(pgdat
->node_id
);
1339 unsigned int nr_succeeded
;
1342 if (list_empty(demote_pages
))
1345 if (target_nid
== NUMA_NO_NODE
)
1348 /* Demotion ignores all cpuset and mempolicy settings */
1349 err
= migrate_pages(demote_pages
, alloc_demote_page
, NULL
,
1350 target_nid
, MIGRATE_ASYNC
, MR_DEMOTION
,
1353 if (current_is_kswapd())
1354 __count_vm_events(PGDEMOTE_KSWAPD
, nr_succeeded
);
1356 __count_vm_events(PGDEMOTE_DIRECT
, nr_succeeded
);
1358 return nr_succeeded
;
1362 * shrink_page_list() returns the number of reclaimed pages
1364 static unsigned int shrink_page_list(struct list_head
*page_list
,
1365 struct pglist_data
*pgdat
,
1366 struct scan_control
*sc
,
1367 struct reclaim_stat
*stat
,
1368 bool ignore_references
)
1370 LIST_HEAD(ret_pages
);
1371 LIST_HEAD(free_pages
);
1372 LIST_HEAD(demote_pages
);
1373 unsigned int nr_reclaimed
= 0;
1374 unsigned int pgactivate
= 0;
1375 bool do_demote_pass
;
1377 memset(stat
, 0, sizeof(*stat
));
1379 do_demote_pass
= can_demote(pgdat
->node_id
, sc
);
1382 while (!list_empty(page_list
)) {
1383 struct address_space
*mapping
;
1385 enum page_references references
= PAGEREF_RECLAIM
;
1386 bool dirty
, writeback
, may_enter_fs
;
1387 unsigned int nr_pages
;
1391 page
= lru_to_page(page_list
);
1392 list_del(&page
->lru
);
1394 if (!trylock_page(page
))
1397 VM_BUG_ON_PAGE(PageActive(page
), page
);
1399 nr_pages
= compound_nr(page
);
1401 /* Account the number of base pages even though THP */
1402 sc
->nr_scanned
+= nr_pages
;
1404 if (unlikely(!page_evictable(page
)))
1405 goto activate_locked
;
1407 if (!sc
->may_unmap
&& page_mapped(page
))
1410 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
1411 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
1414 * The number of dirty pages determines if a node is marked
1415 * reclaim_congested which affects wait_iff_congested. kswapd
1416 * will stall and start writing pages if the tail of the LRU
1417 * is all dirty unqueued pages.
1419 page_check_dirty_writeback(page
, &dirty
, &writeback
);
1420 if (dirty
|| writeback
)
1423 if (dirty
&& !writeback
)
1424 stat
->nr_unqueued_dirty
++;
1427 * Treat this page as congested if the underlying BDI is or if
1428 * pages are cycling through the LRU so quickly that the
1429 * pages marked for immediate reclaim are making it to the
1430 * end of the LRU a second time.
1432 mapping
= page_mapping(page
);
1433 if (((dirty
|| writeback
) && mapping
&&
1434 inode_write_congested(mapping
->host
)) ||
1435 (writeback
&& PageReclaim(page
)))
1436 stat
->nr_congested
++;
1439 * If a page at the tail of the LRU is under writeback, there
1440 * are three cases to consider.
1442 * 1) If reclaim is encountering an excessive number of pages
1443 * under writeback and this page is both under writeback and
1444 * PageReclaim then it indicates that pages are being queued
1445 * for IO but are being recycled through the LRU before the
1446 * IO can complete. Waiting on the page itself risks an
1447 * indefinite stall if it is impossible to writeback the
1448 * page due to IO error or disconnected storage so instead
1449 * note that the LRU is being scanned too quickly and the
1450 * caller can stall after page list has been processed.
1452 * 2) Global or new memcg reclaim encounters a page that is
1453 * not marked for immediate reclaim, or the caller does not
1454 * have __GFP_FS (or __GFP_IO if it's simply going to swap,
1455 * not to fs). In this case mark the page for immediate
1456 * reclaim and continue scanning.
1458 * Require may_enter_fs because we would wait on fs, which
1459 * may not have submitted IO yet. And the loop driver might
1460 * enter reclaim, and deadlock if it waits on a page for
1461 * which it is needed to do the write (loop masks off
1462 * __GFP_IO|__GFP_FS for this reason); but more thought
1463 * would probably show more reasons.
1465 * 3) Legacy memcg encounters a page that is already marked
1466 * PageReclaim. memcg does not have any dirty pages
1467 * throttling so we could easily OOM just because too many
1468 * pages are in writeback and there is nothing else to
1469 * reclaim. Wait for the writeback to complete.
1471 * In cases 1) and 2) we activate the pages to get them out of
1472 * the way while we continue scanning for clean pages on the
1473 * inactive list and refilling from the active list. The
1474 * observation here is that waiting for disk writes is more
1475 * expensive than potentially causing reloads down the line.
1476 * Since they're marked for immediate reclaim, they won't put
1477 * memory pressure on the cache working set any longer than it
1478 * takes to write them to disk.
1480 if (PageWriteback(page
)) {
1482 if (current_is_kswapd() &&
1483 PageReclaim(page
) &&
1484 test_bit(PGDAT_WRITEBACK
, &pgdat
->flags
)) {
1485 stat
->nr_immediate
++;
1486 goto activate_locked
;
1489 } else if (writeback_throttling_sane(sc
) ||
1490 !PageReclaim(page
) || !may_enter_fs
) {
1492 * This is slightly racy - end_page_writeback()
1493 * might have just cleared PageReclaim, then
1494 * setting PageReclaim here end up interpreted
1495 * as PageReadahead - but that does not matter
1496 * enough to care. What we do want is for this
1497 * page to have PageReclaim set next time memcg
1498 * reclaim reaches the tests above, so it will
1499 * then wait_on_page_writeback() to avoid OOM;
1500 * and it's also appropriate in global reclaim.
1502 SetPageReclaim(page
);
1503 stat
->nr_writeback
++;
1504 goto activate_locked
;
1509 wait_on_page_writeback(page
);
1510 /* then go back and try same page again */
1511 list_add_tail(&page
->lru
, page_list
);
1516 if (!ignore_references
)
1517 references
= page_check_references(page
, sc
);
1519 switch (references
) {
1520 case PAGEREF_ACTIVATE
:
1521 goto activate_locked
;
1523 stat
->nr_ref_keep
+= nr_pages
;
1525 case PAGEREF_RECLAIM
:
1526 case PAGEREF_RECLAIM_CLEAN
:
1527 ; /* try to reclaim the page below */
1531 * Before reclaiming the page, try to relocate
1532 * its contents to another node.
1534 if (do_demote_pass
&&
1535 (thp_migration_supported() || !PageTransHuge(page
))) {
1536 list_add(&page
->lru
, &demote_pages
);
1542 * Anonymous process memory has backing store?
1543 * Try to allocate it some swap space here.
1544 * Lazyfree page could be freed directly
1546 if (PageAnon(page
) && PageSwapBacked(page
)) {
1547 if (!PageSwapCache(page
)) {
1548 if (!(sc
->gfp_mask
& __GFP_IO
))
1550 if (page_maybe_dma_pinned(page
))
1552 if (PageTransHuge(page
)) {
1553 /* cannot split THP, skip it */
1554 if (!can_split_huge_page(page
, NULL
))
1555 goto activate_locked
;
1557 * Split pages without a PMD map right
1558 * away. Chances are some or all of the
1559 * tail pages can be freed without IO.
1561 if (!compound_mapcount(page
) &&
1562 split_huge_page_to_list(page
,
1564 goto activate_locked
;
1566 if (!add_to_swap(page
)) {
1567 if (!PageTransHuge(page
))
1568 goto activate_locked_split
;
1569 /* Fallback to swap normal pages */
1570 if (split_huge_page_to_list(page
,
1572 goto activate_locked
;
1573 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
1574 count_vm_event(THP_SWPOUT_FALLBACK
);
1576 if (!add_to_swap(page
))
1577 goto activate_locked_split
;
1580 may_enter_fs
= true;
1582 /* Adding to swap updated mapping */
1583 mapping
= page_mapping(page
);
1585 } else if (unlikely(PageTransHuge(page
))) {
1586 /* Split file THP */
1587 if (split_huge_page_to_list(page
, page_list
))
1592 * THP may get split above, need minus tail pages and update
1593 * nr_pages to avoid accounting tail pages twice.
1595 * The tail pages that are added into swap cache successfully
1598 if ((nr_pages
> 1) && !PageTransHuge(page
)) {
1599 sc
->nr_scanned
-= (nr_pages
- 1);
1604 * The page is mapped into the page tables of one or more
1605 * processes. Try to unmap it here.
1607 if (page_mapped(page
)) {
1608 enum ttu_flags flags
= TTU_BATCH_FLUSH
;
1609 bool was_swapbacked
= PageSwapBacked(page
);
1611 if (unlikely(PageTransHuge(page
)))
1612 flags
|= TTU_SPLIT_HUGE_PMD
;
1614 try_to_unmap(page
, flags
);
1615 if (page_mapped(page
)) {
1616 stat
->nr_unmap_fail
+= nr_pages
;
1617 if (!was_swapbacked
&& PageSwapBacked(page
))
1618 stat
->nr_lazyfree_fail
+= nr_pages
;
1619 goto activate_locked
;
1623 if (PageDirty(page
)) {
1625 * Only kswapd can writeback filesystem pages
1626 * to avoid risk of stack overflow. But avoid
1627 * injecting inefficient single-page IO into
1628 * flusher writeback as much as possible: only
1629 * write pages when we've encountered many
1630 * dirty pages, and when we've already scanned
1631 * the rest of the LRU for clean pages and see
1632 * the same dirty pages again (PageReclaim).
1634 if (page_is_file_lru(page
) &&
1635 (!current_is_kswapd() || !PageReclaim(page
) ||
1636 !test_bit(PGDAT_DIRTY
, &pgdat
->flags
))) {
1638 * Immediately reclaim when written back.
1639 * Similar in principal to deactivate_page()
1640 * except we already have the page isolated
1641 * and know it's dirty
1643 inc_node_page_state(page
, NR_VMSCAN_IMMEDIATE
);
1644 SetPageReclaim(page
);
1646 goto activate_locked
;
1649 if (references
== PAGEREF_RECLAIM_CLEAN
)
1653 if (!sc
->may_writepage
)
1657 * Page is dirty. Flush the TLB if a writable entry
1658 * potentially exists to avoid CPU writes after IO
1659 * starts and then write it out here.
1661 try_to_unmap_flush_dirty();
1662 switch (pageout(page
, mapping
)) {
1666 goto activate_locked
;
1668 stat
->nr_pageout
+= thp_nr_pages(page
);
1670 if (PageWriteback(page
))
1672 if (PageDirty(page
))
1676 * A synchronous write - probably a ramdisk. Go
1677 * ahead and try to reclaim the page.
1679 if (!trylock_page(page
))
1681 if (PageDirty(page
) || PageWriteback(page
))
1683 mapping
= page_mapping(page
);
1686 ; /* try to free the page below */
1691 * If the page has buffers, try to free the buffer mappings
1692 * associated with this page. If we succeed we try to free
1695 * We do this even if the page is PageDirty().
1696 * try_to_release_page() does not perform I/O, but it is
1697 * possible for a page to have PageDirty set, but it is actually
1698 * clean (all its buffers are clean). This happens if the
1699 * buffers were written out directly, with submit_bh(). ext3
1700 * will do this, as well as the blockdev mapping.
1701 * try_to_release_page() will discover that cleanness and will
1702 * drop the buffers and mark the page clean - it can be freed.
1704 * Rarely, pages can have buffers and no ->mapping. These are
1705 * the pages which were not successfully invalidated in
1706 * truncate_cleanup_page(). We try to drop those buffers here
1707 * and if that worked, and the page is no longer mapped into
1708 * process address space (page_count == 1) it can be freed.
1709 * Otherwise, leave the page on the LRU so it is swappable.
1711 if (page_has_private(page
)) {
1712 if (!try_to_release_page(page
, sc
->gfp_mask
))
1713 goto activate_locked
;
1714 if (!mapping
&& page_count(page
) == 1) {
1716 if (put_page_testzero(page
))
1720 * rare race with speculative reference.
1721 * the speculative reference will free
1722 * this page shortly, so we may
1723 * increment nr_reclaimed here (and
1724 * leave it off the LRU).
1732 if (PageAnon(page
) && !PageSwapBacked(page
)) {
1733 /* follow __remove_mapping for reference */
1734 if (!page_ref_freeze(page
, 1))
1737 * The page has only one reference left, which is
1738 * from the isolation. After the caller puts the
1739 * page back on lru and drops the reference, the
1740 * page will be freed anyway. It doesn't matter
1741 * which lru it goes. So we don't bother checking
1744 count_vm_event(PGLAZYFREED
);
1745 count_memcg_page_event(page
, PGLAZYFREED
);
1746 } else if (!mapping
|| !__remove_mapping(mapping
, page
, true,
1747 sc
->target_mem_cgroup
))
1753 * THP may get swapped out in a whole, need account
1756 nr_reclaimed
+= nr_pages
;
1759 * Is there need to periodically free_page_list? It would
1760 * appear not as the counts should be low
1762 if (unlikely(PageTransHuge(page
)))
1763 destroy_compound_page(page
);
1765 list_add(&page
->lru
, &free_pages
);
1768 activate_locked_split
:
1770 * The tail pages that are failed to add into swap cache
1771 * reach here. Fixup nr_scanned and nr_pages.
1774 sc
->nr_scanned
-= (nr_pages
- 1);
1778 /* Not a candidate for swapping, so reclaim swap space. */
1779 if (PageSwapCache(page
) && (mem_cgroup_swap_full(page
) ||
1781 try_to_free_swap(page
);
1782 VM_BUG_ON_PAGE(PageActive(page
), page
);
1783 if (!PageMlocked(page
)) {
1784 int type
= page_is_file_lru(page
);
1785 SetPageActive(page
);
1786 stat
->nr_activate
[type
] += nr_pages
;
1787 count_memcg_page_event(page
, PGACTIVATE
);
1792 list_add(&page
->lru
, &ret_pages
);
1793 VM_BUG_ON_PAGE(PageLRU(page
) || PageUnevictable(page
), page
);
1795 /* 'page_list' is always empty here */
1797 /* Migrate pages selected for demotion */
1798 nr_reclaimed
+= demote_page_list(&demote_pages
, pgdat
);
1799 /* Pages that could not be demoted are still in @demote_pages */
1800 if (!list_empty(&demote_pages
)) {
1801 /* Pages which failed to demoted go back on @page_list for retry: */
1802 list_splice_init(&demote_pages
, page_list
);
1803 do_demote_pass
= false;
1807 pgactivate
= stat
->nr_activate
[0] + stat
->nr_activate
[1];
1809 mem_cgroup_uncharge_list(&free_pages
);
1810 try_to_unmap_flush();
1811 free_unref_page_list(&free_pages
);
1813 list_splice(&ret_pages
, page_list
);
1814 count_vm_events(PGACTIVATE
, pgactivate
);
1816 return nr_reclaimed
;
1819 unsigned int reclaim_clean_pages_from_list(struct zone
*zone
,
1820 struct list_head
*page_list
)
1822 struct scan_control sc
= {
1823 .gfp_mask
= GFP_KERNEL
,
1826 struct reclaim_stat stat
;
1827 unsigned int nr_reclaimed
;
1828 struct page
*page
, *next
;
1829 LIST_HEAD(clean_pages
);
1830 unsigned int noreclaim_flag
;
1832 list_for_each_entry_safe(page
, next
, page_list
, lru
) {
1833 if (!PageHuge(page
) && page_is_file_lru(page
) &&
1834 !PageDirty(page
) && !__PageMovable(page
) &&
1835 !PageUnevictable(page
)) {
1836 ClearPageActive(page
);
1837 list_move(&page
->lru
, &clean_pages
);
1842 * We should be safe here since we are only dealing with file pages and
1843 * we are not kswapd and therefore cannot write dirty file pages. But
1844 * call memalloc_noreclaim_save() anyway, just in case these conditions
1845 * change in the future.
1847 noreclaim_flag
= memalloc_noreclaim_save();
1848 nr_reclaimed
= shrink_page_list(&clean_pages
, zone
->zone_pgdat
, &sc
,
1850 memalloc_noreclaim_restore(noreclaim_flag
);
1852 list_splice(&clean_pages
, page_list
);
1853 mod_node_page_state(zone
->zone_pgdat
, NR_ISOLATED_FILE
,
1854 -(long)nr_reclaimed
);
1856 * Since lazyfree pages are isolated from file LRU from the beginning,
1857 * they will rotate back to anonymous LRU in the end if it failed to
1858 * discard so isolated count will be mismatched.
1859 * Compensate the isolated count for both LRU lists.
1861 mod_node_page_state(zone
->zone_pgdat
, NR_ISOLATED_ANON
,
1862 stat
.nr_lazyfree_fail
);
1863 mod_node_page_state(zone
->zone_pgdat
, NR_ISOLATED_FILE
,
1864 -(long)stat
.nr_lazyfree_fail
);
1865 return nr_reclaimed
;
1869 * Attempt to remove the specified page from its LRU. Only take this page
1870 * if it is of the appropriate PageActive status. Pages which are being
1871 * freed elsewhere are also ignored.
1873 * page: page to consider
1874 * mode: one of the LRU isolation modes defined above
1876 * returns true on success, false on failure.
1878 bool __isolate_lru_page_prepare(struct page
*page
, isolate_mode_t mode
)
1880 /* Only take pages on the LRU. */
1884 /* Compaction should not handle unevictable pages but CMA can do so */
1885 if (PageUnevictable(page
) && !(mode
& ISOLATE_UNEVICTABLE
))
1889 * To minimise LRU disruption, the caller can indicate that it only
1890 * wants to isolate pages it will be able to operate on without
1891 * blocking - clean pages for the most part.
1893 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1894 * that it is possible to migrate without blocking
1896 if (mode
& ISOLATE_ASYNC_MIGRATE
) {
1897 /* All the caller can do on PageWriteback is block */
1898 if (PageWriteback(page
))
1901 if (PageDirty(page
)) {
1902 struct address_space
*mapping
;
1906 * Only pages without mappings or that have a
1907 * ->migratepage callback are possible to migrate
1908 * without blocking. However, we can be racing with
1909 * truncation so it's necessary to lock the page
1910 * to stabilise the mapping as truncation holds
1911 * the page lock until after the page is removed
1912 * from the page cache.
1914 if (!trylock_page(page
))
1917 mapping
= page_mapping(page
);
1918 migrate_dirty
= !mapping
|| mapping
->a_ops
->migratepage
;
1925 if ((mode
& ISOLATE_UNMAPPED
) && page_mapped(page
))
1932 * Update LRU sizes after isolating pages. The LRU size updates must
1933 * be complete before mem_cgroup_update_lru_size due to a sanity check.
1935 static __always_inline
void update_lru_sizes(struct lruvec
*lruvec
,
1936 enum lru_list lru
, unsigned long *nr_zone_taken
)
1940 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++) {
1941 if (!nr_zone_taken
[zid
])
1944 update_lru_size(lruvec
, lru
, zid
, -nr_zone_taken
[zid
]);
1950 * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
1952 * lruvec->lru_lock is heavily contended. Some of the functions that
1953 * shrink the lists perform better by taking out a batch of pages
1954 * and working on them outside the LRU lock.
1956 * For pagecache intensive workloads, this function is the hottest
1957 * spot in the kernel (apart from copy_*_user functions).
1959 * Lru_lock must be held before calling this function.
1961 * @nr_to_scan: The number of eligible pages to look through on the list.
1962 * @lruvec: The LRU vector to pull pages from.
1963 * @dst: The temp list to put pages on to.
1964 * @nr_scanned: The number of pages that were scanned.
1965 * @sc: The scan_control struct for this reclaim session
1966 * @lru: LRU list id for isolating
1968 * returns how many pages were moved onto *@dst.
1970 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1971 struct lruvec
*lruvec
, struct list_head
*dst
,
1972 unsigned long *nr_scanned
, struct scan_control
*sc
,
1975 struct list_head
*src
= &lruvec
->lists
[lru
];
1976 unsigned long nr_taken
= 0;
1977 unsigned long nr_zone_taken
[MAX_NR_ZONES
] = { 0 };
1978 unsigned long nr_skipped
[MAX_NR_ZONES
] = { 0, };
1979 unsigned long skipped
= 0;
1980 unsigned long scan
, total_scan
, nr_pages
;
1981 LIST_HEAD(pages_skipped
);
1982 isolate_mode_t mode
= (sc
->may_unmap
? 0 : ISOLATE_UNMAPPED
);
1986 while (scan
< nr_to_scan
&& !list_empty(src
)) {
1989 page
= lru_to_page(src
);
1990 prefetchw_prev_lru_page(page
, src
, flags
);
1992 nr_pages
= compound_nr(page
);
1993 total_scan
+= nr_pages
;
1995 if (page_zonenum(page
) > sc
->reclaim_idx
) {
1996 list_move(&page
->lru
, &pages_skipped
);
1997 nr_skipped
[page_zonenum(page
)] += nr_pages
;
2002 * Do not count skipped pages because that makes the function
2003 * return with no isolated pages if the LRU mostly contains
2004 * ineligible pages. This causes the VM to not reclaim any
2005 * pages, triggering a premature OOM.
2007 * Account all tail pages of THP. This would not cause
2008 * premature OOM since __isolate_lru_page() returns -EBUSY
2009 * only when the page is being freed somewhere else.
2012 if (!__isolate_lru_page_prepare(page
, mode
)) {
2013 /* It is being freed elsewhere */
2014 list_move(&page
->lru
, src
);
2018 * Be careful not to clear PageLRU until after we're
2019 * sure the page is not being freed elsewhere -- the
2020 * page release code relies on it.
2022 if (unlikely(!get_page_unless_zero(page
))) {
2023 list_move(&page
->lru
, src
);
2027 if (!TestClearPageLRU(page
)) {
2028 /* Another thread is already isolating this page */
2030 list_move(&page
->lru
, src
);
2034 nr_taken
+= nr_pages
;
2035 nr_zone_taken
[page_zonenum(page
)] += nr_pages
;
2036 list_move(&page
->lru
, dst
);
2040 * Splice any skipped pages to the start of the LRU list. Note that
2041 * this disrupts the LRU order when reclaiming for lower zones but
2042 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
2043 * scanning would soon rescan the same pages to skip and put the
2044 * system at risk of premature OOM.
2046 if (!list_empty(&pages_skipped
)) {
2049 list_splice(&pages_skipped
, src
);
2050 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++) {
2051 if (!nr_skipped
[zid
])
2054 __count_zid_vm_events(PGSCAN_SKIP
, zid
, nr_skipped
[zid
]);
2055 skipped
+= nr_skipped
[zid
];
2058 *nr_scanned
= total_scan
;
2059 trace_mm_vmscan_lru_isolate(sc
->reclaim_idx
, sc
->order
, nr_to_scan
,
2060 total_scan
, skipped
, nr_taken
, mode
, lru
);
2061 update_lru_sizes(lruvec
, lru
, nr_zone_taken
);
2066 * isolate_lru_page - tries to isolate a page from its LRU list
2067 * @page: page to isolate from its LRU list
2069 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
2070 * vmstat statistic corresponding to whatever LRU list the page was on.
2072 * Returns 0 if the page was removed from an LRU list.
2073 * Returns -EBUSY if the page was not on an LRU list.
2075 * The returned page will have PageLRU() cleared. If it was found on
2076 * the active list, it will have PageActive set. If it was found on
2077 * the unevictable list, it will have the PageUnevictable bit set. That flag
2078 * may need to be cleared by the caller before letting the page go.
2080 * The vmstat statistic corresponding to the list on which the page was
2081 * found will be decremented.
2085 * (1) Must be called with an elevated refcount on the page. This is a
2086 * fundamental difference from isolate_lru_pages (which is called
2087 * without a stable reference).
2088 * (2) the lru_lock must not be held.
2089 * (3) interrupts must be enabled.
2091 int isolate_lru_page(struct page
*page
)
2095 VM_BUG_ON_PAGE(!page_count(page
), page
);
2096 WARN_RATELIMIT(PageTail(page
), "trying to isolate tail page");
2098 if (TestClearPageLRU(page
)) {
2099 struct lruvec
*lruvec
;
2102 lruvec
= lock_page_lruvec_irq(page
);
2103 del_page_from_lru_list(page
, lruvec
);
2104 unlock_page_lruvec_irq(lruvec
);
2112 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
2113 * then get rescheduled. When there are massive number of tasks doing page
2114 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
2115 * the LRU list will go small and be scanned faster than necessary, leading to
2116 * unnecessary swapping, thrashing and OOM.
2118 static int too_many_isolated(struct pglist_data
*pgdat
, int file
,
2119 struct scan_control
*sc
)
2121 unsigned long inactive
, isolated
;
2123 if (current_is_kswapd())
2126 if (!writeback_throttling_sane(sc
))
2130 inactive
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
2131 isolated
= node_page_state(pgdat
, NR_ISOLATED_FILE
);
2133 inactive
= node_page_state(pgdat
, NR_INACTIVE_ANON
);
2134 isolated
= node_page_state(pgdat
, NR_ISOLATED_ANON
);
2138 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
2139 * won't get blocked by normal direct-reclaimers, forming a circular
2142 if ((sc
->gfp_mask
& (__GFP_IO
| __GFP_FS
)) == (__GFP_IO
| __GFP_FS
))
2145 return isolated
> inactive
;
2149 * move_pages_to_lru() moves pages from private @list to appropriate LRU list.
2150 * On return, @list is reused as a list of pages to be freed by the caller.
2152 * Returns the number of pages moved to the given lruvec.
2154 static unsigned int move_pages_to_lru(struct lruvec
*lruvec
,
2155 struct list_head
*list
)
2157 int nr_pages
, nr_moved
= 0;
2158 LIST_HEAD(pages_to_free
);
2161 while (!list_empty(list
)) {
2162 page
= lru_to_page(list
);
2163 VM_BUG_ON_PAGE(PageLRU(page
), page
);
2164 list_del(&page
->lru
);
2165 if (unlikely(!page_evictable(page
))) {
2166 spin_unlock_irq(&lruvec
->lru_lock
);
2167 putback_lru_page(page
);
2168 spin_lock_irq(&lruvec
->lru_lock
);
2173 * The SetPageLRU needs to be kept here for list integrity.
2175 * #0 move_pages_to_lru #1 release_pages
2176 * if !put_page_testzero
2177 * if (put_page_testzero())
2178 * !PageLRU //skip lru_lock
2180 * list_add(&page->lru,)
2181 * list_add(&page->lru,)
2185 if (unlikely(put_page_testzero(page
))) {
2186 __clear_page_lru_flags(page
);
2188 if (unlikely(PageCompound(page
))) {
2189 spin_unlock_irq(&lruvec
->lru_lock
);
2190 destroy_compound_page(page
);
2191 spin_lock_irq(&lruvec
->lru_lock
);
2193 list_add(&page
->lru
, &pages_to_free
);
2199 * All pages were isolated from the same lruvec (and isolation
2200 * inhibits memcg migration).
2202 VM_BUG_ON_PAGE(!page_matches_lruvec(page
, lruvec
), page
);
2203 add_page_to_lru_list(page
, lruvec
);
2204 nr_pages
= thp_nr_pages(page
);
2205 nr_moved
+= nr_pages
;
2206 if (PageActive(page
))
2207 workingset_age_nonresident(lruvec
, nr_pages
);
2211 * To save our caller's stack, now use input list for pages to free.
2213 list_splice(&pages_to_free
, list
);
2219 * If a kernel thread (such as nfsd for loop-back mounts) services
2220 * a backing device by writing to the page cache it sets PF_LOCAL_THROTTLE.
2221 * In that case we should only throttle if the backing device it is
2222 * writing to is congested. In other cases it is safe to throttle.
2224 static int current_may_throttle(void)
2226 return !(current
->flags
& PF_LOCAL_THROTTLE
) ||
2227 current
->backing_dev_info
== NULL
||
2228 bdi_write_congested(current
->backing_dev_info
);
2232 * shrink_inactive_list() is a helper for shrink_node(). It returns the number
2233 * of reclaimed pages
2235 static unsigned long
2236 shrink_inactive_list(unsigned long nr_to_scan
, struct lruvec
*lruvec
,
2237 struct scan_control
*sc
, enum lru_list lru
)
2239 LIST_HEAD(page_list
);
2240 unsigned long nr_scanned
;
2241 unsigned int nr_reclaimed
= 0;
2242 unsigned long nr_taken
;
2243 struct reclaim_stat stat
;
2244 bool file
= is_file_lru(lru
);
2245 enum vm_event_item item
;
2246 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2247 bool stalled
= false;
2249 while (unlikely(too_many_isolated(pgdat
, file
, sc
))) {
2253 /* wait a bit for the reclaimer. */
2257 /* We are about to die and free our memory. Return now. */
2258 if (fatal_signal_pending(current
))
2259 return SWAP_CLUSTER_MAX
;
2264 spin_lock_irq(&lruvec
->lru_lock
);
2266 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &page_list
,
2267 &nr_scanned
, sc
, lru
);
2269 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, nr_taken
);
2270 item
= current_is_kswapd() ? PGSCAN_KSWAPD
: PGSCAN_DIRECT
;
2271 if (!cgroup_reclaim(sc
))
2272 __count_vm_events(item
, nr_scanned
);
2273 __count_memcg_events(lruvec_memcg(lruvec
), item
, nr_scanned
);
2274 __count_vm_events(PGSCAN_ANON
+ file
, nr_scanned
);
2276 spin_unlock_irq(&lruvec
->lru_lock
);
2281 nr_reclaimed
= shrink_page_list(&page_list
, pgdat
, sc
, &stat
, false);
2283 spin_lock_irq(&lruvec
->lru_lock
);
2284 move_pages_to_lru(lruvec
, &page_list
);
2286 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
2287 item
= current_is_kswapd() ? PGSTEAL_KSWAPD
: PGSTEAL_DIRECT
;
2288 if (!cgroup_reclaim(sc
))
2289 __count_vm_events(item
, nr_reclaimed
);
2290 __count_memcg_events(lruvec_memcg(lruvec
), item
, nr_reclaimed
);
2291 __count_vm_events(PGSTEAL_ANON
+ file
, nr_reclaimed
);
2292 spin_unlock_irq(&lruvec
->lru_lock
);
2294 lru_note_cost(lruvec
, file
, stat
.nr_pageout
);
2295 mem_cgroup_uncharge_list(&page_list
);
2296 free_unref_page_list(&page_list
);
2299 * If dirty pages are scanned that are not queued for IO, it
2300 * implies that flushers are not doing their job. This can
2301 * happen when memory pressure pushes dirty pages to the end of
2302 * the LRU before the dirty limits are breached and the dirty
2303 * data has expired. It can also happen when the proportion of
2304 * dirty pages grows not through writes but through memory
2305 * pressure reclaiming all the clean cache. And in some cases,
2306 * the flushers simply cannot keep up with the allocation
2307 * rate. Nudge the flusher threads in case they are asleep.
2309 if (stat
.nr_unqueued_dirty
== nr_taken
)
2310 wakeup_flusher_threads(WB_REASON_VMSCAN
);
2312 sc
->nr
.dirty
+= stat
.nr_dirty
;
2313 sc
->nr
.congested
+= stat
.nr_congested
;
2314 sc
->nr
.unqueued_dirty
+= stat
.nr_unqueued_dirty
;
2315 sc
->nr
.writeback
+= stat
.nr_writeback
;
2316 sc
->nr
.immediate
+= stat
.nr_immediate
;
2317 sc
->nr
.taken
+= nr_taken
;
2319 sc
->nr
.file_taken
+= nr_taken
;
2321 trace_mm_vmscan_lru_shrink_inactive(pgdat
->node_id
,
2322 nr_scanned
, nr_reclaimed
, &stat
, sc
->priority
, file
);
2323 return nr_reclaimed
;
2327 * shrink_active_list() moves pages from the active LRU to the inactive LRU.
2329 * We move them the other way if the page is referenced by one or more
2332 * If the pages are mostly unmapped, the processing is fast and it is
2333 * appropriate to hold lru_lock across the whole operation. But if
2334 * the pages are mapped, the processing is slow (page_referenced()), so
2335 * we should drop lru_lock around each page. It's impossible to balance
2336 * this, so instead we remove the pages from the LRU while processing them.
2337 * It is safe to rely on PG_active against the non-LRU pages in here because
2338 * nobody will play with that bit on a non-LRU page.
2340 * The downside is that we have to touch page->_refcount against each page.
2341 * But we had to alter page->flags anyway.
2343 static void shrink_active_list(unsigned long nr_to_scan
,
2344 struct lruvec
*lruvec
,
2345 struct scan_control
*sc
,
2348 unsigned long nr_taken
;
2349 unsigned long nr_scanned
;
2350 unsigned long vm_flags
;
2351 LIST_HEAD(l_hold
); /* The pages which were snipped off */
2352 LIST_HEAD(l_active
);
2353 LIST_HEAD(l_inactive
);
2355 unsigned nr_deactivate
, nr_activate
;
2356 unsigned nr_rotated
= 0;
2357 int file
= is_file_lru(lru
);
2358 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2362 spin_lock_irq(&lruvec
->lru_lock
);
2364 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &l_hold
,
2365 &nr_scanned
, sc
, lru
);
2367 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, nr_taken
);
2369 if (!cgroup_reclaim(sc
))
2370 __count_vm_events(PGREFILL
, nr_scanned
);
2371 __count_memcg_events(lruvec_memcg(lruvec
), PGREFILL
, nr_scanned
);
2373 spin_unlock_irq(&lruvec
->lru_lock
);
2375 while (!list_empty(&l_hold
)) {
2377 page
= lru_to_page(&l_hold
);
2378 list_del(&page
->lru
);
2380 if (unlikely(!page_evictable(page
))) {
2381 putback_lru_page(page
);
2385 if (unlikely(buffer_heads_over_limit
)) {
2386 if (page_has_private(page
) && trylock_page(page
)) {
2387 if (page_has_private(page
))
2388 try_to_release_page(page
, 0);
2393 if (page_referenced(page
, 0, sc
->target_mem_cgroup
,
2396 * Identify referenced, file-backed active pages and
2397 * give them one more trip around the active list. So
2398 * that executable code get better chances to stay in
2399 * memory under moderate memory pressure. Anon pages
2400 * are not likely to be evicted by use-once streaming
2401 * IO, plus JVM can create lots of anon VM_EXEC pages,
2402 * so we ignore them here.
2404 if ((vm_flags
& VM_EXEC
) && page_is_file_lru(page
)) {
2405 nr_rotated
+= thp_nr_pages(page
);
2406 list_add(&page
->lru
, &l_active
);
2411 ClearPageActive(page
); /* we are de-activating */
2412 SetPageWorkingset(page
);
2413 list_add(&page
->lru
, &l_inactive
);
2417 * Move pages back to the lru list.
2419 spin_lock_irq(&lruvec
->lru_lock
);
2421 nr_activate
= move_pages_to_lru(lruvec
, &l_active
);
2422 nr_deactivate
= move_pages_to_lru(lruvec
, &l_inactive
);
2423 /* Keep all free pages in l_active list */
2424 list_splice(&l_inactive
, &l_active
);
2426 __count_vm_events(PGDEACTIVATE
, nr_deactivate
);
2427 __count_memcg_events(lruvec_memcg(lruvec
), PGDEACTIVATE
, nr_deactivate
);
2429 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
2430 spin_unlock_irq(&lruvec
->lru_lock
);
2432 mem_cgroup_uncharge_list(&l_active
);
2433 free_unref_page_list(&l_active
);
2434 trace_mm_vmscan_lru_shrink_active(pgdat
->node_id
, nr_taken
, nr_activate
,
2435 nr_deactivate
, nr_rotated
, sc
->priority
, file
);
2438 unsigned long reclaim_pages(struct list_head
*page_list
)
2440 int nid
= NUMA_NO_NODE
;
2441 unsigned int nr_reclaimed
= 0;
2442 LIST_HEAD(node_page_list
);
2443 struct reclaim_stat dummy_stat
;
2445 unsigned int noreclaim_flag
;
2446 struct scan_control sc
= {
2447 .gfp_mask
= GFP_KERNEL
,
2454 noreclaim_flag
= memalloc_noreclaim_save();
2456 while (!list_empty(page_list
)) {
2457 page
= lru_to_page(page_list
);
2458 if (nid
== NUMA_NO_NODE
) {
2459 nid
= page_to_nid(page
);
2460 INIT_LIST_HEAD(&node_page_list
);
2463 if (nid
== page_to_nid(page
)) {
2464 ClearPageActive(page
);
2465 list_move(&page
->lru
, &node_page_list
);
2469 nr_reclaimed
+= shrink_page_list(&node_page_list
,
2471 &sc
, &dummy_stat
, false);
2472 while (!list_empty(&node_page_list
)) {
2473 page
= lru_to_page(&node_page_list
);
2474 list_del(&page
->lru
);
2475 putback_lru_page(page
);
2481 if (!list_empty(&node_page_list
)) {
2482 nr_reclaimed
+= shrink_page_list(&node_page_list
,
2484 &sc
, &dummy_stat
, false);
2485 while (!list_empty(&node_page_list
)) {
2486 page
= lru_to_page(&node_page_list
);
2487 list_del(&page
->lru
);
2488 putback_lru_page(page
);
2492 memalloc_noreclaim_restore(noreclaim_flag
);
2494 return nr_reclaimed
;
2497 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
2498 struct lruvec
*lruvec
, struct scan_control
*sc
)
2500 if (is_active_lru(lru
)) {
2501 if (sc
->may_deactivate
& (1 << is_file_lru(lru
)))
2502 shrink_active_list(nr_to_scan
, lruvec
, sc
, lru
);
2504 sc
->skipped_deactivate
= 1;
2508 return shrink_inactive_list(nr_to_scan
, lruvec
, sc
, lru
);
2512 * The inactive anon list should be small enough that the VM never has
2513 * to do too much work.
2515 * The inactive file list should be small enough to leave most memory
2516 * to the established workingset on the scan-resistant active list,
2517 * but large enough to avoid thrashing the aggregate readahead window.
2519 * Both inactive lists should also be large enough that each inactive
2520 * page has a chance to be referenced again before it is reclaimed.
2522 * If that fails and refaulting is observed, the inactive list grows.
2524 * The inactive_ratio is the target ratio of ACTIVE to INACTIVE pages
2525 * on this LRU, maintained by the pageout code. An inactive_ratio
2526 * of 3 means 3:1 or 25% of the pages are kept on the inactive list.
2529 * memory ratio inactive
2530 * -------------------------------------
2539 static bool inactive_is_low(struct lruvec
*lruvec
, enum lru_list inactive_lru
)
2541 enum lru_list active_lru
= inactive_lru
+ LRU_ACTIVE
;
2542 unsigned long inactive
, active
;
2543 unsigned long inactive_ratio
;
2546 inactive
= lruvec_page_state(lruvec
, NR_LRU_BASE
+ inactive_lru
);
2547 active
= lruvec_page_state(lruvec
, NR_LRU_BASE
+ active_lru
);
2549 gb
= (inactive
+ active
) >> (30 - PAGE_SHIFT
);
2551 inactive_ratio
= int_sqrt(10 * gb
);
2555 return inactive
* inactive_ratio
< active
;
2566 * Determine how aggressively the anon and file LRU lists should be
2567 * scanned. The relative value of each set of LRU lists is determined
2568 * by looking at the fraction of the pages scanned we did rotate back
2569 * onto the active list instead of evict.
2571 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
2572 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
2574 static void get_scan_count(struct lruvec
*lruvec
, struct scan_control
*sc
,
2577 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2578 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
2579 unsigned long anon_cost
, file_cost
, total_cost
;
2580 int swappiness
= mem_cgroup_swappiness(memcg
);
2581 u64 fraction
[ANON_AND_FILE
];
2582 u64 denominator
= 0; /* gcc */
2583 enum scan_balance scan_balance
;
2584 unsigned long ap
, fp
;
2587 /* If we have no swap space, do not bother scanning anon pages. */
2588 if (!sc
->may_swap
|| !can_reclaim_anon_pages(memcg
, pgdat
->node_id
, sc
)) {
2589 scan_balance
= SCAN_FILE
;
2594 * Global reclaim will swap to prevent OOM even with no
2595 * swappiness, but memcg users want to use this knob to
2596 * disable swapping for individual groups completely when
2597 * using the memory controller's swap limit feature would be
2600 if (cgroup_reclaim(sc
) && !swappiness
) {
2601 scan_balance
= SCAN_FILE
;
2606 * Do not apply any pressure balancing cleverness when the
2607 * system is close to OOM, scan both anon and file equally
2608 * (unless the swappiness setting disagrees with swapping).
2610 if (!sc
->priority
&& swappiness
) {
2611 scan_balance
= SCAN_EQUAL
;
2616 * If the system is almost out of file pages, force-scan anon.
2618 if (sc
->file_is_tiny
) {
2619 scan_balance
= SCAN_ANON
;
2624 * If there is enough inactive page cache, we do not reclaim
2625 * anything from the anonymous working right now.
2627 if (sc
->cache_trim_mode
) {
2628 scan_balance
= SCAN_FILE
;
2632 scan_balance
= SCAN_FRACT
;
2634 * Calculate the pressure balance between anon and file pages.
2636 * The amount of pressure we put on each LRU is inversely
2637 * proportional to the cost of reclaiming each list, as
2638 * determined by the share of pages that are refaulting, times
2639 * the relative IO cost of bringing back a swapped out
2640 * anonymous page vs reloading a filesystem page (swappiness).
2642 * Although we limit that influence to ensure no list gets
2643 * left behind completely: at least a third of the pressure is
2644 * applied, before swappiness.
2646 * With swappiness at 100, anon and file have equal IO cost.
2648 total_cost
= sc
->anon_cost
+ sc
->file_cost
;
2649 anon_cost
= total_cost
+ sc
->anon_cost
;
2650 file_cost
= total_cost
+ sc
->file_cost
;
2651 total_cost
= anon_cost
+ file_cost
;
2653 ap
= swappiness
* (total_cost
+ 1);
2654 ap
/= anon_cost
+ 1;
2656 fp
= (200 - swappiness
) * (total_cost
+ 1);
2657 fp
/= file_cost
+ 1;
2661 denominator
= ap
+ fp
;
2663 for_each_evictable_lru(lru
) {
2664 int file
= is_file_lru(lru
);
2665 unsigned long lruvec_size
;
2666 unsigned long low
, min
;
2669 lruvec_size
= lruvec_lru_size(lruvec
, lru
, sc
->reclaim_idx
);
2670 mem_cgroup_protection(sc
->target_mem_cgroup
, memcg
,
2675 * Scale a cgroup's reclaim pressure by proportioning
2676 * its current usage to its memory.low or memory.min
2679 * This is important, as otherwise scanning aggression
2680 * becomes extremely binary -- from nothing as we
2681 * approach the memory protection threshold, to totally
2682 * nominal as we exceed it. This results in requiring
2683 * setting extremely liberal protection thresholds. It
2684 * also means we simply get no protection at all if we
2685 * set it too low, which is not ideal.
2687 * If there is any protection in place, we reduce scan
2688 * pressure by how much of the total memory used is
2689 * within protection thresholds.
2691 * There is one special case: in the first reclaim pass,
2692 * we skip over all groups that are within their low
2693 * protection. If that fails to reclaim enough pages to
2694 * satisfy the reclaim goal, we come back and override
2695 * the best-effort low protection. However, we still
2696 * ideally want to honor how well-behaved groups are in
2697 * that case instead of simply punishing them all
2698 * equally. As such, we reclaim them based on how much
2699 * memory they are using, reducing the scan pressure
2700 * again by how much of the total memory used is under
2703 unsigned long cgroup_size
= mem_cgroup_size(memcg
);
2704 unsigned long protection
;
2706 /* memory.low scaling, make sure we retry before OOM */
2707 if (!sc
->memcg_low_reclaim
&& low
> min
) {
2709 sc
->memcg_low_skipped
= 1;
2714 /* Avoid TOCTOU with earlier protection check */
2715 cgroup_size
= max(cgroup_size
, protection
);
2717 scan
= lruvec_size
- lruvec_size
* protection
/
2721 * Minimally target SWAP_CLUSTER_MAX pages to keep
2722 * reclaim moving forwards, avoiding decrementing
2723 * sc->priority further than desirable.
2725 scan
= max(scan
, SWAP_CLUSTER_MAX
);
2730 scan
>>= sc
->priority
;
2733 * If the cgroup's already been deleted, make sure to
2734 * scrape out the remaining cache.
2736 if (!scan
&& !mem_cgroup_online(memcg
))
2737 scan
= min(lruvec_size
, SWAP_CLUSTER_MAX
);
2739 switch (scan_balance
) {
2741 /* Scan lists relative to size */
2745 * Scan types proportional to swappiness and
2746 * their relative recent reclaim efficiency.
2747 * Make sure we don't miss the last page on
2748 * the offlined memory cgroups because of a
2751 scan
= mem_cgroup_online(memcg
) ?
2752 div64_u64(scan
* fraction
[file
], denominator
) :
2753 DIV64_U64_ROUND_UP(scan
* fraction
[file
],
2758 /* Scan one type exclusively */
2759 if ((scan_balance
== SCAN_FILE
) != file
)
2763 /* Look ma, no brain */
2772 * Anonymous LRU management is a waste if there is
2773 * ultimately no way to reclaim the memory.
2775 static bool can_age_anon_pages(struct pglist_data
*pgdat
,
2776 struct scan_control
*sc
)
2778 /* Aging the anon LRU is valuable if swap is present: */
2779 if (total_swap_pages
> 0)
2782 /* Also valuable if anon pages can be demoted: */
2783 return can_demote(pgdat
->node_id
, sc
);
2786 static void shrink_lruvec(struct lruvec
*lruvec
, struct scan_control
*sc
)
2788 unsigned long nr
[NR_LRU_LISTS
];
2789 unsigned long targets
[NR_LRU_LISTS
];
2790 unsigned long nr_to_scan
;
2792 unsigned long nr_reclaimed
= 0;
2793 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
2794 struct blk_plug plug
;
2797 get_scan_count(lruvec
, sc
, nr
);
2799 /* Record the original scan target for proportional adjustments later */
2800 memcpy(targets
, nr
, sizeof(nr
));
2803 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
2804 * event that can occur when there is little memory pressure e.g.
2805 * multiple streaming readers/writers. Hence, we do not abort scanning
2806 * when the requested number of pages are reclaimed when scanning at
2807 * DEF_PRIORITY on the assumption that the fact we are direct
2808 * reclaiming implies that kswapd is not keeping up and it is best to
2809 * do a batch of work at once. For memcg reclaim one check is made to
2810 * abort proportional reclaim if either the file or anon lru has already
2811 * dropped to zero at the first pass.
2813 scan_adjusted
= (!cgroup_reclaim(sc
) && !current_is_kswapd() &&
2814 sc
->priority
== DEF_PRIORITY
);
2816 blk_start_plug(&plug
);
2817 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
2818 nr
[LRU_INACTIVE_FILE
]) {
2819 unsigned long nr_anon
, nr_file
, percentage
;
2820 unsigned long nr_scanned
;
2822 for_each_evictable_lru(lru
) {
2824 nr_to_scan
= min(nr
[lru
], SWAP_CLUSTER_MAX
);
2825 nr
[lru
] -= nr_to_scan
;
2827 nr_reclaimed
+= shrink_list(lru
, nr_to_scan
,
2834 if (nr_reclaimed
< nr_to_reclaim
|| scan_adjusted
)
2838 * For kswapd and memcg, reclaim at least the number of pages
2839 * requested. Ensure that the anon and file LRUs are scanned
2840 * proportionally what was requested by get_scan_count(). We
2841 * stop reclaiming one LRU and reduce the amount scanning
2842 * proportional to the original scan target.
2844 nr_file
= nr
[LRU_INACTIVE_FILE
] + nr
[LRU_ACTIVE_FILE
];
2845 nr_anon
= nr
[LRU_INACTIVE_ANON
] + nr
[LRU_ACTIVE_ANON
];
2848 * It's just vindictive to attack the larger once the smaller
2849 * has gone to zero. And given the way we stop scanning the
2850 * smaller below, this makes sure that we only make one nudge
2851 * towards proportionality once we've got nr_to_reclaim.
2853 if (!nr_file
|| !nr_anon
)
2856 if (nr_file
> nr_anon
) {
2857 unsigned long scan_target
= targets
[LRU_INACTIVE_ANON
] +
2858 targets
[LRU_ACTIVE_ANON
] + 1;
2860 percentage
= nr_anon
* 100 / scan_target
;
2862 unsigned long scan_target
= targets
[LRU_INACTIVE_FILE
] +
2863 targets
[LRU_ACTIVE_FILE
] + 1;
2865 percentage
= nr_file
* 100 / scan_target
;
2868 /* Stop scanning the smaller of the LRU */
2870 nr
[lru
+ LRU_ACTIVE
] = 0;
2873 * Recalculate the other LRU scan count based on its original
2874 * scan target and the percentage scanning already complete
2876 lru
= (lru
== LRU_FILE
) ? LRU_BASE
: LRU_FILE
;
2877 nr_scanned
= targets
[lru
] - nr
[lru
];
2878 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2879 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2882 nr_scanned
= targets
[lru
] - nr
[lru
];
2883 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2884 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2886 scan_adjusted
= true;
2888 blk_finish_plug(&plug
);
2889 sc
->nr_reclaimed
+= nr_reclaimed
;
2892 * Even if we did not try to evict anon pages at all, we want to
2893 * rebalance the anon lru active/inactive ratio.
2895 if (can_age_anon_pages(lruvec_pgdat(lruvec
), sc
) &&
2896 inactive_is_low(lruvec
, LRU_INACTIVE_ANON
))
2897 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
2898 sc
, LRU_ACTIVE_ANON
);
2901 /* Use reclaim/compaction for costly allocs or under memory pressure */
2902 static bool in_reclaim_compaction(struct scan_control
*sc
)
2904 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
2905 (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
||
2906 sc
->priority
< DEF_PRIORITY
- 2))
2913 * Reclaim/compaction is used for high-order allocation requests. It reclaims
2914 * order-0 pages before compacting the zone. should_continue_reclaim() returns
2915 * true if more pages should be reclaimed such that when the page allocator
2916 * calls try_to_compact_pages() that it will have enough free pages to succeed.
2917 * It will give up earlier than that if there is difficulty reclaiming pages.
2919 static inline bool should_continue_reclaim(struct pglist_data
*pgdat
,
2920 unsigned long nr_reclaimed
,
2921 struct scan_control
*sc
)
2923 unsigned long pages_for_compaction
;
2924 unsigned long inactive_lru_pages
;
2927 /* If not in reclaim/compaction mode, stop */
2928 if (!in_reclaim_compaction(sc
))
2932 * Stop if we failed to reclaim any pages from the last SWAP_CLUSTER_MAX
2933 * number of pages that were scanned. This will return to the caller
2934 * with the risk reclaim/compaction and the resulting allocation attempt
2935 * fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL
2936 * allocations through requiring that the full LRU list has been scanned
2937 * first, by assuming that zero delta of sc->nr_scanned means full LRU
2938 * scan, but that approximation was wrong, and there were corner cases
2939 * where always a non-zero amount of pages were scanned.
2944 /* If compaction would go ahead or the allocation would succeed, stop */
2945 for (z
= 0; z
<= sc
->reclaim_idx
; z
++) {
2946 struct zone
*zone
= &pgdat
->node_zones
[z
];
2947 if (!managed_zone(zone
))
2950 switch (compaction_suitable(zone
, sc
->order
, 0, sc
->reclaim_idx
)) {
2951 case COMPACT_SUCCESS
:
2952 case COMPACT_CONTINUE
:
2955 /* check next zone */
2961 * If we have not reclaimed enough pages for compaction and the
2962 * inactive lists are large enough, continue reclaiming
2964 pages_for_compaction
= compact_gap(sc
->order
);
2965 inactive_lru_pages
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
2966 if (can_reclaim_anon_pages(NULL
, pgdat
->node_id
, sc
))
2967 inactive_lru_pages
+= node_page_state(pgdat
, NR_INACTIVE_ANON
);
2969 return inactive_lru_pages
> pages_for_compaction
;
2972 static void shrink_node_memcgs(pg_data_t
*pgdat
, struct scan_control
*sc
)
2974 struct mem_cgroup
*target_memcg
= sc
->target_mem_cgroup
;
2975 struct mem_cgroup
*memcg
;
2977 memcg
= mem_cgroup_iter(target_memcg
, NULL
, NULL
);
2979 struct lruvec
*lruvec
= mem_cgroup_lruvec(memcg
, pgdat
);
2980 unsigned long reclaimed
;
2981 unsigned long scanned
;
2984 * This loop can become CPU-bound when target memcgs
2985 * aren't eligible for reclaim - either because they
2986 * don't have any reclaimable pages, or because their
2987 * memory is explicitly protected. Avoid soft lockups.
2991 mem_cgroup_calculate_protection(target_memcg
, memcg
);
2993 if (mem_cgroup_below_min(memcg
)) {
2996 * If there is no reclaimable memory, OOM.
2999 } else if (mem_cgroup_below_low(memcg
)) {
3002 * Respect the protection only as long as
3003 * there is an unprotected supply
3004 * of reclaimable memory from other cgroups.
3006 if (!sc
->memcg_low_reclaim
) {
3007 sc
->memcg_low_skipped
= 1;
3010 memcg_memory_event(memcg
, MEMCG_LOW
);
3013 reclaimed
= sc
->nr_reclaimed
;
3014 scanned
= sc
->nr_scanned
;
3016 shrink_lruvec(lruvec
, sc
);
3018 shrink_slab(sc
->gfp_mask
, pgdat
->node_id
, memcg
,
3021 /* Record the group's reclaim efficiency */
3022 vmpressure(sc
->gfp_mask
, memcg
, false,
3023 sc
->nr_scanned
- scanned
,
3024 sc
->nr_reclaimed
- reclaimed
);
3026 } while ((memcg
= mem_cgroup_iter(target_memcg
, memcg
, NULL
)));
3029 static void shrink_node(pg_data_t
*pgdat
, struct scan_control
*sc
)
3031 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
3032 unsigned long nr_reclaimed
, nr_scanned
;
3033 struct lruvec
*target_lruvec
;
3034 bool reclaimable
= false;
3037 target_lruvec
= mem_cgroup_lruvec(sc
->target_mem_cgroup
, pgdat
);
3041 * Flush the memory cgroup stats, so that we read accurate per-memcg
3042 * lruvec stats for heuristics.
3044 mem_cgroup_flush_stats();
3046 memset(&sc
->nr
, 0, sizeof(sc
->nr
));
3048 nr_reclaimed
= sc
->nr_reclaimed
;
3049 nr_scanned
= sc
->nr_scanned
;
3052 * Determine the scan balance between anon and file LRUs.
3054 spin_lock_irq(&target_lruvec
->lru_lock
);
3055 sc
->anon_cost
= target_lruvec
->anon_cost
;
3056 sc
->file_cost
= target_lruvec
->file_cost
;
3057 spin_unlock_irq(&target_lruvec
->lru_lock
);
3060 * Target desirable inactive:active list ratios for the anon
3061 * and file LRU lists.
3063 if (!sc
->force_deactivate
) {
3064 unsigned long refaults
;
3066 refaults
= lruvec_page_state(target_lruvec
,
3067 WORKINGSET_ACTIVATE_ANON
);
3068 if (refaults
!= target_lruvec
->refaults
[0] ||
3069 inactive_is_low(target_lruvec
, LRU_INACTIVE_ANON
))
3070 sc
->may_deactivate
|= DEACTIVATE_ANON
;
3072 sc
->may_deactivate
&= ~DEACTIVATE_ANON
;
3075 * When refaults are being observed, it means a new
3076 * workingset is being established. Deactivate to get
3077 * rid of any stale active pages quickly.
3079 refaults
= lruvec_page_state(target_lruvec
,
3080 WORKINGSET_ACTIVATE_FILE
);
3081 if (refaults
!= target_lruvec
->refaults
[1] ||
3082 inactive_is_low(target_lruvec
, LRU_INACTIVE_FILE
))
3083 sc
->may_deactivate
|= DEACTIVATE_FILE
;
3085 sc
->may_deactivate
&= ~DEACTIVATE_FILE
;
3087 sc
->may_deactivate
= DEACTIVATE_ANON
| DEACTIVATE_FILE
;
3090 * If we have plenty of inactive file pages that aren't
3091 * thrashing, try to reclaim those first before touching
3094 file
= lruvec_page_state(target_lruvec
, NR_INACTIVE_FILE
);
3095 if (file
>> sc
->priority
&& !(sc
->may_deactivate
& DEACTIVATE_FILE
))
3096 sc
->cache_trim_mode
= 1;
3098 sc
->cache_trim_mode
= 0;
3101 * Prevent the reclaimer from falling into the cache trap: as
3102 * cache pages start out inactive, every cache fault will tip
3103 * the scan balance towards the file LRU. And as the file LRU
3104 * shrinks, so does the window for rotation from references.
3105 * This means we have a runaway feedback loop where a tiny
3106 * thrashing file LRU becomes infinitely more attractive than
3107 * anon pages. Try to detect this based on file LRU size.
3109 if (!cgroup_reclaim(sc
)) {
3110 unsigned long total_high_wmark
= 0;
3111 unsigned long free
, anon
;
3114 free
= sum_zone_node_page_state(pgdat
->node_id
, NR_FREE_PAGES
);
3115 file
= node_page_state(pgdat
, NR_ACTIVE_FILE
) +
3116 node_page_state(pgdat
, NR_INACTIVE_FILE
);
3118 for (z
= 0; z
< MAX_NR_ZONES
; z
++) {
3119 struct zone
*zone
= &pgdat
->node_zones
[z
];
3120 if (!managed_zone(zone
))
3123 total_high_wmark
+= high_wmark_pages(zone
);
3127 * Consider anon: if that's low too, this isn't a
3128 * runaway file reclaim problem, but rather just
3129 * extreme pressure. Reclaim as per usual then.
3131 anon
= node_page_state(pgdat
, NR_INACTIVE_ANON
);
3134 file
+ free
<= total_high_wmark
&&
3135 !(sc
->may_deactivate
& DEACTIVATE_ANON
) &&
3136 anon
>> sc
->priority
;
3139 shrink_node_memcgs(pgdat
, sc
);
3141 if (reclaim_state
) {
3142 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
3143 reclaim_state
->reclaimed_slab
= 0;
3146 /* Record the subtree's reclaim efficiency */
3147 vmpressure(sc
->gfp_mask
, sc
->target_mem_cgroup
, true,
3148 sc
->nr_scanned
- nr_scanned
,
3149 sc
->nr_reclaimed
- nr_reclaimed
);
3151 if (sc
->nr_reclaimed
- nr_reclaimed
)
3154 if (current_is_kswapd()) {
3156 * If reclaim is isolating dirty pages under writeback,
3157 * it implies that the long-lived page allocation rate
3158 * is exceeding the page laundering rate. Either the
3159 * global limits are not being effective at throttling
3160 * processes due to the page distribution throughout
3161 * zones or there is heavy usage of a slow backing
3162 * device. The only option is to throttle from reclaim
3163 * context which is not ideal as there is no guarantee
3164 * the dirtying process is throttled in the same way
3165 * balance_dirty_pages() manages.
3167 * Once a node is flagged PGDAT_WRITEBACK, kswapd will
3168 * count the number of pages under pages flagged for
3169 * immediate reclaim and stall if any are encountered
3170 * in the nr_immediate check below.
3172 if (sc
->nr
.writeback
&& sc
->nr
.writeback
== sc
->nr
.taken
)
3173 set_bit(PGDAT_WRITEBACK
, &pgdat
->flags
);
3175 /* Allow kswapd to start writing pages during reclaim.*/
3176 if (sc
->nr
.unqueued_dirty
== sc
->nr
.file_taken
)
3177 set_bit(PGDAT_DIRTY
, &pgdat
->flags
);
3180 * If kswapd scans pages marked for immediate
3181 * reclaim and under writeback (nr_immediate), it
3182 * implies that pages are cycling through the LRU
3183 * faster than they are written so also forcibly stall.
3185 if (sc
->nr
.immediate
)
3186 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
3190 * Tag a node/memcg as congested if all the dirty pages
3191 * scanned were backed by a congested BDI and
3192 * wait_iff_congested will stall.
3194 * Legacy memcg will stall in page writeback so avoid forcibly
3195 * stalling in wait_iff_congested().
3197 if ((current_is_kswapd() ||
3198 (cgroup_reclaim(sc
) && writeback_throttling_sane(sc
))) &&
3199 sc
->nr
.dirty
&& sc
->nr
.dirty
== sc
->nr
.congested
)
3200 set_bit(LRUVEC_CONGESTED
, &target_lruvec
->flags
);
3203 * Stall direct reclaim for IO completions if underlying BDIs
3204 * and node is congested. Allow kswapd to continue until it
3205 * starts encountering unqueued dirty pages or cycling through
3206 * the LRU too quickly.
3208 if (!current_is_kswapd() && current_may_throttle() &&
3209 !sc
->hibernation_mode
&&
3210 test_bit(LRUVEC_CONGESTED
, &target_lruvec
->flags
))
3211 wait_iff_congested(BLK_RW_ASYNC
, HZ
/10);
3213 if (should_continue_reclaim(pgdat
, sc
->nr_reclaimed
- nr_reclaimed
,
3218 * Kswapd gives up on balancing particular nodes after too
3219 * many failures to reclaim anything from them and goes to
3220 * sleep. On reclaim progress, reset the failure counter. A
3221 * successful direct reclaim run will revive a dormant kswapd.
3224 pgdat
->kswapd_failures
= 0;
3228 * Returns true if compaction should go ahead for a costly-order request, or
3229 * the allocation would already succeed without compaction. Return false if we
3230 * should reclaim first.
3232 static inline bool compaction_ready(struct zone
*zone
, struct scan_control
*sc
)
3234 unsigned long watermark
;
3235 enum compact_result suitable
;
3237 suitable
= compaction_suitable(zone
, sc
->order
, 0, sc
->reclaim_idx
);
3238 if (suitable
== COMPACT_SUCCESS
)
3239 /* Allocation should succeed already. Don't reclaim. */
3241 if (suitable
== COMPACT_SKIPPED
)
3242 /* Compaction cannot yet proceed. Do reclaim. */
3246 * Compaction is already possible, but it takes time to run and there
3247 * are potentially other callers using the pages just freed. So proceed
3248 * with reclaim to make a buffer of free pages available to give
3249 * compaction a reasonable chance of completing and allocating the page.
3250 * Note that we won't actually reclaim the whole buffer in one attempt
3251 * as the target watermark in should_continue_reclaim() is lower. But if
3252 * we are already above the high+gap watermark, don't reclaim at all.
3254 watermark
= high_wmark_pages(zone
) + compact_gap(sc
->order
);
3256 return zone_watermark_ok_safe(zone
, 0, watermark
, sc
->reclaim_idx
);
3260 * This is the direct reclaim path, for page-allocating processes. We only
3261 * try to reclaim pages from zones which will satisfy the caller's allocation
3264 * If a zone is deemed to be full of pinned pages then just give it a light
3265 * scan then give up on it.
3267 static void shrink_zones(struct zonelist
*zonelist
, struct scan_control
*sc
)
3271 unsigned long nr_soft_reclaimed
;
3272 unsigned long nr_soft_scanned
;
3274 pg_data_t
*last_pgdat
= NULL
;
3277 * If the number of buffer_heads in the machine exceeds the maximum
3278 * allowed level, force direct reclaim to scan the highmem zone as
3279 * highmem pages could be pinning lowmem pages storing buffer_heads
3281 orig_mask
= sc
->gfp_mask
;
3282 if (buffer_heads_over_limit
) {
3283 sc
->gfp_mask
|= __GFP_HIGHMEM
;
3284 sc
->reclaim_idx
= gfp_zone(sc
->gfp_mask
);
3287 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
3288 sc
->reclaim_idx
, sc
->nodemask
) {
3290 * Take care memory controller reclaiming has small influence
3293 if (!cgroup_reclaim(sc
)) {
3294 if (!cpuset_zone_allowed(zone
,
3295 GFP_KERNEL
| __GFP_HARDWALL
))
3299 * If we already have plenty of memory free for
3300 * compaction in this zone, don't free any more.
3301 * Even though compaction is invoked for any
3302 * non-zero order, only frequent costly order
3303 * reclamation is disruptive enough to become a
3304 * noticeable problem, like transparent huge
3307 if (IS_ENABLED(CONFIG_COMPACTION
) &&
3308 sc
->order
> PAGE_ALLOC_COSTLY_ORDER
&&
3309 compaction_ready(zone
, sc
)) {
3310 sc
->compaction_ready
= true;
3315 * Shrink each node in the zonelist once. If the
3316 * zonelist is ordered by zone (not the default) then a
3317 * node may be shrunk multiple times but in that case
3318 * the user prefers lower zones being preserved.
3320 if (zone
->zone_pgdat
== last_pgdat
)
3324 * This steals pages from memory cgroups over softlimit
3325 * and returns the number of reclaimed pages and
3326 * scanned pages. This works for global memory pressure
3327 * and balancing, not for a memcg's limit.
3329 nr_soft_scanned
= 0;
3330 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
->zone_pgdat
,
3331 sc
->order
, sc
->gfp_mask
,
3333 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
3334 sc
->nr_scanned
+= nr_soft_scanned
;
3335 /* need some check for avoid more shrink_zone() */
3338 /* See comment about same check for global reclaim above */
3339 if (zone
->zone_pgdat
== last_pgdat
)
3341 last_pgdat
= zone
->zone_pgdat
;
3342 shrink_node(zone
->zone_pgdat
, sc
);
3346 * Restore to original mask to avoid the impact on the caller if we
3347 * promoted it to __GFP_HIGHMEM.
3349 sc
->gfp_mask
= orig_mask
;
3352 static void snapshot_refaults(struct mem_cgroup
*target_memcg
, pg_data_t
*pgdat
)
3354 struct lruvec
*target_lruvec
;
3355 unsigned long refaults
;
3357 target_lruvec
= mem_cgroup_lruvec(target_memcg
, pgdat
);
3358 refaults
= lruvec_page_state(target_lruvec
, WORKINGSET_ACTIVATE_ANON
);
3359 target_lruvec
->refaults
[0] = refaults
;
3360 refaults
= lruvec_page_state(target_lruvec
, WORKINGSET_ACTIVATE_FILE
);
3361 target_lruvec
->refaults
[1] = refaults
;
3365 * This is the main entry point to direct page reclaim.
3367 * If a full scan of the inactive list fails to free enough memory then we
3368 * are "out of memory" and something needs to be killed.
3370 * If the caller is !__GFP_FS then the probability of a failure is reasonably
3371 * high - the zone may be full of dirty or under-writeback pages, which this
3372 * caller can't do much about. We kick the writeback threads and take explicit
3373 * naps in the hope that some of these pages can be written. But if the
3374 * allocating task holds filesystem locks which prevent writeout this might not
3375 * work, and the allocation attempt will fail.
3377 * returns: 0, if no pages reclaimed
3378 * else, the number of pages reclaimed
3380 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
3381 struct scan_control
*sc
)
3383 int initial_priority
= sc
->priority
;
3384 pg_data_t
*last_pgdat
;
3388 delayacct_freepages_start();
3390 if (!cgroup_reclaim(sc
))
3391 __count_zid_vm_events(ALLOCSTALL
, sc
->reclaim_idx
, 1);
3394 vmpressure_prio(sc
->gfp_mask
, sc
->target_mem_cgroup
,
3397 shrink_zones(zonelist
, sc
);
3399 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
3402 if (sc
->compaction_ready
)
3406 * If we're getting trouble reclaiming, start doing
3407 * writepage even in laptop mode.
3409 if (sc
->priority
< DEF_PRIORITY
- 2)
3410 sc
->may_writepage
= 1;
3411 } while (--sc
->priority
>= 0);
3414 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
, sc
->reclaim_idx
,
3416 if (zone
->zone_pgdat
== last_pgdat
)
3418 last_pgdat
= zone
->zone_pgdat
;
3420 snapshot_refaults(sc
->target_mem_cgroup
, zone
->zone_pgdat
);
3422 if (cgroup_reclaim(sc
)) {
3423 struct lruvec
*lruvec
;
3425 lruvec
= mem_cgroup_lruvec(sc
->target_mem_cgroup
,
3427 clear_bit(LRUVEC_CONGESTED
, &lruvec
->flags
);
3431 delayacct_freepages_end();
3433 if (sc
->nr_reclaimed
)
3434 return sc
->nr_reclaimed
;
3436 /* Aborted reclaim to try compaction? don't OOM, then */
3437 if (sc
->compaction_ready
)
3441 * We make inactive:active ratio decisions based on the node's
3442 * composition of memory, but a restrictive reclaim_idx or a
3443 * memory.low cgroup setting can exempt large amounts of
3444 * memory from reclaim. Neither of which are very common, so
3445 * instead of doing costly eligibility calculations of the
3446 * entire cgroup subtree up front, we assume the estimates are
3447 * good, and retry with forcible deactivation if that fails.
3449 if (sc
->skipped_deactivate
) {
3450 sc
->priority
= initial_priority
;
3451 sc
->force_deactivate
= 1;
3452 sc
->skipped_deactivate
= 0;
3456 /* Untapped cgroup reserves? Don't OOM, retry. */
3457 if (sc
->memcg_low_skipped
) {
3458 sc
->priority
= initial_priority
;
3459 sc
->force_deactivate
= 0;
3460 sc
->memcg_low_reclaim
= 1;
3461 sc
->memcg_low_skipped
= 0;
3468 static bool allow_direct_reclaim(pg_data_t
*pgdat
)
3471 unsigned long pfmemalloc_reserve
= 0;
3472 unsigned long free_pages
= 0;
3476 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
3479 for (i
= 0; i
<= ZONE_NORMAL
; i
++) {
3480 zone
= &pgdat
->node_zones
[i
];
3481 if (!managed_zone(zone
))
3484 if (!zone_reclaimable_pages(zone
))
3487 pfmemalloc_reserve
+= min_wmark_pages(zone
);
3488 free_pages
+= zone_page_state(zone
, NR_FREE_PAGES
);
3491 /* If there are no reserves (unexpected config) then do not throttle */
3492 if (!pfmemalloc_reserve
)
3495 wmark_ok
= free_pages
> pfmemalloc_reserve
/ 2;
3497 /* kswapd must be awake if processes are being throttled */
3498 if (!wmark_ok
&& waitqueue_active(&pgdat
->kswapd_wait
)) {
3499 if (READ_ONCE(pgdat
->kswapd_highest_zoneidx
) > ZONE_NORMAL
)
3500 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, ZONE_NORMAL
);
3502 wake_up_interruptible(&pgdat
->kswapd_wait
);
3509 * Throttle direct reclaimers if backing storage is backed by the network
3510 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
3511 * depleted. kswapd will continue to make progress and wake the processes
3512 * when the low watermark is reached.
3514 * Returns true if a fatal signal was delivered during throttling. If this
3515 * happens, the page allocator should not consider triggering the OOM killer.
3517 static bool throttle_direct_reclaim(gfp_t gfp_mask
, struct zonelist
*zonelist
,
3518 nodemask_t
*nodemask
)
3522 pg_data_t
*pgdat
= NULL
;
3525 * Kernel threads should not be throttled as they may be indirectly
3526 * responsible for cleaning pages necessary for reclaim to make forward
3527 * progress. kjournald for example may enter direct reclaim while
3528 * committing a transaction where throttling it could forcing other
3529 * processes to block on log_wait_commit().
3531 if (current
->flags
& PF_KTHREAD
)
3535 * If a fatal signal is pending, this process should not throttle.
3536 * It should return quickly so it can exit and free its memory
3538 if (fatal_signal_pending(current
))
3542 * Check if the pfmemalloc reserves are ok by finding the first node
3543 * with a usable ZONE_NORMAL or lower zone. The expectation is that
3544 * GFP_KERNEL will be required for allocating network buffers when
3545 * swapping over the network so ZONE_HIGHMEM is unusable.
3547 * Throttling is based on the first usable node and throttled processes
3548 * wait on a queue until kswapd makes progress and wakes them. There
3549 * is an affinity then between processes waking up and where reclaim
3550 * progress has been made assuming the process wakes on the same node.
3551 * More importantly, processes running on remote nodes will not compete
3552 * for remote pfmemalloc reserves and processes on different nodes
3553 * should make reasonable progress.
3555 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
3556 gfp_zone(gfp_mask
), nodemask
) {
3557 if (zone_idx(zone
) > ZONE_NORMAL
)
3560 /* Throttle based on the first usable node */
3561 pgdat
= zone
->zone_pgdat
;
3562 if (allow_direct_reclaim(pgdat
))
3567 /* If no zone was usable by the allocation flags then do not throttle */
3571 /* Account for the throttling */
3572 count_vm_event(PGSCAN_DIRECT_THROTTLE
);
3575 * If the caller cannot enter the filesystem, it's possible that it
3576 * is due to the caller holding an FS lock or performing a journal
3577 * transaction in the case of a filesystem like ext[3|4]. In this case,
3578 * it is not safe to block on pfmemalloc_wait as kswapd could be
3579 * blocked waiting on the same lock. Instead, throttle for up to a
3580 * second before continuing.
3582 if (!(gfp_mask
& __GFP_FS
))
3583 wait_event_interruptible_timeout(pgdat
->pfmemalloc_wait
,
3584 allow_direct_reclaim(pgdat
), HZ
);
3586 /* Throttle until kswapd wakes the process */
3587 wait_event_killable(zone
->zone_pgdat
->pfmemalloc_wait
,
3588 allow_direct_reclaim(pgdat
));
3590 if (fatal_signal_pending(current
))
3597 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
3598 gfp_t gfp_mask
, nodemask_t
*nodemask
)
3600 unsigned long nr_reclaimed
;
3601 struct scan_control sc
= {
3602 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
3603 .gfp_mask
= current_gfp_context(gfp_mask
),
3604 .reclaim_idx
= gfp_zone(gfp_mask
),
3606 .nodemask
= nodemask
,
3607 .priority
= DEF_PRIORITY
,
3608 .may_writepage
= !laptop_mode
,
3614 * scan_control uses s8 fields for order, priority, and reclaim_idx.
3615 * Confirm they are large enough for max values.
3617 BUILD_BUG_ON(MAX_ORDER
> S8_MAX
);
3618 BUILD_BUG_ON(DEF_PRIORITY
> S8_MAX
);
3619 BUILD_BUG_ON(MAX_NR_ZONES
> S8_MAX
);
3622 * Do not enter reclaim if fatal signal was delivered while throttled.
3623 * 1 is returned so that the page allocator does not OOM kill at this
3626 if (throttle_direct_reclaim(sc
.gfp_mask
, zonelist
, nodemask
))
3629 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3630 trace_mm_vmscan_direct_reclaim_begin(order
, sc
.gfp_mask
);
3632 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3634 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
3635 set_task_reclaim_state(current
, NULL
);
3637 return nr_reclaimed
;
3642 /* Only used by soft limit reclaim. Do not reuse for anything else. */
3643 unsigned long mem_cgroup_shrink_node(struct mem_cgroup
*memcg
,
3644 gfp_t gfp_mask
, bool noswap
,
3646 unsigned long *nr_scanned
)
3648 struct lruvec
*lruvec
= mem_cgroup_lruvec(memcg
, pgdat
);
3649 struct scan_control sc
= {
3650 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
3651 .target_mem_cgroup
= memcg
,
3652 .may_writepage
= !laptop_mode
,
3654 .reclaim_idx
= MAX_NR_ZONES
- 1,
3655 .may_swap
= !noswap
,
3658 WARN_ON_ONCE(!current
->reclaim_state
);
3660 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
3661 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
3663 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc
.order
,
3667 * NOTE: Although we can get the priority field, using it
3668 * here is not a good idea, since it limits the pages we can scan.
3669 * if we don't reclaim here, the shrink_node from balance_pgdat
3670 * will pick up pages from other mem cgroup's as well. We hack
3671 * the priority and make it zero.
3673 shrink_lruvec(lruvec
, &sc
);
3675 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
3677 *nr_scanned
= sc
.nr_scanned
;
3679 return sc
.nr_reclaimed
;
3682 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*memcg
,
3683 unsigned long nr_pages
,
3687 unsigned long nr_reclaimed
;
3688 unsigned int noreclaim_flag
;
3689 struct scan_control sc
= {
3690 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
3691 .gfp_mask
= (current_gfp_context(gfp_mask
) & GFP_RECLAIM_MASK
) |
3692 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
3693 .reclaim_idx
= MAX_NR_ZONES
- 1,
3694 .target_mem_cgroup
= memcg
,
3695 .priority
= DEF_PRIORITY
,
3696 .may_writepage
= !laptop_mode
,
3698 .may_swap
= may_swap
,
3701 * Traverse the ZONELIST_FALLBACK zonelist of the current node to put
3702 * equal pressure on all the nodes. This is based on the assumption that
3703 * the reclaim does not bail out early.
3705 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
3707 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3708 trace_mm_vmscan_memcg_reclaim_begin(0, sc
.gfp_mask
);
3709 noreclaim_flag
= memalloc_noreclaim_save();
3711 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3713 memalloc_noreclaim_restore(noreclaim_flag
);
3714 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
3715 set_task_reclaim_state(current
, NULL
);
3717 return nr_reclaimed
;
3721 static void age_active_anon(struct pglist_data
*pgdat
,
3722 struct scan_control
*sc
)
3724 struct mem_cgroup
*memcg
;
3725 struct lruvec
*lruvec
;
3727 if (!can_age_anon_pages(pgdat
, sc
))
3730 lruvec
= mem_cgroup_lruvec(NULL
, pgdat
);
3731 if (!inactive_is_low(lruvec
, LRU_INACTIVE_ANON
))
3734 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
3736 lruvec
= mem_cgroup_lruvec(memcg
, pgdat
);
3737 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
3738 sc
, LRU_ACTIVE_ANON
);
3739 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
3743 static bool pgdat_watermark_boosted(pg_data_t
*pgdat
, int highest_zoneidx
)
3749 * Check for watermark boosts top-down as the higher zones
3750 * are more likely to be boosted. Both watermarks and boosts
3751 * should not be checked at the same time as reclaim would
3752 * start prematurely when there is no boosting and a lower
3755 for (i
= highest_zoneidx
; i
>= 0; i
--) {
3756 zone
= pgdat
->node_zones
+ i
;
3757 if (!managed_zone(zone
))
3760 if (zone
->watermark_boost
)
3768 * Returns true if there is an eligible zone balanced for the request order
3769 * and highest_zoneidx
3771 static bool pgdat_balanced(pg_data_t
*pgdat
, int order
, int highest_zoneidx
)
3774 unsigned long mark
= -1;
3778 * Check watermarks bottom-up as lower zones are more likely to
3781 for (i
= 0; i
<= highest_zoneidx
; i
++) {
3782 zone
= pgdat
->node_zones
+ i
;
3784 if (!managed_zone(zone
))
3787 mark
= high_wmark_pages(zone
);
3788 if (zone_watermark_ok_safe(zone
, order
, mark
, highest_zoneidx
))
3793 * If a node has no populated zone within highest_zoneidx, it does not
3794 * need balancing by definition. This can happen if a zone-restricted
3795 * allocation tries to wake a remote kswapd.
3803 /* Clear pgdat state for congested, dirty or under writeback. */
3804 static void clear_pgdat_congested(pg_data_t
*pgdat
)
3806 struct lruvec
*lruvec
= mem_cgroup_lruvec(NULL
, pgdat
);
3808 clear_bit(LRUVEC_CONGESTED
, &lruvec
->flags
);
3809 clear_bit(PGDAT_DIRTY
, &pgdat
->flags
);
3810 clear_bit(PGDAT_WRITEBACK
, &pgdat
->flags
);
3814 * Prepare kswapd for sleeping. This verifies that there are no processes
3815 * waiting in throttle_direct_reclaim() and that watermarks have been met.
3817 * Returns true if kswapd is ready to sleep
3819 static bool prepare_kswapd_sleep(pg_data_t
*pgdat
, int order
,
3820 int highest_zoneidx
)
3823 * The throttled processes are normally woken up in balance_pgdat() as
3824 * soon as allow_direct_reclaim() is true. But there is a potential
3825 * race between when kswapd checks the watermarks and a process gets
3826 * throttled. There is also a potential race if processes get
3827 * throttled, kswapd wakes, a large process exits thereby balancing the
3828 * zones, which causes kswapd to exit balance_pgdat() before reaching
3829 * the wake up checks. If kswapd is going to sleep, no process should
3830 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
3831 * the wake up is premature, processes will wake kswapd and get
3832 * throttled again. The difference from wake ups in balance_pgdat() is
3833 * that here we are under prepare_to_wait().
3835 if (waitqueue_active(&pgdat
->pfmemalloc_wait
))
3836 wake_up_all(&pgdat
->pfmemalloc_wait
);
3838 /* Hopeless node, leave it to direct reclaim */
3839 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
3842 if (pgdat_balanced(pgdat
, order
, highest_zoneidx
)) {
3843 clear_pgdat_congested(pgdat
);
3851 * kswapd shrinks a node of pages that are at or below the highest usable
3852 * zone that is currently unbalanced.
3854 * Returns true if kswapd scanned at least the requested number of pages to
3855 * reclaim or if the lack of progress was due to pages under writeback.
3856 * This is used to determine if the scanning priority needs to be raised.
3858 static bool kswapd_shrink_node(pg_data_t
*pgdat
,
3859 struct scan_control
*sc
)
3864 /* Reclaim a number of pages proportional to the number of zones */
3865 sc
->nr_to_reclaim
= 0;
3866 for (z
= 0; z
<= sc
->reclaim_idx
; z
++) {
3867 zone
= pgdat
->node_zones
+ z
;
3868 if (!managed_zone(zone
))
3871 sc
->nr_to_reclaim
+= max(high_wmark_pages(zone
), SWAP_CLUSTER_MAX
);
3875 * Historically care was taken to put equal pressure on all zones but
3876 * now pressure is applied based on node LRU order.
3878 shrink_node(pgdat
, sc
);
3881 * Fragmentation may mean that the system cannot be rebalanced for
3882 * high-order allocations. If twice the allocation size has been
3883 * reclaimed then recheck watermarks only at order-0 to prevent
3884 * excessive reclaim. Assume that a process requested a high-order
3885 * can direct reclaim/compact.
3887 if (sc
->order
&& sc
->nr_reclaimed
>= compact_gap(sc
->order
))
3890 return sc
->nr_scanned
>= sc
->nr_to_reclaim
;
3893 /* Page allocator PCP high watermark is lowered if reclaim is active. */
3895 update_reclaim_active(pg_data_t
*pgdat
, int highest_zoneidx
, bool active
)
3900 for (i
= 0; i
<= highest_zoneidx
; i
++) {
3901 zone
= pgdat
->node_zones
+ i
;
3903 if (!managed_zone(zone
))
3907 set_bit(ZONE_RECLAIM_ACTIVE
, &zone
->flags
);
3909 clear_bit(ZONE_RECLAIM_ACTIVE
, &zone
->flags
);
3914 set_reclaim_active(pg_data_t
*pgdat
, int highest_zoneidx
)
3916 update_reclaim_active(pgdat
, highest_zoneidx
, true);
3920 clear_reclaim_active(pg_data_t
*pgdat
, int highest_zoneidx
)
3922 update_reclaim_active(pgdat
, highest_zoneidx
, false);
3926 * For kswapd, balance_pgdat() will reclaim pages across a node from zones
3927 * that are eligible for use by the caller until at least one zone is
3930 * Returns the order kswapd finished reclaiming at.
3932 * kswapd scans the zones in the highmem->normal->dma direction. It skips
3933 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
3934 * found to have free_pages <= high_wmark_pages(zone), any page in that zone
3935 * or lower is eligible for reclaim until at least one usable zone is
3938 static int balance_pgdat(pg_data_t
*pgdat
, int order
, int highest_zoneidx
)
3941 unsigned long nr_soft_reclaimed
;
3942 unsigned long nr_soft_scanned
;
3943 unsigned long pflags
;
3944 unsigned long nr_boost_reclaim
;
3945 unsigned long zone_boosts
[MAX_NR_ZONES
] = { 0, };
3948 struct scan_control sc
= {
3949 .gfp_mask
= GFP_KERNEL
,
3954 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3955 psi_memstall_enter(&pflags
);
3956 __fs_reclaim_acquire(_THIS_IP_
);
3958 count_vm_event(PAGEOUTRUN
);
3961 * Account for the reclaim boost. Note that the zone boost is left in
3962 * place so that parallel allocations that are near the watermark will
3963 * stall or direct reclaim until kswapd is finished.
3965 nr_boost_reclaim
= 0;
3966 for (i
= 0; i
<= highest_zoneidx
; i
++) {
3967 zone
= pgdat
->node_zones
+ i
;
3968 if (!managed_zone(zone
))
3971 nr_boost_reclaim
+= zone
->watermark_boost
;
3972 zone_boosts
[i
] = zone
->watermark_boost
;
3974 boosted
= nr_boost_reclaim
;
3977 set_reclaim_active(pgdat
, highest_zoneidx
);
3978 sc
.priority
= DEF_PRIORITY
;
3980 unsigned long nr_reclaimed
= sc
.nr_reclaimed
;
3981 bool raise_priority
= true;
3985 sc
.reclaim_idx
= highest_zoneidx
;
3988 * If the number of buffer_heads exceeds the maximum allowed
3989 * then consider reclaiming from all zones. This has a dual
3990 * purpose -- on 64-bit systems it is expected that
3991 * buffer_heads are stripped during active rotation. On 32-bit
3992 * systems, highmem pages can pin lowmem memory and shrinking
3993 * buffers can relieve lowmem pressure. Reclaim may still not
3994 * go ahead if all eligible zones for the original allocation
3995 * request are balanced to avoid excessive reclaim from kswapd.
3997 if (buffer_heads_over_limit
) {
3998 for (i
= MAX_NR_ZONES
- 1; i
>= 0; i
--) {
3999 zone
= pgdat
->node_zones
+ i
;
4000 if (!managed_zone(zone
))
4009 * If the pgdat is imbalanced then ignore boosting and preserve
4010 * the watermarks for a later time and restart. Note that the
4011 * zone watermarks will be still reset at the end of balancing
4012 * on the grounds that the normal reclaim should be enough to
4013 * re-evaluate if boosting is required when kswapd next wakes.
4015 balanced
= pgdat_balanced(pgdat
, sc
.order
, highest_zoneidx
);
4016 if (!balanced
&& nr_boost_reclaim
) {
4017 nr_boost_reclaim
= 0;
4022 * If boosting is not active then only reclaim if there are no
4023 * eligible zones. Note that sc.reclaim_idx is not used as
4024 * buffer_heads_over_limit may have adjusted it.
4026 if (!nr_boost_reclaim
&& balanced
)
4029 /* Limit the priority of boosting to avoid reclaim writeback */
4030 if (nr_boost_reclaim
&& sc
.priority
== DEF_PRIORITY
- 2)
4031 raise_priority
= false;
4034 * Do not writeback or swap pages for boosted reclaim. The
4035 * intent is to relieve pressure not issue sub-optimal IO
4036 * from reclaim context. If no pages are reclaimed, the
4037 * reclaim will be aborted.
4039 sc
.may_writepage
= !laptop_mode
&& !nr_boost_reclaim
;
4040 sc
.may_swap
= !nr_boost_reclaim
;
4043 * Do some background aging of the anon list, to give
4044 * pages a chance to be referenced before reclaiming. All
4045 * pages are rotated regardless of classzone as this is
4046 * about consistent aging.
4048 age_active_anon(pgdat
, &sc
);
4051 * If we're getting trouble reclaiming, start doing writepage
4052 * even in laptop mode.
4054 if (sc
.priority
< DEF_PRIORITY
- 2)
4055 sc
.may_writepage
= 1;
4057 /* Call soft limit reclaim before calling shrink_node. */
4059 nr_soft_scanned
= 0;
4060 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(pgdat
, sc
.order
,
4061 sc
.gfp_mask
, &nr_soft_scanned
);
4062 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
4065 * There should be no need to raise the scanning priority if
4066 * enough pages are already being scanned that that high
4067 * watermark would be met at 100% efficiency.
4069 if (kswapd_shrink_node(pgdat
, &sc
))
4070 raise_priority
= false;
4073 * If the low watermark is met there is no need for processes
4074 * to be throttled on pfmemalloc_wait as they should not be
4075 * able to safely make forward progress. Wake them
4077 if (waitqueue_active(&pgdat
->pfmemalloc_wait
) &&
4078 allow_direct_reclaim(pgdat
))
4079 wake_up_all(&pgdat
->pfmemalloc_wait
);
4081 /* Check if kswapd should be suspending */
4082 __fs_reclaim_release(_THIS_IP_
);
4083 ret
= try_to_freeze();
4084 __fs_reclaim_acquire(_THIS_IP_
);
4085 if (ret
|| kthread_should_stop())
4089 * Raise priority if scanning rate is too low or there was no
4090 * progress in reclaiming pages
4092 nr_reclaimed
= sc
.nr_reclaimed
- nr_reclaimed
;
4093 nr_boost_reclaim
-= min(nr_boost_reclaim
, nr_reclaimed
);
4096 * If reclaim made no progress for a boost, stop reclaim as
4097 * IO cannot be queued and it could be an infinite loop in
4098 * extreme circumstances.
4100 if (nr_boost_reclaim
&& !nr_reclaimed
)
4103 if (raise_priority
|| !nr_reclaimed
)
4105 } while (sc
.priority
>= 1);
4107 if (!sc
.nr_reclaimed
)
4108 pgdat
->kswapd_failures
++;
4111 clear_reclaim_active(pgdat
, highest_zoneidx
);
4113 /* If reclaim was boosted, account for the reclaim done in this pass */
4115 unsigned long flags
;
4117 for (i
= 0; i
<= highest_zoneidx
; i
++) {
4118 if (!zone_boosts
[i
])
4121 /* Increments are under the zone lock */
4122 zone
= pgdat
->node_zones
+ i
;
4123 spin_lock_irqsave(&zone
->lock
, flags
);
4124 zone
->watermark_boost
-= min(zone
->watermark_boost
, zone_boosts
[i
]);
4125 spin_unlock_irqrestore(&zone
->lock
, flags
);
4129 * As there is now likely space, wakeup kcompact to defragment
4132 wakeup_kcompactd(pgdat
, pageblock_order
, highest_zoneidx
);
4135 snapshot_refaults(NULL
, pgdat
);
4136 __fs_reclaim_release(_THIS_IP_
);
4137 psi_memstall_leave(&pflags
);
4138 set_task_reclaim_state(current
, NULL
);
4141 * Return the order kswapd stopped reclaiming at as
4142 * prepare_kswapd_sleep() takes it into account. If another caller
4143 * entered the allocator slow path while kswapd was awake, order will
4144 * remain at the higher level.
4150 * The pgdat->kswapd_highest_zoneidx is used to pass the highest zone index to
4151 * be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is
4152 * not a valid index then either kswapd runs for first time or kswapd couldn't
4153 * sleep after previous reclaim attempt (node is still unbalanced). In that
4154 * case return the zone index of the previous kswapd reclaim cycle.
4156 static enum zone_type
kswapd_highest_zoneidx(pg_data_t
*pgdat
,
4157 enum zone_type prev_highest_zoneidx
)
4159 enum zone_type curr_idx
= READ_ONCE(pgdat
->kswapd_highest_zoneidx
);
4161 return curr_idx
== MAX_NR_ZONES
? prev_highest_zoneidx
: curr_idx
;
4164 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int alloc_order
, int reclaim_order
,
4165 unsigned int highest_zoneidx
)
4170 if (freezing(current
) || kthread_should_stop())
4173 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
4176 * Try to sleep for a short interval. Note that kcompactd will only be
4177 * woken if it is possible to sleep for a short interval. This is
4178 * deliberate on the assumption that if reclaim cannot keep an
4179 * eligible zone balanced that it's also unlikely that compaction will
4182 if (prepare_kswapd_sleep(pgdat
, reclaim_order
, highest_zoneidx
)) {
4184 * Compaction records what page blocks it recently failed to
4185 * isolate pages from and skips them in the future scanning.
4186 * When kswapd is going to sleep, it is reasonable to assume
4187 * that pages and compaction may succeed so reset the cache.
4189 reset_isolation_suitable(pgdat
);
4192 * We have freed the memory, now we should compact it to make
4193 * allocation of the requested order possible.
4195 wakeup_kcompactd(pgdat
, alloc_order
, highest_zoneidx
);
4197 remaining
= schedule_timeout(HZ
/10);
4200 * If woken prematurely then reset kswapd_highest_zoneidx and
4201 * order. The values will either be from a wakeup request or
4202 * the previous request that slept prematurely.
4205 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
,
4206 kswapd_highest_zoneidx(pgdat
,
4209 if (READ_ONCE(pgdat
->kswapd_order
) < reclaim_order
)
4210 WRITE_ONCE(pgdat
->kswapd_order
, reclaim_order
);
4213 finish_wait(&pgdat
->kswapd_wait
, &wait
);
4214 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
4218 * After a short sleep, check if it was a premature sleep. If not, then
4219 * go fully to sleep until explicitly woken up.
4222 prepare_kswapd_sleep(pgdat
, reclaim_order
, highest_zoneidx
)) {
4223 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
4226 * vmstat counters are not perfectly accurate and the estimated
4227 * value for counters such as NR_FREE_PAGES can deviate from the
4228 * true value by nr_online_cpus * threshold. To avoid the zone
4229 * watermarks being breached while under pressure, we reduce the
4230 * per-cpu vmstat threshold while kswapd is awake and restore
4231 * them before going back to sleep.
4233 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
4235 if (!kthread_should_stop())
4238 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
4241 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
4243 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
4245 finish_wait(&pgdat
->kswapd_wait
, &wait
);
4249 * The background pageout daemon, started as a kernel thread
4250 * from the init process.
4252 * This basically trickles out pages so that we have _some_
4253 * free memory available even if there is no other activity
4254 * that frees anything up. This is needed for things like routing
4255 * etc, where we otherwise might have all activity going on in
4256 * asynchronous contexts that cannot page things out.
4258 * If there are applications that are active memory-allocators
4259 * (most normal use), this basically shouldn't matter.
4261 static int kswapd(void *p
)
4263 unsigned int alloc_order
, reclaim_order
;
4264 unsigned int highest_zoneidx
= MAX_NR_ZONES
- 1;
4265 pg_data_t
*pgdat
= (pg_data_t
*)p
;
4266 struct task_struct
*tsk
= current
;
4267 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
4269 if (!cpumask_empty(cpumask
))
4270 set_cpus_allowed_ptr(tsk
, cpumask
);
4273 * Tell the memory management that we're a "memory allocator",
4274 * and that if we need more memory we should get access to it
4275 * regardless (see "__alloc_pages()"). "kswapd" should
4276 * never get caught in the normal page freeing logic.
4278 * (Kswapd normally doesn't need memory anyway, but sometimes
4279 * you need a small amount of memory in order to be able to
4280 * page out something else, and this flag essentially protects
4281 * us from recursively trying to free more memory as we're
4282 * trying to free the first piece of memory in the first place).
4284 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
4287 WRITE_ONCE(pgdat
->kswapd_order
, 0);
4288 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, MAX_NR_ZONES
);
4292 alloc_order
= reclaim_order
= READ_ONCE(pgdat
->kswapd_order
);
4293 highest_zoneidx
= kswapd_highest_zoneidx(pgdat
,
4297 kswapd_try_to_sleep(pgdat
, alloc_order
, reclaim_order
,
4300 /* Read the new order and highest_zoneidx */
4301 alloc_order
= READ_ONCE(pgdat
->kswapd_order
);
4302 highest_zoneidx
= kswapd_highest_zoneidx(pgdat
,
4304 WRITE_ONCE(pgdat
->kswapd_order
, 0);
4305 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, MAX_NR_ZONES
);
4307 ret
= try_to_freeze();
4308 if (kthread_should_stop())
4312 * We can speed up thawing tasks if we don't call balance_pgdat
4313 * after returning from the refrigerator
4319 * Reclaim begins at the requested order but if a high-order
4320 * reclaim fails then kswapd falls back to reclaiming for
4321 * order-0. If that happens, kswapd will consider sleeping
4322 * for the order it finished reclaiming at (reclaim_order)
4323 * but kcompactd is woken to compact for the original
4324 * request (alloc_order).
4326 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, highest_zoneidx
,
4328 reclaim_order
= balance_pgdat(pgdat
, alloc_order
,
4330 if (reclaim_order
< alloc_order
)
4331 goto kswapd_try_sleep
;
4334 tsk
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
);
4340 * A zone is low on free memory or too fragmented for high-order memory. If
4341 * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
4342 * pgdat. It will wake up kcompactd after reclaiming memory. If kswapd reclaim
4343 * has failed or is not needed, still wake up kcompactd if only compaction is
4346 void wakeup_kswapd(struct zone
*zone
, gfp_t gfp_flags
, int order
,
4347 enum zone_type highest_zoneidx
)
4350 enum zone_type curr_idx
;
4352 if (!managed_zone(zone
))
4355 if (!cpuset_zone_allowed(zone
, gfp_flags
))
4358 pgdat
= zone
->zone_pgdat
;
4359 curr_idx
= READ_ONCE(pgdat
->kswapd_highest_zoneidx
);
4361 if (curr_idx
== MAX_NR_ZONES
|| curr_idx
< highest_zoneidx
)
4362 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, highest_zoneidx
);
4364 if (READ_ONCE(pgdat
->kswapd_order
) < order
)
4365 WRITE_ONCE(pgdat
->kswapd_order
, order
);
4367 if (!waitqueue_active(&pgdat
->kswapd_wait
))
4370 /* Hopeless node, leave it to direct reclaim if possible */
4371 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
||
4372 (pgdat_balanced(pgdat
, order
, highest_zoneidx
) &&
4373 !pgdat_watermark_boosted(pgdat
, highest_zoneidx
))) {
4375 * There may be plenty of free memory available, but it's too
4376 * fragmented for high-order allocations. Wake up kcompactd
4377 * and rely on compaction_suitable() to determine if it's
4378 * needed. If it fails, it will defer subsequent attempts to
4379 * ratelimit its work.
4381 if (!(gfp_flags
& __GFP_DIRECT_RECLAIM
))
4382 wakeup_kcompactd(pgdat
, order
, highest_zoneidx
);
4386 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, highest_zoneidx
, order
,
4388 wake_up_interruptible(&pgdat
->kswapd_wait
);
4391 #ifdef CONFIG_HIBERNATION
4393 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
4396 * Rather than trying to age LRUs the aim is to preserve the overall
4397 * LRU order by reclaiming preferentially
4398 * inactive > active > active referenced > active mapped
4400 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
4402 struct scan_control sc
= {
4403 .nr_to_reclaim
= nr_to_reclaim
,
4404 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
4405 .reclaim_idx
= MAX_NR_ZONES
- 1,
4406 .priority
= DEF_PRIORITY
,
4410 .hibernation_mode
= 1,
4412 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
4413 unsigned long nr_reclaimed
;
4414 unsigned int noreclaim_flag
;
4416 fs_reclaim_acquire(sc
.gfp_mask
);
4417 noreclaim_flag
= memalloc_noreclaim_save();
4418 set_task_reclaim_state(current
, &sc
.reclaim_state
);
4420 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
4422 set_task_reclaim_state(current
, NULL
);
4423 memalloc_noreclaim_restore(noreclaim_flag
);
4424 fs_reclaim_release(sc
.gfp_mask
);
4426 return nr_reclaimed
;
4428 #endif /* CONFIG_HIBERNATION */
4431 * This kswapd start function will be called by init and node-hot-add.
4432 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
4434 void kswapd_run(int nid
)
4436 pg_data_t
*pgdat
= NODE_DATA(nid
);
4441 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
4442 if (IS_ERR(pgdat
->kswapd
)) {
4443 /* failure at boot is fatal */
4444 BUG_ON(system_state
< SYSTEM_RUNNING
);
4445 pr_err("Failed to start kswapd on node %d\n", nid
);
4446 pgdat
->kswapd
= NULL
;
4451 * Called by memory hotplug when all memory in a node is offlined. Caller must
4452 * hold mem_hotplug_begin/end().
4454 void kswapd_stop(int nid
)
4456 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
4459 kthread_stop(kswapd
);
4460 NODE_DATA(nid
)->kswapd
= NULL
;
4464 static int __init
kswapd_init(void)
4469 for_each_node_state(nid
, N_MEMORY
)
4474 module_init(kswapd_init
)
4480 * If non-zero call node_reclaim when the number of free pages falls below
4483 int node_reclaim_mode __read_mostly
;
4486 * Priority for NODE_RECLAIM. This determines the fraction of pages
4487 * of a node considered for each zone_reclaim. 4 scans 1/16th of
4490 #define NODE_RECLAIM_PRIORITY 4
4493 * Percentage of pages in a zone that must be unmapped for node_reclaim to
4496 int sysctl_min_unmapped_ratio
= 1;
4499 * If the number of slab pages in a zone grows beyond this percentage then
4500 * slab reclaim needs to occur.
4502 int sysctl_min_slab_ratio
= 5;
4504 static inline unsigned long node_unmapped_file_pages(struct pglist_data
*pgdat
)
4506 unsigned long file_mapped
= node_page_state(pgdat
, NR_FILE_MAPPED
);
4507 unsigned long file_lru
= node_page_state(pgdat
, NR_INACTIVE_FILE
) +
4508 node_page_state(pgdat
, NR_ACTIVE_FILE
);
4511 * It's possible for there to be more file mapped pages than
4512 * accounted for by the pages on the file LRU lists because
4513 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
4515 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
4518 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
4519 static unsigned long node_pagecache_reclaimable(struct pglist_data
*pgdat
)
4521 unsigned long nr_pagecache_reclaimable
;
4522 unsigned long delta
= 0;
4525 * If RECLAIM_UNMAP is set, then all file pages are considered
4526 * potentially reclaimable. Otherwise, we have to worry about
4527 * pages like swapcache and node_unmapped_file_pages() provides
4530 if (node_reclaim_mode
& RECLAIM_UNMAP
)
4531 nr_pagecache_reclaimable
= node_page_state(pgdat
, NR_FILE_PAGES
);
4533 nr_pagecache_reclaimable
= node_unmapped_file_pages(pgdat
);
4535 /* If we can't clean pages, remove dirty pages from consideration */
4536 if (!(node_reclaim_mode
& RECLAIM_WRITE
))
4537 delta
+= node_page_state(pgdat
, NR_FILE_DIRTY
);
4539 /* Watch for any possible underflows due to delta */
4540 if (unlikely(delta
> nr_pagecache_reclaimable
))
4541 delta
= nr_pagecache_reclaimable
;
4543 return nr_pagecache_reclaimable
- delta
;
4547 * Try to free up some pages from this node through reclaim.
4549 static int __node_reclaim(struct pglist_data
*pgdat
, gfp_t gfp_mask
, unsigned int order
)
4551 /* Minimum pages needed in order to stay on node */
4552 const unsigned long nr_pages
= 1 << order
;
4553 struct task_struct
*p
= current
;
4554 unsigned int noreclaim_flag
;
4555 struct scan_control sc
= {
4556 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
4557 .gfp_mask
= current_gfp_context(gfp_mask
),
4559 .priority
= NODE_RECLAIM_PRIORITY
,
4560 .may_writepage
= !!(node_reclaim_mode
& RECLAIM_WRITE
),
4561 .may_unmap
= !!(node_reclaim_mode
& RECLAIM_UNMAP
),
4563 .reclaim_idx
= gfp_zone(gfp_mask
),
4565 unsigned long pflags
;
4567 trace_mm_vmscan_node_reclaim_begin(pgdat
->node_id
, order
,
4571 psi_memstall_enter(&pflags
);
4572 fs_reclaim_acquire(sc
.gfp_mask
);
4574 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
4575 * and we also need to be able to write out pages for RECLAIM_WRITE
4576 * and RECLAIM_UNMAP.
4578 noreclaim_flag
= memalloc_noreclaim_save();
4579 p
->flags
|= PF_SWAPWRITE
;
4580 set_task_reclaim_state(p
, &sc
.reclaim_state
);
4582 if (node_pagecache_reclaimable(pgdat
) > pgdat
->min_unmapped_pages
) {
4584 * Free memory by calling shrink node with increasing
4585 * priorities until we have enough memory freed.
4588 shrink_node(pgdat
, &sc
);
4589 } while (sc
.nr_reclaimed
< nr_pages
&& --sc
.priority
>= 0);
4592 set_task_reclaim_state(p
, NULL
);
4593 current
->flags
&= ~PF_SWAPWRITE
;
4594 memalloc_noreclaim_restore(noreclaim_flag
);
4595 fs_reclaim_release(sc
.gfp_mask
);
4596 psi_memstall_leave(&pflags
);
4598 trace_mm_vmscan_node_reclaim_end(sc
.nr_reclaimed
);
4600 return sc
.nr_reclaimed
>= nr_pages
;
4603 int node_reclaim(struct pglist_data
*pgdat
, gfp_t gfp_mask
, unsigned int order
)
4608 * Node reclaim reclaims unmapped file backed pages and
4609 * slab pages if we are over the defined limits.
4611 * A small portion of unmapped file backed pages is needed for
4612 * file I/O otherwise pages read by file I/O will be immediately
4613 * thrown out if the node is overallocated. So we do not reclaim
4614 * if less than a specified percentage of the node is used by
4615 * unmapped file backed pages.
4617 if (node_pagecache_reclaimable(pgdat
) <= pgdat
->min_unmapped_pages
&&
4618 node_page_state_pages(pgdat
, NR_SLAB_RECLAIMABLE_B
) <=
4619 pgdat
->min_slab_pages
)
4620 return NODE_RECLAIM_FULL
;
4623 * Do not scan if the allocation should not be delayed.
4625 if (!gfpflags_allow_blocking(gfp_mask
) || (current
->flags
& PF_MEMALLOC
))
4626 return NODE_RECLAIM_NOSCAN
;
4629 * Only run node reclaim on the local node or on nodes that do not
4630 * have associated processors. This will favor the local processor
4631 * over remote processors and spread off node memory allocations
4632 * as wide as possible.
4634 if (node_state(pgdat
->node_id
, N_CPU
) && pgdat
->node_id
!= numa_node_id())
4635 return NODE_RECLAIM_NOSCAN
;
4637 if (test_and_set_bit(PGDAT_RECLAIM_LOCKED
, &pgdat
->flags
))
4638 return NODE_RECLAIM_NOSCAN
;
4640 ret
= __node_reclaim(pgdat
, gfp_mask
, order
);
4641 clear_bit(PGDAT_RECLAIM_LOCKED
, &pgdat
->flags
);
4644 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
4651 * check_move_unevictable_pages - check pages for evictability and move to
4652 * appropriate zone lru list
4653 * @pvec: pagevec with lru pages to check
4655 * Checks pages for evictability, if an evictable page is in the unevictable
4656 * lru list, moves it to the appropriate evictable lru list. This function
4657 * should be only used for lru pages.
4659 void check_move_unevictable_pages(struct pagevec
*pvec
)
4661 struct lruvec
*lruvec
= NULL
;
4666 for (i
= 0; i
< pvec
->nr
; i
++) {
4667 struct page
*page
= pvec
->pages
[i
];
4670 if (PageTransTail(page
))
4673 nr_pages
= thp_nr_pages(page
);
4674 pgscanned
+= nr_pages
;
4676 /* block memcg migration during page moving between lru */
4677 if (!TestClearPageLRU(page
))
4680 lruvec
= relock_page_lruvec_irq(page
, lruvec
);
4681 if (page_evictable(page
) && PageUnevictable(page
)) {
4682 del_page_from_lru_list(page
, lruvec
);
4683 ClearPageUnevictable(page
);
4684 add_page_to_lru_list(page
, lruvec
);
4685 pgrescued
+= nr_pages
;
4691 __count_vm_events(UNEVICTABLE_PGRESCUED
, pgrescued
);
4692 __count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
4693 unlock_page_lruvec_irq(lruvec
);
4694 } else if (pgscanned
) {
4695 count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
4698 EXPORT_SYMBOL_GPL(check_move_unevictable_pages
);