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 * Update LRU sizes after isolating pages. The LRU size updates must
1870 * be complete before mem_cgroup_update_lru_size due to a sanity check.
1872 static __always_inline
void update_lru_sizes(struct lruvec
*lruvec
,
1873 enum lru_list lru
, unsigned long *nr_zone_taken
)
1877 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++) {
1878 if (!nr_zone_taken
[zid
])
1881 update_lru_size(lruvec
, lru
, zid
, -nr_zone_taken
[zid
]);
1887 * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
1889 * lruvec->lru_lock is heavily contended. Some of the functions that
1890 * shrink the lists perform better by taking out a batch of pages
1891 * and working on them outside the LRU lock.
1893 * For pagecache intensive workloads, this function is the hottest
1894 * spot in the kernel (apart from copy_*_user functions).
1896 * Lru_lock must be held before calling this function.
1898 * @nr_to_scan: The number of eligible pages to look through on the list.
1899 * @lruvec: The LRU vector to pull pages from.
1900 * @dst: The temp list to put pages on to.
1901 * @nr_scanned: The number of pages that were scanned.
1902 * @sc: The scan_control struct for this reclaim session
1903 * @lru: LRU list id for isolating
1905 * returns how many pages were moved onto *@dst.
1907 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1908 struct lruvec
*lruvec
, struct list_head
*dst
,
1909 unsigned long *nr_scanned
, struct scan_control
*sc
,
1912 struct list_head
*src
= &lruvec
->lists
[lru
];
1913 unsigned long nr_taken
= 0;
1914 unsigned long nr_zone_taken
[MAX_NR_ZONES
] = { 0 };
1915 unsigned long nr_skipped
[MAX_NR_ZONES
] = { 0, };
1916 unsigned long skipped
= 0;
1917 unsigned long scan
, total_scan
, nr_pages
;
1918 LIST_HEAD(pages_skipped
);
1922 while (scan
< nr_to_scan
&& !list_empty(src
)) {
1923 struct list_head
*move_to
= src
;
1926 page
= lru_to_page(src
);
1927 prefetchw_prev_lru_page(page
, src
, flags
);
1929 nr_pages
= compound_nr(page
);
1930 total_scan
+= nr_pages
;
1932 if (page_zonenum(page
) > sc
->reclaim_idx
) {
1933 nr_skipped
[page_zonenum(page
)] += nr_pages
;
1934 move_to
= &pages_skipped
;
1939 * Do not count skipped pages because that makes the function
1940 * return with no isolated pages if the LRU mostly contains
1941 * ineligible pages. This causes the VM to not reclaim any
1942 * pages, triggering a premature OOM.
1943 * Account all tail pages of THP.
1949 if (!sc
->may_unmap
&& page_mapped(page
))
1953 * Be careful not to clear PageLRU until after we're
1954 * sure the page is not being freed elsewhere -- the
1955 * page release code relies on it.
1957 if (unlikely(!get_page_unless_zero(page
)))
1960 if (!TestClearPageLRU(page
)) {
1961 /* Another thread is already isolating this page */
1966 nr_taken
+= nr_pages
;
1967 nr_zone_taken
[page_zonenum(page
)] += nr_pages
;
1970 list_move(&page
->lru
, move_to
);
1974 * Splice any skipped pages to the start of the LRU list. Note that
1975 * this disrupts the LRU order when reclaiming for lower zones but
1976 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
1977 * scanning would soon rescan the same pages to skip and put the
1978 * system at risk of premature OOM.
1980 if (!list_empty(&pages_skipped
)) {
1983 list_splice(&pages_skipped
, src
);
1984 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++) {
1985 if (!nr_skipped
[zid
])
1988 __count_zid_vm_events(PGSCAN_SKIP
, zid
, nr_skipped
[zid
]);
1989 skipped
+= nr_skipped
[zid
];
1992 *nr_scanned
= total_scan
;
1993 trace_mm_vmscan_lru_isolate(sc
->reclaim_idx
, sc
->order
, nr_to_scan
,
1994 total_scan
, skipped
, nr_taken
,
1995 sc
->may_unmap
? 0 : ISOLATE_UNMAPPED
, lru
);
1996 update_lru_sizes(lruvec
, lru
, nr_zone_taken
);
2001 * isolate_lru_page - tries to isolate a page from its LRU list
2002 * @page: page to isolate from its LRU list
2004 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
2005 * vmstat statistic corresponding to whatever LRU list the page was on.
2007 * Returns 0 if the page was removed from an LRU list.
2008 * Returns -EBUSY if the page was not on an LRU list.
2010 * The returned page will have PageLRU() cleared. If it was found on
2011 * the active list, it will have PageActive set. If it was found on
2012 * the unevictable list, it will have the PageUnevictable bit set. That flag
2013 * may need to be cleared by the caller before letting the page go.
2015 * The vmstat statistic corresponding to the list on which the page was
2016 * found will be decremented.
2020 * (1) Must be called with an elevated refcount on the page. This is a
2021 * fundamental difference from isolate_lru_pages (which is called
2022 * without a stable reference).
2023 * (2) the lru_lock must not be held.
2024 * (3) interrupts must be enabled.
2026 int isolate_lru_page(struct page
*page
)
2030 VM_BUG_ON_PAGE(!page_count(page
), page
);
2031 WARN_RATELIMIT(PageTail(page
), "trying to isolate tail page");
2033 if (TestClearPageLRU(page
)) {
2034 struct lruvec
*lruvec
;
2037 lruvec
= lock_page_lruvec_irq(page
);
2038 del_page_from_lru_list(page
, lruvec
);
2039 unlock_page_lruvec_irq(lruvec
);
2047 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
2048 * then get rescheduled. When there are massive number of tasks doing page
2049 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
2050 * the LRU list will go small and be scanned faster than necessary, leading to
2051 * unnecessary swapping, thrashing and OOM.
2053 static int too_many_isolated(struct pglist_data
*pgdat
, int file
,
2054 struct scan_control
*sc
)
2056 unsigned long inactive
, isolated
;
2058 if (current_is_kswapd())
2061 if (!writeback_throttling_sane(sc
))
2065 inactive
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
2066 isolated
= node_page_state(pgdat
, NR_ISOLATED_FILE
);
2068 inactive
= node_page_state(pgdat
, NR_INACTIVE_ANON
);
2069 isolated
= node_page_state(pgdat
, NR_ISOLATED_ANON
);
2073 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
2074 * won't get blocked by normal direct-reclaimers, forming a circular
2077 if ((sc
->gfp_mask
& (__GFP_IO
| __GFP_FS
)) == (__GFP_IO
| __GFP_FS
))
2080 return isolated
> inactive
;
2084 * move_pages_to_lru() moves pages from private @list to appropriate LRU list.
2085 * On return, @list is reused as a list of pages to be freed by the caller.
2087 * Returns the number of pages moved to the given lruvec.
2089 static unsigned int move_pages_to_lru(struct lruvec
*lruvec
,
2090 struct list_head
*list
)
2092 int nr_pages
, nr_moved
= 0;
2093 LIST_HEAD(pages_to_free
);
2096 while (!list_empty(list
)) {
2097 page
= lru_to_page(list
);
2098 VM_BUG_ON_PAGE(PageLRU(page
), page
);
2099 list_del(&page
->lru
);
2100 if (unlikely(!page_evictable(page
))) {
2101 spin_unlock_irq(&lruvec
->lru_lock
);
2102 putback_lru_page(page
);
2103 spin_lock_irq(&lruvec
->lru_lock
);
2108 * The SetPageLRU needs to be kept here for list integrity.
2110 * #0 move_pages_to_lru #1 release_pages
2111 * if !put_page_testzero
2112 * if (put_page_testzero())
2113 * !PageLRU //skip lru_lock
2115 * list_add(&page->lru,)
2116 * list_add(&page->lru,)
2120 if (unlikely(put_page_testzero(page
))) {
2121 __clear_page_lru_flags(page
);
2123 if (unlikely(PageCompound(page
))) {
2124 spin_unlock_irq(&lruvec
->lru_lock
);
2125 destroy_compound_page(page
);
2126 spin_lock_irq(&lruvec
->lru_lock
);
2128 list_add(&page
->lru
, &pages_to_free
);
2134 * All pages were isolated from the same lruvec (and isolation
2135 * inhibits memcg migration).
2137 VM_BUG_ON_PAGE(!page_matches_lruvec(page
, lruvec
), page
);
2138 add_page_to_lru_list(page
, lruvec
);
2139 nr_pages
= thp_nr_pages(page
);
2140 nr_moved
+= nr_pages
;
2141 if (PageActive(page
))
2142 workingset_age_nonresident(lruvec
, nr_pages
);
2146 * To save our caller's stack, now use input list for pages to free.
2148 list_splice(&pages_to_free
, list
);
2154 * If a kernel thread (such as nfsd for loop-back mounts) services
2155 * a backing device by writing to the page cache it sets PF_LOCAL_THROTTLE.
2156 * In that case we should only throttle if the backing device it is
2157 * writing to is congested. In other cases it is safe to throttle.
2159 static int current_may_throttle(void)
2161 return !(current
->flags
& PF_LOCAL_THROTTLE
) ||
2162 current
->backing_dev_info
== NULL
||
2163 bdi_write_congested(current
->backing_dev_info
);
2167 * shrink_inactive_list() is a helper for shrink_node(). It returns the number
2168 * of reclaimed pages
2170 static unsigned long
2171 shrink_inactive_list(unsigned long nr_to_scan
, struct lruvec
*lruvec
,
2172 struct scan_control
*sc
, enum lru_list lru
)
2174 LIST_HEAD(page_list
);
2175 unsigned long nr_scanned
;
2176 unsigned int nr_reclaimed
= 0;
2177 unsigned long nr_taken
;
2178 struct reclaim_stat stat
;
2179 bool file
= is_file_lru(lru
);
2180 enum vm_event_item item
;
2181 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2182 bool stalled
= false;
2184 while (unlikely(too_many_isolated(pgdat
, file
, sc
))) {
2188 /* wait a bit for the reclaimer. */
2192 /* We are about to die and free our memory. Return now. */
2193 if (fatal_signal_pending(current
))
2194 return SWAP_CLUSTER_MAX
;
2199 spin_lock_irq(&lruvec
->lru_lock
);
2201 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &page_list
,
2202 &nr_scanned
, sc
, lru
);
2204 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, nr_taken
);
2205 item
= current_is_kswapd() ? PGSCAN_KSWAPD
: PGSCAN_DIRECT
;
2206 if (!cgroup_reclaim(sc
))
2207 __count_vm_events(item
, nr_scanned
);
2208 __count_memcg_events(lruvec_memcg(lruvec
), item
, nr_scanned
);
2209 __count_vm_events(PGSCAN_ANON
+ file
, nr_scanned
);
2211 spin_unlock_irq(&lruvec
->lru_lock
);
2216 nr_reclaimed
= shrink_page_list(&page_list
, pgdat
, sc
, &stat
, false);
2218 spin_lock_irq(&lruvec
->lru_lock
);
2219 move_pages_to_lru(lruvec
, &page_list
);
2221 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
2222 item
= current_is_kswapd() ? PGSTEAL_KSWAPD
: PGSTEAL_DIRECT
;
2223 if (!cgroup_reclaim(sc
))
2224 __count_vm_events(item
, nr_reclaimed
);
2225 __count_memcg_events(lruvec_memcg(lruvec
), item
, nr_reclaimed
);
2226 __count_vm_events(PGSTEAL_ANON
+ file
, nr_reclaimed
);
2227 spin_unlock_irq(&lruvec
->lru_lock
);
2229 lru_note_cost(lruvec
, file
, stat
.nr_pageout
);
2230 mem_cgroup_uncharge_list(&page_list
);
2231 free_unref_page_list(&page_list
);
2234 * If dirty pages are scanned that are not queued for IO, it
2235 * implies that flushers are not doing their job. This can
2236 * happen when memory pressure pushes dirty pages to the end of
2237 * the LRU before the dirty limits are breached and the dirty
2238 * data has expired. It can also happen when the proportion of
2239 * dirty pages grows not through writes but through memory
2240 * pressure reclaiming all the clean cache. And in some cases,
2241 * the flushers simply cannot keep up with the allocation
2242 * rate. Nudge the flusher threads in case they are asleep.
2244 if (stat
.nr_unqueued_dirty
== nr_taken
)
2245 wakeup_flusher_threads(WB_REASON_VMSCAN
);
2247 sc
->nr
.dirty
+= stat
.nr_dirty
;
2248 sc
->nr
.congested
+= stat
.nr_congested
;
2249 sc
->nr
.unqueued_dirty
+= stat
.nr_unqueued_dirty
;
2250 sc
->nr
.writeback
+= stat
.nr_writeback
;
2251 sc
->nr
.immediate
+= stat
.nr_immediate
;
2252 sc
->nr
.taken
+= nr_taken
;
2254 sc
->nr
.file_taken
+= nr_taken
;
2256 trace_mm_vmscan_lru_shrink_inactive(pgdat
->node_id
,
2257 nr_scanned
, nr_reclaimed
, &stat
, sc
->priority
, file
);
2258 return nr_reclaimed
;
2262 * shrink_active_list() moves pages from the active LRU to the inactive LRU.
2264 * We move them the other way if the page is referenced by one or more
2267 * If the pages are mostly unmapped, the processing is fast and it is
2268 * appropriate to hold lru_lock across the whole operation. But if
2269 * the pages are mapped, the processing is slow (page_referenced()), so
2270 * we should drop lru_lock around each page. It's impossible to balance
2271 * this, so instead we remove the pages from the LRU while processing them.
2272 * It is safe to rely on PG_active against the non-LRU pages in here because
2273 * nobody will play with that bit on a non-LRU page.
2275 * The downside is that we have to touch page->_refcount against each page.
2276 * But we had to alter page->flags anyway.
2278 static void shrink_active_list(unsigned long nr_to_scan
,
2279 struct lruvec
*lruvec
,
2280 struct scan_control
*sc
,
2283 unsigned long nr_taken
;
2284 unsigned long nr_scanned
;
2285 unsigned long vm_flags
;
2286 LIST_HEAD(l_hold
); /* The pages which were snipped off */
2287 LIST_HEAD(l_active
);
2288 LIST_HEAD(l_inactive
);
2290 unsigned nr_deactivate
, nr_activate
;
2291 unsigned nr_rotated
= 0;
2292 int file
= is_file_lru(lru
);
2293 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2297 spin_lock_irq(&lruvec
->lru_lock
);
2299 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &l_hold
,
2300 &nr_scanned
, sc
, lru
);
2302 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, nr_taken
);
2304 if (!cgroup_reclaim(sc
))
2305 __count_vm_events(PGREFILL
, nr_scanned
);
2306 __count_memcg_events(lruvec_memcg(lruvec
), PGREFILL
, nr_scanned
);
2308 spin_unlock_irq(&lruvec
->lru_lock
);
2310 while (!list_empty(&l_hold
)) {
2312 page
= lru_to_page(&l_hold
);
2313 list_del(&page
->lru
);
2315 if (unlikely(!page_evictable(page
))) {
2316 putback_lru_page(page
);
2320 if (unlikely(buffer_heads_over_limit
)) {
2321 if (page_has_private(page
) && trylock_page(page
)) {
2322 if (page_has_private(page
))
2323 try_to_release_page(page
, 0);
2328 if (page_referenced(page
, 0, sc
->target_mem_cgroup
,
2331 * Identify referenced, file-backed active pages and
2332 * give them one more trip around the active list. So
2333 * that executable code get better chances to stay in
2334 * memory under moderate memory pressure. Anon pages
2335 * are not likely to be evicted by use-once streaming
2336 * IO, plus JVM can create lots of anon VM_EXEC pages,
2337 * so we ignore them here.
2339 if ((vm_flags
& VM_EXEC
) && page_is_file_lru(page
)) {
2340 nr_rotated
+= thp_nr_pages(page
);
2341 list_add(&page
->lru
, &l_active
);
2346 ClearPageActive(page
); /* we are de-activating */
2347 SetPageWorkingset(page
);
2348 list_add(&page
->lru
, &l_inactive
);
2352 * Move pages back to the lru list.
2354 spin_lock_irq(&lruvec
->lru_lock
);
2356 nr_activate
= move_pages_to_lru(lruvec
, &l_active
);
2357 nr_deactivate
= move_pages_to_lru(lruvec
, &l_inactive
);
2358 /* Keep all free pages in l_active list */
2359 list_splice(&l_inactive
, &l_active
);
2361 __count_vm_events(PGDEACTIVATE
, nr_deactivate
);
2362 __count_memcg_events(lruvec_memcg(lruvec
), PGDEACTIVATE
, nr_deactivate
);
2364 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
2365 spin_unlock_irq(&lruvec
->lru_lock
);
2367 mem_cgroup_uncharge_list(&l_active
);
2368 free_unref_page_list(&l_active
);
2369 trace_mm_vmscan_lru_shrink_active(pgdat
->node_id
, nr_taken
, nr_activate
,
2370 nr_deactivate
, nr_rotated
, sc
->priority
, file
);
2373 unsigned long reclaim_pages(struct list_head
*page_list
)
2375 int nid
= NUMA_NO_NODE
;
2376 unsigned int nr_reclaimed
= 0;
2377 LIST_HEAD(node_page_list
);
2378 struct reclaim_stat dummy_stat
;
2380 unsigned int noreclaim_flag
;
2381 struct scan_control sc
= {
2382 .gfp_mask
= GFP_KERNEL
,
2389 noreclaim_flag
= memalloc_noreclaim_save();
2391 while (!list_empty(page_list
)) {
2392 page
= lru_to_page(page_list
);
2393 if (nid
== NUMA_NO_NODE
) {
2394 nid
= page_to_nid(page
);
2395 INIT_LIST_HEAD(&node_page_list
);
2398 if (nid
== page_to_nid(page
)) {
2399 ClearPageActive(page
);
2400 list_move(&page
->lru
, &node_page_list
);
2404 nr_reclaimed
+= shrink_page_list(&node_page_list
,
2406 &sc
, &dummy_stat
, false);
2407 while (!list_empty(&node_page_list
)) {
2408 page
= lru_to_page(&node_page_list
);
2409 list_del(&page
->lru
);
2410 putback_lru_page(page
);
2416 if (!list_empty(&node_page_list
)) {
2417 nr_reclaimed
+= shrink_page_list(&node_page_list
,
2419 &sc
, &dummy_stat
, false);
2420 while (!list_empty(&node_page_list
)) {
2421 page
= lru_to_page(&node_page_list
);
2422 list_del(&page
->lru
);
2423 putback_lru_page(page
);
2427 memalloc_noreclaim_restore(noreclaim_flag
);
2429 return nr_reclaimed
;
2432 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
2433 struct lruvec
*lruvec
, struct scan_control
*sc
)
2435 if (is_active_lru(lru
)) {
2436 if (sc
->may_deactivate
& (1 << is_file_lru(lru
)))
2437 shrink_active_list(nr_to_scan
, lruvec
, sc
, lru
);
2439 sc
->skipped_deactivate
= 1;
2443 return shrink_inactive_list(nr_to_scan
, lruvec
, sc
, lru
);
2447 * The inactive anon list should be small enough that the VM never has
2448 * to do too much work.
2450 * The inactive file list should be small enough to leave most memory
2451 * to the established workingset on the scan-resistant active list,
2452 * but large enough to avoid thrashing the aggregate readahead window.
2454 * Both inactive lists should also be large enough that each inactive
2455 * page has a chance to be referenced again before it is reclaimed.
2457 * If that fails and refaulting is observed, the inactive list grows.
2459 * The inactive_ratio is the target ratio of ACTIVE to INACTIVE pages
2460 * on this LRU, maintained by the pageout code. An inactive_ratio
2461 * of 3 means 3:1 or 25% of the pages are kept on the inactive list.
2464 * memory ratio inactive
2465 * -------------------------------------
2474 static bool inactive_is_low(struct lruvec
*lruvec
, enum lru_list inactive_lru
)
2476 enum lru_list active_lru
= inactive_lru
+ LRU_ACTIVE
;
2477 unsigned long inactive
, active
;
2478 unsigned long inactive_ratio
;
2481 inactive
= lruvec_page_state(lruvec
, NR_LRU_BASE
+ inactive_lru
);
2482 active
= lruvec_page_state(lruvec
, NR_LRU_BASE
+ active_lru
);
2484 gb
= (inactive
+ active
) >> (30 - PAGE_SHIFT
);
2486 inactive_ratio
= int_sqrt(10 * gb
);
2490 return inactive
* inactive_ratio
< active
;
2501 * Determine how aggressively the anon and file LRU lists should be
2502 * scanned. The relative value of each set of LRU lists is determined
2503 * by looking at the fraction of the pages scanned we did rotate back
2504 * onto the active list instead of evict.
2506 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
2507 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
2509 static void get_scan_count(struct lruvec
*lruvec
, struct scan_control
*sc
,
2512 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2513 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
2514 unsigned long anon_cost
, file_cost
, total_cost
;
2515 int swappiness
= mem_cgroup_swappiness(memcg
);
2516 u64 fraction
[ANON_AND_FILE
];
2517 u64 denominator
= 0; /* gcc */
2518 enum scan_balance scan_balance
;
2519 unsigned long ap
, fp
;
2522 /* If we have no swap space, do not bother scanning anon pages. */
2523 if (!sc
->may_swap
|| !can_reclaim_anon_pages(memcg
, pgdat
->node_id
, sc
)) {
2524 scan_balance
= SCAN_FILE
;
2529 * Global reclaim will swap to prevent OOM even with no
2530 * swappiness, but memcg users want to use this knob to
2531 * disable swapping for individual groups completely when
2532 * using the memory controller's swap limit feature would be
2535 if (cgroup_reclaim(sc
) && !swappiness
) {
2536 scan_balance
= SCAN_FILE
;
2541 * Do not apply any pressure balancing cleverness when the
2542 * system is close to OOM, scan both anon and file equally
2543 * (unless the swappiness setting disagrees with swapping).
2545 if (!sc
->priority
&& swappiness
) {
2546 scan_balance
= SCAN_EQUAL
;
2551 * If the system is almost out of file pages, force-scan anon.
2553 if (sc
->file_is_tiny
) {
2554 scan_balance
= SCAN_ANON
;
2559 * If there is enough inactive page cache, we do not reclaim
2560 * anything from the anonymous working right now.
2562 if (sc
->cache_trim_mode
) {
2563 scan_balance
= SCAN_FILE
;
2567 scan_balance
= SCAN_FRACT
;
2569 * Calculate the pressure balance between anon and file pages.
2571 * The amount of pressure we put on each LRU is inversely
2572 * proportional to the cost of reclaiming each list, as
2573 * determined by the share of pages that are refaulting, times
2574 * the relative IO cost of bringing back a swapped out
2575 * anonymous page vs reloading a filesystem page (swappiness).
2577 * Although we limit that influence to ensure no list gets
2578 * left behind completely: at least a third of the pressure is
2579 * applied, before swappiness.
2581 * With swappiness at 100, anon and file have equal IO cost.
2583 total_cost
= sc
->anon_cost
+ sc
->file_cost
;
2584 anon_cost
= total_cost
+ sc
->anon_cost
;
2585 file_cost
= total_cost
+ sc
->file_cost
;
2586 total_cost
= anon_cost
+ file_cost
;
2588 ap
= swappiness
* (total_cost
+ 1);
2589 ap
/= anon_cost
+ 1;
2591 fp
= (200 - swappiness
) * (total_cost
+ 1);
2592 fp
/= file_cost
+ 1;
2596 denominator
= ap
+ fp
;
2598 for_each_evictable_lru(lru
) {
2599 int file
= is_file_lru(lru
);
2600 unsigned long lruvec_size
;
2601 unsigned long low
, min
;
2604 lruvec_size
= lruvec_lru_size(lruvec
, lru
, sc
->reclaim_idx
);
2605 mem_cgroup_protection(sc
->target_mem_cgroup
, memcg
,
2610 * Scale a cgroup's reclaim pressure by proportioning
2611 * its current usage to its memory.low or memory.min
2614 * This is important, as otherwise scanning aggression
2615 * becomes extremely binary -- from nothing as we
2616 * approach the memory protection threshold, to totally
2617 * nominal as we exceed it. This results in requiring
2618 * setting extremely liberal protection thresholds. It
2619 * also means we simply get no protection at all if we
2620 * set it too low, which is not ideal.
2622 * If there is any protection in place, we reduce scan
2623 * pressure by how much of the total memory used is
2624 * within protection thresholds.
2626 * There is one special case: in the first reclaim pass,
2627 * we skip over all groups that are within their low
2628 * protection. If that fails to reclaim enough pages to
2629 * satisfy the reclaim goal, we come back and override
2630 * the best-effort low protection. However, we still
2631 * ideally want to honor how well-behaved groups are in
2632 * that case instead of simply punishing them all
2633 * equally. As such, we reclaim them based on how much
2634 * memory they are using, reducing the scan pressure
2635 * again by how much of the total memory used is under
2638 unsigned long cgroup_size
= mem_cgroup_size(memcg
);
2639 unsigned long protection
;
2641 /* memory.low scaling, make sure we retry before OOM */
2642 if (!sc
->memcg_low_reclaim
&& low
> min
) {
2644 sc
->memcg_low_skipped
= 1;
2649 /* Avoid TOCTOU with earlier protection check */
2650 cgroup_size
= max(cgroup_size
, protection
);
2652 scan
= lruvec_size
- lruvec_size
* protection
/
2656 * Minimally target SWAP_CLUSTER_MAX pages to keep
2657 * reclaim moving forwards, avoiding decrementing
2658 * sc->priority further than desirable.
2660 scan
= max(scan
, SWAP_CLUSTER_MAX
);
2665 scan
>>= sc
->priority
;
2668 * If the cgroup's already been deleted, make sure to
2669 * scrape out the remaining cache.
2671 if (!scan
&& !mem_cgroup_online(memcg
))
2672 scan
= min(lruvec_size
, SWAP_CLUSTER_MAX
);
2674 switch (scan_balance
) {
2676 /* Scan lists relative to size */
2680 * Scan types proportional to swappiness and
2681 * their relative recent reclaim efficiency.
2682 * Make sure we don't miss the last page on
2683 * the offlined memory cgroups because of a
2686 scan
= mem_cgroup_online(memcg
) ?
2687 div64_u64(scan
* fraction
[file
], denominator
) :
2688 DIV64_U64_ROUND_UP(scan
* fraction
[file
],
2693 /* Scan one type exclusively */
2694 if ((scan_balance
== SCAN_FILE
) != file
)
2698 /* Look ma, no brain */
2707 * Anonymous LRU management is a waste if there is
2708 * ultimately no way to reclaim the memory.
2710 static bool can_age_anon_pages(struct pglist_data
*pgdat
,
2711 struct scan_control
*sc
)
2713 /* Aging the anon LRU is valuable if swap is present: */
2714 if (total_swap_pages
> 0)
2717 /* Also valuable if anon pages can be demoted: */
2718 return can_demote(pgdat
->node_id
, sc
);
2721 static void shrink_lruvec(struct lruvec
*lruvec
, struct scan_control
*sc
)
2723 unsigned long nr
[NR_LRU_LISTS
];
2724 unsigned long targets
[NR_LRU_LISTS
];
2725 unsigned long nr_to_scan
;
2727 unsigned long nr_reclaimed
= 0;
2728 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
2729 bool proportional_reclaim
;
2730 struct blk_plug plug
;
2732 get_scan_count(lruvec
, sc
, nr
);
2734 /* Record the original scan target for proportional adjustments later */
2735 memcpy(targets
, nr
, sizeof(nr
));
2738 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
2739 * event that can occur when there is little memory pressure e.g.
2740 * multiple streaming readers/writers. Hence, we do not abort scanning
2741 * when the requested number of pages are reclaimed when scanning at
2742 * DEF_PRIORITY on the assumption that the fact we are direct
2743 * reclaiming implies that kswapd is not keeping up and it is best to
2744 * do a batch of work at once. For memcg reclaim one check is made to
2745 * abort proportional reclaim if either the file or anon lru has already
2746 * dropped to zero at the first pass.
2748 proportional_reclaim
= (!cgroup_reclaim(sc
) && !current_is_kswapd() &&
2749 sc
->priority
== DEF_PRIORITY
);
2751 blk_start_plug(&plug
);
2752 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
2753 nr
[LRU_INACTIVE_FILE
]) {
2754 unsigned long nr_anon
, nr_file
, percentage
;
2755 unsigned long nr_scanned
;
2757 for_each_evictable_lru(lru
) {
2759 nr_to_scan
= min(nr
[lru
], SWAP_CLUSTER_MAX
);
2760 nr
[lru
] -= nr_to_scan
;
2762 nr_reclaimed
+= shrink_list(lru
, nr_to_scan
,
2769 if (nr_reclaimed
< nr_to_reclaim
|| proportional_reclaim
)
2773 * For kswapd and memcg, reclaim at least the number of pages
2774 * requested. Ensure that the anon and file LRUs are scanned
2775 * proportionally what was requested by get_scan_count(). We
2776 * stop reclaiming one LRU and reduce the amount scanning
2777 * proportional to the original scan target.
2779 nr_file
= nr
[LRU_INACTIVE_FILE
] + nr
[LRU_ACTIVE_FILE
];
2780 nr_anon
= nr
[LRU_INACTIVE_ANON
] + nr
[LRU_ACTIVE_ANON
];
2783 * It's just vindictive to attack the larger once the smaller
2784 * has gone to zero. And given the way we stop scanning the
2785 * smaller below, this makes sure that we only make one nudge
2786 * towards proportionality once we've got nr_to_reclaim.
2788 if (!nr_file
|| !nr_anon
)
2791 if (nr_file
> nr_anon
) {
2792 unsigned long scan_target
= targets
[LRU_INACTIVE_ANON
] +
2793 targets
[LRU_ACTIVE_ANON
] + 1;
2795 percentage
= nr_anon
* 100 / scan_target
;
2797 unsigned long scan_target
= targets
[LRU_INACTIVE_FILE
] +
2798 targets
[LRU_ACTIVE_FILE
] + 1;
2800 percentage
= nr_file
* 100 / scan_target
;
2803 /* Stop scanning the smaller of the LRU */
2805 nr
[lru
+ LRU_ACTIVE
] = 0;
2808 * Recalculate the other LRU scan count based on its original
2809 * scan target and the percentage scanning already complete
2811 lru
= (lru
== LRU_FILE
) ? LRU_BASE
: LRU_FILE
;
2812 nr_scanned
= targets
[lru
] - nr
[lru
];
2813 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2814 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2817 nr_scanned
= targets
[lru
] - nr
[lru
];
2818 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2819 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2821 blk_finish_plug(&plug
);
2822 sc
->nr_reclaimed
+= nr_reclaimed
;
2825 * Even if we did not try to evict anon pages at all, we want to
2826 * rebalance the anon lru active/inactive ratio.
2828 if (can_age_anon_pages(lruvec_pgdat(lruvec
), sc
) &&
2829 inactive_is_low(lruvec
, LRU_INACTIVE_ANON
))
2830 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
2831 sc
, LRU_ACTIVE_ANON
);
2834 /* Use reclaim/compaction for costly allocs or under memory pressure */
2835 static bool in_reclaim_compaction(struct scan_control
*sc
)
2837 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
2838 (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
||
2839 sc
->priority
< DEF_PRIORITY
- 2))
2846 * Reclaim/compaction is used for high-order allocation requests. It reclaims
2847 * order-0 pages before compacting the zone. should_continue_reclaim() returns
2848 * true if more pages should be reclaimed such that when the page allocator
2849 * calls try_to_compact_pages() that it will have enough free pages to succeed.
2850 * It will give up earlier than that if there is difficulty reclaiming pages.
2852 static inline bool should_continue_reclaim(struct pglist_data
*pgdat
,
2853 unsigned long nr_reclaimed
,
2854 struct scan_control
*sc
)
2856 unsigned long pages_for_compaction
;
2857 unsigned long inactive_lru_pages
;
2860 /* If not in reclaim/compaction mode, stop */
2861 if (!in_reclaim_compaction(sc
))
2865 * Stop if we failed to reclaim any pages from the last SWAP_CLUSTER_MAX
2866 * number of pages that were scanned. This will return to the caller
2867 * with the risk reclaim/compaction and the resulting allocation attempt
2868 * fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL
2869 * allocations through requiring that the full LRU list has been scanned
2870 * first, by assuming that zero delta of sc->nr_scanned means full LRU
2871 * scan, but that approximation was wrong, and there were corner cases
2872 * where always a non-zero amount of pages were scanned.
2877 /* If compaction would go ahead or the allocation would succeed, stop */
2878 for (z
= 0; z
<= sc
->reclaim_idx
; z
++) {
2879 struct zone
*zone
= &pgdat
->node_zones
[z
];
2880 if (!managed_zone(zone
))
2883 switch (compaction_suitable(zone
, sc
->order
, 0, sc
->reclaim_idx
)) {
2884 case COMPACT_SUCCESS
:
2885 case COMPACT_CONTINUE
:
2888 /* check next zone */
2894 * If we have not reclaimed enough pages for compaction and the
2895 * inactive lists are large enough, continue reclaiming
2897 pages_for_compaction
= compact_gap(sc
->order
);
2898 inactive_lru_pages
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
2899 if (can_reclaim_anon_pages(NULL
, pgdat
->node_id
, sc
))
2900 inactive_lru_pages
+= node_page_state(pgdat
, NR_INACTIVE_ANON
);
2902 return inactive_lru_pages
> pages_for_compaction
;
2905 static void shrink_node_memcgs(pg_data_t
*pgdat
, struct scan_control
*sc
)
2907 struct mem_cgroup
*target_memcg
= sc
->target_mem_cgroup
;
2908 struct mem_cgroup
*memcg
;
2910 memcg
= mem_cgroup_iter(target_memcg
, NULL
, NULL
);
2912 struct lruvec
*lruvec
= mem_cgroup_lruvec(memcg
, pgdat
);
2913 unsigned long reclaimed
;
2914 unsigned long scanned
;
2917 * This loop can become CPU-bound when target memcgs
2918 * aren't eligible for reclaim - either because they
2919 * don't have any reclaimable pages, or because their
2920 * memory is explicitly protected. Avoid soft lockups.
2924 mem_cgroup_calculate_protection(target_memcg
, memcg
);
2926 if (mem_cgroup_below_min(memcg
)) {
2929 * If there is no reclaimable memory, OOM.
2932 } else if (mem_cgroup_below_low(memcg
)) {
2935 * Respect the protection only as long as
2936 * there is an unprotected supply
2937 * of reclaimable memory from other cgroups.
2939 if (!sc
->memcg_low_reclaim
) {
2940 sc
->memcg_low_skipped
= 1;
2943 memcg_memory_event(memcg
, MEMCG_LOW
);
2946 reclaimed
= sc
->nr_reclaimed
;
2947 scanned
= sc
->nr_scanned
;
2949 shrink_lruvec(lruvec
, sc
);
2951 shrink_slab(sc
->gfp_mask
, pgdat
->node_id
, memcg
,
2954 /* Record the group's reclaim efficiency */
2955 vmpressure(sc
->gfp_mask
, memcg
, false,
2956 sc
->nr_scanned
- scanned
,
2957 sc
->nr_reclaimed
- reclaimed
);
2959 } while ((memcg
= mem_cgroup_iter(target_memcg
, memcg
, NULL
)));
2962 static void shrink_node(pg_data_t
*pgdat
, struct scan_control
*sc
)
2964 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2965 unsigned long nr_reclaimed
, nr_scanned
;
2966 struct lruvec
*target_lruvec
;
2967 bool reclaimable
= false;
2970 target_lruvec
= mem_cgroup_lruvec(sc
->target_mem_cgroup
, pgdat
);
2974 * Flush the memory cgroup stats, so that we read accurate per-memcg
2975 * lruvec stats for heuristics.
2977 mem_cgroup_flush_stats();
2979 memset(&sc
->nr
, 0, sizeof(sc
->nr
));
2981 nr_reclaimed
= sc
->nr_reclaimed
;
2982 nr_scanned
= sc
->nr_scanned
;
2985 * Determine the scan balance between anon and file LRUs.
2987 spin_lock_irq(&target_lruvec
->lru_lock
);
2988 sc
->anon_cost
= target_lruvec
->anon_cost
;
2989 sc
->file_cost
= target_lruvec
->file_cost
;
2990 spin_unlock_irq(&target_lruvec
->lru_lock
);
2993 * Target desirable inactive:active list ratios for the anon
2994 * and file LRU lists.
2996 if (!sc
->force_deactivate
) {
2997 unsigned long refaults
;
2999 refaults
= lruvec_page_state(target_lruvec
,
3000 WORKINGSET_ACTIVATE_ANON
);
3001 if (refaults
!= target_lruvec
->refaults
[0] ||
3002 inactive_is_low(target_lruvec
, LRU_INACTIVE_ANON
))
3003 sc
->may_deactivate
|= DEACTIVATE_ANON
;
3005 sc
->may_deactivate
&= ~DEACTIVATE_ANON
;
3008 * When refaults are being observed, it means a new
3009 * workingset is being established. Deactivate to get
3010 * rid of any stale active pages quickly.
3012 refaults
= lruvec_page_state(target_lruvec
,
3013 WORKINGSET_ACTIVATE_FILE
);
3014 if (refaults
!= target_lruvec
->refaults
[1] ||
3015 inactive_is_low(target_lruvec
, LRU_INACTIVE_FILE
))
3016 sc
->may_deactivate
|= DEACTIVATE_FILE
;
3018 sc
->may_deactivate
&= ~DEACTIVATE_FILE
;
3020 sc
->may_deactivate
= DEACTIVATE_ANON
| DEACTIVATE_FILE
;
3023 * If we have plenty of inactive file pages that aren't
3024 * thrashing, try to reclaim those first before touching
3027 file
= lruvec_page_state(target_lruvec
, NR_INACTIVE_FILE
);
3028 if (file
>> sc
->priority
&& !(sc
->may_deactivate
& DEACTIVATE_FILE
))
3029 sc
->cache_trim_mode
= 1;
3031 sc
->cache_trim_mode
= 0;
3034 * Prevent the reclaimer from falling into the cache trap: as
3035 * cache pages start out inactive, every cache fault will tip
3036 * the scan balance towards the file LRU. And as the file LRU
3037 * shrinks, so does the window for rotation from references.
3038 * This means we have a runaway feedback loop where a tiny
3039 * thrashing file LRU becomes infinitely more attractive than
3040 * anon pages. Try to detect this based on file LRU size.
3042 if (!cgroup_reclaim(sc
)) {
3043 unsigned long total_high_wmark
= 0;
3044 unsigned long free
, anon
;
3047 free
= sum_zone_node_page_state(pgdat
->node_id
, NR_FREE_PAGES
);
3048 file
= node_page_state(pgdat
, NR_ACTIVE_FILE
) +
3049 node_page_state(pgdat
, NR_INACTIVE_FILE
);
3051 for (z
= 0; z
< MAX_NR_ZONES
; z
++) {
3052 struct zone
*zone
= &pgdat
->node_zones
[z
];
3053 if (!managed_zone(zone
))
3056 total_high_wmark
+= high_wmark_pages(zone
);
3060 * Consider anon: if that's low too, this isn't a
3061 * runaway file reclaim problem, but rather just
3062 * extreme pressure. Reclaim as per usual then.
3064 anon
= node_page_state(pgdat
, NR_INACTIVE_ANON
);
3067 file
+ free
<= total_high_wmark
&&
3068 !(sc
->may_deactivate
& DEACTIVATE_ANON
) &&
3069 anon
>> sc
->priority
;
3072 shrink_node_memcgs(pgdat
, sc
);
3074 if (reclaim_state
) {
3075 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
3076 reclaim_state
->reclaimed_slab
= 0;
3079 /* Record the subtree's reclaim efficiency */
3080 vmpressure(sc
->gfp_mask
, sc
->target_mem_cgroup
, true,
3081 sc
->nr_scanned
- nr_scanned
,
3082 sc
->nr_reclaimed
- nr_reclaimed
);
3084 if (sc
->nr_reclaimed
- nr_reclaimed
)
3087 if (current_is_kswapd()) {
3089 * If reclaim is isolating dirty pages under writeback,
3090 * it implies that the long-lived page allocation rate
3091 * is exceeding the page laundering rate. Either the
3092 * global limits are not being effective at throttling
3093 * processes due to the page distribution throughout
3094 * zones or there is heavy usage of a slow backing
3095 * device. The only option is to throttle from reclaim
3096 * context which is not ideal as there is no guarantee
3097 * the dirtying process is throttled in the same way
3098 * balance_dirty_pages() manages.
3100 * Once a node is flagged PGDAT_WRITEBACK, kswapd will
3101 * count the number of pages under pages flagged for
3102 * immediate reclaim and stall if any are encountered
3103 * in the nr_immediate check below.
3105 if (sc
->nr
.writeback
&& sc
->nr
.writeback
== sc
->nr
.taken
)
3106 set_bit(PGDAT_WRITEBACK
, &pgdat
->flags
);
3108 /* Allow kswapd to start writing pages during reclaim.*/
3109 if (sc
->nr
.unqueued_dirty
== sc
->nr
.file_taken
)
3110 set_bit(PGDAT_DIRTY
, &pgdat
->flags
);
3113 * If kswapd scans pages marked for immediate
3114 * reclaim and under writeback (nr_immediate), it
3115 * implies that pages are cycling through the LRU
3116 * faster than they are written so also forcibly stall.
3118 if (sc
->nr
.immediate
)
3119 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
3123 * Tag a node/memcg as congested if all the dirty pages
3124 * scanned were backed by a congested BDI and
3125 * wait_iff_congested will stall.
3127 * Legacy memcg will stall in page writeback so avoid forcibly
3128 * stalling in wait_iff_congested().
3130 if ((current_is_kswapd() ||
3131 (cgroup_reclaim(sc
) && writeback_throttling_sane(sc
))) &&
3132 sc
->nr
.dirty
&& sc
->nr
.dirty
== sc
->nr
.congested
)
3133 set_bit(LRUVEC_CONGESTED
, &target_lruvec
->flags
);
3136 * Stall direct reclaim for IO completions if underlying BDIs
3137 * and node is congested. Allow kswapd to continue until it
3138 * starts encountering unqueued dirty pages or cycling through
3139 * the LRU too quickly.
3141 if (!current_is_kswapd() && current_may_throttle() &&
3142 !sc
->hibernation_mode
&&
3143 test_bit(LRUVEC_CONGESTED
, &target_lruvec
->flags
))
3144 wait_iff_congested(BLK_RW_ASYNC
, HZ
/10);
3146 if (should_continue_reclaim(pgdat
, sc
->nr_reclaimed
- nr_reclaimed
,
3151 * Kswapd gives up on balancing particular nodes after too
3152 * many failures to reclaim anything from them and goes to
3153 * sleep. On reclaim progress, reset the failure counter. A
3154 * successful direct reclaim run will revive a dormant kswapd.
3157 pgdat
->kswapd_failures
= 0;
3161 * Returns true if compaction should go ahead for a costly-order request, or
3162 * the allocation would already succeed without compaction. Return false if we
3163 * should reclaim first.
3165 static inline bool compaction_ready(struct zone
*zone
, struct scan_control
*sc
)
3167 unsigned long watermark
;
3168 enum compact_result suitable
;
3170 suitable
= compaction_suitable(zone
, sc
->order
, 0, sc
->reclaim_idx
);
3171 if (suitable
== COMPACT_SUCCESS
)
3172 /* Allocation should succeed already. Don't reclaim. */
3174 if (suitable
== COMPACT_SKIPPED
)
3175 /* Compaction cannot yet proceed. Do reclaim. */
3179 * Compaction is already possible, but it takes time to run and there
3180 * are potentially other callers using the pages just freed. So proceed
3181 * with reclaim to make a buffer of free pages available to give
3182 * compaction a reasonable chance of completing and allocating the page.
3183 * Note that we won't actually reclaim the whole buffer in one attempt
3184 * as the target watermark in should_continue_reclaim() is lower. But if
3185 * we are already above the high+gap watermark, don't reclaim at all.
3187 watermark
= high_wmark_pages(zone
) + compact_gap(sc
->order
);
3189 return zone_watermark_ok_safe(zone
, 0, watermark
, sc
->reclaim_idx
);
3193 * This is the direct reclaim path, for page-allocating processes. We only
3194 * try to reclaim pages from zones which will satisfy the caller's allocation
3197 * If a zone is deemed to be full of pinned pages then just give it a light
3198 * scan then give up on it.
3200 static void shrink_zones(struct zonelist
*zonelist
, struct scan_control
*sc
)
3204 unsigned long nr_soft_reclaimed
;
3205 unsigned long nr_soft_scanned
;
3207 pg_data_t
*last_pgdat
= NULL
;
3210 * If the number of buffer_heads in the machine exceeds the maximum
3211 * allowed level, force direct reclaim to scan the highmem zone as
3212 * highmem pages could be pinning lowmem pages storing buffer_heads
3214 orig_mask
= sc
->gfp_mask
;
3215 if (buffer_heads_over_limit
) {
3216 sc
->gfp_mask
|= __GFP_HIGHMEM
;
3217 sc
->reclaim_idx
= gfp_zone(sc
->gfp_mask
);
3220 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
3221 sc
->reclaim_idx
, sc
->nodemask
) {
3223 * Take care memory controller reclaiming has small influence
3226 if (!cgroup_reclaim(sc
)) {
3227 if (!cpuset_zone_allowed(zone
,
3228 GFP_KERNEL
| __GFP_HARDWALL
))
3232 * If we already have plenty of memory free for
3233 * compaction in this zone, don't free any more.
3234 * Even though compaction is invoked for any
3235 * non-zero order, only frequent costly order
3236 * reclamation is disruptive enough to become a
3237 * noticeable problem, like transparent huge
3240 if (IS_ENABLED(CONFIG_COMPACTION
) &&
3241 sc
->order
> PAGE_ALLOC_COSTLY_ORDER
&&
3242 compaction_ready(zone
, sc
)) {
3243 sc
->compaction_ready
= true;
3248 * Shrink each node in the zonelist once. If the
3249 * zonelist is ordered by zone (not the default) then a
3250 * node may be shrunk multiple times but in that case
3251 * the user prefers lower zones being preserved.
3253 if (zone
->zone_pgdat
== last_pgdat
)
3257 * This steals pages from memory cgroups over softlimit
3258 * and returns the number of reclaimed pages and
3259 * scanned pages. This works for global memory pressure
3260 * and balancing, not for a memcg's limit.
3262 nr_soft_scanned
= 0;
3263 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
->zone_pgdat
,
3264 sc
->order
, sc
->gfp_mask
,
3266 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
3267 sc
->nr_scanned
+= nr_soft_scanned
;
3268 /* need some check for avoid more shrink_zone() */
3271 /* See comment about same check for global reclaim above */
3272 if (zone
->zone_pgdat
== last_pgdat
)
3274 last_pgdat
= zone
->zone_pgdat
;
3275 shrink_node(zone
->zone_pgdat
, sc
);
3279 * Restore to original mask to avoid the impact on the caller if we
3280 * promoted it to __GFP_HIGHMEM.
3282 sc
->gfp_mask
= orig_mask
;
3285 static void snapshot_refaults(struct mem_cgroup
*target_memcg
, pg_data_t
*pgdat
)
3287 struct lruvec
*target_lruvec
;
3288 unsigned long refaults
;
3290 target_lruvec
= mem_cgroup_lruvec(target_memcg
, pgdat
);
3291 refaults
= lruvec_page_state(target_lruvec
, WORKINGSET_ACTIVATE_ANON
);
3292 target_lruvec
->refaults
[0] = refaults
;
3293 refaults
= lruvec_page_state(target_lruvec
, WORKINGSET_ACTIVATE_FILE
);
3294 target_lruvec
->refaults
[1] = refaults
;
3298 * This is the main entry point to direct page reclaim.
3300 * If a full scan of the inactive list fails to free enough memory then we
3301 * are "out of memory" and something needs to be killed.
3303 * If the caller is !__GFP_FS then the probability of a failure is reasonably
3304 * high - the zone may be full of dirty or under-writeback pages, which this
3305 * caller can't do much about. We kick the writeback threads and take explicit
3306 * naps in the hope that some of these pages can be written. But if the
3307 * allocating task holds filesystem locks which prevent writeout this might not
3308 * work, and the allocation attempt will fail.
3310 * returns: 0, if no pages reclaimed
3311 * else, the number of pages reclaimed
3313 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
3314 struct scan_control
*sc
)
3316 int initial_priority
= sc
->priority
;
3317 pg_data_t
*last_pgdat
;
3321 delayacct_freepages_start();
3323 if (!cgroup_reclaim(sc
))
3324 __count_zid_vm_events(ALLOCSTALL
, sc
->reclaim_idx
, 1);
3327 vmpressure_prio(sc
->gfp_mask
, sc
->target_mem_cgroup
,
3330 shrink_zones(zonelist
, sc
);
3332 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
3335 if (sc
->compaction_ready
)
3339 * If we're getting trouble reclaiming, start doing
3340 * writepage even in laptop mode.
3342 if (sc
->priority
< DEF_PRIORITY
- 2)
3343 sc
->may_writepage
= 1;
3344 } while (--sc
->priority
>= 0);
3347 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
, sc
->reclaim_idx
,
3349 if (zone
->zone_pgdat
== last_pgdat
)
3351 last_pgdat
= zone
->zone_pgdat
;
3353 snapshot_refaults(sc
->target_mem_cgroup
, zone
->zone_pgdat
);
3355 if (cgroup_reclaim(sc
)) {
3356 struct lruvec
*lruvec
;
3358 lruvec
= mem_cgroup_lruvec(sc
->target_mem_cgroup
,
3360 clear_bit(LRUVEC_CONGESTED
, &lruvec
->flags
);
3364 delayacct_freepages_end();
3366 if (sc
->nr_reclaimed
)
3367 return sc
->nr_reclaimed
;
3369 /* Aborted reclaim to try compaction? don't OOM, then */
3370 if (sc
->compaction_ready
)
3374 * We make inactive:active ratio decisions based on the node's
3375 * composition of memory, but a restrictive reclaim_idx or a
3376 * memory.low cgroup setting can exempt large amounts of
3377 * memory from reclaim. Neither of which are very common, so
3378 * instead of doing costly eligibility calculations of the
3379 * entire cgroup subtree up front, we assume the estimates are
3380 * good, and retry with forcible deactivation if that fails.
3382 if (sc
->skipped_deactivate
) {
3383 sc
->priority
= initial_priority
;
3384 sc
->force_deactivate
= 1;
3385 sc
->skipped_deactivate
= 0;
3389 /* Untapped cgroup reserves? Don't OOM, retry. */
3390 if (sc
->memcg_low_skipped
) {
3391 sc
->priority
= initial_priority
;
3392 sc
->force_deactivate
= 0;
3393 sc
->memcg_low_reclaim
= 1;
3394 sc
->memcg_low_skipped
= 0;
3401 static bool allow_direct_reclaim(pg_data_t
*pgdat
)
3404 unsigned long pfmemalloc_reserve
= 0;
3405 unsigned long free_pages
= 0;
3409 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
3412 for (i
= 0; i
<= ZONE_NORMAL
; i
++) {
3413 zone
= &pgdat
->node_zones
[i
];
3414 if (!managed_zone(zone
))
3417 if (!zone_reclaimable_pages(zone
))
3420 pfmemalloc_reserve
+= min_wmark_pages(zone
);
3421 free_pages
+= zone_page_state(zone
, NR_FREE_PAGES
);
3424 /* If there are no reserves (unexpected config) then do not throttle */
3425 if (!pfmemalloc_reserve
)
3428 wmark_ok
= free_pages
> pfmemalloc_reserve
/ 2;
3430 /* kswapd must be awake if processes are being throttled */
3431 if (!wmark_ok
&& waitqueue_active(&pgdat
->kswapd_wait
)) {
3432 if (READ_ONCE(pgdat
->kswapd_highest_zoneidx
) > ZONE_NORMAL
)
3433 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, ZONE_NORMAL
);
3435 wake_up_interruptible(&pgdat
->kswapd_wait
);
3442 * Throttle direct reclaimers if backing storage is backed by the network
3443 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
3444 * depleted. kswapd will continue to make progress and wake the processes
3445 * when the low watermark is reached.
3447 * Returns true if a fatal signal was delivered during throttling. If this
3448 * happens, the page allocator should not consider triggering the OOM killer.
3450 static bool throttle_direct_reclaim(gfp_t gfp_mask
, struct zonelist
*zonelist
,
3451 nodemask_t
*nodemask
)
3455 pg_data_t
*pgdat
= NULL
;
3458 * Kernel threads should not be throttled as they may be indirectly
3459 * responsible for cleaning pages necessary for reclaim to make forward
3460 * progress. kjournald for example may enter direct reclaim while
3461 * committing a transaction where throttling it could forcing other
3462 * processes to block on log_wait_commit().
3464 if (current
->flags
& PF_KTHREAD
)
3468 * If a fatal signal is pending, this process should not throttle.
3469 * It should return quickly so it can exit and free its memory
3471 if (fatal_signal_pending(current
))
3475 * Check if the pfmemalloc reserves are ok by finding the first node
3476 * with a usable ZONE_NORMAL or lower zone. The expectation is that
3477 * GFP_KERNEL will be required for allocating network buffers when
3478 * swapping over the network so ZONE_HIGHMEM is unusable.
3480 * Throttling is based on the first usable node and throttled processes
3481 * wait on a queue until kswapd makes progress and wakes them. There
3482 * is an affinity then between processes waking up and where reclaim
3483 * progress has been made assuming the process wakes on the same node.
3484 * More importantly, processes running on remote nodes will not compete
3485 * for remote pfmemalloc reserves and processes on different nodes
3486 * should make reasonable progress.
3488 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
3489 gfp_zone(gfp_mask
), nodemask
) {
3490 if (zone_idx(zone
) > ZONE_NORMAL
)
3493 /* Throttle based on the first usable node */
3494 pgdat
= zone
->zone_pgdat
;
3495 if (allow_direct_reclaim(pgdat
))
3500 /* If no zone was usable by the allocation flags then do not throttle */
3504 /* Account for the throttling */
3505 count_vm_event(PGSCAN_DIRECT_THROTTLE
);
3508 * If the caller cannot enter the filesystem, it's possible that it
3509 * is due to the caller holding an FS lock or performing a journal
3510 * transaction in the case of a filesystem like ext[3|4]. In this case,
3511 * it is not safe to block on pfmemalloc_wait as kswapd could be
3512 * blocked waiting on the same lock. Instead, throttle for up to a
3513 * second before continuing.
3515 if (!(gfp_mask
& __GFP_FS
))
3516 wait_event_interruptible_timeout(pgdat
->pfmemalloc_wait
,
3517 allow_direct_reclaim(pgdat
), HZ
);
3519 /* Throttle until kswapd wakes the process */
3520 wait_event_killable(zone
->zone_pgdat
->pfmemalloc_wait
,
3521 allow_direct_reclaim(pgdat
));
3523 if (fatal_signal_pending(current
))
3530 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
3531 gfp_t gfp_mask
, nodemask_t
*nodemask
)
3533 unsigned long nr_reclaimed
;
3534 struct scan_control sc
= {
3535 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
3536 .gfp_mask
= current_gfp_context(gfp_mask
),
3537 .reclaim_idx
= gfp_zone(gfp_mask
),
3539 .nodemask
= nodemask
,
3540 .priority
= DEF_PRIORITY
,
3541 .may_writepage
= !laptop_mode
,
3547 * scan_control uses s8 fields for order, priority, and reclaim_idx.
3548 * Confirm they are large enough for max values.
3550 BUILD_BUG_ON(MAX_ORDER
> S8_MAX
);
3551 BUILD_BUG_ON(DEF_PRIORITY
> S8_MAX
);
3552 BUILD_BUG_ON(MAX_NR_ZONES
> S8_MAX
);
3555 * Do not enter reclaim if fatal signal was delivered while throttled.
3556 * 1 is returned so that the page allocator does not OOM kill at this
3559 if (throttle_direct_reclaim(sc
.gfp_mask
, zonelist
, nodemask
))
3562 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3563 trace_mm_vmscan_direct_reclaim_begin(order
, sc
.gfp_mask
);
3565 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3567 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
3568 set_task_reclaim_state(current
, NULL
);
3570 return nr_reclaimed
;
3575 /* Only used by soft limit reclaim. Do not reuse for anything else. */
3576 unsigned long mem_cgroup_shrink_node(struct mem_cgroup
*memcg
,
3577 gfp_t gfp_mask
, bool noswap
,
3579 unsigned long *nr_scanned
)
3581 struct lruvec
*lruvec
= mem_cgroup_lruvec(memcg
, pgdat
);
3582 struct scan_control sc
= {
3583 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
3584 .target_mem_cgroup
= memcg
,
3585 .may_writepage
= !laptop_mode
,
3587 .reclaim_idx
= MAX_NR_ZONES
- 1,
3588 .may_swap
= !noswap
,
3591 WARN_ON_ONCE(!current
->reclaim_state
);
3593 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
3594 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
3596 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc
.order
,
3600 * NOTE: Although we can get the priority field, using it
3601 * here is not a good idea, since it limits the pages we can scan.
3602 * if we don't reclaim here, the shrink_node from balance_pgdat
3603 * will pick up pages from other mem cgroup's as well. We hack
3604 * the priority and make it zero.
3606 shrink_lruvec(lruvec
, &sc
);
3608 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
3610 *nr_scanned
= sc
.nr_scanned
;
3612 return sc
.nr_reclaimed
;
3615 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*memcg
,
3616 unsigned long nr_pages
,
3620 unsigned long nr_reclaimed
;
3621 unsigned int noreclaim_flag
;
3622 struct scan_control sc
= {
3623 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
3624 .gfp_mask
= (current_gfp_context(gfp_mask
) & GFP_RECLAIM_MASK
) |
3625 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
3626 .reclaim_idx
= MAX_NR_ZONES
- 1,
3627 .target_mem_cgroup
= memcg
,
3628 .priority
= DEF_PRIORITY
,
3629 .may_writepage
= !laptop_mode
,
3631 .may_swap
= may_swap
,
3634 * Traverse the ZONELIST_FALLBACK zonelist of the current node to put
3635 * equal pressure on all the nodes. This is based on the assumption that
3636 * the reclaim does not bail out early.
3638 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
3640 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3641 trace_mm_vmscan_memcg_reclaim_begin(0, sc
.gfp_mask
);
3642 noreclaim_flag
= memalloc_noreclaim_save();
3644 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3646 memalloc_noreclaim_restore(noreclaim_flag
);
3647 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
3648 set_task_reclaim_state(current
, NULL
);
3650 return nr_reclaimed
;
3654 static void age_active_anon(struct pglist_data
*pgdat
,
3655 struct scan_control
*sc
)
3657 struct mem_cgroup
*memcg
;
3658 struct lruvec
*lruvec
;
3660 if (!can_age_anon_pages(pgdat
, sc
))
3663 lruvec
= mem_cgroup_lruvec(NULL
, pgdat
);
3664 if (!inactive_is_low(lruvec
, LRU_INACTIVE_ANON
))
3667 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
3669 lruvec
= mem_cgroup_lruvec(memcg
, pgdat
);
3670 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
3671 sc
, LRU_ACTIVE_ANON
);
3672 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
3676 static bool pgdat_watermark_boosted(pg_data_t
*pgdat
, int highest_zoneidx
)
3682 * Check for watermark boosts top-down as the higher zones
3683 * are more likely to be boosted. Both watermarks and boosts
3684 * should not be checked at the same time as reclaim would
3685 * start prematurely when there is no boosting and a lower
3688 for (i
= highest_zoneidx
; i
>= 0; i
--) {
3689 zone
= pgdat
->node_zones
+ i
;
3690 if (!managed_zone(zone
))
3693 if (zone
->watermark_boost
)
3701 * Returns true if there is an eligible zone balanced for the request order
3702 * and highest_zoneidx
3704 static bool pgdat_balanced(pg_data_t
*pgdat
, int order
, int highest_zoneidx
)
3707 unsigned long mark
= -1;
3711 * Check watermarks bottom-up as lower zones are more likely to
3714 for (i
= 0; i
<= highest_zoneidx
; i
++) {
3715 zone
= pgdat
->node_zones
+ i
;
3717 if (!managed_zone(zone
))
3720 mark
= high_wmark_pages(zone
);
3721 if (zone_watermark_ok_safe(zone
, order
, mark
, highest_zoneidx
))
3726 * If a node has no populated zone within highest_zoneidx, it does not
3727 * need balancing by definition. This can happen if a zone-restricted
3728 * allocation tries to wake a remote kswapd.
3736 /* Clear pgdat state for congested, dirty or under writeback. */
3737 static void clear_pgdat_congested(pg_data_t
*pgdat
)
3739 struct lruvec
*lruvec
= mem_cgroup_lruvec(NULL
, pgdat
);
3741 clear_bit(LRUVEC_CONGESTED
, &lruvec
->flags
);
3742 clear_bit(PGDAT_DIRTY
, &pgdat
->flags
);
3743 clear_bit(PGDAT_WRITEBACK
, &pgdat
->flags
);
3747 * Prepare kswapd for sleeping. This verifies that there are no processes
3748 * waiting in throttle_direct_reclaim() and that watermarks have been met.
3750 * Returns true if kswapd is ready to sleep
3752 static bool prepare_kswapd_sleep(pg_data_t
*pgdat
, int order
,
3753 int highest_zoneidx
)
3756 * The throttled processes are normally woken up in balance_pgdat() as
3757 * soon as allow_direct_reclaim() is true. But there is a potential
3758 * race between when kswapd checks the watermarks and a process gets
3759 * throttled. There is also a potential race if processes get
3760 * throttled, kswapd wakes, a large process exits thereby balancing the
3761 * zones, which causes kswapd to exit balance_pgdat() before reaching
3762 * the wake up checks. If kswapd is going to sleep, no process should
3763 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
3764 * the wake up is premature, processes will wake kswapd and get
3765 * throttled again. The difference from wake ups in balance_pgdat() is
3766 * that here we are under prepare_to_wait().
3768 if (waitqueue_active(&pgdat
->pfmemalloc_wait
))
3769 wake_up_all(&pgdat
->pfmemalloc_wait
);
3771 /* Hopeless node, leave it to direct reclaim */
3772 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
3775 if (pgdat_balanced(pgdat
, order
, highest_zoneidx
)) {
3776 clear_pgdat_congested(pgdat
);
3784 * kswapd shrinks a node of pages that are at or below the highest usable
3785 * zone that is currently unbalanced.
3787 * Returns true if kswapd scanned at least the requested number of pages to
3788 * reclaim or if the lack of progress was due to pages under writeback.
3789 * This is used to determine if the scanning priority needs to be raised.
3791 static bool kswapd_shrink_node(pg_data_t
*pgdat
,
3792 struct scan_control
*sc
)
3797 /* Reclaim a number of pages proportional to the number of zones */
3798 sc
->nr_to_reclaim
= 0;
3799 for (z
= 0; z
<= sc
->reclaim_idx
; z
++) {
3800 zone
= pgdat
->node_zones
+ z
;
3801 if (!managed_zone(zone
))
3804 sc
->nr_to_reclaim
+= max(high_wmark_pages(zone
), SWAP_CLUSTER_MAX
);
3808 * Historically care was taken to put equal pressure on all zones but
3809 * now pressure is applied based on node LRU order.
3811 shrink_node(pgdat
, sc
);
3814 * Fragmentation may mean that the system cannot be rebalanced for
3815 * high-order allocations. If twice the allocation size has been
3816 * reclaimed then recheck watermarks only at order-0 to prevent
3817 * excessive reclaim. Assume that a process requested a high-order
3818 * can direct reclaim/compact.
3820 if (sc
->order
&& sc
->nr_reclaimed
>= compact_gap(sc
->order
))
3823 return sc
->nr_scanned
>= sc
->nr_to_reclaim
;
3826 /* Page allocator PCP high watermark is lowered if reclaim is active. */
3828 update_reclaim_active(pg_data_t
*pgdat
, int highest_zoneidx
, bool active
)
3833 for (i
= 0; i
<= highest_zoneidx
; i
++) {
3834 zone
= pgdat
->node_zones
+ i
;
3836 if (!managed_zone(zone
))
3840 set_bit(ZONE_RECLAIM_ACTIVE
, &zone
->flags
);
3842 clear_bit(ZONE_RECLAIM_ACTIVE
, &zone
->flags
);
3847 set_reclaim_active(pg_data_t
*pgdat
, int highest_zoneidx
)
3849 update_reclaim_active(pgdat
, highest_zoneidx
, true);
3853 clear_reclaim_active(pg_data_t
*pgdat
, int highest_zoneidx
)
3855 update_reclaim_active(pgdat
, highest_zoneidx
, false);
3859 * For kswapd, balance_pgdat() will reclaim pages across a node from zones
3860 * that are eligible for use by the caller until at least one zone is
3863 * Returns the order kswapd finished reclaiming at.
3865 * kswapd scans the zones in the highmem->normal->dma direction. It skips
3866 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
3867 * found to have free_pages <= high_wmark_pages(zone), any page in that zone
3868 * or lower is eligible for reclaim until at least one usable zone is
3871 static int balance_pgdat(pg_data_t
*pgdat
, int order
, int highest_zoneidx
)
3874 unsigned long nr_soft_reclaimed
;
3875 unsigned long nr_soft_scanned
;
3876 unsigned long pflags
;
3877 unsigned long nr_boost_reclaim
;
3878 unsigned long zone_boosts
[MAX_NR_ZONES
] = { 0, };
3881 struct scan_control sc
= {
3882 .gfp_mask
= GFP_KERNEL
,
3887 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3888 psi_memstall_enter(&pflags
);
3889 __fs_reclaim_acquire(_THIS_IP_
);
3891 count_vm_event(PAGEOUTRUN
);
3894 * Account for the reclaim boost. Note that the zone boost is left in
3895 * place so that parallel allocations that are near the watermark will
3896 * stall or direct reclaim until kswapd is finished.
3898 nr_boost_reclaim
= 0;
3899 for (i
= 0; i
<= highest_zoneidx
; i
++) {
3900 zone
= pgdat
->node_zones
+ i
;
3901 if (!managed_zone(zone
))
3904 nr_boost_reclaim
+= zone
->watermark_boost
;
3905 zone_boosts
[i
] = zone
->watermark_boost
;
3907 boosted
= nr_boost_reclaim
;
3910 set_reclaim_active(pgdat
, highest_zoneidx
);
3911 sc
.priority
= DEF_PRIORITY
;
3913 unsigned long nr_reclaimed
= sc
.nr_reclaimed
;
3914 bool raise_priority
= true;
3918 sc
.reclaim_idx
= highest_zoneidx
;
3921 * If the number of buffer_heads exceeds the maximum allowed
3922 * then consider reclaiming from all zones. This has a dual
3923 * purpose -- on 64-bit systems it is expected that
3924 * buffer_heads are stripped during active rotation. On 32-bit
3925 * systems, highmem pages can pin lowmem memory and shrinking
3926 * buffers can relieve lowmem pressure. Reclaim may still not
3927 * go ahead if all eligible zones for the original allocation
3928 * request are balanced to avoid excessive reclaim from kswapd.
3930 if (buffer_heads_over_limit
) {
3931 for (i
= MAX_NR_ZONES
- 1; i
>= 0; i
--) {
3932 zone
= pgdat
->node_zones
+ i
;
3933 if (!managed_zone(zone
))
3942 * If the pgdat is imbalanced then ignore boosting and preserve
3943 * the watermarks for a later time and restart. Note that the
3944 * zone watermarks will be still reset at the end of balancing
3945 * on the grounds that the normal reclaim should be enough to
3946 * re-evaluate if boosting is required when kswapd next wakes.
3948 balanced
= pgdat_balanced(pgdat
, sc
.order
, highest_zoneidx
);
3949 if (!balanced
&& nr_boost_reclaim
) {
3950 nr_boost_reclaim
= 0;
3955 * If boosting is not active then only reclaim if there are no
3956 * eligible zones. Note that sc.reclaim_idx is not used as
3957 * buffer_heads_over_limit may have adjusted it.
3959 if (!nr_boost_reclaim
&& balanced
)
3962 /* Limit the priority of boosting to avoid reclaim writeback */
3963 if (nr_boost_reclaim
&& sc
.priority
== DEF_PRIORITY
- 2)
3964 raise_priority
= false;
3967 * Do not writeback or swap pages for boosted reclaim. The
3968 * intent is to relieve pressure not issue sub-optimal IO
3969 * from reclaim context. If no pages are reclaimed, the
3970 * reclaim will be aborted.
3972 sc
.may_writepage
= !laptop_mode
&& !nr_boost_reclaim
;
3973 sc
.may_swap
= !nr_boost_reclaim
;
3976 * Do some background aging of the anon list, to give
3977 * pages a chance to be referenced before reclaiming. All
3978 * pages are rotated regardless of classzone as this is
3979 * about consistent aging.
3981 age_active_anon(pgdat
, &sc
);
3984 * If we're getting trouble reclaiming, start doing writepage
3985 * even in laptop mode.
3987 if (sc
.priority
< DEF_PRIORITY
- 2)
3988 sc
.may_writepage
= 1;
3990 /* Call soft limit reclaim before calling shrink_node. */
3992 nr_soft_scanned
= 0;
3993 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(pgdat
, sc
.order
,
3994 sc
.gfp_mask
, &nr_soft_scanned
);
3995 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
3998 * There should be no need to raise the scanning priority if
3999 * enough pages are already being scanned that that high
4000 * watermark would be met at 100% efficiency.
4002 if (kswapd_shrink_node(pgdat
, &sc
))
4003 raise_priority
= false;
4006 * If the low watermark is met there is no need for processes
4007 * to be throttled on pfmemalloc_wait as they should not be
4008 * able to safely make forward progress. Wake them
4010 if (waitqueue_active(&pgdat
->pfmemalloc_wait
) &&
4011 allow_direct_reclaim(pgdat
))
4012 wake_up_all(&pgdat
->pfmemalloc_wait
);
4014 /* Check if kswapd should be suspending */
4015 __fs_reclaim_release(_THIS_IP_
);
4016 ret
= try_to_freeze();
4017 __fs_reclaim_acquire(_THIS_IP_
);
4018 if (ret
|| kthread_should_stop())
4022 * Raise priority if scanning rate is too low or there was no
4023 * progress in reclaiming pages
4025 nr_reclaimed
= sc
.nr_reclaimed
- nr_reclaimed
;
4026 nr_boost_reclaim
-= min(nr_boost_reclaim
, nr_reclaimed
);
4029 * If reclaim made no progress for a boost, stop reclaim as
4030 * IO cannot be queued and it could be an infinite loop in
4031 * extreme circumstances.
4033 if (nr_boost_reclaim
&& !nr_reclaimed
)
4036 if (raise_priority
|| !nr_reclaimed
)
4038 } while (sc
.priority
>= 1);
4040 if (!sc
.nr_reclaimed
)
4041 pgdat
->kswapd_failures
++;
4044 clear_reclaim_active(pgdat
, highest_zoneidx
);
4046 /* If reclaim was boosted, account for the reclaim done in this pass */
4048 unsigned long flags
;
4050 for (i
= 0; i
<= highest_zoneidx
; i
++) {
4051 if (!zone_boosts
[i
])
4054 /* Increments are under the zone lock */
4055 zone
= pgdat
->node_zones
+ i
;
4056 spin_lock_irqsave(&zone
->lock
, flags
);
4057 zone
->watermark_boost
-= min(zone
->watermark_boost
, zone_boosts
[i
]);
4058 spin_unlock_irqrestore(&zone
->lock
, flags
);
4062 * As there is now likely space, wakeup kcompact to defragment
4065 wakeup_kcompactd(pgdat
, pageblock_order
, highest_zoneidx
);
4068 snapshot_refaults(NULL
, pgdat
);
4069 __fs_reclaim_release(_THIS_IP_
);
4070 psi_memstall_leave(&pflags
);
4071 set_task_reclaim_state(current
, NULL
);
4074 * Return the order kswapd stopped reclaiming at as
4075 * prepare_kswapd_sleep() takes it into account. If another caller
4076 * entered the allocator slow path while kswapd was awake, order will
4077 * remain at the higher level.
4083 * The pgdat->kswapd_highest_zoneidx is used to pass the highest zone index to
4084 * be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is
4085 * not a valid index then either kswapd runs for first time or kswapd couldn't
4086 * sleep after previous reclaim attempt (node is still unbalanced). In that
4087 * case return the zone index of the previous kswapd reclaim cycle.
4089 static enum zone_type
kswapd_highest_zoneidx(pg_data_t
*pgdat
,
4090 enum zone_type prev_highest_zoneidx
)
4092 enum zone_type curr_idx
= READ_ONCE(pgdat
->kswapd_highest_zoneidx
);
4094 return curr_idx
== MAX_NR_ZONES
? prev_highest_zoneidx
: curr_idx
;
4097 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int alloc_order
, int reclaim_order
,
4098 unsigned int highest_zoneidx
)
4103 if (freezing(current
) || kthread_should_stop())
4106 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
4109 * Try to sleep for a short interval. Note that kcompactd will only be
4110 * woken if it is possible to sleep for a short interval. This is
4111 * deliberate on the assumption that if reclaim cannot keep an
4112 * eligible zone balanced that it's also unlikely that compaction will
4115 if (prepare_kswapd_sleep(pgdat
, reclaim_order
, highest_zoneidx
)) {
4117 * Compaction records what page blocks it recently failed to
4118 * isolate pages from and skips them in the future scanning.
4119 * When kswapd is going to sleep, it is reasonable to assume
4120 * that pages and compaction may succeed so reset the cache.
4122 reset_isolation_suitable(pgdat
);
4125 * We have freed the memory, now we should compact it to make
4126 * allocation of the requested order possible.
4128 wakeup_kcompactd(pgdat
, alloc_order
, highest_zoneidx
);
4130 remaining
= schedule_timeout(HZ
/10);
4133 * If woken prematurely then reset kswapd_highest_zoneidx and
4134 * order. The values will either be from a wakeup request or
4135 * the previous request that slept prematurely.
4138 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
,
4139 kswapd_highest_zoneidx(pgdat
,
4142 if (READ_ONCE(pgdat
->kswapd_order
) < reclaim_order
)
4143 WRITE_ONCE(pgdat
->kswapd_order
, reclaim_order
);
4146 finish_wait(&pgdat
->kswapd_wait
, &wait
);
4147 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
4151 * After a short sleep, check if it was a premature sleep. If not, then
4152 * go fully to sleep until explicitly woken up.
4155 prepare_kswapd_sleep(pgdat
, reclaim_order
, highest_zoneidx
)) {
4156 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
4159 * vmstat counters are not perfectly accurate and the estimated
4160 * value for counters such as NR_FREE_PAGES can deviate from the
4161 * true value by nr_online_cpus * threshold. To avoid the zone
4162 * watermarks being breached while under pressure, we reduce the
4163 * per-cpu vmstat threshold while kswapd is awake and restore
4164 * them before going back to sleep.
4166 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
4168 if (!kthread_should_stop())
4171 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
4174 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
4176 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
4178 finish_wait(&pgdat
->kswapd_wait
, &wait
);
4182 * The background pageout daemon, started as a kernel thread
4183 * from the init process.
4185 * This basically trickles out pages so that we have _some_
4186 * free memory available even if there is no other activity
4187 * that frees anything up. This is needed for things like routing
4188 * etc, where we otherwise might have all activity going on in
4189 * asynchronous contexts that cannot page things out.
4191 * If there are applications that are active memory-allocators
4192 * (most normal use), this basically shouldn't matter.
4194 static int kswapd(void *p
)
4196 unsigned int alloc_order
, reclaim_order
;
4197 unsigned int highest_zoneidx
= MAX_NR_ZONES
- 1;
4198 pg_data_t
*pgdat
= (pg_data_t
*)p
;
4199 struct task_struct
*tsk
= current
;
4200 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
4202 if (!cpumask_empty(cpumask
))
4203 set_cpus_allowed_ptr(tsk
, cpumask
);
4206 * Tell the memory management that we're a "memory allocator",
4207 * and that if we need more memory we should get access to it
4208 * regardless (see "__alloc_pages()"). "kswapd" should
4209 * never get caught in the normal page freeing logic.
4211 * (Kswapd normally doesn't need memory anyway, but sometimes
4212 * you need a small amount of memory in order to be able to
4213 * page out something else, and this flag essentially protects
4214 * us from recursively trying to free more memory as we're
4215 * trying to free the first piece of memory in the first place).
4217 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
4220 WRITE_ONCE(pgdat
->kswapd_order
, 0);
4221 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, MAX_NR_ZONES
);
4225 alloc_order
= reclaim_order
= READ_ONCE(pgdat
->kswapd_order
);
4226 highest_zoneidx
= kswapd_highest_zoneidx(pgdat
,
4230 kswapd_try_to_sleep(pgdat
, alloc_order
, reclaim_order
,
4233 /* Read the new order and highest_zoneidx */
4234 alloc_order
= READ_ONCE(pgdat
->kswapd_order
);
4235 highest_zoneidx
= kswapd_highest_zoneidx(pgdat
,
4237 WRITE_ONCE(pgdat
->kswapd_order
, 0);
4238 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, MAX_NR_ZONES
);
4240 ret
= try_to_freeze();
4241 if (kthread_should_stop())
4245 * We can speed up thawing tasks if we don't call balance_pgdat
4246 * after returning from the refrigerator
4252 * Reclaim begins at the requested order but if a high-order
4253 * reclaim fails then kswapd falls back to reclaiming for
4254 * order-0. If that happens, kswapd will consider sleeping
4255 * for the order it finished reclaiming at (reclaim_order)
4256 * but kcompactd is woken to compact for the original
4257 * request (alloc_order).
4259 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, highest_zoneidx
,
4261 reclaim_order
= balance_pgdat(pgdat
, alloc_order
,
4263 if (reclaim_order
< alloc_order
)
4264 goto kswapd_try_sleep
;
4267 tsk
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
);
4273 * A zone is low on free memory or too fragmented for high-order memory. If
4274 * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
4275 * pgdat. It will wake up kcompactd after reclaiming memory. If kswapd reclaim
4276 * has failed or is not needed, still wake up kcompactd if only compaction is
4279 void wakeup_kswapd(struct zone
*zone
, gfp_t gfp_flags
, int order
,
4280 enum zone_type highest_zoneidx
)
4283 enum zone_type curr_idx
;
4285 if (!managed_zone(zone
))
4288 if (!cpuset_zone_allowed(zone
, gfp_flags
))
4291 pgdat
= zone
->zone_pgdat
;
4292 curr_idx
= READ_ONCE(pgdat
->kswapd_highest_zoneidx
);
4294 if (curr_idx
== MAX_NR_ZONES
|| curr_idx
< highest_zoneidx
)
4295 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, highest_zoneidx
);
4297 if (READ_ONCE(pgdat
->kswapd_order
) < order
)
4298 WRITE_ONCE(pgdat
->kswapd_order
, order
);
4300 if (!waitqueue_active(&pgdat
->kswapd_wait
))
4303 /* Hopeless node, leave it to direct reclaim if possible */
4304 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
||
4305 (pgdat_balanced(pgdat
, order
, highest_zoneidx
) &&
4306 !pgdat_watermark_boosted(pgdat
, highest_zoneidx
))) {
4308 * There may be plenty of free memory available, but it's too
4309 * fragmented for high-order allocations. Wake up kcompactd
4310 * and rely on compaction_suitable() to determine if it's
4311 * needed. If it fails, it will defer subsequent attempts to
4312 * ratelimit its work.
4314 if (!(gfp_flags
& __GFP_DIRECT_RECLAIM
))
4315 wakeup_kcompactd(pgdat
, order
, highest_zoneidx
);
4319 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, highest_zoneidx
, order
,
4321 wake_up_interruptible(&pgdat
->kswapd_wait
);
4324 #ifdef CONFIG_HIBERNATION
4326 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
4329 * Rather than trying to age LRUs the aim is to preserve the overall
4330 * LRU order by reclaiming preferentially
4331 * inactive > active > active referenced > active mapped
4333 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
4335 struct scan_control sc
= {
4336 .nr_to_reclaim
= nr_to_reclaim
,
4337 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
4338 .reclaim_idx
= MAX_NR_ZONES
- 1,
4339 .priority
= DEF_PRIORITY
,
4343 .hibernation_mode
= 1,
4345 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
4346 unsigned long nr_reclaimed
;
4347 unsigned int noreclaim_flag
;
4349 fs_reclaim_acquire(sc
.gfp_mask
);
4350 noreclaim_flag
= memalloc_noreclaim_save();
4351 set_task_reclaim_state(current
, &sc
.reclaim_state
);
4353 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
4355 set_task_reclaim_state(current
, NULL
);
4356 memalloc_noreclaim_restore(noreclaim_flag
);
4357 fs_reclaim_release(sc
.gfp_mask
);
4359 return nr_reclaimed
;
4361 #endif /* CONFIG_HIBERNATION */
4364 * This kswapd start function will be called by init and node-hot-add.
4365 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
4367 void kswapd_run(int nid
)
4369 pg_data_t
*pgdat
= NODE_DATA(nid
);
4374 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
4375 if (IS_ERR(pgdat
->kswapd
)) {
4376 /* failure at boot is fatal */
4377 BUG_ON(system_state
< SYSTEM_RUNNING
);
4378 pr_err("Failed to start kswapd on node %d\n", nid
);
4379 pgdat
->kswapd
= NULL
;
4384 * Called by memory hotplug when all memory in a node is offlined. Caller must
4385 * hold mem_hotplug_begin/end().
4387 void kswapd_stop(int nid
)
4389 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
4392 kthread_stop(kswapd
);
4393 NODE_DATA(nid
)->kswapd
= NULL
;
4397 static int __init
kswapd_init(void)
4402 for_each_node_state(nid
, N_MEMORY
)
4407 module_init(kswapd_init
)
4413 * If non-zero call node_reclaim when the number of free pages falls below
4416 int node_reclaim_mode __read_mostly
;
4419 * Priority for NODE_RECLAIM. This determines the fraction of pages
4420 * of a node considered for each zone_reclaim. 4 scans 1/16th of
4423 #define NODE_RECLAIM_PRIORITY 4
4426 * Percentage of pages in a zone that must be unmapped for node_reclaim to
4429 int sysctl_min_unmapped_ratio
= 1;
4432 * If the number of slab pages in a zone grows beyond this percentage then
4433 * slab reclaim needs to occur.
4435 int sysctl_min_slab_ratio
= 5;
4437 static inline unsigned long node_unmapped_file_pages(struct pglist_data
*pgdat
)
4439 unsigned long file_mapped
= node_page_state(pgdat
, NR_FILE_MAPPED
);
4440 unsigned long file_lru
= node_page_state(pgdat
, NR_INACTIVE_FILE
) +
4441 node_page_state(pgdat
, NR_ACTIVE_FILE
);
4444 * It's possible for there to be more file mapped pages than
4445 * accounted for by the pages on the file LRU lists because
4446 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
4448 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
4451 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
4452 static unsigned long node_pagecache_reclaimable(struct pglist_data
*pgdat
)
4454 unsigned long nr_pagecache_reclaimable
;
4455 unsigned long delta
= 0;
4458 * If RECLAIM_UNMAP is set, then all file pages are considered
4459 * potentially reclaimable. Otherwise, we have to worry about
4460 * pages like swapcache and node_unmapped_file_pages() provides
4463 if (node_reclaim_mode
& RECLAIM_UNMAP
)
4464 nr_pagecache_reclaimable
= node_page_state(pgdat
, NR_FILE_PAGES
);
4466 nr_pagecache_reclaimable
= node_unmapped_file_pages(pgdat
);
4468 /* If we can't clean pages, remove dirty pages from consideration */
4469 if (!(node_reclaim_mode
& RECLAIM_WRITE
))
4470 delta
+= node_page_state(pgdat
, NR_FILE_DIRTY
);
4472 /* Watch for any possible underflows due to delta */
4473 if (unlikely(delta
> nr_pagecache_reclaimable
))
4474 delta
= nr_pagecache_reclaimable
;
4476 return nr_pagecache_reclaimable
- delta
;
4480 * Try to free up some pages from this node through reclaim.
4482 static int __node_reclaim(struct pglist_data
*pgdat
, gfp_t gfp_mask
, unsigned int order
)
4484 /* Minimum pages needed in order to stay on node */
4485 const unsigned long nr_pages
= 1 << order
;
4486 struct task_struct
*p
= current
;
4487 unsigned int noreclaim_flag
;
4488 struct scan_control sc
= {
4489 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
4490 .gfp_mask
= current_gfp_context(gfp_mask
),
4492 .priority
= NODE_RECLAIM_PRIORITY
,
4493 .may_writepage
= !!(node_reclaim_mode
& RECLAIM_WRITE
),
4494 .may_unmap
= !!(node_reclaim_mode
& RECLAIM_UNMAP
),
4496 .reclaim_idx
= gfp_zone(gfp_mask
),
4498 unsigned long pflags
;
4500 trace_mm_vmscan_node_reclaim_begin(pgdat
->node_id
, order
,
4504 psi_memstall_enter(&pflags
);
4505 fs_reclaim_acquire(sc
.gfp_mask
);
4507 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
4508 * and we also need to be able to write out pages for RECLAIM_WRITE
4509 * and RECLAIM_UNMAP.
4511 noreclaim_flag
= memalloc_noreclaim_save();
4512 p
->flags
|= PF_SWAPWRITE
;
4513 set_task_reclaim_state(p
, &sc
.reclaim_state
);
4515 if (node_pagecache_reclaimable(pgdat
) > pgdat
->min_unmapped_pages
) {
4517 * Free memory by calling shrink node with increasing
4518 * priorities until we have enough memory freed.
4521 shrink_node(pgdat
, &sc
);
4522 } while (sc
.nr_reclaimed
< nr_pages
&& --sc
.priority
>= 0);
4525 set_task_reclaim_state(p
, NULL
);
4526 current
->flags
&= ~PF_SWAPWRITE
;
4527 memalloc_noreclaim_restore(noreclaim_flag
);
4528 fs_reclaim_release(sc
.gfp_mask
);
4529 psi_memstall_leave(&pflags
);
4531 trace_mm_vmscan_node_reclaim_end(sc
.nr_reclaimed
);
4533 return sc
.nr_reclaimed
>= nr_pages
;
4536 int node_reclaim(struct pglist_data
*pgdat
, gfp_t gfp_mask
, unsigned int order
)
4541 * Node reclaim reclaims unmapped file backed pages and
4542 * slab pages if we are over the defined limits.
4544 * A small portion of unmapped file backed pages is needed for
4545 * file I/O otherwise pages read by file I/O will be immediately
4546 * thrown out if the node is overallocated. So we do not reclaim
4547 * if less than a specified percentage of the node is used by
4548 * unmapped file backed pages.
4550 if (node_pagecache_reclaimable(pgdat
) <= pgdat
->min_unmapped_pages
&&
4551 node_page_state_pages(pgdat
, NR_SLAB_RECLAIMABLE_B
) <=
4552 pgdat
->min_slab_pages
)
4553 return NODE_RECLAIM_FULL
;
4556 * Do not scan if the allocation should not be delayed.
4558 if (!gfpflags_allow_blocking(gfp_mask
) || (current
->flags
& PF_MEMALLOC
))
4559 return NODE_RECLAIM_NOSCAN
;
4562 * Only run node reclaim on the local node or on nodes that do not
4563 * have associated processors. This will favor the local processor
4564 * over remote processors and spread off node memory allocations
4565 * as wide as possible.
4567 if (node_state(pgdat
->node_id
, N_CPU
) && pgdat
->node_id
!= numa_node_id())
4568 return NODE_RECLAIM_NOSCAN
;
4570 if (test_and_set_bit(PGDAT_RECLAIM_LOCKED
, &pgdat
->flags
))
4571 return NODE_RECLAIM_NOSCAN
;
4573 ret
= __node_reclaim(pgdat
, gfp_mask
, order
);
4574 clear_bit(PGDAT_RECLAIM_LOCKED
, &pgdat
->flags
);
4577 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
4584 * check_move_unevictable_pages - check pages for evictability and move to
4585 * appropriate zone lru list
4586 * @pvec: pagevec with lru pages to check
4588 * Checks pages for evictability, if an evictable page is in the unevictable
4589 * lru list, moves it to the appropriate evictable lru list. This function
4590 * should be only used for lru pages.
4592 void check_move_unevictable_pages(struct pagevec
*pvec
)
4594 struct lruvec
*lruvec
= NULL
;
4599 for (i
= 0; i
< pvec
->nr
; i
++) {
4600 struct page
*page
= pvec
->pages
[i
];
4603 if (PageTransTail(page
))
4606 nr_pages
= thp_nr_pages(page
);
4607 pgscanned
+= nr_pages
;
4609 /* block memcg migration during page moving between lru */
4610 if (!TestClearPageLRU(page
))
4613 lruvec
= relock_page_lruvec_irq(page
, lruvec
);
4614 if (page_evictable(page
) && PageUnevictable(page
)) {
4615 del_page_from_lru_list(page
, lruvec
);
4616 ClearPageUnevictable(page
);
4617 add_page_to_lru_list(page
, lruvec
);
4618 pgrescued
+= nr_pages
;
4624 __count_vm_events(UNEVICTABLE_PGRESCUED
, pgrescued
);
4625 __count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
4626 unlock_page_lruvec_irq(lruvec
);
4627 } else if (pgscanned
) {
4628 count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
4631 EXPORT_SYMBOL_GPL(check_move_unevictable_pages
);