4843 строки
138 KiB
C
4843 строки
138 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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*
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* Swap reorganised 29.12.95, Stephen Tweedie.
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* kswapd added: 7.1.96 sct
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* Removed kswapd_ctl limits, and swap out as many pages as needed
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* to bring the system back to freepages.high: 2.4.97, Rik van Riel.
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* Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
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* Multiqueue VM started 5.8.00, Rik van Riel.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/mm.h>
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#include <linux/sched/mm.h>
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#include <linux/module.h>
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#include <linux/gfp.h>
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#include <linux/kernel_stat.h>
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#include <linux/swap.h>
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#include <linux/pagemap.h>
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#include <linux/init.h>
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#include <linux/highmem.h>
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#include <linux/vmpressure.h>
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#include <linux/vmstat.h>
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#include <linux/file.h>
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#include <linux/writeback.h>
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#include <linux/blkdev.h>
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#include <linux/buffer_head.h> /* for try_to_release_page(),
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buffer_heads_over_limit */
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#include <linux/mm_inline.h>
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#include <linux/backing-dev.h>
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#include <linux/rmap.h>
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#include <linux/topology.h>
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#include <linux/cpu.h>
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#include <linux/cpuset.h>
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#include <linux/compaction.h>
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#include <linux/notifier.h>
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#include <linux/rwsem.h>
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#include <linux/delay.h>
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#include <linux/kthread.h>
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#include <linux/freezer.h>
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#include <linux/memcontrol.h>
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#include <linux/migrate.h>
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#include <linux/delayacct.h>
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#include <linux/sysctl.h>
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#include <linux/oom.h>
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#include <linux/pagevec.h>
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#include <linux/prefetch.h>
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#include <linux/printk.h>
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#include <linux/dax.h>
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#include <linux/psi.h>
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#include <asm/tlbflush.h>
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#include <asm/div64.h>
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#include <linux/swapops.h>
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#include <linux/balloon_compaction.h>
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#include <linux/sched/sysctl.h>
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#include "internal.h"
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#include "swap.h"
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#define CREATE_TRACE_POINTS
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#include <trace/events/vmscan.h>
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struct scan_control {
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/* How many pages shrink_list() should reclaim */
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unsigned long nr_to_reclaim;
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/*
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* Nodemask of nodes allowed by the caller. If NULL, all nodes
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* are scanned.
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*/
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nodemask_t *nodemask;
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/*
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* The memory cgroup that hit its limit and as a result is the
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* primary target of this reclaim invocation.
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*/
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struct mem_cgroup *target_mem_cgroup;
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/*
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* Scan pressure balancing between anon and file LRUs
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*/
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unsigned long anon_cost;
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unsigned long file_cost;
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/* Can active pages be deactivated as part of reclaim? */
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#define DEACTIVATE_ANON 1
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#define DEACTIVATE_FILE 2
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unsigned int may_deactivate:2;
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unsigned int force_deactivate:1;
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unsigned int skipped_deactivate:1;
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/* Writepage batching in laptop mode; RECLAIM_WRITE */
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unsigned int may_writepage:1;
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/* Can mapped pages be reclaimed? */
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unsigned int may_unmap:1;
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/* Can pages be swapped as part of reclaim? */
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unsigned int may_swap:1;
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/*
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* Cgroup memory below memory.low is protected as long as we
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* don't threaten to OOM. If any cgroup is reclaimed at
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* reduced force or passed over entirely due to its memory.low
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* setting (memcg_low_skipped), and nothing is reclaimed as a
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* result, then go back for one more cycle that reclaims the protected
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* memory (memcg_low_reclaim) to avert OOM.
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*/
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unsigned int memcg_low_reclaim:1;
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unsigned int memcg_low_skipped:1;
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unsigned int hibernation_mode:1;
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/* One of the zones is ready for compaction */
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unsigned int compaction_ready:1;
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/* There is easily reclaimable cold cache in the current node */
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unsigned int cache_trim_mode:1;
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/* The file pages on the current node are dangerously low */
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unsigned int file_is_tiny:1;
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/* Always discard instead of demoting to lower tier memory */
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unsigned int no_demotion:1;
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/* Allocation order */
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s8 order;
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/* Scan (total_size >> priority) pages at once */
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s8 priority;
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/* The highest zone to isolate pages for reclaim from */
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s8 reclaim_idx;
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/* This context's GFP mask */
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gfp_t gfp_mask;
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/* Incremented by the number of inactive pages that were scanned */
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unsigned long nr_scanned;
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/* Number of pages freed so far during a call to shrink_zones() */
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unsigned long nr_reclaimed;
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struct {
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unsigned int dirty;
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unsigned int unqueued_dirty;
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unsigned int congested;
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unsigned int writeback;
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unsigned int immediate;
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unsigned int file_taken;
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unsigned int taken;
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} nr;
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/* for recording the reclaimed slab by now */
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struct reclaim_state reclaim_state;
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};
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#ifdef ARCH_HAS_PREFETCHW
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#define prefetchw_prev_lru_page(_page, _base, _field) \
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do { \
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if ((_page)->lru.prev != _base) { \
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struct page *prev; \
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\
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prev = lru_to_page(&(_page->lru)); \
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prefetchw(&prev->_field); \
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} \
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} while (0)
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#else
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#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
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#endif
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/*
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* From 0 .. 200. Higher means more swappy.
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*/
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int vm_swappiness = 60;
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static void set_task_reclaim_state(struct task_struct *task,
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struct reclaim_state *rs)
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{
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/* Check for an overwrite */
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WARN_ON_ONCE(rs && task->reclaim_state);
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/* Check for the nulling of an already-nulled member */
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WARN_ON_ONCE(!rs && !task->reclaim_state);
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task->reclaim_state = rs;
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}
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static LIST_HEAD(shrinker_list);
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static DECLARE_RWSEM(shrinker_rwsem);
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#ifdef CONFIG_MEMCG
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static int shrinker_nr_max;
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/* The shrinker_info is expanded in a batch of BITS_PER_LONG */
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static inline int shrinker_map_size(int nr_items)
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{
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return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
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}
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static inline int shrinker_defer_size(int nr_items)
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{
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return (round_up(nr_items, BITS_PER_LONG) * sizeof(atomic_long_t));
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}
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static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg,
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int nid)
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{
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return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
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lockdep_is_held(&shrinker_rwsem));
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}
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static int expand_one_shrinker_info(struct mem_cgroup *memcg,
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int map_size, int defer_size,
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int old_map_size, int old_defer_size)
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{
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struct shrinker_info *new, *old;
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struct mem_cgroup_per_node *pn;
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int nid;
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int size = map_size + defer_size;
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for_each_node(nid) {
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pn = memcg->nodeinfo[nid];
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old = shrinker_info_protected(memcg, nid);
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/* Not yet online memcg */
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if (!old)
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return 0;
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new = kvmalloc_node(sizeof(*new) + size, GFP_KERNEL, nid);
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if (!new)
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return -ENOMEM;
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new->nr_deferred = (atomic_long_t *)(new + 1);
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new->map = (void *)new->nr_deferred + defer_size;
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/* map: set all old bits, clear all new bits */
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memset(new->map, (int)0xff, old_map_size);
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memset((void *)new->map + old_map_size, 0, map_size - old_map_size);
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/* nr_deferred: copy old values, clear all new values */
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memcpy(new->nr_deferred, old->nr_deferred, old_defer_size);
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memset((void *)new->nr_deferred + old_defer_size, 0,
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defer_size - old_defer_size);
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rcu_assign_pointer(pn->shrinker_info, new);
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kvfree_rcu(old, rcu);
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}
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return 0;
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}
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void free_shrinker_info(struct mem_cgroup *memcg)
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{
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struct mem_cgroup_per_node *pn;
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struct shrinker_info *info;
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int nid;
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for_each_node(nid) {
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pn = memcg->nodeinfo[nid];
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info = rcu_dereference_protected(pn->shrinker_info, true);
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kvfree(info);
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rcu_assign_pointer(pn->shrinker_info, NULL);
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}
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}
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int alloc_shrinker_info(struct mem_cgroup *memcg)
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{
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struct shrinker_info *info;
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int nid, size, ret = 0;
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int map_size, defer_size = 0;
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down_write(&shrinker_rwsem);
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map_size = shrinker_map_size(shrinker_nr_max);
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defer_size = shrinker_defer_size(shrinker_nr_max);
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size = map_size + defer_size;
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for_each_node(nid) {
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info = kvzalloc_node(sizeof(*info) + size, GFP_KERNEL, nid);
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if (!info) {
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free_shrinker_info(memcg);
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ret = -ENOMEM;
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break;
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}
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info->nr_deferred = (atomic_long_t *)(info + 1);
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info->map = (void *)info->nr_deferred + defer_size;
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rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
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}
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up_write(&shrinker_rwsem);
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return ret;
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}
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static inline bool need_expand(int nr_max)
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{
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return round_up(nr_max, BITS_PER_LONG) >
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round_up(shrinker_nr_max, BITS_PER_LONG);
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}
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static int expand_shrinker_info(int new_id)
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{
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int ret = 0;
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int new_nr_max = new_id + 1;
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int map_size, defer_size = 0;
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int old_map_size, old_defer_size = 0;
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struct mem_cgroup *memcg;
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if (!need_expand(new_nr_max))
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goto out;
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if (!root_mem_cgroup)
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goto out;
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lockdep_assert_held(&shrinker_rwsem);
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map_size = shrinker_map_size(new_nr_max);
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defer_size = shrinker_defer_size(new_nr_max);
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old_map_size = shrinker_map_size(shrinker_nr_max);
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old_defer_size = shrinker_defer_size(shrinker_nr_max);
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memcg = mem_cgroup_iter(NULL, NULL, NULL);
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do {
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ret = expand_one_shrinker_info(memcg, map_size, defer_size,
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old_map_size, old_defer_size);
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if (ret) {
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mem_cgroup_iter_break(NULL, memcg);
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goto out;
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}
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} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
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out:
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if (!ret)
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shrinker_nr_max = new_nr_max;
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return ret;
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}
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void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
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{
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if (shrinker_id >= 0 && memcg && !mem_cgroup_is_root(memcg)) {
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struct shrinker_info *info;
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rcu_read_lock();
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info = rcu_dereference(memcg->nodeinfo[nid]->shrinker_info);
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/* Pairs with smp mb in shrink_slab() */
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smp_mb__before_atomic();
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set_bit(shrinker_id, info->map);
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rcu_read_unlock();
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}
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}
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static DEFINE_IDR(shrinker_idr);
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static int prealloc_memcg_shrinker(struct shrinker *shrinker)
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{
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int id, ret = -ENOMEM;
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if (mem_cgroup_disabled())
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return -ENOSYS;
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down_write(&shrinker_rwsem);
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/* This may call shrinker, so it must use down_read_trylock() */
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id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
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if (id < 0)
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goto unlock;
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if (id >= shrinker_nr_max) {
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if (expand_shrinker_info(id)) {
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idr_remove(&shrinker_idr, id);
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goto unlock;
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}
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}
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shrinker->id = id;
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ret = 0;
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unlock:
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up_write(&shrinker_rwsem);
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return ret;
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}
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static void unregister_memcg_shrinker(struct shrinker *shrinker)
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{
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int id = shrinker->id;
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BUG_ON(id < 0);
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lockdep_assert_held(&shrinker_rwsem);
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idr_remove(&shrinker_idr, id);
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}
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static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker,
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struct mem_cgroup *memcg)
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{
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struct shrinker_info *info;
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info = shrinker_info_protected(memcg, nid);
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return atomic_long_xchg(&info->nr_deferred[shrinker->id], 0);
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}
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static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
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struct mem_cgroup *memcg)
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{
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struct shrinker_info *info;
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info = shrinker_info_protected(memcg, nid);
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return atomic_long_add_return(nr, &info->nr_deferred[shrinker->id]);
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}
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void reparent_shrinker_deferred(struct mem_cgroup *memcg)
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{
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int i, nid;
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long nr;
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struct mem_cgroup *parent;
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struct shrinker_info *child_info, *parent_info;
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parent = parent_mem_cgroup(memcg);
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if (!parent)
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parent = root_mem_cgroup;
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/* Prevent from concurrent shrinker_info expand */
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down_read(&shrinker_rwsem);
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for_each_node(nid) {
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child_info = shrinker_info_protected(memcg, nid);
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parent_info = shrinker_info_protected(parent, nid);
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for (i = 0; i < shrinker_nr_max; i++) {
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nr = atomic_long_read(&child_info->nr_deferred[i]);
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atomic_long_add(nr, &parent_info->nr_deferred[i]);
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}
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}
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up_read(&shrinker_rwsem);
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}
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static bool cgroup_reclaim(struct scan_control *sc)
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{
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return sc->target_mem_cgroup;
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}
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/**
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* writeback_throttling_sane - is the usual dirty throttling mechanism available?
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* @sc: scan_control in question
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*
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* The normal page dirty throttling mechanism in balance_dirty_pages() is
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* completely broken with the legacy memcg and direct stalling in
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* shrink_page_list() is used for throttling instead, which lacks all the
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* niceties such as fairness, adaptive pausing, bandwidth proportional
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* allocation and configurability.
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*
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* This function tests whether the vmscan currently in progress can assume
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* that the normal dirty throttling mechanism is operational.
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*/
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static bool writeback_throttling_sane(struct scan_control *sc)
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{
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if (!cgroup_reclaim(sc))
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return true;
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#ifdef CONFIG_CGROUP_WRITEBACK
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if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
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return true;
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#endif
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return false;
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}
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#else
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static int prealloc_memcg_shrinker(struct shrinker *shrinker)
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{
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return -ENOSYS;
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}
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static void unregister_memcg_shrinker(struct shrinker *shrinker)
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{
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}
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static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker,
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struct mem_cgroup *memcg)
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{
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return 0;
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}
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static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
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struct mem_cgroup *memcg)
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{
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return 0;
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}
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static bool cgroup_reclaim(struct scan_control *sc)
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{
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return false;
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}
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static bool writeback_throttling_sane(struct scan_control *sc)
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{
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return true;
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}
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#endif
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static long xchg_nr_deferred(struct shrinker *shrinker,
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struct shrink_control *sc)
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{
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int nid = sc->nid;
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if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
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nid = 0;
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if (sc->memcg &&
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(shrinker->flags & SHRINKER_MEMCG_AWARE))
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return xchg_nr_deferred_memcg(nid, shrinker,
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sc->memcg);
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return atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
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}
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static long add_nr_deferred(long nr, struct shrinker *shrinker,
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struct shrink_control *sc)
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{
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int nid = sc->nid;
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if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
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nid = 0;
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if (sc->memcg &&
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(shrinker->flags & SHRINKER_MEMCG_AWARE))
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return add_nr_deferred_memcg(nr, nid, shrinker,
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|
sc->memcg);
|
|
|
|
return atomic_long_add_return(nr, &shrinker->nr_deferred[nid]);
|
|
}
|
|
|
|
static bool can_demote(int nid, struct scan_control *sc)
|
|
{
|
|
if (!numa_demotion_enabled)
|
|
return false;
|
|
if (sc && sc->no_demotion)
|
|
return false;
|
|
if (next_demotion_node(nid) == NUMA_NO_NODE)
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
|
|
int nid,
|
|
struct scan_control *sc)
|
|
{
|
|
if (memcg == NULL) {
|
|
/*
|
|
* For non-memcg reclaim, is there
|
|
* space in any swap device?
|
|
*/
|
|
if (get_nr_swap_pages() > 0)
|
|
return true;
|
|
} else {
|
|
/* Is the memcg below its swap limit? */
|
|
if (mem_cgroup_get_nr_swap_pages(memcg) > 0)
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* The page can not be swapped.
|
|
*
|
|
* Can it be reclaimed from this node via demotion?
|
|
*/
|
|
return can_demote(nid, sc);
|
|
}
|
|
|
|
/*
|
|
* This misses isolated pages which are not accounted for to save counters.
|
|
* As the data only determines if reclaim or compaction continues, it is
|
|
* not expected that isolated pages will be a dominating factor.
|
|
*/
|
|
unsigned long zone_reclaimable_pages(struct zone *zone)
|
|
{
|
|
unsigned long nr;
|
|
|
|
nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) +
|
|
zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE);
|
|
if (can_reclaim_anon_pages(NULL, zone_to_nid(zone), NULL))
|
|
nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) +
|
|
zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON);
|
|
|
|
return nr;
|
|
}
|
|
|
|
/**
|
|
* lruvec_lru_size - Returns the number of pages on the given LRU list.
|
|
* @lruvec: lru vector
|
|
* @lru: lru to use
|
|
* @zone_idx: zones to consider (use MAX_NR_ZONES - 1 for the whole LRU list)
|
|
*/
|
|
static unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru,
|
|
int zone_idx)
|
|
{
|
|
unsigned long size = 0;
|
|
int zid;
|
|
|
|
for (zid = 0; zid <= zone_idx; zid++) {
|
|
struct zone *zone = &lruvec_pgdat(lruvec)->node_zones[zid];
|
|
|
|
if (!managed_zone(zone))
|
|
continue;
|
|
|
|
if (!mem_cgroup_disabled())
|
|
size += mem_cgroup_get_zone_lru_size(lruvec, lru, zid);
|
|
else
|
|
size += zone_page_state(zone, NR_ZONE_LRU_BASE + lru);
|
|
}
|
|
return size;
|
|
}
|
|
|
|
/*
|
|
* Add a shrinker callback to be called from the vm.
|
|
*/
|
|
int prealloc_shrinker(struct shrinker *shrinker)
|
|
{
|
|
unsigned int size;
|
|
int err;
|
|
|
|
if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
|
|
err = prealloc_memcg_shrinker(shrinker);
|
|
if (err != -ENOSYS)
|
|
return err;
|
|
|
|
shrinker->flags &= ~SHRINKER_MEMCG_AWARE;
|
|
}
|
|
|
|
size = sizeof(*shrinker->nr_deferred);
|
|
if (shrinker->flags & SHRINKER_NUMA_AWARE)
|
|
size *= nr_node_ids;
|
|
|
|
shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
|
|
if (!shrinker->nr_deferred)
|
|
return -ENOMEM;
|
|
|
|
return 0;
|
|
}
|
|
|
|
void free_prealloced_shrinker(struct shrinker *shrinker)
|
|
{
|
|
if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
|
|
down_write(&shrinker_rwsem);
|
|
unregister_memcg_shrinker(shrinker);
|
|
up_write(&shrinker_rwsem);
|
|
return;
|
|
}
|
|
|
|
kfree(shrinker->nr_deferred);
|
|
shrinker->nr_deferred = NULL;
|
|
}
|
|
|
|
void register_shrinker_prepared(struct shrinker *shrinker)
|
|
{
|
|
down_write(&shrinker_rwsem);
|
|
list_add_tail(&shrinker->list, &shrinker_list);
|
|
shrinker->flags |= SHRINKER_REGISTERED;
|
|
up_write(&shrinker_rwsem);
|
|
}
|
|
|
|
int register_shrinker(struct shrinker *shrinker)
|
|
{
|
|
int err = prealloc_shrinker(shrinker);
|
|
|
|
if (err)
|
|
return err;
|
|
register_shrinker_prepared(shrinker);
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(register_shrinker);
|
|
|
|
/*
|
|
* Remove one
|
|
*/
|
|
void unregister_shrinker(struct shrinker *shrinker)
|
|
{
|
|
if (!(shrinker->flags & SHRINKER_REGISTERED))
|
|
return;
|
|
|
|
down_write(&shrinker_rwsem);
|
|
list_del(&shrinker->list);
|
|
shrinker->flags &= ~SHRINKER_REGISTERED;
|
|
if (shrinker->flags & SHRINKER_MEMCG_AWARE)
|
|
unregister_memcg_shrinker(shrinker);
|
|
up_write(&shrinker_rwsem);
|
|
|
|
kfree(shrinker->nr_deferred);
|
|
shrinker->nr_deferred = NULL;
|
|
}
|
|
EXPORT_SYMBOL(unregister_shrinker);
|
|
|
|
/**
|
|
* synchronize_shrinkers - Wait for all running shrinkers to complete.
|
|
*
|
|
* This is equivalent to calling unregister_shrink() and register_shrinker(),
|
|
* but atomically and with less overhead. This is useful to guarantee that all
|
|
* shrinker invocations have seen an update, before freeing memory, similar to
|
|
* rcu.
|
|
*/
|
|
void synchronize_shrinkers(void)
|
|
{
|
|
down_write(&shrinker_rwsem);
|
|
up_write(&shrinker_rwsem);
|
|
}
|
|
EXPORT_SYMBOL(synchronize_shrinkers);
|
|
|
|
#define SHRINK_BATCH 128
|
|
|
|
static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
|
|
struct shrinker *shrinker, int priority)
|
|
{
|
|
unsigned long freed = 0;
|
|
unsigned long long delta;
|
|
long total_scan;
|
|
long freeable;
|
|
long nr;
|
|
long new_nr;
|
|
long batch_size = shrinker->batch ? shrinker->batch
|
|
: SHRINK_BATCH;
|
|
long scanned = 0, next_deferred;
|
|
|
|
freeable = shrinker->count_objects(shrinker, shrinkctl);
|
|
if (freeable == 0 || freeable == SHRINK_EMPTY)
|
|
return freeable;
|
|
|
|
/*
|
|
* copy the current shrinker scan count into a local variable
|
|
* and zero it so that other concurrent shrinker invocations
|
|
* don't also do this scanning work.
|
|
*/
|
|
nr = xchg_nr_deferred(shrinker, shrinkctl);
|
|
|
|
if (shrinker->seeks) {
|
|
delta = freeable >> priority;
|
|
delta *= 4;
|
|
do_div(delta, shrinker->seeks);
|
|
} else {
|
|
/*
|
|
* These objects don't require any IO to create. Trim
|
|
* them aggressively under memory pressure to keep
|
|
* them from causing refetches in the IO caches.
|
|
*/
|
|
delta = freeable / 2;
|
|
}
|
|
|
|
total_scan = nr >> priority;
|
|
total_scan += delta;
|
|
total_scan = min(total_scan, (2 * freeable));
|
|
|
|
trace_mm_shrink_slab_start(shrinker, shrinkctl, nr,
|
|
freeable, delta, total_scan, priority);
|
|
|
|
/*
|
|
* Normally, we should not scan less than batch_size objects in one
|
|
* pass to avoid too frequent shrinker calls, but if the slab has less
|
|
* than batch_size objects in total and we are really tight on memory,
|
|
* we will try to reclaim all available objects, otherwise we can end
|
|
* up failing allocations although there are plenty of reclaimable
|
|
* objects spread over several slabs with usage less than the
|
|
* batch_size.
|
|
*
|
|
* We detect the "tight on memory" situations by looking at the total
|
|
* number of objects we want to scan (total_scan). If it is greater
|
|
* than the total number of objects on slab (freeable), we must be
|
|
* scanning at high prio and therefore should try to reclaim as much as
|
|
* possible.
|
|
*/
|
|
while (total_scan >= batch_size ||
|
|
total_scan >= freeable) {
|
|
unsigned long ret;
|
|
unsigned long nr_to_scan = min(batch_size, total_scan);
|
|
|
|
shrinkctl->nr_to_scan = nr_to_scan;
|
|
shrinkctl->nr_scanned = nr_to_scan;
|
|
ret = shrinker->scan_objects(shrinker, shrinkctl);
|
|
if (ret == SHRINK_STOP)
|
|
break;
|
|
freed += ret;
|
|
|
|
count_vm_events(SLABS_SCANNED, shrinkctl->nr_scanned);
|
|
total_scan -= shrinkctl->nr_scanned;
|
|
scanned += shrinkctl->nr_scanned;
|
|
|
|
cond_resched();
|
|
}
|
|
|
|
/*
|
|
* The deferred work is increased by any new work (delta) that wasn't
|
|
* done, decreased by old deferred work that was done now.
|
|
*
|
|
* And it is capped to two times of the freeable items.
|
|
*/
|
|
next_deferred = max_t(long, (nr + delta - scanned), 0);
|
|
next_deferred = min(next_deferred, (2 * freeable));
|
|
|
|
/*
|
|
* move the unused scan count back into the shrinker in a
|
|
* manner that handles concurrent updates.
|
|
*/
|
|
new_nr = add_nr_deferred(next_deferred, shrinker, shrinkctl);
|
|
|
|
trace_mm_shrink_slab_end(shrinker, shrinkctl->nid, freed, nr, new_nr, total_scan);
|
|
return freed;
|
|
}
|
|
|
|
#ifdef CONFIG_MEMCG
|
|
static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
|
|
struct mem_cgroup *memcg, int priority)
|
|
{
|
|
struct shrinker_info *info;
|
|
unsigned long ret, freed = 0;
|
|
int i;
|
|
|
|
if (!mem_cgroup_online(memcg))
|
|
return 0;
|
|
|
|
if (!down_read_trylock(&shrinker_rwsem))
|
|
return 0;
|
|
|
|
info = shrinker_info_protected(memcg, nid);
|
|
if (unlikely(!info))
|
|
goto unlock;
|
|
|
|
for_each_set_bit(i, info->map, shrinker_nr_max) {
|
|
struct shrink_control sc = {
|
|
.gfp_mask = gfp_mask,
|
|
.nid = nid,
|
|
.memcg = memcg,
|
|
};
|
|
struct shrinker *shrinker;
|
|
|
|
shrinker = idr_find(&shrinker_idr, i);
|
|
if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) {
|
|
if (!shrinker)
|
|
clear_bit(i, info->map);
|
|
continue;
|
|
}
|
|
|
|
/* Call non-slab shrinkers even though kmem is disabled */
|
|
if (!memcg_kmem_enabled() &&
|
|
!(shrinker->flags & SHRINKER_NONSLAB))
|
|
continue;
|
|
|
|
ret = do_shrink_slab(&sc, shrinker, priority);
|
|
if (ret == SHRINK_EMPTY) {
|
|
clear_bit(i, info->map);
|
|
/*
|
|
* After the shrinker reported that it had no objects to
|
|
* free, but before we cleared the corresponding bit in
|
|
* the memcg shrinker map, a new object might have been
|
|
* added. To make sure, we have the bit set in this
|
|
* case, we invoke the shrinker one more time and reset
|
|
* the bit if it reports that it is not empty anymore.
|
|
* The memory barrier here pairs with the barrier in
|
|
* set_shrinker_bit():
|
|
*
|
|
* list_lru_add() shrink_slab_memcg()
|
|
* list_add_tail() clear_bit()
|
|
* <MB> <MB>
|
|
* set_bit() do_shrink_slab()
|
|
*/
|
|
smp_mb__after_atomic();
|
|
ret = do_shrink_slab(&sc, shrinker, priority);
|
|
if (ret == SHRINK_EMPTY)
|
|
ret = 0;
|
|
else
|
|
set_shrinker_bit(memcg, nid, i);
|
|
}
|
|
freed += ret;
|
|
|
|
if (rwsem_is_contended(&shrinker_rwsem)) {
|
|
freed = freed ? : 1;
|
|
break;
|
|
}
|
|
}
|
|
unlock:
|
|
up_read(&shrinker_rwsem);
|
|
return freed;
|
|
}
|
|
#else /* CONFIG_MEMCG */
|
|
static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
|
|
struct mem_cgroup *memcg, int priority)
|
|
{
|
|
return 0;
|
|
}
|
|
#endif /* CONFIG_MEMCG */
|
|
|
|
/**
|
|
* shrink_slab - shrink slab caches
|
|
* @gfp_mask: allocation context
|
|
* @nid: node whose slab caches to target
|
|
* @memcg: memory cgroup whose slab caches to target
|
|
* @priority: the reclaim priority
|
|
*
|
|
* Call the shrink functions to age shrinkable caches.
|
|
*
|
|
* @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
|
|
* unaware shrinkers will receive a node id of 0 instead.
|
|
*
|
|
* @memcg specifies the memory cgroup to target. Unaware shrinkers
|
|
* are called only if it is the root cgroup.
|
|
*
|
|
* @priority is sc->priority, we take the number of objects and >> by priority
|
|
* in order to get the scan target.
|
|
*
|
|
* Returns the number of reclaimed slab objects.
|
|
*/
|
|
static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
|
|
struct mem_cgroup *memcg,
|
|
int priority)
|
|
{
|
|
unsigned long ret, freed = 0;
|
|
struct shrinker *shrinker;
|
|
|
|
/*
|
|
* The root memcg might be allocated even though memcg is disabled
|
|
* via "cgroup_disable=memory" boot parameter. This could make
|
|
* mem_cgroup_is_root() return false, then just run memcg slab
|
|
* shrink, but skip global shrink. This may result in premature
|
|
* oom.
|
|
*/
|
|
if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg))
|
|
return shrink_slab_memcg(gfp_mask, nid, memcg, priority);
|
|
|
|
if (!down_read_trylock(&shrinker_rwsem))
|
|
goto out;
|
|
|
|
list_for_each_entry(shrinker, &shrinker_list, list) {
|
|
struct shrink_control sc = {
|
|
.gfp_mask = gfp_mask,
|
|
.nid = nid,
|
|
.memcg = memcg,
|
|
};
|
|
|
|
ret = do_shrink_slab(&sc, shrinker, priority);
|
|
if (ret == SHRINK_EMPTY)
|
|
ret = 0;
|
|
freed += ret;
|
|
/*
|
|
* Bail out if someone want to register a new shrinker to
|
|
* prevent the registration from being stalled for long periods
|
|
* by parallel ongoing shrinking.
|
|
*/
|
|
if (rwsem_is_contended(&shrinker_rwsem)) {
|
|
freed = freed ? : 1;
|
|
break;
|
|
}
|
|
}
|
|
|
|
up_read(&shrinker_rwsem);
|
|
out:
|
|
cond_resched();
|
|
return freed;
|
|
}
|
|
|
|
static void drop_slab_node(int nid)
|
|
{
|
|
unsigned long freed;
|
|
int shift = 0;
|
|
|
|
do {
|
|
struct mem_cgroup *memcg = NULL;
|
|
|
|
if (fatal_signal_pending(current))
|
|
return;
|
|
|
|
freed = 0;
|
|
memcg = mem_cgroup_iter(NULL, NULL, NULL);
|
|
do {
|
|
freed += shrink_slab(GFP_KERNEL, nid, memcg, 0);
|
|
} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
|
|
} while ((freed >> shift++) > 1);
|
|
}
|
|
|
|
void drop_slab(void)
|
|
{
|
|
int nid;
|
|
|
|
for_each_online_node(nid)
|
|
drop_slab_node(nid);
|
|
}
|
|
|
|
static inline int is_page_cache_freeable(struct folio *folio)
|
|
{
|
|
/*
|
|
* A freeable page cache page is referenced only by the caller
|
|
* that isolated the page, the page cache and optional buffer
|
|
* heads at page->private.
|
|
*/
|
|
return folio_ref_count(folio) - folio_test_private(folio) ==
|
|
1 + folio_nr_pages(folio);
|
|
}
|
|
|
|
/*
|
|
* We detected a synchronous write error writing a folio out. Probably
|
|
* -ENOSPC. We need to propagate that into the address_space for a subsequent
|
|
* fsync(), msync() or close().
|
|
*
|
|
* The tricky part is that after writepage we cannot touch the mapping: nothing
|
|
* prevents it from being freed up. But we have a ref on the folio and once
|
|
* that folio is locked, the mapping is pinned.
|
|
*
|
|
* We're allowed to run sleeping folio_lock() here because we know the caller has
|
|
* __GFP_FS.
|
|
*/
|
|
static void handle_write_error(struct address_space *mapping,
|
|
struct folio *folio, int error)
|
|
{
|
|
folio_lock(folio);
|
|
if (folio_mapping(folio) == mapping)
|
|
mapping_set_error(mapping, error);
|
|
folio_unlock(folio);
|
|
}
|
|
|
|
static bool skip_throttle_noprogress(pg_data_t *pgdat)
|
|
{
|
|
int reclaimable = 0, write_pending = 0;
|
|
int i;
|
|
|
|
/*
|
|
* If kswapd is disabled, reschedule if necessary but do not
|
|
* throttle as the system is likely near OOM.
|
|
*/
|
|
if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
|
|
return true;
|
|
|
|
/*
|
|
* If there are a lot of dirty/writeback pages then do not
|
|
* throttle as throttling will occur when the pages cycle
|
|
* towards the end of the LRU if still under writeback.
|
|
*/
|
|
for (i = 0; i < MAX_NR_ZONES; i++) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
|
|
if (!managed_zone(zone))
|
|
continue;
|
|
|
|
reclaimable += zone_reclaimable_pages(zone);
|
|
write_pending += zone_page_state_snapshot(zone,
|
|
NR_ZONE_WRITE_PENDING);
|
|
}
|
|
if (2 * write_pending <= reclaimable)
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)
|
|
{
|
|
wait_queue_head_t *wqh = &pgdat->reclaim_wait[reason];
|
|
long timeout, ret;
|
|
DEFINE_WAIT(wait);
|
|
|
|
/*
|
|
* Do not throttle IO workers, kthreads other than kswapd or
|
|
* workqueues. They may be required for reclaim to make
|
|
* forward progress (e.g. journalling workqueues or kthreads).
|
|
*/
|
|
if (!current_is_kswapd() &&
|
|
current->flags & (PF_IO_WORKER|PF_KTHREAD)) {
|
|
cond_resched();
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* These figures are pulled out of thin air.
|
|
* VMSCAN_THROTTLE_ISOLATED is a transient condition based on too many
|
|
* parallel reclaimers which is a short-lived event so the timeout is
|
|
* short. Failing to make progress or waiting on writeback are
|
|
* potentially long-lived events so use a longer timeout. This is shaky
|
|
* logic as a failure to make progress could be due to anything from
|
|
* writeback to a slow device to excessive references pages at the tail
|
|
* of the inactive LRU.
|
|
*/
|
|
switch(reason) {
|
|
case VMSCAN_THROTTLE_WRITEBACK:
|
|
timeout = HZ/10;
|
|
|
|
if (atomic_inc_return(&pgdat->nr_writeback_throttled) == 1) {
|
|
WRITE_ONCE(pgdat->nr_reclaim_start,
|
|
node_page_state(pgdat, NR_THROTTLED_WRITTEN));
|
|
}
|
|
|
|
break;
|
|
case VMSCAN_THROTTLE_CONGESTED:
|
|
fallthrough;
|
|
case VMSCAN_THROTTLE_NOPROGRESS:
|
|
if (skip_throttle_noprogress(pgdat)) {
|
|
cond_resched();
|
|
return;
|
|
}
|
|
|
|
timeout = 1;
|
|
|
|
break;
|
|
case VMSCAN_THROTTLE_ISOLATED:
|
|
timeout = HZ/50;
|
|
break;
|
|
default:
|
|
WARN_ON_ONCE(1);
|
|
timeout = HZ;
|
|
break;
|
|
}
|
|
|
|
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
|
|
ret = schedule_timeout(timeout);
|
|
finish_wait(wqh, &wait);
|
|
|
|
if (reason == VMSCAN_THROTTLE_WRITEBACK)
|
|
atomic_dec(&pgdat->nr_writeback_throttled);
|
|
|
|
trace_mm_vmscan_throttled(pgdat->node_id, jiffies_to_usecs(timeout),
|
|
jiffies_to_usecs(timeout - ret),
|
|
reason);
|
|
}
|
|
|
|
/*
|
|
* Account for pages written if tasks are throttled waiting on dirty
|
|
* pages to clean. If enough pages have been cleaned since throttling
|
|
* started then wakeup the throttled tasks.
|
|
*/
|
|
void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio,
|
|
int nr_throttled)
|
|
{
|
|
unsigned long nr_written;
|
|
|
|
node_stat_add_folio(folio, NR_THROTTLED_WRITTEN);
|
|
|
|
/*
|
|
* This is an inaccurate read as the per-cpu deltas may not
|
|
* be synchronised. However, given that the system is
|
|
* writeback throttled, it is not worth taking the penalty
|
|
* of getting an accurate count. At worst, the throttle
|
|
* timeout guarantees forward progress.
|
|
*/
|
|
nr_written = node_page_state(pgdat, NR_THROTTLED_WRITTEN) -
|
|
READ_ONCE(pgdat->nr_reclaim_start);
|
|
|
|
if (nr_written > SWAP_CLUSTER_MAX * nr_throttled)
|
|
wake_up(&pgdat->reclaim_wait[VMSCAN_THROTTLE_WRITEBACK]);
|
|
}
|
|
|
|
/* possible outcome of pageout() */
|
|
typedef enum {
|
|
/* failed to write page out, page is locked */
|
|
PAGE_KEEP,
|
|
/* move page to the active list, page is locked */
|
|
PAGE_ACTIVATE,
|
|
/* page has been sent to the disk successfully, page is unlocked */
|
|
PAGE_SUCCESS,
|
|
/* page is clean and locked */
|
|
PAGE_CLEAN,
|
|
} pageout_t;
|
|
|
|
/*
|
|
* pageout is called by shrink_page_list() for each dirty page.
|
|
* Calls ->writepage().
|
|
*/
|
|
static pageout_t pageout(struct folio *folio, struct address_space *mapping,
|
|
struct swap_iocb **plug)
|
|
{
|
|
/*
|
|
* If the folio is dirty, only perform writeback if that write
|
|
* will be non-blocking. To prevent this allocation from being
|
|
* stalled by pagecache activity. But note that there may be
|
|
* stalls if we need to run get_block(). We could test
|
|
* PagePrivate for that.
|
|
*
|
|
* If this process is currently in __generic_file_write_iter() against
|
|
* this folio's queue, we can perform writeback even if that
|
|
* will block.
|
|
*
|
|
* If the folio is swapcache, write it back even if that would
|
|
* block, for some throttling. This happens by accident, because
|
|
* swap_backing_dev_info is bust: it doesn't reflect the
|
|
* congestion state of the swapdevs. Easy to fix, if needed.
|
|
*/
|
|
if (!is_page_cache_freeable(folio))
|
|
return PAGE_KEEP;
|
|
if (!mapping) {
|
|
/*
|
|
* Some data journaling orphaned folios can have
|
|
* folio->mapping == NULL while being dirty with clean buffers.
|
|
*/
|
|
if (folio_test_private(folio)) {
|
|
if (try_to_free_buffers(&folio->page)) {
|
|
folio_clear_dirty(folio);
|
|
pr_info("%s: orphaned folio\n", __func__);
|
|
return PAGE_CLEAN;
|
|
}
|
|
}
|
|
return PAGE_KEEP;
|
|
}
|
|
if (mapping->a_ops->writepage == NULL)
|
|
return PAGE_ACTIVATE;
|
|
|
|
if (folio_clear_dirty_for_io(folio)) {
|
|
int res;
|
|
struct writeback_control wbc = {
|
|
.sync_mode = WB_SYNC_NONE,
|
|
.nr_to_write = SWAP_CLUSTER_MAX,
|
|
.range_start = 0,
|
|
.range_end = LLONG_MAX,
|
|
.for_reclaim = 1,
|
|
.swap_plug = plug,
|
|
};
|
|
|
|
folio_set_reclaim(folio);
|
|
res = mapping->a_ops->writepage(&folio->page, &wbc);
|
|
if (res < 0)
|
|
handle_write_error(mapping, folio, res);
|
|
if (res == AOP_WRITEPAGE_ACTIVATE) {
|
|
folio_clear_reclaim(folio);
|
|
return PAGE_ACTIVATE;
|
|
}
|
|
|
|
if (!folio_test_writeback(folio)) {
|
|
/* synchronous write or broken a_ops? */
|
|
folio_clear_reclaim(folio);
|
|
}
|
|
trace_mm_vmscan_write_folio(folio);
|
|
node_stat_add_folio(folio, NR_VMSCAN_WRITE);
|
|
return PAGE_SUCCESS;
|
|
}
|
|
|
|
return PAGE_CLEAN;
|
|
}
|
|
|
|
/*
|
|
* Same as remove_mapping, but if the page is removed from the mapping, it
|
|
* gets returned with a refcount of 0.
|
|
*/
|
|
static int __remove_mapping(struct address_space *mapping, struct folio *folio,
|
|
bool reclaimed, struct mem_cgroup *target_memcg)
|
|
{
|
|
int refcount;
|
|
void *shadow = NULL;
|
|
|
|
BUG_ON(!folio_test_locked(folio));
|
|
BUG_ON(mapping != folio_mapping(folio));
|
|
|
|
if (!folio_test_swapcache(folio))
|
|
spin_lock(&mapping->host->i_lock);
|
|
xa_lock_irq(&mapping->i_pages);
|
|
/*
|
|
* The non racy check for a busy page.
|
|
*
|
|
* Must be careful with the order of the tests. When someone has
|
|
* a ref to the page, it may be possible that they dirty it then
|
|
* drop the reference. So if PageDirty is tested before page_count
|
|
* here, then the following race may occur:
|
|
*
|
|
* get_user_pages(&page);
|
|
* [user mapping goes away]
|
|
* write_to(page);
|
|
* !PageDirty(page) [good]
|
|
* SetPageDirty(page);
|
|
* put_page(page);
|
|
* !page_count(page) [good, discard it]
|
|
*
|
|
* [oops, our write_to data is lost]
|
|
*
|
|
* Reversing the order of the tests ensures such a situation cannot
|
|
* escape unnoticed. The smp_rmb is needed to ensure the page->flags
|
|
* load is not satisfied before that of page->_refcount.
|
|
*
|
|
* Note that if SetPageDirty is always performed via set_page_dirty,
|
|
* and thus under the i_pages lock, then this ordering is not required.
|
|
*/
|
|
refcount = 1 + folio_nr_pages(folio);
|
|
if (!folio_ref_freeze(folio, refcount))
|
|
goto cannot_free;
|
|
/* note: atomic_cmpxchg in page_ref_freeze provides the smp_rmb */
|
|
if (unlikely(folio_test_dirty(folio))) {
|
|
folio_ref_unfreeze(folio, refcount);
|
|
goto cannot_free;
|
|
}
|
|
|
|
if (folio_test_swapcache(folio)) {
|
|
swp_entry_t swap = folio_swap_entry(folio);
|
|
mem_cgroup_swapout(folio, swap);
|
|
if (reclaimed && !mapping_exiting(mapping))
|
|
shadow = workingset_eviction(folio, target_memcg);
|
|
__delete_from_swap_cache(&folio->page, swap, shadow);
|
|
xa_unlock_irq(&mapping->i_pages);
|
|
put_swap_page(&folio->page, swap);
|
|
} else {
|
|
void (*freepage)(struct page *);
|
|
|
|
freepage = mapping->a_ops->freepage;
|
|
/*
|
|
* Remember a shadow entry for reclaimed file cache in
|
|
* order to detect refaults, thus thrashing, later on.
|
|
*
|
|
* But don't store shadows in an address space that is
|
|
* already exiting. This is not just an optimization,
|
|
* inode reclaim needs to empty out the radix tree or
|
|
* the nodes are lost. Don't plant shadows behind its
|
|
* back.
|
|
*
|
|
* We also don't store shadows for DAX mappings because the
|
|
* only page cache pages found in these are zero pages
|
|
* covering holes, and because we don't want to mix DAX
|
|
* exceptional entries and shadow exceptional entries in the
|
|
* same address_space.
|
|
*/
|
|
if (reclaimed && folio_is_file_lru(folio) &&
|
|
!mapping_exiting(mapping) && !dax_mapping(mapping))
|
|
shadow = workingset_eviction(folio, target_memcg);
|
|
__filemap_remove_folio(folio, shadow);
|
|
xa_unlock_irq(&mapping->i_pages);
|
|
if (mapping_shrinkable(mapping))
|
|
inode_add_lru(mapping->host);
|
|
spin_unlock(&mapping->host->i_lock);
|
|
|
|
if (freepage != NULL)
|
|
freepage(&folio->page);
|
|
}
|
|
|
|
return 1;
|
|
|
|
cannot_free:
|
|
xa_unlock_irq(&mapping->i_pages);
|
|
if (!folio_test_swapcache(folio))
|
|
spin_unlock(&mapping->host->i_lock);
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* remove_mapping() - Attempt to remove a folio from its mapping.
|
|
* @mapping: The address space.
|
|
* @folio: The folio to remove.
|
|
*
|
|
* If the folio is dirty, under writeback or if someone else has a ref
|
|
* on it, removal will fail.
|
|
* Return: The number of pages removed from the mapping. 0 if the folio
|
|
* could not be removed.
|
|
* Context: The caller should have a single refcount on the folio and
|
|
* hold its lock.
|
|
*/
|
|
long remove_mapping(struct address_space *mapping, struct folio *folio)
|
|
{
|
|
if (__remove_mapping(mapping, folio, false, NULL)) {
|
|
/*
|
|
* Unfreezing the refcount with 1 effectively
|
|
* drops the pagecache ref for us without requiring another
|
|
* atomic operation.
|
|
*/
|
|
folio_ref_unfreeze(folio, 1);
|
|
return folio_nr_pages(folio);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* folio_putback_lru - Put previously isolated folio onto appropriate LRU list.
|
|
* @folio: Folio to be returned to an LRU list.
|
|
*
|
|
* Add previously isolated @folio to appropriate LRU list.
|
|
* The folio may still be unevictable for other reasons.
|
|
*
|
|
* Context: lru_lock must not be held, interrupts must be enabled.
|
|
*/
|
|
void folio_putback_lru(struct folio *folio)
|
|
{
|
|
folio_add_lru(folio);
|
|
folio_put(folio); /* drop ref from isolate */
|
|
}
|
|
|
|
enum page_references {
|
|
PAGEREF_RECLAIM,
|
|
PAGEREF_RECLAIM_CLEAN,
|
|
PAGEREF_KEEP,
|
|
PAGEREF_ACTIVATE,
|
|
};
|
|
|
|
static enum page_references folio_check_references(struct folio *folio,
|
|
struct scan_control *sc)
|
|
{
|
|
int referenced_ptes, referenced_folio;
|
|
unsigned long vm_flags;
|
|
|
|
referenced_ptes = folio_referenced(folio, 1, sc->target_mem_cgroup,
|
|
&vm_flags);
|
|
referenced_folio = folio_test_clear_referenced(folio);
|
|
|
|
/*
|
|
* The supposedly reclaimable folio was found to be in a VM_LOCKED vma.
|
|
* Let the folio, now marked Mlocked, be moved to the unevictable list.
|
|
*/
|
|
if (vm_flags & VM_LOCKED)
|
|
return PAGEREF_ACTIVATE;
|
|
|
|
/* rmap lock contention: rotate */
|
|
if (referenced_ptes == -1)
|
|
return PAGEREF_KEEP;
|
|
|
|
if (referenced_ptes) {
|
|
/*
|
|
* All mapped folios start out with page table
|
|
* references from the instantiating fault, so we need
|
|
* to look twice if a mapped file/anon folio is used more
|
|
* than once.
|
|
*
|
|
* Mark it and spare it for another trip around the
|
|
* inactive list. Another page table reference will
|
|
* lead to its activation.
|
|
*
|
|
* Note: the mark is set for activated folios as well
|
|
* so that recently deactivated but used folios are
|
|
* quickly recovered.
|
|
*/
|
|
folio_set_referenced(folio);
|
|
|
|
if (referenced_folio || referenced_ptes > 1)
|
|
return PAGEREF_ACTIVATE;
|
|
|
|
/*
|
|
* Activate file-backed executable folios after first usage.
|
|
*/
|
|
if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio))
|
|
return PAGEREF_ACTIVATE;
|
|
|
|
return PAGEREF_KEEP;
|
|
}
|
|
|
|
/* Reclaim if clean, defer dirty folios to writeback */
|
|
if (referenced_folio && folio_is_file_lru(folio))
|
|
return PAGEREF_RECLAIM_CLEAN;
|
|
|
|
return PAGEREF_RECLAIM;
|
|
}
|
|
|
|
/* Check if a page is dirty or under writeback */
|
|
static void folio_check_dirty_writeback(struct folio *folio,
|
|
bool *dirty, bool *writeback)
|
|
{
|
|
struct address_space *mapping;
|
|
|
|
/*
|
|
* Anonymous pages are not handled by flushers and must be written
|
|
* from reclaim context. Do not stall reclaim based on them.
|
|
* MADV_FREE anonymous pages are put into inactive file list too.
|
|
* They could be mistakenly treated as file lru. So further anon
|
|
* test is needed.
|
|
*/
|
|
if (!folio_is_file_lru(folio) ||
|
|
(folio_test_anon(folio) && !folio_test_swapbacked(folio))) {
|
|
*dirty = false;
|
|
*writeback = false;
|
|
return;
|
|
}
|
|
|
|
/* By default assume that the folio flags are accurate */
|
|
*dirty = folio_test_dirty(folio);
|
|
*writeback = folio_test_writeback(folio);
|
|
|
|
/* Verify dirty/writeback state if the filesystem supports it */
|
|
if (!folio_test_private(folio))
|
|
return;
|
|
|
|
mapping = folio_mapping(folio);
|
|
if (mapping && mapping->a_ops->is_dirty_writeback)
|
|
mapping->a_ops->is_dirty_writeback(&folio->page, dirty, writeback);
|
|
}
|
|
|
|
static struct page *alloc_demote_page(struct page *page, unsigned long node)
|
|
{
|
|
struct migration_target_control mtc = {
|
|
/*
|
|
* Allocate from 'node', or fail quickly and quietly.
|
|
* When this happens, 'page' will likely just be discarded
|
|
* instead of migrated.
|
|
*/
|
|
.gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) |
|
|
__GFP_THISNODE | __GFP_NOWARN |
|
|
__GFP_NOMEMALLOC | GFP_NOWAIT,
|
|
.nid = node
|
|
};
|
|
|
|
return alloc_migration_target(page, (unsigned long)&mtc);
|
|
}
|
|
|
|
/*
|
|
* Take pages on @demote_list and attempt to demote them to
|
|
* another node. Pages which are not demoted are left on
|
|
* @demote_pages.
|
|
*/
|
|
static unsigned int demote_page_list(struct list_head *demote_pages,
|
|
struct pglist_data *pgdat)
|
|
{
|
|
int target_nid = next_demotion_node(pgdat->node_id);
|
|
unsigned int nr_succeeded;
|
|
|
|
if (list_empty(demote_pages))
|
|
return 0;
|
|
|
|
if (target_nid == NUMA_NO_NODE)
|
|
return 0;
|
|
|
|
/* Demotion ignores all cpuset and mempolicy settings */
|
|
migrate_pages(demote_pages, alloc_demote_page, NULL,
|
|
target_nid, MIGRATE_ASYNC, MR_DEMOTION,
|
|
&nr_succeeded);
|
|
|
|
if (current_is_kswapd())
|
|
__count_vm_events(PGDEMOTE_KSWAPD, nr_succeeded);
|
|
else
|
|
__count_vm_events(PGDEMOTE_DIRECT, nr_succeeded);
|
|
|
|
return nr_succeeded;
|
|
}
|
|
|
|
static bool may_enter_fs(struct folio *folio, gfp_t gfp_mask)
|
|
{
|
|
if (gfp_mask & __GFP_FS)
|
|
return true;
|
|
if (!folio_test_swapcache(folio) || !(gfp_mask & __GFP_IO))
|
|
return false;
|
|
/*
|
|
* We can "enter_fs" for swap-cache with only __GFP_IO
|
|
* providing this isn't SWP_FS_OPS.
|
|
* ->flags can be updated non-atomicially (scan_swap_map_slots),
|
|
* but that will never affect SWP_FS_OPS, so the data_race
|
|
* is safe.
|
|
*/
|
|
return !data_race(page_swap_flags(&folio->page) & SWP_FS_OPS);
|
|
}
|
|
|
|
/*
|
|
* shrink_page_list() returns the number of reclaimed pages
|
|
*/
|
|
static unsigned int shrink_page_list(struct list_head *page_list,
|
|
struct pglist_data *pgdat,
|
|
struct scan_control *sc,
|
|
struct reclaim_stat *stat,
|
|
bool ignore_references)
|
|
{
|
|
LIST_HEAD(ret_pages);
|
|
LIST_HEAD(free_pages);
|
|
LIST_HEAD(demote_pages);
|
|
unsigned int nr_reclaimed = 0;
|
|
unsigned int pgactivate = 0;
|
|
bool do_demote_pass;
|
|
struct swap_iocb *plug = NULL;
|
|
|
|
memset(stat, 0, sizeof(*stat));
|
|
cond_resched();
|
|
do_demote_pass = can_demote(pgdat->node_id, sc);
|
|
|
|
retry:
|
|
while (!list_empty(page_list)) {
|
|
struct address_space *mapping;
|
|
struct folio *folio;
|
|
enum page_references references = PAGEREF_RECLAIM;
|
|
bool dirty, writeback;
|
|
unsigned int nr_pages;
|
|
|
|
cond_resched();
|
|
|
|
folio = lru_to_folio(page_list);
|
|
list_del(&folio->lru);
|
|
|
|
if (!folio_trylock(folio))
|
|
goto keep;
|
|
|
|
VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
|
|
|
|
nr_pages = folio_nr_pages(folio);
|
|
|
|
/* Account the number of base pages */
|
|
sc->nr_scanned += nr_pages;
|
|
|
|
if (unlikely(!folio_evictable(folio)))
|
|
goto activate_locked;
|
|
|
|
if (!sc->may_unmap && folio_mapped(folio))
|
|
goto keep_locked;
|
|
|
|
/*
|
|
* The number of dirty pages determines if a node is marked
|
|
* reclaim_congested. kswapd will stall and start writing
|
|
* folios if the tail of the LRU is all dirty unqueued folios.
|
|
*/
|
|
folio_check_dirty_writeback(folio, &dirty, &writeback);
|
|
if (dirty || writeback)
|
|
stat->nr_dirty += nr_pages;
|
|
|
|
if (dirty && !writeback)
|
|
stat->nr_unqueued_dirty += nr_pages;
|
|
|
|
/*
|
|
* Treat this folio as congested if folios are cycling
|
|
* through the LRU so quickly that the folios marked
|
|
* for immediate reclaim are making it to the end of
|
|
* the LRU a second time.
|
|
*/
|
|
if (writeback && folio_test_reclaim(folio))
|
|
stat->nr_congested += nr_pages;
|
|
|
|
/*
|
|
* If a folio at the tail of the LRU is under writeback, there
|
|
* are three cases to consider.
|
|
*
|
|
* 1) If reclaim is encountering an excessive number
|
|
* of folios under writeback and this folio has both
|
|
* the writeback and reclaim flags set, then it
|
|
* indicates that folios are being queued for I/O but
|
|
* are being recycled through the LRU before the I/O
|
|
* can complete. Waiting on the folio itself risks an
|
|
* indefinite stall if it is impossible to writeback
|
|
* the folio due to I/O error or disconnected storage
|
|
* so instead note that the LRU is being scanned too
|
|
* quickly and the caller can stall after the folio
|
|
* list has been processed.
|
|
*
|
|
* 2) Global or new memcg reclaim encounters a folio that is
|
|
* not marked for immediate reclaim, or the caller does not
|
|
* have __GFP_FS (or __GFP_IO if it's simply going to swap,
|
|
* not to fs). In this case mark the folio for immediate
|
|
* reclaim and continue scanning.
|
|
*
|
|
* Require may_enter_fs() because we would wait on fs, which
|
|
* may not have submitted I/O yet. And the loop driver might
|
|
* enter reclaim, and deadlock if it waits on a folio for
|
|
* which it is needed to do the write (loop masks off
|
|
* __GFP_IO|__GFP_FS for this reason); but more thought
|
|
* would probably show more reasons.
|
|
*
|
|
* 3) Legacy memcg encounters a folio that already has the
|
|
* reclaim flag set. memcg does not have any dirty folio
|
|
* throttling so we could easily OOM just because too many
|
|
* folios are in writeback and there is nothing else to
|
|
* reclaim. Wait for the writeback to complete.
|
|
*
|
|
* In cases 1) and 2) we activate the folios to get them out of
|
|
* the way while we continue scanning for clean folios on the
|
|
* inactive list and refilling from the active list. The
|
|
* observation here is that waiting for disk writes is more
|
|
* expensive than potentially causing reloads down the line.
|
|
* Since they're marked for immediate reclaim, they won't put
|
|
* memory pressure on the cache working set any longer than it
|
|
* takes to write them to disk.
|
|
*/
|
|
if (folio_test_writeback(folio)) {
|
|
/* Case 1 above */
|
|
if (current_is_kswapd() &&
|
|
folio_test_reclaim(folio) &&
|
|
test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {
|
|
stat->nr_immediate += nr_pages;
|
|
goto activate_locked;
|
|
|
|
/* Case 2 above */
|
|
} else if (writeback_throttling_sane(sc) ||
|
|
!folio_test_reclaim(folio) ||
|
|
!may_enter_fs(folio, sc->gfp_mask)) {
|
|
/*
|
|
* This is slightly racy -
|
|
* folio_end_writeback() might have
|
|
* just cleared the reclaim flag, then
|
|
* setting the reclaim flag here ends up
|
|
* interpreted as the readahead flag - but
|
|
* that does not matter enough to care.
|
|
* What we do want is for this folio to
|
|
* have the reclaim flag set next time
|
|
* memcg reclaim reaches the tests above,
|
|
* so it will then wait for writeback to
|
|
* avoid OOM; and it's also appropriate
|
|
* in global reclaim.
|
|
*/
|
|
folio_set_reclaim(folio);
|
|
stat->nr_writeback += nr_pages;
|
|
goto activate_locked;
|
|
|
|
/* Case 3 above */
|
|
} else {
|
|
folio_unlock(folio);
|
|
folio_wait_writeback(folio);
|
|
/* then go back and try same folio again */
|
|
list_add_tail(&folio->lru, page_list);
|
|
continue;
|
|
}
|
|
}
|
|
|
|
if (!ignore_references)
|
|
references = folio_check_references(folio, sc);
|
|
|
|
switch (references) {
|
|
case PAGEREF_ACTIVATE:
|
|
goto activate_locked;
|
|
case PAGEREF_KEEP:
|
|
stat->nr_ref_keep += nr_pages;
|
|
goto keep_locked;
|
|
case PAGEREF_RECLAIM:
|
|
case PAGEREF_RECLAIM_CLEAN:
|
|
; /* try to reclaim the folio below */
|
|
}
|
|
|
|
/*
|
|
* Before reclaiming the folio, try to relocate
|
|
* its contents to another node.
|
|
*/
|
|
if (do_demote_pass &&
|
|
(thp_migration_supported() || !folio_test_large(folio))) {
|
|
list_add(&folio->lru, &demote_pages);
|
|
folio_unlock(folio);
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* Anonymous process memory has backing store?
|
|
* Try to allocate it some swap space here.
|
|
* Lazyfree folio could be freed directly
|
|
*/
|
|
if (folio_test_anon(folio) && folio_test_swapbacked(folio)) {
|
|
if (!folio_test_swapcache(folio)) {
|
|
if (!(sc->gfp_mask & __GFP_IO))
|
|
goto keep_locked;
|
|
if (folio_maybe_dma_pinned(folio))
|
|
goto keep_locked;
|
|
if (folio_test_large(folio)) {
|
|
/* cannot split folio, skip it */
|
|
if (!can_split_folio(folio, NULL))
|
|
goto activate_locked;
|
|
/*
|
|
* Split folios without a PMD map right
|
|
* away. Chances are some or all of the
|
|
* tail pages can be freed without IO.
|
|
*/
|
|
if (!folio_entire_mapcount(folio) &&
|
|
split_folio_to_list(folio,
|
|
page_list))
|
|
goto activate_locked;
|
|
}
|
|
if (!add_to_swap(folio)) {
|
|
if (!folio_test_large(folio))
|
|
goto activate_locked_split;
|
|
/* Fallback to swap normal pages */
|
|
if (split_folio_to_list(folio,
|
|
page_list))
|
|
goto activate_locked;
|
|
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
|
|
count_vm_event(THP_SWPOUT_FALLBACK);
|
|
#endif
|
|
if (!add_to_swap(folio))
|
|
goto activate_locked_split;
|
|
}
|
|
}
|
|
} else if (folio_test_swapbacked(folio) &&
|
|
folio_test_large(folio)) {
|
|
/* Split shmem folio */
|
|
if (split_folio_to_list(folio, page_list))
|
|
goto keep_locked;
|
|
}
|
|
|
|
/*
|
|
* If the folio was split above, the tail pages will make
|
|
* their own pass through this function and be accounted
|
|
* then.
|
|
*/
|
|
if ((nr_pages > 1) && !folio_test_large(folio)) {
|
|
sc->nr_scanned -= (nr_pages - 1);
|
|
nr_pages = 1;
|
|
}
|
|
|
|
/*
|
|
* The folio is mapped into the page tables of one or more
|
|
* processes. Try to unmap it here.
|
|
*/
|
|
if (folio_mapped(folio)) {
|
|
enum ttu_flags flags = TTU_BATCH_FLUSH;
|
|
bool was_swapbacked = folio_test_swapbacked(folio);
|
|
|
|
if (folio_test_pmd_mappable(folio))
|
|
flags |= TTU_SPLIT_HUGE_PMD;
|
|
|
|
try_to_unmap(folio, flags);
|
|
if (folio_mapped(folio)) {
|
|
stat->nr_unmap_fail += nr_pages;
|
|
if (!was_swapbacked &&
|
|
folio_test_swapbacked(folio))
|
|
stat->nr_lazyfree_fail += nr_pages;
|
|
goto activate_locked;
|
|
}
|
|
}
|
|
|
|
mapping = folio_mapping(folio);
|
|
if (folio_test_dirty(folio)) {
|
|
/*
|
|
* Only kswapd can writeback filesystem folios
|
|
* to avoid risk of stack overflow. But avoid
|
|
* injecting inefficient single-folio I/O into
|
|
* flusher writeback as much as possible: only
|
|
* write folios when we've encountered many
|
|
* dirty folios, and when we've already scanned
|
|
* the rest of the LRU for clean folios and see
|
|
* the same dirty folios again (with the reclaim
|
|
* flag set).
|
|
*/
|
|
if (folio_is_file_lru(folio) &&
|
|
(!current_is_kswapd() ||
|
|
!folio_test_reclaim(folio) ||
|
|
!test_bit(PGDAT_DIRTY, &pgdat->flags))) {
|
|
/*
|
|
* Immediately reclaim when written back.
|
|
* Similar in principle to deactivate_page()
|
|
* except we already have the folio isolated
|
|
* and know it's dirty
|
|
*/
|
|
node_stat_mod_folio(folio, NR_VMSCAN_IMMEDIATE,
|
|
nr_pages);
|
|
folio_set_reclaim(folio);
|
|
|
|
goto activate_locked;
|
|
}
|
|
|
|
if (references == PAGEREF_RECLAIM_CLEAN)
|
|
goto keep_locked;
|
|
if (!may_enter_fs(folio, sc->gfp_mask))
|
|
goto keep_locked;
|
|
if (!sc->may_writepage)
|
|
goto keep_locked;
|
|
|
|
/*
|
|
* Folio is dirty. Flush the TLB if a writable entry
|
|
* potentially exists to avoid CPU writes after I/O
|
|
* starts and then write it out here.
|
|
*/
|
|
try_to_unmap_flush_dirty();
|
|
switch (pageout(folio, mapping, &plug)) {
|
|
case PAGE_KEEP:
|
|
goto keep_locked;
|
|
case PAGE_ACTIVATE:
|
|
goto activate_locked;
|
|
case PAGE_SUCCESS:
|
|
stat->nr_pageout += nr_pages;
|
|
|
|
if (folio_test_writeback(folio))
|
|
goto keep;
|
|
if (folio_test_dirty(folio))
|
|
goto keep;
|
|
|
|
/*
|
|
* A synchronous write - probably a ramdisk. Go
|
|
* ahead and try to reclaim the folio.
|
|
*/
|
|
if (!folio_trylock(folio))
|
|
goto keep;
|
|
if (folio_test_dirty(folio) ||
|
|
folio_test_writeback(folio))
|
|
goto keep_locked;
|
|
mapping = folio_mapping(folio);
|
|
fallthrough;
|
|
case PAGE_CLEAN:
|
|
; /* try to free the folio below */
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If the folio has buffers, try to free the buffer
|
|
* mappings associated with this folio. If we succeed
|
|
* we try to free the folio as well.
|
|
*
|
|
* We do this even if the folio is dirty.
|
|
* filemap_release_folio() does not perform I/O, but it
|
|
* is possible for a folio to have the dirty flag set,
|
|
* but it is actually clean (all its buffers are clean).
|
|
* This happens if the buffers were written out directly,
|
|
* with submit_bh(). ext3 will do this, as well as
|
|
* the blockdev mapping. filemap_release_folio() will
|
|
* discover that cleanness and will drop the buffers
|
|
* and mark the folio clean - it can be freed.
|
|
*
|
|
* Rarely, folios can have buffers and no ->mapping.
|
|
* These are the folios which were not successfully
|
|
* invalidated in truncate_cleanup_folio(). We try to
|
|
* drop those buffers here and if that worked, and the
|
|
* folio is no longer mapped into process address space
|
|
* (refcount == 1) it can be freed. Otherwise, leave
|
|
* the folio on the LRU so it is swappable.
|
|
*/
|
|
if (folio_has_private(folio)) {
|
|
if (!filemap_release_folio(folio, sc->gfp_mask))
|
|
goto activate_locked;
|
|
if (!mapping && folio_ref_count(folio) == 1) {
|
|
folio_unlock(folio);
|
|
if (folio_put_testzero(folio))
|
|
goto free_it;
|
|
else {
|
|
/*
|
|
* rare race with speculative reference.
|
|
* the speculative reference will free
|
|
* this folio shortly, so we may
|
|
* increment nr_reclaimed here (and
|
|
* leave it off the LRU).
|
|
*/
|
|
nr_reclaimed += nr_pages;
|
|
continue;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) {
|
|
/* follow __remove_mapping for reference */
|
|
if (!folio_ref_freeze(folio, 1))
|
|
goto keep_locked;
|
|
/*
|
|
* The folio has only one reference left, which is
|
|
* from the isolation. After the caller puts the
|
|
* folio back on the lru and drops the reference, the
|
|
* folio will be freed anyway. It doesn't matter
|
|
* which lru it goes on. So we don't bother checking
|
|
* the dirty flag here.
|
|
*/
|
|
count_vm_events(PGLAZYFREED, nr_pages);
|
|
count_memcg_folio_events(folio, PGLAZYFREED, nr_pages);
|
|
} else if (!mapping || !__remove_mapping(mapping, folio, true,
|
|
sc->target_mem_cgroup))
|
|
goto keep_locked;
|
|
|
|
folio_unlock(folio);
|
|
free_it:
|
|
/*
|
|
* Folio may get swapped out as a whole, need to account
|
|
* all pages in it.
|
|
*/
|
|
nr_reclaimed += nr_pages;
|
|
|
|
/*
|
|
* Is there need to periodically free_page_list? It would
|
|
* appear not as the counts should be low
|
|
*/
|
|
if (unlikely(folio_test_large(folio)))
|
|
destroy_compound_page(&folio->page);
|
|
else
|
|
list_add(&folio->lru, &free_pages);
|
|
continue;
|
|
|
|
activate_locked_split:
|
|
/*
|
|
* The tail pages that are failed to add into swap cache
|
|
* reach here. Fixup nr_scanned and nr_pages.
|
|
*/
|
|
if (nr_pages > 1) {
|
|
sc->nr_scanned -= (nr_pages - 1);
|
|
nr_pages = 1;
|
|
}
|
|
activate_locked:
|
|
/* Not a candidate for swapping, so reclaim swap space. */
|
|
if (folio_test_swapcache(folio) &&
|
|
(mem_cgroup_swap_full(&folio->page) ||
|
|
folio_test_mlocked(folio)))
|
|
try_to_free_swap(&folio->page);
|
|
VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
|
|
if (!folio_test_mlocked(folio)) {
|
|
int type = folio_is_file_lru(folio);
|
|
folio_set_active(folio);
|
|
stat->nr_activate[type] += nr_pages;
|
|
count_memcg_folio_events(folio, PGACTIVATE, nr_pages);
|
|
}
|
|
keep_locked:
|
|
folio_unlock(folio);
|
|
keep:
|
|
list_add(&folio->lru, &ret_pages);
|
|
VM_BUG_ON_FOLIO(folio_test_lru(folio) ||
|
|
folio_test_unevictable(folio), folio);
|
|
}
|
|
/* 'page_list' is always empty here */
|
|
|
|
/* Migrate folios selected for demotion */
|
|
nr_reclaimed += demote_page_list(&demote_pages, pgdat);
|
|
/* Folios that could not be demoted are still in @demote_pages */
|
|
if (!list_empty(&demote_pages)) {
|
|
/* Folios which weren't demoted go back on @page_list for retry: */
|
|
list_splice_init(&demote_pages, page_list);
|
|
do_demote_pass = false;
|
|
goto retry;
|
|
}
|
|
|
|
pgactivate = stat->nr_activate[0] + stat->nr_activate[1];
|
|
|
|
mem_cgroup_uncharge_list(&free_pages);
|
|
try_to_unmap_flush();
|
|
free_unref_page_list(&free_pages);
|
|
|
|
list_splice(&ret_pages, page_list);
|
|
count_vm_events(PGACTIVATE, pgactivate);
|
|
|
|
if (plug)
|
|
swap_write_unplug(plug);
|
|
return nr_reclaimed;
|
|
}
|
|
|
|
unsigned int reclaim_clean_pages_from_list(struct zone *zone,
|
|
struct list_head *page_list)
|
|
{
|
|
struct scan_control sc = {
|
|
.gfp_mask = GFP_KERNEL,
|
|
.may_unmap = 1,
|
|
};
|
|
struct reclaim_stat stat;
|
|
unsigned int nr_reclaimed;
|
|
struct page *page, *next;
|
|
LIST_HEAD(clean_pages);
|
|
unsigned int noreclaim_flag;
|
|
|
|
list_for_each_entry_safe(page, next, page_list, lru) {
|
|
if (!PageHuge(page) && page_is_file_lru(page) &&
|
|
!PageDirty(page) && !__PageMovable(page) &&
|
|
!PageUnevictable(page)) {
|
|
ClearPageActive(page);
|
|
list_move(&page->lru, &clean_pages);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* We should be safe here since we are only dealing with file pages and
|
|
* we are not kswapd and therefore cannot write dirty file pages. But
|
|
* call memalloc_noreclaim_save() anyway, just in case these conditions
|
|
* change in the future.
|
|
*/
|
|
noreclaim_flag = memalloc_noreclaim_save();
|
|
nr_reclaimed = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc,
|
|
&stat, true);
|
|
memalloc_noreclaim_restore(noreclaim_flag);
|
|
|
|
list_splice(&clean_pages, page_list);
|
|
mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
|
|
-(long)nr_reclaimed);
|
|
/*
|
|
* Since lazyfree pages are isolated from file LRU from the beginning,
|
|
* they will rotate back to anonymous LRU in the end if it failed to
|
|
* discard so isolated count will be mismatched.
|
|
* Compensate the isolated count for both LRU lists.
|
|
*/
|
|
mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON,
|
|
stat.nr_lazyfree_fail);
|
|
mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
|
|
-(long)stat.nr_lazyfree_fail);
|
|
return nr_reclaimed;
|
|
}
|
|
|
|
/*
|
|
* Update LRU sizes after isolating pages. The LRU size updates must
|
|
* be complete before mem_cgroup_update_lru_size due to a sanity check.
|
|
*/
|
|
static __always_inline void update_lru_sizes(struct lruvec *lruvec,
|
|
enum lru_list lru, unsigned long *nr_zone_taken)
|
|
{
|
|
int zid;
|
|
|
|
for (zid = 0; zid < MAX_NR_ZONES; zid++) {
|
|
if (!nr_zone_taken[zid])
|
|
continue;
|
|
|
|
update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
|
|
}
|
|
|
|
}
|
|
|
|
/*
|
|
* Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
|
|
*
|
|
* lruvec->lru_lock is heavily contended. Some of the functions that
|
|
* shrink the lists perform better by taking out a batch of pages
|
|
* and working on them outside the LRU lock.
|
|
*
|
|
* For pagecache intensive workloads, this function is the hottest
|
|
* spot in the kernel (apart from copy_*_user functions).
|
|
*
|
|
* Lru_lock must be held before calling this function.
|
|
*
|
|
* @nr_to_scan: The number of eligible pages to look through on the list.
|
|
* @lruvec: The LRU vector to pull pages from.
|
|
* @dst: The temp list to put pages on to.
|
|
* @nr_scanned: The number of pages that were scanned.
|
|
* @sc: The scan_control struct for this reclaim session
|
|
* @lru: LRU list id for isolating
|
|
*
|
|
* returns how many pages were moved onto *@dst.
|
|
*/
|
|
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
|
|
struct lruvec *lruvec, struct list_head *dst,
|
|
unsigned long *nr_scanned, struct scan_control *sc,
|
|
enum lru_list lru)
|
|
{
|
|
struct list_head *src = &lruvec->lists[lru];
|
|
unsigned long nr_taken = 0;
|
|
unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 };
|
|
unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
|
|
unsigned long skipped = 0;
|
|
unsigned long scan, total_scan, nr_pages;
|
|
LIST_HEAD(pages_skipped);
|
|
|
|
total_scan = 0;
|
|
scan = 0;
|
|
while (scan < nr_to_scan && !list_empty(src)) {
|
|
struct list_head *move_to = src;
|
|
struct page *page;
|
|
|
|
page = lru_to_page(src);
|
|
prefetchw_prev_lru_page(page, src, flags);
|
|
|
|
nr_pages = compound_nr(page);
|
|
total_scan += nr_pages;
|
|
|
|
if (page_zonenum(page) > sc->reclaim_idx) {
|
|
nr_skipped[page_zonenum(page)] += nr_pages;
|
|
move_to = &pages_skipped;
|
|
goto move;
|
|
}
|
|
|
|
/*
|
|
* Do not count skipped pages because that makes the function
|
|
* return with no isolated pages if the LRU mostly contains
|
|
* ineligible pages. This causes the VM to not reclaim any
|
|
* pages, triggering a premature OOM.
|
|
* Account all tail pages of THP.
|
|
*/
|
|
scan += nr_pages;
|
|
|
|
if (!PageLRU(page))
|
|
goto move;
|
|
if (!sc->may_unmap && page_mapped(page))
|
|
goto move;
|
|
|
|
/*
|
|
* Be careful not to clear PageLRU until after we're
|
|
* sure the page is not being freed elsewhere -- the
|
|
* page release code relies on it.
|
|
*/
|
|
if (unlikely(!get_page_unless_zero(page)))
|
|
goto move;
|
|
|
|
if (!TestClearPageLRU(page)) {
|
|
/* Another thread is already isolating this page */
|
|
put_page(page);
|
|
goto move;
|
|
}
|
|
|
|
nr_taken += nr_pages;
|
|
nr_zone_taken[page_zonenum(page)] += nr_pages;
|
|
move_to = dst;
|
|
move:
|
|
list_move(&page->lru, move_to);
|
|
}
|
|
|
|
/*
|
|
* Splice any skipped pages to the start of the LRU list. Note that
|
|
* this disrupts the LRU order when reclaiming for lower zones but
|
|
* we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
|
|
* scanning would soon rescan the same pages to skip and waste lots
|
|
* of cpu cycles.
|
|
*/
|
|
if (!list_empty(&pages_skipped)) {
|
|
int zid;
|
|
|
|
list_splice(&pages_skipped, src);
|
|
for (zid = 0; zid < MAX_NR_ZONES; zid++) {
|
|
if (!nr_skipped[zid])
|
|
continue;
|
|
|
|
__count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]);
|
|
skipped += nr_skipped[zid];
|
|
}
|
|
}
|
|
*nr_scanned = total_scan;
|
|
trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan,
|
|
total_scan, skipped, nr_taken,
|
|
sc->may_unmap ? 0 : ISOLATE_UNMAPPED, lru);
|
|
update_lru_sizes(lruvec, lru, nr_zone_taken);
|
|
return nr_taken;
|
|
}
|
|
|
|
/**
|
|
* folio_isolate_lru() - Try to isolate a folio from its LRU list.
|
|
* @folio: Folio to isolate from its LRU list.
|
|
*
|
|
* Isolate a @folio from an LRU list and adjust the vmstat statistic
|
|
* corresponding to whatever LRU list the folio was on.
|
|
*
|
|
* The folio will have its LRU flag cleared. If it was found on the
|
|
* active list, it will have the Active flag set. If it was found on the
|
|
* unevictable list, it will have the Unevictable flag set. These flags
|
|
* may need to be cleared by the caller before letting the page go.
|
|
*
|
|
* Context:
|
|
*
|
|
* (1) Must be called with an elevated refcount on the page. This is a
|
|
* fundamental difference from isolate_lru_pages() (which is called
|
|
* without a stable reference).
|
|
* (2) The lru_lock must not be held.
|
|
* (3) Interrupts must be enabled.
|
|
*
|
|
* Return: 0 if the folio was removed from an LRU list.
|
|
* -EBUSY if the folio was not on an LRU list.
|
|
*/
|
|
int folio_isolate_lru(struct folio *folio)
|
|
{
|
|
int ret = -EBUSY;
|
|
|
|
VM_BUG_ON_FOLIO(!folio_ref_count(folio), folio);
|
|
|
|
if (folio_test_clear_lru(folio)) {
|
|
struct lruvec *lruvec;
|
|
|
|
folio_get(folio);
|
|
lruvec = folio_lruvec_lock_irq(folio);
|
|
lruvec_del_folio(lruvec, folio);
|
|
unlock_page_lruvec_irq(lruvec);
|
|
ret = 0;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
|
|
* then get rescheduled. When there are massive number of tasks doing page
|
|
* allocation, such sleeping direct reclaimers may keep piling up on each CPU,
|
|
* the LRU list will go small and be scanned faster than necessary, leading to
|
|
* unnecessary swapping, thrashing and OOM.
|
|
*/
|
|
static int too_many_isolated(struct pglist_data *pgdat, int file,
|
|
struct scan_control *sc)
|
|
{
|
|
unsigned long inactive, isolated;
|
|
bool too_many;
|
|
|
|
if (current_is_kswapd())
|
|
return 0;
|
|
|
|
if (!writeback_throttling_sane(sc))
|
|
return 0;
|
|
|
|
if (file) {
|
|
inactive = node_page_state(pgdat, NR_INACTIVE_FILE);
|
|
isolated = node_page_state(pgdat, NR_ISOLATED_FILE);
|
|
} else {
|
|
inactive = node_page_state(pgdat, NR_INACTIVE_ANON);
|
|
isolated = node_page_state(pgdat, NR_ISOLATED_ANON);
|
|
}
|
|
|
|
/*
|
|
* GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
|
|
* won't get blocked by normal direct-reclaimers, forming a circular
|
|
* deadlock.
|
|
*/
|
|
if ((sc->gfp_mask & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS))
|
|
inactive >>= 3;
|
|
|
|
too_many = isolated > inactive;
|
|
|
|
/* Wake up tasks throttled due to too_many_isolated. */
|
|
if (!too_many)
|
|
wake_throttle_isolated(pgdat);
|
|
|
|
return too_many;
|
|
}
|
|
|
|
/*
|
|
* move_pages_to_lru() moves pages from private @list to appropriate LRU list.
|
|
* On return, @list is reused as a list of pages to be freed by the caller.
|
|
*
|
|
* Returns the number of pages moved to the given lruvec.
|
|
*/
|
|
static unsigned int move_pages_to_lru(struct lruvec *lruvec,
|
|
struct list_head *list)
|
|
{
|
|
int nr_pages, nr_moved = 0;
|
|
LIST_HEAD(pages_to_free);
|
|
struct page *page;
|
|
|
|
while (!list_empty(list)) {
|
|
page = lru_to_page(list);
|
|
VM_BUG_ON_PAGE(PageLRU(page), page);
|
|
list_del(&page->lru);
|
|
if (unlikely(!page_evictable(page))) {
|
|
spin_unlock_irq(&lruvec->lru_lock);
|
|
putback_lru_page(page);
|
|
spin_lock_irq(&lruvec->lru_lock);
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* The SetPageLRU needs to be kept here for list integrity.
|
|
* Otherwise:
|
|
* #0 move_pages_to_lru #1 release_pages
|
|
* if !put_page_testzero
|
|
* if (put_page_testzero())
|
|
* !PageLRU //skip lru_lock
|
|
* SetPageLRU()
|
|
* list_add(&page->lru,)
|
|
* list_add(&page->lru,)
|
|
*/
|
|
SetPageLRU(page);
|
|
|
|
if (unlikely(put_page_testzero(page))) {
|
|
__clear_page_lru_flags(page);
|
|
|
|
if (unlikely(PageCompound(page))) {
|
|
spin_unlock_irq(&lruvec->lru_lock);
|
|
destroy_compound_page(page);
|
|
spin_lock_irq(&lruvec->lru_lock);
|
|
} else
|
|
list_add(&page->lru, &pages_to_free);
|
|
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* All pages were isolated from the same lruvec (and isolation
|
|
* inhibits memcg migration).
|
|
*/
|
|
VM_BUG_ON_PAGE(!folio_matches_lruvec(page_folio(page), lruvec), page);
|
|
add_page_to_lru_list(page, lruvec);
|
|
nr_pages = thp_nr_pages(page);
|
|
nr_moved += nr_pages;
|
|
if (PageActive(page))
|
|
workingset_age_nonresident(lruvec, nr_pages);
|
|
}
|
|
|
|
/*
|
|
* To save our caller's stack, now use input list for pages to free.
|
|
*/
|
|
list_splice(&pages_to_free, list);
|
|
|
|
return nr_moved;
|
|
}
|
|
|
|
/*
|
|
* If a kernel thread (such as nfsd for loop-back mounts) services a backing
|
|
* device by writing to the page cache it sets PF_LOCAL_THROTTLE. In this case
|
|
* we should not throttle. Otherwise it is safe to do so.
|
|
*/
|
|
static int current_may_throttle(void)
|
|
{
|
|
return !(current->flags & PF_LOCAL_THROTTLE);
|
|
}
|
|
|
|
/*
|
|
* shrink_inactive_list() is a helper for shrink_node(). It returns the number
|
|
* of reclaimed pages
|
|
*/
|
|
static unsigned long
|
|
shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
|
|
struct scan_control *sc, enum lru_list lru)
|
|
{
|
|
LIST_HEAD(page_list);
|
|
unsigned long nr_scanned;
|
|
unsigned int nr_reclaimed = 0;
|
|
unsigned long nr_taken;
|
|
struct reclaim_stat stat;
|
|
bool file = is_file_lru(lru);
|
|
enum vm_event_item item;
|
|
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
|
|
bool stalled = false;
|
|
|
|
while (unlikely(too_many_isolated(pgdat, file, sc))) {
|
|
if (stalled)
|
|
return 0;
|
|
|
|
/* wait a bit for the reclaimer. */
|
|
stalled = true;
|
|
reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED);
|
|
|
|
/* We are about to die and free our memory. Return now. */
|
|
if (fatal_signal_pending(current))
|
|
return SWAP_CLUSTER_MAX;
|
|
}
|
|
|
|
lru_add_drain();
|
|
|
|
spin_lock_irq(&lruvec->lru_lock);
|
|
|
|
nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list,
|
|
&nr_scanned, sc, lru);
|
|
|
|
__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
|
|
item = current_is_kswapd() ? PGSCAN_KSWAPD : PGSCAN_DIRECT;
|
|
if (!cgroup_reclaim(sc))
|
|
__count_vm_events(item, nr_scanned);
|
|
__count_memcg_events(lruvec_memcg(lruvec), item, nr_scanned);
|
|
__count_vm_events(PGSCAN_ANON + file, nr_scanned);
|
|
|
|
spin_unlock_irq(&lruvec->lru_lock);
|
|
|
|
if (nr_taken == 0)
|
|
return 0;
|
|
|
|
nr_reclaimed = shrink_page_list(&page_list, pgdat, sc, &stat, false);
|
|
|
|
spin_lock_irq(&lruvec->lru_lock);
|
|
move_pages_to_lru(lruvec, &page_list);
|
|
|
|
__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
|
|
item = current_is_kswapd() ? PGSTEAL_KSWAPD : PGSTEAL_DIRECT;
|
|
if (!cgroup_reclaim(sc))
|
|
__count_vm_events(item, nr_reclaimed);
|
|
__count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
|
|
__count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
|
|
spin_unlock_irq(&lruvec->lru_lock);
|
|
|
|
lru_note_cost(lruvec, file, stat.nr_pageout);
|
|
mem_cgroup_uncharge_list(&page_list);
|
|
free_unref_page_list(&page_list);
|
|
|
|
/*
|
|
* If dirty pages are scanned that are not queued for IO, it
|
|
* implies that flushers are not doing their job. This can
|
|
* happen when memory pressure pushes dirty pages to the end of
|
|
* the LRU before the dirty limits are breached and the dirty
|
|
* data has expired. It can also happen when the proportion of
|
|
* dirty pages grows not through writes but through memory
|
|
* pressure reclaiming all the clean cache. And in some cases,
|
|
* the flushers simply cannot keep up with the allocation
|
|
* rate. Nudge the flusher threads in case they are asleep.
|
|
*/
|
|
if (stat.nr_unqueued_dirty == nr_taken)
|
|
wakeup_flusher_threads(WB_REASON_VMSCAN);
|
|
|
|
sc->nr.dirty += stat.nr_dirty;
|
|
sc->nr.congested += stat.nr_congested;
|
|
sc->nr.unqueued_dirty += stat.nr_unqueued_dirty;
|
|
sc->nr.writeback += stat.nr_writeback;
|
|
sc->nr.immediate += stat.nr_immediate;
|
|
sc->nr.taken += nr_taken;
|
|
if (file)
|
|
sc->nr.file_taken += nr_taken;
|
|
|
|
trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
|
|
nr_scanned, nr_reclaimed, &stat, sc->priority, file);
|
|
return nr_reclaimed;
|
|
}
|
|
|
|
/*
|
|
* shrink_active_list() moves pages from the active LRU to the inactive LRU.
|
|
*
|
|
* We move them the other way if the page is referenced by one or more
|
|
* processes.
|
|
*
|
|
* If the pages are mostly unmapped, the processing is fast and it is
|
|
* appropriate to hold lru_lock across the whole operation. But if
|
|
* the pages are mapped, the processing is slow (folio_referenced()), so
|
|
* we should drop lru_lock around each page. It's impossible to balance
|
|
* this, so instead we remove the pages from the LRU while processing them.
|
|
* It is safe to rely on PG_active against the non-LRU pages in here because
|
|
* nobody will play with that bit on a non-LRU page.
|
|
*
|
|
* The downside is that we have to touch page->_refcount against each page.
|
|
* But we had to alter page->flags anyway.
|
|
*/
|
|
static void shrink_active_list(unsigned long nr_to_scan,
|
|
struct lruvec *lruvec,
|
|
struct scan_control *sc,
|
|
enum lru_list lru)
|
|
{
|
|
unsigned long nr_taken;
|
|
unsigned long nr_scanned;
|
|
unsigned long vm_flags;
|
|
LIST_HEAD(l_hold); /* The pages which were snipped off */
|
|
LIST_HEAD(l_active);
|
|
LIST_HEAD(l_inactive);
|
|
unsigned nr_deactivate, nr_activate;
|
|
unsigned nr_rotated = 0;
|
|
int file = is_file_lru(lru);
|
|
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
|
|
|
|
lru_add_drain();
|
|
|
|
spin_lock_irq(&lruvec->lru_lock);
|
|
|
|
nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold,
|
|
&nr_scanned, sc, lru);
|
|
|
|
__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
|
|
|
|
if (!cgroup_reclaim(sc))
|
|
__count_vm_events(PGREFILL, nr_scanned);
|
|
__count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned);
|
|
|
|
spin_unlock_irq(&lruvec->lru_lock);
|
|
|
|
while (!list_empty(&l_hold)) {
|
|
struct folio *folio;
|
|
struct page *page;
|
|
|
|
cond_resched();
|
|
folio = lru_to_folio(&l_hold);
|
|
list_del(&folio->lru);
|
|
page = &folio->page;
|
|
|
|
if (unlikely(!page_evictable(page))) {
|
|
putback_lru_page(page);
|
|
continue;
|
|
}
|
|
|
|
if (unlikely(buffer_heads_over_limit)) {
|
|
if (page_has_private(page) && trylock_page(page)) {
|
|
if (page_has_private(page))
|
|
try_to_release_page(page, 0);
|
|
unlock_page(page);
|
|
}
|
|
}
|
|
|
|
/* Referenced or rmap lock contention: rotate */
|
|
if (folio_referenced(folio, 0, sc->target_mem_cgroup,
|
|
&vm_flags) != 0) {
|
|
/*
|
|
* Identify referenced, file-backed active pages and
|
|
* give them one more trip around the active list. So
|
|
* that executable code get better chances to stay in
|
|
* memory under moderate memory pressure. Anon pages
|
|
* are not likely to be evicted by use-once streaming
|
|
* IO, plus JVM can create lots of anon VM_EXEC pages,
|
|
* so we ignore them here.
|
|
*/
|
|
if ((vm_flags & VM_EXEC) && page_is_file_lru(page)) {
|
|
nr_rotated += thp_nr_pages(page);
|
|
list_add(&page->lru, &l_active);
|
|
continue;
|
|
}
|
|
}
|
|
|
|
ClearPageActive(page); /* we are de-activating */
|
|
SetPageWorkingset(page);
|
|
list_add(&page->lru, &l_inactive);
|
|
}
|
|
|
|
/*
|
|
* Move pages back to the lru list.
|
|
*/
|
|
spin_lock_irq(&lruvec->lru_lock);
|
|
|
|
nr_activate = move_pages_to_lru(lruvec, &l_active);
|
|
nr_deactivate = move_pages_to_lru(lruvec, &l_inactive);
|
|
/* Keep all free pages in l_active list */
|
|
list_splice(&l_inactive, &l_active);
|
|
|
|
__count_vm_events(PGDEACTIVATE, nr_deactivate);
|
|
__count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, nr_deactivate);
|
|
|
|
__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
|
|
spin_unlock_irq(&lruvec->lru_lock);
|
|
|
|
mem_cgroup_uncharge_list(&l_active);
|
|
free_unref_page_list(&l_active);
|
|
trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
|
|
nr_deactivate, nr_rotated, sc->priority, file);
|
|
}
|
|
|
|
static unsigned int reclaim_page_list(struct list_head *page_list,
|
|
struct pglist_data *pgdat)
|
|
{
|
|
struct reclaim_stat dummy_stat;
|
|
unsigned int nr_reclaimed;
|
|
struct folio *folio;
|
|
struct scan_control sc = {
|
|
.gfp_mask = GFP_KERNEL,
|
|
.may_writepage = 1,
|
|
.may_unmap = 1,
|
|
.may_swap = 1,
|
|
.no_demotion = 1,
|
|
};
|
|
|
|
nr_reclaimed = shrink_page_list(page_list, pgdat, &sc, &dummy_stat, false);
|
|
while (!list_empty(page_list)) {
|
|
folio = lru_to_folio(page_list);
|
|
list_del(&folio->lru);
|
|
folio_putback_lru(folio);
|
|
}
|
|
|
|
return nr_reclaimed;
|
|
}
|
|
|
|
unsigned long reclaim_pages(struct list_head *page_list)
|
|
{
|
|
int nid;
|
|
unsigned int nr_reclaimed = 0;
|
|
LIST_HEAD(node_page_list);
|
|
struct page *page;
|
|
unsigned int noreclaim_flag;
|
|
|
|
if (list_empty(page_list))
|
|
return nr_reclaimed;
|
|
|
|
noreclaim_flag = memalloc_noreclaim_save();
|
|
|
|
nid = page_to_nid(lru_to_page(page_list));
|
|
do {
|
|
page = lru_to_page(page_list);
|
|
|
|
if (nid == page_to_nid(page)) {
|
|
ClearPageActive(page);
|
|
list_move(&page->lru, &node_page_list);
|
|
continue;
|
|
}
|
|
|
|
nr_reclaimed += reclaim_page_list(&node_page_list, NODE_DATA(nid));
|
|
nid = page_to_nid(lru_to_page(page_list));
|
|
} while (!list_empty(page_list));
|
|
|
|
nr_reclaimed += reclaim_page_list(&node_page_list, NODE_DATA(nid));
|
|
|
|
memalloc_noreclaim_restore(noreclaim_flag);
|
|
|
|
return nr_reclaimed;
|
|
}
|
|
|
|
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
|
|
struct lruvec *lruvec, struct scan_control *sc)
|
|
{
|
|
if (is_active_lru(lru)) {
|
|
if (sc->may_deactivate & (1 << is_file_lru(lru)))
|
|
shrink_active_list(nr_to_scan, lruvec, sc, lru);
|
|
else
|
|
sc->skipped_deactivate = 1;
|
|
return 0;
|
|
}
|
|
|
|
return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
|
|
}
|
|
|
|
/*
|
|
* The inactive anon list should be small enough that the VM never has
|
|
* to do too much work.
|
|
*
|
|
* The inactive file list should be small enough to leave most memory
|
|
* to the established workingset on the scan-resistant active list,
|
|
* but large enough to avoid thrashing the aggregate readahead window.
|
|
*
|
|
* Both inactive lists should also be large enough that each inactive
|
|
* page has a chance to be referenced again before it is reclaimed.
|
|
*
|
|
* If that fails and refaulting is observed, the inactive list grows.
|
|
*
|
|
* The inactive_ratio is the target ratio of ACTIVE to INACTIVE pages
|
|
* on this LRU, maintained by the pageout code. An inactive_ratio
|
|
* of 3 means 3:1 or 25% of the pages are kept on the inactive list.
|
|
*
|
|
* total target max
|
|
* memory ratio inactive
|
|
* -------------------------------------
|
|
* 10MB 1 5MB
|
|
* 100MB 1 50MB
|
|
* 1GB 3 250MB
|
|
* 10GB 10 0.9GB
|
|
* 100GB 31 3GB
|
|
* 1TB 101 10GB
|
|
* 10TB 320 32GB
|
|
*/
|
|
static bool inactive_is_low(struct lruvec *lruvec, enum lru_list inactive_lru)
|
|
{
|
|
enum lru_list active_lru = inactive_lru + LRU_ACTIVE;
|
|
unsigned long inactive, active;
|
|
unsigned long inactive_ratio;
|
|
unsigned long gb;
|
|
|
|
inactive = lruvec_page_state(lruvec, NR_LRU_BASE + inactive_lru);
|
|
active = lruvec_page_state(lruvec, NR_LRU_BASE + active_lru);
|
|
|
|
gb = (inactive + active) >> (30 - PAGE_SHIFT);
|
|
if (gb)
|
|
inactive_ratio = int_sqrt(10 * gb);
|
|
else
|
|
inactive_ratio = 1;
|
|
|
|
return inactive * inactive_ratio < active;
|
|
}
|
|
|
|
enum scan_balance {
|
|
SCAN_EQUAL,
|
|
SCAN_FRACT,
|
|
SCAN_ANON,
|
|
SCAN_FILE,
|
|
};
|
|
|
|
/*
|
|
* Determine how aggressively the anon and file LRU lists should be
|
|
* scanned.
|
|
*
|
|
* nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
|
|
* nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
|
|
*/
|
|
static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
|
|
unsigned long *nr)
|
|
{
|
|
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
|
|
struct mem_cgroup *memcg = lruvec_memcg(lruvec);
|
|
unsigned long anon_cost, file_cost, total_cost;
|
|
int swappiness = mem_cgroup_swappiness(memcg);
|
|
u64 fraction[ANON_AND_FILE];
|
|
u64 denominator = 0; /* gcc */
|
|
enum scan_balance scan_balance;
|
|
unsigned long ap, fp;
|
|
enum lru_list lru;
|
|
|
|
/* If we have no swap space, do not bother scanning anon pages. */
|
|
if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) {
|
|
scan_balance = SCAN_FILE;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* Global reclaim will swap to prevent OOM even with no
|
|
* swappiness, but memcg users want to use this knob to
|
|
* disable swapping for individual groups completely when
|
|
* using the memory controller's swap limit feature would be
|
|
* too expensive.
|
|
*/
|
|
if (cgroup_reclaim(sc) && !swappiness) {
|
|
scan_balance = SCAN_FILE;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* Do not apply any pressure balancing cleverness when the
|
|
* system is close to OOM, scan both anon and file equally
|
|
* (unless the swappiness setting disagrees with swapping).
|
|
*/
|
|
if (!sc->priority && swappiness) {
|
|
scan_balance = SCAN_EQUAL;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* If the system is almost out of file pages, force-scan anon.
|
|
*/
|
|
if (sc->file_is_tiny) {
|
|
scan_balance = SCAN_ANON;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* If there is enough inactive page cache, we do not reclaim
|
|
* anything from the anonymous working right now.
|
|
*/
|
|
if (sc->cache_trim_mode) {
|
|
scan_balance = SCAN_FILE;
|
|
goto out;
|
|
}
|
|
|
|
scan_balance = SCAN_FRACT;
|
|
/*
|
|
* Calculate the pressure balance between anon and file pages.
|
|
*
|
|
* The amount of pressure we put on each LRU is inversely
|
|
* proportional to the cost of reclaiming each list, as
|
|
* determined by the share of pages that are refaulting, times
|
|
* the relative IO cost of bringing back a swapped out
|
|
* anonymous page vs reloading a filesystem page (swappiness).
|
|
*
|
|
* Although we limit that influence to ensure no list gets
|
|
* left behind completely: at least a third of the pressure is
|
|
* applied, before swappiness.
|
|
*
|
|
* With swappiness at 100, anon and file have equal IO cost.
|
|
*/
|
|
total_cost = sc->anon_cost + sc->file_cost;
|
|
anon_cost = total_cost + sc->anon_cost;
|
|
file_cost = total_cost + sc->file_cost;
|
|
total_cost = anon_cost + file_cost;
|
|
|
|
ap = swappiness * (total_cost + 1);
|
|
ap /= anon_cost + 1;
|
|
|
|
fp = (200 - swappiness) * (total_cost + 1);
|
|
fp /= file_cost + 1;
|
|
|
|
fraction[0] = ap;
|
|
fraction[1] = fp;
|
|
denominator = ap + fp;
|
|
out:
|
|
for_each_evictable_lru(lru) {
|
|
int file = is_file_lru(lru);
|
|
unsigned long lruvec_size;
|
|
unsigned long low, min;
|
|
unsigned long scan;
|
|
|
|
lruvec_size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
|
|
mem_cgroup_protection(sc->target_mem_cgroup, memcg,
|
|
&min, &low);
|
|
|
|
if (min || low) {
|
|
/*
|
|
* Scale a cgroup's reclaim pressure by proportioning
|
|
* its current usage to its memory.low or memory.min
|
|
* setting.
|
|
*
|
|
* This is important, as otherwise scanning aggression
|
|
* becomes extremely binary -- from nothing as we
|
|
* approach the memory protection threshold, to totally
|
|
* nominal as we exceed it. This results in requiring
|
|
* setting extremely liberal protection thresholds. It
|
|
* also means we simply get no protection at all if we
|
|
* set it too low, which is not ideal.
|
|
*
|
|
* If there is any protection in place, we reduce scan
|
|
* pressure by how much of the total memory used is
|
|
* within protection thresholds.
|
|
*
|
|
* There is one special case: in the first reclaim pass,
|
|
* we skip over all groups that are within their low
|
|
* protection. If that fails to reclaim enough pages to
|
|
* satisfy the reclaim goal, we come back and override
|
|
* the best-effort low protection. However, we still
|
|
* ideally want to honor how well-behaved groups are in
|
|
* that case instead of simply punishing them all
|
|
* equally. As such, we reclaim them based on how much
|
|
* memory they are using, reducing the scan pressure
|
|
* again by how much of the total memory used is under
|
|
* hard protection.
|
|
*/
|
|
unsigned long cgroup_size = mem_cgroup_size(memcg);
|
|
unsigned long protection;
|
|
|
|
/* memory.low scaling, make sure we retry before OOM */
|
|
if (!sc->memcg_low_reclaim && low > min) {
|
|
protection = low;
|
|
sc->memcg_low_skipped = 1;
|
|
} else {
|
|
protection = min;
|
|
}
|
|
|
|
/* Avoid TOCTOU with earlier protection check */
|
|
cgroup_size = max(cgroup_size, protection);
|
|
|
|
scan = lruvec_size - lruvec_size * protection /
|
|
(cgroup_size + 1);
|
|
|
|
/*
|
|
* Minimally target SWAP_CLUSTER_MAX pages to keep
|
|
* reclaim moving forwards, avoiding decrementing
|
|
* sc->priority further than desirable.
|
|
*/
|
|
scan = max(scan, SWAP_CLUSTER_MAX);
|
|
} else {
|
|
scan = lruvec_size;
|
|
}
|
|
|
|
scan >>= sc->priority;
|
|
|
|
/*
|
|
* If the cgroup's already been deleted, make sure to
|
|
* scrape out the remaining cache.
|
|
*/
|
|
if (!scan && !mem_cgroup_online(memcg))
|
|
scan = min(lruvec_size, SWAP_CLUSTER_MAX);
|
|
|
|
switch (scan_balance) {
|
|
case SCAN_EQUAL:
|
|
/* Scan lists relative to size */
|
|
break;
|
|
case SCAN_FRACT:
|
|
/*
|
|
* Scan types proportional to swappiness and
|
|
* their relative recent reclaim efficiency.
|
|
* Make sure we don't miss the last page on
|
|
* the offlined memory cgroups because of a
|
|
* round-off error.
|
|
*/
|
|
scan = mem_cgroup_online(memcg) ?
|
|
div64_u64(scan * fraction[file], denominator) :
|
|
DIV64_U64_ROUND_UP(scan * fraction[file],
|
|
denominator);
|
|
break;
|
|
case SCAN_FILE:
|
|
case SCAN_ANON:
|
|
/* Scan one type exclusively */
|
|
if ((scan_balance == SCAN_FILE) != file)
|
|
scan = 0;
|
|
break;
|
|
default:
|
|
/* Look ma, no brain */
|
|
BUG();
|
|
}
|
|
|
|
nr[lru] = scan;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Anonymous LRU management is a waste if there is
|
|
* ultimately no way to reclaim the memory.
|
|
*/
|
|
static bool can_age_anon_pages(struct pglist_data *pgdat,
|
|
struct scan_control *sc)
|
|
{
|
|
/* Aging the anon LRU is valuable if swap is present: */
|
|
if (total_swap_pages > 0)
|
|
return true;
|
|
|
|
/* Also valuable if anon pages can be demoted: */
|
|
return can_demote(pgdat->node_id, sc);
|
|
}
|
|
|
|
static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
|
|
{
|
|
unsigned long nr[NR_LRU_LISTS];
|
|
unsigned long targets[NR_LRU_LISTS];
|
|
unsigned long nr_to_scan;
|
|
enum lru_list lru;
|
|
unsigned long nr_reclaimed = 0;
|
|
unsigned long nr_to_reclaim = sc->nr_to_reclaim;
|
|
struct blk_plug plug;
|
|
bool scan_adjusted;
|
|
|
|
get_scan_count(lruvec, sc, nr);
|
|
|
|
/* Record the original scan target for proportional adjustments later */
|
|
memcpy(targets, nr, sizeof(nr));
|
|
|
|
/*
|
|
* Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
|
|
* event that can occur when there is little memory pressure e.g.
|
|
* multiple streaming readers/writers. Hence, we do not abort scanning
|
|
* when the requested number of pages are reclaimed when scanning at
|
|
* DEF_PRIORITY on the assumption that the fact we are direct
|
|
* reclaiming implies that kswapd is not keeping up and it is best to
|
|
* do a batch of work at once. For memcg reclaim one check is made to
|
|
* abort proportional reclaim if either the file or anon lru has already
|
|
* dropped to zero at the first pass.
|
|
*/
|
|
scan_adjusted = (!cgroup_reclaim(sc) && !current_is_kswapd() &&
|
|
sc->priority == DEF_PRIORITY);
|
|
|
|
blk_start_plug(&plug);
|
|
while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
|
|
nr[LRU_INACTIVE_FILE]) {
|
|
unsigned long nr_anon, nr_file, percentage;
|
|
unsigned long nr_scanned;
|
|
|
|
for_each_evictable_lru(lru) {
|
|
if (nr[lru]) {
|
|
nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
|
|
nr[lru] -= nr_to_scan;
|
|
|
|
nr_reclaimed += shrink_list(lru, nr_to_scan,
|
|
lruvec, sc);
|
|
}
|
|
}
|
|
|
|
cond_resched();
|
|
|
|
if (nr_reclaimed < nr_to_reclaim || scan_adjusted)
|
|
continue;
|
|
|
|
/*
|
|
* For kswapd and memcg, reclaim at least the number of pages
|
|
* requested. Ensure that the anon and file LRUs are scanned
|
|
* proportionally what was requested by get_scan_count(). We
|
|
* stop reclaiming one LRU and reduce the amount scanning
|
|
* proportional to the original scan target.
|
|
*/
|
|
nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE];
|
|
nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON];
|
|
|
|
/*
|
|
* It's just vindictive to attack the larger once the smaller
|
|
* has gone to zero. And given the way we stop scanning the
|
|
* smaller below, this makes sure that we only make one nudge
|
|
* towards proportionality once we've got nr_to_reclaim.
|
|
*/
|
|
if (!nr_file || !nr_anon)
|
|
break;
|
|
|
|
if (nr_file > nr_anon) {
|
|
unsigned long scan_target = targets[LRU_INACTIVE_ANON] +
|
|
targets[LRU_ACTIVE_ANON] + 1;
|
|
lru = LRU_BASE;
|
|
percentage = nr_anon * 100 / scan_target;
|
|
} else {
|
|
unsigned long scan_target = targets[LRU_INACTIVE_FILE] +
|
|
targets[LRU_ACTIVE_FILE] + 1;
|
|
lru = LRU_FILE;
|
|
percentage = nr_file * 100 / scan_target;
|
|
}
|
|
|
|
/* Stop scanning the smaller of the LRU */
|
|
nr[lru] = 0;
|
|
nr[lru + LRU_ACTIVE] = 0;
|
|
|
|
/*
|
|
* Recalculate the other LRU scan count based on its original
|
|
* scan target and the percentage scanning already complete
|
|
*/
|
|
lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
|
|
nr_scanned = targets[lru] - nr[lru];
|
|
nr[lru] = targets[lru] * (100 - percentage) / 100;
|
|
nr[lru] -= min(nr[lru], nr_scanned);
|
|
|
|
lru += LRU_ACTIVE;
|
|
nr_scanned = targets[lru] - nr[lru];
|
|
nr[lru] = targets[lru] * (100 - percentage) / 100;
|
|
nr[lru] -= min(nr[lru], nr_scanned);
|
|
|
|
scan_adjusted = true;
|
|
}
|
|
blk_finish_plug(&plug);
|
|
sc->nr_reclaimed += nr_reclaimed;
|
|
|
|
/*
|
|
* Even if we did not try to evict anon pages at all, we want to
|
|
* rebalance the anon lru active/inactive ratio.
|
|
*/
|
|
if (can_age_anon_pages(lruvec_pgdat(lruvec), sc) &&
|
|
inactive_is_low(lruvec, LRU_INACTIVE_ANON))
|
|
shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
|
|
sc, LRU_ACTIVE_ANON);
|
|
}
|
|
|
|
/* Use reclaim/compaction for costly allocs or under memory pressure */
|
|
static bool in_reclaim_compaction(struct scan_control *sc)
|
|
{
|
|
if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
|
|
(sc->order > PAGE_ALLOC_COSTLY_ORDER ||
|
|
sc->priority < DEF_PRIORITY - 2))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* Reclaim/compaction is used for high-order allocation requests. It reclaims
|
|
* order-0 pages before compacting the zone. should_continue_reclaim() returns
|
|
* true if more pages should be reclaimed such that when the page allocator
|
|
* calls try_to_compact_pages() that it will have enough free pages to succeed.
|
|
* It will give up earlier than that if there is difficulty reclaiming pages.
|
|
*/
|
|
static inline bool should_continue_reclaim(struct pglist_data *pgdat,
|
|
unsigned long nr_reclaimed,
|
|
struct scan_control *sc)
|
|
{
|
|
unsigned long pages_for_compaction;
|
|
unsigned long inactive_lru_pages;
|
|
int z;
|
|
|
|
/* If not in reclaim/compaction mode, stop */
|
|
if (!in_reclaim_compaction(sc))
|
|
return false;
|
|
|
|
/*
|
|
* Stop if we failed to reclaim any pages from the last SWAP_CLUSTER_MAX
|
|
* number of pages that were scanned. This will return to the caller
|
|
* with the risk reclaim/compaction and the resulting allocation attempt
|
|
* fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL
|
|
* allocations through requiring that the full LRU list has been scanned
|
|
* first, by assuming that zero delta of sc->nr_scanned means full LRU
|
|
* scan, but that approximation was wrong, and there were corner cases
|
|
* where always a non-zero amount of pages were scanned.
|
|
*/
|
|
if (!nr_reclaimed)
|
|
return false;
|
|
|
|
/* If compaction would go ahead or the allocation would succeed, stop */
|
|
for (z = 0; z <= sc->reclaim_idx; z++) {
|
|
struct zone *zone = &pgdat->node_zones[z];
|
|
if (!managed_zone(zone))
|
|
continue;
|
|
|
|
switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) {
|
|
case COMPACT_SUCCESS:
|
|
case COMPACT_CONTINUE:
|
|
return false;
|
|
default:
|
|
/* check next zone */
|
|
;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If we have not reclaimed enough pages for compaction and the
|
|
* inactive lists are large enough, continue reclaiming
|
|
*/
|
|
pages_for_compaction = compact_gap(sc->order);
|
|
inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
|
|
if (can_reclaim_anon_pages(NULL, pgdat->node_id, sc))
|
|
inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);
|
|
|
|
return inactive_lru_pages > pages_for_compaction;
|
|
}
|
|
|
|
static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
|
|
{
|
|
struct mem_cgroup *target_memcg = sc->target_mem_cgroup;
|
|
struct mem_cgroup *memcg;
|
|
|
|
memcg = mem_cgroup_iter(target_memcg, NULL, NULL);
|
|
do {
|
|
struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
|
|
unsigned long reclaimed;
|
|
unsigned long scanned;
|
|
|
|
/*
|
|
* This loop can become CPU-bound when target memcgs
|
|
* aren't eligible for reclaim - either because they
|
|
* don't have any reclaimable pages, or because their
|
|
* memory is explicitly protected. Avoid soft lockups.
|
|
*/
|
|
cond_resched();
|
|
|
|
mem_cgroup_calculate_protection(target_memcg, memcg);
|
|
|
|
if (mem_cgroup_below_min(memcg)) {
|
|
/*
|
|
* Hard protection.
|
|
* If there is no reclaimable memory, OOM.
|
|
*/
|
|
continue;
|
|
} else if (mem_cgroup_below_low(memcg)) {
|
|
/*
|
|
* Soft protection.
|
|
* Respect the protection only as long as
|
|
* there is an unprotected supply
|
|
* of reclaimable memory from other cgroups.
|
|
*/
|
|
if (!sc->memcg_low_reclaim) {
|
|
sc->memcg_low_skipped = 1;
|
|
continue;
|
|
}
|
|
memcg_memory_event(memcg, MEMCG_LOW);
|
|
}
|
|
|
|
reclaimed = sc->nr_reclaimed;
|
|
scanned = sc->nr_scanned;
|
|
|
|
shrink_lruvec(lruvec, sc);
|
|
|
|
shrink_slab(sc->gfp_mask, pgdat->node_id, memcg,
|
|
sc->priority);
|
|
|
|
/* Record the group's reclaim efficiency */
|
|
vmpressure(sc->gfp_mask, memcg, false,
|
|
sc->nr_scanned - scanned,
|
|
sc->nr_reclaimed - reclaimed);
|
|
|
|
} while ((memcg = mem_cgroup_iter(target_memcg, memcg, NULL)));
|
|
}
|
|
|
|
static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)
|
|
{
|
|
struct reclaim_state *reclaim_state = current->reclaim_state;
|
|
unsigned long nr_reclaimed, nr_scanned;
|
|
struct lruvec *target_lruvec;
|
|
bool reclaimable = false;
|
|
unsigned long file;
|
|
|
|
target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
|
|
|
|
again:
|
|
/*
|
|
* Flush the memory cgroup stats, so that we read accurate per-memcg
|
|
* lruvec stats for heuristics.
|
|
*/
|
|
mem_cgroup_flush_stats();
|
|
|
|
memset(&sc->nr, 0, sizeof(sc->nr));
|
|
|
|
nr_reclaimed = sc->nr_reclaimed;
|
|
nr_scanned = sc->nr_scanned;
|
|
|
|
/*
|
|
* Determine the scan balance between anon and file LRUs.
|
|
*/
|
|
spin_lock_irq(&target_lruvec->lru_lock);
|
|
sc->anon_cost = target_lruvec->anon_cost;
|
|
sc->file_cost = target_lruvec->file_cost;
|
|
spin_unlock_irq(&target_lruvec->lru_lock);
|
|
|
|
/*
|
|
* Target desirable inactive:active list ratios for the anon
|
|
* and file LRU lists.
|
|
*/
|
|
if (!sc->force_deactivate) {
|
|
unsigned long refaults;
|
|
|
|
refaults = lruvec_page_state(target_lruvec,
|
|
WORKINGSET_ACTIVATE_ANON);
|
|
if (refaults != target_lruvec->refaults[0] ||
|
|
inactive_is_low(target_lruvec, LRU_INACTIVE_ANON))
|
|
sc->may_deactivate |= DEACTIVATE_ANON;
|
|
else
|
|
sc->may_deactivate &= ~DEACTIVATE_ANON;
|
|
|
|
/*
|
|
* When refaults are being observed, it means a new
|
|
* workingset is being established. Deactivate to get
|
|
* rid of any stale active pages quickly.
|
|
*/
|
|
refaults = lruvec_page_state(target_lruvec,
|
|
WORKINGSET_ACTIVATE_FILE);
|
|
if (refaults != target_lruvec->refaults[1] ||
|
|
inactive_is_low(target_lruvec, LRU_INACTIVE_FILE))
|
|
sc->may_deactivate |= DEACTIVATE_FILE;
|
|
else
|
|
sc->may_deactivate &= ~DEACTIVATE_FILE;
|
|
} else
|
|
sc->may_deactivate = DEACTIVATE_ANON | DEACTIVATE_FILE;
|
|
|
|
/*
|
|
* If we have plenty of inactive file pages that aren't
|
|
* thrashing, try to reclaim those first before touching
|
|
* anonymous pages.
|
|
*/
|
|
file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE);
|
|
if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE))
|
|
sc->cache_trim_mode = 1;
|
|
else
|
|
sc->cache_trim_mode = 0;
|
|
|
|
/*
|
|
* Prevent the reclaimer from falling into the cache trap: as
|
|
* cache pages start out inactive, every cache fault will tip
|
|
* the scan balance towards the file LRU. And as the file LRU
|
|
* shrinks, so does the window for rotation from references.
|
|
* This means we have a runaway feedback loop where a tiny
|
|
* thrashing file LRU becomes infinitely more attractive than
|
|
* anon pages. Try to detect this based on file LRU size.
|
|
*/
|
|
if (!cgroup_reclaim(sc)) {
|
|
unsigned long total_high_wmark = 0;
|
|
unsigned long free, anon;
|
|
int z;
|
|
|
|
free = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES);
|
|
file = node_page_state(pgdat, NR_ACTIVE_FILE) +
|
|
node_page_state(pgdat, NR_INACTIVE_FILE);
|
|
|
|
for (z = 0; z < MAX_NR_ZONES; z++) {
|
|
struct zone *zone = &pgdat->node_zones[z];
|
|
if (!managed_zone(zone))
|
|
continue;
|
|
|
|
total_high_wmark += high_wmark_pages(zone);
|
|
}
|
|
|
|
/*
|
|
* Consider anon: if that's low too, this isn't a
|
|
* runaway file reclaim problem, but rather just
|
|
* extreme pressure. Reclaim as per usual then.
|
|
*/
|
|
anon = node_page_state(pgdat, NR_INACTIVE_ANON);
|
|
|
|
sc->file_is_tiny =
|
|
file + free <= total_high_wmark &&
|
|
!(sc->may_deactivate & DEACTIVATE_ANON) &&
|
|
anon >> sc->priority;
|
|
}
|
|
|
|
shrink_node_memcgs(pgdat, sc);
|
|
|
|
if (reclaim_state) {
|
|
sc->nr_reclaimed += reclaim_state->reclaimed_slab;
|
|
reclaim_state->reclaimed_slab = 0;
|
|
}
|
|
|
|
/* Record the subtree's reclaim efficiency */
|
|
vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
|
|
sc->nr_scanned - nr_scanned,
|
|
sc->nr_reclaimed - nr_reclaimed);
|
|
|
|
if (sc->nr_reclaimed - nr_reclaimed)
|
|
reclaimable = true;
|
|
|
|
if (current_is_kswapd()) {
|
|
/*
|
|
* If reclaim is isolating dirty pages under writeback,
|
|
* it implies that the long-lived page allocation rate
|
|
* is exceeding the page laundering rate. Either the
|
|
* global limits are not being effective at throttling
|
|
* processes due to the page distribution throughout
|
|
* zones or there is heavy usage of a slow backing
|
|
* device. The only option is to throttle from reclaim
|
|
* context which is not ideal as there is no guarantee
|
|
* the dirtying process is throttled in the same way
|
|
* balance_dirty_pages() manages.
|
|
*
|
|
* Once a node is flagged PGDAT_WRITEBACK, kswapd will
|
|
* count the number of pages under pages flagged for
|
|
* immediate reclaim and stall if any are encountered
|
|
* in the nr_immediate check below.
|
|
*/
|
|
if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken)
|
|
set_bit(PGDAT_WRITEBACK, &pgdat->flags);
|
|
|
|
/* Allow kswapd to start writing pages during reclaim.*/
|
|
if (sc->nr.unqueued_dirty == sc->nr.file_taken)
|
|
set_bit(PGDAT_DIRTY, &pgdat->flags);
|
|
|
|
/*
|
|
* If kswapd scans pages marked for immediate
|
|
* reclaim and under writeback (nr_immediate), it
|
|
* implies that pages are cycling through the LRU
|
|
* faster than they are written so forcibly stall
|
|
* until some pages complete writeback.
|
|
*/
|
|
if (sc->nr.immediate)
|
|
reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
|
|
}
|
|
|
|
/*
|
|
* Tag a node/memcg as congested if all the dirty pages were marked
|
|
* for writeback and immediate reclaim (counted in nr.congested).
|
|
*
|
|
* Legacy memcg will stall in page writeback so avoid forcibly
|
|
* stalling in reclaim_throttle().
|
|
*/
|
|
if ((current_is_kswapd() ||
|
|
(cgroup_reclaim(sc) && writeback_throttling_sane(sc))) &&
|
|
sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
|
|
set_bit(LRUVEC_CONGESTED, &target_lruvec->flags);
|
|
|
|
/*
|
|
* Stall direct reclaim for IO completions if the lruvec is
|
|
* node is congested. Allow kswapd to continue until it
|
|
* starts encountering unqueued dirty pages or cycling through
|
|
* the LRU too quickly.
|
|
*/
|
|
if (!current_is_kswapd() && current_may_throttle() &&
|
|
!sc->hibernation_mode &&
|
|
test_bit(LRUVEC_CONGESTED, &target_lruvec->flags))
|
|
reclaim_throttle(pgdat, VMSCAN_THROTTLE_CONGESTED);
|
|
|
|
if (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed,
|
|
sc))
|
|
goto again;
|
|
|
|
/*
|
|
* Kswapd gives up on balancing particular nodes after too
|
|
* many failures to reclaim anything from them and goes to
|
|
* sleep. On reclaim progress, reset the failure counter. A
|
|
* successful direct reclaim run will revive a dormant kswapd.
|
|
*/
|
|
if (reclaimable)
|
|
pgdat->kswapd_failures = 0;
|
|
}
|
|
|
|
/*
|
|
* Returns true if compaction should go ahead for a costly-order request, or
|
|
* the allocation would already succeed without compaction. Return false if we
|
|
* should reclaim first.
|
|
*/
|
|
static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
|
|
{
|
|
unsigned long watermark;
|
|
enum compact_result suitable;
|
|
|
|
suitable = compaction_suitable(zone, sc->order, 0, sc->reclaim_idx);
|
|
if (suitable == COMPACT_SUCCESS)
|
|
/* Allocation should succeed already. Don't reclaim. */
|
|
return true;
|
|
if (suitable == COMPACT_SKIPPED)
|
|
/* Compaction cannot yet proceed. Do reclaim. */
|
|
return false;
|
|
|
|
/*
|
|
* Compaction is already possible, but it takes time to run and there
|
|
* are potentially other callers using the pages just freed. So proceed
|
|
* with reclaim to make a buffer of free pages available to give
|
|
* compaction a reasonable chance of completing and allocating the page.
|
|
* Note that we won't actually reclaim the whole buffer in one attempt
|
|
* as the target watermark in should_continue_reclaim() is lower. But if
|
|
* we are already above the high+gap watermark, don't reclaim at all.
|
|
*/
|
|
watermark = high_wmark_pages(zone) + compact_gap(sc->order);
|
|
|
|
return zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx);
|
|
}
|
|
|
|
static void consider_reclaim_throttle(pg_data_t *pgdat, struct scan_control *sc)
|
|
{
|
|
/*
|
|
* If reclaim is making progress greater than 12% efficiency then
|
|
* wake all the NOPROGRESS throttled tasks.
|
|
*/
|
|
if (sc->nr_reclaimed > (sc->nr_scanned >> 3)) {
|
|
wait_queue_head_t *wqh;
|
|
|
|
wqh = &pgdat->reclaim_wait[VMSCAN_THROTTLE_NOPROGRESS];
|
|
if (waitqueue_active(wqh))
|
|
wake_up(wqh);
|
|
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Do not throttle kswapd or cgroup reclaim on NOPROGRESS as it will
|
|
* throttle on VMSCAN_THROTTLE_WRITEBACK if there are too many pages
|
|
* under writeback and marked for immediate reclaim at the tail of the
|
|
* LRU.
|
|
*/
|
|
if (current_is_kswapd() || cgroup_reclaim(sc))
|
|
return;
|
|
|
|
/* Throttle if making no progress at high prioities. */
|
|
if (sc->priority == 1 && !sc->nr_reclaimed)
|
|
reclaim_throttle(pgdat, VMSCAN_THROTTLE_NOPROGRESS);
|
|
}
|
|
|
|
/*
|
|
* This is the direct reclaim path, for page-allocating processes. We only
|
|
* try to reclaim pages from zones which will satisfy the caller's allocation
|
|
* request.
|
|
*
|
|
* If a zone is deemed to be full of pinned pages then just give it a light
|
|
* scan then give up on it.
|
|
*/
|
|
static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
|
|
{
|
|
struct zoneref *z;
|
|
struct zone *zone;
|
|
unsigned long nr_soft_reclaimed;
|
|
unsigned long nr_soft_scanned;
|
|
gfp_t orig_mask;
|
|
pg_data_t *last_pgdat = NULL;
|
|
pg_data_t *first_pgdat = NULL;
|
|
|
|
/*
|
|
* If the number of buffer_heads in the machine exceeds the maximum
|
|
* allowed level, force direct reclaim to scan the highmem zone as
|
|
* highmem pages could be pinning lowmem pages storing buffer_heads
|
|
*/
|
|
orig_mask = sc->gfp_mask;
|
|
if (buffer_heads_over_limit) {
|
|
sc->gfp_mask |= __GFP_HIGHMEM;
|
|
sc->reclaim_idx = gfp_zone(sc->gfp_mask);
|
|
}
|
|
|
|
for_each_zone_zonelist_nodemask(zone, z, zonelist,
|
|
sc->reclaim_idx, sc->nodemask) {
|
|
/*
|
|
* Take care memory controller reclaiming has small influence
|
|
* to global LRU.
|
|
*/
|
|
if (!cgroup_reclaim(sc)) {
|
|
if (!cpuset_zone_allowed(zone,
|
|
GFP_KERNEL | __GFP_HARDWALL))
|
|
continue;
|
|
|
|
/*
|
|
* If we already have plenty of memory free for
|
|
* compaction in this zone, don't free any more.
|
|
* Even though compaction is invoked for any
|
|
* non-zero order, only frequent costly order
|
|
* reclamation is disruptive enough to become a
|
|
* noticeable problem, like transparent huge
|
|
* page allocations.
|
|
*/
|
|
if (IS_ENABLED(CONFIG_COMPACTION) &&
|
|
sc->order > PAGE_ALLOC_COSTLY_ORDER &&
|
|
compaction_ready(zone, sc)) {
|
|
sc->compaction_ready = true;
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* Shrink each node in the zonelist once. If the
|
|
* zonelist is ordered by zone (not the default) then a
|
|
* node may be shrunk multiple times but in that case
|
|
* the user prefers lower zones being preserved.
|
|
*/
|
|
if (zone->zone_pgdat == last_pgdat)
|
|
continue;
|
|
|
|
/*
|
|
* This steals pages from memory cgroups over softlimit
|
|
* and returns the number of reclaimed pages and
|
|
* scanned pages. This works for global memory pressure
|
|
* and balancing, not for a memcg's limit.
|
|
*/
|
|
nr_soft_scanned = 0;
|
|
nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone->zone_pgdat,
|
|
sc->order, sc->gfp_mask,
|
|
&nr_soft_scanned);
|
|
sc->nr_reclaimed += nr_soft_reclaimed;
|
|
sc->nr_scanned += nr_soft_scanned;
|
|
/* need some check for avoid more shrink_zone() */
|
|
}
|
|
|
|
if (!first_pgdat)
|
|
first_pgdat = zone->zone_pgdat;
|
|
|
|
/* See comment about same check for global reclaim above */
|
|
if (zone->zone_pgdat == last_pgdat)
|
|
continue;
|
|
last_pgdat = zone->zone_pgdat;
|
|
shrink_node(zone->zone_pgdat, sc);
|
|
}
|
|
|
|
if (first_pgdat)
|
|
consider_reclaim_throttle(first_pgdat, sc);
|
|
|
|
/*
|
|
* Restore to original mask to avoid the impact on the caller if we
|
|
* promoted it to __GFP_HIGHMEM.
|
|
*/
|
|
sc->gfp_mask = orig_mask;
|
|
}
|
|
|
|
static void snapshot_refaults(struct mem_cgroup *target_memcg, pg_data_t *pgdat)
|
|
{
|
|
struct lruvec *target_lruvec;
|
|
unsigned long refaults;
|
|
|
|
target_lruvec = mem_cgroup_lruvec(target_memcg, pgdat);
|
|
refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_ANON);
|
|
target_lruvec->refaults[0] = refaults;
|
|
refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_FILE);
|
|
target_lruvec->refaults[1] = refaults;
|
|
}
|
|
|
|
/*
|
|
* This is the main entry point to direct page reclaim.
|
|
*
|
|
* If a full scan of the inactive list fails to free enough memory then we
|
|
* are "out of memory" and something needs to be killed.
|
|
*
|
|
* If the caller is !__GFP_FS then the probability of a failure is reasonably
|
|
* high - the zone may be full of dirty or under-writeback pages, which this
|
|
* caller can't do much about. We kick the writeback threads and take explicit
|
|
* naps in the hope that some of these pages can be written. But if the
|
|
* allocating task holds filesystem locks which prevent writeout this might not
|
|
* work, and the allocation attempt will fail.
|
|
*
|
|
* returns: 0, if no pages reclaimed
|
|
* else, the number of pages reclaimed
|
|
*/
|
|
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
|
|
struct scan_control *sc)
|
|
{
|
|
int initial_priority = sc->priority;
|
|
pg_data_t *last_pgdat;
|
|
struct zoneref *z;
|
|
struct zone *zone;
|
|
retry:
|
|
delayacct_freepages_start();
|
|
|
|
if (!cgroup_reclaim(sc))
|
|
__count_zid_vm_events(ALLOCSTALL, sc->reclaim_idx, 1);
|
|
|
|
do {
|
|
vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
|
|
sc->priority);
|
|
sc->nr_scanned = 0;
|
|
shrink_zones(zonelist, sc);
|
|
|
|
if (sc->nr_reclaimed >= sc->nr_to_reclaim)
|
|
break;
|
|
|
|
if (sc->compaction_ready)
|
|
break;
|
|
|
|
/*
|
|
* If we're getting trouble reclaiming, start doing
|
|
* writepage even in laptop mode.
|
|
*/
|
|
if (sc->priority < DEF_PRIORITY - 2)
|
|
sc->may_writepage = 1;
|
|
} while (--sc->priority >= 0);
|
|
|
|
last_pgdat = NULL;
|
|
for_each_zone_zonelist_nodemask(zone, z, zonelist, sc->reclaim_idx,
|
|
sc->nodemask) {
|
|
if (zone->zone_pgdat == last_pgdat)
|
|
continue;
|
|
last_pgdat = zone->zone_pgdat;
|
|
|
|
snapshot_refaults(sc->target_mem_cgroup, zone->zone_pgdat);
|
|
|
|
if (cgroup_reclaim(sc)) {
|
|
struct lruvec *lruvec;
|
|
|
|
lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup,
|
|
zone->zone_pgdat);
|
|
clear_bit(LRUVEC_CONGESTED, &lruvec->flags);
|
|
}
|
|
}
|
|
|
|
delayacct_freepages_end();
|
|
|
|
if (sc->nr_reclaimed)
|
|
return sc->nr_reclaimed;
|
|
|
|
/* Aborted reclaim to try compaction? don't OOM, then */
|
|
if (sc->compaction_ready)
|
|
return 1;
|
|
|
|
/*
|
|
* We make inactive:active ratio decisions based on the node's
|
|
* composition of memory, but a restrictive reclaim_idx or a
|
|
* memory.low cgroup setting can exempt large amounts of
|
|
* memory from reclaim. Neither of which are very common, so
|
|
* instead of doing costly eligibility calculations of the
|
|
* entire cgroup subtree up front, we assume the estimates are
|
|
* good, and retry with forcible deactivation if that fails.
|
|
*/
|
|
if (sc->skipped_deactivate) {
|
|
sc->priority = initial_priority;
|
|
sc->force_deactivate = 1;
|
|
sc->skipped_deactivate = 0;
|
|
goto retry;
|
|
}
|
|
|
|
/* Untapped cgroup reserves? Don't OOM, retry. */
|
|
if (sc->memcg_low_skipped) {
|
|
sc->priority = initial_priority;
|
|
sc->force_deactivate = 0;
|
|
sc->memcg_low_reclaim = 1;
|
|
sc->memcg_low_skipped = 0;
|
|
goto retry;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static bool allow_direct_reclaim(pg_data_t *pgdat)
|
|
{
|
|
struct zone *zone;
|
|
unsigned long pfmemalloc_reserve = 0;
|
|
unsigned long free_pages = 0;
|
|
int i;
|
|
bool wmark_ok;
|
|
|
|
if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
|
|
return true;
|
|
|
|
for (i = 0; i <= ZONE_NORMAL; i++) {
|
|
zone = &pgdat->node_zones[i];
|
|
if (!managed_zone(zone))
|
|
continue;
|
|
|
|
if (!zone_reclaimable_pages(zone))
|
|
continue;
|
|
|
|
pfmemalloc_reserve += min_wmark_pages(zone);
|
|
free_pages += zone_page_state(zone, NR_FREE_PAGES);
|
|
}
|
|
|
|
/* If there are no reserves (unexpected config) then do not throttle */
|
|
if (!pfmemalloc_reserve)
|
|
return true;
|
|
|
|
wmark_ok = free_pages > pfmemalloc_reserve / 2;
|
|
|
|
/* kswapd must be awake if processes are being throttled */
|
|
if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) {
|
|
if (READ_ONCE(pgdat->kswapd_highest_zoneidx) > ZONE_NORMAL)
|
|
WRITE_ONCE(pgdat->kswapd_highest_zoneidx, ZONE_NORMAL);
|
|
|
|
wake_up_interruptible(&pgdat->kswapd_wait);
|
|
}
|
|
|
|
return wmark_ok;
|
|
}
|
|
|
|
/*
|
|
* Throttle direct reclaimers if backing storage is backed by the network
|
|
* and the PFMEMALLOC reserve for the preferred node is getting dangerously
|
|
* depleted. kswapd will continue to make progress and wake the processes
|
|
* when the low watermark is reached.
|
|
*
|
|
* Returns true if a fatal signal was delivered during throttling. If this
|
|
* happens, the page allocator should not consider triggering the OOM killer.
|
|
*/
|
|
static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
|
|
nodemask_t *nodemask)
|
|
{
|
|
struct zoneref *z;
|
|
struct zone *zone;
|
|
pg_data_t *pgdat = NULL;
|
|
|
|
/*
|
|
* Kernel threads should not be throttled as they may be indirectly
|
|
* responsible for cleaning pages necessary for reclaim to make forward
|
|
* progress. kjournald for example may enter direct reclaim while
|
|
* committing a transaction where throttling it could forcing other
|
|
* processes to block on log_wait_commit().
|
|
*/
|
|
if (current->flags & PF_KTHREAD)
|
|
goto out;
|
|
|
|
/*
|
|
* If a fatal signal is pending, this process should not throttle.
|
|
* It should return quickly so it can exit and free its memory
|
|
*/
|
|
if (fatal_signal_pending(current))
|
|
goto out;
|
|
|
|
/*
|
|
* Check if the pfmemalloc reserves are ok by finding the first node
|
|
* with a usable ZONE_NORMAL or lower zone. The expectation is that
|
|
* GFP_KERNEL will be required for allocating network buffers when
|
|
* swapping over the network so ZONE_HIGHMEM is unusable.
|
|
*
|
|
* Throttling is based on the first usable node and throttled processes
|
|
* wait on a queue until kswapd makes progress and wakes them. There
|
|
* is an affinity then between processes waking up and where reclaim
|
|
* progress has been made assuming the process wakes on the same node.
|
|
* More importantly, processes running on remote nodes will not compete
|
|
* for remote pfmemalloc reserves and processes on different nodes
|
|
* should make reasonable progress.
|
|
*/
|
|
for_each_zone_zonelist_nodemask(zone, z, zonelist,
|
|
gfp_zone(gfp_mask), nodemask) {
|
|
if (zone_idx(zone) > ZONE_NORMAL)
|
|
continue;
|
|
|
|
/* Throttle based on the first usable node */
|
|
pgdat = zone->zone_pgdat;
|
|
if (allow_direct_reclaim(pgdat))
|
|
goto out;
|
|
break;
|
|
}
|
|
|
|
/* If no zone was usable by the allocation flags then do not throttle */
|
|
if (!pgdat)
|
|
goto out;
|
|
|
|
/* Account for the throttling */
|
|
count_vm_event(PGSCAN_DIRECT_THROTTLE);
|
|
|
|
/*
|
|
* If the caller cannot enter the filesystem, it's possible that it
|
|
* is due to the caller holding an FS lock or performing a journal
|
|
* transaction in the case of a filesystem like ext[3|4]. In this case,
|
|
* it is not safe to block on pfmemalloc_wait as kswapd could be
|
|
* blocked waiting on the same lock. Instead, throttle for up to a
|
|
* second before continuing.
|
|
*/
|
|
if (!(gfp_mask & __GFP_FS))
|
|
wait_event_interruptible_timeout(pgdat->pfmemalloc_wait,
|
|
allow_direct_reclaim(pgdat), HZ);
|
|
else
|
|
/* Throttle until kswapd wakes the process */
|
|
wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
|
|
allow_direct_reclaim(pgdat));
|
|
|
|
if (fatal_signal_pending(current))
|
|
return true;
|
|
|
|
out:
|
|
return false;
|
|
}
|
|
|
|
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
|
|
gfp_t gfp_mask, nodemask_t *nodemask)
|
|
{
|
|
unsigned long nr_reclaimed;
|
|
struct scan_control sc = {
|
|
.nr_to_reclaim = SWAP_CLUSTER_MAX,
|
|
.gfp_mask = current_gfp_context(gfp_mask),
|
|
.reclaim_idx = gfp_zone(gfp_mask),
|
|
.order = order,
|
|
.nodemask = nodemask,
|
|
.priority = DEF_PRIORITY,
|
|
.may_writepage = !laptop_mode,
|
|
.may_unmap = 1,
|
|
.may_swap = 1,
|
|
};
|
|
|
|
/*
|
|
* scan_control uses s8 fields for order, priority, and reclaim_idx.
|
|
* Confirm they are large enough for max values.
|
|
*/
|
|
BUILD_BUG_ON(MAX_ORDER > S8_MAX);
|
|
BUILD_BUG_ON(DEF_PRIORITY > S8_MAX);
|
|
BUILD_BUG_ON(MAX_NR_ZONES > S8_MAX);
|
|
|
|
/*
|
|
* Do not enter reclaim if fatal signal was delivered while throttled.
|
|
* 1 is returned so that the page allocator does not OOM kill at this
|
|
* point.
|
|
*/
|
|
if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask))
|
|
return 1;
|
|
|
|
set_task_reclaim_state(current, &sc.reclaim_state);
|
|
trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask);
|
|
|
|
nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
|
|
|
|
trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
|
|
set_task_reclaim_state(current, NULL);
|
|
|
|
return nr_reclaimed;
|
|
}
|
|
|
|
#ifdef CONFIG_MEMCG
|
|
|
|
/* Only used by soft limit reclaim. Do not reuse for anything else. */
|
|
unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,
|
|
gfp_t gfp_mask, bool noswap,
|
|
pg_data_t *pgdat,
|
|
unsigned long *nr_scanned)
|
|
{
|
|
struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
|
|
struct scan_control sc = {
|
|
.nr_to_reclaim = SWAP_CLUSTER_MAX,
|
|
.target_mem_cgroup = memcg,
|
|
.may_writepage = !laptop_mode,
|
|
.may_unmap = 1,
|
|
.reclaim_idx = MAX_NR_ZONES - 1,
|
|
.may_swap = !noswap,
|
|
};
|
|
|
|
WARN_ON_ONCE(!current->reclaim_state);
|
|
|
|
sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
|
|
(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
|
|
|
|
trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
|
|
sc.gfp_mask);
|
|
|
|
/*
|
|
* NOTE: Although we can get the priority field, using it
|
|
* here is not a good idea, since it limits the pages we can scan.
|
|
* if we don't reclaim here, the shrink_node from balance_pgdat
|
|
* will pick up pages from other mem cgroup's as well. We hack
|
|
* the priority and make it zero.
|
|
*/
|
|
shrink_lruvec(lruvec, &sc);
|
|
|
|
trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
|
|
|
|
*nr_scanned = sc.nr_scanned;
|
|
|
|
return sc.nr_reclaimed;
|
|
}
|
|
|
|
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
|
|
unsigned long nr_pages,
|
|
gfp_t gfp_mask,
|
|
bool may_swap)
|
|
{
|
|
unsigned long nr_reclaimed;
|
|
unsigned int noreclaim_flag;
|
|
struct scan_control sc = {
|
|
.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
|
|
.gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) |
|
|
(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
|
|
.reclaim_idx = MAX_NR_ZONES - 1,
|
|
.target_mem_cgroup = memcg,
|
|
.priority = DEF_PRIORITY,
|
|
.may_writepage = !laptop_mode,
|
|
.may_unmap = 1,
|
|
.may_swap = may_swap,
|
|
};
|
|
/*
|
|
* Traverse the ZONELIST_FALLBACK zonelist of the current node to put
|
|
* equal pressure on all the nodes. This is based on the assumption that
|
|
* the reclaim does not bail out early.
|
|
*/
|
|
struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
|
|
|
|
set_task_reclaim_state(current, &sc.reclaim_state);
|
|
trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask);
|
|
noreclaim_flag = memalloc_noreclaim_save();
|
|
|
|
nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
|
|
|
|
memalloc_noreclaim_restore(noreclaim_flag);
|
|
trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
|
|
set_task_reclaim_state(current, NULL);
|
|
|
|
return nr_reclaimed;
|
|
}
|
|
#endif
|
|
|
|
static void age_active_anon(struct pglist_data *pgdat,
|
|
struct scan_control *sc)
|
|
{
|
|
struct mem_cgroup *memcg;
|
|
struct lruvec *lruvec;
|
|
|
|
if (!can_age_anon_pages(pgdat, sc))
|
|
return;
|
|
|
|
lruvec = mem_cgroup_lruvec(NULL, pgdat);
|
|
if (!inactive_is_low(lruvec, LRU_INACTIVE_ANON))
|
|
return;
|
|
|
|
memcg = mem_cgroup_iter(NULL, NULL, NULL);
|
|
do {
|
|
lruvec = mem_cgroup_lruvec(memcg, pgdat);
|
|
shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
|
|
sc, LRU_ACTIVE_ANON);
|
|
memcg = mem_cgroup_iter(NULL, memcg, NULL);
|
|
} while (memcg);
|
|
}
|
|
|
|
static bool pgdat_watermark_boosted(pg_data_t *pgdat, int highest_zoneidx)
|
|
{
|
|
int i;
|
|
struct zone *zone;
|
|
|
|
/*
|
|
* Check for watermark boosts top-down as the higher zones
|
|
* are more likely to be boosted. Both watermarks and boosts
|
|
* should not be checked at the same time as reclaim would
|
|
* start prematurely when there is no boosting and a lower
|
|
* zone is balanced.
|
|
*/
|
|
for (i = highest_zoneidx; i >= 0; i--) {
|
|
zone = pgdat->node_zones + i;
|
|
if (!managed_zone(zone))
|
|
continue;
|
|
|
|
if (zone->watermark_boost)
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* Returns true if there is an eligible zone balanced for the request order
|
|
* and highest_zoneidx
|
|
*/
|
|
static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx)
|
|
{
|
|
int i;
|
|
unsigned long mark = -1;
|
|
struct zone *zone;
|
|
|
|
/*
|
|
* Check watermarks bottom-up as lower zones are more likely to
|
|
* meet watermarks.
|
|
*/
|
|
for (i = 0; i <= highest_zoneidx; i++) {
|
|
zone = pgdat->node_zones + i;
|
|
|
|
if (!managed_zone(zone))
|
|
continue;
|
|
|
|
if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)
|
|
mark = wmark_pages(zone, WMARK_PROMO);
|
|
else
|
|
mark = high_wmark_pages(zone);
|
|
if (zone_watermark_ok_safe(zone, order, mark, highest_zoneidx))
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* If a node has no managed zone within highest_zoneidx, it does not
|
|
* need balancing by definition. This can happen if a zone-restricted
|
|
* allocation tries to wake a remote kswapd.
|
|
*/
|
|
if (mark == -1)
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/* Clear pgdat state for congested, dirty or under writeback. */
|
|
static void clear_pgdat_congested(pg_data_t *pgdat)
|
|
{
|
|
struct lruvec *lruvec = mem_cgroup_lruvec(NULL, pgdat);
|
|
|
|
clear_bit(LRUVEC_CONGESTED, &lruvec->flags);
|
|
clear_bit(PGDAT_DIRTY, &pgdat->flags);
|
|
clear_bit(PGDAT_WRITEBACK, &pgdat->flags);
|
|
}
|
|
|
|
/*
|
|
* Prepare kswapd for sleeping. This verifies that there are no processes
|
|
* waiting in throttle_direct_reclaim() and that watermarks have been met.
|
|
*
|
|
* Returns true if kswapd is ready to sleep
|
|
*/
|
|
static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order,
|
|
int highest_zoneidx)
|
|
{
|
|
/*
|
|
* The throttled processes are normally woken up in balance_pgdat() as
|
|
* soon as allow_direct_reclaim() is true. But there is a potential
|
|
* race between when kswapd checks the watermarks and a process gets
|
|
* throttled. There is also a potential race if processes get
|
|
* throttled, kswapd wakes, a large process exits thereby balancing the
|
|
* zones, which causes kswapd to exit balance_pgdat() before reaching
|
|
* the wake up checks. If kswapd is going to sleep, no process should
|
|
* be sleeping on pfmemalloc_wait, so wake them now if necessary. If
|
|
* the wake up is premature, processes will wake kswapd and get
|
|
* throttled again. The difference from wake ups in balance_pgdat() is
|
|
* that here we are under prepare_to_wait().
|
|
*/
|
|
if (waitqueue_active(&pgdat->pfmemalloc_wait))
|
|
wake_up_all(&pgdat->pfmemalloc_wait);
|
|
|
|
/* Hopeless node, leave it to direct reclaim */
|
|
if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
|
|
return true;
|
|
|
|
if (pgdat_balanced(pgdat, order, highest_zoneidx)) {
|
|
clear_pgdat_congested(pgdat);
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* kswapd shrinks a node of pages that are at or below the highest usable
|
|
* zone that is currently unbalanced.
|
|
*
|
|
* Returns true if kswapd scanned at least the requested number of pages to
|
|
* reclaim or if the lack of progress was due to pages under writeback.
|
|
* This is used to determine if the scanning priority needs to be raised.
|
|
*/
|
|
static bool kswapd_shrink_node(pg_data_t *pgdat,
|
|
struct scan_control *sc)
|
|
{
|
|
struct zone *zone;
|
|
int z;
|
|
|
|
/* Reclaim a number of pages proportional to the number of zones */
|
|
sc->nr_to_reclaim = 0;
|
|
for (z = 0; z <= sc->reclaim_idx; z++) {
|
|
zone = pgdat->node_zones + z;
|
|
if (!managed_zone(zone))
|
|
continue;
|
|
|
|
sc->nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX);
|
|
}
|
|
|
|
/*
|
|
* Historically care was taken to put equal pressure on all zones but
|
|
* now pressure is applied based on node LRU order.
|
|
*/
|
|
shrink_node(pgdat, sc);
|
|
|
|
/*
|
|
* Fragmentation may mean that the system cannot be rebalanced for
|
|
* high-order allocations. If twice the allocation size has been
|
|
* reclaimed then recheck watermarks only at order-0 to prevent
|
|
* excessive reclaim. Assume that a process requested a high-order
|
|
* can direct reclaim/compact.
|
|
*/
|
|
if (sc->order && sc->nr_reclaimed >= compact_gap(sc->order))
|
|
sc->order = 0;
|
|
|
|
return sc->nr_scanned >= sc->nr_to_reclaim;
|
|
}
|
|
|
|
/* Page allocator PCP high watermark is lowered if reclaim is active. */
|
|
static inline void
|
|
update_reclaim_active(pg_data_t *pgdat, int highest_zoneidx, bool active)
|
|
{
|
|
int i;
|
|
struct zone *zone;
|
|
|
|
for (i = 0; i <= highest_zoneidx; i++) {
|
|
zone = pgdat->node_zones + i;
|
|
|
|
if (!managed_zone(zone))
|
|
continue;
|
|
|
|
if (active)
|
|
set_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
|
|
else
|
|
clear_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
|
|
}
|
|
}
|
|
|
|
static inline void
|
|
set_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
|
|
{
|
|
update_reclaim_active(pgdat, highest_zoneidx, true);
|
|
}
|
|
|
|
static inline void
|
|
clear_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
|
|
{
|
|
update_reclaim_active(pgdat, highest_zoneidx, false);
|
|
}
|
|
|
|
/*
|
|
* For kswapd, balance_pgdat() will reclaim pages across a node from zones
|
|
* that are eligible for use by the caller until at least one zone is
|
|
* balanced.
|
|
*
|
|
* Returns the order kswapd finished reclaiming at.
|
|
*
|
|
* kswapd scans the zones in the highmem->normal->dma direction. It skips
|
|
* zones which have free_pages > high_wmark_pages(zone), but once a zone is
|
|
* found to have free_pages <= high_wmark_pages(zone), any page in that zone
|
|
* or lower is eligible for reclaim until at least one usable zone is
|
|
* balanced.
|
|
*/
|
|
static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)
|
|
{
|
|
int i;
|
|
unsigned long nr_soft_reclaimed;
|
|
unsigned long nr_soft_scanned;
|
|
unsigned long pflags;
|
|
unsigned long nr_boost_reclaim;
|
|
unsigned long zone_boosts[MAX_NR_ZONES] = { 0, };
|
|
bool boosted;
|
|
struct zone *zone;
|
|
struct scan_control sc = {
|
|
.gfp_mask = GFP_KERNEL,
|
|
.order = order,
|
|
.may_unmap = 1,
|
|
};
|
|
|
|
set_task_reclaim_state(current, &sc.reclaim_state);
|
|
psi_memstall_enter(&pflags);
|
|
__fs_reclaim_acquire(_THIS_IP_);
|
|
|
|
count_vm_event(PAGEOUTRUN);
|
|
|
|
/*
|
|
* Account for the reclaim boost. Note that the zone boost is left in
|
|
* place so that parallel allocations that are near the watermark will
|
|
* stall or direct reclaim until kswapd is finished.
|
|
*/
|
|
nr_boost_reclaim = 0;
|
|
for (i = 0; i <= highest_zoneidx; i++) {
|
|
zone = pgdat->node_zones + i;
|
|
if (!managed_zone(zone))
|
|
continue;
|
|
|
|
nr_boost_reclaim += zone->watermark_boost;
|
|
zone_boosts[i] = zone->watermark_boost;
|
|
}
|
|
boosted = nr_boost_reclaim;
|
|
|
|
restart:
|
|
set_reclaim_active(pgdat, highest_zoneidx);
|
|
sc.priority = DEF_PRIORITY;
|
|
do {
|
|
unsigned long nr_reclaimed = sc.nr_reclaimed;
|
|
bool raise_priority = true;
|
|
bool balanced;
|
|
bool ret;
|
|
|
|
sc.reclaim_idx = highest_zoneidx;
|
|
|
|
/*
|
|
* If the number of buffer_heads exceeds the maximum allowed
|
|
* then consider reclaiming from all zones. This has a dual
|
|
* purpose -- on 64-bit systems it is expected that
|
|
* buffer_heads are stripped during active rotation. On 32-bit
|
|
* systems, highmem pages can pin lowmem memory and shrinking
|
|
* buffers can relieve lowmem pressure. Reclaim may still not
|
|
* go ahead if all eligible zones for the original allocation
|
|
* request are balanced to avoid excessive reclaim from kswapd.
|
|
*/
|
|
if (buffer_heads_over_limit) {
|
|
for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
|
|
zone = pgdat->node_zones + i;
|
|
if (!managed_zone(zone))
|
|
continue;
|
|
|
|
sc.reclaim_idx = i;
|
|
break;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If the pgdat is imbalanced then ignore boosting and preserve
|
|
* the watermarks for a later time and restart. Note that the
|
|
* zone watermarks will be still reset at the end of balancing
|
|
* on the grounds that the normal reclaim should be enough to
|
|
* re-evaluate if boosting is required when kswapd next wakes.
|
|
*/
|
|
balanced = pgdat_balanced(pgdat, sc.order, highest_zoneidx);
|
|
if (!balanced && nr_boost_reclaim) {
|
|
nr_boost_reclaim = 0;
|
|
goto restart;
|
|
}
|
|
|
|
/*
|
|
* If boosting is not active then only reclaim if there are no
|
|
* eligible zones. Note that sc.reclaim_idx is not used as
|
|
* buffer_heads_over_limit may have adjusted it.
|
|
*/
|
|
if (!nr_boost_reclaim && balanced)
|
|
goto out;
|
|
|
|
/* Limit the priority of boosting to avoid reclaim writeback */
|
|
if (nr_boost_reclaim && sc.priority == DEF_PRIORITY - 2)
|
|
raise_priority = false;
|
|
|
|
/*
|
|
* Do not writeback or swap pages for boosted reclaim. The
|
|
* intent is to relieve pressure not issue sub-optimal IO
|
|
* from reclaim context. If no pages are reclaimed, the
|
|
* reclaim will be aborted.
|
|
*/
|
|
sc.may_writepage = !laptop_mode && !nr_boost_reclaim;
|
|
sc.may_swap = !nr_boost_reclaim;
|
|
|
|
/*
|
|
* Do some background aging of the anon list, to give
|
|
* pages a chance to be referenced before reclaiming. All
|
|
* pages are rotated regardless of classzone as this is
|
|
* about consistent aging.
|
|
*/
|
|
age_active_anon(pgdat, &sc);
|
|
|
|
/*
|
|
* If we're getting trouble reclaiming, start doing writepage
|
|
* even in laptop mode.
|
|
*/
|
|
if (sc.priority < DEF_PRIORITY - 2)
|
|
sc.may_writepage = 1;
|
|
|
|
/* Call soft limit reclaim before calling shrink_node. */
|
|
sc.nr_scanned = 0;
|
|
nr_soft_scanned = 0;
|
|
nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(pgdat, sc.order,
|
|
sc.gfp_mask, &nr_soft_scanned);
|
|
sc.nr_reclaimed += nr_soft_reclaimed;
|
|
|
|
/*
|
|
* There should be no need to raise the scanning priority if
|
|
* enough pages are already being scanned that that high
|
|
* watermark would be met at 100% efficiency.
|
|
*/
|
|
if (kswapd_shrink_node(pgdat, &sc))
|
|
raise_priority = false;
|
|
|
|
/*
|
|
* If the low watermark is met there is no need for processes
|
|
* to be throttled on pfmemalloc_wait as they should not be
|
|
* able to safely make forward progress. Wake them
|
|
*/
|
|
if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
|
|
allow_direct_reclaim(pgdat))
|
|
wake_up_all(&pgdat->pfmemalloc_wait);
|
|
|
|
/* Check if kswapd should be suspending */
|
|
__fs_reclaim_release(_THIS_IP_);
|
|
ret = try_to_freeze();
|
|
__fs_reclaim_acquire(_THIS_IP_);
|
|
if (ret || kthread_should_stop())
|
|
break;
|
|
|
|
/*
|
|
* Raise priority if scanning rate is too low or there was no
|
|
* progress in reclaiming pages
|
|
*/
|
|
nr_reclaimed = sc.nr_reclaimed - nr_reclaimed;
|
|
nr_boost_reclaim -= min(nr_boost_reclaim, nr_reclaimed);
|
|
|
|
/*
|
|
* If reclaim made no progress for a boost, stop reclaim as
|
|
* IO cannot be queued and it could be an infinite loop in
|
|
* extreme circumstances.
|
|
*/
|
|
if (nr_boost_reclaim && !nr_reclaimed)
|
|
break;
|
|
|
|
if (raise_priority || !nr_reclaimed)
|
|
sc.priority--;
|
|
} while (sc.priority >= 1);
|
|
|
|
if (!sc.nr_reclaimed)
|
|
pgdat->kswapd_failures++;
|
|
|
|
out:
|
|
clear_reclaim_active(pgdat, highest_zoneidx);
|
|
|
|
/* If reclaim was boosted, account for the reclaim done in this pass */
|
|
if (boosted) {
|
|
unsigned long flags;
|
|
|
|
for (i = 0; i <= highest_zoneidx; i++) {
|
|
if (!zone_boosts[i])
|
|
continue;
|
|
|
|
/* Increments are under the zone lock */
|
|
zone = pgdat->node_zones + i;
|
|
spin_lock_irqsave(&zone->lock, flags);
|
|
zone->watermark_boost -= min(zone->watermark_boost, zone_boosts[i]);
|
|
spin_unlock_irqrestore(&zone->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* As there is now likely space, wakeup kcompact to defragment
|
|
* pageblocks.
|
|
*/
|
|
wakeup_kcompactd(pgdat, pageblock_order, highest_zoneidx);
|
|
}
|
|
|
|
snapshot_refaults(NULL, pgdat);
|
|
__fs_reclaim_release(_THIS_IP_);
|
|
psi_memstall_leave(&pflags);
|
|
set_task_reclaim_state(current, NULL);
|
|
|
|
/*
|
|
* Return the order kswapd stopped reclaiming at as
|
|
* prepare_kswapd_sleep() takes it into account. If another caller
|
|
* entered the allocator slow path while kswapd was awake, order will
|
|
* remain at the higher level.
|
|
*/
|
|
return sc.order;
|
|
}
|
|
|
|
/*
|
|
* The pgdat->kswapd_highest_zoneidx is used to pass the highest zone index to
|
|
* be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is
|
|
* not a valid index then either kswapd runs for first time or kswapd couldn't
|
|
* sleep after previous reclaim attempt (node is still unbalanced). In that
|
|
* case return the zone index of the previous kswapd reclaim cycle.
|
|
*/
|
|
static enum zone_type kswapd_highest_zoneidx(pg_data_t *pgdat,
|
|
enum zone_type prev_highest_zoneidx)
|
|
{
|
|
enum zone_type curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
|
|
|
|
return curr_idx == MAX_NR_ZONES ? prev_highest_zoneidx : curr_idx;
|
|
}
|
|
|
|
static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order,
|
|
unsigned int highest_zoneidx)
|
|
{
|
|
long remaining = 0;
|
|
DEFINE_WAIT(wait);
|
|
|
|
if (freezing(current) || kthread_should_stop())
|
|
return;
|
|
|
|
prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
|
|
|
|
/*
|
|
* Try to sleep for a short interval. Note that kcompactd will only be
|
|
* woken if it is possible to sleep for a short interval. This is
|
|
* deliberate on the assumption that if reclaim cannot keep an
|
|
* eligible zone balanced that it's also unlikely that compaction will
|
|
* succeed.
|
|
*/
|
|
if (prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
|
|
/*
|
|
* Compaction records what page blocks it recently failed to
|
|
* isolate pages from and skips them in the future scanning.
|
|
* When kswapd is going to sleep, it is reasonable to assume
|
|
* that pages and compaction may succeed so reset the cache.
|
|
*/
|
|
reset_isolation_suitable(pgdat);
|
|
|
|
/*
|
|
* We have freed the memory, now we should compact it to make
|
|
* allocation of the requested order possible.
|
|
*/
|
|
wakeup_kcompactd(pgdat, alloc_order, highest_zoneidx);
|
|
|
|
remaining = schedule_timeout(HZ/10);
|
|
|
|
/*
|
|
* If woken prematurely then reset kswapd_highest_zoneidx and
|
|
* order. The values will either be from a wakeup request or
|
|
* the previous request that slept prematurely.
|
|
*/
|
|
if (remaining) {
|
|
WRITE_ONCE(pgdat->kswapd_highest_zoneidx,
|
|
kswapd_highest_zoneidx(pgdat,
|
|
highest_zoneidx));
|
|
|
|
if (READ_ONCE(pgdat->kswapd_order) < reclaim_order)
|
|
WRITE_ONCE(pgdat->kswapd_order, reclaim_order);
|
|
}
|
|
|
|
finish_wait(&pgdat->kswapd_wait, &wait);
|
|
prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
|
|
}
|
|
|
|
/*
|
|
* After a short sleep, check if it was a premature sleep. If not, then
|
|
* go fully to sleep until explicitly woken up.
|
|
*/
|
|
if (!remaining &&
|
|
prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
|
|
trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
|
|
|
|
/*
|
|
* vmstat counters are not perfectly accurate and the estimated
|
|
* value for counters such as NR_FREE_PAGES can deviate from the
|
|
* true value by nr_online_cpus * threshold. To avoid the zone
|
|
* watermarks being breached while under pressure, we reduce the
|
|
* per-cpu vmstat threshold while kswapd is awake and restore
|
|
* them before going back to sleep.
|
|
*/
|
|
set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
|
|
|
|
if (!kthread_should_stop())
|
|
schedule();
|
|
|
|
set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
|
|
} else {
|
|
if (remaining)
|
|
count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
|
|
else
|
|
count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
|
|
}
|
|
finish_wait(&pgdat->kswapd_wait, &wait);
|
|
}
|
|
|
|
/*
|
|
* The background pageout daemon, started as a kernel thread
|
|
* from the init process.
|
|
*
|
|
* This basically trickles out pages so that we have _some_
|
|
* free memory available even if there is no other activity
|
|
* that frees anything up. This is needed for things like routing
|
|
* etc, where we otherwise might have all activity going on in
|
|
* asynchronous contexts that cannot page things out.
|
|
*
|
|
* If there are applications that are active memory-allocators
|
|
* (most normal use), this basically shouldn't matter.
|
|
*/
|
|
static int kswapd(void *p)
|
|
{
|
|
unsigned int alloc_order, reclaim_order;
|
|
unsigned int highest_zoneidx = MAX_NR_ZONES - 1;
|
|
pg_data_t *pgdat = (pg_data_t *)p;
|
|
struct task_struct *tsk = current;
|
|
const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
|
|
|
|
if (!cpumask_empty(cpumask))
|
|
set_cpus_allowed_ptr(tsk, cpumask);
|
|
|
|
/*
|
|
* Tell the memory management that we're a "memory allocator",
|
|
* and that if we need more memory we should get access to it
|
|
* regardless (see "__alloc_pages()"). "kswapd" should
|
|
* never get caught in the normal page freeing logic.
|
|
*
|
|
* (Kswapd normally doesn't need memory anyway, but sometimes
|
|
* you need a small amount of memory in order to be able to
|
|
* page out something else, and this flag essentially protects
|
|
* us from recursively trying to free more memory as we're
|
|
* trying to free the first piece of memory in the first place).
|
|
*/
|
|
tsk->flags |= PF_MEMALLOC | PF_KSWAPD;
|
|
set_freezable();
|
|
|
|
WRITE_ONCE(pgdat->kswapd_order, 0);
|
|
WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
|
|
atomic_set(&pgdat->nr_writeback_throttled, 0);
|
|
for ( ; ; ) {
|
|
bool ret;
|
|
|
|
alloc_order = reclaim_order = READ_ONCE(pgdat->kswapd_order);
|
|
highest_zoneidx = kswapd_highest_zoneidx(pgdat,
|
|
highest_zoneidx);
|
|
|
|
kswapd_try_sleep:
|
|
kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order,
|
|
highest_zoneidx);
|
|
|
|
/* Read the new order and highest_zoneidx */
|
|
alloc_order = READ_ONCE(pgdat->kswapd_order);
|
|
highest_zoneidx = kswapd_highest_zoneidx(pgdat,
|
|
highest_zoneidx);
|
|
WRITE_ONCE(pgdat->kswapd_order, 0);
|
|
WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
|
|
|
|
ret = try_to_freeze();
|
|
if (kthread_should_stop())
|
|
break;
|
|
|
|
/*
|
|
* We can speed up thawing tasks if we don't call balance_pgdat
|
|
* after returning from the refrigerator
|
|
*/
|
|
if (ret)
|
|
continue;
|
|
|
|
/*
|
|
* Reclaim begins at the requested order but if a high-order
|
|
* reclaim fails then kswapd falls back to reclaiming for
|
|
* order-0. If that happens, kswapd will consider sleeping
|
|
* for the order it finished reclaiming at (reclaim_order)
|
|
* but kcompactd is woken to compact for the original
|
|
* request (alloc_order).
|
|
*/
|
|
trace_mm_vmscan_kswapd_wake(pgdat->node_id, highest_zoneidx,
|
|
alloc_order);
|
|
reclaim_order = balance_pgdat(pgdat, alloc_order,
|
|
highest_zoneidx);
|
|
if (reclaim_order < alloc_order)
|
|
goto kswapd_try_sleep;
|
|
}
|
|
|
|
tsk->flags &= ~(PF_MEMALLOC | PF_KSWAPD);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* A zone is low on free memory or too fragmented for high-order memory. If
|
|
* kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
|
|
* pgdat. It will wake up kcompactd after reclaiming memory. If kswapd reclaim
|
|
* has failed or is not needed, still wake up kcompactd if only compaction is
|
|
* needed.
|
|
*/
|
|
void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
|
|
enum zone_type highest_zoneidx)
|
|
{
|
|
pg_data_t *pgdat;
|
|
enum zone_type curr_idx;
|
|
|
|
if (!managed_zone(zone))
|
|
return;
|
|
|
|
if (!cpuset_zone_allowed(zone, gfp_flags))
|
|
return;
|
|
|
|
pgdat = zone->zone_pgdat;
|
|
curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
|
|
|
|
if (curr_idx == MAX_NR_ZONES || curr_idx < highest_zoneidx)
|
|
WRITE_ONCE(pgdat->kswapd_highest_zoneidx, highest_zoneidx);
|
|
|
|
if (READ_ONCE(pgdat->kswapd_order) < order)
|
|
WRITE_ONCE(pgdat->kswapd_order, order);
|
|
|
|
if (!waitqueue_active(&pgdat->kswapd_wait))
|
|
return;
|
|
|
|
/* Hopeless node, leave it to direct reclaim if possible */
|
|
if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ||
|
|
(pgdat_balanced(pgdat, order, highest_zoneidx) &&
|
|
!pgdat_watermark_boosted(pgdat, highest_zoneidx))) {
|
|
/*
|
|
* There may be plenty of free memory available, but it's too
|
|
* fragmented for high-order allocations. Wake up kcompactd
|
|
* and rely on compaction_suitable() to determine if it's
|
|
* needed. If it fails, it will defer subsequent attempts to
|
|
* ratelimit its work.
|
|
*/
|
|
if (!(gfp_flags & __GFP_DIRECT_RECLAIM))
|
|
wakeup_kcompactd(pgdat, order, highest_zoneidx);
|
|
return;
|
|
}
|
|
|
|
trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, highest_zoneidx, order,
|
|
gfp_flags);
|
|
wake_up_interruptible(&pgdat->kswapd_wait);
|
|
}
|
|
|
|
#ifdef CONFIG_HIBERNATION
|
|
/*
|
|
* Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
|
|
* freed pages.
|
|
*
|
|
* Rather than trying to age LRUs the aim is to preserve the overall
|
|
* LRU order by reclaiming preferentially
|
|
* inactive > active > active referenced > active mapped
|
|
*/
|
|
unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
|
|
{
|
|
struct scan_control sc = {
|
|
.nr_to_reclaim = nr_to_reclaim,
|
|
.gfp_mask = GFP_HIGHUSER_MOVABLE,
|
|
.reclaim_idx = MAX_NR_ZONES - 1,
|
|
.priority = DEF_PRIORITY,
|
|
.may_writepage = 1,
|
|
.may_unmap = 1,
|
|
.may_swap = 1,
|
|
.hibernation_mode = 1,
|
|
};
|
|
struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
|
|
unsigned long nr_reclaimed;
|
|
unsigned int noreclaim_flag;
|
|
|
|
fs_reclaim_acquire(sc.gfp_mask);
|
|
noreclaim_flag = memalloc_noreclaim_save();
|
|
set_task_reclaim_state(current, &sc.reclaim_state);
|
|
|
|
nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
|
|
|
|
set_task_reclaim_state(current, NULL);
|
|
memalloc_noreclaim_restore(noreclaim_flag);
|
|
fs_reclaim_release(sc.gfp_mask);
|
|
|
|
return nr_reclaimed;
|
|
}
|
|
#endif /* CONFIG_HIBERNATION */
|
|
|
|
/*
|
|
* This kswapd start function will be called by init and node-hot-add.
|
|
*/
|
|
void kswapd_run(int nid)
|
|
{
|
|
pg_data_t *pgdat = NODE_DATA(nid);
|
|
|
|
if (pgdat->kswapd)
|
|
return;
|
|
|
|
pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
|
|
if (IS_ERR(pgdat->kswapd)) {
|
|
/* failure at boot is fatal */
|
|
BUG_ON(system_state < SYSTEM_RUNNING);
|
|
pr_err("Failed to start kswapd on node %d\n", nid);
|
|
pgdat->kswapd = NULL;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Called by memory hotplug when all memory in a node is offlined. Caller must
|
|
* hold mem_hotplug_begin/end().
|
|
*/
|
|
void kswapd_stop(int nid)
|
|
{
|
|
struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
|
|
|
|
if (kswapd) {
|
|
kthread_stop(kswapd);
|
|
NODE_DATA(nid)->kswapd = NULL;
|
|
}
|
|
}
|
|
|
|
static int __init kswapd_init(void)
|
|
{
|
|
int nid;
|
|
|
|
swap_setup();
|
|
for_each_node_state(nid, N_MEMORY)
|
|
kswapd_run(nid);
|
|
return 0;
|
|
}
|
|
|
|
module_init(kswapd_init)
|
|
|
|
#ifdef CONFIG_NUMA
|
|
/*
|
|
* Node reclaim mode
|
|
*
|
|
* If non-zero call node_reclaim when the number of free pages falls below
|
|
* the watermarks.
|
|
*/
|
|
int node_reclaim_mode __read_mostly;
|
|
|
|
/*
|
|
* Priority for NODE_RECLAIM. This determines the fraction of pages
|
|
* of a node considered for each zone_reclaim. 4 scans 1/16th of
|
|
* a zone.
|
|
*/
|
|
#define NODE_RECLAIM_PRIORITY 4
|
|
|
|
/*
|
|
* Percentage of pages in a zone that must be unmapped for node_reclaim to
|
|
* occur.
|
|
*/
|
|
int sysctl_min_unmapped_ratio = 1;
|
|
|
|
/*
|
|
* If the number of slab pages in a zone grows beyond this percentage then
|
|
* slab reclaim needs to occur.
|
|
*/
|
|
int sysctl_min_slab_ratio = 5;
|
|
|
|
static inline unsigned long node_unmapped_file_pages(struct pglist_data *pgdat)
|
|
{
|
|
unsigned long file_mapped = node_page_state(pgdat, NR_FILE_MAPPED);
|
|
unsigned long file_lru = node_page_state(pgdat, NR_INACTIVE_FILE) +
|
|
node_page_state(pgdat, NR_ACTIVE_FILE);
|
|
|
|
/*
|
|
* It's possible for there to be more file mapped pages than
|
|
* accounted for by the pages on the file LRU lists because
|
|
* tmpfs pages accounted for as ANON can also be FILE_MAPPED
|
|
*/
|
|
return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
|
|
}
|
|
|
|
/* Work out how many page cache pages we can reclaim in this reclaim_mode */
|
|
static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
|
|
{
|
|
unsigned long nr_pagecache_reclaimable;
|
|
unsigned long delta = 0;
|
|
|
|
/*
|
|
* If RECLAIM_UNMAP is set, then all file pages are considered
|
|
* potentially reclaimable. Otherwise, we have to worry about
|
|
* pages like swapcache and node_unmapped_file_pages() provides
|
|
* a better estimate
|
|
*/
|
|
if (node_reclaim_mode & RECLAIM_UNMAP)
|
|
nr_pagecache_reclaimable = node_page_state(pgdat, NR_FILE_PAGES);
|
|
else
|
|
nr_pagecache_reclaimable = node_unmapped_file_pages(pgdat);
|
|
|
|
/* If we can't clean pages, remove dirty pages from consideration */
|
|
if (!(node_reclaim_mode & RECLAIM_WRITE))
|
|
delta += node_page_state(pgdat, NR_FILE_DIRTY);
|
|
|
|
/* Watch for any possible underflows due to delta */
|
|
if (unlikely(delta > nr_pagecache_reclaimable))
|
|
delta = nr_pagecache_reclaimable;
|
|
|
|
return nr_pagecache_reclaimable - delta;
|
|
}
|
|
|
|
/*
|
|
* Try to free up some pages from this node through reclaim.
|
|
*/
|
|
static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
|
|
{
|
|
/* Minimum pages needed in order to stay on node */
|
|
const unsigned long nr_pages = 1 << order;
|
|
struct task_struct *p = current;
|
|
unsigned int noreclaim_flag;
|
|
struct scan_control sc = {
|
|
.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
|
|
.gfp_mask = current_gfp_context(gfp_mask),
|
|
.order = order,
|
|
.priority = NODE_RECLAIM_PRIORITY,
|
|
.may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE),
|
|
.may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP),
|
|
.may_swap = 1,
|
|
.reclaim_idx = gfp_zone(gfp_mask),
|
|
};
|
|
unsigned long pflags;
|
|
|
|
trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order,
|
|
sc.gfp_mask);
|
|
|
|
cond_resched();
|
|
psi_memstall_enter(&pflags);
|
|
fs_reclaim_acquire(sc.gfp_mask);
|
|
/*
|
|
* We need to be able to allocate from the reserves for RECLAIM_UNMAP
|
|
*/
|
|
noreclaim_flag = memalloc_noreclaim_save();
|
|
set_task_reclaim_state(p, &sc.reclaim_state);
|
|
|
|
if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages ||
|
|
node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) > pgdat->min_slab_pages) {
|
|
/*
|
|
* Free memory by calling shrink node with increasing
|
|
* priorities until we have enough memory freed.
|
|
*/
|
|
do {
|
|
shrink_node(pgdat, &sc);
|
|
} while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
|
|
}
|
|
|
|
set_task_reclaim_state(p, NULL);
|
|
memalloc_noreclaim_restore(noreclaim_flag);
|
|
fs_reclaim_release(sc.gfp_mask);
|
|
psi_memstall_leave(&pflags);
|
|
|
|
trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed);
|
|
|
|
return sc.nr_reclaimed >= nr_pages;
|
|
}
|
|
|
|
int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
|
|
{
|
|
int ret;
|
|
|
|
/*
|
|
* Node reclaim reclaims unmapped file backed pages and
|
|
* slab pages if we are over the defined limits.
|
|
*
|
|
* A small portion of unmapped file backed pages is needed for
|
|
* file I/O otherwise pages read by file I/O will be immediately
|
|
* thrown out if the node is overallocated. So we do not reclaim
|
|
* if less than a specified percentage of the node is used by
|
|
* unmapped file backed pages.
|
|
*/
|
|
if (node_pagecache_reclaimable(pgdat) <= pgdat->min_unmapped_pages &&
|
|
node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) <=
|
|
pgdat->min_slab_pages)
|
|
return NODE_RECLAIM_FULL;
|
|
|
|
/*
|
|
* Do not scan if the allocation should not be delayed.
|
|
*/
|
|
if (!gfpflags_allow_blocking(gfp_mask) || (current->flags & PF_MEMALLOC))
|
|
return NODE_RECLAIM_NOSCAN;
|
|
|
|
/*
|
|
* Only run node reclaim on the local node or on nodes that do not
|
|
* have associated processors. This will favor the local processor
|
|
* over remote processors and spread off node memory allocations
|
|
* as wide as possible.
|
|
*/
|
|
if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id())
|
|
return NODE_RECLAIM_NOSCAN;
|
|
|
|
if (test_and_set_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags))
|
|
return NODE_RECLAIM_NOSCAN;
|
|
|
|
ret = __node_reclaim(pgdat, gfp_mask, order);
|
|
clear_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags);
|
|
|
|
if (!ret)
|
|
count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
|
|
|
|
return ret;
|
|
}
|
|
#endif
|
|
|
|
/**
|
|
* check_move_unevictable_pages - check pages for evictability and move to
|
|
* appropriate zone lru list
|
|
* @pvec: pagevec with lru pages to check
|
|
*
|
|
* Checks pages for evictability, if an evictable page is in the unevictable
|
|
* lru list, moves it to the appropriate evictable lru list. This function
|
|
* should be only used for lru pages.
|
|
*/
|
|
void check_move_unevictable_pages(struct pagevec *pvec)
|
|
{
|
|
struct lruvec *lruvec = NULL;
|
|
int pgscanned = 0;
|
|
int pgrescued = 0;
|
|
int i;
|
|
|
|
for (i = 0; i < pvec->nr; i++) {
|
|
struct page *page = pvec->pages[i];
|
|
struct folio *folio = page_folio(page);
|
|
int nr_pages;
|
|
|
|
if (PageTransTail(page))
|
|
continue;
|
|
|
|
nr_pages = thp_nr_pages(page);
|
|
pgscanned += nr_pages;
|
|
|
|
/* block memcg migration during page moving between lru */
|
|
if (!TestClearPageLRU(page))
|
|
continue;
|
|
|
|
lruvec = folio_lruvec_relock_irq(folio, lruvec);
|
|
if (page_evictable(page) && PageUnevictable(page)) {
|
|
del_page_from_lru_list(page, lruvec);
|
|
ClearPageUnevictable(page);
|
|
add_page_to_lru_list(page, lruvec);
|
|
pgrescued += nr_pages;
|
|
}
|
|
SetPageLRU(page);
|
|
}
|
|
|
|
if (lruvec) {
|
|
__count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
|
|
__count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
|
|
unlock_page_lruvec_irq(lruvec);
|
|
} else if (pgscanned) {
|
|
count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(check_move_unevictable_pages);
|