forked from mirrors/linux
4236 lines
121 KiB
C
4236 lines
121 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/mm/vmscan.c
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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/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 "internal.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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/* 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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* Cgroups are not reclaimed below their configured memory.low,
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* unless we threaten to OOM. If any cgroups are skipped due to
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* memory.low and nothing was reclaimed, go back for memory.low.
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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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/* 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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};
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#ifdef ARCH_HAS_PREFETCH
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#define prefetch_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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prefetch(&prev->_field); \
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} \
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} while (0)
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#else
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#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
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#endif
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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 .. 100. Higher means more swappy.
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*/
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int vm_swappiness = 60;
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/*
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* The total number of pages which are beyond the high watermark within all
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* zones.
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*/
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unsigned long vm_total_pages;
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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_KMEM
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/*
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* We allow subsystems to populate their shrinker-related
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* LRU lists before register_shrinker_prepared() is called
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* for the shrinker, since we don't want to impose
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* restrictions on their internal registration order.
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* In this case shrink_slab_memcg() may find corresponding
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* bit is set in the shrinkers map.
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*
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* This value is used by the function to detect registering
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* shrinkers and to skip do_shrink_slab() calls for them.
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*/
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#define SHRINKER_REGISTERING ((struct shrinker *)~0UL)
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static DEFINE_IDR(shrinker_idr);
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static int shrinker_nr_max;
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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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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_REGISTERING, 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 (memcg_expand_shrinker_maps(id)) {
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idr_remove(&shrinker_idr, id);
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goto unlock;
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}
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shrinker_nr_max = id + 1;
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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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down_write(&shrinker_rwsem);
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idr_remove(&shrinker_idr, id);
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up_write(&shrinker_rwsem);
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}
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#else /* CONFIG_MEMCG_KMEM */
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static int prealloc_memcg_shrinker(struct shrinker *shrinker)
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{
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return 0;
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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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#endif /* CONFIG_MEMCG_KMEM */
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#ifdef CONFIG_MEMCG
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static bool global_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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* sane_reclaim - is the usual dirty throttling mechanism operational?
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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 sane_reclaim(struct scan_control *sc)
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{
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struct mem_cgroup *memcg = sc->target_mem_cgroup;
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if (!memcg)
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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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static void set_memcg_congestion(pg_data_t *pgdat,
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struct mem_cgroup *memcg,
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bool congested)
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{
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struct mem_cgroup_per_node *mn;
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if (!memcg)
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return;
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mn = mem_cgroup_nodeinfo(memcg, pgdat->node_id);
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WRITE_ONCE(mn->congested, congested);
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}
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static bool memcg_congested(pg_data_t *pgdat,
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struct mem_cgroup *memcg)
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{
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struct mem_cgroup_per_node *mn;
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mn = mem_cgroup_nodeinfo(memcg, pgdat->node_id);
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return READ_ONCE(mn->congested);
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}
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#else
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static bool global_reclaim(struct scan_control *sc)
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{
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return true;
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}
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static bool sane_reclaim(struct scan_control *sc)
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{
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return true;
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}
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static inline void set_memcg_congestion(struct pglist_data *pgdat,
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struct mem_cgroup *memcg, bool congested)
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{
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}
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static inline bool memcg_congested(struct pglist_data *pgdat,
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struct mem_cgroup *memcg)
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{
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return false;
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}
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#endif
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/*
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* This misses isolated pages which are not accounted for to save counters.
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* As the data only determines if reclaim or compaction continues, it is
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* not expected that isolated pages will be a dominating factor.
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*/
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unsigned long zone_reclaimable_pages(struct zone *zone)
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{
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unsigned long nr;
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nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) +
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zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE);
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if (get_nr_swap_pages() > 0)
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nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) +
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zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON);
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return nr;
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}
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/**
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* lruvec_lru_size - Returns the number of pages on the given LRU list.
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* @lruvec: lru vector
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* @lru: lru to use
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* @zone_idx: zones to consider (use MAX_NR_ZONES for the whole LRU list)
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*/
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unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone_idx)
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{
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unsigned long lru_size;
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int zid;
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if (!mem_cgroup_disabled())
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lru_size = mem_cgroup_get_lru_size(lruvec, lru);
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else
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lru_size = node_page_state(lruvec_pgdat(lruvec), NR_LRU_BASE + lru);
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for (zid = zone_idx + 1; zid < MAX_NR_ZONES; zid++) {
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struct zone *zone = &lruvec_pgdat(lruvec)->node_zones[zid];
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unsigned long size;
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if (!managed_zone(zone))
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continue;
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if (!mem_cgroup_disabled())
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size = mem_cgroup_get_zone_lru_size(lruvec, lru, zid);
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else
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size = zone_page_state(&lruvec_pgdat(lruvec)->node_zones[zid],
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NR_ZONE_LRU_BASE + lru);
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lru_size -= min(size, lru_size);
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}
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return lru_size;
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}
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/*
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* Add a shrinker callback to be called from the vm.
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*/
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int prealloc_shrinker(struct shrinker *shrinker)
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{
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size_t size = sizeof(*shrinker->nr_deferred);
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if (shrinker->flags & SHRINKER_NUMA_AWARE)
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size *= nr_node_ids;
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shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
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if (!shrinker->nr_deferred)
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return -ENOMEM;
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if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
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if (prealloc_memcg_shrinker(shrinker))
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goto free_deferred;
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}
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return 0;
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free_deferred:
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kfree(shrinker->nr_deferred);
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shrinker->nr_deferred = NULL;
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return -ENOMEM;
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}
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void free_prealloced_shrinker(struct shrinker *shrinker)
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{
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if (!shrinker->nr_deferred)
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return;
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if (shrinker->flags & SHRINKER_MEMCG_AWARE)
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unregister_memcg_shrinker(shrinker);
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kfree(shrinker->nr_deferred);
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shrinker->nr_deferred = NULL;
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}
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void register_shrinker_prepared(struct shrinker *shrinker)
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{
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down_write(&shrinker_rwsem);
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list_add_tail(&shrinker->list, &shrinker_list);
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#ifdef CONFIG_MEMCG_KMEM
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if (shrinker->flags & SHRINKER_MEMCG_AWARE)
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idr_replace(&shrinker_idr, shrinker, shrinker->id);
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#endif
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up_write(&shrinker_rwsem);
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}
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int register_shrinker(struct shrinker *shrinker)
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{
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int err = prealloc_shrinker(shrinker);
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if (err)
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return err;
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register_shrinker_prepared(shrinker);
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return 0;
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}
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EXPORT_SYMBOL(register_shrinker);
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/*
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* Remove one
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*/
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void unregister_shrinker(struct shrinker *shrinker)
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{
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if (!shrinker->nr_deferred)
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return;
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if (shrinker->flags & SHRINKER_MEMCG_AWARE)
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unregister_memcg_shrinker(shrinker);
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down_write(&shrinker_rwsem);
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list_del(&shrinker->list);
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up_write(&shrinker_rwsem);
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kfree(shrinker->nr_deferred);
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shrinker->nr_deferred = NULL;
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}
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EXPORT_SYMBOL(unregister_shrinker);
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#define SHRINK_BATCH 128
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static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
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struct shrinker *shrinker, int priority)
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{
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unsigned long freed = 0;
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unsigned long long delta;
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long total_scan;
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long freeable;
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long nr;
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long new_nr;
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int nid = shrinkctl->nid;
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long batch_size = shrinker->batch ? shrinker->batch
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: SHRINK_BATCH;
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long scanned = 0, next_deferred;
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if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
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nid = 0;
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freeable = shrinker->count_objects(shrinker, shrinkctl);
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if (freeable == 0 || freeable == SHRINK_EMPTY)
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return freeable;
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/*
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* copy the current shrinker scan count into a local variable
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* and zero it so that other concurrent shrinker invocations
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* don't also do this scanning work.
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*/
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nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
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total_scan = nr;
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if (shrinker->seeks) {
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delta = freeable >> priority;
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delta *= 4;
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do_div(delta, shrinker->seeks);
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} else {
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/*
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* These objects don't require any IO to create. Trim
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* them aggressively under memory pressure to keep
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* them from causing refetches in the IO caches.
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*/
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delta = freeable / 2;
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}
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|
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/*
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* Make sure we apply some minimal pressure on default priority
|
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* even on small cgroups. Stale objects are not only consuming memory
|
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* by themselves, but can also hold a reference to a dying cgroup,
|
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* preventing it from being reclaimed. A dying cgroup with all
|
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* corresponding structures like per-cpu stats and kmem caches
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* can be really big, so it may lead to a significant waste of memory.
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*/
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delta = max_t(unsigned long long, delta, min(freeable, batch_size));
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|
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total_scan += delta;
|
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if (total_scan < 0) {
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pr_err("shrink_slab: %pF negative objects to delete nr=%ld\n",
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shrinker->scan_objects, total_scan);
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total_scan = freeable;
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next_deferred = nr;
|
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} else
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next_deferred = total_scan;
|
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|
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/*
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* We need to avoid excessive windup on filesystem shrinkers
|
|
* due to large numbers of GFP_NOFS allocations causing the
|
|
* shrinkers to return -1 all the time. This results in a large
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* nr being built up so when a shrink that can do some work
|
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* comes along it empties the entire cache due to nr >>>
|
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* freeable. This is bad for sustaining a working set in
|
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* memory.
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*
|
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* Hence only allow the shrinker to scan the entire cache when
|
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* a large delta change is calculated directly.
|
|
*/
|
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if (delta < freeable / 4)
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total_scan = min(total_scan, freeable / 2);
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|
|
/*
|
|
* Avoid risking looping forever due to too large nr value:
|
|
* never try to free more than twice the estimate number of
|
|
* freeable entries.
|
|
*/
|
|
if (total_scan > freeable * 2)
|
|
total_scan = freeable * 2;
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|
|
|
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();
|
|
}
|
|
|
|
if (next_deferred >= scanned)
|
|
next_deferred -= scanned;
|
|
else
|
|
next_deferred = 0;
|
|
/*
|
|
* move the unused scan count back into the shrinker in a
|
|
* manner that handles concurrent updates. If we exhausted the
|
|
* scan, there is no need to do an update.
|
|
*/
|
|
if (next_deferred > 0)
|
|
new_nr = atomic_long_add_return(next_deferred,
|
|
&shrinker->nr_deferred[nid]);
|
|
else
|
|
new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);
|
|
|
|
trace_mm_shrink_slab_end(shrinker, nid, freed, nr, new_nr, total_scan);
|
|
return freed;
|
|
}
|
|
|
|
#ifdef CONFIG_MEMCG_KMEM
|
|
static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
|
|
struct mem_cgroup *memcg, int priority)
|
|
{
|
|
struct memcg_shrinker_map *map;
|
|
unsigned long ret, freed = 0;
|
|
int i;
|
|
|
|
if (!memcg_kmem_enabled() || !mem_cgroup_online(memcg))
|
|
return 0;
|
|
|
|
if (!down_read_trylock(&shrinker_rwsem))
|
|
return 0;
|
|
|
|
map = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_map,
|
|
true);
|
|
if (unlikely(!map))
|
|
goto unlock;
|
|
|
|
for_each_set_bit(i, map->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 == SHRINKER_REGISTERING)) {
|
|
if (!shrinker)
|
|
clear_bit(i, map->map);
|
|
continue;
|
|
}
|
|
|
|
ret = do_shrink_slab(&sc, shrinker, priority);
|
|
if (ret == SHRINK_EMPTY) {
|
|
clear_bit(i, map->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
|
|
* memcg_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
|
|
memcg_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_KMEM */
|
|
static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
|
|
struct mem_cgroup *memcg, int priority)
|
|
{
|
|
return 0;
|
|
}
|
|
#endif /* CONFIG_MEMCG_KMEM */
|
|
|
|
/**
|
|
* 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;
|
|
|
|
if (!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 regsitration 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;
|
|
}
|
|
|
|
void drop_slab_node(int nid)
|
|
{
|
|
unsigned long freed;
|
|
|
|
do {
|
|
struct mem_cgroup *memcg = NULL;
|
|
|
|
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 > 10);
|
|
}
|
|
|
|
void drop_slab(void)
|
|
{
|
|
int nid;
|
|
|
|
for_each_online_node(nid)
|
|
drop_slab_node(nid);
|
|
}
|
|
|
|
static inline int is_page_cache_freeable(struct page *page)
|
|
{
|
|
/*
|
|
* 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.
|
|
*/
|
|
int page_cache_pins = PageTransHuge(page) && PageSwapCache(page) ?
|
|
HPAGE_PMD_NR : 1;
|
|
return page_count(page) - page_has_private(page) == 1 + page_cache_pins;
|
|
}
|
|
|
|
static int may_write_to_inode(struct inode *inode, struct scan_control *sc)
|
|
{
|
|
if (current->flags & PF_SWAPWRITE)
|
|
return 1;
|
|
if (!inode_write_congested(inode))
|
|
return 1;
|
|
if (inode_to_bdi(inode) == current->backing_dev_info)
|
|
return 1;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* We detected a synchronous write error writing a page 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 page and once
|
|
* that page is locked, the mapping is pinned.
|
|
*
|
|
* We're allowed to run sleeping lock_page() here because we know the caller has
|
|
* __GFP_FS.
|
|
*/
|
|
static void handle_write_error(struct address_space *mapping,
|
|
struct page *page, int error)
|
|
{
|
|
lock_page(page);
|
|
if (page_mapping(page) == mapping)
|
|
mapping_set_error(mapping, error);
|
|
unlock_page(page);
|
|
}
|
|
|
|
/* 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 page *page, struct address_space *mapping,
|
|
struct scan_control *sc)
|
|
{
|
|
/*
|
|
* If the page 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 page's queue, we can perform writeback even if that
|
|
* will block.
|
|
*
|
|
* If the page 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(page))
|
|
return PAGE_KEEP;
|
|
if (!mapping) {
|
|
/*
|
|
* Some data journaling orphaned pages can have
|
|
* page->mapping == NULL while being dirty with clean buffers.
|
|
*/
|
|
if (page_has_private(page)) {
|
|
if (try_to_free_buffers(page)) {
|
|
ClearPageDirty(page);
|
|
pr_info("%s: orphaned page\n", __func__);
|
|
return PAGE_CLEAN;
|
|
}
|
|
}
|
|
return PAGE_KEEP;
|
|
}
|
|
if (mapping->a_ops->writepage == NULL)
|
|
return PAGE_ACTIVATE;
|
|
if (!may_write_to_inode(mapping->host, sc))
|
|
return PAGE_KEEP;
|
|
|
|
if (clear_page_dirty_for_io(page)) {
|
|
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,
|
|
};
|
|
|
|
SetPageReclaim(page);
|
|
res = mapping->a_ops->writepage(page, &wbc);
|
|
if (res < 0)
|
|
handle_write_error(mapping, page, res);
|
|
if (res == AOP_WRITEPAGE_ACTIVATE) {
|
|
ClearPageReclaim(page);
|
|
return PAGE_ACTIVATE;
|
|
}
|
|
|
|
if (!PageWriteback(page)) {
|
|
/* synchronous write or broken a_ops? */
|
|
ClearPageReclaim(page);
|
|
}
|
|
trace_mm_vmscan_writepage(page);
|
|
inc_node_page_state(page, 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 page *page,
|
|
bool reclaimed)
|
|
{
|
|
unsigned long flags;
|
|
int refcount;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
BUG_ON(mapping != page_mapping(page));
|
|
|
|
xa_lock_irqsave(&mapping->i_pages, flags);
|
|
/*
|
|
* 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.
|
|
*/
|
|
if (unlikely(PageTransHuge(page)) && PageSwapCache(page))
|
|
refcount = 1 + HPAGE_PMD_NR;
|
|
else
|
|
refcount = 2;
|
|
if (!page_ref_freeze(page, refcount))
|
|
goto cannot_free;
|
|
/* note: atomic_cmpxchg in page_ref_freeze provides the smp_rmb */
|
|
if (unlikely(PageDirty(page))) {
|
|
page_ref_unfreeze(page, refcount);
|
|
goto cannot_free;
|
|
}
|
|
|
|
if (PageSwapCache(page)) {
|
|
swp_entry_t swap = { .val = page_private(page) };
|
|
mem_cgroup_swapout(page, swap);
|
|
__delete_from_swap_cache(page, swap);
|
|
xa_unlock_irqrestore(&mapping->i_pages, flags);
|
|
put_swap_page(page, swap);
|
|
} else {
|
|
void (*freepage)(struct page *);
|
|
void *shadow = NULL;
|
|
|
|
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 optizimation,
|
|
* 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 && page_is_file_cache(page) &&
|
|
!mapping_exiting(mapping) && !dax_mapping(mapping))
|
|
shadow = workingset_eviction(mapping, page);
|
|
__delete_from_page_cache(page, shadow);
|
|
xa_unlock_irqrestore(&mapping->i_pages, flags);
|
|
|
|
if (freepage != NULL)
|
|
freepage(page);
|
|
}
|
|
|
|
return 1;
|
|
|
|
cannot_free:
|
|
xa_unlock_irqrestore(&mapping->i_pages, flags);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Attempt to detach a locked page from its ->mapping. If it is dirty or if
|
|
* someone else has a ref on the page, abort and return 0. If it was
|
|
* successfully detached, return 1. Assumes the caller has a single ref on
|
|
* this page.
|
|
*/
|
|
int remove_mapping(struct address_space *mapping, struct page *page)
|
|
{
|
|
if (__remove_mapping(mapping, page, false)) {
|
|
/*
|
|
* Unfreezing the refcount with 1 rather than 2 effectively
|
|
* drops the pagecache ref for us without requiring another
|
|
* atomic operation.
|
|
*/
|
|
page_ref_unfreeze(page, 1);
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* putback_lru_page - put previously isolated page onto appropriate LRU list
|
|
* @page: page to be put back to appropriate lru list
|
|
*
|
|
* Add previously isolated @page to appropriate LRU list.
|
|
* Page may still be unevictable for other reasons.
|
|
*
|
|
* lru_lock must not be held, interrupts must be enabled.
|
|
*/
|
|
void putback_lru_page(struct page *page)
|
|
{
|
|
lru_cache_add(page);
|
|
put_page(page); /* drop ref from isolate */
|
|
}
|
|
|
|
enum page_references {
|
|
PAGEREF_RECLAIM,
|
|
PAGEREF_RECLAIM_CLEAN,
|
|
PAGEREF_KEEP,
|
|
PAGEREF_ACTIVATE,
|
|
};
|
|
|
|
static enum page_references page_check_references(struct page *page,
|
|
struct scan_control *sc)
|
|
{
|
|
int referenced_ptes, referenced_page;
|
|
unsigned long vm_flags;
|
|
|
|
referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup,
|
|
&vm_flags);
|
|
referenced_page = TestClearPageReferenced(page);
|
|
|
|
/*
|
|
* Mlock lost the isolation race with us. Let try_to_unmap()
|
|
* move the page to the unevictable list.
|
|
*/
|
|
if (vm_flags & VM_LOCKED)
|
|
return PAGEREF_RECLAIM;
|
|
|
|
if (referenced_ptes) {
|
|
if (PageSwapBacked(page))
|
|
return PAGEREF_ACTIVATE;
|
|
/*
|
|
* All mapped pages start out with page table
|
|
* references from the instantiating fault, so we need
|
|
* to look twice if a mapped file page 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 pages as well
|
|
* so that recently deactivated but used pages are
|
|
* quickly recovered.
|
|
*/
|
|
SetPageReferenced(page);
|
|
|
|
if (referenced_page || referenced_ptes > 1)
|
|
return PAGEREF_ACTIVATE;
|
|
|
|
/*
|
|
* Activate file-backed executable pages after first usage.
|
|
*/
|
|
if (vm_flags & VM_EXEC)
|
|
return PAGEREF_ACTIVATE;
|
|
|
|
return PAGEREF_KEEP;
|
|
}
|
|
|
|
/* Reclaim if clean, defer dirty pages to writeback */
|
|
if (referenced_page && !PageSwapBacked(page))
|
|
return PAGEREF_RECLAIM_CLEAN;
|
|
|
|
return PAGEREF_RECLAIM;
|
|
}
|
|
|
|
/* Check if a page is dirty or under writeback */
|
|
static void page_check_dirty_writeback(struct page *page,
|
|
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
|
|
*/
|
|
if (!page_is_file_cache(page) ||
|
|
(PageAnon(page) && !PageSwapBacked(page))) {
|
|
*dirty = false;
|
|
*writeback = false;
|
|
return;
|
|
}
|
|
|
|
/* By default assume that the page flags are accurate */
|
|
*dirty = PageDirty(page);
|
|
*writeback = PageWriteback(page);
|
|
|
|
/* Verify dirty/writeback state if the filesystem supports it */
|
|
if (!page_has_private(page))
|
|
return;
|
|
|
|
mapping = page_mapping(page);
|
|
if (mapping && mapping->a_ops->is_dirty_writeback)
|
|
mapping->a_ops->is_dirty_writeback(page, dirty, writeback);
|
|
}
|
|
|
|
/*
|
|
* shrink_page_list() returns the number of reclaimed pages
|
|
*/
|
|
static unsigned long shrink_page_list(struct list_head *page_list,
|
|
struct pglist_data *pgdat,
|
|
struct scan_control *sc,
|
|
enum ttu_flags ttu_flags,
|
|
struct reclaim_stat *stat,
|
|
bool force_reclaim)
|
|
{
|
|
LIST_HEAD(ret_pages);
|
|
LIST_HEAD(free_pages);
|
|
int pgactivate = 0;
|
|
unsigned nr_unqueued_dirty = 0;
|
|
unsigned nr_dirty = 0;
|
|
unsigned nr_congested = 0;
|
|
unsigned nr_reclaimed = 0;
|
|
unsigned nr_writeback = 0;
|
|
unsigned nr_immediate = 0;
|
|
unsigned nr_ref_keep = 0;
|
|
unsigned nr_unmap_fail = 0;
|
|
|
|
cond_resched();
|
|
|
|
while (!list_empty(page_list)) {
|
|
struct address_space *mapping;
|
|
struct page *page;
|
|
int may_enter_fs;
|
|
enum page_references references = PAGEREF_RECLAIM_CLEAN;
|
|
bool dirty, writeback;
|
|
|
|
cond_resched();
|
|
|
|
page = lru_to_page(page_list);
|
|
list_del(&page->lru);
|
|
|
|
if (!trylock_page(page))
|
|
goto keep;
|
|
|
|
VM_BUG_ON_PAGE(PageActive(page), page);
|
|
|
|
sc->nr_scanned++;
|
|
|
|
if (unlikely(!page_evictable(page)))
|
|
goto activate_locked;
|
|
|
|
if (!sc->may_unmap && page_mapped(page))
|
|
goto keep_locked;
|
|
|
|
/* Double the slab pressure for mapped and swapcache pages */
|
|
if ((page_mapped(page) || PageSwapCache(page)) &&
|
|
!(PageAnon(page) && !PageSwapBacked(page)))
|
|
sc->nr_scanned++;
|
|
|
|
may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
|
|
(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
|
|
|
|
/*
|
|
* The number of dirty pages determines if a node is marked
|
|
* reclaim_congested which affects wait_iff_congested. kswapd
|
|
* will stall and start writing pages if the tail of the LRU
|
|
* is all dirty unqueued pages.
|
|
*/
|
|
page_check_dirty_writeback(page, &dirty, &writeback);
|
|
if (dirty || writeback)
|
|
nr_dirty++;
|
|
|
|
if (dirty && !writeback)
|
|
nr_unqueued_dirty++;
|
|
|
|
/*
|
|
* Treat this page as congested if the underlying BDI is or if
|
|
* pages are cycling through the LRU so quickly that the
|
|
* pages marked for immediate reclaim are making it to the
|
|
* end of the LRU a second time.
|
|
*/
|
|
mapping = page_mapping(page);
|
|
if (((dirty || writeback) && mapping &&
|
|
inode_write_congested(mapping->host)) ||
|
|
(writeback && PageReclaim(page)))
|
|
nr_congested++;
|
|
|
|
/*
|
|
* If a page at the tail of the LRU is under writeback, there
|
|
* are three cases to consider.
|
|
*
|
|
* 1) If reclaim is encountering an excessive number of pages
|
|
* under writeback and this page is both under writeback and
|
|
* PageReclaim then it indicates that pages are being queued
|
|
* for IO but are being recycled through the LRU before the
|
|
* IO can complete. Waiting on the page itself risks an
|
|
* indefinite stall if it is impossible to writeback the
|
|
* page due to IO error or disconnected storage so instead
|
|
* note that the LRU is being scanned too quickly and the
|
|
* caller can stall after page list has been processed.
|
|
*
|
|
* 2) Global or new memcg reclaim encounters a page 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 page for immediate
|
|
* reclaim and continue scanning.
|
|
*
|
|
* Require may_enter_fs because we would wait on fs, which
|
|
* may not have submitted IO yet. And the loop driver might
|
|
* enter reclaim, and deadlock if it waits on a page 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 page that is already marked
|
|
* PageReclaim. memcg does not have any dirty pages
|
|
* throttling so we could easily OOM just because too many
|
|
* pages are in writeback and there is nothing else to
|
|
* reclaim. Wait for the writeback to complete.
|
|
*
|
|
* In cases 1) and 2) we activate the pages to get them out of
|
|
* the way while we continue scanning for clean pages 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 (PageWriteback(page)) {
|
|
/* Case 1 above */
|
|
if (current_is_kswapd() &&
|
|
PageReclaim(page) &&
|
|
test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {
|
|
nr_immediate++;
|
|
goto activate_locked;
|
|
|
|
/* Case 2 above */
|
|
} else if (sane_reclaim(sc) ||
|
|
!PageReclaim(page) || !may_enter_fs) {
|
|
/*
|
|
* This is slightly racy - end_page_writeback()
|
|
* might have just cleared PageReclaim, then
|
|
* setting PageReclaim here end up interpreted
|
|
* as PageReadahead - but that does not matter
|
|
* enough to care. What we do want is for this
|
|
* page to have PageReclaim set next time memcg
|
|
* reclaim reaches the tests above, so it will
|
|
* then wait_on_page_writeback() to avoid OOM;
|
|
* and it's also appropriate in global reclaim.
|
|
*/
|
|
SetPageReclaim(page);
|
|
nr_writeback++;
|
|
goto activate_locked;
|
|
|
|
/* Case 3 above */
|
|
} else {
|
|
unlock_page(page);
|
|
wait_on_page_writeback(page);
|
|
/* then go back and try same page again */
|
|
list_add_tail(&page->lru, page_list);
|
|
continue;
|
|
}
|
|
}
|
|
|
|
if (!force_reclaim)
|
|
references = page_check_references(page, sc);
|
|
|
|
switch (references) {
|
|
case PAGEREF_ACTIVATE:
|
|
goto activate_locked;
|
|
case PAGEREF_KEEP:
|
|
nr_ref_keep++;
|
|
goto keep_locked;
|
|
case PAGEREF_RECLAIM:
|
|
case PAGEREF_RECLAIM_CLEAN:
|
|
; /* try to reclaim the page below */
|
|
}
|
|
|
|
/*
|
|
* Anonymous process memory has backing store?
|
|
* Try to allocate it some swap space here.
|
|
* Lazyfree page could be freed directly
|
|
*/
|
|
if (PageAnon(page) && PageSwapBacked(page)) {
|
|
if (!PageSwapCache(page)) {
|
|
if (!(sc->gfp_mask & __GFP_IO))
|
|
goto keep_locked;
|
|
if (PageTransHuge(page)) {
|
|
/* cannot split THP, skip it */
|
|
if (!can_split_huge_page(page, NULL))
|
|
goto activate_locked;
|
|
/*
|
|
* Split pages without a PMD map right
|
|
* away. Chances are some or all of the
|
|
* tail pages can be freed without IO.
|
|
*/
|
|
if (!compound_mapcount(page) &&
|
|
split_huge_page_to_list(page,
|
|
page_list))
|
|
goto activate_locked;
|
|
}
|
|
if (!add_to_swap(page)) {
|
|
if (!PageTransHuge(page))
|
|
goto activate_locked;
|
|
/* Fallback to swap normal pages */
|
|
if (split_huge_page_to_list(page,
|
|
page_list))
|
|
goto activate_locked;
|
|
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
|
|
count_vm_event(THP_SWPOUT_FALLBACK);
|
|
#endif
|
|
if (!add_to_swap(page))
|
|
goto activate_locked;
|
|
}
|
|
|
|
may_enter_fs = 1;
|
|
|
|
/* Adding to swap updated mapping */
|
|
mapping = page_mapping(page);
|
|
}
|
|
} else if (unlikely(PageTransHuge(page))) {
|
|
/* Split file THP */
|
|
if (split_huge_page_to_list(page, page_list))
|
|
goto keep_locked;
|
|
}
|
|
|
|
/*
|
|
* The page is mapped into the page tables of one or more
|
|
* processes. Try to unmap it here.
|
|
*/
|
|
if (page_mapped(page)) {
|
|
enum ttu_flags flags = ttu_flags | TTU_BATCH_FLUSH;
|
|
|
|
if (unlikely(PageTransHuge(page)))
|
|
flags |= TTU_SPLIT_HUGE_PMD;
|
|
if (!try_to_unmap(page, flags)) {
|
|
nr_unmap_fail++;
|
|
goto activate_locked;
|
|
}
|
|
}
|
|
|
|
if (PageDirty(page)) {
|
|
/*
|
|
* Only kswapd can writeback filesystem pages
|
|
* to avoid risk of stack overflow. But avoid
|
|
* injecting inefficient single-page IO into
|
|
* flusher writeback as much as possible: only
|
|
* write pages when we've encountered many
|
|
* dirty pages, and when we've already scanned
|
|
* the rest of the LRU for clean pages and see
|
|
* the same dirty pages again (PageReclaim).
|
|
*/
|
|
if (page_is_file_cache(page) &&
|
|
(!current_is_kswapd() || !PageReclaim(page) ||
|
|
!test_bit(PGDAT_DIRTY, &pgdat->flags))) {
|
|
/*
|
|
* Immediately reclaim when written back.
|
|
* Similar in principal to deactivate_page()
|
|
* except we already have the page isolated
|
|
* and know it's dirty
|
|
*/
|
|
inc_node_page_state(page, NR_VMSCAN_IMMEDIATE);
|
|
SetPageReclaim(page);
|
|
|
|
goto activate_locked;
|
|
}
|
|
|
|
if (references == PAGEREF_RECLAIM_CLEAN)
|
|
goto keep_locked;
|
|
if (!may_enter_fs)
|
|
goto keep_locked;
|
|
if (!sc->may_writepage)
|
|
goto keep_locked;
|
|
|
|
/*
|
|
* Page is dirty. Flush the TLB if a writable entry
|
|
* potentially exists to avoid CPU writes after IO
|
|
* starts and then write it out here.
|
|
*/
|
|
try_to_unmap_flush_dirty();
|
|
switch (pageout(page, mapping, sc)) {
|
|
case PAGE_KEEP:
|
|
goto keep_locked;
|
|
case PAGE_ACTIVATE:
|
|
goto activate_locked;
|
|
case PAGE_SUCCESS:
|
|
if (PageWriteback(page))
|
|
goto keep;
|
|
if (PageDirty(page))
|
|
goto keep;
|
|
|
|
/*
|
|
* A synchronous write - probably a ramdisk. Go
|
|
* ahead and try to reclaim the page.
|
|
*/
|
|
if (!trylock_page(page))
|
|
goto keep;
|
|
if (PageDirty(page) || PageWriteback(page))
|
|
goto keep_locked;
|
|
mapping = page_mapping(page);
|
|
case PAGE_CLEAN:
|
|
; /* try to free the page below */
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If the page has buffers, try to free the buffer mappings
|
|
* associated with this page. If we succeed we try to free
|
|
* the page as well.
|
|
*
|
|
* We do this even if the page is PageDirty().
|
|
* try_to_release_page() does not perform I/O, but it is
|
|
* possible for a page to have PageDirty 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.
|
|
* try_to_release_page() will discover that cleanness and will
|
|
* drop the buffers and mark the page clean - it can be freed.
|
|
*
|
|
* Rarely, pages can have buffers and no ->mapping. These are
|
|
* the pages which were not successfully invalidated in
|
|
* truncate_complete_page(). We try to drop those buffers here
|
|
* and if that worked, and the page is no longer mapped into
|
|
* process address space (page_count == 1) it can be freed.
|
|
* Otherwise, leave the page on the LRU so it is swappable.
|
|
*/
|
|
if (page_has_private(page)) {
|
|
if (!try_to_release_page(page, sc->gfp_mask))
|
|
goto activate_locked;
|
|
if (!mapping && page_count(page) == 1) {
|
|
unlock_page(page);
|
|
if (put_page_testzero(page))
|
|
goto free_it;
|
|
else {
|
|
/*
|
|
* rare race with speculative reference.
|
|
* the speculative reference will free
|
|
* this page shortly, so we may
|
|
* increment nr_reclaimed here (and
|
|
* leave it off the LRU).
|
|
*/
|
|
nr_reclaimed++;
|
|
continue;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (PageAnon(page) && !PageSwapBacked(page)) {
|
|
/* follow __remove_mapping for reference */
|
|
if (!page_ref_freeze(page, 1))
|
|
goto keep_locked;
|
|
if (PageDirty(page)) {
|
|
page_ref_unfreeze(page, 1);
|
|
goto keep_locked;
|
|
}
|
|
|
|
count_vm_event(PGLAZYFREED);
|
|
count_memcg_page_event(page, PGLAZYFREED);
|
|
} else if (!mapping || !__remove_mapping(mapping, page, true))
|
|
goto keep_locked;
|
|
/*
|
|
* At this point, we have no other references and there is
|
|
* no way to pick any more up (removed from LRU, removed
|
|
* from pagecache). Can use non-atomic bitops now (and
|
|
* we obviously don't have to worry about waking up a process
|
|
* waiting on the page lock, because there are no references.
|
|
*/
|
|
__ClearPageLocked(page);
|
|
free_it:
|
|
nr_reclaimed++;
|
|
|
|
/*
|
|
* Is there need to periodically free_page_list? It would
|
|
* appear not as the counts should be low
|
|
*/
|
|
if (unlikely(PageTransHuge(page))) {
|
|
mem_cgroup_uncharge(page);
|
|
(*get_compound_page_dtor(page))(page);
|
|
} else
|
|
list_add(&page->lru, &free_pages);
|
|
continue;
|
|
|
|
activate_locked:
|
|
/* Not a candidate for swapping, so reclaim swap space. */
|
|
if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
|
|
PageMlocked(page)))
|
|
try_to_free_swap(page);
|
|
VM_BUG_ON_PAGE(PageActive(page), page);
|
|
if (!PageMlocked(page)) {
|
|
SetPageActive(page);
|
|
pgactivate++;
|
|
count_memcg_page_event(page, PGACTIVATE);
|
|
}
|
|
keep_locked:
|
|
unlock_page(page);
|
|
keep:
|
|
list_add(&page->lru, &ret_pages);
|
|
VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
|
|
}
|
|
|
|
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 (stat) {
|
|
stat->nr_dirty = nr_dirty;
|
|
stat->nr_congested = nr_congested;
|
|
stat->nr_unqueued_dirty = nr_unqueued_dirty;
|
|
stat->nr_writeback = nr_writeback;
|
|
stat->nr_immediate = nr_immediate;
|
|
stat->nr_activate = pgactivate;
|
|
stat->nr_ref_keep = nr_ref_keep;
|
|
stat->nr_unmap_fail = nr_unmap_fail;
|
|
}
|
|
return nr_reclaimed;
|
|
}
|
|
|
|
unsigned long reclaim_clean_pages_from_list(struct zone *zone,
|
|
struct list_head *page_list)
|
|
{
|
|
struct scan_control sc = {
|
|
.gfp_mask = GFP_KERNEL,
|
|
.priority = DEF_PRIORITY,
|
|
.may_unmap = 1,
|
|
};
|
|
unsigned long ret;
|
|
struct page *page, *next;
|
|
LIST_HEAD(clean_pages);
|
|
|
|
list_for_each_entry_safe(page, next, page_list, lru) {
|
|
if (page_is_file_cache(page) && !PageDirty(page) &&
|
|
!__PageMovable(page)) {
|
|
ClearPageActive(page);
|
|
list_move(&page->lru, &clean_pages);
|
|
}
|
|
}
|
|
|
|
ret = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc,
|
|
TTU_IGNORE_ACCESS, NULL, true);
|
|
list_splice(&clean_pages, page_list);
|
|
mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -ret);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Attempt to remove the specified page from its LRU. Only take this page
|
|
* if it is of the appropriate PageActive status. Pages which are being
|
|
* freed elsewhere are also ignored.
|
|
*
|
|
* page: page to consider
|
|
* mode: one of the LRU isolation modes defined above
|
|
*
|
|
* returns 0 on success, -ve errno on failure.
|
|
*/
|
|
int __isolate_lru_page(struct page *page, isolate_mode_t mode)
|
|
{
|
|
int ret = -EINVAL;
|
|
|
|
/* Only take pages on the LRU. */
|
|
if (!PageLRU(page))
|
|
return ret;
|
|
|
|
/* Compaction should not handle unevictable pages but CMA can do so */
|
|
if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE))
|
|
return ret;
|
|
|
|
ret = -EBUSY;
|
|
|
|
/*
|
|
* To minimise LRU disruption, the caller can indicate that it only
|
|
* wants to isolate pages it will be able to operate on without
|
|
* blocking - clean pages for the most part.
|
|
*
|
|
* ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
|
|
* that it is possible to migrate without blocking
|
|
*/
|
|
if (mode & ISOLATE_ASYNC_MIGRATE) {
|
|
/* All the caller can do on PageWriteback is block */
|
|
if (PageWriteback(page))
|
|
return ret;
|
|
|
|
if (PageDirty(page)) {
|
|
struct address_space *mapping;
|
|
bool migrate_dirty;
|
|
|
|
/*
|
|
* Only pages without mappings or that have a
|
|
* ->migratepage callback are possible to migrate
|
|
* without blocking. However, we can be racing with
|
|
* truncation so it's necessary to lock the page
|
|
* to stabilise the mapping as truncation holds
|
|
* the page lock until after the page is removed
|
|
* from the page cache.
|
|
*/
|
|
if (!trylock_page(page))
|
|
return ret;
|
|
|
|
mapping = page_mapping(page);
|
|
migrate_dirty = !mapping || mapping->a_ops->migratepage;
|
|
unlock_page(page);
|
|
if (!migrate_dirty)
|
|
return ret;
|
|
}
|
|
}
|
|
|
|
if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
|
|
return ret;
|
|
|
|
if (likely(get_page_unless_zero(page))) {
|
|
/*
|
|
* 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.
|
|
*/
|
|
ClearPageLRU(page);
|
|
ret = 0;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
|
|
/*
|
|
* Update LRU sizes after isolating pages. The LRU size updates must
|
|
* be complete before mem_cgroup_update_lru_size due to a santity 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]);
|
|
#ifdef CONFIG_MEMCG
|
|
mem_cgroup_update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
|
|
#endif
|
|
}
|
|
|
|
}
|
|
|
|
/*
|
|
* zone_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).
|
|
*
|
|
* Appropriate locks 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
|
|
* @mode: One of the LRU isolation modes
|
|
* @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,
|
|
isolate_mode_t mode, 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);
|
|
|
|
scan = 0;
|
|
for (total_scan = 0;
|
|
scan < nr_to_scan && nr_taken < nr_to_scan && !list_empty(src);
|
|
total_scan++) {
|
|
struct page *page;
|
|
|
|
page = lru_to_page(src);
|
|
prefetchw_prev_lru_page(page, src, flags);
|
|
|
|
VM_BUG_ON_PAGE(!PageLRU(page), page);
|
|
|
|
if (page_zonenum(page) > sc->reclaim_idx) {
|
|
list_move(&page->lru, &pages_skipped);
|
|
nr_skipped[page_zonenum(page)]++;
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
scan++;
|
|
switch (__isolate_lru_page(page, mode)) {
|
|
case 0:
|
|
nr_pages = hpage_nr_pages(page);
|
|
nr_taken += nr_pages;
|
|
nr_zone_taken[page_zonenum(page)] += nr_pages;
|
|
list_move(&page->lru, dst);
|
|
break;
|
|
|
|
case -EBUSY:
|
|
/* else it is being freed elsewhere */
|
|
list_move(&page->lru, src);
|
|
continue;
|
|
|
|
default:
|
|
BUG();
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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 put the
|
|
* system at risk of premature OOM.
|
|
*/
|
|
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, mode, lru);
|
|
update_lru_sizes(lruvec, lru, nr_zone_taken);
|
|
return nr_taken;
|
|
}
|
|
|
|
/**
|
|
* isolate_lru_page - tries to isolate a page from its LRU list
|
|
* @page: page to isolate from its LRU list
|
|
*
|
|
* Isolates a @page from an LRU list, clears PageLRU and adjusts the
|
|
* vmstat statistic corresponding to whatever LRU list the page was on.
|
|
*
|
|
* Returns 0 if the page was removed from an LRU list.
|
|
* Returns -EBUSY if the page was not on an LRU list.
|
|
*
|
|
* The returned page will have PageLRU() cleared. If it was found on
|
|
* the active list, it will have PageActive set. If it was found on
|
|
* the unevictable list, it will have the PageUnevictable bit set. That flag
|
|
* may need to be cleared by the caller before letting the page go.
|
|
*
|
|
* The vmstat statistic corresponding to the list on which the page was
|
|
* found will be decremented.
|
|
*
|
|
* Restrictions:
|
|
*
|
|
* (1) Must be called with an elevated refcount on the page. This is a
|
|
* fundamentnal 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.
|
|
*/
|
|
int isolate_lru_page(struct page *page)
|
|
{
|
|
int ret = -EBUSY;
|
|
|
|
VM_BUG_ON_PAGE(!page_count(page), page);
|
|
WARN_RATELIMIT(PageTail(page), "trying to isolate tail page");
|
|
|
|
if (PageLRU(page)) {
|
|
struct zone *zone = page_zone(page);
|
|
struct lruvec *lruvec;
|
|
|
|
spin_lock_irq(zone_lru_lock(zone));
|
|
lruvec = mem_cgroup_page_lruvec(page, zone->zone_pgdat);
|
|
if (PageLRU(page)) {
|
|
int lru = page_lru(page);
|
|
get_page(page);
|
|
ClearPageLRU(page);
|
|
del_page_from_lru_list(page, lruvec, lru);
|
|
ret = 0;
|
|
}
|
|
spin_unlock_irq(zone_lru_lock(zone));
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
|
|
* then get resheduled. 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;
|
|
|
|
if (current_is_kswapd())
|
|
return 0;
|
|
|
|
if (!sane_reclaim(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;
|
|
|
|
return isolated > inactive;
|
|
}
|
|
|
|
static noinline_for_stack void
|
|
putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list)
|
|
{
|
|
struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
|
|
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
|
|
LIST_HEAD(pages_to_free);
|
|
|
|
/*
|
|
* Put back any unfreeable pages.
|
|
*/
|
|
while (!list_empty(page_list)) {
|
|
struct page *page = lru_to_page(page_list);
|
|
int lru;
|
|
|
|
VM_BUG_ON_PAGE(PageLRU(page), page);
|
|
list_del(&page->lru);
|
|
if (unlikely(!page_evictable(page))) {
|
|
spin_unlock_irq(&pgdat->lru_lock);
|
|
putback_lru_page(page);
|
|
spin_lock_irq(&pgdat->lru_lock);
|
|
continue;
|
|
}
|
|
|
|
lruvec = mem_cgroup_page_lruvec(page, pgdat);
|
|
|
|
SetPageLRU(page);
|
|
lru = page_lru(page);
|
|
add_page_to_lru_list(page, lruvec, lru);
|
|
|
|
if (is_active_lru(lru)) {
|
|
int file = is_file_lru(lru);
|
|
int numpages = hpage_nr_pages(page);
|
|
reclaim_stat->recent_rotated[file] += numpages;
|
|
}
|
|
if (put_page_testzero(page)) {
|
|
__ClearPageLRU(page);
|
|
__ClearPageActive(page);
|
|
del_page_from_lru_list(page, lruvec, lru);
|
|
|
|
if (unlikely(PageCompound(page))) {
|
|
spin_unlock_irq(&pgdat->lru_lock);
|
|
mem_cgroup_uncharge(page);
|
|
(*get_compound_page_dtor(page))(page);
|
|
spin_lock_irq(&pgdat->lru_lock);
|
|
} else
|
|
list_add(&page->lru, &pages_to_free);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* To save our caller's stack, now use input list for pages to free.
|
|
*/
|
|
list_splice(&pages_to_free, page_list);
|
|
}
|
|
|
|
/*
|
|
* If a kernel thread (such as nfsd for loop-back mounts) services
|
|
* a backing device by writing to the page cache it sets PF_LESS_THROTTLE.
|
|
* In that case we should only throttle if the backing device it is
|
|
* writing to is congested. In other cases it is safe to throttle.
|
|
*/
|
|
static int current_may_throttle(void)
|
|
{
|
|
return !(current->flags & PF_LESS_THROTTLE) ||
|
|
current->backing_dev_info == NULL ||
|
|
bdi_write_congested(current->backing_dev_info);
|
|
}
|
|
|
|
/*
|
|
* shrink_inactive_list() is a helper for shrink_node(). It returns the number
|
|
* of reclaimed pages
|
|
*/
|
|
static noinline_for_stack 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 long nr_reclaimed = 0;
|
|
unsigned long nr_taken;
|
|
struct reclaim_stat stat = {};
|
|
isolate_mode_t isolate_mode = 0;
|
|
int file = is_file_lru(lru);
|
|
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
|
|
struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
|
|
bool stalled = false;
|
|
|
|
while (unlikely(too_many_isolated(pgdat, file, sc))) {
|
|
if (stalled)
|
|
return 0;
|
|
|
|
/* wait a bit for the reclaimer. */
|
|
msleep(100);
|
|
stalled = true;
|
|
|
|
/* We are about to die and free our memory. Return now. */
|
|
if (fatal_signal_pending(current))
|
|
return SWAP_CLUSTER_MAX;
|
|
}
|
|
|
|
lru_add_drain();
|
|
|
|
if (!sc->may_unmap)
|
|
isolate_mode |= ISOLATE_UNMAPPED;
|
|
|
|
spin_lock_irq(&pgdat->lru_lock);
|
|
|
|
nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list,
|
|
&nr_scanned, sc, isolate_mode, lru);
|
|
|
|
__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
|
|
reclaim_stat->recent_scanned[file] += nr_taken;
|
|
|
|
if (current_is_kswapd()) {
|
|
if (global_reclaim(sc))
|
|
__count_vm_events(PGSCAN_KSWAPD, nr_scanned);
|
|
count_memcg_events(lruvec_memcg(lruvec), PGSCAN_KSWAPD,
|
|
nr_scanned);
|
|
} else {
|
|
if (global_reclaim(sc))
|
|
__count_vm_events(PGSCAN_DIRECT, nr_scanned);
|
|
count_memcg_events(lruvec_memcg(lruvec), PGSCAN_DIRECT,
|
|
nr_scanned);
|
|
}
|
|
spin_unlock_irq(&pgdat->lru_lock);
|
|
|
|
if (nr_taken == 0)
|
|
return 0;
|
|
|
|
nr_reclaimed = shrink_page_list(&page_list, pgdat, sc, 0,
|
|
&stat, false);
|
|
|
|
spin_lock_irq(&pgdat->lru_lock);
|
|
|
|
if (current_is_kswapd()) {
|
|
if (global_reclaim(sc))
|
|
__count_vm_events(PGSTEAL_KSWAPD, nr_reclaimed);
|
|
count_memcg_events(lruvec_memcg(lruvec), PGSTEAL_KSWAPD,
|
|
nr_reclaimed);
|
|
} else {
|
|
if (global_reclaim(sc))
|
|
__count_vm_events(PGSTEAL_DIRECT, nr_reclaimed);
|
|
count_memcg_events(lruvec_memcg(lruvec), PGSTEAL_DIRECT,
|
|
nr_reclaimed);
|
|
}
|
|
|
|
putback_inactive_pages(lruvec, &page_list);
|
|
|
|
__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
|
|
|
|
spin_unlock_irq(&pgdat->lru_lock);
|
|
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* This moves pages from the active list to the inactive list.
|
|
*
|
|
* We move them the other way if the page is referenced by one or more
|
|
* processes, from rmap.
|
|
*
|
|
* If the pages are mostly unmapped, the processing is fast and it is
|
|
* appropriate to hold zone_lru_lock across the whole operation. But if
|
|
* the pages are mapped, the processing is slow (page_referenced()) so we
|
|
* should drop zone_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.
|
|
*
|
|
* Returns the number of pages moved to the given lru.
|
|
*/
|
|
|
|
static unsigned move_active_pages_to_lru(struct lruvec *lruvec,
|
|
struct list_head *list,
|
|
struct list_head *pages_to_free,
|
|
enum lru_list lru)
|
|
{
|
|
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
|
|
struct page *page;
|
|
int nr_pages;
|
|
int nr_moved = 0;
|
|
|
|
while (!list_empty(list)) {
|
|
page = lru_to_page(list);
|
|
lruvec = mem_cgroup_page_lruvec(page, pgdat);
|
|
|
|
VM_BUG_ON_PAGE(PageLRU(page), page);
|
|
SetPageLRU(page);
|
|
|
|
nr_pages = hpage_nr_pages(page);
|
|
update_lru_size(lruvec, lru, page_zonenum(page), nr_pages);
|
|
list_move(&page->lru, &lruvec->lists[lru]);
|
|
|
|
if (put_page_testzero(page)) {
|
|
__ClearPageLRU(page);
|
|
__ClearPageActive(page);
|
|
del_page_from_lru_list(page, lruvec, lru);
|
|
|
|
if (unlikely(PageCompound(page))) {
|
|
spin_unlock_irq(&pgdat->lru_lock);
|
|
mem_cgroup_uncharge(page);
|
|
(*get_compound_page_dtor(page))(page);
|
|
spin_lock_irq(&pgdat->lru_lock);
|
|
} else
|
|
list_add(&page->lru, pages_to_free);
|
|
} else {
|
|
nr_moved += nr_pages;
|
|
}
|
|
}
|
|
|
|
if (!is_active_lru(lru)) {
|
|
__count_vm_events(PGDEACTIVATE, nr_moved);
|
|
count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
|
|
nr_moved);
|
|
}
|
|
|
|
return nr_moved;
|
|
}
|
|
|
|
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);
|
|
struct page *page;
|
|
struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
|
|
unsigned nr_deactivate, nr_activate;
|
|
unsigned nr_rotated = 0;
|
|
isolate_mode_t isolate_mode = 0;
|
|
int file = is_file_lru(lru);
|
|
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
|
|
|
|
lru_add_drain();
|
|
|
|
if (!sc->may_unmap)
|
|
isolate_mode |= ISOLATE_UNMAPPED;
|
|
|
|
spin_lock_irq(&pgdat->lru_lock);
|
|
|
|
nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold,
|
|
&nr_scanned, sc, isolate_mode, lru);
|
|
|
|
__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
|
|
reclaim_stat->recent_scanned[file] += nr_taken;
|
|
|
|
__count_vm_events(PGREFILL, nr_scanned);
|
|
count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned);
|
|
|
|
spin_unlock_irq(&pgdat->lru_lock);
|
|
|
|
while (!list_empty(&l_hold)) {
|
|
cond_resched();
|
|
page = lru_to_page(&l_hold);
|
|
list_del(&page->lru);
|
|
|
|
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);
|
|
}
|
|
}
|
|
|
|
if (page_referenced(page, 0, sc->target_mem_cgroup,
|
|
&vm_flags)) {
|
|
nr_rotated += hpage_nr_pages(page);
|
|
/*
|
|
* 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_cache(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(&pgdat->lru_lock);
|
|
/*
|
|
* Count referenced pages from currently used mappings as rotated,
|
|
* even though only some of them are actually re-activated. This
|
|
* helps balance scan pressure between file and anonymous pages in
|
|
* get_scan_count.
|
|
*/
|
|
reclaim_stat->recent_rotated[file] += nr_rotated;
|
|
|
|
nr_activate = move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru);
|
|
nr_deactivate = move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE);
|
|
__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
|
|
spin_unlock_irq(&pgdat->lru_lock);
|
|
|
|
mem_cgroup_uncharge_list(&l_hold);
|
|
free_unref_page_list(&l_hold);
|
|
trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
|
|
nr_deactivate, nr_rotated, sc->priority, file);
|
|
}
|
|
|
|
/*
|
|
* 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_list_is_low(struct lruvec *lruvec, bool file,
|
|
struct mem_cgroup *memcg,
|
|
struct scan_control *sc, bool actual_reclaim)
|
|
{
|
|
enum lru_list active_lru = file * LRU_FILE + LRU_ACTIVE;
|
|
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
|
|
enum lru_list inactive_lru = file * LRU_FILE;
|
|
unsigned long inactive, active;
|
|
unsigned long inactive_ratio;
|
|
unsigned long refaults;
|
|
unsigned long gb;
|
|
|
|
/*
|
|
* If we don't have swap space, anonymous page deactivation
|
|
* is pointless.
|
|
*/
|
|
if (!file && !total_swap_pages)
|
|
return false;
|
|
|
|
inactive = lruvec_lru_size(lruvec, inactive_lru, sc->reclaim_idx);
|
|
active = lruvec_lru_size(lruvec, active_lru, sc->reclaim_idx);
|
|
|
|
if (memcg)
|
|
refaults = memcg_page_state(memcg, WORKINGSET_ACTIVATE);
|
|
else
|
|
refaults = node_page_state(pgdat, WORKINGSET_ACTIVATE);
|
|
|
|
/*
|
|
* When refaults are being observed, it means a new workingset
|
|
* is being established. Disable active list protection to get
|
|
* rid of the stale workingset quickly.
|
|
*/
|
|
if (file && actual_reclaim && lruvec->refaults != refaults) {
|
|
inactive_ratio = 0;
|
|
} else {
|
|
gb = (inactive + active) >> (30 - PAGE_SHIFT);
|
|
if (gb)
|
|
inactive_ratio = int_sqrt(10 * gb);
|
|
else
|
|
inactive_ratio = 1;
|
|
}
|
|
|
|
if (actual_reclaim)
|
|
trace_mm_vmscan_inactive_list_is_low(pgdat->node_id, sc->reclaim_idx,
|
|
lruvec_lru_size(lruvec, inactive_lru, MAX_NR_ZONES), inactive,
|
|
lruvec_lru_size(lruvec, active_lru, MAX_NR_ZONES), active,
|
|
inactive_ratio, file);
|
|
|
|
return inactive * inactive_ratio < active;
|
|
}
|
|
|
|
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
|
|
struct lruvec *lruvec, struct mem_cgroup *memcg,
|
|
struct scan_control *sc)
|
|
{
|
|
if (is_active_lru(lru)) {
|
|
if (inactive_list_is_low(lruvec, is_file_lru(lru),
|
|
memcg, sc, true))
|
|
shrink_active_list(nr_to_scan, lruvec, sc, lru);
|
|
return 0;
|
|
}
|
|
|
|
return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
|
|
}
|
|
|
|
enum scan_balance {
|
|
SCAN_EQUAL,
|
|
SCAN_FRACT,
|
|
SCAN_ANON,
|
|
SCAN_FILE,
|
|
};
|
|
|
|
/*
|
|
* Determine how aggressively the anon and file LRU lists should be
|
|
* scanned. The relative value of each set of LRU lists is determined
|
|
* by looking at the fraction of the pages scanned we did rotate back
|
|
* onto the active list instead of evict.
|
|
*
|
|
* 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 mem_cgroup *memcg,
|
|
struct scan_control *sc, unsigned long *nr,
|
|
unsigned long *lru_pages)
|
|
{
|
|
int swappiness = mem_cgroup_swappiness(memcg);
|
|
struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
|
|
u64 fraction[2];
|
|
u64 denominator = 0; /* gcc */
|
|
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
|
|
unsigned long anon_prio, file_prio;
|
|
enum scan_balance scan_balance;
|
|
unsigned long anon, file;
|
|
unsigned long ap, fp;
|
|
enum lru_list lru;
|
|
|
|
/* If we have no swap space, do not bother scanning anon pages. */
|
|
if (!sc->may_swap || mem_cgroup_get_nr_swap_pages(memcg) <= 0) {
|
|
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 (!global_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;
|
|
}
|
|
|
|
/*
|
|
* 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 (global_reclaim(sc)) {
|
|
unsigned long pgdatfile;
|
|
unsigned long pgdatfree;
|
|
int z;
|
|
unsigned long total_high_wmark = 0;
|
|
|
|
pgdatfree = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES);
|
|
pgdatfile = 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);
|
|
}
|
|
|
|
if (unlikely(pgdatfile + pgdatfree <= total_high_wmark)) {
|
|
/*
|
|
* Force SCAN_ANON if there are enough inactive
|
|
* anonymous pages on the LRU in eligible zones.
|
|
* Otherwise, the small LRU gets thrashed.
|
|
*/
|
|
if (!inactive_list_is_low(lruvec, false, memcg, sc, false) &&
|
|
lruvec_lru_size(lruvec, LRU_INACTIVE_ANON, sc->reclaim_idx)
|
|
>> sc->priority) {
|
|
scan_balance = SCAN_ANON;
|
|
goto out;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If there is enough inactive page cache, i.e. if the size of the
|
|
* inactive list is greater than that of the active list *and* the
|
|
* inactive list actually has some pages to scan on this priority, we
|
|
* do not reclaim anything from the anonymous working set right now.
|
|
* Without the second condition we could end up never scanning an
|
|
* lruvec even if it has plenty of old anonymous pages unless the
|
|
* system is under heavy pressure.
|
|
*/
|
|
if (!inactive_list_is_low(lruvec, true, memcg, sc, false) &&
|
|
lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, sc->reclaim_idx) >> sc->priority) {
|
|
scan_balance = SCAN_FILE;
|
|
goto out;
|
|
}
|
|
|
|
scan_balance = SCAN_FRACT;
|
|
|
|
/*
|
|
* With swappiness at 100, anonymous and file have the same priority.
|
|
* This scanning priority is essentially the inverse of IO cost.
|
|
*/
|
|
anon_prio = swappiness;
|
|
file_prio = 200 - anon_prio;
|
|
|
|
/*
|
|
* OK, so we have swap space and a fair amount of page cache
|
|
* pages. We use the recently rotated / recently scanned
|
|
* ratios to determine how valuable each cache is.
|
|
*
|
|
* Because workloads change over time (and to avoid overflow)
|
|
* we keep these statistics as a floating average, which ends
|
|
* up weighing recent references more than old ones.
|
|
*
|
|
* anon in [0], file in [1]
|
|
*/
|
|
|
|
anon = lruvec_lru_size(lruvec, LRU_ACTIVE_ANON, MAX_NR_ZONES) +
|
|
lruvec_lru_size(lruvec, LRU_INACTIVE_ANON, MAX_NR_ZONES);
|
|
file = lruvec_lru_size(lruvec, LRU_ACTIVE_FILE, MAX_NR_ZONES) +
|
|
lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, MAX_NR_ZONES);
|
|
|
|
spin_lock_irq(&pgdat->lru_lock);
|
|
if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
|
|
reclaim_stat->recent_scanned[0] /= 2;
|
|
reclaim_stat->recent_rotated[0] /= 2;
|
|
}
|
|
|
|
if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
|
|
reclaim_stat->recent_scanned[1] /= 2;
|
|
reclaim_stat->recent_rotated[1] /= 2;
|
|
}
|
|
|
|
/*
|
|
* The amount of pressure on anon vs file pages is inversely
|
|
* proportional to the fraction of recently scanned pages on
|
|
* each list that were recently referenced and in active use.
|
|
*/
|
|
ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
|
|
ap /= reclaim_stat->recent_rotated[0] + 1;
|
|
|
|
fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
|
|
fp /= reclaim_stat->recent_rotated[1] + 1;
|
|
spin_unlock_irq(&pgdat->lru_lock);
|
|
|
|
fraction[0] = ap;
|
|
fraction[1] = fp;
|
|
denominator = ap + fp + 1;
|
|
out:
|
|
*lru_pages = 0;
|
|
for_each_evictable_lru(lru) {
|
|
int file = is_file_lru(lru);
|
|
unsigned long size;
|
|
unsigned long scan;
|
|
|
|
size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
|
|
scan = size >> 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(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
|
|
* because of a round-off error.
|
|
*/
|
|
scan = 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) {
|
|
size = 0;
|
|
scan = 0;
|
|
}
|
|
break;
|
|
default:
|
|
/* Look ma, no brain */
|
|
BUG();
|
|
}
|
|
|
|
*lru_pages += size;
|
|
nr[lru] = scan;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* This is a basic per-node page freer. Used by both kswapd and direct reclaim.
|
|
*/
|
|
static void shrink_node_memcg(struct pglist_data *pgdat, struct mem_cgroup *memcg,
|
|
struct scan_control *sc, unsigned long *lru_pages)
|
|
{
|
|
struct lruvec *lruvec = mem_cgroup_lruvec(pgdat, memcg);
|
|
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, memcg, sc, nr, lru_pages);
|
|
|
|
/* 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 = (global_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, memcg, 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 (inactive_list_is_low(lruvec, false, memcg, sc, true))
|
|
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_zone() 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,
|
|
unsigned long nr_scanned,
|
|
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;
|
|
|
|
/* Consider stopping depending on scan and reclaim activity */
|
|
if (sc->gfp_mask & __GFP_RETRY_MAYFAIL) {
|
|
/*
|
|
* For __GFP_RETRY_MAYFAIL allocations, stop reclaiming if the
|
|
* full LRU list has been scanned and we are still failing
|
|
* to reclaim pages. This full LRU scan is potentially
|
|
* expensive but a __GFP_RETRY_MAYFAIL caller really wants to succeed
|
|
*/
|
|
if (!nr_reclaimed && !nr_scanned)
|
|
return false;
|
|
} else {
|
|
/*
|
|
* For non-__GFP_RETRY_MAYFAIL allocations which can presumably
|
|
* fail without consequence, 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 faster at the risk reclaim/compaction and
|
|
* the resulting allocation attempt fails
|
|
*/
|
|
if (!nr_reclaimed)
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* 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 (get_nr_swap_pages() > 0)
|
|
inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);
|
|
if (sc->nr_reclaimed < pages_for_compaction &&
|
|
inactive_lru_pages > pages_for_compaction)
|
|
return true;
|
|
|
|
/* 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 */
|
|
;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
static bool pgdat_memcg_congested(pg_data_t *pgdat, struct mem_cgroup *memcg)
|
|
{
|
|
return test_bit(PGDAT_CONGESTED, &pgdat->flags) ||
|
|
(memcg && memcg_congested(pgdat, memcg));
|
|
}
|
|
|
|
static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
|
|
{
|
|
struct reclaim_state *reclaim_state = current->reclaim_state;
|
|
unsigned long nr_reclaimed, nr_scanned;
|
|
bool reclaimable = false;
|
|
|
|
do {
|
|
struct mem_cgroup *root = sc->target_mem_cgroup;
|
|
struct mem_cgroup_reclaim_cookie reclaim = {
|
|
.pgdat = pgdat,
|
|
.priority = sc->priority,
|
|
};
|
|
unsigned long node_lru_pages = 0;
|
|
struct mem_cgroup *memcg;
|
|
|
|
memset(&sc->nr, 0, sizeof(sc->nr));
|
|
|
|
nr_reclaimed = sc->nr_reclaimed;
|
|
nr_scanned = sc->nr_scanned;
|
|
|
|
memcg = mem_cgroup_iter(root, NULL, &reclaim);
|
|
do {
|
|
unsigned long lru_pages;
|
|
unsigned long reclaimed;
|
|
unsigned long scanned;
|
|
|
|
switch (mem_cgroup_protected(root, memcg)) {
|
|
case MEMCG_PROT_MIN:
|
|
/*
|
|
* Hard protection.
|
|
* If there is no reclaimable memory, OOM.
|
|
*/
|
|
continue;
|
|
case MEMCG_PROT_LOW:
|
|
/*
|
|
* 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);
|
|
break;
|
|
case MEMCG_PROT_NONE:
|
|
break;
|
|
}
|
|
|
|
reclaimed = sc->nr_reclaimed;
|
|
scanned = sc->nr_scanned;
|
|
shrink_node_memcg(pgdat, memcg, sc, &lru_pages);
|
|
node_lru_pages += lru_pages;
|
|
|
|
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);
|
|
|
|
/*
|
|
* Direct reclaim and kswapd have to scan all memory
|
|
* cgroups to fulfill the overall scan target for the
|
|
* node.
|
|
*
|
|
* Limit reclaim, on the other hand, only cares about
|
|
* nr_to_reclaim pages to be reclaimed and it will
|
|
* retry with decreasing priority if one round over the
|
|
* whole hierarchy is not sufficient.
|
|
*/
|
|
if (!global_reclaim(sc) &&
|
|
sc->nr_reclaimed >= sc->nr_to_reclaim) {
|
|
mem_cgroup_iter_break(root, memcg);
|
|
break;
|
|
}
|
|
} while ((memcg = mem_cgroup_iter(root, memcg, &reclaim)));
|
|
|
|
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);
|
|
|
|
/*
|
|
* Tag a node as congested if all the dirty pages
|
|
* scanned were backed by a congested BDI and
|
|
* wait_iff_congested will stall.
|
|
*/
|
|
if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
|
|
set_bit(PGDAT_CONGESTED, &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 marked for immediate
|
|
* reclaim and under writeback (nr_immediate), it
|
|
* implies that pages are cycling through the LRU
|
|
* faster than they are written so also forcibly stall.
|
|
*/
|
|
if (sc->nr.immediate)
|
|
congestion_wait(BLK_RW_ASYNC, HZ/10);
|
|
}
|
|
|
|
/*
|
|
* Legacy memcg will stall in page writeback so avoid forcibly
|
|
* stalling in wait_iff_congested().
|
|
*/
|
|
if (!global_reclaim(sc) && sane_reclaim(sc) &&
|
|
sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
|
|
set_memcg_congestion(pgdat, root, true);
|
|
|
|
/*
|
|
* Stall direct reclaim for IO completions if underlying BDIs
|
|
* and node is congested. Allow kswapd to continue until it
|
|
* starts encountering unqueued dirty pages or cycling through
|
|
* the LRU too quickly.
|
|
*/
|
|
if (!sc->hibernation_mode && !current_is_kswapd() &&
|
|
current_may_throttle() && pgdat_memcg_congested(pgdat, root))
|
|
wait_iff_congested(BLK_RW_ASYNC, HZ/10);
|
|
|
|
} while (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed,
|
|
sc->nr_scanned - nr_scanned, sc));
|
|
|
|
/*
|
|
* 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;
|
|
|
|
return reclaimable;
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
|
|
/*
|
|
* 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 (global_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() */
|
|
}
|
|
|
|
/* 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);
|
|
}
|
|
|
|
/*
|
|
* 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 *root_memcg, pg_data_t *pgdat)
|
|
{
|
|
struct mem_cgroup *memcg;
|
|
|
|
memcg = mem_cgroup_iter(root_memcg, NULL, NULL);
|
|
do {
|
|
unsigned long refaults;
|
|
struct lruvec *lruvec;
|
|
|
|
if (memcg)
|
|
refaults = memcg_page_state(memcg, WORKINGSET_ACTIVATE);
|
|
else
|
|
refaults = node_page_state(pgdat, WORKINGSET_ACTIVATE);
|
|
|
|
lruvec = mem_cgroup_lruvec(pgdat, memcg);
|
|
lruvec->refaults = refaults;
|
|
} while ((memcg = mem_cgroup_iter(root_memcg, memcg, NULL)));
|
|
}
|
|
|
|
/*
|
|
* 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 (global_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);
|
|
set_memcg_congestion(last_pgdat, sc->target_mem_cgroup, false);
|
|
}
|
|
|
|
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;
|
|
|
|
/* Untapped cgroup reserves? Don't OOM, retry. */
|
|
if (sc->memcg_low_skipped) {
|
|
sc->priority = initial_priority;
|
|
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)) {
|
|
pgdat->kswapd_classzone_idx = min(pgdat->kswapd_classzone_idx,
|
|
(enum zone_type)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);
|
|
|
|
goto check_pending;
|
|
}
|
|
|
|
/* Throttle until kswapd wakes the process */
|
|
wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
|
|
allow_direct_reclaim(pgdat));
|
|
|
|
check_pending:
|
|
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;
|
|
|
|
trace_mm_vmscan_direct_reclaim_begin(order,
|
|
sc.may_writepage,
|
|
sc.gfp_mask,
|
|
sc.reclaim_idx);
|
|
|
|
nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
|
|
|
|
trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
|
|
|
|
return nr_reclaimed;
|
|
}
|
|
|
|
#ifdef CONFIG_MEMCG
|
|
|
|
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 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,
|
|
};
|
|
unsigned long lru_pages;
|
|
|
|
sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
|
|
(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
|
|
|
|
trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
|
|
sc.may_writepage,
|
|
sc.gfp_mask,
|
|
sc.reclaim_idx);
|
|
|
|
/*
|
|
* 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_node_memcg(pgdat, memcg, &sc, &lru_pages);
|
|
|
|
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)
|
|
{
|
|
struct zonelist *zonelist;
|
|
unsigned long nr_reclaimed;
|
|
unsigned long pflags;
|
|
int nid;
|
|
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,
|
|
};
|
|
|
|
/*
|
|
* Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
|
|
* take care of from where we get pages. So the node where we start the
|
|
* scan does not need to be the current node.
|
|
*/
|
|
nid = mem_cgroup_select_victim_node(memcg);
|
|
|
|
zonelist = &NODE_DATA(nid)->node_zonelists[ZONELIST_FALLBACK];
|
|
|
|
trace_mm_vmscan_memcg_reclaim_begin(0,
|
|
sc.may_writepage,
|
|
sc.gfp_mask,
|
|
sc.reclaim_idx);
|
|
|
|
psi_memstall_enter(&pflags);
|
|
noreclaim_flag = memalloc_noreclaim_save();
|
|
|
|
nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
|
|
|
|
memalloc_noreclaim_restore(noreclaim_flag);
|
|
psi_memstall_leave(&pflags);
|
|
|
|
trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
|
|
|
|
return nr_reclaimed;
|
|
}
|
|
#endif
|
|
|
|
static void age_active_anon(struct pglist_data *pgdat,
|
|
struct scan_control *sc)
|
|
{
|
|
struct mem_cgroup *memcg;
|
|
|
|
if (!total_swap_pages)
|
|
return;
|
|
|
|
memcg = mem_cgroup_iter(NULL, NULL, NULL);
|
|
do {
|
|
struct lruvec *lruvec = mem_cgroup_lruvec(pgdat, memcg);
|
|
|
|
if (inactive_list_is_low(lruvec, false, memcg, sc, true))
|
|
shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
|
|
sc, LRU_ACTIVE_ANON);
|
|
|
|
memcg = mem_cgroup_iter(NULL, memcg, NULL);
|
|
} while (memcg);
|
|
}
|
|
|
|
/*
|
|
* Returns true if there is an eligible zone balanced for the request order
|
|
* and classzone_idx
|
|
*/
|
|
static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)
|
|
{
|
|
int i;
|
|
unsigned long mark = -1;
|
|
struct zone *zone;
|
|
|
|
for (i = 0; i <= classzone_idx; i++) {
|
|
zone = pgdat->node_zones + i;
|
|
|
|
if (!managed_zone(zone))
|
|
continue;
|
|
|
|
mark = high_wmark_pages(zone);
|
|
if (zone_watermark_ok_safe(zone, order, mark, classzone_idx))
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* If a node has no populated zone within classzone_idx, 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)
|
|
{
|
|
clear_bit(PGDAT_CONGESTED, &pgdat->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 classzone_idx)
|
|
{
|
|
/*
|
|
* 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, classzone_idx)) {
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* 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 is 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 classzone_idx)
|
|
{
|
|
int i;
|
|
unsigned long nr_soft_reclaimed;
|
|
unsigned long nr_soft_scanned;
|
|
unsigned long pflags;
|
|
struct zone *zone;
|
|
struct scan_control sc = {
|
|
.gfp_mask = GFP_KERNEL,
|
|
.order = order,
|
|
.priority = DEF_PRIORITY,
|
|
.may_writepage = !laptop_mode,
|
|
.may_unmap = 1,
|
|
.may_swap = 1,
|
|
};
|
|
|
|
psi_memstall_enter(&pflags);
|
|
__fs_reclaim_acquire();
|
|
|
|
count_vm_event(PAGEOUTRUN);
|
|
|
|
do {
|
|
unsigned long nr_reclaimed = sc.nr_reclaimed;
|
|
bool raise_priority = true;
|
|
bool ret;
|
|
|
|
sc.reclaim_idx = classzone_idx;
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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 (pgdat_balanced(pgdat, sc.order, classzone_idx))
|
|
goto out;
|
|
|
|
/*
|
|
* 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();
|
|
ret = try_to_freeze();
|
|
__fs_reclaim_acquire();
|
|
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;
|
|
if (raise_priority || !nr_reclaimed)
|
|
sc.priority--;
|
|
} while (sc.priority >= 1);
|
|
|
|
if (!sc.nr_reclaimed)
|
|
pgdat->kswapd_failures++;
|
|
|
|
out:
|
|
snapshot_refaults(NULL, pgdat);
|
|
__fs_reclaim_release();
|
|
psi_memstall_leave(&pflags);
|
|
/*
|
|
* 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;
|
|
}
|
|
|
|
/*
|
|
* pgdat->kswapd_classzone_idx is the highest zone index that a recent
|
|
* allocation request woke kswapd for. When kswapd has not woken recently,
|
|
* the value is MAX_NR_ZONES which is not a valid index. This compares a
|
|
* given classzone and returns it or the highest classzone index kswapd
|
|
* was recently woke for.
|
|
*/
|
|
static enum zone_type kswapd_classzone_idx(pg_data_t *pgdat,
|
|
enum zone_type classzone_idx)
|
|
{
|
|
if (pgdat->kswapd_classzone_idx == MAX_NR_ZONES)
|
|
return classzone_idx;
|
|
|
|
return max(pgdat->kswapd_classzone_idx, classzone_idx);
|
|
}
|
|
|
|
static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order,
|
|
unsigned int classzone_idx)
|
|
{
|
|
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, classzone_idx)) {
|
|
/*
|
|
* 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, classzone_idx);
|
|
|
|
remaining = schedule_timeout(HZ/10);
|
|
|
|
/*
|
|
* If woken prematurely then reset kswapd_classzone_idx and
|
|
* order. The values will either be from a wakeup request or
|
|
* the previous request that slept prematurely.
|
|
*/
|
|
if (remaining) {
|
|
pgdat->kswapd_classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx);
|
|
pgdat->kswapd_order = max(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, classzone_idx)) {
|
|
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 classzone_idx = MAX_NR_ZONES - 1;
|
|
pg_data_t *pgdat = (pg_data_t*)p;
|
|
struct task_struct *tsk = current;
|
|
|
|
struct reclaim_state reclaim_state = {
|
|
.reclaimed_slab = 0,
|
|
};
|
|
const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
|
|
|
|
if (!cpumask_empty(cpumask))
|
|
set_cpus_allowed_ptr(tsk, cpumask);
|
|
current->reclaim_state = &reclaim_state;
|
|
|
|
/*
|
|
* 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_SWAPWRITE | PF_KSWAPD;
|
|
set_freezable();
|
|
|
|
pgdat->kswapd_order = 0;
|
|
pgdat->kswapd_classzone_idx = MAX_NR_ZONES;
|
|
for ( ; ; ) {
|
|
bool ret;
|
|
|
|
alloc_order = reclaim_order = pgdat->kswapd_order;
|
|
classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx);
|
|
|
|
kswapd_try_sleep:
|
|
kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order,
|
|
classzone_idx);
|
|
|
|
/* Read the new order and classzone_idx */
|
|
alloc_order = reclaim_order = pgdat->kswapd_order;
|
|
classzone_idx = kswapd_classzone_idx(pgdat, 0);
|
|
pgdat->kswapd_order = 0;
|
|
pgdat->kswapd_classzone_idx = 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, classzone_idx,
|
|
alloc_order);
|
|
reclaim_order = balance_pgdat(pgdat, alloc_order, classzone_idx);
|
|
if (reclaim_order < alloc_order)
|
|
goto kswapd_try_sleep;
|
|
}
|
|
|
|
tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD);
|
|
current->reclaim_state = NULL;
|
|
|
|
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 classzone_idx)
|
|
{
|
|
pg_data_t *pgdat;
|
|
|
|
if (!managed_zone(zone))
|
|
return;
|
|
|
|
if (!cpuset_zone_allowed(zone, gfp_flags))
|
|
return;
|
|
pgdat = zone->zone_pgdat;
|
|
pgdat->kswapd_classzone_idx = kswapd_classzone_idx(pgdat,
|
|
classzone_idx);
|
|
pgdat->kswapd_order = max(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, classzone_idx)) {
|
|
/*
|
|
* 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, classzone_idx);
|
|
return;
|
|
}
|
|
|
|
trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, classzone_idx, 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 reclaim_state reclaim_state;
|
|
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);
|
|
struct task_struct *p = current;
|
|
unsigned long nr_reclaimed;
|
|
unsigned int noreclaim_flag;
|
|
|
|
fs_reclaim_acquire(sc.gfp_mask);
|
|
noreclaim_flag = memalloc_noreclaim_save();
|
|
reclaim_state.reclaimed_slab = 0;
|
|
p->reclaim_state = &reclaim_state;
|
|
|
|
nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
|
|
|
|
p->reclaim_state = NULL;
|
|
memalloc_noreclaim_restore(noreclaim_flag);
|
|
fs_reclaim_release(sc.gfp_mask);
|
|
|
|
return nr_reclaimed;
|
|
}
|
|
#endif /* CONFIG_HIBERNATION */
|
|
|
|
/* It's optimal to keep kswapds on the same CPUs as their memory, but
|
|
not required for correctness. So if the last cpu in a node goes
|
|
away, we get changed to run anywhere: as the first one comes back,
|
|
restore their cpu bindings. */
|
|
static int kswapd_cpu_online(unsigned int cpu)
|
|
{
|
|
int nid;
|
|
|
|
for_each_node_state(nid, N_MEMORY) {
|
|
pg_data_t *pgdat = NODE_DATA(nid);
|
|
const struct cpumask *mask;
|
|
|
|
mask = cpumask_of_node(pgdat->node_id);
|
|
|
|
if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
|
|
/* One of our CPUs online: restore mask */
|
|
set_cpus_allowed_ptr(pgdat->kswapd, mask);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* This kswapd start function will be called by init and node-hot-add.
|
|
* On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
|
|
*/
|
|
int kswapd_run(int nid)
|
|
{
|
|
pg_data_t *pgdat = NODE_DATA(nid);
|
|
int ret = 0;
|
|
|
|
if (pgdat->kswapd)
|
|
return 0;
|
|
|
|
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);
|
|
ret = PTR_ERR(pgdat->kswapd);
|
|
pgdat->kswapd = NULL;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* 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, ret;
|
|
|
|
swap_setup();
|
|
for_each_node_state(nid, N_MEMORY)
|
|
kswapd_run(nid);
|
|
ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
|
|
"mm/vmscan:online", kswapd_cpu_online,
|
|
NULL);
|
|
WARN_ON(ret < 0);
|
|
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;
|
|
|
|
#define RECLAIM_OFF 0
|
|
#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
|
|
#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
|
|
#define RECLAIM_UNMAP (1<<2) /* Unmap pages during reclaim */
|
|
|
|
/*
|
|
* 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;
|
|
struct reclaim_state reclaim_state;
|
|
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),
|
|
};
|
|
|
|
cond_resched();
|
|
fs_reclaim_acquire(sc.gfp_mask);
|
|
/*
|
|
* We need to be able to allocate from the reserves for RECLAIM_UNMAP
|
|
* and we also need to be able to write out pages for RECLAIM_WRITE
|
|
* and RECLAIM_UNMAP.
|
|
*/
|
|
noreclaim_flag = memalloc_noreclaim_save();
|
|
p->flags |= PF_SWAPWRITE;
|
|
reclaim_state.reclaimed_slab = 0;
|
|
p->reclaim_state = &reclaim_state;
|
|
|
|
if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_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);
|
|
}
|
|
|
|
p->reclaim_state = NULL;
|
|
current->flags &= ~PF_SWAPWRITE;
|
|
memalloc_noreclaim_restore(noreclaim_flag);
|
|
fs_reclaim_release(sc.gfp_mask);
|
|
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(pgdat, NR_SLAB_RECLAIMABLE) <= 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
|
|
|
|
/*
|
|
* page_evictable - test whether a page is evictable
|
|
* @page: the page to test
|
|
*
|
|
* Test whether page is evictable--i.e., should be placed on active/inactive
|
|
* lists vs unevictable list.
|
|
*
|
|
* Reasons page might not be evictable:
|
|
* (1) page's mapping marked unevictable
|
|
* (2) page is part of an mlocked VMA
|
|
*
|
|
*/
|
|
int page_evictable(struct page *page)
|
|
{
|
|
int ret;
|
|
|
|
/* Prevent address_space of inode and swap cache from being freed */
|
|
rcu_read_lock();
|
|
ret = !mapping_unevictable(page_mapping(page)) && !PageMlocked(page);
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* 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;
|
|
struct pglist_data *pgdat = NULL;
|
|
int pgscanned = 0;
|
|
int pgrescued = 0;
|
|
int i;
|
|
|
|
for (i = 0; i < pvec->nr; i++) {
|
|
struct page *page = pvec->pages[i];
|
|
struct pglist_data *pagepgdat = page_pgdat(page);
|
|
|
|
pgscanned++;
|
|
if (pagepgdat != pgdat) {
|
|
if (pgdat)
|
|
spin_unlock_irq(&pgdat->lru_lock);
|
|
pgdat = pagepgdat;
|
|
spin_lock_irq(&pgdat->lru_lock);
|
|
}
|
|
lruvec = mem_cgroup_page_lruvec(page, pgdat);
|
|
|
|
if (!PageLRU(page) || !PageUnevictable(page))
|
|
continue;
|
|
|
|
if (page_evictable(page)) {
|
|
enum lru_list lru = page_lru_base_type(page);
|
|
|
|
VM_BUG_ON_PAGE(PageActive(page), page);
|
|
ClearPageUnevictable(page);
|
|
del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE);
|
|
add_page_to_lru_list(page, lruvec, lru);
|
|
pgrescued++;
|
|
}
|
|
}
|
|
|
|
if (pgdat) {
|
|
__count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
|
|
__count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
|
|
spin_unlock_irq(&pgdat->lru_lock);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(check_move_unevictable_pages);
|