3782 lines
107 KiB
C
3782 lines
107 KiB
C
/*
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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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#include <linux/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/prefetch.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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/* 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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/* How many pages shrink_list() should reclaim */
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unsigned long nr_to_reclaim;
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unsigned long hibernation_mode;
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/* This context's GFP mask */
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gfp_t gfp_mask;
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int may_writepage;
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/* Can mapped pages be reclaimed? */
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int may_unmap;
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/* Can pages be swapped as part of reclaim? */
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int may_swap;
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int order;
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/* Scan (total_size >> priority) pages at once */
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int priority;
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/*
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* The memory cgroup that hit its limit and as a result is the
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* primary target of this reclaim invocation.
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*/
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struct mem_cgroup *target_mem_cgroup;
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/*
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* 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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#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
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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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unsigned long vm_total_pages; /* The total number of pages which the VM controls */
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static LIST_HEAD(shrinker_list);
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static DECLARE_RWSEM(shrinker_rwsem);
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#ifdef CONFIG_MEMCG
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static 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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#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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#endif
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unsigned long zone_reclaimable_pages(struct zone *zone)
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{
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int nr;
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nr = zone_page_state(zone, NR_ACTIVE_FILE) +
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zone_page_state(zone, NR_INACTIVE_FILE);
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if (get_nr_swap_pages() > 0)
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nr += zone_page_state(zone, NR_ACTIVE_ANON) +
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zone_page_state(zone, NR_INACTIVE_ANON);
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return nr;
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}
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bool zone_reclaimable(struct zone *zone)
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{
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return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
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}
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static unsigned long get_lru_size(struct lruvec *lruvec, enum lru_list lru)
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{
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if (!mem_cgroup_disabled())
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return mem_cgroup_get_lru_size(lruvec, lru);
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return zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru);
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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 register_shrinker(struct shrinker *shrinker)
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{
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size_t size = sizeof(*shrinker->nr_deferred);
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/*
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* If we only have one possible node in the system anyway, save
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* ourselves the trouble and disable NUMA aware behavior. This way we
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* will save memory and some small loop time later.
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*/
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if (nr_node_ids == 1)
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shrinker->flags &= ~SHRINKER_NUMA_AWARE;
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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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down_write(&shrinker_rwsem);
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list_add_tail(&shrinker->list, &shrinker_list);
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up_write(&shrinker_rwsem);
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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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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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}
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EXPORT_SYMBOL(unregister_shrinker);
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#define SHRINK_BATCH 128
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static unsigned long
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shrink_slab_node(struct shrink_control *shrinkctl, struct shrinker *shrinker,
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unsigned long nr_pages_scanned, unsigned long lru_pages)
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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 max_pass;
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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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max_pass = shrinker->count_objects(shrinker, shrinkctl);
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if (max_pass == 0)
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return 0;
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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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delta = (4 * nr_pages_scanned) / shrinker->seeks;
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delta *= max_pass;
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do_div(delta, lru_pages + 1);
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total_scan += delta;
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if (total_scan < 0) {
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printk(KERN_ERR
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"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 = max_pass;
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}
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/*
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* We need to avoid excessive windup on filesystem shrinkers
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* due to large numbers of GFP_NOFS allocations causing the
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* 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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* max_pass. 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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*/
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if (delta < max_pass / 4)
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total_scan = min(total_scan, max_pass / 2);
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/*
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* Avoid risking looping forever due to too large nr value:
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* never try to free more than twice the estimate number of
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* freeable entries.
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*/
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if (total_scan > max_pass * 2)
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total_scan = max_pass * 2;
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trace_mm_shrink_slab_start(shrinker, shrinkctl, nr,
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nr_pages_scanned, lru_pages,
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max_pass, delta, total_scan);
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while (total_scan >= batch_size) {
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unsigned long ret;
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shrinkctl->nr_to_scan = batch_size;
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ret = shrinker->scan_objects(shrinker, shrinkctl);
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if (ret == SHRINK_STOP)
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break;
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freed += ret;
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count_vm_events(SLABS_SCANNED, batch_size);
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total_scan -= batch_size;
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cond_resched();
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}
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/*
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* move the unused scan count back into the shrinker in a
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* manner that handles concurrent updates. If we exhausted the
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* scan, there is no need to do an update.
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*/
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if (total_scan > 0)
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new_nr = atomic_long_add_return(total_scan,
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&shrinker->nr_deferred[nid]);
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else
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new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);
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trace_mm_shrink_slab_end(shrinker, freed, nr, new_nr);
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return freed;
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}
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/*
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* Call the shrink functions to age shrinkable caches
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*
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* Here we assume it costs one seek to replace a lru page and that it also
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* takes a seek to recreate a cache object. With this in mind we age equal
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* percentages of the lru and ageable caches. This should balance the seeks
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* generated by these structures.
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*
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* If the vm encountered mapped pages on the LRU it increase the pressure on
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* slab to avoid swapping.
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*
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* We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
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*
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* `lru_pages' represents the number of on-LRU pages in all the zones which
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* are eligible for the caller's allocation attempt. It is used for balancing
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* slab reclaim versus page reclaim.
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*
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* Returns the number of slab objects which we shrunk.
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*/
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unsigned long shrink_slab(struct shrink_control *shrinkctl,
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unsigned long nr_pages_scanned,
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unsigned long lru_pages)
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{
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struct shrinker *shrinker;
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unsigned long freed = 0;
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if (nr_pages_scanned == 0)
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nr_pages_scanned = SWAP_CLUSTER_MAX;
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if (!down_read_trylock(&shrinker_rwsem)) {
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/*
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* If we would return 0, our callers would understand that we
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* have nothing else to shrink and give up trying. By returning
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* 1 we keep it going and assume we'll be able to shrink next
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* time.
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*/
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freed = 1;
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goto out;
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}
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list_for_each_entry(shrinker, &shrinker_list, list) {
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for_each_node_mask(shrinkctl->nid, shrinkctl->nodes_to_scan) {
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if (!node_online(shrinkctl->nid))
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continue;
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if (!(shrinker->flags & SHRINKER_NUMA_AWARE) &&
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(shrinkctl->nid != 0))
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break;
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freed += shrink_slab_node(shrinkctl, shrinker,
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nr_pages_scanned, lru_pages);
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}
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}
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up_read(&shrinker_rwsem);
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out:
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cond_resched();
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return freed;
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}
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static inline int is_page_cache_freeable(struct page *page)
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{
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/*
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* A freeable page cache page is referenced only by the caller
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* that isolated the page, the page cache radix tree and
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* optional buffer heads at page->private.
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*/
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return page_count(page) - page_has_private(page) == 2;
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}
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static int may_write_to_queue(struct backing_dev_info *bdi,
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struct scan_control *sc)
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{
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if (current->flags & PF_SWAPWRITE)
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return 1;
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if (!bdi_write_congested(bdi))
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return 1;
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if (bdi == current->backing_dev_info)
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return 1;
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return 0;
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}
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/*
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* We detected a synchronous write error writing a page out. Probably
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* -ENOSPC. We need to propagate that into the address_space for a subsequent
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* fsync(), msync() or close().
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*
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* The tricky part is that after writepage we cannot touch the mapping: nothing
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* prevents it from being freed up. But we have a ref on the page and once
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* that page is locked, the mapping is pinned.
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*
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* We're allowed to run sleeping lock_page() here because we know the caller has
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* __GFP_FS.
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*/
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static void handle_write_error(struct address_space *mapping,
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struct page *page, int error)
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{
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lock_page(page);
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if (page_mapping(page) == mapping)
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mapping_set_error(mapping, error);
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unlock_page(page);
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}
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/* possible outcome of pageout() */
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typedef enum {
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/* failed to write page out, page is locked */
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PAGE_KEEP,
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/* move page to the active list, page is locked */
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PAGE_ACTIVATE,
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/* page has been sent to the disk successfully, page is unlocked */
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PAGE_SUCCESS,
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/* page is clean and locked */
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PAGE_CLEAN,
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} pageout_t;
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/*
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* pageout is called by shrink_page_list() for each dirty page.
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* Calls ->writepage().
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*/
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static pageout_t pageout(struct page *page, struct address_space *mapping,
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struct scan_control *sc)
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{
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/*
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* If the page is dirty, only perform writeback if that write
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* will be non-blocking. To prevent this allocation from being
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* stalled by pagecache activity. But note that there may be
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* stalls if we need to run get_block(). We could test
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* PagePrivate for that.
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*
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* If this process is currently in __generic_file_aio_write() against
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* this page's queue, we can perform writeback even if that
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* will block.
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*
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* If the page is swapcache, write it back even if that would
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* block, for some throttling. This happens by accident, because
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* swap_backing_dev_info is bust: it doesn't reflect the
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* congestion state of the swapdevs. Easy to fix, if needed.
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*/
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if (!is_page_cache_freeable(page))
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return PAGE_KEEP;
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if (!mapping) {
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/*
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* Some data journaling orphaned pages can have
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* page->mapping == NULL while being dirty with clean buffers.
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*/
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if (page_has_private(page)) {
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if (try_to_free_buffers(page)) {
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ClearPageDirty(page);
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printk("%s: orphaned page\n", __func__);
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return PAGE_CLEAN;
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}
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}
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return PAGE_KEEP;
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}
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if (mapping->a_ops->writepage == NULL)
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return PAGE_ACTIVATE;
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if (!may_write_to_queue(mapping->backing_dev_info, sc))
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return PAGE_KEEP;
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if (clear_page_dirty_for_io(page)) {
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int res;
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struct writeback_control wbc = {
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.sync_mode = WB_SYNC_NONE,
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.nr_to_write = SWAP_CLUSTER_MAX,
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.range_start = 0,
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.range_end = LLONG_MAX,
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.for_reclaim = 1,
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};
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SetPageReclaim(page);
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res = mapping->a_ops->writepage(page, &wbc);
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if (res < 0)
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handle_write_error(mapping, page, res);
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if (res == AOP_WRITEPAGE_ACTIVATE) {
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ClearPageReclaim(page);
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return PAGE_ACTIVATE;
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}
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if (!PageWriteback(page)) {
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/* synchronous write or broken a_ops? */
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ClearPageReclaim(page);
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}
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trace_mm_vmscan_writepage(page, trace_reclaim_flags(page));
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inc_zone_page_state(page, NR_VMSCAN_WRITE);
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return PAGE_SUCCESS;
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}
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return PAGE_CLEAN;
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}
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|
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/*
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* Same as remove_mapping, but if the page is removed from the mapping, it
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* gets returned with a refcount of 0.
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*/
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static int __remove_mapping(struct address_space *mapping, struct page *page)
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{
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BUG_ON(!PageLocked(page));
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BUG_ON(mapping != page_mapping(page));
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|
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spin_lock_irq(&mapping->tree_lock);
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/*
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* The non racy check for a busy page.
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*
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* Must be careful with the order of the tests. When someone has
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* a ref to the page, it may be possible that they dirty it then
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* drop the reference. So if PageDirty is tested before page_count
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* here, then the following race may occur:
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*
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* get_user_pages(&page);
|
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* [user mapping goes away]
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* 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->_count.
|
|
*
|
|
* Note that if SetPageDirty is always performed via set_page_dirty,
|
|
* and thus under tree_lock, then this ordering is not required.
|
|
*/
|
|
if (!page_freeze_refs(page, 2))
|
|
goto cannot_free;
|
|
/* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
|
|
if (unlikely(PageDirty(page))) {
|
|
page_unfreeze_refs(page, 2);
|
|
goto cannot_free;
|
|
}
|
|
|
|
if (PageSwapCache(page)) {
|
|
swp_entry_t swap = { .val = page_private(page) };
|
|
__delete_from_swap_cache(page);
|
|
spin_unlock_irq(&mapping->tree_lock);
|
|
swapcache_free(swap, page);
|
|
} else {
|
|
void (*freepage)(struct page *);
|
|
|
|
freepage = mapping->a_ops->freepage;
|
|
|
|
__delete_from_page_cache(page);
|
|
spin_unlock_irq(&mapping->tree_lock);
|
|
mem_cgroup_uncharge_cache_page(page);
|
|
|
|
if (freepage != NULL)
|
|
freepage(page);
|
|
}
|
|
|
|
return 1;
|
|
|
|
cannot_free:
|
|
spin_unlock_irq(&mapping->tree_lock);
|
|
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)) {
|
|
/*
|
|
* Unfreezing the refcount with 1 rather than 2 effectively
|
|
* drops the pagecache ref for us without requiring another
|
|
* atomic operation.
|
|
*/
|
|
page_unfreeze_refs(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)
|
|
{
|
|
bool is_unevictable;
|
|
int was_unevictable = PageUnevictable(page);
|
|
|
|
VM_BUG_ON(PageLRU(page));
|
|
|
|
redo:
|
|
ClearPageUnevictable(page);
|
|
|
|
if (page_evictable(page)) {
|
|
/*
|
|
* For evictable pages, we can use the cache.
|
|
* In event of a race, worst case is we end up with an
|
|
* unevictable page on [in]active list.
|
|
* We know how to handle that.
|
|
*/
|
|
is_unevictable = false;
|
|
lru_cache_add(page);
|
|
} else {
|
|
/*
|
|
* Put unevictable pages directly on zone's unevictable
|
|
* list.
|
|
*/
|
|
is_unevictable = true;
|
|
add_page_to_unevictable_list(page);
|
|
/*
|
|
* When racing with an mlock or AS_UNEVICTABLE clearing
|
|
* (page is unlocked) make sure that if the other thread
|
|
* does not observe our setting of PG_lru and fails
|
|
* isolation/check_move_unevictable_pages,
|
|
* we see PG_mlocked/AS_UNEVICTABLE cleared below and move
|
|
* the page back to the evictable list.
|
|
*
|
|
* The other side is TestClearPageMlocked() or shmem_lock().
|
|
*/
|
|
smp_mb();
|
|
}
|
|
|
|
/*
|
|
* page's status can change while we move it among lru. If an evictable
|
|
* page is on unevictable list, it never be freed. To avoid that,
|
|
* check after we added it to the list, again.
|
|
*/
|
|
if (is_unevictable && page_evictable(page)) {
|
|
if (!isolate_lru_page(page)) {
|
|
put_page(page);
|
|
goto redo;
|
|
}
|
|
/* This means someone else dropped this page from LRU
|
|
* So, it will be freed or putback to LRU again. There is
|
|
* nothing to do here.
|
|
*/
|
|
}
|
|
|
|
if (was_unevictable && !is_unevictable)
|
|
count_vm_event(UNEVICTABLE_PGRESCUED);
|
|
else if (!was_unevictable && is_unevictable)
|
|
count_vm_event(UNEVICTABLE_PGCULLED);
|
|
|
|
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)) {
|
|
*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 zone *zone,
|
|
struct scan_control *sc,
|
|
enum ttu_flags ttu_flags,
|
|
unsigned long *ret_nr_dirty,
|
|
unsigned long *ret_nr_unqueued_dirty,
|
|
unsigned long *ret_nr_congested,
|
|
unsigned long *ret_nr_writeback,
|
|
unsigned long *ret_nr_immediate,
|
|
bool force_reclaim)
|
|
{
|
|
LIST_HEAD(ret_pages);
|
|
LIST_HEAD(free_pages);
|
|
int pgactivate = 0;
|
|
unsigned long nr_unqueued_dirty = 0;
|
|
unsigned long nr_dirty = 0;
|
|
unsigned long nr_congested = 0;
|
|
unsigned long nr_reclaimed = 0;
|
|
unsigned long nr_writeback = 0;
|
|
unsigned long nr_immediate = 0;
|
|
|
|
cond_resched();
|
|
|
|
mem_cgroup_uncharge_start();
|
|
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(PageActive(page));
|
|
VM_BUG_ON(page_zone(page) != zone);
|
|
|
|
sc->nr_scanned++;
|
|
|
|
if (unlikely(!page_evictable(page)))
|
|
goto cull_mlocked;
|
|
|
|
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))
|
|
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 zone 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 ((mapping && bdi_write_congested(mapping->backing_dev_info)) ||
|
|
(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 reclaim encounters a page, memcg encounters a
|
|
* page that is not marked for immediate reclaim or
|
|
* the caller does not have __GFP_IO. In this case mark
|
|
* the page for immediate reclaim and continue scanning.
|
|
*
|
|
* __GFP_IO is checked because a loop driver thread 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.
|
|
*
|
|
* Don't require __GFP_FS, since we're not going into the
|
|
* FS, just waiting on its writeback completion. Worryingly,
|
|
* ext4 gfs2 and xfs allocate pages with
|
|
* grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so testing
|
|
* may_enter_fs here is liable to OOM on them.
|
|
*
|
|
* 3) memcg encounters a page that is not 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.
|
|
*/
|
|
if (PageWriteback(page)) {
|
|
/* Case 1 above */
|
|
if (current_is_kswapd() &&
|
|
PageReclaim(page) &&
|
|
zone_is_reclaim_writeback(zone)) {
|
|
nr_immediate++;
|
|
goto keep_locked;
|
|
|
|
/* Case 2 above */
|
|
} else if (global_reclaim(sc) ||
|
|
!PageReclaim(page) || !(sc->gfp_mask & __GFP_IO)) {
|
|
/*
|
|
* 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 keep_locked;
|
|
|
|
/* Case 3 above */
|
|
} else {
|
|
wait_on_page_writeback(page);
|
|
}
|
|
}
|
|
|
|
if (!force_reclaim)
|
|
references = page_check_references(page, sc);
|
|
|
|
switch (references) {
|
|
case PAGEREF_ACTIVATE:
|
|
goto activate_locked;
|
|
case PAGEREF_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.
|
|
*/
|
|
if (PageAnon(page) && !PageSwapCache(page)) {
|
|
if (!(sc->gfp_mask & __GFP_IO))
|
|
goto keep_locked;
|
|
if (!add_to_swap(page, page_list))
|
|
goto activate_locked;
|
|
may_enter_fs = 1;
|
|
|
|
/* Adding to swap updated mapping */
|
|
mapping = page_mapping(page);
|
|
}
|
|
|
|
/*
|
|
* The page is mapped into the page tables of one or more
|
|
* processes. Try to unmap it here.
|
|
*/
|
|
if (page_mapped(page) && mapping) {
|
|
switch (try_to_unmap(page, ttu_flags)) {
|
|
case SWAP_FAIL:
|
|
goto activate_locked;
|
|
case SWAP_AGAIN:
|
|
goto keep_locked;
|
|
case SWAP_MLOCK:
|
|
goto cull_mlocked;
|
|
case SWAP_SUCCESS:
|
|
; /* try to free the page below */
|
|
}
|
|
}
|
|
|
|
if (PageDirty(page)) {
|
|
/*
|
|
* Only kswapd can writeback filesystem pages to
|
|
* avoid risk of stack overflow but only writeback
|
|
* if many dirty pages have been encountered.
|
|
*/
|
|
if (page_is_file_cache(page) &&
|
|
(!current_is_kswapd() ||
|
|
!zone_is_reclaim_dirty(zone))) {
|
|
/*
|
|
* Immediately reclaim when written back.
|
|
* Similar in principal to deactivate_page()
|
|
* except we already have the page isolated
|
|
* and know it's dirty
|
|
*/
|
|
inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
|
|
SetPageReclaim(page);
|
|
|
|
goto keep_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, try to write it out here */
|
|
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 (!mapping || !__remove_mapping(mapping, page))
|
|
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.
|
|
*/
|
|
__clear_page_locked(page);
|
|
free_it:
|
|
nr_reclaimed++;
|
|
|
|
/*
|
|
* Is there need to periodically free_page_list? It would
|
|
* appear not as the counts should be low
|
|
*/
|
|
list_add(&page->lru, &free_pages);
|
|
continue;
|
|
|
|
cull_mlocked:
|
|
if (PageSwapCache(page))
|
|
try_to_free_swap(page);
|
|
unlock_page(page);
|
|
putback_lru_page(page);
|
|
continue;
|
|
|
|
activate_locked:
|
|
/* Not a candidate for swapping, so reclaim swap space. */
|
|
if (PageSwapCache(page) && vm_swap_full())
|
|
try_to_free_swap(page);
|
|
VM_BUG_ON(PageActive(page));
|
|
SetPageActive(page);
|
|
pgactivate++;
|
|
keep_locked:
|
|
unlock_page(page);
|
|
keep:
|
|
list_add(&page->lru, &ret_pages);
|
|
VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
|
|
}
|
|
|
|
free_hot_cold_page_list(&free_pages, 1);
|
|
|
|
list_splice(&ret_pages, page_list);
|
|
count_vm_events(PGACTIVATE, pgactivate);
|
|
mem_cgroup_uncharge_end();
|
|
*ret_nr_dirty += nr_dirty;
|
|
*ret_nr_congested += nr_congested;
|
|
*ret_nr_unqueued_dirty += nr_unqueued_dirty;
|
|
*ret_nr_writeback += nr_writeback;
|
|
*ret_nr_immediate += nr_immediate;
|
|
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, dummy1, dummy2, dummy3, dummy4, dummy5;
|
|
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) &&
|
|
!isolated_balloon_page(page)) {
|
|
ClearPageActive(page);
|
|
list_move(&page->lru, &clean_pages);
|
|
}
|
|
}
|
|
|
|
ret = shrink_page_list(&clean_pages, zone, &sc,
|
|
TTU_UNMAP|TTU_IGNORE_ACCESS,
|
|
&dummy1, &dummy2, &dummy3, &dummy4, &dummy5, true);
|
|
list_splice(&clean_pages, page_list);
|
|
__mod_zone_page_state(zone, 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_CLEAN means that only clean pages should be isolated. This
|
|
* is used by reclaim when it is cannot write to backing storage
|
|
*
|
|
* ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
|
|
* that it is possible to migrate without blocking
|
|
*/
|
|
if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
|
|
/* All the caller can do on PageWriteback is block */
|
|
if (PageWriteback(page))
|
|
return ret;
|
|
|
|
if (PageDirty(page)) {
|
|
struct address_space *mapping;
|
|
|
|
/* ISOLATE_CLEAN means only clean pages */
|
|
if (mode & ISOLATE_CLEAN)
|
|
return ret;
|
|
|
|
/*
|
|
* Only pages without mappings or that have a
|
|
* ->migratepage callback are possible to migrate
|
|
* without blocking
|
|
*/
|
|
mapping = page_mapping(page);
|
|
if (mapping && !mapping->a_ops->migratepage)
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* 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 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 scan;
|
|
|
|
for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
|
|
struct page *page;
|
|
int nr_pages;
|
|
|
|
page = lru_to_page(src);
|
|
prefetchw_prev_lru_page(page, src, flags);
|
|
|
|
VM_BUG_ON(!PageLRU(page));
|
|
|
|
switch (__isolate_lru_page(page, mode)) {
|
|
case 0:
|
|
nr_pages = hpage_nr_pages(page);
|
|
mem_cgroup_update_lru_size(lruvec, lru, -nr_pages);
|
|
list_move(&page->lru, dst);
|
|
nr_taken += nr_pages;
|
|
break;
|
|
|
|
case -EBUSY:
|
|
/* else it is being freed elsewhere */
|
|
list_move(&page->lru, src);
|
|
continue;
|
|
|
|
default:
|
|
BUG();
|
|
}
|
|
}
|
|
|
|
*nr_scanned = scan;
|
|
trace_mm_vmscan_lru_isolate(sc->order, nr_to_scan, scan,
|
|
nr_taken, mode, is_file_lru(lru));
|
|
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_count(page));
|
|
|
|
if (PageLRU(page)) {
|
|
struct zone *zone = page_zone(page);
|
|
struct lruvec *lruvec;
|
|
|
|
spin_lock_irq(&zone->lru_lock);
|
|
lruvec = mem_cgroup_page_lruvec(page, zone);
|
|
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);
|
|
}
|
|
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 zone *zone, int file,
|
|
struct scan_control *sc)
|
|
{
|
|
unsigned long inactive, isolated;
|
|
|
|
if (current_is_kswapd())
|
|
return 0;
|
|
|
|
if (!global_reclaim(sc))
|
|
return 0;
|
|
|
|
if (file) {
|
|
inactive = zone_page_state(zone, NR_INACTIVE_FILE);
|
|
isolated = zone_page_state(zone, NR_ISOLATED_FILE);
|
|
} else {
|
|
inactive = zone_page_state(zone, NR_INACTIVE_ANON);
|
|
isolated = zone_page_state(zone, 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_IOFS) == GFP_IOFS)
|
|
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 zone *zone = lruvec_zone(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(PageLRU(page));
|
|
list_del(&page->lru);
|
|
if (unlikely(!page_evictable(page))) {
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
putback_lru_page(page);
|
|
spin_lock_irq(&zone->lru_lock);
|
|
continue;
|
|
}
|
|
|
|
lruvec = mem_cgroup_page_lruvec(page, zone);
|
|
|
|
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(&zone->lru_lock);
|
|
(*get_compound_page_dtor(page))(page);
|
|
spin_lock_irq(&zone->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);
|
|
}
|
|
|
|
/*
|
|
* shrink_inactive_list() is a helper for shrink_zone(). 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;
|
|
unsigned long nr_dirty = 0;
|
|
unsigned long nr_congested = 0;
|
|
unsigned long nr_unqueued_dirty = 0;
|
|
unsigned long nr_writeback = 0;
|
|
unsigned long nr_immediate = 0;
|
|
isolate_mode_t isolate_mode = 0;
|
|
int file = is_file_lru(lru);
|
|
struct zone *zone = lruvec_zone(lruvec);
|
|
struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
|
|
|
|
while (unlikely(too_many_isolated(zone, file, sc))) {
|
|
congestion_wait(BLK_RW_ASYNC, HZ/10);
|
|
|
|
/* 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;
|
|
if (!sc->may_writepage)
|
|
isolate_mode |= ISOLATE_CLEAN;
|
|
|
|
spin_lock_irq(&zone->lru_lock);
|
|
|
|
nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list,
|
|
&nr_scanned, sc, isolate_mode, lru);
|
|
|
|
__mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
|
|
__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
|
|
|
|
if (global_reclaim(sc)) {
|
|
zone->pages_scanned += nr_scanned;
|
|
if (current_is_kswapd())
|
|
__count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scanned);
|
|
else
|
|
__count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scanned);
|
|
}
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
|
|
if (nr_taken == 0)
|
|
return 0;
|
|
|
|
nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP,
|
|
&nr_dirty, &nr_unqueued_dirty, &nr_congested,
|
|
&nr_writeback, &nr_immediate,
|
|
false);
|
|
|
|
spin_lock_irq(&zone->lru_lock);
|
|
|
|
reclaim_stat->recent_scanned[file] += nr_taken;
|
|
|
|
if (global_reclaim(sc)) {
|
|
if (current_is_kswapd())
|
|
__count_zone_vm_events(PGSTEAL_KSWAPD, zone,
|
|
nr_reclaimed);
|
|
else
|
|
__count_zone_vm_events(PGSTEAL_DIRECT, zone,
|
|
nr_reclaimed);
|
|
}
|
|
|
|
putback_inactive_pages(lruvec, &page_list);
|
|
|
|
__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
|
|
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
|
|
free_hot_cold_page_list(&page_list, 1);
|
|
|
|
/*
|
|
* 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 zone is flagged ZONE_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 (nr_writeback && nr_writeback == nr_taken)
|
|
zone_set_flag(zone, ZONE_WRITEBACK);
|
|
|
|
/*
|
|
* memcg will stall in page writeback so only consider forcibly
|
|
* stalling for global reclaim
|
|
*/
|
|
if (global_reclaim(sc)) {
|
|
/*
|
|
* Tag a zone as congested if all the dirty pages scanned were
|
|
* backed by a congested BDI and wait_iff_congested will stall.
|
|
*/
|
|
if (nr_dirty && nr_dirty == nr_congested)
|
|
zone_set_flag(zone, ZONE_CONGESTED);
|
|
|
|
/*
|
|
* If dirty pages are scanned that are not queued for IO, it
|
|
* implies that flushers are not keeping up. In this case, flag
|
|
* the zone ZONE_TAIL_LRU_DIRTY and kswapd will start writing
|
|
* pages from reclaim context. It will forcibly stall in the
|
|
* next check.
|
|
*/
|
|
if (nr_unqueued_dirty == nr_taken)
|
|
zone_set_flag(zone, ZONE_TAIL_LRU_DIRTY);
|
|
|
|
/*
|
|
* In addition, 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 (nr_unqueued_dirty == nr_taken || nr_immediate)
|
|
congestion_wait(BLK_RW_ASYNC, HZ/10);
|
|
}
|
|
|
|
/*
|
|
* Stall direct reclaim for IO completions if underlying BDIs or zone
|
|
* 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())
|
|
wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
|
|
|
|
trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
|
|
zone_idx(zone),
|
|
nr_scanned, nr_reclaimed,
|
|
sc->priority,
|
|
trace_shrink_flags(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->_count against each page.
|
|
* But we had to alter page->flags anyway.
|
|
*/
|
|
|
|
static void move_active_pages_to_lru(struct lruvec *lruvec,
|
|
struct list_head *list,
|
|
struct list_head *pages_to_free,
|
|
enum lru_list lru)
|
|
{
|
|
struct zone *zone = lruvec_zone(lruvec);
|
|
unsigned long pgmoved = 0;
|
|
struct page *page;
|
|
int nr_pages;
|
|
|
|
while (!list_empty(list)) {
|
|
page = lru_to_page(list);
|
|
lruvec = mem_cgroup_page_lruvec(page, zone);
|
|
|
|
VM_BUG_ON(PageLRU(page));
|
|
SetPageLRU(page);
|
|
|
|
nr_pages = hpage_nr_pages(page);
|
|
mem_cgroup_update_lru_size(lruvec, lru, nr_pages);
|
|
list_move(&page->lru, &lruvec->lists[lru]);
|
|
pgmoved += nr_pages;
|
|
|
|
if (put_page_testzero(page)) {
|
|
__ClearPageLRU(page);
|
|
__ClearPageActive(page);
|
|
del_page_from_lru_list(page, lruvec, lru);
|
|
|
|
if (unlikely(PageCompound(page))) {
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
(*get_compound_page_dtor(page))(page);
|
|
spin_lock_irq(&zone->lru_lock);
|
|
} else
|
|
list_add(&page->lru, pages_to_free);
|
|
}
|
|
}
|
|
__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
|
|
if (!is_active_lru(lru))
|
|
__count_vm_events(PGDEACTIVATE, pgmoved);
|
|
}
|
|
|
|
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 long nr_rotated = 0;
|
|
isolate_mode_t isolate_mode = 0;
|
|
int file = is_file_lru(lru);
|
|
struct zone *zone = lruvec_zone(lruvec);
|
|
|
|
lru_add_drain();
|
|
|
|
if (!sc->may_unmap)
|
|
isolate_mode |= ISOLATE_UNMAPPED;
|
|
if (!sc->may_writepage)
|
|
isolate_mode |= ISOLATE_CLEAN;
|
|
|
|
spin_lock_irq(&zone->lru_lock);
|
|
|
|
nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold,
|
|
&nr_scanned, sc, isolate_mode, lru);
|
|
if (global_reclaim(sc))
|
|
zone->pages_scanned += nr_scanned;
|
|
|
|
reclaim_stat->recent_scanned[file] += nr_taken;
|
|
|
|
__count_zone_vm_events(PGREFILL, zone, nr_scanned);
|
|
__mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
|
|
__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
|
|
spin_unlock_irq(&zone->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 */
|
|
list_add(&page->lru, &l_inactive);
|
|
}
|
|
|
|
/*
|
|
* Move pages back to the lru list.
|
|
*/
|
|
spin_lock_irq(&zone->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_ratio.
|
|
*/
|
|
reclaim_stat->recent_rotated[file] += nr_rotated;
|
|
|
|
move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru);
|
|
move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE);
|
|
__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
|
|
free_hot_cold_page_list(&l_hold, 1);
|
|
}
|
|
|
|
#ifdef CONFIG_SWAP
|
|
static int inactive_anon_is_low_global(struct zone *zone)
|
|
{
|
|
unsigned long active, inactive;
|
|
|
|
active = zone_page_state(zone, NR_ACTIVE_ANON);
|
|
inactive = zone_page_state(zone, NR_INACTIVE_ANON);
|
|
|
|
if (inactive * zone->inactive_ratio < active)
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* inactive_anon_is_low - check if anonymous pages need to be deactivated
|
|
* @lruvec: LRU vector to check
|
|
*
|
|
* Returns true if the zone does not have enough inactive anon pages,
|
|
* meaning some active anon pages need to be deactivated.
|
|
*/
|
|
static int inactive_anon_is_low(struct lruvec *lruvec)
|
|
{
|
|
/*
|
|
* If we don't have swap space, anonymous page deactivation
|
|
* is pointless.
|
|
*/
|
|
if (!total_swap_pages)
|
|
return 0;
|
|
|
|
if (!mem_cgroup_disabled())
|
|
return mem_cgroup_inactive_anon_is_low(lruvec);
|
|
|
|
return inactive_anon_is_low_global(lruvec_zone(lruvec));
|
|
}
|
|
#else
|
|
static inline int inactive_anon_is_low(struct lruvec *lruvec)
|
|
{
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
/**
|
|
* inactive_file_is_low - check if file pages need to be deactivated
|
|
* @lruvec: LRU vector to check
|
|
*
|
|
* When the system is doing streaming IO, memory pressure here
|
|
* ensures that active file pages get deactivated, until more
|
|
* than half of the file pages are on the inactive list.
|
|
*
|
|
* Once we get to that situation, protect the system's working
|
|
* set from being evicted by disabling active file page aging.
|
|
*
|
|
* This uses a different ratio than the anonymous pages, because
|
|
* the page cache uses a use-once replacement algorithm.
|
|
*/
|
|
static int inactive_file_is_low(struct lruvec *lruvec)
|
|
{
|
|
unsigned long inactive;
|
|
unsigned long active;
|
|
|
|
inactive = get_lru_size(lruvec, LRU_INACTIVE_FILE);
|
|
active = get_lru_size(lruvec, LRU_ACTIVE_FILE);
|
|
|
|
return active > inactive;
|
|
}
|
|
|
|
static int inactive_list_is_low(struct lruvec *lruvec, enum lru_list lru)
|
|
{
|
|
if (is_file_lru(lru))
|
|
return inactive_file_is_low(lruvec);
|
|
else
|
|
return inactive_anon_is_low(lruvec);
|
|
}
|
|
|
|
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
|
|
struct lruvec *lruvec, struct scan_control *sc)
|
|
{
|
|
if (is_active_lru(lru)) {
|
|
if (inactive_list_is_low(lruvec, lru))
|
|
shrink_active_list(nr_to_scan, lruvec, sc, lru);
|
|
return 0;
|
|
}
|
|
|
|
return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
|
|
}
|
|
|
|
static int vmscan_swappiness(struct scan_control *sc)
|
|
{
|
|
if (global_reclaim(sc))
|
|
return vm_swappiness;
|
|
return mem_cgroup_swappiness(sc->target_mem_cgroup);
|
|
}
|
|
|
|
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 scan_control *sc,
|
|
unsigned long *nr)
|
|
{
|
|
struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
|
|
u64 fraction[2];
|
|
u64 denominator = 0; /* gcc */
|
|
struct zone *zone = lruvec_zone(lruvec);
|
|
unsigned long anon_prio, file_prio;
|
|
enum scan_balance scan_balance;
|
|
unsigned long anon, file, free;
|
|
bool force_scan = false;
|
|
unsigned long ap, fp;
|
|
enum lru_list lru;
|
|
|
|
/*
|
|
* If the zone or memcg is small, nr[l] can be 0. This
|
|
* results in no scanning on this priority and a potential
|
|
* priority drop. Global direct reclaim can go to the next
|
|
* zone and tends to have no problems. Global kswapd is for
|
|
* zone balancing and it needs to scan a minimum amount. When
|
|
* reclaiming for a memcg, a priority drop can cause high
|
|
* latencies, so it's better to scan a minimum amount there as
|
|
* well.
|
|
*/
|
|
if (current_is_kswapd() && !zone_reclaimable(zone))
|
|
force_scan = true;
|
|
if (!global_reclaim(sc))
|
|
force_scan = true;
|
|
|
|
/* If we have no swap space, do not bother scanning anon pages. */
|
|
if (!sc->may_swap || (get_nr_swap_pages() <= 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) && !vmscan_swappiness(sc)) {
|
|
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 && vmscan_swappiness(sc)) {
|
|
scan_balance = SCAN_EQUAL;
|
|
goto out;
|
|
}
|
|
|
|
anon = get_lru_size(lruvec, LRU_ACTIVE_ANON) +
|
|
get_lru_size(lruvec, LRU_INACTIVE_ANON);
|
|
file = get_lru_size(lruvec, LRU_ACTIVE_FILE) +
|
|
get_lru_size(lruvec, LRU_INACTIVE_FILE);
|
|
|
|
/*
|
|
* If it's foreseeable that reclaiming the file cache won't be
|
|
* enough to get the zone back into a desirable shape, we have
|
|
* to swap. Better start now and leave the - probably heavily
|
|
* thrashing - remaining file pages alone.
|
|
*/
|
|
if (global_reclaim(sc)) {
|
|
free = zone_page_state(zone, NR_FREE_PAGES);
|
|
if (unlikely(file + free <= high_wmark_pages(zone))) {
|
|
scan_balance = SCAN_ANON;
|
|
goto out;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* There is enough inactive page cache, do not reclaim
|
|
* anything from the anonymous working set right now.
|
|
*/
|
|
if (!inactive_file_is_low(lruvec)) {
|
|
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 = vmscan_swappiness(sc);
|
|
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]
|
|
*/
|
|
spin_lock_irq(&zone->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(&zone->lru_lock);
|
|
|
|
fraction[0] = ap;
|
|
fraction[1] = fp;
|
|
denominator = ap + fp + 1;
|
|
out:
|
|
for_each_evictable_lru(lru) {
|
|
int file = is_file_lru(lru);
|
|
unsigned long size;
|
|
unsigned long scan;
|
|
|
|
size = get_lru_size(lruvec, lru);
|
|
scan = size >> sc->priority;
|
|
|
|
if (!scan && force_scan)
|
|
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.
|
|
*/
|
|
scan = div64_u64(scan * fraction[file], denominator);
|
|
break;
|
|
case SCAN_FILE:
|
|
case SCAN_ANON:
|
|
/* Scan one type exclusively */
|
|
if ((scan_balance == SCAN_FILE) != file)
|
|
scan = 0;
|
|
break;
|
|
default:
|
|
/* Look ma, no brain */
|
|
BUG();
|
|
}
|
|
nr[lru] = scan;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
|
|
*/
|
|
static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
|
|
{
|
|
unsigned long nr[NR_LRU_LISTS];
|
|
unsigned long targets[NR_LRU_LISTS];
|
|
unsigned long nr_to_scan;
|
|
enum lru_list lru;
|
|
unsigned long nr_reclaimed = 0;
|
|
unsigned long nr_to_reclaim = sc->nr_to_reclaim;
|
|
struct blk_plug plug;
|
|
bool scan_adjusted = false;
|
|
|
|
get_scan_count(lruvec, sc, nr);
|
|
|
|
/* Record the original scan target for proportional adjustments later */
|
|
memcpy(targets, nr, sizeof(nr));
|
|
|
|
blk_start_plug(&plug);
|
|
while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
|
|
nr[LRU_INACTIVE_FILE]) {
|
|
unsigned long nr_anon, nr_file, percentage;
|
|
unsigned long nr_scanned;
|
|
|
|
for_each_evictable_lru(lru) {
|
|
if (nr[lru]) {
|
|
nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
|
|
nr[lru] -= nr_to_scan;
|
|
|
|
nr_reclaimed += shrink_list(lru, nr_to_scan,
|
|
lruvec, sc);
|
|
}
|
|
}
|
|
|
|
if (nr_reclaimed < nr_to_reclaim || scan_adjusted)
|
|
continue;
|
|
|
|
/*
|
|
* For global direct reclaim, reclaim only the number of pages
|
|
* requested. Less care is taken to scan proportionally as it
|
|
* is more important to minimise direct reclaim stall latency
|
|
* than it is to properly age the LRU lists.
|
|
*/
|
|
if (global_reclaim(sc) && !current_is_kswapd())
|
|
break;
|
|
|
|
/*
|
|
* For kswapd and memcg, reclaim at least the number of pages
|
|
* requested. Ensure that the anon and file LRUs shrink
|
|
* 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];
|
|
|
|
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_anon_is_low(lruvec))
|
|
shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
|
|
sc, LRU_ACTIVE_ANON);
|
|
|
|
throttle_vm_writeout(sc->gfp_mask);
|
|
}
|
|
|
|
/* 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 zone *zone,
|
|
unsigned long nr_reclaimed,
|
|
unsigned long nr_scanned,
|
|
struct scan_control *sc)
|
|
{
|
|
unsigned long pages_for_compaction;
|
|
unsigned long inactive_lru_pages;
|
|
|
|
/* 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_REPEAT) {
|
|
/*
|
|
* For __GFP_REPEAT 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_REPEAT caller really wants to succeed
|
|
*/
|
|
if (!nr_reclaimed && !nr_scanned)
|
|
return false;
|
|
} else {
|
|
/*
|
|
* For non-__GFP_REPEAT 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 = (2UL << sc->order);
|
|
inactive_lru_pages = zone_page_state(zone, NR_INACTIVE_FILE);
|
|
if (get_nr_swap_pages() > 0)
|
|
inactive_lru_pages += zone_page_state(zone, 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 */
|
|
switch (compaction_suitable(zone, sc->order)) {
|
|
case COMPACT_PARTIAL:
|
|
case COMPACT_CONTINUE:
|
|
return false;
|
|
default:
|
|
return true;
|
|
}
|
|
}
|
|
|
|
static void shrink_zone(struct zone *zone, struct scan_control *sc)
|
|
{
|
|
unsigned long nr_reclaimed, nr_scanned;
|
|
|
|
do {
|
|
struct mem_cgroup *root = sc->target_mem_cgroup;
|
|
struct mem_cgroup_reclaim_cookie reclaim = {
|
|
.zone = zone,
|
|
.priority = sc->priority,
|
|
};
|
|
struct mem_cgroup *memcg;
|
|
|
|
nr_reclaimed = sc->nr_reclaimed;
|
|
nr_scanned = sc->nr_scanned;
|
|
|
|
memcg = mem_cgroup_iter(root, NULL, &reclaim);
|
|
do {
|
|
struct lruvec *lruvec;
|
|
|
|
lruvec = mem_cgroup_zone_lruvec(zone, memcg);
|
|
|
|
shrink_lruvec(lruvec, sc);
|
|
|
|
/*
|
|
* Direct reclaim and kswapd have to scan all memory
|
|
* cgroups to fulfill the overall scan target for the
|
|
* zone.
|
|
*
|
|
* 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;
|
|
}
|
|
memcg = mem_cgroup_iter(root, memcg, &reclaim);
|
|
} while (memcg);
|
|
|
|
vmpressure(sc->gfp_mask, sc->target_mem_cgroup,
|
|
sc->nr_scanned - nr_scanned,
|
|
sc->nr_reclaimed - nr_reclaimed);
|
|
|
|
} while (should_continue_reclaim(zone, sc->nr_reclaimed - nr_reclaimed,
|
|
sc->nr_scanned - nr_scanned, sc));
|
|
}
|
|
|
|
/* Returns true if compaction should go ahead for a high-order request */
|
|
static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
|
|
{
|
|
unsigned long balance_gap, watermark;
|
|
bool watermark_ok;
|
|
|
|
/* Do not consider compaction for orders reclaim is meant to satisfy */
|
|
if (sc->order <= PAGE_ALLOC_COSTLY_ORDER)
|
|
return false;
|
|
|
|
/*
|
|
* Compaction takes time to run and there are potentially other
|
|
* callers using the pages just freed. Continue reclaiming until
|
|
* there is a buffer of free pages available to give compaction
|
|
* a reasonable chance of completing and allocating the page
|
|
*/
|
|
balance_gap = min(low_wmark_pages(zone),
|
|
(zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
|
|
KSWAPD_ZONE_BALANCE_GAP_RATIO);
|
|
watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order);
|
|
watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0);
|
|
|
|
/*
|
|
* If compaction is deferred, reclaim up to a point where
|
|
* compaction will have a chance of success when re-enabled
|
|
*/
|
|
if (compaction_deferred(zone, sc->order))
|
|
return watermark_ok;
|
|
|
|
/* If compaction is not ready to start, keep reclaiming */
|
|
if (!compaction_suitable(zone, sc->order))
|
|
return false;
|
|
|
|
return watermark_ok;
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
*
|
|
* We reclaim from a zone even if that zone is over high_wmark_pages(zone).
|
|
* Because:
|
|
* a) The caller may be trying to free *extra* pages to satisfy a higher-order
|
|
* allocation or
|
|
* b) The target zone may be at high_wmark_pages(zone) but the lower zones
|
|
* must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
|
|
* zone defense algorithm.
|
|
*
|
|
* If a zone is deemed to be full of pinned pages then just give it a light
|
|
* scan then give up on it.
|
|
*
|
|
* This function returns true if a zone is being reclaimed for a costly
|
|
* high-order allocation and compaction is ready to begin. This indicates to
|
|
* the caller that it should consider retrying the allocation instead of
|
|
* further reclaim.
|
|
*/
|
|
static bool 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;
|
|
bool aborted_reclaim = false;
|
|
|
|
/*
|
|
* 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
|
|
*/
|
|
if (buffer_heads_over_limit)
|
|
sc->gfp_mask |= __GFP_HIGHMEM;
|
|
|
|
for_each_zone_zonelist_nodemask(zone, z, zonelist,
|
|
gfp_zone(sc->gfp_mask), sc->nodemask) {
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
/*
|
|
* Take care memory controller reclaiming has small influence
|
|
* to global LRU.
|
|
*/
|
|
if (global_reclaim(sc)) {
|
|
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
|
|
continue;
|
|
if (sc->priority != DEF_PRIORITY &&
|
|
!zone_reclaimable(zone))
|
|
continue; /* Let kswapd poll it */
|
|
if (IS_ENABLED(CONFIG_COMPACTION)) {
|
|
/*
|
|
* 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 (compaction_ready(zone, sc)) {
|
|
aborted_reclaim = true;
|
|
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,
|
|
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() */
|
|
}
|
|
|
|
shrink_zone(zone, sc);
|
|
}
|
|
|
|
return aborted_reclaim;
|
|
}
|
|
|
|
/* All zones in zonelist are unreclaimable? */
|
|
static bool all_unreclaimable(struct zonelist *zonelist,
|
|
struct scan_control *sc)
|
|
{
|
|
struct zoneref *z;
|
|
struct zone *zone;
|
|
|
|
for_each_zone_zonelist_nodemask(zone, z, zonelist,
|
|
gfp_zone(sc->gfp_mask), sc->nodemask) {
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
|
|
continue;
|
|
if (zone_reclaimable(zone))
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* 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,
|
|
struct shrink_control *shrink)
|
|
{
|
|
unsigned long total_scanned = 0;
|
|
struct reclaim_state *reclaim_state = current->reclaim_state;
|
|
struct zoneref *z;
|
|
struct zone *zone;
|
|
unsigned long writeback_threshold;
|
|
bool aborted_reclaim;
|
|
|
|
delayacct_freepages_start();
|
|
|
|
if (global_reclaim(sc))
|
|
count_vm_event(ALLOCSTALL);
|
|
|
|
do {
|
|
vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
|
|
sc->priority);
|
|
sc->nr_scanned = 0;
|
|
aborted_reclaim = shrink_zones(zonelist, sc);
|
|
|
|
/*
|
|
* Don't shrink slabs when reclaiming memory from over limit
|
|
* cgroups but do shrink slab at least once when aborting
|
|
* reclaim for compaction to avoid unevenly scanning file/anon
|
|
* LRU pages over slab pages.
|
|
*/
|
|
if (global_reclaim(sc)) {
|
|
unsigned long lru_pages = 0;
|
|
|
|
nodes_clear(shrink->nodes_to_scan);
|
|
for_each_zone_zonelist(zone, z, zonelist,
|
|
gfp_zone(sc->gfp_mask)) {
|
|
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
|
|
continue;
|
|
|
|
lru_pages += zone_reclaimable_pages(zone);
|
|
node_set(zone_to_nid(zone),
|
|
shrink->nodes_to_scan);
|
|
}
|
|
|
|
shrink_slab(shrink, sc->nr_scanned, lru_pages);
|
|
if (reclaim_state) {
|
|
sc->nr_reclaimed += reclaim_state->reclaimed_slab;
|
|
reclaim_state->reclaimed_slab = 0;
|
|
}
|
|
}
|
|
total_scanned += sc->nr_scanned;
|
|
if (sc->nr_reclaimed >= sc->nr_to_reclaim)
|
|
goto out;
|
|
|
|
/*
|
|
* If we're getting trouble reclaiming, start doing
|
|
* writepage even in laptop mode.
|
|
*/
|
|
if (sc->priority < DEF_PRIORITY - 2)
|
|
sc->may_writepage = 1;
|
|
|
|
/*
|
|
* Try to write back as many pages as we just scanned. This
|
|
* tends to cause slow streaming writers to write data to the
|
|
* disk smoothly, at the dirtying rate, which is nice. But
|
|
* that's undesirable in laptop mode, where we *want* lumpy
|
|
* writeout. So in laptop mode, write out the whole world.
|
|
*/
|
|
writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
|
|
if (total_scanned > writeback_threshold) {
|
|
wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
|
|
WB_REASON_TRY_TO_FREE_PAGES);
|
|
sc->may_writepage = 1;
|
|
}
|
|
} while (--sc->priority >= 0 && !aborted_reclaim);
|
|
|
|
out:
|
|
delayacct_freepages_end();
|
|
|
|
if (sc->nr_reclaimed)
|
|
return sc->nr_reclaimed;
|
|
|
|
/*
|
|
* As hibernation is going on, kswapd is freezed so that it can't mark
|
|
* the zone into all_unreclaimable. Thus bypassing all_unreclaimable
|
|
* check.
|
|
*/
|
|
if (oom_killer_disabled)
|
|
return 0;
|
|
|
|
/* Aborted reclaim to try compaction? don't OOM, then */
|
|
if (aborted_reclaim)
|
|
return 1;
|
|
|
|
/* top priority shrink_zones still had more to do? don't OOM, then */
|
|
if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc))
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static bool pfmemalloc_watermark_ok(pg_data_t *pgdat)
|
|
{
|
|
struct zone *zone;
|
|
unsigned long pfmemalloc_reserve = 0;
|
|
unsigned long free_pages = 0;
|
|
int i;
|
|
bool wmark_ok;
|
|
|
|
for (i = 0; i <= ZONE_NORMAL; i++) {
|
|
zone = &pgdat->node_zones[i];
|
|
pfmemalloc_reserve += min_wmark_pages(zone);
|
|
free_pages += zone_page_state(zone, NR_FREE_PAGES);
|
|
}
|
|
|
|
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->classzone_idx = min(pgdat->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 zone *zone;
|
|
int high_zoneidx = gfp_zone(gfp_mask);
|
|
pg_data_t *pgdat;
|
|
|
|
/*
|
|
* 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 */
|
|
first_zones_zonelist(zonelist, high_zoneidx, NULL, &zone);
|
|
pgdat = zone->zone_pgdat;
|
|
if (pfmemalloc_watermark_ok(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,
|
|
pfmemalloc_watermark_ok(pgdat), HZ);
|
|
|
|
goto check_pending;
|
|
}
|
|
|
|
/* Throttle until kswapd wakes the process */
|
|
wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
|
|
pfmemalloc_watermark_ok(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 = {
|
|
.gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
|
|
.may_writepage = !laptop_mode,
|
|
.nr_to_reclaim = SWAP_CLUSTER_MAX,
|
|
.may_unmap = 1,
|
|
.may_swap = 1,
|
|
.order = order,
|
|
.priority = DEF_PRIORITY,
|
|
.target_mem_cgroup = NULL,
|
|
.nodemask = nodemask,
|
|
};
|
|
struct shrink_control shrink = {
|
|
.gfp_mask = sc.gfp_mask,
|
|
};
|
|
|
|
/*
|
|
* 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(gfp_mask, zonelist, nodemask))
|
|
return 1;
|
|
|
|
trace_mm_vmscan_direct_reclaim_begin(order,
|
|
sc.may_writepage,
|
|
gfp_mask);
|
|
|
|
nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
|
|
|
|
trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
|
|
|
|
return nr_reclaimed;
|
|
}
|
|
|
|
#ifdef CONFIG_MEMCG
|
|
|
|
unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
|
|
gfp_t gfp_mask, bool noswap,
|
|
struct zone *zone,
|
|
unsigned long *nr_scanned)
|
|
{
|
|
struct scan_control sc = {
|
|
.nr_scanned = 0,
|
|
.nr_to_reclaim = SWAP_CLUSTER_MAX,
|
|
.may_writepage = !laptop_mode,
|
|
.may_unmap = 1,
|
|
.may_swap = !noswap,
|
|
.order = 0,
|
|
.priority = 0,
|
|
.target_mem_cgroup = memcg,
|
|
};
|
|
struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
|
|
|
|
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);
|
|
|
|
/*
|
|
* 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_zone from balance_pgdat
|
|
* will pick up pages from other mem cgroup's as well. We hack
|
|
* the priority and make it zero.
|
|
*/
|
|
shrink_lruvec(lruvec, &sc);
|
|
|
|
trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
|
|
|
|
*nr_scanned = sc.nr_scanned;
|
|
return sc.nr_reclaimed;
|
|
}
|
|
|
|
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
|
|
gfp_t gfp_mask,
|
|
bool noswap)
|
|
{
|
|
struct zonelist *zonelist;
|
|
unsigned long nr_reclaimed;
|
|
int nid;
|
|
struct scan_control sc = {
|
|
.may_writepage = !laptop_mode,
|
|
.may_unmap = 1,
|
|
.may_swap = !noswap,
|
|
.nr_to_reclaim = SWAP_CLUSTER_MAX,
|
|
.order = 0,
|
|
.priority = DEF_PRIORITY,
|
|
.target_mem_cgroup = memcg,
|
|
.nodemask = NULL, /* we don't care the placement */
|
|
.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
|
|
(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
|
|
};
|
|
struct shrink_control shrink = {
|
|
.gfp_mask = sc.gfp_mask,
|
|
};
|
|
|
|
/*
|
|
* 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;
|
|
|
|
trace_mm_vmscan_memcg_reclaim_begin(0,
|
|
sc.may_writepage,
|
|
sc.gfp_mask);
|
|
|
|
nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
|
|
|
|
trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
|
|
|
|
return nr_reclaimed;
|
|
}
|
|
#endif
|
|
|
|
static void age_active_anon(struct zone *zone, 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_zone_lruvec(zone, memcg);
|
|
|
|
if (inactive_anon_is_low(lruvec))
|
|
shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
|
|
sc, LRU_ACTIVE_ANON);
|
|
|
|
memcg = mem_cgroup_iter(NULL, memcg, NULL);
|
|
} while (memcg);
|
|
}
|
|
|
|
static bool zone_balanced(struct zone *zone, int order,
|
|
unsigned long balance_gap, int classzone_idx)
|
|
{
|
|
if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone) +
|
|
balance_gap, classzone_idx, 0))
|
|
return false;
|
|
|
|
if (IS_ENABLED(CONFIG_COMPACTION) && order &&
|
|
!compaction_suitable(zone, order))
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* pgdat_balanced() is used when checking if a node is balanced.
|
|
*
|
|
* For order-0, all zones must be balanced!
|
|
*
|
|
* For high-order allocations only zones that meet watermarks and are in a
|
|
* zone allowed by the callers classzone_idx are added to balanced_pages. The
|
|
* total of balanced pages must be at least 25% of the zones allowed by
|
|
* classzone_idx for the node to be considered balanced. Forcing all zones to
|
|
* be balanced for high orders can cause excessive reclaim when there are
|
|
* imbalanced zones.
|
|
* The choice of 25% is due to
|
|
* o a 16M DMA zone that is balanced will not balance a zone on any
|
|
* reasonable sized machine
|
|
* o On all other machines, the top zone must be at least a reasonable
|
|
* percentage of the middle zones. For example, on 32-bit x86, highmem
|
|
* would need to be at least 256M for it to be balance a whole node.
|
|
* Similarly, on x86-64 the Normal zone would need to be at least 1G
|
|
* to balance a node on its own. These seemed like reasonable ratios.
|
|
*/
|
|
static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)
|
|
{
|
|
unsigned long managed_pages = 0;
|
|
unsigned long balanced_pages = 0;
|
|
int i;
|
|
|
|
/* Check the watermark levels */
|
|
for (i = 0; i <= classzone_idx; i++) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
managed_pages += zone->managed_pages;
|
|
|
|
/*
|
|
* A special case here:
|
|
*
|
|
* balance_pgdat() skips over all_unreclaimable after
|
|
* DEF_PRIORITY. Effectively, it considers them balanced so
|
|
* they must be considered balanced here as well!
|
|
*/
|
|
if (!zone_reclaimable(zone)) {
|
|
balanced_pages += zone->managed_pages;
|
|
continue;
|
|
}
|
|
|
|
if (zone_balanced(zone, order, 0, i))
|
|
balanced_pages += zone->managed_pages;
|
|
else if (!order)
|
|
return false;
|
|
}
|
|
|
|
if (order)
|
|
return balanced_pages >= (managed_pages >> 2);
|
|
else
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* 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, long remaining,
|
|
int classzone_idx)
|
|
{
|
|
/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
|
|
if (remaining)
|
|
return false;
|
|
|
|
/*
|
|
* There is a potential race between when kswapd checks its watermarks
|
|
* and a process gets throttled. There is also a potential race if
|
|
* processes get throttled, kswapd wakes, a large process exits therby
|
|
* balancing the zones that causes kswapd to miss a wakeup. If kswapd
|
|
* is going to sleep, no process should be sleeping on pfmemalloc_wait
|
|
* so wake them now if necessary. If necessary, processes will wake
|
|
* kswapd and get throttled again
|
|
*/
|
|
if (waitqueue_active(&pgdat->pfmemalloc_wait)) {
|
|
wake_up(&pgdat->pfmemalloc_wait);
|
|
return false;
|
|
}
|
|
|
|
return pgdat_balanced(pgdat, order, classzone_idx);
|
|
}
|
|
|
|
/*
|
|
* kswapd shrinks the zone by the number of pages required to reach
|
|
* the high watermark.
|
|
*
|
|
* 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_zone(struct zone *zone,
|
|
int classzone_idx,
|
|
struct scan_control *sc,
|
|
unsigned long lru_pages,
|
|
unsigned long *nr_attempted)
|
|
{
|
|
int testorder = sc->order;
|
|
unsigned long balance_gap;
|
|
struct reclaim_state *reclaim_state = current->reclaim_state;
|
|
struct shrink_control shrink = {
|
|
.gfp_mask = sc->gfp_mask,
|
|
};
|
|
bool lowmem_pressure;
|
|
|
|
/* Reclaim above the high watermark. */
|
|
sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone));
|
|
|
|
/*
|
|
* Kswapd reclaims only single pages with compaction enabled. Trying
|
|
* too hard to reclaim until contiguous free pages have become
|
|
* available can hurt performance by evicting too much useful data
|
|
* from memory. Do not reclaim more than needed for compaction.
|
|
*/
|
|
if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
|
|
compaction_suitable(zone, sc->order) !=
|
|
COMPACT_SKIPPED)
|
|
testorder = 0;
|
|
|
|
/*
|
|
* We put equal pressure on every zone, unless one zone has way too
|
|
* many pages free already. The "too many pages" is defined as the
|
|
* high wmark plus a "gap" where the gap is either the low
|
|
* watermark or 1% of the zone, whichever is smaller.
|
|
*/
|
|
balance_gap = min(low_wmark_pages(zone),
|
|
(zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
|
|
KSWAPD_ZONE_BALANCE_GAP_RATIO);
|
|
|
|
/*
|
|
* If there is no low memory pressure or the zone is balanced then no
|
|
* reclaim is necessary
|
|
*/
|
|
lowmem_pressure = (buffer_heads_over_limit && is_highmem(zone));
|
|
if (!lowmem_pressure && zone_balanced(zone, testorder,
|
|
balance_gap, classzone_idx))
|
|
return true;
|
|
|
|
shrink_zone(zone, sc);
|
|
nodes_clear(shrink.nodes_to_scan);
|
|
node_set(zone_to_nid(zone), shrink.nodes_to_scan);
|
|
|
|
reclaim_state->reclaimed_slab = 0;
|
|
shrink_slab(&shrink, sc->nr_scanned, lru_pages);
|
|
sc->nr_reclaimed += reclaim_state->reclaimed_slab;
|
|
|
|
/* Account for the number of pages attempted to reclaim */
|
|
*nr_attempted += sc->nr_to_reclaim;
|
|
|
|
zone_clear_flag(zone, ZONE_WRITEBACK);
|
|
|
|
/*
|
|
* If a zone reaches its high watermark, consider it to be no longer
|
|
* congested. It's possible there are dirty pages backed by congested
|
|
* BDIs but as pressure is relieved, speculatively avoid congestion
|
|
* waits.
|
|
*/
|
|
if (zone_reclaimable(zone) &&
|
|
zone_balanced(zone, testorder, 0, classzone_idx)) {
|
|
zone_clear_flag(zone, ZONE_CONGESTED);
|
|
zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY);
|
|
}
|
|
|
|
return sc->nr_scanned >= sc->nr_to_reclaim;
|
|
}
|
|
|
|
/*
|
|
* For kswapd, balance_pgdat() will work across all this node's zones until
|
|
* they are all at high_wmark_pages(zone).
|
|
*
|
|
* Returns the final order kswapd was reclaiming at
|
|
*
|
|
* There is special handling here for zones which are full of pinned pages.
|
|
* This can happen if the pages are all mlocked, or if they are all used by
|
|
* device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
|
|
* What we do is to detect the case where all pages in the zone have been
|
|
* scanned twice and there has been zero successful reclaim. Mark the zone as
|
|
* dead and from now on, only perform a short scan. Basically we're polling
|
|
* the zone for when the problem goes away.
|
|
*
|
|
* 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), we scan that zone and the
|
|
* lower zones regardless of the number of free pages in the lower zones. This
|
|
* interoperates with the page allocator fallback scheme to ensure that aging
|
|
* of pages is balanced across the zones.
|
|
*/
|
|
static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
|
|
int *classzone_idx)
|
|
{
|
|
int i;
|
|
int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
|
|
unsigned long nr_soft_reclaimed;
|
|
unsigned long nr_soft_scanned;
|
|
struct scan_control sc = {
|
|
.gfp_mask = GFP_KERNEL,
|
|
.priority = DEF_PRIORITY,
|
|
.may_unmap = 1,
|
|
.may_swap = 1,
|
|
.may_writepage = !laptop_mode,
|
|
.order = order,
|
|
.target_mem_cgroup = NULL,
|
|
};
|
|
count_vm_event(PAGEOUTRUN);
|
|
|
|
do {
|
|
unsigned long lru_pages = 0;
|
|
unsigned long nr_attempted = 0;
|
|
bool raise_priority = true;
|
|
bool pgdat_needs_compaction = (order > 0);
|
|
|
|
sc.nr_reclaimed = 0;
|
|
|
|
/*
|
|
* Scan in the highmem->dma direction for the highest
|
|
* zone which needs scanning
|
|
*/
|
|
for (i = pgdat->nr_zones - 1; i >= 0; i--) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
if (sc.priority != DEF_PRIORITY &&
|
|
!zone_reclaimable(zone))
|
|
continue;
|
|
|
|
/*
|
|
* Do some background aging of the anon list, to give
|
|
* pages a chance to be referenced before reclaiming.
|
|
*/
|
|
age_active_anon(zone, &sc);
|
|
|
|
/*
|
|
* If the number of buffer_heads in the machine
|
|
* exceeds the maximum allowed level and this node
|
|
* has a highmem zone, force kswapd to reclaim from
|
|
* it to relieve lowmem pressure.
|
|
*/
|
|
if (buffer_heads_over_limit && is_highmem_idx(i)) {
|
|
end_zone = i;
|
|
break;
|
|
}
|
|
|
|
if (!zone_balanced(zone, order, 0, 0)) {
|
|
end_zone = i;
|
|
break;
|
|
} else {
|
|
/*
|
|
* If balanced, clear the dirty and congested
|
|
* flags
|
|
*/
|
|
zone_clear_flag(zone, ZONE_CONGESTED);
|
|
zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY);
|
|
}
|
|
}
|
|
|
|
if (i < 0)
|
|
goto out;
|
|
|
|
for (i = 0; i <= end_zone; i++) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
lru_pages += zone_reclaimable_pages(zone);
|
|
|
|
/*
|
|
* If any zone is currently balanced then kswapd will
|
|
* not call compaction as it is expected that the
|
|
* necessary pages are already available.
|
|
*/
|
|
if (pgdat_needs_compaction &&
|
|
zone_watermark_ok(zone, order,
|
|
low_wmark_pages(zone),
|
|
*classzone_idx, 0))
|
|
pgdat_needs_compaction = false;
|
|
}
|
|
|
|
/*
|
|
* If we're getting trouble reclaiming, start doing writepage
|
|
* even in laptop mode.
|
|
*/
|
|
if (sc.priority < DEF_PRIORITY - 2)
|
|
sc.may_writepage = 1;
|
|
|
|
/*
|
|
* Now scan the zone in the dma->highmem direction, stopping
|
|
* at the last zone which needs scanning.
|
|
*
|
|
* We do this because the page allocator works in the opposite
|
|
* direction. This prevents the page allocator from allocating
|
|
* pages behind kswapd's direction of progress, which would
|
|
* cause too much scanning of the lower zones.
|
|
*/
|
|
for (i = 0; i <= end_zone; i++) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
if (sc.priority != DEF_PRIORITY &&
|
|
!zone_reclaimable(zone))
|
|
continue;
|
|
|
|
sc.nr_scanned = 0;
|
|
|
|
nr_soft_scanned = 0;
|
|
/*
|
|
* Call soft limit reclaim before calling shrink_zone.
|
|
*/
|
|
nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
|
|
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_zone(zone, end_zone, &sc,
|
|
lru_pages, &nr_attempted))
|
|
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) &&
|
|
pfmemalloc_watermark_ok(pgdat))
|
|
wake_up(&pgdat->pfmemalloc_wait);
|
|
|
|
/*
|
|
* Fragmentation may mean that the system cannot be rebalanced
|
|
* for high-order allocations in all zones. If twice the
|
|
* allocation size has been reclaimed and the zones are still
|
|
* not balanced then recheck the watermarks at order-0 to
|
|
* prevent kswapd reclaiming excessively. Assume that a
|
|
* process requested a high-order can direct reclaim/compact.
|
|
*/
|
|
if (order && sc.nr_reclaimed >= 2UL << order)
|
|
order = sc.order = 0;
|
|
|
|
/* Check if kswapd should be suspending */
|
|
if (try_to_freeze() || kthread_should_stop())
|
|
break;
|
|
|
|
/*
|
|
* Compact if necessary and kswapd is reclaiming at least the
|
|
* high watermark number of pages as requsted
|
|
*/
|
|
if (pgdat_needs_compaction && sc.nr_reclaimed > nr_attempted)
|
|
compact_pgdat(pgdat, order);
|
|
|
|
/*
|
|
* Raise priority if scanning rate is too low or there was no
|
|
* progress in reclaiming pages
|
|
*/
|
|
if (raise_priority || !sc.nr_reclaimed)
|
|
sc.priority--;
|
|
} while (sc.priority >= 1 &&
|
|
!pgdat_balanced(pgdat, order, *classzone_idx));
|
|
|
|
out:
|
|
/*
|
|
* Return the order we were reclaiming at so prepare_kswapd_sleep()
|
|
* makes a decision on the order we were last reclaiming at. However,
|
|
* if another caller entered the allocator slow path while kswapd
|
|
* was awake, order will remain at the higher level
|
|
*/
|
|
*classzone_idx = end_zone;
|
|
return order;
|
|
}
|
|
|
|
static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, 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 */
|
|
if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) {
|
|
remaining = schedule_timeout(HZ/10);
|
|
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 (prepare_kswapd_sleep(pgdat, order, remaining, 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);
|
|
|
|
/*
|
|
* 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);
|
|
|
|
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 long order, new_order;
|
|
unsigned balanced_order;
|
|
int classzone_idx, new_classzone_idx;
|
|
int balanced_classzone_idx;
|
|
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);
|
|
|
|
lockdep_set_current_reclaim_state(GFP_KERNEL);
|
|
|
|
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();
|
|
|
|
order = new_order = 0;
|
|
balanced_order = 0;
|
|
classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
|
|
balanced_classzone_idx = classzone_idx;
|
|
for ( ; ; ) {
|
|
bool ret;
|
|
|
|
/*
|
|
* If the last balance_pgdat was unsuccessful it's unlikely a
|
|
* new request of a similar or harder type will succeed soon
|
|
* so consider going to sleep on the basis we reclaimed at
|
|
*/
|
|
if (balanced_classzone_idx >= new_classzone_idx &&
|
|
balanced_order == new_order) {
|
|
new_order = pgdat->kswapd_max_order;
|
|
new_classzone_idx = pgdat->classzone_idx;
|
|
pgdat->kswapd_max_order = 0;
|
|
pgdat->classzone_idx = pgdat->nr_zones - 1;
|
|
}
|
|
|
|
if (order < new_order || classzone_idx > new_classzone_idx) {
|
|
/*
|
|
* Don't sleep if someone wants a larger 'order'
|
|
* allocation or has tigher zone constraints
|
|
*/
|
|
order = new_order;
|
|
classzone_idx = new_classzone_idx;
|
|
} else {
|
|
kswapd_try_to_sleep(pgdat, balanced_order,
|
|
balanced_classzone_idx);
|
|
order = pgdat->kswapd_max_order;
|
|
classzone_idx = pgdat->classzone_idx;
|
|
new_order = order;
|
|
new_classzone_idx = classzone_idx;
|
|
pgdat->kswapd_max_order = 0;
|
|
pgdat->classzone_idx = pgdat->nr_zones - 1;
|
|
}
|
|
|
|
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) {
|
|
trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
|
|
balanced_classzone_idx = classzone_idx;
|
|
balanced_order = balance_pgdat(pgdat, order,
|
|
&balanced_classzone_idx);
|
|
}
|
|
}
|
|
|
|
current->reclaim_state = NULL;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* A zone is low on free memory, so wake its kswapd task to service it.
|
|
*/
|
|
void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
|
|
{
|
|
pg_data_t *pgdat;
|
|
|
|
if (!populated_zone(zone))
|
|
return;
|
|
|
|
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
|
|
return;
|
|
pgdat = zone->zone_pgdat;
|
|
if (pgdat->kswapd_max_order < order) {
|
|
pgdat->kswapd_max_order = order;
|
|
pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
|
|
}
|
|
if (!waitqueue_active(&pgdat->kswapd_wait))
|
|
return;
|
|
if (zone_balanced(zone, order, 0, 0))
|
|
return;
|
|
|
|
trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
|
|
wake_up_interruptible(&pgdat->kswapd_wait);
|
|
}
|
|
|
|
/*
|
|
* The reclaimable count would be mostly accurate.
|
|
* The less reclaimable pages may be
|
|
* - mlocked pages, which will be moved to unevictable list when encountered
|
|
* - mapped pages, which may require several travels to be reclaimed
|
|
* - dirty pages, which is not "instantly" reclaimable
|
|
*/
|
|
unsigned long global_reclaimable_pages(void)
|
|
{
|
|
int nr;
|
|
|
|
nr = global_page_state(NR_ACTIVE_FILE) +
|
|
global_page_state(NR_INACTIVE_FILE);
|
|
|
|
if (get_nr_swap_pages() > 0)
|
|
nr += global_page_state(NR_ACTIVE_ANON) +
|
|
global_page_state(NR_INACTIVE_ANON);
|
|
|
|
return nr;
|
|
}
|
|
|
|
#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 = {
|
|
.gfp_mask = GFP_HIGHUSER_MOVABLE,
|
|
.may_swap = 1,
|
|
.may_unmap = 1,
|
|
.may_writepage = 1,
|
|
.nr_to_reclaim = nr_to_reclaim,
|
|
.hibernation_mode = 1,
|
|
.order = 0,
|
|
.priority = DEF_PRIORITY,
|
|
};
|
|
struct shrink_control shrink = {
|
|
.gfp_mask = sc.gfp_mask,
|
|
};
|
|
struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
|
|
struct task_struct *p = current;
|
|
unsigned long nr_reclaimed;
|
|
|
|
p->flags |= PF_MEMALLOC;
|
|
lockdep_set_current_reclaim_state(sc.gfp_mask);
|
|
reclaim_state.reclaimed_slab = 0;
|
|
p->reclaim_state = &reclaim_state;
|
|
|
|
nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
|
|
|
|
p->reclaim_state = NULL;
|
|
lockdep_clear_current_reclaim_state();
|
|
p->flags &= ~PF_MEMALLOC;
|
|
|
|
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 cpu_callback(struct notifier_block *nfb, unsigned long action,
|
|
void *hcpu)
|
|
{
|
|
int nid;
|
|
|
|
if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
|
|
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 NOTIFY_OK;
|
|
}
|
|
|
|
/*
|
|
* 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_BOOTING);
|
|
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 lock_memory_hotplug().
|
|
*/
|
|
void kswapd_stop(int nid)
|
|
{
|
|
struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
|
|
|
|
if (kswapd) {
|
|
kthread_stop(kswapd);
|
|
NODE_DATA(nid)->kswapd = NULL;
|
|
}
|
|
}
|
|
|
|
static int __init kswapd_init(void)
|
|
{
|
|
int nid;
|
|
|
|
swap_setup();
|
|
for_each_node_state(nid, N_MEMORY)
|
|
kswapd_run(nid);
|
|
hotcpu_notifier(cpu_callback, 0);
|
|
return 0;
|
|
}
|
|
|
|
module_init(kswapd_init)
|
|
|
|
#ifdef CONFIG_NUMA
|
|
/*
|
|
* Zone reclaim mode
|
|
*
|
|
* If non-zero call zone_reclaim when the number of free pages falls below
|
|
* the watermarks.
|
|
*/
|
|
int zone_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_SWAP (1<<2) /* Swap pages out during reclaim */
|
|
|
|
/*
|
|
* Priority for ZONE_RECLAIM. This determines the fraction of pages
|
|
* of a node considered for each zone_reclaim. 4 scans 1/16th of
|
|
* a zone.
|
|
*/
|
|
#define ZONE_RECLAIM_PRIORITY 4
|
|
|
|
/*
|
|
* Percentage of pages in a zone that must be unmapped for zone_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 zone_unmapped_file_pages(struct zone *zone)
|
|
{
|
|
unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
|
|
unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
|
|
zone_page_state(zone, 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 long zone_pagecache_reclaimable(struct zone *zone)
|
|
{
|
|
long nr_pagecache_reclaimable;
|
|
long delta = 0;
|
|
|
|
/*
|
|
* If RECLAIM_SWAP is set, then all file pages are considered
|
|
* potentially reclaimable. Otherwise, we have to worry about
|
|
* pages like swapcache and zone_unmapped_file_pages() provides
|
|
* a better estimate
|
|
*/
|
|
if (zone_reclaim_mode & RECLAIM_SWAP)
|
|
nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
|
|
else
|
|
nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
|
|
|
|
/* If we can't clean pages, remove dirty pages from consideration */
|
|
if (!(zone_reclaim_mode & RECLAIM_WRITE))
|
|
delta += zone_page_state(zone, 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 zone through reclaim.
|
|
*/
|
|
static int __zone_reclaim(struct zone *zone, 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;
|
|
struct scan_control sc = {
|
|
.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
|
|
.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
|
|
.may_swap = 1,
|
|
.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
|
|
.gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
|
|
.order = order,
|
|
.priority = ZONE_RECLAIM_PRIORITY,
|
|
};
|
|
struct shrink_control shrink = {
|
|
.gfp_mask = sc.gfp_mask,
|
|
};
|
|
unsigned long nr_slab_pages0, nr_slab_pages1;
|
|
|
|
cond_resched();
|
|
/*
|
|
* We need to be able to allocate from the reserves for RECLAIM_SWAP
|
|
* and we also need to be able to write out pages for RECLAIM_WRITE
|
|
* and RECLAIM_SWAP.
|
|
*/
|
|
p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
|
|
lockdep_set_current_reclaim_state(gfp_mask);
|
|
reclaim_state.reclaimed_slab = 0;
|
|
p->reclaim_state = &reclaim_state;
|
|
|
|
if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
|
|
/*
|
|
* Free memory by calling shrink zone with increasing
|
|
* priorities until we have enough memory freed.
|
|
*/
|
|
do {
|
|
shrink_zone(zone, &sc);
|
|
} while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
|
|
}
|
|
|
|
nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
|
|
if (nr_slab_pages0 > zone->min_slab_pages) {
|
|
/*
|
|
* shrink_slab() does not currently allow us to determine how
|
|
* many pages were freed in this zone. So we take the current
|
|
* number of slab pages and shake the slab until it is reduced
|
|
* by the same nr_pages that we used for reclaiming unmapped
|
|
* pages.
|
|
*/
|
|
nodes_clear(shrink.nodes_to_scan);
|
|
node_set(zone_to_nid(zone), shrink.nodes_to_scan);
|
|
for (;;) {
|
|
unsigned long lru_pages = zone_reclaimable_pages(zone);
|
|
|
|
/* No reclaimable slab or very low memory pressure */
|
|
if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
|
|
break;
|
|
|
|
/* Freed enough memory */
|
|
nr_slab_pages1 = zone_page_state(zone,
|
|
NR_SLAB_RECLAIMABLE);
|
|
if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Update nr_reclaimed by the number of slab pages we
|
|
* reclaimed from this zone.
|
|
*/
|
|
nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
|
|
if (nr_slab_pages1 < nr_slab_pages0)
|
|
sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
|
|
}
|
|
|
|
p->reclaim_state = NULL;
|
|
current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
|
|
lockdep_clear_current_reclaim_state();
|
|
return sc.nr_reclaimed >= nr_pages;
|
|
}
|
|
|
|
int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
|
|
{
|
|
int node_id;
|
|
int ret;
|
|
|
|
/*
|
|
* Zone 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 zone is overallocated. So we do not reclaim
|
|
* if less than a specified percentage of the zone is used by
|
|
* unmapped file backed pages.
|
|
*/
|
|
if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
|
|
zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
|
|
return ZONE_RECLAIM_FULL;
|
|
|
|
if (!zone_reclaimable(zone))
|
|
return ZONE_RECLAIM_FULL;
|
|
|
|
/*
|
|
* Do not scan if the allocation should not be delayed.
|
|
*/
|
|
if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
|
|
return ZONE_RECLAIM_NOSCAN;
|
|
|
|
/*
|
|
* Only run zone reclaim on the local zone or on zones 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.
|
|
*/
|
|
node_id = zone_to_nid(zone);
|
|
if (node_state(node_id, N_CPU) && node_id != numa_node_id())
|
|
return ZONE_RECLAIM_NOSCAN;
|
|
|
|
if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
|
|
return ZONE_RECLAIM_NOSCAN;
|
|
|
|
ret = __zone_reclaim(zone, gfp_mask, order);
|
|
zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
|
|
|
|
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)
|
|
{
|
|
return !mapping_unevictable(page_mapping(page)) && !PageMlocked(page);
|
|
}
|
|
|
|
#ifdef CONFIG_SHMEM
|
|
/**
|
|
* check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
|
|
* @pages: array of pages to check
|
|
* @nr_pages: number of pages to check
|
|
*
|
|
* Checks pages for evictability and moves them to the appropriate lru list.
|
|
*
|
|
* This function is only used for SysV IPC SHM_UNLOCK.
|
|
*/
|
|
void check_move_unevictable_pages(struct page **pages, int nr_pages)
|
|
{
|
|
struct lruvec *lruvec;
|
|
struct zone *zone = NULL;
|
|
int pgscanned = 0;
|
|
int pgrescued = 0;
|
|
int i;
|
|
|
|
for (i = 0; i < nr_pages; i++) {
|
|
struct page *page = pages[i];
|
|
struct zone *pagezone;
|
|
|
|
pgscanned++;
|
|
pagezone = page_zone(page);
|
|
if (pagezone != zone) {
|
|
if (zone)
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
zone = pagezone;
|
|
spin_lock_irq(&zone->lru_lock);
|
|
}
|
|
lruvec = mem_cgroup_page_lruvec(page, zone);
|
|
|
|
if (!PageLRU(page) || !PageUnevictable(page))
|
|
continue;
|
|
|
|
if (page_evictable(page)) {
|
|
enum lru_list lru = page_lru_base_type(page);
|
|
|
|
VM_BUG_ON(PageActive(page));
|
|
ClearPageUnevictable(page);
|
|
del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE);
|
|
add_page_to_lru_list(page, lruvec, lru);
|
|
pgrescued++;
|
|
}
|
|
}
|
|
|
|
if (zone) {
|
|
__count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
|
|
__count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
}
|
|
}
|
|
#endif /* CONFIG_SHMEM */
|
|
|
|
static void warn_scan_unevictable_pages(void)
|
|
{
|
|
printk_once(KERN_WARNING
|
|
"%s: The scan_unevictable_pages sysctl/node-interface has been "
|
|
"disabled for lack of a legitimate use case. If you have "
|
|
"one, please send an email to linux-mm@kvack.org.\n",
|
|
current->comm);
|
|
}
|
|
|
|
/*
|
|
* scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
|
|
* all nodes' unevictable lists for evictable pages
|
|
*/
|
|
unsigned long scan_unevictable_pages;
|
|
|
|
int scan_unevictable_handler(struct ctl_table *table, int write,
|
|
void __user *buffer,
|
|
size_t *length, loff_t *ppos)
|
|
{
|
|
warn_scan_unevictable_pages();
|
|
proc_doulongvec_minmax(table, write, buffer, length, ppos);
|
|
scan_unevictable_pages = 0;
|
|
return 0;
|
|
}
|
|
|
|
#ifdef CONFIG_NUMA
|
|
/*
|
|
* per node 'scan_unevictable_pages' attribute. On demand re-scan of
|
|
* a specified node's per zone unevictable lists for evictable pages.
|
|
*/
|
|
|
|
static ssize_t read_scan_unevictable_node(struct device *dev,
|
|
struct device_attribute *attr,
|
|
char *buf)
|
|
{
|
|
warn_scan_unevictable_pages();
|
|
return sprintf(buf, "0\n"); /* always zero; should fit... */
|
|
}
|
|
|
|
static ssize_t write_scan_unevictable_node(struct device *dev,
|
|
struct device_attribute *attr,
|
|
const char *buf, size_t count)
|
|
{
|
|
warn_scan_unevictable_pages();
|
|
return 1;
|
|
}
|
|
|
|
|
|
static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
|
|
read_scan_unevictable_node,
|
|
write_scan_unevictable_node);
|
|
|
|
int scan_unevictable_register_node(struct node *node)
|
|
{
|
|
return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages);
|
|
}
|
|
|
|
void scan_unevictable_unregister_node(struct node *node)
|
|
{
|
|
device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages);
|
|
}
|
|
#endif
|