vmscan.c 99.8 KB
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/*
 *  linux/mm/vmscan.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 *  Swap reorganised 29.12.95, Stephen Tweedie.
 *  kswapd added: 7.1.96  sct
 *  Removed kswapd_ctl limits, and swap out as many pages as needed
 *  to bring the system back to freepages.high: 2.4.97, Rik van Riel.
 *  Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
 *  Multiqueue VM started 5.8.00, Rik van Riel.
 */

#include <linux/mm.h>
#include <linux/module.h>
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#include <linux/gfp.h>
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#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/highmem.h>
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#include <linux/vmstat.h>
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#include <linux/file.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
#include <linux/buffer_head.h>	/* for try_to_release_page(),
					buffer_heads_over_limit */
#include <linux/mm_inline.h>
#include <linux/pagevec.h>
#include <linux/backing-dev.h>
#include <linux/rmap.h>
#include <linux/topology.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
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#include <linux/compaction.h>
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#include <linux/notifier.h>
#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>
#include <asm/div64.h>

#include <linux/swapops.h>

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#include "internal.h"

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#define CREATE_TRACE_POINTS
#include <trace/events/vmscan.h>

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/*
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 * reclaim_mode determines how the inactive list is shrunk
 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages
 * RECLAIM_MODE_ASYNC:  Do not block
 * RECLAIM_MODE_SYNC:   Allow blocking e.g. call wait_on_page_writeback
 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference
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 *			page from the LRU and reclaim all pages within a
 *			naturally aligned range
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 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of
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 *			order-0 pages and then compact the zone
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 */
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typedef unsigned __bitwise__ reclaim_mode_t;
#define RECLAIM_MODE_SINGLE		((__force reclaim_mode_t)0x01u)
#define RECLAIM_MODE_ASYNC		((__force reclaim_mode_t)0x02u)
#define RECLAIM_MODE_SYNC		((__force reclaim_mode_t)0x04u)
#define RECLAIM_MODE_LUMPYRECLAIM	((__force reclaim_mode_t)0x08u)
#define RECLAIM_MODE_COMPACTION		((__force reclaim_mode_t)0x10u)
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struct scan_control {
	/* Incremented by the number of inactive pages that were scanned */
	unsigned long nr_scanned;

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	/* Number of pages freed so far during a call to shrink_zones() */
	unsigned long nr_reclaimed;

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	/* How many pages shrink_list() should reclaim */
	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? */
	int may_unmap;
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	/* Can pages be swapped as part of reclaim? */
	int may_swap;

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	int order;
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	/*
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	 * Intend to reclaim enough continuous memory rather than reclaim
	 * enough amount of memory. i.e, mode for high order allocation.
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	 */
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	reclaim_mode_t reclaim_mode;
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	/*
	 * The memory cgroup that hit its limit and as a result is the
	 * primary target of this reclaim invocation.
	 */
	struct mem_cgroup *target_mem_cgroup;
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	/*
	 * Nodemask of nodes allowed by the caller. If NULL, all nodes
	 * are scanned.
	 */
	nodemask_t	*nodemask;
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};

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struct mem_cgroup_zone {
	struct mem_cgroup *mem_cgroup;
	struct zone *zone;
};

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#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))

#ifdef ARCH_HAS_PREFETCH
#define prefetch_prev_lru_page(_page, _base, _field)			\
	do {								\
		if ((_page)->lru.prev != _base) {			\
			struct page *prev;				\
									\
			prev = lru_to_page(&(_page->lru));		\
			prefetch(&prev->_field);			\
		}							\
	} while (0)
#else
#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
#endif

#ifdef ARCH_HAS_PREFETCHW
#define prefetchw_prev_lru_page(_page, _base, _field)			\
	do {								\
		if ((_page)->lru.prev != _base) {			\
			struct page *prev;				\
									\
			prev = lru_to_page(&(_page->lru));		\
			prefetchw(&prev->_field);			\
		}							\
	} while (0)
#else
#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
#endif

/*
 * From 0 .. 100.  Higher means more swappy.
 */
int vm_swappiness = 60;
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long vm_total_pages;	/* The total number of pages which the VM controls */
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static LIST_HEAD(shrinker_list);
static DECLARE_RWSEM(shrinker_rwsem);

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#ifdef CONFIG_CGROUP_MEM_RES_CTLR
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static bool global_reclaim(struct scan_control *sc)
{
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	return !sc->target_mem_cgroup;
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}

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static bool scanning_global_lru(struct mem_cgroup_zone *mz)
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{
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	return !mz->mem_cgroup;
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}
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#else
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static bool global_reclaim(struct scan_control *sc)
{
	return true;
}

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static bool scanning_global_lru(struct mem_cgroup_zone *mz)
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{
	return true;
}
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#endif

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static struct zone_reclaim_stat *get_reclaim_stat(struct mem_cgroup_zone *mz)
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{
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	if (!scanning_global_lru(mz))
		return mem_cgroup_get_reclaim_stat(mz->mem_cgroup, mz->zone);
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	return &mz->zone->reclaim_stat;
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}

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static unsigned long zone_nr_lru_pages(struct mem_cgroup_zone *mz,
				       enum lru_list lru)
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{
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	if (!scanning_global_lru(mz))
		return mem_cgroup_zone_nr_lru_pages(mz->mem_cgroup,
						    zone_to_nid(mz->zone),
						    zone_idx(mz->zone),
						    BIT(lru));
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	return zone_page_state(mz->zone, NR_LRU_BASE + lru);
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}


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/*
 * Add a shrinker callback to be called from the vm
 */
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void register_shrinker(struct shrinker *shrinker)
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{
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	atomic_long_set(&shrinker->nr_in_batch, 0);
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	down_write(&shrinker_rwsem);
	list_add_tail(&shrinker->list, &shrinker_list);
	up_write(&shrinker_rwsem);
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}
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EXPORT_SYMBOL(register_shrinker);
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/*
 * Remove one
 */
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void unregister_shrinker(struct shrinker *shrinker)
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{
	down_write(&shrinker_rwsem);
	list_del(&shrinker->list);
	up_write(&shrinker_rwsem);
}
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EXPORT_SYMBOL(unregister_shrinker);
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static inline int do_shrinker_shrink(struct shrinker *shrinker,
				     struct shrink_control *sc,
				     unsigned long nr_to_scan)
{
	sc->nr_to_scan = nr_to_scan;
	return (*shrinker->shrink)(shrinker, sc);
}

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#define SHRINK_BATCH 128
/*
 * Call the shrink functions to age shrinkable caches
 *
 * Here we assume it costs one seek to replace a lru page and that it also
 * takes a seek to recreate a cache object.  With this in mind we age equal
 * percentages of the lru and ageable caches.  This should balance the seeks
 * generated by these structures.
 *
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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.
 *
 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
 *
 * `lru_pages' represents the number of on-LRU pages in all the zones which
 * are eligible for the caller's allocation attempt.  It is used for balancing
 * slab reclaim versus page reclaim.
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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 *shrink,
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			  unsigned long nr_pages_scanned,
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			  unsigned long lru_pages)
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{
	struct shrinker *shrinker;
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	unsigned long ret = 0;
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	if (nr_pages_scanned == 0)
		nr_pages_scanned = SWAP_CLUSTER_MAX;
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	if (!down_read_trylock(&shrinker_rwsem)) {
		/* Assume we'll be able to shrink next time */
		ret = 1;
		goto out;
	}
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	list_for_each_entry(shrinker, &shrinker_list, list) {
		unsigned long long delta;
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		long total_scan;
		long max_pass;
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		int shrink_ret = 0;
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		long nr;
		long new_nr;
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		long batch_size = shrinker->batch ? shrinker->batch
						  : SHRINK_BATCH;
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		max_pass = do_shrinker_shrink(shrinker, shrink, 0);
		if (max_pass <= 0)
			continue;

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		/*
		 * copy the current shrinker scan count into a local variable
		 * and zero it so that other concurrent shrinker invocations
		 * don't also do this scanning work.
		 */
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		nr = atomic_long_xchg(&shrinker->nr_in_batch, 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;
		if (total_scan < 0) {
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			printk(KERN_ERR "shrink_slab: %pF negative objects to "
			       "delete nr=%ld\n",
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			       shrinker->shrink, total_scan);
			total_scan = max_pass;
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		}

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		/*
		 * We need to avoid excessive windup on filesystem shrinkers
		 * due to large numbers of GFP_NOFS allocations causing the
		 * shrinkers to return -1 all the time. This results in a large
		 * nr being built up so when a shrink that can do some work
		 * comes along it empties the entire cache due to nr >>>
		 * max_pass.  This is bad for sustaining a working set in
		 * memory.
		 *
		 * Hence only allow the shrinker to scan the entire cache when
		 * a large delta change is calculated directly.
		 */
		if (delta < max_pass / 4)
			total_scan = min(total_scan, max_pass / 2);

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		/*
		 * Avoid risking looping forever due to too large nr value:
		 * never try to free more than twice the estimate number of
		 * freeable entries.
		 */
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		if (total_scan > max_pass * 2)
			total_scan = max_pass * 2;
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		trace_mm_shrink_slab_start(shrinker, shrink, nr,
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					nr_pages_scanned, lru_pages,
					max_pass, delta, total_scan);

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		while (total_scan >= batch_size) {
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			int nr_before;
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			nr_before = do_shrinker_shrink(shrinker, shrink, 0);
			shrink_ret = do_shrinker_shrink(shrinker, shrink,
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							batch_size);
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			if (shrink_ret == -1)
				break;
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			if (shrink_ret < nr_before)
				ret += nr_before - shrink_ret;
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			count_vm_events(SLABS_SCANNED, batch_size);
			total_scan -= batch_size;
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			cond_resched();
		}

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		/*
		 * move the unused scan count back into the shrinker in a
		 * manner that handles concurrent updates. If we exhausted the
		 * scan, there is no need to do an update.
		 */
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		if (total_scan > 0)
			new_nr = atomic_long_add_return(total_scan,
					&shrinker->nr_in_batch);
		else
			new_nr = atomic_long_read(&shrinker->nr_in_batch);
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		trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr);
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	}
	up_read(&shrinker_rwsem);
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out:
	cond_resched();
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	return ret;
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}

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static void set_reclaim_mode(int priority, struct scan_control *sc,
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				   bool sync)
{
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	reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
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	/*
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	 * Initially assume we are entering either lumpy reclaim or
	 * reclaim/compaction.Depending on the order, we will either set the
	 * sync mode or just reclaim order-0 pages later.
377
	 */
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	if (COMPACTION_BUILD)
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		sc->reclaim_mode = RECLAIM_MODE_COMPACTION;
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	else
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		sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM;
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	/*
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	 * Avoid using lumpy reclaim or reclaim/compaction if possible by
	 * restricting when its set to either costly allocations or when
	 * under memory pressure
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	 */
	if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
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		sc->reclaim_mode |= syncmode;
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	else if (sc->order && priority < DEF_PRIORITY - 2)
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		sc->reclaim_mode |= syncmode;
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	else
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		sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
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}

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static void reset_reclaim_mode(struct scan_control *sc)
397
{
398
	sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
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}

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static inline int is_page_cache_freeable(struct page *page)
{
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	/*
	 * A freeable page cache page is referenced only by the caller
	 * that isolated the page, the page cache radix tree and
	 * optional buffer heads at page->private.
	 */
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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,
			      struct scan_control *sc)
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{
414
	if (current->flags & PF_SWAPWRITE)
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		return 1;
	if (!bdi_write_congested(bdi))
		return 1;
	if (bdi == current->backing_dev_info)
		return 1;
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	/* lumpy reclaim for hugepage often need a lot of write */
	if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
		return 1;
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	return 0;
}

/*
 * We detected a synchronous write error writing a page out.  Probably
 * -ENOSPC.  We need to propagate that into the address_space for a subsequent
 * fsync(), msync() or close().
 *
 * The tricky part is that after writepage we cannot touch the mapping: nothing
 * prevents it from being freed up.  But we have a ref on the page and once
 * that page is locked, the mapping is pinned.
 *
 * We're allowed to run sleeping lock_page() here because we know the caller has
 * __GFP_FS.
 */
static void handle_write_error(struct address_space *mapping,
				struct page *page, int error)
{
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	lock_page(page);
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	if (page_mapping(page) == mapping)
		mapping_set_error(mapping, error);
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	unlock_page(page);
}

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/* possible outcome of pageout() */
typedef enum {
	/* failed to write page out, page is locked */
	PAGE_KEEP,
	/* move page to the active list, page is locked */
	PAGE_ACTIVATE,
	/* page has been sent to the disk successfully, page is unlocked */
	PAGE_SUCCESS,
	/* page is clean and locked */
	PAGE_CLEAN,
} pageout_t;

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/*
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 * pageout is called by shrink_page_list() for each dirty page.
 * Calls ->writepage().
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 */
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static pageout_t pageout(struct page *page, struct address_space *mapping,
465
			 struct scan_control *sc)
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{
	/*
	 * If the page is dirty, only perform writeback if that write
	 * will be non-blocking.  To prevent this allocation from being
	 * stalled by pagecache activity.  But note that there may be
	 * stalls if we need to run get_block().  We could test
	 * PagePrivate for that.
	 *
474
	 * 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
	 * will block.
	 *
	 * If the page is swapcache, write it back even if that would
	 * block, for some throttling. This happens by accident, because
	 * swap_backing_dev_info is bust: it doesn't reflect the
	 * congestion state of the swapdevs.  Easy to fix, if needed.
	 */
	if (!is_page_cache_freeable(page))
		return PAGE_KEEP;
	if (!mapping) {
		/*
		 * Some data journaling orphaned pages can have
		 * page->mapping == NULL while being dirty with clean buffers.
		 */
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		if (page_has_private(page)) {
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			if (try_to_free_buffers(page)) {
				ClearPageDirty(page);
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				printk("%s: orphaned page\n", __func__);
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				return PAGE_CLEAN;
			}
		}
		return PAGE_KEEP;
	}
	if (mapping->a_ops->writepage == NULL)
		return PAGE_ACTIVATE;
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	if (!may_write_to_queue(mapping->backing_dev_info, sc))
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		return PAGE_KEEP;

	if (clear_page_dirty_for_io(page)) {
		int res;
		struct writeback_control wbc = {
			.sync_mode = WB_SYNC_NONE,
			.nr_to_write = SWAP_CLUSTER_MAX,
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			.range_start = 0,
			.range_end = LLONG_MAX,
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			.for_reclaim = 1,
		};

		SetPageReclaim(page);
		res = mapping->a_ops->writepage(page, &wbc);
		if (res < 0)
			handle_write_error(mapping, page, res);
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		if (res == AOP_WRITEPAGE_ACTIVATE) {
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			ClearPageReclaim(page);
			return PAGE_ACTIVATE;
		}
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		if (!PageWriteback(page)) {
			/* synchronous write or broken a_ops? */
			ClearPageReclaim(page);
		}
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		trace_mm_vmscan_writepage(page,
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			trace_reclaim_flags(page, sc->reclaim_mode));
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		inc_zone_page_state(page, NR_VMSCAN_WRITE);
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		return PAGE_SUCCESS;
	}

	return PAGE_CLEAN;
}

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/*
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 * Same as remove_mapping, but if the page is removed from the mapping, it
 * gets returned with a refcount of 0.
539
 */
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static int __remove_mapping(struct address_space *mapping, struct page *page)
541
{
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	BUG_ON(!PageLocked(page));
	BUG_ON(mapping != page_mapping(page));
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	spin_lock_irq(&mapping->tree_lock);
546
	/*
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	 * The non racy check for a busy page.
	 *
	 * Must be careful with the order of the tests. When someone has
	 * a ref to the page, it may be possible that they dirty it then
	 * drop the reference. So if PageDirty is tested before page_count
	 * here, then the following race may occur:
	 *
	 * get_user_pages(&page);
	 * [user mapping goes away]
	 * write_to(page);
	 *				!PageDirty(page)    [good]
	 * SetPageDirty(page);
	 * put_page(page);
	 *				!page_count(page)   [good, discard it]
	 *
	 * [oops, our write_to data is lost]
	 *
	 * Reversing the order of the tests ensures such a situation cannot
	 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
	 * load is not satisfied before that of page->_count.
	 *
	 * Note that if SetPageDirty is always performed via set_page_dirty,
	 * and thus under tree_lock, then this ordering is not required.
570
	 */
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	if (!page_freeze_refs(page, 2))
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		goto cannot_free;
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	/* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
	if (unlikely(PageDirty(page))) {
		page_unfreeze_refs(page, 2);
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		goto cannot_free;
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	}
578 579 580 581

	if (PageSwapCache(page)) {
		swp_entry_t swap = { .val = page_private(page) };
		__delete_from_swap_cache(page);
N
Nick Piggin 已提交
582
		spin_unlock_irq(&mapping->tree_lock);
583
		swapcache_free(swap, page);
N
Nick Piggin 已提交
584
	} else {
585 586 587 588
		void (*freepage)(struct page *);

		freepage = mapping->a_ops->freepage;

589
		__delete_from_page_cache(page);
N
Nick Piggin 已提交
590
		spin_unlock_irq(&mapping->tree_lock);
591
		mem_cgroup_uncharge_cache_page(page);
592 593 594

		if (freepage != NULL)
			freepage(page);
595 596 597 598 599
	}

	return 1;

cannot_free:
N
Nick Piggin 已提交
600
	spin_unlock_irq(&mapping->tree_lock);
601 602 603
	return 0;
}

N
Nick Piggin 已提交
604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623
/*
 * 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;
}

L
Lee Schermerhorn 已提交
624 625 626 627 628 629 630 631 632 633 634 635 636
/**
 * 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)
{
	int lru;
	int active = !!TestClearPageActive(page);
637
	int was_unevictable = PageUnevictable(page);
L
Lee Schermerhorn 已提交
638 639 640 641 642 643 644 645 646 647 648 649 650

	VM_BUG_ON(PageLRU(page));

redo:
	ClearPageUnevictable(page);

	if (page_evictable(page, NULL)) {
		/*
		 * 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.
		 */
651
		lru = active + page_lru_base_type(page);
L
Lee Schermerhorn 已提交
652 653 654 655 656 657 658 659
		lru_cache_add_lru(page, lru);
	} else {
		/*
		 * Put unevictable pages directly on zone's unevictable
		 * list.
		 */
		lru = LRU_UNEVICTABLE;
		add_page_to_unevictable_list(page);
660
		/*
661 662 663 664 665
		 * 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_page,
		 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
666 667
		 * the page back to the evictable list.
		 *
668
		 * The other side is TestClearPageMlocked() or shmem_lock().
669 670
		 */
		smp_mb();
L
Lee Schermerhorn 已提交
671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688
	}

	/*
	 * 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 (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
		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.
		 */
	}

689 690 691 692 693
	if (was_unevictable && lru != LRU_UNEVICTABLE)
		count_vm_event(UNEVICTABLE_PGRESCUED);
	else if (!was_unevictable && lru == LRU_UNEVICTABLE)
		count_vm_event(UNEVICTABLE_PGCULLED);

L
Lee Schermerhorn 已提交
694 695 696
	put_page(page);		/* drop ref from isolate */
}

697 698 699
enum page_references {
	PAGEREF_RECLAIM,
	PAGEREF_RECLAIM_CLEAN,
700
	PAGEREF_KEEP,
701 702 703 704
	PAGEREF_ACTIVATE,
};

static enum page_references page_check_references(struct page *page,
705
						  struct mem_cgroup_zone *mz,
706 707
						  struct scan_control *sc)
{
708
	int referenced_ptes, referenced_page;
709 710
	unsigned long vm_flags;

711
	referenced_ptes = page_referenced(page, 1, mz->mem_cgroup, &vm_flags);
712
	referenced_page = TestClearPageReferenced(page);
713 714

	/* Lumpy reclaim - ignore references */
715
	if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
716 717 718 719 720 721 722 723 724
		return PAGEREF_RECLAIM;

	/*
	 * 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;

725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743
	if (referenced_ptes) {
		if (PageAnon(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);

744
		if (referenced_page || referenced_ptes > 1)
745 746
			return PAGEREF_ACTIVATE;

747 748 749 750 751 752
		/*
		 * Activate file-backed executable pages after first usage.
		 */
		if (vm_flags & VM_EXEC)
			return PAGEREF_ACTIVATE;

753 754
		return PAGEREF_KEEP;
	}
755 756

	/* Reclaim if clean, defer dirty pages to writeback */
757
	if (referenced_page && !PageSwapBacked(page))
758 759 760
		return PAGEREF_RECLAIM_CLEAN;

	return PAGEREF_RECLAIM;
761 762
}

L
Linus Torvalds 已提交
763
/*
A
Andrew Morton 已提交
764
 * shrink_page_list() returns the number of reclaimed pages
L
Linus Torvalds 已提交
765
 */
A
Andrew Morton 已提交
766
static unsigned long shrink_page_list(struct list_head *page_list,
767
				      struct mem_cgroup_zone *mz,
768
				      struct scan_control *sc,
769 770 771
				      int priority,
				      unsigned long *ret_nr_dirty,
				      unsigned long *ret_nr_writeback)
L
Linus Torvalds 已提交
772 773
{
	LIST_HEAD(ret_pages);
774
	LIST_HEAD(free_pages);
L
Linus Torvalds 已提交
775
	int pgactivate = 0;
776 777
	unsigned long nr_dirty = 0;
	unsigned long nr_congested = 0;
778
	unsigned long nr_reclaimed = 0;
779
	unsigned long nr_writeback = 0;
L
Linus Torvalds 已提交
780 781 782 783

	cond_resched();

	while (!list_empty(page_list)) {
784
		enum page_references references;
L
Linus Torvalds 已提交
785 786 787 788 789 790 791 792 793
		struct address_space *mapping;
		struct page *page;
		int may_enter_fs;

		cond_resched();

		page = lru_to_page(page_list);
		list_del(&page->lru);

N
Nick Piggin 已提交
794
		if (!trylock_page(page))
L
Linus Torvalds 已提交
795 796
			goto keep;

N
Nick Piggin 已提交
797
		VM_BUG_ON(PageActive(page));
798
		VM_BUG_ON(page_zone(page) != mz->zone);
L
Linus Torvalds 已提交
799 800

		sc->nr_scanned++;
801

N
Nick Piggin 已提交
802 803
		if (unlikely(!page_evictable(page, NULL)))
			goto cull_mlocked;
L
Lee Schermerhorn 已提交
804

805
		if (!sc->may_unmap && page_mapped(page))
806 807
			goto keep_locked;

L
Linus Torvalds 已提交
808 809 810 811
		/* Double the slab pressure for mapped and swapcache pages */
		if (page_mapped(page) || PageSwapCache(page))
			sc->nr_scanned++;

812 813 814 815
		may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
			(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));

		if (PageWriteback(page)) {
816
			nr_writeback++;
817
			/*
818 819 820 821
			 * Synchronous reclaim cannot queue pages for
			 * writeback due to the possibility of stack overflow
			 * but if it encounters a page under writeback, wait
			 * for the IO to complete.
822
			 */
823
			if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
824
			    may_enter_fs)
825
				wait_on_page_writeback(page);
826 827 828 829
			else {
				unlock_page(page);
				goto keep_lumpy;
			}
830
		}
L
Linus Torvalds 已提交
831

832
		references = page_check_references(page, mz, sc);
833 834
		switch (references) {
		case PAGEREF_ACTIVATE:
L
Linus Torvalds 已提交
835
			goto activate_locked;
836 837
		case PAGEREF_KEEP:
			goto keep_locked;
838 839 840 841
		case PAGEREF_RECLAIM:
		case PAGEREF_RECLAIM_CLEAN:
			; /* try to reclaim the page below */
		}
L
Linus Torvalds 已提交
842 843 844 845 846

		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
N
Nick Piggin 已提交
847
		if (PageAnon(page) && !PageSwapCache(page)) {
848 849
			if (!(sc->gfp_mask & __GFP_IO))
				goto keep_locked;
850
			if (!add_to_swap(page))
L
Linus Torvalds 已提交
851
				goto activate_locked;
852
			may_enter_fs = 1;
N
Nick Piggin 已提交
853
		}
L
Linus Torvalds 已提交
854 855 856 857 858 859 860 861

		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) {
862
			switch (try_to_unmap(page, TTU_UNMAP)) {
L
Linus Torvalds 已提交
863 864 865 866
			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
N
Nick Piggin 已提交
867 868
			case SWAP_MLOCK:
				goto cull_mlocked;
L
Linus Torvalds 已提交
869 870 871 872 873 874
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
875 876
			nr_dirty++;

877 878
			/*
			 * Only kswapd can writeback filesystem pages to
879 880
			 * avoid risk of stack overflow but do not writeback
			 * unless under significant pressure.
881
			 */
882 883
			if (page_is_file_cache(page) &&
					(!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) {
884 885 886 887 888 889 890 891 892
				/*
				 * 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);

893 894 895
				goto keep_locked;
			}

896
			if (references == PAGEREF_RECLAIM_CLEAN)
L
Linus Torvalds 已提交
897
				goto keep_locked;
898
			if (!may_enter_fs)
L
Linus Torvalds 已提交
899
				goto keep_locked;
900
			if (!sc->may_writepage)
L
Linus Torvalds 已提交
901 902 903
				goto keep_locked;

			/* Page is dirty, try to write it out here */
904
			switch (pageout(page, mapping, sc)) {
L
Linus Torvalds 已提交
905
			case PAGE_KEEP:
906
				nr_congested++;
L
Linus Torvalds 已提交
907 908 909 910
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
911 912 913
				if (PageWriteback(page))
					goto keep_lumpy;
				if (PageDirty(page))
L
Linus Torvalds 已提交
914
					goto keep;
915

L
Linus Torvalds 已提交
916 917 918 919
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
N
Nick Piggin 已提交
920
				if (!trylock_page(page))
L
Linus Torvalds 已提交
921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939
					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
L
Lee Schermerhorn 已提交
940
		 * will do this, as well as the blockdev mapping.
L
Linus Torvalds 已提交
941 942 943 944 945 946 947 948 949 950
		 * 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.
		 */
951
		if (page_has_private(page)) {
L
Linus Torvalds 已提交
952 953
			if (!try_to_release_page(page, sc->gfp_mask))
				goto activate_locked;
N
Nick Piggin 已提交
954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969
			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;
				}
			}
L
Linus Torvalds 已提交
970 971
		}

N
Nick Piggin 已提交
972
		if (!mapping || !__remove_mapping(mapping, page))
973
			goto keep_locked;
L
Linus Torvalds 已提交
974

N
Nick Piggin 已提交
975 976 977 978 979 980 981 982
		/*
		 * 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);
N
Nick Piggin 已提交
983
free_it:
984
		nr_reclaimed++;
985 986 987 988 989 990

		/*
		 * Is there need to periodically free_page_list? It would
		 * appear not as the counts should be low
		 */
		list_add(&page->lru, &free_pages);
L
Linus Torvalds 已提交
991 992
		continue;

N
Nick Piggin 已提交
993
cull_mlocked:
994 995
		if (PageSwapCache(page))
			try_to_free_swap(page);
N
Nick Piggin 已提交
996 997
		unlock_page(page);
		putback_lru_page(page);
998
		reset_reclaim_mode(sc);
N
Nick Piggin 已提交
999 1000
		continue;

L
Linus Torvalds 已提交
1001
activate_locked:
1002 1003
		/* Not a candidate for swapping, so reclaim swap space. */
		if (PageSwapCache(page) && vm_swap_full())
1004
			try_to_free_swap(page);
L
Lee Schermerhorn 已提交
1005
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
1006 1007 1008 1009 1010
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
1011
		reset_reclaim_mode(sc);
1012
keep_lumpy:
L
Linus Torvalds 已提交
1013
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
1014
		VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
L
Linus Torvalds 已提交
1015
	}
1016

1017 1018 1019 1020 1021 1022
	/*
	 * Tag a zone as congested if all the dirty pages encountered were
	 * backed by a congested BDI. In this case, reclaimers should just
	 * back off and wait for congestion to clear because further reclaim
	 * will encounter the same problem
	 */
1023
	if (nr_dirty && nr_dirty == nr_congested && global_reclaim(sc))
1024
		zone_set_flag(mz->zone, ZONE_CONGESTED);
1025

1026
	free_hot_cold_page_list(&free_pages, 1);
1027

L
Linus Torvalds 已提交
1028
	list_splice(&ret_pages, page_list);
1029
	count_vm_events(PGACTIVATE, pgactivate);
1030 1031
	*ret_nr_dirty += nr_dirty;
	*ret_nr_writeback += nr_writeback;
1032
	return nr_reclaimed;
L
Linus Torvalds 已提交
1033 1034
}

A
Andy Whitcroft 已提交
1035 1036 1037 1038 1039 1040 1041 1042 1043 1044
/*
 * 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.
 */
1045
int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
A
Andy Whitcroft 已提交
1046
{
1047
	bool all_lru_mode;
A
Andy Whitcroft 已提交
1048 1049 1050 1051 1052 1053
	int ret = -EINVAL;

	/* Only take pages on the LRU. */
	if (!PageLRU(page))
		return ret;

1054 1055 1056
	all_lru_mode = (mode & (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) ==
		(ISOLATE_ACTIVE|ISOLATE_INACTIVE);

A
Andy Whitcroft 已提交
1057 1058 1059 1060 1061
	/*
	 * When checking the active state, we need to be sure we are
	 * dealing with comparible boolean values.  Take the logical not
	 * of each.
	 */
1062
	if (!all_lru_mode && !PageActive(page) != !(mode & ISOLATE_ACTIVE))
A
Andy Whitcroft 已提交
1063 1064
		return ret;

1065
	if (!all_lru_mode && !!page_is_file_cache(page) != file)
1066 1067
		return ret;

L
Lee Schermerhorn 已提交
1068 1069 1070 1071 1072 1073 1074 1075
	/*
	 * When this function is being called for lumpy reclaim, we
	 * initially look into all LRU pages, active, inactive and
	 * unevictable; only give shrink_page_list evictable pages.
	 */
	if (PageUnevictable(page))
		return ret;

A
Andy Whitcroft 已提交
1076
	ret = -EBUSY;
K
KAMEZAWA Hiroyuki 已提交
1077

1078 1079 1080
	if ((mode & ISOLATE_CLEAN) && (PageDirty(page) || PageWriteback(page)))
		return ret;

1081 1082 1083
	if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
		return ret;

A
Andy Whitcroft 已提交
1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096
	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;
}

L
Linus Torvalds 已提交
1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110
/*
 * 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.
 * @src:	The LRU list to pull pages off.
 * @dst:	The temp list to put pages on to.
 * @scanned:	The number of pages that were scanned.
A
Andy Whitcroft 已提交
1111 1112
 * @order:	The caller's attempted allocation order
 * @mode:	One of the LRU isolation modes
1113
 * @file:	True [1] if isolating file [!anon] pages
L
Linus Torvalds 已提交
1114 1115 1116
 *
 * returns how many pages were moved onto *@dst.
 */
1117 1118
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
		struct list_head *src, struct list_head *dst,
1119 1120
		unsigned long *scanned, int order, isolate_mode_t mode,
		int file)
L
Linus Torvalds 已提交
1121
{
1122
	unsigned long nr_taken = 0;
1123 1124 1125
	unsigned long nr_lumpy_taken = 0;
	unsigned long nr_lumpy_dirty = 0;
	unsigned long nr_lumpy_failed = 0;
1126
	unsigned long scan;
L
Linus Torvalds 已提交
1127

1128
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
1129 1130 1131 1132 1133 1134
		struct page *page;
		unsigned long pfn;
		unsigned long end_pfn;
		unsigned long page_pfn;
		int zone_id;

L
Linus Torvalds 已提交
1135 1136 1137
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
1138
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
1139

1140
		switch (__isolate_lru_page(page, mode, file)) {
A
Andy Whitcroft 已提交
1141
		case 0:
1142
			mem_cgroup_lru_del(page);
A
Andy Whitcroft 已提交
1143
			list_move(&page->lru, dst);
1144
			nr_taken += hpage_nr_pages(page);
A
Andy Whitcroft 已提交
1145 1146 1147 1148 1149 1150
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
			continue;
1151

A
Andy Whitcroft 已提交
1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163
		default:
			BUG();
		}

		if (!order)
			continue;

		/*
		 * Attempt to take all pages in the order aligned region
		 * surrounding the tag page.  Only take those pages of
		 * the same active state as that tag page.  We may safely
		 * round the target page pfn down to the requested order
L
Lucas De Marchi 已提交
1164
		 * as the mem_map is guaranteed valid out to MAX_ORDER,
A
Andy Whitcroft 已提交
1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183
		 * where that page is in a different zone we will detect
		 * it from its zone id and abort this block scan.
		 */
		zone_id = page_zone_id(page);
		page_pfn = page_to_pfn(page);
		pfn = page_pfn & ~((1 << order) - 1);
		end_pfn = pfn + (1 << order);
		for (; pfn < end_pfn; pfn++) {
			struct page *cursor_page;

			/* The target page is in the block, ignore it. */
			if (unlikely(pfn == page_pfn))
				continue;

			/* Avoid holes within the zone. */
			if (unlikely(!pfn_valid_within(pfn)))
				break;

			cursor_page = pfn_to_page(pfn);
1184

A
Andy Whitcroft 已提交
1185 1186
			/* Check that we have not crossed a zone boundary. */
			if (unlikely(page_zone_id(cursor_page) != zone_id))
1187
				break;
1188 1189 1190 1191 1192 1193

			/*
			 * If we don't have enough swap space, reclaiming of
			 * anon page which don't already have a swap slot is
			 * pointless.
			 */
1194
			if (nr_swap_pages <= 0 && PageSwapBacked(cursor_page) &&
1195 1196
			    !PageSwapCache(cursor_page))
				break;
1197

1198
			if (__isolate_lru_page(cursor_page, mode, file) == 0) {
1199
				mem_cgroup_lru_del(cursor_page);
A
Andy Whitcroft 已提交
1200
				list_move(&cursor_page->lru, dst);
1201
				nr_taken += hpage_nr_pages(cursor_page);
1202 1203 1204
				nr_lumpy_taken++;
				if (PageDirty(cursor_page))
					nr_lumpy_dirty++;
A
Andy Whitcroft 已提交
1205
				scan++;
1206
			} else {
1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220
				/*
				 * Check if the page is freed already.
				 *
				 * We can't use page_count() as that
				 * requires compound_head and we don't
				 * have a pin on the page here. If a
				 * page is tail, we may or may not
				 * have isolated the head, so assume
				 * it's not free, it'd be tricky to
				 * track the head status without a
				 * page pin.
				 */
				if (!PageTail(cursor_page) &&
				    !atomic_read(&cursor_page->_count))
1221 1222
					continue;
				break;
A
Andy Whitcroft 已提交
1223 1224
			}
		}
1225 1226 1227 1228

		/* If we break out of the loop above, lumpy reclaim failed */
		if (pfn < end_pfn)
			nr_lumpy_failed++;
L
Linus Torvalds 已提交
1229 1230 1231
	}

	*scanned = scan;
1232 1233 1234 1235 1236

	trace_mm_vmscan_lru_isolate(order,
			nr_to_scan, scan,
			nr_taken,
			nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
1237
			mode, file);
L
Linus Torvalds 已提交
1238 1239 1240
	return nr_taken;
}

1241 1242 1243 1244
static unsigned long isolate_pages(unsigned long nr, struct mem_cgroup_zone *mz,
				   struct list_head *dst,
				   unsigned long *scanned, int order,
				   isolate_mode_t mode, int active, int file)
1245
{
1246
	struct lruvec *lruvec;
1247
	int lru = LRU_BASE;
1248 1249

	lruvec = mem_cgroup_zone_lruvec(mz->zone, mz->mem_cgroup);
1250
	if (active)
1251 1252 1253
		lru += LRU_ACTIVE;
	if (file)
		lru += LRU_FILE;
1254
	return isolate_lru_pages(nr, &lruvec->lists[lru], dst,
1255
				 scanned, order, mode, file);
1256 1257
}

A
Andy Whitcroft 已提交
1258 1259 1260 1261
/*
 * clear_active_flags() is a helper for shrink_active_list(), clearing
 * any active bits from the pages in the list.
 */
1262 1263
static unsigned long clear_active_flags(struct list_head *page_list,
					unsigned int *count)
A
Andy Whitcroft 已提交
1264 1265
{
	int nr_active = 0;
1266
	int lru;
A
Andy Whitcroft 已提交
1267 1268
	struct page *page;

1269
	list_for_each_entry(page, page_list, lru) {
1270
		int numpages = hpage_nr_pages(page);
1271
		lru = page_lru_base_type(page);
A
Andy Whitcroft 已提交
1272
		if (PageActive(page)) {
1273
			lru += LRU_ACTIVE;
A
Andy Whitcroft 已提交
1274
			ClearPageActive(page);
1275
			nr_active += numpages;
A
Andy Whitcroft 已提交
1276
		}
1277
		if (count)
1278
			count[lru] += numpages;
1279
	}
A
Andy Whitcroft 已提交
1280 1281 1282 1283

	return nr_active;
}

1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294
/**
 * 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
L
Lee Schermerhorn 已提交
1295 1296 1297
 * 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.
1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312
 *
 * 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;

1313 1314
	VM_BUG_ON(!page_count(page));

1315 1316 1317 1318
	if (PageLRU(page)) {
		struct zone *zone = page_zone(page);

		spin_lock_irq(&zone->lru_lock);
1319
		if (PageLRU(page)) {
L
Lee Schermerhorn 已提交
1320
			int lru = page_lru(page);
1321
			ret = 0;
1322
			get_page(page);
1323
			ClearPageLRU(page);
1324 1325

			del_page_from_lru_list(zone, page, lru);
1326 1327 1328 1329 1330 1331
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342
/*
 * Are there way too many processes in the direct reclaim path already?
 */
static int too_many_isolated(struct zone *zone, int file,
		struct scan_control *sc)
{
	unsigned long inactive, isolated;

	if (current_is_kswapd())
		return 0;

1343
	if (!global_reclaim(sc))
1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356
		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);
	}

	return isolated > inactive;
}

1357 1358 1359 1360
/*
 * TODO: Try merging with migrations version of putback_lru_pages
 */
static noinline_for_stack void
1361 1362 1363
putback_lru_pages(struct mem_cgroup_zone *mz, struct scan_control *sc,
		  unsigned long nr_anon, unsigned long nr_file,
		  struct list_head *page_list)
1364 1365 1366
{
	struct page *page;
	struct pagevec pvec;
1367 1368
	struct zone *zone = mz->zone;
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386

	pagevec_init(&pvec, 1);

	/*
	 * Put back any unfreeable pages.
	 */
	spin_lock(&zone->lru_lock);
	while (!list_empty(page_list)) {
		int lru;
		page = lru_to_page(page_list);
		VM_BUG_ON(PageLRU(page));
		list_del(&page->lru);
		if (unlikely(!page_evictable(page, NULL))) {
			spin_unlock_irq(&zone->lru_lock);
			putback_lru_page(page);
			spin_lock_irq(&zone->lru_lock);
			continue;
		}
1387
		SetPageLRU(page);
1388
		lru = page_lru(page);
1389
		add_page_to_lru_list(zone, page, lru);
1390 1391
		if (is_active_lru(lru)) {
			int file = is_file_lru(lru);
1392 1393
			int numpages = hpage_nr_pages(page);
			reclaim_stat->recent_rotated[file] += numpages;
1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407
		}
		if (!pagevec_add(&pvec, page)) {
			spin_unlock_irq(&zone->lru_lock);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
	__mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
	__mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);

	spin_unlock_irq(&zone->lru_lock);
	pagevec_release(&pvec);
}

1408 1409 1410 1411 1412 1413
static noinline_for_stack void
update_isolated_counts(struct mem_cgroup_zone *mz,
		       struct scan_control *sc,
		       unsigned long *nr_anon,
		       unsigned long *nr_file,
		       struct list_head *isolated_list)
1414 1415
{
	unsigned long nr_active;
1416
	struct zone *zone = mz->zone;
1417
	unsigned int count[NR_LRU_LISTS] = { 0, };
1418
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440

	nr_active = clear_active_flags(isolated_list, count);
	__count_vm_events(PGDEACTIVATE, nr_active);

	__mod_zone_page_state(zone, NR_ACTIVE_FILE,
			      -count[LRU_ACTIVE_FILE]);
	__mod_zone_page_state(zone, NR_INACTIVE_FILE,
			      -count[LRU_INACTIVE_FILE]);
	__mod_zone_page_state(zone, NR_ACTIVE_ANON,
			      -count[LRU_ACTIVE_ANON]);
	__mod_zone_page_state(zone, NR_INACTIVE_ANON,
			      -count[LRU_INACTIVE_ANON]);

	*nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
	*nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
	__mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
	__mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);

	reclaim_stat->recent_scanned[0] += *nr_anon;
	reclaim_stat->recent_scanned[1] += *nr_file;
}

1441
/*
1442
 * Returns true if a direct reclaim should wait on pages under writeback.
1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460
 *
 * If we are direct reclaiming for contiguous pages and we do not reclaim
 * everything in the list, try again and wait for writeback IO to complete.
 * This will stall high-order allocations noticeably. Only do that when really
 * need to free the pages under high memory pressure.
 */
static inline bool should_reclaim_stall(unsigned long nr_taken,
					unsigned long nr_freed,
					int priority,
					struct scan_control *sc)
{
	int lumpy_stall_priority;

	/* kswapd should not stall on sync IO */
	if (current_is_kswapd())
		return false;

	/* Only stall on lumpy reclaim */
1461
	if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1462 1463
		return false;

1464
	/* If we have reclaimed everything on the isolated list, no stall */
1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481
	if (nr_freed == nr_taken)
		return false;

	/*
	 * For high-order allocations, there are two stall thresholds.
	 * High-cost allocations stall immediately where as lower
	 * order allocations such as stacks require the scanning
	 * priority to be much higher before stalling.
	 */
	if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
		lumpy_stall_priority = DEF_PRIORITY;
	else
		lumpy_stall_priority = DEF_PRIORITY / 3;

	return priority <= lumpy_stall_priority;
}

L
Linus Torvalds 已提交
1482
/*
A
Andrew Morton 已提交
1483 1484
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
1485
 */
1486
static noinline_for_stack unsigned long
1487 1488
shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz,
		     struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1489 1490
{
	LIST_HEAD(page_list);
1491
	unsigned long nr_scanned;
1492
	unsigned long nr_reclaimed = 0;
1493 1494 1495
	unsigned long nr_taken;
	unsigned long nr_anon;
	unsigned long nr_file;
1496 1497
	unsigned long nr_dirty = 0;
	unsigned long nr_writeback = 0;
1498
	isolate_mode_t reclaim_mode = ISOLATE_INACTIVE;
1499
	struct zone *zone = mz->zone;
1500

1501
	while (unlikely(too_many_isolated(zone, file, sc))) {
1502
		congestion_wait(BLK_RW_ASYNC, HZ/10);
1503 1504 1505 1506 1507 1508

		/* We are about to die and free our memory. Return now. */
		if (fatal_signal_pending(current))
			return SWAP_CLUSTER_MAX;
	}

1509
	set_reclaim_mode(priority, sc, false);
1510 1511 1512
	if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
		reclaim_mode |= ISOLATE_ACTIVE;

L
Linus Torvalds 已提交
1513
	lru_add_drain();
1514 1515 1516 1517 1518 1519

	if (!sc->may_unmap)
		reclaim_mode |= ISOLATE_UNMAPPED;
	if (!sc->may_writepage)
		reclaim_mode |= ISOLATE_CLEAN;

L
Linus Torvalds 已提交
1520
	spin_lock_irq(&zone->lru_lock);
1521

1522 1523 1524
	nr_taken = isolate_pages(nr_to_scan, mz, &page_list,
				 &nr_scanned, sc->order,
				 reclaim_mode, 0, file);
1525
	if (global_reclaim(sc)) {
1526 1527 1528 1529 1530 1531 1532 1533
		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);
	}
1534

1535 1536 1537 1538
	if (nr_taken == 0) {
		spin_unlock_irq(&zone->lru_lock);
		return 0;
	}
A
Andy Whitcroft 已提交
1539

1540
	update_isolated_counts(mz, sc, &nr_anon, &nr_file, &page_list);
L
Linus Torvalds 已提交
1541

1542
	spin_unlock_irq(&zone->lru_lock);
1543

1544
	nr_reclaimed = shrink_page_list(&page_list, mz, sc, priority,
1545
						&nr_dirty, &nr_writeback);
1546

1547 1548
	/* Check if we should syncronously wait for writeback */
	if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1549
		set_reclaim_mode(priority, sc, true);
1550
		nr_reclaimed += shrink_page_list(&page_list, mz, sc,
1551
					priority, &nr_dirty, &nr_writeback);
1552
	}
1553

1554 1555 1556 1557
	local_irq_disable();
	if (current_is_kswapd())
		__count_vm_events(KSWAPD_STEAL, nr_reclaimed);
	__count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
N
Nick Piggin 已提交
1558

1559
	putback_lru_pages(mz, sc, nr_anon, nr_file, &page_list);
1560

1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586
	/*
	 * 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.
	 *
	 * This scales the number of dirty pages that must be under writeback
	 * before throttling depending on priority. It is a simple backoff
	 * function that has the most effect in the range DEF_PRIORITY to
	 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
	 * in trouble and reclaim is considered to be in trouble.
	 *
	 * DEF_PRIORITY   100% isolated pages must be PageWriteback to throttle
	 * DEF_PRIORITY-1  50% must be PageWriteback
	 * DEF_PRIORITY-2  25% must be PageWriteback, kswapd in trouble
	 * ...
	 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
	 *                     isolated page is PageWriteback
	 */
	if (nr_writeback && nr_writeback >= (nr_taken >> (DEF_PRIORITY-priority)))
		wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);

1587 1588 1589 1590
	trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
		zone_idx(zone),
		nr_scanned, nr_reclaimed,
		priority,
1591
		trace_shrink_flags(file, sc->reclaim_mode));
1592
	return nr_reclaimed;
L
Linus Torvalds 已提交
1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611
}

/*
 * 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.
 */
1612

1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623
static void move_active_pages_to_lru(struct zone *zone,
				     struct list_head *list,
				     enum lru_list lru)
{
	unsigned long pgmoved = 0;
	struct pagevec pvec;
	struct page *page;

	pagevec_init(&pvec, 1);

	while (!list_empty(list)) {
1624 1625
		struct lruvec *lruvec;

1626 1627 1628 1629 1630
		page = lru_to_page(list);

		VM_BUG_ON(PageLRU(page));
		SetPageLRU(page);

1631 1632
		lruvec = mem_cgroup_lru_add_list(zone, page, lru);
		list_move(&page->lru, &lruvec->lists[lru]);
1633
		pgmoved += hpage_nr_pages(page);
1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646

		if (!pagevec_add(&pvec, page) || list_empty(list)) {
			spin_unlock_irq(&zone->lru_lock);
			if (buffer_heads_over_limit)
				pagevec_strip(&pvec);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
	__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
	if (!is_active_lru(lru))
		__count_vm_events(PGDEACTIVATE, pgmoved);
}
1647

1648 1649 1650 1651
static void shrink_active_list(unsigned long nr_pages,
			       struct mem_cgroup_zone *mz,
			       struct scan_control *sc,
			       int priority, int file)
L
Linus Torvalds 已提交
1652
{
1653
	unsigned long nr_taken;
1654
	unsigned long pgscanned;
1655
	unsigned long vm_flags;
L
Linus Torvalds 已提交
1656
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
1657
	LIST_HEAD(l_active);
1658
	LIST_HEAD(l_inactive);
L
Linus Torvalds 已提交
1659
	struct page *page;
1660
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1661
	unsigned long nr_rotated = 0;
1662
	isolate_mode_t reclaim_mode = ISOLATE_ACTIVE;
1663
	struct zone *zone = mz->zone;
L
Linus Torvalds 已提交
1664 1665

	lru_add_drain();
1666 1667 1668 1669 1670 1671

	if (!sc->may_unmap)
		reclaim_mode |= ISOLATE_UNMAPPED;
	if (!sc->may_writepage)
		reclaim_mode |= ISOLATE_CLEAN;

L
Linus Torvalds 已提交
1672
	spin_lock_irq(&zone->lru_lock);
1673 1674 1675 1676

	nr_taken = isolate_pages(nr_pages, mz, &l_hold,
				 &pgscanned, sc->order,
				 reclaim_mode, 1, file);
1677

1678 1679 1680
	if (global_reclaim(sc))
		zone->pages_scanned += pgscanned;

1681
	reclaim_stat->recent_scanned[file] += nr_taken;
1682

1683
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
1684
	if (file)
1685
		__mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1686
	else
1687
		__mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
K
KOSAKI Motohiro 已提交
1688
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
L
Linus Torvalds 已提交
1689 1690 1691 1692 1693 1694
	spin_unlock_irq(&zone->lru_lock);

	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
1695

L
Lee Schermerhorn 已提交
1696 1697 1698 1699 1700
		if (unlikely(!page_evictable(page, NULL))) {
			putback_lru_page(page);
			continue;
		}

1701
		if (page_referenced(page, 0, mz->mem_cgroup, &vm_flags)) {
1702
			nr_rotated += hpage_nr_pages(page);
1703 1704 1705 1706 1707 1708 1709 1710 1711
			/*
			 * 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.
			 */
1712
			if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1713 1714 1715 1716
				list_add(&page->lru, &l_active);
				continue;
			}
		}
1717

1718
		ClearPageActive(page);	/* we are de-activating */
L
Linus Torvalds 已提交
1719 1720 1721
		list_add(&page->lru, &l_inactive);
	}

1722
	/*
1723
	 * Move pages back to the lru list.
1724
	 */
1725
	spin_lock_irq(&zone->lru_lock);
1726
	/*
1727 1728 1729 1730
	 * 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.
1731
	 */
1732
	reclaim_stat->recent_rotated[file] += nr_rotated;
1733

1734 1735 1736 1737
	move_active_pages_to_lru(zone, &l_active,
						LRU_ACTIVE + file * LRU_FILE);
	move_active_pages_to_lru(zone, &l_inactive,
						LRU_BASE   + file * LRU_FILE);
K
KOSAKI Motohiro 已提交
1738
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1739
	spin_unlock_irq(&zone->lru_lock);
L
Linus Torvalds 已提交
1740 1741
}

1742
#ifdef CONFIG_SWAP
1743
static int inactive_anon_is_low_global(struct zone *zone)
1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755
{
	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;
}

1756 1757 1758 1759 1760 1761 1762 1763
/**
 * inactive_anon_is_low - check if anonymous pages need to be deactivated
 * @zone: zone to check
 * @sc:   scan control of this context
 *
 * Returns true if the zone does not have enough inactive anon pages,
 * meaning some active anon pages need to be deactivated.
 */
1764
static int inactive_anon_is_low(struct mem_cgroup_zone *mz)
1765
{
1766 1767 1768 1769 1770 1771 1772
	/*
	 * If we don't have swap space, anonymous page deactivation
	 * is pointless.
	 */
	if (!total_swap_pages)
		return 0;

1773 1774 1775 1776 1777
	if (!scanning_global_lru(mz))
		return mem_cgroup_inactive_anon_is_low(mz->mem_cgroup,
						       mz->zone);

	return inactive_anon_is_low_global(mz->zone);
1778
}
1779
#else
1780
static inline int inactive_anon_is_low(struct mem_cgroup_zone *mz)
1781 1782 1783 1784
{
	return 0;
}
#endif
1785

1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797
static int inactive_file_is_low_global(struct zone *zone)
{
	unsigned long active, inactive;

	active = zone_page_state(zone, NR_ACTIVE_FILE);
	inactive = zone_page_state(zone, NR_INACTIVE_FILE);

	return (active > inactive);
}

/**
 * inactive_file_is_low - check if file pages need to be deactivated
1798
 * @mz: memory cgroup and zone to check
1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809
 *
 * 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.
 */
1810
static int inactive_file_is_low(struct mem_cgroup_zone *mz)
1811
{
1812 1813 1814
	if (!scanning_global_lru(mz))
		return mem_cgroup_inactive_file_is_low(mz->mem_cgroup,
						       mz->zone);
1815

1816
	return inactive_file_is_low_global(mz->zone);
1817 1818
}

1819
static int inactive_list_is_low(struct mem_cgroup_zone *mz, int file)
1820 1821
{
	if (file)
1822
		return inactive_file_is_low(mz);
1823
	else
1824
		return inactive_anon_is_low(mz);
1825 1826
}

1827
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1828 1829
				 struct mem_cgroup_zone *mz,
				 struct scan_control *sc, int priority)
1830
{
1831 1832
	int file = is_file_lru(lru);

1833
	if (is_active_lru(lru)) {
1834 1835
		if (inactive_list_is_low(mz, file))
			shrink_active_list(nr_to_scan, mz, sc, priority, file);
1836 1837 1838
		return 0;
	}

1839
	return shrink_inactive_list(nr_to_scan, mz, sc, priority, file);
1840 1841
}

1842 1843
static int vmscan_swappiness(struct mem_cgroup_zone *mz,
			     struct scan_control *sc)
1844
{
1845
	if (global_reclaim(sc))
1846
		return vm_swappiness;
1847
	return mem_cgroup_swappiness(mz->mem_cgroup);
1848 1849
}

1850 1851 1852 1853 1854 1855
/*
 * 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.
 *
1856
 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1857
 */
1858 1859
static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
			   unsigned long *nr, int priority)
1860 1861 1862 1863
{
	unsigned long anon, file, free;
	unsigned long anon_prio, file_prio;
	unsigned long ap, fp;
1864
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1865 1866 1867
	u64 fraction[2], denominator;
	enum lru_list l;
	int noswap = 0;
1868
	bool force_scan = false;
1869

1870 1871 1872 1873 1874 1875 1876 1877 1878 1879
	/*
	 * 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.
	 */
1880
	if (current_is_kswapd() && mz->zone->all_unreclaimable)
1881
		force_scan = true;
1882
	if (!global_reclaim(sc))
1883
		force_scan = true;
1884 1885 1886 1887 1888 1889 1890 1891 1892

	/* If we have no swap space, do not bother scanning anon pages. */
	if (!sc->may_swap || (nr_swap_pages <= 0)) {
		noswap = 1;
		fraction[0] = 0;
		fraction[1] = 1;
		denominator = 1;
		goto out;
	}
1893

1894 1895 1896 1897
	anon  = zone_nr_lru_pages(mz, LRU_ACTIVE_ANON) +
		zone_nr_lru_pages(mz, LRU_INACTIVE_ANON);
	file  = zone_nr_lru_pages(mz, LRU_ACTIVE_FILE) +
		zone_nr_lru_pages(mz, LRU_INACTIVE_FILE);
1898

1899
	if (global_reclaim(sc)) {
1900
		free  = zone_page_state(mz->zone, NR_FREE_PAGES);
1901 1902
		/* If we have very few page cache pages,
		   force-scan anon pages. */
1903
		if (unlikely(file + free <= high_wmark_pages(mz->zone))) {
1904 1905 1906 1907
			fraction[0] = 1;
			fraction[1] = 0;
			denominator = 1;
			goto out;
1908
		}
1909 1910
	}

1911 1912 1913 1914
	/*
	 * With swappiness at 100, anonymous and file have the same priority.
	 * This scanning priority is essentially the inverse of IO cost.
	 */
1915 1916
	anon_prio = vmscan_swappiness(mz, sc);
	file_prio = 200 - vmscan_swappiness(mz, sc);
1917

1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928
	/*
	 * 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]
	 */
1929
	spin_lock_irq(&mz->zone->lru_lock);
1930 1931 1932
	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
		reclaim_stat->recent_scanned[0] /= 2;
		reclaim_stat->recent_rotated[0] /= 2;
1933 1934
	}

1935 1936 1937
	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
		reclaim_stat->recent_scanned[1] /= 2;
		reclaim_stat->recent_rotated[1] /= 2;
1938 1939 1940
	}

	/*
1941 1942 1943
	 * 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.
1944
	 */
1945 1946
	ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
	ap /= reclaim_stat->recent_rotated[0] + 1;
1947

1948 1949
	fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
	fp /= reclaim_stat->recent_rotated[1] + 1;
1950
	spin_unlock_irq(&mz->zone->lru_lock);
1951

1952 1953 1954 1955 1956 1957 1958
	fraction[0] = ap;
	fraction[1] = fp;
	denominator = ap + fp + 1;
out:
	for_each_evictable_lru(l) {
		int file = is_file_lru(l);
		unsigned long scan;
1959

1960
		scan = zone_nr_lru_pages(mz, l);
1961 1962
		if (priority || noswap) {
			scan >>= priority;
1963 1964
			if (!scan && force_scan)
				scan = SWAP_CLUSTER_MAX;
1965 1966
			scan = div64_u64(scan * fraction[file], denominator);
		}
1967
		nr[l] = scan;
1968
	}
1969
}
1970

1971 1972 1973 1974 1975 1976 1977
/*
 * Reclaim/compaction depends on a number of pages being freed. To avoid
 * disruption to the system, a small number of order-0 pages continue to be
 * rotated and reclaimed in the normal fashion. However, by the time we get
 * back to the allocator and call try_to_compact_zone(), we ensure that
 * there are enough free pages for it to be likely successful
 */
1978
static inline bool should_continue_reclaim(struct mem_cgroup_zone *mz,
1979 1980 1981 1982 1983 1984 1985 1986
					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 */
1987
	if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1988 1989
		return false;

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
	/* 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;
	}
2012 2013 2014 2015 2016 2017

	/*
	 * If we have not reclaimed enough pages for compaction and the
	 * inactive lists are large enough, continue reclaiming
	 */
	pages_for_compaction = (2UL << sc->order);
2018
	inactive_lru_pages = zone_nr_lru_pages(mz, LRU_INACTIVE_FILE);
2019
	if (nr_swap_pages > 0)
2020
		inactive_lru_pages += zone_nr_lru_pages(mz, LRU_INACTIVE_ANON);
2021 2022 2023 2024 2025
	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 */
2026
	switch (compaction_suitable(mz->zone, sc->order)) {
2027 2028 2029 2030 2031 2032 2033 2034
	case COMPACT_PARTIAL:
	case COMPACT_CONTINUE:
		return false;
	default:
		return true;
	}
}

L
Linus Torvalds 已提交
2035 2036 2037
/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
2038 2039
static void shrink_mem_cgroup_zone(int priority, struct mem_cgroup_zone *mz,
				   struct scan_control *sc)
L
Linus Torvalds 已提交
2040
{
2041
	unsigned long nr[NR_LRU_LISTS];
2042
	unsigned long nr_to_scan;
2043
	enum lru_list l;
2044
	unsigned long nr_reclaimed, nr_scanned;
2045
	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
2046
	struct blk_plug plug;
2047

2048 2049
restart:
	nr_reclaimed = 0;
2050
	nr_scanned = sc->nr_scanned;
2051
	get_scan_count(mz, sc, nr, priority);
L
Linus Torvalds 已提交
2052

2053
	blk_start_plug(&plug);
2054 2055
	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
					nr[LRU_INACTIVE_FILE]) {
L
Lee Schermerhorn 已提交
2056
		for_each_evictable_lru(l) {
2057
			if (nr[l]) {
K
KOSAKI Motohiro 已提交
2058 2059
				nr_to_scan = min_t(unsigned long,
						   nr[l], SWAP_CLUSTER_MAX);
2060
				nr[l] -= nr_to_scan;
L
Linus Torvalds 已提交
2061

2062
				nr_reclaimed += shrink_list(l, nr_to_scan,
2063
							    mz, sc, priority);
2064
			}
L
Linus Torvalds 已提交
2065
		}
2066 2067 2068 2069 2070 2071 2072 2073
		/*
		 * On large memory systems, scan >> priority can become
		 * really large. This is fine for the starting priority;
		 * we want to put equal scanning pressure on each zone.
		 * However, if the VM has a harder time of freeing pages,
		 * with multiple processes reclaiming pages, the total
		 * freeing target can get unreasonably large.
		 */
2074
		if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
2075
			break;
L
Linus Torvalds 已提交
2076
	}
2077
	blk_finish_plug(&plug);
2078
	sc->nr_reclaimed += nr_reclaimed;
2079

2080 2081 2082 2083
	/*
	 * Even if we did not try to evict anon pages at all, we want to
	 * rebalance the anon lru active/inactive ratio.
	 */
2084 2085
	if (inactive_anon_is_low(mz))
		shrink_active_list(SWAP_CLUSTER_MAX, mz, sc, priority, 0);
2086

2087
	/* reclaim/compaction might need reclaim to continue */
2088
	if (should_continue_reclaim(mz, nr_reclaimed,
2089 2090 2091
					sc->nr_scanned - nr_scanned, sc))
		goto restart;

2092
	throttle_vm_writeout(sc->gfp_mask);
L
Linus Torvalds 已提交
2093 2094
}

2095 2096 2097
static void shrink_zone(int priority, struct zone *zone,
			struct scan_control *sc)
{
2098 2099
	struct mem_cgroup *root = sc->target_mem_cgroup;
	struct mem_cgroup_reclaim_cookie reclaim = {
2100
		.zone = zone,
2101
		.priority = priority,
2102
	};
2103 2104 2105 2106 2107 2108 2109 2110
	struct mem_cgroup *memcg;

	memcg = mem_cgroup_iter(root, NULL, &reclaim);
	do {
		struct mem_cgroup_zone mz = {
			.mem_cgroup = memcg,
			.zone = zone,
		};
2111

2112 2113 2114 2115 2116 2117
		shrink_mem_cgroup_zone(priority, &mz, sc);
		/*
		 * Limit reclaim has historically picked one memcg and
		 * scanned it with decreasing priority levels until
		 * nr_to_reclaim had been reclaimed.  This priority
		 * cycle is thus over after a single memcg.
2118 2119 2120 2121
		 *
		 * Direct reclaim and kswapd, on the other hand, have
		 * to scan all memory cgroups to fulfill the overall
		 * scan target for the zone.
2122 2123 2124 2125 2126 2127 2128
		 */
		if (!global_reclaim(sc)) {
			mem_cgroup_iter_break(root, memcg);
			break;
		}
		memcg = mem_cgroup_iter(root, memcg, &reclaim);
	} while (memcg);
2129 2130
}

L
Linus Torvalds 已提交
2131 2132 2133 2134 2135
/*
 * 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.
 *
2136 2137
 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
 * Because:
L
Linus Torvalds 已提交
2138 2139
 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
 *    allocation or
2140 2141 2142
 * 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.
L
Linus Torvalds 已提交
2143 2144 2145
 *
 * If a zone is deemed to be full of pinned pages then just give it a light
 * scan then give up on it.
2146 2147 2148 2149
 *
 * This function returns true if a zone is being reclaimed for a costly
 * high-order allocation and compaction is either ready to begin or deferred.
 * This indicates to the caller that it should retry the allocation or fail.
L
Linus Torvalds 已提交
2150
 */
2151
static bool shrink_zones(int priority, struct zonelist *zonelist,
2152
					struct scan_control *sc)
L
Linus Torvalds 已提交
2153
{
2154
	struct zoneref *z;
2155
	struct zone *zone;
2156 2157
	unsigned long nr_soft_reclaimed;
	unsigned long nr_soft_scanned;
2158
	bool should_abort_reclaim = false;
2159

2160 2161
	for_each_zone_zonelist_nodemask(zone, z, zonelist,
					gfp_zone(sc->gfp_mask), sc->nodemask) {
2162
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
2163
			continue;
2164 2165 2166 2167
		/*
		 * Take care memory controller reclaiming has small influence
		 * to global LRU.
		 */
2168
		if (global_reclaim(sc)) {
2169 2170
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
2171
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2172
				continue;	/* Let kswapd poll it */
2173 2174
			if (COMPACTION_BUILD) {
				/*
2175 2176 2177 2178 2179 2180 2181
				 * 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
				 * noticable problem, like transparent huge page
				 * allocations.
2182 2183 2184
				 */
				if (sc->order > PAGE_ALLOC_COSTLY_ORDER &&
					(compaction_suitable(zone, sc->order) ||
2185 2186
					 compaction_deferred(zone))) {
					should_abort_reclaim = true;
2187
					continue;
2188
				}
2189
			}
2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202
			/*
			 * 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() */
2203
		}
2204

2205
		shrink_zone(priority, zone, sc);
L
Linus Torvalds 已提交
2206
	}
2207 2208

	return should_abort_reclaim;
2209 2210 2211 2212 2213 2214 2215
}

static bool zone_reclaimable(struct zone *zone)
{
	return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
}

2216
/* All zones in zonelist are unreclaimable? */
2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228
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;
2229 2230
		if (!zone->all_unreclaimable)
			return false;
2231 2232
	}

2233
	return true;
L
Linus Torvalds 已提交
2234
}
2235

L
Linus Torvalds 已提交
2236 2237 2238 2239 2240 2241 2242 2243
/*
 * 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
2244 2245 2246 2247
 * 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.
2248 2249 2250
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
2251
 */
2252
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2253 2254
					struct scan_control *sc,
					struct shrink_control *shrink)
L
Linus Torvalds 已提交
2255 2256
{
	int priority;
2257
	unsigned long total_scanned = 0;
L
Linus Torvalds 已提交
2258
	struct reclaim_state *reclaim_state = current->reclaim_state;
2259
	struct zoneref *z;
2260
	struct zone *zone;
2261
	unsigned long writeback_threshold;
L
Linus Torvalds 已提交
2262

2263
	get_mems_allowed();
2264 2265
	delayacct_freepages_start();

2266
	if (global_reclaim(sc))
2267
		count_vm_event(ALLOCSTALL);
L
Linus Torvalds 已提交
2268 2269

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2270
		sc->nr_scanned = 0;
2271
		if (!priority)
2272
			disable_swap_token(sc->target_mem_cgroup);
2273 2274 2275
		if (shrink_zones(priority, zonelist, sc))
			break;

2276 2277 2278 2279
		/*
		 * Don't shrink slabs when reclaiming memory from
		 * over limit cgroups
		 */
2280
		if (global_reclaim(sc)) {
2281
			unsigned long lru_pages = 0;
2282 2283
			for_each_zone_zonelist(zone, z, zonelist,
					gfp_zone(sc->gfp_mask)) {
2284 2285 2286 2287 2288 2289
				if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
					continue;

				lru_pages += zone_reclaimable_pages(zone);
			}

2290
			shrink_slab(shrink, sc->nr_scanned, lru_pages);
2291
			if (reclaim_state) {
2292
				sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2293 2294
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
2295
		}
2296
		total_scanned += sc->nr_scanned;
2297
		if (sc->nr_reclaimed >= sc->nr_to_reclaim)
L
Linus Torvalds 已提交
2298 2299 2300 2301 2302 2303 2304 2305 2306
			goto out;

		/*
		 * 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.
		 */
2307 2308
		writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
		if (total_scanned > writeback_threshold) {
2309 2310
			wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
						WB_REASON_TRY_TO_FREE_PAGES);
2311
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
2312 2313 2314
		}

		/* Take a nap, wait for some writeback to complete */
2315
		if (!sc->hibernation_mode && sc->nr_scanned &&
2316 2317 2318 2319
		    priority < DEF_PRIORITY - 2) {
			struct zone *preferred_zone;

			first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2320 2321
						&cpuset_current_mems_allowed,
						&preferred_zone);
2322 2323
			wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
		}
L
Linus Torvalds 已提交
2324
	}
2325

L
Linus Torvalds 已提交
2326
out:
2327
	delayacct_freepages_end();
2328
	put_mems_allowed();
2329

2330 2331 2332
	if (sc->nr_reclaimed)
		return sc->nr_reclaimed;

2333 2334 2335 2336 2337 2338 2339 2340
	/*
	 * 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;

2341
	/* top priority shrink_zones still had more to do? don't OOM, then */
2342
	if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc))
2343 2344 2345
		return 1;

	return 0;
L
Linus Torvalds 已提交
2346 2347
}

2348
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2349
				gfp_t gfp_mask, nodemask_t *nodemask)
2350
{
2351
	unsigned long nr_reclaimed;
2352 2353 2354
	struct scan_control sc = {
		.gfp_mask = gfp_mask,
		.may_writepage = !laptop_mode,
2355
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2356
		.may_unmap = 1,
2357
		.may_swap = 1,
2358
		.order = order,
2359
		.target_mem_cgroup = NULL,
2360
		.nodemask = nodemask,
2361
	};
2362 2363 2364
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
2365

2366 2367 2368 2369
	trace_mm_vmscan_direct_reclaim_begin(order,
				sc.may_writepage,
				gfp_mask);

2370
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2371 2372 2373 2374

	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);

	return nr_reclaimed;
2375 2376
}

2377
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
2378

2379
unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
2380
						gfp_t gfp_mask, bool noswap,
2381 2382
						struct zone *zone,
						unsigned long *nr_scanned)
2383 2384
{
	struct scan_control sc = {
2385
		.nr_scanned = 0,
2386
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2387 2388 2389 2390
		.may_writepage = !laptop_mode,
		.may_unmap = 1,
		.may_swap = !noswap,
		.order = 0,
2391
		.target_mem_cgroup = memcg,
2392
	};
2393
	struct mem_cgroup_zone mz = {
2394
		.mem_cgroup = memcg,
2395 2396
		.zone = zone,
	};
2397

2398 2399
	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2400 2401 2402 2403 2404

	trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
						      sc.may_writepage,
						      sc.gfp_mask);

2405 2406 2407 2408 2409 2410 2411
	/*
	 * 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.
	 */
2412
	shrink_mem_cgroup_zone(0, &mz, &sc);
2413 2414 2415

	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);

2416
	*nr_scanned = sc.nr_scanned;
2417 2418 2419
	return sc.nr_reclaimed;
}

2420
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
K
KOSAKI Motohiro 已提交
2421
					   gfp_t gfp_mask,
2422
					   bool noswap)
2423
{
2424
	struct zonelist *zonelist;
2425
	unsigned long nr_reclaimed;
2426
	int nid;
2427 2428
	struct scan_control sc = {
		.may_writepage = !laptop_mode,
2429
		.may_unmap = 1,
2430
		.may_swap = !noswap,
2431
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2432
		.order = 0,
2433
		.target_mem_cgroup = memcg,
2434
		.nodemask = NULL, /* we don't care the placement */
2435 2436 2437 2438 2439
		.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
				(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
	};
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
2440 2441
	};

2442 2443 2444 2445 2446
	/*
	 * 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.
	 */
2447
	nid = mem_cgroup_select_victim_node(memcg);
2448 2449

	zonelist = NODE_DATA(nid)->node_zonelists;
2450 2451 2452 2453 2454

	trace_mm_vmscan_memcg_reclaim_begin(0,
					    sc.may_writepage,
					    sc.gfp_mask);

2455
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2456 2457 2458 2459

	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);

	return nr_reclaimed;
2460 2461 2462
}
#endif

2463 2464 2465
static void age_active_anon(struct zone *zone, struct scan_control *sc,
			    int priority)
{
2466
	struct mem_cgroup *memcg;
2467

2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483
	if (!total_swap_pages)
		return;

	memcg = mem_cgroup_iter(NULL, NULL, NULL);
	do {
		struct mem_cgroup_zone mz = {
			.mem_cgroup = memcg,
			.zone = zone,
		};

		if (inactive_anon_is_low(&mz))
			shrink_active_list(SWAP_CLUSTER_MAX, &mz,
					   sc, priority, 0);

		memcg = mem_cgroup_iter(NULL, memcg, NULL);
	} while (memcg);
2484 2485
}

2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496
/*
 * pgdat_balanced is used when checking if a node is 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
L
Lucas De Marchi 已提交
2497
 *     percentage of the middle zones. For example, on 32-bit x86, highmem
2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510
 *     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, unsigned long balanced_pages,
						int classzone_idx)
{
	unsigned long present_pages = 0;
	int i;

	for (i = 0; i <= classzone_idx; i++)
		present_pages += pgdat->node_zones[i].present_pages;

S
Shaohua Li 已提交
2511 2512
	/* A special case here: if zone has no page, we think it's balanced */
	return balanced_pages >= (present_pages >> 2);
2513 2514
}

2515
/* is kswapd sleeping prematurely? */
2516 2517
static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
					int classzone_idx)
2518
{
2519
	int i;
2520 2521
	unsigned long balanced = 0;
	bool all_zones_ok = true;
2522 2523 2524

	/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
	if (remaining)
2525
		return true;
2526

2527
	/* Check the watermark levels */
2528
	for (i = 0; i <= classzone_idx; i++) {
2529 2530 2531 2532 2533
		struct zone *zone = pgdat->node_zones + i;

		if (!populated_zone(zone))
			continue;

2534 2535 2536 2537 2538 2539 2540 2541
		/*
		 * balance_pgdat() skips over all_unreclaimable after
		 * DEF_PRIORITY. Effectively, it considers them balanced so
		 * they must be considered balanced here as well if kswapd
		 * is to sleep
		 */
		if (zone->all_unreclaimable) {
			balanced += zone->present_pages;
2542
			continue;
2543
		}
2544

2545
		if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2546
							i, 0))
2547 2548 2549
			all_zones_ok = false;
		else
			balanced += zone->present_pages;
2550
	}
2551

2552 2553 2554 2555 2556 2557
	/*
	 * For high-order requests, the balanced zones must contain at least
	 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
	 * must be balanced
	 */
	if (order)
2558
		return !pgdat_balanced(pgdat, balanced, classzone_idx);
2559 2560
	else
		return !all_zones_ok;
2561 2562
}

L
Linus Torvalds 已提交
2563 2564
/*
 * For kswapd, balance_pgdat() will work across all this node's zones until
2565
 * they are all at high_wmark_pages(zone).
L
Linus Torvalds 已提交
2566
 *
2567
 * Returns the final order kswapd was reclaiming at
L
Linus Torvalds 已提交
2568 2569 2570 2571 2572 2573 2574 2575 2576 2577
 *
 * 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
2578 2579 2580 2581 2582
 * 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.
L
Linus Torvalds 已提交
2583
 */
2584
static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2585
							int *classzone_idx)
L
Linus Torvalds 已提交
2586 2587
{
	int all_zones_ok;
2588
	unsigned long balanced;
L
Linus Torvalds 已提交
2589 2590
	int priority;
	int i;
2591
	int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */
2592
	unsigned long total_scanned;
L
Linus Torvalds 已提交
2593
	struct reclaim_state *reclaim_state = current->reclaim_state;
2594 2595
	unsigned long nr_soft_reclaimed;
	unsigned long nr_soft_scanned;
2596 2597
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
2598
		.may_unmap = 1,
2599
		.may_swap = 1,
2600 2601 2602 2603 2604
		/*
		 * kswapd doesn't want to be bailed out while reclaim. because
		 * we want to put equal scanning pressure on each zone.
		 */
		.nr_to_reclaim = ULONG_MAX,
A
Andy Whitcroft 已提交
2605
		.order = order,
2606
		.target_mem_cgroup = NULL,
2607
	};
2608 2609 2610
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
L
Linus Torvalds 已提交
2611 2612
loop_again:
	total_scanned = 0;
2613
	sc.nr_reclaimed = 0;
C
Christoph Lameter 已提交
2614
	sc.may_writepage = !laptop_mode;
2615
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
2616 2617 2618

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
		unsigned long lru_pages = 0;
2619
		int has_under_min_watermark_zone = 0;
L
Linus Torvalds 已提交
2620

2621 2622
		/* The swap token gets in the way of swapout... */
		if (!priority)
2623
			disable_swap_token(NULL);
2624

L
Linus Torvalds 已提交
2625
		all_zones_ok = 1;
2626
		balanced = 0;
L
Linus Torvalds 已提交
2627

2628 2629 2630 2631 2632 2633
		/*
		 * 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;
L
Linus Torvalds 已提交
2634

2635 2636
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
2637

2638
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2639
				continue;
L
Linus Torvalds 已提交
2640

2641 2642 2643 2644
			/*
			 * Do some background aging of the anon list, to give
			 * pages a chance to be referenced before reclaiming.
			 */
2645
			age_active_anon(zone, &sc, priority);
2646

2647
			if (!zone_watermark_ok_safe(zone, order,
2648
					high_wmark_pages(zone), 0, 0)) {
2649
				end_zone = i;
A
Andrew Morton 已提交
2650
				break;
2651 2652 2653
			} else {
				/* If balanced, clear the congested flag */
				zone_clear_flag(zone, ZONE_CONGESTED);
L
Linus Torvalds 已提交
2654 2655
			}
		}
A
Andrew Morton 已提交
2656 2657 2658
		if (i < 0)
			goto out;

L
Linus Torvalds 已提交
2659 2660 2661
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

2662
			lru_pages += zone_reclaimable_pages(zone);
L
Linus Torvalds 已提交
2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675
		}

		/*
		 * 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;
2676
			int nr_slab;
2677
			unsigned long balance_gap;
L
Linus Torvalds 已提交
2678

2679
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
2680 2681
				continue;

2682
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
L
Linus Torvalds 已提交
2683 2684 2685
				continue;

			sc.nr_scanned = 0;
2686

2687
			nr_soft_scanned = 0;
2688 2689 2690
			/*
			 * Call soft limit reclaim before calling shrink_zone.
			 */
2691 2692 2693 2694 2695
			nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
							order, sc.gfp_mask,
							&nr_soft_scanned);
			sc.nr_reclaimed += nr_soft_reclaimed;
			total_scanned += nr_soft_scanned;
2696

2697
			/*
2698 2699 2700 2701 2702 2703
			 * 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.
2704
			 */
2705 2706 2707 2708
			balance_gap = min(low_wmark_pages(zone),
				(zone->present_pages +
					KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
				KSWAPD_ZONE_BALANCE_GAP_RATIO);
2709
			if (!zone_watermark_ok_safe(zone, order,
2710
					high_wmark_pages(zone) + balance_gap,
2711
					end_zone, 0)) {
2712
				shrink_zone(priority, zone, &sc);
2713

2714 2715 2716 2717 2718 2719 2720 2721 2722
				reclaim_state->reclaimed_slab = 0;
				nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
				sc.nr_reclaimed += reclaim_state->reclaimed_slab;
				total_scanned += sc.nr_scanned;

				if (nr_slab == 0 && !zone_reclaimable(zone))
					zone->all_unreclaimable = 1;
			}

L
Linus Torvalds 已提交
2723 2724 2725 2726 2727 2728
			/*
			 * If we've done a decent amount of scanning and
			 * the reclaim ratio is low, start doing writepage
			 * even in laptop mode
			 */
			if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2729
			    total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
L
Linus Torvalds 已提交
2730
				sc.may_writepage = 1;
2731

2732 2733 2734
			if (zone->all_unreclaimable) {
				if (end_zone && end_zone == i)
					end_zone--;
2735
				continue;
2736
			}
2737

2738
			if (!zone_watermark_ok_safe(zone, order,
2739 2740 2741 2742 2743 2744 2745
					high_wmark_pages(zone), end_zone, 0)) {
				all_zones_ok = 0;
				/*
				 * We are still under min water mark.  This
				 * means that we have a GFP_ATOMIC allocation
				 * failure risk. Hurry up!
				 */
2746
				if (!zone_watermark_ok_safe(zone, order,
2747 2748
					    min_wmark_pages(zone), end_zone, 0))
					has_under_min_watermark_zone = 1;
2749 2750 2751 2752 2753 2754 2755 2756 2757
			} else {
				/*
				 * 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,
				 * spectulatively avoid congestion waits
				 */
				zone_clear_flag(zone, ZONE_CONGESTED);
2758
				if (i <= *classzone_idx)
2759
					balanced += zone->present_pages;
2760
			}
2761

L
Linus Torvalds 已提交
2762
		}
2763
		if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
L
Linus Torvalds 已提交
2764 2765 2766 2767 2768
			break;		/* kswapd: all done */
		/*
		 * OK, kswapd is getting into trouble.  Take a nap, then take
		 * another pass across the zones.
		 */
2769 2770 2771 2772 2773 2774
		if (total_scanned && (priority < DEF_PRIORITY - 2)) {
			if (has_under_min_watermark_zone)
				count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
			else
				congestion_wait(BLK_RW_ASYNC, HZ/10);
		}
L
Linus Torvalds 已提交
2775 2776 2777 2778 2779 2780 2781

		/*
		 * We do this so kswapd doesn't build up large priorities for
		 * example when it is freeing in parallel with allocators. It
		 * matches the direct reclaim path behaviour in terms of impact
		 * on zone->*_priority.
		 */
2782
		if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
L
Linus Torvalds 已提交
2783 2784 2785
			break;
	}
out:
2786 2787 2788

	/*
	 * order-0: All zones must meet high watermark for a balanced node
2789 2790
	 * high-order: Balanced zones must make up at least 25% of the node
	 *             for the node to be balanced
2791
	 */
2792
	if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
L
Linus Torvalds 已提交
2793
		cond_resched();
2794 2795 2796

		try_to_freeze();

2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813
		/*
		 * Fragmentation may mean that the system cannot be
		 * rebalanced for high-order allocations in all zones.
		 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
		 * it means the zones have been fully scanned and are still
		 * not balanced. For high-order allocations, there is
		 * little point trying all over again as kswapd may
		 * infinite loop.
		 *
		 * Instead, recheck all watermarks at order-0 as they
		 * are the most important. If watermarks are ok, kswapd will go
		 * back to sleep. High-order users can still perform direct
		 * reclaim if they wish.
		 */
		if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
			order = sc.order = 0;

L
Linus Torvalds 已提交
2814 2815 2816
		goto loop_again;
	}

2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843
	/*
	 * If kswapd was reclaiming at a higher order, it has the option of
	 * sleeping without all zones being balanced. Before it does, it must
	 * ensure that the watermarks for order-0 on *all* zones are met and
	 * that the congestion flags are cleared. The congestion flag must
	 * be cleared as kswapd is the only mechanism that clears the flag
	 * and it is potentially going to sleep here.
	 */
	if (order) {
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

			if (!populated_zone(zone))
				continue;

			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
				continue;

			/* Confirm the zone is balanced for order-0 */
			if (!zone_watermark_ok(zone, 0,
					high_wmark_pages(zone), 0, 0)) {
				order = sc.order = 0;
				goto loop_again;
			}

			/* If balanced, clear the congested flag */
			zone_clear_flag(zone, ZONE_CONGESTED);
2844 2845
			if (i <= *classzone_idx)
				balanced += zone->present_pages;
2846 2847 2848
		}
	}

2849 2850 2851 2852 2853 2854
	/*
	 * Return the order we were reclaiming at so sleeping_prematurely()
	 * 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
	 */
2855
	*classzone_idx = end_zone;
2856
	return order;
L
Linus Torvalds 已提交
2857 2858
}

2859
static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2860 2861 2862 2863 2864 2865 2866 2867 2868 2869
{
	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 */
2870
	if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2871 2872 2873 2874 2875 2876 2877 2878 2879
		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.
	 */
2880
	if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902
		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);
		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);
}

L
Linus Torvalds 已提交
2903 2904
/*
 * The background pageout daemon, started as a kernel thread
2905
 * from the init process.
L
Linus Torvalds 已提交
2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917
 *
 * 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)
{
2918
	unsigned long order, new_order;
2919
	unsigned balanced_order;
2920
	int classzone_idx, new_classzone_idx;
2921
	int balanced_classzone_idx;
L
Linus Torvalds 已提交
2922 2923
	pg_data_t *pgdat = (pg_data_t*)p;
	struct task_struct *tsk = current;
2924

L
Linus Torvalds 已提交
2925 2926 2927
	struct reclaim_state reclaim_state = {
		.reclaimed_slab = 0,
	};
2928
	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
L
Linus Torvalds 已提交
2929

2930 2931
	lockdep_set_current_reclaim_state(GFP_KERNEL);

R
Rusty Russell 已提交
2932
	if (!cpumask_empty(cpumask))
2933
		set_cpus_allowed_ptr(tsk, cpumask);
L
Linus Torvalds 已提交
2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947
	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).
	 */
2948
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2949
	set_freezable();
L
Linus Torvalds 已提交
2950

2951
	order = new_order = 0;
2952
	balanced_order = 0;
2953
	classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
2954
	balanced_classzone_idx = classzone_idx;
L
Linus Torvalds 已提交
2955
	for ( ; ; ) {
2956
		int ret;
2957

2958 2959 2960 2961 2962
		/*
		 * 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
		 */
2963 2964
		if (balanced_classzone_idx >= new_classzone_idx &&
					balanced_order == new_order) {
2965 2966 2967 2968 2969 2970
			new_order = pgdat->kswapd_max_order;
			new_classzone_idx = pgdat->classzone_idx;
			pgdat->kswapd_max_order =  0;
			pgdat->classzone_idx = pgdat->nr_zones - 1;
		}

2971
		if (order < new_order || classzone_idx > new_classzone_idx) {
L
Linus Torvalds 已提交
2972 2973
			/*
			 * Don't sleep if someone wants a larger 'order'
2974
			 * allocation or has tigher zone constraints
L
Linus Torvalds 已提交
2975 2976
			 */
			order = new_order;
2977
			classzone_idx = new_classzone_idx;
L
Linus Torvalds 已提交
2978
		} else {
2979 2980
			kswapd_try_to_sleep(pgdat, balanced_order,
						balanced_classzone_idx);
L
Linus Torvalds 已提交
2981
			order = pgdat->kswapd_max_order;
2982
			classzone_idx = pgdat->classzone_idx;
2983 2984
			new_order = order;
			new_classzone_idx = classzone_idx;
2985
			pgdat->kswapd_max_order = 0;
2986
			pgdat->classzone_idx = pgdat->nr_zones - 1;
L
Linus Torvalds 已提交
2987 2988
		}

2989 2990 2991 2992 2993 2994 2995 2996
		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
		 */
2997 2998
		if (!ret) {
			trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2999 3000 3001
			balanced_classzone_idx = classzone_idx;
			balanced_order = balance_pgdat(pgdat, order,
						&balanced_classzone_idx);
3002
		}
L
Linus Torvalds 已提交
3003 3004 3005 3006 3007 3008 3009
	}
	return 0;
}

/*
 * A zone is low on free memory, so wake its kswapd task to service it.
 */
3010
void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
L
Linus Torvalds 已提交
3011 3012 3013
{
	pg_data_t *pgdat;

3014
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
3015 3016
		return;

3017
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
3018
		return;
3019
	pgdat = zone->zone_pgdat;
3020
	if (pgdat->kswapd_max_order < order) {
L
Linus Torvalds 已提交
3021
		pgdat->kswapd_max_order = order;
3022 3023
		pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
	}
3024
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
3025
		return;
3026 3027 3028 3029
	if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
		return;

	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
3030
	wake_up_interruptible(&pgdat->kswapd_wait);
L
Linus Torvalds 已提交
3031 3032
}

3033 3034 3035 3036 3037 3038 3039 3040
/*
 * 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)
3041
{
3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065
	int nr;

	nr = global_page_state(NR_ACTIVE_FILE) +
	     global_page_state(NR_INACTIVE_FILE);

	if (nr_swap_pages > 0)
		nr += global_page_state(NR_ACTIVE_ANON) +
		      global_page_state(NR_INACTIVE_ANON);

	return nr;
}

unsigned long zone_reclaimable_pages(struct zone *zone)
{
	int nr;

	nr = zone_page_state(zone, NR_ACTIVE_FILE) +
	     zone_page_state(zone, NR_INACTIVE_FILE);

	if (nr_swap_pages > 0)
		nr += zone_page_state(zone, NR_ACTIVE_ANON) +
		      zone_page_state(zone, NR_INACTIVE_ANON);

	return nr;
3066 3067
}

3068
#ifdef CONFIG_HIBERNATION
L
Linus Torvalds 已提交
3069
/*
3070
 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3071 3072 3073 3074 3075
 * 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
L
Linus Torvalds 已提交
3076
 */
3077
unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
L
Linus Torvalds 已提交
3078
{
3079 3080
	struct reclaim_state reclaim_state;
	struct scan_control sc = {
3081 3082 3083
		.gfp_mask = GFP_HIGHUSER_MOVABLE,
		.may_swap = 1,
		.may_unmap = 1,
3084
		.may_writepage = 1,
3085 3086 3087
		.nr_to_reclaim = nr_to_reclaim,
		.hibernation_mode = 1,
		.order = 0,
L
Linus Torvalds 已提交
3088
	};
3089 3090 3091 3092
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
3093 3094
	struct task_struct *p = current;
	unsigned long nr_reclaimed;
L
Linus Torvalds 已提交
3095

3096 3097 3098 3099
	p->flags |= PF_MEMALLOC;
	lockdep_set_current_reclaim_state(sc.gfp_mask);
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
3100

3101
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
3102

3103 3104 3105
	p->reclaim_state = NULL;
	lockdep_clear_current_reclaim_state();
	p->flags &= ~PF_MEMALLOC;
3106

3107
	return nr_reclaimed;
L
Linus Torvalds 已提交
3108
}
3109
#endif /* CONFIG_HIBERNATION */
L
Linus Torvalds 已提交
3110 3111 3112 3113 3114

/* 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. */
3115
static int __devinit cpu_callback(struct notifier_block *nfb,
3116
				  unsigned long action, void *hcpu)
L
Linus Torvalds 已提交
3117
{
3118
	int nid;
L
Linus Torvalds 已提交
3119

3120
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
3121
		for_each_node_state(nid, N_HIGH_MEMORY) {
3122
			pg_data_t *pgdat = NODE_DATA(nid);
3123 3124 3125
			const struct cpumask *mask;

			mask = cpumask_of_node(pgdat->node_id);
3126

3127
			if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
3128
				/* One of our CPUs online: restore mask */
3129
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
3130 3131 3132 3133 3134
		}
	}
	return NOTIFY_OK;
}

3135 3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156
/*
 * 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);
		printk("Failed to start kswapd on node %d\n",nid);
		ret = -1;
	}
	return ret;
}

3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167
/*
 * Called by memory hotplug when all memory in a node is offlined.
 */
void kswapd_stop(int nid)
{
	struct task_struct *kswapd = NODE_DATA(nid)->kswapd;

	if (kswapd)
		kthread_stop(kswapd);
}

L
Linus Torvalds 已提交
3168 3169
static int __init kswapd_init(void)
{
3170
	int nid;
3171

L
Linus Torvalds 已提交
3172
	swap_setup();
3173
	for_each_node_state(nid, N_HIGH_MEMORY)
3174
 		kswapd_run(nid);
L
Linus Torvalds 已提交
3175 3176 3177 3178 3179
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
3180 3181 3182 3183 3184 3185 3186 3187 3188 3189

#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;

3190
#define RECLAIM_OFF 0
3191
#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
3192 3193 3194
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

3195 3196 3197 3198 3199 3200 3201
/*
 * 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

3202 3203 3204 3205 3206 3207
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

3208 3209 3210 3211 3212 3213
/*
 * 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;

3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255
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;
}

3256 3257 3258
/*
 * Try to free up some pages from this zone through reclaim.
 */
3259
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3260
{
3261
	/* Minimum pages needed in order to stay on node */
3262
	const unsigned long nr_pages = 1 << order;
3263 3264
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
3265
	int priority;
3266 3267
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3268
		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3269
		.may_swap = 1,
3270 3271
		.nr_to_reclaim = max_t(unsigned long, nr_pages,
				       SWAP_CLUSTER_MAX),
3272
		.gfp_mask = gfp_mask,
3273
		.order = order,
3274
	};
3275 3276 3277
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
3278
	unsigned long nr_slab_pages0, nr_slab_pages1;
3279 3280

	cond_resched();
3281 3282 3283 3284 3285 3286
	/*
	 * 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;
3287
	lockdep_set_current_reclaim_state(gfp_mask);
3288 3289
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
3290

3291
	if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3292 3293 3294 3295 3296 3297
		/*
		 * Free memory by calling shrink zone with increasing
		 * priorities until we have enough memory freed.
		 */
		priority = ZONE_RECLAIM_PRIORITY;
		do {
3298
			shrink_zone(priority, zone, &sc);
3299
			priority--;
3300
		} while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3301
	}
3302

3303 3304
	nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (nr_slab_pages0 > zone->min_slab_pages) {
3305
		/*
3306
		 * shrink_slab() does not currently allow us to determine how
3307 3308 3309 3310
		 * 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.
3311
		 *
3312 3313
		 * Note that shrink_slab will free memory on all zones and may
		 * take a long time.
3314
		 */
3315 3316 3317 3318
		for (;;) {
			unsigned long lru_pages = zone_reclaimable_pages(zone);

			/* No reclaimable slab or very low memory pressure */
3319
			if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3320 3321 3322 3323 3324 3325 3326 3327
				break;

			/* Freed enough memory */
			nr_slab_pages1 = zone_page_state(zone,
							NR_SLAB_RECLAIMABLE);
			if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
				break;
		}
3328 3329 3330 3331 3332

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
3333 3334 3335
		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;
3336 3337
	}

3338
	p->reclaim_state = NULL;
3339
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3340
	lockdep_clear_current_reclaim_state();
3341
	return sc.nr_reclaimed >= nr_pages;
3342
}
3343 3344 3345 3346

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
3347
	int ret;
3348 3349

	/*
3350 3351
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
3352
	 *
3353 3354 3355 3356 3357
	 * 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.
3358
	 */
3359 3360
	if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
	    zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3361
		return ZONE_RECLAIM_FULL;
3362

3363
	if (zone->all_unreclaimable)
3364
		return ZONE_RECLAIM_FULL;
3365

3366
	/*
3367
	 * Do not scan if the allocation should not be delayed.
3368
	 */
3369
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3370
		return ZONE_RECLAIM_NOSCAN;
3371 3372 3373 3374 3375 3376 3377

	/*
	 * 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.
	 */
3378
	node_id = zone_to_nid(zone);
3379
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3380
		return ZONE_RECLAIM_NOSCAN;
3381 3382

	if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3383 3384
		return ZONE_RECLAIM_NOSCAN;

3385 3386 3387
	ret = __zone_reclaim(zone, gfp_mask, order);
	zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);

3388 3389 3390
	if (!ret)
		count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);

3391
	return ret;
3392
}
3393
#endif
L
Lee Schermerhorn 已提交
3394 3395 3396 3397 3398 3399 3400

/*
 * page_evictable - test whether a page is evictable
 * @page: the page to test
 * @vma: the VMA in which the page is or will be mapped, may be NULL
 *
 * Test whether page is evictable--i.e., should be placed on active/inactive
N
Nick Piggin 已提交
3401 3402
 * lists vs unevictable list.  The vma argument is !NULL when called from the
 * fault path to determine how to instantate a new page.
L
Lee Schermerhorn 已提交
3403 3404
 *
 * Reasons page might not be evictable:
3405
 * (1) page's mapping marked unevictable
N
Nick Piggin 已提交
3406
 * (2) page is part of an mlocked VMA
3407
 *
L
Lee Schermerhorn 已提交
3408 3409 3410 3411
 */
int page_evictable(struct page *page, struct vm_area_struct *vma)
{

3412 3413 3414
	if (mapping_unevictable(page_mapping(page)))
		return 0;

N
Nick Piggin 已提交
3415 3416
	if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
		return 0;
L
Lee Schermerhorn 已提交
3417 3418 3419

	return 1;
}
3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433

/**
 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
 * @page: page to check evictability and move to appropriate lru list
 * @zone: zone page is in
 *
 * Checks a page for evictability and moves the page to the appropriate
 * zone lru list.
 *
 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
 * have PageUnevictable set.
 */
static void check_move_unevictable_page(struct page *page, struct zone *zone)
{
3434
	struct lruvec *lruvec;
3435

3436
	VM_BUG_ON(PageActive(page));
3437 3438 3439
retry:
	ClearPageUnevictable(page);
	if (page_evictable(page, NULL)) {
3440
		enum lru_list l = page_lru_base_type(page);
3441

3442
		__dec_zone_state(zone, NR_UNEVICTABLE);
3443 3444 3445
		lruvec = mem_cgroup_lru_move_lists(zone, page,
						   LRU_UNEVICTABLE, l);
		list_move(&page->lru, &lruvec->lists[l]);
3446 3447 3448 3449 3450 3451 3452
		__inc_zone_state(zone, NR_INACTIVE_ANON + l);
		__count_vm_event(UNEVICTABLE_PGRESCUED);
	} else {
		/*
		 * rotate unevictable list
		 */
		SetPageUnevictable(page);
3453 3454 3455
		lruvec = mem_cgroup_lru_move_lists(zone, page, LRU_UNEVICTABLE,
						   LRU_UNEVICTABLE);
		list_move(&page->lru, &lruvec->lists[LRU_UNEVICTABLE]);
3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514
		if (page_evictable(page, NULL))
			goto retry;
	}
}

/**
 * scan_mapping_unevictable_pages - scan an address space for evictable pages
 * @mapping: struct address_space to scan for evictable pages
 *
 * Scan all pages in mapping.  Check unevictable pages for
 * evictability and move them to the appropriate zone lru list.
 */
void scan_mapping_unevictable_pages(struct address_space *mapping)
{
	pgoff_t next = 0;
	pgoff_t end   = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
			 PAGE_CACHE_SHIFT;
	struct zone *zone;
	struct pagevec pvec;

	if (mapping->nrpages == 0)
		return;

	pagevec_init(&pvec, 0);
	while (next < end &&
		pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
		int i;
		int pg_scanned = 0;

		zone = NULL;

		for (i = 0; i < pagevec_count(&pvec); i++) {
			struct page *page = pvec.pages[i];
			pgoff_t page_index = page->index;
			struct zone *pagezone = page_zone(page);

			pg_scanned++;
			if (page_index > next)
				next = page_index;
			next++;

			if (pagezone != zone) {
				if (zone)
					spin_unlock_irq(&zone->lru_lock);
				zone = pagezone;
				spin_lock_irq(&zone->lru_lock);
			}

			if (PageLRU(page) && PageUnevictable(page))
				check_move_unevictable_page(page, zone);
		}
		if (zone)
			spin_unlock_irq(&zone->lru_lock);
		pagevec_release(&pvec);

		count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
	}

}
3515

3516
static void warn_scan_unevictable_pages(void)
3517
{
3518
	printk_once(KERN_WARNING
3519
		    "%s: The scan_unevictable_pages sysctl/node-interface has been "
3520
		    "disabled for lack of a legitimate use case.  If you have "
3521 3522
		    "one, please send an email to linux-mm@kvack.org.\n",
		    current->comm);
3523 3524 3525 3526 3527 3528 3529 3530 3531
}

/*
 * 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,
3532
			   void __user *buffer,
3533 3534
			   size_t *length, loff_t *ppos)
{
3535
	warn_scan_unevictable_pages();
3536
	proc_doulongvec_minmax(table, write, buffer, length, ppos);
3537 3538 3539 3540
	scan_unevictable_pages = 0;
	return 0;
}

3541
#ifdef CONFIG_NUMA
3542 3543 3544 3545 3546
/*
 * per node 'scan_unevictable_pages' attribute.  On demand re-scan of
 * a specified node's per zone unevictable lists for evictable pages.
 */

3547 3548
static ssize_t read_scan_unevictable_node(struct device *dev,
					  struct device_attribute *attr,
3549 3550
					  char *buf)
{
3551
	warn_scan_unevictable_pages();
3552 3553 3554
	return sprintf(buf, "0\n");	/* always zero; should fit... */
}

3555 3556
static ssize_t write_scan_unevictable_node(struct device *dev,
					   struct device_attribute *attr,
3557 3558
					const char *buf, size_t count)
{
3559
	warn_scan_unevictable_pages();
3560 3561 3562 3563
	return 1;
}


3564
static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3565 3566 3567 3568 3569
			read_scan_unevictable_node,
			write_scan_unevictable_node);

int scan_unevictable_register_node(struct node *node)
{
3570
	return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages);
3571 3572 3573 3574
}

void scan_unevictable_unregister_node(struct node *node)
{
3575
	device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages);
3576
}
3577
#endif