vmscan.c 92.4 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 <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 swappiness;
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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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	/* Which cgroup do we reclaim from */
	struct mem_cgroup *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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};

#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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#define scanning_global_lru(sc)	(!(sc)->mem_cgroup)
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#else
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#define scanning_global_lru(sc)	(1)
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#endif

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static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
						  struct scan_control *sc)
{
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	if (!scanning_global_lru(sc))
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		return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);

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	return &zone->reclaim_stat;
}

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static unsigned long zone_nr_lru_pages(struct zone *zone,
				struct scan_control *sc, enum lru_list lru)
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{
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	if (!scanning_global_lru(sc))
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		return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);

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	return zone_page_state(zone, NR_LRU_BASE + lru);
}


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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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	shrinker->nr = 0;
	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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#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(unsigned long scanned, gfp_t gfp_mask,
			unsigned long lru_pages)
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{
	struct shrinker *shrinker;
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	unsigned long ret = 0;
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	if (scanned == 0)
		scanned = SWAP_CLUSTER_MAX;

	if (!down_read_trylock(&shrinker_rwsem))
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		return 1;	/* Assume we'll be able to shrink next time */
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	list_for_each_entry(shrinker, &shrinker_list, list) {
		unsigned long long delta;
		unsigned long total_scan;
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		unsigned long max_pass;
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		max_pass = (*shrinker->shrink)(shrinker, 0, gfp_mask);
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		delta = (4 * scanned) / shrinker->seeks;
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		delta *= max_pass;
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		do_div(delta, lru_pages + 1);
		shrinker->nr += delta;
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		if (shrinker->nr < 0) {
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			printk(KERN_ERR "shrink_slab: %pF negative objects to "
			       "delete nr=%ld\n",
			       shrinker->shrink, shrinker->nr);
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			shrinker->nr = max_pass;
		}

		/*
		 * Avoid risking looping forever due to too large nr value:
		 * never try to free more than twice the estimate number of
		 * freeable entries.
		 */
		if (shrinker->nr > max_pass * 2)
			shrinker->nr = max_pass * 2;
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		total_scan = shrinker->nr;
		shrinker->nr = 0;

		while (total_scan >= SHRINK_BATCH) {
			long this_scan = SHRINK_BATCH;
			int shrink_ret;
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			int nr_before;
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			nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask);
			shrink_ret = (*shrinker->shrink)(shrinker, this_scan,
								gfp_mask);
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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, this_scan);
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			total_scan -= this_scan;

			cond_resched();
		}

		shrinker->nr += total_scan;
	}
	up_read(&shrinker_rwsem);
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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.
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	 */
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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)
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{
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	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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{
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	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,
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			 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.
	 *
393
	 * 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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		/*
		 * Wait on writeback if requested to. This happens when
		 * direct reclaiming a large contiguous area and the
		 * first attempt to free a range of pages fails.
		 */
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		if (PageWriteback(page) &&
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		    (sc->reclaim_mode & RECLAIM_MODE_SYNC))
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			wait_on_page_writeback(page);

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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.
467
 */
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static int __remove_mapping(struct address_space *mapping, struct page *page)
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{
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	BUG_ON(!PageLocked(page));
	BUG_ON(mapping != page_mapping(page));
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	spin_lock_irq(&mapping->tree_lock);
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	/*
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	 * The non racy check for a busy page.
	 *
	 * 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.
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	 */
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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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	}
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	if (PageSwapCache(page)) {
		swp_entry_t swap = { .val = page_private(page) };
		__delete_from_swap_cache(page);
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		spin_unlock_irq(&mapping->tree_lock);
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		swapcache_free(swap, page);
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	} else {
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		void (*freepage)(struct page *);

		freepage = mapping->a_ops->freepage;

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		__delete_from_page_cache(page);
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		spin_unlock_irq(&mapping->tree_lock);
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		mem_cgroup_uncharge_cache_page(page);
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		if (freepage != NULL)
			freepage(page);
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	}

	return 1;

cannot_free:
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	spin_unlock_irq(&mapping->tree_lock);
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	return 0;
}

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/*
 * 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;
}

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/**
 * 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);
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	int was_unevictable = PageUnevictable(page);
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	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.
		 */
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		lru = active + page_lru_base_type(page);
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580 581 582 583 584 585 586 587
		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);
588 589 590 591 592 593 594 595 596 597
		/*
		 * When racing with an mlock clearing (page is
		 * unlocked), make sure that if the other thread does
		 * not observe our setting of PG_lru and fails
		 * isolation, we see PG_mlocked cleared below and move
		 * the page back to the evictable list.
		 *
		 * The other side is TestClearPageMlocked().
		 */
		smp_mb();
L
Lee Schermerhorn 已提交
598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615
	}

	/*
	 * 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.
		 */
	}

616 617 618 619 620
	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
621 622 623
	put_page(page);		/* drop ref from isolate */
}

624 625 626
enum page_references {
	PAGEREF_RECLAIM,
	PAGEREF_RECLAIM_CLEAN,
627
	PAGEREF_KEEP,
628 629 630 631 632 633
	PAGEREF_ACTIVATE,
};

static enum page_references page_check_references(struct page *page,
						  struct scan_control *sc)
{
634
	int referenced_ptes, referenced_page;
635 636
	unsigned long vm_flags;

637 638
	referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
	referenced_page = TestClearPageReferenced(page);
639 640

	/* Lumpy reclaim - ignore references */
641
	if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
642 643 644 645 646 647 648 649 650
		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;

651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674
	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);

		if (referenced_page)
			return PAGEREF_ACTIVATE;

		return PAGEREF_KEEP;
	}
675 676

	/* Reclaim if clean, defer dirty pages to writeback */
677
	if (referenced_page && !PageSwapBacked(page))
678 679 680
		return PAGEREF_RECLAIM_CLEAN;

	return PAGEREF_RECLAIM;
681 682
}

683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700
static noinline_for_stack void free_page_list(struct list_head *free_pages)
{
	struct pagevec freed_pvec;
	struct page *page, *tmp;

	pagevec_init(&freed_pvec, 1);

	list_for_each_entry_safe(page, tmp, free_pages, lru) {
		list_del(&page->lru);
		if (!pagevec_add(&freed_pvec, page)) {
			__pagevec_free(&freed_pvec);
			pagevec_reinit(&freed_pvec);
		}
	}

	pagevec_free(&freed_pvec);
}

L
Linus Torvalds 已提交
701
/*
A
Andrew Morton 已提交
702
 * shrink_page_list() returns the number of reclaimed pages
L
Linus Torvalds 已提交
703
 */
A
Andrew Morton 已提交
704
static unsigned long shrink_page_list(struct list_head *page_list,
705
				      struct zone *zone,
706
				      struct scan_control *sc)
L
Linus Torvalds 已提交
707 708
{
	LIST_HEAD(ret_pages);
709
	LIST_HEAD(free_pages);
L
Linus Torvalds 已提交
710
	int pgactivate = 0;
711 712
	unsigned long nr_dirty = 0;
	unsigned long nr_congested = 0;
713
	unsigned long nr_reclaimed = 0;
L
Linus Torvalds 已提交
714 715 716 717

	cond_resched();

	while (!list_empty(page_list)) {
718
		enum page_references references;
L
Linus Torvalds 已提交
719 720 721 722 723 724 725 726 727
		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
728
		if (!trylock_page(page))
L
Linus Torvalds 已提交
729 730
			goto keep;

N
Nick Piggin 已提交
731
		VM_BUG_ON(PageActive(page));
732
		VM_BUG_ON(page_zone(page) != zone);
L
Linus Torvalds 已提交
733 734

		sc->nr_scanned++;
735

N
Nick Piggin 已提交
736 737
		if (unlikely(!page_evictable(page, NULL)))
			goto cull_mlocked;
L
Lee Schermerhorn 已提交
738

739
		if (!sc->may_unmap && page_mapped(page))
740 741
			goto keep_locked;

L
Linus Torvalds 已提交
742 743 744 745
		/* Double the slab pressure for mapped and swapcache pages */
		if (page_mapped(page) || PageSwapCache(page))
			sc->nr_scanned++;

746 747 748 749 750 751 752 753 754 755 756 757
		may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
			(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));

		if (PageWriteback(page)) {
			/*
			 * Synchronous reclaim is performed in two passes,
			 * first an asynchronous pass over the list to
			 * start parallel writeback, and a second synchronous
			 * pass to wait for the IO to complete.  Wait here
			 * for any page for which writeback has already
			 * started.
			 */
758
			if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
759
			    may_enter_fs)
760
				wait_on_page_writeback(page);
761 762 763 764
			else {
				unlock_page(page);
				goto keep_lumpy;
			}
765
		}
L
Linus Torvalds 已提交
766

767 768 769
		references = page_check_references(page, sc);
		switch (references) {
		case PAGEREF_ACTIVATE:
L
Linus Torvalds 已提交
770
			goto activate_locked;
771 772
		case PAGEREF_KEEP:
			goto keep_locked;
773 774 775 776
		case PAGEREF_RECLAIM:
		case PAGEREF_RECLAIM_CLEAN:
			; /* try to reclaim the page below */
		}
L
Linus Torvalds 已提交
777 778 779 780 781

		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
N
Nick Piggin 已提交
782
		if (PageAnon(page) && !PageSwapCache(page)) {
783 784
			if (!(sc->gfp_mask & __GFP_IO))
				goto keep_locked;
785
			if (!add_to_swap(page))
L
Linus Torvalds 已提交
786
				goto activate_locked;
787
			may_enter_fs = 1;
N
Nick Piggin 已提交
788
		}
L
Linus Torvalds 已提交
789 790 791 792 793 794 795 796

		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) {
797
			switch (try_to_unmap(page, TTU_UNMAP)) {
L
Linus Torvalds 已提交
798 799 800 801
			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
N
Nick Piggin 已提交
802 803
			case SWAP_MLOCK:
				goto cull_mlocked;
L
Linus Torvalds 已提交
804 805 806 807 808 809
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
810 811
			nr_dirty++;

812
			if (references == PAGEREF_RECLAIM_CLEAN)
L
Linus Torvalds 已提交
813
				goto keep_locked;
814
			if (!may_enter_fs)
L
Linus Torvalds 已提交
815
				goto keep_locked;
816
			if (!sc->may_writepage)
L
Linus Torvalds 已提交
817 818 819
				goto keep_locked;

			/* Page is dirty, try to write it out here */
820
			switch (pageout(page, mapping, sc)) {
L
Linus Torvalds 已提交
821
			case PAGE_KEEP:
822
				nr_congested++;
L
Linus Torvalds 已提交
823 824 825 826
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
827 828 829
				if (PageWriteback(page))
					goto keep_lumpy;
				if (PageDirty(page))
L
Linus Torvalds 已提交
830
					goto keep;
831

L
Linus Torvalds 已提交
832 833 834 835
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
N
Nick Piggin 已提交
836
				if (!trylock_page(page))
L
Linus Torvalds 已提交
837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855
					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
856
		 * will do this, as well as the blockdev mapping.
L
Linus Torvalds 已提交
857 858 859 860 861 862 863 864 865 866
		 * 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.
		 */
867
		if (page_has_private(page)) {
L
Linus Torvalds 已提交
868 869
			if (!try_to_release_page(page, sc->gfp_mask))
				goto activate_locked;
N
Nick Piggin 已提交
870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885
			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
886 887
		}

N
Nick Piggin 已提交
888
		if (!mapping || !__remove_mapping(mapping, page))
889
			goto keep_locked;
L
Linus Torvalds 已提交
890

N
Nick Piggin 已提交
891 892 893 894 895 896 897 898
		/*
		 * 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
899
free_it:
900
		nr_reclaimed++;
901 902 903 904 905 906

		/*
		 * 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
907 908
		continue;

N
Nick Piggin 已提交
909
cull_mlocked:
910 911
		if (PageSwapCache(page))
			try_to_free_swap(page);
N
Nick Piggin 已提交
912 913
		unlock_page(page);
		putback_lru_page(page);
914
		reset_reclaim_mode(sc);
N
Nick Piggin 已提交
915 916
		continue;

L
Linus Torvalds 已提交
917
activate_locked:
918 919
		/* Not a candidate for swapping, so reclaim swap space. */
		if (PageSwapCache(page) && vm_swap_full())
920
			try_to_free_swap(page);
L
Lee Schermerhorn 已提交
921
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
922 923 924 925 926
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
927
		reset_reclaim_mode(sc);
928
keep_lumpy:
L
Linus Torvalds 已提交
929
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
930
		VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
L
Linus Torvalds 已提交
931
	}
932

933 934 935 936 937 938
	/*
	 * 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
	 */
939
	if (nr_dirty == nr_congested && nr_dirty != 0)
940 941
		zone_set_flag(zone, ZONE_CONGESTED);

942 943
	free_page_list(&free_pages);

L
Linus Torvalds 已提交
944
	list_splice(&ret_pages, page_list);
945
	count_vm_events(PGACTIVATE, pgactivate);
946
	return nr_reclaimed;
L
Linus Torvalds 已提交
947 948
}

A
Andy Whitcroft 已提交
949 950 951 952 953 954 955 956 957 958
/*
 * 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.
 */
959
int __isolate_lru_page(struct page *page, int mode, int file)
A
Andy Whitcroft 已提交
960 961 962 963 964 965 966 967 968 969 970 971 972 973 974
{
	int ret = -EINVAL;

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

	/*
	 * When checking the active state, we need to be sure we are
	 * dealing with comparible boolean values.  Take the logical not
	 * of each.
	 */
	if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
		return ret;

975
	if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
976 977
		return ret;

L
Lee Schermerhorn 已提交
978 979 980 981 982 983 984 985
	/*
	 * 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
986
	ret = -EBUSY;
K
KAMEZAWA Hiroyuki 已提交
987

A
Andy Whitcroft 已提交
988 989 990 991 992 993 994 995 996 997 998 999 1000
	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
1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014
/*
 * 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
1015 1016
 * @order:	The caller's attempted allocation order
 * @mode:	One of the LRU isolation modes
1017
 * @file:	True [1] if isolating file [!anon] pages
L
Linus Torvalds 已提交
1018 1019 1020
 *
 * returns how many pages were moved onto *@dst.
 */
1021 1022
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
		struct list_head *src, struct list_head *dst,
1023
		unsigned long *scanned, int order, int mode, int file)
L
Linus Torvalds 已提交
1024
{
1025
	unsigned long nr_taken = 0;
1026 1027 1028
	unsigned long nr_lumpy_taken = 0;
	unsigned long nr_lumpy_dirty = 0;
	unsigned long nr_lumpy_failed = 0;
1029
	unsigned long scan;
L
Linus Torvalds 已提交
1030

1031
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
1032 1033 1034 1035 1036 1037
		struct page *page;
		unsigned long pfn;
		unsigned long end_pfn;
		unsigned long page_pfn;
		int zone_id;

L
Linus Torvalds 已提交
1038 1039 1040
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
1041
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
1042

1043
		switch (__isolate_lru_page(page, mode, file)) {
A
Andy Whitcroft 已提交
1044 1045
		case 0:
			list_move(&page->lru, dst);
1046
			mem_cgroup_del_lru(page);
1047
			nr_taken += hpage_nr_pages(page);
A
Andy Whitcroft 已提交
1048 1049 1050 1051 1052
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
1053
			mem_cgroup_rotate_lru_list(page, page_lru(page));
A
Andy Whitcroft 已提交
1054
			continue;
1055

A
Andy Whitcroft 已提交
1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067
		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
1068
		 * as the mem_map is guaranteed valid out to MAX_ORDER,
A
Andy Whitcroft 已提交
1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087
		 * 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);
1088

A
Andy Whitcroft 已提交
1089 1090
			/* Check that we have not crossed a zone boundary. */
			if (unlikely(page_zone_id(cursor_page) != zone_id))
1091
				break;
1092 1093 1094 1095 1096 1097 1098

			/*
			 * If we don't have enough swap space, reclaiming of
			 * anon page which don't already have a swap slot is
			 * pointless.
			 */
			if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
1099 1100
			    !PageSwapCache(cursor_page))
				break;
1101

1102
			if (__isolate_lru_page(cursor_page, mode, file) == 0) {
A
Andy Whitcroft 已提交
1103
				list_move(&cursor_page->lru, dst);
1104
				mem_cgroup_del_lru(cursor_page);
1105
				nr_taken += hpage_nr_pages(page);
1106 1107 1108
				nr_lumpy_taken++;
				if (PageDirty(cursor_page))
					nr_lumpy_dirty++;
A
Andy Whitcroft 已提交
1109
				scan++;
1110
			} else {
1111 1112 1113 1114
				/* the page is freed already. */
				if (!page_count(cursor_page))
					continue;
				break;
A
Andy Whitcroft 已提交
1115 1116
			}
		}
1117 1118 1119 1120

		/* If we break out of the loop above, lumpy reclaim failed */
		if (pfn < end_pfn)
			nr_lumpy_failed++;
L
Linus Torvalds 已提交
1121 1122 1123
	}

	*scanned = scan;
1124 1125 1126 1127 1128 1129

	trace_mm_vmscan_lru_isolate(order,
			nr_to_scan, scan,
			nr_taken,
			nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
			mode);
L
Linus Torvalds 已提交
1130 1131 1132
	return nr_taken;
}

1133 1134 1135 1136
static unsigned long isolate_pages_global(unsigned long nr,
					struct list_head *dst,
					unsigned long *scanned, int order,
					int mode, struct zone *z,
1137
					int active, int file)
1138
{
1139
	int lru = LRU_BASE;
1140
	if (active)
1141 1142 1143 1144
		lru += LRU_ACTIVE;
	if (file)
		lru += LRU_FILE;
	return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1145
								mode, file);
1146 1147
}

A
Andy Whitcroft 已提交
1148 1149 1150 1151
/*
 * clear_active_flags() is a helper for shrink_active_list(), clearing
 * any active bits from the pages in the list.
 */
1152 1153
static unsigned long clear_active_flags(struct list_head *page_list,
					unsigned int *count)
A
Andy Whitcroft 已提交
1154 1155
{
	int nr_active = 0;
1156
	int lru;
A
Andy Whitcroft 已提交
1157 1158
	struct page *page;

1159
	list_for_each_entry(page, page_list, lru) {
1160
		int numpages = hpage_nr_pages(page);
1161
		lru = page_lru_base_type(page);
A
Andy Whitcroft 已提交
1162
		if (PageActive(page)) {
1163
			lru += LRU_ACTIVE;
A
Andy Whitcroft 已提交
1164
			ClearPageActive(page);
1165
			nr_active += numpages;
A
Andy Whitcroft 已提交
1166
		}
1167
		if (count)
1168
			count[lru] += numpages;
1169
	}
A
Andy Whitcroft 已提交
1170 1171 1172 1173

	return nr_active;
}

1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184
/**
 * 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
1185 1186 1187
 * 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.
1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207
 *
 * 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;

	if (PageLRU(page)) {
		struct zone *zone = page_zone(page);

		spin_lock_irq(&zone->lru_lock);
		if (PageLRU(page) && get_page_unless_zero(page)) {
L
Lee Schermerhorn 已提交
1208
			int lru = page_lru(page);
1209 1210
			ret = 0;
			ClearPageLRU(page);
1211 1212

			del_page_from_lru_list(zone, page, lru);
1213 1214 1215 1216 1217 1218
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243
/*
 * 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;

	if (!scanning_global_lru(sc))
		return 0;

	if (file) {
		inactive = zone_page_state(zone, NR_INACTIVE_FILE);
		isolated = zone_page_state(zone, NR_ISOLATED_FILE);
	} else {
		inactive = zone_page_state(zone, NR_INACTIVE_ANON);
		isolated = zone_page_state(zone, NR_ISOLATED_ANON);
	}

	return isolated > inactive;
}

1244 1245 1246 1247
/*
 * TODO: Try merging with migrations version of putback_lru_pages
 */
static noinline_for_stack void
1248
putback_lru_pages(struct zone *zone, struct scan_control *sc,
1249 1250 1251 1252 1253
				unsigned long nr_anon, unsigned long nr_file,
				struct list_head *page_list)
{
	struct page *page;
	struct pagevec pvec;
1254
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272

	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;
		}
1273
		SetPageLRU(page);
1274
		lru = page_lru(page);
1275
		add_page_to_lru_list(zone, page, lru);
1276 1277
		if (is_active_lru(lru)) {
			int file = is_file_lru(lru);
1278 1279
			int numpages = hpage_nr_pages(page);
			reclaim_stat->recent_rotated[file] += numpages;
1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293
		}
		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);
}

1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324
static noinline_for_stack void update_isolated_counts(struct zone *zone,
					struct scan_control *sc,
					unsigned long *nr_anon,
					unsigned long *nr_file,
					struct list_head *isolated_list)
{
	unsigned long nr_active;
	unsigned int count[NR_LRU_LISTS] = { 0, };
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);

	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;
}

1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344
/*
 * Returns true if the caller should wait to clean dirty/writeback pages.
 *
 * 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 */
1345
	if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365
		return false;

	/* If we have relaimed everything on the isolated list, no stall */
	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
1366
/*
A
Andrew Morton 已提交
1367 1368
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
1369
 */
1370 1371 1372
static noinline_for_stack unsigned long
shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
			struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1373 1374
{
	LIST_HEAD(page_list);
1375
	unsigned long nr_scanned;
1376
	unsigned long nr_reclaimed = 0;
1377 1378 1379
	unsigned long nr_taken;
	unsigned long nr_anon;
	unsigned long nr_file;
1380

1381
	while (unlikely(too_many_isolated(zone, file, sc))) {
1382
		congestion_wait(BLK_RW_ASYNC, HZ/10);
1383 1384 1385 1386 1387 1388

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

1389
	set_reclaim_mode(priority, sc, false);
L
Linus Torvalds 已提交
1390 1391
	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1392

1393 1394 1395
	if (scanning_global_lru(sc)) {
		nr_taken = isolate_pages_global(nr_to_scan,
			&page_list, &nr_scanned, sc->order,
1396
			sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1397
					ISOLATE_BOTH : ISOLATE_INACTIVE,
1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408
			zone, 0, file);
		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);
	} else {
		nr_taken = mem_cgroup_isolate_pages(nr_to_scan,
			&page_list, &nr_scanned, sc->order,
1409
			sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1410
					ISOLATE_BOTH : ISOLATE_INACTIVE,
1411 1412 1413 1414 1415 1416 1417
			zone, sc->mem_cgroup,
			0, file);
		/*
		 * mem_cgroup_isolate_pages() keeps track of
		 * scanned pages on its own.
		 */
	}
1418

1419 1420 1421 1422
	if (nr_taken == 0) {
		spin_unlock_irq(&zone->lru_lock);
		return 0;
	}
A
Andy Whitcroft 已提交
1423

1424
	update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
L
Linus Torvalds 已提交
1425

1426
	spin_unlock_irq(&zone->lru_lock);
1427

1428
	nr_reclaimed = shrink_page_list(&page_list, zone, sc);
1429

1430 1431
	/* Check if we should syncronously wait for writeback */
	if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1432
		set_reclaim_mode(priority, sc, true);
1433
		nr_reclaimed += shrink_page_list(&page_list, zone, sc);
1434
	}
1435

1436 1437 1438 1439
	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
1440

1441
	putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
1442 1443 1444 1445 1446

	trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
		zone_idx(zone),
		nr_scanned, nr_reclaimed,
		priority,
1447
		trace_shrink_flags(file, sc->reclaim_mode));
1448
	return nr_reclaimed;
L
Linus Torvalds 已提交
1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467
}

/*
 * 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.
 */
1468

1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486
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)) {
		page = lru_to_page(list);

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

		list_move(&page->lru, &zone->lru[lru].list);
		mem_cgroup_add_lru_list(page, lru);
1487
		pgmoved += hpage_nr_pages(page);
1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500

		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);
}
1501

A
Andrew Morton 已提交
1502
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1503
			struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1504
{
1505
	unsigned long nr_taken;
1506
	unsigned long pgscanned;
1507
	unsigned long vm_flags;
L
Linus Torvalds 已提交
1508
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
1509
	LIST_HEAD(l_active);
1510
	LIST_HEAD(l_inactive);
L
Linus Torvalds 已提交
1511
	struct page *page;
1512
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1513
	unsigned long nr_rotated = 0;
L
Linus Torvalds 已提交
1514 1515 1516

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1517
	if (scanning_global_lru(sc)) {
1518 1519 1520 1521
		nr_taken = isolate_pages_global(nr_pages, &l_hold,
						&pgscanned, sc->order,
						ISOLATE_ACTIVE, zone,
						1, file);
1522
		zone->pages_scanned += pgscanned;
1523 1524 1525 1526 1527 1528 1529 1530 1531
	} else {
		nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
						&pgscanned, sc->order,
						ISOLATE_ACTIVE, zone,
						sc->mem_cgroup, 1, file);
		/*
		 * mem_cgroup_isolate_pages() keeps track of
		 * scanned pages on its own.
		 */
1532
	}
1533

1534
	reclaim_stat->recent_scanned[file] += nr_taken;
1535

1536
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
1537
	if (file)
1538
		__mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1539
	else
1540
		__mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
K
KOSAKI Motohiro 已提交
1541
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
L
Linus Torvalds 已提交
1542 1543 1544 1545 1546 1547
	spin_unlock_irq(&zone->lru_lock);

	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
1548

L
Lee Schermerhorn 已提交
1549 1550 1551 1552 1553
		if (unlikely(!page_evictable(page, NULL))) {
			putback_lru_page(page);
			continue;
		}

1554
		if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1555
			nr_rotated += hpage_nr_pages(page);
1556 1557 1558 1559 1560 1561 1562 1563 1564
			/*
			 * 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.
			 */
1565
			if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1566 1567 1568 1569
				list_add(&page->lru, &l_active);
				continue;
			}
		}
1570

1571
		ClearPageActive(page);	/* we are de-activating */
L
Linus Torvalds 已提交
1572 1573 1574
		list_add(&page->lru, &l_inactive);
	}

1575
	/*
1576
	 * Move pages back to the lru list.
1577
	 */
1578
	spin_lock_irq(&zone->lru_lock);
1579
	/*
1580 1581 1582 1583
	 * 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.
1584
	 */
1585
	reclaim_stat->recent_rotated[file] += nr_rotated;
1586

1587 1588 1589 1590
	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
1591
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1592
	spin_unlock_irq(&zone->lru_lock);
L
Linus Torvalds 已提交
1593 1594
}

1595
#ifdef CONFIG_SWAP
1596
static int inactive_anon_is_low_global(struct zone *zone)
1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608
{
	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;
}

1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620
/**
 * 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.
 */
static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
{
	int low;

1621 1622 1623 1624 1625 1626 1627
	/*
	 * If we don't have swap space, anonymous page deactivation
	 * is pointless.
	 */
	if (!total_swap_pages)
		return 0;

1628
	if (scanning_global_lru(sc))
1629 1630
		low = inactive_anon_is_low_global(zone);
	else
1631
		low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1632 1633
	return low;
}
1634 1635 1636 1637 1638 1639 1640
#else
static inline int inactive_anon_is_low(struct zone *zone,
					struct scan_control *sc)
{
	return 0;
}
#endif
1641

1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677
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
 * @zone: zone to check
 * @sc:   scan control of this context
 *
 * When the system is doing streaming IO, memory pressure here
 * ensures that active file pages get deactivated, until more
 * than half of the file pages are on the inactive list.
 *
 * Once we get to that situation, protect the system's working
 * set from being evicted by disabling active file page aging.
 *
 * This uses a different ratio than the anonymous pages, because
 * the page cache uses a use-once replacement algorithm.
 */
static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
{
	int low;

	if (scanning_global_lru(sc))
		low = inactive_file_is_low_global(zone);
	else
		low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
	return low;
}

1678 1679 1680 1681 1682 1683 1684 1685 1686
static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
				int file)
{
	if (file)
		return inactive_file_is_low(zone, sc);
	else
		return inactive_anon_is_low(zone, sc);
}

1687
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1688 1689
	struct zone *zone, struct scan_control *sc, int priority)
{
1690 1691
	int file = is_file_lru(lru);

1692 1693 1694
	if (is_active_lru(lru)) {
		if (inactive_list_is_low(zone, sc, file))
		    shrink_active_list(nr_to_scan, zone, sc, priority, file);
1695 1696 1697
		return 0;
	}

R
Rik van Riel 已提交
1698
	return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1699 1700
}

1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720
/*
 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
 * until we collected @swap_cluster_max pages to scan.
 */
static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
				       unsigned long *nr_saved_scan)
{
	unsigned long nr;

	*nr_saved_scan += nr_to_scan;
	nr = *nr_saved_scan;

	if (nr >= SWAP_CLUSTER_MAX)
		*nr_saved_scan = 0;
	else
		nr = 0;

	return nr;
}

1721 1722 1723 1724 1725 1726
/*
 * 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.
 *
1727
 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1728
 */
1729 1730
static void get_scan_count(struct zone *zone, struct scan_control *sc,
					unsigned long *nr, int priority)
1731 1732 1733 1734
{
	unsigned long anon, file, free;
	unsigned long anon_prio, file_prio;
	unsigned long ap, fp;
1735
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747
	u64 fraction[2], denominator;
	enum lru_list l;
	int noswap = 0;

	/* 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;
	}
1748

1749 1750 1751 1752
	anon  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
		zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
	file  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
		zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1753

1754
	if (scanning_global_lru(sc)) {
1755 1756 1757
		free  = zone_page_state(zone, NR_FREE_PAGES);
		/* If we have very few page cache pages,
		   force-scan anon pages. */
1758
		if (unlikely(file + free <= high_wmark_pages(zone))) {
1759 1760 1761 1762
			fraction[0] = 1;
			fraction[1] = 0;
			denominator = 1;
			goto out;
1763
		}
1764 1765
	}

1766 1767 1768 1769 1770 1771 1772
	/*
	 * With swappiness at 100, anonymous and file have the same priority.
	 * This scanning priority is essentially the inverse of IO cost.
	 */
	anon_prio = sc->swappiness;
	file_prio = 200 - sc->swappiness;

1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783
	/*
	 * 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]
	 */
1784
	spin_lock_irq(&zone->lru_lock);
1785 1786 1787
	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
		reclaim_stat->recent_scanned[0] /= 2;
		reclaim_stat->recent_rotated[0] /= 2;
1788 1789
	}

1790 1791 1792
	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
		reclaim_stat->recent_scanned[1] /= 2;
		reclaim_stat->recent_rotated[1] /= 2;
1793 1794 1795
	}

	/*
1796 1797 1798
	 * 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.
1799
	 */
1800 1801
	ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
	ap /= reclaim_stat->recent_rotated[0] + 1;
1802

1803 1804
	fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
	fp /= reclaim_stat->recent_rotated[1] + 1;
1805
	spin_unlock_irq(&zone->lru_lock);
1806

1807 1808 1809 1810 1811 1812 1813
	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;
1814

1815 1816 1817 1818 1819 1820 1821 1822
		scan = zone_nr_lru_pages(zone, sc, l);
		if (priority || noswap) {
			scan >>= priority;
			scan = div64_u64(scan * fraction[file], denominator);
		}
		nr[l] = nr_scan_try_batch(scan,
					  &reclaim_stat->nr_saved_scan[l]);
	}
1823
}
1824

1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840
/*
 * 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
 */
static inline bool should_continue_reclaim(struct zone *zone,
					unsigned long nr_reclaimed,
					unsigned long nr_scanned,
					struct scan_control *sc)
{
	unsigned long pages_for_compaction;
	unsigned long inactive_lru_pages;

	/* If not in reclaim/compaction mode, stop */
1841
	if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1842 1843
		return false;

1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865
	/* 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;
	}
1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887

	/*
	 * If we have not reclaimed enough pages for compaction and the
	 * inactive lists are large enough, continue reclaiming
	 */
	pages_for_compaction = (2UL << sc->order);
	inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) +
				zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
	if (sc->nr_reclaimed < pages_for_compaction &&
			inactive_lru_pages > pages_for_compaction)
		return true;

	/* If compaction would go ahead or the allocation would succeed, stop */
	switch (compaction_suitable(zone, sc->order)) {
	case COMPACT_PARTIAL:
	case COMPACT_CONTINUE:
		return false;
	default:
		return true;
	}
}

L
Linus Torvalds 已提交
1888 1889 1890
/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
1891
static void shrink_zone(int priority, struct zone *zone,
1892
				struct scan_control *sc)
L
Linus Torvalds 已提交
1893
{
1894
	unsigned long nr[NR_LRU_LISTS];
1895
	unsigned long nr_to_scan;
1896
	enum lru_list l;
1897
	unsigned long nr_reclaimed, nr_scanned;
1898
	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1899

1900 1901
restart:
	nr_reclaimed = 0;
1902
	nr_scanned = sc->nr_scanned;
1903
	get_scan_count(zone, sc, nr, priority);
L
Linus Torvalds 已提交
1904

1905 1906
	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
					nr[LRU_INACTIVE_FILE]) {
L
Lee Schermerhorn 已提交
1907
		for_each_evictable_lru(l) {
1908
			if (nr[l]) {
K
KOSAKI Motohiro 已提交
1909 1910
				nr_to_scan = min_t(unsigned long,
						   nr[l], SWAP_CLUSTER_MAX);
1911
				nr[l] -= nr_to_scan;
L
Linus Torvalds 已提交
1912

1913 1914
				nr_reclaimed += shrink_list(l, nr_to_scan,
							    zone, sc, priority);
1915
			}
L
Linus Torvalds 已提交
1916
		}
1917 1918 1919 1920 1921 1922 1923 1924
		/*
		 * 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.
		 */
1925
		if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
1926
			break;
L
Linus Torvalds 已提交
1927
	}
1928
	sc->nr_reclaimed += nr_reclaimed;
1929

1930 1931 1932 1933
	/*
	 * Even if we did not try to evict anon pages at all, we want to
	 * rebalance the anon lru active/inactive ratio.
	 */
1934
	if (inactive_anon_is_low(zone, sc))
1935 1936
		shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);

1937 1938 1939 1940 1941
	/* reclaim/compaction might need reclaim to continue */
	if (should_continue_reclaim(zone, nr_reclaimed,
					sc->nr_scanned - nr_scanned, sc))
		goto restart;

1942
	throttle_vm_writeout(sc->gfp_mask);
L
Linus Torvalds 已提交
1943 1944 1945 1946 1947 1948 1949
}

/*
 * 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.
 *
1950 1951
 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
 * Because:
L
Linus Torvalds 已提交
1952 1953
 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
 *    allocation or
1954 1955 1956
 * 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
1957 1958 1959 1960
 *
 * If a zone is deemed to be full of pinned pages then just give it a light
 * scan then give up on it.
 */
1961
static void shrink_zones(int priority, struct zonelist *zonelist,
1962
					struct scan_control *sc)
L
Linus Torvalds 已提交
1963
{
1964
	struct zoneref *z;
1965
	struct zone *zone;
1966

1967 1968
	for_each_zone_zonelist_nodemask(zone, z, zonelist,
					gfp_zone(sc->gfp_mask), sc->nodemask) {
1969
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
1970
			continue;
1971 1972 1973 1974
		/*
		 * Take care memory controller reclaiming has small influence
		 * to global LRU.
		 */
1975
		if (scanning_global_lru(sc)) {
1976 1977
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
1978
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1979 1980
				continue;	/* Let kswapd poll it */
		}
1981

1982
		shrink_zone(priority, zone, sc);
L
Linus Torvalds 已提交
1983
	}
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
}

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

/*
 * As hibernation is going on, kswapd is freezed so that it can't mark
 * the zone into all_unreclaimable. It can't handle OOM during hibernation.
 * So let's check zone's unreclaimable in direct reclaim as well as kswapd.
 */
static bool all_unreclaimable(struct zonelist *zonelist,
		struct scan_control *sc)
{
	struct zoneref *z;
	struct zone *zone;
	bool all_unreclaimable = true;

	for_each_zone_zonelist_nodemask(zone, z, zonelist,
			gfp_zone(sc->gfp_mask), sc->nodemask) {
		if (!populated_zone(zone))
			continue;
		if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
			continue;
		if (zone_reclaimable(zone)) {
			all_unreclaimable = false;
			break;
		}
	}

2015
	return all_unreclaimable;
L
Linus Torvalds 已提交
2016
}
2017

L
Linus Torvalds 已提交
2018 2019 2020 2021 2022 2023 2024 2025
/*
 * 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
2026 2027 2028 2029
 * 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.
2030 2031 2032
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
2033
 */
2034
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2035
					struct scan_control *sc)
L
Linus Torvalds 已提交
2036 2037
{
	int priority;
2038
	unsigned long total_scanned = 0;
L
Linus Torvalds 已提交
2039
	struct reclaim_state *reclaim_state = current->reclaim_state;
2040
	struct zoneref *z;
2041
	struct zone *zone;
2042
	unsigned long writeback_threshold;
L
Linus Torvalds 已提交
2043

2044
	get_mems_allowed();
2045 2046
	delayacct_freepages_start();

2047
	if (scanning_global_lru(sc))
2048
		count_vm_event(ALLOCSTALL);
L
Linus Torvalds 已提交
2049 2050

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2051
		sc->nr_scanned = 0;
2052 2053
		if (!priority)
			disable_swap_token();
2054
		shrink_zones(priority, zonelist, sc);
2055 2056 2057 2058
		/*
		 * Don't shrink slabs when reclaiming memory from
		 * over limit cgroups
		 */
2059
		if (scanning_global_lru(sc)) {
2060
			unsigned long lru_pages = 0;
2061 2062
			for_each_zone_zonelist(zone, z, zonelist,
					gfp_zone(sc->gfp_mask)) {
2063 2064 2065 2066 2067 2068
				if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
					continue;

				lru_pages += zone_reclaimable_pages(zone);
			}

2069
			shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
2070
			if (reclaim_state) {
2071
				sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2072 2073
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
2074
		}
2075
		total_scanned += sc->nr_scanned;
2076
		if (sc->nr_reclaimed >= sc->nr_to_reclaim)
L
Linus Torvalds 已提交
2077 2078 2079 2080 2081 2082 2083 2084 2085
			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.
		 */
2086 2087
		writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
		if (total_scanned > writeback_threshold) {
2088
			wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
2089
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
2090 2091 2092
		}

		/* Take a nap, wait for some writeback to complete */
2093
		if (!sc->hibernation_mode && sc->nr_scanned &&
2094 2095 2096 2097
		    priority < DEF_PRIORITY - 2) {
			struct zone *preferred_zone;

			first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2098 2099
						&cpuset_current_mems_allowed,
						&preferred_zone);
2100 2101
			wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
		}
L
Linus Torvalds 已提交
2102
	}
2103

L
Linus Torvalds 已提交
2104
out:
2105
	delayacct_freepages_end();
2106
	put_mems_allowed();
2107

2108 2109 2110 2111
	if (sc->nr_reclaimed)
		return sc->nr_reclaimed;

	/* top priority shrink_zones still had more to do? don't OOM, then */
2112
	if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
2113 2114 2115
		return 1;

	return 0;
L
Linus Torvalds 已提交
2116 2117
}

2118
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2119
				gfp_t gfp_mask, nodemask_t *nodemask)
2120
{
2121
	unsigned long nr_reclaimed;
2122 2123 2124
	struct scan_control sc = {
		.gfp_mask = gfp_mask,
		.may_writepage = !laptop_mode,
2125
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2126
		.may_unmap = 1,
2127
		.may_swap = 1,
2128 2129 2130
		.swappiness = vm_swappiness,
		.order = order,
		.mem_cgroup = NULL,
2131
		.nodemask = nodemask,
2132 2133
	};

2134 2135 2136 2137 2138 2139 2140 2141 2142
	trace_mm_vmscan_direct_reclaim_begin(order,
				sc.may_writepage,
				gfp_mask);

	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);

	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);

	return nr_reclaimed;
2143 2144
}

2145
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
2146

2147 2148 2149
unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
						gfp_t gfp_mask, bool noswap,
						unsigned int swappiness,
2150
						struct zone *zone)
2151 2152
{
	struct scan_control sc = {
2153
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2154 2155 2156 2157 2158 2159 2160 2161 2162
		.may_writepage = !laptop_mode,
		.may_unmap = 1,
		.may_swap = !noswap,
		.swappiness = swappiness,
		.order = 0,
		.mem_cgroup = mem,
	};
	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2163 2164 2165 2166 2167

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

2168 2169 2170 2171 2172 2173 2174 2175
	/*
	 * NOTE: Although we can get the priority field, using it
	 * here is not a good idea, since it limits the pages we can scan.
	 * if we don't reclaim here, the shrink_zone from balance_pgdat
	 * will pick up pages from other mem cgroup's as well. We hack
	 * the priority and make it zero.
	 */
	shrink_zone(0, zone, &sc);
2176 2177 2178

	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);

2179 2180 2181
	return sc.nr_reclaimed;
}

2182
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
K
KOSAKI Motohiro 已提交
2183 2184 2185
					   gfp_t gfp_mask,
					   bool noswap,
					   unsigned int swappiness)
2186
{
2187
	struct zonelist *zonelist;
2188
	unsigned long nr_reclaimed;
2189 2190
	struct scan_control sc = {
		.may_writepage = !laptop_mode,
2191
		.may_unmap = 1,
2192
		.may_swap = !noswap,
2193
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
K
KOSAKI Motohiro 已提交
2194
		.swappiness = swappiness,
2195 2196
		.order = 0,
		.mem_cgroup = mem_cont,
2197
		.nodemask = NULL, /* we don't care the placement */
2198 2199
	};

2200 2201 2202
	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
	zonelist = NODE_DATA(numa_node_id())->node_zonelists;
2203 2204 2205 2206 2207 2208 2209 2210 2211 2212

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

	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);

	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);

	return nr_reclaimed;
2213 2214 2215
}
#endif

2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226
/*
 * 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
2227
 *     percentage of the middle zones. For example, on 32-bit x86, highmem
2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243
 *     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;

	return balanced_pages > (present_pages >> 2);
}

2244
/* is kswapd sleeping prematurely? */
2245 2246
static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
					int classzone_idx)
2247
{
2248
	int i;
2249 2250
	unsigned long balanced = 0;
	bool all_zones_ok = true;
2251 2252 2253

	/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
	if (remaining)
2254
		return true;
2255

2256
	/* Check the watermark levels */
2257 2258 2259 2260 2261 2262
	for (i = 0; i < pgdat->nr_zones; i++) {
		struct zone *zone = pgdat->node_zones + i;

		if (!populated_zone(zone))
			continue;

2263 2264 2265 2266 2267 2268 2269 2270
		/*
		 * 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;
2271
			continue;
2272
		}
2273

2274
		if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2275
							classzone_idx, 0))
2276 2277 2278
			all_zones_ok = false;
		else
			balanced += zone->present_pages;
2279
	}
2280

2281 2282 2283 2284 2285 2286
	/*
	 * 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)
2287
		return pgdat_balanced(pgdat, balanced, classzone_idx);
2288 2289
	else
		return !all_zones_ok;
2290 2291
}

L
Linus Torvalds 已提交
2292 2293
/*
 * For kswapd, balance_pgdat() will work across all this node's zones until
2294
 * they are all at high_wmark_pages(zone).
L
Linus Torvalds 已提交
2295
 *
2296
 * Returns the final order kswapd was reclaiming at
L
Linus Torvalds 已提交
2297 2298 2299 2300 2301 2302 2303 2304 2305 2306
 *
 * 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
2307 2308 2309 2310 2311
 * 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
2312
 */
2313
static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2314
							int *classzone_idx)
L
Linus Torvalds 已提交
2315 2316
{
	int all_zones_ok;
2317
	unsigned long balanced;
L
Linus Torvalds 已提交
2318 2319
	int priority;
	int i;
2320
	int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */
2321
	unsigned long total_scanned;
L
Linus Torvalds 已提交
2322
	struct reclaim_state *reclaim_state = current->reclaim_state;
2323 2324
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
2325
		.may_unmap = 1,
2326
		.may_swap = 1,
2327 2328 2329 2330 2331
		/*
		 * 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,
2332
		.swappiness = vm_swappiness,
A
Andy Whitcroft 已提交
2333
		.order = order,
2334
		.mem_cgroup = NULL,
2335
	};
L
Linus Torvalds 已提交
2336 2337
loop_again:
	total_scanned = 0;
2338
	sc.nr_reclaimed = 0;
C
Christoph Lameter 已提交
2339
	sc.may_writepage = !laptop_mode;
2340
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
2341 2342 2343

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
		unsigned long lru_pages = 0;
2344
		int has_under_min_watermark_zone = 0;
L
Linus Torvalds 已提交
2345

2346 2347 2348 2349
		/* The swap token gets in the way of swapout... */
		if (!priority)
			disable_swap_token();

L
Linus Torvalds 已提交
2350
		all_zones_ok = 1;
2351
		balanced = 0;
L
Linus Torvalds 已提交
2352

2353 2354 2355 2356 2357 2358
		/*
		 * 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
2359

2360 2361
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
2362

2363
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2364
				continue;
L
Linus Torvalds 已提交
2365

2366 2367 2368 2369
			/*
			 * Do some background aging of the anon list, to give
			 * pages a chance to be referenced before reclaiming.
			 */
2370
			if (inactive_anon_is_low(zone, &sc))
2371 2372 2373
				shrink_active_list(SWAP_CLUSTER_MAX, zone,
							&sc, priority, 0);

2374
			if (!zone_watermark_ok_safe(zone, order,
2375
					high_wmark_pages(zone), 0, 0)) {
2376
				end_zone = i;
2377
				*classzone_idx = i;
A
Andrew Morton 已提交
2378
				break;
L
Linus Torvalds 已提交
2379 2380
			}
		}
A
Andrew Morton 已提交
2381 2382 2383
		if (i < 0)
			goto out;

L
Linus Torvalds 已提交
2384 2385 2386
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

2387
			lru_pages += zone_reclaimable_pages(zone);
L
Linus Torvalds 已提交
2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400
		}

		/*
		 * 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;
2401
			int nr_slab;
2402
			unsigned long balance_gap;
L
Linus Torvalds 已提交
2403

2404
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
2405 2406
				continue;

2407
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
L
Linus Torvalds 已提交
2408 2409 2410
				continue;

			sc.nr_scanned = 0;
2411 2412 2413 2414 2415

			/*
			 * Call soft limit reclaim before calling shrink_zone.
			 * For now we ignore the return value
			 */
2416 2417
			mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask);

2418
			/*
2419 2420 2421 2422 2423 2424
			 * 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.
2425
			 */
2426 2427 2428 2429
			balance_gap = min(low_wmark_pages(zone),
				(zone->present_pages +
					KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
				KSWAPD_ZONE_BALANCE_GAP_RATIO);
2430
			if (!zone_watermark_ok_safe(zone, order,
2431 2432
					high_wmark_pages(zone) + balance_gap,
					end_zone, 0))
2433
				shrink_zone(priority, zone, &sc);
L
Linus Torvalds 已提交
2434
			reclaim_state->reclaimed_slab = 0;
2435 2436
			nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
						lru_pages);
2437
			sc.nr_reclaimed += reclaim_state->reclaimed_slab;
L
Linus Torvalds 已提交
2438
			total_scanned += sc.nr_scanned;
2439

2440
			if (zone->all_unreclaimable)
L
Linus Torvalds 已提交
2441
				continue;
2442
			if (nr_slab == 0 &&
2443
			    !zone_reclaimable(zone))
2444
				zone->all_unreclaimable = 1;
L
Linus Torvalds 已提交
2445 2446 2447 2448 2449 2450
			/*
			 * 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 &&
2451
			    total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
L
Linus Torvalds 已提交
2452
				sc.may_writepage = 1;
2453

2454
			if (!zone_watermark_ok_safe(zone, order,
2455 2456 2457 2458 2459 2460 2461
					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!
				 */
2462
				if (!zone_watermark_ok_safe(zone, order,
2463 2464
					    min_wmark_pages(zone), end_zone, 0))
					has_under_min_watermark_zone = 1;
2465 2466 2467 2468 2469 2470 2471 2472 2473
			} 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);
2474
				if (i <= *classzone_idx)
2475
					balanced += zone->present_pages;
2476
			}
2477

L
Linus Torvalds 已提交
2478
		}
2479
		if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
L
Linus Torvalds 已提交
2480 2481 2482 2483 2484
			break;		/* kswapd: all done */
		/*
		 * OK, kswapd is getting into trouble.  Take a nap, then take
		 * another pass across the zones.
		 */
2485 2486 2487 2488 2489 2490
		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
2491 2492 2493 2494 2495 2496 2497

		/*
		 * 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.
		 */
2498
		if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
L
Linus Torvalds 已提交
2499 2500 2501
			break;
	}
out:
2502 2503 2504

	/*
	 * order-0: All zones must meet high watermark for a balanced node
2505 2506
	 * high-order: Balanced zones must make up at least 25% of the node
	 *             for the node to be balanced
2507
	 */
2508
	if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
L
Linus Torvalds 已提交
2509
		cond_resched();
2510 2511 2512

		try_to_freeze();

2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529
		/*
		 * 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
2530 2531 2532
		goto loop_again;
	}

2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562
	/*
	 * 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);
		}
	}

2563 2564 2565 2566 2567 2568
	/*
	 * 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
	 */
2569
	*classzone_idx = end_zone;
2570
	return order;
L
Linus Torvalds 已提交
2571 2572
}

2573
static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2574 2575 2576 2577 2578 2579 2580 2581 2582 2583
{
	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 */
2584
	if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2585 2586 2587 2588 2589 2590 2591 2592 2593
		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.
	 */
2594
	if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616
		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
2617 2618
/*
 * The background pageout daemon, started as a kernel thread
2619
 * from the init process.
L
Linus Torvalds 已提交
2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632
 *
 * This basically trickles out pages so that we have _some_
 * free memory available even if there is no other activity
 * that frees anything up. This is needed for things like routing
 * etc, where we otherwise might have all activity going on in
 * asynchronous contexts that cannot page things out.
 *
 * If there are applications that are active memory-allocators
 * (most normal use), this basically shouldn't matter.
 */
static int kswapd(void *p)
{
	unsigned long order;
2633
	int classzone_idx;
L
Linus Torvalds 已提交
2634 2635
	pg_data_t *pgdat = (pg_data_t*)p;
	struct task_struct *tsk = current;
2636

L
Linus Torvalds 已提交
2637 2638 2639
	struct reclaim_state reclaim_state = {
		.reclaimed_slab = 0,
	};
2640
	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
L
Linus Torvalds 已提交
2641

2642 2643
	lockdep_set_current_reclaim_state(GFP_KERNEL);

R
Rusty Russell 已提交
2644
	if (!cpumask_empty(cpumask))
2645
		set_cpus_allowed_ptr(tsk, cpumask);
L
Linus Torvalds 已提交
2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659
	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).
	 */
2660
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2661
	set_freezable();
L
Linus Torvalds 已提交
2662 2663

	order = 0;
2664
	classzone_idx = MAX_NR_ZONES - 1;
L
Linus Torvalds 已提交
2665 2666
	for ( ; ; ) {
		unsigned long new_order;
2667
		int new_classzone_idx;
2668
		int ret;
2669

L
Linus Torvalds 已提交
2670
		new_order = pgdat->kswapd_max_order;
2671
		new_classzone_idx = pgdat->classzone_idx;
L
Linus Torvalds 已提交
2672
		pgdat->kswapd_max_order = 0;
2673 2674
		pgdat->classzone_idx = MAX_NR_ZONES - 1;
		if (order < new_order || classzone_idx > new_classzone_idx) {
L
Linus Torvalds 已提交
2675 2676
			/*
			 * Don't sleep if someone wants a larger 'order'
2677
			 * allocation or has tigher zone constraints
L
Linus Torvalds 已提交
2678 2679
			 */
			order = new_order;
2680
			classzone_idx = new_classzone_idx;
L
Linus Torvalds 已提交
2681
		} else {
2682
			kswapd_try_to_sleep(pgdat, order, classzone_idx);
L
Linus Torvalds 已提交
2683
			order = pgdat->kswapd_max_order;
2684
			classzone_idx = pgdat->classzone_idx;
2685 2686
			pgdat->kswapd_max_order = 0;
			pgdat->classzone_idx = MAX_NR_ZONES - 1;
L
Linus Torvalds 已提交
2687 2688
		}

2689 2690 2691 2692 2693 2694 2695 2696
		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
		 */
2697 2698
		if (!ret) {
			trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2699
			order = balance_pgdat(pgdat, order, &classzone_idx);
2700
		}
L
Linus Torvalds 已提交
2701 2702 2703 2704 2705 2706 2707
	}
	return 0;
}

/*
 * A zone is low on free memory, so wake its kswapd task to service it.
 */
2708
void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
L
Linus Torvalds 已提交
2709 2710 2711
{
	pg_data_t *pgdat;

2712
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
2713 2714
		return;

2715
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
2716
		return;
2717
	pgdat = zone->zone_pgdat;
2718
	if (pgdat->kswapd_max_order < order) {
L
Linus Torvalds 已提交
2719
		pgdat->kswapd_max_order = order;
2720 2721
		pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
	}
2722
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
2723
		return;
2724 2725 2726 2727
	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);
2728
	wake_up_interruptible(&pgdat->kswapd_wait);
L
Linus Torvalds 已提交
2729 2730
}

2731 2732 2733 2734 2735 2736 2737 2738
/*
 * 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)
2739
{
2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763
	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;
2764 2765
}

2766
#ifdef CONFIG_HIBERNATION
L
Linus Torvalds 已提交
2767
/*
2768
 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2769 2770 2771 2772 2773
 * 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
2774
 */
2775
unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
L
Linus Torvalds 已提交
2776
{
2777 2778
	struct reclaim_state reclaim_state;
	struct scan_control sc = {
2779 2780 2781
		.gfp_mask = GFP_HIGHUSER_MOVABLE,
		.may_swap = 1,
		.may_unmap = 1,
2782
		.may_writepage = 1,
2783 2784 2785 2786
		.nr_to_reclaim = nr_to_reclaim,
		.hibernation_mode = 1,
		.swappiness = vm_swappiness,
		.order = 0,
L
Linus Torvalds 已提交
2787
	};
2788 2789 2790
	struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
	struct task_struct *p = current;
	unsigned long nr_reclaimed;
L
Linus Torvalds 已提交
2791

2792 2793 2794 2795
	p->flags |= PF_MEMALLOC;
	lockdep_set_current_reclaim_state(sc.gfp_mask);
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2796

2797
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
2798

2799 2800 2801
	p->reclaim_state = NULL;
	lockdep_clear_current_reclaim_state();
	p->flags &= ~PF_MEMALLOC;
2802

2803
	return nr_reclaimed;
L
Linus Torvalds 已提交
2804
}
2805
#endif /* CONFIG_HIBERNATION */
L
Linus Torvalds 已提交
2806 2807 2808 2809 2810

/* 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. */
2811
static int __devinit cpu_callback(struct notifier_block *nfb,
2812
				  unsigned long action, void *hcpu)
L
Linus Torvalds 已提交
2813
{
2814
	int nid;
L
Linus Torvalds 已提交
2815

2816
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2817
		for_each_node_state(nid, N_HIGH_MEMORY) {
2818
			pg_data_t *pgdat = NODE_DATA(nid);
2819 2820 2821
			const struct cpumask *mask;

			mask = cpumask_of_node(pgdat->node_id);
2822

2823
			if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
2824
				/* One of our CPUs online: restore mask */
2825
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
2826 2827 2828 2829 2830
		}
	}
	return NOTIFY_OK;
}

2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852
/*
 * 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;
}

2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863
/*
 * 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
2864 2865
static int __init kswapd_init(void)
{
2866
	int nid;
2867

L
Linus Torvalds 已提交
2868
	swap_setup();
2869
	for_each_node_state(nid, N_HIGH_MEMORY)
2870
 		kswapd_run(nid);
L
Linus Torvalds 已提交
2871 2872 2873 2874 2875
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
2876 2877 2878 2879 2880 2881 2882 2883 2884 2885

#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;

2886
#define RECLAIM_OFF 0
2887
#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
2888 2889 2890
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

2891 2892 2893 2894 2895 2896 2897
/*
 * 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

2898 2899 2900 2901 2902 2903
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

2904 2905 2906 2907 2908 2909
/*
 * 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;

2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951
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;
}

2952 2953 2954
/*
 * Try to free up some pages from this zone through reclaim.
 */
2955
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2956
{
2957
	/* Minimum pages needed in order to stay on node */
2958
	const unsigned long nr_pages = 1 << order;
2959 2960
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
2961
	int priority;
2962 2963
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2964
		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2965
		.may_swap = 1,
2966 2967
		.nr_to_reclaim = max_t(unsigned long, nr_pages,
				       SWAP_CLUSTER_MAX),
2968
		.gfp_mask = gfp_mask,
2969
		.swappiness = vm_swappiness,
2970
		.order = order,
2971
	};
2972
	unsigned long nr_slab_pages0, nr_slab_pages1;
2973 2974

	cond_resched();
2975 2976 2977 2978 2979 2980
	/*
	 * 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;
2981
	lockdep_set_current_reclaim_state(gfp_mask);
2982 2983
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2984

2985
	if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
2986 2987 2988 2989 2990 2991
		/*
		 * Free memory by calling shrink zone with increasing
		 * priorities until we have enough memory freed.
		 */
		priority = ZONE_RECLAIM_PRIORITY;
		do {
2992
			shrink_zone(priority, zone, &sc);
2993
			priority--;
2994
		} while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2995
	}
2996

2997 2998
	nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (nr_slab_pages0 > zone->min_slab_pages) {
2999
		/*
3000
		 * shrink_slab() does not currently allow us to determine how
3001 3002 3003 3004
		 * 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.
3005
		 *
3006 3007
		 * Note that shrink_slab will free memory on all zones and may
		 * take a long time.
3008
		 */
3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021
		for (;;) {
			unsigned long lru_pages = zone_reclaimable_pages(zone);

			/* No reclaimable slab or very low memory pressure */
			if (!shrink_slab(sc.nr_scanned, gfp_mask, lru_pages))
				break;

			/* Freed enough memory */
			nr_slab_pages1 = zone_page_state(zone,
							NR_SLAB_RECLAIMABLE);
			if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
				break;
		}
3022 3023 3024 3025 3026

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
3027 3028 3029
		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;
3030 3031
	}

3032
	p->reclaim_state = NULL;
3033
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3034
	lockdep_clear_current_reclaim_state();
3035
	return sc.nr_reclaimed >= nr_pages;
3036
}
3037 3038 3039 3040

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
3041
	int ret;
3042 3043

	/*
3044 3045
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
3046
	 *
3047 3048 3049 3050 3051
	 * 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.
3052
	 */
3053 3054
	if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
	    zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3055
		return ZONE_RECLAIM_FULL;
3056

3057
	if (zone->all_unreclaimable)
3058
		return ZONE_RECLAIM_FULL;
3059

3060
	/*
3061
	 * Do not scan if the allocation should not be delayed.
3062
	 */
3063
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3064
		return ZONE_RECLAIM_NOSCAN;
3065 3066 3067 3068 3069 3070 3071

	/*
	 * 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.
	 */
3072
	node_id = zone_to_nid(zone);
3073
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3074
		return ZONE_RECLAIM_NOSCAN;
3075 3076

	if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3077 3078
		return ZONE_RECLAIM_NOSCAN;

3079 3080 3081
	ret = __zone_reclaim(zone, gfp_mask, order);
	zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);

3082 3083 3084
	if (!ret)
		count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);

3085
	return ret;
3086
}
3087
#endif
L
Lee Schermerhorn 已提交
3088 3089 3090 3091 3092 3093 3094

/*
 * 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
3095 3096
 * 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
3097 3098
 *
 * Reasons page might not be evictable:
3099
 * (1) page's mapping marked unevictable
N
Nick Piggin 已提交
3100
 * (2) page is part of an mlocked VMA
3101
 *
L
Lee Schermerhorn 已提交
3102 3103 3104 3105
 */
int page_evictable(struct page *page, struct vm_area_struct *vma)
{

3106 3107 3108
	if (mapping_unevictable(page_mapping(page)))
		return 0;

N
Nick Piggin 已提交
3109 3110
	if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
		return 0;
L
Lee Schermerhorn 已提交
3111 3112 3113

	return 1;
}
3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132

/**
 * 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)
{
	VM_BUG_ON(PageActive(page));

retry:
	ClearPageUnevictable(page);
	if (page_evictable(page, NULL)) {
3133
		enum lru_list l = page_lru_base_type(page);
3134

3135 3136
		__dec_zone_state(zone, NR_UNEVICTABLE);
		list_move(&page->lru, &zone->lru[l].list);
K
KAMEZAWA Hiroyuki 已提交
3137
		mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
3138 3139 3140 3141 3142 3143 3144 3145
		__inc_zone_state(zone, NR_INACTIVE_ANON + l);
		__count_vm_event(UNEVICTABLE_PGRESCUED);
	} else {
		/*
		 * rotate unevictable list
		 */
		SetPageUnevictable(page);
		list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
K
KAMEZAWA Hiroyuki 已提交
3146
		mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205
		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);
	}

}
3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217

/**
 * scan_zone_unevictable_pages - check unevictable list for evictable pages
 * @zone - zone of which to scan the unevictable list
 *
 * Scan @zone's unevictable LRU lists to check for pages that have become
 * evictable.  Move those that have to @zone's inactive list where they
 * become candidates for reclaim, unless shrink_inactive_zone() decides
 * to reactivate them.  Pages that are still unevictable are rotated
 * back onto @zone's unevictable list.
 */
#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
3218
static void scan_zone_unevictable_pages(struct zone *zone)
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 3256 3257 3258 3259
{
	struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
	unsigned long scan;
	unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);

	while (nr_to_scan > 0) {
		unsigned long batch_size = min(nr_to_scan,
						SCAN_UNEVICTABLE_BATCH_SIZE);

		spin_lock_irq(&zone->lru_lock);
		for (scan = 0;  scan < batch_size; scan++) {
			struct page *page = lru_to_page(l_unevictable);

			if (!trylock_page(page))
				continue;

			prefetchw_prev_lru_page(page, l_unevictable, flags);

			if (likely(PageLRU(page) && PageUnevictable(page)))
				check_move_unevictable_page(page, zone);

			unlock_page(page);
		}
		spin_unlock_irq(&zone->lru_lock);

		nr_to_scan -= batch_size;
	}
}


/**
 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
 *
 * A really big hammer:  scan all zones' unevictable LRU lists to check for
 * pages that have become evictable.  Move those back to the zones'
 * inactive list where they become candidates for reclaim.
 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
 * and we add swap to the system.  As such, it runs in the context of a task
 * that has possibly/probably made some previously unevictable pages
 * evictable.
 */
3260
static void scan_all_zones_unevictable_pages(void)
3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275
{
	struct zone *zone;

	for_each_zone(zone) {
		scan_zone_unevictable_pages(zone);
	}
}

/*
 * 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,
3276
			   void __user *buffer,
3277 3278
			   size_t *length, loff_t *ppos)
{
3279
	proc_doulongvec_minmax(table, write, buffer, length, ppos);
3280 3281 3282 3283 3284 3285 3286 3287

	if (write && *(unsigned long *)table->data)
		scan_all_zones_unevictable_pages();

	scan_unevictable_pages = 0;
	return 0;
}

3288
#ifdef CONFIG_NUMA
3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334
/*
 * per node 'scan_unevictable_pages' attribute.  On demand re-scan of
 * a specified node's per zone unevictable lists for evictable pages.
 */

static ssize_t read_scan_unevictable_node(struct sys_device *dev,
					  struct sysdev_attribute *attr,
					  char *buf)
{
	return sprintf(buf, "0\n");	/* always zero; should fit... */
}

static ssize_t write_scan_unevictable_node(struct sys_device *dev,
					   struct sysdev_attribute *attr,
					const char *buf, size_t count)
{
	struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
	struct zone *zone;
	unsigned long res;
	unsigned long req = strict_strtoul(buf, 10, &res);

	if (!req)
		return 1;	/* zero is no-op */

	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
		if (!populated_zone(zone))
			continue;
		scan_zone_unevictable_pages(zone);
	}
	return 1;
}


static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
			read_scan_unevictable_node,
			write_scan_unevictable_node);

int scan_unevictable_register_node(struct node *node)
{
	return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
}

void scan_unevictable_unregister_node(struct node *node)
{
	sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);
}
3335
#endif