vmscan.c 93.4 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 <linux/oom.h>
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#include <linux/prefetch.h>
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#include <asm/tlbflush.h>
#include <asm/div64.h>

#include <linux/swapops.h>

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#include "internal.h"

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

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

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

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	/* How many pages shrink_list() should reclaim */
	unsigned long nr_to_reclaim;

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	unsigned long hibernation_mode;

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	/* This context's GFP mask */
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	gfp_t gfp_mask;
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	int may_writepage;

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	/* Can mapped pages be reclaimed? */
	int may_unmap;
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	/* Can pages be swapped as part of reclaim? */
	int may_swap;

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	int 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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static inline int do_shrinker_shrink(struct shrinker *shrinker,
				     struct shrink_control *sc,
				     unsigned long nr_to_scan)
{
	sc->nr_to_scan = nr_to_scan;
	return (*shrinker->shrink)(shrinker, sc);
}

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#define SHRINK_BATCH 128
/*
 * Call the shrink functions to age shrinkable caches
 *
 * Here we assume it costs one seek to replace a lru page and that it also
 * takes a seek to recreate a cache object.  With this in mind we age equal
 * percentages of the lru and ageable caches.  This should balance the seeks
 * generated by these structures.
 *
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 * If the vm encountered mapped pages on the LRU it increase the pressure on
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 * slab to avoid swapping.
 *
 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
 *
 * `lru_pages' represents the number of on-LRU pages in all the zones which
 * are eligible for the caller's allocation attempt.  It is used for balancing
 * slab reclaim versus page reclaim.
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 *
 * Returns the number of slab objects which we shrunk.
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 */
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unsigned long shrink_slab(struct shrink_control *shrink,
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			  unsigned long nr_pages_scanned,
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			  unsigned long lru_pages)
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{
	struct shrinker *shrinker;
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	unsigned long ret = 0;
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	if (nr_pages_scanned == 0)
		nr_pages_scanned = SWAP_CLUSTER_MAX;
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	if (!down_read_trylock(&shrinker_rwsem)) {
		/* Assume we'll be able to shrink next time */
		ret = 1;
		goto out;
	}
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	list_for_each_entry(shrinker, &shrinker_list, list) {
		unsigned long long delta;
		unsigned long total_scan;
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		unsigned long max_pass;
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		max_pass = do_shrinker_shrink(shrinker, shrink, 0);
		delta = (4 * nr_pages_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 = do_shrinker_shrink(shrinker, shrink, 0);
			shrink_ret = do_shrinker_shrink(shrinker, shrink,
							this_scan);
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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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out:
	cond_resched();
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	return ret;
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}

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static void set_reclaim_mode(int priority, struct scan_control *sc,
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				   bool sync)
{
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	reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
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	/*
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	 * Initially assume we are entering either lumpy reclaim or
	 * reclaim/compaction.Depending on the order, we will either set the
	 * sync mode or just reclaim order-0 pages later.
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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.
	 *
409
	 * 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.
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 */
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static int __remove_mapping(struct address_space *mapping, struct page *page)
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{
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	BUG_ON(!PageLocked(page));
	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);
581
	int was_unevictable = PageUnevictable(page);
L
Lee Schermerhorn 已提交
582 583 584 585 586 587 588 589 590 591 592 593 594

	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.
		 */
595
		lru = active + page_lru_base_type(page);
L
Lee Schermerhorn 已提交
596 597 598 599 600 601 602 603
		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);
604 605 606 607 608 609 610 611 612 613
		/*
		 * 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
614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631
	}

	/*
	 * 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.
		 */
	}

632 633 634 635 636
	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
637 638 639
	put_page(page);		/* drop ref from isolate */
}

640 641 642
enum page_references {
	PAGEREF_RECLAIM,
	PAGEREF_RECLAIM_CLEAN,
643
	PAGEREF_KEEP,
644 645 646 647 648 649
	PAGEREF_ACTIVATE,
};

static enum page_references page_check_references(struct page *page,
						  struct scan_control *sc)
{
650
	int referenced_ptes, referenced_page;
651 652
	unsigned long vm_flags;

653 654
	referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
	referenced_page = TestClearPageReferenced(page);
655 656

	/* Lumpy reclaim - ignore references */
657
	if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
658 659 660 661 662 663 664 665 666
		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;

667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690
	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;
	}
691 692

	/* Reclaim if clean, defer dirty pages to writeback */
693
	if (referenced_page && !PageSwapBacked(page))
694 695 696
		return PAGEREF_RECLAIM_CLEAN;

	return PAGEREF_RECLAIM;
697 698
}

699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716
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
717
/*
A
Andrew Morton 已提交
718
 * shrink_page_list() returns the number of reclaimed pages
L
Linus Torvalds 已提交
719
 */
A
Andrew Morton 已提交
720
static unsigned long shrink_page_list(struct list_head *page_list,
721
				      struct zone *zone,
722
				      struct scan_control *sc)
L
Linus Torvalds 已提交
723 724
{
	LIST_HEAD(ret_pages);
725
	LIST_HEAD(free_pages);
L
Linus Torvalds 已提交
726
	int pgactivate = 0;
727 728
	unsigned long nr_dirty = 0;
	unsigned long nr_congested = 0;
729
	unsigned long nr_reclaimed = 0;
L
Linus Torvalds 已提交
730 731 732 733

	cond_resched();

	while (!list_empty(page_list)) {
734
		enum page_references references;
L
Linus Torvalds 已提交
735 736 737 738 739 740 741 742 743
		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
744
		if (!trylock_page(page))
L
Linus Torvalds 已提交
745 746
			goto keep;

N
Nick Piggin 已提交
747
		VM_BUG_ON(PageActive(page));
748
		VM_BUG_ON(page_zone(page) != zone);
L
Linus Torvalds 已提交
749 750

		sc->nr_scanned++;
751

N
Nick Piggin 已提交
752 753
		if (unlikely(!page_evictable(page, NULL)))
			goto cull_mlocked;
L
Lee Schermerhorn 已提交
754

755
		if (!sc->may_unmap && page_mapped(page))
756 757
			goto keep_locked;

L
Linus Torvalds 已提交
758 759 760 761
		/* Double the slab pressure for mapped and swapcache pages */
		if (page_mapped(page) || PageSwapCache(page))
			sc->nr_scanned++;

762 763 764 765 766 767 768 769 770 771 772 773
		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.
			 */
774
			if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
775
			    may_enter_fs)
776
				wait_on_page_writeback(page);
777 778 779 780
			else {
				unlock_page(page);
				goto keep_lumpy;
			}
781
		}
L
Linus Torvalds 已提交
782

783 784 785
		references = page_check_references(page, sc);
		switch (references) {
		case PAGEREF_ACTIVATE:
L
Linus Torvalds 已提交
786
			goto activate_locked;
787 788
		case PAGEREF_KEEP:
			goto keep_locked;
789 790 791 792
		case PAGEREF_RECLAIM:
		case PAGEREF_RECLAIM_CLEAN:
			; /* try to reclaim the page below */
		}
L
Linus Torvalds 已提交
793 794 795 796 797

		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
N
Nick Piggin 已提交
798
		if (PageAnon(page) && !PageSwapCache(page)) {
799 800
			if (!(sc->gfp_mask & __GFP_IO))
				goto keep_locked;
801
			if (!add_to_swap(page))
L
Linus Torvalds 已提交
802
				goto activate_locked;
803
			may_enter_fs = 1;
N
Nick Piggin 已提交
804
		}
L
Linus Torvalds 已提交
805 806 807 808 809 810 811 812

		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) {
813
			switch (try_to_unmap(page, TTU_UNMAP)) {
L
Linus Torvalds 已提交
814 815 816 817
			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
N
Nick Piggin 已提交
818 819
			case SWAP_MLOCK:
				goto cull_mlocked;
L
Linus Torvalds 已提交
820 821 822 823 824 825
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
826 827
			nr_dirty++;

828
			if (references == PAGEREF_RECLAIM_CLEAN)
L
Linus Torvalds 已提交
829
				goto keep_locked;
830
			if (!may_enter_fs)
L
Linus Torvalds 已提交
831
				goto keep_locked;
832
			if (!sc->may_writepage)
L
Linus Torvalds 已提交
833 834 835
				goto keep_locked;

			/* Page is dirty, try to write it out here */
836
			switch (pageout(page, mapping, sc)) {
L
Linus Torvalds 已提交
837
			case PAGE_KEEP:
838
				nr_congested++;
L
Linus Torvalds 已提交
839 840 841 842
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
843 844 845
				if (PageWriteback(page))
					goto keep_lumpy;
				if (PageDirty(page))
L
Linus Torvalds 已提交
846
					goto keep;
847

L
Linus Torvalds 已提交
848 849 850 851
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
N
Nick Piggin 已提交
852
				if (!trylock_page(page))
L
Linus Torvalds 已提交
853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871
					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
872
		 * will do this, as well as the blockdev mapping.
L
Linus Torvalds 已提交
873 874 875 876 877 878 879 880 881 882
		 * 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.
		 */
883
		if (page_has_private(page)) {
L
Linus Torvalds 已提交
884 885
			if (!try_to_release_page(page, sc->gfp_mask))
				goto activate_locked;
N
Nick Piggin 已提交
886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901
			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
902 903
		}

N
Nick Piggin 已提交
904
		if (!mapping || !__remove_mapping(mapping, page))
905
			goto keep_locked;
L
Linus Torvalds 已提交
906

N
Nick Piggin 已提交
907 908 909 910 911 912 913 914
		/*
		 * 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
915
free_it:
916
		nr_reclaimed++;
917 918 919 920 921 922

		/*
		 * 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
923 924
		continue;

N
Nick Piggin 已提交
925
cull_mlocked:
926 927
		if (PageSwapCache(page))
			try_to_free_swap(page);
N
Nick Piggin 已提交
928 929
		unlock_page(page);
		putback_lru_page(page);
930
		reset_reclaim_mode(sc);
N
Nick Piggin 已提交
931 932
		continue;

L
Linus Torvalds 已提交
933
activate_locked:
934 935
		/* Not a candidate for swapping, so reclaim swap space. */
		if (PageSwapCache(page) && vm_swap_full())
936
			try_to_free_swap(page);
L
Lee Schermerhorn 已提交
937
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
938 939 940 941 942
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
943
		reset_reclaim_mode(sc);
944
keep_lumpy:
L
Linus Torvalds 已提交
945
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
946
		VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
L
Linus Torvalds 已提交
947
	}
948

949 950 951 952 953 954
	/*
	 * 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
	 */
K
KAMEZAWA Hiroyuki 已提交
955
	if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
956 957
		zone_set_flag(zone, ZONE_CONGESTED);

958 959
	free_page_list(&free_pages);

L
Linus Torvalds 已提交
960
	list_splice(&ret_pages, page_list);
961
	count_vm_events(PGACTIVATE, pgactivate);
962
	return nr_reclaimed;
L
Linus Torvalds 已提交
963 964
}

A
Andy Whitcroft 已提交
965 966 967 968 969 970 971 972 973 974
/*
 * 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.
 */
975
int __isolate_lru_page(struct page *page, int mode, int file)
A
Andy Whitcroft 已提交
976 977 978 979 980 981 982 983 984 985 986 987 988 989 990
{
	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;

991
	if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
992 993
		return ret;

L
Lee Schermerhorn 已提交
994 995 996 997 998 999 1000 1001
	/*
	 * 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
1002
	ret = -EBUSY;
K
KAMEZAWA Hiroyuki 已提交
1003

A
Andy Whitcroft 已提交
1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016
	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
1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030
/*
 * 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
1031 1032
 * @order:	The caller's attempted allocation order
 * @mode:	One of the LRU isolation modes
1033
 * @file:	True [1] if isolating file [!anon] pages
L
Linus Torvalds 已提交
1034 1035 1036
 *
 * returns how many pages were moved onto *@dst.
 */
1037 1038
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
		struct list_head *src, struct list_head *dst,
1039
		unsigned long *scanned, int order, int mode, int file)
L
Linus Torvalds 已提交
1040
{
1041
	unsigned long nr_taken = 0;
1042 1043 1044
	unsigned long nr_lumpy_taken = 0;
	unsigned long nr_lumpy_dirty = 0;
	unsigned long nr_lumpy_failed = 0;
1045
	unsigned long scan;
L
Linus Torvalds 已提交
1046

1047
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
1048 1049 1050 1051 1052 1053
		struct page *page;
		unsigned long pfn;
		unsigned long end_pfn;
		unsigned long page_pfn;
		int zone_id;

L
Linus Torvalds 已提交
1054 1055 1056
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
1057
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
1058

1059
		switch (__isolate_lru_page(page, mode, file)) {
A
Andy Whitcroft 已提交
1060 1061
		case 0:
			list_move(&page->lru, dst);
1062
			mem_cgroup_del_lru(page);
1063
			nr_taken += hpage_nr_pages(page);
A
Andy Whitcroft 已提交
1064 1065 1066 1067 1068
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
1069
			mem_cgroup_rotate_lru_list(page, page_lru(page));
A
Andy Whitcroft 已提交
1070
			continue;
1071

A
Andy Whitcroft 已提交
1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083
		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
1084
		 * as the mem_map is guaranteed valid out to MAX_ORDER,
A
Andy Whitcroft 已提交
1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103
		 * 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);
1104

A
Andy Whitcroft 已提交
1105 1106
			/* Check that we have not crossed a zone boundary. */
			if (unlikely(page_zone_id(cursor_page) != zone_id))
1107
				break;
1108 1109 1110 1111 1112 1113 1114

			/*
			 * 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) &&
1115 1116
			    !PageSwapCache(cursor_page))
				break;
1117

1118
			if (__isolate_lru_page(cursor_page, mode, file) == 0) {
A
Andy Whitcroft 已提交
1119
				list_move(&cursor_page->lru, dst);
1120
				mem_cgroup_del_lru(cursor_page);
1121
				nr_taken += hpage_nr_pages(page);
1122 1123 1124
				nr_lumpy_taken++;
				if (PageDirty(cursor_page))
					nr_lumpy_dirty++;
A
Andy Whitcroft 已提交
1125
				scan++;
1126
			} else {
1127 1128 1129 1130
				/* the page is freed already. */
				if (!page_count(cursor_page))
					continue;
				break;
A
Andy Whitcroft 已提交
1131 1132
			}
		}
1133 1134 1135 1136

		/* If we break out of the loop above, lumpy reclaim failed */
		if (pfn < end_pfn)
			nr_lumpy_failed++;
L
Linus Torvalds 已提交
1137 1138 1139
	}

	*scanned = scan;
1140 1141 1142 1143 1144 1145

	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
1146 1147 1148
	return nr_taken;
}

1149 1150 1151 1152
static unsigned long isolate_pages_global(unsigned long nr,
					struct list_head *dst,
					unsigned long *scanned, int order,
					int mode, struct zone *z,
1153
					int active, int file)
1154
{
1155
	int lru = LRU_BASE;
1156
	if (active)
1157 1158 1159 1160
		lru += LRU_ACTIVE;
	if (file)
		lru += LRU_FILE;
	return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1161
								mode, file);
1162 1163
}

A
Andy Whitcroft 已提交
1164 1165 1166 1167
/*
 * clear_active_flags() is a helper for shrink_active_list(), clearing
 * any active bits from the pages in the list.
 */
1168 1169
static unsigned long clear_active_flags(struct list_head *page_list,
					unsigned int *count)
A
Andy Whitcroft 已提交
1170 1171
{
	int nr_active = 0;
1172
	int lru;
A
Andy Whitcroft 已提交
1173 1174
	struct page *page;

1175
	list_for_each_entry(page, page_list, lru) {
1176
		int numpages = hpage_nr_pages(page);
1177
		lru = page_lru_base_type(page);
A
Andy Whitcroft 已提交
1178
		if (PageActive(page)) {
1179
			lru += LRU_ACTIVE;
A
Andy Whitcroft 已提交
1180
			ClearPageActive(page);
1181
			nr_active += numpages;
A
Andy Whitcroft 已提交
1182
		}
1183
		if (count)
1184
			count[lru] += numpages;
1185
	}
A
Andy Whitcroft 已提交
1186 1187 1188 1189

	return nr_active;
}

1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200
/**
 * 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
1201 1202 1203
 * 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.
1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218
 *
 * 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;

1219 1220
	VM_BUG_ON(!page_count(page));

1221 1222 1223 1224
	if (PageLRU(page)) {
		struct zone *zone = page_zone(page);

		spin_lock_irq(&zone->lru_lock);
1225
		if (PageLRU(page)) {
L
Lee Schermerhorn 已提交
1226
			int lru = page_lru(page);
1227
			ret = 0;
1228
			get_page(page);
1229
			ClearPageLRU(page);
1230 1231

			del_page_from_lru_list(zone, page, lru);
1232 1233 1234 1235 1236 1237
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262
/*
 * 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;
}

1263 1264 1265 1266
/*
 * TODO: Try merging with migrations version of putback_lru_pages
 */
static noinline_for_stack void
1267
putback_lru_pages(struct zone *zone, struct scan_control *sc,
1268 1269 1270 1271 1272
				unsigned long nr_anon, unsigned long nr_file,
				struct list_head *page_list)
{
	struct page *page;
	struct pagevec pvec;
1273
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291

	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;
		}
1292
		SetPageLRU(page);
1293
		lru = page_lru(page);
1294
		add_page_to_lru_list(zone, page, lru);
1295 1296
		if (is_active_lru(lru)) {
			int file = is_file_lru(lru);
1297 1298
			int numpages = hpage_nr_pages(page);
			reclaim_stat->recent_rotated[file] += numpages;
1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312
		}
		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);
}

1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343
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;
}

1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363
/*
 * 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 */
1364
	if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384
		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
1385
/*
A
Andrew Morton 已提交
1386 1387
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
1388
 */
1389 1390 1391
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
1392 1393
{
	LIST_HEAD(page_list);
1394
	unsigned long nr_scanned;
1395
	unsigned long nr_reclaimed = 0;
1396 1397 1398
	unsigned long nr_taken;
	unsigned long nr_anon;
	unsigned long nr_file;
1399

1400
	while (unlikely(too_many_isolated(zone, file, sc))) {
1401
		congestion_wait(BLK_RW_ASYNC, HZ/10);
1402 1403 1404 1405 1406 1407

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

1408
	set_reclaim_mode(priority, sc, false);
L
Linus Torvalds 已提交
1409 1410
	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1411

1412 1413 1414
	if (scanning_global_lru(sc)) {
		nr_taken = isolate_pages_global(nr_to_scan,
			&page_list, &nr_scanned, sc->order,
1415
			sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1416
					ISOLATE_BOTH : ISOLATE_INACTIVE,
1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427
			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,
1428
			sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1429
					ISOLATE_BOTH : ISOLATE_INACTIVE,
1430 1431 1432 1433 1434 1435 1436
			zone, sc->mem_cgroup,
			0, file);
		/*
		 * mem_cgroup_isolate_pages() keeps track of
		 * scanned pages on its own.
		 */
	}
1437

1438 1439 1440 1441
	if (nr_taken == 0) {
		spin_unlock_irq(&zone->lru_lock);
		return 0;
	}
A
Andy Whitcroft 已提交
1442

1443
	update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
L
Linus Torvalds 已提交
1444

1445
	spin_unlock_irq(&zone->lru_lock);
1446

1447
	nr_reclaimed = shrink_page_list(&page_list, zone, sc);
1448

1449 1450
	/* Check if we should syncronously wait for writeback */
	if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1451
		set_reclaim_mode(priority, sc, true);
1452
		nr_reclaimed += shrink_page_list(&page_list, zone, sc);
1453
	}
1454

1455 1456 1457 1458
	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
1459

1460
	putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
1461 1462 1463 1464 1465

	trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
		zone_idx(zone),
		nr_scanned, nr_reclaimed,
		priority,
1466
		trace_shrink_flags(file, sc->reclaim_mode));
1467
	return nr_reclaimed;
L
Linus Torvalds 已提交
1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486
}

/*
 * 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.
 */
1487

1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505
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);
1506
		pgmoved += hpage_nr_pages(page);
1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519

		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);
}
1520

A
Andrew Morton 已提交
1521
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1522
			struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1523
{
1524
	unsigned long nr_taken;
1525
	unsigned long pgscanned;
1526
	unsigned long vm_flags;
L
Linus Torvalds 已提交
1527
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
1528
	LIST_HEAD(l_active);
1529
	LIST_HEAD(l_inactive);
L
Linus Torvalds 已提交
1530
	struct page *page;
1531
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1532
	unsigned long nr_rotated = 0;
L
Linus Torvalds 已提交
1533 1534 1535

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1536
	if (scanning_global_lru(sc)) {
1537 1538 1539 1540
		nr_taken = isolate_pages_global(nr_pages, &l_hold,
						&pgscanned, sc->order,
						ISOLATE_ACTIVE, zone,
						1, file);
1541
		zone->pages_scanned += pgscanned;
1542 1543 1544 1545 1546 1547 1548 1549 1550
	} 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.
		 */
1551
	}
1552

1553
	reclaim_stat->recent_scanned[file] += nr_taken;
1554

1555
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
1556
	if (file)
1557
		__mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1558
	else
1559
		__mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
K
KOSAKI Motohiro 已提交
1560
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
L
Linus Torvalds 已提交
1561 1562 1563 1564 1565 1566
	spin_unlock_irq(&zone->lru_lock);

	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
1567

L
Lee Schermerhorn 已提交
1568 1569 1570 1571 1572
		if (unlikely(!page_evictable(page, NULL))) {
			putback_lru_page(page);
			continue;
		}

1573
		if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1574
			nr_rotated += hpage_nr_pages(page);
1575 1576 1577 1578 1579 1580 1581 1582 1583
			/*
			 * 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.
			 */
1584
			if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1585 1586 1587 1588
				list_add(&page->lru, &l_active);
				continue;
			}
		}
1589

1590
		ClearPageActive(page);	/* we are de-activating */
L
Linus Torvalds 已提交
1591 1592 1593
		list_add(&page->lru, &l_inactive);
	}

1594
	/*
1595
	 * Move pages back to the lru list.
1596
	 */
1597
	spin_lock_irq(&zone->lru_lock);
1598
	/*
1599 1600 1601 1602
	 * 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.
1603
	 */
1604
	reclaim_stat->recent_rotated[file] += nr_rotated;
1605

1606 1607 1608 1609
	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
1610
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1611
	spin_unlock_irq(&zone->lru_lock);
L
Linus Torvalds 已提交
1612 1613
}

1614
#ifdef CONFIG_SWAP
1615
static int inactive_anon_is_low_global(struct zone *zone)
1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627
{
	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;
}

1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639
/**
 * 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;

1640 1641 1642 1643 1644 1645 1646
	/*
	 * If we don't have swap space, anonymous page deactivation
	 * is pointless.
	 */
	if (!total_swap_pages)
		return 0;

1647
	if (scanning_global_lru(sc))
1648 1649
		low = inactive_anon_is_low_global(zone);
	else
1650
		low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1651 1652
	return low;
}
1653 1654 1655 1656 1657 1658 1659
#else
static inline int inactive_anon_is_low(struct zone *zone,
					struct scan_control *sc)
{
	return 0;
}
#endif
1660

1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696
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;
}

1697 1698 1699 1700 1701 1702 1703 1704 1705
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);
}

1706
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1707 1708
	struct zone *zone, struct scan_control *sc, int priority)
{
1709 1710
	int file = is_file_lru(lru);

1711 1712 1713
	if (is_active_lru(lru)) {
		if (inactive_list_is_low(zone, sc, file))
		    shrink_active_list(nr_to_scan, zone, sc, priority, file);
1714 1715 1716
		return 0;
	}

R
Rik van Riel 已提交
1717
	return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1718 1719
}

1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739
/*
 * 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;
}

1740 1741 1742 1743 1744 1745
/*
 * 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.
 *
1746
 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1747
 */
1748 1749
static void get_scan_count(struct zone *zone, struct scan_control *sc,
					unsigned long *nr, int priority)
1750 1751 1752 1753
{
	unsigned long anon, file, free;
	unsigned long anon_prio, file_prio;
	unsigned long ap, fp;
1754
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766
	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;
	}
1767

1768 1769 1770 1771
	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);
1772

1773
	if (scanning_global_lru(sc)) {
1774 1775 1776
		free  = zone_page_state(zone, NR_FREE_PAGES);
		/* If we have very few page cache pages,
		   force-scan anon pages. */
1777
		if (unlikely(file + free <= high_wmark_pages(zone))) {
1778 1779 1780 1781
			fraction[0] = 1;
			fraction[1] = 0;
			denominator = 1;
			goto out;
1782
		}
1783 1784
	}

1785 1786 1787 1788 1789 1790 1791
	/*
	 * 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;

1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802
	/*
	 * 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]
	 */
1803
	spin_lock_irq(&zone->lru_lock);
1804 1805 1806
	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
		reclaim_stat->recent_scanned[0] /= 2;
		reclaim_stat->recent_rotated[0] /= 2;
1807 1808
	}

1809 1810 1811
	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
		reclaim_stat->recent_scanned[1] /= 2;
		reclaim_stat->recent_rotated[1] /= 2;
1812 1813 1814
	}

	/*
1815 1816 1817
	 * 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.
1818
	 */
1819 1820
	ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
	ap /= reclaim_stat->recent_rotated[0] + 1;
1821

1822 1823
	fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
	fp /= reclaim_stat->recent_rotated[1] + 1;
1824
	spin_unlock_irq(&zone->lru_lock);
1825

1826 1827 1828 1829 1830 1831 1832
	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;
1833

1834 1835 1836 1837 1838 1839 1840 1841
		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]);
	}
1842
}
1843

1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859
/*
 * 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 */
1860
	if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1861 1862
		return false;

1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884
	/* 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;
	}
1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906

	/*
	 * 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
1907 1908 1909
/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
1910
static void shrink_zone(int priority, struct zone *zone,
1911
				struct scan_control *sc)
L
Linus Torvalds 已提交
1912
{
1913
	unsigned long nr[NR_LRU_LISTS];
1914
	unsigned long nr_to_scan;
1915
	enum lru_list l;
1916
	unsigned long nr_reclaimed, nr_scanned;
1917
	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1918

1919 1920
restart:
	nr_reclaimed = 0;
1921
	nr_scanned = sc->nr_scanned;
1922
	get_scan_count(zone, sc, nr, priority);
L
Linus Torvalds 已提交
1923

1924 1925
	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
					nr[LRU_INACTIVE_FILE]) {
L
Lee Schermerhorn 已提交
1926
		for_each_evictable_lru(l) {
1927
			if (nr[l]) {
K
KOSAKI Motohiro 已提交
1928 1929
				nr_to_scan = min_t(unsigned long,
						   nr[l], SWAP_CLUSTER_MAX);
1930
				nr[l] -= nr_to_scan;
L
Linus Torvalds 已提交
1931

1932 1933
				nr_reclaimed += shrink_list(l, nr_to_scan,
							    zone, sc, priority);
1934
			}
L
Linus Torvalds 已提交
1935
		}
1936 1937 1938 1939 1940 1941 1942 1943
		/*
		 * 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.
		 */
1944
		if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
1945
			break;
L
Linus Torvalds 已提交
1946
	}
1947
	sc->nr_reclaimed += nr_reclaimed;
1948

1949 1950 1951 1952
	/*
	 * Even if we did not try to evict anon pages at all, we want to
	 * rebalance the anon lru active/inactive ratio.
	 */
1953
	if (inactive_anon_is_low(zone, sc))
1954 1955
		shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);

1956 1957 1958 1959 1960
	/* reclaim/compaction might need reclaim to continue */
	if (should_continue_reclaim(zone, nr_reclaimed,
					sc->nr_scanned - nr_scanned, sc))
		goto restart;

1961
	throttle_vm_writeout(sc->gfp_mask);
L
Linus Torvalds 已提交
1962 1963 1964 1965 1966 1967 1968
}

/*
 * 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.
 *
1969 1970
 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
 * Because:
L
Linus Torvalds 已提交
1971 1972
 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
 *    allocation or
1973 1974 1975
 * 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
1976 1977 1978 1979
 *
 * If a zone is deemed to be full of pinned pages then just give it a light
 * scan then give up on it.
 */
1980
static void shrink_zones(int priority, struct zonelist *zonelist,
1981
					struct scan_control *sc)
L
Linus Torvalds 已提交
1982
{
1983
	struct zoneref *z;
1984
	struct zone *zone;
1985

1986 1987
	for_each_zone_zonelist_nodemask(zone, z, zonelist,
					gfp_zone(sc->gfp_mask), sc->nodemask) {
1988
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
1989
			continue;
1990 1991 1992 1993
		/*
		 * Take care memory controller reclaiming has small influence
		 * to global LRU.
		 */
1994
		if (scanning_global_lru(sc)) {
1995 1996
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
1997
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1998 1999
				continue;	/* Let kswapd poll it */
		}
2000

2001
		shrink_zone(priority, zone, sc);
L
Linus Torvalds 已提交
2002
	}
2003 2004 2005 2006 2007 2008 2009
}

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

2010
/* All zones in zonelist are unreclaimable? */
2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022
static bool all_unreclaimable(struct zonelist *zonelist,
		struct scan_control *sc)
{
	struct zoneref *z;
	struct zone *zone;

	for_each_zone_zonelist_nodemask(zone, z, zonelist,
			gfp_zone(sc->gfp_mask), sc->nodemask) {
		if (!populated_zone(zone))
			continue;
		if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
			continue;
2023 2024
		if (!zone->all_unreclaimable)
			return false;
2025 2026
	}

2027
	return true;
L
Linus Torvalds 已提交
2028
}
2029

L
Linus Torvalds 已提交
2030 2031 2032 2033 2034 2035 2036 2037
/*
 * 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
2038 2039 2040 2041
 * 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.
2042 2043 2044
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
2045
 */
2046
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2047 2048
					struct scan_control *sc,
					struct shrink_control *shrink)
L
Linus Torvalds 已提交
2049 2050
{
	int priority;
2051
	unsigned long total_scanned = 0;
L
Linus Torvalds 已提交
2052
	struct reclaim_state *reclaim_state = current->reclaim_state;
2053
	struct zoneref *z;
2054
	struct zone *zone;
2055
	unsigned long writeback_threshold;
L
Linus Torvalds 已提交
2056

2057
	get_mems_allowed();
2058 2059
	delayacct_freepages_start();

2060
	if (scanning_global_lru(sc))
2061
		count_vm_event(ALLOCSTALL);
L
Linus Torvalds 已提交
2062 2063

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2064
		sc->nr_scanned = 0;
2065 2066
		if (!priority)
			disable_swap_token();
2067
		shrink_zones(priority, zonelist, sc);
2068 2069 2070 2071
		/*
		 * Don't shrink slabs when reclaiming memory from
		 * over limit cgroups
		 */
2072
		if (scanning_global_lru(sc)) {
2073
			unsigned long lru_pages = 0;
2074 2075
			for_each_zone_zonelist(zone, z, zonelist,
					gfp_zone(sc->gfp_mask)) {
2076 2077 2078 2079 2080 2081
				if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
					continue;

				lru_pages += zone_reclaimable_pages(zone);
			}

2082
			shrink_slab(shrink, sc->nr_scanned, lru_pages);
2083
			if (reclaim_state) {
2084
				sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2085 2086
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
2087
		}
2088
		total_scanned += sc->nr_scanned;
2089
		if (sc->nr_reclaimed >= sc->nr_to_reclaim)
L
Linus Torvalds 已提交
2090 2091 2092 2093 2094 2095 2096 2097 2098
			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.
		 */
2099 2100
		writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
		if (total_scanned > writeback_threshold) {
2101
			wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
2102
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
2103 2104 2105
		}

		/* Take a nap, wait for some writeback to complete */
2106
		if (!sc->hibernation_mode && sc->nr_scanned &&
2107 2108 2109 2110
		    priority < DEF_PRIORITY - 2) {
			struct zone *preferred_zone;

			first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2111 2112
						&cpuset_current_mems_allowed,
						&preferred_zone);
2113 2114
			wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
		}
L
Linus Torvalds 已提交
2115
	}
2116

L
Linus Torvalds 已提交
2117
out:
2118
	delayacct_freepages_end();
2119
	put_mems_allowed();
2120

2121 2122 2123
	if (sc->nr_reclaimed)
		return sc->nr_reclaimed;

2124 2125 2126 2127 2128 2129 2130 2131
	/*
	 * As hibernation is going on, kswapd is freezed so that it can't mark
	 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
	 * check.
	 */
	if (oom_killer_disabled)
		return 0;

2132
	/* top priority shrink_zones still had more to do? don't OOM, then */
2133
	if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
2134 2135 2136
		return 1;

	return 0;
L
Linus Torvalds 已提交
2137 2138
}

2139
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2140
				gfp_t gfp_mask, nodemask_t *nodemask)
2141
{
2142
	unsigned long nr_reclaimed;
2143 2144 2145
	struct scan_control sc = {
		.gfp_mask = gfp_mask,
		.may_writepage = !laptop_mode,
2146
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2147
		.may_unmap = 1,
2148
		.may_swap = 1,
2149 2150 2151
		.swappiness = vm_swappiness,
		.order = order,
		.mem_cgroup = NULL,
2152
		.nodemask = nodemask,
2153
	};
2154 2155 2156
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
2157

2158 2159 2160 2161
	trace_mm_vmscan_direct_reclaim_begin(order,
				sc.may_writepage,
				gfp_mask);

2162
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2163 2164 2165 2166

	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);

	return nr_reclaimed;
2167 2168
}

2169
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
2170

2171 2172 2173
unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
						gfp_t gfp_mask, bool noswap,
						unsigned int swappiness,
2174 2175
						struct zone *zone,
						unsigned long *nr_scanned)
2176 2177
{
	struct scan_control sc = {
2178
		.nr_scanned = 0,
2179
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2180 2181 2182 2183 2184 2185 2186
		.may_writepage = !laptop_mode,
		.may_unmap = 1,
		.may_swap = !noswap,
		.swappiness = swappiness,
		.order = 0,
		.mem_cgroup = mem,
	};
2187

2188 2189
	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2190 2191 2192 2193 2194

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

2195 2196 2197 2198 2199 2200 2201 2202
	/*
	 * 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);
2203 2204 2205

	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);

2206
	*nr_scanned = sc.nr_scanned;
2207 2208 2209
	return sc.nr_reclaimed;
}

2210
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
K
KOSAKI Motohiro 已提交
2211 2212 2213
					   gfp_t gfp_mask,
					   bool noswap,
					   unsigned int swappiness)
2214
{
2215
	struct zonelist *zonelist;
2216
	unsigned long nr_reclaimed;
2217 2218
	struct scan_control sc = {
		.may_writepage = !laptop_mode,
2219
		.may_unmap = 1,
2220
		.may_swap = !noswap,
2221
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
K
KOSAKI Motohiro 已提交
2222
		.swappiness = swappiness,
2223 2224
		.order = 0,
		.mem_cgroup = mem_cont,
2225
		.nodemask = NULL, /* we don't care the placement */
2226 2227 2228 2229 2230
		.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
				(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
	};
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
2231 2232
	};

2233
	zonelist = NODE_DATA(numa_node_id())->node_zonelists;
2234 2235 2236 2237 2238

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

2239
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2240 2241 2242 2243

	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);

	return nr_reclaimed;
2244 2245 2246
}
#endif

2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257
/*
 * 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
2258
 *     percentage of the middle zones. For example, on 32-bit x86, highmem
2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274
 *     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);
}

2275
/* is kswapd sleeping prematurely? */
2276 2277
static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
					int classzone_idx)
2278
{
2279
	int i;
2280 2281
	unsigned long balanced = 0;
	bool all_zones_ok = true;
2282 2283 2284

	/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
	if (remaining)
2285
		return true;
2286

2287
	/* Check the watermark levels */
2288 2289 2290 2291 2292 2293
	for (i = 0; i < pgdat->nr_zones; i++) {
		struct zone *zone = pgdat->node_zones + i;

		if (!populated_zone(zone))
			continue;

2294 2295 2296 2297 2298 2299 2300 2301
		/*
		 * 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;
2302
			continue;
2303
		}
2304

2305
		if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2306
							classzone_idx, 0))
2307 2308 2309
			all_zones_ok = false;
		else
			balanced += zone->present_pages;
2310
	}
2311

2312 2313 2314 2315 2316 2317
	/*
	 * 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)
2318
		return !pgdat_balanced(pgdat, balanced, classzone_idx);
2319 2320
	else
		return !all_zones_ok;
2321 2322
}

L
Linus Torvalds 已提交
2323 2324
/*
 * For kswapd, balance_pgdat() will work across all this node's zones until
2325
 * they are all at high_wmark_pages(zone).
L
Linus Torvalds 已提交
2326
 *
2327
 * Returns the final order kswapd was reclaiming at
L
Linus Torvalds 已提交
2328 2329 2330 2331 2332 2333 2334 2335 2336 2337
 *
 * 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
2338 2339 2340 2341 2342
 * 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
2343
 */
2344
static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2345
							int *classzone_idx)
L
Linus Torvalds 已提交
2346 2347
{
	int all_zones_ok;
2348
	unsigned long balanced;
L
Linus Torvalds 已提交
2349 2350
	int priority;
	int i;
2351
	int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */
2352
	unsigned long total_scanned;
L
Linus Torvalds 已提交
2353
	struct reclaim_state *reclaim_state = current->reclaim_state;
2354 2355
	unsigned long nr_soft_reclaimed;
	unsigned long nr_soft_scanned;
2356 2357
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
2358
		.may_unmap = 1,
2359
		.may_swap = 1,
2360 2361 2362 2363 2364
		/*
		 * 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,
2365
		.swappiness = vm_swappiness,
A
Andy Whitcroft 已提交
2366
		.order = order,
2367
		.mem_cgroup = NULL,
2368
	};
2369 2370 2371
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
L
Linus Torvalds 已提交
2372 2373
loop_again:
	total_scanned = 0;
2374
	sc.nr_reclaimed = 0;
C
Christoph Lameter 已提交
2375
	sc.may_writepage = !laptop_mode;
2376
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
2377 2378 2379

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
		unsigned long lru_pages = 0;
2380
		int has_under_min_watermark_zone = 0;
L
Linus Torvalds 已提交
2381

2382 2383 2384 2385
		/* The swap token gets in the way of swapout... */
		if (!priority)
			disable_swap_token();

L
Linus Torvalds 已提交
2386
		all_zones_ok = 1;
2387
		balanced = 0;
L
Linus Torvalds 已提交
2388

2389 2390 2391 2392 2393 2394
		/*
		 * 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
2395

2396 2397
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
2398

2399
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2400
				continue;
L
Linus Torvalds 已提交
2401

2402 2403 2404 2405
			/*
			 * Do some background aging of the anon list, to give
			 * pages a chance to be referenced before reclaiming.
			 */
2406
			if (inactive_anon_is_low(zone, &sc))
2407 2408 2409
				shrink_active_list(SWAP_CLUSTER_MAX, zone,
							&sc, priority, 0);

2410
			if (!zone_watermark_ok_safe(zone, order,
2411
					high_wmark_pages(zone), 0, 0)) {
2412
				end_zone = i;
2413
				*classzone_idx = i;
A
Andrew Morton 已提交
2414
				break;
L
Linus Torvalds 已提交
2415 2416
			}
		}
A
Andrew Morton 已提交
2417 2418 2419
		if (i < 0)
			goto out;

L
Linus Torvalds 已提交
2420 2421 2422
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

2423
			lru_pages += zone_reclaimable_pages(zone);
L
Linus Torvalds 已提交
2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436
		}

		/*
		 * 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;
2437
			int nr_slab;
2438
			unsigned long balance_gap;
L
Linus Torvalds 已提交
2439

2440
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
2441 2442
				continue;

2443
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
L
Linus Torvalds 已提交
2444 2445 2446
				continue;

			sc.nr_scanned = 0;
2447

2448
			nr_soft_scanned = 0;
2449 2450 2451
			/*
			 * Call soft limit reclaim before calling shrink_zone.
			 */
2452 2453 2454 2455 2456
			nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
							order, sc.gfp_mask,
							&nr_soft_scanned);
			sc.nr_reclaimed += nr_soft_reclaimed;
			total_scanned += nr_soft_scanned;
2457

2458
			/*
2459 2460 2461 2462 2463 2464
			 * 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.
2465
			 */
2466 2467 2468 2469
			balance_gap = min(low_wmark_pages(zone),
				(zone->present_pages +
					KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
				KSWAPD_ZONE_BALANCE_GAP_RATIO);
2470
			if (!zone_watermark_ok_safe(zone, order,
2471 2472
					high_wmark_pages(zone) + balance_gap,
					end_zone, 0))
2473
				shrink_zone(priority, zone, &sc);
L
Linus Torvalds 已提交
2474
			reclaim_state->reclaimed_slab = 0;
2475
			nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
2476
			sc.nr_reclaimed += reclaim_state->reclaimed_slab;
L
Linus Torvalds 已提交
2477
			total_scanned += sc.nr_scanned;
2478

2479
			if (zone->all_unreclaimable)
L
Linus Torvalds 已提交
2480
				continue;
2481
			if (nr_slab == 0 &&
2482
			    !zone_reclaimable(zone))
2483
				zone->all_unreclaimable = 1;
L
Linus Torvalds 已提交
2484 2485 2486 2487 2488 2489
			/*
			 * 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 &&
2490
			    total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
L
Linus Torvalds 已提交
2491
				sc.may_writepage = 1;
2492

2493
			if (!zone_watermark_ok_safe(zone, order,
2494 2495 2496 2497 2498 2499 2500
					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!
				 */
2501
				if (!zone_watermark_ok_safe(zone, order,
2502 2503
					    min_wmark_pages(zone), end_zone, 0))
					has_under_min_watermark_zone = 1;
2504 2505 2506 2507 2508 2509 2510 2511 2512
			} 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);
2513
				if (i <= *classzone_idx)
2514
					balanced += zone->present_pages;
2515
			}
2516

L
Linus Torvalds 已提交
2517
		}
2518
		if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
L
Linus Torvalds 已提交
2519 2520 2521 2522 2523
			break;		/* kswapd: all done */
		/*
		 * OK, kswapd is getting into trouble.  Take a nap, then take
		 * another pass across the zones.
		 */
2524 2525 2526 2527 2528 2529
		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
2530 2531 2532 2533 2534 2535 2536

		/*
		 * 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.
		 */
2537
		if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
L
Linus Torvalds 已提交
2538 2539 2540
			break;
	}
out:
2541 2542 2543

	/*
	 * order-0: All zones must meet high watermark for a balanced node
2544 2545
	 * high-order: Balanced zones must make up at least 25% of the node
	 *             for the node to be balanced
2546
	 */
2547
	if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
L
Linus Torvalds 已提交
2548
		cond_resched();
2549 2550 2551

		try_to_freeze();

2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568
		/*
		 * 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
2569 2570 2571
		goto loop_again;
	}

2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601
	/*
	 * 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);
		}
	}

2602 2603 2604 2605 2606 2607
	/*
	 * 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
	 */
2608
	*classzone_idx = end_zone;
2609
	return order;
L
Linus Torvalds 已提交
2610 2611
}

2612
static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2613 2614 2615 2616 2617 2618 2619 2620 2621 2622
{
	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 */
2623
	if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2624 2625 2626 2627 2628 2629 2630 2631 2632
		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.
	 */
2633
	if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655
		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
2656 2657
/*
 * The background pageout daemon, started as a kernel thread
2658
 * from the init process.
L
Linus Torvalds 已提交
2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671
 *
 * 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;
2672
	int classzone_idx;
L
Linus Torvalds 已提交
2673 2674
	pg_data_t *pgdat = (pg_data_t*)p;
	struct task_struct *tsk = current;
2675

L
Linus Torvalds 已提交
2676 2677 2678
	struct reclaim_state reclaim_state = {
		.reclaimed_slab = 0,
	};
2679
	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
L
Linus Torvalds 已提交
2680

2681 2682
	lockdep_set_current_reclaim_state(GFP_KERNEL);

R
Rusty Russell 已提交
2683
	if (!cpumask_empty(cpumask))
2684
		set_cpus_allowed_ptr(tsk, cpumask);
L
Linus Torvalds 已提交
2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698
	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).
	 */
2699
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2700
	set_freezable();
L
Linus Torvalds 已提交
2701 2702

	order = 0;
2703
	classzone_idx = MAX_NR_ZONES - 1;
L
Linus Torvalds 已提交
2704 2705
	for ( ; ; ) {
		unsigned long new_order;
2706
		int new_classzone_idx;
2707
		int ret;
2708

L
Linus Torvalds 已提交
2709
		new_order = pgdat->kswapd_max_order;
2710
		new_classzone_idx = pgdat->classzone_idx;
L
Linus Torvalds 已提交
2711
		pgdat->kswapd_max_order = 0;
2712 2713
		pgdat->classzone_idx = MAX_NR_ZONES - 1;
		if (order < new_order || classzone_idx > new_classzone_idx) {
L
Linus Torvalds 已提交
2714 2715
			/*
			 * Don't sleep if someone wants a larger 'order'
2716
			 * allocation or has tigher zone constraints
L
Linus Torvalds 已提交
2717 2718
			 */
			order = new_order;
2719
			classzone_idx = new_classzone_idx;
L
Linus Torvalds 已提交
2720
		} else {
2721
			kswapd_try_to_sleep(pgdat, order, classzone_idx);
L
Linus Torvalds 已提交
2722
			order = pgdat->kswapd_max_order;
2723
			classzone_idx = pgdat->classzone_idx;
2724 2725
			pgdat->kswapd_max_order = 0;
			pgdat->classzone_idx = MAX_NR_ZONES - 1;
L
Linus Torvalds 已提交
2726 2727
		}

2728 2729 2730 2731 2732 2733 2734 2735
		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
		 */
2736 2737
		if (!ret) {
			trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2738
			order = balance_pgdat(pgdat, order, &classzone_idx);
2739
		}
L
Linus Torvalds 已提交
2740 2741 2742 2743 2744 2745 2746
	}
	return 0;
}

/*
 * A zone is low on free memory, so wake its kswapd task to service it.
 */
2747
void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
L
Linus Torvalds 已提交
2748 2749 2750
{
	pg_data_t *pgdat;

2751
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
2752 2753
		return;

2754
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
2755
		return;
2756
	pgdat = zone->zone_pgdat;
2757
	if (pgdat->kswapd_max_order < order) {
L
Linus Torvalds 已提交
2758
		pgdat->kswapd_max_order = order;
2759 2760
		pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
	}
2761
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
2762
		return;
2763 2764 2765 2766
	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);
2767
	wake_up_interruptible(&pgdat->kswapd_wait);
L
Linus Torvalds 已提交
2768 2769
}

2770 2771 2772 2773 2774 2775 2776 2777
/*
 * 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)
2778
{
2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802
	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;
2803 2804
}

2805
#ifdef CONFIG_HIBERNATION
L
Linus Torvalds 已提交
2806
/*
2807
 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2808 2809 2810 2811 2812
 * 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
2813
 */
2814
unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
L
Linus Torvalds 已提交
2815
{
2816 2817
	struct reclaim_state reclaim_state;
	struct scan_control sc = {
2818 2819 2820
		.gfp_mask = GFP_HIGHUSER_MOVABLE,
		.may_swap = 1,
		.may_unmap = 1,
2821
		.may_writepage = 1,
2822 2823 2824 2825
		.nr_to_reclaim = nr_to_reclaim,
		.hibernation_mode = 1,
		.swappiness = vm_swappiness,
		.order = 0,
L
Linus Torvalds 已提交
2826
	};
2827 2828 2829 2830
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2831 2832
	struct task_struct *p = current;
	unsigned long nr_reclaimed;
L
Linus Torvalds 已提交
2833

2834 2835 2836 2837
	p->flags |= PF_MEMALLOC;
	lockdep_set_current_reclaim_state(sc.gfp_mask);
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2838

2839
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2840

2841 2842 2843
	p->reclaim_state = NULL;
	lockdep_clear_current_reclaim_state();
	p->flags &= ~PF_MEMALLOC;
2844

2845
	return nr_reclaimed;
L
Linus Torvalds 已提交
2846
}
2847
#endif /* CONFIG_HIBERNATION */
L
Linus Torvalds 已提交
2848 2849 2850 2851 2852

/* 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. */
2853
static int __devinit cpu_callback(struct notifier_block *nfb,
2854
				  unsigned long action, void *hcpu)
L
Linus Torvalds 已提交
2855
{
2856
	int nid;
L
Linus Torvalds 已提交
2857

2858
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2859
		for_each_node_state(nid, N_HIGH_MEMORY) {
2860
			pg_data_t *pgdat = NODE_DATA(nid);
2861 2862 2863
			const struct cpumask *mask;

			mask = cpumask_of_node(pgdat->node_id);
2864

2865
			if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
2866
				/* One of our CPUs online: restore mask */
2867
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
2868 2869 2870 2871 2872
		}
	}
	return NOTIFY_OK;
}

2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894
/*
 * 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;
}

2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905
/*
 * 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
2906 2907
static int __init kswapd_init(void)
{
2908
	int nid;
2909

L
Linus Torvalds 已提交
2910
	swap_setup();
2911
	for_each_node_state(nid, N_HIGH_MEMORY)
2912
 		kswapd_run(nid);
L
Linus Torvalds 已提交
2913 2914 2915 2916 2917
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
2918 2919 2920 2921 2922 2923 2924 2925 2926 2927

#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;

2928
#define RECLAIM_OFF 0
2929
#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
2930 2931 2932
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

2933 2934 2935 2936 2937 2938 2939
/*
 * 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

2940 2941 2942 2943 2944 2945
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

2946 2947 2948 2949 2950 2951
/*
 * 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;

2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993
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;
}

2994 2995 2996
/*
 * Try to free up some pages from this zone through reclaim.
 */
2997
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2998
{
2999
	/* Minimum pages needed in order to stay on node */
3000
	const unsigned long nr_pages = 1 << order;
3001 3002
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
3003
	int priority;
3004 3005
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3006
		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3007
		.may_swap = 1,
3008 3009
		.nr_to_reclaim = max_t(unsigned long, nr_pages,
				       SWAP_CLUSTER_MAX),
3010
		.gfp_mask = gfp_mask,
3011
		.swappiness = vm_swappiness,
3012
		.order = order,
3013
	};
3014 3015 3016
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
3017
	unsigned long nr_slab_pages0, nr_slab_pages1;
3018 3019

	cond_resched();
3020 3021 3022 3023 3024 3025
	/*
	 * 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;
3026
	lockdep_set_current_reclaim_state(gfp_mask);
3027 3028
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
3029

3030
	if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3031 3032 3033 3034 3035 3036
		/*
		 * Free memory by calling shrink zone with increasing
		 * priorities until we have enough memory freed.
		 */
		priority = ZONE_RECLAIM_PRIORITY;
		do {
3037
			shrink_zone(priority, zone, &sc);
3038
			priority--;
3039
		} while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3040
	}
3041

3042 3043
	nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (nr_slab_pages0 > zone->min_slab_pages) {
3044
		/*
3045
		 * shrink_slab() does not currently allow us to determine how
3046 3047 3048 3049
		 * 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.
3050
		 *
3051 3052
		 * Note that shrink_slab will free memory on all zones and may
		 * take a long time.
3053
		 */
3054 3055 3056 3057
		for (;;) {
			unsigned long lru_pages = zone_reclaimable_pages(zone);

			/* No reclaimable slab or very low memory pressure */
3058
			if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3059 3060 3061 3062 3063 3064 3065 3066
				break;

			/* Freed enough memory */
			nr_slab_pages1 = zone_page_state(zone,
							NR_SLAB_RECLAIMABLE);
			if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
				break;
		}
3067 3068 3069 3070 3071

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
3072 3073 3074
		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;
3075 3076
	}

3077
	p->reclaim_state = NULL;
3078
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3079
	lockdep_clear_current_reclaim_state();
3080
	return sc.nr_reclaimed >= nr_pages;
3081
}
3082 3083 3084 3085

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
3086
	int ret;
3087 3088

	/*
3089 3090
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
3091
	 *
3092 3093 3094 3095 3096
	 * 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.
3097
	 */
3098 3099
	if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
	    zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3100
		return ZONE_RECLAIM_FULL;
3101

3102
	if (zone->all_unreclaimable)
3103
		return ZONE_RECLAIM_FULL;
3104

3105
	/*
3106
	 * Do not scan if the allocation should not be delayed.
3107
	 */
3108
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3109
		return ZONE_RECLAIM_NOSCAN;
3110 3111 3112 3113 3114 3115 3116

	/*
	 * 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.
	 */
3117
	node_id = zone_to_nid(zone);
3118
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3119
		return ZONE_RECLAIM_NOSCAN;
3120 3121

	if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3122 3123
		return ZONE_RECLAIM_NOSCAN;

3124 3125 3126
	ret = __zone_reclaim(zone, gfp_mask, order);
	zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);

3127 3128 3129
	if (!ret)
		count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);

3130
	return ret;
3131
}
3132
#endif
L
Lee Schermerhorn 已提交
3133 3134 3135 3136 3137 3138 3139

/*
 * 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
3140 3141
 * 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
3142 3143
 *
 * Reasons page might not be evictable:
3144
 * (1) page's mapping marked unevictable
N
Nick Piggin 已提交
3145
 * (2) page is part of an mlocked VMA
3146
 *
L
Lee Schermerhorn 已提交
3147 3148 3149 3150
 */
int page_evictable(struct page *page, struct vm_area_struct *vma)
{

3151 3152 3153
	if (mapping_unevictable(page_mapping(page)))
		return 0;

N
Nick Piggin 已提交
3154 3155
	if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
		return 0;
L
Lee Schermerhorn 已提交
3156 3157 3158

	return 1;
}
3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177

/**
 * 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)) {
3178
		enum lru_list l = page_lru_base_type(page);
3179

3180 3181
		__dec_zone_state(zone, NR_UNEVICTABLE);
		list_move(&page->lru, &zone->lru[l].list);
K
KAMEZAWA Hiroyuki 已提交
3182
		mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
3183 3184 3185 3186 3187 3188 3189 3190
		__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
3191
		mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250
		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);
	}

}
3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262

/**
 * 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 */
3263
static void scan_zone_unevictable_pages(struct zone *zone)
3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304
{
	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.
 */
3305
static void scan_all_zones_unevictable_pages(void)
3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320
{
	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,
3321
			   void __user *buffer,
3322 3323
			   size_t *length, loff_t *ppos)
{
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	proc_doulongvec_minmax(table, write, buffer, length, ppos);
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	if (write && *(unsigned long *)table->data)
		scan_all_zones_unevictable_pages();

	scan_unevictable_pages = 0;
	return 0;
}

3333
#ifdef CONFIG_NUMA
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/*
 * 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);
}
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#endif