vmscan.c 72.5 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>
#include <linux/slab.h>
#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>
#include <linux/notifier.h>
#include <linux/rwsem.h>
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#include <linux/delay.h>
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#include <linux/kthread.h>
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#include <linux/freezer.h>
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#include <linux/memcontrol.h>
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#include <linux/delayacct.h>
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#include <linux/sysctl.h>
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#include <asm/tlbflush.h>
#include <asm/div64.h>

#include <linux/swapops.h>

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#include "internal.h"

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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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	/* 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 pages be swapped as part of reclaim? */
	int may_swap;

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	/* This context's SWAP_CLUSTER_MAX. If freeing memory for
	 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
	 * In this context, it doesn't matter that we scan the
	 * whole list at once. */
	int swap_cluster_max;
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	int swappiness;
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	int all_unreclaimable;
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	int order;
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	/* Which cgroup do we reclaim from */
	struct mem_cgroup *mem_cgroup;

	/* Pluggable isolate pages callback */
	unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
			unsigned long *scanned, int order, int mode,
			struct zone *z, struct mem_cgroup *mem_cont,
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			int active, int file);
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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 scan_global_lru(sc)	(!(sc)->mem_cgroup)
#else
#define scan_global_lru(sc)	(1)
#endif

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static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
						  struct scan_control *sc)
{
	return &zone->reclaim_stat;
}

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static unsigned long zone_nr_pages(struct zone *zone, struct scan_control *sc,
				   enum lru_list lru)
{
	return zone_page_state(zone, NR_LRU_BASE + lru);
}


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/*
 * Add a shrinker callback to be called from the vm
 */
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void register_shrinker(struct shrinker *shrinker)
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{
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	shrinker->nr = 0;
	down_write(&shrinker_rwsem);
	list_add_tail(&shrinker->list, &shrinker_list);
	up_write(&shrinker_rwsem);
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}
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EXPORT_SYMBOL(register_shrinker);
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/*
 * Remove one
 */
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void unregister_shrinker(struct shrinker *shrinker)
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{
	down_write(&shrinker_rwsem);
	list_del(&shrinker->list);
	up_write(&shrinker_rwsem);
}
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EXPORT_SYMBOL(unregister_shrinker);
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#define SHRINK_BATCH 128
/*
 * Call the shrink functions to age shrinkable caches
 *
 * Here we assume it costs one seek to replace a lru page and that it also
 * takes a seek to recreate a cache object.  With this in mind we age equal
 * percentages of the lru and ageable caches.  This should balance the seeks
 * generated by these structures.
 *
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 * If the vm encountered mapped pages on the LRU it increase the pressure on
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 * slab to avoid swapping.
 *
 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
 *
 * `lru_pages' represents the number of on-LRU pages in all the zones which
 * are eligible for the caller's allocation attempt.  It is used for balancing
 * slab reclaim versus page reclaim.
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 *
 * Returns the number of slab objects which we shrunk.
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 */
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unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
			unsigned long lru_pages)
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{
	struct shrinker *shrinker;
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	unsigned long ret = 0;
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	if (scanned == 0)
		scanned = SWAP_CLUSTER_MAX;

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

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

		while (total_scan >= SHRINK_BATCH) {
			long this_scan = SHRINK_BATCH;
			int shrink_ret;
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			int nr_before;
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			nr_before = (*shrinker->shrink)(0, gfp_mask);
			shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
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			if (shrink_ret == -1)
				break;
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			if (shrink_ret < nr_before)
				ret += nr_before - shrink_ret;
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			count_vm_events(SLABS_SCANNED, this_scan);
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			total_scan -= this_scan;

			cond_resched();
		}

		shrinker->nr += total_scan;
	}
	up_read(&shrinker_rwsem);
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	return ret;
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}

/* Called without lock on whether page is mapped, so answer is unstable */
static inline int page_mapping_inuse(struct page *page)
{
	struct address_space *mapping;

	/* Page is in somebody's page tables. */
	if (page_mapped(page))
		return 1;

	/* Be more reluctant to reclaim swapcache than pagecache */
	if (PageSwapCache(page))
		return 1;

	mapping = page_mapping(page);
	if (!mapping)
		return 0;

	/* File is mmap'd by somebody? */
	return mapping_mapped(mapping);
}

static inline int is_page_cache_freeable(struct page *page)
{
	return page_count(page) - !!PagePrivate(page) == 2;
}

static int may_write_to_queue(struct backing_dev_info *bdi)
{
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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;
	return 0;
}

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

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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,
						enum pageout_io sync_writeback)
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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.
	 *
	 * If this process is currently in generic_file_write() against
	 * this page's queue, we can perform writeback even if that
	 * will block.
	 *
	 * If the page is swapcache, write it back even if that would
	 * block, for some throttling. This happens by accident, because
	 * swap_backing_dev_info is bust: it doesn't reflect the
	 * congestion state of the swapdevs.  Easy to fix, if needed.
	 * See swapfile.c:page_queue_congested().
	 */
	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 (PagePrivate(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;
	if (!may_write_to_queue(mapping->backing_dev_info))
		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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			.nonblocking = 1,
			.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.
		 */
		if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
			wait_on_page_writeback(page);

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		if (!PageWriteback(page)) {
			/* synchronous write or broken a_ops? */
			ClearPageReclaim(page);
		}
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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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		swap_free(swap);
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	} else {
		__remove_from_page_cache(page);
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		spin_unlock_irq(&mapping->tree_lock);
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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.
 */
#ifdef CONFIG_UNEVICTABLE_LRU
void putback_lru_page(struct page *page)
{
	int lru;
	int active = !!TestClearPageActive(page);
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	int was_unevictable = PageUnevictable(page);
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	VM_BUG_ON(PageLRU(page));

redo:
	ClearPageUnevictable(page);

	if (page_evictable(page, NULL)) {
		/*
		 * For evictable pages, we can use the cache.
		 * In event of a race, worst case is we end up with an
		 * unevictable page on [in]active list.
		 * We know how to handle that.
		 */
		lru = active + page_is_file_cache(page);
		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);
	}

	/*
	 * 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.
		 */
	}

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	if (was_unevictable && lru != LRU_UNEVICTABLE)
		count_vm_event(UNEVICTABLE_PGRESCUED);
	else if (!was_unevictable && lru == LRU_UNEVICTABLE)
		count_vm_event(UNEVICTABLE_PGCULLED);

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	put_page(page);		/* drop ref from isolate */
}

#else /* CONFIG_UNEVICTABLE_LRU */

void putback_lru_page(struct page *page)
{
	int lru;
	VM_BUG_ON(PageLRU(page));

	lru = !!TestClearPageActive(page) + page_is_file_cache(page);
	lru_cache_add_lru(page, lru);
	put_page(page);
}
#endif /* CONFIG_UNEVICTABLE_LRU */


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/*
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 * shrink_page_list() returns the number of reclaimed pages
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 */
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static unsigned long shrink_page_list(struct list_head *page_list,
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					struct scan_control *sc,
					enum pageout_io sync_writeback)
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{
	LIST_HEAD(ret_pages);
	struct pagevec freed_pvec;
	int pgactivate = 0;
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	unsigned long nr_reclaimed = 0;
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	cond_resched();

	pagevec_init(&freed_pvec, 1);
	while (!list_empty(page_list)) {
		struct address_space *mapping;
		struct page *page;
		int may_enter_fs;
		int referenced;

		cond_resched();

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

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		if (!trylock_page(page))
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			goto keep;

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		VM_BUG_ON(PageActive(page));
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		sc->nr_scanned++;
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		if (unlikely(!page_evictable(page, NULL)))
			goto cull_mlocked;
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		if (!sc->may_swap && page_mapped(page))
			goto keep_locked;

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		/* Double the slab pressure for mapped and swapcache pages */
		if (page_mapped(page) || PageSwapCache(page))
			sc->nr_scanned++;

610 611 612 613 614 615 616 617 618 619 620 621 622 623
		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.
			 */
			if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
				wait_on_page_writeback(page);
624
			else
625 626
				goto keep_locked;
		}
L
Linus Torvalds 已提交
627

628
		referenced = page_referenced(page, 1, sc->mem_cgroup);
L
Linus Torvalds 已提交
629
		/* In active use or really unfreeable?  Activate it. */
A
Andy Whitcroft 已提交
630 631
		if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
					referenced && page_mapping_inuse(page))
L
Linus Torvalds 已提交
632 633 634 635 636 637
			goto activate_locked;

		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
N
Nick Piggin 已提交
638
		if (PageAnon(page) && !PageSwapCache(page)) {
639 640
			if (!(sc->gfp_mask & __GFP_IO))
				goto keep_locked;
641
			if (!add_to_swap(page))
L
Linus Torvalds 已提交
642
				goto activate_locked;
643
			may_enter_fs = 1;
N
Nick Piggin 已提交
644
		}
L
Linus Torvalds 已提交
645 646 647 648 649 650 651 652

		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) {
653
			switch (try_to_unmap(page, 0)) {
L
Linus Torvalds 已提交
654 655 656 657
			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
N
Nick Piggin 已提交
658 659
			case SWAP_MLOCK:
				goto cull_mlocked;
L
Linus Torvalds 已提交
660 661 662 663 664 665
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
A
Andy Whitcroft 已提交
666
			if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
L
Linus Torvalds 已提交
667
				goto keep_locked;
668
			if (!may_enter_fs)
L
Linus Torvalds 已提交
669
				goto keep_locked;
670
			if (!sc->may_writepage)
L
Linus Torvalds 已提交
671 672 673
				goto keep_locked;

			/* Page is dirty, try to write it out here */
674
			switch (pageout(page, mapping, sync_writeback)) {
L
Linus Torvalds 已提交
675 676 677 678 679
			case PAGE_KEEP:
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
680
				if (PageWriteback(page) || PageDirty(page))
L
Linus Torvalds 已提交
681 682 683 684 685
					goto keep;
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
N
Nick Piggin 已提交
686
				if (!trylock_page(page))
L
Linus Torvalds 已提交
687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705
					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
706
		 * will do this, as well as the blockdev mapping.
L
Linus Torvalds 已提交
707 708 709 710 711 712 713 714 715 716 717 718 719
		 * try_to_release_page() will discover that cleanness and will
		 * drop the buffers and mark the page clean - it can be freed.
		 *
		 * Rarely, pages can have buffers and no ->mapping.  These are
		 * the pages which were not successfully invalidated in
		 * truncate_complete_page().  We try to drop those buffers here
		 * and if that worked, and the page is no longer mapped into
		 * process address space (page_count == 1) it can be freed.
		 * Otherwise, leave the page on the LRU so it is swappable.
		 */
		if (PagePrivate(page)) {
			if (!try_to_release_page(page, sc->gfp_mask))
				goto activate_locked;
N
Nick Piggin 已提交
720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735
			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
736 737
		}

N
Nick Piggin 已提交
738
		if (!mapping || !__remove_mapping(mapping, page))
739
			goto keep_locked;
L
Linus Torvalds 已提交
740

N
Nick Piggin 已提交
741 742 743 744 745 746 747 748
		/*
		 * 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
749
free_it:
750
		nr_reclaimed++;
N
Nick Piggin 已提交
751 752 753 754
		if (!pagevec_add(&freed_pvec, page)) {
			__pagevec_free(&freed_pvec);
			pagevec_reinit(&freed_pvec);
		}
L
Linus Torvalds 已提交
755 756
		continue;

N
Nick Piggin 已提交
757
cull_mlocked:
758 759
		if (PageSwapCache(page))
			try_to_free_swap(page);
N
Nick Piggin 已提交
760 761 762 763
		unlock_page(page);
		putback_lru_page(page);
		continue;

L
Linus Torvalds 已提交
764
activate_locked:
765 766
		/* Not a candidate for swapping, so reclaim swap space. */
		if (PageSwapCache(page) && vm_swap_full())
767
			try_to_free_swap(page);
L
Lee Schermerhorn 已提交
768
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
769 770 771 772 773 774
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
775
		VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
L
Linus Torvalds 已提交
776 777 778
	}
	list_splice(&ret_pages, page_list);
	if (pagevec_count(&freed_pvec))
N
Nick Piggin 已提交
779
		__pagevec_free(&freed_pvec);
780
	count_vm_events(PGACTIVATE, pgactivate);
781
	return nr_reclaimed;
L
Linus Torvalds 已提交
782 783
}

A
Andy Whitcroft 已提交
784 785 786 787 788 789 790 791 792 793 794 795 796 797 798
/* LRU Isolation modes. */
#define ISOLATE_INACTIVE 0	/* Isolate inactive pages. */
#define ISOLATE_ACTIVE 1	/* Isolate active pages. */
#define ISOLATE_BOTH 2		/* Isolate both active and inactive pages. */

/*
 * 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.
 */
799
int __isolate_lru_page(struct page *page, int mode, int file)
A
Andy Whitcroft 已提交
800 801 802 803 804 805 806 807 808 809 810 811 812 813 814
{
	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;

815 816 817
	if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
		return ret;

L
Lee Schermerhorn 已提交
818 819 820 821 822 823 824 825
	/*
	 * 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
826
	ret = -EBUSY;
K
KAMEZAWA Hiroyuki 已提交
827

A
Andy Whitcroft 已提交
828 829 830 831 832 833 834 835
	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;
K
KAMEZAWA Hiroyuki 已提交
836
		mem_cgroup_del_lru(page);
A
Andy Whitcroft 已提交
837 838 839 840 841
	}

	return ret;
}

L
Linus Torvalds 已提交
842 843 844 845 846 847 848 849 850 851 852 853 854 855
/*
 * 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
856 857
 * @order:	The caller's attempted allocation order
 * @mode:	One of the LRU isolation modes
858
 * @file:	True [1] if isolating file [!anon] pages
L
Linus Torvalds 已提交
859 860 861
 *
 * returns how many pages were moved onto *@dst.
 */
862 863
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
		struct list_head *src, struct list_head *dst,
864
		unsigned long *scanned, int order, int mode, int file)
L
Linus Torvalds 已提交
865
{
866
	unsigned long nr_taken = 0;
867
	unsigned long scan;
L
Linus Torvalds 已提交
868

869
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
870 871 872 873 874 875
		struct page *page;
		unsigned long pfn;
		unsigned long end_pfn;
		unsigned long page_pfn;
		int zone_id;

L
Linus Torvalds 已提交
876 877 878
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
879
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
880

881
		switch (__isolate_lru_page(page, mode, file)) {
A
Andy Whitcroft 已提交
882 883
		case 0:
			list_move(&page->lru, dst);
884
			nr_taken++;
A
Andy Whitcroft 已提交
885 886 887 888 889 890
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
			continue;
891

A
Andy Whitcroft 已提交
892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923
		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
		 * as the mem_map is guarenteed valid out to MAX_ORDER,
		 * 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);
924

A
Andy Whitcroft 已提交
925 926 927
			/* Check that we have not crossed a zone boundary. */
			if (unlikely(page_zone_id(cursor_page) != zone_id))
				continue;
928
			switch (__isolate_lru_page(cursor_page, mode, file)) {
A
Andy Whitcroft 已提交
929 930 931 932 933 934 935 936 937 938
			case 0:
				list_move(&cursor_page->lru, dst);
				nr_taken++;
				scan++;
				break;

			case -EBUSY:
				/* else it is being freed elsewhere */
				list_move(&cursor_page->lru, src);
			default:
L
Lee Schermerhorn 已提交
939
				break;	/* ! on LRU or wrong list */
A
Andy Whitcroft 已提交
940 941
			}
		}
L
Linus Torvalds 已提交
942 943 944 945 946 947
	}

	*scanned = scan;
	return nr_taken;
}

948 949 950 951 952
static unsigned long isolate_pages_global(unsigned long nr,
					struct list_head *dst,
					unsigned long *scanned, int order,
					int mode, struct zone *z,
					struct mem_cgroup *mem_cont,
953
					int active, int file)
954
{
955
	int lru = LRU_BASE;
956
	if (active)
957 958 959 960 961
		lru += LRU_ACTIVE;
	if (file)
		lru += LRU_FILE;
	return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
								mode, !!file);
962 963
}

A
Andy Whitcroft 已提交
964 965 966 967
/*
 * clear_active_flags() is a helper for shrink_active_list(), clearing
 * any active bits from the pages in the list.
 */
968 969
static unsigned long clear_active_flags(struct list_head *page_list,
					unsigned int *count)
A
Andy Whitcroft 已提交
970 971
{
	int nr_active = 0;
972
	int lru;
A
Andy Whitcroft 已提交
973 974
	struct page *page;

975 976
	list_for_each_entry(page, page_list, lru) {
		lru = page_is_file_cache(page);
A
Andy Whitcroft 已提交
977
		if (PageActive(page)) {
978
			lru += LRU_ACTIVE;
A
Andy Whitcroft 已提交
979 980 981
			ClearPageActive(page);
			nr_active++;
		}
982 983
		count[lru]++;
	}
A
Andy Whitcroft 已提交
984 985 986 987

	return nr_active;
}

988 989 990 991 992 993 994 995 996 997 998
/**
 * 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
999 1000 1001
 * 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.
1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021
 *
 * The vmstat statistic corresponding to the list on which the page was
 * found will be decremented.
 *
 * Restrictions:
 * (1) Must be called with an elevated refcount on the page. This is a
 *     fundamentnal difference from isolate_lru_pages (which is called
 *     without a stable reference).
 * (2) the lru_lock must not be held.
 * (3) interrupts must be enabled.
 */
int isolate_lru_page(struct page *page)
{
	int ret = -EBUSY;

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

		spin_lock_irq(&zone->lru_lock);
		if (PageLRU(page) && get_page_unless_zero(page)) {
L
Lee Schermerhorn 已提交
1022
			int lru = page_lru(page);
1023 1024
			ret = 0;
			ClearPageLRU(page);
1025 1026

			del_page_from_lru_list(zone, page, lru);
1027 1028 1029 1030 1031 1032
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

L
Linus Torvalds 已提交
1033
/*
A
Andrew Morton 已提交
1034 1035
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
1036
 */
A
Andrew Morton 已提交
1037
static unsigned long shrink_inactive_list(unsigned long max_scan,
R
Rik van Riel 已提交
1038 1039
			struct zone *zone, struct scan_control *sc,
			int priority, int file)
L
Linus Torvalds 已提交
1040 1041 1042
{
	LIST_HEAD(page_list);
	struct pagevec pvec;
1043
	unsigned long nr_scanned = 0;
1044
	unsigned long nr_reclaimed = 0;
1045
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
L
Linus Torvalds 已提交
1046 1047 1048 1049 1050

	pagevec_init(&pvec, 1);

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1051
	do {
L
Linus Torvalds 已提交
1052
		struct page *page;
1053 1054 1055
		unsigned long nr_taken;
		unsigned long nr_scan;
		unsigned long nr_freed;
A
Andy Whitcroft 已提交
1056
		unsigned long nr_active;
1057
		unsigned int count[NR_LRU_LISTS] = { 0, };
R
Rik van Riel 已提交
1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070
		int mode = ISOLATE_INACTIVE;

		/*
		 * If we need a large contiguous chunk of memory, or have
		 * trouble getting a small set of contiguous pages, we
		 * will reclaim both active and inactive pages.
		 *
		 * We use the same threshold as pageout congestion_wait below.
		 */
		if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
			mode = ISOLATE_BOTH;
		else if (sc->order && priority < DEF_PRIORITY - 2)
			mode = ISOLATE_BOTH;
L
Linus Torvalds 已提交
1071

1072
		nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1073 1074 1075
			     &page_list, &nr_scan, sc->order, mode,
				zone, sc->mem_cgroup, 0, file);
		nr_active = clear_active_flags(&page_list, count);
1076
		__count_vm_events(PGDEACTIVATE, nr_active);
A
Andy Whitcroft 已提交
1077

1078 1079 1080 1081 1082 1083 1084 1085 1086 1087
		__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]);

		if (scan_global_lru(sc)) {
1088
			zone->pages_scanned += nr_scan;
1089 1090 1091 1092 1093 1094 1095 1096
			reclaim_stat->recent_scanned[0] +=
						      count[LRU_INACTIVE_ANON];
			reclaim_stat->recent_scanned[0] +=
						      count[LRU_ACTIVE_ANON];
			reclaim_stat->recent_scanned[1] +=
						      count[LRU_INACTIVE_FILE];
			reclaim_stat->recent_scanned[1] +=
						      count[LRU_ACTIVE_FILE];
1097
		}
L
Linus Torvalds 已提交
1098 1099
		spin_unlock_irq(&zone->lru_lock);

1100
		nr_scanned += nr_scan;
1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116
		nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);

		/*
		 * If we are direct reclaiming for contiguous pages and we do
		 * not reclaim everything in the list, try again and wait
		 * for IO to complete. This will stall high-order allocations
		 * but that should be acceptable to the caller
		 */
		if (nr_freed < nr_taken && !current_is_kswapd() &&
					sc->order > PAGE_ALLOC_COSTLY_ORDER) {
			congestion_wait(WRITE, HZ/10);

			/*
			 * The attempt at page out may have made some
			 * of the pages active, mark them inactive again.
			 */
1117
			nr_active = clear_active_flags(&page_list, count);
1118 1119 1120 1121 1122 1123
			count_vm_events(PGDEACTIVATE, nr_active);

			nr_freed += shrink_page_list(&page_list, sc,
							PAGEOUT_IO_SYNC);
		}

1124
		nr_reclaimed += nr_freed;
N
Nick Piggin 已提交
1125 1126
		local_irq_disable();
		if (current_is_kswapd()) {
1127 1128
			__count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
			__count_vm_events(KSWAPD_STEAL, nr_freed);
1129
		} else if (scan_global_lru(sc))
1130
			__count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
1131

S
Shantanu Goel 已提交
1132
		__count_zone_vm_events(PGSTEAL, zone, nr_freed);
N
Nick Piggin 已提交
1133

1134 1135 1136
		if (nr_taken == 0)
			goto done;

N
Nick Piggin 已提交
1137
		spin_lock(&zone->lru_lock);
L
Linus Torvalds 已提交
1138 1139 1140 1141
		/*
		 * Put back any unfreeable pages.
		 */
		while (!list_empty(&page_list)) {
L
Lee Schermerhorn 已提交
1142
			int lru;
L
Linus Torvalds 已提交
1143
			page = lru_to_page(&page_list);
N
Nick Piggin 已提交
1144
			VM_BUG_ON(PageLRU(page));
L
Linus Torvalds 已提交
1145
			list_del(&page->lru);
L
Lee Schermerhorn 已提交
1146 1147 1148 1149 1150 1151 1152 1153 1154
			if (unlikely(!page_evictable(page, NULL))) {
				spin_unlock_irq(&zone->lru_lock);
				putback_lru_page(page);
				spin_lock_irq(&zone->lru_lock);
				continue;
			}
			SetPageLRU(page);
			lru = page_lru(page);
			add_page_to_lru_list(zone, page, lru);
1155 1156
			if (PageActive(page) && scan_global_lru(sc)) {
				int file = !!page_is_file_cache(page);
1157
				reclaim_stat->recent_rotated[file]++;
1158
			}
L
Linus Torvalds 已提交
1159 1160 1161 1162 1163 1164
			if (!pagevec_add(&pvec, page)) {
				spin_unlock_irq(&zone->lru_lock);
				__pagevec_release(&pvec);
				spin_lock_irq(&zone->lru_lock);
			}
		}
1165
  	} while (nr_scanned < max_scan);
1166
	spin_unlock(&zone->lru_lock);
L
Linus Torvalds 已提交
1167
done:
1168
	local_irq_enable();
L
Linus Torvalds 已提交
1169
	pagevec_release(&pvec);
1170
	return nr_reclaimed;
L
Linus Torvalds 已提交
1171 1172
}

1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186
/*
 * We are about to scan this zone at a certain priority level.  If that priority
 * level is smaller (ie: more urgent) than the previous priority, then note
 * that priority level within the zone.  This is done so that when the next
 * process comes in to scan this zone, it will immediately start out at this
 * priority level rather than having to build up its own scanning priority.
 * Here, this priority affects only the reclaim-mapped threshold.
 */
static inline void note_zone_scanning_priority(struct zone *zone, int priority)
{
	if (priority < zone->prev_priority)
		zone->prev_priority = priority;
}

L
Linus Torvalds 已提交
1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203
/*
 * 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.
 */
1204 1205


A
Andrew Morton 已提交
1206
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1207
			struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1208
{
1209
	unsigned long pgmoved;
L
Linus Torvalds 已提交
1210
	int pgdeactivate = 0;
1211
	unsigned long pgscanned;
L
Linus Torvalds 已提交
1212
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
1213
	LIST_HEAD(l_inactive);
L
Linus Torvalds 已提交
1214 1215
	struct page *page;
	struct pagevec pvec;
1216
	enum lru_list lru;
1217
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
L
Linus Torvalds 已提交
1218 1219 1220

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1221 1222
	pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
					ISOLATE_ACTIVE, zone,
1223
					sc->mem_cgroup, 1, file);
1224 1225 1226 1227
	/*
	 * zone->pages_scanned is used for detect zone's oom
	 * mem_cgroup remembers nr_scan by itself.
	 */
1228
	if (scan_global_lru(sc)) {
1229
		zone->pages_scanned += pgscanned;
1230
		reclaim_stat->recent_scanned[!!file] += pgmoved;
1231
	}
1232

1233 1234 1235 1236
	if (file)
		__mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
	else
		__mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
L
Linus Torvalds 已提交
1237 1238
	spin_unlock_irq(&zone->lru_lock);

1239
	pgmoved = 0;
L
Linus Torvalds 已提交
1240 1241 1242 1243
	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
1244

L
Lee Schermerhorn 已提交
1245 1246 1247 1248 1249
		if (unlikely(!page_evictable(page, NULL))) {
			putback_lru_page(page);
			continue;
		}

1250 1251 1252 1253 1254
		/* page_referenced clears PageReferenced */
		if (page_mapping_inuse(page) &&
		    page_referenced(page, 0, sc->mem_cgroup))
			pgmoved++;

L
Linus Torvalds 已提交
1255 1256 1257
		list_add(&page->lru, &l_inactive);
	}

1258 1259 1260 1261 1262 1263 1264
	/*
	 * Move the pages to the [file or anon] inactive list.
	 */
	pagevec_init(&pvec, 1);
	pgmoved = 0;
	lru = LRU_BASE + file * LRU_FILE;

1265
	spin_lock_irq(&zone->lru_lock);
1266
	/*
1267 1268 1269 1270 1271
	 * Count referenced pages from currently used mappings as
	 * rotated, even though they are moved to the inactive list.
	 * This helps balance scan pressure between file and anonymous
	 * pages in get_scan_ratio.
	 */
1272
	if (scan_global_lru(sc))
1273
		reclaim_stat->recent_rotated[!!file] += pgmoved;
1274

L
Linus Torvalds 已提交
1275 1276 1277
	while (!list_empty(&l_inactive)) {
		page = lru_to_page(&l_inactive);
		prefetchw_prev_lru_page(page, &l_inactive, flags);
N
Nick Piggin 已提交
1278
		VM_BUG_ON(PageLRU(page));
N
Nick Piggin 已提交
1279
		SetPageLRU(page);
N
Nick Piggin 已提交
1280
		VM_BUG_ON(!PageActive(page));
N
Nick Piggin 已提交
1281 1282
		ClearPageActive(page);

1283
		list_move(&page->lru, &zone->lru[lru].list);
K
KAMEZAWA Hiroyuki 已提交
1284
		mem_cgroup_add_lru_list(page, lru);
L
Linus Torvalds 已提交
1285 1286
		pgmoved++;
		if (!pagevec_add(&pvec, page)) {
1287
			__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
L
Linus Torvalds 已提交
1288 1289 1290 1291 1292 1293 1294 1295 1296
			spin_unlock_irq(&zone->lru_lock);
			pgdeactivate += pgmoved;
			pgmoved = 0;
			if (buffer_heads_over_limit)
				pagevec_strip(&pvec);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
1297
	__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
L
Linus Torvalds 已提交
1298 1299 1300 1301 1302 1303
	pgdeactivate += pgmoved;
	if (buffer_heads_over_limit) {
		spin_unlock_irq(&zone->lru_lock);
		pagevec_strip(&pvec);
		spin_lock_irq(&zone->lru_lock);
	}
1304 1305 1306
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
	__count_vm_events(PGDEACTIVATE, pgdeactivate);
	spin_unlock_irq(&zone->lru_lock);
1307 1308
	if (vm_swap_full())
		pagevec_swap_free(&pvec);
L
Linus Torvalds 已提交
1309

N
Nick Piggin 已提交
1310
	pagevec_release(&pvec);
L
Linus Torvalds 已提交
1311 1312
}

1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332
/**
 * inactive_anon_is_low - check if anonymous pages need to be deactivated
 * @zone: zone to check
 *
 * Returns true if the zone does not have enough inactive anon pages,
 * meaning some active anon pages need to be deactivated.
 */
static int inactive_anon_is_low(struct zone *zone)
{
	unsigned long active, inactive;

	active = zone_page_state(zone, NR_ACTIVE_ANON);
	inactive = zone_page_state(zone, NR_INACTIVE_ANON);

	if (inactive * zone->inactive_ratio < active)
		return 1;

	return 0;
}

1333
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1334 1335
	struct zone *zone, struct scan_control *sc, int priority)
{
1336 1337
	int file = is_file_lru(lru);

1338 1339 1340 1341 1342 1343 1344
	if (lru == LRU_ACTIVE_FILE) {
		shrink_active_list(nr_to_scan, zone, sc, priority, file);
		return 0;
	}

	if (lru == LRU_ACTIVE_ANON &&
	    (!scan_global_lru(sc) || inactive_anon_is_low(zone))) {
1345
		shrink_active_list(nr_to_scan, zone, sc, priority, file);
1346 1347
		return 0;
	}
R
Rik van Riel 已提交
1348
	return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365
}

/*
 * 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.
 *
 * percent[0] specifies how much pressure to put on ram/swap backed
 * memory, while percent[1] determines pressure on the file LRUs.
 */
static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
					unsigned long *percent)
{
	unsigned long anon, file, free;
	unsigned long anon_prio, file_prio;
	unsigned long ap, fp;
1366
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1367 1368 1369 1370 1371 1372 1373 1374

	/* If we have no swap space, do not bother scanning anon pages. */
	if (nr_swap_pages <= 0) {
		percent[0] = 0;
		percent[1] = 100;
		return;
	}

1375 1376 1377 1378
	anon  = zone_nr_pages(zone, sc, LRU_ACTIVE_ANON) +
		zone_nr_pages(zone, sc, LRU_INACTIVE_ANON);
	file  = zone_nr_pages(zone, sc, LRU_ACTIVE_FILE) +
		zone_nr_pages(zone, sc, LRU_INACTIVE_FILE);
1379 1380
	free  = zone_page_state(zone, NR_FREE_PAGES);

1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398
	/* If we have very few page cache pages, force-scan anon pages. */
	if (unlikely(file + free <= zone->pages_high)) {
		percent[0] = 100;
		percent[1] = 0;
		return;
	}

	/*
	 * 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]
	 */
1399
	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1400
		spin_lock_irq(&zone->lru_lock);
1401 1402
		reclaim_stat->recent_scanned[0] /= 2;
		reclaim_stat->recent_rotated[0] /= 2;
1403 1404 1405
		spin_unlock_irq(&zone->lru_lock);
	}

1406
	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1407
		spin_lock_irq(&zone->lru_lock);
1408 1409
		reclaim_stat->recent_scanned[1] /= 2;
		reclaim_stat->recent_rotated[1] /= 2;
1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420
		spin_unlock_irq(&zone->lru_lock);
	}

	/*
	 * 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;

	/*
1421 1422 1423
	 * 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.
1424
	 */
1425 1426
	ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
	ap /= reclaim_stat->recent_rotated[0] + 1;
1427

1428 1429
	fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
	fp /= reclaim_stat->recent_rotated[1] + 1;
1430 1431 1432 1433

	/* Normalize to percentages */
	percent[0] = 100 * ap / (ap + fp + 1);
	percent[1] = 100 - percent[0];
1434 1435
}

1436

L
Linus Torvalds 已提交
1437 1438 1439
/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
1440
static void shrink_zone(int priority, struct zone *zone,
1441
				struct scan_control *sc)
L
Linus Torvalds 已提交
1442
{
1443
	unsigned long nr[NR_LRU_LISTS];
1444
	unsigned long nr_to_scan;
1445
	unsigned long percent[2];	/* anon @ 0; file @ 1 */
1446
	enum lru_list l;
1447 1448
	unsigned long nr_reclaimed = sc->nr_reclaimed;
	unsigned long swap_cluster_max = sc->swap_cluster_max;
L
Linus Torvalds 已提交
1449

1450 1451
	get_scan_ratio(zone, sc, percent);

L
Lee Schermerhorn 已提交
1452
	for_each_evictable_lru(l) {
1453 1454 1455
		if (scan_global_lru(sc)) {
			int file = is_file_lru(l);
			int scan;
1456

1457 1458 1459 1460 1461
			scan = zone_page_state(zone, NR_LRU_BASE + l);
			if (priority) {
				scan >>= priority;
				scan = (scan * percent[file]) / 100;
			}
1462
			zone->lru[l].nr_scan += scan;
1463
			nr[l] = zone->lru[l].nr_scan;
1464
			if (nr[l] >= swap_cluster_max)
1465 1466 1467
				zone->lru[l].nr_scan = 0;
			else
				nr[l] = 0;
1468 1469 1470 1471 1472 1473 1474 1475
		} else {
			/*
			 * This reclaim occurs not because zone memory shortage
			 * but because memory controller hits its limit.
			 * Don't modify zone reclaim related data.
			 */
			nr[l] = mem_cgroup_calc_reclaim(sc->mem_cgroup, zone,
								priority, l);
1476
		}
1477
	}
L
Linus Torvalds 已提交
1478

1479 1480
	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
					nr[LRU_INACTIVE_FILE]) {
L
Lee Schermerhorn 已提交
1481
		for_each_evictable_lru(l) {
1482
			if (nr[l]) {
1483
				nr_to_scan = min(nr[l], swap_cluster_max);
1484
				nr[l] -= nr_to_scan;
L
Linus Torvalds 已提交
1485

1486 1487
				nr_reclaimed += shrink_list(l, nr_to_scan,
							    zone, sc, priority);
1488
			}
L
Linus Torvalds 已提交
1489
		}
1490 1491 1492 1493 1494 1495 1496 1497
		/*
		 * 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.
		 */
1498
		if (nr_reclaimed > swap_cluster_max &&
1499 1500
			priority < DEF_PRIORITY && !current_is_kswapd())
			break;
L
Linus Torvalds 已提交
1501 1502
	}

1503 1504
	sc->nr_reclaimed = nr_reclaimed;

1505 1506 1507 1508 1509 1510 1511 1512 1513
	/*
	 * Even if we did not try to evict anon pages at all, we want to
	 * rebalance the anon lru active/inactive ratio.
	 */
	if (!scan_global_lru(sc) || inactive_anon_is_low(zone))
		shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
	else if (!scan_global_lru(sc))
		shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);

1514
	throttle_vm_writeout(sc->gfp_mask);
L
Linus Torvalds 已提交
1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530
}

/*
 * This is the direct reclaim path, for page-allocating processes.  We only
 * try to reclaim pages from zones which will satisfy the caller's allocation
 * request.
 *
 * We reclaim from a zone even if that zone is over pages_high.  Because:
 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
 *    allocation or
 * b) The zones may be over pages_high but they must go *over* pages_high to
 *    satisfy the `incremental min' zone defense algorithm.
 *
 * If a zone is deemed to be full of pinned pages then just give it a light
 * scan then give up on it.
 */
1531
static void shrink_zones(int priority, struct zonelist *zonelist,
1532
					struct scan_control *sc)
L
Linus Torvalds 已提交
1533
{
1534
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1535
	struct zoneref *z;
1536
	struct zone *zone;
1537

1538
	sc->all_unreclaimable = 1;
1539
	for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1540
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
1541
			continue;
1542 1543 1544 1545 1546 1547 1548 1549
		/*
		 * Take care memory controller reclaiming has small influence
		 * to global LRU.
		 */
		if (scan_global_lru(sc)) {
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
			note_zone_scanning_priority(zone, priority);
L
Linus Torvalds 已提交
1550

1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563
			if (zone_is_all_unreclaimable(zone) &&
						priority != DEF_PRIORITY)
				continue;	/* Let kswapd poll it */
			sc->all_unreclaimable = 0;
		} else {
			/*
			 * Ignore cpuset limitation here. We just want to reduce
			 * # of used pages by us regardless of memory shortage.
			 */
			sc->all_unreclaimable = 0;
			mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
							priority);
		}
1564

1565
		shrink_zone(priority, zone, sc);
L
Linus Torvalds 已提交
1566 1567
	}
}
1568

L
Linus Torvalds 已提交
1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580
/*
 * This is the main entry point to direct page reclaim.
 *
 * If a full scan of the inactive list fails to free enough memory then we
 * are "out of memory" and something needs to be killed.
 *
 * If the caller is !__GFP_FS then the probability of a failure is reasonably
 * high - the zone may be full of dirty or under-writeback pages, which this
 * caller can't do much about.  We kick pdflush 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.
1581 1582 1583
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
1584
 */
1585
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1586
					struct scan_control *sc)
L
Linus Torvalds 已提交
1587 1588
{
	int priority;
1589
	unsigned long ret = 0;
1590
	unsigned long total_scanned = 0;
L
Linus Torvalds 已提交
1591 1592
	struct reclaim_state *reclaim_state = current->reclaim_state;
	unsigned long lru_pages = 0;
1593
	struct zoneref *z;
1594
	struct zone *zone;
1595
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
L
Linus Torvalds 已提交
1596

1597 1598
	delayacct_freepages_start();

1599 1600 1601 1602 1603 1604
	if (scan_global_lru(sc))
		count_vm_event(ALLOCSTALL);
	/*
	 * mem_cgroup will not do shrink_slab.
	 */
	if (scan_global_lru(sc)) {
1605
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
L
Linus Torvalds 已提交
1606

1607 1608
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
L
Linus Torvalds 已提交
1609

1610
			lru_pages += zone_lru_pages(zone);
1611
		}
L
Linus Torvalds 已提交
1612 1613 1614
	}

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1615
		sc->nr_scanned = 0;
1616 1617
		if (!priority)
			disable_swap_token();
1618
		shrink_zones(priority, zonelist, sc);
1619 1620 1621 1622
		/*
		 * Don't shrink slabs when reclaiming memory from
		 * over limit cgroups
		 */
1623
		if (scan_global_lru(sc)) {
1624
			shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1625
			if (reclaim_state) {
1626
				sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1627 1628
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
1629
		}
1630
		total_scanned += sc->nr_scanned;
1631 1632
		if (sc->nr_reclaimed >= sc->swap_cluster_max) {
			ret = sc->nr_reclaimed;
L
Linus Torvalds 已提交
1633 1634 1635 1636 1637 1638 1639 1640 1641 1642
			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.
		 */
1643 1644
		if (total_scanned > sc->swap_cluster_max +
					sc->swap_cluster_max / 2) {
1645
			wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1646
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
1647 1648 1649
		}

		/* Take a nap, wait for some writeback to complete */
1650
		if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1651
			congestion_wait(WRITE, HZ/10);
L
Linus Torvalds 已提交
1652
	}
1653
	/* top priority shrink_zones still had more to do? don't OOM, then */
1654
	if (!sc->all_unreclaimable && scan_global_lru(sc))
1655
		ret = sc->nr_reclaimed;
L
Linus Torvalds 已提交
1656
out:
1657 1658 1659 1660 1661 1662 1663 1664 1665
	/*
	 * Now that we've scanned all the zones at this priority level, note
	 * that level within the zone so that the next thread which performs
	 * scanning of this zone will immediately start out at this priority
	 * level.  This affects only the decision whether or not to bring
	 * mapped pages onto the inactive list.
	 */
	if (priority < 0)
		priority = 0;
L
Linus Torvalds 已提交
1666

1667
	if (scan_global_lru(sc)) {
1668
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1669 1670 1671 1672 1673 1674 1675 1676

			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;

			zone->prev_priority = priority;
		}
	} else
		mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
L
Linus Torvalds 已提交
1677

1678 1679
	delayacct_freepages_end();

L
Linus Torvalds 已提交
1680 1681 1682
	return ret;
}

1683 1684
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
								gfp_t gfp_mask)
1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696
{
	struct scan_control sc = {
		.gfp_mask = gfp_mask,
		.may_writepage = !laptop_mode,
		.swap_cluster_max = SWAP_CLUSTER_MAX,
		.may_swap = 1,
		.swappiness = vm_swappiness,
		.order = order,
		.mem_cgroup = NULL,
		.isolate_pages = isolate_pages_global,
	};

1697
	return do_try_to_free_pages(zonelist, &sc);
1698 1699
}

1700
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1701

1702
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1703 1704
						gfp_t gfp_mask,
					   bool noswap)
1705 1706 1707 1708 1709 1710 1711 1712 1713 1714
{
	struct scan_control sc = {
		.may_writepage = !laptop_mode,
		.may_swap = 1,
		.swap_cluster_max = SWAP_CLUSTER_MAX,
		.swappiness = vm_swappiness,
		.order = 0,
		.mem_cgroup = mem_cont,
		.isolate_pages = mem_cgroup_isolate_pages,
	};
1715
	struct zonelist *zonelist;
1716

1717 1718 1719
	if (noswap)
		sc.may_swap = 0;

1720 1721 1722 1723
	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
	zonelist = NODE_DATA(numa_node_id())->node_zonelists;
	return do_try_to_free_pages(zonelist, &sc);
1724 1725 1726
}
#endif

L
Linus Torvalds 已提交
1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747
/*
 * For kswapd, balance_pgdat() will work across all this node's zones until
 * they are all at pages_high.
 *
 * Returns the number of pages which were actually freed.
 *
 * There is special handling here for zones which are full of pinned pages.
 * This can happen if the pages are all mlocked, or if they are all used by
 * device drivers (say, ZONE_DMA).  Or if they are all in use by hugetlb.
 * What we do is to detect the case where all pages in the zone have been
 * scanned twice and there has been zero successful reclaim.  Mark the zone as
 * dead and from now on, only perform a short scan.  Basically we're polling
 * the zone for when the problem goes away.
 *
 * kswapd scans the zones in the highmem->normal->dma direction.  It skips
 * zones which have free_pages > pages_high, but once a zone is found to have
 * free_pages <= pages_high, 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.
 */
1748
static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
L
Linus Torvalds 已提交
1749 1750 1751 1752
{
	int all_zones_ok;
	int priority;
	int i;
1753
	unsigned long total_scanned;
L
Linus Torvalds 已提交
1754
	struct reclaim_state *reclaim_state = current->reclaim_state;
1755 1756 1757
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
		.may_swap = 1,
1758 1759
		.swap_cluster_max = SWAP_CLUSTER_MAX,
		.swappiness = vm_swappiness,
A
Andy Whitcroft 已提交
1760
		.order = order,
1761 1762
		.mem_cgroup = NULL,
		.isolate_pages = isolate_pages_global,
1763
	};
1764 1765 1766 1767 1768
	/*
	 * temp_priority is used to remember the scanning priority at which
	 * this zone was successfully refilled to free_pages == pages_high.
	 */
	int temp_priority[MAX_NR_ZONES];
L
Linus Torvalds 已提交
1769 1770 1771

loop_again:
	total_scanned = 0;
1772
	sc.nr_reclaimed = 0;
C
Christoph Lameter 已提交
1773
	sc.may_writepage = !laptop_mode;
1774
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
1775

1776 1777
	for (i = 0; i < pgdat->nr_zones; i++)
		temp_priority[i] = DEF_PRIORITY;
L
Linus Torvalds 已提交
1778 1779 1780 1781 1782

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
		int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */
		unsigned long lru_pages = 0;

1783 1784 1785 1786
		/* The swap token gets in the way of swapout... */
		if (!priority)
			disable_swap_token();

L
Linus Torvalds 已提交
1787 1788
		all_zones_ok = 1;

1789 1790 1791 1792 1793 1794
		/*
		 * 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
1795

1796 1797
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
1798

1799 1800
			if (zone_is_all_unreclaimable(zone) &&
			    priority != DEF_PRIORITY)
1801
				continue;
L
Linus Torvalds 已提交
1802

1803 1804 1805 1806 1807 1808 1809 1810
			/*
			 * Do some background aging of the anon list, to give
			 * pages a chance to be referenced before reclaiming.
			 */
			if (inactive_anon_is_low(zone))
				shrink_active_list(SWAP_CLUSTER_MAX, zone,
							&sc, priority, 0);

1811 1812 1813
			if (!zone_watermark_ok(zone, order, zone->pages_high,
					       0, 0)) {
				end_zone = i;
A
Andrew Morton 已提交
1814
				break;
L
Linus Torvalds 已提交
1815 1816
			}
		}
A
Andrew Morton 已提交
1817 1818 1819
		if (i < 0)
			goto out;

L
Linus Torvalds 已提交
1820 1821 1822
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

1823
			lru_pages += zone_lru_pages(zone);
L
Linus Torvalds 已提交
1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836
		}

		/*
		 * 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;
1837
			int nr_slab;
L
Linus Torvalds 已提交
1838

1839
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
1840 1841
				continue;

1842 1843
			if (zone_is_all_unreclaimable(zone) &&
					priority != DEF_PRIORITY)
L
Linus Torvalds 已提交
1844 1845
				continue;

1846 1847 1848
			if (!zone_watermark_ok(zone, order, zone->pages_high,
					       end_zone, 0))
				all_zones_ok = 0;
1849
			temp_priority[i] = priority;
L
Linus Torvalds 已提交
1850
			sc.nr_scanned = 0;
1851
			note_zone_scanning_priority(zone, priority);
1852 1853 1854 1855 1856 1857
			/*
			 * We put equal pressure on every zone, unless one
			 * zone has way too many pages free already.
			 */
			if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
						end_zone, 0))
1858
				shrink_zone(priority, zone, &sc);
L
Linus Torvalds 已提交
1859
			reclaim_state->reclaimed_slab = 0;
1860 1861
			nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
						lru_pages);
1862
			sc.nr_reclaimed += reclaim_state->reclaimed_slab;
L
Linus Torvalds 已提交
1863
			total_scanned += sc.nr_scanned;
1864
			if (zone_is_all_unreclaimable(zone))
L
Linus Torvalds 已提交
1865
				continue;
1866
			if (nr_slab == 0 && zone->pages_scanned >=
1867
						(zone_lru_pages(zone) * 6))
1868 1869
					zone_set_flag(zone,
						      ZONE_ALL_UNRECLAIMABLE);
L
Linus Torvalds 已提交
1870 1871 1872 1873 1874 1875
			/*
			 * 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 &&
1876
			    total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
L
Linus Torvalds 已提交
1877 1878 1879 1880 1881 1882 1883 1884
				sc.may_writepage = 1;
		}
		if (all_zones_ok)
			break;		/* kswapd: all done */
		/*
		 * OK, kswapd is getting into trouble.  Take a nap, then take
		 * another pass across the zones.
		 */
1885
		if (total_scanned && priority < DEF_PRIORITY - 2)
1886
			congestion_wait(WRITE, HZ/10);
L
Linus Torvalds 已提交
1887 1888 1889 1890 1891 1892 1893

		/*
		 * 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.
		 */
1894
		if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
L
Linus Torvalds 已提交
1895 1896 1897
			break;
	}
out:
1898 1899 1900 1901 1902
	/*
	 * Note within each zone the priority level at which this zone was
	 * brought into a happy state.  So that the next thread which scans this
	 * zone will start out at that priority level.
	 */
L
Linus Torvalds 已提交
1903 1904 1905
	for (i = 0; i < pgdat->nr_zones; i++) {
		struct zone *zone = pgdat->node_zones + i;

1906
		zone->prev_priority = temp_priority[i];
L
Linus Torvalds 已提交
1907 1908 1909
	}
	if (!all_zones_ok) {
		cond_resched();
1910 1911 1912

		try_to_freeze();

1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929
		/*
		 * 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
1930 1931 1932
		goto loop_again;
	}

1933
	return sc.nr_reclaimed;
L
Linus Torvalds 已提交
1934 1935 1936 1937
}

/*
 * The background pageout daemon, started as a kernel thread
1938
 * from the init process.
L
Linus Torvalds 已提交
1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957
 *
 * 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;
	pg_data_t *pgdat = (pg_data_t*)p;
	struct task_struct *tsk = current;
	DEFINE_WAIT(wait);
	struct reclaim_state reclaim_state = {
		.reclaimed_slab = 0,
	};
1958
	node_to_cpumask_ptr(cpumask, pgdat->node_id);
L
Linus Torvalds 已提交
1959

R
Rusty Russell 已提交
1960
	if (!cpumask_empty(cpumask))
1961
		set_cpus_allowed_ptr(tsk, cpumask);
L
Linus Torvalds 已提交
1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975
	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).
	 */
1976
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
1977
	set_freezable();
L
Linus Torvalds 已提交
1978 1979 1980 1981

	order = 0;
	for ( ; ; ) {
		unsigned long new_order;
1982

L
Linus Torvalds 已提交
1983 1984 1985 1986 1987 1988 1989 1990 1991 1992
		prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
		new_order = pgdat->kswapd_max_order;
		pgdat->kswapd_max_order = 0;
		if (order < new_order) {
			/*
			 * Don't sleep if someone wants a larger 'order'
			 * allocation
			 */
			order = new_order;
		} else {
1993 1994 1995
			if (!freezing(current))
				schedule();

L
Linus Torvalds 已提交
1996 1997 1998 1999
			order = pgdat->kswapd_max_order;
		}
		finish_wait(&pgdat->kswapd_wait, &wait);

2000 2001 2002 2003 2004 2005
		if (!try_to_freeze()) {
			/* We can speed up thawing tasks if we don't call
			 * balance_pgdat after returning from the refrigerator
			 */
			balance_pgdat(pgdat, order);
		}
L
Linus Torvalds 已提交
2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
	}
	return 0;
}

/*
 * A zone is low on free memory, so wake its kswapd task to service it.
 */
void wakeup_kswapd(struct zone *zone, int order)
{
	pg_data_t *pgdat;

2017
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
2018 2019 2020
		return;

	pgdat = zone->zone_pgdat;
R
Rohit Seth 已提交
2021
	if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
L
Linus Torvalds 已提交
2022 2023 2024
		return;
	if (pgdat->kswapd_max_order < order)
		pgdat->kswapd_max_order = order;
2025
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
2026
		return;
2027
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
2028
		return;
2029
	wake_up_interruptible(&pgdat->kswapd_wait);
L
Linus Torvalds 已提交
2030 2031
}

2032 2033 2034 2035 2036 2037 2038 2039
unsigned long global_lru_pages(void)
{
	return global_page_state(NR_ACTIVE_ANON)
		+ global_page_state(NR_ACTIVE_FILE)
		+ global_page_state(NR_INACTIVE_ANON)
		+ global_page_state(NR_INACTIVE_FILE);
}

L
Linus Torvalds 已提交
2040 2041
#ifdef CONFIG_PM
/*
2042 2043 2044 2045 2046 2047
 * Helper function for shrink_all_memory().  Tries to reclaim 'nr_pages' pages
 * from LRU lists system-wide, for given pass and priority, and returns the
 * number of reclaimed pages
 *
 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
 */
2048 2049
static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
				      int pass, struct scan_control *sc)
2050 2051 2052
{
	struct zone *zone;
	unsigned long nr_to_scan, ret = 0;
2053
	enum lru_list l;
2054 2055 2056 2057 2058 2059

	for_each_zone(zone) {

		if (!populated_zone(zone))
			continue;

2060
		if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
2061 2062
			continue;

L
Lee Schermerhorn 已提交
2063 2064
		for_each_evictable_lru(l) {
			/* For pass = 0, we don't shrink the active list */
2065 2066
			if (pass == 0 &&
				(l == LRU_ACTIVE || l == LRU_ACTIVE_FILE))
2067 2068 2069 2070 2071 2072 2073
				continue;

			zone->lru[l].nr_scan +=
				(zone_page_state(zone, NR_LRU_BASE + l)
								>> prio) + 1;
			if (zone->lru[l].nr_scan >= nr_pages || pass > 3) {
				zone->lru[l].nr_scan = 0;
2074
				nr_to_scan = min(nr_pages,
2075 2076 2077 2078 2079 2080
					zone_page_state(zone,
							NR_LRU_BASE + l));
				ret += shrink_list(l, nr_to_scan, zone,
								sc, prio);
				if (ret >= nr_pages)
					return ret;
2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094
			}
		}
	}

	return ret;
}

/*
 * Try to free `nr_pages' of memory, system-wide, and return the number of
 * freed pages.
 *
 * Rather than trying to age LRUs the aim is to preserve the overall
 * LRU order by reclaiming preferentially
 * inactive > active > active referenced > active mapped
L
Linus Torvalds 已提交
2095
 */
2096
unsigned long shrink_all_memory(unsigned long nr_pages)
L
Linus Torvalds 已提交
2097
{
2098
	unsigned long lru_pages, nr_slab;
2099
	unsigned long ret = 0;
2100 2101 2102 2103 2104 2105 2106 2107
	int pass;
	struct reclaim_state reclaim_state;
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
		.may_swap = 0,
		.swap_cluster_max = nr_pages,
		.may_writepage = 1,
		.swappiness = vm_swappiness,
2108
		.isolate_pages = isolate_pages_global,
L
Linus Torvalds 已提交
2109 2110 2111
	};

	current->reclaim_state = &reclaim_state;
2112

2113
	lru_pages = global_lru_pages();
2114
	nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
2115 2116 2117 2118 2119
	/* If slab caches are huge, it's better to hit them first */
	while (nr_slab >= lru_pages) {
		reclaim_state.reclaimed_slab = 0;
		shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
		if (!reclaim_state.reclaimed_slab)
L
Linus Torvalds 已提交
2120
			break;
2121 2122 2123 2124 2125 2126

		ret += reclaim_state.reclaimed_slab;
		if (ret >= nr_pages)
			goto out;

		nr_slab -= reclaim_state.reclaimed_slab;
L
Linus Torvalds 已提交
2127
	}
2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154

	/*
	 * We try to shrink LRUs in 5 passes:
	 * 0 = Reclaim from inactive_list only
	 * 1 = Reclaim from active list but don't reclaim mapped
	 * 2 = 2nd pass of type 1
	 * 3 = Reclaim mapped (normal reclaim)
	 * 4 = 2nd pass of type 3
	 */
	for (pass = 0; pass < 5; pass++) {
		int prio;

		/* Force reclaiming mapped pages in the passes #3 and #4 */
		if (pass > 2) {
			sc.may_swap = 1;
			sc.swappiness = 100;
		}

		for (prio = DEF_PRIORITY; prio >= 0; prio--) {
			unsigned long nr_to_scan = nr_pages - ret;

			sc.nr_scanned = 0;
			ret += shrink_all_zones(nr_to_scan, prio, pass, &sc);
			if (ret >= nr_pages)
				goto out;

			reclaim_state.reclaimed_slab = 0;
2155
			shrink_slab(sc.nr_scanned, sc.gfp_mask,
2156
					global_lru_pages());
2157 2158 2159 2160 2161
			ret += reclaim_state.reclaimed_slab;
			if (ret >= nr_pages)
				goto out;

			if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
2162
				congestion_wait(WRITE, HZ / 10);
2163
		}
2164
	}
2165 2166 2167 2168 2169

	/*
	 * If ret = 0, we could not shrink LRUs, but there may be something
	 * in slab caches
	 */
2170
	if (!ret) {
2171 2172
		do {
			reclaim_state.reclaimed_slab = 0;
2173
			shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
2174 2175
			ret += reclaim_state.reclaimed_slab;
		} while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
2176
	}
2177 2178

out:
L
Linus Torvalds 已提交
2179
	current->reclaim_state = NULL;
2180

L
Linus Torvalds 已提交
2181 2182 2183 2184 2185 2186 2187 2188
	return ret;
}
#endif

/* 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. */
2189
static int __devinit cpu_callback(struct notifier_block *nfb,
2190
				  unsigned long action, void *hcpu)
L
Linus Torvalds 已提交
2191
{
2192
	int nid;
L
Linus Torvalds 已提交
2193

2194
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2195
		for_each_node_state(nid, N_HIGH_MEMORY) {
2196 2197 2198
			pg_data_t *pgdat = NODE_DATA(nid);
			node_to_cpumask_ptr(mask, pgdat->node_id);

2199
			if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
2200
				/* One of our CPUs online: restore mask */
2201
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
2202 2203 2204 2205 2206
		}
	}
	return NOTIFY_OK;
}

2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228
/*
 * 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;
}

L
Linus Torvalds 已提交
2229 2230
static int __init kswapd_init(void)
{
2231
	int nid;
2232

L
Linus Torvalds 已提交
2233
	swap_setup();
2234
	for_each_node_state(nid, N_HIGH_MEMORY)
2235
 		kswapd_run(nid);
L
Linus Torvalds 已提交
2236 2237 2238 2239 2240
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
2241 2242 2243 2244 2245 2246 2247 2248 2249 2250

#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;

2251
#define RECLAIM_OFF 0
2252
#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
2253 2254 2255
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

2256 2257 2258 2259 2260 2261 2262
/*
 * 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

2263 2264 2265 2266 2267 2268
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

2269 2270 2271 2272 2273 2274
/*
 * 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;

2275 2276 2277
/*
 * Try to free up some pages from this zone through reclaim.
 */
2278
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2279
{
2280
	/* Minimum pages needed in order to stay on node */
2281
	const unsigned long nr_pages = 1 << order;
2282 2283
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
2284
	int priority;
2285 2286 2287
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
		.may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2288 2289
		.swap_cluster_max = max_t(unsigned long, nr_pages,
					SWAP_CLUSTER_MAX),
2290
		.gfp_mask = gfp_mask,
2291
		.swappiness = vm_swappiness,
2292
		.isolate_pages = isolate_pages_global,
2293
	};
2294
	unsigned long slab_reclaimable;
2295 2296 2297

	disable_swap_token();
	cond_resched();
2298 2299 2300 2301 2302 2303
	/*
	 * 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;
2304 2305
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2306

2307 2308 2309 2310 2311 2312 2313 2314 2315
	if (zone_page_state(zone, NR_FILE_PAGES) -
		zone_page_state(zone, NR_FILE_MAPPED) >
		zone->min_unmapped_pages) {
		/*
		 * Free memory by calling shrink zone with increasing
		 * priorities until we have enough memory freed.
		 */
		priority = ZONE_RECLAIM_PRIORITY;
		do {
2316
			note_zone_scanning_priority(zone, priority);
2317
			shrink_zone(priority, zone, &sc);
2318
			priority--;
2319
		} while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2320
	}
2321

2322 2323
	slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (slab_reclaimable > zone->min_slab_pages) {
2324
		/*
2325
		 * shrink_slab() does not currently allow us to determine how
2326 2327 2328 2329
		 * 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.
2330
		 *
2331 2332
		 * Note that shrink_slab will free memory on all zones and may
		 * take a long time.
2333
		 */
2334
		while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2335 2336
			zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
				slab_reclaimable - nr_pages)
2337
			;
2338 2339 2340 2341 2342

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
2343
		sc.nr_reclaimed += slab_reclaimable -
2344
			zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2345 2346
	}

2347
	p->reclaim_state = NULL;
2348
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2349
	return sc.nr_reclaimed >= nr_pages;
2350
}
2351 2352 2353 2354

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
2355
	int ret;
2356 2357

	/*
2358 2359
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
2360
	 *
2361 2362 2363 2364 2365
	 * 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.
2366
	 */
2367
	if (zone_page_state(zone, NR_FILE_PAGES) -
2368 2369 2370
	    zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
	    && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
			<= zone->min_slab_pages)
2371
		return 0;
2372

2373 2374 2375
	if (zone_is_all_unreclaimable(zone))
		return 0;

2376
	/*
2377
	 * Do not scan if the allocation should not be delayed.
2378
	 */
2379
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2380 2381 2382 2383 2384 2385 2386 2387
			return 0;

	/*
	 * 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.
	 */
2388
	node_id = zone_to_nid(zone);
2389
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2390
		return 0;
2391 2392 2393 2394 2395 2396 2397

	if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
		return 0;
	ret = __zone_reclaim(zone, gfp_mask, order);
	zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);

	return ret;
2398
}
2399
#endif
L
Lee Schermerhorn 已提交
2400 2401 2402 2403 2404 2405 2406 2407

#ifdef CONFIG_UNEVICTABLE_LRU
/*
 * 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
2408 2409
 * 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
2410 2411
 *
 * Reasons page might not be evictable:
2412
 * (1) page's mapping marked unevictable
N
Nick Piggin 已提交
2413
 * (2) page is part of an mlocked VMA
2414
 *
L
Lee Schermerhorn 已提交
2415 2416 2417 2418
 */
int page_evictable(struct page *page, struct vm_area_struct *vma)
{

2419 2420 2421
	if (mapping_unevictable(page_mapping(page)))
		return 0;

N
Nick Piggin 已提交
2422 2423
	if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
		return 0;
L
Lee Schermerhorn 已提交
2424 2425 2426

	return 1;
}
2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446

/**
 * 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)) {
		enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
2447

2448 2449
		__dec_zone_state(zone, NR_UNEVICTABLE);
		list_move(&page->lru, &zone->lru[l].list);
K
KAMEZAWA Hiroyuki 已提交
2450
		mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2451 2452 2453 2454 2455 2456 2457 2458
		__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
2459
		mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518
		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);
	}

}
2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530

/**
 * 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 */
2531
static void scan_zone_unevictable_pages(struct zone *zone)
2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572
{
	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.
 */
2573
static void scan_all_zones_unevictable_pages(void)
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 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647
{
	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,
			   struct file *file, void __user *buffer,
			   size_t *length, loff_t *ppos)
{
	proc_doulongvec_minmax(table, write, file, buffer, length, ppos);

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

	scan_unevictable_pages = 0;
	return 0;
}

/*
 * 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);
}

L
Lee Schermerhorn 已提交
2648
#endif