vmscan.c 71.3 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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/*
 * 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);
	}
	mem_cgroup_move_lists(page, lru);

	/*
	 * 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);
	mem_cgroup_move_lists(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++;

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		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);
613
			else
614 615
				goto keep_locked;
		}
L
Linus Torvalds 已提交
616

617
		referenced = page_referenced(page, 1, sc->mem_cgroup);
L
Linus Torvalds 已提交
618
		/* In active use or really unfreeable?  Activate it. */
A
Andy Whitcroft 已提交
619 620
		if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
					referenced && page_mapping_inuse(page))
L
Linus Torvalds 已提交
621 622 623 624 625 626
			goto activate_locked;

		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
N
Nick Piggin 已提交
627
		if (PageAnon(page) && !PageSwapCache(page)) {
628 629
			if (!(sc->gfp_mask & __GFP_IO))
				goto keep_locked;
630
			if (!add_to_swap(page))
L
Linus Torvalds 已提交
631
				goto activate_locked;
632
			may_enter_fs = 1;
N
Nick Piggin 已提交
633
		}
L
Linus Torvalds 已提交
634 635 636 637 638 639 640 641

		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) {
642
			switch (try_to_unmap(page, 0)) {
L
Linus Torvalds 已提交
643 644 645 646
			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
N
Nick Piggin 已提交
647 648
			case SWAP_MLOCK:
				goto cull_mlocked;
L
Linus Torvalds 已提交
649 650 651 652 653 654
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
A
Andy Whitcroft 已提交
655
			if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
L
Linus Torvalds 已提交
656
				goto keep_locked;
657
			if (!may_enter_fs)
L
Linus Torvalds 已提交
658
				goto keep_locked;
659
			if (!sc->may_writepage)
L
Linus Torvalds 已提交
660 661 662
				goto keep_locked;

			/* Page is dirty, try to write it out here */
663
			switch (pageout(page, mapping, sync_writeback)) {
L
Linus Torvalds 已提交
664 665 666 667 668
			case PAGE_KEEP:
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
669
				if (PageWriteback(page) || PageDirty(page))
L
Linus Torvalds 已提交
670 671 672 673 674
					goto keep;
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
N
Nick Piggin 已提交
675
				if (!trylock_page(page))
L
Linus Torvalds 已提交
676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694
					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
695
		 * will do this, as well as the blockdev mapping.
L
Linus Torvalds 已提交
696 697 698 699 700 701 702 703 704 705 706 707 708
		 * 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
709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724
			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
725 726
		}

N
Nick Piggin 已提交
727
		if (!mapping || !__remove_mapping(mapping, page))
728
			goto keep_locked;
L
Linus Torvalds 已提交
729

N
Nick Piggin 已提交
730 731 732 733 734 735 736 737
		/*
		 * 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
738
free_it:
739
		nr_reclaimed++;
N
Nick Piggin 已提交
740 741 742 743
		if (!pagevec_add(&freed_pvec, page)) {
			__pagevec_free(&freed_pvec);
			pagevec_reinit(&freed_pvec);
		}
L
Linus Torvalds 已提交
744 745
		continue;

N
Nick Piggin 已提交
746
cull_mlocked:
747 748
		if (PageSwapCache(page))
			try_to_free_swap(page);
N
Nick Piggin 已提交
749 750 751 752
		unlock_page(page);
		putback_lru_page(page);
		continue;

L
Linus Torvalds 已提交
753
activate_locked:
754 755
		/* Not a candidate for swapping, so reclaim swap space. */
		if (PageSwapCache(page) && vm_swap_full())
756
			try_to_free_swap(page);
L
Lee Schermerhorn 已提交
757
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
758 759 760 761 762 763
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
764
		VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
L
Linus Torvalds 已提交
765 766 767
	}
	list_splice(&ret_pages, page_list);
	if (pagevec_count(&freed_pvec))
N
Nick Piggin 已提交
768
		__pagevec_free(&freed_pvec);
769
	count_vm_events(PGACTIVATE, pgactivate);
770
	return nr_reclaimed;
L
Linus Torvalds 已提交
771 772
}

A
Andy Whitcroft 已提交
773 774 775 776 777 778 779 780 781 782 783 784 785 786 787
/* 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.
 */
788
int __isolate_lru_page(struct page *page, int mode, int file)
A
Andy Whitcroft 已提交
789 790 791 792 793 794 795 796 797 798 799 800 801 802 803
{
	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;

804 805 806
	if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
		return ret;

L
Lee Schermerhorn 已提交
807 808 809 810 811 812 813 814
	/*
	 * 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
815 816 817 818 819 820 821 822 823 824 825 826 827 828
	ret = -EBUSY;
	if (likely(get_page_unless_zero(page))) {
		/*
		 * Be careful not to clear PageLRU until after we're
		 * sure the page is not being freed elsewhere -- the
		 * page release code relies on it.
		 */
		ClearPageLRU(page);
		ret = 0;
	}

	return ret;
}

L
Linus Torvalds 已提交
829 830 831 832 833 834 835 836 837 838 839 840 841 842
/*
 * 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
843 844
 * @order:	The caller's attempted allocation order
 * @mode:	One of the LRU isolation modes
845
 * @file:	True [1] if isolating file [!anon] pages
L
Linus Torvalds 已提交
846 847 848
 *
 * returns how many pages were moved onto *@dst.
 */
849 850
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
		struct list_head *src, struct list_head *dst,
851
		unsigned long *scanned, int order, int mode, int file)
L
Linus Torvalds 已提交
852
{
853
	unsigned long nr_taken = 0;
854
	unsigned long scan;
L
Linus Torvalds 已提交
855

856
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
857 858 859 860 861 862
		struct page *page;
		unsigned long pfn;
		unsigned long end_pfn;
		unsigned long page_pfn;
		int zone_id;

L
Linus Torvalds 已提交
863 864 865
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
866
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
867

868
		switch (__isolate_lru_page(page, mode, file)) {
A
Andy Whitcroft 已提交
869 870
		case 0:
			list_move(&page->lru, dst);
871
			nr_taken++;
A
Andy Whitcroft 已提交
872 873 874 875 876 877
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
			continue;
878

A
Andy Whitcroft 已提交
879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910
		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);
911

A
Andy Whitcroft 已提交
912 913 914
			/* Check that we have not crossed a zone boundary. */
			if (unlikely(page_zone_id(cursor_page) != zone_id))
				continue;
915
			switch (__isolate_lru_page(cursor_page, mode, file)) {
A
Andy Whitcroft 已提交
916 917 918 919 920 921 922 923 924 925
			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
926
				break;	/* ! on LRU or wrong list */
A
Andy Whitcroft 已提交
927 928
			}
		}
L
Linus Torvalds 已提交
929 930 931 932 933 934
	}

	*scanned = scan;
	return nr_taken;
}

935 936 937 938 939
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,
940
					int active, int file)
941
{
942
	int lru = LRU_BASE;
943
	if (active)
944 945 946 947 948
		lru += LRU_ACTIVE;
	if (file)
		lru += LRU_FILE;
	return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
								mode, !!file);
949 950
}

A
Andy Whitcroft 已提交
951 952 953 954
/*
 * clear_active_flags() is a helper for shrink_active_list(), clearing
 * any active bits from the pages in the list.
 */
955 956
static unsigned long clear_active_flags(struct list_head *page_list,
					unsigned int *count)
A
Andy Whitcroft 已提交
957 958
{
	int nr_active = 0;
959
	int lru;
A
Andy Whitcroft 已提交
960 961
	struct page *page;

962 963
	list_for_each_entry(page, page_list, lru) {
		lru = page_is_file_cache(page);
A
Andy Whitcroft 已提交
964
		if (PageActive(page)) {
965
			lru += LRU_ACTIVE;
A
Andy Whitcroft 已提交
966 967 968
			ClearPageActive(page);
			nr_active++;
		}
969 970
		count[lru]++;
	}
A
Andy Whitcroft 已提交
971 972 973 974

	return nr_active;
}

975 976 977 978 979 980 981 982 983 984 985
/**
 * 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
986 987 988
 * 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.
989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008
 *
 * 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
1009
			int lru = page_lru(page);
1010 1011
			ret = 0;
			ClearPageLRU(page);
1012 1013

			del_page_from_lru_list(zone, page, lru);
1014 1015 1016 1017 1018 1019
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

L
Linus Torvalds 已提交
1020
/*
A
Andrew Morton 已提交
1021 1022
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
1023
 */
A
Andrew Morton 已提交
1024
static unsigned long shrink_inactive_list(unsigned long max_scan,
R
Rik van Riel 已提交
1025 1026
			struct zone *zone, struct scan_control *sc,
			int priority, int file)
L
Linus Torvalds 已提交
1027 1028 1029
{
	LIST_HEAD(page_list);
	struct pagevec pvec;
1030
	unsigned long nr_scanned = 0;
1031
	unsigned long nr_reclaimed = 0;
L
Linus Torvalds 已提交
1032 1033 1034 1035 1036

	pagevec_init(&pvec, 1);

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1037
	do {
L
Linus Torvalds 已提交
1038
		struct page *page;
1039 1040 1041
		unsigned long nr_taken;
		unsigned long nr_scan;
		unsigned long nr_freed;
A
Andy Whitcroft 已提交
1042
		unsigned long nr_active;
1043
		unsigned int count[NR_LRU_LISTS] = { 0, };
R
Rik van Riel 已提交
1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056
		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
1057

1058
		nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1059 1060 1061
			     &page_list, &nr_scan, sc->order, mode,
				zone, sc->mem_cgroup, 0, file);
		nr_active = clear_active_flags(&page_list, count);
1062
		__count_vm_events(PGDEACTIVATE, nr_active);
A
Andy Whitcroft 已提交
1063

1064 1065 1066 1067 1068 1069 1070 1071 1072 1073
		__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)) {
1074
			zone->pages_scanned += nr_scan;
1075 1076 1077 1078 1079
			zone->recent_scanned[0] += count[LRU_INACTIVE_ANON];
			zone->recent_scanned[0] += count[LRU_ACTIVE_ANON];
			zone->recent_scanned[1] += count[LRU_INACTIVE_FILE];
			zone->recent_scanned[1] += count[LRU_ACTIVE_FILE];
		}
L
Linus Torvalds 已提交
1080 1081
		spin_unlock_irq(&zone->lru_lock);

1082
		nr_scanned += nr_scan;
1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098
		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.
			 */
1099
			nr_active = clear_active_flags(&page_list, count);
1100 1101 1102 1103 1104 1105
			count_vm_events(PGDEACTIVATE, nr_active);

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

1106
		nr_reclaimed += nr_freed;
N
Nick Piggin 已提交
1107 1108
		local_irq_disable();
		if (current_is_kswapd()) {
1109 1110
			__count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
			__count_vm_events(KSWAPD_STEAL, nr_freed);
1111
		} else if (scan_global_lru(sc))
1112
			__count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
1113

S
Shantanu Goel 已提交
1114
		__count_zone_vm_events(PGSTEAL, zone, nr_freed);
N
Nick Piggin 已提交
1115

1116 1117 1118
		if (nr_taken == 0)
			goto done;

N
Nick Piggin 已提交
1119
		spin_lock(&zone->lru_lock);
L
Linus Torvalds 已提交
1120 1121 1122 1123
		/*
		 * Put back any unfreeable pages.
		 */
		while (!list_empty(&page_list)) {
L
Lee Schermerhorn 已提交
1124
			int lru;
L
Linus Torvalds 已提交
1125
			page = lru_to_page(&page_list);
N
Nick Piggin 已提交
1126
			VM_BUG_ON(PageLRU(page));
L
Linus Torvalds 已提交
1127
			list_del(&page->lru);
L
Lee Schermerhorn 已提交
1128 1129 1130 1131 1132 1133 1134 1135 1136 1137
			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);
			mem_cgroup_move_lists(page, lru);
1138 1139 1140 1141
			if (PageActive(page) && scan_global_lru(sc)) {
				int file = !!page_is_file_cache(page);
				zone->recent_rotated[file]++;
			}
L
Linus Torvalds 已提交
1142 1143 1144 1145 1146 1147
			if (!pagevec_add(&pvec, page)) {
				spin_unlock_irq(&zone->lru_lock);
				__pagevec_release(&pvec);
				spin_lock_irq(&zone->lru_lock);
			}
		}
1148
  	} while (nr_scanned < max_scan);
1149
	spin_unlock(&zone->lru_lock);
L
Linus Torvalds 已提交
1150
done:
1151
	local_irq_enable();
L
Linus Torvalds 已提交
1152
	pagevec_release(&pvec);
1153
	return nr_reclaimed;
L
Linus Torvalds 已提交
1154 1155
}

1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169
/*
 * 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
1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186
/*
 * 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.
 */
1187 1188


A
Andrew Morton 已提交
1189
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1190
			struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1191
{
1192
	unsigned long pgmoved;
L
Linus Torvalds 已提交
1193
	int pgdeactivate = 0;
1194
	unsigned long pgscanned;
L
Linus Torvalds 已提交
1195
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
1196
	LIST_HEAD(l_inactive);
L
Linus Torvalds 已提交
1197 1198
	struct page *page;
	struct pagevec pvec;
1199
	enum lru_list lru;
L
Linus Torvalds 已提交
1200 1201 1202

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1203 1204
	pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
					ISOLATE_ACTIVE, zone,
1205
					sc->mem_cgroup, 1, file);
1206 1207 1208 1209
	/*
	 * zone->pages_scanned is used for detect zone's oom
	 * mem_cgroup remembers nr_scan by itself.
	 */
1210
	if (scan_global_lru(sc)) {
1211
		zone->pages_scanned += pgscanned;
1212 1213
		zone->recent_scanned[!!file] += pgmoved;
	}
1214

1215 1216 1217 1218
	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
1219 1220
	spin_unlock_irq(&zone->lru_lock);

1221
	pgmoved = 0;
L
Linus Torvalds 已提交
1222 1223 1224 1225
	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
1226

L
Lee Schermerhorn 已提交
1227 1228 1229 1230 1231
		if (unlikely(!page_evictable(page, NULL))) {
			putback_lru_page(page);
			continue;
		}

1232 1233 1234 1235 1236
		/* page_referenced clears PageReferenced */
		if (page_mapping_inuse(page) &&
		    page_referenced(page, 0, sc->mem_cgroup))
			pgmoved++;

L
Linus Torvalds 已提交
1237 1238 1239
		list_add(&page->lru, &l_inactive);
	}

1240 1241 1242 1243 1244 1245 1246
	/*
	 * Move the pages to the [file or anon] inactive list.
	 */
	pagevec_init(&pvec, 1);
	pgmoved = 0;
	lru = LRU_BASE + file * LRU_FILE;

1247
	spin_lock_irq(&zone->lru_lock);
1248
	/*
1249 1250 1251 1252 1253
	 * 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.
	 */
1254 1255
	if (scan_global_lru(sc))
		zone->recent_rotated[!!file] += pgmoved;
1256

L
Linus Torvalds 已提交
1257 1258 1259
	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
1260
		VM_BUG_ON(PageLRU(page));
N
Nick Piggin 已提交
1261
		SetPageLRU(page);
N
Nick Piggin 已提交
1262
		VM_BUG_ON(!PageActive(page));
N
Nick Piggin 已提交
1263 1264
		ClearPageActive(page);

1265
		list_move(&page->lru, &zone->lru[lru].list);
L
Lee Schermerhorn 已提交
1266
		mem_cgroup_move_lists(page, lru);
L
Linus Torvalds 已提交
1267 1268
		pgmoved++;
		if (!pagevec_add(&pvec, page)) {
1269
			__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
L
Linus Torvalds 已提交
1270 1271 1272 1273 1274 1275 1276 1277 1278
			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);
		}
	}
1279
	__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
L
Linus Torvalds 已提交
1280 1281 1282 1283 1284 1285
	pgdeactivate += pgmoved;
	if (buffer_heads_over_limit) {
		spin_unlock_irq(&zone->lru_lock);
		pagevec_strip(&pvec);
		spin_lock_irq(&zone->lru_lock);
	}
1286 1287 1288
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
	__count_vm_events(PGDEACTIVATE, pgdeactivate);
	spin_unlock_irq(&zone->lru_lock);
1289 1290
	if (vm_swap_full())
		pagevec_swap_free(&pvec);
L
Linus Torvalds 已提交
1291

N
Nick Piggin 已提交
1292
	pagevec_release(&pvec);
L
Linus Torvalds 已提交
1293 1294
}

1295
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1296 1297
	struct zone *zone, struct scan_control *sc, int priority)
{
1298 1299
	int file = is_file_lru(lru);

1300 1301 1302 1303 1304 1305 1306
	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))) {
1307
		shrink_active_list(nr_to_scan, zone, sc, priority, file);
1308 1309
		return 0;
	}
R
Rik van Riel 已提交
1310
	return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335
}

/*
 * 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;

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

1336 1337 1338 1339 1340 1341
	anon  = zone_page_state(zone, NR_ACTIVE_ANON) +
		zone_page_state(zone, NR_INACTIVE_ANON);
	file  = zone_page_state(zone, NR_ACTIVE_FILE) +
		zone_page_state(zone, NR_INACTIVE_FILE);
	free  = zone_page_state(zone, NR_FREE_PAGES);

1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381
	/* 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]
	 */
	if (unlikely(zone->recent_scanned[0] > anon / 4)) {
		spin_lock_irq(&zone->lru_lock);
		zone->recent_scanned[0] /= 2;
		zone->recent_rotated[0] /= 2;
		spin_unlock_irq(&zone->lru_lock);
	}

	if (unlikely(zone->recent_scanned[1] > file / 4)) {
		spin_lock_irq(&zone->lru_lock);
		zone->recent_scanned[1] /= 2;
		zone->recent_rotated[1] /= 2;
		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;

	/*
1382 1383 1384
	 * 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.
1385 1386 1387 1388 1389 1390 1391 1392 1393 1394
	 */
	ap = (anon_prio + 1) * (zone->recent_scanned[0] + 1);
	ap /= zone->recent_rotated[0] + 1;

	fp = (file_prio + 1) * (zone->recent_scanned[1] + 1);
	fp /= zone->recent_rotated[1] + 1;

	/* Normalize to percentages */
	percent[0] = 100 * ap / (ap + fp + 1);
	percent[1] = 100 - percent[0];
1395 1396
}

1397

L
Linus Torvalds 已提交
1398 1399 1400
/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
1401
static void shrink_zone(int priority, struct zone *zone,
1402
				struct scan_control *sc)
L
Linus Torvalds 已提交
1403
{
1404
	unsigned long nr[NR_LRU_LISTS];
1405
	unsigned long nr_to_scan;
1406
	unsigned long percent[2];	/* anon @ 0; file @ 1 */
1407
	enum lru_list l;
1408 1409
	unsigned long nr_reclaimed = sc->nr_reclaimed;
	unsigned long swap_cluster_max = sc->swap_cluster_max;
L
Linus Torvalds 已提交
1410

1411 1412
	get_scan_ratio(zone, sc, percent);

L
Lee Schermerhorn 已提交
1413
	for_each_evictable_lru(l) {
1414 1415 1416
		if (scan_global_lru(sc)) {
			int file = is_file_lru(l);
			int scan;
1417

1418 1419 1420 1421 1422
			scan = zone_page_state(zone, NR_LRU_BASE + l);
			if (priority) {
				scan >>= priority;
				scan = (scan * percent[file]) / 100;
			}
1423
			zone->lru[l].nr_scan += scan;
1424
			nr[l] = zone->lru[l].nr_scan;
1425
			if (nr[l] >= swap_cluster_max)
1426 1427 1428
				zone->lru[l].nr_scan = 0;
			else
				nr[l] = 0;
1429 1430 1431 1432 1433 1434 1435 1436
		} 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);
1437
		}
1438
	}
L
Linus Torvalds 已提交
1439

1440 1441
	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
					nr[LRU_INACTIVE_FILE]) {
L
Lee Schermerhorn 已提交
1442
		for_each_evictable_lru(l) {
1443
			if (nr[l]) {
1444
				nr_to_scan = min(nr[l], swap_cluster_max);
1445
				nr[l] -= nr_to_scan;
L
Linus Torvalds 已提交
1446

1447 1448
				nr_reclaimed += shrink_list(l, nr_to_scan,
							    zone, sc, priority);
1449
			}
L
Linus Torvalds 已提交
1450
		}
1451 1452 1453 1454 1455 1456 1457 1458
		/*
		 * 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.
		 */
1459
		if (nr_reclaimed > swap_cluster_max &&
1460 1461
			priority < DEF_PRIORITY && !current_is_kswapd())
			break;
L
Linus Torvalds 已提交
1462 1463
	}

1464 1465
	sc->nr_reclaimed = nr_reclaimed;

1466 1467 1468 1469 1470 1471 1472 1473 1474
	/*
	 * 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);

1475
	throttle_vm_writeout(sc->gfp_mask);
L
Linus Torvalds 已提交
1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491
}

/*
 * 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.
 */
1492
static void shrink_zones(int priority, struct zonelist *zonelist,
1493
					struct scan_control *sc)
L
Linus Torvalds 已提交
1494
{
1495
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1496
	struct zoneref *z;
1497
	struct zone *zone;
1498

1499
	sc->all_unreclaimable = 1;
1500
	for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1501
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
1502
			continue;
1503 1504 1505 1506 1507 1508 1509 1510
		/*
		 * 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
1511

1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524
			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);
		}
1525

1526
		shrink_zone(priority, zone, sc);
L
Linus Torvalds 已提交
1527 1528
	}
}
1529

L
Linus Torvalds 已提交
1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541
/*
 * 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.
1542 1543 1544
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
1545
 */
1546
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1547
					struct scan_control *sc)
L
Linus Torvalds 已提交
1548 1549
{
	int priority;
1550
	unsigned long ret = 0;
1551
	unsigned long total_scanned = 0;
L
Linus Torvalds 已提交
1552 1553
	struct reclaim_state *reclaim_state = current->reclaim_state;
	unsigned long lru_pages = 0;
1554
	struct zoneref *z;
1555
	struct zone *zone;
1556
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
L
Linus Torvalds 已提交
1557

1558 1559
	delayacct_freepages_start();

1560 1561 1562 1563 1564 1565
	if (scan_global_lru(sc))
		count_vm_event(ALLOCSTALL);
	/*
	 * mem_cgroup will not do shrink_slab.
	 */
	if (scan_global_lru(sc)) {
1566
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
L
Linus Torvalds 已提交
1567

1568 1569
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
L
Linus Torvalds 已提交
1570

1571
			lru_pages += zone_lru_pages(zone);
1572
		}
L
Linus Torvalds 已提交
1573 1574 1575
	}

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1576
		sc->nr_scanned = 0;
1577 1578
		if (!priority)
			disable_swap_token();
1579
		shrink_zones(priority, zonelist, sc);
1580 1581 1582 1583
		/*
		 * Don't shrink slabs when reclaiming memory from
		 * over limit cgroups
		 */
1584
		if (scan_global_lru(sc)) {
1585
			shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1586
			if (reclaim_state) {
1587
				sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1588 1589
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
1590
		}
1591
		total_scanned += sc->nr_scanned;
1592 1593
		if (sc->nr_reclaimed >= sc->swap_cluster_max) {
			ret = sc->nr_reclaimed;
L
Linus Torvalds 已提交
1594 1595 1596 1597 1598 1599 1600 1601 1602 1603
			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.
		 */
1604 1605
		if (total_scanned > sc->swap_cluster_max +
					sc->swap_cluster_max / 2) {
1606
			wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1607
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
1608 1609 1610
		}

		/* Take a nap, wait for some writeback to complete */
1611
		if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1612
			congestion_wait(WRITE, HZ/10);
L
Linus Torvalds 已提交
1613
	}
1614
	/* top priority shrink_zones still had more to do? don't OOM, then */
1615
	if (!sc->all_unreclaimable && scan_global_lru(sc))
1616
		ret = sc->nr_reclaimed;
L
Linus Torvalds 已提交
1617
out:
1618 1619 1620 1621 1622 1623 1624 1625 1626
	/*
	 * 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
1627

1628
	if (scan_global_lru(sc)) {
1629
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1630 1631 1632 1633 1634 1635 1636 1637

			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
1638

1639 1640
	delayacct_freepages_end();

L
Linus Torvalds 已提交
1641 1642 1643
	return ret;
}

1644 1645
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
								gfp_t gfp_mask)
1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657
{
	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,
	};

1658
	return do_try_to_free_pages(zonelist, &sc);
1659 1660
}

1661
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1662

1663 1664
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
						gfp_t gfp_mask)
1665 1666 1667 1668 1669 1670 1671 1672 1673 1674
{
	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,
	};
1675
	struct zonelist *zonelist;
1676

1677 1678 1679 1680
	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);
1681 1682 1683
}
#endif

L
Linus Torvalds 已提交
1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704
/*
 * 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.
 */
1705
static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
L
Linus Torvalds 已提交
1706 1707 1708 1709
{
	int all_zones_ok;
	int priority;
	int i;
1710
	unsigned long total_scanned;
L
Linus Torvalds 已提交
1711
	struct reclaim_state *reclaim_state = current->reclaim_state;
1712 1713 1714
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
		.may_swap = 1,
1715 1716
		.swap_cluster_max = SWAP_CLUSTER_MAX,
		.swappiness = vm_swappiness,
A
Andy Whitcroft 已提交
1717
		.order = order,
1718 1719
		.mem_cgroup = NULL,
		.isolate_pages = isolate_pages_global,
1720
	};
1721 1722 1723 1724 1725
	/*
	 * 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
1726 1727 1728

loop_again:
	total_scanned = 0;
1729
	sc.nr_reclaimed = 0;
C
Christoph Lameter 已提交
1730
	sc.may_writepage = !laptop_mode;
1731
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
1732

1733 1734
	for (i = 0; i < pgdat->nr_zones; i++)
		temp_priority[i] = DEF_PRIORITY;
L
Linus Torvalds 已提交
1735 1736 1737 1738 1739

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

1740 1741 1742 1743
		/* The swap token gets in the way of swapout... */
		if (!priority)
			disable_swap_token();

L
Linus Torvalds 已提交
1744 1745
		all_zones_ok = 1;

1746 1747 1748 1749 1750 1751
		/*
		 * 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
1752

1753 1754
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
1755

1756 1757
			if (zone_is_all_unreclaimable(zone) &&
			    priority != DEF_PRIORITY)
1758
				continue;
L
Linus Torvalds 已提交
1759

1760 1761 1762 1763 1764 1765 1766 1767
			/*
			 * 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);

1768 1769 1770
			if (!zone_watermark_ok(zone, order, zone->pages_high,
					       0, 0)) {
				end_zone = i;
A
Andrew Morton 已提交
1771
				break;
L
Linus Torvalds 已提交
1772 1773
			}
		}
A
Andrew Morton 已提交
1774 1775 1776
		if (i < 0)
			goto out;

L
Linus Torvalds 已提交
1777 1778 1779
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

1780
			lru_pages += zone_lru_pages(zone);
L
Linus Torvalds 已提交
1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793
		}

		/*
		 * 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;
1794
			int nr_slab;
L
Linus Torvalds 已提交
1795

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

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

1803 1804 1805
			if (!zone_watermark_ok(zone, order, zone->pages_high,
					       end_zone, 0))
				all_zones_ok = 0;
1806
			temp_priority[i] = priority;
L
Linus Torvalds 已提交
1807
			sc.nr_scanned = 0;
1808
			note_zone_scanning_priority(zone, priority);
1809 1810 1811 1812 1813 1814
			/*
			 * 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))
1815
				shrink_zone(priority, zone, &sc);
L
Linus Torvalds 已提交
1816
			reclaim_state->reclaimed_slab = 0;
1817 1818
			nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
						lru_pages);
1819
			sc.nr_reclaimed += reclaim_state->reclaimed_slab;
L
Linus Torvalds 已提交
1820
			total_scanned += sc.nr_scanned;
1821
			if (zone_is_all_unreclaimable(zone))
L
Linus Torvalds 已提交
1822
				continue;
1823
			if (nr_slab == 0 && zone->pages_scanned >=
1824
						(zone_lru_pages(zone) * 6))
1825 1826
					zone_set_flag(zone,
						      ZONE_ALL_UNRECLAIMABLE);
L
Linus Torvalds 已提交
1827 1828 1829 1830 1831 1832
			/*
			 * 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 &&
1833
			    total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
L
Linus Torvalds 已提交
1834 1835 1836 1837 1838 1839 1840 1841
				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.
		 */
1842
		if (total_scanned && priority < DEF_PRIORITY - 2)
1843
			congestion_wait(WRITE, HZ/10);
L
Linus Torvalds 已提交
1844 1845 1846 1847 1848 1849 1850

		/*
		 * 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.
		 */
1851
		if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
L
Linus Torvalds 已提交
1852 1853 1854
			break;
	}
out:
1855 1856 1857 1858 1859
	/*
	 * 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
1860 1861 1862
	for (i = 0; i < pgdat->nr_zones; i++) {
		struct zone *zone = pgdat->node_zones + i;

1863
		zone->prev_priority = temp_priority[i];
L
Linus Torvalds 已提交
1864 1865 1866
	}
	if (!all_zones_ok) {
		cond_resched();
1867 1868 1869

		try_to_freeze();

1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886
		/*
		 * 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
1887 1888 1889
		goto loop_again;
	}

1890
	return sc.nr_reclaimed;
L
Linus Torvalds 已提交
1891 1892 1893 1894
}

/*
 * The background pageout daemon, started as a kernel thread
1895
 * from the init process.
L
Linus Torvalds 已提交
1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914
 *
 * 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,
	};
1915
	node_to_cpumask_ptr(cpumask, pgdat->node_id);
L
Linus Torvalds 已提交
1916

R
Rusty Russell 已提交
1917
	if (!cpumask_empty(cpumask))
1918
		set_cpus_allowed_ptr(tsk, cpumask);
L
Linus Torvalds 已提交
1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932
	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).
	 */
1933
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
1934
	set_freezable();
L
Linus Torvalds 已提交
1935 1936 1937 1938

	order = 0;
	for ( ; ; ) {
		unsigned long new_order;
1939

L
Linus Torvalds 已提交
1940 1941 1942 1943 1944 1945 1946 1947 1948 1949
		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 {
1950 1951 1952
			if (!freezing(current))
				schedule();

L
Linus Torvalds 已提交
1953 1954 1955 1956
			order = pgdat->kswapd_max_order;
		}
		finish_wait(&pgdat->kswapd_wait, &wait);

1957 1958 1959 1960 1961 1962
		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
1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973
	}
	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;

1974
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
1975 1976 1977
		return;

	pgdat = zone->zone_pgdat;
R
Rohit Seth 已提交
1978
	if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
L
Linus Torvalds 已提交
1979 1980 1981
		return;
	if (pgdat->kswapd_max_order < order)
		pgdat->kswapd_max_order = order;
1982
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
1983
		return;
1984
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
1985
		return;
1986
	wake_up_interruptible(&pgdat->kswapd_wait);
L
Linus Torvalds 已提交
1987 1988
}

1989 1990 1991 1992 1993 1994 1995 1996
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
1997 1998
#ifdef CONFIG_PM
/*
1999 2000 2001 2002 2003 2004
 * 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
 */
2005 2006
static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
				      int pass, struct scan_control *sc)
2007 2008 2009
{
	struct zone *zone;
	unsigned long nr_to_scan, ret = 0;
2010
	enum lru_list l;
2011 2012 2013 2014 2015 2016

	for_each_zone(zone) {

		if (!populated_zone(zone))
			continue;

2017
		if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
2018 2019
			continue;

L
Lee Schermerhorn 已提交
2020 2021
		for_each_evictable_lru(l) {
			/* For pass = 0, we don't shrink the active list */
2022 2023
			if (pass == 0 &&
				(l == LRU_ACTIVE || l == LRU_ACTIVE_FILE))
2024 2025 2026 2027 2028 2029 2030
				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;
2031
				nr_to_scan = min(nr_pages,
2032 2033 2034 2035 2036 2037
					zone_page_state(zone,
							NR_LRU_BASE + l));
				ret += shrink_list(l, nr_to_scan, zone,
								sc, prio);
				if (ret >= nr_pages)
					return ret;
2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051
			}
		}
	}

	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
2052
 */
2053
unsigned long shrink_all_memory(unsigned long nr_pages)
L
Linus Torvalds 已提交
2054
{
2055
	unsigned long lru_pages, nr_slab;
2056
	unsigned long ret = 0;
2057 2058 2059 2060 2061 2062 2063 2064
	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,
2065
		.isolate_pages = isolate_pages_global,
L
Linus Torvalds 已提交
2066 2067 2068
	};

	current->reclaim_state = &reclaim_state;
2069

2070
	lru_pages = global_lru_pages();
2071
	nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
2072 2073 2074 2075 2076
	/* 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
2077
			break;
2078 2079 2080 2081 2082 2083

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

		nr_slab -= reclaim_state.reclaimed_slab;
L
Linus Torvalds 已提交
2084
	}
2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111

	/*
	 * 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;
2112
			shrink_slab(sc.nr_scanned, sc.gfp_mask,
2113
					global_lru_pages());
2114 2115 2116 2117 2118
			ret += reclaim_state.reclaimed_slab;
			if (ret >= nr_pages)
				goto out;

			if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
2119
				congestion_wait(WRITE, HZ / 10);
2120
		}
2121
	}
2122 2123 2124 2125 2126

	/*
	 * If ret = 0, we could not shrink LRUs, but there may be something
	 * in slab caches
	 */
2127
	if (!ret) {
2128 2129
		do {
			reclaim_state.reclaimed_slab = 0;
2130
			shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
2131 2132
			ret += reclaim_state.reclaimed_slab;
		} while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
2133
	}
2134 2135

out:
L
Linus Torvalds 已提交
2136
	current->reclaim_state = NULL;
2137

L
Linus Torvalds 已提交
2138 2139 2140 2141 2142 2143 2144 2145
	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. */
2146
static int __devinit cpu_callback(struct notifier_block *nfb,
2147
				  unsigned long action, void *hcpu)
L
Linus Torvalds 已提交
2148
{
2149
	int nid;
L
Linus Torvalds 已提交
2150

2151
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2152
		for_each_node_state(nid, N_HIGH_MEMORY) {
2153 2154 2155
			pg_data_t *pgdat = NODE_DATA(nid);
			node_to_cpumask_ptr(mask, pgdat->node_id);

2156
			if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
2157
				/* One of our CPUs online: restore mask */
2158
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
2159 2160 2161 2162 2163
		}
	}
	return NOTIFY_OK;
}

2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185
/*
 * 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;
}

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Linus Torvalds 已提交
2186 2187
static int __init kswapd_init(void)
{
2188
	int nid;
2189

L
Linus Torvalds 已提交
2190
	swap_setup();
2191
	for_each_node_state(nid, N_HIGH_MEMORY)
2192
 		kswapd_run(nid);
L
Linus Torvalds 已提交
2193 2194 2195 2196 2197
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
2198 2199 2200 2201 2202 2203 2204 2205 2206 2207

#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;

2208
#define RECLAIM_OFF 0
2209
#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
2210 2211 2212
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

2213 2214 2215 2216 2217 2218 2219
/*
 * 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

2220 2221 2222 2223 2224 2225
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

2226 2227 2228 2229 2230 2231
/*
 * 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;

2232 2233 2234
/*
 * Try to free up some pages from this zone through reclaim.
 */
2235
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2236
{
2237
	/* Minimum pages needed in order to stay on node */
2238
	const unsigned long nr_pages = 1 << order;
2239 2240
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
2241
	int priority;
2242 2243 2244
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
		.may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2245 2246
		.swap_cluster_max = max_t(unsigned long, nr_pages,
					SWAP_CLUSTER_MAX),
2247
		.gfp_mask = gfp_mask,
2248
		.swappiness = vm_swappiness,
2249
		.isolate_pages = isolate_pages_global,
2250
	};
2251
	unsigned long slab_reclaimable;
2252 2253 2254

	disable_swap_token();
	cond_resched();
2255 2256 2257 2258 2259 2260
	/*
	 * 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;
2261 2262
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2263

2264 2265 2266 2267 2268 2269 2270 2271 2272
	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 {
2273
			note_zone_scanning_priority(zone, priority);
2274
			shrink_zone(priority, zone, &sc);
2275
			priority--;
2276
		} while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2277
	}
2278

2279 2280
	slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (slab_reclaimable > zone->min_slab_pages) {
2281
		/*
2282
		 * shrink_slab() does not currently allow us to determine how
2283 2284 2285 2286
		 * 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.
2287
		 *
2288 2289
		 * Note that shrink_slab will free memory on all zones and may
		 * take a long time.
2290
		 */
2291
		while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2292 2293
			zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
				slab_reclaimable - nr_pages)
2294
			;
2295 2296 2297 2298 2299

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
2300
		sc.nr_reclaimed += slab_reclaimable -
2301
			zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2302 2303
	}

2304
	p->reclaim_state = NULL;
2305
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2306
	return sc.nr_reclaimed >= nr_pages;
2307
}
2308 2309 2310 2311

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
2312
	int ret;
2313 2314

	/*
2315 2316
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
2317
	 *
2318 2319 2320 2321 2322
	 * 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.
2323
	 */
2324
	if (zone_page_state(zone, NR_FILE_PAGES) -
2325 2326 2327
	    zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
	    && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
			<= zone->min_slab_pages)
2328
		return 0;
2329

2330 2331 2332
	if (zone_is_all_unreclaimable(zone))
		return 0;

2333
	/*
2334
	 * Do not scan if the allocation should not be delayed.
2335
	 */
2336
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2337 2338 2339 2340 2341 2342 2343 2344
			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.
	 */
2345
	node_id = zone_to_nid(zone);
2346
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2347
		return 0;
2348 2349 2350 2351 2352 2353 2354

	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;
2355
}
2356
#endif
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Lee Schermerhorn 已提交
2357 2358 2359 2360 2361 2362 2363 2364

#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
2365 2366
 * 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
2367 2368
 *
 * Reasons page might not be evictable:
2369
 * (1) page's mapping marked unevictable
N
Nick Piggin 已提交
2370
 * (2) page is part of an mlocked VMA
2371
 *
L
Lee Schermerhorn 已提交
2372 2373 2374 2375
 */
int page_evictable(struct page *page, struct vm_area_struct *vma)
{

2376 2377 2378
	if (mapping_unevictable(page_mapping(page)))
		return 0;

N
Nick Piggin 已提交
2379 2380
	if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
		return 0;
L
Lee Schermerhorn 已提交
2381 2382 2383

	return 1;
}
2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403

/**
 * 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);
2404

2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473
		__dec_zone_state(zone, NR_UNEVICTABLE);
		list_move(&page->lru, &zone->lru[l].list);
		__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);
		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);
	}

}
2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485

/**
 * 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 */
2486
static void scan_zone_unevictable_pages(struct zone *zone)
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 2519 2520 2521 2522 2523 2524 2525 2526 2527
{
	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.
 */
2528
static void scan_all_zones_unevictable_pages(void)
2529 2530 2531 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 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602
{
	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
2603
#endif