vmscan.c 57.9 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 <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;

	/* 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,
			int active);
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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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/*
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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);

		if (TestSetPageLocked(page))
			goto keep;

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		VM_BUG_ON(PageActive(page));
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		sc->nr_scanned++;
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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);
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			else
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				goto keep_locked;
		}
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		referenced = page_referenced(page, 1, sc->mem_cgroup);
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		/* In active use or really unfreeable?  Activate it. */
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		if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
					referenced && page_mapping_inuse(page))
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			goto activate_locked;

#ifdef CONFIG_SWAP
		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
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		if (PageAnon(page) && !PageSwapCache(page))
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			if (!add_to_swap(page, GFP_ATOMIC))
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				goto activate_locked;
#endif /* CONFIG_SWAP */

		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) {
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			switch (try_to_unmap(page, 0)) {
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			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
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			if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
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				goto keep_locked;
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			if (!may_enter_fs)
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				goto keep_locked;
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			if (!sc->may_writepage)
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				goto keep_locked;

			/* Page is dirty, try to write it out here */
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			switch (pageout(page, mapping, sync_writeback)) {
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			case PAGE_KEEP:
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
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				if (PageWriteback(page) || PageDirty(page))
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					goto keep;
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
				if (TestSetPageLocked(page))
					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
		 * will do this, as well as the blockdev mapping. 
		 * 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
619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634
			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
635 636
		}

N
Nick Piggin 已提交
637
		if (!mapping || !__remove_mapping(mapping, page))
638
			goto keep_locked;
L
Linus Torvalds 已提交
639 640

		unlock_page(page);
N
Nick Piggin 已提交
641
free_it:
642
		nr_reclaimed++;
N
Nick Piggin 已提交
643 644 645 646
		if (!pagevec_add(&freed_pvec, page)) {
			__pagevec_free(&freed_pvec);
			pagevec_reinit(&freed_pvec);
		}
L
Linus Torvalds 已提交
647 648 649 650 651 652 653 654 655
		continue;

activate_locked:
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
656
		VM_BUG_ON(PageLRU(page));
L
Linus Torvalds 已提交
657 658 659
	}
	list_splice(&ret_pages, page_list);
	if (pagevec_count(&freed_pvec))
N
Nick Piggin 已提交
660
		__pagevec_free(&freed_pvec);
661
	count_vm_events(PGACTIVATE, pgactivate);
662
	return nr_reclaimed;
L
Linus Torvalds 已提交
663 664
}

A
Andy Whitcroft 已提交
665 666 667 668 669 670 671 672 673 674 675 676 677 678 679
/* 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.
 */
680
int __isolate_lru_page(struct page *page, int mode)
A
Andy Whitcroft 已提交
681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709
{
	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;

	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
710 711 712 713 714 715 716 717 718 719 720 721 722 723
/*
 * 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
724 725
 * @order:	The caller's attempted allocation order
 * @mode:	One of the LRU isolation modes
L
Linus Torvalds 已提交
726 727 728
 *
 * returns how many pages were moved onto *@dst.
 */
729 730
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
		struct list_head *src, struct list_head *dst,
A
Andy Whitcroft 已提交
731
		unsigned long *scanned, int order, int mode)
L
Linus Torvalds 已提交
732
{
733
	unsigned long nr_taken = 0;
734
	unsigned long scan;
L
Linus Torvalds 已提交
735

736
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
737 738 739 740 741 742
		struct page *page;
		unsigned long pfn;
		unsigned long end_pfn;
		unsigned long page_pfn;
		int zone_id;

L
Linus Torvalds 已提交
743 744 745
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
746
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
747

A
Andy Whitcroft 已提交
748 749 750
		switch (__isolate_lru_page(page, mode)) {
		case 0:
			list_move(&page->lru, dst);
751
			nr_taken++;
A
Andy Whitcroft 已提交
752 753 754 755 756 757
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
			continue;
758

A
Andy Whitcroft 已提交
759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807
		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);
			/* Check that we have not crossed a zone boundary. */
			if (unlikely(page_zone_id(cursor_page) != zone_id))
				continue;
			switch (__isolate_lru_page(cursor_page, mode)) {
			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:
				break;
			}
		}
L
Linus Torvalds 已提交
808 809 810 811 812 813
	}

	*scanned = scan;
	return nr_taken;
}

814 815 816 817 818 819 820 821 822 823 824 825 826 827 828
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,
					int active)
{
	if (active)
		return isolate_lru_pages(nr, &z->active_list, dst,
						scanned, order, mode);
	else
		return isolate_lru_pages(nr, &z->inactive_list, dst,
						scanned, order, mode);
}

A
Andy Whitcroft 已提交
829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846
/*
 * clear_active_flags() is a helper for shrink_active_list(), clearing
 * any active bits from the pages in the list.
 */
static unsigned long clear_active_flags(struct list_head *page_list)
{
	int nr_active = 0;
	struct page *page;

	list_for_each_entry(page, page_list, lru)
		if (PageActive(page)) {
			ClearPageActive(page);
			nr_active++;
		}

	return nr_active;
}

L
Linus Torvalds 已提交
847
/*
A
Andrew Morton 已提交
848 849
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
850
 */
A
Andrew Morton 已提交
851 852
static unsigned long shrink_inactive_list(unsigned long max_scan,
				struct zone *zone, struct scan_control *sc)
L
Linus Torvalds 已提交
853 854 855
{
	LIST_HEAD(page_list);
	struct pagevec pvec;
856
	unsigned long nr_scanned = 0;
857
	unsigned long nr_reclaimed = 0;
L
Linus Torvalds 已提交
858 859 860 861 862

	pagevec_init(&pvec, 1);

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
863
	do {
L
Linus Torvalds 已提交
864
		struct page *page;
865 866 867
		unsigned long nr_taken;
		unsigned long nr_scan;
		unsigned long nr_freed;
A
Andy Whitcroft 已提交
868
		unsigned long nr_active;
L
Linus Torvalds 已提交
869

870
		nr_taken = sc->isolate_pages(sc->swap_cluster_max,
A
Andy Whitcroft 已提交
871 872
			     &page_list, &nr_scan, sc->order,
			     (sc->order > PAGE_ALLOC_COSTLY_ORDER)?
873 874
					     ISOLATE_BOTH : ISOLATE_INACTIVE,
				zone, sc->mem_cgroup, 0);
A
Andy Whitcroft 已提交
875
		nr_active = clear_active_flags(&page_list);
876
		__count_vm_events(PGDEACTIVATE, nr_active);
A
Andy Whitcroft 已提交
877 878 879 880

		__mod_zone_page_state(zone, NR_ACTIVE, -nr_active);
		__mod_zone_page_state(zone, NR_INACTIVE,
						-(nr_taken - nr_active));
881 882
		if (scan_global_lru(sc))
			zone->pages_scanned += nr_scan;
L
Linus Torvalds 已提交
883 884
		spin_unlock_irq(&zone->lru_lock);

885
		nr_scanned += nr_scan;
886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908
		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.
			 */
			nr_active = clear_active_flags(&page_list);
			count_vm_events(PGDEACTIVATE, nr_active);

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

909
		nr_reclaimed += nr_freed;
N
Nick Piggin 已提交
910 911
		local_irq_disable();
		if (current_is_kswapd()) {
912 913
			__count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
			__count_vm_events(KSWAPD_STEAL, nr_freed);
914
		} else if (scan_global_lru(sc))
915
			__count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
916

S
Shantanu Goel 已提交
917
		__count_zone_vm_events(PGSTEAL, zone, nr_freed);
N
Nick Piggin 已提交
918

919 920 921
		if (nr_taken == 0)
			goto done;

N
Nick Piggin 已提交
922
		spin_lock(&zone->lru_lock);
L
Linus Torvalds 已提交
923 924 925 926 927
		/*
		 * Put back any unfreeable pages.
		 */
		while (!list_empty(&page_list)) {
			page = lru_to_page(&page_list);
N
Nick Piggin 已提交
928
			VM_BUG_ON(PageLRU(page));
N
Nick Piggin 已提交
929
			SetPageLRU(page);
L
Linus Torvalds 已提交
930 931 932 933 934 935 936 937 938 939 940
			list_del(&page->lru);
			if (PageActive(page))
				add_page_to_active_list(zone, page);
			else
				add_page_to_inactive_list(zone, page);
			if (!pagevec_add(&pvec, page)) {
				spin_unlock_irq(&zone->lru_lock);
				__pagevec_release(&pvec);
				spin_lock_irq(&zone->lru_lock);
			}
		}
941
  	} while (nr_scanned < max_scan);
942
	spin_unlock(&zone->lru_lock);
L
Linus Torvalds 已提交
943
done:
944
	local_irq_enable();
L
Linus Torvalds 已提交
945
	pagevec_release(&pvec);
946
	return nr_reclaimed;
L
Linus Torvalds 已提交
947 948
}

949 950 951 952 953 954 955 956 957 958 959 960 961 962
/*
 * 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;
}

N
Nick Piggin 已提交
963 964
static inline int zone_is_near_oom(struct zone *zone)
{
965 966
	return zone->pages_scanned >= (zone_page_state(zone, NR_ACTIVE)
				+ zone_page_state(zone, NR_INACTIVE))*3;
N
Nick Piggin 已提交
967 968
}

969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075
/*
 * Determine we should try to reclaim mapped pages.
 * This is called only when sc->mem_cgroup is NULL.
 */
static int calc_reclaim_mapped(struct scan_control *sc, struct zone *zone,
				int priority)
{
	long mapped_ratio;
	long distress;
	long swap_tendency;
	long imbalance;
	int reclaim_mapped = 0;
	int prev_priority;

	if (scan_global_lru(sc) && zone_is_near_oom(zone))
		return 1;
	/*
	 * `distress' is a measure of how much trouble we're having
	 * reclaiming pages.  0 -> no problems.  100 -> great trouble.
	 */
	if (scan_global_lru(sc))
		prev_priority = zone->prev_priority;
	else
		prev_priority = mem_cgroup_get_reclaim_priority(sc->mem_cgroup);

	distress = 100 >> min(prev_priority, priority);

	/*
	 * The point of this algorithm is to decide when to start
	 * reclaiming mapped memory instead of just pagecache.  Work out
	 * how much memory
	 * is mapped.
	 */
	if (scan_global_lru(sc))
		mapped_ratio = ((global_page_state(NR_FILE_MAPPED) +
				global_page_state(NR_ANON_PAGES)) * 100) /
					vm_total_pages;
	else
		mapped_ratio = mem_cgroup_calc_mapped_ratio(sc->mem_cgroup);

	/*
	 * Now decide how much we really want to unmap some pages.  The
	 * mapped ratio is downgraded - just because there's a lot of
	 * mapped memory doesn't necessarily mean that page reclaim
	 * isn't succeeding.
	 *
	 * The distress ratio is important - we don't want to start
	 * going oom.
	 *
	 * A 100% value of vm_swappiness overrides this algorithm
	 * altogether.
	 */
	swap_tendency = mapped_ratio / 2 + distress + sc->swappiness;

	/*
	 * If there's huge imbalance between active and inactive
	 * (think active 100 times larger than inactive) we should
	 * become more permissive, or the system will take too much
	 * cpu before it start swapping during memory pressure.
	 * Distress is about avoiding early-oom, this is about
	 * making swappiness graceful despite setting it to low
	 * values.
	 *
	 * Avoid div by zero with nr_inactive+1, and max resulting
	 * value is vm_total_pages.
	 */
	if (scan_global_lru(sc)) {
		imbalance  = zone_page_state(zone, NR_ACTIVE);
		imbalance /= zone_page_state(zone, NR_INACTIVE) + 1;
	} else
		imbalance = mem_cgroup_reclaim_imbalance(sc->mem_cgroup);

	/*
	 * Reduce the effect of imbalance if swappiness is low,
	 * this means for a swappiness very low, the imbalance
	 * must be much higher than 100 for this logic to make
	 * the difference.
	 *
	 * Max temporary value is vm_total_pages*100.
	 */
	imbalance *= (vm_swappiness + 1);
	imbalance /= 100;

	/*
	 * If not much of the ram is mapped, makes the imbalance
	 * less relevant, it's high priority we refill the inactive
	 * list with mapped pages only in presence of high ratio of
	 * mapped pages.
	 *
	 * Max temporary value is vm_total_pages*100.
	 */
	imbalance *= mapped_ratio;
	imbalance /= 100;

	/* apply imbalance feedback to swap_tendency */
	swap_tendency += imbalance;

	/*
	 * Now use this metric to decide whether to start moving mapped
	 * memory onto the inactive list.
	 */
	if (swap_tendency >= 100)
		reclaim_mapped = 1;

	return reclaim_mapped;
}

L
Linus Torvalds 已提交
1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092
/*
 * 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.
 */
1093 1094


A
Andrew Morton 已提交
1095
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1096
				struct scan_control *sc, int priority)
L
Linus Torvalds 已提交
1097
{
1098
	unsigned long pgmoved;
L
Linus Torvalds 已提交
1099
	int pgdeactivate = 0;
1100
	unsigned long pgscanned;
L
Linus Torvalds 已提交
1101 1102 1103 1104 1105 1106
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
	LIST_HEAD(l_inactive);	/* Pages to go onto the inactive_list */
	LIST_HEAD(l_active);	/* Pages to go onto the active_list */
	struct page *page;
	struct pagevec pvec;
	int reclaim_mapped = 0;
1107

1108 1109
	if (sc->may_swap)
		reclaim_mapped = calc_reclaim_mapped(sc, zone, priority);
L
Linus Torvalds 已提交
1110 1111 1112

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1113 1114 1115
	pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
					ISOLATE_ACTIVE, zone,
					sc->mem_cgroup, 1);
1116 1117 1118 1119 1120 1121 1122
	/*
	 * zone->pages_scanned is used for detect zone's oom
	 * mem_cgroup remembers nr_scan by itself.
	 */
	if (scan_global_lru(sc))
		zone->pages_scanned += pgscanned;

1123
	__mod_zone_page_state(zone, NR_ACTIVE, -pgmoved);
L
Linus Torvalds 已提交
1124 1125 1126 1127 1128 1129 1130 1131 1132
	spin_unlock_irq(&zone->lru_lock);

	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
		if (page_mapped(page)) {
			if (!reclaim_mapped ||
			    (total_swap_pages == 0 && PageAnon(page)) ||
1133
			    page_referenced(page, 0, sc->mem_cgroup)) {
L
Linus Torvalds 已提交
1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146
				list_add(&page->lru, &l_active);
				continue;
			}
		}
		list_add(&page->lru, &l_inactive);
	}

	pagevec_init(&pvec, 1);
	pgmoved = 0;
	spin_lock_irq(&zone->lru_lock);
	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
1147
		VM_BUG_ON(PageLRU(page));
N
Nick Piggin 已提交
1148
		SetPageLRU(page);
N
Nick Piggin 已提交
1149
		VM_BUG_ON(!PageActive(page));
N
Nick Piggin 已提交
1150 1151
		ClearPageActive(page);

L
Linus Torvalds 已提交
1152
		list_move(&page->lru, &zone->inactive_list);
1153
		mem_cgroup_move_lists(page, false);
L
Linus Torvalds 已提交
1154 1155
		pgmoved++;
		if (!pagevec_add(&pvec, page)) {
1156
			__mod_zone_page_state(zone, NR_INACTIVE, pgmoved);
L
Linus Torvalds 已提交
1157 1158 1159 1160 1161 1162 1163 1164 1165
			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);
		}
	}
1166
	__mod_zone_page_state(zone, NR_INACTIVE, pgmoved);
L
Linus Torvalds 已提交
1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177
	pgdeactivate += pgmoved;
	if (buffer_heads_over_limit) {
		spin_unlock_irq(&zone->lru_lock);
		pagevec_strip(&pvec);
		spin_lock_irq(&zone->lru_lock);
	}

	pgmoved = 0;
	while (!list_empty(&l_active)) {
		page = lru_to_page(&l_active);
		prefetchw_prev_lru_page(page, &l_active, flags);
N
Nick Piggin 已提交
1178
		VM_BUG_ON(PageLRU(page));
N
Nick Piggin 已提交
1179
		SetPageLRU(page);
N
Nick Piggin 已提交
1180
		VM_BUG_ON(!PageActive(page));
1181

L
Linus Torvalds 已提交
1182
		list_move(&page->lru, &zone->active_list);
1183
		mem_cgroup_move_lists(page, true);
L
Linus Torvalds 已提交
1184 1185
		pgmoved++;
		if (!pagevec_add(&pvec, page)) {
1186
			__mod_zone_page_state(zone, NR_ACTIVE, pgmoved);
L
Linus Torvalds 已提交
1187 1188 1189 1190 1191 1192
			pgmoved = 0;
			spin_unlock_irq(&zone->lru_lock);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
1193
	__mod_zone_page_state(zone, NR_ACTIVE, pgmoved);
N
Nick Piggin 已提交
1194

1195 1196 1197
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
	__count_vm_events(PGDEACTIVATE, pgdeactivate);
	spin_unlock_irq(&zone->lru_lock);
L
Linus Torvalds 已提交
1198

N
Nick Piggin 已提交
1199
	pagevec_release(&pvec);
L
Linus Torvalds 已提交
1200 1201 1202 1203 1204
}

/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
1205 1206
static unsigned long shrink_zone(int priority, struct zone *zone,
				struct scan_control *sc)
L
Linus Torvalds 已提交
1207 1208 1209
{
	unsigned long nr_active;
	unsigned long nr_inactive;
1210
	unsigned long nr_to_scan;
1211
	unsigned long nr_reclaimed = 0;
L
Linus Torvalds 已提交
1212

1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244
	if (scan_global_lru(sc)) {
		/*
		 * Add one to nr_to_scan just to make sure that the kernel
		 * will slowly sift through the active list.
		 */
		zone->nr_scan_active +=
			(zone_page_state(zone, NR_ACTIVE) >> priority) + 1;
		nr_active = zone->nr_scan_active;
		zone->nr_scan_inactive +=
			(zone_page_state(zone, NR_INACTIVE) >> priority) + 1;
		nr_inactive = zone->nr_scan_inactive;
		if (nr_inactive >= sc->swap_cluster_max)
			zone->nr_scan_inactive = 0;
		else
			nr_inactive = 0;

		if (nr_active >= sc->swap_cluster_max)
			zone->nr_scan_active = 0;
		else
			nr_active = 0;
	} else {
		/*
		 * This reclaim occurs not because zone memory shortage but
		 * because memory controller hits its limit.
		 * Then, don't modify zone reclaim related data.
		 */
		nr_active = mem_cgroup_calc_reclaim_active(sc->mem_cgroup,
					zone, priority);

		nr_inactive = mem_cgroup_calc_reclaim_inactive(sc->mem_cgroup,
					zone, priority);
	}
L
Linus Torvalds 已提交
1245 1246 1247 1248


	while (nr_active || nr_inactive) {
		if (nr_active) {
1249
			nr_to_scan = min(nr_active,
L
Linus Torvalds 已提交
1250
					(unsigned long)sc->swap_cluster_max);
1251
			nr_active -= nr_to_scan;
1252
			shrink_active_list(nr_to_scan, zone, sc, priority);
L
Linus Torvalds 已提交
1253 1254 1255
		}

		if (nr_inactive) {
1256
			nr_to_scan = min(nr_inactive,
L
Linus Torvalds 已提交
1257
					(unsigned long)sc->swap_cluster_max);
1258
			nr_inactive -= nr_to_scan;
A
Andrew Morton 已提交
1259 1260
			nr_reclaimed += shrink_inactive_list(nr_to_scan, zone,
								sc);
L
Linus Torvalds 已提交
1261 1262 1263
		}
	}

1264
	throttle_vm_writeout(sc->gfp_mask);
1265
	return nr_reclaimed;
L
Linus Torvalds 已提交
1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283
}

/*
 * 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.
 *
 * Returns the number of reclaimed pages.
 *
 * If a zone is deemed to be full of pinned pages then just give it a light
 * scan then give up on it.
 */
1284
static unsigned long shrink_zones(int priority, struct zonelist *zonelist,
1285
					struct scan_control *sc)
L
Linus Torvalds 已提交
1286
{
1287
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1288
	unsigned long nr_reclaimed = 0;
1289
	struct zoneref *z;
1290
	struct zone *zone;
1291

1292
	sc->all_unreclaimable = 1;
1293
	for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1294
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
1295
			continue;
1296 1297 1298 1299 1300 1301 1302 1303
		/*
		 * 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
1304

1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317
			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);
		}
1318

1319
		nr_reclaimed += shrink_zone(priority, zone, sc);
L
Linus Torvalds 已提交
1320
	}
1321

1322
	return nr_reclaimed;
L
Linus Torvalds 已提交
1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336
}
 
/*
 * 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.
1337 1338 1339
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
1340
 */
1341
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1342
					struct scan_control *sc)
L
Linus Torvalds 已提交
1343 1344
{
	int priority;
1345
	unsigned long ret = 0;
1346
	unsigned long total_scanned = 0;
1347
	unsigned long nr_reclaimed = 0;
L
Linus Torvalds 已提交
1348 1349
	struct reclaim_state *reclaim_state = current->reclaim_state;
	unsigned long lru_pages = 0;
1350
	struct zoneref *z;
1351
	struct zone *zone;
1352
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
L
Linus Torvalds 已提交
1353

1354 1355
	delayacct_freepages_start();

1356 1357 1358 1359 1360 1361
	if (scan_global_lru(sc))
		count_vm_event(ALLOCSTALL);
	/*
	 * mem_cgroup will not do shrink_slab.
	 */
	if (scan_global_lru(sc)) {
1362
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
L
Linus Torvalds 已提交
1363

1364 1365
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
L
Linus Torvalds 已提交
1366

1367 1368 1369
			lru_pages += zone_page_state(zone, NR_ACTIVE)
					+ zone_page_state(zone, NR_INACTIVE);
		}
L
Linus Torvalds 已提交
1370 1371 1372
	}

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1373
		sc->nr_scanned = 0;
1374 1375
		if (!priority)
			disable_swap_token();
1376
		nr_reclaimed += shrink_zones(priority, zonelist, sc);
1377 1378 1379 1380
		/*
		 * Don't shrink slabs when reclaiming memory from
		 * over limit cgroups
		 */
1381
		if (scan_global_lru(sc)) {
1382
			shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1383 1384 1385 1386
			if (reclaim_state) {
				nr_reclaimed += reclaim_state->reclaimed_slab;
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
1387
		}
1388 1389
		total_scanned += sc->nr_scanned;
		if (nr_reclaimed >= sc->swap_cluster_max) {
1390
			ret = nr_reclaimed;
L
Linus Torvalds 已提交
1391 1392 1393 1394 1395 1396 1397 1398 1399 1400
			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.
		 */
1401 1402
		if (total_scanned > sc->swap_cluster_max +
					sc->swap_cluster_max / 2) {
1403
			wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1404
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
1405 1406 1407
		}

		/* Take a nap, wait for some writeback to complete */
1408
		if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1409
			congestion_wait(WRITE, HZ/10);
L
Linus Torvalds 已提交
1410
	}
1411
	/* top priority shrink_caches still had more to do? don't OOM, then */
1412
	if (!sc->all_unreclaimable && scan_global_lru(sc))
1413
		ret = nr_reclaimed;
L
Linus Torvalds 已提交
1414
out:
1415 1416 1417 1418 1419 1420 1421 1422 1423
	/*
	 * 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
1424

1425
	if (scan_global_lru(sc)) {
1426
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1427 1428 1429 1430 1431 1432 1433 1434

			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
1435

1436 1437
	delayacct_freepages_end();

L
Linus Torvalds 已提交
1438 1439 1440
	return ret;
}

1441 1442
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
								gfp_t gfp_mask)
1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454
{
	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,
	};

1455
	return do_try_to_free_pages(zonelist, &sc);
1456 1457
}

1458
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1459

1460 1461
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
						gfp_t gfp_mask)
1462 1463 1464 1465 1466 1467 1468 1469 1470 1471
{
	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,
	};
1472
	struct zonelist *zonelist;
1473

1474 1475 1476 1477
	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);
1478 1479 1480
}
#endif

L
Linus Torvalds 已提交
1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501
/*
 * 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.
 */
1502
static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
L
Linus Torvalds 已提交
1503 1504 1505 1506
{
	int all_zones_ok;
	int priority;
	int i;
1507
	unsigned long total_scanned;
1508
	unsigned long nr_reclaimed;
L
Linus Torvalds 已提交
1509
	struct reclaim_state *reclaim_state = current->reclaim_state;
1510 1511 1512
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
		.may_swap = 1,
1513 1514
		.swap_cluster_max = SWAP_CLUSTER_MAX,
		.swappiness = vm_swappiness,
A
Andy Whitcroft 已提交
1515
		.order = order,
1516 1517
		.mem_cgroup = NULL,
		.isolate_pages = isolate_pages_global,
1518
	};
1519 1520 1521 1522 1523
	/*
	 * 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
1524 1525 1526

loop_again:
	total_scanned = 0;
1527
	nr_reclaimed = 0;
C
Christoph Lameter 已提交
1528
	sc.may_writepage = !laptop_mode;
1529
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
1530

1531 1532
	for (i = 0; i < pgdat->nr_zones; i++)
		temp_priority[i] = DEF_PRIORITY;
L
Linus Torvalds 已提交
1533 1534 1535 1536 1537

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

1538 1539 1540 1541
		/* The swap token gets in the way of swapout... */
		if (!priority)
			disable_swap_token();

L
Linus Torvalds 已提交
1542 1543
		all_zones_ok = 1;

1544 1545 1546 1547 1548 1549
		/*
		 * 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
1550

1551 1552
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
1553

1554 1555
			if (zone_is_all_unreclaimable(zone) &&
			    priority != DEF_PRIORITY)
1556
				continue;
L
Linus Torvalds 已提交
1557

1558 1559 1560
			if (!zone_watermark_ok(zone, order, zone->pages_high,
					       0, 0)) {
				end_zone = i;
A
Andrew Morton 已提交
1561
				break;
L
Linus Torvalds 已提交
1562 1563
			}
		}
A
Andrew Morton 已提交
1564 1565 1566
		if (i < 0)
			goto out;

L
Linus Torvalds 已提交
1567 1568 1569
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

1570 1571
			lru_pages += zone_page_state(zone, NR_ACTIVE)
					+ zone_page_state(zone, NR_INACTIVE);
L
Linus Torvalds 已提交
1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584
		}

		/*
		 * 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;
1585
			int nr_slab;
L
Linus Torvalds 已提交
1586

1587
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
1588 1589
				continue;

1590 1591
			if (zone_is_all_unreclaimable(zone) &&
					priority != DEF_PRIORITY)
L
Linus Torvalds 已提交
1592 1593
				continue;

1594 1595 1596
			if (!zone_watermark_ok(zone, order, zone->pages_high,
					       end_zone, 0))
				all_zones_ok = 0;
1597
			temp_priority[i] = priority;
L
Linus Torvalds 已提交
1598
			sc.nr_scanned = 0;
1599
			note_zone_scanning_priority(zone, priority);
1600 1601 1602 1603 1604 1605 1606
			/*
			 * 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))
				nr_reclaimed += shrink_zone(priority, zone, &sc);
L
Linus Torvalds 已提交
1607
			reclaim_state->reclaimed_slab = 0;
1608 1609
			nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
						lru_pages);
1610
			nr_reclaimed += reclaim_state->reclaimed_slab;
L
Linus Torvalds 已提交
1611
			total_scanned += sc.nr_scanned;
1612
			if (zone_is_all_unreclaimable(zone))
L
Linus Torvalds 已提交
1613
				continue;
1614
			if (nr_slab == 0 && zone->pages_scanned >=
1615 1616
				(zone_page_state(zone, NR_ACTIVE)
				+ zone_page_state(zone, NR_INACTIVE)) * 6)
1617 1618
					zone_set_flag(zone,
						      ZONE_ALL_UNRECLAIMABLE);
L
Linus Torvalds 已提交
1619 1620 1621 1622 1623 1624
			/*
			 * 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 &&
1625
			    total_scanned > nr_reclaimed + nr_reclaimed / 2)
L
Linus Torvalds 已提交
1626 1627 1628 1629 1630 1631 1632 1633
				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.
		 */
1634
		if (total_scanned && priority < DEF_PRIORITY - 2)
1635
			congestion_wait(WRITE, HZ/10);
L
Linus Torvalds 已提交
1636 1637 1638 1639 1640 1641 1642

		/*
		 * 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.
		 */
1643
		if (nr_reclaimed >= SWAP_CLUSTER_MAX)
L
Linus Torvalds 已提交
1644 1645 1646
			break;
	}
out:
1647 1648 1649 1650 1651
	/*
	 * 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
1652 1653 1654
	for (i = 0; i < pgdat->nr_zones; i++) {
		struct zone *zone = pgdat->node_zones + i;

1655
		zone->prev_priority = temp_priority[i];
L
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1656 1657 1658
	}
	if (!all_zones_ok) {
		cond_resched();
1659 1660 1661

		try_to_freeze();

L
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1662 1663 1664
		goto loop_again;
	}

1665
	return nr_reclaimed;
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1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689
}

/*
 * The background pageout daemon, started as a kernel thread
 * from the init process. 
 *
 * 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,
	};
1690
	node_to_cpumask_ptr(cpumask, pgdat->node_id);
L
Linus Torvalds 已提交
1691

1692 1693
	if (!cpus_empty(*cpumask))
		set_cpus_allowed_ptr(tsk, cpumask);
L
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1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707
	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).
	 */
1708
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
1709
	set_freezable();
L
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1710 1711 1712 1713

	order = 0;
	for ( ; ; ) {
		unsigned long new_order;
1714

L
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1715 1716 1717 1718 1719 1720 1721 1722 1723 1724
		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 {
1725 1726 1727
			if (!freezing(current))
				schedule();

L
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1728 1729 1730 1731
			order = pgdat->kswapd_max_order;
		}
		finish_wait(&pgdat->kswapd_wait, &wait);

1732 1733 1734 1735 1736 1737
		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
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1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748
	}
	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;

1749
	if (!populated_zone(zone))
L
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1750 1751 1752
		return;

	pgdat = zone->zone_pgdat;
R
Rohit Seth 已提交
1753
	if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
L
Linus Torvalds 已提交
1754 1755 1756
		return;
	if (pgdat->kswapd_max_order < order)
		pgdat->kswapd_max_order = order;
1757
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
1758
		return;
1759
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
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1760
		return;
1761
	wake_up_interruptible(&pgdat->kswapd_wait);
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1762 1763 1764 1765
}

#ifdef CONFIG_PM
/*
1766 1767 1768 1769 1770 1771
 * 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
 */
1772 1773
static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
				      int pass, struct scan_control *sc)
1774 1775 1776 1777 1778 1779 1780 1781 1782
{
	struct zone *zone;
	unsigned long nr_to_scan, ret = 0;

	for_each_zone(zone) {

		if (!populated_zone(zone))
			continue;

1783
		if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
1784 1785 1786 1787
			continue;

		/* For pass = 0 we don't shrink the active list */
		if (pass > 0) {
1788 1789
			zone->nr_scan_active +=
				(zone_page_state(zone, NR_ACTIVE) >> prio) + 1;
1790 1791
			if (zone->nr_scan_active >= nr_pages || pass > 3) {
				zone->nr_scan_active = 0;
1792 1793
				nr_to_scan = min(nr_pages,
					zone_page_state(zone, NR_ACTIVE));
1794
				shrink_active_list(nr_to_scan, zone, sc, prio);
1795 1796 1797
			}
		}

1798 1799
		zone->nr_scan_inactive +=
			(zone_page_state(zone, NR_INACTIVE) >> prio) + 1;
1800 1801
		if (zone->nr_scan_inactive >= nr_pages || pass > 3) {
			zone->nr_scan_inactive = 0;
1802 1803
			nr_to_scan = min(nr_pages,
				zone_page_state(zone, NR_INACTIVE));
1804 1805 1806 1807 1808 1809 1810 1811 1812
			ret += shrink_inactive_list(nr_to_scan, zone, sc);
			if (ret >= nr_pages)
				return ret;
		}
	}

	return ret;
}

1813 1814
static unsigned long count_lru_pages(void)
{
1815
	return global_page_state(NR_ACTIVE) + global_page_state(NR_INACTIVE);
1816 1817
}

1818 1819 1820 1821 1822 1823 1824
/*
 * 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
1825
 */
1826
unsigned long shrink_all_memory(unsigned long nr_pages)
L
Linus Torvalds 已提交
1827
{
1828
	unsigned long lru_pages, nr_slab;
1829
	unsigned long ret = 0;
1830 1831 1832 1833 1834 1835 1836 1837
	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,
1838
		.isolate_pages = isolate_pages_global,
L
Linus Torvalds 已提交
1839 1840 1841
	};

	current->reclaim_state = &reclaim_state;
1842

1843
	lru_pages = count_lru_pages();
1844
	nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
1845 1846 1847 1848 1849
	/* 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)
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1850
			break;
1851 1852 1853 1854 1855 1856

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

		nr_slab -= reclaim_state.reclaimed_slab;
L
Linus Torvalds 已提交
1857
	}
1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884

	/*
	 * 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;
1885 1886
			shrink_slab(sc.nr_scanned, sc.gfp_mask,
					count_lru_pages());
1887 1888 1889 1890 1891
			ret += reclaim_state.reclaimed_slab;
			if (ret >= nr_pages)
				goto out;

			if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
1892
				congestion_wait(WRITE, HZ / 10);
1893
		}
1894
	}
1895 1896 1897 1898 1899

	/*
	 * If ret = 0, we could not shrink LRUs, but there may be something
	 * in slab caches
	 */
1900
	if (!ret) {
1901 1902
		do {
			reclaim_state.reclaimed_slab = 0;
1903
			shrink_slab(nr_pages, sc.gfp_mask, count_lru_pages());
1904 1905
			ret += reclaim_state.reclaimed_slab;
		} while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
1906
	}
1907 1908

out:
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1909
	current->reclaim_state = NULL;
1910

L
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1911 1912 1913 1914 1915 1916 1917 1918
	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. */
1919
static int __devinit cpu_callback(struct notifier_block *nfb,
1920
				  unsigned long action, void *hcpu)
L
Linus Torvalds 已提交
1921
{
1922
	int nid;
L
Linus Torvalds 已提交
1923

1924
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
1925
		for_each_node_state(nid, N_HIGH_MEMORY) {
1926 1927 1928 1929
			pg_data_t *pgdat = NODE_DATA(nid);
			node_to_cpumask_ptr(mask, pgdat->node_id);

			if (any_online_cpu(*mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
1930
				/* One of our CPUs online: restore mask */
1931
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
1932 1933 1934 1935 1936
		}
	}
	return NOTIFY_OK;
}

1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958
/*
 * This kswapd start function will be called by init and node-hot-add.
 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
 */
int kswapd_run(int nid)
{
	pg_data_t *pgdat = NODE_DATA(nid);
	int ret = 0;

	if (pgdat->kswapd)
		return 0;

	pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
	if (IS_ERR(pgdat->kswapd)) {
		/* failure at boot is fatal */
		BUG_ON(system_state == SYSTEM_BOOTING);
		printk("Failed to start kswapd on node %d\n",nid);
		ret = -1;
	}
	return ret;
}

L
Linus Torvalds 已提交
1959 1960
static int __init kswapd_init(void)
{
1961
	int nid;
1962

L
Linus Torvalds 已提交
1963
	swap_setup();
1964
	for_each_node_state(nid, N_HIGH_MEMORY)
1965
 		kswapd_run(nid);
L
Linus Torvalds 已提交
1966 1967 1968 1969 1970
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
1971 1972 1973 1974 1975 1976 1977 1978 1979 1980

#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;

1981 1982 1983 1984 1985
#define RECLAIM_OFF 0
#define RECLAIM_ZONE (1<<0)	/* Run shrink_cache on the zone */
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

1986 1987 1988 1989 1990 1991 1992
/*
 * 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

1993 1994 1995 1996 1997 1998
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

1999 2000 2001 2002 2003 2004
/*
 * 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;

2005 2006 2007
/*
 * Try to free up some pages from this zone through reclaim.
 */
2008
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2009
{
2010
	/* Minimum pages needed in order to stay on node */
2011
	const unsigned long nr_pages = 1 << order;
2012 2013
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
2014
	int priority;
2015
	unsigned long nr_reclaimed = 0;
2016 2017 2018
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
		.may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2019 2020
		.swap_cluster_max = max_t(unsigned long, nr_pages,
					SWAP_CLUSTER_MAX),
2021
		.gfp_mask = gfp_mask,
2022
		.swappiness = vm_swappiness,
2023
		.isolate_pages = isolate_pages_global,
2024
	};
2025
	unsigned long slab_reclaimable;
2026 2027 2028

	disable_swap_token();
	cond_resched();
2029 2030 2031 2032 2033 2034
	/*
	 * 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;
2035 2036
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2037

2038 2039 2040 2041 2042 2043 2044 2045 2046
	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 {
2047
			note_zone_scanning_priority(zone, priority);
2048 2049 2050 2051
			nr_reclaimed += shrink_zone(priority, zone, &sc);
			priority--;
		} while (priority >= 0 && nr_reclaimed < nr_pages);
	}
2052

2053 2054
	slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (slab_reclaimable > zone->min_slab_pages) {
2055
		/*
2056
		 * shrink_slab() does not currently allow us to determine how
2057 2058 2059 2060
		 * 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.
2061
		 *
2062 2063
		 * Note that shrink_slab will free memory on all zones and may
		 * take a long time.
2064
		 */
2065
		while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2066 2067
			zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
				slab_reclaimable - nr_pages)
2068
			;
2069 2070 2071 2072 2073 2074 2075

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
		nr_reclaimed += slab_reclaimable -
			zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2076 2077
	}

2078
	p->reclaim_state = NULL;
2079
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2080
	return nr_reclaimed >= nr_pages;
2081
}
2082 2083 2084 2085

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
2086
	int ret;
2087 2088

	/*
2089 2090
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
2091
	 *
2092 2093 2094 2095 2096
	 * 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.
2097
	 */
2098
	if (zone_page_state(zone, NR_FILE_PAGES) -
2099 2100 2101
	    zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
	    && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
			<= zone->min_slab_pages)
2102
		return 0;
2103

2104 2105 2106
	if (zone_is_all_unreclaimable(zone))
		return 0;

2107
	/*
2108
	 * Do not scan if the allocation should not be delayed.
2109
	 */
2110
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2111 2112 2113 2114 2115 2116 2117 2118
			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.
	 */
2119
	node_id = zone_to_nid(zone);
2120
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2121
		return 0;
2122 2123 2124 2125 2126 2127 2128

	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;
2129
}
2130
#endif