blob: 210c46abdf6b699eda863cbe52930f07d8b185ac [file] [log] [blame]
/*
* 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>
#include <linux/vmstat.h>
#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>
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/memcontrol.h>
#include <linux/delayacct.h>
#include <linux/sysctl.h>
#include <asm/tlbflush.h>
#include <asm/div64.h>
#include <linux/swapops.h>
#include "internal.h"
struct scan_control {
/* Incremented by the number of inactive pages that were scanned */
unsigned long nr_scanned;
/* Number of pages freed so far during a call to shrink_zones() */
unsigned long nr_reclaimed;
/* How many pages shrink_list() should reclaim */
unsigned long nr_to_reclaim;
unsigned long hibernation_mode;
/* This context's GFP mask */
gfp_t gfp_mask;
int may_writepage;
/* Can mapped pages be reclaimed? */
int may_unmap;
/* Can pages be swapped as part of reclaim? */
int may_swap;
int swappiness;
int all_unreclaimable;
int order;
/* Which cgroup do we reclaim from */
struct mem_cgroup *mem_cgroup;
/*
* Nodemask of nodes allowed by the caller. If NULL, all nodes
* are scanned.
*/
nodemask_t *nodemask;
/* 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, int file);
};
#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;
long vm_total_pages; /* The total number of pages which the VM controls */
static LIST_HEAD(shrinker_list);
static DECLARE_RWSEM(shrinker_rwsem);
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
#define scanning_global_lru(sc) (!(sc)->mem_cgroup)
#else
#define scanning_global_lru(sc) (1)
#endif
static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
struct scan_control *sc)
{
if (!scanning_global_lru(sc))
return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
return &zone->reclaim_stat;
}
static unsigned long zone_nr_lru_pages(struct zone *zone,
struct scan_control *sc, enum lru_list lru)
{
if (!scanning_global_lru(sc))
return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);
return zone_page_state(zone, NR_LRU_BASE + lru);
}
/*
* Add a shrinker callback to be called from the vm
*/
void register_shrinker(struct shrinker *shrinker)
{
shrinker->nr = 0;
down_write(&shrinker_rwsem);
list_add_tail(&shrinker->list, &shrinker_list);
up_write(&shrinker_rwsem);
}
EXPORT_SYMBOL(register_shrinker);
/*
* Remove one
*/
void unregister_shrinker(struct shrinker *shrinker)
{
down_write(&shrinker_rwsem);
list_del(&shrinker->list);
up_write(&shrinker_rwsem);
}
EXPORT_SYMBOL(unregister_shrinker);
#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.
*
* If the vm encountered mapped pages on the LRU it increase the pressure on
* 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.
*
* Returns the number of slab objects which we shrunk.
*/
unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
unsigned long lru_pages)
{
struct shrinker *shrinker;
unsigned long ret = 0;
if (scanned == 0)
scanned = SWAP_CLUSTER_MAX;
if (!down_read_trylock(&shrinker_rwsem))
return 1; /* Assume we'll be able to shrink next time */
list_for_each_entry(shrinker, &shrinker_list, list) {
unsigned long long delta;
unsigned long total_scan;
unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
delta = (4 * scanned) / shrinker->seeks;
delta *= max_pass;
do_div(delta, lru_pages + 1);
shrinker->nr += delta;
if (shrinker->nr < 0) {
printk(KERN_ERR "shrink_slab: %pF negative objects to "
"delete nr=%ld\n",
shrinker->shrink, shrinker->nr);
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;
total_scan = shrinker->nr;
shrinker->nr = 0;
while (total_scan >= SHRINK_BATCH) {
long this_scan = SHRINK_BATCH;
int shrink_ret;
int nr_before;
nr_before = (*shrinker->shrink)(0, gfp_mask);
shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
if (shrink_ret == -1)
break;
if (shrink_ret < nr_before)
ret += nr_before - shrink_ret;
count_vm_events(SLABS_SCANNED, this_scan);
total_scan -= this_scan;
cond_resched();
}
shrinker->nr += total_scan;
}
up_read(&shrinker_rwsem);
return ret;
}
/* 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)
{
/*
* A freeable page cache page is referenced only by the caller
* that isolated the page, the page cache radix tree and
* optional buffer heads at page->private.
*/
return page_count(page) - page_has_private(page) == 2;
}
static int may_write_to_queue(struct backing_dev_info *bdi)
{
if (current->flags & PF_SWAPWRITE)
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);
if (page_mapping(page) == mapping)
mapping_set_error(mapping, error);
unlock_page(page);
}
/* Request for sync pageout. */
enum pageout_io {
PAGEOUT_IO_ASYNC,
PAGEOUT_IO_SYNC,
};
/* 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;
/*
* pageout is called by shrink_page_list() for each dirty page.
* Calls ->writepage().
*/
static pageout_t pageout(struct page *page, struct address_space *mapping,
enum pageout_io sync_writeback)
{
/*
* 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_aio_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.
*/
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.
*/
if (page_has_private(page)) {
if (try_to_free_buffers(page)) {
ClearPageDirty(page);
printk("%s: orphaned page\n", __func__);
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,
.range_start = 0,
.range_end = LLONG_MAX,
.nonblocking = 1,
.for_reclaim = 1,
};
SetPageReclaim(page);
res = mapping->a_ops->writepage(page, &wbc);
if (res < 0)
handle_write_error(mapping, page, res);
if (res == AOP_WRITEPAGE_ACTIVATE) {
ClearPageReclaim(page);
return PAGE_ACTIVATE;
}
/*
* 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);
if (!PageWriteback(page)) {
/* synchronous write or broken a_ops? */
ClearPageReclaim(page);
}
inc_zone_page_state(page, NR_VMSCAN_WRITE);
return PAGE_SUCCESS;
}
return PAGE_CLEAN;
}
/*
* Same as remove_mapping, but if the page is removed from the mapping, it
* gets returned with a refcount of 0.
*/
static int __remove_mapping(struct address_space *mapping, struct page *page)
{
BUG_ON(!PageLocked(page));
BUG_ON(mapping != page_mapping(page));
spin_lock_irq(&mapping->tree_lock);
/*
* 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.
*/
if (!page_freeze_refs(page, 2))
goto cannot_free;
/* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
if (unlikely(PageDirty(page))) {
page_unfreeze_refs(page, 2);
goto cannot_free;
}
if (PageSwapCache(page)) {
swp_entry_t swap = { .val = page_private(page) };
__delete_from_swap_cache(page);
spin_unlock_irq(&mapping->tree_lock);
swapcache_free(swap, page);
} else {
__remove_from_page_cache(page);
spin_unlock_irq(&mapping->tree_lock);
mem_cgroup_uncharge_cache_page(page);
}
return 1;
cannot_free:
spin_unlock_irq(&mapping->tree_lock);
return 0;
}
/*
* 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;
}
/**
* putback_lru_page - put previously isolated page onto appropriate LRU list
* @page: page to be put back to appropriate lru list
*
* Add previously isolated @page to appropriate LRU list.
* Page may still be unevictable for other reasons.
*
* lru_lock must not be held, interrupts must be enabled.
*/
void putback_lru_page(struct page *page)
{
int lru;
int active = !!TestClearPageActive(page);
int was_unevictable = PageUnevictable(page);
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_lru_base_type(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);
/*
* When racing with an mlock clearing (page is
* unlocked), make sure that if the other thread does
* not observe our setting of PG_lru and fails
* isolation, we see PG_mlocked cleared below and move
* the page back to the evictable list.
*
* The other side is TestClearPageMlocked().
*/
smp_mb();
}
/*
* 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.
*/
}
if (was_unevictable && lru != LRU_UNEVICTABLE)
count_vm_event(UNEVICTABLE_PGRESCUED);
else if (!was_unevictable && lru == LRU_UNEVICTABLE)
count_vm_event(UNEVICTABLE_PGCULLED);
put_page(page); /* drop ref from isolate */
}
/*
* shrink_page_list() returns the number of reclaimed pages
*/
static unsigned long shrink_page_list(struct list_head *page_list,
struct scan_control *sc,
enum pageout_io sync_writeback)
{
LIST_HEAD(ret_pages);
struct pagevec freed_pvec;
int pgactivate = 0;
unsigned long nr_reclaimed = 0;
unsigned long vm_flags;
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 (!trylock_page(page))
goto keep;
VM_BUG_ON(PageActive(page));
sc->nr_scanned++;
if (unlikely(!page_evictable(page, NULL)))
goto cull_mlocked;
if (!sc->may_unmap && page_mapped(page))
goto keep_locked;
/* Double the slab pressure for mapped and swapcache pages */
if (page_mapped(page) || PageSwapCache(page))
sc->nr_scanned++;
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);
else
goto keep_locked;
}
referenced = page_referenced(page, 1,
sc->mem_cgroup, &vm_flags);
/*
* In active use or really unfreeable? Activate it.
* If page which have PG_mlocked lost isoltation race,
* try_to_unmap moves it to unevictable list
*/
if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
referenced && page_mapping_inuse(page)
&& !(vm_flags & VM_LOCKED))
goto activate_locked;
/*
* Anonymous process memory has backing store?
* Try to allocate it some swap space here.
*/
if (PageAnon(page) && !PageSwapCache(page)) {
if (!(sc->gfp_mask & __GFP_IO))
goto keep_locked;
if (!add_to_swap(page))
goto activate_locked;
may_enter_fs = 1;
}
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) {
switch (try_to_unmap(page, TTU_UNMAP)) {
case SWAP_FAIL:
goto activate_locked;
case SWAP_AGAIN:
goto keep_locked;
case SWAP_MLOCK:
goto cull_mlocked;
case SWAP_SUCCESS:
; /* try to free the page below */
}
}
if (PageDirty(page)) {
if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
goto keep_locked;
if (!may_enter_fs)
goto keep_locked;
if (!sc->may_writepage)
goto keep_locked;
/* Page is dirty, try to write it out here */
switch (pageout(page, mapping, sync_writeback)) {
case PAGE_KEEP:
goto keep_locked;
case PAGE_ACTIVATE:
goto activate_locked;
case PAGE_SUCCESS:
if (PageWriteback(page) || PageDirty(page))
goto keep;
/*
* A synchronous write - probably a ramdisk. Go
* ahead and try to reclaim the page.
*/
if (!trylock_page(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 (page_has_private(page)) {
if (!try_to_release_page(page, sc->gfp_mask))
goto activate_locked;
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;
}
}
}
if (!mapping || !__remove_mapping(mapping, page))
goto keep_locked;
/*
* 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);
free_it:
nr_reclaimed++;
if (!pagevec_add(&freed_pvec, page)) {
__pagevec_free(&freed_pvec);
pagevec_reinit(&freed_pvec);
}
continue;
cull_mlocked:
if (PageSwapCache(page))
try_to_free_swap(page);
unlock_page(page);
putback_lru_page(page);
continue;
activate_locked:
/* Not a candidate for swapping, so reclaim swap space. */
if (PageSwapCache(page) && vm_swap_full())
try_to_free_swap(page);
VM_BUG_ON(PageActive(page));
SetPageActive(page);
pgactivate++;
keep_locked:
unlock_page(page);
keep:
list_add(&page->lru, &ret_pages);
VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
}
list_splice(&ret_pages, page_list);
if (pagevec_count(&freed_pvec))
__pagevec_free(&freed_pvec);
count_vm_events(PGACTIVATE, pgactivate);
return nr_reclaimed;
}
/* 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.
*/
int __isolate_lru_page(struct page *page, int mode, int file)
{
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;
if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
return ret;
/*
* 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;
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;
}
/*
* 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.
* @order: The caller's attempted allocation order
* @mode: One of the LRU isolation modes
* @file: True [1] if isolating file [!anon] pages
*
* returns how many pages were moved onto *@dst.
*/
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
struct list_head *src, struct list_head *dst,
unsigned long *scanned, int order, int mode, int file)
{
unsigned long nr_taken = 0;
unsigned long scan;
for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
struct page *page;
unsigned long pfn;
unsigned long end_pfn;
unsigned long page_pfn;
int zone_id;
page = lru_to_page(src);
prefetchw_prev_lru_page(page, src, flags);
VM_BUG_ON(!PageLRU(page));
switch (__isolate_lru_page(page, mode, file)) {
case 0:
list_move(&page->lru, dst);
mem_cgroup_del_lru(page);
nr_taken++;
break;
case -EBUSY:
/* else it is being freed elsewhere */
list_move(&page->lru, src);
mem_cgroup_rotate_lru_list(page, page_lru(page));
continue;
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;
/*
* If we don't have enough swap space, reclaiming of
* anon page which don't already have a swap slot is
* pointless.
*/
if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
!PageSwapCache(cursor_page))
continue;
if (__isolate_lru_page(cursor_page, mode, file) == 0) {
list_move(&cursor_page->lru, dst);
mem_cgroup_del_lru(cursor_page);
nr_taken++;
scan++;
}
}
}
*scanned = scan;
return nr_taken;
}
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, int file)
{
int lru = LRU_BASE;
if (active)
lru += LRU_ACTIVE;
if (file)
lru += LRU_FILE;
return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
mode, file);
}
/*
* 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,
unsigned int *count)
{
int nr_active = 0;
int lru;
struct page *page;
list_for_each_entry(page, page_list, lru) {
lru = page_lru_base_type(page);
if (PageActive(page)) {
lru += LRU_ACTIVE;
ClearPageActive(page);
nr_active++;
}
count[lru]++;
}
return nr_active;
}
/**
* 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
* 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.
*
* 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)) {
int lru = page_lru(page);
ret = 0;
ClearPageLRU(page);
del_page_from_lru_list(zone, page, lru);
}
spin_unlock_irq(&zone->lru_lock);
}
return ret;
}
/*
* Are there way too many processes in the direct reclaim path already?
*/
static int too_many_isolated(struct zone *zone, int file,
struct scan_control *sc)
{
unsigned long inactive, isolated;
if (current_is_kswapd())
return 0;
if (!scanning_global_lru(sc))
return 0;
if (file) {
inactive = zone_page_state(zone, NR_INACTIVE_FILE);
isolated = zone_page_state(zone, NR_ISOLATED_FILE);
} else {
inactive = zone_page_state(zone, NR_INACTIVE_ANON);
isolated = zone_page_state(zone, NR_ISOLATED_ANON);
}
return isolated > inactive;
}
/*
* Returns true if the caller should wait to clean dirty/writeback pages.
*
* If we are direct reclaiming for contiguous pages and we do not reclaim
* everything in the list, try again and wait for writeback IO to complete.
* This will stall high-order allocations noticeably. Only do that when really
* need to free the pages under high memory pressure.
*/
static inline bool should_reclaim_stall(unsigned long nr_taken,
unsigned long nr_freed,
int priority,
int lumpy_reclaim,
struct scan_control *sc)
{
int lumpy_stall_priority;
/* kswapd should not stall on sync IO */
if (current_is_kswapd())
return false;
/* Only stall on lumpy reclaim */
if (!lumpy_reclaim)
return false;
/* If we have relaimed everything on the isolated list, no stall */
if (nr_freed == nr_taken)
return false;
/*
* For high-order allocations, there are two stall thresholds.
* High-cost allocations stall immediately where as lower
* order allocations such as stacks require the scanning
* priority to be much higher before stalling.
*/
if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
lumpy_stall_priority = DEF_PRIORITY;
else
lumpy_stall_priority = DEF_PRIORITY / 3;
return priority <= lumpy_stall_priority;
}
/*
* shrink_inactive_list() is a helper for shrink_zone(). It returns the number
* of reclaimed pages
*/
static unsigned long shrink_inactive_list(unsigned long max_scan,
struct zone *zone, struct scan_control *sc,
int priority, int file)
{
LIST_HEAD(page_list);
struct pagevec pvec;
unsigned long nr_scanned = 0;
unsigned long nr_reclaimed = 0;
struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
int lumpy_reclaim = 0;
while (unlikely(too_many_isolated(zone, file, sc))) {
congestion_wait(BLK_RW_ASYNC, HZ/10);
/* We are about to die and free our memory. Return now. */
if (fatal_signal_pending(current))
return SWAP_CLUSTER_MAX;
}
/*
* 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)
lumpy_reclaim = 1;
else if (sc->order && priority < DEF_PRIORITY - 2)
lumpy_reclaim = 1;
pagevec_init(&pvec, 1);
lru_add_drain();
spin_lock_irq(&zone->lru_lock);
do {
struct page *page;
unsigned long nr_taken;
unsigned long nr_scan;
unsigned long nr_freed;
unsigned long nr_active;
unsigned int count[NR_LRU_LISTS] = { 0, };
int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE;
unsigned long nr_anon;
unsigned long nr_file;
nr_taken = sc->isolate_pages(SWAP_CLUSTER_MAX,
&page_list, &nr_scan, sc->order, mode,
zone, sc->mem_cgroup, 0, file);
if (scanning_global_lru(sc)) {
zone->pages_scanned += nr_scan;
if (current_is_kswapd())
__count_zone_vm_events(PGSCAN_KSWAPD, zone,
nr_scan);
else
__count_zone_vm_events(PGSCAN_DIRECT, zone,
nr_scan);
}
if (nr_taken == 0)
goto done;
nr_active = clear_active_flags(&page_list, count);
__count_vm_events(PGDEACTIVATE, nr_active);
__mod_zone_page_state(zone, NR_ACTIVE_FILE,
-count[LRU_ACTIVE_FILE]);
__mod_zone_page_state(zone, NR_INACTIVE_FILE,
-count[LRU_INACTIVE_FILE]);
__mod_zone_page_state(zone, NR_ACTIVE_ANON,
-count[LRU_ACTIVE_ANON]);
__mod_zone_page_state(zone, NR_INACTIVE_ANON,
-count[LRU_INACTIVE_ANON]);
nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
__mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
__mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
reclaim_stat->recent_scanned[0] += nr_anon;
reclaim_stat->recent_scanned[1] += nr_file;
spin_unlock_irq(&zone->lru_lock);
nr_scanned += nr_scan;
nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
/* Check if we should syncronously wait for writeback */
if (should_reclaim_stall(nr_taken, nr_freed, priority,
lumpy_reclaim, sc)) {
congestion_wait(BLK_RW_ASYNC, 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);
count_vm_events(PGDEACTIVATE, nr_active);
nr_freed += shrink_page_list(&page_list, sc,
PAGEOUT_IO_SYNC);
}
nr_reclaimed += nr_freed;
local_irq_disable();
if (current_is_kswapd())
__count_vm_events(KSWAPD_STEAL, nr_freed);
__count_zone_vm_events(PGSTEAL, zone, nr_freed);
spin_lock(&zone->lru_lock);
/*
* Put back any unfreeable pages.
*/
while (!list_empty(&page_list)) {
int lru;
page = lru_to_page(&page_list);
VM_BUG_ON(PageLRU(page));
list_del(&page->lru);
if (unlikely(!page_evictable(page, NULL))) {
spin_unlock_irq(&zone->lru_lock);
putback_lru_page(page);
spin_lock_irq(&zone->lru_lock);
continue;
}
SetPageLRU(page);
lru = page_lru(page);
add_page_to_lru_list(zone, page, lru);
if (is_active_lru(lru)) {
int file = is_file_lru(lru);
reclaim_stat->recent_rotated[file]++;
}
if (!pagevec_add(&pvec, page)) {
spin_unlock_irq(&zone->lru_lock);
__pagevec_release(&pvec);
spin_lock_irq(&zone->lru_lock);
}
}
__mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
__mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
} while (nr_scanned < max_scan);
done:
spin_unlock_irq(&zone->lru_lock);
pagevec_release(&pvec);
return nr_reclaimed;
}
/*
* 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;
}
/*
* 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.
*/
static void move_active_pages_to_lru(struct zone *zone,
struct list_head *list,
enum lru_list lru)
{
unsigned long pgmoved = 0;
struct pagevec pvec;
struct page *page;
pagevec_init(&pvec, 1);
while (!list_empty(list)) {
page = lru_to_page(list);
VM_BUG_ON(PageLRU(page));
SetPageLRU(page);
list_move(&page->lru, &zone->lru[lru].list);
mem_cgroup_add_lru_list(page, lru);
pgmoved++;
if (!pagevec_add(&pvec, page) || list_empty(list)) {
spin_unlock_irq(&zone->lru_lock);
if (buffer_heads_over_limit)
pagevec_strip(&pvec);
__pagevec_release(&pvec);
spin_lock_irq(&zone->lru_lock);
}
}
__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
if (!is_active_lru(lru))
__count_vm_events(PGDEACTIVATE, pgmoved);
}
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
struct scan_control *sc, int priority, int file)
{
unsigned long nr_taken;
unsigned long pgscanned;
unsigned long vm_flags;
LIST_HEAD(l_hold); /* The pages which were snipped off */
LIST_HEAD(l_active);
LIST_HEAD(l_inactive);
struct page *page;
struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
unsigned long nr_rotated = 0;
lru_add_drain();
spin_lock_irq(&zone->lru_lock);
nr_taken = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
ISOLATE_ACTIVE, zone,
sc->mem_cgroup, 1, file);
/*
* zone->pages_scanned is used for detect zone's oom
* mem_cgroup remembers nr_scan by itself.
*/
if (scanning_global_lru(sc)) {
zone->pages_scanned += pgscanned;
}
reclaim_stat->recent_scanned[file] += nr_taken;
__count_zone_vm_events(PGREFILL, zone, pgscanned);
if (file)
__mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
else
__mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
spin_unlock_irq(&zone->lru_lock);
while (!list_empty(&l_hold)) {
cond_resched();
page = lru_to_page(&l_hold);
list_del(&page->lru);
if (unlikely(!page_evictable(page, NULL))) {
putback_lru_page(page);
continue;
}
/* page_referenced clears PageReferenced */
if (page_mapping_inuse(page) &&
page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
nr_rotated++;
/*
* Identify referenced, file-backed active pages and
* give them one more trip around the active list. So
* that executable code get better chances to stay in
* memory under moderate memory pressure. Anon pages
* are not likely to be evicted by use-once streaming
* IO, plus JVM can create lots of anon VM_EXEC pages,
* so we ignore them here.
*/
if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
list_add(&page->lru, &l_active);
continue;
}
}
ClearPageActive(page); /* we are de-activating */
list_add(&page->lru, &l_inactive);
}
/*
* Move pages back to the lru list.
*/
spin_lock_irq(&zone->lru_lock);
/*
* Count referenced pages from currently used mappings as rotated,
* even though only some of them are actually re-activated. This
* helps balance scan pressure between file and anonymous pages in
* get_scan_ratio.
*/
reclaim_stat->recent_rotated[file] += nr_rotated;
move_active_pages_to_lru(zone, &l_active,
LRU_ACTIVE + file * LRU_FILE);
move_active_pages_to_lru(zone, &l_inactive,
LRU_BASE + file * LRU_FILE);
__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
spin_unlock_irq(&zone->lru_lock);
}
static int inactive_anon_is_low_global(struct zone *zone)
{
unsigned long active, inactive;
active = zone_page_state(zone, NR_ACTIVE_ANON);
inactive = zone_page_state(zone, NR_INACTIVE_ANON);
if (inactive * zone->inactive_ratio < active)
return 1;
return 0;
}
/**
* inactive_anon_is_low - check if anonymous pages need to be deactivated
* @zone: zone to check
* @sc: scan control of this context
*
* Returns true if the zone does not have enough inactive anon pages,
* meaning some active anon pages need to be deactivated.
*/
static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
{
int low;
if (scanning_global_lru(sc))
low = inactive_anon_is_low_global(zone);
else
low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
return low;
}
static int inactive_file_is_low_global(struct zone *zone)
{
unsigned long active, inactive;
active = zone_page_state(zone, NR_ACTIVE_FILE);
inactive = zone_page_state(zone, NR_INACTIVE_FILE);
return (active > inactive);
}
/**
* inactive_file_is_low - check if file pages need to be deactivated
* @zone: zone to check
* @sc: scan control of this context
*
* When the system is doing streaming IO, memory pressure here
* ensures that active file pages get deactivated, until more
* than half of the file pages are on the inactive list.
*
* Once we get to that situation, protect the system's working
* set from being evicted by disabling active file page aging.
*
* This uses a different ratio than the anonymous pages, because
* the page cache uses a use-once replacement algorithm.
*/
static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
{
int low;
if (scanning_global_lru(sc))
low = inactive_file_is_low_global(zone);
else
low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
return low;
}
static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
int file)
{
if (file)
return inactive_file_is_low(zone, sc);
else
return inactive_anon_is_low(zone, sc);
}
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
struct zone *zone, struct scan_control *sc, int priority)
{
int file = is_file_lru(lru);
if (is_active_lru(lru)) {
if (inactive_list_is_low(zone, sc, file))
shrink_active_list(nr_to_scan, zone, sc, priority, file);
return 0;
}
return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
}
/*
* 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;
struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
if (scanning_global_lru(sc)) {
free = zone_page_state(zone, NR_FREE_PAGES);
/* If we have very few page cache pages,
force-scan anon pages. */
if (unlikely(file + free <= high_wmark_pages(zone))) {
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(reclaim_stat->recent_scanned[0] > anon / 4)) {
spin_lock_irq(&zone->lru_lock);
reclaim_stat->recent_scanned[0] /= 2;
reclaim_stat->recent_rotated[0] /= 2;
spin_unlock_irq(&zone->lru_lock);
}
if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
spin_lock_irq(&zone->lru_lock);
reclaim_stat->recent_scanned[1] /= 2;
reclaim_stat->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;
/*
* 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.
*/
ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
ap /= reclaim_stat->recent_rotated[0] + 1;
fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
fp /= reclaim_stat->recent_rotated[1] + 1;
/* Normalize to percentages */
percent[0] = 100 * ap / (ap + fp + 1);
percent[1] = 100 - percent[0];
}
/*
* Smallish @nr_to_scan's are deposited in @nr_saved_scan,
* until we collected @swap_cluster_max pages to scan.
*/
static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
unsigned long *nr_saved_scan)
{
unsigned long nr;
*nr_saved_scan += nr_to_scan;
nr = *nr_saved_scan;
if (nr >= SWAP_CLUSTER_MAX)
*nr_saved_scan = 0;
else
nr = 0;
return nr;
}
/*
* This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
*/
static void shrink_zone(int priority, struct zone *zone,
struct scan_control *sc)
{
unsigned long nr[NR_LRU_LISTS];
unsigned long nr_to_scan;
unsigned long percent[2]; /* anon @ 0; file @ 1 */
enum lru_list l;
unsigned long nr_reclaimed = sc->nr_reclaimed;
unsigned long nr_to_reclaim = sc->nr_to_reclaim;
struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
int noswap = 0;
/* If we have no swap space, do not bother scanning anon pages. */
if (!sc->may_swap || (nr_swap_pages <= 0)) {
noswap = 1;
percent[0] = 0;
percent[1] = 100;
} else
get_scan_ratio(zone, sc, percent);
for_each_evictable_lru(l) {
int file = is_file_lru(l);
unsigned long scan;
scan = zone_nr_lru_pages(zone, sc, l);
if (priority || noswap) {
scan >>= priority;
scan = (scan * percent[file]) / 100;
}
nr[l] = nr_scan_try_batch(scan,
&reclaim_stat->nr_saved_scan[l]);
}
while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
nr[LRU_INACTIVE_FILE]) {
for_each_evictable_lru(l) {
if (nr[l]) {
nr_to_scan = min_t(unsigned long,
nr[l], SWAP_CLUSTER_MAX);
nr[l] -= nr_to_scan;
nr_reclaimed += shrink_list(l, nr_to_scan,
zone, sc, priority);
}
}
/*
* 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.
*/
if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
break;
}
sc->nr_reclaimed = nr_reclaimed;
/*
* Even if we did not try to evict anon pages at all, we want to
* rebalance the anon lru active/inactive ratio.
*/
if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0)
shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
throttle_vm_writeout(sc->gfp_mask);
}
/*
* 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 high_wmark_pages(zone).
* Because:
* a) The caller may be trying to free *extra* pages to satisfy a higher-order
* allocation or
* b) The target zone may be at high_wmark_pages(zone) but the lower zones
* must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
* zone defense algorithm.
*
* If a zone is deemed to be full of pinned pages then just give it a light
* scan then give up on it.
*/
static void shrink_zones(int priority, struct zonelist *zonelist,
struct scan_control *sc)
{
enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
struct zoneref *z;
struct zone *zone;
sc->all_unreclaimable = 1;
for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
sc->nodemask) {
if (!populated_zone(zone))
continue;
/*
* Take care memory controller reclaiming has small influence
* to global LRU.
*/
if (scanning_global_lru(sc)) {
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
continue;
note_zone_scanning_priority(zone, priority);
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);
}
shrink_zone(priority, zone, sc);
}
}
/*
* 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 the writeback threads and take explicit
* naps in the hope that some of these pages can be written. But if the
* allocating task holds filesystem locks which prevent writeout this might not
* work, and the allocation attempt will fail.
*
* returns: 0, if no pages reclaimed
* else, the number of pages reclaimed
*/
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
struct scan_control *sc)
{
int priority;
unsigned long ret = 0;
unsigned long total_scanned = 0;
struct reclaim_state *reclaim_state = current->reclaim_state;
unsigned long lru_pages = 0;
struct zoneref *z;
struct zone *zone;
enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
unsigned long writeback_threshold;
delayacct_freepages_start();
if (scanning_global_lru(sc))
count_vm_event(ALLOCSTALL);
/*
* mem_cgroup will not do shrink_slab.
*/
if (scanning_global_lru(sc)) {
for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
continue;
lru_pages += zone_reclaimable_pages(zone);
}
}
for (priority = DEF_PRIORITY; priority >= 0; priority--) {
sc->nr_scanned = 0;
if (!priority)
disable_swap_token();
shrink_zones(priority, zonelist, sc);
/*
* Don't shrink slabs when reclaiming memory from
* over limit cgroups
*/
if (scanning_global_lru(sc)) {
shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
if (reclaim_state) {
sc->nr_reclaimed += reclaim_state->reclaimed_slab;
reclaim_state->reclaimed_slab = 0;
}
}
total_scanned += sc->nr_scanned;
if (sc->nr_reclaimed >= sc->nr_to_reclaim) {
ret = sc->nr_reclaimed;
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.
*/
writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
if (total_scanned > writeback_threshold) {
wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
sc->may_writepage = 1;
}
/* Take a nap, wait for some writeback to complete */
if (!sc->hibernation_mode && sc->nr_scanned &&
priority < DEF_PRIORITY - 2)
congestion_wait(BLK_RW_ASYNC, HZ/10);
}
/* top priority shrink_zones still had more to do? don't OOM, then */
if (!sc->all_unreclaimable && scanning_global_lru(sc))
ret = sc->nr_reclaimed;
out:
/*
* 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;
if (scanning_global_lru(sc)) {
for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
continue;
zone->prev_priority = priority;
}
} else
mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
delayacct_freepages_end();
return ret;
}
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
gfp_t gfp_mask, nodemask_t *nodemask)
{
struct scan_control sc = {
.gfp_mask = gfp_mask,
.may_writepage = !laptop_mode,
.nr_to_reclaim = SWAP_CLUSTER_MAX,
.may_unmap = 1,
.may_swap = 1,
.swappiness = vm_swappiness,
.order = order,
.mem_cgroup = NULL,
.isolate_pages = isolate_pages_global,
.nodemask = nodemask,
};
return do_try_to_free_pages(zonelist, &sc);
}
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
gfp_t gfp_mask, bool noswap,
unsigned int swappiness,
struct zone *zone, int nid)
{
struct scan_control sc = {
.may_writepage = !laptop_mode,
.may_unmap = 1,
.may_swap = !noswap,
.swappiness = swappiness,
.order = 0,
.mem_cgroup = mem,
.isolate_pages = mem_cgroup_isolate_pages,
};
nodemask_t nm = nodemask_of_node(nid);
sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
sc.nodemask = &nm;
sc.nr_reclaimed = 0;
sc.nr_scanned = 0;
/*
* NOTE: Although we can get the priority field, using it
* here is not a good idea, since it limits the pages we can scan.
* if we don't reclaim here, the shrink_zone from balance_pgdat
* will pick up pages from other mem cgroup's as well. We hack
* the priority and make it zero.
*/
shrink_zone(0, zone, &sc);
return sc.nr_reclaimed;
}
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
gfp_t gfp_mask,
bool noswap,
unsigned int swappiness)
{
struct zonelist *zonelist;
struct scan_control sc = {
.may_writepage = !laptop_mode,
.may_unmap = 1,
.may_swap = !noswap,
.nr_to_reclaim = SWAP_CLUSTER_MAX,
.swappiness = swappiness,
.order = 0,
.mem_cgroup = mem_cont,
.isolate_pages = mem_cgroup_isolate_pages,
.nodemask = NULL, /* we don't care the placement */
};
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);
}
#endif
/* is kswapd sleeping prematurely? */
static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
{
int i;
/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
if (remaining)
return 1;
/* If after HZ/10, a zone is below the high mark, it's premature */
for (i = 0; i < pgdat->nr_zones; i++) {
struct zone *zone = pgdat->node_zones + i;
if (!populated_zone(zone))
continue;
if (zone_is_all_unreclaimable(zone))
continue;
if (!zone_watermark_ok(zone, order, high_wmark_pages(zone),
0, 0))
return 1;
}
return 0;
}
/*
* For kswapd, balance_pgdat() will work across all this node's zones until
* they are all at high_wmark_pages(zone).
*
* 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 > high_wmark_pages(zone), but once a zone is
* found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
* lower zones regardless of the number of free pages in the lower zones. This
* interoperates with the page allocator fallback scheme to ensure that aging
* of pages is balanced across the zones.
*/
static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
{
int all_zones_ok;
int priority;
int i;
unsigned long total_scanned;
struct reclaim_state *reclaim_state = current->reclaim_state;
struct scan_control sc = {
.gfp_mask = GFP_KERNEL,
.may_unmap = 1,
.may_swap = 1,
/*
* kswapd doesn't want to be bailed out while reclaim. because
* we want to put equal scanning pressure on each zone.
*/
.nr_to_reclaim = ULONG_MAX,
.swappiness = vm_swappiness,
.order = order,
.mem_cgroup = NULL,
.isolate_pages = isolate_pages_global,
};
/*
* temp_priority is used to remember the scanning priority at which
* this zone was successfully refilled to
* free_pages == high_wmark_pages(zone).
*/
int temp_priority[MAX_NR_ZONES];
loop_again:
total_scanned = 0;
sc.nr_reclaimed = 0;
sc.may_writepage = !laptop_mode;
count_vm_event(PAGEOUTRUN);
for (i = 0; i < pgdat->nr_zones; i++)
temp_priority[i] = DEF_PRIORITY;
for (priority = DEF_PRIORITY; priority >= 0; priority--) {
int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
unsigned long lru_pages = 0;
int has_under_min_watermark_zone = 0;
/* The swap token gets in the way of swapout... */
if (!priority)
disable_swap_token();
all_zones_ok = 1;
/*
* 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;
if (!populated_zone(zone))
continue;
if (zone_is_all_unreclaimable(zone) &&
priority != DEF_PRIORITY)
continue;
/*
* Do some background aging of the anon list, to give
* pages a chance to be referenced before reclaiming.
*/
if (inactive_anon_is_low(zone, &sc))
shrink_active_list(SWAP_CLUSTER_MAX, zone,
&sc, priority, 0);
if (!zone_watermark_ok(zone, order,
high_wmark_pages(zone), 0, 0)) {
end_zone = i;
break;
}
}
if (i < 0)
goto out;
for (i = 0; i <= end_zone; i++) {
struct zone *zone = pgdat->node_zones + i;
lru_pages += zone_reclaimable_pages(zone);
}
/*
* 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;
int nr_slab;
int nid, zid;
if (!populated_zone(zone))
continue;
if (zone_is_all_unreclaimable(zone) &&
priority != DEF_PRIORITY)
continue;
if (!zone_watermark_ok(zone, order,
high_wmark_pages(zone), end_zone, 0))
all_zones_ok = 0;
temp_priority[i] = priority;
sc.nr_scanned = 0;
note_zone_scanning_priority(zone, priority);
nid = pgdat->node_id;
zid = zone_idx(zone);
/*
* Call soft limit reclaim before calling shrink_zone.
* For now we ignore the return value
*/
mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask,
nid, zid);
/*
* We put equal pressure on every zone, unless one
* zone has way too many pages free already.
*/
if (!zone_watermark_ok(zone, order,
8*high_wmark_pages(zone), end_zone, 0))
shrink_zone(priority, zone, &sc);
reclaim_state->reclaimed_slab = 0;
nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
lru_pages);
sc.nr_reclaimed += reclaim_state->reclaimed_slab;
total_scanned += sc.nr_scanned;
if (zone_is_all_unreclaimable(zone))
continue;
if (nr_slab == 0 && zone->pages_scanned >=
(zone_reclaimable_pages(zone) * 6))
zone_set_flag(zone,
ZONE_ALL_UNRECLAIMABLE);
/*
* 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 &&
total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
sc.may_writepage = 1;
/*
* We are still under min water mark. it mean we have
* GFP_ATOMIC allocation failure risk. Hurry up!
*/
if (!zone_watermark_ok(zone, order, min_wmark_pages(zone),
end_zone, 0))
has_under_min_watermark_zone = 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.
*/
if (total_scanned && (priority < DEF_PRIORITY - 2)) {
if (has_under_min_watermark_zone)
count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
else
congestion_wait(BLK_RW_ASYNC, HZ/10);
}
/*
* 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.
*/
if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
break;
}
out:
/*
* 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.
*/
for (i = 0; i < pgdat->nr_zones; i++) {
struct zone *zone = pgdat->node_zones + i;
zone->prev_priority = temp_priority[i];
}
if (!all_zones_ok) {
cond_resched();
try_to_freeze();
/*
* 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;
goto loop_again;
}
return sc.nr_reclaimed;
}
/*
* 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,
};
const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
lockdep_set_current_reclaim_state(GFP_KERNEL);
if (!cpumask_empty(cpumask))
set_cpus_allowed_ptr(tsk, cpumask);
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).
*/
tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
set_freezable();
order = 0;
for ( ; ; ) {
unsigned long new_order;
int ret;
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 {
if (!freezing(current) && !kthread_should_stop()) {
long remaining = 0;
/* Try to sleep for a short interval */
if (!sleeping_prematurely(pgdat, order, remaining)) {
remaining = schedule_timeout(HZ/10);
finish_wait(&pgdat->kswapd_wait, &wait);
prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
}
/*
* After a short sleep, check if it was a
* premature sleep. If not, then go fully
* to sleep until explicitly woken up
*/
if (!sleeping_prematurely(pgdat, order, remaining))
schedule();
else {
if (remaining)
count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
else
count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
}
}
order = pgdat->kswapd_max_order;
}
finish_wait(&pgdat->kswapd_wait, &wait);
ret = try_to_freeze();
if (kthread_should_stop())
break;
/*
* We can speed up thawing tasks if we don't call balance_pgdat
* after returning from the refrigerator
*/
if (!ret)
balance_pgdat(pgdat, order);
}
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;
if (!populated_zone(zone))
return;
pgdat = zone->zone_pgdat;
if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
return;
if (pgdat->kswapd_max_order < order)
pgdat->kswapd_max_order = order;
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
return;
if (!waitqueue_active(&pgdat->kswapd_wait))
return;
wake_up_interruptible(&pgdat->kswapd_wait);
}
/*
* The reclaimable count would be mostly accurate.
* The less reclaimable pages may be
* - mlocked pages, which will be moved to unevictable list when encountered
* - mapped pages, which may require several travels to be reclaimed
* - dirty pages, which is not "instantly" reclaimable
*/
unsigned long global_reclaimable_pages(void)
{
int nr;
nr = global_page_state(NR_ACTIVE_FILE) +
global_page_state(NR_INACTIVE_FILE);
if (nr_swap_pages > 0)
nr += global_page_state(NR_ACTIVE_ANON) +
global_page_state(NR_INACTIVE_ANON);
return nr;
}
unsigned long zone_reclaimable_pages(struct zone *zone)
{
int nr;
nr = zone_page_state(zone, NR_ACTIVE_FILE) +
zone_page_state(zone, NR_INACTIVE_FILE);
if (nr_swap_pages > 0)
nr += zone_page_state(zone, NR_ACTIVE_ANON) +
zone_page_state(zone, NR_INACTIVE_ANON);
return nr;
}
#ifdef CONFIG_HIBERNATION
/*
* Try to free `nr_to_reclaim' 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
*/
unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
{
struct reclaim_state reclaim_state;
struct scan_control sc = {
.gfp_mask = GFP_HIGHUSER_MOVABLE,
.may_swap = 1,
.may_unmap = 1,
.may_writepage = 1,
.nr_to_reclaim = nr_to_reclaim,
.hibernation_mode = 1,
.swappiness = vm_swappiness,
.order = 0,
.isolate_pages = isolate_pages_global,
};
struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
struct task_struct *p = current;
unsigned long nr_reclaimed;
p->flags |= PF_MEMALLOC;
lockdep_set_current_reclaim_state(sc.gfp_mask);
reclaim_state.reclaimed_slab = 0;
p->reclaim_state = &reclaim_state;
nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
p->reclaim_state = NULL;
lockdep_clear_current_reclaim_state();
p->flags &= ~PF_MEMALLOC;
return nr_reclaimed;
}
#endif /* CONFIG_HIBERNATION */
/* 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. */
static int __devinit cpu_callback(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
int nid;
if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
for_each_node_state(nid, N_HIGH_MEMORY) {
pg_data_t *pgdat = NODE_DATA(nid);
const struct cpumask *mask;
mask = cpumask_of_node(pgdat->node_id);
if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
/* One of our CPUs online: restore mask */
set_cpus_allowed_ptr(pgdat->kswapd, mask);
}
}
return NOTIFY_OK;
}
/*
* 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;
}
/*
* Called by memory hotplug when all memory in a node is offlined.
*/
void kswapd_stop(int nid)
{
struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
if (kswapd)
kthread_stop(kswapd);
}
static int __init kswapd_init(void)
{
int nid;
swap_setup();
for_each_node_state(nid, N_HIGH_MEMORY)
kswapd_run(nid);
hotcpu_notifier(cpu_callback, 0);
return 0;
}
module_init(kswapd_init)
#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;
#define RECLAIM_OFF 0
#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
/*
* 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
/*
* Percentage of pages in a zone that must be unmapped for zone_reclaim to
* occur.
*/
int sysctl_min_unmapped_ratio = 1;
/*
* 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;
static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
{
unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
zone_page_state(zone, NR_ACTIVE_FILE);
/*
* It's possible for there to be more file mapped pages than
* accounted for by the pages on the file LRU lists because
* tmpfs pages accounted for as ANON can also be FILE_MAPPED
*/
return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
}
/* Work out how many page cache pages we can reclaim in this reclaim_mode */
static long zone_pagecache_reclaimable(struct zone *zone)
{
long nr_pagecache_reclaimable;
long delta = 0;
/*
* If RECLAIM_SWAP is set, then all file pages are considered
* potentially reclaimable. Otherwise, we have to worry about
* pages like swapcache and zone_unmapped_file_pages() provides
* a better estimate
*/
if (zone_reclaim_mode & RECLAIM_SWAP)
nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
else
nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
/* If we can't clean pages, remove dirty pages from consideration */
if (!(zone_reclaim_mode & RECLAIM_WRITE))
delta += zone_page_state(zone, NR_FILE_DIRTY);
/* Watch for any possible underflows due to delta */
if (unlikely(delta > nr_pagecache_reclaimable))
delta = nr_pagecache_reclaimable;
return nr_pagecache_reclaimable - delta;
}
/*
* Try to free up some pages from this zone through reclaim.
*/
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
/* Minimum pages needed in order to stay on node */
const unsigned long nr_pages = 1 << order;
struct task_struct *p = current;
struct reclaim_state reclaim_state;
int priority;
struct scan_control sc = {
.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
.may_swap = 1,
.nr_to_reclaim = max_t(unsigned long, nr_pages,
SWAP_CLUSTER_MAX),
.gfp_mask = gfp_mask,
.swappiness = vm_swappiness,
.order = order,
.isolate_pages = isolate_pages_global,
};
unsigned long slab_reclaimable;
disable_swap_token();
cond_resched();
/*
* 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;
reclaim_state.reclaimed_slab = 0;
p->reclaim_state = &reclaim_state;
if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
/*
* Free memory by calling shrink zone with increasing
* priorities until we have enough memory freed.
*/
priority = ZONE_RECLAIM_PRIORITY;
do {
note_zone_scanning_priority(zone, priority);
shrink_zone(priority, zone, &sc);
priority--;
} while (priority >= 0 && sc.nr_reclaimed < nr_pages);
}
slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
if (slab_reclaimable > zone->min_slab_pages) {
/*
* shrink_slab() does not currently allow us to determine how
* 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.
*
* Note that shrink_slab will free memory on all zones and may
* take a long time.
*/
while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
slab_reclaimable - nr_pages)
;
/*
* Update nr_reclaimed by the number of slab pages we
* reclaimed from this zone.
*/
sc.nr_reclaimed += slab_reclaimable -
zone_page_state(zone, NR_SLAB_RECLAIMABLE);
}
p->reclaim_state = NULL;
current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
return sc.nr_reclaimed >= nr_pages;
}
int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
int node_id;
int ret;
/*
* Zone reclaim reclaims unmapped file backed pages and
* slab pages if we are over the defined limits.
*
* 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.
*/
if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
return ZONE_RECLAIM_FULL;
if (zone_is_all_unreclaimable(zone))
return ZONE_RECLAIM_FULL;
/*
* Do not scan if the allocation should not be delayed.
*/
if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
return ZONE_RECLAIM_NOSCAN;
/*
* 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.
*/
node_id = zone_to_nid(zone);
if (node_state(node_id, N_CPU) && node_id != numa_node_id())
return ZONE_RECLAIM_NOSCAN;
if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
return ZONE_RECLAIM_NOSCAN;
ret = __zone_reclaim(zone, gfp_mask, order);
zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
if (!ret)
count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
return ret;
}
#endif
/*
* 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
* lists vs unevictable list. The vma argument is !NULL when called from the
* fault path to determine how to instantate a new page.
*
* Reasons page might not be evictable:
* (1) page's mapping marked unevictable
* (2) page is part of an mlocked VMA
*
*/
int page_evictable(struct page *page, struct vm_area_struct *vma)
{
if (mapping_unevictable(page_mapping(page)))
return 0;
if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
return 0;
return 1;
}
/**
* 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 = page_lru_base_type(page);
__dec_zone_state(zone, NR_UNEVICTABLE);
list_move(&page->lru, &zone->lru[l].list);
mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
__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);
mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
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);
}
}
/**
* 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 */
static void scan_zone_unevictable_pages(struct zone *zone)
{
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.
*/
static void scan_all_zones_unevictable_pages(void)
{
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,
void __user *buffer,
size_t *length, loff_t *ppos)
{
proc_doulongvec_minmax(table, write, 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);
}