linux_dsm_epyc7002/mm/vmscan.c
Andrew Morton 4dd4b92021 revert "kswapd should only wait on IO if there is IO"
Revert commit f1a9ee758d:

  Author: Rik van Riel <riel@redhat.com>
  Date:   Thu Feb 7 00:14:08 2008 -0800

    kswapd should only wait on IO if there is IO

    The current kswapd (and try_to_free_pages) code has an oddity where the
    code will wait on IO, even if there is no IO in flight.  This problem is
    notable especially when the system scans through many unfreeable pages,
    causing unnecessary stalls in the VM.

    Additionally, tasks without __GFP_FS or __GFP_IO in the direct reclaim path
    will sleep if a significant number of pages are encountered that should be
    written out.  This gives kswapd a chance to write out those pages, while
    the direct reclaim task sleeps.

    Signed-off-by: Rik van Riel <riel@redhat.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Because of large latencies and interactivity problems reported by Carlos,
here: http://lkml.org/lkml/2008/3/22/211

Cc: Rik van Riel <riel@redhat.com>
Cc: "Carlos R.  Mafra" <crmafra2@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-03-24 19:22:19 -07:00

2093 lines
57 KiB
C

/*
* 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 <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;
/* This context's GFP mask */
gfp_t gfp_mask;
int may_writepage;
/* Can pages be swapped as part of reclaim? */
int may_swap;
/* 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;
int swappiness;
int all_unreclaimable;
int order;
/* 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);
};
#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 scan_global_lru(sc) (!(sc)->mem_cgroup)
#else
#define scan_global_lru(sc) (1)
#endif
/*
* 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 "%s: nr=%ld\n",
__FUNCTION__, 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)
{
return page_count(page) - !!PagePrivate(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_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.
*/
if (PagePrivate(page)) {
if (try_to_free_buffers(page)) {
ClearPageDirty(page);
printk("%s: orphaned page\n", __FUNCTION__);
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;
}
/*
* 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)
{
BUG_ON(!PageLocked(page));
BUG_ON(mapping != page_mapping(page));
write_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 (unlikely(page_count(page) != 2))
goto cannot_free;
smp_rmb();
if (unlikely(PageDirty(page)))
goto cannot_free;
if (PageSwapCache(page)) {
swp_entry_t swap = { .val = page_private(page) };
__delete_from_swap_cache(page);
write_unlock_irq(&mapping->tree_lock);
swap_free(swap);
__put_page(page); /* The pagecache ref */
return 1;
}
__remove_from_page_cache(page);
write_unlock_irq(&mapping->tree_lock);
__put_page(page);
return 1;
cannot_free:
write_unlock_irq(&mapping->tree_lock);
return 0;
}
/*
* 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;
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;
VM_BUG_ON(PageActive(page));
sc->nr_scanned++;
if (!sc->may_swap && 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);
/* In active use or really unfreeable? Activate it. */
if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
referenced && page_mapping_inuse(page))
goto activate_locked;
#ifdef CONFIG_SWAP
/*
* Anonymous process memory has backing store?
* Try to allocate it some swap space here.
*/
if (PageAnon(page) && !PageSwapCache(page))
if (!add_to_swap(page, GFP_ATOMIC))
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) {
switch (try_to_unmap(page, 0)) {
case SWAP_FAIL:
goto activate_locked;
case SWAP_AGAIN:
goto keep_locked;
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 (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;
if (!mapping && page_count(page) == 1)
goto free_it;
}
if (!mapping || !remove_mapping(mapping, page))
goto keep_locked;
free_it:
unlock_page(page);
nr_reclaimed++;
if (!pagevec_add(&freed_pvec, page))
__pagevec_release_nonlru(&freed_pvec);
continue;
activate_locked:
SetPageActive(page);
pgactivate++;
keep_locked:
unlock_page(page);
keep:
list_add(&page->lru, &ret_pages);
VM_BUG_ON(PageLRU(page));
}
list_splice(&ret_pages, page_list);
if (pagevec_count(&freed_pvec))
__pagevec_release_nonlru(&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 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;
}
/*
* 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
*
* 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)
{
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)) {
case 0:
list_move(&page->lru, dst);
nr_taken++;
break;
case -EBUSY:
/* else it is being freed elsewhere */
list_move(&page->lru, src);
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;
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;
}
}
}
*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)
{
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);
}
/*
* 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;
}
/*
* 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)
{
LIST_HEAD(page_list);
struct pagevec pvec;
unsigned long nr_scanned = 0;
unsigned long nr_reclaimed = 0;
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;
nr_taken = sc->isolate_pages(sc->swap_cluster_max,
&page_list, &nr_scan, sc->order,
(sc->order > PAGE_ALLOC_COSTLY_ORDER)?
ISOLATE_BOTH : ISOLATE_INACTIVE,
zone, sc->mem_cgroup, 0);
nr_active = clear_active_flags(&page_list);
__count_vm_events(PGDEACTIVATE, nr_active);
__mod_zone_page_state(zone, NR_ACTIVE, -nr_active);
__mod_zone_page_state(zone, NR_INACTIVE,
-(nr_taken - nr_active));
if (scan_global_lru(sc))
zone->pages_scanned += nr_scan;
spin_unlock_irq(&zone->lru_lock);
nr_scanned += nr_scan;
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);
}
nr_reclaimed += nr_freed;
local_irq_disable();
if (current_is_kswapd()) {
__count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
__count_vm_events(KSWAPD_STEAL, nr_freed);
} else if (scan_global_lru(sc))
__count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
__count_zone_vm_events(PGSTEAL, zone, nr_freed);
if (nr_taken == 0)
goto done;
spin_lock(&zone->lru_lock);
/*
* Put back any unfreeable pages.
*/
while (!list_empty(&page_list)) {
page = lru_to_page(&page_list);
VM_BUG_ON(PageLRU(page));
SetPageLRU(page);
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);
}
}
} while (nr_scanned < max_scan);
spin_unlock(&zone->lru_lock);
done:
local_irq_enable();
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;
}
static inline int zone_is_near_oom(struct zone *zone)
{
return zone->pages_scanned >= (zone_page_state(zone, NR_ACTIVE)
+ zone_page_state(zone, NR_INACTIVE))*3;
}
/*
* 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;
}
/*
* 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 shrink_active_list(unsigned long nr_pages, struct zone *zone,
struct scan_control *sc, int priority)
{
unsigned long pgmoved;
int pgdeactivate = 0;
unsigned long pgscanned;
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;
if (sc->may_swap)
reclaim_mapped = calc_reclaim_mapped(sc, zone, priority);
lru_add_drain();
spin_lock_irq(&zone->lru_lock);
pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
ISOLATE_ACTIVE, zone,
sc->mem_cgroup, 1);
/*
* 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;
__mod_zone_page_state(zone, NR_ACTIVE, -pgmoved);
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)) ||
page_referenced(page, 0, sc->mem_cgroup)) {
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);
VM_BUG_ON(PageLRU(page));
SetPageLRU(page);
VM_BUG_ON(!PageActive(page));
ClearPageActive(page);
list_move(&page->lru, &zone->inactive_list);
mem_cgroup_move_lists(page, false);
pgmoved++;
if (!pagevec_add(&pvec, page)) {
__mod_zone_page_state(zone, NR_INACTIVE, pgmoved);
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);
}
}
__mod_zone_page_state(zone, NR_INACTIVE, pgmoved);
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);
VM_BUG_ON(PageLRU(page));
SetPageLRU(page);
VM_BUG_ON(!PageActive(page));
list_move(&page->lru, &zone->active_list);
mem_cgroup_move_lists(page, true);
pgmoved++;
if (!pagevec_add(&pvec, page)) {
__mod_zone_page_state(zone, NR_ACTIVE, pgmoved);
pgmoved = 0;
spin_unlock_irq(&zone->lru_lock);
__pagevec_release(&pvec);
spin_lock_irq(&zone->lru_lock);
}
}
__mod_zone_page_state(zone, NR_ACTIVE, pgmoved);
__count_zone_vm_events(PGREFILL, zone, pgscanned);
__count_vm_events(PGDEACTIVATE, pgdeactivate);
spin_unlock_irq(&zone->lru_lock);
pagevec_release(&pvec);
}
/*
* This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
*/
static unsigned long shrink_zone(int priority, struct zone *zone,
struct scan_control *sc)
{
unsigned long nr_active;
unsigned long nr_inactive;
unsigned long nr_to_scan;
unsigned long nr_reclaimed = 0;
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);
}
while (nr_active || nr_inactive) {
if (nr_active) {
nr_to_scan = min(nr_active,
(unsigned long)sc->swap_cluster_max);
nr_active -= nr_to_scan;
shrink_active_list(nr_to_scan, zone, sc, priority);
}
if (nr_inactive) {
nr_to_scan = min(nr_inactive,
(unsigned long)sc->swap_cluster_max);
nr_inactive -= nr_to_scan;
nr_reclaimed += shrink_inactive_list(nr_to_scan, zone,
sc);
}
}
throttle_vm_writeout(sc->gfp_mask);
return nr_reclaimed;
}
/*
* 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.
*/
static unsigned long shrink_zones(int priority, struct zone **zones,
struct scan_control *sc)
{
unsigned long nr_reclaimed = 0;
int i;
sc->all_unreclaimable = 1;
for (i = 0; zones[i] != NULL; i++) {
struct zone *zone = zones[i];
if (!populated_zone(zone))
continue;
/*
* 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);
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);
}
nr_reclaimed += shrink_zone(priority, zone, sc);
}
return nr_reclaimed;
}
/*
* 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.
*/
static unsigned long do_try_to_free_pages(struct zone **zones, gfp_t gfp_mask,
struct scan_control *sc)
{
int priority;
int ret = 0;
unsigned long total_scanned = 0;
unsigned long nr_reclaimed = 0;
struct reclaim_state *reclaim_state = current->reclaim_state;
unsigned long lru_pages = 0;
int i;
if (scan_global_lru(sc))
count_vm_event(ALLOCSTALL);
/*
* mem_cgroup will not do shrink_slab.
*/
if (scan_global_lru(sc)) {
for (i = 0; zones[i] != NULL; i++) {
struct zone *zone = zones[i];
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
continue;
lru_pages += zone_page_state(zone, NR_ACTIVE)
+ zone_page_state(zone, NR_INACTIVE);
}
}
for (priority = DEF_PRIORITY; priority >= 0; priority--) {
sc->nr_scanned = 0;
if (!priority)
disable_swap_token();
nr_reclaimed += shrink_zones(priority, zones, sc);
/*
* Don't shrink slabs when reclaiming memory from
* over limit cgroups
*/
if (scan_global_lru(sc)) {
shrink_slab(sc->nr_scanned, gfp_mask, lru_pages);
if (reclaim_state) {
nr_reclaimed += reclaim_state->reclaimed_slab;
reclaim_state->reclaimed_slab = 0;
}
}
total_scanned += sc->nr_scanned;
if (nr_reclaimed >= sc->swap_cluster_max) {
ret = 1;
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.
*/
if (total_scanned > sc->swap_cluster_max +
sc->swap_cluster_max / 2) {
wakeup_pdflush(laptop_mode ? 0 : total_scanned);
sc->may_writepage = 1;
}
/* Take a nap, wait for some writeback to complete */
if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
congestion_wait(WRITE, HZ/10);
}
/* top priority shrink_caches still had more to do? don't OOM, then */
if (!sc->all_unreclaimable && scan_global_lru(sc))
ret = 1;
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 (scan_global_lru(sc)) {
for (i = 0; zones[i] != NULL; i++) {
struct zone *zone = zones[i];
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
continue;
zone->prev_priority = priority;
}
} else
mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
return ret;
}
unsigned long try_to_free_pages(struct zone **zones, int order, gfp_t gfp_mask)
{
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,
};
return do_try_to_free_pages(zones, gfp_mask, &sc);
}
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
gfp_t gfp_mask)
{
struct scan_control sc = {
.gfp_mask = gfp_mask,
.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,
};
struct zone **zones;
int target_zone = gfp_zone(GFP_HIGHUSER_MOVABLE);
zones = NODE_DATA(numa_node_id())->node_zonelists[target_zone].zones;
if (do_try_to_free_pages(zones, sc.gfp_mask, &sc))
return 1;
return 0;
}
#endif
/*
* 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.
*/
static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
{
int all_zones_ok;
int priority;
int i;
unsigned long total_scanned;
unsigned long nr_reclaimed;
struct reclaim_state *reclaim_state = current->reclaim_state;
struct scan_control sc = {
.gfp_mask = GFP_KERNEL,
.may_swap = 1,
.swap_cluster_max = SWAP_CLUSTER_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 == pages_high.
*/
int temp_priority[MAX_NR_ZONES];
loop_again:
total_scanned = 0;
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;
/* 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;
if (!zone_watermark_ok(zone, order, zone->pages_high,
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_page_state(zone, NR_ACTIVE)
+ zone_page_state(zone, NR_INACTIVE);
}
/*
* 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;
if (!populated_zone(zone))
continue;
if (zone_is_all_unreclaimable(zone) &&
priority != DEF_PRIORITY)
continue;
if (!zone_watermark_ok(zone, order, zone->pages_high,
end_zone, 0))
all_zones_ok = 0;
temp_priority[i] = priority;
sc.nr_scanned = 0;
note_zone_scanning_priority(zone, priority);
/*
* 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);
reclaim_state->reclaimed_slab = 0;
nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
lru_pages);
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_page_state(zone, NR_ACTIVE)
+ zone_page_state(zone, NR_INACTIVE)) * 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 > nr_reclaimed + nr_reclaimed / 2)
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.
*/
if (total_scanned && priority < DEF_PRIORITY - 2)
congestion_wait(WRITE, 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 (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();
goto loop_again;
}
return 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,
};
cpumask_t cpumask;
cpumask = node_to_cpumask(pgdat->node_id);
if (!cpus_empty(cpumask))
set_cpus_allowed(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;
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))
schedule();
order = pgdat->kswapd_max_order;
}
finish_wait(&pgdat->kswapd_wait, &wait);
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);
}
}
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, zone->pages_low, 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);
}
#ifdef CONFIG_PM
/*
* 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
*/
static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
int pass, struct scan_control *sc)
{
struct zone *zone;
unsigned long nr_to_scan, ret = 0;
for_each_zone(zone) {
if (!populated_zone(zone))
continue;
if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
continue;
/* For pass = 0 we don't shrink the active list */
if (pass > 0) {
zone->nr_scan_active +=
(zone_page_state(zone, NR_ACTIVE) >> prio) + 1;
if (zone->nr_scan_active >= nr_pages || pass > 3) {
zone->nr_scan_active = 0;
nr_to_scan = min(nr_pages,
zone_page_state(zone, NR_ACTIVE));
shrink_active_list(nr_to_scan, zone, sc, prio);
}
}
zone->nr_scan_inactive +=
(zone_page_state(zone, NR_INACTIVE) >> prio) + 1;
if (zone->nr_scan_inactive >= nr_pages || pass > 3) {
zone->nr_scan_inactive = 0;
nr_to_scan = min(nr_pages,
zone_page_state(zone, NR_INACTIVE));
ret += shrink_inactive_list(nr_to_scan, zone, sc);
if (ret >= nr_pages)
return ret;
}
}
return ret;
}
static unsigned long count_lru_pages(void)
{
return global_page_state(NR_ACTIVE) + global_page_state(NR_INACTIVE);
}
/*
* 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
*/
unsigned long shrink_all_memory(unsigned long nr_pages)
{
unsigned long lru_pages, nr_slab;
unsigned long ret = 0;
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,
.isolate_pages = isolate_pages_global,
};
current->reclaim_state = &reclaim_state;
lru_pages = count_lru_pages();
nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
/* 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)
break;
ret += reclaim_state.reclaimed_slab;
if (ret >= nr_pages)
goto out;
nr_slab -= reclaim_state.reclaimed_slab;
}
/*
* 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;
shrink_slab(sc.nr_scanned, sc.gfp_mask,
count_lru_pages());
ret += reclaim_state.reclaimed_slab;
if (ret >= nr_pages)
goto out;
if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
congestion_wait(WRITE, HZ / 10);
}
}
/*
* If ret = 0, we could not shrink LRUs, but there may be something
* in slab caches
*/
if (!ret) {
do {
reclaim_state.reclaimed_slab = 0;
shrink_slab(nr_pages, sc.gfp_mask, count_lru_pages());
ret += reclaim_state.reclaimed_slab;
} while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
}
out:
current->reclaim_state = NULL;
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. */
static int __devinit cpu_callback(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
pg_data_t *pgdat;
cpumask_t mask;
int nid;
if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
for_each_node_state(nid, N_HIGH_MEMORY) {
pgdat = NODE_DATA(nid);
mask = node_to_cpumask(pgdat->node_id);
if (any_online_cpu(mask) != NR_CPUS)
/* One of our CPUs online: restore mask */
set_cpus_allowed(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;
}
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_cache 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;
/*
* 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;
unsigned long nr_reclaimed = 0;
struct scan_control sc = {
.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
.may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
.swap_cluster_max = max_t(unsigned long, nr_pages,
SWAP_CLUSTER_MAX),
.gfp_mask = gfp_mask,
.swappiness = vm_swappiness,
.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_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 {
note_zone_scanning_priority(zone, priority);
nr_reclaimed += shrink_zone(priority, zone, &sc);
priority--;
} while (priority >= 0 && 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.
*/
nr_reclaimed += slab_reclaimable -
zone_page_state(zone, NR_SLAB_RECLAIMABLE);
}
p->reclaim_state = NULL;
current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
return 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_page_state(zone, NR_FILE_PAGES) -
zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
&& zone_page_state(zone, NR_SLAB_RECLAIMABLE)
<= zone->min_slab_pages)
return 0;
if (zone_is_all_unreclaimable(zone))
return 0;
/*
* Do not scan if the allocation should not be delayed.
*/
if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
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.
*/
node_id = zone_to_nid(zone);
if (node_state(node_id, N_CPU) && node_id != numa_node_id())
return 0;
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;
}
#endif