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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2012-01-12 17:18:57 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-01-12 20:13:07 -0800
commit36b62ad539498d00c2d280a151abad5f7630fa73 (patch)
tree553409901df6210e4a698c1991f9d455199e098b /mm
parentdc67d50465f249bb357bf85b3ed1f642eb00130a (diff)
memcg: simplify corner case handling of LRU.
This patch simplifies LRU handling of racy case (memcg+SwapCache). At charging, SwapCache tend to be on LRU already. So, before overwriting pc->mem_cgroup, the page must be removed from LRU and added to LRU later. This patch does spin_lock(zone->lru_lock); if (PageLRU(page)) remove from LRU overwrite pc->mem_cgroup if (PageLRU(page)) add to new LRU. spin_unlock(zone->lru_lock); And guarantee all pages are not on LRU at modifying pc->mem_cgroup. This patch also unfies lru handling of replace_page_cache() and swapin. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Miklos Szeredi <mszeredi@suse.cz> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Ying Han <yinghan@google.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memcontrol.c109
1 files changed, 16 insertions, 93 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 71bac4d720d7..d58bb5fa4403 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1137,86 +1137,6 @@ struct lruvec *mem_cgroup_lru_move_lists(struct zone *zone,
}
/*
- * At handling SwapCache and other FUSE stuff, pc->mem_cgroup may be changed
- * while it's linked to lru because the page may be reused after it's fully
- * uncharged. To handle that, unlink page_cgroup from LRU when charge it again.
- * It's done under lock_page and expected that zone->lru_lock isnever held.
- */
-static void mem_cgroup_lru_del_before_commit(struct page *page)
-{
- enum lru_list lru;
- unsigned long flags;
- struct zone *zone = page_zone(page);
- struct page_cgroup *pc = lookup_page_cgroup(page);
-
- /*
- * Doing this check without taking ->lru_lock seems wrong but this
- * is safe. Because if page_cgroup's USED bit is unset, the page
- * will not be added to any memcg's LRU. If page_cgroup's USED bit is
- * set, the commit after this will fail, anyway.
- * This all charge/uncharge is done under some mutual execustion.
- * So, we don't need to taking care of changes in USED bit.
- */
- if (likely(!PageLRU(page)))
- return;
-
- spin_lock_irqsave(&zone->lru_lock, flags);
- lru = page_lru(page);
- /*
- * The uncharged page could still be registered to the LRU of
- * the stale pc->mem_cgroup.
- *
- * As pc->mem_cgroup is about to get overwritten, the old LRU
- * accounting needs to be taken care of. Let root_mem_cgroup
- * babysit the page until the new memcg is responsible for it.
- *
- * The PCG_USED bit is guarded by lock_page() as the page is
- * swapcache/pagecache.
- */
- if (PageLRU(page) && PageCgroupAcctLRU(pc) && !PageCgroupUsed(pc)) {
- del_page_from_lru_list(zone, page, lru);
- add_page_to_lru_list(zone, page, lru);
- }
- spin_unlock_irqrestore(&zone->lru_lock, flags);
-}
-
-static void mem_cgroup_lru_add_after_commit(struct page *page)
-{
- enum lru_list lru;
- unsigned long flags;
- struct zone *zone = page_zone(page);
- struct page_cgroup *pc = lookup_page_cgroup(page);
- /*
- * putback: charge:
- * SetPageLRU SetPageCgroupUsed
- * smp_mb smp_mb
- * PageCgroupUsed && add to memcg LRU PageLRU && add to memcg LRU
- *
- * Ensure that one of the two sides adds the page to the memcg
- * LRU during a race.
- */
- smp_mb();
- /* taking care of that the page is added to LRU while we commit it */
- if (likely(!PageLRU(page)))
- return;
- spin_lock_irqsave(&zone->lru_lock, flags);
- lru = page_lru(page);
- /*
- * If the page is not on the LRU, someone will soon put it
- * there. If it is, and also already accounted for on the
- * memcg-side, it must be on the right lruvec as setting
- * pc->mem_cgroup and PageCgroupUsed is properly ordered.
- * Otherwise, root_mem_cgroup has been babysitting the page
- * during the charge. Move it to the new memcg now.
- */
- if (PageLRU(page) && !PageCgroupAcctLRU(pc)) {
- del_page_from_lru_list(zone, page, lru);
- add_page_to_lru_list(zone, page, lru);
- }
- spin_unlock_irqrestore(&zone->lru_lock, flags);
-}
-
-/*
* Checks whether given mem is same or in the root_mem_cgroup's
* hierarchy subtree
*/
@@ -2775,14 +2695,27 @@ __mem_cgroup_commit_charge_lrucare(struct page *page, struct mem_cgroup *memcg,
enum charge_type ctype)
{
struct page_cgroup *pc = lookup_page_cgroup(page);
+ struct zone *zone = page_zone(page);
+ unsigned long flags;
+ bool removed = false;
+
/*
* In some case, SwapCache, FUSE(splice_buf->radixtree), the page
* is already on LRU. It means the page may on some other page_cgroup's
* LRU. Take care of it.
*/
- mem_cgroup_lru_del_before_commit(page);
+ spin_lock_irqsave(&zone->lru_lock, flags);
+ if (PageLRU(page)) {
+ del_page_from_lru_list(zone, page, page_lru(page));
+ ClearPageLRU(page);
+ removed = true;
+ }
__mem_cgroup_commit_charge(memcg, page, 1, pc, ctype);
- mem_cgroup_lru_add_after_commit(page);
+ if (removed) {
+ add_page_to_lru_list(zone, page, page_lru(page));
+ SetPageLRU(page);
+ }
+ spin_unlock_irqrestore(&zone->lru_lock, flags);
return;
}
@@ -3383,9 +3316,7 @@ void mem_cgroup_replace_page_cache(struct page *oldpage,
{
struct mem_cgroup *memcg;
struct page_cgroup *pc;
- struct zone *zone;
enum charge_type type = MEM_CGROUP_CHARGE_TYPE_CACHE;
- unsigned long flags;
if (mem_cgroup_disabled())
return;
@@ -3401,20 +3332,12 @@ void mem_cgroup_replace_page_cache(struct page *oldpage,
if (PageSwapBacked(oldpage))
type = MEM_CGROUP_CHARGE_TYPE_SHMEM;
- zone = page_zone(newpage);
- pc = lookup_page_cgroup(newpage);
/*
* Even if newpage->mapping was NULL before starting replacement,
* the newpage may be on LRU(or pagevec for LRU) already. We lock
* LRU while we overwrite pc->mem_cgroup.
*/
- spin_lock_irqsave(&zone->lru_lock, flags);
- if (PageLRU(newpage))
- del_page_from_lru_list(zone, newpage, page_lru(newpage));
- __mem_cgroup_commit_charge(memcg, newpage, 1, pc, type);
- if (PageLRU(newpage))
- add_page_to_lru_list(zone, newpage, page_lru(newpage));
- spin_unlock_irqrestore(&zone->lru_lock, flags);
+ __mem_cgroup_commit_charge_lrucare(newpage, memcg, type);
}
#ifdef CONFIG_DEBUG_VM

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