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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2012-01-12 17:18:20 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-01-12 20:13:05 -0800
commite94c8a9cbce1aee4af9e1285802785481b7f93c5 (patch)
tree14d496e62c2e8d59a8954ff10368d59d8dfaea03 /mm
parent6b208e3f6e35aa76d254c395bdcd984b17c6b626 (diff)
memcg: make mem_cgroup_split_huge_fixup() more efficient
In split_huge_page(), mem_cgroup_split_huge_fixup() is called to handle page_cgroup modifcations. It takes move_lock_page_cgroup() and modifies page_cgroup and LRU accounting jobs and called HPAGE_PMD_SIZE - 1 times. But thinking again, - compound_lock() is held at move_accout...then, it's not necessary to take move_lock_page_cgroup(). - LRU is locked and all tail pages will go into the same LRU as head is now on. - page_cgroup is contiguous in huge page range. This patch fixes mem_cgroup_split_huge_fixup() as to be called once per hugepage and reduce costs for spliting. [akpm@linux-foundation.org: fix typo, per Michal] Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Reviewed-by: Michal Hocko <mhocko@suse.cz> Cc: Balbir Singh <bsingharora@gmail.com> Cc: David Rientjes <rientjes@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/huge_memory.c3
-rw-r--r--mm/memcontrol.c34
2 files changed, 19 insertions, 18 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 36b3d988b4ef..db522e160cca 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1207,6 +1207,8 @@ static void __split_huge_page_refcount(struct page *page)
/* prevent PageLRU to go away from under us, and freeze lru stats */
spin_lock_irq(&zone->lru_lock);
compound_lock(page);
+ /* complete memcg works before add pages to LRU */
+ mem_cgroup_split_huge_fixup(page);
for (i = 1; i < HPAGE_PMD_NR; i++) {
struct page *page_tail = page + i;
@@ -1278,7 +1280,6 @@ static void __split_huge_page_refcount(struct page *page)
BUG_ON(!PageDirty(page_tail));
BUG_ON(!PageSwapBacked(page_tail));
- mem_cgroup_split_huge_fixup(page, page_tail);
lru_add_page_tail(zone, page, page_tail);
}
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 972878b648c2..42174612cc0b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2553,39 +2553,39 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
(1 << PCG_ACCT_LRU) | (1 << PCG_MIGRATION))
/*
* Because tail pages are not marked as "used", set it. We're under
- * zone->lru_lock, 'splitting on pmd' and compund_lock.
+ * zone->lru_lock, 'splitting on pmd' and compound_lock.
+ * charge/uncharge will be never happen and move_account() is done under
+ * compound_lock(), so we don't have to take care of races.
*/
-void mem_cgroup_split_huge_fixup(struct page *head, struct page *tail)
+void mem_cgroup_split_huge_fixup(struct page *head)
{
struct page_cgroup *head_pc = lookup_page_cgroup(head);
- struct page_cgroup *tail_pc = lookup_page_cgroup(tail);
- unsigned long flags;
+ struct page_cgroup *pc;
+ int i;
if (mem_cgroup_disabled())
return;
- /*
- * We have no races with charge/uncharge but will have races with
- * page state accounting.
- */
- move_lock_page_cgroup(head_pc, &flags);
+ for (i = 1; i < HPAGE_PMD_NR; i++) {
+ pc = head_pc + i;
+ pc->mem_cgroup = head_pc->mem_cgroup;
+ smp_wmb();/* see __commit_charge() */
+ /*
+ * LRU flags cannot be copied because we need to add tail
+ * page to LRU by generic call and our hooks will be called.
+ */
+ pc->flags = head_pc->flags & ~PCGF_NOCOPY_AT_SPLIT;
+ }
- tail_pc->mem_cgroup = head_pc->mem_cgroup;
- smp_wmb(); /* see __commit_charge() */
if (PageCgroupAcctLRU(head_pc)) {
enum lru_list lru;
struct mem_cgroup_per_zone *mz;
-
/*
- * LRU flags cannot be copied because we need to add tail
- *.page to LRU by generic call and our hook will be called.
* We hold lru_lock, then, reduce counter directly.
*/
lru = page_lru(head);
mz = page_cgroup_zoneinfo(head_pc->mem_cgroup, head);
- MEM_CGROUP_ZSTAT(mz, lru) -= 1;
+ MEM_CGROUP_ZSTAT(mz, lru) -= HPAGE_PMD_NR - 1;
}
- tail_pc->flags = head_pc->flags & ~PCGF_NOCOPY_AT_SPLIT;
- move_unlock_page_cgroup(head_pc, &flags);
}
#endif

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