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Message-Id: <20111117103308.063f78df.kamezawa.hiroyu@jp.fujitsu.com>
Date: Thu, 17 Nov 2011 10:33:08 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: "linux-mm@...ck.org" <linux-mm@...ck.org>
Cc: cgroups@...r.kernel.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"hannes@...xchg.org" <hannes@...xchg.org>, mhocko@...e.cz,
Andrea Arcangeli <aarcange@...hat.com>,
Balbir Singh <bsingharora@...il.com>
Subject: [PATCH] fix mem_cgroup_split_huge_fixup to work efficiently.
I'll send this again when mm is shipped.
I sometimes see mem_cgroup_split_huge_fixup() in perf report and noticed
it's very slow. This fixes it. Any comments are welcome.
==
Subject: [PATCH] fix mem_cgroup_split_huge_fixup to work efficiently.
at split_huge_page(), mem_cgroup_split_huge_fixup() is called to
handle page_cgroup modifcations. It takes move_lock_page_cgroup()
and modify 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.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
---
include/linux/memcontrol.h | 5 ++---
mm/huge_memory.c | 3 ++-
mm/memcontrol.c | 32 ++++++++++++++++----------------
3 files changed, 20 insertions(+), 20 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index b87068a..0a22a19 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -154,7 +154,7 @@ u64 mem_cgroup_get_limit(struct mem_cgroup *memcg);
void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-void mem_cgroup_split_huge_fixup(struct page *head, struct page *tail);
+void mem_cgroup_split_huge_fixup(struct page *head);
#endif
#ifdef CONFIG_DEBUG_VM
@@ -357,8 +357,7 @@ u64 mem_cgroup_get_limit(struct mem_cgroup *memcg)
return 0;
}
-static inline void mem_cgroup_split_huge_fixup(struct page *head,
- struct page *tail)
+static inline void mem_cgroup_split_huge_fixup(struct page *head)
{
}
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4298aba..aa6cdae 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 6aff93c..99101f1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2523,38 +2523,38 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
/*
* Because tail pages are not marked as "used", set it. We're under
* zone->lru_lock, 'splitting on pmd' and compund_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
--
1.7.4.1
--
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