diff options
| author | KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> | 2012-03-21 16:34:26 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-03-21 17:55:02 -0700 |
| commit | 4331f7d339ee0b54603344b9d13662a9c022540c (patch) | |
| tree | ea67ad19a4dff0f8bf7d335bb7ab148ecfb4d329 /include/linux/memcontrol.h | |
| parent | 2ff76f1193f8481f7e6c29304eea4006e8e51569 (diff) | |
memcg: fix performance of mem_cgroup_begin_update_page_stat()
mem_cgroup_begin_update_page_stat() should be very fast because it's
called very frequently. Now, it needs to look up page_cgroup and its
memcg....this is slow.
This patch adds a global variable to check "any memcg is moving or not".
With this, the caller doesn't need to visit page_cgroup and memcg.
Here is a test result. A test program makes page faults onto a file,
MAP_SHARED and makes each page's page_mapcount(page) > 1, and free the
range by madvise() and page fault again. This program causes 26214400
times of page fault onto a file(size was 1G.) and shows shows the cost of
mem_cgroup_begin_update_page_stat().
Before this patch for mem_cgroup_begin_update_page_stat()
[kamezawa@bluextal test]$ time ./mmap 1G
real 0m21.765s
user 0m5.999s
sys 0m15.434s
27.46% mmap mmap [.] reader
21.15% mmap [kernel.kallsyms] [k] page_fault
9.17% mmap [kernel.kallsyms] [k] filemap_fault
2.96% mmap [kernel.kallsyms] [k] __do_fault
2.83% mmap [kernel.kallsyms] [k] __mem_cgroup_begin_update_page_stat
After this patch
[root@bluextal test]# time ./mmap 1G
real 0m21.373s
user 0m6.113s
sys 0m15.016s
In usual path, calls to __mem_cgroup_begin_update_page_stat() goes away.
Note: we may be able to remove this optimization in future if
we can get pointer to memcg directly from struct page.
[akpm@linux-foundation.org: don't return a void]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Greg Thelen <gthelen@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/memcontrol.h')
| -rw-r--r-- | include/linux/memcontrol.h | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index bf7ae01fc93b..f94efd2f6c27 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -144,6 +144,8 @@ static inline bool mem_cgroup_disabled(void) void __mem_cgroup_begin_update_page_stat(struct page *page, bool *locked, unsigned long *flags); +extern atomic_t memcg_moving; + static inline void mem_cgroup_begin_update_page_stat(struct page *page, bool *locked, unsigned long *flags) { @@ -151,7 +153,8 @@ static inline void mem_cgroup_begin_update_page_stat(struct page *page, return; rcu_read_lock(); *locked = false; - return __mem_cgroup_begin_update_page_stat(page, locked, flags); + if (atomic_read(&memcg_moving)) + __mem_cgroup_begin_update_page_stat(page, locked, flags); } void __mem_cgroup_end_update_page_stat(struct page *page, |