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| author | Johannes Weiner <hannes@cmpxchg.org> | 2014-12-10 15:44:25 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-12-10 17:41:08 -0800 |
| commit | 312722cbb2a6e12b74177f025a8ee7189816b04b (patch) | |
| tree | 12d1d918accab6dd2b7f94a058071b2372f33352 /mm/memcontrol.c | |
| parent | e544a4e74e02108035de69f97fde7bdf19dba978 (diff) | |
| download | lwn-312722cbb2a6e12b74177f025a8ee7189816b04b.tar.gz lwn-312722cbb2a6e12b74177f025a8ee7189816b04b.zip | |
mm: memcontrol: shorten the page statistics update slowpath
While moving charges from one memcg to another, page stat updates must
acquire the old memcg's move_lock to prevent double accounting. That
situation is denoted by an increased memcg->move_accounting. However, the
charge moving code declares this way too early for now, even before
summing up the RSS and pre-allocating destination charges.
Shorten this slowpath mode by increasing memcg->move_accounting only right
before walking the task's address space with the intention of actually
moving the pages.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
| -rw-r--r-- | mm/memcontrol.c | 21 |
1 files changed, 8 insertions, 13 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 9d30129b0d4a..9073d07c1149 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5333,8 +5333,6 @@ static void __mem_cgroup_clear_mc(void) static void mem_cgroup_clear_mc(void) { - struct mem_cgroup *from = mc.from; - /* * we must clear moving_task before waking up waiters at the end of * task migration. @@ -5345,8 +5343,6 @@ static void mem_cgroup_clear_mc(void) mc.from = NULL; mc.to = NULL; spin_unlock(&mc.lock); - - atomic_dec(&from->moving_account); } static int mem_cgroup_can_attach(struct cgroup_subsys_state *css, @@ -5380,15 +5376,6 @@ static int mem_cgroup_can_attach(struct cgroup_subsys_state *css, VM_BUG_ON(mc.moved_charge); VM_BUG_ON(mc.moved_swap); - /* - * Signal mem_cgroup_begin_page_stat() to take - * the memcg's move_lock while we're moving - * its pages to another memcg. Then wait for - * already started RCU-only updates to finish. - */ - atomic_inc(&from->moving_account); - synchronize_rcu(); - spin_lock(&mc.lock); mc.from = from; mc.to = memcg; @@ -5520,6 +5507,13 @@ static void mem_cgroup_move_charge(struct mm_struct *mm) struct vm_area_struct *vma; lru_add_drain_all(); + /* + * Signal mem_cgroup_begin_page_stat() to take the memcg's + * move_lock while we're moving its pages to another memcg. + * Then wait for already started RCU-only updates to finish. + */ + atomic_inc(&mc.from->moving_account); + synchronize_rcu(); retry: if (unlikely(!down_read_trylock(&mm->mmap_sem))) { /* @@ -5552,6 +5546,7 @@ retry: break; } up_read(&mm->mmap_sem); + atomic_dec(&mc.from->moving_account); } static void mem_cgroup_move_task(struct cgroup_subsys_state *css, |