From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: Michal Hocko <mhocko@suse.cz>
Cc: linux-mm@kvack.org, Balbir Singh <bsingharora@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/4] memcg: get rid of percpu_charge_mutex lock
Date: Mon, 25 Jul 2011 10:18:40 +0900 [thread overview]
Message-ID: <20110725101840.f2796524.kamezawa.hiroyu@jp.fujitsu.com> (raw)
In-Reply-To: <a9244082ba28c4c2e4a6997311d5493bdaa117e9.1311338634.git.mhocko@suse.cz>
On Fri, 22 Jul 2011 13:20:25 +0200
Michal Hocko <mhocko@suse.cz> wrote:
> percpu_charge_mutex protects from multiple simultaneous per-cpu charge
> caches draining because we might end up having too many work items.
> At least this was the case until 26fe6168 (memcg: fix percpu cached
> charge draining frequency) when we introduced a more targeted draining
> for async mode.
> Now that also sync draining is targeted we can safely remove mutex
> because we will not send more work than the current number of CPUs.
> FLUSHING_CACHED_CHARGE protects from sending the same work multiple
> times and stock->nr_pages == 0 protects from pointless sending a work
> if there is obviously nothing to be done. This is of course racy but we
> can live with it as the race window is really small (we would have to
> see FLUSHING_CACHED_CHARGE cleared while nr_pages would be still
> non-zero).
> The only remaining place where we can race is synchronous mode when we
> rely on FLUSHING_CACHED_CHARGE test which might have been set by other
> drainer on the same group but we should wait in that case as well.
>
> Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
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next prev parent reply other threads:[~2011-07-25 1:28 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-22 12:43 [PATCH 0/4 v2] memcg: cleanup per-cpu charge caches Michal Hocko
2011-07-21 7:38 ` [PATCH 1/4] memcg: do not try to drain per-cpu caches without pages Michal Hocko
2011-07-25 1:16 ` KAMEZAWA Hiroyuki
2011-08-17 19:49 ` [patch] memcg: pin execution to current cpu while draining stock Johannes Weiner
2011-08-18 0:24 ` KAMEZAWA Hiroyuki
2011-08-18 5:56 ` Michal Hocko
2011-07-22 10:24 ` [PATCH 2/4] memcg: unify sync and async per-cpu charge cache draining Michal Hocko
2011-07-22 10:27 ` [PATCH 3/4] memcg: add mem_cgroup_same_or_subtree helper Michal Hocko
2011-07-22 11:20 ` [PATCH 4/4] memcg: get rid of percpu_charge_mutex lock Michal Hocko
2011-07-25 1:18 ` KAMEZAWA Hiroyuki [this message]
2011-08-08 18:47 ` Johannes Weiner
2011-08-08 21:47 ` Michal Hocko
2011-08-08 23:19 ` Johannes Weiner
2011-08-09 7:26 ` Michal Hocko
2011-08-09 9:31 ` [PATCH RFC] memcg: fix drain_all_stock crash Michal Hocko
2011-08-09 9:32 ` KAMEZAWA Hiroyuki
2011-08-09 9:45 ` Michal Hocko
2011-08-09 9:53 ` KAMEZAWA Hiroyuki
2011-08-09 10:09 ` Michal Hocko
2011-08-09 10:07 ` KAMEZAWA Hiroyuki
2011-08-09 11:46 ` Michal Hocko
2011-08-09 23:54 ` KAMEZAWA Hiroyuki
2011-08-10 7:29 ` Michal Hocko
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