linux-kernel - Re: [PATCH 4/4] memcg: get rid of percpu_charge

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Date:	Mon, 25 Jul 2011 10:18:40 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	linux-mm@...ck.org, Balbir Singh <bsingharora@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] memcg: get rid of percpu_charge_mutex lock

On Fri, 22 Jul 2011 13:20:25 +0200
Michal Hocko <mhocko@...e.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@...e.cz>

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/