linux-kernel - Re: [PATCH 10/11] memcg: allow a memcg with kmem charges to be destructed.

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

Date:	Mon, 25 Jun 2012 11:34:42 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Glauber Costa <glommer@...allels.com>
Cc:	cgroups@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Christoph Lameter <cl@...ux.com>, devel@...nvz.org,
	kamezawa.hiroyu@...fujitsu.com,
	Pekka Enberg <penberg@...helsinki.fi>,
	Suleiman Souhlal <suleiman@...gle.com>
Subject: Re: [PATCH 10/11] memcg: allow a memcg with kmem charges to be
 destructed.

On Mon, Jun 25, 2012 at 06:15:27PM +0400, Glauber Costa wrote:
> Because the ultimate goal of the kmem tracking in memcg is to
> track slab pages as well, we can't guarantee that we'll always
> be able to point a page to a particular process, and migrate
> the charges along with it - since in the common case, a page
> will contain data belonging to multiple processes.
> 
> Because of that, when we destroy a memcg, we only make sure
> the destruction will succeed by discounting the kmem charges
> from the user charges when we try to empty the cgroup.
> 
> Signed-off-by: Glauber Costa <glommer@...allels.com>
> CC: Christoph Lameter <cl@...ux.com>
> CC: Pekka Enberg <penberg@...helsinki.fi>
> CC: Michal Hocko <mhocko@...e.cz>
> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> CC: Johannes Weiner <hannes@...xchg.org>
> CC: Suleiman Souhlal <suleiman@...gle.com>
> ---
>  mm/memcontrol.c |   10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index a6a440b..bb9b6fe 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -598,6 +598,11 @@ static void disarm_kmem_keys(struct mem_cgroup *memcg)
>  {
>  	if (test_bit(KMEM_ACCOUNTED_THIS, &memcg->kmem_accounted))
>  		static_key_slow_dec(&mem_cgroup_kmem_enabled_key);
> +	/*
> +	 * This check can't live in kmem destruction function,
> +	 * since the charges will outlive the cgroup
> +	 */
> +	BUG_ON(res_counter_read_u64(&memcg->kmem, RES_USAGE) != 0);

WARN_ON() please.  Misaccounted kernel usually is better than dead
kernel.

Thanks.

-- 
tejun
--
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/