From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: [PATCH 10/11] memcg: allow a memcg with kmem charges to be destructed. Date: Tue, 26 Jun 2012 02:25:46 +0400 Message-ID: <4FE8E56A.6080601@parallels.com> References: <1340633728-12785-1-git-send-email-glommer@parallels.com> <1340633728-12785-11-git-send-email-glommer@parallels.com> <20120625183442.GG3869@google.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120625183442.GG3869-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Tejun Heo Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Andrew Morton , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Frederic Weisbecker , David Rientjes , Pekka Enberg , Michal Hocko , Johannes Weiner , Christoph Lameter , devel-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org, Pekka Enberg , Suleiman Souhlal On 06/25/2012 10:34 PM, Tejun Heo wrote: > 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 >> CC: Christoph Lameter >> CC: Pekka Enberg >> CC: Michal Hocko >> CC: Kamezawa Hiroyuki >> CC: Johannes Weiner >> CC: Suleiman Souhlal >> --- >> 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. > You're absolutely right, will change.