From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx182.postini.com [74.125.245.182]) by kanga.kvack.org (Postfix) with SMTP id 16B4C6B004D for ; Tue, 26 Jun 2012 12:40:02 -0400 (EDT) Message-ID: <4FE9E53C.2050700@parallels.com> Date: Tue, 26 Jun 2012 20:37:16 +0400 From: Glauber Costa MIME-Version: 1.0 Subject: Re: [PATCH 2/2] memcg: first step towards hierarchical controller References: <1340725634-9017-1-git-send-email-glommer@parallels.com> <1340725634-9017-3-git-send-email-glommer@parallels.com> <20120626161501.GI9566@tiehlicka.suse.cz> In-Reply-To: <20120626161501.GI9566@tiehlicka.suse.cz> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, kamezawa.hiroyu@jp.fujitsu.com, Johannes Weiner , Andrew Morton , Tejun Heo On 06/26/2012 08:15 PM, Michal Hocko wrote: > On Tue 26-06-12 19:47:14, Glauber Costa wrote: >> Okay, so after recent discussions, I am proposing the following >> patch. It won't remove hierarchy, or anything like that. Just default >> to true in the root cgroup, and print a warning once if you try >> to set it back to 0. >> >> I am not adding it to feature-removal-schedule.txt because I don't >> view it as a consensus. Rather, changing the default would allow us >> to give it a time around in the open, and see if people complain >> and what we can learn about that. >> >> Signed-off-by: Glauber Costa >> Acked-by: Johannes Weiner >> CC: Michal Hocko >> CC: Kamezawa Hiroyuki >> CC: Tejun Heo >> --- >> mm/memcontrol.c | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 85f7790..c37e4c1 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -3993,6 +3993,10 @@ static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft, >> if (memcg->use_hierarchy == val) >> goto out; >> >> + WARN_ONCE(!parent_memcg && memcg->use_hierarchy, > > Do you have to test anything here at all? The test above will get you > out without doing anything if you are not trying to change anything. > The default is true so you have to be trying to disable it. > > If you omit !parent_memcg test as well you will get a bonus of the early > warning even if somebody has cgconfig.conf like this: > > group a/b/c { > memory { > memory.use_hierarchy = 0; > [...] > } > } > > which worked previously... > True there is a risk of a "false warning" when somebody just tries to > set disable hierarchy when it is (and never was) allowed but I do not > think this is that bad. Well, a false warning is not that bad. It is better to be vocal. I will wait for Kame to put his comments, and I can resend with that change. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org