From: Wanpeng Li <liwanp@linux.vnet.ibm.com>
To: Mike Galbraith <bitbucket@online.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sched/auto_group: fix consume memory even if add 'noautogroup' in the cmdline
Date: Tue, 7 Jan 2014 07:23:48 +0800 [thread overview]
Message-ID: <52cb3b0f.2a82440a.5285.ffff9642SMTPIN_ADDED_BROKEN@mx.google.com> (raw)
In-Reply-To: <1389016976.5536.10.camel@marge.simpson.net>
On Mon, Jan 06, 2014 at 03:02:56PM +0100, Mike Galbraith wrote:
>On Mon, 2014-01-06 at 13:17 +0100, Peter Zijlstra wrote:
>> On Fri, Dec 27, 2013 at 06:22:31PM +0800, Wanpeng Li wrote:
>> > We have a server which have 200 CPUs and 8G memory, there is auto_group creation
>>
>> I'm hoping that is 8T, otherwise that's a severely under provisioned
>> system, that's a mere 40M per cpu, does that even work?
>>
>> > which will almost consume 12MB memory even if add 'noautogroup' in the kernel
>> > boot parameter. In addtion, SLUB per cpu partial caches freeing that is local to
>> > a processor which requires the taking of locks at the price of more indeterminism
>> > in the latency of the free. This patch fix it by check noautogroup earlier to avoid
>> > free after unnecessary memory consumption.
>>
>> That's just a bad changelog. It fails to explain the actual problem and
>> it babbles about unrelated things like SLUB details.
>>
>> Also, I'm not entirely sure what the intention was of this code, I've so
>> far tried to ignore the entire autogroup fest...
>>
>> It looks like it creates and maintains the entire autogroup hierarchy,
>> such that if you at runtime enable the sysclt and move tasks 'back' to
>> the root cgroup you get the autogroup behaviour.
>>
>> Was this intended? Mike?
>
>Yeah, it was intended that autogroups always exist if you config it in.
>We could make is such that noautogroup makes it irreversibly off/dead.
>
>People with 200 ram starved CPUs can turn it off in their .config too :)
Thanks for your great explaination.
Regards,
Wanpeng Li
>
>-Mike
>
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prev parent reply other threads:[~2014-01-06 23:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-27 10:22 Wanpeng Li
2014-01-06 12:17 ` Peter Zijlstra
2014-01-06 14:02 ` Mike Galbraith
2014-01-06 23:23 ` Wanpeng Li [this message]
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