linux-kernel - Re: [PATCH v2 09/11] memcg: propagate kmem limiting information to children

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Message-ID: <20120821100007.GE19797@dhcp22.suse.cz>
Date:	Tue, 21 Aug 2012 12:00:07 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Glauber Costa <glommer@...allels.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	cgroups@...r.kernel.org, devel@...nvz.org,
	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	kamezawa.hiroyu@...fujitsu.com, Christoph Lameter <cl@...ux.com>,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Suleiman Souhlal <suleiman@...gle.com>
Subject: Re: [PATCH v2 09/11] memcg: propagate kmem limiting information to
 children

On Tue 21-08-12 13:22:09, Glauber Costa wrote:
> On 08/21/2012 11:54 AM, Michal Hocko wrote:
[...]
> > But maybe you have a good use case for that?
> > 
> Honestly, I don't. For my particular use case, this would be always on,
> and end of story. I was operating under the belief that being able to
> say "Oh, I regret", and then turning it off would be beneficial, even at
> the expense of the - self contained - complication.
> 
> For the general sanity of the interface, it is also a bit simpler to say
> "if kmem is unlimited, x happens", which is a verifiable statement, than
> to have a statement that is dependent on past history. 

OK, fair point. We shouldn't rely on the history. Maybe
memory.kmem.limit_in_bytes could return some special value like -1 in
such a case?

> But all of those need of course, as you pointed out, to be traded off
> by the code complexity.
> 
> I am fine with either, I just need a clear sign from you guys so I don't
> keep deimplementing and reimplementing this forever.

I would be for make it simple now and go with additional features later
when there is a demand for them. Maybe we will have runtimg switch for
user memory accounting as well one day.

But let's see what others think?
-- 
Michal Hocko
SUSE Labs
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