linux-kernel - Re: [PATCH v5 06/14] memcg: kmem controller infrastructure

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Message-ID: <alpine.DEB.2.00.1210181502270.30894@chino.kir.corp.google.com>
Date:	Thu, 18 Oct 2012 15:06:54 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Glauber Costa <glommer@...allels.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Tejun Heo <tj@...nel.org>, Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	kamezawa.hiroyu@...fujitsu.com, Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>, devel@...nvz.org,
	linux-kernel@...r.kernel.org, Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH v5 06/14] memcg: kmem controller infrastructure

On Thu, 18 Oct 2012, Glauber Costa wrote:

> > Do we actually need to test PF_KTHREAD when current->mm == NULL? 
> > Perhaps because of aio threads whcih temporarily adopt a userspace mm?
> 
> I believe so. I remember I discussed this in the past with David
> Rientjes and he advised me to test for both.
> 

PF_KTHREAD can do use_mm() to assume an ->mm but hopefully they aren't 
allocating slab while doing so.  Have you considered actually charging 
current->mm->owner for that memory, though, since the kthread will have 
freed the memory before unuse_mm() or otherwise have charged it on behalf 
of a user process, i.e. only exempting PF_KTHREAD?
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