linux-kernel - Re: [PATCH 17/23] kmem controller charge/uncharge infrastructure

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Message-ID: <alpine.DEB.2.00.1204241322390.753@chino.kir.corp.google.com>
Date:	Tue, 24 Apr 2012 13:25:57 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Glauber Costa <glommer@...allels.com>
cc:	Frederic Weisbecker <fweisbec@...il.com>, cgroups@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, devel@...nvz.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Greg Thelen <gthelen@...gle.com>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH 17/23] kmem controller charge/uncharge infrastructure

On Tue, 24 Apr 2012, Glauber Costa wrote:

> I think memcg is not necessarily wrong. That is because threads in a process
> share an address space, and you will eventually need to map a page to deliver
> it to userspace. The mm struct points you to the owner of that.
> 
> But that is not necessarily true for things that live in the kernel address
> space.
> 
> Do you view this differently ?
> 

Yes, for user memory, I see charging to p->mm->owner as allowing that 
process to eventually move and be charged to a different memcg and there's 
no way to do proper accounting if the charge is split amongst different 
memcgs because of thread membership to a set of memcgs.  This is 
consistent with charges for shared memory being moved when a thread 
mapping it moves to a new memcg, as well.
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