linux-kernel - Re: [PATCH 07/11] mm: Allocate kernel pages to the right memcg

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Date:	Mon, 25 Jun 2012 11:07:47 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Glauber Costa <glommer@...allels.com>
Cc:	cgroups@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Christoph Lameter <cl@...ux.com>, devel@...nvz.org,
	kamezawa.hiroyu@...fujitsu.com,
	Pekka Enberg <penberg@...helsinki.fi>,
	Suleiman Souhlal <suleiman@...gle.com>
Subject: Re: [PATCH 07/11] mm: Allocate kernel pages to the right memcg

On Mon, Jun 25, 2012 at 06:15:24PM +0400, Glauber Costa wrote:
> When a process tries to allocate a page with the __GFP_KMEMCG flag,
> the page allocator will call the corresponding memcg functions to
> validate the allocation. Tasks in the root memcg can always proceed.
> 
> To avoid adding markers to the page - and a kmem flag that would
> necessarily follow, as much as doing page_cgroup lookups for no
> reason, whoever is marking its allocations with __GFP_KMEMCG flag
> is responsible for telling the page allocator that this is such an
> allocation at free_pages() time. This is done by the invocation of
> __free_accounted_pages() and free_accounted_pages().

Shouldn't we be documenting that in the code somewhere, preferably in
the function comments?

-- 
tejun
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