linux-kernel - Re: [PATCH v5 07/14] mm: Allocate kernel pages to the right memcg

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Message-Id: <20121017151221.4c420e5a.akpm@linux-foundation.org>
Date:	Wed, 17 Oct 2012 15:12:21 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Glauber Costa <glommer@...allels.com>
Cc:	<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>,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>, <devel@...nvz.org>,
	<linux-kernel@...r.kernel.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Suleiman Souhlal <suleiman@...gle.com>
Subject: Re: [PATCH v5 07/14] mm: Allocate kernel pages to the right memcg

On Tue, 16 Oct 2012 14:16:44 +0400
Glauber Costa <glommer@...allels.com> 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.

Well, why?  Was that the correct decision?

> This is done by the invocation of
> __free_accounted_pages() and free_accounted_pages().

These are very general-sounding names.  I'd expect the identifiers to
contain "memcg" and/or "kmem", to identify what's going on.

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