From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Christoph Lameter <cl@linux.com>
Cc: Glauber Costa <glommer@parallels.com>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
Tejun Heo <tj@kernel.org>,
Frederic Weisbecker <fweisbeck@gmail.com>,
devel@openvz.org, kamezawa.hiroyu@jp.fujitsu.com,
Pekka Enberg <penberg@cs.helsinki.fi>,
Michal Hocko <mhocko@suse.cz>,
Johannes Weiner <hannes@cmpxchg.org>,
Suleiman Souhlal <suleiman@google.com>
Subject: Re: [PATCH 2/4] Add a __GFP_SLABMEMCG flag
Date: Sat, 09 Jun 2012 09:56:56 +0900 [thread overview]
Message-ID: <1339203416.6893.10.camel@dabdike.int.hansenpartnership.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1206081430380.4213@router.home>
On Fri, 2012-06-08 at 14:31 -0500, Christoph Lameter wrote:
> On Fri, 8 Jun 2012, Glauber Costa wrote:
>
> > */
> > #define __GFP_NOTRACK_FALSE_POSITIVE (__GFP_NOTRACK)
> >
> > -#define __GFP_BITS_SHIFT 25 /* Room for N __GFP_FOO bits */
> > +#define __GFP_BITS_SHIFT 26 /* Room for N __GFP_FOO bits */
> > #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
>
> Please make this conditional on CONFIG_MEMCG or so. The bit can be useful
> in particular on 32 bit architectures.
I really don't think that's at all a good idea. It's asking for trouble
when we don't spot we have a flag overlap. It also means that we're
trusting the reuser to know that their use case can never clash with
CONFIG_MEMGC and I can't think of any configuration where this is
possible currently.
I think making the flag define of __GFP_SLABMEMCG conditional might be a
reasonable idea so we get a compile failure if anyone tries to use it
when !CONFIG_MEMCG.
James
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next prev parent reply other threads:[~2012-06-09 0:57 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-08 9:43 [PATCH 0/4] kmem memcg proposed core changes Glauber Costa
2012-06-08 9:43 ` [PATCH 1/4] memcg: kmem controller dispatch infrastructure Glauber Costa
2012-06-08 9:43 ` [PATCH 2/4] Add a __GFP_SLABMEMCG flag Glauber Costa
2012-06-08 19:31 ` Christoph Lameter
2012-06-09 0:56 ` James Bottomley [this message]
2012-06-09 8:24 ` Glauber Costa
2012-06-11 14:24 ` Christoph Lameter
2012-06-12 14:36 ` James Bottomley
2012-06-09 8:19 ` Glauber Costa
2012-06-08 9:43 ` [PATCH 3/4] don't do __ClearPageSlab before freeing slab page Glauber Costa
2012-06-08 9:43 ` [PATCH 4/4] mm: Allocate kernel pages to the right memcg Glauber Costa
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