linux-kernel - Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree

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Message-ID: <20120921201602.GN7264@google.com>
Date:	Fri, 21 Sep 2012 13:16:02 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Pekka Enberg <penberg@...nel.org>
Cc:	Glauber Costa <glommer@...allels.com>,
	Christoph Lameter <cl@...ux.com>, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org, kamezawa.hiroyu@...fujitsu.com,
	devel@...nvz.org, linux-mm@...ck.org,
	Suleiman Souhlal <suleiman@...gle.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page
 in kfree

On Fri, Sep 21, 2012 at 11:14:45PM +0300, Pekka Enberg wrote:
> On Fri, Sep 21, 2012 at 11:07 PM, Tejun Heo <tj@...nel.org> wrote:
> > Not necessarily disagreeing, but I don't think it's helpful to set the
> > bar impossibly high.  Even static_key doesn't have "exactly *zero*"
> > impact.  Let's stick to as minimal as possible when not in use and
> > reasonable in use.
> 
> For !CONFIG_MEMCG_KMEM, it should be exactly zero. No need to play
> games with static_key.

Ah, misread, though you were talking about MEMCG_KMEM && not in use.
Yeap, if turned off in Kconfig, it shouldn't have any performance
overhead.

Thanks.

-- 
tejun
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