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Date: Wed, 25 Jan 2012 17:04:16 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Glauber Costa <glommer@parallels.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>, Ingo Molnar <mingo@elte.hu>,
        linux-kernel@vger.kernel.org,
        Russell King - ARM Linux <linux@arm.linux.org.uk>,
        Paul Tuner <pjt@google.com>
Subject: Re: [PATCH v2] proc:  speedup /proc/stat handling
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On Wed, 25 Jan 2012 06:29:32 +0100
Eric Dumazet <eric.dumazet@gmail.com> wrote:

> Le mardi 24 janvier 2012 __ 17:27 -0800, Andrew Morton a __crit :
> 
> > I had a fiddle on an 8-way x86_64 machine.  I'm unable to demonstrate
> > any improvement for either of
> > 
> > time (for i in $(seq 1000); do; cat /proc/self/stat > /dev/null; done)
> > time (for i in $(seq 1000); do; cat /proc/1/stat > /dev/null; done)
> > 
> > oh well.
> 
> What size is /proc/stat ?

About 40mm, but it depends on the font size.

> wc -c /proc/stat
> 
> If under 4096, there is no problem with existing code.

akpm2:/home/akpm> wc -c /proc/stat 
2800 /proc/stat

> I had the problem on a 16-way machine.

OK..