linux-kernel - Re: [PATCH v2] proc: speedup /proc/stat handling

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Date:	Wed, 25 Jan 2012 01:22:25 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Glauber Costa <glommer@...allels.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Paul Tuner <pjt@...gle.com>
Subject: Re: [PATCH v2] proc:  speedup /proc/stat handling

Le mardi 24 janvier 2012 à 16:12 -0800, Andrew Morton a écrit :

> Did you measure the improvement from this patch?

Unfortunately I can not reboot the server where I noticed this
performance problem.

On the smaller one, performance improvement is about 20%, because the
second run of show_stat() can use data present in cpu cache.

On big machines, I guess the 128 bytes per possible cpu reservation can
avoid the second run. (since a typical cpuXXX line is smaller than 128
bytes)

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