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
Date: Tue, 24 Jan 2012 16:12:21 -0800 [thread overview]
Message-ID: <20120124161221.032325d1.akpm@linux-foundation.org> (raw)
In-Reply-To: <1327449683.14373.12.camel@edumazet-laptop>
On Wed, 25 Jan 2012 01:01:23 +0100
Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On a typical 16 cpus machine, "cat /proc/stat" gives more than 4096
> bytes, and is slow :
It is pretty bad:
akpm:/usr/src/25> time (for i in $(seq 1000); do; cat /proc/self/stat > /dev/null; done)
(; for i in $(seq 1000); do; cat /proc/self/stat > /dev/null; done; ) 0.05s user 0.94s system 29% cpu 3.367 total
(29% CPU?)
> # strace -T -o /tmp/STRACE cat /proc/stat | wc -c
> 5826
> # grep "cpu " /tmp/STRACE
> read(0, "cpu 1949310 19 2144714 12117253"..., 32768) = 5826 <0.001504>
>
Did you measure the improvement from this patch?
> Thats partly because show_stat() must be called twice since initial
> buffer size is too small (4096 bytes for less than 32 possible cpus)
>
> Fix this by :
>
> 1) Taking into account nr_irqs in the initial buffer sizing.
>
> 2) Using ksize() to allow better filling of initial buffer.
next prev parent reply other threads:[~2012-01-25 0:12 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-20 15:59 [PATCH] " Eric Dumazet
2012-01-20 22:55 ` Andrew Morton
2012-01-23 10:16 ` KAMEZAWA Hiroyuki
2012-01-23 10:33 ` Glauber Costa
2012-01-24 1:25 ` KAMEZAWA Hiroyuki
2012-01-25 0:01 ` [PATCH v2] " Eric Dumazet
2012-01-25 0:12 ` Andrew Morton [this message]
2012-01-25 0:22 ` Eric Dumazet
2012-01-25 1:27 ` Andrew Morton
2012-01-25 5:29 ` Eric Dumazet
2012-01-26 1:04 ` Andrew Morton
2012-01-26 9:55 ` KAMEZAWA Hiroyuki
2012-01-27 0:43 ` Andrew Morton
2012-01-27 1:09 ` KAMEZAWA Hiroyuki
2012-01-27 1:18 ` Andrew Morton
2012-01-30 5:16 ` [PATCH] Add num_to_str() for speedup /proc/stat KAMEZAWA Hiroyuki
2012-01-30 23:20 ` Andrew Morton
2012-01-30 23:58 ` KAMEZAWA Hiroyuki
2012-02-01 14:43 ` Andrea Righi
2012-02-01 23:46 ` KAMEZAWA Hiroyuki
2012-01-27 7:09 ` [PATCH v2] proc: speedup /proc/stat handling Eric Dumazet
2012-01-25 0:18 ` KAMEZAWA Hiroyuki
2012-01-25 0:26 ` Eric Dumazet
2012-01-30 8:06 ` Jörg-Volker Peetz
2012-01-30 9:25 ` Eric Dumazet
2012-01-30 10:00 ` Jörg-Volker Peetz
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