From: Glauber Costa <glommer@parallels.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
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] proc: speedup /proc/stat handling
Date: Mon, 23 Jan 2012 14:33:54 +0400 [thread overview]
Message-ID: <4F1D3792.4090800@parallels.com> (raw)
In-Reply-To: <20120123191643.21ffba0c.kamezawa.hiroyu@jp.fujitsu.com>
On 01/23/2012 02:16 PM, KAMEZAWA Hiroyuki wrote:
> On Fri, 20 Jan 2012 16:59:24 +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 :
>>
>> # 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>
>>
>>
>> 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.
>>
>> 3) Reduce the bloat on "intr ..." line :
>> Dont output trailing " 0" values at the end of irq range.
>>
>> An alternative to 1) would be to remember the largest m->count reached
>> in show_stat()
>>
>
> nice catch. But how about using usual seq_file rather than single_open() ?
> I just don't like multi-page buffer for this small file...very much.
>
> A rough patch here, maybe optimization will not be enough. (IOW, this may be slow.)
>
I myself don't like it very much, at least at first sight.
Even with optimizations applied, I doubt we can make this approach
faster than what we currently do for /proc/stat.
Also, the code gets a lot harder to read and grasp. Problem is, unlike
most of the stuff using seq_file, /proc/stat shows a lot of different
kinds of information, not a single kind of easily indexable information.
next prev parent reply other threads:[~2012-01-23 10:34 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-20 15:59 [PATCH] proc: speedup /proc/stat handling Eric Dumazet
2012-01-20 22:55 ` Andrew Morton
2012-01-23 10:16 ` KAMEZAWA Hiroyuki
2012-01-23 10:33 ` Glauber Costa [this message]
2012-01-24 1:25 ` KAMEZAWA Hiroyuki
2012-01-25 0:01 ` [PATCH v2] " Eric Dumazet
2012-01-25 0:12 ` Andrew Morton
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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