linux-kernel - Re: [PATCH] perf script: Add a python script to statistic direct io behavior

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Date:	Fri, 01 Feb 2013 10:56:42 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	David Ahern <dsahern@...il.com>
Cc:	chenggang.qin@...il.com, linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Yanmin Zhang <yanmin.zhang@...el.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Mike Galbraith <efault@....de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Chenggang Qin <chenggang.qcg@...baba-inc.com>
Subject: Re: [PATCH] perf script: Add a python script to statistic direct io behavior

Hi,

On Thu, 31 Jan 2013 09:25:49 -0700, David Ahern wrote:
> Hi
>
> On 1/31/13 2:08 AM, chenggang.qin@...il.com wrote:
>> From: chenggang.qin@...il.com
>>
>> This patch depends on a prev patch: https://lkml.org/lkml/2013/1/29/47
>>
>> If the engineers want to analyze the direct io behavior of some applications
>> without source code, perf tools with some appropriate tracepoints events in the
>> VFS subsystem are excellent choice.
>>
>> Many database systems use their own page cache subsystems and use the direct IO
>> to access the disks. Sometimes, the system engineers need to know the misses rate
>> of the database system's page cache. This requirements can be satisfied by recording
>> the database's file access behavior through the way of direct IO. So, we use 2
>> tracepoint events to record the system wide's direct IO behavior. The 2 tracepoint
>> events are:
>> 1) vfs:direct_io_read
>> 2) vfs:direct_io_write
>> they were introduced by the patch: https://lkml.org/lkml/2013/1/29/47
>> The script direct-io.py are introduced by this patch can record the 2 tracepoint
>> events, analyse the sample data, and give a concise report.
>
> What does this option provide that the I/O accounting with taskstats
> (e.g., iotop) does not provide?

Maybe it's better to put this into 'blktrace' tool once the TPs are
accepted.

Thanks,
Namhyung

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