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From: Namhyung Kim <namhyung@kernel.org>
To: David Ahern <dsahern@gmail.com>
Cc: chenggang.qin@gmail.com, linux-kernel@vger.kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@redhat.com>,
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        Yanmin Zhang <yanmin.zhang@intel.com>,
        Wu Fengguang <fengguang.wu@intel.com>, Mike Galbraith <efault@gmx.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Chenggang Qin <chenggang.qcg@alibaba-inc.com>
Subject: Re: [PATCH] perf script: Add a python script to statistic direct io behavior
References: <510a34c6.c750420a.037e.74c6@mx.google.com>
	<510A9B0D.6000503@gmail.com>
Date: Fri, 01 Feb 2013 10:56:42 +0900
In-Reply-To: <510A9B0D.6000503@gmail.com> (David Ahern's message of "Thu, 31
	Jan 2013 09:25:49 -0700")
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Hi,

On Thu, 31 Jan 2013 09:25:49 -0700, David Ahern wrote:
> Hi
>
> On 1/31/13 2:08 AM, chenggang.qin@gmail.com wrote:
>> From: chenggang.qin@gmail.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