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

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Date:	Thu, 31 Jan 2013 09:25:49 -0700
From:	David Ahern <dsahern@...il.com>
To:	chenggang.qin@...il.com
CC:	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>,
	Namhyung Kim <namhyung@...il.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 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?

David

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