linux-kernel - Re: [PATCH 4/4] tracing, page-allocator: Add a postprocessing script for page-allocator-related ftrace events

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Date:	Tue, 04 Aug 2009 14:27:16 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Mel Gorman <mel@....ul.ie>, Larry Woodman <lwoodman@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: [PATCH 4/4] tracing, page-allocator: Add a postprocessing script
 for page-allocator-related ftrace events

Andrew Morton wrote:
> On Tue,  4 Aug 2009 19:12:26 +0100 Mel Gorman <mel@....ul.ie> wrote:
> 
>> This patch adds a simple post-processing script for the page-allocator-related
>> trace events. It can be used to give an indication of who the most
>> allocator-intensive processes are and how often the zone lock was taken
>> during the tracing period. Example output looks like
>>
>> find-2840
>>  o pages allocd            = 1877
>>  o pages allocd under lock = 1817
>>  o pages freed directly    = 9
>>  o pcpu refills            = 1078
>>  o migrate fallbacks       = 48
>>    - fragmentation causing = 48
>>      - severe              = 46
>>      - moderate            = 2
>>    - changed migratetype   = 7
> 
> The usual way of accumulating and presenting such measurements is via
> /proc/vmstat.  How do we justify adding a completely new and different
> way of doing something which we already do?

Mel's tracing is more akin to BSD process accounting,
where these statistics are kept on a per-process basis.

Nothing in /proc allows us to see statistics on a per
process basis on process exit.

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