linux-kernel - RE: [PATCH 0/4] delayacct: save max CPU/IO/SWAP/RECLAIM delays

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Message-ID: <65795E11DBF1E645A09CEC7EAEE94B9CB5816C48@USINDEVS02.corp.hds.com>
Date:	Tue, 29 Nov 2011 17:34:45 -0500
From:	Satoru Moriya <satoru.moriya@....com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"bsingharora@...il.com" <bsingharora@...il.com>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"kobayashi.kk@...s.nec.co.jp" <kobayashi.kk@...s.nec.co.jp>,
	Randy Dunlap <rdunlap@...otime.net>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Seiji Aguchi <seiji.aguchi@....com>
Subject: RE: [PATCH 0/4] delayacct: save max CPU/IO/SWAP/RECLAIM delays

On 11/29/2011 04:23 AM, Peter Zijlstra wrote:
> On Mon, 2011-11-28 at 17:44 -0500, Satoru Moriya wrote:
>> In the latency sensitive systems, we usually focus on the worst latency.
>> And so, it is useful to save max delays into the per-task delay 
>> accounting functionality.
>>
> 
> No!!!
> 
> Linus told us to be bastards, so there you have it.
> 
> There's way too many different accounting crap thingies around. And 
> now I get a patch without any justification what so ever. So no, piss off.

I agree that there are other ways to get max latency.

I think that with delayacct we can easily get delay statistics
which each task or task-group encountered in their life time
because delayacct records "per-task" delay.

But I just may not know better tools/functions.

Do you think which tools/functions is the best one (to extend)?
ftrace? perf?

Regards,
Satoru