linux-kernel - Re: [RFC][PATCH v2 5/7] taskstats: Improve cumulative CPU time accounting

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Message-ID: <20101115184910.549a828b@mschwide.boeblingen.de.ibm.com>
Date:	Mon, 15 Nov 2010 18:49:10 +0100
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Michael Holzheu <holzheu@...ux.vnet.ibm.com>,
	Shailabh Nagar <nagar1234@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Venkatesh Pallipadi <venki@...gle.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Ingo Molnar <mingo@...e.hu>, John stultz <johnstul@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Subject: Re: [RFC][PATCH v2 5/7] taskstats: Improve cumulative CPU time
 accounting

On Mon, 15 Nov 2010 17:03:56 +0100
Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:

> On Mon, 2010-11-15 at 16:55 +0100, Martin Schwidefsky wrote:
> >  What we want is a low-overhead tool that precisely shows
> > where the cpu spent its time (or didn't because of steal time). The
> > granularity target is tenths of microseconds, something that should be
> > possible with decent hardware. 
> 
> To what purpose? 
 
Is that a trick question? Why do we have tools like "top"? Or process
accounting? The point is that the quality of the numbers we get right
now is rather bad, the overhead of scanning /proc is horrendous and
the 10ms granularity is rather coarse.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

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