linux-kernel - Re: [PATCH: 2.6.18.1] delayacct: cpu_count in taskstats updated correctly

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Message-ID: <Pine.LNX.4.63.0610270919500.9454@honbori.ifi.uio.no>
Date:	Fri, 27 Oct 2006 09:23:05 +0200 (CEST)
From:	Martin Tostrup Setek <martitse@...dent.matnat.uio.no>
To:	David Rientjes <rientjes@...washington.edu>
cc:	Martin Tostrup Setek <martitse@...dent.matnat.uio.no>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH: 2.6.18.1] delayacct: cpu_count in taskstats updated
 correctly

On Thu, 26 Oct 2006, David Rientjes wrote:
> I don't see a cpu_delay, I see a cpu_delay_total.  This is the CPU's
> cumulative delay and is only accessible through the user-space accounting
> program Documentation/accounting/getdelays.c.  It reports the number of
> delay values recorded and the real total, virtual total, and delay total;
> each of these are cumulative.

Yes, I reread the docs more carefully. You are right, and I was wrong.

> In the use case for cpu_count, taking the difference of two successive
> cpu_count readings as reported by getdelays.c would find the number of
> delays experienced in that interval.  This is described in the program's
> documentation so by definition the count must be cumulative.  It is also
> possible to find the average delay but dividing cpu_delay_total by
> cpu_count.
>
> The original code is correct and accumulation is appropriate.

Thanks for setting me straight. I withdraw the patch.

Martin
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