From: Stephen Rothwell <sfr@canb.auug.org.au>
To: "Con Kolivas" <kernel@kolivas.org>
Cc: "Vassili Karpov" <av1474@comtv.ru>, linux-kernel@vger.kernel.org
Subject: Re: CPU load
Date: Mon, 12 Feb 2007 16:55:54 +1100 [thread overview]
Message-ID: <20070212165554.42d12419.sfr@canb.auug.org.au> (raw)
In-Reply-To: <8cd998d50702112144y38958d27saec4196f6f5d5236@mail.gmail.com>
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On Mon, 12 Feb 2007 16:44:22 +1100 "Con Kolivas" <kernel@kolivas.org> wrote:
>
> The kernel looks at what is using cpu _only_ during the timer
> interrupt. Which means if your HZ is 1000 it looks at what is running
> at precisely the moment those 1000 timer ticks occur. It is
> theoretically possible using this measurement system to use >99% cpu
> and record 0 usage if you time your cpu usage properly. It gets even
> more inaccurate at lower HZ values for the same reason.
That is not true on all architecures, some do more accurate accounting by
recording the times at user/kernel/interrupt transitions ...
--
Cheers,
Stephen Rothwell sfr@canb.auug.org.au
http://www.canb.auug.org.au/~sfr/
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next prev parent reply other threads:[~2007-02-12 5:55 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-02-12 5:33 CPU load Vassili Karpov
2007-02-12 5:44 ` Con Kolivas
2007-02-12 5:54 ` malc
2007-02-12 6:12 ` Con Kolivas
2007-02-12 7:10 ` malc
2007-02-12 7:29 ` Con Kolivas
2007-02-12 5:55 ` Stephen Rothwell [this message]
2007-02-12 6:08 ` Con Kolivas
2007-02-12 14:32 ` Pavel Machek
2007-02-13 22:01 ` malc
2007-02-13 22:08 ` Con Kolivas
2007-02-14 7:28 ` malc
2007-02-14 8:09 ` Con Kolivas
2007-02-14 20:45 ` Pavel Machek
2007-02-25 10:35 ` malc
2007-02-26 9:28 ` Pavel Machek
2007-02-26 10:42 ` malc
2007-02-26 16:38 ` Randy Dunlap
2007-02-12 18:05 ` malc
-- strict thread matches above, loose matches on Subject: below --
2007-02-12 16:57 Andrew Burgess
2007-02-12 18:15 ` malc
2002-07-10 14:50 David Chow
2002-07-10 16:54 ` William Lee Irwin III
2002-07-10 17:49 ` Robert Love
2002-07-26 17:38 ` David Chow
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