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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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  parent reply	other threads:[~2007-02-12  5:55 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-12  5:33 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 --
2018-03-27 11:44 CPU Load Ryan Meulenkamp
2018-03-29  1:24 ` Andre McCurdy
2018-03-29  6:42   ` Jussi Laako
2007-02-12 16:57 CPU load 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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