linux-kernel - Re: CPU load

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Date:	Mon, 12 Feb 2007 08:54:25 +0300 (MSK)
From:	malc <av1474@...tv.ru>
To:	Con Kolivas <kernel@...ivas.org>
cc:	linux-kernel@...r.kernel.org
Subject: Re: CPU load

On Mon, 12 Feb 2007, Con Kolivas wrote:

> On 12/02/07, Vassili Karpov <av1474@...tv.ru> wrote:

[..snip..]

> 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.

Thank you very much. This somewhat contradicts what i saw (and outlined
in usnet article), namely the mplayer+/dev/rtc case. Unless ofcourse
/dev/rtc interrupt is considered to be the same as the interrupt from
PIT (on X86 that is)

P.S. Perhaps it worth documenting this in the documentation? I caused
      me, and perhaps quite a few other people, a great deal of pain and
      frustration.

-- 
vale
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