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Date: Tue, 16 Apr 2002 12:12:11 -0400
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From: Chris Friesen <cfriesen@nortelnetworks.com>
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To: Rik van Riel <riel@conectiva.com.br>
Cc: Mark Mielke <mark@mark.mielke.cc>,
        Terje Eggestad <terje.eggestad@scali.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Liam Girdwood <l_girdwood@bitwise.co.uk>,
        BALBIR SINGH <balbir.singh@wipro.com>,
        William Olaf Fraczyk <olaf@navi.pl>,
        Lee Irwin III <wli@holomorphy.com>
Subject: Re: Why HZ on i386 is 100 ?
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Rik van Riel wrote:
> 
> On Tue, 16 Apr 2002, Mark Mielke wrote:
> 
> > Increasing the HZ can only improve responsiveness, however, there is a
> > cost (mentioned by others). The cost is that the scheduler is executed
> > more often per second. If the scheduler does the same amount of work
> > per tick, but there are more ticks per second, the scheduler does more
> > work overall, and the CPU is free for use by the processes less.
> 
> Why are you discussing Linux 1.2 ?
> 
> Linux is not running the scheduler each cpu tick and hasn't
> done this for years.

Very true.  However it does run the timer/clock code every tick, which is still
additional overhead when the tick time is reduced.

The basic idea (increased overhead at higher HZ) is sound, the details are not.

Chris

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