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From: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
To: "'Davide Libenzi'" <davidel@xmailserver.org>, davidm@hpl.hp.com
Cc: Linus Torvalds <torvalds@transmeta.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: RE: Why HZ on i386 is 100 ?
Date: Tue, 16 Apr 2002 17:33:06 -0700
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If you change HZ to 1000, you need to change PROC_CHANGE_PENALTY
accordingly.  Otherwise, process would get preempted before its time slice
gets expired.  The net effect is more context switch than necessary, which
could explain the 10% difference.


-----Original Message-----
From: Davide Libenzi [mailto:davidel@xmailserver.org]
Sent: Tuesday, April 16, 2002 11:10 AM
To: davidm@hpl.hp.com
Cc: Linus Torvalds; Linux Kernel Mailing List
Subject: Re: Why HZ on i386 is 100 ?


On Tue, 16 Apr 2002, David Mosberger wrote:

> >>>>> On Tue, 16 Apr 2002 10:18:18 -0700 (PDT), Davide Libenzi
<davidel@xmailserver.org> said:
>
>   Davide> i still have pieces of paper on my desk about tests done on
>   Davide> my dual piii where by hacking HZ to 1000 the kernel build
>   Davide> time went from an average of 2min:30sec to an average
>   Davide> 2min:43sec. that is pretty close to 10%
>
> Did you keep the timeslice roughly constant?

it was 2.5.1 time and it was still ruled by TICK_SCALE that made the
timeslice to drop from 60ms ( 100HZ ) to 21ms ( 1000HZ ).




- Davide


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