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From: John Baldwin <jhb@freebsd.org>
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Date: Thu, 1 Jun 2006 14:41:07 -0400
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Cc: Jeremie Le Hen <jeremie@le-hen.org>
Subject: Re: [fbsd] timer goes sluggish
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On Tuesday 30 May 2006 18:32, Jeremie Le Hen wrote:
> Hi,
> 
> On Mon, May 29, 2006 at 05:31:03PM +0200, Jeremie Le Hen wrote:
> > Hi,
> > 
> > I won't write too much, the following session will tell much more:
> > 
> > % jarjarbinks:root# ntpdate -b chronos.cru.fr
> > % 29 May 17:08:44 ntpdate[4254]: step time server 195.220.94.163 offset 
0.000273 sec
> > % jarjarbinks:root# sysctl kern.timecounter.hardware
> > % kern.timecounter.hardware: ACPI-fast
> > % jarjarbinks:root# while : ; do date ; sleep 1 ; done
> > % Mon May 29 17:08:56 CEST 2006
> > % Mon May 29 17:09:03 CEST 2006
> > % Mon May 29 17:09:09 CEST 2006
> > % Mon May 29 17:09:16 CEST 2006
> > % Mon May 29 17:09:22 CEST 2006
> > % ^C
> 
> Sometimes, I feel dumb.
> 
> I noticed that the clock sped up when the CPU makes heavy computing,
> which meant there was some power saving on idleness.
> 
> I dug a bit I found that hw.acpi.cpu.cx_lowest=C4.
> Setting it hw.acpi.cpu.cx_lowest=C1 makes the clock goes ``in time'' :).

If you are using APIC, try disabling APIC and see if it works ok with higher 
Cx states.

-- 
John Baldwin