[fbsd] Re: [fbsd] timer goes sluggish
Jeremie Le Hen
jeremie at le-hen.org
Sat Aug 5 09:00:52 UTC 2006
Hi John,
On Thu, Jun 01, 2006 at 02:41:07PM -0400, John Baldwin wrote:
> 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.
Sorry for the delay.
I was indeed using APIC, and got a chance to disable it. I am writing
this mail with C4 state set and it works flawlessly:
% # sysctl hw.acpi.cpu.cx_lowest
% hw.acpi.cpu.cx_lowest: C4
% # while : ; do date ; sleep 1 ; done
% Sat Aug 5 10:54:19 UTC 2006
% Sat Aug 5 10:54:20 UTC 2006
% Sat Aug 5 10:54:21 UTC 2006
% Sat Aug 5 10:54:22 UTC 2006
What's the point in disabling apic ? Am I supposed to lose some
features along with the apic support removal, or is it something I
won't notice ?
Thank you.
--
Jeremie Le Hen
< jeremie at le-hen dot org >< ttz at chchile dot org >
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