Re: [fbsd] timer goes sluggish

On Wed, 31 May 2006, 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'' :).
:
:> % jarjarbinks:root# ntpdate -b chronos.cru.fr
:> % 29 May 17:09:32 ntpdate[4266]: step time server 195.220.94.163 offset 0.000937 sec
:> % jarjarbinks:root# sysctl kern.timecounter.hardware=TSC
:> % kern.timecounter.hardware: ACPI-fast -> TSC
:> % jarjarbinks:root# while : ; do date ; sleep 1 ; done
:> % Mon May 29 17:09:41 CEST 2006
:> % Mon May 29 17:09:42 CEST 2006
:> % Mon May 29 17:09:43 CEST 2006
:> % Mon May 29 17:09:44 CEST 2006
:> % Mon May 29 17:09:45 CEST 2006
:> % ^C
:> % jarjarbinks:root# ntpdate -b chronos.cru.fr
:> % 29 May 17:10:16 ntpdate[4278]: step time server 195.220.94.163 offset 29.503343 sec
:
:Likewise, we the above sysctl set, this behaviour disappears.  However,
:I think humbly that this breaks POLA.  I am pretty confident there is
:a good technical reason for this, but it is quite puzzling to have
:the computer clock drifting lagging that much.
:
:
:As an additional question, is there a reason to have
:performance_cx_lowest="LOW" in etc/defaults/rc.conf ?
:

I think the problem lays within the name of the host.

J/K.!
Cheers,
Andrew
--
arr_at_watson.org