timer goes sluggish

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
% 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

I know this is a FAQ when CPU frequency throttling is used, but this is
not the case here.  I killed powerd(8) and dev.cpu.0.freq is set to its
highest frequency (1733).

IOW, using ACPI-fast as timecounter leads to have "sleep 1" actually
sleep for 6~7 seconds.  Using TSC as timecounter is even weirder since it
desynchronize the computer's clock.

I attached the dmesg of my computer, and can provide verbose dmesg if
need, or anything else requested to help debugging.

Thank you.
Regards,
-- 
Jeremie Le Hen
< jeremie at le-hen dot org >< ttz at chchile dot org >