Re: kern/45626: System time does not advance correctly when noatime is specified for /var

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Fri, Nov 18, 2011 at 01:25:03PM +0000, Donald Allen wrote:
>  [...]
>  sysctl -a | grep kern.timecounter
>  
>  which I did:
>  
>  kern.timecounter.choice = TSC(q=3000, f=67750617510 Hz) clockinterrupt(q=0,
>  f=100 Hz) ichlpcib0(q=1000, f=3579545 Hz) hpet0(q=2000, f=14318179 Hz)
>  ACPI-Fast(q=1000, f=3579545 Hz) lapic(q=-100, f=266097187 Hz) i8254(q=100,
>  f=1193182 Hz) dummy(q=-1000000, f=1000000 Hz)
>  kern.timecounter.hardware = TSC
>  kern.timecounter.timestepwarnings = 0

TSC is clearly wrong here, I'm sure you don't have a 67Ghz CPU :)

>  
>  He also suggested trying
>  
>  sysctl -w kern.timecounter.hardware=hpet0
>  >
>  > and see if that fixes it.
>  >
>  
>  It does:
> [...]
>  However, after doing this, the system behaved in odd ways. I had trouble
>  shutting X down, the system seemed not to be hearing the (USB) keyboard (I
>  couldn't log in after doing ctrl-alt-f2). I finally got it shut down and
>  rebooted, ending this experiment.
>  
>  I then decided to try a newer kernel, and installed the kernel from the
>  11/17 snapshot. Upon booting the system this morning (with all the file
>  systems, including /var, mounted async,noatime), I quickly observed the
>  clock problem.

You should try setting
kern.timecounter.hardware=hpet0
in /etc/sysctl.conf, so that the change is applied at boot.
The odd behavior you see may be caused by processes started before
the timecounter change.

You can also try other available timecounters (try ichlpcib0 or i8254
for exampe).

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--