Re: Linux 2.6.29-rc6

[Jesper Krogh]

Thomas Gleixner wrote:
> On Thu, 26 Feb 2009, john stultz wrote:
> > On Thu, 2009-02-26 at 22:35 +0100, Jesper Krogh wrote:
> > > john stultz wrote:
> > > > On Thu, Feb 26, 2009 at 12:43 PM, Jesper Krogh <jesper@xxxxxxxx> wrote:
> > > > > Linus Torvalds wrote:
> > > > > > On Thu, 26 Feb 2009, Jesper Krogh wrote:
> > > > > > > 2.6.26.8 doesnt have this problem.
> > > > > > >
> > > > > > > The "current_clocsource" is the same on both systems.
> > > > > > >
> > > > > > > $ cat /sys/devices/system/clocksource/clocksource0/current_clocksource
> > > > > > > tsc
> > > > > > What does the frequency calibrate to? It should be in the dmesg. Does it
> > > > > > differ by a big amount?
> > > > > Non-working:
> > > > > $ dmesg | grep -i freq
> > > > > [    0.004007] Calibrating delay loop (skipped), value calculated using
> > > > > timer frequency.. 4620.05 BogoMIPS (lpj=9240104)
> > > > >
> > > > > 2.6.26.8 doesn't have that information.
> > > > I'm surprised the clocksource watchdog isn't catching it.
> > > >
> > > > What's the output from:
> > > > cat /sys/devices/system/clocksource/clocksource0/available_clocksource
> > > $ cat /sys/devices/system/clocksource/clocksource0/available_clocksource
> > > tsc acpi_pm jiffies
> > Hmm. Does booting w/ "clocksourc=acpi_pm" also show the severe (~550ppm,
> > which NTP can't handle) drift?
> >
> > >From the dmesg, I don't see any major calibration difference right off. 
> >
> > So I'd suspect something like TSC halting in idle could be causing
> > problems, but the watchdog should catch that as well. My only guess at
> > this point is that the ACPI PM is halting in idle along with the TSC. 
>
> But why would it do that on 29-rc6 and not on 2.6.28.8 ? I'm not aware
> of changes which might cause that.

My comparison is 2.6.26.8 not 2.6.28.8 .. so fairly old.

It is a small cluster, so I'm slipping some test-kernels in when the
cluster is idle.

--
Jesper
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