[Xen-users] RE: [Xen-devel] Xen 4 TSC problems

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

Just a wild guess, but this in Olivier's posted output:

(XEN) Platform timer appears to have unexpectedly wrapped 10 or more times.

and the fact that a 32-bit HPET wrap is ~300 seconds and, with the
"10 or more times", 10 * 300 seconds is 3000 seconds, might be a clue
(or a complete red herring, but I thought it worth mentioning).

Mark and Olivier, it would be interesting to know if you are
using the same processor/system.

> -----Original Message-----
> From: Keir Fraser [mailto:keir.xen@xxxxxxxxx]
> Sent: Thursday, February 24, 2011 7:52 AM
> To: Olivier Hanesse; Jan Beulich
> Cc: Mark Adams; Jeremy Fitzhardinge; xen-devel@xxxxxxxxxxxxxxxxxxx; Xen
> Users; Dan Magenheimer; Keir Fraser
> Subject: Re: [Xen-devel] Xen 4 TSC problems
> 
> On 24/02/2011 14:20, "Olivier Hanesse" <olivier.hanesse@xxxxxxxxx>
> wrote:
> 
> > Both dom0 and domUs are affected by this" jump".
> >
> > I expect to see something like "TSC marked as reliable, warp = 0".
> > I got this on newer hardware with same config/distros.
> 
> It depends on the CPU itself, older CPUs do not have the super-stable
> TSC
> features. But that should never cause a massive 3000s time jump.
> 
> > Is there a way to measure if it is a TSC warp ? to point out a cpu
> tsc issue ?
> 
> The TSC warps or out-of-sync issues that we could reasonably expect
> would be
> on the order of microseconds. A 3000s warp is something else entirely.
> Xen
> is very confused and/or some TSC or platform timer has jumped a long
> way
> (indicating a hardware/firmware issue).
> 
>  -- Keir
> 
> >
> > 2011/2/24 Jan Beulich <JBeulich@xxxxxxxxxx>
> >>>>> On 24.02.11 at 12:57, Olivier Hanesse <olivier.hanesse@xxxxxxxxx>
> wrote:
> >>> I tried to turn off cstates with max_cstate=0 without success
> (still "not
> >>> reliable").
> >>>
> >>> With cpuidle=0, I also got :
> >>>
> >>> (XEN) TSC has constant rate, deep Cstates possible, so not
> reliable,
> >>> warp=3022 (count=1)
> >>
> >> This message by itself isn't telling much I believe.
> >>
> >>> xm info | grep command
> >>> xen_commandline        : dom0_mem=512M cpuidle=0 loglvl=all
> guest_loglvl=all
> >>> dom0_max_vcpus=1 dom0_vcpus_pin console=vga,com1 com1=19200,8n1
> >>>
> >>> Keir :
> >>>
> >>> Using clocksource=pit :
> >>>
> >>> (XEN) Platform timer is 1.193MHz PIT
> >>>
> >>> I also got :
> >>>
> >>> (XEN) TSC has constant rate, deep Cstates possible, so not
> reliable,
> >>> warp=3262 (count=2)
> >>
> >> The question is whether any of this eliminates the time jumps seen
> >> by your DomU-s (from your past mails I wasn't actually sure whether
> >> Dom0 also experienced this problem, albeit it would be odd if it
> didn't).
> >>
> >> Jan
> >>
> >> Jan
> >>
> >
> >
> 
> 

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