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Re: [Xen-devel] Xen 4 TSC problems

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] Xen 4 TSC problems
From: Olivier Hanesse <olivier.hanesse@xxxxxxxxx>
Date: Thu, 24 Feb 2011 15:20:01 +0100
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Keir Fraser <keir@xxxxxxx>, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Xen Users <xen-users@xxxxxxxxxxxxxxxxxxx>, Mark Adams <mark@xxxxxxxxxxxxxxxxxx>
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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.

Is there a way to measure if it is a TSC warp ? to point out a cpu tsc issue ?

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).



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