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Re: [Xen-devel] A clocksource question

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Subject: Re: [Xen-devel] A clocksource question
From: Joanna Rutkowska <joanna@xxxxxxxxxxxxxxxxxxxxxx>
Date: Thu, 11 Mar 2010 01:15:20 +0100
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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On 03/11/2010 01:07 AM, Dan Magenheimer wrote:
>> Clocksource tsc unstable (delta = 62752834 ns)
>> hrtimer: interrupt too slow, forcing clock min delta to 412700358 ns
>>> I don't remember if 3.4.2 ended up with tsc emulation, but if it does
>>> you might try enabling it.
>> TSC emulation? But I'm running only PV guests. Not sure what do you
>> mean
>> by this, or how to enable it?
> I don't think there is any TSC emulation (or more properly "rdtsc emulation")
> in 3.4.x, certainly not without a special Xen boot option.
> The TSC delta is troubling...

Actually I'm getting this also when booting Dom0 (pvops
with clocksource=jifffies:

Clocksource tsc unstable (delta = 62528016 ns)

But, there are not visible problems like kbd hiccup or process
scheduling in VM (besides wallclock drift in Dom0 which is annoying).

> if you hadn't said you had turned
> off all power management, I would have guessed a problem with
> C-state management.  Maybe Xen is discovering some power management
> capability not visible in BIOS settings?
I'm not very much of an ACPI expert, so if there are any output I can
send, just let me know.


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