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Re: [Xen-devel] A clocksource question

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: Re: [Xen-devel] A clocksource question
From: Joanna Rutkowska <joanna@xxxxxxxxxxxxxxxxxxxxxx>
Date: Thu, 11 Mar 2010 02:19:47 +0100
Cc: Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
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On 11/03/2010 02:06, Jeremy Fitzhardinge wrote:
> On 03/10/2010 04:52 PM, Joanna Rutkowska wrote:
>> BTW, how does the clocksource=jiffies work on a pvops kernel in Dom0?
> Not very well.  clocksource=jiffies just sets up timer interrupts at
> approx 100ms intervals and assumes that's 100ms.  You get very low res
> timers and timekeeping.

So, how to explain that there is no wallclock drift *at all*, even in a
long run -- uptime of a few days, in Dom0, when it uses the jiffies source?

Anyway, I assume that the "xen" clock source is much more fine grained
(1ms?) and so, maybe my kbd hiccups are caused by some code executed by
the timer interrupt too frequently (maybe too much code executes per
each timer interrupt, because of some other bug)? Just a though...


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