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[Xen-devel] RE: s_time going backwards on same processor?

To: "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>, "Xen-Devel (E-mail)" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] RE: s_time going backwards on same processor?
From: "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx>
Date: Wed, 23 Jul 2008 05:48:50 -0600
Cc: Dave Winchell <dwinchell@xxxxxxxxxxxxxxx>
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> No matter what happens to the underlying platform timer, it should be
> impossible for Xen system time to go backwards on any given 
> processor. The
> calibration function never sets the TSC and system timestamps 
> for the next
> time record any earlier than current TSC value and current 
> computed system
> time value. Hence it should be impossible for system time to 
> be computed as
> earlier than that time record.

OK, that corresponds with my reading of the code.  I just
wanted to ensure there wasn't some subtle point I was missing.

When I again have access to my test machine, I will try to
reproduce it and provide more information if I can.

Thanks,
Dan


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