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RE: [Xen-devel] RTC going backwards?

To: "Rob Gardner" <rob.gardner@xxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] RTC going backwards?
From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Date: Tue, 5 Apr 2005 21:20:28 +0100
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Thread-index: AcU6Go2L3WWur3LKQpSg5E9axb4tggAAModg
Thread-topic: [Xen-devel] RTC going backwards?
> Is it possible to call NOW() in xen, and then sometime later 
> call it again and get a slightly smaller value (ie, by a few 
> thousand ns)? Is there something that makes small corrections 
> to the rtc once in a while? 
> I'm trying to track down a bug in some code I'm developing 
> and it looks like time really does go backwards sometimes.

NOW() uses get_s_time (system time), which should always be greater or
equal to the previous value.

If you're running a domain 0 with xntpd, then Xen's wall clock time time
(as opposed to system time) can indeed go backwards if domain 0 pushes
down adjustments to it. 

Ian

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