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Re: [Xen-devel] Time in Xen

To: "Ian C. Blenke" <ian@xxxxxxxxxx>
Subject: Re: [Xen-devel] Time in Xen
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Mon, 27 Oct 2003 21:46:42 +0000
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> > All other domains always track Xen's wall-clock time: setting the
> > date, or running ntpd, on these domains will not affect their
> > wall-clock time!! If this is a problem then I can add a sysctl which
> > would turn this off if desired (i.e., setting the flag would prevent
> > the domain from tracking Xen's estimate of wall-clock time).
> For development environments, it really would help to be able to disable
> this behavior. There's nothing quite like fiddling with the clock,
> troubleshooting some timestamp behavior, only to find the system time
> "fixed" after a testing run. 

Okay, I can add a command-line option and/or sysctl switch to modify
this behaviour quite easily. I have some other tweaks I'll be making
shortly, so I'll add this at the same time.

> UML's system clock is really more a suggestion than a real usable time
> source as a result of some of the host's system time confusion.  Try a
> "sleep 10" in a UML image, and see how long it *really* takes.  I'd hate
> to see this happen to Xen as well.

I'm not sure what you mean. Neither Xen nor Xenolinux "lose"
ticks. There are still some more cleanups to be made to the time
interface, but Xen does at least provide a stable time base.

 -- Keir

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