Re: [Xen-devel] Re: [PATCH] clocksource=tsc

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 18/7/08 15:19, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

> So perhaps the compromise which I've (admittedly accidentally)
> crafted is the right answer for now.  And the right answer for
> later is to update the PV time mechanisms (in a backwards
> compatible way of course) to determine if an ideal timesource
> is available and use it if it is.

Well, maybe, although I don't see we have any guarantee that 'platform
system time' and Xen's get_s_time won't diverge in absolute terms as time
passes. The scale factors each use are calculated somewhat independently.
Actually I think it may get it right just now, but it looks rather fragile
and it stores up trouble for systems with long uptimes if you get it wrong.
There's no particular reason not to generate fresh time records every few
seconds and use those both in Xen and in guests, using the existing
compute-system-time algorithm.

 -- Keir



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