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Re: proposal: stop using the xen_system_time timecounter in dom0



At Fri, 21 Jun 2024 09:26:55 +0200, Martin Husemann <martin%duskware.de@localhost> wrote:
Subject: Re: proposal:  stop using the xen_system_time timecounter in dom0
>
> However, in this case an easy workaround would be to lower the quality
> estimate of the timecounter if the cpu in use does not have an
> invariant TSC - I think we do something like that (with a bad list and
> some cpu ident magic) on some other timecounters, maybe that logic could
> be reused here?

That's exactly what I am proposing, in a sense.

Don't use (i.e. register) xen_system_time as a timecounter in dom0.

Then you get the normal set of available timecounters for the available
hardware (including possibly TSC, or possibly not) as a GENERIC kernel
will get and all the same logic for measuring them and rating their
quality will be used and the best one will win.

In dom0 xen_system_time's fiction is unnecessary, confusing, possibly
actually of lower quality even when reliable, and often simply wrong and
unreliable; yet it forcibly claims to be the highest quality timecounter.

--
					Greg A. Woods <gwoods%acm.org@localhost>

Kelowna, BC     +1 250 762-7675           RoboHack <woods%robohack.ca@localhost>
Planix, Inc. <woods%planix.com@localhost>     Avoncote Farms <woods%avoncote.ca@localhost>

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