Re: [PATCH 0/3] Improve TSC as a clocksource under VMware

[Alok Kataria <akataria@vmware.com>]

On Tue, 2008-10-21 at 02:50 -0700, Pavel Machek wrote:
> > Hi,
> >
> > This patch set makes some changes to the TSC code, so that it is always
> > used as the default clocksource when running under VMware.
> > The first 2 patches do the ground work of adding code to detect if we
> > are running under VMware.
> > The third patch adds a tsc_reliable flag which tells us that TSC is
> > reliable on this system, so that we can skip some tests which can
> > potentially mark TSC as unstable. Details under individual patch
> > headers.
> 
> How do you _know_ TSC is stable under VMWare? 

Since we implement it that way :)
The hypervisor takes care of providing a constant rate TSC to the guest
on such systems which have variable frequency.

Thanks,
Alok

> AFAICT, accesses to TSC
> are not virtualized and system VMWare runs on may still use frequency
> scaling, no?
>                                                                         Pavel
> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html