Re: [Xen-devel] Re: [patch 14/21] Xen-paravirt: Add XEN config options and disableunsupported config options.

[Zachary Amsden <zach@xxxxxxxxxx>]

Keir Fraser wrote:
> On 16/2/07 17:46, "Jeremy Fitzhardinge" <jeremy@xxxxxxxx> wrote:
>
>   
> > Keir Fraser wrote:
> >     
> > > This initial patchset does not include save/restore support anyway, so in
> > > fact it would be consistent to have CONFIG_PREEMPT configurable. I'm sure
> > > that we are going to have some nasty bugs to fix up as a result, but we
> > > can't fix them until we find them! Then we can convert our save/restore code
> > > to use the freezer before submitting it for inclusion.
> > >       
> > OK.  So that makes the only config restriction the 100Hz ticks.
> >     
> We can extend the Xen timer interface quite easily and get rid of this one
> too. In fact it doesn't *much* matter if the CONFIG_HZ differs from the Xen
> ticker rate -- we modified the Linux timer ISR to handle timer interrupts at
> arbitrary times already. The only drawback is that jiffies updates in burts
> if CONFIG_HZ is higher than the actual tick rate, and this can affect some
> calibration constants and cause Linux to print out some weird values at
> start-of-day.
>   
That's why we'd very much like to get a get_cpu_speed paravirt-op 
implemented.  I think this would be useful to work around these problems 
for Xen as well.
Zach

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