lkml.org 
[lkml]   [2007]   [Jan]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: kvm & dyntick

* Avi Kivity <avi@qumranet.com> wrote:

> >( for this to work on my system i have added a 'hyper' clocksource
> > hypercall API for KVM guests to use - this is needed instead of the
> > running-to-slowly TSC. )
> >
>
> What's the problem with the TSC? The only issue I'm aware of is that
> the tsc might go backwards if the vcpu is migrated to another host cpu
> (easily fixed).

this is not a problem of KVM - this is a problem of this laptop: its TSC
stops when going idle. So the TSC is fundamentally unusable for reliable
timekeeping - and qemu doesnt offer pmtimer emulation to fall back to,
so the dyntick kernel refused to go high-res under KVM. Once i added the
hyper clocksource to fall back to, it could utilize the PIT and the
lapic for clock-events.

Ingo
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-01-14 10:05    [from the cache]
©2003-2011 Jasper Spaans