Re: Make QEmu HPET disabled by default for KVM?

[Gleb Natapov <gleb@redhat.com>]

On Thu, Mar 11, 2010 at 10:28:12AM +0200, Avi Kivity wrote:
> On 03/11/2010 10:23 AM, Sheng Yang wrote:
> >>>I have kept --no-hpet in my setup for
> >>>months...
> >>Any details about the problems?  HPET is important to some guests.
> >>
> >Seems like HPET reaction is too slow to satisfy some guests(for it would
> >replace PIT).
> >
> >Here is the thread last time.
> >
> >http://thread.gmane.org/gmane.comp.emulators.kvm.devel/44899
> >
> 
> Thanks.  We can address this in three ways: first, adjust the guest
> not to do timing related tests when virtualized (since no matter
> what we do, the tests may fail).  Second, I think we should
> implement userspace ack notifiers (similar to tpr access notifiers
> already present).  Third, we can implement a kernel hpet, which,
> after we solve the zillion bug it introduces, will also give a nice
> performance improvement for hpet intensive workloads.
> 
Second will not solve the problem. Presence of ack notifiers will not
make HPET interrupt arrive faster.

--
			Gleb.