Re: [Qemu-devel] [RESEND][PATCH 0/3] Fix guest time drift under heavy load.

[Gleb Natapov]

On Sat, Nov 08, 2008 at 10:36:20AM +0200, Gleb Natapov wrote:
> > I think the best ones are going to be intense host workload (and let's  
> > see how much is needed before we start drifting badly) and high guest  
> > frequencies with hosts that lack high resolution timers.  I think with a  
> > high resolution guest and no host overcommit, it should be very  
> > difficult to produce drift regardless of what the guest is doing.
> >
> Later I'll try to generate load on a host an see how this affects
> guest's time drift.
> 
Just did that. Run qemu process bound to CPU 1 (taskset 1 qemu ...).
Run busy loop on the same CPU (taskset 1 bash -c "while true; do x='x'; done")
Run disk test utility as before inside a guest. After 40 minutes time
drift is almost 1 minute, but the drift was not gradual i.e I observed
gradual drift of 1 second per ~6 minutest, but sometimes there were jumps
of ~10 seconds. 

--
                        Gleb.