Re: [kvm-devel] [Qemu-devel] [PATCH] [RFC] Fix time drift of rtc clock + general support

[Avi Kivity]

Avi Kivity wrote:
> Paul Brook wrote:
> >  
> > > > a new timer will be fired to try inject it again soon (==0.1msec)
> > > >       
> >
> > If the guest is missing interrupts, the chances of a 0.1ms interval 
> > working are not great.  Most likely It's either going trigger 
> > immediately, or be delayed significantly and you're going to end up 
> > even further behind.   
>
> If 0.1 ms is within qemu's timeslice, then qemu should get the wakeup 
> on time (assuming a host with high resolution timers).
>
> > If triggering immediately is OK then why not do that all the time?
> >   
>
> Triggering immediately doesn't help, the guest likely has interrupts 
> blocked processing the same interrupt.
>
> > If triggering immediately is not acceptable then you're still going 
> > to loose interrupts.
> >   
>
> You're still accounting for them, so if the load decreases eventually 
> it's going to catch up.

btw, the better solution here is to wait until the guest is ready for 
timer interrupt injection again, but that's not as easy as arming a timer.

--
Do not meddle in the internals of kernels, for they are subtle and quick to 
panic.