Re: [Qemu-devel] Main loop

[malc]

On Mon, 28 Sep 2009, Glauber Costa wrote:

> > > Glauber spent some time with the IO thread recently.  Any reason you 
> > > didn't
> > > start with the existing IO thread (besides the fact that it doesn't work 
> > > with
> > > TCG)?
> > > 
> > 
> > Because i wasn't writing a replacement for IO Thread to begin with (btw it
> > does work with TCG), what it doesn't do is play nicely with icount[1], 
> > work on Windows, and for mysterious reasons still requires alarm timers, 
> > it also deadlocks for me when killing QEMU windows while running smp 
> > guest, but that's easily corrected mistake somewhere i guess.
> 
> You wasn't, but you ended up doing so, since it is unlikely that they 
> will both live in the end. I am still reading your patch, and I still 
> have to struggle a little bit to understand it. Can you please tell us 
> why do you think your approach is better?
> 
> The current I/O thread currently works with both kvm and tcg. For KVM, I 
> am quite close (expecting to post patches today) that enables the 
> in-kernel irqchip for it, and pretty close to do smp.
> 
> Note that I don't think it requires alarm timers at all, by design. So, 
> again, why should we drop what we have in favour of your implementation?

Now that we have talked i see the problem and it basically boils down
to this: kvm can(and does) run multiple vcpus in multiple threads,
qemu always uses one, on top of this you are mainly interested in KVM
and i'm _only_ interested in TCG. The way i see it the best approach
would be to factor out main loop into separate file and let QEMU and
KVM go their own separate ways w.r.t. this new entity.

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