Messages in this thread | | | Date | Mon, 22 Mar 2010 21:29:37 +0100 | From | Ingo Molnar <> | Subject | Re: [RFC] Unify KVM kernel-space and user-space code into a single project |
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* Avi Kivity <avi@redhat.com> wrote:
> > I think you didnt understand my point. I am talking about 'perf kvm top' > > hanging if Qemu hangs. > > Use non-blocking I/O, report that guest as dead. No point in profiling it, > it isn't making any progress.
Erm, at what point do i decide that a guest is 'dead' versus 'just lagged due to lots of IO' ?
Also, do you realize that you increase complexity (the use of non-blocking IO), just to protect against something that wouldnt happen if the right solution was used in the first place?
> > With a proper in-kernel enumeration the kernel would always guarantee the > > functionality, even if the vcpu does not make progress (i.e. it's "hung"). > > > > With this implemented in Qemu we lose that kind of robustness guarantee. > > If qemu has a bug in the resource enumeration code, you can't profile one > guest. If the kernel has a bug in the resource enumeration code, the system > either panics or needs to be rebooted later.
This is really simple code, not rocket science. If there's a bug in it we'll fix it. On the other hand a 500KLOC+ piece of Qemu code has lots of places to hang, so that is a large cross section.
Ingo
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