On 07/14/2011 04:00 PM, Sasha Levin wrote:
> > Why? virtio is mature. It's not some early boot thing which fails and > kills the guest. Even if you get an oops, usually the guest is still alive. virtio is mature, /tools/kvm isn't :) > > > It's not just virtio which can fail running on virtio-console, it's also > > the threadpool, the eventfd mechanism and even the PCI management > > module. You can't really debug it if you can't depend on your debugging > > mechanism to properly work. > > Wait, those are guest things, not host things. Yes, as you said in the previous mail, both KVM and virtio are very stable. /tools/kvm was the one who was being debugged most of the time.
I still don't follow. The guest oopses? dmesg | less. An issue with tools/kvm? gdb -p `pgrep kvm`.
> > So far, serial is the simplest, most effective, and never-failing method > > we had for working on guests, I don't see how we can work without it at > > the moment. > > I really can't remember the last time I used the serial console for the > guest. In the early early days, sure, but now? > I don't know, if it works fine why not use it when you need simple serial connection? It's also useful for kernel hackers who break early boot things :)
I'm not advocating removing it! I'm just questioning the need for optimization.
> That's not what scaling means (not to say that it wouldn't be nice to > fix coalesced mmio). > > btw, why are you so eager to run 1024 vcpu guests? usually, if you have > a need for such large systems, you're really performance sensitive. > It's not a good case for virtualization. > > I may have went too far with 1024, I have only tested it on 254 vcpus so far - I'll change that in my patch. It's also not just a KVM issue. Take for example the RCU issue which we were able to detect with /tools/kvm just by trying more than 30 vcpus and noticing that RCU was broken with a recent kernel. Testing the kernel on guests with large amount of vcpus or virtual memory might prove beneficial not only for KVM itself.
Non-performance testing of really large guests is a valid use case, I agree. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
