On 12/01/2010 11:34 PM, Stefan Hajnoczi wrote:
>> The guest CPU utilization numbers include an efficiency metric: %vcpu >> per MB/sec. Here we see significant improvements too. Guests that >> previously couldn't get more CPU work done now have regained some >> breathing space. > > Thanks for those numbers. The guest improvements were expected, but the > host numbers surprised me. Do you have an explanation as to why total host > load should decrease? The first vcpu does virtqueue kick - it holds the guest driver vblk->lock across kick. Before this kick completes a second vcpu tries to acquire vblk->lock, finds it is contended, and spins. So we're burning CPU due to the long vblk->lock hold times. With virtio-ioeventfd those kick times are reduced an there is less contention on vblk->lock.
Makes sense. -- 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
