On Wed, Jul 18, 2012 at 4:40 PM, Michael S. Tsirkin <m...@redhat.com> wrote: > On Wed, Jul 18, 2012 at 04:07:45PM +0100, Stefan Hajnoczi wrote: >> Optimize for the MSI-X enabled and vector unmasked case where it is >> possible to issue the KVM ioctl() directly instead of using irqfd. > > Why? Is an ioctl faster?
I have no benchmark results comparing irqfd against direct ioctl. It would be interesting to know if this "optimization" is worthwhile and how much of a win it is. The reasoning is that the irqfd code path signals an eventfd and then kvm.ko's poll handler injects the interrupt. The ioctl calls straight into kvm.ko and skips the signalling/poll step. Stefan
