On Mon, Nov 15, 2010 at 11:20 AM, Stefan Hajnoczi <stefa...@gmail.com> wrote: > On Sun, Nov 14, 2010 at 12:19 PM, Avi Kivity <a...@redhat.com> wrote: >> On 11/14/2010 01:05 PM, Avi Kivity wrote: >>>> >>>> I agree, but let's enable virtio-ioeventfd carefully because bad code >>>> is out there. >>> >>> >>> Sure. Note as long as the thread waiting on ioeventfd doesn't consume too >>> much cpu, it will awaken quickly and we won't have the "transaction per >>> timeslice" effect. >>> >>> btw, what about virtio-blk with linux-aio? Have you benchmarked that with >>> and without ioeventfd? >>> >> >> And, what about efficiency? As in bits/cycle? > > We are running benchmarks with this latest patch and will report results.
Full results here (thanks to Khoa Huynh): http://wiki.qemu.org/Features/VirtioIoeventfd The host CPU utilization is scaled to 16 CPUs so a 2-3% reduction is actually in the 32-48% range for a single CPU. 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. Stefan
