Re: [libvirt] Performance about x-data-plane

> The expensive part is the virtqueue kick. Recently we tried polling the > virtqueue instead of waiting for the ioeventfd file descriptor and got > double-digit performance improvements: > https://lists.gnu.org/archive/html/qemu-devel/2016-12/msg00148.html > > If you want to understand the performance of your benchmark you'll have > compare host/guest disk stats (e.g. request lifetime, disk utilization, > queue depth, average request size) to check that the bare metal and > guest workloads are really sending comparable I/O patterns to the > physical disk. > > Then you using Linux and/or QEMU tracing to analyze the request latency > by looking at interesting points in the request lifecycle like virtqueue > kick, host Linux AIO io_submit(2), etc. > Thank you. I will look into "polling the virtqueue" as you said above. Currently, I just use blktrace to see disk stats and add logs in the I/O workload to see the time latency for each request. What kind of tools are you using to analyze request lifecycle like virtqueue kick, host Linux AIO iosubmit, etc. Do you trace the lifecycle like this (http://www.linux-kvm.org/page/Virtio/Block/Latency#Performance_data) but it seems to be out of date. Does it (http://repo.or.cz/qemu-kvm/stefanha.git/shortlog/refs/heads/tracing-dev-0...) still work on QEMU 2.4.1?