Virtio/Block/Latency
From KVM
This page describes how virtio-blk latency can be measured. The aim is to build a picture of the latency at different layers of the virtualization stack for virtio-blk.
Benchmarks
Single-threaded read or write benchmarks are suitable for measuring virtio-blk latency.
I use a simple sequential read C program which prints the average time per read operation at the end.