On Mon, Sep 02, 2013 at 05:24:09PM +0900, Jonghwan Choi wrote: > Nowdays i measured io performance with Virtio-Blk-Data-Plane. > There was something strange in test. > When vcpu count is 1, io performance is increased in test > But vcpu count is over 2, io performance is decreased in test. > > i used 3.10.9 stable kernel, qemu(1.4.2) & fio 2.1 > > What should i check in my test?
It's hard to say without any details on your benchmark configuration. In general, x-data-plane=on performs well with SMP guests and with multiple disks. This is because the dataplane threads can process I/O requests without contending on the QEMU global mutex or the iothread event loop. In order to investigate further, please post: 1. The fio results so it's clear which cases performed worse and by how much. 2. The fio job files. 3. The QEMU command-line to launch the guest. 4. The host disk configuration (e.g. file systems, local SATA/FibreChannel/NFS, etc). 5. The basic host specs including RAM and number of logical CPUs. Stefan
