Re: [Qemu-devel] virtio-blk performance regression and qemu-kvm

[Stefan Hajnoczi]

On Fri, Feb 10, 2012 at 2:36 PM, Dongsu Park
<address@hidden> wrote:
>  Now I'm running benchmarks with both qemu-kvm 0.14.1 and 1.0.
>
>  - Sequential read (Running inside guest)
>   # fio -name iops -rw=read -size=1G -iodepth 1 \
>    -filename /dev/vdb -ioengine libaio -direct=1 -bs=4096
>
>  - Sequential write (Running inside guest)
>   # fio -name iops -rw=write -size=1G -iodepth 1 \
>    -filename /dev/vdb -ioengine libaio -direct=1 -bs=4096
>
>  For each one, I tested 3 times to get the average.
>
>  Result:
>
>  seqread with qemu-kvm 0.14.1   67,0 MByte/s
>  seqread with qemu-kvm 1.0      30,9 MByte/s
>
>  seqwrite with qemu-kvm 0.14.1  65,8 MByte/s
>  seqwrite with qemu-kvm 1.0     30,5 MByte/s

Please retry with the following commit or simply qemu-kvm.git/master.
Avi discovered a performance regression which was introduced when the
block layer was converted to use coroutines:

$ git describe 39a7a362e16bb27e98738d63f24d1ab5811e26a8
v1.0-327-g39a7a36

(This commit is not in 1.0!)

Please post your qemu-kvm command-line.

67 MB/s sequential 4 KB read means 67 * 1024 / 4 = 17152 requests per
second, so 58 microseconds per request.

Please post the fio output so we can double-check what is reported.

Stefan