[Qemu-devel] Re: [PATCH v5 0/4] virtio: Use ioeventfd for virtqueue notify

[Stefan Hajnoczi]

On Mon, Dec 13, 2010 at 4:12 PM, Michael S. Tsirkin <address@hidden> wrote:
> On Mon, Dec 13, 2010 at 03:27:06PM +0000, Stefan Hajnoczi wrote:
>> On Mon, Dec 13, 2010 at 1:36 PM, Michael S. Tsirkin <address@hidden> wrote:
>> > On Mon, Dec 13, 2010 at 03:35:38PM +0200, Michael S. Tsirkin wrote:
>> >> On Mon, Dec 13, 2010 at 01:11:27PM +0000, Stefan Hajnoczi wrote:
>> >> > Fresh results:
>> >> >
>> >> > 192.168.0.1 - host (runs netperf)
>> >> > 192.168.0.2 - guest (runs netserver)
>> >> >
>> >> > host$ src/netperf -H 192.168.0.2 -- -m 200
>> >> >
>> >> > ioeventfd=on
>> >> > TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.0.2
>> >> > (192.168.0.2) port 0 AF_INET
>> >> > Recv   Send    Send
>> >> > Socket Socket  Message  Elapsed
>> >> > Size   Size    Size     Time     Throughput
>> >> > bytes  bytes   bytes    secs.    10^6bits/sec
>> >> >  87380  16384    200    10.00    1759.25
>> >> >
>> >> > ioeventfd=off
>> >> > TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.0.2
>> >> > (192.168.0.2) port 0 AF_INET
>> >> > Recv   Send    Send
>> >> > Socket Socket  Message  Elapsed
>> >> > Size   Size    Size     Time     Throughput
>> >> > bytes  bytes   bytes    secs.    10^6bits/sec
>> >> >
>> >> >  87380  16384    200    10.00    1757.15
>> >> >
>> >> > The results vary approx +/- 3% between runs.
>> >> >
>> >> > Invocation:
>> >> > $ x86_64-softmmu/qemu-system-x86_64 -m 4096 -enable-kvm -netdev
>> >> > type=tap,id=net0,ifname=tap0,script=no,downscript=no -device
>> >> > virtio-net-pci,netdev=net0,ioeventfd=on|off -vnc :0 -drive
>> >> > if=virtio,cache=none,file=$HOME/rhel6-autobench-raw.img
>> >> >
>> >> > I am running qemu.git with v5 patches, based off
>> >> > 36888c6335422f07bbc50bf3443a39f24b90c7c6.
>> >> >
>> >> > Host:
>> >> > 1 Quad-Core AMD Opteron(tm) Processor 2350 @ 2 GHz
>> >> > 8 GB RAM
>> >> > RHEL 6 host
>> >> >
>> >> > Next I will try the patches on latest qemu-kvm.git
>> >> >
>> >> > Stefan
>> >>
>> >> One interesting thing is that I put virtio-net earlier on
>> >> command line.
>> >
>> > Sorry I mean I put it after disk, you put it before.
>>
>> I can't find a measurable difference when swapping -drive and -netdev.
>
> One other concern I have is that we are apparently using
> ioeventfd for all VQs. E.g. for virtio-net we probably should not
> use it for the control VQ - it's a waste of resources.

One option is a per-device (block, net, etc) bitmap that masks out
virtqueues.  Is that something you'd like to see?

I'm tempted to mask out the RX vq too and see how that affects the
qemu-kvm.git specific issue.

Stefan