On Sun, Dec 12, 2010 at 9:09 PM, Michael S. Tsirkin <m...@redhat.com> wrote: > On Sun, Dec 12, 2010 at 10:56:34PM +0200, Michael S. Tsirkin wrote: >> On Sun, Dec 12, 2010 at 10:42:28PM +0200, Michael S. Tsirkin wrote: >> > On Sun, Dec 12, 2010 at 10:41:28PM +0200, Michael S. Tsirkin wrote: >> > > On Sun, Dec 12, 2010 at 03:02:04PM +0000, Stefan Hajnoczi wrote: >> > > > See below for the v5 changelog. >> > > > >> > > > Due to lack of connectivity I am sending from GMail. Git should >> > > > retain my >> > > > stefa...@linux.vnet.ibm.com From address. >> > > > >> > > > Virtqueue notify is currently handled synchronously in userspace >> > > > virtio. This >> > > > prevents the vcpu from executing guest code while hardware emulation >> > > > code >> > > > handles the notify. >> > > > >> > > > On systems that support KVM, the ioeventfd mechanism can be used to >> > > > make >> > > > virtqueue notify a lightweight exit by deferring hardware emulation to >> > > > the >> > > > iothread and allowing the VM to continue execution. This model is >> > > > similar to >> > > > how vhost receives virtqueue notifies. >> > > > >> > > > The result of this change is improved performance for userspace virtio >> > > > devices. >> > > > Virtio-blk throughput increases especially for multithreaded scenarios >> > > > and >> > > > virtio-net transmit throughput increases substantially. >> > > >> > > Interestingly, I see decreased throughput for small message >> > > host to get netperf runs. >> > > >> > > The command that I used was: >> > > netperf -H $vguest -- -m 200 >> > > >> > > And the results are: >> > > - with ioeventfd=off >> > > TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 11.0.0.104 >> > > (11.0.0.104) port 0 AF_INET : demo >> > > Recv Send Send Utilization Service >> > > Demand >> > > Socket Socket Message Elapsed Send Recv Send >> > > Recv >> > > Size Size Size Time Throughput local remote local >> > > remote >> > > bytes bytes bytes secs. 10^6bits/s % S % S us/KB >> > > us/KB >> > > >> > > 87380 16384 200 10.00 3035.48 15.50 99.30 6.695 >> > > 2.680 >> > > >> > > - with ioeventfd=on >> > > TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 11.0.0.104 >> > > (11.0.0.104) port 0 AF_INET : demo >> > > Recv Send Send Utilization Service >> > > Demand >> > > Socket Socket Message Elapsed Send Recv Send >> > > Recv >> > > Size Size Size Time Throughput local remote local >> > > remote >> > > bytes bytes bytes secs. 10^6bits/s % S % S us/KB >> > > us/KB >> > > >> > > 87380 16384 200 10.00 1770.95 18.16 51.65 13.442 >> > > 2.389 >> > > >> > > >> > > Do you see this behaviour too? >> > >> > Just a note: this is with the patchset ported to qemu-kvm. >> >> And just another note: the trend is reversed for larged messages, >> e.g. with 1.5k messages ioeventfd=on outputforms ioeventfd=off. > > Another datapoint where I see a regression is with 4000 byte messages > for guest to host traffic. > > ioeventfd=off > set_up_server could not establish a listen endpoint for port 12865 with > family AF_UNSPEC > TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 11.0.0.4 (11.0.0.4) > port 0 AF_INET : demo > Recv Send Send Utilization Service Demand > Socket Socket Message Elapsed Send Recv Send Recv > Size Size Size Time Throughput local remote local remote > bytes bytes bytes secs. 10^6bits/s % S % S us/KB us/KB > > 87380 16384 4000 10.00 7717.56 98.80 15.11 1.049 2.566 > > ioeventfd=on > TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 11.0.0.4 (11.0.0.4) > port 0 AF_INET : demo > Recv Send Send Utilization Service Demand > Socket Socket Message Elapsed Send Recv Send Recv > Size Size Size Time Throughput local remote local remote > bytes bytes bytes secs. 10^6bits/s % S % S us/KB us/KB > > 87380 16384 4000 10.00 3965.86 87.69 15.29 1.811 5.055
Interesting. I posted the following results in an earlier version of this patch: "Sridhar Samudrala <s...@us.ibm.com> collected the following data for virtio-net with 2.6.36-rc1 on the host and 2.6.34 on the guest. Guest to Host TCP_STREAM throughput(Mb/sec) ------------------------------------------- Msg Size vhost-net virtio-net virtio-net/ioeventfd 65536 12755 6430 7590 16384 8499 3084 5764 4096 4723 1578 3659" Here we got a throughput improvement where you got a regression. Your virtio-net ioeventfd=off throughput is much higher than what we got (different hardware and configuration, but still I didn't know that virtio-net reaches 7 Gbit/s!). I have focussed on the block side of things. Any thoughts about the virtio-net performance we're seeing? " 1024 1827 981 2060 Host to Guest TCP_STREAM throughput(Mb/sec) ------------------------------------------- Msg Size vhost-net virtio-net virtio-net/ioeventfd 65536 11156 5790 5853 16384 10787 5575 5691 4096 10452 5556 4277 1024 4437 3671 5277 Guest to Host TCP_RR latency(transactions/sec) ---------------------------------------------- Msg Size vhost-net virtio-net virtio-net/ioeventfd 1 9903 3459 3425 4096 7185 1931 1899 16384 6108 2102 1923 65536 3161 1610 1744" I'll also run the netperf tests you posted to check what I get. Stefan