On Thu, 2010-07-22 at 19:53 -0400, Balachandar wrote: > I am resending this email as Freddie didn't use 'reply to all' when > replying to this message. I am also updating to answer Freddie's > questions.. > > I can see that virtio network performance is poorer than emaulated > e1000 nic. I did some simple ping test and with emulated e1000 the > average rtt is around 600 microsec. With virtio the average rtt is 800 > microsec. I am using a tap + bridge configuration. I run kvm as > follows > > kvm -m 512 -hda vdisk.img \ > -net nic,model=virtio \ > -net tap,ifname=tap0,script=qemu-ifup,downscript=no With newer qemu-kvm, you need to use -netdev tap to enable checksum/gso offloads. Try -net nic,model=virtio,netdev=tap0 -netdev tap,ifname=tap0,id=tap0,vhost=on,script=qemu-ifup,downscript=no Thanks Sridhar > > I am running Debian squeeze distribution with guest and host kernel 2.6.34. > > Does anyone else see some results like this or is it only me? Could > changing the distribution help as i am running a testing one? > > Actually we are having a custom application which just measures > ping-pong latency. The results that i get with virtio is around 750 > micro seconds. The result i get with emulated e1000 is around 250 > micro sec. Also i tried to use vhost but the virtio latency remained > the same. > > Also i tried the tests with guest and host 2.6.26 kernel. I get better > results for virtio than e1000. I get 550 for e1000 and 500 for virtio. > > Actually my application needs as minimum latency as needed. I am ready > to trade-off throughput and cpu utilization. I was very excited when i > saw the vhost-net module with people claiming low latencies. I am > worried that i am missing some performance offered by virtio and > vhost. > > > Thanks, > Bala > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
