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Date: Fri, 5 Dec 2014 15:36:57 -0800 From: Nick H <nickkvm@...il.com> To: Madhu Challa <challa@...ronetworks.com> Cc: netdev@...r.kernel.org Subject: Re: KVM vs Xen-PV netperf numbers Please do not top post.. Comments inline: On Fri, Dec 5, 2014 at 12:20 PM, Madhu Challa <challa@...ronetworks.com> wrote: > Could you please attach your kvm command line. If you are running ubuntu you > might also want to verify you have > > # To load the vhost_net module, which in some cases can speed up > # network performance, set VHOST_NET_ENABLED to 1. > VHOST_NET_ENABLED=1 > > in /etc/default/qemu-kvm sudo qemu-system-x86_64 -hda vdisk.img -smp 4 -netdev type=tap,vhost=on,script=/usr/bin/qemu-ifup,id=net0 -device virtio-net-pci,netdev=net0,mac=00:AD:44:44:CB:02 -m 8192 N > > Thanks. > > On Fri, Dec 5, 2014 at 12:02 PM, Nick H <nickkvm@...il.com> wrote: >> >> Hello >> >> Not sure I have the right audience, I have two VM's on similar hosts. >> One VM is KVM + virtio + vhost based while other is Xen PV with xen >> netfront driver. Running a simple netperf test for 1400 byte packets >> on both VM's, I see wider difference between throughput as follows. >> >> Xen-pv throughput comes to : >> >> ./netperf -H 10.xx.xx.49 -l 20 -t UDP_STREAM -- -m 1400 >> MIGRATED UDP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to >> 10.xx.xx.49 (10.xx.xx.49) port 0 AF_INET : demo >> Socket Message Elapsed Messages >> Size Size Time Okay Errors Throughput >> bytes bytes secs # # 10^6bits/sec >> >> 212992 1400 20.00 1910549 0 1069.89 >> 262144 20.00 1704789 954.66 >> >> whereas KVM virtio number comes to : >> >> ./netperf -t UDP_STREAM -l 10 -H 10.xx.xx.49 -- -m 1400 >> MIGRATED UDP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to >> 10.xx.xx.49 (10.xx.xx.49) port 0 AF_INET : demo >> Socket Message Elapsed Messages >> Size Size Time Okay Errors Throughput >> bytes bytes secs # # 10^6bits/sec >> >> 212992 1400 10.00 155060 0 173.65 >> 262144 10.00 155060 173.65 >> >> I built a custom kernel where I simply free up the (UDP only) skb in >> virtio: xmit_skb() routine and I count how many skb's I have received. >> Surprisingly it was not too high either: >> >> ./netperf -t UDP_STREAM -l 10 -H 10.xx.xx.49 -- -m 1400 >> MIGRATED UDP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to >> 10.xx.xx.49 (10.xx.xx.49) port 0 AF_INET : demo >> Socket Message Elapsed Messages >> Size Size Time Okay Errors Throughput >> bytes bytes secs # # 10^6bits/sec >> >> 212992 1400 10.00 224792 0 251.74 >> 262144 10.00 0 0.00 >> >> >> 1910549 packets pumped in xen pv driver versus 212992 packets pumped >> in case of virtio driver. Assuming the data path inside the kernel is >> same for both drivers , and I have eliminated virtio's >> virtqueue_kick() call by freeing the packet ahead in my experiment, >> can all this overhead attributed to system call overhead in case of >> KVM+virtio combination ? Anything I am missing ? >> >> The KVM setup is based off: >> Linux ubn-nested 3.17.0+ #16 SMP Thu Dec 4 12:00:09 PST 2014 x86_64 >> x86_64 x86_64 GNU/Linux >> >> Regards >> N >> -- >> To unsubscribe from this list: send the line "unsubscribe netdev" in >> the body of a message to majordomo@...r.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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