On Mon, Jul 14, 2014 at 10:44:58AM +0000, Wangkai (Kevin,C) wrote: > Here the detail network: > > +--------------------------------------------+ > | The host add tap1 and eth10 to bridge 'br1'| +--------+ > | +------------+ | | send | > | | VM eth1-+-tap1 --- bridge --- eth10 --+---------------------+ packets| > | +------------+ | | | > +--------------------------------------------+ +--------+ > > Qemu start vm by virtio, use tap interface, option is: > -net nic,vlan=101, model=virtio -net > tap,vlan=101,ifname=tap1,script=no,downscript=no
Use the newer -netdev/-device syntax to get offload support and slightly better performance: -netdev tap,id=tap0,ifname=tap1,script=no,downscript=no \ -device virtio-net-pci,netdev=tap0 > And add tap1 and eth10 to bridge br1 in the host: > Brctl addif br1 tap1 > Brctl addif br1 eth10 > > total recv 505387 time 2000925 us: > means call tap_send once dealing 505387 packets, the packet payload was 300 > bytes, and > time use for tap_send() was 2,000,925 micro-seconds, time was measured by > record time stamp > at function tap_send() start and end. > > We just test the performance of VM. That is 150 MB of incoming packets in a single tap_send(). Network rx queues are maybe a few 1000 packets so I wonder what is going on here. Maybe more packets are arriving while QEMU is reading them and we keep looping. That's strange though because the virtio-net rx virtqueue should fill up (it only has 256 entries). Can you investigate more and find out exactly what is going on? It's not clear yet that adding a budget is the solution or just hiding a deeper problem. Stefan
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