[dpdk-users] vhost-user dequeue-zero-copy only works on virtio-0.9/0.95

["Chen, Junjie J" <junjie.j.chen@intel.com>]

Hi

We met a strange issue when using dequeue-zero-copy feature in VM2VM performance test, dequeue-zero-copy feature ONLY works fine along with Qemu version < 2.7. After some investigation, we found actually the feature works fine with virtio-0.9, with Qemu version >= 2.7, we can set -disable-legacy=off,disable-modern=on to make it work.  Any idea on this? Thanks in advanced.

Following are commands I use.

Testpmd:
./x86_64-native-linuxapp-gcc/app/testpmd -c 0xe -n 4 --socket-mem 1024,1024 --vdev 'eth_vhost0,iface=/tmp/vhost-net,queues=1,dequeue-zero-copy=1' --vdev 'eth_vhost1,iface=/tmp/vhost-net1,queues=1,dequeue-zero-copy=1' -- -i --nb-cores=1

Vm1:
./x86_64-softmmu/qemu-system-x86_64 -name vm0 -enable-kvm \
    -chardev socket,path=/tmp/vm0_qga0.sock,server,nowait,id=vm0_qga0 \
    -device virtio-serial -device virtserialport,chardev=vm0_qga0,name=org.qemu.guest_agent.0 \
    -daemonize -monitor unix:/tmp/vm0_monitor.sock,server,nowait \
    -net nic,vlan=0,macaddr=00:00:00:ef:58:4f,addr=1f \
    -net user,vlan=0,hostfwd=tcp:10.67.111.120:6093-:22 \
    -chardev socket,id=char0,path=/tmp/vhost-net \
    -netdev type=vhost-user,id=netdev0,chardev=char0,vhostforce \
    -device virtio-net-pci,netdev=netdev0,mac=52:54:00:00:00:01,disable-legacy=on,disable-modern=off \
    -cpu host \
    -smp 1 \
    -m 2048 \
    -object memory-backend-file,id=mem,size=2048M,mem-path=/mnt/huge_1GB,share=on \
    -numa node,memdev=mem \
    -mem-prealloc \
    -drive file=/root/vm-img/ubuntu.qcow2-1 \
    -vnc :4

Vm2:
./x86_64-softmmu/qemu-system-x86_64 -name vm1 -enable-kvm \
    -chardev socket,path=/tmp/vm1_qga0.sock,server,nowait,id=vm1_qga0 \
    -device virtio-serial -device virtserialport,chardev=vm1_qga0,name=org.qemu.guest_agent.0 \
    -daemonize -monitor unix:/tmp/vm1_monitor.sock,server,nowait \
    -net nic,vlan=0,macaddr=00:00:00:0b:81:d1,addr=1f \
    -net user,vlan=0,hostfwd=tcp:10.67.111.120:6133-:22 \
    -chardev socket,id=char0,path=/tmp/vhost-net1 \
    -netdev type=vhost-user,id=netdev0,chardev=char0,vhostforce \
    -device virtio-net-pci,netdev=netdev0,mac=52:54:00:00:00:02,disable-legacy=on,disable-modern=off \
    -cpu host \
    -smp 1 \
    -m 2048 \
    -object memory-backend-file,id=mem,size=2048M,mem-path=/mnt/huge_1GB,share=on \
    -numa node,memdev=mem \
    -mem-prealloc \
    -drive file=/root/vm-img/ubuntu.qcow2-2 \
    -vnc :5
Cheers
JJ