[Qemu-devel] [Bug 1066055] [NEW] Network performance regression with vde_switch

[Edivaldo de Araujo Pereira]

Public bug reported:

I've noticed a significant network performance regression when using
vde_switch, starting about one week ago (10/05/2012); before that date,
I used to get about 1.5 Gbits host to guest, but now I can only get
about 320 Mbits; I didn't find any modification in net/vde.*, just in
hw/virtio*.

My command line: 
 qemu-system-i386 -cdrom /bpd/bpd.iso -m 512 -boot d -enable-kvm \
  -localtime -ctrl-grab -usbdevice tablet \
  -device 
virtio-net-pci,mac=52:54:00:18:01:01,netdev=vde0,tx=bh,ioeventfd=on,x-txburst=32
 \
  -netdev vde,id=vde0 -vga std -tb-size 2M -cpu host -clock unix

My host runs a kernel 3.6.1 and my guest runs a kernel 3.5.4; the same
problem happens with other host and guest versions, too.

I know there are better ways of running a guest, but using vde I get a
cleaner environment in the host (just one tun/tap interface to
manage...), which is quite good when running some accademic experiments.

Interestingly, at the same time I've noticed a performance enhancement
of about 25~30 % when using a tun/tap interface, bridged or not.

Thank you, very much.

Edivaldo de Araujo Pereira

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1066055

Title:
  Network performance regression with vde_switch

Status in QEMU:
  New

Bug description:
  I've noticed a significant network performance regression when using
  vde_switch, starting about one week ago (10/05/2012); before that
  date, I used to get about 1.5 Gbits host to guest, but now I can only
  get about 320 Mbits; I didn't find any modification in net/vde.*, just
  in hw/virtio*.

  My command line: 
   qemu-system-i386 -cdrom /bpd/bpd.iso -m 512 -boot d -enable-kvm \
    -localtime -ctrl-grab -usbdevice tablet \
    -device 
virtio-net-pci,mac=52:54:00:18:01:01,netdev=vde0,tx=bh,ioeventfd=on,x-txburst=32
 \
    -netdev vde,id=vde0 -vga std -tb-size 2M -cpu host -clock unix

  My host runs a kernel 3.6.1 and my guest runs a kernel 3.5.4; the same
  problem happens with other host and guest versions, too.

  I know there are better ways of running a guest, but using vde I get a
  cleaner environment in the host (just one tun/tap interface to
  manage...), which is quite good when running some accademic
  experiments.

  Interestingly, at the same time I've noticed a performance enhancement
  of about 25~30 % when using a tun/tap interface, bridged or not.

  Thank you, very much.

  Edivaldo de Araujo Pereira

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