e1000 nic TCP performances

[Vincent Autefage]

Hi,

Here is the context :

$ qemu -name A -m 1024 -net nic vlan=0,model=e1000 -net socket,vlan=0,listen=127.0.0.1:7000
$ qemu -name B -m 1024 -net nic vlan=0,model=e1000 -net socket,vlan=0,connect=127.0.0.1:7000

The bandwidth is really tiny :

    . Iperf3 reports about 30 Mb/sec
    . NetPerf reports about 50 Mb/sec

With UDP sockets, there is no problem at all :

    . Iperf3 reports about 1 Gb/sec
    . NetPerf reports about 950 Mb/sec

I've noticed this fact only with the e1000 NIC, not with others (rtl8139,virtio, etc.)
I've used the main GIT version of QEMU.

Thanks in advance.

See you,
VInce

[Stefan Hajnoczi (stefanha)]

On Fri, Sep 20, 2013 at 05:21:23PM -0000, Vincent Autefage wrote:
> Here is the context :
>
> $ qemu -name A -m 1024 -net nic vlan=0,model=e1000 -net socket,vlan=0,listen=127.0.0.1:7000
> $ qemu -name B -m 1024 -net nic vlan=0,model=e1000 -net socket,vlan=0,connect=127.0.0.1:7000
>
> The bandwidth is really tiny :
>
> . Iperf3 reports about 30 Mb/sec
> . NetPerf reports about 50 Mb/sec
>
>
> With UDP sockets, there is no problem at all :
>
> . Iperf3 reports about 1 Gb/sec
> . NetPerf reports about 950 Mb/sec
>
>
> I've noticed this fact only with the e1000 NIC, not with others (rtl8139,virtio, etc.)
> I've used the main GIT version of QEMU.

It's interesting that you see good performance over -netdev socket TCP
with the other NIC models.

I don't know what the issue would be, you'll probably need to dig
further to discover the problem. Using wireshark might be a good start.
Try to figure out where the delay is incurred and then instrument that
code to find out the cause.

Stefan

[Thomas Huth (th-huth)]

Looking through old bug tickets... can you still reproduce this issue with the latest version of QEMU? Or could we close this ticket nowadays?

[Launchpad Janitor (janitor)]

[Expired for QEMU because there has been no activity for 60 days.]