e1000 nic TCP performances

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