ixgbe unstable performance at 1Gb/s

[Charles <charles.vejnar@unige.ch>]

Hi,

I hope I am posting on the right mailing-list. If not, sorry; please redirect me
to the right place. Thanks.

I have a new motherboard with integrated Intel X540 10GBase-T. For now, I want
to use it at 1Gb/s.

The bandwidth is only of ~300 Mbit/s (with Iperf). It's actually very unstable
(always varies between 100 to 800 Mbit/s during the transfer).

If I do "ethtool -K eth1 ntuple on", things are a bit better but still very
unstable bandwidth. If I add the kernel parameter "pci=nomsi", everything is
fine (and normal, with the same performance, ~950 MBit/s, as a 1Gbit/s NIC).

I also run the set_irq_affinity.sh script, w/o noticing a difference.

The only weird thing I have found is with ethtoll -S eth1:

    tx_queue_0_packets: 304262
     tx_queue_1_packets: 0
     tx_queue_2_packets: 0
     tx_queue_3_packets: 1
     tx_queue_4_packets: 502939
     tx_queue_5_packets: 677967
     tx_queue_6_packets: 459869
     tx_queue_7_packets: 0
     tx_queue_8_packets: 0
     tx_queue_9_packets: 0
     tx_queue_10_packets: 632626
     tx_queue_11_packets: 1719870
     tx_queue_12_packets: 0
     tx_queue_13_packets: 449811
     tx_queue_14_packets: 0
.......

I am using ArchLinux with kernel 3.5.4. Please ask for more details.

Any help would be appreciated. Thanks

Charles