4.2.4. Performance Tuning

Slow packet processing

  • Packet processing performance is not as high as expected.
  • Follow the advice provided in fast-path.sh config -i when using the advanced configuration.
  • If running in a VM, check that the qemu instance handling your VM is pinned on specific cores. See CPU Pinning for VMs section for details.

Performance drop with Mellanox ConnectX-3 devices

  • Packet processing is slower than expected
  • On Dell and SuperMicro servers, PCI read buffer may be misconfigured for ConnectX-3/ConnectX-3-Pro NICs. Check the output of setpci -s <NIC_PCI_address> 68.w. For instance:

    # lspci | grep Mellanox
    04:00.0 Ethernet controller: Mellanox Technologies MT27520 Family [ConnectX-3 Pro]
    # setpci -s 04:00.0 68.w


    Beware with the following command, it is known to cause spontaneous reboot on some systems.

    If the value is below 0x5020 (here that’s the case), set it to 0x5020:

    # setpci -s 04:00.0 68.w=5020