4.2.3. Performance Tuning

Slow packet processing

Symptoms

  • Packet processing performance is not as high as expected.

Hints

  • 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

Symptoms:

  • Packet processing is slower than expected

Hints:

  • 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
202e

    Warning

    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