0 Replies Latest reply on Jul 10, 2018 11:01 PM by keithbannister

    rx_fifo_errors and rx_dropped errors using VMA where CPU user less than 40%




      I'm getting rx_fifo errors and rx_dropped_errors receiving UDP packets. I have 8 applications each receiving ~8000 byte UDP packets from 7 different pieces of hardware with different IP addresses. The packet and data rate is identical for each application - totalling 440k packets/sec and 29 Gbit/sec respectively. The packets are all transmitted synchronously, at a rate of 2x8000 byte packets every 1.5 ms for each of 56 different hardware cards.


      In this mode, rx_dropped and rx_fifo_errors increased at a few tens of packets per second. Attached is a dump of what ethtool shows. vma_stats shows no dropped packets. Each application is bound with numactl to NUMA node 1 (which is is where the NIC is attached). top shows each core on that node is running at < 40% CPU. The switch shows no dropped packets.


      Libvma configuration as shown below. I had the same problem when not using libvma (i.e. vanilla linux kernel packet processing).


      Can anyone give me some hints on where to look to reduce the number of lost packets?


      Many thanks in advance,





      export VMA_MTU=9000 #don't need to set - should be intelligent but we'll set it anyway for now

      export VMA_RX_BUFS=32768 # number of buffers -each of 1xMTU. Default is 200000 = 1 GB!

      export VMA_RX_WRE=4096 # number work requests

      export VMA_RX_POLL=0 # Don't waste CPU time polling. WE don't  need to

      export VMA_TX_BUFS=256 # Dont need many of these, so make it smalle

      export VMA_TX_WRE=32 # Don't need to tx so make this small to save memory


      export VMA_MEM_ALLOC_TYPE=0

      export VMA_THREAD_MODE=0 # all socket processing is single threaded


      export VMA_CQ_KEEP_QP_FULL=0 # this does packet drops according ot the docs??

      export VMA_SPEC=throughput

      ban115@tethys:~$ lspci -v  | grep  -A 10 ellanox

      84:00.0 Ethernet controller: Mellanox Technologies MT27500 Family [ConnectX-3]

          Subsystem: Mellanox Technologies MT27500 Family [ConnectX-3]

          Flags: bus master, fast devsel, latency 0, IRQ 74, NUMA node 1

          Memory at c9800000 (64-bit, non-prefetchable) [size=1M]

          Memory at c9000000 (64-bit, prefetchable) [size=8M]

          Expansion ROM at <ignored> [disabled]

          Capabilities: <access denied>

          Kernel driver in use: mlx4_core

          Kernel modules: mlx4_core



      ban115@tethys:~$ numactl --hardware

      available: 2 nodes (0-1)

      node 0 cpus: 0 2 4 6 8 10 12 14

      node 0 size: 15968 MB

      node 0 free: 129 MB

      node 1 cpus: 1 3 5 7 9 11 13 15

      node 1 size: 16114 MB

      node 1 free: 2106 MB

      node distances:

      node   0   1

        0:  10  21

        1:  21  10