155. metrics

The Metrics implements a mechanism by which producers can publish numeric information for later querying by consumers. Here dpdk-procinfo process is the consumers. latency stats and bit rate are the two implements based on metrics lib.

The dpdk-procinfo process use new command line option “–metrics” to display metrics statistics.

Functionality:

  • The library will register ethdev Rx/Tx callbacks for each active port, queue combinations.
  • The library will register latency stats names with new metrics library.
  • Rx packets will be marked with time stamp on each sampling interval.
  • On Tx side, packets with time stamp will be considered for calculating the minimum, maximum, average latencies and also jitter.
  • Average latency is calculated using exponential weighted moving average method.
  • Minimum and maximum latencies will be low and high latency values observed so far.
  • Jitter calculation is done based on inter packet delay variation.

note: DPDK technical document refer to doc/guides/prog_guide/metrics_lib.rst

155.1. latency stats

Latency stats measures minimum, average and maximum latencies, and jitter in nano seconds.

155.2. bit rate

Calculates peak and average bit-rate statistics.

155.3. Prerequisites

2x Intel® 82599 (Niantic) NICs (2x 10GbE full duplex optical ports per NIC) plugged into the available PCIe Gen2 8-lane slots in two different configurations.

port topology diagram:

packet generator                         DUT
 .-----------.                      .-----------.
 | .-------. |                      | .-------. |
 | | portA | | <------------------> | | port0 | |
 | | portB | | <------------------> | | port1 | |
 | '-------' |                      | '-------' |
 |           |                      |    nic    |
 '-----------'                      '-----------'

155.4. Test content

155.4.1. latency stats

The idea behind the testing process is to send different frames number of different packets from packet generator to the DUT while these are being forwarded back by the app and measure some of statistics. These data are queried by the dpdk-proc app.

  • min_latencyy_ns
    • Minimum latency in nano seconds
  • max_latencyy_ns
    • Maximum latency in nano seconds
  • avg_latencyy_ns
    • Average latency in nano seconds
  • jittery_ns
    • Latency variation

155.4.2. bit rate

The idea behind the testing process is to send different frames number of different packets from packet generator to the DUT while these are being forwarded back by the app and measure some of statistics. These data are queried by the dpdk-proc app.

  • mean_bits_in
    • Average rx bits rate
  • mean_bits_out
    • Average tx bits rate
  • peak_bits_in
    • peak rx bits rate
  • peak_bits_out
    • peak tx bits rate
  • ewma_bits_in
    • Average inbound bit-rate (EWMA smoothed)
  • ewma_bits_out
    • Average outbound bit-rate (EWMA smoothed)

155.4.3. transmission packet format

UDP format:

[Ether()/IP()/UDP()/Raw('\0'*60)]

155.4.4. transmission Frames size

Then measure the forwarding throughput for different frame sizes.

Frame size(64/128/256/512/1024)

155.5. Test Case : test latency stats

  1. Connect two physical ports to traffic generator.

  2. bind two ports to igb_uio driver:

    ./tools/dpdk_nic_bind.py --bind=igb_uio 0000:xx:00.0 0000:xx:00.1
    
  3. Start testpmd, set it in io fwd mode:

    ./testpmd -c 0x30 -n 4  -- -i --latencystats=2
    testpmd> set fwd io
    testpmd> start
    
  4. Configure packet flow in packet generator.

  5. Use packet generator to send packets, continue traffic lasting several minitues.

  6. run dpdk-proc to get latency stats data, query data at a average interval and get 5 times data:

    ./app/dpdk-procinfo -- --metrics
    
  7. latency stats has no reference standard data, only check non-zero and logic reasonable value.

155.6. Test Case : test bit rate

  1. Connect two physical ports to traffic generator.

  2. bind two ports to igb_uio driver.

    ./tools/dpdk_nic_bind.py –bind=igb_uio 00:08.0 00:08.1

  3. Start testpmd, set it in io fwd mode:

    ./testpmd -c 0x30 -n 4  -- -i --bitrate-stats=2
    testpmd> set fwd io
    testpmd> start
    
  4. Configure packet flow in packet generator.

  5. Use packet generator to send packets, continue traffic lasting several minitues.

  6. run dpdk-proc to get latency stats data, query data at a average interval and get 5 times data:

    ./app/dpdk-procinfo -- --metrics
    
  7. Compare dpdk statistics data with packet generator statistics data.

155.7. Test Case : test bit rate peak value

  1. Connect two physical ports to traffic generator.

  2. bind two ports to igb_uio driver:

    ./tools/dpdk_nic_bind.py --bind=igb_uio 00:08.0 00:08.1
    
  3. Start testpmd, set it in io fwd mode:

    ./testpmd -c 0x30 -n 4  -- -i --bitrate-stats=2
    testpmd> set fwd io
    testpmd> start
    
  4. Configure packet flow in packet generator.

  5. Use packet generator to send packets, continue traffic lasting several minitues.

  6. run dpdk-proc to get latency stats data, query data at a average interval and get 5 times data:

    ./app/dpdk-procinfo -- --metrics
    
  7. decline packet generator rate percent from 100%/80%/60%/20%, loop step 5/6.

  8. check peak_bits_out/peak_bits_in should keep the first max value when packet generator work with decreasing traffic rate percent.