2.3. Test Methodology

2.3.1. Multi-Core and Multi-Threading

Intel Hyper-Threading - CSIT rls1804 performance tests are executed with SUT servers’ Intel XEON processors configured in Intel Hyper-Threading Disabled mode (BIOS setting). This is the simplest configuration used to establish baseline single-thread single-core application packet processing and forwarding performance. Subsequent releases of CSIT will add performance tests with Intel Hyper-Threading Enabled (requires BIOS settings change and hard reboot of server).

Multi-core Tests - CSIT rls1804 multi-core tests are executed in the following VPP thread and core configurations:

  1. 1t1c - 1 VPP worker thread on 1 CPU physical core.
  2. 2t2c - 2 VPP worker threads on 2 CPU physical cores.
  3. 4t4c - 4 VPP worker threads on 4 CPU physical cores.

VPP worker threads are the data plane threads. VPP control thread is running on a separate non-isolated core together with other Linux processes. Note that in quite a few test cases running VPP workers on 2 or 4 physical cores hits the I/O bandwidth or packets-per-second limit of tested NIC.

Section throughput_speedup_multi_core includes a set of graphs illustrating packet throughout speedup when running VPP on multiple cores.

2.3.2. Packet Throughput

Following values are measured and reported for packet throughput tests:

  • NDR binary search per RFC 2544:
    • Packet rate: “RATE: <aggregate packet rate in packets-per-second> pps (2x <per direction packets-per-second>)”;
    • Aggregate bandwidth: “BANDWIDTH: <aggregate bandwidth in Gigabits per second> Gbps (untagged)”;
  • PDR binary search per RFC 2544:
    • Packet rate: “RATE: <aggregate packet rate in packets-per-second> pps (2x <per direction packets-per-second>)”;
    • Aggregate bandwidth: “BANDWIDTH: <aggregate bandwidth in Gigabits per second> Gbps (untagged)”;
    • Packet loss tolerance: “LOSS_ACCEPTANCE <accepted percentage of packets lost at PDR rate>”;
  • NDR and PDR are measured for the following L2 frame sizes (untagged Ethernet):
    • IPv4 payload: 64B, IMIX_v4_1 (28x64B,16x570B,4x1518B), 1518B, 9000B;
    • IPv6 payload: 78B, 1518B, 9000B;
  • NDR and PDR binary search resolution is determined by the final value of the rate change, referred to as the final step:
    • The final step is set to 50kpps for all NIC to NIC tests and all L2 frame sizes except 9000B (changed from 100kpps used in previous releases).
    • The final step is set to 10kpps for all remaining tests, including 9000B and all vhost VM and memif Container tests.

All rates are reported from external Traffic Generator perspective.

2.3.3. Maximum Receive Rate (MRR)

MRR tests measure the packet forwarding rate under the maximum load offered by traffic generator over a set trial duration, regardless of packet loss. Maximum load for specified Ethernet frame size is set to the bi-directional link rate.

Current parameters for MRR tests:

  • Ethernet frame sizes: 64B (78B for IPv6 tests) for all tests, IMIX for selected tests (vhost, memif); all quoted sizes include frame CRC, but exclude per frame transmission overhead of 20B (preamble, inter frame gap).
  • Maximum load offered: 10GE and 40GE link (sub-)rates depending on NIC tested, with the actual packet rate depending on frame size, transmission overhead and traffic generator NIC forwarding capacity.
    • For 10GE NICs the maximum packet rate load is 2* 14.88 Mpps for 64B, a 10GE bi-directional link rate.
    • For 40GE NICs the maximum packet rate load is 2* 18.75 Mpps for 64B, a 40GE bi-directional link sub-rate limited by TG 40GE NIC used, XL710.
  • Trial duration: 10sec.

Similarly to NDR/PDR throughput tests, MRR test should be reporting bi- directional link rate (or NIC rate, if lower) if tested VPP configuration can handle the packet rate higher than bi-directional link rate, e.g. large packet tests and/or multi-core tests.

MRR tests are used for continuous performance trending and for comparison between releases.

2.3.4. Packet Latency

TRex Traffic Generator (TG) is used for measuring latency of VPP DUTs. Reported latency values are measured using following methodology:

  • Latency tests are performed at 10%, 50% of discovered NDR rate (non drop rate) for each NDR throughput test and packet size (except IMIX).
  • TG sends dedicated latency streams, one per direction, each at the rate of 10kpps at the prescribed packet size; these are sent in addition to the main load streams.
  • TG reports min/avg/max latency values per stream direction, hence two sets of latency values are reported per test case; future release of TRex is expected to report latency percentiles.
  • Reported latency values are aggregate across two SUTs due to three node topology used for all performance tests; for per SUT latency, reported value should be divided by two.
  • 1usec is the measurement accuracy advertised by TRex TG for the setup used in FD.io labs used by CSIT project.
  • TRex setup introduces an always-on error of about 2*2usec per latency flow - additonal Tx/Rx interface latency induced by TRex SW writing and reading packet timestamps on CPU cores without HW acceleration on NICs closer to the interface line.

2.3.5. vhostuser with KVM VMs

FD.io CSIT performance lab is testing VPP vhost with KVM VMs using following environment settings:

  • Tests with varying Qemu virtio queue (a.k.a. vring) sizes: [vr256] default 256 descriptors, [vr1024] 1024 descriptors to optimize for packet throughput.
  • Tests with varying Linux CFS settings: [cfs] default settings, [cfsrr1] CFS RoundRobin(1) policy applied to all data plane threads handling test packet path including all VPP worker threads and all Qemu testpmd poll-mode threads.
  • Resulting test cases are all combinations with [vr256,vr1024] and [cfs,cfsrr1] settings.
  • Adjusted Linux kernel CFS scheduler policy for data plane threads used in CSIT is documented in CSIT Performance Environment Tuning wiki. The purpose is to verify performance impact (MRR and NDR/PDR throughput) and same test measurements repeatability, by making VPP and VM data plane threads less susceptible to other Linux OS system tasks hijacking CPU cores running those data plane threads.

2.3.6. Memif with LXC and Docker Containers

CSIT rls1804 includes tests taking advantage of VPP memif virtual interface (shared memory interface) to interconnect VPP running in Containers. VPP vswitch instance runs in bare-metal user-mode handling NIC interfaces and connecting over memif (Slave side) to VPPs running in Linux Container or in Docker Container (DRC) configured with memif (Master side). LXCs and DRCs run in a priviliged mode with VPP data plane worker threads pinned to dedicated physical CPU cores per usual CSIT practice. All VPP instances run the same version of software. This test topology is equivalent to existing tests with vhost-user and VMs as described earlier in Tested Physical Topologies.

More information about CSIT LXC and DRC setup and control is available in Container Orchestration in CSIT.

2.3.7. Memif with K8s Pods/Containers

CSIT rls1804 includes tests of VPP topologies running in K8s orchestrated Pods/Containers and connected over memif virtual interfaces. In order to provide simple topology coding flexibility and extensibility container orchestration is done with Kubernetes using Docker images for all container applications including VPP. Ligato is used for the Pod/Container networking orchestration that is integrated with K8s, including memif support.

In these tests VPP vswitch runs in a K8s Pod with Docker Container (DRC) handling NIC interfaces and connecting over memif to more instances of VPP running in Pods/DRCs. All DRCs run in a priviliged mode with VPP data plane worker threads pinned to dedicated physical CPU cores per usual CSIT practice. All VPP instances run the same version of software. This test topology is equivalent to existing tests with vhost-user and VMs as described earlier in Tested Physical Topologies.

Further documentation is available in Container Orchestration in CSIT.

2.3.8. IPSec with Intel QAT HW cards

VPP IPSec performance tests are using DPDK cryptodev device driver in combination with HW cryptodev devices - Intel QAT 8950 50G - present in LF FD.io physical testbeds. DPDK cryptodev can be used for all IPSec data plane functions supported by VPP.

Currently CSIT rls1804 implements following IPSec test cases:

  • AES-GCM, CBC-SHA1 ciphers, in combination with IPv4 routed-forwarding with Intel xl710 NIC.
  • CBC-SHA1 ciphers, in combination with LISP-GPE overlay tunneling for IPv4-over-IPv4 with Intel xl710 NIC.

2.3.9. TRex Traffic Generator Usage

TRex traffic generator is used for all CSIT performance tests. TRex stateless mode is used to measure NDR and PDR throughputs using binary search (NDR and PDR discovery tests) and for quick checks of DUT performance against the reference NDRs (NDR check tests) for specific configuration.

TRex is installed and run on the TG compute node. The typical procedure is:

  • If the TRex is not already installed on TG, it is installed in the suite setup phase - see TRex intallation.

  • TRex configuration is set in its configuration file

    /etc/trex_cfg.yaml

  • TRex is started in the background mode

    $ sh -c 'cd <t-rex-install-dir>/scripts/ && sudo nohup ./t-rex-64 -i -c 7 --iom 0 > /tmp/trex.log 2>&1 &' > /dev/null

  • There are traffic streams dynamically prepared for each test, based on traffic profiles. The traffic is sent and the statistics obtained using trex_stl_lib.api.STLClient.

Measuring packet loss

  • Create an instance of STLClient
  • Connect to the client
  • Add all streams
  • Clear statistics
  • Send the traffic for defined time
  • Get the statistics

If there is a warm-up phase required, the traffic is sent also before test and the statistics are ignored.

Measuring latency

If measurement of latency is requested, two more packet streams are created (one for each direction) with TRex flow_stats parameter set to STLFlowLatencyStats. In that case, returned statistics will also include min/avg/max latency values.

2.3.10. TCP/IP tests with WRK tool

WRK HTTP benchmarking tool is used for experimental TCP/IP and HTTP tests of VPP TCP/IP stack and built-in static HTTP server. WRK has been chosen as it is capable of generating significant TCP/IP and HTTP loads by scaling number of threads across multi-core processors.

This in turn enables quite high scale benchmarking of the main TCP/IP and HTTP service including HTTP TCP/IP Connections-Per-Second (CPS), HTTP Requests-Per-Second and HTTP Bandwidth Throughput.

The initial tests are designed as follows:

  • HTTP and TCP/IP Connections-Per-Second (CPS)
    • WRK configured to use 8 threads across 8 cores, 1 thread per core.
    • Maximum of 50 concurrent connections across all WRK threads.
    • Timeout for server responses set to 5 seconds.
    • Test duration is 30 seconds.
    • Expected HTTP test sequence:
      • Single HTTP GET Request sent per open connection.
      • Connection close after valid HTTP reply.
      • Resulting flow sequence - 8 packets: >S,<S-A,>A,>Req,<Rep,>F,<F,> A.
  • HTTP Requests-Per-Second
    • WRK configured to use 8 threads across 8 cores, 1 thread per core.
    • Maximum of 50 concurrent connections across all WRK threads.
    • Timeout for server responses set to 5 seconds.
    • Test duration is 30 seconds.
    • Expected HTTP test sequence:
      • Multiple HTTP GET Requests sent in sequence per open connection.
      • Connection close after set test duration time.
      • Resulting flow sequence: >S,<S-A,>A,>Req[1],<Rep[1],..,>Req[n],<Rep[n],>F,<F,>A.