Per Thread Resources

Per Thread Resources #

CSIT test framework is managing mapping of the following resources per thread:

  1. Cores, physical cores (pcores) allocated as pairs of sibling logical cores (lcores) if server in HyperThreading/SMT mode, or as single lcores if server not in HyperThreading/SMT mode. Note that if server’s processors are running in HyperThreading/SMT mode sibling lcores are always used.
  2. Receive Queues (RxQ), packet receive queues allocated on each physical and logical interface tested.
  3. Transmit Queues(TxQ), packet transmit queues allocated on each physical and logical interface tested.

Approach to mapping per thread resources depends on the application/DUT tested (VPP or DPDK apps) and associated thread types, as follows:

  1. Data-plane workers, used for data-plane packet processing, when no feature workers present.

    • Cores: data-plane workers are typically tested in 1, 2 and 4 pcore configurations, running on single lcore per pcore or on sibling lcores per pcore. Result is a set of {T}t{C}c thread-core configurations, where{T} stands for a total number of threads (lcores), and {C} for a total number of pcores. Tested configurations are encoded in CSIT test case names, e.g. “1c”, “2c”, “4c”, and test tags “2T1C” (or “1T1C”), “4T2C” (or “2T2C”), “8T4C” (or “4T4C”).
    • Interface Receive Queues (RxQ): as of CSIT-2106 release, number of RxQs used on each physical or virtual interface is equal to the number of data-plane workers. In other words each worker has a dedicated RxQ on each interface tested. This ensures packet processing load to be equal for each worker, subject to RSS flow load balancing efficacy. Note: Before CSIT-2106 total number of RxQs across all interfaces of specific type was equal to the number of data-plane workers.
    • Interface Transmit Queues (TxQ): number of TxQs used on each physical or virtual interface is equal to the number of data-plane workers. In other words each worker has a dedicated TxQ on each interface tested.
    • Applies to VPP and DPDK Testpmd and L3Fwd.

  2. Data-plane and feature workers (e.g. IPsec async crypto workers), the latter dedicated to specific feature processing.

    • Cores: data-plane and feature workers are tested in 2, 3 and 4 pcore configurations, running on single lcore per pcore or on sibling lcores per pcore. This results in a two sets of thread-core combinations separated by “-”, {T}t{C}c-{T}t{C}c, with the leading set denoting total number of threads (lcores) and pcores used for data-plane workers, and the trailing set denoting total number of lcores and pcores used for feature workers. Accordingly, tested configurations are encoded in CSIT test case names, e.g. “1c-1c”, “1c-2c”, “1c-3c”, and test tags “2T1C_2T1C” (or “1T1C_1T1C”), “2T1C_4T2C” (or “1T1C_2T2C”), “2T1C_6T3C” (or “1T1C_3T3C”).
    • RxQ and TxQ: no RxQs and no TxQs are used by feature workers.
    • Applies to VPP only.

  3. Management/main worker, control plane and management.

    • Cores: single lcore.
    • RxQ: not used (VPP default behaviour).
    • TxQ: single TxQ per interface, allocated but not used (VPP default behaviour).
    • Applies to VPP only.

VPP Thread Configuration #

Mapping of cores and RxQs to VPP data-plane worker threads is done in the VPP startup.conf during test suite setup:

  1. corelist-workers <list_of_cores>: List of logical cores to run VPP data-plane workers and feature workers. The actual lcores' allocations depends on HyperThreading/SMT server configuration and per test core configuration.

    • For tests without feature workers, by default, all CPU cores configured in startup.conf are used for data-plane workers.
    • For tests with feature workers, CSIT code distributes lcores across data-plane and feature workers.

  2. num-rx-queues <value>: Number of Rx queues used per interface.

Mapping of TxQs to VPP data-plane worker threads uses the default VPP setting of one TxQ per interface per data-plane worker.

DPDK Thread Configuration #

Mapping of cores and RxQs to DPDK Testpmd/L3Fwd data-plane worker threads is done in the startup CLI:

  1. -l <list_of_cores> - List of logical cores to run DPDK application.
  2. nb-cores=<N> - Number of forwarding cores.
  3. rxq=<N> - Number of Rx queues used per interface.