ROS 2 Real-time Working Group Online Meeting 18 - May 26, 2020 - Meeting Minutes

Next Generation ROS
14

For 2020-August-18 Real-time Working Group

As I can not find the right place, let me report progress about “4.1 Performance testing (with an emphasis on determinism) in 2020-August-04” here.

In short words, we(ISP) are now surveying what is already done and what should be done.

We are surveying following:

[g3] is CI and uses [g1] internally.

They have some similarities and differences as below.

  • Each tool measures topic trip-time(pub -> sub)
    [g1] checks combination of DDS/RMW
    [g2] checks complex topology
  • Executor:
    • [g1] uses SingleThreadedExecutor.
      std::this_thread::sleep_until is used for publishers,
      Executor::spin_some is used for subscribers.
    • [g2] uses StaticSingleThreadedExecutor.
      This uses Executor::spin but has an original thread model.
  • Communication mechanism
    • [g1] uses only topic
    • [g2] uses topic/service but not action/pamameter.
  • Memory usage/Data model
    • [g1] allocates unique_ptr at first, and publishs it by reference
    • [g2] uses unique_ptr or shared_ptr according to option but make_unique/make_shared for each loop
    • Which are optimal for real-time? Or Should we use TLFSAllocator and MessageMemoryPoolStrategy?
  • and so on

We now preparing a comparison table.

At the same time, we should define conditions and metrics.
Following are described in some literatures:

  • conditions
    • HW setting
    • OS setting(kernel build, kernels threads, kernel parameters, …)
    • ROS2 process setting(memory/scheduling as in pendulum, affinity, …)
    • system stress
  • metrics
    • timer precision
      • [g1] and [g2] do not measure this
    • packet trip-time(1-way, 2-way)
      In ROS2, topic/service/action/(parameter) may be the targets.
      • only topic is common target now
    • time of procedures (may be callback in ros2)
      • [g1] [g2] has rather simple callback(only takes statistics)
    • each values should be worst execuion time (WCET)
      • need to measure at least a few hours.
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