isolcpus and taskset for multithreaded executor

[hyos]

README.md suggests using isolcpus=2,3 and gives an example of how to run a single-threaded executor on CPU2 by taskset -c 2.

But there is a problem when someone wants to test a multi-threaded executor. isolcpus basically disables load balancing, so a process can use only one CPU even if ran with taskset -c 2,3. For a process to use multiple isolated CPUs, RT priority class (e.g., SCHED_FIFO) is needed since the Linux RT scheduler performs like a global work-conserving scheduler for all assigned CPUs. In short, we need something like:

taskset -c 2,3 chrt -f 90 <path_to_multithreaded_executor>

I guess colcon test scripts need to be updated so that, when TEST_PLATFORM is enabled, it runs executors with taskset and chrt.

[razr]

@hyos do you want to provide a PR for it?

[hyos]

@razr I am not sure exactly which part of the script needs to be modified. Can someone help?

[flynneva]

@hyos @razr it should be the command within the cmake scripts either in the generate_traces.cmake script in the cmake directory or in the main CMake file of autoware_reference_system.

I think the right way to implement this would be to add a cmake arg to enable / disable the use of it.

I can look into this tomorrow if no ones implemented it by then