Rayon does not work well with the optick profiling and performance logging library

[vladkvit]

I made a sample repo (that contains a sample capture) to demonstrate the issue - https://github.com/vladkvit/test_rayon_optick

When rayon's par_iter() is used, none of the optick::event!() calls are logged from the spawned threads. I'm curious if this is an issue on the optick side or the rayon side, would love someone more knowledgeable to take a look.

FWIW, I also cross-posted the issue here - bombomby/optick-rs#9

[cuviper]

If optick is using thread-specific state, then it wouldn't surprise me at all that it fails to see inside the rayon thread-pool. I've never used it, but at a glance optick::start_capture() does look like it's only for the current thread.

You might be able to use a ThreadPoolBuilder::start_handler to turn it on, but it will probably still get confused about the hierarchy of events due to rayon's work-stealing. See also #915.