Bug in sleep() function - main thread work affecting sleep duration on running tasks

[algunion]

@dlakelan

In Julia as I understand it there’s sometimes confusing terminology. People talk about spawning threads with @spawn for example. Unless I’m mistaken:

1. @spawn creates tasks which can run on any thread
2. Thread migration was introduced a while back, maybe version 1.5 ish
3. If you create a task that can migrate you don’t really have control over what thread that task runs on

Given all of that, is the issue that if you have a high compute task and it gets scheduled onto thread number 1 everything borks? Or is it if you do computation in the task running the REPL it borks?

You are right - however, in the current scenario (MWE running with nthreads > 1), the actual behavior looks like a task spawned on a free and interactive thread is migrating to the main thread where intensive work is being done (I tested it even with 12 threads - the same result). Obviously, I am not saying that is literally what happens.

I am pretty confident that in the current MWEs scenario (both the one in OP and the sever related one) it is not just a misuse/misinterpretation of @spawn concept.

I think we agree that not having control over where a task will run doesn’t imply that the task will migrate to the most busy thread when it can migrate on any of the other 10 free threads. In the MWEs context, although migration is not actually happening, the responsivity of the tasks running on a different thread from the main thread is actually dependent on the main thread being free (however, keep in mind the MWE context - I am not saying that any task is behaving the same).