Reasons to spawn builtin threads vs tokio blocking tasks?

[willhansen]

Based on my current understanding, a blocking task is basically just a thread that can also yield control with await (probably not as fast as non-blocking tasks, because it is its own thread), and also have await called on its join.

I'm only seeing upsides here. If I'm already using non-blocking tasks for stuff, is there any reason to use a built-in thread rather than a blocking task?

[Darksonn]

When you use spawn_blocking, that uses up one of the threads in the spawn_blocking threadpool. For threads that just hang around forever, you shouldn't do this, because you are essentially reducing the limit on the threadpool size by one.

[willhansen]

But that limit is "very large by default" (512), and also configurable at the runtime level. That seems less like a "reason not to do it" and more like a "thing to keep in mind if you're doing something crazy" type of thing.