> you might be better off just offloading a synchronous op to a worker thread to not block the UI.
I believe it should be the answer. If your computations are tolerably fast, then you could do it without async, but if they are not, then it is better to use preemptive multitasking for them. The overhead on the kernel scheduler will be small, because you don't start 10k of threads concurrently eating CPU time. Probably the overhead of starting a thread doesn't matter either with long tasks. As a bonus you could also do blocking i/o operations without thinking about blocking.
I believe it should be the answer. If your computations are tolerably fast, then you could do it without async, but if they are not, then it is better to use preemptive multitasking for them. The overhead on the kernel scheduler will be small, because you don't start 10k of threads concurrently eating CPU time. Probably the overhead of starting a thread doesn't matter either with long tasks. As a bonus you could also do blocking i/o operations without thinking about blocking.