Goroutines don't map directly to OS threads though, do they? So in practice it only matters for "hard" threads. I have no idea about what the Go scheduler looks

Goroutines don't map directly to OS threads though, do they? So in practice it only matters for "hard" threads. I have no idea about what the Go scheduler looks like though, so I can't say if there's a direct relation between the two (coroutine stack vs. thread stack). Also the default pthread stack size is (usually) 2MB which is indeed non negligible if you have a ton of threads, but with pthread_attr_setstacksize you can lower it. I can't seem to find the actual minimal size at the moment but I have a vague memory that you can reduce it to 16kB portably. I'm currently working on a multithreaded Rust program with a bunch of threads and strong memory constraints and I use the runtime to reduce the stack to 64kB, it seems to work just fine. And again, given that the language is garbage collected I can't help but find it a bit amusing that they're being stingy with a few MB of VMEM per thread. I guess that frees virtual memory for use in the balasts!