[kevincox]

> Is there a cost transferring stacks on virtual threads across platform threads?

You shouldn't need to "transfer" the stack. There isn't really a "platform stack", that is just whatever your stack pointer is pointing at. So it is perfectly fine to allocate many stacks and switch between them within one OS thread just by changing the stack pointer.

Of course if you are allocating a "full stack" then the main question is what is the point? IIUC the biggest cost of threads is the memory allocated to the stack. So unless you are doing something clever you don't get much benefit. There are many approaches here but I guess it is up to the runtime to pick one.

[aardvark179]

The largest cost is that you are allocating a fixed size stack, and that usually has to be big enough for whatever thread you might run. Virtual threads only have a stack as big as they require, and that’s likely to be fairly small. A lot of thought went into the foot print of virtual threads, we had long discussions about individual fields!