> What if I e.g. want to call a library that is known to be non-blocking, or make a syscall that is non-blocking which is not pre-wrapped by the Java standard library?
My understanding is that pinning only enters the equation if you need to yield while a native frame is on the stack. If that call is non-blocking, then by definition you'll call into it and return without needing to yield the current task.
A non-blocking call should give you some way to tell when the job you've requested has completed, of course, and then you need to either poll for it or arrange to be told when it's done. You don't want to spinlock in a virtual thread (you're just hogging an OS thread continuously, which is exactly what pinning is), so either way, you'll end up blocking -- but as long as you're blocking after returning from the native call, you should be fine.
> Does that mean any kind of native code is currently paying some extra cost due to the possibility of being blocking?
I have no special insight, but I imagine any costs are only incurred if a yield actually occurs with native code on the stack. Only then would the yield logic pin the current task to the current thread.
My understanding is that pinning only enters the equation if you need to yield while a native frame is on the stack. If that call is non-blocking, then by definition you'll call into it and return without needing to yield the current task.
A non-blocking call should give you some way to tell when the job you've requested has completed, of course, and then you need to either poll for it or arrange to be told when it's done. You don't want to spinlock in a virtual thread (you're just hogging an OS thread continuously, which is exactly what pinning is), so either way, you'll end up blocking -- but as long as you're blocking after returning from the native call, you should be fine.
> Does that mean any kind of native code is currently paying some extra cost due to the possibility of being blocking?
I have no special insight, but I imagine any costs are only incurred if a yield actually occurs with native code on the stack. Only then would the yield logic pin the current task to the current thread.