It is not exactly async memory, but at the turn of the millennium a few unices experimented with scheduler activations: the kernel would upcall back into the ap

It is not exactly async memory, but at the turn of the millennium a few unices experimented with scheduler activations: the kernel would upcall back into the application whenever a thread would block for any reason, allowing rescheduling of the user space thread. In the end, the complexity wasn't worth it at the time, bit it is possible that something like that could be brought back in the fitire