An asynchronous interrupt would be more expensive, but if you can send it to another core, you do not need to pay the cost on this core, in particular you do no

An asynchronous interrupt would be more expensive, but if you can send it to another core, you do not need to pay the cost on this core, in particular you do not need to enter the kernel. This is particularly useful for remote wakeups when you want to schedule a thread on an another core. As I mentioned elsewhere, intel was planning to add user-mode interrupts specifically for this sort of scenarios.