A new, fast, lightweight mechanism for calling procedures between processes is available in Solaris: doors. Dorrs are a low-latency method of invoking a procedure in local process. A door server contains a thread that sleeps, waiting for an invocation for the door client. A client makes a call to the server through the door, along with a small (16 Kbyte) payload. When the call is made from a door client to a door server, scheduling control is passed directly to the thread in the door server. Once a door server is finished handling the request, it passes control and response back to the calling thread. The scheduling control allows ultra-low-latency turnaround because the client does not need to waint for the server thread to be scheduled to complete the request.