What is Real-time scheduling policy, memory locking?

A real-time scheduling policy (SCHED_FIFO or SCHED_RR in Linux) gives a thread a static priority above every ordinary thread: a runnable real-time thread preempts any ordinary one and, under SCHED_FIFO, runs without time slicing until it blocks, yields or is preempted by a higher priority. Memory locking (mlock, mlockall) keeps a process’s pages in physical memory: they are never paged out, and with MCL_FUTURE every page of every later mapping is made present when the mapping is created.