The Linux memory management code does its best to ensure that memory will always be available when some part of the system needs it. That effort notwithstanding, it is still possible for a system to reach a point where no memory is available. At that point, things can grind to a painful halt, with the only possible solution (other than rebooting the system) being to kill off processes until a sufficient amount of memory is freed up. That grim task falls to the out-of-memory (OOM) killer. Anybody who has ever had the OOM killer unleashed on a system knows that it does not always pick the best processes to kill, so it is not surprising that making the OOM killer smarter is a recurring theme in Linux virtual memory development.