A memory interface includes a buffer for storing requests for accessing a volatile memory, which includes at least two ranks of memory cell of a memory channel The memory interface monitors the requests to access each rank in the buffer. Upon detecting from the requests that a given rank of the at least two ranks is to be idle for a time period exceeding a time threshold, the circuitry signals a controller to command the given rank to enter a self-refresh mode independent of a refresh mode of other ranks. The memory interface is coupled to a processor, which executes an operating system (OS) kernel to prioritize memory allocation from a prioritized rank of the at least two ranks over the given rank, and migrates allocated memory blocks from the given rank to the prioritized rank to increase a probability of idleness of the given rank.