A system monitors and dynamically changes memory mapping in a runtime of a computing system. The computing system has various memory resources, and multiple possible mappings that indicate how data is to be stored in and subsequently accessed from the memory resources. The performance of each memory mapping may be different under different runtime or load conditions of the computing device. A memory controller can monitor runtime performance of the current memory mapping and dynamically change memory mappings at runtime based on monitored or observed performance of the memory mappings. The performance monitoring can be modified for any of a number of different granularities possible within the system, from the byte level to memory channel.