The present application is directed to a memory-access-multiplexing memory controller that can multiplex memory accesses from multiple hardware threads, cores, and processors according to externally specified policies or parameters, including policies or parameters set by management layers within a virtualized computer system. A memory-access-multiplexing memory controller provides, at the physical-hardware level, a basis for ensuring rational and policy-driven sharing of the memory-access resource among multiple hardware threads, cores, and/or processors.