A study of performance impact of memory controller features in multi-processor server environment

With the growing imbalance between processor and memory performance it becomes more and more important to optimize the memory controller features to obtain the maximum possible performance out of the memory subsystem. This paper presents a study of the performance impact of several memory controller features in multi-processor (MP) server environments that use a DDR/DDR2 based memory subsystem. The results from our studies show that significant performance improvements can be obtained by carefully optimizing the memory controller features. For instance, one of our studies shows that in a system with an in-order shared bus connecting the CPUs and memory controller, an intelligent read-to-write switching memory controller feature can provide the same order of benefit as doubling the number of interleaved memory ranks. Another study shows that much lower average loaded read latency across a wider range of throughput can be obtained by a delayed write scheduling feature.