An Experimental Study on the Effect of Asymmetric Memory Latency of New Memory on Application Performance

As DRAM reaches its density limitation, various new memory technologies such as STT-RAM and PCM are emerging as contenders for next generation memory. As these new types of memory, which we refer to as New Memory (NM), are byte addressable and nonvolatile, they are anticipated to, partially or wholly, take on the role of main memory and storage. The goal of this study is to evaluate how the read/write latency gap between the DRAM and NM and the asymmetric read and write latency of NM will affect the performance of applications. To this end, using an in-house ARM based embedded system that allows us to individually adjust the read and write latency. First, we use controlled, synthetic workloads to evaluate the latency effects. The main finding here, among others, is that write latency has little effect on performance due to various hardware mechanisms employed in current cache hardware. We then run the Stream, LMbench and PARSEC 3.0 benchmarks that represent real life applications with various memory latency settings. We find that write latency has virtually no effect and the effect of read latency is limited only to applications with very low cache hit rates.