Exploring The Design Space Of Page Management For Multi-Tiered Memory Systems

With the arrival of tiered memory systems comprising various types of memory, such as DRAM and SCM, the operating system support for memory management is becoming increasingly important. However, the way that operating systems currently manage pages was designed under the assumption that all the memory has the same capabilities based on DRAM. This oversimplification leads to non-optimal memory usage in tiered memory systems. This study performs an in-depth analysis of page management schemes in the current Linux design extending NUMA to support systems equipped with both DRAM and SCM (Intel's DCPMM). In such multi-tiered memory systems, we find that the critical factor in performance is not only the access locality but also the access tier of memory. When considering both characteristics, there are several alternatives to page placement. However, current operating systems only prioritize access locality. This paper explores the design space of page management schemes, called AutoTiering, to use multi-tiered memory systems effectively. Our evaluation results show that our proposed techniques can significantly improve performance for various workloads, compared to the stock Linux kernel, by unlocking the potential of the multi-tiered memory hierarchy.