Phoenix: A Dynamically Reconfigurable Hybrid Memory System Combining Caching and Migration

Abstract: With the growing memory requirements of modern data-intensive applications for high performance and large capacity, building hybrid memory systems with different memory technologies has become a dominant trend to satisfy these demands. For better system performance, frequently accessed hot data is fetched into the fast and capacity-limited near memory (NM) while cold data is evicted to the slow and large far memory (FM). In prior works, NM is used as a cache of FM (cNM), part of OS-visible memory (mNM), and a fixed capacity of cNM and mNM. This paper presents Phoenix, a novel hybrid memory architecture that harnesses the advantages of both cNM and mNM. The ratio of cNM to mNM is adjustable during runtime to better exploit both temporal and spatial locality benefits for different memory access patterns. All cNM and mNM space is multiplexed to mitigate the data movement overhead for the mode switch between cNM and mNM. In our evaluations, Phoenix outperforms state-of-the-art designs by an average of 18.2% and consumes orders of magnitude less metadata storage space.