AGDM: An Adaptive Granularity Data Migration Strategy for Hybrid Memory Systems

Hybrid memory systems show strong potential to satisfy the growing memory demands of modern applications by combining different memory technologies. Due to the different performance characteristics of hybrid memories, a data migration strategy that migrates hot data to a faster memory is critical to the overall performance. Prior works have focused on identifying hot data and migration decisions. However, we find that the fix-sized global migration granularity in existing data migration schemes results in suboptimal performance on most workloads. The key observation is that the optimal migration granularity varies with access patterns. This paper proposes AGDM, an access-pattern-aware Adaptive Granularity Data Migration strategy for hybrid memory systems. AGDM tracks memory access patterns in runtime and accordingly adopts the most appropriate migration mode and granularity. The novel remapping-migration decoupled metadata organization enables AGDM to set local optimal gran-ularities for memory regions with different access patterns. Our evaluation shows that, compared to the state-of-the-art scheme, AGDM gets an average performance improvement of 20.06% with 29.98% energy savings.