MAC: Migration-aware compilation for STT-RAM based hybrid cache in embedded systems

Hybrid caches consisting of both STT-RAM and SRAM have been proposed recently for energy efficiency. To explore the advantages of hybrid cache, most work on hybrid caches employs migration based strategies to dynamically move write-intensive data from STT-RAM to SRAM. Migrations require additional read and write operations for data movement and may lead to significant overheads. To address this issue, this paper proposes a Migration-Aware Compilation (MAC) approach to improve the energy efficiency and performance of STT-RAM based hybrid cache. By re-arranging data layout, the data access pattern in memory blocks is changed such that the number of migrations is reduced without any hardware modification. The reduction of migration overheads in turn improves energy efficiency and performance. The experimental results show that with the proposed approach, on average, the number of write operations on STT-RAM is reduced by 13.4%, the number of migrations is reduced by 16.1%, the total dynamic energy is reduced by 8.5%, and the total latency is reduced by 12.1%.