Migration-aware loop retiming for STT-RAM based hybrid cache for embedded systems

Keni Qiu, Mengying Zhao, Chenchen Fu, Liang Shi, Chun Jason Xue

Abstract: In hybrid cache architecture consisting of both STT-RAM and SRAM, migration based techniques have been proposed. The migration technique dynamically moves write-intensive and read-intensive data between STT-RAM and SRAM to explore the advantage of hybrid cache. Meanwhile, migrations induce extra read and write overhead during data movements. For loops with intensive data array operations, we observe that migration overhead is significant and migrations closely correlate to the interleaved read and write access pattern in a memory block. This paper proposes a loop retiming framework to reduce the migration overhead by changing the interleaved memory access pattern. The experimental results show that with the proposed method, migrations are significantly reduced without any hardware modification. As a result, energy efficiency and performance of hybrid cache can be improved.