OAP: An obstruction-aware cache management policy for STT-RAM last-level caches

Emerging memory technologies are explored as potential alternatives to traditional SRAM/DRAM-based memory architecture in future microprocessor designs. Among various emerging memory technologies, Spin-Torque Transfer RAM (STT-RAM) has the benefits of fast read latency, low leakage power, and high density, and therefore has been investigated as a promising candidate for last-level cache (LLC)¹. One of the major disadvantages for STT-RAM is the latency and energy overhead associated with the write operations. In particular, a long-latency write operation to STT-RAM cache may obstruct other cache accesses and result in severe performance degradation. Consequently, mitigation techniques to minimize the write overhead are required in order to successfully adopt this new technology for cache design. In this paper, we propose an obstruction-aware cache management policy called OAP. OAP monitors the cache to periodically detect LLC-obstruction processes, and manage the cache accesses from different processes. The experimental results on a 4-core architecture with an 8MB STT-RAM L3 cache shows that the performance can be improved by 14% on average and up to 42%, with a reduction of energy consumption by 64%².