Write Buffer-Oriented Energy Reduction in the L1 Data Cache for Embedded Systems

Abstract

In resource-constrained embedded systems, on-chip cache memories play an important role in both performance and energy consumption. In contrast to read operations, scant regard has been paid to optimizing write operations even though the energy consumed by write operations in the data cache constitutes a large portion of the total energy consumption. Consequently, this paper proposes a write buffer-oriented (WO) cache architecture that reduces energy consumption in the L1 data cache. Observing that write operations are very likely to be merged in the write buffer because of their high localities, we construct the proposed WO cache architecture to utilize two schemes. First, the write operations update the write buffer but not the L1 data cache, which is updated later by the write buffer after the write operations are merged. Write merging significantly reduces write accesses to the data cache and, consequently, energy consumption. Second, we further reduce energy consumption in the write buffer by filtering out unnecessary read accesses to the write buffer using a read hit predictor. In this paper, we show that the proposed WO cache architecture is applicable to the conventional embedded processors that support both write-through and write-back policies. Further, the experimental results verify that the proposed cache architecture reduces energy consumption in data caches up to 14%