Abstract
In a sectored cache, a cache line is divided into several subblocks. Each subblock is a basic coherence unit. In this way partial block invalidation can be done on the cache lines in order to eliminate false sharing on invalidate-based multiprocessors. Sectored caches often include a facility, called bounteous transfers, to supply extra subblocks after transferring the missed subblock on a read miss. Unfortunately, previous works on sectored caches concentrated mainly on solving the false sharing problem, while overlooked the prefetching effects of bounteous transfer. In this paper, we evaluate the performance impacts of bounteous transfer based on a MESI-based sectored cache. Three different types of bounteous transfer are evaluated: bounteous transfer with valid subblocks (BT-V), bounteous transfer with clean subblocks (BT-C), and bounteous transfer disabled (No-BT). We simulated the execution of typical benchmarks, FFT, LU, Radix, SOR, on the MESI-based sectored cache. Two metrics script U sign-rate and ℛ-rate are proposed to help observe the sharing granularities and coherence overhead. Evaluation results show that different benchmarks work better with different kinds of bounteous transfer and using bounteous transfer carelessly may result in performance degradation.