Coherent Temporal Streams in PARSEC

Abstract

Off-Chip miss latency remains a bottleneck even in the modern chip multiprocessors. Recent research advocates memory streaming techniques to alleviate the performance bottleneck caused by the high latencies of off-chip memory accesses. Memory streaming prefetches data by predicting recurring sequences of misses. Coherent read misses are one of the contributors in off-chip read misses for multithread workloads running on multi-chip multiprocessors. In this paper, we investigate off-chip coherent read misses using information-theoretic analysis of coherent read misses collected using execution-driven simulation of Princeton Application Repository for Shared-Memory Computers PARSEC). We found that coherent read misses recur system-wide in the same order forming sequences of two or more misses called streams. We show that 54% to 95% misses are part of streams. Our investigations have proved to be useful that streaming using multiple recurrences of the same stream cannot predict certain fraction of stream misses i.e. at least 10% to 60%. We demonstrate that 80% to 90% streams have length less than or equal to 8, 45% to 60% streams recur two times and then never repeat, finally streams recur after hundreds or thousands of misses.