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Communication Dans Un Congrès Année : 2009

MLP-Aware Runahead Threads in a Simultaneous Multithreading Processor

Résumé

Threads experiencing long-latency loads on a simultaneous multithreading (SMT) processor may clog shared processor resources without making forward progress, thereby starving other threads and reducing overall system throughput. An elegant solution to the long-latency load problem in SMT processors is to employ runahead execution. Runahead threads do not block commit on a long-latency load but instead execute subsequent instructions in a speculative execution mode to expose memory-level parallelism (MLP) through prefetching. The key benefit of runahead SMT threads is twofold: (i) runahead threads do not clog resources on a long-latency load, and (ii) runahead threads exploit fardistance MLP. This paper proposes MLP-aware runahead threads: runahead execution is only initiated in case there is far-distance MLP to be exploited. By doing so, useless runahead executions are eliminated, thereby reducing the number of speculatively executed instructions (and thus energy consumption) while preserving the performance of the runahead thread and potentially improving the performance of the co-executing thread(s). Our experimental results show that MLP-aware runahead threads reduce the number of speculatively executed instructions by 13.9% and 10.1% for two-program and four-program workloads, respectively, compared to MLP-agnostic runahead threads while achieving comparable system throughput and job turnaround time.

Dates et versions

inria-00445500 , version 1 (08-01-2010)

Identifiants

Citer

Kenzo van Craeynest, Stijn Eyerman, Lieven Eeckhout. MLP-Aware Runahead Threads in a Simultaneous Multithreading Processor. HiPEAC 2009 - High Performance and Embedded Architectures and Compilers, Jan 2009, Paphos, Cyprus. ⟨10.1007/978-3-540-92990-1_10⟩. ⟨inria-00445500⟩

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