WiDir: A Wireless-Enabled Directory cache coherence protocol
Document typeConference report
PublisherInstitute of Electrical and Electronics Engineers (IEEE)
Rights accessOpen Access
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ProjectWiPLASH - Architecting More Than Moore – Wireless Plasticity for Heterogeneous Massive Computer Architectures (EC-H2020-863337)
As the core count in shared-memory manycores keeps increasing, it is becoming increasingly harder to design cache-coherence protocols that deliver high performance without an inordinate increase in complexity and cost. In particular, sharing patterns where a group of cores frequently reads and writes a shared variable are hard to support efficiently. Hence, programmers end up tuning their applications to avoid these patterns, hurting the programmability of shared memory. To address this problem, this paper uses the recently-proposed on-chip wireless network technology to augment a conventional invalidation-based directory cache coherence protocol. We call the resulting protocol WiDir. WiDir seamlessly transitions between wired and wireless coherence transactions for a given line based on the access patterns in a programmer-transparent manner. In this paper, we describe the protocol transitions in detail. Further, an evaluation using SPLASH and PARSEC applications shows that WiDir substantially reduces the memory stall time of applications. As a result, for 64-core runs, WiDir reduces the execution time of applications by an average of 22% compared to a conventional directory protocol. Moreover, WiDir is more scalable. These benefits are obtained with a very modest power cost.
CitationFranques, A. [et al.]. WiDir: A Wireless-Enabled Directory cache coherence protocol. A: International Symposium on High-Performance Computer Architecture. "27th IEEE International Symposium on High Performance Computer Architecture: 27 February-3 March 2021, virtual event: proceedings". Institute of Electrical and Electronics Engineers (IEEE), 2021, p. 304-317. ISBN 978-0-7381-2337-0. DOI 10.1109/HPCA51647.2021.00034.