2017 EuroLLVM Developers’ Meeting: S. Ainsworth “Software Prefetching for Indirect Memory Accesses”

Описание: http://www.LLVM.org/devmtg/2017-03/
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Software Prefetching for Indirect Memory Accesses - Sam Ainsworth, University of Cambridge

Slides: http://llvm.org/devmtg/2017-03//asset...
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Many modern data processing and HPC workloads are heavily memory-latency bound. A tempting proposition to solve this is software prefetching, where special non-blocking loads are used to bring data into the cache hierarchy just before being required. However, these are difficult to insert to effectively improve performance, and techniques for automatic insertion are currently limited.

This paper develops a novel compiler pass to automatically generate software prefetches for indirect memory accesses, a special class of irregular accesses often seen in high-performance workloads. We evaluate this across a wide set of systems, all of which gain benefit from the technique. Across a set of memory-bound benchmarks, our automated pass achieves average speedups of 1.3x and 1.1x for an Intel Haswell processor and an ARM Cortex-A57, both out-of-order cores, and improvements of 2.1x and 3.7x for the in-order ARM Cortex-A53 and Intel Xeon Phi.
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