Analysis of Hardware Prefetching Across Virtual Page Boundaries

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Provided by: Association for Computing Machinery
Topic: Hardware
Format: PDF
Data cache prefetching in the L2 is at the forefront of prefetching research. In this paper, the authors analyze the impact of virtual page boundaries on these prefetchers. Conservative measurements on real hardware show that 30-50% of consecutive virtual pages are mapped to pages which are not consecutive in physical memory. Advanced hardware prefetching techniques that detect access patterns which span virtual page boundaries often end up prefetching data that is from the wrong physical page. Meanwhile, current simulation techniques for evaluating prefetching algorithms assume that all virtual pages are mapped consecutively. They show that not accounting for virtual page boundaries in simulation can lead to overestimates of as much as 29% (9% on average).
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