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Whose Cache Line Is It Anyway?

Whose Cache Line Is It Anyway?. Operating System Support for Live Detection and Repair of False Sharing. Mihir Nanavati , Mark Spear, Nathan Taylor, Shriram Rajagopalan , Dutch T. Meyer, William Aiello, and Andrew Warfield University of British Columbia.

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Whose Cache Line Is It Anyway?

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  1. Whose Cache Line Is It Anyway? Operating System Support for LiveDetection and Repair of False Sharing MihirNanavati, Mark Spear, Nathan Taylor, ShriramRajagopalan, Dutch T. Meyer, William Aiello, and Andrew Warfield University of British Columbia

  2. Mondriaan Memory Protection [ASPLOS ’02, SOSP ’05]

  3. Byte-granularity, software-only remapping

  4. False Sharing

  5. Control VM (Dom0) Target System Xen + Hardware Memory

  6. Dynamic Detection and Mitigation of False Sharing

  7. T1 T2 Write 0x300 Write 0x308 Read 0x300 Cache 0x300 0x340 Main Memory

  8. Cache Line C Structure With Padding With Allocator Metadata

  9. Time (s) No. of Cores

  10. Time (s) No. of Cores

  11. Time (s) No. of Cores

  12. Time (s) No. of Cores

  13. Time (s) 7.5x No. of Cores Linux Kernel [OSDI ’10], JVM [Dice, 2012], Software Transactional Memory [HPCA ’06]

  14. Dynamic Detection and Mitigation of False Sharing

  15. Modify access locations Modify access frequency Sheriff [OOPSLA ’11]

  16. T1 T2 Isolated Page Underlay Page

  17. Dynamic Detection and Mitigation of False Sharing

  18. Persistent, high-frequency false sharing

  19. Very Fast and Imprecise Fast and Somewhat Precise Slow and Precise

  20. Performance Counters Log Page Reads Instruction Emulation Log-Analysis Rules for remapper What are the byte ranges being accessed? What pages are involved in the contention? Does contention exist? Does this signify false sharing?

  21. Dynamic Detection and Mitigation of False Sharing

  22. T1 T2 Isolated Page Underlay Page

  23. Don’t be Evil Harmful

  24. Fault Driven Redirection

  25. ?! It’s a Fault?! Original Code Code Cache

  26. Original Code Code Cache

  27. Catch all accesses via data path Avoid code trampolines Amortize page fault cost

  28. “Know When You are Beaten”

  29. T1 T2 Isolated Page Underlay Page

  30. Evaluation

  31. Remappings Established Progress (million records) 160 M/sec 110 M/sec Time (ms) Version with false sharing under Plastic Coherence Invalidations Source-fixed Version

  32. CCBench Phoenix Parsec 5.4x Normalized Performance 3.6x 1.4x

  33. Low overhead runtime detection Byte-granularity remapping Speedup of up to 5.4x

  34. Performance Optimizations Security Enhancements

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