Prefetch compilation tests

By: Eric Bron (eric.bron.delete@this.zvisuel.privatefortest.com), April 21, 2013 12:52 am
Room: Moderated Discussions
> Cool! I'll keep an eye on it (hopefully someone can fill in some of the missing details).

there is now a remark from Sergey Kostrov who is a very frequent poster at the IDZ forums, he is reporting 0% speedup from software prefetch on Ivy Bridge unlike with previous CPUs, and he removed prefetch hints for the code path concerned

he mentions Intel's C++ documentation as a source of information, though I have not found more details about the implementation in recent cores there but it piqued my curiosity to test again and more extensively the compiler automatic insertion of prefetch instructions "optimization", tests with a workload of mine (a pure software 3D renderer) on a Core i7 3770K below

relevant compiler options: /O3 /Qopt-prefetch[:n]
where "n" is the amount of prefetch instructions added, values from 0 to 4
MT scores are with 8 threads and ST scores with a single thread


n      MT           ST
0      182 fps      49 fps
1     179.8 fps    48.50 fps
2     179 fps      48.55 fps
3-4   166 fps      45.74 fps

best scores are with n=0 i.e. prefetch insertion disabled... the worse slowdown (around 9%) is for the MT case with the most agressive setting

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Haskell Compilation ImprovementSymmetry2013/04/09 10:41 AM
  Haskell Compilation ImprovementEric Bron2013/04/09 11:56 AM
  Haskell Compilation ImprovementLinus Torvalds2013/04/09 12:03 PM
    Haskell Compilation ImprovementEduardoS2013/04/09 12:20 PM
      Haskell Compilation ImprovementLinus Torvalds2013/04/09 12:31 PM
        Haskell Compilation ImprovementEduardoS2013/04/09 12:49 PM
    Haskell Compilation Improvement2013/04/11 01:36 AM
      Haskell Compilation ImprovementEric Bron2013/04/11 03:58 AM
        Haskell Compilation ImprovementBrendan2013/04/11 07:06 AM
          Haskell Compilation ImprovementSymmetry2013/04/11 07:45 AM
            Haskell Compilation ImprovementBrendan2013/04/11 11:31 AM
          Haskell Compilation ImprovementEric Bron2013/04/11 08:57 AM
            Haskell Compilation ImprovementBrendan2013/04/11 11:26 AM
              Haskell Compilation ImprovementEric Bron2013/04/11 11:36 AM
                Haskell Compilation ImprovementBrendan2013/04/11 05:00 PM
                  Haskell Compilation ImprovementDavid Kanter2013/04/11 08:50 PM
                    Software prefetching in JVMsGabriele Svelto2013/04/12 03:31 PM
                  Haskell Compilation ImprovementEric Bron2013/04/12 09:12 AM
                    Haskell Compilation ImprovementBrendan2013/04/12 11:40 AM
                      Haskell Compilation ImprovementEric Bron2013/04/12 12:15 PM
                        Haskell Compilation ImprovementBrendan2013/04/12 03:34 PM
                          Haskell Compilation ImprovementEric Bron2013/04/12 10:44 PM
                            Haskell Compilation ImprovementBrendan2013/04/13 02:20 AM
                              Haskell Compilation ImprovementEric Bron2013/04/13 02:32 AM
                                Haskell Compilation ImprovementBrendan2013/04/13 10:18 AM
                                  Haskell Compilation ImprovementEric Bron2013/04/14 01:04 AM
                          Haskell Compilation ImprovementEric Bron2013/04/15 08:34 AM
                            Haskell Compilation ImprovementBrendan2013/04/16 03:26 PM
                              Prefetch compilation testsEric Bron2013/04/21 12:52 AM
        Haskell Compilation Improvementanon2013/04/11 07:14 AM
          Haskell Compilation ImprovementMichael S2013/04/11 07:27 AM
            Haskell Compilation Improvementanon2013/04/11 08:25 AM
              Haskell Compilation ImprovementMichael S2013/04/11 08:37 AM
                Haskell Compilation Improvementbakaneko2013/04/11 09:39 AM
                  Haskell Compilation ImprovementEric Bron2013/04/11 10:08 AM
                    Haskell Compilation Improvementbakaneko2013/04/11 10:36 AM
                    Haskell Compilation Improvementanon2013/04/11 10:54 AM
                      Haskell Compilation ImprovementEric Bron2013/04/11 11:10 AM
                        Haskell Compilation Improvementanon2013/04/11 11:18 AM
                          Haskell Compilation ImprovementEric Bron2013/04/11 11:27 AM
                            Haskell Compilation Improvementanon2013/04/11 12:02 PM
                              Haskell Compilation ImprovementEric Bron2013/04/11 12:09 PM
                                Haskell Compilation ImprovementEric Bron2013/04/11 12:12 PM
                                Haskell Compilation Improvementanon2013/04/11 12:14 PM
                                  Haskell Compilation ImprovementEric Bron2013/04/11 12:30 PM
                                    Haskell Compilation Improvementanon2013/04/11 11:30 PM
                                      Haskell Compilation ImprovementEric Bron2013/04/12 09:25 AM
                                        Haskell Compilation Improvementanon2013/04/12 07:12 PM
                                          Haskell Compilation ImprovementEric Bron2013/04/12 10:51 PM
                                  Prefetch *hints*Konrad Schwarz2013/04/12 08:24 AM
                        Haskell Compilation ImprovementLinus Torvalds2013/04/11 12:56 PM
                          Inherent advantage of software prefetchJouni Osmala2013/04/11 09:41 PM
                            Inherent advantage of software prefetchSeni2013/04/13 03:40 AM
                            Another example: software scatter gather (NT)Megol2013/04/14 02:39 AM
                          Haskell Compilation ImprovementMaynard Handley2013/12/31 05:26 PM
                            Haskell Compilation ImprovementTREZA2013/12/31 05:44 PM
                              Haskell Compilation ImprovementMaynard Handley2013/12/31 07:49 PM
                                Haskell Compilation Improvementanon2013/12/31 10:39 PM
                                  Haskell Compilation ImprovementMaynard Handley2014/01/01 02:04 AM
                                  Haskell Compilation Improvementbakaneko2014/01/01 05:31 AM
                                Haskell Compilation ImprovementGabriele Svelto2014/01/02 07:57 AM
                                  Haskell Compilation ImprovementMichael S2014/01/02 08:37 AM
                                    Haskell Compilation ImprovementGabriele Svelto2014/01/02 10:09 AM
                                    Haskell Compilation ImprovementTREZA2014/01/02 12:43 PM
                            Haskell Compilation ImprovementMaynard Handley2013/12/31 06:07 PM
                            Future core architectures. (Was Haskell Compilation Improvement)Maynard Handley2014/01/03 12:06 AM
                              Speculative multi-threadingDavid Kanter2014/01/03 02:12 AM
                                Speculative multi-threadingMaynard Handley2014/01/03 05:01 AM
                              Future core architectures. (Was Haskell Compilation Improvement)Seni2014/01/03 01:09 PM
                              Future core architectures. (Was Haskell Compilation Improvement)Linus Torvalds2014/01/03 01:27 PM
                            Haskell Compilation ImprovementKonrad Schwarz2014/01/04 09:38 AM
              Haskell Compilation ImprovementEric Bron2013/04/11 09:23 AM
          Haskell Compilation ImprovementEric Bron2013/04/11 08:50 AM
            Haskell Compilation ImprovementEugene Nalimov2013/04/11 09:20 AM
              Haskell Compilation ImprovementEric Bron2013/04/11 09:28 AM
                Haskell Compilation ImprovementEduardoS2013/04/11 07:30 PM
            Haskell Compilation Improvementanon2013/04/11 10:19 AM
              Haskell Compilation ImprovementEric Bron2013/04/11 10:30 AM
                Haskell Compilation Improvementanon2013/04/11 10:50 AM
                  Haskell Compilation ImprovementEric Bron2013/04/11 11:03 AM
                    Haskell Compilation Improvementanon2013/04/11 11:16 AM
                      Haskell Compilation ImprovementEric Bron2013/04/11 11:24 AM
                        Haskell Compilation Improvementanon2013/04/11 12:09 PM
                          Haskell Compilation ImprovementEric Bron2013/04/11 12:43 PM
                            Haskell Compilation Improvementanon2013/04/11 11:27 PM
                              Haskell Compilation ImprovementEric Bron2013/04/12 12:15 AM
                                Haskell Compilation Improvementanon2013/04/12 07:14 PM
                                  Haskell Compilation ImprovementEric Bron2013/04/12 11:01 PM
                      Haskell Compilation ImprovementLinus Torvalds2013/04/11 01:05 PM
                        Haskell Compilation Improvementanon2013/04/11 10:42 PM
                        Haskell Compilation ImprovementRobert David Graham2013/04/12 02:12 PM
        Software prefetch architecturePaul A. Clayton2013/04/11 08:54 AM
          Software prefetch architectureEric Bron2013/04/11 09:06 AM
            Software prefetch architectureMegol2013/04/15 11:03 AM
              Software prefetch architectureEric Bron2013/04/15 11:30 AM
  low barMichael S2013/04/09 04:38 PM
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