150 GFLOP/s measured?

Article: PhysX87: Software Deficiency
By: Michael S (already5chosen.delete@this.yahoo.com), July 28, 2010 12:38 am
Room: Moderated Discussions
a reader (a@b.c) on 7/26/10 wrote:
---------------------------
>>
>>I never found that article or 'discovery' to be particularly impressive. Largely
>>because you could find out almost everything you needed to know about the replay mechanism in Intel's tuning manuals.
>>
>
>really? didn't find any mention of the replay mechanism
>in intel's optimization manual.
>
>intel used to tell people to put pause instruction in
>tight spin loops on P4. make sense given the existence
>of the reply loop. but it's a leap to say intel is
>really telling people about the replay mechanisms.
>
>
>>I also think their architectural analysis really missed the point of replay.
>>
>>It's actually a good idea, especially compared to traditional techniques for undoing
>>speculation. The nice thing about replay is that it allows you to selectively replay/undo
>>a subset of the execution window. Of course, the problem was really the implementation...
>>
>>David
>
>no argument there. replay is a good speculation mechanism.
>won't be surprised it has existed prior to P4. what might
>have caused it to perform badly on P4 is probably L1D too
>small, that would lead to excessive looping and power draw.
>

IMHO, L1D too small is a minor problem. BTW, for Prescott and up it's not so small. The bigger problem is combination of:
A. Write Through policy
B. Relatively small write buffer between L1 and L2
C. Even this small write buffer is probably not "fully associative" or something like that. See Linus's post above. The worst thing about it is a absence of documentation.
D. Replay caused by store unit running out of places in write buffer is really expensive.


>what impressed me about that article is that those guys
>highlighted a scenario where aggressive scheduling
>lead to latencies that were quadratic of the length of
>the dependency chain. also they attempted to cause a
>livelock. those cleverness are orthogonal to whether
>they really understood the purpose of replay.
>
>

Nothing like that happens on PSC. And still on average, except for server workloads, PSC doesn't perform better than NWD.

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TopicPosted ByDate
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            A bit off baseIan Ameline2010/07/11 06:51 AM
  A bit off baseDavid Kanter2010/07/07 08:46 PM
    A bit off baseAnon2010/07/07 11:47 PM
      A bit off baseanon2010/07/08 01:15 AM
        A bit off baseGabriele Svelto2010/07/08 03:11 AM
          Physics engine historyPeter Clare2010/07/08 03:49 AM
            Physics engine historyNull Pointer Exception2010/07/08 05:07 AM
              Physics engine historyRalf2010/07/08 02:09 PM
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                  Physics engine historysJ2010/07/08 10:36 PM
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                      Physics engine historysJ2010/07/13 05:35 AM
                    Physics engine historyDavid Kanter2010/07/09 08:25 AM
                      Physics engine historysJ2010/07/13 05:49 AM
                      Physics engine historyfvdbergh2010/07/13 06:27 AM
    A bit off baseJohn Mann2010/07/08 10:11 AM
      A bit off baseDavid Kanter2010/07/08 10:31 AM
        150 GFLOP/s measured?anon2010/07/08 06:10 PM
          150 GFLOP/s measured?David Kanter2010/07/08 06:53 PM
            150 GFLOP/s measured?Aaron Spink2010/07/08 08:05 PM
              150 GFLOP/s measured?anon2010/07/08 08:31 PM
                150 GFLOP/s measured?Aaron Spink2010/07/08 09:43 PM
                  150 GFLOP/s measured?David Kanter2010/07/08 10:27 PM
                    150 GFLOP/s measured?Ian Ollmann2010/07/19 12:14 AM
                      150 GFLOP/s measured?anon2010/07/19 05:39 AM
                        150 GFLOP/s measured?hobold2010/07/19 06:26 AM
                          Philosophy for achieving peakDavid Kanter2010/07/19 10:49 AM
                      150 GFLOP/s measured?Linus Torvalds2010/07/19 06:36 AM
                        150 GFLOP/s measured?Richard Cownie2010/07/19 07:42 AM
                          150 GFLOP/s measured?Aaron Spink2010/07/19 07:56 AM
                            150 GFLOP/s measured?hobold2010/07/19 08:30 AM
                              150 GFLOP/s measured?Groo2010/07/19 01:31 PM
                                150 GFLOP/s measured?hobold2010/07/19 03:17 PM
                                  150 GFLOP/s measured?Groo2010/07/19 05:18 PM
                              150 GFLOP/s measured?Anon2010/07/19 05:18 PM
                            150 GFLOP/s measured?Mark Roulo2010/07/19 10:47 AM
                              150 GFLOP/s measured?slacker2010/07/19 11:55 AM
                                150 GFLOP/s measured?Mark Roulo2010/07/19 12:00 PM
                              150 GFLOP/s measured?anonymous422010/07/25 11:31 AM
                            150 GFLOP/s measured?Richard Cownie2010/07/19 11:41 AM
                              150 GFLOP/s measured?Linus Torvalds2010/07/19 01:57 PM
                                150 GFLOP/s measured?Richard Cownie2010/07/19 03:10 PM
                                150 GFLOP/s measured?Richard Cownie2010/07/19 03:10 PM
                                  150 GFLOP/s measured?hobold2010/07/19 03:25 PM
                                  150 GFLOP/s measured?Linus Torvalds2010/07/19 03:31 PM
                                    150 GFLOP/s measured?Richard Cownie2010/07/20 05:04 AM
                                150 GFLOP/s measured?jrl2010/07/20 12:18 AM
                            150 GFLOP/s measured?anonymous422010/07/25 11:00 AM
                              150 GFLOP/s measured?David Kanter2010/07/25 11:52 AM
                          150 GFLOP/s measured?Anon2010/07/19 05:15 PM
                            150 GFLOP/s measured?Linus Torvalds2010/07/19 06:27 PM
                              150 GFLOP/s measured?Anon2010/07/19 08:54 PM
                                150 GFLOP/s measured?anon2010/07/19 10:45 PM
                        150 GFLOP/s measured?hobold2010/07/19 08:14 AM
                          150 GFLOP/s measured?Linus Torvalds2010/07/19 10:56 AM
                            150 GFLOP/s measured?a reader2010/07/21 07:16 PM
                              150 GFLOP/s measured?Linus Torvalds2010/07/21 08:05 PM
                                150 GFLOP/s measured?anon2010/07/22 01:09 AM
                                  150 GFLOP/s measured?a reader2010/07/22 06:53 PM
                                    150 GFLOP/s measured?gallier22010/07/23 04:58 AM
                                      150 GFLOP/s measured?a reader2010/07/25 07:35 AM
                                        150 GFLOP/s measured?David Kanter2010/07/25 10:49 AM
                                          150 GFLOP/s measured?a reader2010/07/26 06:03 PM
                                            150 GFLOP/s measured?Michael S2010/07/28 12:38 AM
                                              150 GFLOP/s measured?Gabriele Svelto2010/07/28 12:44 AM
                                    150 GFLOP/s measured?anon2010/07/23 03:55 PM
                                      150 GFLOP/s measured?slacker2010/07/23 11:48 PM
                                        150 GFLOP/s measured?anon2010/07/24 01:36 AM
                                    150 GFLOP/s measured?Vincent Diepeveen2010/07/27 04:37 PM
                                      150 GFLOP/s measured??2010/07/27 10:42 PM
                                        150 GFLOP/s measured?slacker2010/07/28 04:55 AM
                                      Intel's clock rate projectionsAM2010/07/28 01:03 AM
                                        nostalgia ain't what it used to besomeone2010/07/28 04:38 AM
                                          Intel's clock rate projectionsAM2010/07/28 09:12 PM
                        Separate the OoO-ness from speculative-ness?2010/07/20 06:19 AM
                          Separate the OoO-ness from speculative-nessMark Christiansen2010/07/20 01:26 PM
                          Separate the OoO-ness from speculative-nessslacker2010/07/20 05:04 PM
                            Separate the OoO-ness from speculative-nessMatt Sayler2010/07/20 05:10 PM
                              Separate the OoO-ness from speculative-nessslacker2010/07/20 08:37 PM
                                Separate the OoO-ness from speculative-ness?2010/07/20 10:51 PM
                                  Separate the OoO-ness from speculative-nessanon2010/07/21 01:16 AM
                                    Separate the OoO-ness from speculative-ness?2010/07/21 06:05 AM
                                      Software conventionsPaul A. Clayton2010/07/21 07:52 AM
                                        Software conventions?2010/07/22 04:43 AM
                                      SpeculationDavid Kanter2010/07/21 09:32 AM
                                        Pipelining affects the ISA?2010/07/22 09:58 PM
                                          Pipelining affects the ISA?2010/07/22 10:14 PM
                                          Pipelining affects the ISArwessel2010/07/22 11:03 PM
                                            Pipelining affects the ISA?2010/07/23 04:50 AM
                                            Pipelining affects the ISA?2010/07/23 05:10 AM
                                              Pipelining affects the ISAThiago Kurovski2010/07/23 01:59 PM
                                                Pipelining affects the ISAanon2010/07/24 06:35 AM
                                                  Pipelining affects the ISAThiago Kurovski2010/07/24 10:12 AM
                                          Pipelining affects the ISAGabriele Svelto2010/07/26 01:50 AM
                                            Pipelining affects the ISAIlleglWpns2010/07/26 04:14 AM
                                              Pipelining affects the ISAMichael S2010/07/26 02:33 PM
                                      Separate the OoO-ness from speculative-nessanon2010/07/21 04:53 PM
                                        Separate the OoO-ness from speculative-ness?2010/07/22 03:15 AM
                                          Separate the OoO-ness from speculative-nessanon2010/07/22 03:27 AM
                                      Separate the OoO-ness from speculative-nessslacker2010/07/21 06:45 PM
                                        Separate the OoO-ness from speculative-nessanon2010/07/22 12:57 AM
                                        Separate the OoO-ness from speculative-ness?2010/07/22 04:26 AM
                                          Separate the OoO-ness from speculative-nessDan Downs2010/07/22 07:14 AM
                                          Confusing and not very useful definitionDavid Kanter2010/07/22 11:41 AM
                                            Confusing and not very useful definition?2010/07/22 09:58 PM
                                              Confusing and not very useful definitionUngo2010/07/24 11:06 AM
                                                Confusing and not very useful definition?2010/07/25 09:23 PM
                            Separate the OoO-ness from speculative-nesssomeone2010/07/20 07:02 PM
                              Separate the OoO-ness from speculative-nessThiago Kurovski2010/07/21 03:13 PM
            You are just quoting SINGLE precision flops? OMG what planet do you live? Vincent Diepeveen2010/07/19 09:26 AM
              The prior poster was talking about SP (NT)David Kanter2010/07/19 10:34 AM
                All FFT's need double precisionVincent Diepeveen2010/07/19 01:02 PM
                  All FFT's need double precisionDavid Kanter2010/07/19 01:09 PM
                    All FFT's need double precisionVincent Diepeveen2010/07/19 03:06 PM
                  All FFT's need double precision - notMichael S2010/07/20 12:16 AM
                    All FFT's need double precision - notUngo2010/07/20 11:04 PM
                      All FFT's need double precision - notMichael S2010/07/21 01:35 PM
                      All FFT's need double precision - notEduardoS2010/07/21 01:52 PM
                        All FFT's need double precision - notAnon2010/07/21 04:23 PM
                          All FFT's need double precision - notRicardo B2010/07/26 06:46 AM
                        I'm on a boat!anon2010/07/22 10:42 AM
                        All FFT's need double precision - notVincent Diepeveen2010/07/24 10:39 PM
                          All FFT's need double precision - notslacker2010/07/25 02:27 AM
                            All FFT's need double precision - notRicardo B2010/07/26 06:40 AM
                          All FFT's need double precision - notEduardoS2010/07/25 07:37 AM
                            All FFT's need double precision - notMichael S2010/07/25 09:43 AM
                    All FFT's need double precision - notVincent Diepeveen2010/07/24 10:19 PM
      A bit off baseEduardoS2010/07/08 03:08 PM
        A bit off baseGroo2010/07/08 05:11 PM
          A bit off basejohn mann2010/07/08 05:58 PM
            All right...let's cool it...David Kanter2010/07/08 06:54 PM
    A bit off baseVincent Diepeveen2010/07/19 02:36 PM
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