Avoiding ping pong

By: Jouni Osmala (josmala.delete@this.cc.hut.fi), December 8, 2014 1:45 am
Room: Moderated Discussions
> >
> > or people using DAGs to explain why reference count is a solid
> > solution when complex object graphs typically have cycles
>
> Oh, I agree. My example was the simple case. The really complex cases are much worse.
>
> I seriously don't believe that the future is parallel. People who think you can solve it with compilers
> or programming languages (or better programmers) are so far out to lunch that it's not even funny.
>
> Parallelism works well in simplified cases with fairly clear interfaces and models. You find
> parallelism in servers with independent queries, in HPC, in kernels, in databases. And even
> there, people work really hard to make it work at all, and tend to expressly limit their models
> to be more amenable to it (eg databases do some things much better than others, so DB admins
> make sure that they lay out their data in order to cater to the limitations).
>
> Of course, other programming models can work. Neural networks are inherently very
> parallel indeed. And you don't need smarter programmers to program them either..
>
> Linus

Future is parallel in one way or another, simply because diminishing returns on improving serial we are pretty close to a point where improving some serial programs always means making other serial programs running slower because trade offs required just like P4. The trade off between adding serial and parallel performance to hardware, programmers almost always overestimate the amount of potential serial performance improvement relative the amount of improvement of peak parallel performance. Then they start discounting from that parallel number the percentage of non-parallel problems, and amdahl's law and everything, while hardware people have closer to realistic number as base number.

The real question for adding more parallel performance is this, is the subset of problems where there is enough parallerism available important enough to warrant adding more parallel performance, given the low relative cost of doing it. And another is how important is the subset of problems that you can force through those simple interfaces to become parallel. As for most things we already are running fast enough so adding parallerism isn't about making all things go faster, its more about handling Bigger datasets in acceptable time. We won't see UI spaghetti code that runs faster than human it interacts with become parallel, but we see that spaghetti code give simple working threads each a piece of enormous data set to be processed, and now to problem becomes only creating splits in large data set on natural boundaries and keeping pointers to said boundaries.
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ARMv8 getting atomic operationsdmcq2014/12/02 04:32 PM
  ARMv8 getting atomic operationsMaynard Handley2014/12/02 06:33 PM
    ARMv8 getting atomic operationsDoug S2014/12/02 09:30 PM
      ARMv8 getting atomic operationsdmcq2014/12/03 02:16 AM
      ARMv8 getting atomic operationsMaynard Handley2014/12/03 08:20 AM
      ARMv8 getting atomic operationsBrett2014/12/03 03:46 PM
    ARMv8 getting atomic operationsAndreas2014/12/03 05:51 AM
      ARMv8 getting atomic operationsLinus Torvalds2014/12/03 10:15 AM
        ARMv8 getting atomic operationsanon2014/12/03 04:08 PM
          Guaranteed transactionsPaul A. Clayton2014/12/03 07:04 PM
            Guaranteed transactionsanon2014/12/03 07:38 PM
              Avoiding ping pongPaul A. Clayton2014/12/04 08:11 AM
                Avoiding ping ponganon2014/12/04 09:15 AM
                  OoO window is limitedPaul A. Clayton2014/12/04 12:06 PM
                Avoiding ping pongAaron Spink2014/12/04 11:01 AM
                  Avoiding ping pongKonrad Schwarz2014/12/04 12:10 PM
                    Avoiding ping pongAaron Spink2014/12/04 01:31 PM
                    Avoiding ping pongGabriele Svelto2014/12/04 01:49 PM
                      Avoiding ping pongKonrad Schwarz2014/12/04 10:08 PM
                        Avoiding ping pongGabriele Svelto2014/12/04 11:04 PM
                          Avoiding ping pongEric Bron nli2014/12/05 01:28 AM
                            Avoiding ping pongKonrad Schwarz2014/12/05 02:37 AM
                              Avoiding ping pongEric Bron nli2014/12/05 03:23 AM
                                Avoiding ping pongKlimax2014/12/05 04:47 AM
                                  Avoiding ping pongEric Bron2014/12/05 05:24 AM
                              Avoiding ping pongGabriele Svelto2014/12/05 09:38 AM
                                Avoiding ping pongKonrad Schwarz2014/12/07 01:28 PM
                                  Avoiding ping pongGabriele Svelto2014/12/08 06:10 PM
                                    Avoiding ping pongKonrad Schwarz2014/12/09 04:12 AM
                                      Avoiding ping pongGabriele Svelto2014/12/09 06:31 AM
                                        Avoiding ping ponganon2014/12/09 10:24 PM
                            Avoiding ping pongGabriele Svelto2014/12/05 09:17 AM
                              Avoiding ping pongEric Bron2014/12/05 09:32 AM
                                Avoiding ping pongGabriele Svelto2014/12/05 11:45 AM
                                  Avoiding ping pongEric Bron2014/12/06 01:20 AM
                                    Avoiding ping pongnksingh2014/12/06 02:42 AM
                                      Avoiding ping pongEric Bron2014/12/06 03:04 AM
                                        Avoiding ping pongGiGNiC2014/12/06 05:27 AM
                                          Avoiding ping pongEric Bron nli2014/12/06 05:44 AM
                                          Avoiding ping pongEric Bron2014/12/06 06:07 AM
                                            Avoiding ping pongnksingh2014/12/07 03:06 PM
                                              Avoiding ping pongEric Bron2014/12/08 03:17 AM
                                                Avoiding ping pongGiGNiC2014/12/08 10:53 AM
                                                Avoiding ping pongnksingh2014/12/08 04:53 PM
                                                  Avoiding ping pongEric Bron2014/12/09 12:33 AM
                                    Avoiding ping pongdmsc2014/12/06 03:12 AM
                                      Avoiding ping pongEric Bron2014/12/06 03:25 AM
                                        Avoiding ping pongKlimax2014/12/06 04:49 AM
                                          Avoiding ping pongrwessel2014/12/07 01:34 AM
                                        Avoiding ping pongdmsc2014/12/06 06:39 AM
                                        Avoiding ping pongKonrad Schwarz2014/12/07 01:37 PM
                                          Avoiding ping pongMichael S2014/12/07 03:37 PM
                                            Avoiding ping pongKonrad Schwarz2014/12/08 03:35 AM
                          Avoiding ping pongKonrad Schwarz2014/12/05 02:30 AM
                        Avoiding ping pongLinus Torvalds2014/12/05 11:58 AM
                          Avoiding ping pongEric Bron2014/12/06 01:42 AM
                            Avoiding ping pongnksingh2014/12/06 02:51 AM
                              Avoiding ping pongEric Bron2014/12/06 03:08 AM
                            Avoiding ping pongLinus Torvalds2014/12/06 12:25 PM
                              Avoiding ping pongnksingh2014/12/07 02:26 PM
                                Avoiding ping pongEric Bron2014/12/08 03:35 AM
                                  Avoiding ping pongBrett2014/12/08 09:00 AM
                                    Avoiding ping pongEric Bron2014/12/08 09:48 AM
                                    Avoiding ping pongrwessel2014/12/08 11:52 AM
                                      Avoiding ping pongBrett2014/12/08 12:58 PM
                                      Avoiding ping pongDoug S2014/12/08 01:04 PM
                              Avoiding ping pongJouni Osmala2014/12/08 01:45 AM
                                Avoiding ping ponganon2014/12/08 04:44 AM
                                  Avoiding ping pongJouni Osmala2014/12/08 12:10 PM
                                    Avoiding ping pongLinus Torvalds2014/12/08 12:34 PM
                                      Avoiding ping pongJouni Osmala2014/12/08 02:47 PM
                                        Avoiding ping pongLinus Torvalds2014/12/08 07:08 PM
                                          Avoiding ping pongGabriele Svelto2014/12/09 06:48 AM
                                            Avoiding ping pongMaynard Handley2014/12/09 10:41 AM
                                              Avoiding ping pongPatrick Chase2014/12/09 12:06 PM
                                              Avoiding ping pongGabriele Svelto2014/12/09 12:52 PM
                                                Avoiding ping pongPatrick Chase2014/12/09 01:08 PM
                                            Why read RWT or Reddit when you can get journalists to do it for you?Rob Thorpe2015/01/02 07:20 AM
                                              Why read RWT or Reddit when you can get journalists to do it for you?juanrga2015/01/02 10:21 AM
                                                Why read RWT or Reddit when you can get journalists to do it for you?EduardoS2015/01/02 10:37 AM
                                                  Why read RWT or Reddit when you can get journalists to do it for you?juanrga2015/01/03 11:00 AM
                                                Why read RWT or Reddit when you can get journalists to do it for you?Eric Bron nli2015/01/02 01:28 PM
                                                  Why read RWT or Reddit when you can get journalists to do it for you?juanrga2015/01/03 11:02 AM
                                                    Why read RWT or Reddit when you can get journalists to do it for you?Michael S2015/01/03 11:36 AM
                                                      Why read RWT or Reddit when you can get journalists to do it for you?juanrga2015/01/03 12:11 PM
                                                        Why read RWT or Reddit when you can get journalists to do it for you?Michael S2015/01/03 12:30 PM
                                                          Why read RWT or Reddit when you can get journalists to do it for you?Eric Bron2015/01/03 01:57 PM
                                                            KNL cacheDavid Kanter2015/01/03 06:36 PM
                                                              KNL cacheEric Bron2015/01/04 02:34 AM
                                                                KNL cacheMichael S2015/01/04 03:11 AM
                                                                  KNL cacheEric Bron2015/01/04 03:57 AM
                                                                    KNL cacheMichael S2015/01/04 04:21 AM
                                                                      KNL cacheEric Bron2015/01/04 04:58 AM
                                                          Why read RWT or Reddit when you can get journalists to do it for you?juanrga2015/01/07 04:47 AM
                                                            Why read RWT or Reddit when you can get journalists to do it for you?Michael S2015/01/07 07:27 AM
                                                              Manycores vs multicoresjuanrga2015/01/10 03:10 PM
                                                                Manycores vs multicoresAaron Spink2015/01/10 04:32 PM
                                                                  Manycores vs multicoresjuanrga2015/01/10 05:32 PM
                                                                    Manycores vs multicoresExophase2015/01/10 05:49 PM
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                                                                    Manycores vs multicoresAaron Spink2015/01/10 06:21 PM
                                                                      Manycores vs multicoresjuanrga2015/01/10 07:25 PM
                                                                        Manycores vs multicoresAaron Spink2015/01/10 08:11 PM
                                                                          Manycores vs multicoresJouni Osmala2015/01/11 03:50 AM
                                                                            Manycores vs multicoresjuanrga2015/01/11 07:58 AM
                                                                            Manycores vs multicorescoppice2015/01/12 09:01 PM
                                                                              Manycores vs multicoresJouni Osmala2015/01/13 03:38 AM
                                                                        Manycores vs multicoresanon2015/01/11 02:19 AM
                                                                      Manycores vs multicoresMichael S2015/01/11 04:44 AM
                                                                        Manycores vs multicoresAaron Spink2015/01/11 04:55 PM
                                                                          Manycores vs multicoresMichael S2015/01/12 03:41 AM
                                                                            Manycores vs multicoresEric Bron2015/01/12 05:29 AM
                                                                              Manycores vs multicoresEric Bron2015/01/12 05:30 AM
                                                        Why read RWT or Reddit when you can get journalists to do it for you?Eric Bron2015/01/03 01:54 PM
                                                          Why read RWT or Reddit when you can get journalists to do it for you?juanrga2015/01/07 04:48 AM
                                                            Why read RWT or Reddit when you can get journalists to do it for you?Eric Bron2015/01/07 06:41 AM
                                                              Manycores vs multicoresjuanrga2015/01/10 03:14 PM
                                                    Why read RWT or Reddit when you can get journalists to do it for you?Eric Bron2015/01/03 01:42 PM
                                                      Why read RWT or Reddit when you can get journalists to do it for you?juanrga2015/01/07 05:03 AM
                                                        Why read RWT or Reddit when you can get journalists to do it for you?Eric Bron2015/01/07 06:45 AM
                                                        Why read RWT or Reddit when you can get journalists to do it for you?Linus Torvalds2015/01/08 02:09 PM
                                                          Pink unicorns for salejuanrga2015/01/10 04:09 PM
                                                        Intentionally picking a competitors slow part is cheating ...Mark Roulo2015/01/08 05:37 PM
                                                          Intentionally picking a competitors slow part is cheating ...coppice2015/01/08 10:38 PM
                                                            Intentionally picking a competitors slow part is cheating ...Mark Roulo2015/01/09 08:13 AM
                                                              Intentionally picking a competitors slow part is cheating ...Anon2015/01/10 01:00 AM
                                                              Intentionally picking a competitors slow part is cheating ...David Hess2015/01/11 12:03 PM
                                                            Intentionally picking a competitors slow part is cheating ...someone2015/01/09 09:31 AM
                                                              Intentionally picking a competitors slow part is cheating ...coppice2015/01/12 08:45 PM
                                                                Intentionally picking a competitors slow part is cheating ...coppice2015/01/12 08:47 PM
                                                                  Intentionally picking a competitors slow part is cheating ...Michael S2015/01/13 06:53 AM
                                                                    Intentionally picking a competitors slow part is cheating ...coppice2015/01/13 08:44 AM
                                                                      Intentionally picking a competitors slow part is cheating ...Michael S2015/01/13 09:01 AM
                                                                        Intentionally picking a competitors slow part is cheating ...coppice2015/01/13 07:35 PM
                                                                      Core sizesjuanrga2015/01/13 11:28 AM
                                                          NVIDIA'S FIRST CPU IS A WINNER (Linley Gwennap)juanrga2015/01/10 03:34 PM
                                                        Why read RWT or Reddit when you can get journalists to do it for you?Patrick Chase2015/01/08 06:02 PM
                                                        Why read RWT or Reddit when you can get journalists to do it for you?coppice2015/01/08 09:18 PM
                                                          Why read RWT or Reddit when you can get journalists to do it for you?Patrick Chase2015/01/09 10:54 AM
                                                            Why read RWT or Reddit when you can get journalists to do it for you?Mark Roulo2015/01/09 11:59 AM
                                                              Why read RWT or Reddit when you can get journalists to do it for you?Patrick Chase2015/01/09 02:20 PM
                                                                Why read RWT or Reddit when you can get journalists to do it for you?Eric Bron2015/01/09 02:30 PM
                                                            Alternatives to OOOE (again)juanrga2015/01/10 03:50 PM
                                                              Alternatives to OOOE (again)David Kanter2015/01/10 11:10 PM
                                                                Alternatives to OOOE (again)juanrga2015/01/11 07:30 AM
                                                            Why read RWT or Reddit when you can get journalists to do it for you?Gabriele Svelto2015/01/10 11:53 PM
                                              Why read RWT or Reddit when you can get journalists to do it for you?Fake Linus Torvalds2015/01/03 11:14 AM
                                                Why read RWT or Reddit when you can get journalists to do it for you?Rob Thorpe2015/01/03 07:25 PM
                                          Avoiding ping pongMaynard Handley2014/12/09 10:33 AM
                                            Avoiding ping pongPatrick Chase2014/12/09 12:54 PM
                                              Avoiding ping pongMaynard Handley2014/12/09 05:56 PM
                                      Avoiding ping pongSalvatore De Dominicis2014/12/09 07:51 AM
                                        Avoiding ping pongPatrick Chase2014/12/09 01:00 PM
                                      Avoiding ping pongook2014/12/11 02:31 AM
                                      Avoiding ping pongArt Scott2014/12/19 09:19 PM
                                        Avoiding ping pongEric Bron nli2014/12/20 03:05 AM
                                      What about specialization?Troll?2015/01/02 06:55 AM
                                        What about specialization?Ungo2015/01/04 02:27 PM
                                      Avoiding ping pongfewwef2015/01/05 07:16 PM
                                      Avoiding ping pongV.Krishn2015/01/08 05:11 AM
                                    Avoiding ping pongGabriele Svelto2014/12/08 06:32 PM
                                    Avoiding ping ponganon2014/12/08 10:37 PM
                            Avoiding ping pongKonrad Schwarz2014/12/10 05:23 AM
                              Avoiding ping pongLinus Torvalds2014/12/10 10:56 AM
                          Object reference lockingDavid W2014/12/08 10:36 PM
                            Object reference lockingPatrick Chase2014/12/09 03:52 PM
                              Object reference lockingDavid W2014/12/11 04:18 AM
                    ISA != interface for "most programmers"Paul A. Clayton2014/12/04 02:34 PM
                      ISA != interface for "most programmers"rwessel2014/12/04 06:50 PM
                  Interesting! (exporting hot lines/cache-aware ISA); "Please sir, I want some more" (NT)Paul A. Clayton2014/12/04 01:26 PM
                  Avoiding ping pongMichael S2014/12/06 02:48 PM
          ARMv8 getting atomic operationsLinus Torvalds2014/12/04 11:05 AM
            LL/SC idiom recognition is not admitting RMW superiorityPaul A. Clayton2014/12/04 01:34 PM
            ARMv8 getting atomic operationsanon2014/12/04 09:17 PM
    ARMv8 getting atomic operationsPatrick Chase2014/12/03 11:09 AM
  limited ordernksingh2014/12/04 09:17 PM
    I didn't understand this either. (NT)Konrad Schwarz2014/12/04 09:32 PM
    limited orderdmcq2014/12/05 01:13 AM
    limited orderbakaneko2014/12/05 08:11 AM
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