Fitting time slices to execution phases

By: Gabriele Svelto (gabriele.svelto.delete@this.gmail.com), August 21, 2018 3:54 pm
Room: Moderated Discussions
Linus Torvalds (torvalds.delete@this.linux-foundation.org) on August 21, 2018 3:31 pm wrote:
> So you can solve it other ways. One way is to have the remote atomics, and just do the statistics update
> "somewhere else" and asynchronously. That's a lovely model in many ways, but it's not portable.

The only implementation of that I know of are in Freescale's POWER network processors. They added remote atomics which they advertised specifically for use in statistics. IIRC the actual operations were executed in the L3 cache. They worked by setting up a cache-inhibited range of memory and then used what they called "decorated operations" (i.e. loads or stores plus an operation) to access it; you couldn't access the same area as cached memory, it just didn't work. Here's some more info:

Decorated Operations for QorIQ P3/P4/P5 Processors

One big downside they had was that they could not be executed speculatively, they were effectively serializing instructions. The issue was that a speculatively executed instruction would trigger an atomic operation even if the instruction was later squashed if the speculation turned out to be wrong. The remote atomic machinery had no access to the core and thus no way to know that the instruction had been squashed, and would merrily execute it anyway.
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TopicPosted ByDate
ARM turns to a god and a heroAM2018/08/16 09:32 AM
  ARM turns to a god and a heroMaynard Handley2018/08/16 09:41 AM
    ARM turns to a god and a heroDoug S2018/08/16 11:11 AM
    ARM turns to a god and a heroGeoff Langdale2018/08/16 11:59 PM
      ARM turns to a god and a herodmcq2018/08/17 05:12 AM
  ARM is somewhat misleadingAdrian2018/08/16 11:56 PM
    It's marketing materialGabriele Svelto2018/08/17 01:00 AM
      It's marketing materialMichael S2018/08/17 03:13 AM
        It's marketing materialdmcq2018/08/17 05:23 AM
          It's marketing materialAndrei Frumusanu2018/08/17 07:25 AM
        It's marketing materialLinus Torvalds2018/08/17 11:20 AM
          It's marketing materialGroo2018/08/17 01:44 PM
            It's marketing materialDoug S2018/08/17 02:14 PM
          promises and deliveriesAM2018/08/17 02:32 PM
            promises and deliveriesPassing Through2018/08/17 03:02 PM
              Just by way of clarification Passing Through2018/08/17 03:15 PM
                Just by way of clarification AM2018/08/18 12:49 PM
                  Just by way of clarification Passing Through2018/08/18 01:34 PM
                    This ain't the nineties any longerPassing Through2018/08/18 01:54 PM
                      This ain't the nineties any longerMaynard Handley2018/08/18 02:50 PM
                        This ain't the nineties any longerPassing Through2018/08/18 03:57 PM
                          This ain't the nineties any longerPassing Through2018/09/06 02:42 PM
                            This ain't the nineties any longerMaynard Handley2018/09/07 04:10 PM
                              This ain't the nineties any longerPassing Through2018/09/07 04:48 PM
                                This ain't the nineties any longerMaynard Handley2018/09/07 05:22 PM
                Just by way of clarification Wilco2018/08/18 01:26 PM
                  Just by way of clarification Passing Through2018/08/18 01:39 PM
                  Just by way of clarification none2018/08/18 10:52 PM
                    Just by way of clarification dmcq2018/08/19 08:32 AM
                      Just by way of clarification none2018/08/19 08:54 AM
                        Just by way of clarification dmcq2018/08/19 11:24 AM
                          Just by way of clarification none2018/08/19 11:52 AM
                  Just by way of clarification Gabriele Svelto2018/08/19 06:41 AM
                    Just by way of clarification Passing Through2018/08/19 09:25 AM
                      Whiteboards at Gatwick airport anyone? Passing Through2018/08/20 04:24 AM
          It's marketing materialMichael S2018/08/18 11:12 AM
          It's marketing materialBrett2018/08/18 05:22 PM
            It's marketing materialBrett2018/08/18 05:33 PM
              It's marketing materialAdrian2018/08/19 01:21 AM
        A76AM2018/08/17 02:45 PM
          A76Michael S2018/08/18 11:20 AM
            A76AM2018/08/18 12:39 PM
              A76Michael S2018/08/18 12:49 PM
                A76AM2018/08/18 01:06 PM
                  A76Doug S2018/08/18 01:43 PM
                    A76Maynard Handley2018/08/18 02:42 PM
                      A76Maynard Handley2018/08/18 04:22 PM
                        Why write zeros when one can use metadata?Paul A. Clayton2018/08/18 06:19 PM
                          Why write zeros when one can use metadata?Maynard Handley2018/08/19 11:12 AM
                            Dictionary compress might apply to memcopyPaul A. Clayton2018/08/19 01:45 PM
                        Instructions for zeroingKonrad Schwarz2018/08/30 06:37 AM
                          Instructions for zeroingMaynard Handley2018/08/30 08:41 AM
                          Instructions for zeroingAdrian2018/08/30 11:37 AM
                            dcbz -> dcbzl (was: Instructions for zeroing)hobold2018/08/31 01:50 AM
                              dcbz -> dcbzl (was: Instructions for zeroing)dmcq2018/09/01 05:28 AM
                      A76Travis2018/08/19 11:36 AM
                        A76Maynard Handley2018/08/19 12:22 PM
                          A76Travis2018/08/19 02:07 PM
                            A76Maynard Handley2018/08/19 06:24 PM
                        Remote atomicsmatthew2018/08/19 12:51 PM
                          Remote atomicsMichael S2018/08/19 01:58 PM
                            Remote atomicsmatthew2018/08/19 02:32 PM
                              Remote atomicsMichael S2018/08/19 02:36 PM
                                Remote atomicsmatthew2018/08/19 02:48 PM
                                  Remote atomicsMichael S2018/08/19 03:16 PM
                                    Remote atomicsRicardo B2018/08/20 10:05 AM
                            Remote atomicsdmcq2018/08/19 02:33 PM
                          Remote atomicsTravis2018/08/19 02:32 PM
                            Remote atomicsMichael S2018/08/19 02:46 PM
                              Remote atomicsTravis2018/08/19 05:35 PM
                                Remote atomicsMichael S2018/08/20 03:29 AM
                            Remote atomicsmatthew2018/08/19 07:58 PM
                              Remote atomicsanon2018/08/20 12:59 AM
                                Remote atomicsTravis2018/08/20 10:26 AM
                              Remote atomicsTravis2018/08/20 09:57 AM
                              Remote atomicsLinus Torvalds2018/08/20 04:29 PM
                                Fitting time slices to execution phasesPaul A. Clayton2018/08/21 09:09 AM
                                  Fitting time slices to execution phasesLinus Torvalds2018/08/21 02:34 PM
                                    Fitting time slices to execution phasesLinus Torvalds2018/08/21 03:31 PM
                                      Fitting time slices to execution phasesGabriele Svelto2018/08/21 03:54 PM
                                        Fitting time slices to execution phasesLinus Torvalds2018/08/21 04:26 PM
                                      Fitting time slices to execution phasesTravis2018/08/21 04:21 PM
                                        Fitting time slices to execution phasesLinus Torvalds2018/08/21 04:39 PM
                                          Fitting time slices to execution phasesTravis2018/08/21 04:59 PM
                                            Fitting time slices to execution phasesLinus Torvalds2018/08/21 05:13 PM
                                      Fitting time slices to execution phasesanon2018/08/21 04:27 PM
                                        Fitting time slices to execution phasesLinus Torvalds2018/08/21 06:02 PM
                                          Fitting time slices to execution phasesEtienne2018/08/22 02:28 AM
                                        Fitting time slices to execution phasesGabriele Svelto2018/08/22 03:07 PM
                                          Fitting time slices to execution phasesTravis2018/08/22 04:00 PM
                                          Fitting time slices to execution phasesanon2018/08/22 06:52 PM
                                    Fitting time slices to execution phasesTravis2018/08/21 04:37 PM
                                    Is preventing misuse that complex?Paul A. Clayton2018/08/23 05:42 AM
                                      Is preventing misuse that complex?Linus Torvalds2018/08/23 12:46 PM
                                        Is preventing misuse that complex?Travis2018/08/23 01:29 PM
                                          Is preventing misuse that complex?Travis2018/08/23 01:33 PM
                                            Is preventing misuse that complex?Jeff S.2018/08/24 07:57 AM
                                              Is preventing misuse that complex?Travis2018/08/24 08:47 AM
                                          Is preventing misuse that complex?Linus Torvalds2018/08/23 02:30 PM
                                            Is preventing misuse that complex?Travis2018/08/23 03:11 PM
                                              Is preventing misuse that complex?Linus Torvalds2018/08/24 01:00 PM
                                                Is preventing misuse that complex?Gabriele Svelto2018/08/24 01:25 PM
                                                  Is preventing misuse that complex?Linus Torvalds2018/08/24 01:33 PM
                                  Fitting time slices to execution phasesTravis2018/08/21 03:54 PM
                                rseq: holy grail rwlock?Travis2018/08/21 03:18 PM
                                  rseq: holy grail rwlock?Linus Torvalds2018/08/21 03:59 PM
                                    rseq: holy grail rwlock?Travis2018/08/21 04:27 PM
                                      rseq: holy grail rwlock?Linus Torvalds2018/08/21 05:10 PM
                                        rseq: holy grail rwlock?Travis2018/08/21 06:21 PM
                  ARM design housesMichael S2018/08/21 05:07 AM
                    ARM design housesWilco2018/08/22 12:38 PM
                      ARM design housesMichael S2018/08/22 02:21 PM
                        ARM design housesWilco2018/08/22 03:23 PM
                          ARM design housesMichael S2018/08/29 01:58 AM
                            Qualcomm's core naming scheme really, really sucksHeikki Kultala2018/08/29 02:19 AM
                A76Maynard Handley2018/08/18 02:07 PM
                  A76Michael S2018/08/18 02:32 PM
                    A76Maynard Handley2018/08/18 02:52 PM
                      A76Michael S2018/08/18 03:04 PM
    ARM is somewhat misleadingjuanrga2018/08/17 01:20 AM
    Surprised??Alberto2018/08/17 01:52 AM
      Surprised??Alberto2018/08/17 02:10 AM
      Surprised??none2018/08/17 02:46 AM
      Garbage talkAndrei Frumusanu2018/08/17 07:30 AM
        Garbage talkMichael S2018/08/17 07:43 AM
          Garbage talkAndrei Frumusanu2018/08/17 09:51 AM
            Garbage talkMichael S2018/08/18 11:29 AM
        Garbage talkAdrian2018/08/17 08:28 AM
          Garbage talkAlberto2018/08/17 09:20 AM
          Garbage talkAndrei Frumusanu2018/08/17 09:48 AM
            Garbage talkAdrian2018/08/17 10:17 AM
              Garbage talkAndrei Frumusanu2018/08/17 10:36 AM
                Garbage talkAdrian2018/08/17 02:53 PM
                  Garbage talkAndrei Frumusanu2018/08/18 12:17 AM
        More like a religion he?? ARM has an easy life :)Alberto2018/08/17 09:13 AM
          More like a religion he?? ARM has an easy life :)Andrei Frumusanu2018/08/17 09:34 AM
            More like a religion he?? ARM has an easy life :)Alberto2018/08/17 10:03 AM
              More like a religion he?? ARM has an easy life :)Andrei Frumusanu2018/08/17 10:43 AM
              More like a religion he?? ARM has an easy life :)Doug S2018/08/17 02:17 PM
              15W phone SoCsAM2018/08/17 03:04 PM
          More like a religion he?? ARM has an easy life :)Maynard Handley2018/08/17 12:29 PM
  my future stuff will be better than your old stuff, hey I'm a god at last (NT)Eric Bron2018/08/18 03:34 AM
    my future stuff will be better than your old stuff, hey I'm a god at lastnone2018/08/18 08:34 AM
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