SPEC is NOT a representation of average workloads

By: Maynard Handley (name99.delete@this.name99.org), November 18, 2020 9:22 am
Room: Moderated Discussions
Adrian (a.delete@this.acm.org) on November 18, 2020 8:15 am wrote:
> Dummond D. Slow (mental.delete@this.protozoa.us) on November 18, 2020 7:48 am wrote:
> >
> > Interesting but "long dependency chains"don't disqualify it as a benchmark, does
> > it. I doubt that it is very expceptional and no other software does that.
> >
> > I hope eventually we get some very comparable HT/noHT CPU in AnandTech benchmark for comparing,
> > in the meantime I found this https://www.anandtech.com/bench/product/2622?vs=2652
> > Skylake @ 3,8-4,2GHz 4c/4t versus 4,0-4,2 4c/8t (sadly also has more L2 cache due to Intel's segmenting).
>
>
>
> A few of the workloads in which I am interested have long dependency chains,
> so there are people for which such benchmarks are interesting.
>
>
> This fact from Andrei, that Cinebench contains long dependency chains,
> explains very well why M1 is less good in it than in other benchmarks.
>
>
> Among 2 CPUs having the same average performance, a benchmark that contains
> long dependency chains will favor the one having a low IPC and a high clock
> frequency, against the one having a high IPC and a low clock frequency.
>

How long is a "long dependency chain"?

The role of the issue queue (what Intel calls "Scheduler Size") is buffer dependency chains and allow you to move execution beyond them, so this is not a trivial question.
If the dependency chains are, say, 30 instructions in length then an issue queue of ~100 entries can run three such chains in parallel.
If the dependency chains are, say, 100 instructions in length, and CPU A has an issue queue of ~100 while CPU B has an issue queue of ~300 then CPU B will be able to run instructions 3x as fast as CPU A all other things being considered.

Even apart from this question (which is a question about the programs) there is a question on the CPU side of how good the issue scheduler(s) are. In particular are the schedulers somehow tracking and informed of criticality?
Adding criticality to the scheduler is not easy (I don't think we have any confirmed cases in the literature) but if you do add that to your scheduler, you can be more certain of running those dependency chains as fast as theoretically possible, while delaying less important work till it can find free slots; whereas if you don't track criticality you may be wasting cycles by giving them to non-critical instructions that just happen to be older than the critical instructions in the chain.
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TopicPosted ByDate
1st round of M1 GPU benchmarksMaynard Handley2020/11/16 12:46 PM
  1st round of M1 GPU benchmarksAdrian2020/11/16 01:02 PM
    1st round of M1 GPU benchmarksI_vs2020/11/17 01:18 AM
  1st round of M1 GPU benchmarksRType2020/11/16 01:06 PM
    1st round of M1 GPU benchmarksMaynard Handley2020/11/16 01:45 PM
      And the NZ'ers are first to deliver cinebench scoresMaynard Handley2020/11/16 02:58 PM
        And the NZ'ers are first to deliver cinebench scoresWill2020/11/16 03:30 PM
          re: "scaling"Dummond D. Slow2020/11/16 04:06 PM
            re: "scaling"Maynard Handley2020/11/16 04:29 PM
              re: "scaling"Dummond D. Slow2020/11/16 04:51 PM
                re: "scaling"Maynard Handley2020/11/16 05:51 PM
                  re: "scaling"Dummond D. Slow2020/11/16 06:22 PM
                    re: "scaling"Maynard Handley2020/11/16 06:23 PM
                      re: "scaling"Maynard Handley2020/11/16 06:27 PM
                        re: "scaling"Dummond D. Slow2020/11/16 06:37 PM
                          re: "scaling"Chester2020/11/16 08:25 PM
                          Actual power consumption values.Dummond D. Slow2020/11/17 07:05 AM
                    re: "scaling"Doug S2020/11/17 10:25 AM
                      Apple loses a lot by not having turbo and SMTDummond D. Slow2020/11/17 11:18 AM
                        Apple loses a lot by not having turbo and SMTDoug S2020/11/17 12:21 PM
                          Apple loses a lot by not having turbo and SMTblaine2020/11/19 05:18 PM
                            Apple loses a lot by not having turbo and SMTDummond D. Slow2020/11/19 05:31 PM
                        Apple loses a lot by not having turbo and SMTTJ2020/11/18 01:10 AM
                          Cinebench is NOT a representation of average workloadsAndrei F2020/11/18 05:21 AM
                            SPEC is NOT a representation of average workloadsChester2020/11/18 07:02 AM
                              SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 07:17 AM
                                SPEC is NOT a representation of average workloadsnone2020/11/18 08:18 AM
                                  x264 without SIMD is nonsenseDummond D. Slow2020/11/18 08:31 AM
                                  SPEC is NOT a representation of average workloadsMaynard Handley2020/11/18 09:13 AM
                                    SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 09:21 AM
                                      SPEC is NOT a representation of average workloadsWilco2020/11/18 09:42 AM
                                        role of hand-optimized assembly in multimedia encodersDummond D. Slow2020/11/18 11:06 AM
                                          role of hand-optimized assembly in multimedia encodersdifferent anon2020/11/18 01:27 PM
                                            role of hand-optimized assembly in multimedia encodersDummond D. Slow2020/11/18 02:47 PM
                                              role of hand-optimized assembly in multimedia encodersDummond D. Slow2021/05/18 12:29 PM
                                          role of hand-optimized assembly in multimedia encodersRichardC2020/11/18 03:42 PM
                                          role of hand-optimized assembly in multimedia encodersnone2020/11/19 07:17 AM
                                      SPEC is NOT a representation of average workloadsnone2020/11/18 10:14 AM
                                        SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 11:17 AM
                                      SPEC is NOT a representation of average workloadsMaynard Handley2020/11/18 11:03 AM
                                        SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 11:25 AM
                                          SPEC is NOT a representation of average workloadsMaynard Handley2020/11/18 12:03 PM
                                            SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 02:57 PM
                                              SPEC is NOT a representation of average workloadsMaynard Handley2020/11/18 04:36 PM
                                                SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 04:50 PM
                                                  SPEC is NOT a representation of average workloadsDoug S2020/11/19 09:13 AM
                                                    SPEC is NOT a representation of average workloads-.-2020/11/19 02:34 PM
                                                    SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/19 02:35 PM
                                              SPEC is NOT a representation of average workloadsEtienne Lorrain2020/11/19 04:04 AM
                                                SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/19 05:58 AM
                                SPEC is NOT a representation of average workloadsChester2020/11/18 02:06 PM
                                  about bitratesDummond D. Slow2020/11/18 03:04 PM
                                    about bitratesChester2020/11/19 02:45 PM
                                  SPEC is NOT a representation of average workloadsOok2020/11/18 03:05 PM
                                    SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 03:21 PM
                                  SPEC is NOT a representation of average workloadsNoSpammer2020/11/19 06:48 AM
                              SPEC is NOT a representation of average workloadsAndrei F2020/11/18 07:44 AM
                                SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 07:48 AM
                                  SPEC is NOT a representation of average workloadsAdrian2020/11/18 08:15 AM
                                    SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 08:41 AM
                                      SPEC is NOT a representation of average workloadsAdrian2020/11/18 09:04 AM
                                        SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 09:32 AM
                                          SPEC is NOT a representation of average workloadsAdrian2020/11/18 10:26 AM
                                    SPEC is NOT a representation of average workloadsMaynard Handley2020/11/18 09:22 AM
                                      SPEC is NOT a representation of average workloadsAdrian2020/11/18 10:28 AM
                                  SPEC is NOT a representation of average workloadsAndrei F2020/11/18 08:34 AM
                                    SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 09:00 AM
                                    SPEC is NOT a representation of average workloadsChester2020/11/18 02:18 PM
                                    SPEC is NOT a representation of average workloadsJukka Larja2020/11/20 08:03 AM
                                SPEC is NOT a representation of average workloadsChester2020/11/18 02:13 PM
                              SPEC is NOT a representation of average workloadsnone2020/11/18 08:07 AM
                                SPEC is NOT a representation of average workloadsMichael S2020/11/18 01:33 PM
                                  Interesting, thanks! (NT)none2020/11/19 07:03 AM
                            Cinebench is NOT a representation of average workloadsrwessel2020/11/18 07:03 AM
                              Cinebench is NOT a representation of average workloadsDoug S2020/11/18 07:44 AM
                                Cinebench is NOT a representation of average workloadsDummond D. Slow2020/11/18 07:52 AM
                                  Cinebench is NOT a representation of average workloadsDoug S2020/11/18 02:59 PM
                                    Cinebench is NOT a representation of average workloadsDummond D. Slow2020/11/18 03:12 PM
                                      Cinebench is NOT a representation of average workloadsDoug S2020/11/19 09:19 AM
                                        Cinebench is NOT a representation of average workloadsDummond D. Slow2020/11/19 03:03 PM
                                          Cinebench is NOT a representation of average workloadsUngo2020/11/19 08:12 PM
                                            Cinebench is NOT a representation of average workloadsDummond D. Slow2020/11/20 08:45 AM
                                It's not really SMT or adding small coresDummond D. Slow2020/11/18 07:58 AM
                                  It's not really SMT or adding small coresDoug S2020/11/18 03:02 PM
                                    It's not really SMT or adding small coresDummond D. Slow2020/11/18 03:27 PM
                                Cinebench is NOT a representation of average workloadsxyz2020/11/18 12:14 PM
                                  Cinebench is NOT a representation of average workloadsMaynard Handley2020/11/18 12:54 PM
                                    Cinebench is NOT a representation of average workloadsGabriele Svelto2020/11/18 01:41 PM
                                      Cinebench is NOT a representation of average workloadsMaynard Handley2020/11/18 01:52 PM
                                        Cinebench is NOT a representation of average workloadsGabriele Svelto2020/11/18 02:05 PM
                            Cinebench is NOT a representation of average workloadsTJ2020/11/18 11:46 AM
                            SMT shines in IO heavy & commercial DB workloadsxyz2020/11/18 12:05 PM
                            "Average workloads" don't exist (NT)Foo_2020/11/19 02:55 AM
                          Apple loses a lot by not having turbo and SMTDummond D. Slow2020/11/18 07:02 AM
                            Apple loses a lot by not having turbo and SMTMaynard Handley2020/11/18 08:37 AM
                              Apple loses a lot by not having turbo and SMTDummond D. Slow2020/11/18 08:55 AM
                              Apple loses a lot by not having turbo and SMTDavid Hess2020/11/18 12:12 PM
                                Apple loses a lot by not having turbo and SMTMaynard Handley2020/11/18 01:12 PM
                                  Apple loses a lot by not having turbo and SMTJörn Engel2020/11/18 04:04 PM
                                    Apple loses a lot by not having turbo and SMTanonymou52020/11/18 04:37 PM
                                      Apple loses a lot by not having turbo and SMTJörn Engel2020/11/19 03:28 AM
                                  Apple loses a lot by not having turbo and SMTDavid Hess'2020/11/19 06:25 PM
                          Apple loses a lot by not having turbo and SMTAdrian2020/11/18 07:23 AM
                            Apple loses a lot by not having turbo and SMTgallier22020/11/18 11:21 PM
                              Apple loses a lot by not having turbo and SMTJames2020/11/19 01:22 AM
                                Apple loses a lot by not having turbo and SMTWilco2020/11/19 04:06 AM
                              Apple loses a lot by not having turbo and SMTanonymou52020/11/19 01:34 AM
                                Apple loses a lot by not having turbo and SMTgallier22020/11/19 08:04 AM
                                  big.LITTLE with different ISAsJames2020/11/19 08:41 AM
                                    big.LITTLE with different ISAsgallier22020/11/20 02:36 AM
                                    big.LITTLE with different ISAsanon2020/11/20 12:31 PM
                              Apple loses a lot by not having turbo and SMTAdrian2020/11/19 01:56 AM
                        Apple loses a lot by not having turbo and SMTJon Masters2020/11/18 11:46 AM
                          Apple loses a lot by not having turbo and SMTanonymou52020/11/18 02:41 PM
                          Apple loses a lot by not having turbo and SMTDummond D. Slow2020/11/18 03:17 PM
                            Apple loses a lot by not having turbo and SMTMaynard Handley2020/11/18 04:46 PM
                              Apple loses a lot by not having turbo and SMTJon Masters2020/11/18 11:31 PM
                                Apple loses a lot by not having turbo and SMTDummond D. Slow2020/11/19 06:01 AM
                              Apple loses a lot by not having turbo and SMTAdrian2020/11/19 01:50 AM
                                Apple loses a lot by not having turbo and SMTAdrian2020/11/19 02:10 AM
                                Apple loses a lot by not having turbo and SMTMaynard Handley2020/11/19 09:13 AM
                                  Apple loses a lot by not having turbo and SMTDummond D. Slow2020/11/19 03:10 PM
                        Apple loses a lot by not having turbo and SMTjuanrga2020/11/19 01:49 AM
                    re: "scaling"sr2020/11/17 11:39 AM
                      re: "scaling"Adrian2020/11/17 12:41 PM
                        re: "scaling"Adrian2020/11/17 12:52 PM
                          re: "scaling"Chester2020/11/17 05:29 PM
                  re: "scaling"anonymou52020/11/16 07:18 PM
                    re: "scaling"Maynard Handley2020/11/16 07:44 PM
        And the NZ'ers are first to deliver cinebench scoresDummond D. Slow2020/11/16 04:12 PM
          And the NZ'ers are first to deliver cinebench scoresMaynard Handley2020/11/16 04:31 PM
            And the NZ'ers are first to deliver cinebench scoresDummond D. Slow2020/11/16 04:46 PM
        And the NZ'ers are first to deliver cinebench scoresMaynard Handley2020/11/16 06:04 PM
          And the NZ'ers are first to deliver cinebench scoresDummond D. Slow2020/11/16 06:28 PM
  1st round of M1 GPU benchmarksRayla2020/11/16 03:16 PM
    1st round of M1 GPU benchmarksChester2020/11/16 08:17 PM
  Phoronix Mac mini M1 benchanon52020/11/20 10:51 AM
    Phoronix Mac mini M1 benchPer Hesselgren2020/11/24 09:04 AM
      Phoronix Mac mini M1 benchPaul2020/11/25 02:08 AM
        Phoronix Mac mini M1 benchPaul2020/11/25 02:12 AM
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