lmbench is horribly broken

By: Linus Torvalds (torvalds.delete@this.linux-foundation.org), March 19, 2017 3:51 pm
Room: Moderated Discussions
Exophase (exophase.delete@this.gmail.com) on March 18, 2017 4:26 pm wrote:
>
> Sorry but I'm still having a hard time with this. And I might be missing something still.
> But as far as I understand it with lmbench's thrash_initialize the order in which memory
> accesses and page table accesses are made is random.

Absolutely.

lmbench tries to emulate a pretty extreme pointer chasing load. That is, after all, where memory latency is most noticeable.

It's more random than most loads are in reality, and real loads obviously are never purely about pointer chasing, but it's not at all a horrible test-case for one very specific issue.
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TopicPosted ByDate
ARM A73 benchmarksSymmetry2017/03/14 06:24 AM
  ARM A73 benchmarksPer Hesselgren2017/03/14 07:18 AM
    ARM A73 benchmarks-latencyPer Hesselgren2017/03/14 08:58 AM
      ARM A73 benchmarks-latencySymmetry2017/03/14 10:12 AM
        ARM A73 benchmarks-latencyPer Hesselgren2017/03/14 03:54 PM
          ARM A73 benchmarks-latencyWilco2017/03/15 01:45 AM
            ARM A73 benchmarks-latencyPer Hesselgren2017/03/15 02:57 AM
              ARM A73 benchmarks-latencyPer Hesselgren2017/03/15 03:00 AM
                ARM A73 benchmarks-latencyPer Hesselgren2017/03/15 03:01 AM
                  clickable linkMichael S2017/03/15 04:05 AM
            ARM A73 benchmarks-latencyLinus Torvalds2017/03/15 10:05 AM
              ARM A73 benchmarks-latencyIreland2017/03/15 05:02 PM
              ARM A73 benchmarks-latencyGabriele Svelto2017/03/16 03:45 AM
                ARM A73 benchmarks-latencyLinus Torvalds2017/03/16 02:01 PM
                  lmbench is horribly brokenWilco2017/03/16 04:57 PM
                    lmbench is horribly brokenLinus Torvalds2017/03/16 06:49 PM
                      lmbench is horribly brokenLinus Torvalds2017/03/17 01:10 PM
                        lmbench is horribly brokenLinus Torvalds2017/03/17 01:52 PM
                        lmbench is horribly brokenExophase2017/03/17 02:31 PM
                          lmbench is horribly brokenGabriele Svelto2017/03/17 03:20 PM
                          lmbench is horribly brokenLinus Torvalds2017/03/17 05:56 PM
                            lmbench is horribly brokenExophase2017/03/17 06:21 PM
                              lmbench is horribly brokenLinus Torvalds2017/03/17 06:43 PM
                                lmbench is horribly brokenIreland2017/03/17 07:37 PM
                                  lmbench is horribly brokenbakaneko2017/03/18 11:17 AM
                                    lmbench is horribly brokenIreland2017/03/18 12:23 PM
                                      lmbench is horribly brokenanon2017/03/18 07:35 PM
                                      lmbench is horribly brokenbakaneko2017/03/21 08:08 AM
                                        lmbench is horribly brokenIreland2017/03/21 03:14 PM
                                lmbench is horribly brokenGabriele Svelto2017/03/18 04:01 PM
                                  accessing dram RichardC2017/03/18 06:33 PM
                                lmbench is horribly brokenExophase2017/03/18 04:26 PM
                                  lmbench is horribly brokenWilco2017/03/18 05:40 PM
                                    benchmarking reality?Anon2017/03/19 02:29 PM
                                    lmbench is horribly brokenLinus Torvalds2017/03/19 04:25 PM
                                      mea culpa (lmbench is horribly broken)Linus Torvalds2017/03/19 06:05 PM
                                        mea culpa (lmbench is horribly broken)Bill Broadley2017/03/21 01:41 AM
                                          mea culpa (lmbench is horribly broken)Linus Torvalds2017/03/21 09:01 AM
                                            mea culpa (lmbench is horribly broken)Linus Torvalds2017/03/21 11:14 AM
                                            mea culpa (lmbench is horribly broken)Linus Torvalds2017/03/21 05:03 PM
                                              mea culpa (lmbench is horribly broken)Etienne2017/03/22 04:37 AM
                                              mea culpa (lmbench is horribly broken)Tim McCaffrey2017/03/22 08:54 AM
                                                mea culpa (lmbench is horribly broken)Tim McCaffrey2017/03/22 09:34 AM
                                                mea culpa (lmbench is horribly broken)Linus Torvalds2017/03/22 10:35 AM
                                                  mea culpa (lmbench is horribly broken)Ireland2017/03/22 12:11 PM
                                                    mea culpa (lmbench is horribly broken)Ireland2017/03/22 12:26 PM
                                                    mea culpa (lmbench is horribly broken)rwessel2017/03/22 03:03 PM
                                                      mea culpa (lmbench is horribly broken)Ireland2017/03/22 03:35 PM
                                                  mea culpa (lmbench is horribly broken)Linus Torvalds2017/03/22 01:35 PM
                                                    mea culpa (lmbench is horribly broken)Gabriele Svelto2017/03/23 08:05 AM
                                                      mea culpa (lmbench is horribly broken)Linus Torvalds2017/03/23 10:43 AM
                                                        mea culpa (lmbench is horribly broken)Gabriele Svelto2017/03/23 01:56 PM
                                                          mea culpa (lmbench is horribly broken)Ireland2017/03/23 02:36 PM
                                                  mea culpa (lmbench is horribly broken)Travis2017/03/22 01:38 PM
                                              mea culpa (lmbench is horribly broken)anon2017/03/22 07:22 PM
                                                mea culpa (lmbench is horribly broken)Travis2017/03/22 08:57 PM
                                                  mea culpa (lmbench is horribly broken)anon2017/03/23 12:44 AM
                                                    mea culpa (lmbench is horribly broken)Michael S2017/03/23 05:59 PM
                                                      mea culpa (lmbench is horribly broken)Travis2017/03/23 09:03 PM
                                                    power8 numbersoctoploid2017/03/24 11:47 PM
                                                      power8 numbers stride=128octoploid2017/03/25 04:36 AM
                                                        power8 numbers stride=128Linus Torvalds2017/03/25 10:50 AM
                                                          power8 numbers stride=128Gabriele Svelto2017/03/25 11:27 PM
                                              mea culpa (lmbench is horribly broken)anon2017/03/23 01:14 AM
                                                mea culpa (lmbench is horribly broken)Linus Torvalds2017/03/23 11:22 AM
                                                  Thank you. Associativity misses explain it.anon2017/03/23 10:48 PM
                                                    Thank you. Associativity misses explain it.Linus Torvalds2017/03/24 01:26 PM
                                                      Thank you. Associativity misses explain it.Travis2017/03/24 10:01 PM
                                                        thanks should read "but if it is any TYPE of mix" (NT)Travis2017/03/24 10:02 PM
                                                        Thank you. Associativity misses explain it.Linus Torvalds2017/03/25 12:10 PM
                                                          Thank you. Associativity misses explain it.Travis2017/03/25 04:08 PM
                                                            Thank you. Associativity misses explain it.Linus Torvalds2017/03/26 10:27 AM
                                  lmbench is horribly brokenLinus Torvalds2017/03/19 03:51 PM
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