lmbench is horribly broken

By: Gabriele Svelto (gabriele.svelto.delete@this.gmail.com), March 18, 2017 4:01 pm
Room: Moderated Discussions
Linus Torvalds (torvalds.delete@this.linux-foundation.org) on March 17, 2017 6:43 pm wrote:
> When a CPU cache hierarchy grows a level (say, it gets a L3 cache, or it gets an external
> L4 cache, or whatever), the memory latency tends to invariably go up, exactly because there
> is now more cache lookup going on before the memory access is really started.

On a side note, isn't this a modern thing? IIRC back in the day when power wasn't a limiter to performance we used to send out both the access to the LLC and to memory at the same time to reduce latency in case of an LLC miss (and I'm talking of the times where LLC meant off-chip L2). The reason it's not done today is that it would burn far too much power to do so.
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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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