lmbench is horribly broken

By: Gabriele Svelto (gabriele.svelto.delete@this.gmail.com), March 17, 2017 3:20 pm
Room: Moderated Discussions
Exophase (exophase.delete@this.gmail.com) on March 17, 2017 2:31 pm wrote:
> Now yes, of course you can argue that the double memory access case is useful too, but I have
> a suspicion that in the real world it's more common on LLC misses to hit the TLB or at least
> the cache when loading the TLB than it is not.

That's true in the case your workload has a certain amount of locality so when you miss in your LLC, the following misses end up "around" the previous one and thus hit the TLB entry you just reloaded. Generally speaking since TLBs rarely cover the entirety of the LLC there's a good chance that you have at least a TLB miss for each "group" of LLC misses that go out to a certain region. The relative amount of TLB misses will depend on the workload (with HPC type of codes accessing very large, very sparse arrays representing the absolute worst case where you approach one TLB miss per LLC miss). I suspect that very large in-memory databases also suffer from very high TLB-miss-per-LLC-miss ratios which would explain the widespread use of huge pages for those kind of workloads.
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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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