Hi, On Fri, Aug 02, 2019 at 11:37:15AM -0400 Julien Desfossez wrote: > We tested both Aaron's and Tim's patches and here are our results. > > Test setup: > - 2 1-thread sysbench, one running the cpu benchmark, the other one the > mem benchmark > - both started at the same time > - both are pinned on the same core (2 hardware threads) > - 10 30-seconds runs > - test script: https://paste.debian.net/plainh/834cf45c > - only showing the CPU events/sec (higher is better) > - tested 4 tag configurations: > - no tag > - sysbench mem untagged, sysbench cpu tagged > - sysbench mem tagged, sysbench cpu untagged > - both tagged with a different tag > - "Alone" is the sysbench CPU running alone on the core, no tag > - "nosmt" is both sysbench pinned on the same hardware thread, no tag > - "Tim's full patchset + sched" is an experiment with Tim's patchset > combined with Aaron's "hack patch" to get rid of the remaining deep > idle cases > - In all test cases, both tasks can run simultaneously (which was not > the case without those patches), but the standard deviation is a > pretty good indicator of the fairness/consistency. > > No tag > ------ > Test Average Stdev > Alone 1306.90 0.94 > nosmt 649.95 1.44 > Aaron's full patchset: 828.15 32.45 > Aaron's first 2 patches: 832.12 36.53 > Aaron's 3rd patch alone: 864.21 3.68 > Tim's full patchset: 852.50 4.11 > Tim's full patchset + sched: 852.59 8.25 > > Sysbench mem untagged, sysbench cpu tagged > ------------------------------------------ > Test Average Stdev > Alone 1306.90 0.94 > nosmt 649.95 1.44 > Aaron's full patchset: 586.06 1.77 > Aaron's first 2 patches: 630.08 47.30 > Aaron's 3rd patch alone: 1086.65 246.54 > Tim's full patchset: 852.50 4.11 > Tim's full patchset + sched: 390.49 15.76 > > Sysbench mem tagged, sysbench cpu untagged > ------------------------------------------ > Test Average Stdev > Alone 1306.90 0.94 > nosmt 649.95 1.44 > Aaron's full patchset: 583.77 3.52 > Aaron's first 2 patches: 513.63 63.09 > Aaron's 3rd patch alone: 1171.23 3.35 > Tim's full patchset: 564.04 58.05 > Tim's full patchset + sched: 1026.16 49.43 > > Both sysbench tagged > -------------------- > Test Average Stdev > Alone 1306.90 0.94 > nosmt 649.95 1.44 > Aaron's full patchset: 582.15 3.75 > Aaron's first 2 patches: 561.07 91.61 > Aaron's 3rd patch alone: 638.49 231.06 > Tim's full patchset: 679.43 70.07 > Tim's full patchset + sched: 664.34 210.14 >
Sorry if I'm missing something obvious here but with only 2 processes of interest shouldn't one tagged and one untagged be about the same as both tagged? In both cases the 2 sysbenches should not be running on the core at the same time. There will be times when oher non-related threads could share the core with the untagged one. Is that enough to account for this difference? Thanks, Phil > So in terms of fairness, Aaron's full patchset is the most consistent, but > only > Tim's patchset performs better than nosmt in some conditions. > > Of course, this is one of the worst case scenario, as soon as we have > multithreaded applications on overcommitted systems, core scheduling performs > better than nosmt. > > Thanks, > > Julien --
