Public bug reported: [Impact]
When running erlang benchmark: https://github.com/jessestimpson/ets_load_benchmark_public.git Spwan more processes, the performance drops rapidly compare to 1 process, this issue was introduced on 5.18 kernel, 5.17 doesn't have this issue. Description of benchmark: n = number of processes f = % of performance relative to n = 1 r = raw rate, t = time 5.17 benchmark result: n,f,r,t 1,1.0,9120867,5.003 2,0.5061354891733854,4616394,5.001 4,0.08950992302914515,816408,5.006 8,0.01184452801350521,108032,5.098 16,0.010647457942399005,97114,5.182 32,0.010625520850290194,96913,5.672 64,0.010831249272826072,98790,12.418 128,0.010497878077414494,95749,27.061 256,0.010104340575500272,92160,57.469 5.18 benchmark result: n,f,r,t 1,1.0,9382016,5.004 2,0.4953986691824555,4647838,5.001 4,0.10023648870773996,940420,5.005 8,0.008932429179095262,83804,6.195 16,0.0018372315021540654,17236,9.243 32,9.585592402608068e-4,8993,22.119 64,8.145250697989274e-4,7641,91.865 128,7.778153535259693e-4,7297,278.728 256,7.679856301480621e-4,7205,633.869 This can be reproduced on noble 6.8 kernel: n,f,r,t 1,1.0,9319448,5.005 2,0.48816914209026224,4549467,5.001 4,0.08824585392034001,822402,5.004 8,0.0023127649346702354,21553,6.444 16,0.0010507673678827175,9792,10.905 32,8.959956782593959e-4,8350,22.648 64,0.0013944409643284223,12995,6.551 128,7.658929844955412e-4,7137,294.023 256,7.462181950964878e-4,6954,619.978 and plucky 6.14 kernel: n,f,r,t 1,1.0,9321196,5.005 2,0.5362295256010277,4998300,5.001 4,0.09392833281067568,875524,5.005 8,0.07644864029595455,712592,5.015 16,0.0013813520394405897,12875,9.658 32,7.711512948349701e-4,7188,19.553 64,0.0013429338424364038,12517,7.042 128,7.457826804441801e-4,6951,110.797 256,7.542013889959581e-4,7030,677.621 [Fix] Upstream fixes this issue in cpuidle governor: commit 85975daeaa4d6ec560bfcd354fc9c08ad7f38888 Author: Rafael J. Wysocki <[email protected]> Date: Thu Feb 6 15:29:05 2025 +0100 cpuidle: menu: Avoid discarding useful information and also a follwoing commit to fix the above commit: commit fa3fa55de0d6177fdcaf6fc254f13cc8f33c3eed Author: Rafael J. Wysocki <[email protected]> Date: Mon Aug 11 17:03:11 2025 +0200 cpuidle: governors: menu: Avoid using invalid recent intervals data Marc has reported that commit 85975daeaa4d ("cpuidle: menu: Avoid discarding useful information") caused the number of wakeup interrupts to increase on an idle system [1], which was not expected to happen after merely allowing shallower idle states to be selected by the governor in some cases. [Test Plan] Use the following steps can easily reproduce the issue: sudo apt install erlang-base -y git clone https://github.com/jessestimpson/ets_load_benchmark_public.git cd ets_load_benchmark_public erlc ets_load_benchmark.erl erl -noshell -s ets_load_benchmark -eval 'init:stop().' [Where problems could occur] These patches fix the cpuidle governor issue and are verified by upstream, if something really goes wrong, it could only affect cpu idle policy and cause more power consumption. ** Affects: linux (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2122006 Title: Performance degrades rapidly when spawning more processes to run benchmark To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2122006/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
