Messages in this thread |  | | From | Vincent Guittot <> | Date | Thu, 21 Oct 2021 14:42:03 +0200 | Subject | Re: [PATCH v3 0/5] Improve newidle lb cost tracking and early abort |
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On Thu, 21 Oct 2021 at 11:52, Mel Gorman <mgorman@suse.de> wrote: > > On Tue, Oct 19, 2021 at 02:35:32PM +0200, Vincent Guittot wrote: > > This patchset updates newidle lb cost tracking and early abort: > > > > The time spent running update_blocked_averages is now accounted in the 1st > > sched_domain level. This time can be significant and move the cost of > > newidle lb above the avg_idle time. > > > > The decay of max_newidle_lb_cost is modified to start only when the field > > has not been updated for a while. Recent update will not be decayed > > immediatlybut only after a while. > > > > The condition of an avg_idle lower than sysctl_sched_migration_cost has > > been removed as the 500us value is quite large and prevent opportunity to > > pull task on the newly idle CPU for at least 1st domain levels. > > > > Monitoring sd->max_newidle_lb_cost on cpu0 of a Arm64 system > > THX2 (2 nodes * 28 cores * 4 cpus) during the benchmarks gives the > > following results: > > min avg max > > SMT: 1us 33us 273us - this one includes the update of blocked load > > MC: 7us 49us 398us > > NUMA: 10us 45us 158us > > > > > > Some results for hackbench -l $LOOPS -g $group : > > group tip/sched/core + this patchset > > 1 15.189(+/- 2%) 14.987(+/- 2%) +1% > > 4 4.336(+/- 3%) 4.322(+/- 5%) +0% > > 16 3.654(+/- 1%) 2.922(+/- 3%) +20% > > 32 3.209(+/- 1%) 2.919(+/- 3%) +9% > > 64 2.965(+/- 1%) 2.826(+/- 1%) +4% > > 128 2.954(+/- 1%) 2.993(+/- 8%) -1% > > 256 2.951(+/- 1%) 2.894(+/- 1%) +2% > > > > I read the patches earlier but had queued tests and waiting on the results > before Acking. The hackbench results were not bad, not a universal win, > but wins more than it loses with small decreaseds in system CPU usage.
Thanks for running tests
> > Most other results showed small gains or losses, nothing overly dramatic > and mostly within the noise. > > -- > Mel Gorman > SUSE Labs
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