Messages in this thread | | | Subject | Re: [RESEND PATCH v5 2/2] sched/fair: Scan cluster before scanning LLC in wake-up path | From | Yicong Yang <> | Date | Thu, 21 Jul 2022 20:42:12 +0800 |
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On 2022/7/21 18:33, Peter Zijlstra wrote: > On Thu, Jul 21, 2022 at 09:38:04PM +1200, Barry Song wrote: >> On Wed, Jul 20, 2022 at 11:15 PM Peter Zijlstra <peterz@infradead.org> wrote: >>> >>> On Wed, Jul 20, 2022 at 04:11:50PM +0800, Yicong Yang wrote: >>>> + /* TODO: Support SMT system with cluster topology */ >>>> + if (!sched_smt_active() && sd) { >>>> + for_each_cpu_and(cpu, cpus, sched_domain_span(sd)) { >>> >>> So that's no SMT and no wrap iteration.. >>> >>> Does something like this work? >>> >>> --- >>> --- a/kernel/sched/fair.c >>> +++ b/kernel/sched/fair.c >>> @@ -6437,6 +6437,30 @@ static int select_idle_cpu(struct task_s >>> } >>> } >>> >>> + if (IS_ENABLED(CONFIG_SCHED_CLUSTER) && >>> + static_branch_unlikely(&sched_cluster_active)) { >>> + struct sched_domain *sdc = rcu_dereference(per_cpu(sd_cluster, target)); >>> + if (sdc) { >>> + for_each_cpu_wrap(cpu, sched_domain_span(sdc), target + 1) { >>> + if (!cpumask_test_cpu(cpu, cpus)) >>> + continue; >>> + >>> + if (has_idle_core) { >>> + i = select_idle_core(p, cpu, cpus, &idle_cpu); >>> + if ((unsigned int)i < nr_cpumask_bits) >>> + return i; >>> + } else { >>> + if (--nr <= 0) >>> + return -1; >>> + idle_cpu = __select_idle_cpu(cpu, p); >>> + if ((unsigned int)idle_cpu < nr_cpumask_bits) >>> + break; >> >> Guess here it should be "return idle_cpu", but not "break". as "break" >> will make us scan more >> other cpus outside the cluster if we have found idle_cpu within the cluster. >>
That can explain why the performance regress when underload.
>> Yicong, >> Please test Peter's code with the above change. > > Indeed. Sorry for that. >
The performance's still positive based on the tip/sched/core used in this patch's commit. 70fb5ccf2ebb ("sched/fair: Introduce SIS_UTIL to search idle CPU based on sum of util_avg").
On numa 0: tip/core patched Hmean 1 345.89 ( 0.00%) 398.43 * 15.19%* Hmean 2 697.77 ( 0.00%) 794.40 * 13.85%* Hmean 4 1392.51 ( 0.00%) 1577.60 * 13.29%* Hmean 8 2800.61 ( 0.00%) 3118.38 * 11.35%* Hmean 16 5514.27 ( 0.00%) 6124.51 * 11.07%* Hmean 32 10869.81 ( 0.00%) 10690.97 * -1.65%* Hmean 64 8315.22 ( 0.00%) 8520.73 * 2.47%* Hmean 128 6324.47 ( 0.00%) 7253.65 * 14.69%*
On numa 0-1: tip/core patched Hmean 1 348.68 ( 0.00%) 397.74 * 14.07%* Hmean 2 693.57 ( 0.00%) 795.54 * 14.70%* Hmean 4 1369.26 ( 0.00%) 1548.72 * 13.11%* Hmean 8 2772.99 ( 0.00%) 3055.54 * 10.19%* Hmean 16 4825.83 ( 0.00%) 5936.64 * 23.02%* Hmean 32 10250.32 ( 0.00%) 11780.59 * 14.93%* Hmean 64 16309.51 ( 0.00%) 19864.38 * 21.80%* Hmean 128 13022.32 ( 0.00%) 16365.43 * 25.67%* Hmean 256 11335.79 ( 0.00%) 13991.33 * 23.43%*
Hi Peter,
Do you want me to respin a v6 based on your change?
Thanks, Yicong
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