Messages in this thread | | | Subject | Re: [PATCH v3 5/7] sched: SIS_CORE to disable idle core search | From | Subhra Mazumdar <> | Date | Sun, 14 Jul 2019 06:46:01 +0530 |
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On 7/4/19 6:04 PM, Parth Shah wrote: > Same experiment with hackbench and with perf analysis shows increase in L1 > cache miss rate with these patches > (Lower is better) > Baseline(%) Patch(%) > ----------------------- ------------- ----------- > Total Cache miss rate 17.01 19(-11%) > L1 icache miss rate 5.45 6.7(-22%) > > > > So is is possible for idle_cpu search to try checking target_cpu first and > then goto sliding window if not found. > Below diff works as expected in IBM POWER9 system and resolves the problem > of far wakeup upto large extent. > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index ff2e9b5c3ac5..fae035ce1162 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6161,6 +6161,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t > u64 time, cost; > s64 delta; > int cpu, limit, floor, target_tmp, nr = INT_MAX; > + struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask); > > this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); > if (!this_sd) > @@ -6198,16 +6199,22 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t > > time = local_clock(); > > - for_each_cpu_wrap(cpu, sched_domain_span(sd), target_tmp) { > + cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed); > + for_each_cpu_wrap(cpu, cpu_smt_mask(target), target) { > + __cpumask_clear_cpu(cpu, cpus); > + if (available_idle_cpu(cpu)) > + goto idle_cpu_exit; > + } > + > + for_each_cpu_wrap(cpu, cpus, target_tmp) { > per_cpu(next_cpu, target) = cpu; > if (!--nr) > return -1; > - if (!cpumask_test_cpu(cpu, &p->cpus_allowed)) > - continue; > if (available_idle_cpu(cpu)) > break; > } > > +idle_cpu_exit: > time = local_clock() - time; > cost = this_sd->avg_scan_cost; > delta = (s64)(time - cost) / 8; > > > > Best, > Parth How about calling select_idle_smt before select_idle_cpu from select_idle_sibling? That should have the same effect.
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