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> >>> + if (fits > 0) { > >>> + if (prefer_idle_cores && on_idle_core) > >>> + return cpu; > >>> + if (!prefer_idle_cores) > >>> + return cpu; > >> > >> nit. > >> > >> Can the above two be re-wittern as: > >> > >> if (!prefer_idle_cores || on_idle_core) > >> return cpu; > >> > >> since they are equivalent. > > > > Oh yes, indeed. > > Also, can we just rewrite this Patch as: > > (Includes feedback from Vincent; Only build tested) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 700d0f145ca6..cffd5649b54e 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -7946,6 +7946,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool > static int > select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target) > { > + bool prefers_idle_core = sched_smt_active() && test_idle_cores(target); > unsigned long task_util, util_min, util_max, best_cap = 0; > int fits, best_fits = 0; > int cpu, best_cpu = -1; > @@ -7959,6 +7960,7 @@ select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target) > util_max = uclamp_eff_value(p, UCLAMP_MAX); > > for_each_cpu_wrap(cpu, cpus, target) { > + bool preferred_core = !prefers_idle_core || is_core_idle(cpu); > unsigned long cpu_cap = capacity_of(cpu); > > if (!choose_idle_cpu(cpu, p)) > @@ -7967,7 +7969,7 @@ select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target) > fits = util_fits_cpu(task_util, util_min, util_max, cpu); > > /* This CPU fits with all requirements */ > - if (fits > 0) > + if (fits > 0 && preferred_core) > return cpu; > /* > * Only the min performance hint (i.e. uclamp_min) doesn't fit. > @@ -7976,6 +7978,14 @@ select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target) > else if (fits < 0) > cpu_cap = get_actual_cpu_capacity(cpu); > > + /* > + * If we are on an preferred core, translate the range of fits > + * from [-1, 1] to [-4, -2]. This ensures that an idle core > + * is always given priority over (paritally) busy core. > + */ > + if (preferred_core) > + fits -= 3; > + Ah, I like this trick. Yes, this definitely makes the patch more compact. > /* > * First, select CPU which fits better (-1 being better than 0). > * Then, select the one with best capacity at same level. > --- > > My naive eyes say it should be equivalent of what you have but maybe > I'm wrong? It seems correct to my naive eyes as well. Will test this out to make sure. Unfortunately I just lost access to my system (bummer), I found another Vera machine, but this one has a version of the firmware that exposes all CPUs with the same highest_perf... so I can still do some testing, but not the same one with SD_ASYM_CPUCAPACITY + SMT. I should get access to the previous system with the different highest_perf values on Monday. Thanks, -Andrea