Messages in this thread |  | | Subject | Re: [RESEND PATCH] sched/fair: consider RT/IRQ pressure in select_idle_sibling | From | Dietmar Eggemann <> | Date | Wed, 14 Feb 2018 10:11:21 +0100 |
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On 02/09/2018 11:05 PM, Rohit Jain wrote: > > On 02/09/2018 07:46 AM, Dietmar Eggemann wrote: >> On 02/09/2018 01:53 PM, Peter Zijlstra wrote: >>> On Mon, Jan 29, 2018 at 03:27:09PM -0800, Rohit Jain wrote: >> >> [...] >> >>>> @@ -6173,8 +6183,15 @@ static int select_idle_cpu(struct task_struct >>>> *p, struct sched_domain *sd, int t >>>> return -1; >>>> if (!cpumask_test_cpu(cpu, &p->cpus_allowed)) >>>> continue; >>>> + if (idle_cpu(cpu)) { >>>> + if (full_capacity(cpu)) { >>>> + best_cpu = cpu; >>>> + break; >>>> + } else if (capacity_of(cpu) > best_cap) { >>>> + best_cap = capacity_of(cpu); >>>> + best_cpu = cpu; >>>> + } >>>> + } >>> >>> No need for the else. And you'll note you're once again inconsistent >>> with your previous self. >>> >>> But here I worry about big.little a wee bit. I think we're allowed big >>> and little cores on the same L3 these days, and you can't directly >>> compare capacity between them. >>> >>> Morten / Dietmar, any comments? >> >> Yes, for DynamIQ (big.little successor) systems, those cpus can have >> different capacity_orig_of() values already. >> > > OK, given that there are asymmetric capacities in L3 cores, we would > probably have something like the below(?) in select_idle_cpu: > > if (!cpumask_test_cpu(cpu, &p->cpus_allowed)) > continue; > + if (idle_cpu(cpu) && !reduced_capacity(cpu)) > + break; >
Only returning the first idle cpu w/o reduced capacity will definitely work better here on future DynamIQ systems than trying to find the best_cap cpu by taking capacity_of() into consideration.
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