Messages in this thread |  | | Subject | Re: [RESEND PATCH] sched/fair: consider RT/IRQ pressure in select_idle_sibling | From | Rohit Jain <> | Date | Tue, 6 Feb 2018 09:36:19 -0800 |
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On 02/05/2018 10:42 PM, Joel Fernandes wrote: > On Tue, Jan 30, 2018 at 11:47 AM, Rohit Jain <rohit.k.jain@oracle.com> wrote: > [...] >>>> @@ -6102,7 +6107,8 @@ static int select_idle_core(struct task_struct *p, >>>> struct sched_domain *sd, int >>>> */ >>>> static int select_idle_smt(struct task_struct *p, struct sched_domain >>>> *sd, int target) >>>> { >>>> - int cpu; >>>> + int cpu, rcpu = -1; >>>> + unsigned long max_cap = 0; >>>> >>>> if (!static_branch_likely(&sched_smt_present)) >>>> return -1; >>>> @@ -6110,11 +6116,13 @@ static int select_idle_smt(struct task_struct *p, >>>> struct sched_domain *sd, int t >>>> for_each_cpu(cpu, cpu_smt_mask(target)) { >>>> if (!cpumask_test_cpu(cpu, &p->cpus_allowed)) >>>> continue; >>>> - if (idle_cpu(cpu)) >>>> - return cpu; >>>> + if (idle_cpu(cpu) && (capacity_of(cpu) > max_cap)) { >>>> + max_cap = capacity_of(cpu); >>>> + rcpu = cpu; >>> At the SMT level, do you need to bother with choosing best capacity >>> among threads? If RT is eating into one of the SMT thread's underlying >>> capacity, it would eat into the other's. Wondering what's the benefit >>> of doing this here. >> >> Yes, you are right because of SD_SHARE_CPUCAPACITY, however the benefit >> is that if don't do this check, we might end up picking a SMT thread >> which has "high" RT/IRQ activity and be on the run queue for a while, >> till the pull side can bail us out. > Do your tests show a difference in results though with such change > (for select_idle_smt)?
I don't have the numbers readily available, but I did see a measurable difference with the select_idle_smt changes.
Thanks, Rohit
> > thanks, > > - Joel
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