Re: [PATCH v5 08/10] cpufreq/schedutil: take into account interrupt

Vincent Guittot
2018-05-28T12:06:30Z

Hi Juri,

On 28 May 2018 at 12:41, Juri Lelli <juri.lelli@redhat.com> wrote:
> Hi Vincent,
>
> On 25/05/18 15:12, Vincent Guittot wrote:
>> The time spent under interrupt can be significant but it is not reflected
>> in the utilization of CPU when deciding to choose an OPP. Now that we have
>> access to this metric, schedutil can take it into account when selecting
>> the OPP for a CPU.
>> The CPU utilization is :
>> irq util_avg + (1 - irq util_avg / max capacity ) * /Sum rq util_avg
>
> IIUC the code below you actually propose that
>
> util = [(max_cap - util_irq) * util_rq] / max_cap + util_irq
>
> where
>
> util_rq = /Sum rq util_avg
> util_irq = irq util_avg
>
> So, which one is what you have in mind? Or am I wrong? :)

mmh ... aren't they equal ?

util = [(max_cap - util_irq) * util_rq] / max_cap + util_irq
util = [(max_cap/max_cap - util_irq/max_cap) * util_rq] + util_irq
util = [(1 - util_irq/max_cap) * util_rq] + util_irq
util = util_irq + [(1 - util_irq/max_cap) * util_rq]

>
> [...]
>
>> static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
>> @@ -190,9 +192,17 @@ static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
>> if (rq->rt.rt_nr_running) {
>> util = sg_cpu->max;
>> } else {
>> + /* Sum rq utilization*/
>> util = sg_cpu->util_dl;
>> util += sg_cpu->util_cfs;
>> util += sg_cpu->util_rt;
>> +
>> + /* Weight rq's utilization to the normal context */
>> + util *= (sg_cpu->max - sg_cpu->util_irq);
>> + util /= sg_cpu->max;
>> +
>> + /* Add interrupt utilization */
>> + util += sg_cpu->util_irq;
>
> Thanks,
>
> - Juri