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SubjectRe: [PATCH 07/11] cpufreq/schedutil: take into account interrupt
On 28-06-18, 17:45, 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.
> rqs utilization don't see the time spend under interrupt context and report
> their value in the normal context time window. We need to compensate this when
> adding interrupt utilization
>
> The CPU utilization is :
> irq util_avg + (1 - irq util_avg / max capacity ) * /Sum rq util_avg
>
> A test with iperf on hikey (octo arm64) gives:
> iperf -c server_address -r -t 5
>
> w/o patch w/ patch
> Tx 276 Mbits/sec 304 Mbits/sec +10%
> Rx 299 Mbits/sec 328 Mbits/sec +09%
>
> 8 iterations
> stdev is lower than 1%
> Only WFI idle state is enable (shallowest diel state)
>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> ---
> kernel/sched/cpufreq_schedutil.c | 25 +++++++++++++++++++++----
> kernel/sched/sched.h | 13 +++++++++++++
> 2 files changed, 34 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index edfbfc1..b77bfef 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -58,6 +58,7 @@ struct sugov_cpu {
> unsigned long util_dl;
> unsigned long bw_dl;
> unsigned long util_rt;
> + unsigned long util_irq;
> unsigned long max;
>
> /* The field below is for single-CPU policies only: */
> @@ -190,21 +191,30 @@ static void sugov_get_util(struct sugov_cpu *sg_cpu)
> sg_cpu->util_dl = cpu_util_dl(rq);
> sg_cpu->bw_dl = cpu_bw_dl(rq);
> sg_cpu->util_rt = cpu_util_rt(rq);
> + sg_cpu->util_irq = cpu_util_irq(rq);
> }
>
> static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
> {
> struct rq *rq = cpu_rq(sg_cpu->cpu);
> - unsigned long util;
> + unsigned long util, max = sg_cpu->max;
>
> if (rq->rt.rt_nr_running)
> return sg_cpu->max;
>
> + if (unlikely(sg_cpu->util_irq >= max))
> + return max;
> +
> + /* Sum rq utilization */
> util = sg_cpu->util_cfs;
> util += sg_cpu->util_rt;
>
> - if ((util + sg_cpu->util_dl) >= sg_cpu->max)
> - return sg_cpu->max;
> + /*
> + * Interrupt time is not seen by rqs utilization nso we can compare

nso ?

> + * them with the CPU capacity
> + */
> + if ((util + sg_cpu->util_dl) >= max)
> + return max;
>
> /*
> * As there is still idle time on the CPU, we need to compute the
> @@ -220,10 +230,17 @@ static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
> * ready for such an interface. So, we only do the latter for now.
> */
>
> + /* Weight rqs utilization to normal context window */
> + util *= (max - sg_cpu->util_irq);
> + util /= max;
> +
> + /* Add interrupt utilization */
> + util += sg_cpu->util_irq;
> +
> /* Add DL bandwidth requirement */
> util += sg_cpu->bw_dl;
>
> - return min(sg_cpu->max, util);
> + return min(max, util);
> }
>
> /**
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 377be2b..9438e68 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -2221,4 +2221,17 @@ static inline unsigned long cpu_util_rt(struct rq *rq)
> {
> return rq->avg_rt.util_avg;
> }
> +
> +#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
> +static inline unsigned long cpu_util_irq(struct rq *rq)
> +{
> + return rq->avg_irq.util_avg;
> +}
> +#else
> +static inline unsigned long cpu_util_irq(struct rq *rq)
> +{
> + return 0;
> +}
> +
> +#endif
> #endif

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

--
viresh

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