Re: [PATCH 1/2] sched: cpufreq: ignore SMT when determining max cpu capacity

Rafael J. Wysocki
2016-08-31T01:28:23Z

On Friday, August 26, 2016 11:40:47 AM Steve Muckle wrote:
> PELT does not consider SMT when scaling its utilization values via
> arch_scale_cpu_capacity(). The value in rq->cpu_capacity_orig does
> take SMT into consideration though and therefore may be smaller than
> the utilization reported by PELT.
>
> On an Intel i7-3630QM for example rq->cpu_capacity_orig is 589 but
> util_avg scales up to 1024. This means that a 50% utilized CPU will show
> up in schedutil as ~86% busy.
>
> Fix this by using the same CPU scaling value in schedutil as that which
> is used by PELT.
>
> Signed-off-by: Steve Muckle <smuckle@linaro.org>

This is fine by me.

Peter, any objections?

> ---
> kernel/sched/cpufreq_schedutil.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 60d985f4dc47..cb8a77b1ef1b 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -147,7 +147,9 @@ static unsigned int get_next_freq(struct sugov_cpu *sg_cpu, unsigned long util,
> static void sugov_get_util(unsigned long *util, unsigned long *max)
> {
> struct rq *rq = this_rq();
> - unsigned long cfs_max = rq->cpu_capacity_orig;
> + unsigned long cfs_max;
> +
> + cfs_max = arch_scale_cpu_capacity(NULL, smp_processor_id());
>
> *util = min(rq->cfs.avg.util_avg, cfs_max);
> *max = cfs_max;
>

Thanks,
Rafael