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SubjectRe: [RFC 1/4] sched: extend the usage of cpu_power_orig
Hi Vincent,

On 03/28/2014 06:52 PM, Vincent Guittot wrote:
> cpu_power_orig is only changed for SMT system in order to reflect the lower
> capacity of CPUs. Heterogenous system also have to reflect an original
> capacity that is different from the default value.

There is no parameter 'cpu_power_orig' till your fourth patch right?
Why is this term being used in this patch?

Besides, both parameters power and power_orig are changed for SMT
systems to reflect the lower capacity of the CPUs.Why is there a mention
of only power_orig?

IMO, the subject of the patch is not clearly reflecting the main
intention of the patch. There is nothing done to change the way
cpu_power is used; rather you are changing the way the cpu_power is
being set to be flexible, thus allowing for the right power value to be
set on heterogeneous systems.

'Allow archs to set the cpu_power instead of falling to default value'
or something similar would be more appropriate. What do you think?

Regards
Preeti U Murthy
>
> Create a more generic function arch_scale_cpu_power that can be also used by
> non SMT platform to set cpu_power_orig.
>
> The weak behavior of arch_scale_cpu_power is the previous SMT one in order to
> keep backward compatibility in the use of cpu_power_orig.
>
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> ---
> kernel/sched/fair.c | 24 ++++++++++++++++--------
> 1 file changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 7e9bd0b..ed42061 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5559,6 +5559,20 @@ unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
> return default_scale_smt_power(sd, cpu);
> }
>
> +unsigned long __weak arch_scale_cpu_power(struct sched_domain *sd, int cpu)
> +{
> + unsigned long weight = sd->span_weight;
> +
> + if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
> + if (sched_feat(ARCH_POWER))
> + return arch_scale_smt_power(sd, cpu);
> + else
> + return default_scale_smt_power(sd, cpu);
> + }
> +
> + return SCHED_POWER_SCALE;
> +}
> +
> static unsigned long scale_rt_power(int cpu)
> {
> struct rq *rq = cpu_rq(cpu);
> @@ -5590,18 +5604,12 @@ static unsigned long scale_rt_power(int cpu)
>
> static void update_cpu_power(struct sched_domain *sd, int cpu)
> {
> - unsigned long weight = sd->span_weight;
> unsigned long power = SCHED_POWER_SCALE;
> struct sched_group *sdg = sd->groups;
>
> - if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
> - if (sched_feat(ARCH_POWER))
> - power *= arch_scale_smt_power(sd, cpu);
> - else
> - power *= default_scale_smt_power(sd, cpu);
> + power *= arch_scale_cpu_power(sd, cpu);
>
> - power >>= SCHED_POWER_SHIFT;
> - }
> + power >>= SCHED_POWER_SHIFT;
>
> sdg->sgp->power_orig = power;
>



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