On 09/10/2014 07:20 PM, Peter Zijlstra wrote:
> On Sat, Aug 30, 2014 at 10:37:40PM +0530, Preeti U Murthy wrote:
>>> - if ((sd->flags & SD_SHARE_CPUCAPACITY) && weight > 1) {
>>> - if (sched_feat(ARCH_CAPACITY))
>>
>> Aren't you missing this check above? I understand that it is not
>> crucial, but that would also mean removing ARCH_CAPACITY sched_feat
>> altogether, wouldn't it?
>
> Yes he's missing that, I added the below bit on top.
>
> So the argument last time:
> lkml.kernel.org/r/20140709105721.gt19...@twins.programming.kicks-ass.net
> was that you cannot put sched_feat(ARCH_CAPACITY) inside a weak arch_*
> function. The test has to be outside, seeing how it needs to decide to
> call the arch function at all (or revert to the default implementation).
>
> ---
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5700,7 +5700,7 @@ unsigned long __weak arch_scale_freq_cap
> return default_scale_capacity(sd, cpu);
> }
>
> -unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int
> cpu)
> +static unsigned long default_scale_cpu_capacity(struct sched_domain *sd, int
> cpu)
> {
> if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1))
> return sd->smt_gain / sd->span_weight;
> @@ -5708,6 +5708,11 @@ unsigned long __weak arch_scale_cpu_capa
> return SCHED_CAPACITY_SCALE;
> }
>
> +unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int
> cpu)
> +{
> + return default_scale_cpu_capacity(sd, cpu);
> +}
> +
> static unsigned long scale_rt_capacity(int cpu)
> {
> struct rq *rq = cpu_rq(cpu);
> @@ -5747,7 +5752,10 @@ static void update_cpu_capacity(struct s
> unsigned long capacity = SCHED_CAPACITY_SCALE;
> struct sched_group *sdg = sd->groups;
>
> - capacity *= arch_scale_cpu_capacity(sd, cpu);
> + if (sched_feat(ARCH_CAPACITY))
> + capacity *= arch_scale_cpu_capacity(sd, cpu);
> + else
> + capacity *= default_scale_cpu_capacity(sd, cpu);
>
> capacity >>= SCHED_CAPACITY_SHIFT;
>
>
Alright, I see now. Thanks!
Regards
Preeti U Murthy
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