[PATCH v3 04/12] sched: Allow all archs to set the power_orig

On 9 July 2014 12:57, Peter Zijlstra [off-list ref] wrote:

On Mon, Jun 30, 2014 at 06:05:35PM +0200, Vincent Guittot wrote:

quoted

power_orig is only changed for system with a SMT sched_domain level 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.

Create a more generic function arch_scale_cpu_power that can be also used by
non SMT platform to set 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 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 148b277..f0bba5f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c

@@ -5614,6 +5614,20 @@ unsigned long __weak arch_scale_smt_capacity(struct sched_domain *sd, int cpu)
      return default_scale_smt_capacity(sd, cpu);
 }

+unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
+{
+     unsigned long weight = sd->span_weight;
+
+     if ((sd->flags & SD_SHARE_CPUCAPACITY) && weight > 1) {
+             if (sched_feat(ARCH_CAPACITY))
+                     return arch_scale_smt_capacity(sd, cpu);
+             else
+                     return default_scale_smt_capacity(sd, cpu);
+     }
+
+     return SCHED_CAPACITY_SCALE;
+}

The only caller of arch_scale_smt_capacity is now an arch_ function
itself; which makes it entirely redundant, no?

Also, sched_feat() and default_scale_smt_capability() aren't available
to arch implementations of this function and can thus not retain
semantics.

Seeing how we currently don't have any arch_scale_smt_capacity
implementations other than the default we can easily replace it entirely
with something like:

unsigned long __weak arch_scale_cpu_capacity()
{
        if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1))
                return sd->smt_gain / sd->span_weight;

        return SCHED_CAPACITY_SCALE;
}

Hmm?

That's fair. i'm going to clean up and remove unused function