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Subject[RFC][PATCH 5/8] sched: dynamic cpu_power
Recompute the cpu_power for each cpu during load-balance

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
kernel/sched.c | 38 +++++++++++++++++++++++++++++++++++---
1 file changed, 35 insertions(+), 3 deletions(-)

Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -3691,14 +3691,46 @@ static inline int check_power_save_busie
}
#endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */

-static void update_sched_power(struct sched_domain *sd)
+unsigned long __weak arch_smt_gain(struct sched_domain *sd, int cpu)
+{
+ unsigned long weight = cpumask_weight(sched_domain_span(sd));
+ unsigned long smt_gain = sd->smt_gain;
+
+ smt_gain /= weight;
+
+ return smt_gain;
+}
+
+static void update_cpu_power(struct sched_domain *sd, int cpu)
+{
+ unsigned long weight = cpumask_weight(sched_domain_span(sd));
+ unsigned long power = SCHED_LOAD_SCALE;
+ struct sched_group *sdg = sd->groups;
+ unsigned long old = sdg->__cpu_power;
+
+ /* here we could scale based on cpufreq */
+
+ if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
+ power *= arch_smt_gain(sd, cpu);
+ power >>= SCHED_LOAD_SHIFT;
+ }
+
+ /* here we could scale based on RT time */
+
+ if (power != old) {
+ sdg->__cpu_power = power;
+ sdg->reciprocal_cpu_power = reciprocal_value(power);
+ }
+}
+
+static void update_group_power(struct sched_domain *sd, int cpu)
{
struct sched_domain *child = sd->child;
struct sched_group *group, *sdg = sd->groups;
unsigned long power = sdg->__cpu_power;

if (!child) {
- /* compute cpu power for this cpu */
+ update_cpu_power(sd, cpu);
return;
}

@@ -3743,7 +3775,7 @@ static inline void update_sg_lb_stats(st
if (local_group) {
balance_cpu = group_first_cpu(group);
if (balance_cpu == this_cpu)
- update_sched_power(sd);
+ update_group_power(sd, this_cpu);
}

/* Tally up the load of all CPUs in the group */
--



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