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SubjectRe: [RFC][PATCH 5/8] sched: dynamic cpu_power
On Tue, Sep 01, 2009 at 10:34:36AM +0200, Peter Zijlstra wrote:
> Recompute the cpu_power for each cpu during load-balance

This patch rocks! Atleast in theory, it does :-)

>
> 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 */
>
> --

--
Thanks and Regards
gautham


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