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sched/fair: Shrink sg_lb_stats and play memset games 

We can shrink sg_lb_stats because rq::nr_running is an unsigned int
and cpu numbers are 'int'

Before:
  sgs:        /* size: 72, cachelines: 2, members: 10 */
  sds:        /* size: 184, cachelines: 3, members: 7 */

After:
  sgs:        /* size: 56, cachelines: 1, members: 10 */
  sds:        /* size: 152, cachelines: 3, members: 7 */

Further we can avoid clearing all of sds since we do a total
clear/assignment of sg_stats in update_sg_lb_stats() with exception of
busiest_stat.avg_load which is referenced in update_sd_pick_busiest().

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-0klzmz9okll8wc0nsudguc9p@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2013-08-19 15:22:57 +02:00 committed by Ingo Molnar
parent 56cf515b4b
commit 147c5fc2ba
1 changed files with 26 additions and 7 deletions
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33
kernel/sched/fair.c
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@ -4237,12 +4237,12 @@ static unsigned long task_h_load(struct task_struct *p)
struct sg_lb_stats {
unsigned long avg_load; /*Avg load across the CPUs of the group */
unsigned long group_load; /* Total load over the CPUs of the group */
unsigned long sum_nr_running; /* Nr tasks running in the group */
unsigned long sum_weighted_load; /* Weighted load of group's tasks */
unsigned long load_per_task;
unsigned long group_capacity;
unsigned long idle_cpus;
unsigned long group_weight;
unsigned int sum_nr_running; /* Nr tasks running in the group */
unsigned int group_capacity;
unsigned int idle_cpus;
unsigned int group_weight;
int group_imb; /* Is there an imbalance in the group ? */
int group_has_capacity; /* Is there extra capacity in the group? */
};
@ -4258,10 +4258,29 @@ struct sd_lb_stats {
unsigned long total_pwr; /* Total power of all groups in sd */
unsigned long avg_load; /* Average load across all groups in sd */
struct sg_lb_stats local_stat; /* Statistics of the local group */
struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
struct sg_lb_stats local_stat; /* Statistics of the local group */
};
static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
{
/*
* Skimp on the clearing to avoid duplicate work. We can avoid clearing
* local_stat because update_sg_lb_stats() does a full clear/assignment.
* We must however clear busiest_stat::avg_load because
* update_sd_pick_busiest() reads this before assignment.
*/
*sds = (struct sd_lb_stats){
.busiest = NULL,
.local = NULL,
.total_load = 0UL,
.total_pwr = 0UL,
.busiest_stat = {
.avg_load = 0UL,
},
};
}
/**
* get_sd_load_idx - Obtain the load index for a given sched domain.
* @sd: The sched_domain whose load_idx is to be obtained.
@ -4615,7 +4634,7 @@ static inline void update_sd_lb_stats(struct lb_env *env,
*/
if (prefer_sibling && !local_group &&
sds->local && sds->local_stat.group_has_capacity)
sgs->group_capacity = min(sgs->group_capacity, 1UL);
sgs->group_capacity = min(sgs->group_capacity, 1U);
/* Now, start updating sd_lb_stats */
sds->total_load += sgs->group_load;
@ -4846,7 +4865,7 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
struct sg_lb_stats *local, *busiest;
struct sd_lb_stats sds;
memset(&sds, 0, sizeof(sds));
init_sd_lb_stats(&sds);
/*
* Compute the various statistics relavent for load balancing at