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sched/fair: Rework and comment the group_capacity code 

Pull out the group_capacity computation so that we can more clearly
comment its issues.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-az1hl1ya55k361nkeh9bj0yw@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2013-08-28 11:50:34 +02:00 committed by Ingo Molnar
parent 863bffc808
commit b37d931685
1 changed files with 24 additions and 8 deletions
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32
kernel/sched/fair.c
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@ -4553,6 +4553,27 @@ static inline int sg_imbalanced(struct sched_group *group)
return group->sgp->imbalance;
}
/*
* Compute the group capacity.
*
* For now the capacity is simply the number of power units in the group_power.
* A power unit represents a full core.
*
* This has an issue where N*frac(smt_power) >= 1, in that case we'll see extra
* 'cores' that aren't actually there.
*/
static inline int sg_capacity(struct lb_env *env, struct sched_group *group)
{
unsigned int power = group->sgp->power;
unsigned int capacity = DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE);
if (!capacity)
capacity = fix_small_capacity(env->sd, group);
return capacity;
}
/**
* update_sg_lb_stats - Update sched_group's statistics for load balancing.
* @env: The load balancing environment.
@ -4596,16 +4617,11 @@ static inline void update_sg_lb_stats(struct lb_env *env,
if (sgs->sum_nr_running)
sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
sgs->group_imb = sg_imbalanced(group);
sgs->group_capacity =
DIV_ROUND_CLOSEST(sgs->group_power, SCHED_POWER_SCALE);
if (!sgs->group_capacity)
sgs->group_capacity = fix_small_capacity(env->sd, group);
sgs->group_weight = group->group_weight;
sgs->group_imb = sg_imbalanced(group);
sgs->group_capacity = sg_capacity(env, group);
if (sgs->group_capacity > sgs->sum_nr_running)
sgs->group_has_capacity = 1;
}