Subject: sched, fair: Rework and comment the group_capacity code
From: Peter Zijlstra <pet...@infradead.org>
Date: Wed Aug 28 11:50:34 CEST 2013
Pull out the group_capacity computation so that we can more clearly
comment its issues.
Signed-off-by: Peter Zijlstra <pet...@infradead.org>
---
kernel/sched/fair.c | 32 ++++++++++++++++++++++++--------
1 file changed, 24 insertions(+), 8 deletions(-)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4551,6 +4551,27 @@ static inline int sg_imbalanced(struct s
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.
@@ -4594,16 +4615,11 @@ static inline void update_sg_lb_stats(st
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;
}
--
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