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From: Venkatesh Pallipadi on 1 Jul 2010 19:20
commit 871e35b moved update_group_power() call in update_sg_lb_stats(),
resulting in it being called for each group, even though it only updates
the power of local group. As a result we have frequent redundant
update_group_power() calls.

Move it back under "if (local_group)" condition.

This reduces the number of calls to update_group_power by a factor of 4
on my 4 core in 4 NUMA nodes test system.

Signed-off-by: Venkatesh Pallipadi <venki(a)google.com>
---
kernel/sched_fair.c | 7 ++++---
1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index a878b53..369d53d 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -2359,8 +2359,11 @@ static inline void update_sg_lb_stats(struct sched_domain *sd,
unsigned int balance_cpu = -1, first_idle_cpu = 0;
unsigned long avg_load_per_task = 0;

- if (local_group)
+ if (local_group) {
balance_cpu = group_first_cpu(group);
+ update_group_power(sd, this_cpu);
+ }
+

/* Tally up the load of all CPUs in the group */
max_cpu_load = 0;
@@ -2406,8 +2409,6 @@ static inline void update_sg_lb_stats(struct sched_domain *sd,
return;
}

- update_group_power(sd, this_cpu);
-
/* Adjust by relative CPU power of the group */
sgs->avg_load = (sgs->group_load * SCHED_LOAD_SCALE) / group->cpu_power;

--
1.7.1

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