linux-kernel - [PATCH] sched/fair: Fix load_above_capacity fixed point arithmetic width

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Date:	Wed, 10 Aug 2016 11:27:27 +0100
From:	Dietmar Eggemann <dietmar.eggemann@....com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Cc:	Morten Rasmussen <morten.rasmussen@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Yuyang Du <yuyang.du@...el.com>
Subject: [PATCH] sched/fair: Fix load_above_capacity fixed point arithmetic width

Since commit 2159197d6677 ("sched/core: Enable increased load resolution
on 64-bit kernels") we now have two different fixed point units for
load.
load_above_capacity has to have 10 bit fixed point unit like PELT
whereas NICE_0_LOAD has 20 bit fixed point unit on 64-bit kernels.
Fix this by scaling down NICE_0_LOAD when multiplying
load_above_capacity with it.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
Acked-by: Morten Rasmussen <morten.rasmussen@....com>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 4088eedea763..fe4093807852 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7147,7 +7147,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
 		load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
 		if (load_above_capacity > busiest->group_capacity) {
 			load_above_capacity -= busiest->group_capacity;
-			load_above_capacity *= NICE_0_LOAD;
+			load_above_capacity *= scale_load_down(NICE_0_LOAD);
 			load_above_capacity /= busiest->group_capacity;
 		} else
 			load_above_capacity = ~0UL;
-- 
1.9.1