sched: speed up update_load_add/_sub()

speed up update_load_add/_sub() by not delaying the division - this
reduces CPU pipeline dependencies.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 5 insertions, 4 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 3209e2cc2c2e..992a1fae72a7 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -697,16 +697,17 @@ calc_delta_fair(unsigned long delta_exec, struct load_weight *lw)
         return calc_delta_mine(delta_exec, NICE_0_LOAD, lw);
 }
 
-static void update_load_add(struct load_weight *lw, unsigned long inc)
+static inline void update_load_add(struct load_weight *lw, unsigned long inc)
 {
         lw->weight += inc;
-        lw->inv_weight = 0;
+        lw->inv_weight = WMULT_CONST / lw->weight;
 }
 
-static void update_load_sub(struct load_weight *lw, unsigned long dec)
+static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
 {
         lw->weight -= dec;
-        lw->inv_weight = 0;
+        if (likely(lw->weight))
+                lw->inv_weight = WMULT_CONST / lw->weight;
 }
 
 /*