Just noticed this while looking at a bug.
--
Avoid an expensive integer divide 3 times per CPU per tick.
Signed-off-by: Nick Piggin <[email protected]>
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -2887,13 +2887,14 @@ static void active_load_balance(struct r
static void update_load(struct rq *this_rq)
{
unsigned long this_load;
- int i, scale;
+ int i;
this_load = this_rq->raw_weighted_load;
/* Update our load: */
- for (i = 0, scale = 1; i < 3; i++, scale <<= 1) {
+ for (i = 0; i < 3; i++) {
unsigned long old_load, new_load;
+ int scale;
old_load = this_rq->cpu_load[i];
new_load = this_load;
@@ -2902,9 +2903,11 @@ static void update_load(struct rq *this_
* prevents us from getting stuck on 9 if the load is 10, for
* example.
*/
+ scale = 1 << i;
if (new_load > old_load)
new_load += scale-1;
- this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) / scale;
+ this_rq->cpu_load[i] = (old_load*(scale-1) + new_load)
+ >> i; /* (divide by 'scale') */
}
}
-
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