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| author | Joonsoo Kim <iamjoonsoo.kim@lge.com> | 2013-08-06 17:36:41 +0900 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2013-09-02 08:26:59 +0200 |
| commit | 95a79b805b935f4a7b685aa8a117d916c638323e (patch) | |
| tree | e9c7380555d30bf5eea04219aba179696c82b7e5 /kernel | |
| parent | a4f61cc03e443647211a5ae0ab8f8cda2e9e1043 (diff) | |
| download | linux-95a79b805b935f4a7b685aa8a117d916c638323e.tar.bz2 | |
sched: Remove one division operation in find_busiest_queue()
Remove one division operation in find_busiest_queue() by using
crosswise multiplication:
wl_i / power_i > wl_j / power_j :=
wl_i * power_j > wl_j * power_i
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
[ Expanded the changelog. ]
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1375778203-31343-2-git-send-email-iamjoonsoo.kim@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/fair.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index f918635efe09..8aa217f62a9e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4968,7 +4968,7 @@ static struct rq *find_busiest_queue(struct lb_env *env, struct sched_group *group) { struct rq *busiest = NULL, *rq; - unsigned long max_load = 0; + unsigned long busiest_load = 0, busiest_power = 1; int i; for_each_cpu(i, sched_group_cpus(group)) { @@ -4998,11 +4998,15 @@ static struct rq *find_busiest_queue(struct lb_env *env, * the weighted_cpuload() scaled with the cpu power, so that * the load can be moved away from the cpu that is potentially * running at a lower capacity. + * + * Thus we're looking for max(wl_i / power_i), crosswise + * multiplication to rid ourselves of the division works out + * to: wl_i * power_j > wl_j * power_i; where j is our + * previous maximum. */ - wl = (wl * SCHED_POWER_SCALE) / power; - - if (wl > max_load) { - max_load = wl; + if (wl * busiest_power > busiest_load * power) { + busiest_load = wl; + busiest_power = power; busiest = rq; } } |