Messages in this thread Patch in this message | | | Date | Fri, 16 Aug 2013 12:12:22 +0200 | From | Peter Zijlstra <> | Subject | [PATCH 1/6] sched: Remove one division operation in find_busiest_queue() |
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From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
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> [peterz: expanded changelog] Signed-off-by: Peter Zijlstra <peterz@infradead.org> --- kernel/sched/fair.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
--- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5018,7 +5018,7 @@ static struct rq *find_busiest_queue(str struct sched_group *group) { struct rq *busiest = NULL, *rq; - unsigned long max_load = 0; + unsigned long busiest_load = 0, busiest_power = SCHED_POWER_SCALE; int i; for_each_cpu(i, sched_group_cpus(group)) { @@ -5049,10 +5049,9 @@ static struct rq *find_busiest_queue(str * the load can be moved away from the cpu that is potentially * running at a lower capacity. */ - 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; } }
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