Commit 4423af84 authored by Huang Shijie's avatar Huang Shijie Committed by Peter Zijlstra
Browse files

sched/fair: optimize the PLACE_LAG when se->vlag is zero 



When PLACE_LAG is enabled, from the relationship:
            vl_i = (W + w_i)*vl'_i / W
we know that if vl'_i(se->vlag) is zero, the vl_i is zero too.

So if se->vlag is zero, there is no need to waste cycles to
do the calculation.

Signed-off-by: default avatarHuang Shijie <shijie@os.amperecomputing.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarChristoph Lameter (Ampere) <cl@linux.com>
Link: https://lkml.kernel.org/r/20241001070021.10626-1-shijie@os.amperecomputing.com
parent e31488c9

kernel/sched/fair.c

+1 −1
Original line number Diff line number Diff line
@@ -5280,7 +5280,7 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 
	 *

	 * EEVDF: placement strategy #1 / #2

	 */

	if (sched_feat(PLACE_LAG) && cfs_rq->nr_running) {

	if (sched_feat(PLACE_LAG) && cfs_rq->nr_running && se->vlag) {

		struct sched_entity *curr = cfs_rq->curr;

		unsigned long load;