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

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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: Huang Shijie <shijie@os.amperecomputing.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Christoph Lameter (Ampere) <cl@linux.com>
Link: https://lkml.kernel.org/r/20241001070021.10626-1-shijie@os.amperecomputing.com
This commit is contained in:
Huang Shijie 2024-10-01 15:00:21 +08:00 committed by Peter Zijlstra
parent e31488c9df
commit 4423af84b2
1 changed files with 1 additions and 1 deletions
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2
kernel/sched/fair.c
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@ -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;