Messages in this thread Patch in this message | | | From | Dietmar Eggemann <> | Subject | [PATCH] sched/fair: Return early from update_tg_cfs_load() if delta == 0 | Date | Tue, 1 Jun 2021 10:36:16 +0200 |
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In case the _avg delta is 0 there is no need to update se's _avg (level n) nor cfs_rq's _avg (level n-1). These values stay the same.
Since cfs_rq's _avg isn't changed, i.e. no load is propagated down, cfs_rq's _sum should stay the same as well.
So bail out after se's _sum has been updated.
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> ---
This patch is against current tip/sched/urgent, commit f268c3737eca ("tick/nohz: Only check for RCU deferred wakeup on user/guest entry when needed"). It needs commit 7c7ad626d9a0 ("sched/fair: Keep load_avg and load_sum synced").
kernel/sched/fair.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e7c8277e3d54..ce8e0e10e5d4 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3548,9 +3548,12 @@ update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq load_sum = (s64)se_weight(se) * runnable_sum; load_avg = div_s64(load_sum, divider); + se->avg.load_sum = runnable_sum; + delta = load_avg - se->avg.load_avg; + if (!delta) + return; - se->avg.load_sum = runnable_sum; se->avg.load_avg = load_avg; add_positive(&cfs_rq->avg.load_avg, delta); -- 2.25.1
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