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Message-ID: <20231006164826.335223-1-daniel.m.jordan@oracle.com>
Date: Fri, 6 Oct 2023 12:48:26 -0400
From: Daniel Jordan <daniel.m.jordan@...cle.com>
To: peterz@...radead.org
Cc: bristot@...hat.com, bsegall@...gle.com, chris.hyser@...cle.com,
corbet@....net, dietmar.eggemann@....com, efault@....de,
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qyousef@...alina.io, rostedt@...dmis.org, tglx@...utronix.de,
tim.c.chen@...ux.intel.com, timj@....org,
vincent.guittot@...aro.org, youssefesmat@...omium.org,
yu.c.chen@...el.com, daniel.m.jordan@...cle.com
Subject: [PATCH] sched/fair: Always update_curr() before placing at enqueue
Placing wants current's vruntime and the cfs_rq's min_vruntime up to
date so that avg_runtime() is too, and similarly it wants the entity to
be re-weighted and lag adjusted so vslice and vlag are fresh, so always
do update_curr() and update_cfs_group() beforehand.
There doesn't seem to be a reason to treat the 'curr' case specially
after e8f331bcc270 since vruntime doesn't get normalized anymore.
Fixes: e8f331bcc270 ("sched/smp: Use lag to simplify cross-runqueue placement")
Signed-off-by: Daniel Jordan <daniel.m.jordan@...cle.com>
---
Not sure what the XXX above place_entity() is for, maybe it can go away?
Based on tip/sched/core.
kernel/sched/fair.c | 14 ++------------
1 file changed, 2 insertions(+), 12 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 04fbcbda97d5f..db2ca9bf9cc49 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5047,15 +5047,6 @@ static inline bool cfs_bandwidth_used(void);
static void
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
- bool curr = cfs_rq->curr == se;
-
- /*
- * If we're the current task, we must renormalise before calling
- * update_curr().
- */
- if (curr)
- place_entity(cfs_rq, se, flags);
-
update_curr(cfs_rq);
/*
@@ -5080,8 +5071,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
* XXX now that the entity has been re-weighted, and it's lag adjusted,
* we can place the entity.
*/
- if (!curr)
- place_entity(cfs_rq, se, flags);
+ place_entity(cfs_rq, se, flags);
account_entity_enqueue(cfs_rq, se);
@@ -5091,7 +5081,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
check_schedstat_required();
update_stats_enqueue_fair(cfs_rq, se, flags);
- if (!curr)
+ if (cfs_rq->curr != se)
__enqueue_entity(cfs_rq, se);
se->on_rq = 1;
--
2.41.0
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