linux-kernel - [tip: sched/core] sched/fair: Reorder throttle_cfs

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Message-ID: <160500731014.11244.11693121696022661111.tip-bot2@tip-bot2>
Date:   Tue, 10 Nov 2020 11:21:50 -0000
From:   "tip-bot2 for Peng Wang" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Peng Wang <rocking@...ux.alibaba.com>,
        Ingo Molnar <mingo@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Phil Auld <pauld@...hat.com>, Ben Segall <bsegall@...gle.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/fair: Reorder throttle_cfs_rq() path

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     b6d37a764a5b852db63101b3f2db0e699574b903
Gitweb:        https://git.kernel.org/tip/b6d37a764a5b852db63101b3f2db0e699574b903
Author:        Peng Wang <rocking@...ux.alibaba.com>
AuthorDate:    Tue, 10 Nov 2020 10:11:59 +08:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 10 Nov 2020 12:20:12 +01:00

sched/fair: Reorder throttle_cfs_rq() path

As commit:

  39f23ce07b93 ("sched/fair: Fix unthrottle_cfs_rq() for leaf_cfs_rq list")

does in unthrottle_cfs_rq(), throttle_cfs_rq() can also use the same
pattern as dequeue_task_fair().

No functional changes.

Signed-off-by: Peng Wang <rocking@...ux.alibaba.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Phil Auld <pauld@...hat.com>
Cc: Ben Segall <bsegall@...gle.com>
Link: https://lore.kernel.org/r/f11dd2e3ab35cc538e2eb57bf0c99b6eaffce127.1604973978.git.rocking@linux.alibaba.com
---
 kernel/sched/fair.c | 34 +++++++++++++++++++++++-----------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 52cacfc..2755a7e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4788,25 +4788,37 @@ static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
 		struct cfs_rq *qcfs_rq = cfs_rq_of(se);
 		/* throttled entity or throttle-on-deactivate */
 		if (!se->on_rq)
-			break;
+			goto done;
 
-		if (dequeue) {
-			dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
-		} else {
-			update_load_avg(qcfs_rq, se, 0);
-			se_update_runnable(se);
-		}
+		dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
 
 		qcfs_rq->h_nr_running -= task_delta;
 		qcfs_rq->idle_h_nr_running -= idle_task_delta;
 
-		if (qcfs_rq->load.weight)
-			dequeue = 0;
+		if (qcfs_rq->load.weight) {
+			/* Avoid re-evaluating load for this entity: */
+			se = parent_entity(se);
+			break;
+		}
 	}
 
-	if (!se)
-		sub_nr_running(rq, task_delta);
+	for_each_sched_entity(se) {
+		struct cfs_rq *qcfs_rq = cfs_rq_of(se);
+		/* throttled entity or throttle-on-deactivate */
+		if (!se->on_rq)
+			goto done;
+
+		update_load_avg(qcfs_rq, se, 0);
+		se_update_runnable(se);
 
+		qcfs_rq->h_nr_running -= task_delta;
+		qcfs_rq->idle_h_nr_running -= idle_task_delta;
+	}
+
+	/* At this point se is NULL and we are at root level*/
+	sub_nr_running(rq, task_delta);
+
+done:
 	/*
 	 * Note: distribution will already see us throttled via the
 	 * throttled-list.  rq->lock protects completion.