linux-kernel - [tip: sched/core] sched/fair: Cleanup pick_task

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Message-ID: <172396219197.2215.9997555285176136397.tip-bot2@tip-bot2>
Date: Sun, 18 Aug 2024 06:23:11 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Ben Segall <bsegall@...gle.com>, Valentin Schneider <vschneid@...hat.com>,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/fair: Cleanup pick_task_fair() vs throttle

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

Commit-ID:     8e2e13ac6122915bd98315237b0317495e391be0
Gitweb:        https://git.kernel.org/tip/8e2e13ac6122915bd98315237b0317495e391be0
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Wed, 03 Apr 2024 09:50:07 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Sat, 17 Aug 2024 11:06:40 +02:00

sched/fair: Cleanup pick_task_fair() vs throttle

Per 54d27365cae8 ("sched/fair: Prevent throttling in early
pick_next_task_fair()") the reason check_cfs_rq_runtime() is under the
'if (curr)' check is to ensure the (downward) traversal does not
result in an empty cfs_rq.

But then the pick_task_fair() 'copy' of all this made it restart the
traversal anyway, so that seems to solve the issue too.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Ben Segall <bsegall@...gle.com>
Reviewed-by: Valentin Schneider <vschneid@...hat.com>
Tested-by: Valentin Schneider <vschneid@...hat.com>
Link: https://lkml.kernel.org/r/20240727105028.501679876@infradead.org
---
 kernel/sched/fair.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8201f0f..7ba1ca5 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8471,11 +8471,11 @@ again:
 				update_curr(cfs_rq);
 			else
 				curr = NULL;
-
-			if (unlikely(check_cfs_rq_runtime(cfs_rq)))
-				goto again;
 		}
 
+		if (unlikely(check_cfs_rq_runtime(cfs_rq)))
+			goto again;
+
 		se = pick_next_entity(cfs_rq);
 		cfs_rq = group_cfs_rq(se);
 	} while (cfs_rq);