linux-kernel - [PATCH v2] sched/eevdf: Force propagating min_slice of cfs

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Message-Id: <20241031094822.30531-1-dtcccc@linux.alibaba.com>
Date: Thu, 31 Oct 2024 17:48:22 +0800
From: Tianchen Ding <dtcccc@...ux.alibaba.com>
To: linux-kernel@...r.kernel.org
Cc: Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
	Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>
Subject: [PATCH v2] sched/eevdf: Force propagating min_slice of cfs_rq when a task changing slice

When a task changes slice and its cgroup se is already on_rq, the cgroup
se will not be enqueued again, and hence the root->min_slice leaves
unchanged.

Force propagating it when se doesn't need to be enqueued (or dequeued).
Ensure the se hierarchy always get the latest min_slice.

Fixes: aef6987d8954 ("sched/eevdf: Propagate min_slice up the cgroup hierarchy")
Signed-off-by: Tianchen Ding <dtcccc@...ux.alibaba.com>
---
v2:
Add a check about effectiveness of se->run_node. Thanks to the kernel
test robot.
---
 kernel/sched/fair.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6512258dc71f..ffac002a8807 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7017,6 +7017,8 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 		update_cfs_group(se);
 
 		se->slice = slice;
+		if (se != cfs_rq->curr)
+			min_vruntime_cb_propagate(&se->run_node, NULL);
 		slice = cfs_rq_min_slice(cfs_rq);
 
 		cfs_rq->h_nr_running++;
@@ -7141,6 +7143,8 @@ static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags)
 		update_cfs_group(se);
 
 		se->slice = slice;
+		if (se != cfs_rq->curr)
+			min_vruntime_cb_propagate(&se->run_node, NULL);
 		slice = cfs_rq_min_slice(cfs_rq);
 
 		cfs_rq->h_nr_running -= h_nr_running;
-- 
2.39.3