linux-kernel - [PATCH v3] sched_ext: Implement SCX_OPS_TRACK

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Message-ID: <20250623063033.76808-2-henry.hj@antgroup.com>
Date: Mon, 23 Jun 2025 14:30:33 +0800
From: "Henry Huang" <henry.hj@...group.com>
To: changwoo@...lia.com,
	arighi@...dia.com,
	tj@...nel.org,
	void@...ifault.com
Cc: "谈鉴锋" <henry.tjf@...group.com>,
  "Yan Yan(cailing)" <yanyan.yan@...group.com>,
   <linux-kernel@...r.kernel.org>,
   <sched-ext@...ts.linux.dev>,
  "Henry Huang" <henry.hj@...group.com>
Subject: [PATCH v3] sched_ext: Implement SCX_OPS_TRACK_MIGRATION

For some BPF-schedulers, they should do something when
task is doing migration, such as updating per-cpu map.
If SCX_OPS_TRACK_MIGRATION is set, runnable/quiescent
would be called whether task is doing migration or not.

Signed-off-by: Henry Huang <henry.hj@...group.com>
Reviewed-by: Andrea Righi <arighi@...dia.com>
---
 kernel/sched/ext.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index b498d86..376e028 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -161,6 +161,12 @@ enum scx_ops_flags {
 	SCX_OPS_BUILTIN_IDLE_PER_NODE	= 1LLU << 6,
 
 	/*
+	 * If set, runnable/quiescent ops would be called whether the task is
+	 * doing migration or not.
+	 */
+	SCX_OPS_TRACK_MIGRATION		= 1LLU << 7,
+
+	/*
 	 * CPU cgroup support flags
 	 */
 	SCX_OPS_HAS_CGROUP_WEIGHT	= 1LLU << 16,	/* DEPRECATED, will be removed on 6.18 */
@@ -172,6 +178,7 @@ enum scx_ops_flags {
 					  SCX_OPS_ALLOW_QUEUED_WAKEUP |
 					  SCX_OPS_SWITCH_PARTIAL |
 					  SCX_OPS_BUILTIN_IDLE_PER_NODE |
+					  SCX_OPS_TRACK_MIGRATION |
 					  SCX_OPS_HAS_CGROUP_WEIGHT,
 
 	/* high 8 bits are internal, don't include in SCX_OPS_ALL_FLAGS */
@@ -870,6 +877,7 @@ enum scx_enq_flags {
 	SCX_ENQ_WAKEUP		= ENQUEUE_WAKEUP,
 	SCX_ENQ_HEAD		= ENQUEUE_HEAD,
 	SCX_ENQ_CPU_SELECTED	= ENQUEUE_RQ_SELECTED,
+	SCX_ENQ_MIGRATING	= ENQUEUE_MIGRATING,
 
 	/* high 32bits are SCX specific */
 
@@ -913,6 +921,7 @@ enum scx_enq_flags {
 enum scx_deq_flags {
 	/* expose select DEQUEUE_* flags as enums */
 	SCX_DEQ_SLEEP		= DEQUEUE_SLEEP,
+	SCX_DEQ_MIGRATING	= DEQUEUE_MIGRATING,
 
 	/* high 32bits are SCX specific */
 
@@ -2390,7 +2399,11 @@ static void enqueue_task_scx(struct rq *rq, struct task_struct *p, int enq_flags
 	rq->scx.nr_running++;
 	add_nr_running(rq, 1);
 
-	if (SCX_HAS_OP(sch, runnable) && !task_on_rq_migrating(p))
+	if (task_on_rq_migrating(p))
+		enq_flags |= SCX_ENQ_MIGRATING;
+
+	if (SCX_HAS_OP(sch, runnable) &&
+	    ((sch->ops.flags & SCX_OPS_TRACK_MIGRATION) || !(enq_flags & SCX_ENQ_MIGRATING)))
 		SCX_CALL_OP_TASK(sch, SCX_KF_REST, runnable, rq, p, enq_flags);
 
 	if (enq_flags & SCX_ENQ_WAKEUP)
@@ -2463,6 +2476,9 @@ static bool dequeue_task_scx(struct rq *rq, struct task_struct *p, int deq_flags
 		return true;
 	}
 
+	if (task_on_rq_migrating(p))
+		deq_flags |= SCX_DEQ_MIGRATING;
+
 	ops_dequeue(rq, p, deq_flags);
 
 	/*
@@ -2482,7 +2498,8 @@ static bool dequeue_task_scx(struct rq *rq, struct task_struct *p, int deq_flags
 		SCX_CALL_OP_TASK(sch, SCX_KF_REST, stopping, rq, p, false);
 	}
 
-	if (SCX_HAS_OP(sch, quiescent) && !task_on_rq_migrating(p))
+	if (SCX_HAS_OP(sch, quiescent) &&
+	    ((sch->ops.flags & SCX_OPS_TRACK_MIGRATION) || !(deq_flags & SCX_DEQ_MIGRATING)))
 		SCX_CALL_OP_TASK(sch, SCX_KF_REST, quiescent, rq, p, deq_flags);
 
 	if (deq_flags & SCX_DEQ_SLEEP)
@@ -5495,6 +5512,11 @@ static int validate_ops(struct scx_sched *sch, const struct sched_ext_ops *ops)
 		return -EINVAL;
 	}
 
+	if ((ops->flags & SCX_OPS_TRACK_MIGRATION) && (!ops->runnable || !ops->quiescent)) {
+		scx_error(sch, "SCX_OPS_TRACK_MIGRATION requires ops.runnable() and ops.quiescent() to be implemented");
+		return -EINVAL;
+	}
+
 	if (ops->flags & SCX_OPS_HAS_CGROUP_WEIGHT)
 		pr_warn("SCX_OPS_HAS_CGROUP_WEIGHT is deprecated and a noop\n");
 
-- 
Henry