linux-kernel - Re: [PATCH 03/13] sched_ext: Refactor do_enqueue

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Message-ID: <aRGSd7kqynnhRAWk@gpd4>
Date: Mon, 10 Nov 2025 08:21:27 +0100
From: Andrea Righi <arighi@...dia.com>
To: Tejun Heo <tj@...nel.org>
Cc: David Vernet <void@...ifault.com>, Changwoo Min <changwoo@...lia.com>,
	Dan Schatzberg <schatzberg.dan@...il.com>,
	Emil Tsalapatis <etsal@...a.com>, sched-ext@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/13] sched_ext: Refactor do_enqueue_task() local and
 global DSQ paths

On Sun, Nov 09, 2025 at 08:31:02AM -1000, Tejun Heo wrote:
> The local and global DSQ enqueue paths in do_enqueue_task() share the same
> slice refill logic. Factor out the common code into a shared enqueue label.
> This makes adding new enqueue cases easier. No functional changes.

Reviewed-by: Andrea Righi <arighi@...dia.com>

Thanks,
-Andrea

> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> ---
>  kernel/sched/ext.c | 21 ++++++++++++---------
>  1 file changed, 12 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index 2ce226018dbe..a29bfadde89d 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -1282,6 +1282,7 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
>  {
>  	struct scx_sched *sch = scx_root;
>  	struct task_struct **ddsp_taskp;
> +	struct scx_dispatch_q *dsq;
>  	unsigned long qseq;
>  
>  	WARN_ON_ONCE(!(p->scx.flags & SCX_TASK_QUEUED));
> @@ -1349,8 +1350,17 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
>  direct:
>  	direct_dispatch(sch, p, enq_flags);
>  	return;
> -
> +local_norefill:
> +	dispatch_enqueue(sch, &rq->scx.local_dsq, p, enq_flags);
> +	return;
>  local:
> +	dsq = &rq->scx.local_dsq;
> +	goto enqueue;
> +global:
> +	dsq = find_global_dsq(sch, p);
> +	goto enqueue;
> +
> +enqueue:
>  	/*
>  	 * For task-ordering, slice refill must be treated as implying the end
>  	 * of the current slice. Otherwise, the longer @p stays on the CPU, the
> @@ -1358,14 +1368,7 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
>  	 */
>  	touch_core_sched(rq, p);
>  	refill_task_slice_dfl(sch, p);
> -local_norefill:
> -	dispatch_enqueue(sch, &rq->scx.local_dsq, p, enq_flags);
> -	return;
> -
> -global:
> -	touch_core_sched(rq, p);	/* see the comment in local: */
> -	refill_task_slice_dfl(sch, p);
> -	dispatch_enqueue(sch, find_global_dsq(sch, p), p, enq_flags);
> +	dispatch_enqueue(sch, dsq, p, enq_flags);
>  }
>  
>  static bool task_runnable(const struct task_struct *p)
> -- 
> 2.51.1
>