linux-kernel - Re: [PATCH v2 03/10] sched/ext: Add a DL server for sched

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Message-ID: <e68f33de-fdec-4448-840b-79f0d987b2a5@nvidia.com>
Date: Thu, 12 Jun 2025 12:54:44 -0400
From: Joel Fernandes <joelagnelf@...dia.com>
To: Tejun Heo <tj@...nel.org>
Cc: linux-kernel@...r.kernel.org, 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>,
 David Vernet <void@...ifault.com>, Andrea Righi <arighi@...dia.com>,
 Changwoo Min <changwoo@...lia.com>,
 Luigi De Matteis <ldematteis123@...il.com>
Subject: Re: [PATCH v2 03/10] sched/ext: Add a DL server for sched_ext tasks



On 6/2/2025 8:23 PM, Tejun Heo wrote:
> On Mon, Jun 02, 2025 at 02:00:59PM -0400, Joel Fernandes wrote:
> ...
>> @@ -2308,6 +2311,15 @@ static void enqueue_task_scx(struct rq *rq, struct task_struct *p, int enq_flags
>>  	if (enq_flags & SCX_ENQ_WAKEUP)
>>  		touch_core_sched(rq, p);
>>  
>> +	if (rq->scx.nr_running == 1) {
>> +		/* Account for idle runtime */
>> +		if (!rq->nr_running)
>> +			dl_server_update_idle_time(rq, rq->curr, &rq->ext_server);
>> +
>> +		/* Start dl_server if this is the first task being enqueued */
>> +		dl_server_start(&rq->ext_server);
>> +	}
> The following patch from Peter isn't upstream yet but SCX probably should do
> something similar. Otherwise, the start/stop overhead can become pretty
> expensive:
> 
>  https://lore.kernel.org/all/20250520094538.086709102@infradead.org/

Right. If it is Ok with you, we can do that after this patchset can be merged,
that way we can use the 'dl_server_idle' addition to 'sched_dl_entity', from
that patch as well.

thanks,

 - Joel