linux-kernel - Re: [PATCH] sched: Optimize pick_next_task for idle_sched

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Date:   Thu, 23 Feb 2017 17:37:37 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Pavan Kondeti <pkondeti@...eaurora.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] sched: Optimize pick_next_task for idle_sched_class too

On Thu, Feb 23, 2017 at 04:25:33PM +0100, Peter Zijlstra wrote:
> 
> Ah, I read your question wrong. Yes I think you're right, we now loose
> the pull when the last RT task goes away.
> 
> Hmm.. how to fix that nicely..

Something like so perhaps? This would make a pull happen when the last
RT task on this CPU goes away.

Steve?

---
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 9f3e40226dec..283d591078b0 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1336,6 +1336,9 @@ static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
 	dequeue_rt_entity(rt_se, flags);
 
 	dequeue_pushable_task(rq, p);
+
+	if (!rq->rt.rt_nr_running)
+		queue_pull_task(rq);
 }
 
 /*