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Message-ID: <4acce183-b486-44d0-b9e5-affb957ee366@redhat.com>
Date: Wed, 21 Feb 2024 09:39:59 +0100
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Subject: Re: [PATCH 06/10] sched: server: Don't start hrtick for DL server
 tasks
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To: "Joel Fernandes (Google)" <joel@joelfernandes.org>,
 linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
 Peter Zijlstra <peterz@infradead.org>, Juri Lelli <juri.lelli@redhat.com>,
 Vincent Guittot <vincent.guittot@linaro.org>
Cc: Suleiman Souhlal <suleiman@google.com>,
 Youssef Esmat <youssefesmat@google.com>, David Vernet <void@manifault.com>,
 Thomas Gleixner <tglx@linutronix.de>, "Paul E . McKenney"
 <paulmck@kernel.org>, joseph.salisbury@canonical.com,
 Luca Abeni <luca.abeni@santannapisa.it>,
 Tommaso Cucinotta <tommaso.cucinotta@santannapisa.it>,
 Vineeth Pillai <vineeth@bitbyteword.org>,
 Shuah Khan <skhan@linuxfoundation.org>, Phil Auld <pauld@redhat.com>,
 Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
 Valentin Schneider <vschneid@redhat.com>,
 Dietmar Eggemann <dietmar.eggemann@arm.com>,
 Steven Rostedt <rostedt@goodmis.org>
References: <20240216183108.1564958-1-joel@joelfernandes.org>
 <20240216183108.1564958-7-joel@joelfernandes.org>
From: Daniel Bristot de Oliveira <bristot@redhat.com>
In-Reply-To: <20240216183108.1564958-7-joel@joelfernandes.org>
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On 2/16/24 19:31, Joel Fernandes (Google) wrote:
> From: Suleiman Souhlal <suleiman@google.com>
> 
> Otherwise, we might start it even for tasks in a sched class that should
> have it off.

If the task is fair, but it is running inside a DL reservation, we want the
hrtick for the dl reservation.

This is one of the reasons why we are moving to the DL server, having microseconds
granularity for the boost duration (runtime).

-- Daniel

> 
> Signed-off-by: Suleiman Souhlal <suleiman@google.com>
> ---
>  kernel/sched/deadline.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 8fafe3f8b59c..5adfc15803c3 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -2325,11 +2325,12 @@ static struct task_struct *pick_next_task_dl(struct rq *rq)
>  	if (!p)
>  		return p;
>  
> -	if (!p->dl_server)
> +	if (!p->dl_server) {
>  		set_next_task_dl(rq, p, true);
>  
> -	if (hrtick_enabled(rq))
> -		start_hrtick_dl(rq, &p->dl);
> +		if (hrtick_enabled(rq))
> +			start_hrtick_dl(rq, &p->dl);
> +	}
>  
>  	return p;
>  }