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From: luca abeni <luca.abeni@santannapisa.it>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: linux-kernel@vger.kernel.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	"Paul E . McKenney" <paulmck@linux.ibm.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	Quentin Perret <quentin.perret@arm.com>,
	Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Patrick Bellasi <patrick.bellasi@arm.com>,
	Tommaso Cucinotta <tommaso.cucinotta@santannapisa.it>
Subject: Re: [RFC PATCH 2/6] sched/dl: Capacity-aware migrations
Date: Mon, 8 Jul 2019 09:41:36 +0200	[thread overview]
Message-ID: <20190708094136.7bce5f46@sweethome> (raw)
In-Reply-To: <b920d85b-4228-52fd-22db-3a0c26cf8ebd@arm.com>

Hi Dietmar,

On Thu, 4 Jul 2019 14:05:22 +0200
Dietmar Eggemann <dietmar.eggemann@arm.com> wrote:

> On 5/6/19 6:48 AM, Luca Abeni wrote:
> 
> [...]
> 
> > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> > index 5b981eeeb944..3436f3d8fa8f 100644
> > --- a/kernel/sched/deadline.c
> > +++ b/kernel/sched/deadline.c
> > @@ -1584,6 +1584,9 @@ select_task_rq_dl(struct task_struct *p, int
> > cpu, int sd_flag, int flags) if (sd_flag != SD_BALANCE_WAKE)
> >  		goto out;
> >  
> > +	if (dl_entity_is_special(&p->dl))
> > +		goto out;  
> 
> I wonder if this is really required. The if condition
> 
> 1591         if (unlikely(dl_task(curr)) &&
> 1592             (curr->nr_cpus_allowed < 2 ||
> 1593              !dl_entity_preempt(&p->dl, &curr->dl)) &&
> 1594             (p->nr_cpus_allowed > 1)) {
> 
> further below uses '!dl_entity_preempt(&p->dl, &curr->dl))' which
> returns 'dl_entity_is_special(a) || ...'

Uhm... I do not remember the details; I remember that the check fixed
something during the development of the patchset, but I did not check
if it was still needed when I forward-ported the patches...

So, maybe it worked around some bugs in previous versions of the
kernel, but is not needed now.



				Luca

  reply	other threads:[~2019-07-08  8:41 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-06  4:48 [RFC PATCH 0/6] Capacity awareness for SCHED_DEADLINE Luca Abeni
2019-05-06  4:48 ` [RFC PATCH 1/6] sched/dl: Improve deadline admission control for asymmetric CPU capacities Luca Abeni
2019-05-07 13:48   ` Quentin Perret
2019-05-07 13:55     ` Vincent Guittot
2019-05-07 14:02       ` Quentin Perret
2019-05-07 14:25     ` luca abeni
2019-05-07 14:31       ` Quentin Perret
2019-05-07 14:43         ` luca abeni
2019-07-08 11:22           ` Dietmar Eggemann
2019-07-08 15:05             ` Quentin Perret
2019-06-18 16:41   ` Alessio Balsini
2019-05-06  4:48 ` [RFC PATCH 2/6] sched/dl: Capacity-aware migrations Luca Abeni
2019-05-07 13:35   ` Quentin Perret
2019-05-07 14:17     ` luca abeni
2019-05-07 15:04       ` Quentin Perret
2019-05-07 14:10   ` Quentin Perret
2019-05-07 14:41     ` luca abeni
2019-05-07 15:02       ` Quentin Perret
2019-05-08  8:04   ` Juri Lelli
2019-05-08  8:17     ` luca abeni
2019-07-04 12:05   ` Dietmar Eggemann
2019-07-08  7:41     ` luca abeni [this message]
2019-07-08 10:41       ` Dietmar Eggemann
2019-05-06  4:48 ` [RFC PATCH 3/6] sched/dl: Try better placement even for deadline tasks that do not block Luca Abeni
2019-05-07 14:13   ` Quentin Perret
2019-05-07 16:00     ` Morten Rasmussen
2019-05-08  8:01   ` Juri Lelli
2019-05-08  8:14     ` luca abeni
2019-05-08  9:22       ` Juri Lelli
2019-07-08 13:55   ` Peter Zijlstra
2019-07-09 13:24     ` luca abeni
2019-07-09 13:42       ` Peter Zijlstra
2019-07-11 11:17         ` Dietmar Eggemann
2019-07-11 12:00           ` Peter Zijlstra
2019-07-11 15:33             ` Dietmar Eggemann
2019-07-09 14:44       ` Dietmar Eggemann
2019-05-06  4:48 ` [RFC PATCH 4/6] sched/dl: Improve capacity-aware wakeup Luca Abeni
2019-05-08  9:08   ` Juri Lelli
2019-05-08  9:24     ` luca abeni
2019-05-08 12:05       ` Juri Lelli
2019-05-08 12:47         ` luca abeni
2019-05-08 13:10           ` Juri Lelli
2019-05-08 14:12             ` luca abeni
2019-05-06  4:48 ` [RFC PATCH 5/6] sched/dl: If the task does not fit anywhere, select the fastest core Luca Abeni
2019-05-06  4:48 ` [RFC PATCH 6/6] sched/dl: Try not to select a too fast core Luca Abeni
2019-05-07 15:57   ` Quentin Perret
2019-05-08  6:26     ` luca abeni
2019-05-09 13:46       ` Quentin Perret

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