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From: Joel Fernandes <joel@joelfernandes.org>
To: byungchul park <byungchul.park@lge.com>
Cc: peterz@infradead.org, mingo@kernel.org, rostedt@goodmis.org,
	tglx@linutronix.de, raistlin@linux.it,
	linux-kernel@vger.kernel.org, juri.lelli@gmail.com,
	bristot@redhat.com, kernel-team@lge.com
Subject: Re: [RESEND, v3, 2/2] sched/deadline: Initialize cp->elements[].cpu to an invalid value
Date: Thu, 31 May 2018 23:18:41 -0700	[thread overview]
Message-ID: <20180601061841.GA191514@joelaf.mtv.corp.google.com> (raw)
In-Reply-To: <20180601061255.GA189147@joelaf.mtv.corp.google.com>

On Thu, May 31, 2018 at 11:12:55PM -0700, Joel Fernandes wrote:
> On Mon, Jan 08, 2018 at 03:14:41PM +0900, byungchul park wrote:
> > Currently, migrating tasks to cpu0 unconditionally happens when the
> > heap is empty, since cp->elements[].cpu was initialized to 0(=cpu0).
> > We have to distinguish between the empty case and cpu0 to avoid the
> > unnecessary migrations. Therefore, it has to return an invalid value
> > e.i. -1 in that case.
> > 
> > Signed-off-by: Byungchul Park <byungchul.park@lge.com>
> > Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> > Acked-by: Daniel Bristot de Oliveira <bristot@redhat.com>
> > ---
> >  kernel/sched/cpudeadline.c | 10 +++++++++-
> >  1 file changed, 9 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> > index 9f02035..bcf903f 100644
> > --- a/kernel/sched/cpudeadline.c
> > +++ b/kernel/sched/cpudeadline.c
> > @@ -138,6 +138,12 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
> >  		int best_cpu = cpudl_maximum_cpu(cp);
> >  		WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
> >  
> > +		/*
> > +		 * The heap tree is empty for now, just return.
> > +		 */
> > +		if (best_cpu == -1)
> > +			return 0;
> > +
> >  		if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) &&
> >  		    dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) {
> >  			if (later_mask)
> > @@ -265,8 +271,10 @@ int cpudl_init(struct cpudl *cp)
> >  		return -ENOMEM;
> >  	}
> >  
> > -	for_each_possible_cpu(i)
> > +	for_each_possible_cpu(i) {
> > +		cp->elements[i].cpu = -1;
> >  		cp->elements[i].idx = IDX_INVALID;
> 
> Shouldn't you also set cp->elements[cpu].cpu to -1 in cpudl_clear (when you
> set cp->elements[cpu].cpu to IDX_INVALID there)?

I messed up my words, I meant : "when setting cp->elements[cpu].idx to
IDX_INVALID there". Which means I need to call it a day :-)

- Joel

  reply	other threads:[~2018-06-01  6:18 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-08  6:14 [RESEND PATCH v3 1/2] sched/deadline: Add cpudl_maximum_dl() for clean-up Byungchul Park
2018-01-08  6:14 ` [RESEND PATCH v3 2/2] sched/deadline: Initialize cp->elements[].cpu to an invalid value Byungchul Park
2018-06-01  6:12   ` [RESEND, v3, " Joel Fernandes
2018-06-01  6:18     ` Joel Fernandes [this message]
2018-06-01  7:10       ` Byungchul Park
2018-06-01 15:52         ` Joel Fernandes
2018-06-03  5:20           ` Byungchul Park
2018-01-11  9:07 ` [RESEND PATCH v3 1/2] sched/deadline: Add cpudl_maximum_dl() for clean-up Peter Zijlstra
2018-02-09  0:37   ` Byungchul Park
2018-02-26  7:51   ` Byungchul Park
2018-03-13  5:52   ` Byungchul Park
2018-04-23  7:01     ` Byungchul Park
2018-05-09  6:33   ` Byungchul Park
2018-05-25  5:13     ` Byungchul Park
2018-06-01  3:07       ` Byungchul Park
2018-06-01  6:02         ` Joel Fernandes
2018-06-01  6:30           ` Byungchul Park

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