From: Peter Zijlstra <peterz@infradead.org>
To: Juri Lelli <juri.lelli@arm.com>
Cc: Steve Muckle <steve.muckle@linaro.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Linux PM list <linux-pm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
Viresh Kumar <viresh.kumar@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks
Date: Thu, 11 Feb 2016 16:26:25 +0100 [thread overview]
Message-ID: <20160211152625.GM6357@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160211122429.GM11415@e106622-lin>
On Thu, Feb 11, 2016 at 12:24:29PM +0000, Juri Lelli wrote:
> Hi Peter,
>
> On 11/02/16 12:59, Peter Zijlstra wrote:
> > On Tue, Feb 09, 2016 at 05:02:33PM -0800, Steve Muckle wrote:
> > > > Index: linux-pm/kernel/sched/deadline.c
> > > > ===================================================================
> > > > --- linux-pm.orig/kernel/sched/deadline.c
> > > > +++ linux-pm/kernel/sched/deadline.c
> > > > @@ -1197,6 +1197,9 @@ static void task_tick_dl(struct rq *rq,
> > > > {
> > > > update_curr_dl(rq);
> > > >
> > > > + /* Kick cpufreq to prevent it from stalling. */
> > > > + cpufreq_kick();
> > > > +
> > > > /*
> > > > * Even when we have runtime, update_curr_dl() might have resulted in us
> > > > * not being the leftmost task anymore. In that case NEED_RESCHED will
> > >
> > > I think additional hooks such as enqueue/dequeue would be needed in
> > > RT/DL. The task tick callbacks will only run if a task in that class is
> > > executing at the time of the tick. There could be intermittent RT/DL
> > > task activity in a frequency domain (the only task activity there, no
> > > CFS tasks) that doesn't happen to overlap the tick. Worst case the task
> > > activity could be periodic in such a way that it never overlaps the tick
> > > and the update is never made.
> >
> > No, for RT (RR/FIFO) we do not have enough information to do anything
> > useful. Basically RR/FIFO should result in running 100% whenever we
> > schedule such a task.
> >
> > That means RR/FIFO want a hook in pick_next_task_rt() to bump the freq
> > to 100% and leave it there until something else gets to run.
> >
>
> Vincent is trying to play with rt_avg (in the last sched-freq thread) to
> see if we can get some information about RT as well. I understand that
> from a theoretical perspective that's not much we can say of such tasks,
> and bumping to max can be the only sensible thing to do, but there are
> users of RT (ehm, Android) that will probably see differences in energy
> consumption if we do so. Yeah, maybe the should use a different policy,
> yes.
Can't we just leave broken people get broken results? Trying to use
rt_avg for this is just insane. We should ensure that people using this
thing correctly get correct results, the rest can take a hike.
Using rt_avg gets us to the place where people who want to do the right
thing cannot, and that is bad.
> > For DL it basically wants to set a minimum freq based on reserved
> > utilization, so that is __setparam_dl() or somewhere around there.
> >
>
> I think we could do better than this once Luca's reclaiming stuff gets
> in. The reserved bw is usually somewhat pessimistic. But this is a
> different discussion, maybe.
Sure, there's cleverer things that can be done. But a simple one would
indeed be the min guarantee based on accepted bandwidth.
next prev parent reply other threads:[~2016-02-11 15:26 UTC|newest]
Thread overview: 134+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-29 22:52 [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks Rafael J. Wysocki
2016-01-29 22:53 ` [PATCH 1/3] cpufreq: Add a mechanism for registering " Rafael J. Wysocki
2016-02-04 3:31 ` Viresh Kumar
2016-01-29 22:56 ` [PATCH 2/3] cpufreq: intel_pstate: Replace timers with " Rafael J. Wysocki
2016-01-29 22:59 ` [PATCH 3/3] cpufreq: governor: " Rafael J. Wysocki
2016-02-03 1:16 ` [Update][PATCH " Rafael J. Wysocki
2016-02-04 4:49 ` Viresh Kumar
2016-02-04 10:54 ` Rafael J. Wysocki
2016-02-05 1:28 ` [PATCH 3/3 v3] " Rafael J. Wysocki
2016-02-05 6:50 ` Viresh Kumar
2016-02-05 13:36 ` Rafael J. Wysocki
2016-02-05 14:47 ` Viresh Kumar
2016-02-05 23:10 ` Rafael J. Wysocki
2016-02-07 9:10 ` Viresh Kumar
2016-02-07 14:43 ` Rafael J. Wysocki
2016-02-08 2:08 ` Rafael J. Wysocki
2016-02-08 11:52 ` Viresh Kumar
2016-02-08 12:52 ` Rafael J. Wysocki
2016-02-08 13:40 ` Rafael J. Wysocki
2016-02-05 23:01 ` Rafael J. Wysocki
2016-02-06 3:40 ` [PATCH 3/3 v4] " Rafael J. Wysocki
2016-02-07 9:20 ` Viresh Kumar
2016-02-07 14:36 ` Rafael J. Wysocki
2016-02-07 14:50 ` [PATCH 3/3 v5] " Rafael J. Wysocki
2016-02-07 15:36 ` Viresh Kumar
2016-02-09 10:01 ` Gautham R Shenoy
2016-02-09 18:49 ` Rafael J. Wysocki
2016-02-03 22:20 ` [PATCH 0/3] cpufreq: " Rafael J. Wysocki
2016-02-04 0:08 ` Srinivas Pandruvada
2016-02-04 17:16 ` Rafael J. Wysocki
2016-02-04 10:51 ` Juri Lelli
2016-02-04 17:19 ` Rafael J. Wysocki
2016-02-08 23:06 ` Rafael J. Wysocki
2016-02-09 0:39 ` Steve Muckle
2016-02-09 1:01 ` Rafael J. Wysocki
2016-02-09 20:05 ` Rafael J. Wysocki
2016-02-10 1:02 ` Steve Muckle
2016-02-10 1:57 ` Rafael J. Wysocki
2016-02-10 3:09 ` Rafael J. Wysocki
2016-02-10 19:47 ` Steve Muckle
2016-02-10 21:49 ` Rafael J. Wysocki
2016-02-10 22:07 ` Steve Muckle
2016-02-10 22:12 ` Rafael J. Wysocki
2016-02-11 11:59 ` Peter Zijlstra
2016-02-11 12:24 ` Juri Lelli
2016-02-11 15:26 ` Peter Zijlstra [this message]
2016-02-11 18:23 ` Vincent Guittot
2016-02-12 14:04 ` Peter Zijlstra
2016-02-12 14:48 ` Vincent Guittot
2016-03-01 13:58 ` Peter Zijlstra
2016-03-01 14:17 ` Juri Lelli
2016-03-01 14:24 ` Peter Zijlstra
2016-03-01 14:26 ` Peter Zijlstra
2016-03-01 14:42 ` Juri Lelli
2016-03-01 15:04 ` Peter Zijlstra
2016-03-01 19:49 ` Rafael J. Wysocki
2016-03-01 14:58 ` Vincent Guittot
2016-02-11 17:06 ` Steve Muckle
2016-02-11 17:30 ` Peter Zijlstra
2016-02-11 17:34 ` Rafael J. Wysocki
2016-02-11 17:38 ` Peter Zijlstra
2016-02-11 18:52 ` Steve Muckle
2016-02-11 19:04 ` Rafael J. Wysocki
2016-02-12 13:43 ` Rafael J. Wysocki
2016-02-12 14:10 ` Peter Zijlstra
2016-02-12 16:01 ` Rafael J. Wysocki
2016-02-12 16:15 ` Rafael J. Wysocki
2016-02-12 16:53 ` Ashwin Chaugule
2016-02-12 23:14 ` Rafael J. Wysocki
2016-02-12 17:02 ` Doug Smythies
2016-02-12 23:17 ` Rafael J. Wysocki
2016-02-10 12:33 ` Juri Lelli
2016-02-10 13:23 ` Rafael J. Wysocki
2016-02-10 14:03 ` Juri Lelli
2016-02-10 14:26 ` Rafael J. Wysocki
2016-02-10 14:46 ` Juri Lelli
2016-02-10 15:46 ` Rafael J. Wysocki
2016-02-10 16:05 ` Juri Lelli
2016-02-11 11:51 ` Peter Zijlstra
2016-02-11 12:08 ` Rafael J. Wysocki
2016-02-11 15:29 ` Peter Zijlstra
2016-02-11 15:58 ` Rafael J. Wysocki
2016-02-11 20:47 ` Rafael J. Wysocki
2016-02-10 15:17 ` [PATCH v6 " Rafael J. Wysocki
2016-02-10 15:21 ` [PATCH v6 1/3] cpufreq: Add mechanism for registering " Rafael J. Wysocki
2016-02-10 23:01 ` [PATCH v7 " Rafael J. Wysocki
2016-02-11 17:30 ` [PATCH v8 " Rafael J. Wysocki
2016-02-12 13:16 ` [PATCH v9 " Rafael J. Wysocki
2016-02-15 21:47 ` [PATCH v10 " Rafael J. Wysocki
2016-02-18 20:22 ` Rafael J. Wysocki
2016-02-19 8:09 ` Juri Lelli
2016-02-19 16:42 ` Srinivas Pandruvada
2016-02-19 17:26 ` Juri Lelli
2016-02-19 22:26 ` Rafael J. Wysocki
2016-02-22 9:42 ` Juri Lelli
2016-02-22 21:41 ` Rafael J. Wysocki
2016-02-23 11:10 ` Juri Lelli
2016-02-24 1:52 ` Rafael J. Wysocki
2016-02-22 10:45 ` Viresh Kumar
2016-02-19 17:28 ` Steve Muckle
2016-02-19 22:35 ` Rafael J. Wysocki
2016-02-23 3:58 ` Steve Muckle
2016-02-22 10:52 ` Peter Zijlstra
2016-02-22 14:33 ` Vincent Guittot
2016-02-22 15:31 ` Peter Zijlstra
2016-02-22 14:40 ` Juri Lelli
2016-02-22 15:42 ` Peter Zijlstra
2016-02-22 21:46 ` Rafael J. Wysocki
2016-02-19 22:14 ` Rafael J. Wysocki
2016-02-22 9:32 ` Juri Lelli
2016-02-22 21:26 ` Rafael J. Wysocki
2016-02-23 11:01 ` Juri Lelli
2016-02-24 2:01 ` Rafael J. Wysocki
2016-03-08 19:24 ` Michael Turquette
2016-03-08 20:40 ` Rafael J. Wysocki
[not found] ` <20160308220632.4103.13377@quark.deferred.io>
2016-03-08 22:43 ` Rafael J. Wysocki
2016-03-09 12:35 ` Peter Zijlstra
2016-03-09 13:22 ` Rafael J. Wysocki
2016-03-09 13:32 ` Ingo Molnar
2016-03-09 13:39 ` Rafael J. Wysocki
2016-03-10 2:12 ` Vincent Guittot
2016-02-10 15:25 ` [PATCH v6 2/3] cpufreq: intel_pstate: Replace timers with " Rafael J. Wysocki
2016-02-10 15:36 ` [PATCH v6 3/3] cpufreq: governor: " Rafael J. Wysocki
2016-02-10 23:11 ` [PATCH v6 0/3] cpufreq: " Doug Smythies
2016-02-10 23:17 ` Rafael J. Wysocki
2016-02-11 22:50 ` Doug Smythies
2016-02-11 23:28 ` Rafael J. Wysocki
2016-02-12 1:02 ` Doug Smythies
2016-02-12 1:20 ` Rafael J. Wysocki
2016-02-12 7:25 ` Doug Smythies
2016-02-12 13:39 ` Rafael J. Wysocki
2016-02-12 17:33 ` Doug Smythies
2016-02-12 23:21 ` Rafael J. Wysocki
2016-02-11 6:02 ` Srinivas Pandruvada
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