From: Steve Muckle <steve.muckle@linaro.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
Peter Zijlstra <peterz@infradead.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>,
Juri Lelli <juri.lelli@arm.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks
Date: Tue, 9 Feb 2016 17:02:33 -0800 [thread overview]
Message-ID: <56BA8C29.4090905@linaro.org> (raw)
In-Reply-To: <5387313.xAhVpzgZCg@vostro.rjw.lan>
On 02/09/2016 12:05 PM, Rafael J. Wysocki wrote:
>>> One concern I had was, given that the lone scheduler update hook is in
>>> CFS, is it possible for governor updates to be stalled due to RT or DL
>>> task activity?
>>
>> I don't think they may be completely stalled, but I'd prefer Peter to
>> answer that as he suggested to do it this way.
>
> In any case, if that concern turns out to be significant in practice, it may
> be addressed like in the appended modification of patch [1/3] from the $subject
> series.
>
> With that things look like before from the cpufreq side, but the other sched
> classes also get a chance to trigger a cpufreq update. The drawback is the
> cpu_clock() call instead of passing the time value from update_load_avg(), but
> I guess we can live with that if necessary.
>
> FWIW, this modification doesn't seem to break things on my test machine.
>
...
> Index: linux-pm/kernel/sched/rt.c
> ===================================================================
> --- linux-pm.orig/kernel/sched/rt.c
> +++ linux-pm/kernel/sched/rt.c
> @@ -2212,6 +2212,9 @@ static void task_tick_rt(struct rq *rq,
>
> update_curr_rt(rq);
>
> + /* Kick cpufreq to prevent it from stalling. */
> + cpufreq_kick();
> +
> watchdog(rq, p);
>
> /*
> 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.
thanks,
steve
next prev parent reply other threads:[~2016-02-10 1:02 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 [this message]
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
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=56BA8C29.4090905@linaro.org \
--to=steve.muckle@linaro.org \
--cc=juri.lelli@arm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=peterz@infradead.org \
--cc=rafael@kernel.org \
--cc=rjw@rjwysocki.net \
--cc=srinivas.pandruvada@linux.intel.com \
--cc=tglx@linutronix.de \
--cc=viresh.kumar@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).