From: Steve Muckle <steve.muckle@linaro.org>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
Linux PM list <linux-pm@vger.kernel.org>,
Juri Lelli <juri.lelli@arm.com>,
ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
Viresh Kumar <viresh.kumar@linaro.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Michael Turquette <mturquette@baylibre.com>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH v2 6/10] cpufreq: Support for fast frequency switching
Date: Fri, 4 Mar 2016 15:56:48 -0800 [thread overview]
Message-ID: <56DA20C0.1070803@linaro.org> (raw)
In-Reply-To: <CAJZ5v0jh7qcmYjDXCdO3Pid4XyuuxQfsKAmWDLXYcrkx0t-phw@mail.gmail.com>
On 03/04/2016 03:18 PM, Rafael J. Wysocki wrote:
> In fact, the mechanism may be relatively simple if I'm not mistaken.
>
> In the "fast switch" case, the governor may spawn a work item that
> will just execute cpufreq_get() on policy->cpu. That will notice that
> policy->cur is different from the real current frequency and will
> re-adjust.
>
> Of course, cpufreq_driver_fast_switch() will need to be modified so it
> doesn't update policy->cur then perhaps with a comment that the
> governor using it will be responsible for that.
>
> And the governor will need to avoid spawning that work item too often
> (basically, if one has been spawned already and hasn't completed, no
> need to spawn a new one, and maybe rate-limit it?), but all that looks
> reasonably straightforward.
It is another option though definitely a compromise. The semantics seem
different since you'd potentially have multiple freq changes before a
single notifier went through, so stuff might still break. The fast path
would also be more expensive given the workqueue activity that could
translate into additional task wakeups.
Honestly I wonder if it's better to just try the "no notifiers with fast
drivers" approach to start. The notifiers could always be added if
platform owners complain that they absolutely require them.
thanks,
Steve
next prev parent reply other threads:[~2016-03-04 23:57 UTC|newest]
Thread overview: 159+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-02 1:56 [PATCH 0/6] cpufreq: schedutil governor Rafael J. Wysocki
2016-03-02 2:04 ` [PATCH 1/6] cpufreq: Reduce cpufreq_update_util() overhead a bit Rafael J. Wysocki
2016-03-03 5:48 ` Viresh Kumar
2016-03-03 11:47 ` Juri Lelli
2016-03-03 13:04 ` Peter Zijlstra
2016-03-02 2:05 ` [PATCH 2/6][Resend] cpufreq: acpi-cpufreq: Make read and write operations more efficient Rafael J. Wysocki
2016-03-02 2:08 ` [PATCH 3/6] cpufreq: governor: New data type for management part of dbs_data Rafael J. Wysocki
2016-03-03 5:53 ` Viresh Kumar
2016-03-03 19:26 ` Rafael J. Wysocki
2016-03-04 5:49 ` Viresh Kumar
2016-03-02 2:10 ` [PATCH 4/6] cpufreq: governor: Move abstract gov_tunables code to a seperate file Rafael J. Wysocki
2016-03-03 6:03 ` Viresh Kumar
2016-03-02 2:12 ` [PATCH 5/6] cpufreq: Support for fast frequency switching Rafael J. Wysocki
2016-03-03 6:00 ` Viresh Kumar
2016-03-04 2:15 ` Rafael J. Wysocki
2016-03-03 11:16 ` Peter Zijlstra
2016-03-03 20:56 ` Rafael J. Wysocki
2016-03-03 21:12 ` Peter Zijlstra
2016-03-03 11:18 ` Peter Zijlstra
2016-03-03 19:39 ` Rafael J. Wysocki
2016-03-02 2:27 ` [PATCH 6/6] cpufreq: schedutil: New governor based on scheduler utilization data Rafael J. Wysocki
2016-03-02 17:10 ` Vincent Guittot
2016-03-02 17:58 ` Rafael J. Wysocki
2016-03-02 22:49 ` Rafael J. Wysocki
2016-03-03 12:20 ` Peter Zijlstra
2016-03-03 12:32 ` Juri Lelli
2016-03-03 16:24 ` Rafael J. Wysocki
2016-03-03 16:37 ` Peter Zijlstra
2016-03-03 16:47 ` Peter Zijlstra
2016-03-04 1:14 ` Rafael J. Wysocki
2016-03-03 16:55 ` Juri Lelli
2016-03-03 16:56 ` Peter Zijlstra
2016-03-03 17:14 ` Juri Lelli
2016-03-03 14:01 ` Vincent Guittot
2016-03-03 15:38 ` Peter Zijlstra
2016-03-03 16:28 ` Peter Zijlstra
2016-03-03 16:42 ` Peter Zijlstra
2016-03-03 17:28 ` Dietmar Eggemann
2016-03-03 18:26 ` Peter Zijlstra
2016-03-03 19:14 ` Dietmar Eggemann
2016-03-08 13:09 ` Peter Zijlstra
2016-03-03 18:58 ` Rafael J. Wysocki
2016-03-03 13:07 ` Vincent Guittot
2016-03-03 20:06 ` Steve Muckle
2016-03-03 20:20 ` Rafael J. Wysocki
2016-03-03 21:37 ` Steve Muckle
2016-03-07 2:41 ` Rafael J. Wysocki
2016-03-08 11:27 ` Peter Zijlstra
2016-03-08 18:00 ` Rafael J. Wysocki
2016-03-08 19:26 ` Peter Zijlstra
2016-03-08 20:05 ` Rafael J. Wysocki
2016-03-09 10:15 ` Juri Lelli
2016-03-09 23:41 ` Rafael J. Wysocki
2016-03-10 4:30 ` Juri Lelli
2016-03-10 21:01 ` Rafael J. Wysocki
2016-03-10 23:19 ` Michael Turquette
2016-03-10 23:19 ` Michael Turquette
2016-03-09 16:39 ` Peter Zijlstra
2016-03-09 23:28 ` Rafael J. Wysocki
2016-03-10 3:44 ` Vincent Guittot
2016-03-10 10:07 ` Peter Zijlstra
2016-03-10 10:26 ` Vincent Guittot
[not found] ` <CAKfTPtCbjgbJn+68NJPCnmPFtcHD0wGmZRYaw37zSqPXNpo_Uw@mail.gmail.com>
2016-03-10 10:30 ` Peter Zijlstra
2016-03-10 10:56 ` Peter Zijlstra
2016-03-10 22:28 ` Rafael J. Wysocki
2016-03-10 8:43 ` Peter Zijlstra
2016-03-04 2:56 ` [PATCH v2 0/10] cpufreq: schedutil governor Rafael J. Wysocki
2016-03-04 2:58 ` [PATCH v2 1/10] cpufreq: Reduce cpufreq_update_util() overhead a bit Rafael J. Wysocki
2016-03-09 12:39 ` Peter Zijlstra
2016-03-09 14:17 ` Rafael J. Wysocki
2016-03-09 15:29 ` Peter Zijlstra
2016-03-09 21:35 ` Rafael J. Wysocki
2016-03-10 9:19 ` Peter Zijlstra
2016-03-04 2:59 ` [PATCH v2 2/10][Resend] cpufreq: acpi-cpufreq: Make read and write operations more efficient Rafael J. Wysocki
2016-03-04 3:01 ` [PATCH v2 3/10] cpufreq: governor: New data type for management part of dbs_data Rafael J. Wysocki
2016-03-04 5:52 ` Viresh Kumar
2016-03-04 3:03 ` [PATCH v2 4/10] cpufreq: governor: Move abstract gov_attr_set code to seperate file Rafael J. Wysocki
2016-03-04 5:52 ` Viresh Kumar
2016-03-04 3:05 ` [PATCH v2 5/10] cpufreq: Move governor attribute set headers to cpufreq.h Rafael J. Wysocki
2016-03-04 5:53 ` Viresh Kumar
2016-03-04 3:07 ` [PATCH v2 6/10] cpufreq: Support for fast frequency switching Rafael J. Wysocki
2016-03-04 22:18 ` Steve Muckle
2016-03-04 22:32 ` Rafael J. Wysocki
2016-03-04 22:40 ` Rafael J. Wysocki
2016-03-04 23:18 ` Rafael J. Wysocki
2016-03-04 23:56 ` Steve Muckle [this message]
2016-03-05 0:18 ` Rafael J. Wysocki
2016-03-05 11:58 ` Ingo Molnar
2016-03-05 16:49 ` Peter Zijlstra
2016-03-06 2:17 ` Rafael J. Wysocki
2016-03-07 8:00 ` Peter Zijlstra
2016-03-07 13:15 ` Rafael J. Wysocki
2016-03-07 13:32 ` Peter Zijlstra
2016-03-07 13:42 ` Rafael J. Wysocki
2016-03-04 22:58 ` Rafael J. Wysocki
2016-03-04 23:59 ` Steve Muckle
2016-03-04 3:12 ` [PATCH v2 7/10] cpufreq: Rework the scheduler hooks for triggering updates Rafael J. Wysocki
2016-03-04 3:14 ` [PATCH v2 8/10] cpufreq: Move scheduler-related code to the sched directory Rafael J. Wysocki
2016-03-04 3:18 ` [PATCH v2 9/10] cpufreq: sched: Re-introduce cpufreq_update_util() Rafael J. Wysocki
2016-03-04 10:50 ` Juri Lelli
2016-03-04 12:58 ` Rafael J. Wysocki
2016-03-04 13:30 ` [PATCH v3 " Rafael J. Wysocki
2016-03-04 21:21 ` Steve Muckle
2016-03-04 21:27 ` Rafael J. Wysocki
2016-03-04 21:36 ` Rafael J. Wysocki
2016-03-04 3:35 ` [PATCH v2 10/10] cpufreq: schedutil: New governor based on scheduler utilization data Rafael J. Wysocki
2016-03-04 11:26 ` Juri Lelli
2016-03-04 13:19 ` Rafael J. Wysocki
2016-03-04 15:56 ` Srinivas Pandruvada
2016-03-08 2:23 ` [PATCH v3 0/7] cpufreq: schedutil governor Rafael J. Wysocki
2016-03-08 2:25 ` [PATCH v3 1/7][Resend] cpufreq: Rework the scheduler hooks for triggering updates Rafael J. Wysocki
2016-03-09 13:41 ` Peter Zijlstra
2016-03-09 14:02 ` Rafael J. Wysocki
2016-03-08 2:26 ` [PATCH v3 2/7][Resend] cpufreq: Move scheduler-related code to the sched directory Rafael J. Wysocki
2016-03-08 2:28 ` [PATCH v3 3/7][Resend] cpufreq: governor: New data type for management part of dbs_data Rafael J. Wysocki
2016-03-08 2:29 ` [PATCH v3 4/7][Resend] cpufreq: governor: Move abstract gov_attr_set code to seperate file Rafael J. Wysocki
2016-03-08 2:38 ` [PATCH v3 5/7] cpufreq: Support for fast frequency switching Rafael J. Wysocki
2016-03-08 2:41 ` [PATCH v3 6/7] cpufreq: sched: Re-introduce cpufreq_update_util() Rafael J. Wysocki
2016-03-08 2:50 ` [PATCH v3 7/7] cpufreq: schedutil: New governor based on scheduler utilization data Rafael J. Wysocki
2016-03-16 14:41 ` [PATCH v4 0/7] cpufreq: schedutil governor Rafael J. Wysocki
2016-03-16 14:43 ` [PATCH v4 1/7] cpufreq: sched: Helpers to add and remove update_util hooks Rafael J. Wysocki
2016-03-16 14:44 ` [PATCH v4 2/7] cpufreq: governor: New data type for management part of dbs_data Rafael J. Wysocki
2016-03-16 14:45 ` [PATCH v4 3/7] cpufreq: governor: Move abstract gov_attr_set code to seperate file Rafael J. Wysocki
2016-03-16 14:46 ` [PATCH v4 4/7] cpufreq: Move governor attribute set headers to cpufreq.h Rafael J. Wysocki
2016-03-16 14:47 ` [PATCH v4 5/7] cpufreq: Move governor symbols " Rafael J. Wysocki
2016-03-16 14:52 ` [PATCH v4 6/7] cpufreq: Support for fast frequency switching Rafael J. Wysocki
2016-03-16 15:35 ` Peter Zijlstra
2016-03-16 16:58 ` Rafael J. Wysocki
2016-03-16 15:43 ` Peter Zijlstra
2016-03-16 16:58 ` Rafael J. Wysocki
2016-03-16 14:59 ` [PATCH v4 7/7] cpufreq: schedutil: New governor based on scheduler utilization data Rafael J. Wysocki
2016-03-16 17:35 ` Peter Zijlstra
2016-03-16 21:42 ` Rafael J. Wysocki
2016-03-16 17:36 ` Peter Zijlstra
2016-03-16 21:34 ` Rafael J. Wysocki
2016-03-16 17:52 ` Peter Zijlstra
2016-03-16 21:38 ` Rafael J. Wysocki
2016-03-16 22:39 ` Peter Zijlstra
2016-03-16 17:53 ` Peter Zijlstra
2016-03-16 21:48 ` Rafael J. Wysocki
2016-03-16 18:14 ` Peter Zijlstra
2016-03-16 21:38 ` Rafael J. Wysocki
2016-03-16 22:40 ` Peter Zijlstra
2016-03-16 22:53 ` Rafael J. Wysocki
2016-03-16 15:27 ` [PATCH v4 0/7] cpufreq: schedutil governor Peter Zijlstra
2016-03-16 16:20 ` Rafael J. Wysocki
2016-03-16 23:51 ` [PATCH v5 6/7][Update] cpufreq: Support for fast frequency switching Rafael J. Wysocki
2016-03-17 11:35 ` Juri Lelli
2016-03-17 11:40 ` Peter Zijlstra
2016-03-17 11:48 ` Juri Lelli
2016-03-17 12:53 ` Rafael J. Wysocki
2016-03-17 0:01 ` [PATCH v5 7/7][Update] cpufreq: schedutil: New governor based on scheduler utilization data Rafael J. Wysocki
2016-03-17 11:30 ` Juri Lelli
2016-03-17 12:54 ` Rafael J. Wysocki
2016-03-17 11:36 ` Peter Zijlstra
2016-03-17 12:54 ` Rafael J. Wysocki
2016-03-17 15:54 ` [PATCH v6 6/7][Update] cpufreq: Support for fast frequency switching Rafael J. Wysocki
2016-03-17 16:01 ` [PATCH v6 7/7][Update] cpufreq: schedutil: New governor based on scheduler utilization data Rafael J. Wysocki
2016-03-18 12:34 ` Patrick Bellasi
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