From: Viresh Kumar <viresh.kumar@linaro.org>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Rafael Wysocki <rjw@rjwysocki.net>,
Juri Lelli <juri.lelli@arm.com>,
Lists linaro-kernel <linaro-kernel@lists.linaro.org>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
Saravana Kannan <skannan@codeaurora.org>,
Peter Zijlstra <peterz@infradead.org>,
Michael Turquette <mturquette@baylibre.com>,
Steve Muckle <steve.muckle@linaro.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Morten Rasmussen <morten.rasmussen@arm.com>,
dietmar.eggemann@arm.com,
Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V3 12/13] cpufreq: ondemand: Traverse list of policy_dbs in update_sampling_rate()
Date: Mon, 8 Feb 2016 19:04:46 +0530 [thread overview]
Message-ID: <20160208133446.GK8294@vireshk> (raw)
In-Reply-To: <CAJZ5v0iVbzuPdNLyTcih5-U7c7AJOZ_zqmHkLN0AckCPzZpDFw@mail.gmail.com>
On 08-02-16, 14:32, Rafael J. Wysocki wrote:
> > - * If new rate is smaller than the old, simply updating
> > - * dbs_tuners_int.sampling_rate might not be appropriate. For example, if the
> > - * original sampling_rate was 1 second and the requested new sampling rate is 10
> > - * ms because the user needs immediate reaction from ondemand governor, but not
> > - * sure if higher frequency will be required or not, then, the governor may
> > - * change the sampling rate too late; up to 1 second later. Thus, if we are
> > - * reducing the sampling rate, we need to make the new value effective
> > - * immediately.
>
> The comment still applies.
Why? It talks about the case where we have reduced sampling rate, but
that's not the case anymore. We *always* update sample_delay_ns now.
> Moreover, please extend it to say that this must be called with
> dbs_data->mutex held (or it looks racy otherwise).
Yeah, that can be done.
WARNING: multiple messages have this Message-ID (diff)
From: Viresh Kumar <viresh.kumar@linaro.org>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Rafael Wysocki <rjw@rjwysocki.net>,
Juri Lelli <juri.lelli@arm.com>,
Lists linaro-kernel <linaro-kernel@lists.linaro.org>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
Saravana Kannan <skannan@codeaurora.org>,
Peter Zijlstra <peterz@infradead.org>,
Michael Turquette <mturquette@baylibre.com>,
Steve Muckle <steve.muckle@linaro.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Morten Rasmussen <morten.rasmussen@arm.com>,
dietmar.eggemann@arm.com,
Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V3 12/13] cpufreq: ondemand: Traverse list of policy_dbs in update_sampling_rate()
Date: Mon, 8 Feb 2016 19:04:46 +0530 [thread overview]
Message-ID: <20160208133446.GK8294@vireshk> (raw)
In-Reply-To: <CAJZ5v0iVbzuPdNLyTcih5-U7c7AJOZ_zqmHkLN0AckCPzZpDFw@mail.gmail.com>
On 08-02-16, 14:32, Rafael J. Wysocki wrote:
> > - * If new rate is smaller than the old, simply updating
> > - * dbs_tuners_int.sampling_rate might not be appropriate. For example, if the
> > - * original sampling_rate was 1 second and the requested new sampling rate is 10
> > - * ms because the user needs immediate reaction from ondemand governor, but not
> > - * sure if higher frequency will be required or not, then, the governor may
> > - * change the sampling rate too late; up to 1 second later. Thus, if we are
> > - * reducing the sampling rate, we need to make the new value effective
> > - * immediately.
>
> The comment still applies.
Why? It talks about the case where we have reduced sampling rate, but
that's not the case anymore. We *always* update sample_delay_ns now.
> Moreover, please extend it to say that this must be called with
> dbs_data->mutex held (or it looks racy otherwise).
Yeah, that can be done.
--
viresh
next prev parent reply other threads:[~2016-02-08 13:34 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-08 11:39 [PATCH V3 00/13] cpufreq: governors: Fix ABBA lockups Viresh Kumar
2016-02-08 11:39 ` [PATCH V3 01/13] cpufreq: governor: Create generic macro for global tuners Viresh Kumar
2016-02-08 16:33 ` Rafael J. Wysocki
2016-02-08 11:39 ` [PATCH V3 02/13] cpufreq: governor: Move common tunables to 'struct dbs_data' Viresh Kumar
2016-02-08 11:39 ` [PATCH V3 03/13] cpufreq: governor: New sysfs show/store callbacks for governor tunables Viresh Kumar
2016-02-08 17:07 ` Viresh Kumar
2016-02-08 21:28 ` Rafael J. Wysocki
2016-02-08 21:36 ` Rafael J. Wysocki
2016-02-09 3:21 ` Viresh Kumar
2016-02-09 20:20 ` Rafael J. Wysocki
2016-02-08 11:39 ` [PATCH V3 04/13] cpufreq: governor: Drop unused macros for creating governor tunable attributes Viresh Kumar
2016-02-08 11:39 ` [PATCH V3 05/13] Revert "cpufreq: Drop rwsem lock around CPUFREQ_GOV_POLICY_EXIT" Viresh Kumar
2016-02-08 11:39 ` [PATCH V3 06/13] cpufreq: Merge cpufreq_offline_prepare/finish routines Viresh Kumar
2016-02-08 11:39 ` [PATCH V3 07/13] cpufreq: Call __cpufreq_governor() with policy->rwsem held Viresh Kumar
2016-02-08 11:39 ` [PATCH V3 08/13] cpufreq: Remove cpufreq_governor_lock Viresh Kumar
2016-02-08 11:39 ` [PATCH V3 09/13] cpufreq: governor: Move common sysfs tunables to cpufreq_governor.c Viresh Kumar
2016-02-08 12:58 ` Rafael J. Wysocki
2016-02-08 13:03 ` Viresh Kumar
2016-02-08 13:24 ` Rafael J. Wysocki
2016-02-08 11:39 ` [PATCH V3 10/13] cpufreq: governor: No need to manage state machine now Viresh Kumar
2016-02-08 11:39 ` [PATCH V3 11/13] cpufreq: governor: Keep list of policy_dbs within dbs_data Viresh Kumar
2016-02-08 13:21 ` Rafael J. Wysocki
2016-02-08 13:30 ` Viresh Kumar
2016-02-08 13:35 ` Rafael J. Wysocki
2016-02-08 11:39 ` [PATCH V3 12/13] cpufreq: ondemand: Traverse list of policy_dbs in update_sampling_rate() Viresh Kumar
2016-02-08 13:32 ` Rafael J. Wysocki
2016-02-08 13:34 ` Viresh Kumar [this message]
2016-02-08 13:34 ` Viresh Kumar
2016-02-08 13:37 ` Rafael J. Wysocki
2016-02-08 17:20 ` Viresh Kumar
2016-02-08 22:05 ` Rafael J. Wysocki
2016-02-08 22:08 ` Rafael J. Wysocki
2016-02-08 11:39 ` [PATCH V3 13/13] cpufreq: conservative: Update sample_delay_ns immediately Viresh Kumar
2016-02-08 12:51 ` [PATCH V3 00/13] cpufreq: governors: Fix ABBA lockups Shilpasri G Bhat
2016-02-08 12:54 ` Viresh Kumar
2016-02-08 16:39 ` Juri Lelli
2016-02-08 16:55 ` Viresh Kumar
2016-02-08 21:43 ` Rafael J. Wysocki
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