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From: Quentin Perret <qperret@google.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Vincent Donnefort <vincent.donnefort@arm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	rjw@rjwysocki.net, vincent.guittot@linaro.org,
	linux-kernel@vger.kernel.org, ionela.voinescu@arm.com,
	lukasz.luba@arm.com, dietmar.eggemann@arm.com
Subject: Re: [PATCH v2 3/3] PM / EM: Skip inefficient OPPs
Date: Tue, 1 Jun 2021 09:07:41 +0000	[thread overview]
Message-ID: <YLX43QT+5r/4zHoP@google.com> (raw)
In-Reply-To: <20210601085628.75atoc4e34uttqqw@vireshk-i7>

On Tuesday 01 Jun 2021 at 14:26:28 (+0530), Viresh Kumar wrote:
> On 01-06-21, 09:47, Vincent Donnefort wrote:
> > Seems like no one has been really convinced about the arguments in favor of
> > keeping inefficiencies into EM :) Let me then give a shot with marking the OPPs
> > for the next version.
> 
> Right, I think this is what you should do:
> 
> - Add another flag for OPP entries, and mark them inefficient.
> 
> - Whoever traverses the list to find the next frequency (cpufreq here), checks
>   that flag somehow (or replicates that to its own table) and get the right
>   frequency out.

Just to reiterate here what was discussed on IRC the other day, I still
feel that the choice of an efficient OPP or not is a policy decision,
and should be left to the governor.

It's not obvious to me that the userspace govenor for instance wants any
of this. Same thing with e.g. the powersave governor if the lowest OPPs
are inefficient (yes skipping them will not impact energy, but it will
impact instantaneous power).

So if we're going to move that logic to the cpufreq core, then we'll
probably want two separate APIs and make sure to use the effiency-aware
one is used only from the places where that makes sense.

Thanks,
Quentin

  reply	other threads:[~2021-06-01  9:07 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-21 16:54 [PATCH v2 0/3] EM / PM: Inefficient OPPs Vincent Donnefort
2021-05-21 16:54 ` [PATCH v2 1/3] PM / EM: Fix inefficient state detection Vincent Donnefort
2021-05-24 12:41   ` Lukasz Luba
2021-05-25  9:50   ` Quentin Perret
2021-05-21 16:54 ` [PATCH v2 2/3] PM / EM: Extend em_perf_domain with a flag field Vincent Donnefort
2021-05-24 12:44   ` Lukasz Luba
2021-05-25  9:54   ` Quentin Perret
2021-05-21 16:54 ` [PATCH v2 3/3] PM / EM: Skip inefficient OPPs Vincent Donnefort
2021-05-24 12:55   ` Lukasz Luba
2021-05-25  8:48   ` Peter Zijlstra
2021-05-25  9:21     ` Vincent Donnefort
2021-05-25 10:00       ` Vincent Donnefort
2021-05-28  5:09     ` Viresh Kumar
2021-06-01  8:47       ` Vincent Donnefort
2021-06-01  8:56         ` Viresh Kumar
2021-06-01  9:07           ` Quentin Perret [this message]
2021-06-01  9:13             ` Viresh Kumar
2021-05-25  9:33   ` Quentin Perret
2021-05-25  9:46     ` Vincent Donnefort
2021-05-25 11:03       ` Lukasz Luba
2021-05-25 13:06         ` Quentin Perret
2021-05-25 13:34           ` Lukasz Luba
2021-05-25  9:47     ` Vincent Donnefort
2021-05-28  5:04   ` Viresh Kumar
2021-05-28  9:00     ` Lukasz Luba
2021-05-26  3:47 ` [PATCH v2 0/3] EM / PM: Inefficient OPPs Viresh Kumar
2021-05-26  8:56   ` Lukasz Luba
2021-05-26  9:33     ` Viresh Kumar
2021-05-27  7:13       ` Lukasz Luba
2021-05-26  9:01   ` Vincent Donnefort
2021-05-26  9:38     ` Viresh Kumar
2021-05-26  9:39       ` Viresh Kumar
2021-05-26 10:24       ` Lukasz Luba
2021-05-26 10:39         ` Lukasz Luba
2021-05-26 11:50           ` Lukasz Luba
2021-05-26 13:49       ` Vincent Donnefort

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