From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Michael Turquette <mturquette@baylibre.com>,
peterz@infradead.org, rjw@rjwysocki.net
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
Juri.Lelli@arm.com, steve.muckle@linaro.org,
morten.rasmussen@arm.com, vincent.guittot@linaro.org,
Michael Turquette <mturquette+renesas@baylibre.com>
Subject: Re: [PATCH 8/8] sched: prefer cpufreq_scale_freq_capacity
Date: Wed, 16 Mar 2016 19:44:33 +0000 [thread overview]
Message-ID: <56E9B7A1.5030806@arm.com> (raw)
In-Reply-To: <20160315204630.30639.60702@quark.deferred.io>
On 15/03/16 20:46, Michael Turquette wrote:
> Quoting Dietmar Eggemann (2016-03-15 12:13:58)
>> On 14/03/16 05:22, Michael Turquette wrote:
[...]
>> For me this independence of the scheduler code towards the actual
>> implementation of the Frequency Invariant Engine (FEI) was actually a
>> feature.
>
> I do not agree that it is a strength; I think it is confusing. My
> opinion is that cpufreq drivers should implement
> arch_scale_freq_capacity. Having a sane fallback
> (cpufreq_scale_freq_capacity) simply means that you can remove the
> boilerplate from the arm32 and arm64 code, which is a win.
>
> Furthermore, if we have multiple competing implementations of
> arch_scale_freq_invariance, wouldn't it be better for all of them to
> live in cpufreq drivers? This means we would only need to implement a
> single run-time "selector".
>
> On the other hand, if the implementation lives in arch code and we have
> various implementations of arch_scale_freq_capacity within an
> architecture, then each arch would need to implement this selector
> function. Even worse then if we have a split where some implementations
> live in drivers/cpufreq (e.g. intel_pstate) and others in arch/arm and
> others in arch/arm64 ... now we have three selectors.
OK, now I see your point. What I don't understand is the fact why you
want different foo_scale_freq_capacity() implementations per cpufreq
drivers. IMHO we want to do the cpufreq.c based implementation to
abstract from that (at least for target_index() cpufreq drivers).
intel_pstate (setpolicy()) is an exception but my humble guess is that
systems with intel_pstate driver have X86_FEATURE_APERFMPERF support.
> Note that this has nothing to do with cpu microarch invariance. I'm
> happy for that to stay in arch code because we can have heterogeneous
> cpus that do not scale frequency, and thus would not enable cpufreq.
> But if your platform scales cpu frequency, then really cpufreq should be
> in the loop.
Agreed.
>
>>
>> In EAS RFC5.2 (linux-arm.org/linux-power.git energy_model_rfc_v5.2 ,
>> which hasn't been posted to LKML) we establish the link in the ARCH code
>> (arch/arm64/include/asm/topology.h).
>
> Right, sorry again about preemptively posting the patch. Total brainfart
> on my part.
>
>>
>> #ifdef CONFIG_CPU_FREQ
>> #define arch_scale_freq_capacity cpufreq_scale_freq_capacity
>> ...
>> +#endif
>
> The above is no longer necessary with this patch. Same question as
> above: why insist on the arch boilerplate?
OK.
[...]
next prev parent reply other threads:[~2016-03-16 19:44 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-14 5:22 [PATCH 0/8] schedutil enhancements Michael Turquette
2016-03-14 5:22 ` [PATCH 1/8] sched/cpufreq: remove cpufreq_trigger_update() Michael Turquette
2016-03-15 21:14 ` Peter Zijlstra
[not found] ` <20160315214545.30639.98727@quark.deferred.io>
2016-03-15 21:49 ` Peter Zijlstra
2016-03-16 8:00 ` Peter Zijlstra
2016-03-14 5:22 ` [PATCH 2/8] sched/fair: add margin to utilization update Michael Turquette
2016-03-15 21:16 ` Peter Zijlstra
[not found] ` <20160315212848.30639.38747@quark.deferred.io>
2016-03-15 21:43 ` Peter Zijlstra
2016-03-16 2:52 ` Steve Muckle
2016-03-16 22:12 ` Michael Turquette
2016-03-14 5:22 ` [PATCH 3/8] sched/cpufreq: new cfs capacity margin helpers Michael Turquette
2016-03-15 21:17 ` Peter Zijlstra
2016-03-14 5:22 ` [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Michael Turquette
2016-03-15 21:20 ` Peter Zijlstra
[not found] ` <20160315214043.30639.75507@quark.deferred.io>
2016-03-15 21:48 ` Peter Zijlstra
[not found] ` <20160315223701.30639.43127@quark.deferred.io>
2016-03-16 3:36 ` Steve Muckle
2016-03-16 8:05 ` Peter Zijlstra
2016-03-16 10:02 ` Juri Lelli
2016-03-16 17:55 ` Steve Muckle
2016-03-16 22:05 ` Michael Turquette
2016-03-17 9:40 ` Juri Lelli
2016-03-17 13:55 ` Steve Muckle
2016-03-17 15:53 ` Patrick Bellasi
2016-03-17 17:54 ` Juri Lelli
2016-03-17 18:56 ` Michael Turquette
2016-03-17 22:34 ` Rafael J. Wysocki
2016-03-16 12:45 ` Rafael J. Wysocki
2016-03-16 22:03 ` Michael Turquette
2016-03-14 5:22 ` [PATCH 5/8] sched/cpufreq: pass sched class into cpufreq_update_util Michael Turquette
2016-03-15 21:25 ` Peter Zijlstra
[not found] ` <20160315220609.30639.67271@quark.deferred.io>
2016-03-16 3:55 ` Steve Muckle
2016-03-16 7:41 ` Peter Zijlstra
2016-03-16 8:29 ` Vincent Guittot
2016-03-16 8:53 ` Peter Zijlstra
2016-03-16 9:16 ` Vincent Guittot
2016-03-16 12:39 ` Rafael J. Wysocki
2016-03-16 13:10 ` Peter Zijlstra
2016-03-16 13:23 ` Rafael J. Wysocki
2016-03-16 13:43 ` Peter Zijlstra
2016-03-14 5:22 ` [PATCH 6/8] cpufreq/schedutil: sum per-sched class utilization Michael Turquette
2016-03-15 21:29 ` Peter Zijlstra
[not found] ` <20160315220951.30639.12872@quark.deferred.io>
2016-03-16 7:38 ` Peter Zijlstra
2016-03-16 18:20 ` Steve Muckle
2016-03-16 18:36 ` Peter Zijlstra
2016-03-16 19:12 ` Steve Muckle
2016-03-14 5:22 ` [PATCH 7/8] cpufreq: Frequency invariant scheduler load-tracking support Michael Turquette
2016-03-15 19:13 ` Dietmar Eggemann
2016-03-15 20:19 ` Michael Turquette
2016-03-15 21:32 ` Peter Zijlstra
2016-03-16 18:33 ` Dietmar Eggemann
2016-03-15 21:34 ` Peter Zijlstra
2016-03-14 5:22 ` [PATCH 8/8] sched: prefer cpufreq_scale_freq_capacity Michael Turquette
2016-03-15 19:13 ` Dietmar Eggemann
2016-03-15 20:46 ` Michael Turquette
2016-03-16 19:44 ` Dietmar Eggemann [this message]
2016-03-16 20:07 ` Peter Zijlstra
2016-03-16 21:32 ` Rafael J. Wysocki
2016-03-15 21:37 ` Peter Zijlstra
[not found] ` <20160315222721.30639.28332@quark.deferred.io>
2016-03-16 7:47 ` Peter Zijlstra
2016-03-16 12:41 ` Peter Zijlstra
2016-03-16 0:08 ` [PATCH 0/8] schedutil enhancements Rafael J. Wysocki
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