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From: Quentin Perret <quentin.perret@arm.com>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: peterz@infradead.org, rjw@rjwysocki.net,
	linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	gregkh@linuxfoundation.org, mingo@redhat.com,
	morten.rasmussen@arm.com, chris.redpath@arm.com,
	patrick.bellasi@arm.com, valentin.schneider@arm.com,
	vincent.guittot@linaro.org, thara.gopinath@linaro.org,
	viresh.kumar@linaro.org, tkjos@google.com,
	joel@joelfernandes.org, smuckle@google.com,
	adharmap@codeaurora.org, skannan@codeaurora.org,
	pkondeti@codeaurora.org, juri.lelli@redhat.com,
	edubezval@gmail.com, srinivas.pandruvada@linux.intel.com,
	currojerez@riseup.net, javi.merino@kernel.org
Subject: Re: [PATCH v6 07/14] sched/topology: Introduce sched_energy_present static key
Date: Fri, 7 Sep 2018 09:24:23 +0100	[thread overview]
Message-ID: <20180907082139.ogsdxambyryhgsu4@queper01-lin> (raw)
In-Reply-To: <e4e9d572-94ba-9d01-d18a-aa0ddd6fd357@arm.com>

On Thursday 06 Sep 2018 at 16:49:47 (-0700), Dietmar Eggemann wrote:
> I would prefer a sched_feature. I guess it has to be disabled by default so
> that other systems don't have to check rcu_dereference(rd->pd) in the wakeup
> path.

Right, this is what I had in mind too. I guess downstream kernels can
always carry a patch that changes the default if they want it enabled
without messing around in userspace.

> But since at the beginning EAS will be the only user of the EM there is no
> need to change the static key sched_energy_present right now.

Indeed, I could add a patch introducing this sched_feat in the series
that migrates IPA to using the EM framework (to be posted later). It is
just not required until we have a new user.

However that IPA-related patchset would then change the default
behaviour for users who used to get EAS enabled automatically, but
wouldn't after updating their kernel (meaning they'd now have to flip
switches by hand whereas it used to "just work"). Not sure if that
qualifies as "breaking users" (cf. Linus' rule #1 of kernel
development) ...

Thanks,
Quentin

  reply	other threads:[~2018-09-07  8:24 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-20  9:44 [PATCH v6 00/14] Energy Aware Scheduling Quentin Perret
2018-08-20  9:44 ` [PATCH v6 01/14] sched: Relocate arch_scale_cpu_capacity Quentin Perret
2018-08-20  9:44 ` [PATCH v6 02/14] sched/cpufreq: Factor out utilization to frequency mapping Quentin Perret
2018-09-10  9:29   ` Rafael J. Wysocki
2018-08-20  9:44 ` [PATCH v6 03/14] PM: Introduce an Energy Model management framework Quentin Perret
2018-08-29 10:04   ` Patrick Bellasi
2018-08-29 13:28     ` Quentin Perret
2018-08-31  9:04       ` Patrick Bellasi
2018-09-11  9:34       ` Andrea Parri
2018-09-11 12:32         ` Quentin Perret
2018-09-11 13:31           ` Andrea Parri
2018-09-10  9:44   ` Rafael J. Wysocki
2018-09-10 10:38     ` Quentin Perret
2018-09-10 10:40       ` Rafael J. Wysocki
2018-08-20  9:44 ` [PATCH v6 04/14] PM / EM: Expose the Energy Model in sysfs Quentin Perret
2018-09-06  6:56   ` Dietmar Eggemann
2018-09-06 14:09     ` Quentin Perret
2018-09-07  0:14       ` Dietmar Eggemann
2018-08-20  9:44 ` [PATCH v6 05/14] sched/topology: Reference the Energy Model of CPUs when available Quentin Perret
2018-08-29 16:22   ` Patrick Bellasi
2018-08-29 16:56     ` Quentin Perret
2018-08-30 10:00       ` Patrick Bellasi
2018-08-30 10:47         ` Quentin Perret
2018-08-30 12:50           ` Patrick Bellasi
2018-08-20  9:44 ` [PATCH v6 06/14] sched/topology: Lowest CPU asymmetry sched_domain level pointer Quentin Perret
2018-08-20  9:44 ` [PATCH v6 07/14] sched/topology: Introduce sched_energy_present static key Quentin Perret
2018-08-29 16:50   ` Patrick Bellasi
2018-08-29 17:20     ` Quentin Perret
2018-08-30  9:23       ` Patrick Bellasi
2018-08-30  9:57         ` Quentin Perret
2018-08-30 10:18           ` Patrick Bellasi
2018-09-06  6:06   ` Dietmar Eggemann
2018-09-06  9:29     ` Quentin Perret
2018-09-06 23:49       ` Dietmar Eggemann
2018-09-07  8:24         ` Quentin Perret [this message]
2018-08-20  9:44 ` [PATCH v6 08/14] sched/fair: Clean-up update_sg_lb_stats parameters Quentin Perret
2018-08-20  9:44 ` [PATCH v6 09/14] sched: Add over-utilization/tipping point indicator Quentin Perret
2018-08-20  9:44 ` [PATCH v6 10/14] sched/cpufreq: Refactor the utilization aggregation method Quentin Perret
2018-09-10  9:53   ` Rafael J. Wysocki
2018-09-10 10:07     ` Quentin Perret
2018-09-10 10:25       ` Rafael J. Wysocki
2018-08-20  9:44 ` [PATCH v6 11/14] sched/fair: Introduce an energy estimation helper function Quentin Perret
2018-08-20  9:44 ` [PATCH v6 12/14] sched/fair: Select an energy-efficient CPU on task wake-up Quentin Perret
2018-08-20  9:44 ` [PATCH v6 13/14] sched/topology: Make Energy Aware Scheduling depend on schedutil Quentin Perret
2018-09-04 10:59   ` Quentin Perret
2018-09-06  9:18     ` Rafael J. Wysocki
2018-09-06 14:38       ` Quentin Perret
2018-09-07  8:52         ` Rafael J. Wysocki
2018-09-07  8:56           ` Rafael J. Wysocki
2018-09-07  9:02             ` Quentin Perret
2018-09-07 15:29           ` Quentin Perret
2018-09-09 20:13             ` Rafael J. Wysocki
2018-09-10  8:24               ` Quentin Perret
2018-09-10  8:55                 ` Rafael J. Wysocki
2018-09-10  9:43                   ` Quentin Perret
2018-08-20  9:44 ` [PATCH v6 14/14] OPTIONAL: cpufreq: dt: Register an Energy Model Quentin Perret
2018-09-10  9:12 ` [PATCH v6 00/14] Energy Aware Scheduling Rafael J. Wysocki

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