From: Quentin Perret <quentin.perret@arm.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>,
linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Thara Gopinath <thara.gopinath@linaro.org>,
linux-pm@vger.kernel.org,
Morten Rasmussen <morten.rasmussen@arm.com>,
Chris Redpath <chris.redpath@arm.com>,
Patrick Bellasi <patrick.bellasi@arm.com>,
Valentin Schneider <valentin.schneider@arm.com>,
"Rafael J . Wysocki" <rjw@rjwysocki.net>,
Vincent Guittot <vincent.guittot@linaro.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
Todd Kjos <tkjos@google.com>, Joel Fernandes <joelaf@google.com>
Subject: Re: [RFC PATCH 2/6] sched: Introduce energy models of CPUs
Date: Wed, 21 Mar 2018 00:45:22 +0000 [thread overview]
Message-ID: <20180321004521.GA3174@queper01-VirtualBox> (raw)
In-Reply-To: <20180320095215.GB23359@kroah.com>
On Tuesday 20 Mar 2018 at 10:52:15 (+0100), Greg Kroah-Hartman wrote:
> On Tue, Mar 20, 2018 at 09:43:08AM +0000, Dietmar Eggemann wrote:
> > From: Quentin Perret <quentin.perret@arm.com>
> >
> > The energy consumption of each CPU in the system is modeled with a list
> > of values representing its dissipated power and compute capacity at each
> > available Operating Performance Point (OPP). These values are derived
> > from existing information in the kernel (currently used by the thermal
> > subsystem) and don't require the introduction of new platform-specific
> > tunables. The energy model is also provided with a simple representation
> > of all frequency domains as cpumasks, hence enabling the scheduler to be
> > aware of dependencies between CPUs. The data required to build the energy
> > model is provided by the OPP library which enables an abstract view of
> > the platform from the scheduler. The new data structures holding these
> > models and the routines to populate them are stored in
> > kernel/sched/energy.c.
> >
> > For the sake of simplicity, it is assumed in the energy model that all
> > CPUs in a frequency domain share the same micro-architecture. As long as
> > this assumption is correct, the energy models of different CPUs belonging
> > to the same frequency domain are equal. Hence, this commit builds only one
> > energy model per frequency domain, and links all relevant CPUs to it in
> > order to save time and memory. If needed for future hardware platforms,
> > relaxing this assumption should imply relatively simple modifications in
> > the code but a significantly higher algorithmic complexity.
> >
> > As it appears that energy-aware scheduling really makes a difference on
> > heterogeneous systems (e.g. big.LITTLE platforms), it is restricted to
> > systems having:
> >
> > 1. SD_ASYM_CPUCAPACITY flag set
> > 2. Dynamic Voltage and Frequency Scaling (DVFS) is enabled
> > 3. Available power estimates for the OPPs of all possible CPUs
> >
> > Moreover, the scheduler is notified of the energy model availability
> > using a static key in order to minimize the overhead on non-energy-aware
> > systems.
> >
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Signed-off-by: Quentin Perret <quentin.perret@arm.com>
> > Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
> >
> > ---
> > This patch depends on additional infrastructure being merged in the OPP
> > core. As this infrastructure can also be useful for other clients, the
> > related patches have been posted separately [1].
> >
> > [1] https://marc.info/?l=linux-pm&m=151635516419249&w=2
> > ---
> > include/linux/sched/energy.h | 31 +++++++
> > kernel/sched/Makefile | 2 +-
> > kernel/sched/energy.c | 190 +++++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 222 insertions(+), 1 deletion(-)
> > create mode 100644 include/linux/sched/energy.h
> > create mode 100644 kernel/sched/energy.c
> >
> > diff --git a/include/linux/sched/energy.h b/include/linux/sched/energy.h
> > new file mode 100644
> > index 000000000000..b4f43564ffe4
> > --- /dev/null
> > +++ b/include/linux/sched/energy.h
> > @@ -0,0 +1,31 @@
> > +#ifndef _LINUX_SCHED_ENERGY_H
> > +#define _LINUX_SCHED_ENERGY_H
>
> No copyright or license info? Not good :(
>
> > --- /dev/null
> > +++ b/kernel/sched/energy.c
> > @@ -0,0 +1,190 @@
> > +/*
> > + * Released under the GPLv2 only.
> > + * SPDX-License-Identifier: GPL-2.0
>
> Please read the documentation for the SPDX lines on how to do them
> correctly. Newer versions of checkpatch.pl will catch this, but that is
> in linux-next for the moment.
>
> And once you have the SPDX line, the "Released under..." line is not
> needed.
>
>
> > + *
> > + * Energy-aware scheduling models
> > + *
> > + * Copyright (C) 2018, Arm Ltd.
> > + * Written by: Quentin Perret, Arm Ltd.
> > + *
> > + * This file is subject to the terms and conditions of the GNU General Public
> > + * License. See the file "COPYING" in the main directory of this archive
> > + * for more details.
>
> This paragraph is not needed at all.
Right, I will fix all the licence issues and add one to the new header
file. I took example on existing files a while ago when I first wrote
the patches and forgot to update them later on. Sorry about that.
>
> > + */
> > +
> > +#define pr_fmt(fmt) "sched-energy: " fmt
> > +
> > +#include <linux/sched/topology.h>
> > +#include <linux/sched/energy.h>
> > +#include <linux/pm_opp.h>
> > +
> > +#include "sched.h"
> > +
> > +DEFINE_STATIC_KEY_FALSE(sched_energy_present);
> > +struct sched_energy_model ** __percpu energy_model;
> > +
> > +/*
> > + * A copy of the cpumasks representing the frequency domains is kept private
> > + * to the scheduler. They are stacked in a dynamically allocated linked list
> > + * as we don't know how many frequency domains the system has.
> > + */
> > +LIST_HEAD(freq_domains);
>
> global variable? If so, please prefix it with something more unique
> than "freq_".
Will do.
>
> > +#ifdef CONFIG_PM_OPP
>
> #ifdefs go in .h files, not .c files, right?
Yes good point. Actually, I might be able to tweak only kernel/sched/Makefile
to ensure we have CONFIG_PM_OPP. I will look into it.
>
> thanks,
>
> greg k-h
Thanks,
Quentin
next prev parent reply other threads:[~2018-03-21 0:45 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-20 9:43 [RFC PATCH 0/6] Energy Aware Scheduling Dietmar Eggemann
2018-03-20 9:43 ` [RFC PATCH 1/6] sched/fair: Create util_fits_capacity() Dietmar Eggemann
2018-03-20 9:43 ` [RFC PATCH 2/6] sched: Introduce energy models of CPUs Dietmar Eggemann
2018-03-20 9:52 ` Greg Kroah-Hartman
2018-03-21 0:45 ` Quentin Perret [this message]
2018-03-25 13:48 ` Quentin Perret
2018-03-26 22:26 ` Dietmar Eggemann
2018-04-09 12:01 ` Peter Zijlstra
2018-04-09 13:45 ` Quentin Perret
2018-04-09 15:32 ` Peter Zijlstra
2018-04-09 16:42 ` Quentin Perret
2018-04-10 6:55 ` Rafael J. Wysocki
2018-04-10 9:31 ` Quentin Perret
2018-04-10 10:20 ` Rafael J. Wysocki
2018-03-20 9:43 ` [RFC PATCH 3/6] sched: Add over-utilization/tipping point indicator Dietmar Eggemann
2018-04-09 9:40 ` Peter Zijlstra
2018-04-09 9:47 ` Peter Zijlstra
2018-04-09 9:53 ` Dietmar Eggemann
2018-04-09 11:49 ` Peter Zijlstra
2018-03-20 9:43 ` [RFC PATCH 4/6] sched/fair: Introduce an energy estimation helper function Dietmar Eggemann
2018-03-21 9:04 ` Juri Lelli
2018-03-21 12:26 ` Patrick Bellasi
2018-03-21 12:59 ` Juri Lelli
2018-03-21 13:55 ` Quentin Perret
2018-03-21 15:15 ` Juri Lelli
2018-03-21 16:26 ` Morten Rasmussen
2018-03-21 17:02 ` Juri Lelli
2018-03-21 14:02 ` Quentin Perret
2018-03-21 21:15 ` Dietmar Eggemann
2018-03-21 12:39 ` Patrick Bellasi
2018-03-21 14:26 ` Quentin Perret
2018-03-21 14:50 ` Juri Lelli
2018-03-21 15:54 ` Patrick Bellasi
2018-03-22 5:05 ` Quentin Perret
2018-03-20 9:43 ` [RFC PATCH 5/6] sched/fair: Select an energy-efficient CPU on task wake-up Dietmar Eggemann
2018-03-21 15:35 ` Patrick Bellasi
2018-03-22 20:10 ` Joel Fernandes
2018-03-23 15:47 ` Morten Rasmussen
2018-03-24 1:13 ` Joel Fernandes
2018-03-24 1:34 ` Quentin Perret
2018-03-24 6:06 ` Joel Fernandes
2018-03-24 1:22 ` Quentin Perret
2018-03-25 1:52 ` Quentin Perret
2018-03-22 16:27 ` Joel Fernandes
2018-03-22 18:06 ` Patrick Bellasi
2018-03-22 20:19 ` Joel Fernandes
2018-03-24 1:47 ` Quentin Perret
2018-03-25 0:12 ` Joel Fernandes
2018-03-23 16:00 ` Morten Rasmussen
2018-03-24 0:36 ` Joel Fernandes
2018-03-25 1:38 ` Quentin Perret
2018-03-20 9:43 ` [RFC PATCH 6/6] drivers: base: arch_topology.c: Enable EAS for arm/arm64 platforms Dietmar Eggemann
2018-03-20 9:49 ` Greg Kroah-Hartman
2018-03-20 15:20 ` Dietmar Eggemann
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