linux-kernel - Re: [PATCH v2 1/2] cpufreq / sched: Pass flags to cpufreq_update

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Date:   Sat, 20 Aug 2016 03:08:01 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Linux PM list <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Steve Muckle <steve.muckle@...aro.org>,
        Juri Lelli <juri.lelli@....com>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v2 1/2] cpufreq / sched: Pass flags to cpufreq_update_util()

On Friday, August 19, 2016 03:26:21 PM Krzysztof Kozlowski wrote:
> On Fri, Aug 12, 2016 at 2:04 AM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > It is useful to know the reason why cpufreq_update_util() has just
> > been called and that can be passed as flags to cpufreq_update_util()
> > and to the ->func() callback in struct update_util_data.  However,
> > doing that in addition to passing the util and max arguments they
> > already take would be clumsy, so avoid it.
> >
> > Instead, use the observation that the schedutil governor is part
> > of the scheduler proper, so it can access scheduler data directly.
> > This allows the util and max arguments of cpufreq_update_util()
> > and the ->func() callback in struct update_util_data to be replaced
> > with a flags one, but schedutil has to be modified to follow.
> >
> > Thus make the schedutil governor obtain the CFS utilization
> > information from the scheduler and use the "RT" and "DL" flags
> > instead of the special utilization value of ULONG_MAX to track
> > updates from the RT and DL sched classes.  Make it non-modular
> > too to avoid having to export scheduler variables to modules at
> > large.
> >
> > Next, update all of the other users of cpufreq_update_util()
> > and the ->func() callback in struct update_util_data accordingly.
> >
> > Suggested-by: Peter Zijlstra <peterz@...radead.org>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >
> > v1 -> v2: Do not check cpu_of(rq) against smp_processor_id() in
> >           cfs_rq_util_change().
> >
> > ---
> >  drivers/cpufreq/Kconfig            |    5 --
> >  drivers/cpufreq/cpufreq_governor.c |    2 -
> >  drivers/cpufreq/intel_pstate.c     |    2 -
> >  include/linux/sched.h              |   12 ++++--
> >  kernel/sched/cpufreq.c             |    2 -
> >  kernel/sched/cpufreq_schedutil.c   |   67 ++++++++++++++++++++-----------------
> >  kernel/sched/deadline.c            |    4 +-
> >  kernel/sched/fair.c                |   10 +----
> >  kernel/sched/rt.c                  |    4 +-
> >  kernel/sched/sched.h               |   31 +++++------------
> >  10 files changed, 66 insertions(+), 73 deletions(-)
> 
> (...)
> 
> > --- linux-pm.orig/drivers/cpufreq/Kconfig
> > +++ linux-pm/drivers/cpufreq/Kconfig
> > @@ -194,7 +194,7 @@ config CPU_FREQ_GOV_CONSERVATIVE
> >           If in doubt, say N.
> >
> >  config CPU_FREQ_GOV_SCHEDUTIL
> > -       tristate "'schedutil' cpufreq policy governor"
> > +       bool "'schedutil' cpufreq policy governor"
> 
> If you change such symbols please remember to update also all the
> defconfigs. Without the update they start to show errors.

Are there defconfigs that use this particular one?

Thanks,
Rafael