linux-kernel - Re: v5.7: new core kernel option missing help text

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Message-ID: <CAKfTPtCPSk8wAyVeFDeywbUF6qQcjKw2OsvweW3MLLLdOdK+oQ@mail.gmail.com>
Date:   Fri, 5 Jun 2020 09:03:11 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Valentin Schneider <valentin.schneider@....com>
Cc:     Thara Gopinath <thara.gopinath@...aro.org>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: v5.7: new core kernel option missing help text

On Thu, 4 Jun 2020 at 17:38, Valentin Schneider
<valentin.schneider@....com> wrote:
>
>
> On 04/06/20 14:05, Thara Gopinath wrote:
> > On Thu, 4 Jun 2020 at 06:56, Valentin Schneider <valentin.schneider@....com>
> >>
> >> Right, s/defconfig/arch kconfig/ or somesuch.
> >>
> >
> >  CPU_FREQ_THERMAL also has to be enabled for this to be effective.
> > Since arm64 defconfig enables  CPU_FREQ_THERMAL  (by enabling CPU_THERMAL),
> > it should be ok to enable it in arm64/Kconfig. (same with arm/Kconfig)
> >
> > Another option is to select the  SCHED_THERMAL_PRESSURE when
> > CPU_FREQ_THERMAL
> > is enabled in drivers/thermal/Kconfig.
> >
>
> So interestingly while arch_set_thermal_pressure() (which just writes to a
> pcpu variable) is defined in sched/core.c, arch_scale_thermal_pressure()
> (which just returns aforementionned pcpu variable) is defined in
> arch_topology...
>
> I'm thinking at this point we might as well turn the
> arch_scale_thermal_pressure() stub into what arch_topology does. This would
> effectively let any architecture use thermal pressure, providing they use
> cpufreq cooling.
>
> If we want to keep changes contained to Kconfigs, for now I think the
> safest would be:
>
> ---
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 16fbf74030fe..1e92080dc275 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -46,6 +46,7 @@ config ARM
>         select EDAC_ATOMIC_SCRUB
>         select GENERIC_ALLOCATOR
>         select GENERIC_ARCH_TOPOLOGY if ARM_CPU_TOPOLOGY
> +       select SCHED_THERMAL_PRESSURE if GENERIC_ARCH_TOPOLOGY

I think that SCHED_THERMAL_PRESSURE depends on ARM_CPU_TOPOLOGY but
not on GENERIC_ARCH_TOPOLOGY.
ARM_CPU_TOPOLOGY is used to define arch_scale_thermal_pressure for arm
architecture
and we only use the header file of the generic arch_topology.h.
Function like arch_set_thermal_pressure() is in sched/core.c

>         select GENERIC_ATOMIC64 if CPU_V7M || CPU_V6 || !CPU_32v6K || !AEABI
>         select GENERIC_CLOCKEVENTS_BROADCAST if SMP
>         select GENERIC_CPU_AUTOPROBE
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 552d36cacc05..cc1944fbae51 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -98,6 +98,7 @@ config ARM64
>         select FRAME_POINTER
>         select GENERIC_ALLOCATOR
>         select GENERIC_ARCH_TOPOLOGY
> +       select SCHED_THERMAL_PRESSURE
>         select GENERIC_CLOCKEVENTS
>         select GENERIC_CLOCKEVENTS_BROADCAST
>         select GENERIC_CPU_AUTOPROBE
> diff --git a/init/Kconfig b/init/Kconfig
> index 74a5ac65644f..ba846f6e805b 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -439,8 +439,11 @@ config HAVE_SCHED_AVG_IRQ
>         depends on SMP
>
>  config SCHED_THERMAL_PRESSURE
> -       bool "Enable periodic averaging of thermal pressure"
> +       def_bool n
>         depends on SMP
> +       depends on CPU_FREQ_THERMAL
> +       help
> +         <helpful thing here>
>
>  config BSD_PROCESS_ACCT
>         bool "BSD Process Accounting"
> ---
>
>
>
> > Warm Regards
> > Thara