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From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Qian Cai <cai@lca.pw>, Valentin Schneider <valentin.schneider@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	linux-pm@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Amit Daniel Kachhap <amit.kachhap@gmail.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Russell King <linux@armlinux.org.uk>,
	Thara Gopinath <thara.gopinath@linaro.org>,
	linux-kernel@vger.kernel.org, Sudeep Holla <sudeep.holla@arm.com>,
	Ingo Molnar <mingo@kernel.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 2/3] sched: Cleanup SCHED_THERMAL_PRESSURE kconfig entry
Date: Mon, 27 Jul 2020 19:45:49 +0200	[thread overview]
Message-ID: <16f8c1d4-778b-3ab8-f328-bae80f3973b4@arm.com> (raw)
In-Reply-To: <20200727141825.GA4174@lca.pw>

On 27/07/2020 16:18, Qian Cai wrote:
> On Sun, Jul 12, 2020 at 05:59:16PM +0100, Valentin Schneider wrote:
>> As Russell pointed out [1], this option is severely lacking in the
>> documentation department, and figuring out if one has the required
>> dependencies to benefit from turning it on is not straightforward.
>>
>> Make it non user-visible, and add a bit of help to it. While at it, make it
>> depend on CPU_FREQ_THERMAL.
>>
>> [1]: https://lkml.kernel.org/r/20200603173150.GB1551@shell.armlinux.org.uk
>>
>> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
>> ---
>>  init/Kconfig | 15 ++++++++++++++-
>>  1 file changed, 14 insertions(+), 1 deletion(-)
>>
>> diff --git a/init/Kconfig b/init/Kconfig
>> index 0498af567f70..0a97d85568b2 100644
>> --- a/init/Kconfig
>> +++ b/init/Kconfig
>> @@ -492,8 +492,21 @@ config HAVE_SCHED_AVG_IRQ
>>  	depends on SMP
>>  
>>  config SCHED_THERMAL_PRESSURE
>> -	bool "Enable periodic averaging of thermal pressure"
>> +	bool
>>  	depends on SMP
>> +	depends on CPU_FREQ_THERMAL
>> +	help
>> +	  Select this option to enable thermal pressure accounting in the
>> +	  scheduler. Thermal pressure is the value conveyed to the scheduler
>> +	  that reflects the reduction in CPU compute capacity resulted from
>> +	  thermal throttling. Thermal throttling occurs when the performance of
>> +	  a CPU is capped due to high operating temperatures.
>> +
>> +	  If selected, the scheduler will be able to balance tasks accordingly,
>> +	  i.e. put less load on throttled CPUs than on non/less throttled ones.
>> +
>> +	  This requires the architecture to implement
>> +	  arch_set_thermal_pressure() and arch_get_thermal_pressure().
>>  
>>  config BSD_PROCESS_ACCT
>>  	bool "BSD Process Accounting"
>> -- 
> 
> On arm64 linux-next (20200727),
> 
> https://gitlab.com/cailca/linux-mm/-/blob/master/arm64.config
> 
> WARNING: unmet direct dependencies detected for SCHED_THERMAL_PRESSURE
>   Depends on [n]: SMP [=y] && CPU_FREQ_THERMAL [=n]
>   Selected by [y]:
>   - ARM64 [=y]

Not sure, but:

(1) do we wan to let people enable SCHED_THERMAL_PRESSURE for arm64 so
arm64 can potentially run w/o a CPU freq cooling device?

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 2d4abbc9f8d0..baffe8b66da2 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -192,7 +192,6 @@ config ARM64
        select PCI_SYSCALL if PCI
        select POWER_RESET
        select POWER_SUPPLY
-       select SCHED_THERMAL_PRESSURE
        select SPARSE_IRQ
        select SWIOTLB
        select SYSCTL_EXCEPTION_TRACE
diff --git a/init/Kconfig b/init/Kconfig
index 37b089f87804..8b36e07fb230 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -492,7 +492,7 @@ config HAVE_SCHED_AVG_IRQ
        depends on SMP

 config SCHED_THERMAL_PRESSURE
-       bool
+       bool "Thermal pressure accounting"
        depends on SMP
        depends on CPU_FREQ_THERMAL
        help

Or

(2) should SCHED_THERMAL_PRESSURE for arm64 be enabled by default?

But then it makes no sense to allow the removal of CONFIG_CPU_FREQ_THERMAL.

linux-next/master$ make ARCH=arm64 defconfig

// Remove CONFIG_CPU_FREQ_THERMAL
linux-next/master$ grep CPU_FREQ_THERMAL .config
# CONFIG_CPU_FREQ_THERMAL is not set

linux-next/master$ make
scripts/kconfig/conf  --syncconfig Kconfig

WARNING: unmet direct dependencies detected for SCHED_THERMAL_PRESSURE
  Depends on [n]: SMP [=y] && CPU_FREQ_THERMAL [=n]
  Selected by [y]:
  - ARM64 [=y]

WARNING: unmet direct dependencies detected for SCHED_THERMAL_PRESSURE
  Depends on [n]: SMP [=y] && CPU_FREQ_THERMAL [=n]
  Selected by [y]:
  - ARM64 [=y]

WARNING: unmet direct dependencies detected for SCHED_THERMAL_PRESSURE
  Depends on [n]: SMP [=y] && CPU_FREQ_THERMAL [=n]
  Selected by [y]:
  - ARM64 [=y]
  HOSTCC  scripts/dtc/dtc.o

---

There is a similar issue with arm.

I would prefer for (1).

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  reply	other threads:[~2020-07-27 17:47 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-12 16:59 [PATCH v2 0/3] sched, arch_topology: Thermal pressure configuration cleanup Valentin Schneider
2020-07-12 16:59 ` [PATCH v2 1/3] arch_topology, sched/core: Cleanup thermal pressure definition Valentin Schneider
2020-07-13 14:32   ` Thara Gopinath
2020-07-12 16:59 ` [PATCH v2 2/3] sched: Cleanup SCHED_THERMAL_PRESSURE kconfig entry Valentin Schneider
2020-07-27 14:18   ` Qian Cai
2020-07-27 17:45     ` Dietmar Eggemann [this message]
2020-07-28 16:16       ` Valentin Schneider
2020-07-29  8:07         ` Dietmar Eggemann
2020-07-29 13:09         ` Quentin Perret
2020-07-29 13:29           ` Valentin Schneider
2020-07-12 16:59 ` [PATCH v2 3/3] arm, arm64: Select CONFIG_SCHED_THERMAL_PRESSURE Valentin Schneider
2020-07-13 10:03   ` Catalin Marinas
2020-07-13 10:29     ` Valentin Schneider
2020-07-13 10:37 ` [PATCH v2 0/3] sched, arch_topology: Thermal pressure configuration cleanup Peter Zijlstra
2020-07-13 12:03 ` Vincent Guittot

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