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SubjectRe: [PATCH] sched/fair: check for idle core
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On Wednesday, October 21, 2020 3:10:26 PM CEST Peter Zijlstra wrote:
> On Wed, Oct 21, 2020 at 02:19:50PM +0200, Peter Zijlstra wrote:
> > On Wed, Oct 21, 2020 at 01:56:55PM +0200, Julia Lawall wrote:
> > > Prior to 5.8, my machine was using intel_pstate and had few background
> > > tasks. Thus the problem wasn't visible in practice. Starting with 5.8
> > > the kernel decided that intel_cpufreq would be more appropriate, which
> > > introduced kworkers every 0.004 seconds on all cores.
> >
> > That still doesn't make any sense. Are you running the legacy on-demand
> > thing or something?
> >
> > Rafael, Srinivas, Viresh, how come it defaults to that?
>
> Does we want something like this?
>
> ---
> arch/x86/configs/i386_defconfig | 3 +--
> arch/x86/configs/x86_64_defconfig | 3 +--
> drivers/cpufreq/Kconfig | 7 +++++--
> 3 files changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/configs/i386_defconfig b/arch/x86/configs/i386_defconfig
> index 78210793d357..c343ad459737 100644
> --- a/arch/x86/configs/i386_defconfig
> +++ b/arch/x86/configs/i386_defconfig
> @@ -41,8 +41,7 @@ CONFIG_PM_DEBUG=y
> CONFIG_PM_TRACE_RTC=y
> CONFIG_ACPI_DOCK=y
> CONFIG_ACPI_BGRT=y
> -CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE=y
> -CONFIG_CPU_FREQ_GOV_ONDEMAND=y
> +CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL=y
> CONFIG_X86_ACPI_CPUFREQ=y
> CONFIG_EFI_VARS=y
> CONFIG_KPROBES=y
> diff --git a/arch/x86/configs/x86_64_defconfig b/arch/x86/configs/x86_64_defconfig
> index 9936528e1939..23e1ea85c1ec 100644
> --- a/arch/x86/configs/x86_64_defconfig
> +++ b/arch/x86/configs/x86_64_defconfig
> @@ -38,8 +38,7 @@ CONFIG_PM_DEBUG=y
> CONFIG_PM_TRACE_RTC=y
> CONFIG_ACPI_DOCK=y
> CONFIG_ACPI_BGRT=y
> -CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE=y
> -CONFIG_CPU_FREQ_GOV_ONDEMAND=y
> +CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL=y
> CONFIG_X86_ACPI_CPUFREQ=y
> CONFIG_IA32_EMULATION=y
> CONFIG_EFI_VARS=y
> diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
> index 2c7171e0b001..8dfca6e9b836 100644
> --- a/drivers/cpufreq/Kconfig
> +++ b/drivers/cpufreq/Kconfig
> @@ -37,8 +37,7 @@ config CPU_FREQ_STAT
> choice
> prompt "Default CPUFreq governor"
> default CPU_FREQ_DEFAULT_GOV_USERSPACE if ARM_SA1100_CPUFREQ || ARM_SA1110_CPUFREQ
> - default CPU_FREQ_DEFAULT_GOV_SCHEDUTIL if ARM64 || ARM
> - default CPU_FREQ_DEFAULT_GOV_SCHEDUTIL if X86_INTEL_PSTATE && SMP
> + default CPU_FREQ_DEFAULT_GOV_SCHEDUTIL if SMP
> default CPU_FREQ_DEFAULT_GOV_PERFORMANCE
> help
> This option sets which CPUFreq governor shall be loaded at
> @@ -71,6 +70,7 @@ config CPU_FREQ_DEFAULT_GOV_USERSPACE
>
> config CPU_FREQ_DEFAULT_GOV_ONDEMAND
> bool "ondemand"
> + depends on !SMP
> select CPU_FREQ_GOV_ONDEMAND
> select CPU_FREQ_GOV_PERFORMANCE
> help
> @@ -83,6 +83,7 @@ config CPU_FREQ_DEFAULT_GOV_ONDEMAND
>
> config CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
> bool "conservative"
> + depends on !SMP
> select CPU_FREQ_GOV_CONSERVATIVE
> select CPU_FREQ_GOV_PERFORMANCE
> help

The changes above should work.

> @@ -144,6 +145,7 @@ config CPU_FREQ_GOV_USERSPACE
>
> config CPU_FREQ_GOV_ONDEMAND
> tristate "'ondemand' cpufreq policy governor"
> + depends on !SMP

But I don't think that we can do this and the one below.

> select CPU_FREQ_GOV_COMMON
> help
> 'ondemand' - This driver adds a dynamic cpufreq policy governor.
> @@ -163,6 +165,7 @@ config CPU_FREQ_GOV_ONDEMAND
> config CPU_FREQ_GOV_CONSERVATIVE
> tristate "'conservative' cpufreq governor"
> depends on CPU_FREQ
> + depends on !SMP
> select CPU_FREQ_GOV_COMMON
> help
> 'conservative' - this driver is rather similar to the 'ondemand'
>




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