Re: [patch V2 09/28] x86/Kconfig: Select SCHED_SMT if SMP enabled

[Konrad Rzeszutek Wilk]

On Sun, Nov 25, 2018 at 07:33:37PM +0100, Thomas Gleixner wrote:
> CONFIG_SCHED_SMT is enabled by all distros, so there is not a real point to
> have it configurable. The runtime overhead in the core scheduler code is
> minimal because the actual SMT scheduling parts are conditional on a static
> key.
> 
> This allows to expose the scheduler's SMT state static key to the
> speculation control code. Alternatively the scheduler's static key could be
> made always available when CONFIG_SMP is enabled, but that's just adding an
> unused static key to every other architecture for nothing.
> 
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>


> 
> ---
>  arch/x86/Kconfig |    8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)
> 
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1001,13 +1001,7 @@ config NR_CPUS
>  	  to the kernel image.
>  
>  config SCHED_SMT
> -	bool "SMT (Hyperthreading) scheduler support"
> -	depends on SMP
> -	---help---
> -	  SMT scheduler support improves the CPU scheduler's decision making
> -	  when dealing with Intel Pentium 4 chips with HyperThreading at a
> -	  cost of slightly increased overhead in some places. If unsure say
> -	  N here.
> +	def_bool y if SMP
>  
>  config SCHED_MC
>  	def_bool y
> 
>