Re: [PATCH] sched: Add CONFIG_SCHED_CORE help text

[Hugh Dickins]

On Tue, 25 May 2021, Peter Zijlstra wrote:

> Subject: sched: Add CONFIG_SCHED_CORE help text
> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Date: Tue May 25 08:53:28 CEST 2021
> 
> Hugh noted that the SCHED_CORE Kconfig option could do with a help
> text.
> 
> Requested-by: Hugh Dickins <hughd@xxxxxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

Thanks,
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
if necessary (but there's more than enough of me there already).

> ---
>  kernel/Kconfig.preempt |   14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> --- a/kernel/Kconfig.preempt
> +++ b/kernel/Kconfig.preempt
> @@ -104,4 +104,18 @@ config SCHED_CORE
>  	bool "Core Scheduling for SMT"
>  	default y
>  	depends on SCHED_SMT
> +	help
> +	  This option permits Core Scheduling, a means of coordinated task
> +	  selection across SMT siblings. When enabled -- see
> +	  prctl(PR_SCHED_CORE) -- task selection ensures that all SMT siblings
> +	  will execute a task from the same 'core group', forcing idle when no
> +	  matching task is found.
> +
> +	  Use of this feature includes:
> +	   - mitigation of some (not all) SMT side channels;
> +	   - limiting SMT interference to improve determinism and/or performance.
> +
> +	  SCHED_CORE is default enabled when SCHED_SMT is enabled -- when
> +	  unused there should be no impact on performance.
> +