linux-kernel - Re: [PATCH v2 4/7] sched/fair: Introduce sched_smt_siblings

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Date:   Thu, 22 Dec 2022 16:56:22 +0000
From:   Valentin Schneider <vschneid@...hat.com>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Ricardo Neri <ricardo.neri@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Len Brown <len.brown@...el.com>, Mel Gorman <mgorman@...e.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        "Tim C . Chen" <tim.c.chen@...el.com>
Subject: Re: [PATCH v2 4/7] sched/fair: Introduce sched_smt_siblings_idle()

On 22/11/22 12:35, Ricardo Neri wrote:
> Architectures that implement arch_asym_cpu_priority() may need to know the
> idle state of the SMT siblings of a CPU. The scheduler has this information
> and functionality. Expose it.
>
> Move the existing functionality outside of the NUMA code.
>

test_idle_cores() does something similar without an iteration, did you
consider using that instead?

> Cc: Ben Segall <bsegall@...gle.com>
> Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
> Cc: Dietmar Eggemann <dietmar.eggemann@....com>
> Cc: Len Brown <len.brown@...el.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Cc: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Tim C. Chen <tim.c.chen@...el.com>
> Cc: Valentin Schneider <vschneid@...hat.com>
> Cc: x86@...nel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> ---
> Changes since v1:
>  * Introduced this patch.
> ---
>  include/linux/sched.h |  2 ++
>  kernel/sched/fair.c   | 39 ++++++++++++++++++++++-----------------
>  2 files changed, 24 insertions(+), 17 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index ffb6eb55cd13..0d01c64ac737 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -2426,4 +2426,6 @@ static inline void sched_core_fork(struct task_struct *p) { }
>  
>  extern void sched_set_stop_task(int cpu, struct task_struct *stop);
>  
> +extern bool sched_smt_siblings_idle(int cpu);
> +
>  #endif
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 0e4251f83807..9517c48df50e 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -1052,6 +1052,28 @@ update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
>   * Scheduling class queueing methods:
>   */
>  
> +static inline bool is_core_idle(int cpu)
> +{
> +#ifdef CONFIG_SCHED_SMT
> +	int sibling;
> +
> +	for_each_cpu(sibling, cpu_smt_mask(cpu)) {
> +		if (cpu == sibling)
> +			continue;
> +
> +		if (!idle_cpu(sibling))
> +			return false;
> +	}
> +#endif
> +
> +	return true;
> +}
> +
> +bool sched_smt_siblings_idle(int cpu)
> +{
> +	return is_core_idle(cpu);
> +}
> +
>  #ifdef CONFIG_NUMA
>  #define NUMA_IMBALANCE_MIN 2
>  
> @@ -1691,23 +1713,6 @@ struct numa_stats {
>  	int idle_cpu;
>  };
>  
> -static inline bool is_core_idle(int cpu)
> -{
> -#ifdef CONFIG_SCHED_SMT
> -	int sibling;
> -
> -	for_each_cpu(sibling, cpu_smt_mask(cpu)) {
> -		if (cpu == sibling)
> -			continue;
> -
> -		if (!idle_cpu(sibling))
> -			return false;
> -	}
> -#endif
> -
> -	return true;
> -}
> -
>  struct task_numa_env {
>  	struct task_struct *p;
>  
> -- 
> 2.25.1