linux-kernel - Re: [PATCH] sched/isolation: delete redundant housekeeping

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Message-ID: <20211124091316.5259d22f@gandalf.local.home>
Date:   Wed, 24 Nov 2021 09:13:16 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Aili Yao <yaoaili126@...il.com>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        bsegall@...gle.com, mgorman@...e.de, linux-kernel@...r.kernel.org,
        yaoaili@...gsoft.com
Subject: Re: [PATCH] sched/isolation: delete redundant
 housekeeping_overridden check

On Wed, 24 Nov 2021 15:42:14 +0800
Aili Yao <yaoaili126@...il.com> wrote:

> Signed-off-by: Aili Yao <yaoaili@...gsoft.com>
> ---
>  include/linux/sched/isolation.h | 9 ++-------
>  kernel/sched/isolation.c        | 4 ++--
>  2 files changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
> index cc9f393e2a70..3ccc19e52186 100644
> --- a/include/linux/sched/isolation.h
> +++ b/include/linux/sched/isolation.h
> @@ -23,9 +23,8 @@ extern int housekeeping_any_cpu(enum hk_flags flags);
>  extern const struct cpumask *housekeeping_cpumask(enum hk_flags flags);
>  extern bool housekeeping_enabled(enum hk_flags flags);
>  extern void housekeeping_affine(struct task_struct *t, enum hk_flags flags);
> -extern bool housekeeping_test_cpu(int cpu, enum hk_flags flags);
> +extern bool housekeeping_cpu(int cpu, enum hk_flags flags);

Now you added an unneeded function call (which is also expensive).

There's a reason the static_branch was inlined.

-- Steve

>  extern void __init housekeeping_init(void);
> -
>  #else
>  
>  static inline int housekeeping_any_cpu(enum hk_flags flags)
> @@ -46,15 +45,11 @@ static inline bool housekeeping_enabled(enum hk_flags flags)
>  static inline void housekeeping_affine(struct task_struct *t,
>  				       enum hk_flags flags) { }
>  static inline void housekeeping_init(void) { }
> -#endif /* CONFIG_CPU_ISOLATION */
>  
>  static inline bool housekeeping_cpu(int cpu, enum hk_flags flags)
>  {
> -#ifdef CONFIG_CPU_ISOLATION
> -	if (static_branch_unlikely(&housekeeping_overridden))
> -		return housekeeping_test_cpu(cpu, flags);
> -#endif
>  	return true;
>  }
> +#endif /* CONFIG_CPU_ISOLATION */
>  
>  #endif /* _LINUX_SCHED_ISOLATION_H */
> diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
> index 7f06eaf12818..b5e81df4b04a 100644
> --- a/kernel/sched/isolation.c
> +++ b/kernel/sched/isolation.c
> @@ -54,14 +54,14 @@ void housekeeping_affine(struct task_struct *t, enum hk_flags flags)
>  }
>  EXPORT_SYMBOL_GPL(housekeeping_affine);
>  
> -bool housekeeping_test_cpu(int cpu, enum hk_flags flags)
> +bool housekeeping_cpu(int cpu, enum hk_flags flags)
>  {
>  	if (static_branch_unlikely(&housekeeping_overridden))
>  		if (housekeeping_flags & flags)
>  			return cpumask_test_cpu(cpu, housekeeping_mask);
>  	return true;
>  }
> -EXPORT_SYMBOL_GPL(housekeeping_test_cpu);
> +EXPORT_SYMBOL_GPL(housekeeping_cpu);