Re: [PATCH 08/10] psi: pressure stall information for CPU, memory, and IO

[Peter Zijlstra <peterz@infradead.org>]

On Thu, Jul 12, 2018 at 01:29:40PM -0400, Johannes Weiner wrote:
> diff --git a/include/linux/sched/stat.h b/include/linux/sched/stat.h
> index 04f1321d14c4..ac39435d1521 100644
> --- a/include/linux/sched/stat.h
> +++ b/include/linux/sched/stat.h
> @@ -28,10 +28,14 @@ static inline int sched_info_on(void)
>  	return 1;
>  #elif defined(CONFIG_TASK_DELAY_ACCT)
>  	extern int delayacct_on;
> +	if (delayacct_on)
> +		return 1;
> +#elif defined(CONFIG_PSI)
> +	extern int psi_disabled;
> +	if (!psi_disabled)
> +		return 1;
>  #endif
> +	return 0;
>  }

Doesn't that want to be something like:

static inline bool sched_info_on(void)
{
#ifdef CONFIG_SCHEDSTAT
	return true;
#else /* !SCHEDSTAT */
#ifdef CONFIG_TASK_DELAY_ACCT
	extern int delayacct_on;
	if (delayacct_on)
		return true;
#endif /* DELAYACCT */
#ifdef CONFIG_PSI
	extern int psi_disabled;
	if (!psi_disabled)
		return true;
#endif
	return false;
#endif /* !SCHEDSTATE */
}

Such that if you build a TASK_DELAY_ACCT && PSI kernel, and boot with
nodelayacct, you still get sched_info_on().