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

[Peter Zijlstra]

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().