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

From: Peter Zijlstra <peterz@infradead.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Ingo Molnar <mingo@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Tejun Heo <tj@kernel.org>, Suren Baghdasaryan <surenb@google.com>,
	Vinayak Menon <vinmenon@codeaurora.org>,
	Christopher Lameter <cl@linux.com>,
	Mike Galbraith <efault@gmx.de>,
	Shakeel Butt <shakeelb@google.com>,
	linux-mm@kvack.org, cgroups@vger.kernel.org,
	linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 08/10] psi: pressure stall information for CPU, memory, and IO
Date: Tue, 17 Jul 2018 16:21:57 +0200	[thread overview]
Message-ID: <20180717142157.GF2494@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20180712172942.10094-9-hannes@cmpxchg.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().