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

From: Johannes Weiner <hannes@cmpxchg.org>
To: Peter Zijlstra <peterz@infradead.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: Wed, 18 Jul 2018 18:11:39 -0400	[thread overview]
Message-ID: <20180718221139.GF2838@cmpxchg.org> (raw)
In-Reply-To: <20180717151705.GH2494@hirez.programming.kicks-ass.net>

On Tue, Jul 17, 2018 at 05:17:05PM +0200, Peter Zijlstra wrote:
> On Thu, Jul 12, 2018 at 01:29:40PM -0400, Johannes Weiner wrote:
> > @@ -457,6 +457,22 @@ config TASK_IO_ACCOUNTING
> >  
> >  	  Say N if unsure.
> >  
> > +config PSI
> > +	bool "Pressure stall information tracking"
> > +	select SCHED_INFO
> 
> What's the deal here? AFAICT it does not in fact use SCHED_INFO for
> _anything_. You just hooked into the sched_info_{en,de}queue() hooks,
> but you don't use any of the sched_info data.
> 
> So the dependency is an artificial one that should not exist.

You're right, it doesn't strictly depend on it. I'll split that out.