Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for systems and workloads

From: Peter Zijlstra <peterz@infradead.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Ingo Molnar <mingo@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Rik van Riel <riel@redhat.com>, Mel Gorman <mgorman@suse.de>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	kernel-team@fb.com
Subject: Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for systems and workloads
Date: Tue, 1 Aug 2017 09:57:28 +0200	[thread overview]
Message-ID: <20170801075728.GE6524@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20170731184142.GA30943@cmpxchg.org>

On Mon, Jul 31, 2017 at 02:41:42PM -0400, Johannes Weiner wrote:
> On Mon, Jul 31, 2017 at 10:31:11AM +0200, Peter Zijlstra wrote:

> > So could you start by describing what actual statistics we need? Because
> > as is the scheduler already does a gazillion stats and why can't re
> > repurpose some of those?
> 
> If that's possible, that would be great of course.
> 
> We want to be able to tell how many tasks in a domain (the system or a
> memory cgroup) are inside a memdelay section as opposed to how many

And you haven't even defined wth a memdelay section is yet..

> are in a "productive" state such as runnable or iowait. Then derive
> from that whether the domain as a whole is unproductive (all non-idle
> tasks memdelayed), or partially unproductive (some delayed, but CPUs
> are productive or there are iowait tasks). Then derive the percentages
> of walltime the domain spends partially or fully unproductive.
> 
> For that we need per-domain counters for
> 
> 	1) nr of tasks in memdelay sections
> 	2) nr of iowait or runnable/queued tasks that are NOT inside
> 	   memdelay sections

And I still have no clue..