linux-kernel - Re: [RFC PATCH 2/3] sched: Introduce Window-Assisted CPU utilization Tracking

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Message-ID: <20161028073804.GR3102@twins.programming.kicks-ass.net>
Date:   Fri, 28 Oct 2016 09:38:04 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vikram Mulukutla <markivx@...eaurora.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Srivatsa Vaddagiri <vatsa@...eaurora.org>,
        Steve Muckle <steve.muckle@...aro.org>,
        Olav Haugan <ohaugan@...eaurora.org>,
        Syed Rameez Mustafa <rameezmustafa@...eaurora.org>,
        Joonwoo Park <joonwoop@...eaurora.org>,
        Pavankumar Kondeti <pkondeti@...eaurora.org>,
        Saravana Kannan <skannan@...eaurora.org>,
        Bryan Huntsman <bryanh@...eaurora.org>,
        Juri Lelli <juri.lelli@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Chris Redpath <chris.redpath@....com>,
        Robin Randhawa <robin.randhawa@....com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Todd Kjos <tkjos@...gle.com>,
        Srinath Sridharan <srinathsr@...gle.com>,
        Andres Oportus <andresoportus@...gle.com>,
        Leo Yan <leo.yan@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Vikram Mulukutla <markivx@...eauorora.org>
Subject: Re: [RFC PATCH 2/3] sched: Introduce Window-Assisted CPU utilization
 Tracking

On Fri, Oct 28, 2016 at 12:10:41AM -0700, Vikram Mulukutla wrote:
> +static int cpu_is_waiting_on_io(struct rq *rq)
> +{
> +	if (!walt_io_is_busy)
> +		return 0;
> +
> +	return atomic_read(&rq->nr_iowait);
> +}

This is just drug induced nonsense. The per-cpu nr_iowait number is
completely without meaning.