linux-kernel - Re: [PATCH 2/6] cpufreq: schedutil: ignore the sugov kthread for frequencies selections

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Message-ID: <20170306093541.0cb8d4d3@gandalf.local.home>
Date:   Mon, 6 Mar 2017 09:35:41 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        John Stultz <john.stultz@...aro.org>,
        Juri Lelli <juri.lelli@....com>, Todd Kjos <tkjos@...roid.com>,
        Tim Murray <timmurray@...gle.com>,
        Andres Oportus <andresoportus@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Chris Redpath <chris.redpath@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH 2/6] cpufreq: schedutil: ignore the sugov kthread for
 frequencies selections

On Thu,  2 Mar 2017 15:45:03 +0000
Patrick Bellasi <patrick.bellasi@....com> wrote:
 
> @@ -287,6 +289,10 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
>  		goto done;
>  	}
>  
> +	/* Skip updates generated by sugov kthreads */
> +	if (curr == sg_policy->thread)

I think you want to put in an "unlikely()" around that statement. I'm
assuming you don't care about he performance of scheduling in the sugov
thread. At least tell gcc to optimize for the false path.

-- Steve

> +		goto done;
> +
>  	sg_cpu->util = util;
>  	sg_cpu->max = max;
>  	sg_cpu->flags = flags;