linux-kernel - Re: [PATCH v9 05/10] cpuidle: Return nohz hint from cpuidle

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Message-ID: <20180406075837.GH4082@hirez.programming.kicks-ass.net>
Date:   Fri, 6 Apr 2018 09:58:37 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Thomas Ilsche <thomas.ilsche@...dresden.de>,
        Doug Smythies <dsmythies@...us.net>,
        Rik van Riel <riel@...riel.com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        Mike Galbraith <mgalbraith@...e.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Len Brown <len.brown@...el.com>
Subject: Re: [PATCH v9 05/10] cpuidle: Return nohz hint from cpuidle_select()

On Fri, Apr 06, 2018 at 04:44:14AM +0200, Frederic Weisbecker wrote:
> You can move that to tick_sched_do_timer() to avoid code duplication.

I expect the reason I didn't was that it didn't have @ts, but that's
easily fixable.

> Also these constants are very opaque. And even with proper symbols it wouldn't look
> right to extend ts->inidle that way.
> 
> Perhaps you should add a field such as ts->got_idle_tick under the boolean fields
> after the below patch:

> @@ -45,14 +45,17 @@ struct tick_sched {
>  	struct hrtimer			sched_timer;
>  	unsigned long			check_clocks;
>  	enum tick_nohz_mode		nohz_mode;
> +
> +	unsigned int			inidle		: 1;
> +	unsigned int			tick_stopped	: 1;
> +	unsigned int			idle_active	: 1;
> +	unsigned int			do_timer_last	: 1;

That would generate worse code, but yes, the C might be prettier.