linux-kernel - Re: [RFC/RFT][PATCH v2 2/6] sched: idle: Do not stop the tick upfront in the idle loop

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Message-ID: <2273590.04PyvAHADg@aspire.rjw.lan>
Date:   Thu, 08 Mar 2018 10:05:52 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Frederic Weisbecker <fweisbec@...il.com>,
        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>
Subject: Re: [RFC/RFT][PATCH v2 2/6] sched: idle: Do not stop the tick upfront in the idle loop

On Thursday, March 8, 2018 12:39:12 AM CET Frederic Weisbecker wrote:
> On Tue, Mar 06, 2018 at 10:02:15AM +0100, Rafael J. Wysocki wrote:
> > Index: linux-pm/kernel/sched/idle.c
> > ===================================================================
> > --- linux-pm.orig/kernel/sched/idle.c
> > +++ linux-pm/kernel/sched/idle.c
> > @@ -220,13 +220,17 @@ static void do_idle(void)
> >  	 */
> >  
> >  	__current_set_polling();
> > -	tick_nohz_idle_enter();
> > +	tick_nohz_idle_prepare();
> 
> Since we leave tick_nohz_idle_exit() unchanged, can we keep tick_nohz_idle_prepare()
> under the name tick_nohz_idle_enter() so that we stay symetric? And then make xen call
> the two functions:
> 
>     tick_nohz_idle_enter();
>     tick_nohz_idle_go_idle();

No problem with that.

> Also can we rename tick_nohz_idle_go_idle() to tick_nohz_idle_stop_tick() ?
> This will be more self-explanatory.

But it doesn't always stop the tick which is why I chose the other name.