linux-kernel - Re: [patch V3 19/22] timer: Forward wheel clock whenever possible

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Date:	Sat, 25 Jun 2016 10:55:38 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Richard Cochran <richardcochran@...il.com>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Chris Mason <clm@...com>,
	Arjan van de Ven <arjan@...radead.org>, rt@...utronix.de,
	Rik van Riel <riel@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	George Spelvin <linux@...encehorizons.net>,
	Len Brown <lenb@...nel.org>,
	Josh Triplett <josh@...htriplett.org>
Subject: Re: [patch V3 19/22] timer: Forward wheel clock whenever possible

On Fri, 24 Jun 2016, Richard Cochran wrote:

> On Fri, Jun 24, 2016 at 02:32:19PM -0000, Thomas Gleixner wrote:
> > @@ -809,6 +815,12 @@ static void tick_nohz_restart_sched_tick
> >  	tick_do_update_jiffies64(now);
> >  	cpu_load_update_nohz_stop();
> >  
> > +	/*
> > +	 * Clear the timer idle flag, so we avoid IPIs on remote queueing and
> > +	 * the clock forward checks in the enqueue path.
> > +	 */
> > +	timer_clear_idle();
> 
> Since function calls timer_clear_idle() already ...
>
> >  	calc_load_exit_idle();
> >  	touch_softlockup_watchdog_sched();
> >  	/*
> > @@ -1025,6 +1037,7 @@ void tick_nohz_idle_exit(void)
> >  		tick_nohz_stop_idle(ts, now);
> >  
> >  	if (ts->tick_stopped) {
> > +		timer_clear_idle();
> >  		tick_nohz_restart_sched_tick(ts, now);
> >  		tick_nohz_account_idle_ticks(ts);
> >  	}
> 
> ... there is no need to call timer_clear_idle() here.

Indeed.