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

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Message-ID: <20160624204519.GA13368@netboy>
Date:	Fri, 24 Jun 2016 22:45:20 +0200
From:	Richard Cochran <richardcochran@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
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, 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.

Thanks,
Richard