linux-kernel - Re: [PATCH v9 06/10] time: tick-sched: Split tick_nohz_stop_sched

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Message-ID: <20180407023623.GA16600@lerouge>
Date:   Sat, 7 Apr 2018 04:36:25 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.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 06/10] time: tick-sched: Split
 tick_nohz_stop_sched_tick()

On Wed, Apr 04, 2018 at 10:41:13AM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> In order to address the issue with short idle duration predictions
> by the idle governor after the scheduler tick has been stopped, split
> tick_nohz_stop_sched_tick() into two separate routines, one computing
> the time to the next timer event and the other simply stopping the
> tick when the time to the next timer event is known.
> 
> Prepare these two routines to be called separately, as one of them
> will be called by the idle governor in the cpuidle_select() code
> path after subsequent changes.
> 
> Update the former callers of tick_nohz_stop_sched_tick() to use
> the new routines, tick_nohz_next_event() and tick_nohz_stop_tick(),
> instead of it and move the updates of the sleep_length field in
> struct tick_sched into __tick_nohz_idle_stop_tick() as it doesn't
> need to be updated anywhere else.
> 
> There should be no intentional visible changes in functionality
> resulting from this change.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Reviewed-by: Frederic Weisbecker <frederic@...nel.org>

Thanks! And sorry for the slow reviews, the changes are sensitive
and I want to make sure we are not breaking some subtlety.