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

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Date:   Sat, 07 Apr 2018 18:36:34 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Frederic Weisbecker <frederic@...nel.org>
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 Saturday, April 7, 2018 4:36:25 AM CEST Frederic Weisbecker wrote:
> 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

Right, very much so.

> and I want to make sure we are not breaking some subtlety.

Thanks a lot for doing that!