linux-kernel - Re: [RFT][PATCH v4 1/7] time: tick-sched: Reorganize idle tick management code

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Message-ID: <22374739.VLR6IT0dbg@aspire.rjw.lan>
Date:   Thu, 15 Mar 2018 13:33:54 +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>,
        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>
Subject: Re: [RFT][PATCH v4 1/7] time: tick-sched: Reorganize idle tick management code

On Wednesday, March 14, 2018 4:49:39 PM CET Frederic Weisbecker wrote:
> On Mon, Mar 12, 2018 at 10:47:41AM +0100, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > 
> > Prepare the scheduler tick code for reworking the idle loop to
> > avoid stopping the tick in some cases.
> > 
> > Move away the tick_nohz_start_idle() invocation from
> > __tick_nohz_idle_enter(), rename the latter to
> > __tick_nohz_idle_stop_tick() and define tick_nohz_idle_stop_tick()
> > as a wrapper around it for calling it from the outside.
> > 
> > Make tick_nohz_idle_enter() only call tick_nohz_start_idle() instead
> > of calling the entire __tick_nohz_idle_enter(), add another wrapper
> > disabling and enabling interrupts around tick_nohz_idle_stop_tick()
> > and make the current callers of tick_nohz_idle_enter() call it too
> > to retain their current functionality.
> 
> Perhaps we should have a higher level description of what the patch does.
> After all the low level part is already described in the diff.
> 
> Ie: we are splitting the nohz idle entry call to decouple the idle time
> stats accounting and preparatory work from the actual tick stop code, that
> in order to later be able to delay the tick stop once we reach more
> power-knowledgeable callers.

OK