From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Linux PM <linux-pm@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Thomas Ilsche <thomas.ilsche@tu-dresden.de>,
Doug Smythies <dsmythies@telus.net>,
Rik van Riel <riel@surriel.com>,
Aubrey Li <aubrey.li@linux.intel.com>,
Mike Galbraith <mgalbraith@suse.de>,
LKML <linux-kernel@vger.kernel.org>,
Len Brown <len.brown@intel.com>
Subject: Re: [PATCH v9 00/10] sched/cpuidle: Idle loop rework
Date: Sun, 08 Apr 2018 18:32:45 +0200 [thread overview]
Message-ID: <1607755.Sz6cLBVOsW@aspire.rjw.lan> (raw)
In-Reply-To: <1736751.LdhZHb50jq@aspire.rjw.lan>
On Wednesday, April 4, 2018 10:32:12 AM CEST Rafael J. Wysocki wrote:
> Hi All,
>
> Thanks a lot for the feedback so far!
>
> For the motivation/summary, please refer to the BZ entry at
>
> https://bugzilla.kernel.org/show_bug.cgi?id=199227
>
> created for collecting information related to this patch series. Some v7.3
> testing results from Len and Doug are in there already.
>
> The testing so far shows significant idle power improvements, both in terms of
> reducing the average idle power (about 10% on some systems) and in terms of
> reducing the idle power noise (in the vast majority of cases, with this series
> applied the idle power is mostly stable around the power floor of the system).
> The average power is also reduced in some non-idle workloads and there are
> some performance improvements in them.
>
> It also is reported that the series generally addresses the problem it has been
> motivated by (ie. the "powernightmares" issue).
>
> This revision is mostly a re-send of the v8 with three patches changed as
> follows.
>
> > Patch 1 prepares the tick-sched code for the subsequent modifications and it
> > doesn't change the code's functionality (at least not intentionally).
> >
> > Patch 2 starts pushing the tick stopping decision deeper into the idle
> > loop, but that is limited to do_idle() and tick_nohz_irq_exit().
> >
> > Patch 3 makes cpuidle_idle_call() decide whether or not to stop the tick
> > and sets the stage for the subsequent changes.
> >
> > Patch 4 is a new one just for the TICK_USEC definition changes.
> >
> > Patch 5 adds a bool pointer argument to cpuidle_select() and the ->select
> > governor callback allowing them to return a "nohz" hint on whether or not to
> > stop the tick to the caller. It also adds code to decide what value to
> > return as "nohz" to the menu governor and modifies its correction factor
> > computations to take running tick into account if need be.
> >
> > Patch 6 (which is new) contains some changes that previously were included
> > into the big reordering patch (patch [6/8] in the v7). Essentially, it does
> > more tick-sched code reorganization in preparation for the subsequent changes
> > (and should not modify the functionality).
>
> Patch 7 is a new version of its v8 counterpart. It makes fewer changes to the
> existing code and adds a special function for the handling of the use case it
> is about. It still makes some hrtimer code modifications allowing it to return
> the time to the next event with one timer excluded (which needs to be done with
> respect to the tick timer), though.
>
> Patch 8 reorders the idle state selection with respect to the stopping of
> the tick and causes the additional "nohz" hint from cpuidle_select() to be
> used for deciding whether or not to stop the tick. It is a rebased version
> of its v8 counterpart.
>
> Patch 9 causes the menu governor to refine the state selection in case the
> tick is not going to be stopped and the already selected state does not fit
> the interval before the next tick time. It is a new version that avoids
> using state 0 if it has been disabled (if state 0 has been disabled, the
> governor only should use it when no states are enabled at all).
>
> > Patch 10 Deals with the situation in which the tick was stopped previously,
> > but the idle governor still predicts short idle (it has not changed).
>
> This series is complementary to the poll_idle() patches discussed recently
>
> https://patchwork.kernel.org/patch/10282237/
> https://patchwork.kernel.org/patch/10311775/
>
> that have been merged for v4.17 already.
>
> There is a new git branch containing the current series at
>
> git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git \
> idle-loop-v9
The v9 along with some cleanups suggested by Frederic on top of it and with
ACKs from Peter (obtained on IRC) is now available from the pm-cpuidle branch
in the linux-pm.git tree.
It has been added to my linux-next branch, so it probably will be picked up by
linux-next tomorrow and I have a plan to push it for v4.17 in the second half
of the next week unless a major issue with it is found in the meantime.
Thanks,
Rafael
next prev parent reply other threads:[~2018-04-08 16:32 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-04 8:32 [PATCH v9 00/10] sched/cpuidle: Idle loop rework Rafael J. Wysocki
2018-04-04 8:33 ` [PATCH v9 01/10] time: tick-sched: Reorganize idle tick management code Rafael J. Wysocki
2018-04-04 8:34 ` [PATCH v9 02/10] sched: idle: Do not stop the tick upfront in the idle loop Rafael J. Wysocki
2018-04-04 8:36 ` [PATCH v9 03/10] sched: idle: Do not stop the tick before cpuidle_idle_call() Rafael J. Wysocki
2018-04-04 8:38 ` [PATCH v9 04/10] jiffies: Introduce USER_TICK_USEC and redefine TICK_USEC Rafael J. Wysocki
2018-04-06 1:09 ` Frederic Weisbecker
2018-04-06 7:20 ` Rafael J. Wysocki
2018-04-04 8:39 ` [PATCH v9 05/10] cpuidle: Return nohz hint from cpuidle_select() Rafael J. Wysocki
2018-04-06 2:44 ` Frederic Weisbecker
2018-04-06 7:24 ` Rafael J. Wysocki
2018-04-06 14:19 ` Frederic Weisbecker
2018-04-06 7:58 ` Peter Zijlstra
2018-04-06 14:23 ` Frederic Weisbecker
2018-04-06 8:11 ` Rafael J. Wysocki
2018-04-06 12:56 ` Rafael J. Wysocki
2018-04-06 15:28 ` Frederic Weisbecker
2018-04-06 14:28 ` Frederic Weisbecker
2018-04-04 8:41 ` [PATCH v9 06/10] time: tick-sched: Split tick_nohz_stop_sched_tick() Rafael J. Wysocki
2018-04-07 2:36 ` Frederic Weisbecker
2018-04-07 16:36 ` Rafael J. Wysocki
2018-04-04 8:45 ` [PATCH v9 07/10] time: hrtimer: Introduce hrtimer_next_event_without() Rafael J. Wysocki
2018-04-07 14:46 ` Frederic Weisbecker
2018-04-08 8:20 ` Rafael J. Wysocki
2018-04-08 17:58 ` Frederic Weisbecker
2018-04-04 8:47 ` [PATCH v9 08/10] sched: idle: Select idle state before stopping the tick Rafael J. Wysocki
2018-04-09 2:41 ` Frederic Weisbecker
2018-04-04 8:49 ` [PATCH v9 09/10] cpuidle: menu: Refine idle state selection for running tick Rafael J. Wysocki
2018-04-05 12:27 ` Peter Zijlstra
2018-04-05 13:51 ` Rafael J. Wysocki
2018-04-05 12:32 ` Peter Zijlstra
2018-04-05 13:52 ` Rafael J. Wysocki
2018-04-04 8:50 ` [PATCH v9 10/10] cpuidle: menu: Avoid selecting shallow states with stopped tick Rafael J. Wysocki
2018-04-05 12:47 ` Peter Zijlstra
2018-04-05 13:49 ` Rafael J. Wysocki
2018-04-05 14:11 ` Peter Zijlstra
2018-04-05 14:13 ` Peter Zijlstra
2018-04-05 14:29 ` Rafael J. Wysocki
2018-04-08 16:32 ` Rafael J. Wysocki [this message]
2018-04-09 15:58 ` [PATCH v9 00/10] sched/cpuidle: Idle loop rework Thomas Ilsche
2018-04-10 7:03 ` Rafael J. Wysocki
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