Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH v9 00/10] sched/cpuidle: Idle loop rework | Date | Sun, 08 Apr 2018 18:32:45 +0200 |
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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
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