Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [RFT][PATCH v7 5/8] cpuidle: Return nohz hint from cpuidle_select() | Date | Thu, 22 Mar 2018 18:21:28 +0100 |
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On Thursday, March 22, 2018 4:41:54 PM CET Doug Smythies wrote: > On 2018.03.21 23:25 Doug Smythies wrote: > > On 2018.03.21 15:15 Rafael J. Wysocki wrote: > >> On Wed, Mar 21, 2018 at 6:59 PM, Thomas Ilsche wrote: > >>> On 2018-03-21 15:36, Rafael J. Wysocki wrote: > >>>> > >>>> So please disregard this one entirely and take the v7.2 replacement > >>>> instead of it:https://patchwork.kernel.org/patch/10299429/ > >>>> > >>>> The current versions (including the above) is in the git branch at > >>>> > >>>> git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git \ > >>>> idle-loop-v7.2 > >>> > >>> With v7.2 (tested on SKL-SP from git) I see similar behavior in idle > >>> as with v5: several cores which just keep the sched tick enabled. > >>> Worse yet, some go only in C1 (not even C1E!?) despite sleeping the > >>> full sched tick. > >>> The resulting power consumption is ~105 W instead of ~ 70 W. > >>> > >>> https://wwwpub.zih.tu-dresden.de/~tilsche/powernightmares/v7_2_skl_sp_idle.png > >>> > >>> I have briefly ran v7 and I believe it was also affected. > > I am not seeing any issues at all with V7. > > >> > >> Then it looks like menu_select() stubbornly thinks that the idle > >> duration will be within the tick boundary on those cores. > >> > >> That may be because the bumping up of the correction factor in > >> menu_reflect() is too conservative or it may be necessary to do > >> something radical to measured_us in menu_update() in case of a tick > >> wakeup combined with a large next_timer_us value. > >> > >> For starters, please see if the attached patch (on top of the > >> idle-loop-v7.2 git branch) changes this behavior in any way. > > > > O.K. I am seeing some weirdness. > > On my system with both V7.2 and V7.2 plus this patch, I observe > > A spike in Idle State 1 residency every 34+ minutes. And slightly > > higher average idle power than before. > > (I might not have done V7 idle tests long enough). > > I re-did the idle test on V7, and for longer. > It is great. > See line added to the idle graph for V7.2+: > > http://fast.smythies.com/rjw_v72p_v7_idle.png > > > > > It can be seen in the frequency sweep I did earlier today, with V7.2: > > > > http://fast.smythies.com/rjw_freq_sweep_72_combined.png > > > > Despite the note on the graph that says it might be real, I don't think > > it is (I forgot to delete the note). > > > > With V7.2+ sometimes the event occurs at 17 minute intervals. > > Here is a idle graph (for reference: we have seen idle package power > > pretty steady at ~3.7 watts before). > > Now shown on the new graph. Link above.
Thanks for the data!
I will send another update of patch [5/8] shortly which is closer to the original v7 of it than the v7.[1-2].
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