Messages in this thread | | | From | "Doug Smythies" <> | Subject | RE: [RFT][PATCH v7 5/8] cpuidle: Return nohz hint from cpuidle_select() | Date | Wed, 21 Mar 2018 23:24:44 -0700 |
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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. > > 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).
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).
http://fast.smythies.com/rjw_v72p_idle.png
... Doug
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