On 2018.03.21 15:15 Rafael J. Wysocki wrote:

On Wed, Mar 21, 2018 at 6:59 PM, Thomas Ilsche wrote:

quoted

On 2018-03-21 15:36, Rafael J. Wysocki wrote:

quoted

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