Re: [PATCH v2 00/13] sched/fair/schedutil: Better manage system response time

[Tom Gebhardt]

Hi Christian,

Thanks for trying to replicate -- and your result actually confirms the
picture: without Peter's ttwu series, Vincent's fix has no measurable
effect. That's consistent with what I see: the improvement from patch 12 /
Vincent's fix only shows up *on top of* the ttwu patches, not standalone.

So the interaction seems to be:

  ttwu patches alone        → −22% vs. 6.6 at OC
  ttwu + util_est fix       → −1.2% vs. 6.6 at OC  (large recovery)
  vanilla 7.0 (no ttwu)     → −26% vs. 6.6 at OC
  vanilla 7.0 + util_est    → no significant change  (your result)

This suggests the ttwu series changes something in the dequeue path that
exposes the util_est timing issue, and the fix only matters in that context.

I would be happy to push the exact tree so you can reproduce it directly.
However, I currently have a hardware issue with the Pi and cannot test or
prepare the tree right now. I'll push it to GitHub as soon as I'm back up
and let you know here.

Tom