Re: [regression] cross core scheduling frequency drop bisected to 0c313cb20732

Mike Galbraith
2016-04-10T14:54:08Z

On Sun, 2016-04-10 at 11:35 +0200, Mike Galbraith wrote:
> On Sun, 2016-04-10 at 05:44 +0200, Rafael J. Wysocki wrote:
> > On Sat, Apr 9, 2016 at 6:39 PM, Mike Galbraith <
> > umgwanakikbuti@gmail.com> wrote:
> > >
> > > Hm, setting gov=performance, and taking the average of 3 30 second
> > > interval PkgWatt samples as pipe-test runs..
> > >
> > > 714KHz/28.03Ws = 25.46
> > > 877KHz/30.28Ws = 28.96
> > >
> > > ..for pipe-test, the tradeoff look a bit more like red than green.
> >
> > Well, fair enough, but that's just pipe-test, and what about the
> > people who don't see the performance gain and see the energy loss,
> > like Doug?
>
> Perhaps Doug sees increased power because he's not throttling no_hz,
> whereas I am, so he burns more power getting _to_ idle? Dunno, maybe
> he'll try the attached. If it's a general case energy loser, so be it,
> numbers talk, bs walks and all that ;-)

And here are the rest of my numbers..

> tbench 1 2 4 8
> base 752 1283 2250 3362
>
> select_idle_sibling() off
> 735 1344 2080 2884
> delta .977 1.047 .924 .857
>
> select_idle_sibling() on, 0c313cb20732 reverted
> 816 1317 2240 3388
> delta 1.085 1.026 .995 1.007 vs base
> delta 1.110 .979 1.076 1.174 vs off
> (^hm)

tbench 2 turboboost off
base 1215 1.00 1215/32.24=37.68
revert 1252 1.03 1252/35.82=34.95=loser

tbench 2 throughput hm is apparently a turboboost oddity, and..

tbench (turboboost back on)
power 1 2 4 8
base 23.88 37.41 54.64 62.25
revert 31.25 42.53 55.11 62.66

MB/s/Ws 1 2 4 8
base 31.49 34.29 41.17 54.00
revert 26.11 30.96 40.64 54.06

..while single pipe-test pair said green/green, tbench numbers say
throughput green, but energy efficiency red across the board.

-Mike