RE: [RFC/RFT][PATCH 0/4] cpufreq / sched: iowait boost in intel_pstate and schedutil

On 2016.09.04 16:55 Rafael J. Wysocki wrote:

On Sunday, September 04, 2016 08:54:49 AM Doug Smythies wrote:

quoted

On 2016.09.02 17:57 Rafael J. Wysocki wrote:

quoted

This is a new version of the "iowait boost" series I posted a few weeks
ago.  Since the first two patches from that series have been reworked and
are in linux-next now, I've rebased this series on top of my linux-next
branch.

In addition to that I took the Doug's feedback into account in the
intel_pstate patches [2-3/4].

You got ahead of me a little.
Recall the suggestion for the addition of some filtering was based
on energy savings. And further that it might make sense to use
average pstate as input to the filter (your new patch 3 of 4).
In my testing (of the old patch set) I have been finding that some
of those energy savings are being given back by the average pstate
method, putting its value added into question.

Switching to the new patch set, I made two kernels (based on 4.8-rc4
+ your pre-requisite 2 patches):
rfc4: has all 4 patches.
rfc2: has patches 1, 2, 4. (does not have the average pstate change)

Using my SpecPower simulator test at 20% load I get:

Unpatched (reference): ~5905 Joules

19.68 watts

quoted

rfc4: ~ 6232 Joules (+5.5%)

20.77 watts

quoted

rfc2: ~ 6075 Joules (+2.9%)

20.25 watts

quoted

Old rfc, no filter (restated): ~7197 Joules (+21.9%)
Old rfc + old iir filter V2: ~5967 Joules (+1%)
Old rfc + old ave pstate method: ~6275 Joules (+6.3%)

The above numbers are all an average of 4 runs of 300 seconds each.
See further down for why I added normalized watts.

quoted

Srinivas was getting considerably different, but still
encouraging, numbers on the real SpecPower test beds.

I would like to suggest/ask that those real SpecPower tests be done
first so as to decide a preferred way forward. I'll also re-do my
simulator tests over a longer time period and at some other loads
(currently 20% is hard coded).

The reason I made patch [3/4] separate was to make it easier to test without
that change.  That is, apply [1-2/4] and see what difference it makes.

I'd like to see the results from that if poss.

O.K., that is what I was doing anyway.
I have some more data from my SpecPower simulator test:

Note: My calibration was out by quite a bit, so what I called 20%
was actually about 36.4%. While I knew it was out, I didn't know it
was that much, but I didn't care as it wasn't really relevant to
the compare type tests I was doing. I'll just use "X" in the table
below, where X ~= 18.2% on a real SpecPower.

Big numbers are Joules (package Joules from turbostat)
Smaller numbers are watts, 1500 Seconds test run time.

Load:		idle	0.5X	X	2X	3X	4X	5X	100%
Unpatched:	5757	11050	16048	29012	47575	61313	76634	81737
		3.84	7.37	10.70	19.34	31.72	40.88	51.09	54.49

rfc4:		5723	11323	17079	31561	47666	62625	76286	81664
		3.82	7.55	11.39	21.04	31.78	41.75	50.86	54.44
		-0.6%	2.5%	6.4%	8.8%	0.2%	2.1%	-0.5%	-0.1%

rfc2:		5769	11319	17140	30533	45158	61387	75690	81722
		3.85	7.55	11.43	20.36	30.11	40.92	50.46	54.48
		0.2%	2.4%	6.8%	5.2%	-5.1%	0.1%	-1.2%	0.0%

And again, 2nd run:

		idle	0.5X	X	2X	3X	4X	5X	100%
Unpatched:	5708	11037	16075	29147	45913	61165	76650	81695
		3.81	7.36	10.72	19.43	30.61	40.78	51.10	54.46

rfc4:		5770	11303	17023	31508	47653	62520	75798	81725
		3.85	7.54	11.35	21.01	31.77	41.68	50.53	54.48
		1.1%	2.4%	5.9%	8.1%	3.8%	2.2%	-1.1%	0.0%

rfc2:		5793	11242	17044	30258	45178	61526	75631	81669
		3.86	7.49	11.36	20.17	30.12	41.02	50.42	54.45
		1.5%	1.9%	6.0%	3.8%	-1.6%	0.6%	-1.3%	0.0%

Note: Comparing the 2X data to the further above numbers
from the other day shows more run to run variability than
I had expected. (I have very very few services running
on my test server, so background idle is really quite
idle.)

... Doug