RE: [RFC/RFT][PATCH v3 0/6] sched/cpuidle: Idle loop rework

[Doug Smythies]

On 2018.03.09 07:19 Rik van Riel wrote:
> On Fri, 2018-03-09 at 10:34 +0100, Rafael J. Wysocki wrote:
>> Hi All,
>> 
>> Thanks a lot for the discussion and testing so far!
>> 
>> This is a total respin of the whole series, so please look at it
>> afresh.
>> Patches 2 and 3 are the most similar to their previous versions, but
>> still they are different enough.
>
> This series gives no RCU errors on startup,
> and no CPUs seem to be getting stuck any more.

Confirmed on my test server. Boot is normal and no other errors, so far.

Part 1: Idle test:

I was able to repeat Mike's higher power issue under very light load,
well no load in my case, with V2.

V3 is much better.

A one hour trace on my very idle server was 22 times smaller with V3
than V2, and mainly due to idle state 4 not exiting and re-entering
every tick time for great periods of time.

Disclaimer: From past experience, 1 hour is not nearly long enough
for this test. Issues tend to come in bunches, sometimes many hours
apart.

V2:
Idle State 4: Entries: 1359560
CPU: 0: Entries: 125305
CPU: 1: Entries: 62489
CPU: 2: Entries: 10203
CPU: 3: Entries: 108107
CPU: 4: Entries: 19915
CPU: 5: Entries: 430253
CPU: 6: Entries: 564650
CPU: 7: Entries: 38638

V3:
Idle State 4: Entries: 64505
CPU: 0: Entries: 13060
CPU: 1: Entries: 5266
CPU: 2: Entries: 15744
CPU: 3: Entries: 5574
CPU: 4: Entries: 8425
CPU: 5: Entries: 6270
CPU: 6: Entries: 5592
CPU: 7: Entries: 4574

Kernel 4.16-rc4:
Idle State 4: Entries: 61390
CPU: 0: Entries: 9529
CPU: 1: Entries: 10556
CPU: 2: Entries: 5478
CPU: 3: Entries: 5991
CPU: 4: Entries: 3686
CPU: 5: Entries: 7610
CPU: 6: Entries: 11074
CPU: 7: Entries: 7466

With apologies to those that do not like the term "PowerNightmares",
it has become very ingrained in my tools:

V2:
1 hour idle Summary:

Idle State 0: Total Entries: 113 : PowerNightmares: 56 : Not PN time (seconds): 0.001224 : PN time: 65.543239 : Ratio: 53548.397792
Idle State 1: Total Entries: 1015 : PowerNightmares: 42 : Not PN time (seconds): 0.053986 : PN time: 21.054470 : Ratio: 389.998703
Idle State 2: Total Entries: 1382 : PowerNightmares: 17 : Not PN time (seconds): 0.728686 : PN time: 6.046906 : Ratio: 8.298370
Idle State 3: Total Entries: 113 : PowerNightmares: 13 : Not PN time (seconds): 0.069055 : PN time: 6.021458 : Ratio: 87.198002

V3:
1 hour idle Summary: Average processor package power 3.78 watts

Idle State 0: Total Entries: 134 : PowerNightmares: 109 : Not PN time (seconds): 0.000477 : PN time: 144.719723 : Ratio: 303395.646541
Idle State 1: Total Entries: 1104 : PowerNightmares: 84 : Not PN time (seconds): 0.052639 : PN time: 74.639142 : Ratio: 1417.943768
Idle State 2: Total Entries: 968 : PowerNightmares: 141 : Not PN time (seconds): 0.325953 : PN time: 128.235137 : Ratio: 393.416035
Idle State 3: Total Entries: 295 : PowerNightmares: 103 : Not PN time (seconds): 0.164884 : PN time: 97.159421 : Ratio: 589.259243

Kernel 4.16-rc4: Average processor package power (excluding a few minutes of abnormal power) 3.70 watts.
1 hour idle Summary:

Idle State 0: Total Entries: 168 : PowerNightmares: 59 : Not PN time (seconds): 0.001323 : PN time: 81.802197 : Ratio: 61830.836545
Idle State 1: Total Entries: 1669 : PowerNightmares: 78 : Not PN time (seconds): 0.022003 : PN time: 37.477413 : Ratio: 1703.286509
Idle State 2: Total Entries: 1447 : PowerNightmares: 30 : Not PN time (seconds): 0.502672 : PN time: 0.789344 : Ratio: 1.570296
Idle State 3: Total Entries: 176 : PowerNightmares: 0 : Not PN time (seconds): 0.259425 : PN time: 0.000000 : Ratio: 0.000000

Part 2: 100% load on one CPU test. Test duration 4 hours

V3: Summary: Average processor package power 26.75 watts

Idle State 0: Total Entries: 10039 : PowerNightmares: 7186 : Not PN time (seconds): 0.067477 : PN time: 6215.220295 : Ratio: 92108.722903
Idle State 1: Total Entries: 17268 : PowerNightmares: 195 : Not PN time (seconds): 0.213049 : PN time: 55.905323 : Ratio: 262.405939
Idle State 2: Total Entries: 5858 : PowerNightmares: 676 : Not PN time (seconds): 2.578006 : PN time: 167.282069 : Ratio: 64.888161
Idle State 3: Total Entries: 1500 : PowerNightmares: 488 : Not PN time (seconds): 0.772463 : PN time: 125.514015 : Ratio: 162.485472

Kernel 4.16-rc4: Summary: Average processor package power 27.41 watts

Idle State 0: Total Entries: 9096 : PowerNightmares: 6540 : Not PN time (seconds): 0.051532 : PN time: 7886.309553 : Ratio: 153037.133492
Idle State 1: Total Entries: 28731 : PowerNightmares: 215 : Not PN time (seconds): 0.211999 : PN time: 77.395467 : Ratio: 365.074679
Idle State 2: Total Entries: 4474 : PowerNightmares: 97 : Not PN time (seconds): 1.959059 : PN time: 0.874112 : Ratio: 0.446190
Idle State 3: Total Entries: 2319 : PowerNightmares: 0 : Not PN time (seconds): 1.663376 : PN time: 0.000000 : Ratio: 0.000000

Graph of package power verses time: http://fast.smythies.com/rjwv3_100.png

... Doug