Re: scheduler vs hardware? (was Re: another i7 (linux) bug?)

Luca Zini
2010-01-22T11:22:36Z

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First of all sorry for misunderstanding with Alex Chiang, I was trying to
collect some data from other i7 mobile users to try to isolate the problem
before posting.

I tried different things: I disabled speedstep from the bios and the results
where more sensible (higher priority lower execution time). The same thing
happens if I disable throttling by software selecting "aggressive powersave"
settings.

So I suppose that is something related directly or indirectly to frequency
scaling or turbo boost (unfortunately I have no bios option to disable only
turbo boost)
Here are the results of the same test of Peter Zijlstra

time sudo nice -n 19 lame -b 256 -V0 -h youcantdothat.wav 2&> /dev/null

real 0m1.105s
user 0m1.090s
sys 0m0.010s

time sudo nice -n 0 lame -b 256 -V0 -h youcantdothat.wav 2&> /dev/null

real 0m1.108s
user 0m1.100s
sys 0m0.010s

time sudo nice -n -20 lame -b 256 -V0 -h youcantdothat.wav 2&> /dev/null

real 0m1.354s
user 0m1.330s
sys 0m0.000s

They are almost the same results that I obtained before.
Looking at top there are no other process that is using the cpu (main are
Xorg and kopete).

I tested this on 2.6.31-17-server (ubuntu 9.10) 2.6.31-17-generic (ubuntu
9.10) and the default kernel of fedora 12 (live cd).
As soon as possible I'll try 33-rc5 as requested by Mike Galbraith (now I
can't shut down the computer).

Ok, a last minute update!
I slightly modified i7z to save a log to disk. If i7z output are reliable I
suppose that it can show is the problem:
with nice set to 19 a processor 3 reach the maximum speed, with nice set to
-20 its maximum value is 300-400 mhz under the maximum value. (I attach the
two logs named as the nice level used obtained running lame on a bigger file)
Please note that logs may have some value read before and/or after the
start/end of the running process (lame).

The next update will be the results with 33-rc5 kernel.

Luca

[-- Attachment #2: log-20 --]
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Processor 0: 1062.13 (7.99x) 1 99.7 0 98.5
Processor 1: 1246.75 (9.37x) 1 99.8 0 99
Processor 2: 1113.41 (8.37x) 1 99.8 0 98.4
Processor 3: 1477.30 (11.11x) 4.67 95.7 0 85.7
Processor 0: 1109.70 (8.34x) 1 99.7 2.93 95.8
Processor 1: 2316.51 (17.42x) 5.5 92 0 91.7
Processor 2: 1114.96 (8.38x) 1 99.8 14.9 83.7
Processor 3: 1225.48 (9.21x) 9.95 92.4 1.33 67.6
Processor 0: 1877.15 (14.11x) 1 99.8 29.6 69.9
Processor 1: 1914.75 (14.40x) 1 99.2 1 98.1
Processor 2: 1955.22 (14.70x) 1 99.8 0 99.4
Processor 3: 2402.49 (18.06x) 38.8 41.6 0 0
Processor 0: 2114.28 (15.90x) 12 84.1 0 35.4
Processor 1: 1528.62 (11.49x) 1 99.8 25.4 73.2
Processor 2: 1582.10 (11.90x) 1 99.9 74.2 25.2
Processor 3: 2359.66 (17.74x) 14.6 78.3 18.6 56
Processor 0: 2242.78 (16.86x) 16.3 77.1 0 0
Processor 1: 1591.62 (11.97x) 1 99.9 87.9 10.9
Processor 2: 1885.84 (14.18x) 1 100 99.2 1
Processor 3: 2035.81 (15.31x) 1.77 97.7 15 75.4
Processor 0: 2280.59 (17.15x) 18.3 73.8 1 70.4
Processor 1: 1906.72 (14.34x) 1 99.7 26.9 72
Processor 2: 1778.56 (13.37x) 1 99.9 70.9 28.6
Processor 3: 1077.58 (8.10x) 8.56 94.2 3.66 4.79
Processor 0: 2009.19 (15.11x) 7.07 91.1 1 88.3
Processor 1: 1708.96 (12.85x) 1 99.8 37.3 61.5
Processor 2: 1673.01 (12.58x) 1 99.9 13.4 85.9
Processor 3: 1421.09 (10.68x) 12.1 89.2 1 21.8

[-- Attachment #3: log19 --]
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Processor 0: 935.30 (7.03x) 1 99.8 0 73.4
Processor 1: 938.46 (7.06x) 1 99.9 0 98.3
Processor 2: 932.33 (7.01x) 1 99.9 0 97.7
Processor 3: 1017.69 (7.65x) 6.09 96.1 0 92.1
Processor 0: 1040.73 (7.83x) 1 99.8 0 99.1
Processor 1: 1062.37 (7.99x) 1 99.7 0 96.1
Processor 2: 1047.94 (7.88x) 1 99.8 1 97.7
Processor 3: 1941.75 (14.60x) 11.1 86.5 2.98 81.5
Processor 0: 1940.64 (14.59x) 1 99.5 0 72.7
Processor 1: 1600.11 (12.03x) 1 99.8 11.5 86
Processor 2: 2141.58 (16.10x) 1 100 99.6 1
Processor 3: 2760.11 (20.75x) 83.2 0 4.33 11.6
Processor 0: 2331.59 (17.53x) 1 99.4 5.98 93
Processor 1: 2287.80 (17.20x) 1 99.8 0 97.6
Processor 2: 2122.39 (15.96x) 1 100 88.5 11.1
Processor 3: 2774.36 (20.86x) 99.9 0 0 0
Processor 0: 2322.64 (17.46x) 1 99.5 1 98.6
Processor 1: 2275.29 (17.11x) 1 99.8 1 97.9
Processor 2: 2268.43 (17.06x) 1 99.8 0 99.5
Processor 3: 2779.36 (20.90x) 99.9 0 0 0
Processor 0: 2277.58 (17.12x) 1 99.8 0 99.6
Processor 1: 2372.66 (17.84x) 1 99.5 0 99.2
Processor 2: 2346.90 (17.65x) 1 99.8 0 99.5
Processor 3: 2783.34 (20.93x) 99.9 0 0 0