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SubjectRe: [PATCH 1/1] sched/cputime: Mitigate performance regression in times()/clock_gettime()
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Hello Ingo,

thank you for your reply.

Ingo Molnar <mingo@kernel.org>
> Nice detective work! I'm wondering, where do we stand if compared with a
> pre-6e998916dfe3 kernel?

The data follows. A considerable part of the performance loss is recovered;
something is still on the table.

"3.18-pre-bug" is the parent of 6e998916dfe3, i.e. 6e998916dfe3^1
"3.18-bug" is the revision 6e998916dfe3 itself.
Figures are in seconds. Percentages refer to 3.18-pre-bug, negative = worse.


times()

threads 3.18-pre-bug 3.18-bug 4.7.0-rc7 4.7.0-rc7-patched

2 2.27 ( 0.00%) 3.73 (-64.71%) 3.65 (-61.14%) 3.06 (-35.16%)
5 2.78 ( 0.00%) 3.77 (-35.56%) 3.45 (-23.98%) 3.25 (-16.79%)
8 2.79 ( 0.00%) 4.41 (-57.71%) 3.52 (-26.05%) 3.26 (-16.53%)
12 3.02 ( 0.00%) 3.56 (-17.94%) 3.29 ( -9.08%) 3.37 (-11.74%)
21 3.10 ( 0.00%) 4.61 (-48.74%) 4.07 (-31.34%) 3.90 (-25.89%)
30 3.33 ( 0.00%) 5.75 (-72.53%) 3.87 (-16.01%) 3.36 ( -0.81%)
48 2.96 ( 0.00%) 6.06 (-105.04%) 3.79 (-28.10%) 3.11 ( -5.14%)
79 2.88 ( 0.00%) 6.24 (-116.83%) 3.88 (-34.81%) 3.16 ( -9.84%)
110 2.98 ( 0.00%) 6.37 (-114.08%) 3.90 (-31.12%) 3.25 ( -9.07%)
128 3.10 ( 0.00%) 6.35 (-104.61%) 4.00 (-28.87%) 3.31 ( -6.57%)


clock_gettime()

threads 3.18-pre-bug 3.18-bug 4.7.0-rc7 4.7.0-rc7-patched

2 2.23 ( 0.00%) 3.68 (-64.56%) 3.48 (-55.48%) 3.25 (-45.41%)
5 2.83 ( 0.00%) 3.78 (-33.42%) 3.33 (-17.43%) 3.17 (-12.03%)
8 2.84 ( 0.00%) 4.31 (-52.12%) 3.37 (-18.76%) 3.22 (-13.43%)
12 3.09 ( 0.00%) 3.61 (-16.74%) 3.32 ( -7.17%) 3.36 ( -8.47%)
21 3.14 ( 0.00%) 4.63 (-47.36%) 4.01 (-27.71%) 3.92 (-24.68%)
30 3.28 ( 0.00%) 5.75 (-75.37%) 3.63 (-10.80%) 3.40 ( -3.69%)
48 3.02 ( 0.00%) 6.05 (-100.56%) 3.71 (-22.99%) 3.16 ( -4.64%)
79 2.88 ( 0.00%) 6.30 (-118.90%) 3.75 (-30.26%) 3.28 (-13.93%)
110 2.95 ( 0.00%) 6.46 (-119.00%) 3.81 (-29.24%) 3.38 (-14.69%)
128 3.05 ( 0.00%) 6.42 (-110.08%) 3.88 (-27.04%) 3.38 (-10.70%)


Regards,
Giovanni Gherdovich

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