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SubjectRe: [rfc][patch] sched: remove smpnice

* Andrew Morton <akpm@osdl.org> wrote:

> In that case I think we're better off fixing both problems rather than
> fixing neither.
>
> Suresh, Martin, Ingo, Nick and Con: please drop everything,
> triple-check and test this:

Peter's latest patch looks good to me, code-wise.

i also did some testing. Find below the test results of running 12 types
of benchmarks (running each benchmark at least 3 times), on 4 separate
kernels, on 3 separate boxes (altogether giving 12 separate bootups and
432 testresults).

the 4 kernels i used are:

v2.6.15: vanilla 2.6.15
-rc2: v2.6.16-rc2-git4
-rc2-nosmpnice: v2.6.16-rc2-git4 + Nick's nosmpnice patch
-rc2-smpnice2: v2.6.16-rc2-git4 + Peter's latest smpnice patch

[ Test method: the same set of 4 kernel images was used on each of the
boxes. The same .config was used to build all the kernel images:
SMP+SMT, no debugging and preempt-off. Each kernel instance did 3
tests of every test-row, and the table contains the fastest, "MIN"
result. (the precise method: there were at least 3 tests done, and
the test-scripts detected 3 consecutive test-results that are within a
given spread. I.e. outliers automatically cause a restart of that
test.) ]
here are the numbers (time units, smaller is better, percentage is
relative to the baseline v2.6.15 column):

2/4-way HT P4-Xeon box: (smaller is better)
======================
MIN v2.6.15 -rc2 -rc2-nosmpnice -rc2-smpnice2
---------------------------------------------------------------------------
ctx-2: 3.51 4.13 ( 17%) 4.68 ( 33%) 3.65 ( 3%)
ctx-20: 4.44 4.72 ( 6%) 4.41 ( 0%) 4.40 ( 0%)
ctx-200: 8.15 8.58 ( 5%) 8.54 ( 4%) 8.06 ( -1%)
mmap: 784.00 756.00 ( -3%) 768.00 ( -2%) 763.00 ( -2%)
select: 69.17 70.09 ( 1%) 69.04 ( 0%) 69.24 ( 0%)
proc-exec: 153.77 156.03 ( 1%) 158.14 ( 2%) 158.11 ( 2%)
proc-fork: 136.66 137.83 ( 0%) 138.78 ( 1%) 139.79 ( 2%)
syscall-open: 5.02 4.66 ( -7%) 4.82 ( -4%) 4.77 ( -4%)
hackbench-10: 0.77 0.82 ( 6%) 0.85 ( 10%) 0.79 ( 2%)
hackbench-20: 1.56 1.49 ( -4%) 1.38 (-11%) 1.42 ( -8%)
hackbench-50: 4.20 4.02 ( -4%) 3.57 (-15%) 3.48 (-17%)
volano: 18.53 20.07 ( 8%) 19.09 ( 3%) 19.33 ( 4%)
as can be seen, the -rc2 slowdown is gone on this box. -nosmpnice and
-smpnice2 are equivalent, within noise => good.

1/2-way dual-core Athlon64 box: (smaller is better)
==============================
MIN v2.6.15 -rc2 -rc2-nosmpnice -rc2-smpnice2
---------------------------------------------------------------------------
ctx-2: 1.10 1.22 ( 10%) 1.33 ( 20%) 1.23 ( 11%)
ctx-20: 1.36 1.38 ( 1%) 1.32 ( -2%) 1.34 ( -1%)
ctx-200: 2.99 3.36 ( 12%) 3.82 ( 27%) 3.70 ( 23%)
mmap: 371.00 336.00 ( -9%) 332.00 (-10%) 426.00 ( 14%)
select: 19.04 18.94 ( 0%) 18.13 ( -4%) 18.43 ( -3%)
proc-exec: 984.00 998.50 ( 1%) 1017.83 ( 3%) 1004.83 ( 2%)
proc-fork: 87.98 92.11 ( 4%) 90.56 ( 2%) 93.38 ( 6%)
syscall-open: 3.22 3.31 ( 2%) 3.48 ( 8%) 3.66 ( 13%)
hackbench-10: 0.61 0.63 ( 3%) 0.60 ( 0%) 0.60 ( -1%)
hackbench-20: 1.14 1.20 ( 5%) 1.17 ( 2%) 1.15 ( 0%)
hackbench-50: 2.72 2.88 ( 6%) 2.82 ( 3%) 2.78 ( 2%)
volano: 9.68 10.26 ( 6%) 10.15 ( 4%) 9.98 ( 3%)
here the fluctuation of the numbers is higher (caching artifacts on this
box prevent a less noisy measurement.) , but it can be seen that most of
the -rc2 slowdown is gone, and in fact -smpnice2 seems to be a small net
win over -nosmpnice => good.

1-way P4 box: (smaller is better)
============
MIN v2.6.15 -rc2 -rc2-nosmpnice -rc2-smpnice2
---------------------------------------------------------------------------
mmap: 889.00 859.00 ( -3%) 862.00 ( -3%) 855.00 ( -3%)
ctx-2: 2.26 2.27 ( 0%) 2.36 ( 4%) 2.25 ( 0%)
select: 78.98 79.13 ( 0%) 77.30 ( -2%) 79.09 ( 0%)
ctx-20: 2.57 2.65 ( 3%) 2.60 ( 1%) 2.60 ( 1%)
ctx-200: 7.58 7.66 ( 1%) 7.66 ( 1%) 7.50 ( -1%)
proc-exec: 173.28 172.28 ( 0%) 172.40 ( 0%) 172.28 ( 0%)
proc-fork: 155.38 153.38 ( -1%) 155.60 ( 0%) 153.33 ( -1%)
syscall-open: 5.30 5.32 ( 0%) 5.37 ( 1%) 5.32 ( 0%)
hackbench-10: 1.92 1.90 ( -1%) 1.89 ( -1%) 1.85 ( -4%)
hackbench-20: 3.88 3.64 ( -6%) 3.65 ( -6%) 3.61 ( -6%)
hackbench-50: 9.75 9.48 ( -2%) 9.28 ( -4%) 9.24 ( -5%)
volano: 28.18 28.99 ( 2%) 28.40 ( 0%) 27.63 ( -1%)
this confirms that smpnice has no effect on an UP box => good.

all in one, my conclusion is that Peter's patch fixes the smpnice
slowdown on a wide range of boxes:

Acked-by: Ingo Molnar <mingo@elte.hu>

Ingo
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