Benchmarking with --enable-atomic-refcount

[Rik]

1/10/14

John,

I get a different, and slower performing, result with atomic reference
counting.

I built the dev branch with simple flags (-O2) and with/without
--enable-atomic-refcount.  I disabled frequency scaling in the processor so
each test was running at a fixed frequency and the comparison would be
fair.  I also ran each test 3 times to see if there was any variability
(not much).  Using 'time make check' as the actual benchmark I got the
following:

Without atomic-refcount
276.757u 33.510s 5:31.48 93.5%  0+0k 123608+21184io 567pf+0w
275.973u 33.010s 5:21.02 96.2%  0+0k 280+21056io 0pf+0w
276.189u 32.442s 5:20.39 96.3%  0+0k 0+21040io 0pf+0w

Mean of User+System: 309.29

With atomic-refcount
313.647u 34.046s 6:00.00 96.5%  0+0k 0+21104io 0pf+0w
314.567u 33.998s 6:00.85 96.5%  0+0k 0+21072io 0pf+0w
311.943u 32.382s 5:55.87 96.7%  0+0k 152+21080io 0pf+0w

Mean of User+System: 346.86

% change: +12.1%

Since we have conflicting results maybe somebody else needs to run the
tests as well.  I ran 'make clean' in between re-configuring Octave.  It
shouldn't be necessary, but you never know what kind of cruft accumulates.

--Rik