From: Kyle Schmitt <kyleaschmitt@...>
Date: 2008-02-22T23:10:46+09:00
Subject: Re: [OT] Re: [QUIZ #157] 32bit vs 64bit vs UML performance

OK, I didn't have a 32bit install on a 64 bit capable box that was
unused, so I compiled a 32bit and a 64bit ruby stable on one of the
larger boxes (2 dual core 3ghz opterons, 16gb of ram, aside from
forcing 64 and 32 bits, they had the same compilation flags) and let
it run through those benchmarks overnight.  Setting it was a good way
to spend 10 minutes.

The interesting part is that the 32bit build ran slightly faster than
the 64bit build, even though this is a 64 bit linux box.
The average time for a complete run of the benchmark differed by 30 seconds.
32 bit:130.19040000000000000000
64 bit:160.51990000000000000000

I'll be the first to admit this wasn't the best test, considering the
box wasn't in single user mode, but each run was niced to  -20, there
were several gigs of ram free even during the tests, and the system
load before the test started was under 0.3.

Now the question is, what does that actually _tell_ us?
Here are the options as far as I can see, but I'd be interested to
know what others there may be...
1) The load time for 64 bit ruby takes longer
2) The core ruby language needs some re-writes/tuning to work properly
for 64 bit.
3) or.. just a few portions of the ruby language need re-writes/tuning
to work properly for 64 bit.

--Kyle