Benchmarks: AMD64 vs i386 on Dual 246 Opteron

[ray at redshift.com]

At 07:35 PM 7/28/2005 -0400, Martin Cracauer wrote:
| > While this sounded like a long shot, I loaded FreeBSD 5.4 i386 on the machine
| > and after applying the exact same configuration to the OS, Apache, PHP and
| > MySQL, re-ran the benchmarks.  Much to my surprise, just changing the OS
from 64
| > bit to 32 bit caused the machine to double in speed.  The results are attached
| > in an Excel spreadsheet.  So the exact same machine, running the identical
| > configuration, performed roughly twice as fast when running FreeBSD 5.4 i386 vs
| > FreeBSD 5.4 AMD64.  Something about this seems so wrong to me :-)
| 
| I'm sorry but I cannot support these findings.  I don't have
| cut'n'paste numbers handy, but generally 64 bits speed up things quite
| a bit for me.  I have seen slowdown in 64 bit mode in e.g. bzip2 but
| generally there is a speedup.

On the AMD64, I am pretty sure that I did *not* include the following lines like
I normally do on the i386:

options         SMP                     # Symmetric MultiProcessor Kernel
device          apic                    # I/O APIC

I seem to remember on one of the first AMD64 installs I did, the apic line
produced some sort of compiler error.  However, in looking over the AMD64 branch
on another machine (with 5.3 on it), I do see there is a SMP config file that
includes the GENERIC conf file and then tags on options SMP.  

So this may be a problem in my benchmarks and I will have to repeat the tests
when I have another Dual Opteron server down here.  For whatever reason, I was
under the impression the AMD64 kernel config file supported SMP by default, but
now I'm wondering.  

Ray