Which CPUTYPE for a dualcore Xeon on AMD64

[Martin Cracauer]

Martin Turgeon wrote on Sun, Jun 24, 2007 at 07:32:22PM -0400: 
> Hi,
> 
> I recently installed AMD64 6.2 Release on 2 PowerEdge servers, both with
> dual core Xeon (3070 and 5110). 

I extensively benchmarked different compiler options on Xeon 5160 (3.0
GHz Core2) with gcc-4.1.2 and gcc-4.2.

Apart from very minor differences the best was plain "-O3
-finline-limit=xxx" where xxx was different by code, some code ran
faster with 400 and other code with 750 (both beating the 600
default).  The inline limit made a bigger difference than most of the
other options and I actually ended up compiling parts of my code with
a differen inline-limit than others.

The result was within a percent of all highly tuned CPU-specific
options like -march=k8 -msse3 -mfpmath=sse -ffast-math, and I went
through most iterations.  This means that locking your code to one
x86_64 implementation and locking out either AMD or Intel is not worth
the trouble.

Testing was done on gcc-4.2.1 and later partially verified with
gcc-4.2.  Gcc-4.2 was a little slower overall but the same options
were about the same speed.

I also tested with Intel's icc 9.0 which didn't even come close to
either gcc, even if you were willing to wait 10 times as long for
compilation to finish (for inter-object file optimizations).  No
inlining limit would bring Intel's icc code size down to close what
gcc had and subsequently performance was bad.

gcc-3.4 was blown out of the water by gcc-4, too.

Martin
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Martin Cracauer <cracauer at cons.org>   http://www.cons.org/cracauer/
FreeBSD - where you want to go, today.      http://www.freebsd.org/