Benchmarks: AMD64 vs i386 on Dual 246 Opteron

[Erich Dollansky]

Hi,

ray at redshift.com wrote:

> 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

I do not wonder at all.

I did some software development for PA-RISC and SPARC machines. Naiv as 
I am, I started with the perfect 64 bit program which resulted in bad 
performance.

I then collected hints of how to mix 8, 16, 32 and 64 bit data to make 
the program much faster. The TCP/IP based application run then five 
times faster on the same machine compared to the plain 64 bit program.

64 bit programs copy to many unused information around.

It will be very difficult to tune a huge source base to maximum 
performance and keep it compatible between 32 and 64 bit.

The pointers mentioned by you are only a small part of the problem. The 
main problem is - at least in my program, and as far as what I saw in 
the sources here - the data handling.

Erich