Only 70% of theoretical peak performance on FreeBSD 8/amd64, Corei7 920

[Maho NAKATA]

Hi FreeBSD developers,
[the original article in Japanese can be found at
http://blog.goo.ne.jp/nakatamaho/e/b5f6fbc3cc6e1ac4947463eb1ca4eb0a ] 

*Abstract*
I compared the peak performance of FreeBSD 8.0/amd64 and Ubuntu 9.10 amd64 using dgemm
(a linear algebra routine, matrix-matrix multiplication).
I obtained only 70% of theoretical peak performance on FreeBSD 8/amd64 and
almost 95% on Ubuntu 9.10 /amd64. I'm really disappointed.

*Introduction*
I'm a friend of Gotoh Kazushige, the principal developers of GotoBLAS. He told me that
FreeBSD is not suitable OS for scientific computing or high performance computing. He says
(in Japanese and my translation):

> I guess FreeBSD does page coloring, but I don't think FreeBSD considers very large cache
> size which recent CPU has. Support of a very large cache on Linux is still not very will
> sophisticated, but on *BSDs, its worst; they uses too fine memory allocation method, 
> so we cannot expect large continuous physical memory allocation. 
> Moreover, process scheduling is not so nice as *BSD employs an algorithm that
> changes physical CPUs in turn instead of allocating one core for such kind of jobs.
> Take your own benchmark, and you'll see..

*Result*
Machine: Core i7 920 (42.56-44.8Gflops) / DDR3 1066
OS: FreeBSD 8.0/amd64 and Ubuntu 9.10
GotoBLAS2: 1.13

dgemm result
OS      : FLOPS           : percent in peak
FreeBSD : 32.0 GFlops     : 71%
Ubuntu  : 42.0-42.7GFlops : 93.8%-95.3%

Thanks,
-- Nakata Maho http://accc.riken.jp/maho/ , http://ja.openoffice.org/ 
   Nakata Maho's PGP public keys: http://accc.riken.jp/maho/maho.pgp.txt