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

Adrian Chadd adrian at freebsd.org
Mon Apr 12 10:00:50 UTC 2010


Of course, what would be helpful is actually figuring out what is
going on rather than some conjecture. :)

With what he said, tweaking memory allocation under FreeBSD and/or
linux would change the performance characteristics and either validate
or disprove his assumptions?


Adrian

On 12 April 2010 12:12, Maho NAKATA <chat95 at mac.com> wrote:
> 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
>
>
>
>
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