amd64 optimized gcc?

[Kövesdán Gábor]

Hello,

As for the optimization, I'm very interested how fast can be an actual 
optimized system. The stock release doesn't optimizes too much, afaik it 
uses -O. I have been experimenting for a while with building the whole 
system with my custom cflags, and yesterday I succeeded. I managed to 
build the whole system with

CFLAGS=-s -Os -march=athlon64
COPTFLAGS=-s -Os -march=athlon64

I might have used -O2 instead of -Os but not -O3 which made a 
compilation error.
The -s is for srtipping the binaries and libs, because this is intended 
to be used on a production system, where we use stable software 
releases, thus we don't need debug symbols
And I ripped out the softwares I don't need with macros. (named, 
sendmail, games, ...) Unfortunately I don't have a machine for testing 
purposes but I would ty it. If I provide You such a disc would You try 
it in the same way? I'm not sure it is a working a disc, but it should 
be. I haven't read that anybody made such discs.

Cheers,

Gábor Kövesdán

Nicolas Blais wrote:

>I am developping a software that follows a random()-dependant algorithm which 
>is extremely cpu intensif. 
>I decided to run on different platforms to see how it performed based on cpu 
>and os (in a way of benchmarking) and I'm surprised by the numbers:
>
>Reference times for benchmark (5e+07 run of the algorithm):
>
>(FreeBSD/i386)  Venice (S939, 512K L2 cache) Athlon64 3000 overclocked @ 2655 
>Mhz : 78.3072 s (638511 r/s)
>                Note: Cool 'n' Quiet! Disabled in BIOS.
>		Note: 1 G RAM
>
>(FreeBSD/amd64)  Venice (S939, 512K L2 cache) Athlon64 3000 overclocked @ 2655 
>Mhz : 71.2521 s (701732 r/s)
>                Note: Cool 'n' Quiet! Disabled in BIOS.
>		Note: 1 G RAM
>
>(Knoppix/i386)  Clawhammer (S747, 1MB L2 cache) Athlon64 3200 @ 2000 Mhz : 
>133.858 s (373325 r/s)
>                Note: Compaq R3240CA Laptop, Cool 'n' Quiet! forced by BIOS.
>		Note: 512 M RAM
>
>(FreeBSD/amd64) Clawhammer (S747, 1MB L2 cache) Athlon64 3200 @ 2000 Mhz : 
>47.2754 s (1057630 r/s)
>                Note: Compaq R3240CA Laptop, Cool 'n' Quiet! forced by BIOS.
>                sysctl hw.acpi.cpu.px_control=-1
>		Note: 512 M RAM
>
>(FreeBSD/i386)  Pentium II @ 233 Mhz : 538.136 s (92913.3 r/s)
>		Note: 192 M RAM
>
>Not surprising is the Pentium II :).  What is surprising is that amd64 FreeBSD 
>seems to execute code faster than i386 FreeBSD, so I'm wondering if gcc 
>(amd64) really optimizes code for the cpu. If it is, I would probably move my 
>httpd server to amd64...
>
>Also, maybe less surprising is that Knoppix sucks running the algorithm for 
>some reason and that L2 cache really is a big factor (my Laptop outperforms 
>my heavily overclocked box).
>
>Any comments?
>  
>