amd64 optimized gcc?

[Michael VInce]

Interesting.
I have been playing with GCC optimizations my self latterly and have 
been wondering how much it helps, haven't done any benchmarks though.
I some times wonder if the GCC people are doing good working with 
optimization flags.

I recently lost my hard drive on my ASUS A4K (AMD64) laptop,
so bought a new 16meg cache 80gig Toshiba hard drive for it, while I 
wait for warranty to come through on my old one.
I did a buildworld under  'CPUTYPE=athlon64' in make.conf and 'CFLAGS= 
-O2 -pipe -funroll-loops' for the the kernel.
I also used both to build all my ports including xorg and KDE.
All this combined has made my laptop feel a lot faster. After I load up 
openoffice2 (via Linux emu) once I can fully reopen a xls file in about 
1.5 seconds, I believe the HD cache must be playing a bit part in that.

Mike

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?
>  
>