[nSLUG] Software Freedom Day

Ian Campbell ian at slu.ms
Sat Sep 12 23:25:55 ADT 2009

On Sat, Sep 12, 2009 at 09:59:55PM -0300, Daniel Morrison wrote:
> http://www.tuxradar.com/content/ubuntu-904-32-bit-vs-64-bit-benchmarks

What they mention, but don't mark particularly clear, is that it's not
a comparison between 32 and 64bit it's a comparison between optimized
and unoptimized code.

What's funny is that even without modern flags for GCC there are still
only 3 convincing victories for 64bit (kernel, ogg, blender) and of
those only the kernel one is actually a benefit of a 64bit proc as GCC
benefits from more GP registers.

Ogg has cpu-specific ASM code, on a 32bit compile it's just using
stock instructions. On the x86_64 builds it's using SSE2 so it gets a
performance increase -- shocking. On the other hand, if they'd tested
with LAME instead they would have gotten matching results for the two
installs, LAME determines which optimizations to use at runtime.

I've never looked at Blender's code but I'd be very surprised if it
wasn't the same issue at play.

Note as well that it's ONLY applications that take advantage of those
extensions that get any significant speed boost, the vast majority of
your applications will run exactly the same. As a Slackware user,
you're better off just building anything like that by hand and keeping
a 32bit system unless you're over 4G ;)

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