Re: Quad Xeon vs. Dual Itanium

On Fri, Feb 13, 2004 at 11:24:05AM -0500, Andrew Sullivan wrote:
> On Fri, Feb 13, 2004 at 10:44:55PM +0800, Lincoln Yeoh wrote:
> > Hmm, do you mean 64 bit postgresql on Solaris-Sparc isn't significantly
> > better performance-wise than 32 bit postgresql on Solaris-Sparc?
>
> Not in any test I've ever run.  I haven't tried again lately, mind
> you.  And I never had the Sun compiler, which, for all I know, does a
> better job with 64 bit binaries than gcc.

As a general rule 64 bit binaries tend to run slower than 32 bit
binaries on any given architecture. The 32 bit binaries still get to
use 64 bit data values if they feel so inclined, so that's nothing
special. But all the pointers in the 64 bit build are twice the size,
so the memory footprint is larger, it makes less efficient use of
cache, it takes longer to read data from main memory and so on. If you
need direct access to a lot of memory, and your application is
structured to use it, then a 64 bit model can be a big win, but
usually not otherwise.

Forte C is a lot better than gcc for Solaris/SPARC (unsurprisingly)
but 32 bit builds still seem a little faster than 64 bit builds. There
are some benchmarks I looked at recently that show that, but I don't
seem to be able to find the article right now.

Cheers,
  Steve