[CentOS] Re: 32-bit vs 64-bit CentOS on 64-bit hardware

Tue Apr 17 11:55:57 UTC 2007
Jeremy Sanders <jss at ast.cam.ac.uk>

chrism at imntv.com wrote:

> If you don't need to access greater than 4GB RAM, is there any benefit
> to running the 64-bit version of CentOS vs the 32-bit one?  That's
> assuming, of course, that the target machine utilizes a 64-bit capable
> processor.  I hadn't seen any noticeable difference, but I haven't done
> any benchmarking either.

Using AMD chips, 64 bit mode is significantly faster than 32 bit mode (20 to
30 percent, depending on the code), due to the extra registers. I don't
think this is the case for Intel chips. We run all our 64 bit desktops in
64 bit mode, and it's not too hard to get closed source 32 bit apps
working.

There are also advantages for things like LVM+RAID+XFS, as I believe the
stack size is larger, so it's less likely to crash.

Also, consider that not all of 4GB of RAM can be used in 32 bit mode. The
kernel takes up a large chunk of 4GB (depending on kernel compilation
options), so this limits the amount accessed by a single process.

Jeremy

-- 
Jeremy Sanders <jss at ast.cam.ac.uk>   http://www-xray.ast.cam.ac.uk/~jss/
X-Ray Group, Institute of Astronomy, University of Cambridge, UK.
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