[ltp] Should I use 64-bit or 32-bit for my new Thinkpads?

[Theodore Tso]

On Sat, Feb 16, 2008 at 04:35:49PM -0500, David A. Desrosiers wrote:
> Should I install a 64-bit Linux on the T61p, or stick with a 32-bit Linux? 
> I'm not sure a 64-bit version of Linux would really give me any benefits, 
> and it would certainly limit what software I can run by a fairly 
> significant amount (the Adobe Flash plugin for Firefox being one good 
> example).

What I've done is to install 32-bit Ubuntu on my system, and then
install a 64-bit kernel.  So by default my userspace is 32-bits, so
that things like w32codecs and firefox plugins work, but I can also
use a 64-bit KVM and play with some 64-bit programs where it matters.

Whether or not 64-bits or 32-bits is better is an interesting
question, and it probably really depends on the individual program.
64-bits means that longs and pointers are twice as big; if you don't
need them to be that big, it's just wasted memory and memory
bandwidth.  On the other hand, 64-bit programs do have numerically
twice as many registers as 32-bit programs.  So that can speed up
things --- but if you are using more memory to the point where you
start swapping, that will slow things down.  One estimate I've seen is
that on average programs take 20% more memory when they go from 32-bit
to 64-bit, but of course that very much depends on the program.

In any case, if you install a 64-bit kernel, you can run either 32-bit
or 64-bit userspace programs.  I chose to install a 32-bit userspace,
and then manually compile or install 64-bit programs as necessary, but
you could also install a 64-bit userspace, and then have a few 32-bit
programs installed as necessary.  I'm a big believer in trying to
minimize memory utilization, so I went with the first option.

   	       	  	      	   		- Ted