Paul (no@thanks.com) on 5/13/07 wrote:
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>One sane answer is running 32 bit user space executables on a 64 bit kernel and
>only compiling for 64 bit when you actually need the address space This is the approach
>Solaris on UltraSPARC has taken for years.

Why do you consider that sane? You suddenly need to have 32bit and 64bit versions of all libs... It is a mess and annoying. You get one vendor giving you only 32bit libs, the other only 64bit and you end up writing tons of code to work around that. It adds disk space, compile time when you have to provide both, additional issues that arise when a customer somehow manages to have 32 and 64 bit libs in different versions installed.

Another issue is that you now need to have both 32 and 64 bit versions of the libs in ram... One of the large applications developed where I work was designed to have all 32 bit process with the exception of 2 large processes that needed a 64 bit address space... Worked well until we added a 64bit 3rd party library... So we ported and recompiled everything in 64bit - and our memory usage dropped about 3%... The larger binary size needed less additional memory than saved by not having two sets of libs everywhere.

To me, the only excuse for allowing 32bit apps to run on a 64bit OS is backwards compatibility.

Peter.