Switching to a 64 bit kernel
Jakub Jelinek
jakub at redhat.com
Mon Mar 19 11:57:37 UTC 2007
On Mon, Mar 19, 2007 at 08:39:52AM +0000, Eur Ing Chris Green wrote:
> ... and while there are *some* advantages to running a 64-bit system
> there are also downsides still.
>
> Advantages (that I can remember):-
> You can use huge amounts of memory efficiently (i.e. if you have
> more than 4Gb or memory)
>
> Some other things may run more efficiently
Where "some other things" mean the vast majority of programs.
64-bit programs (or kernel) on x86_64 has twice as many general purpose
registers available as 32-bit programs have and on the register starved
i?86 that makes a huge difference. Also, 64-bit programs can use
better addressing modes (%rip addressing which removes the need to have
a PIC register in shared libraries) and use better calling conventions.
On x86_64 generally these advantages measurably overweight the bigger
cache and memory footprint (as pointers and long vars in data are now
twice as big as for 32-bit programs and even 64-bit code on x86_64
is slightly bigger than 32-bit code).
So, unless you rely on binary only kernel drivers that are only
available for i686, installing x86_64 distro is a win.
Jakub
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