Re: Upgrade RHEL3 x86_64 to RHEL4 x86?

[Terje Bless <link pobox com>]

Tom Sightler <ttsig tuxyturvy com> wrote:

>Just because I'm curious, why did you do this anyway?  I understand that
>the box doesn't NEED it, but it can take advantage of it, and it's the
>same price so why not run the distro that takes full advantage of the
>capabilities?

Because I, perhaps erroneously, have assumed that the 64bit version introduces a
not insignificant overhead, and because I observe many problems reported on
mailinglists — often with maintaining 32bit compatibility in userspace — that
suggest the 64bit version isn't worth the extra hassle unless I actually need to
address more memory than this application currently needs.

That said, when the cross-arch upgrade ran into a brick wall, I did consider
leaving the system with the 64bit version; the downsides of that vs. a reinstall
aren't sufficiently clear to me and the app in question may eventually need gobs
of RAM to play in.

I don't know, perhaps I'm just being superstitious. :-)


Then again, the box (Dell PE1850) is an EM64T whose only claim to 64bit'ed-ness,
as far as I know, is an ability to take somewhere in excess of 8GB RAM.
Otherwise it's a fundamentally 32bit system, and probably — I'm not particularly
well versed at CPU tech, or the finer detail of system architecture — register
starved to boot, so the last thing you want is to bog it down dealing with 64bit
addressing.


>We've got several applications that see significant performance
>improvement running on the 64-bit version rather than the 32-bit
>version.

If that's the case I would very much like to see some numbers!

What sort of applications? How much memory? Did you actually benchmark x86 vs.
x86_64 on the same OS/HW combination?

Am I really going to have to reinstall the box /again/ this weekend? :-)

-- 
  >You mean you've been out of the secret-loop these past 5 years?
  No, no. Of course not. BBEdit has been leading a “secret life” for the last
  five years, too.     It just involved stiletto heels and fishnet stockings.
                                          -- Jon Guyer <jguyer his com>