From: Lionel Bouton <lionel-subscription@...>
Date: 2008-02-22T05:13:10+09:00
Subject: [OT] Re: [QUIZ #157] 32bit vs 64bit vs UML performance

Bill Kelly wrote:
>
> From: "Lionel Bouton" <lionel-subscription@bouton.name>
>>
>> Anyway, I can live with the fact that Ruby is 25% slower on data 
>> crunching when PostgreSQL can fly. In the future I'll simply use 
>> 32bit systems for web frontends if my benchmarks confirm this trend.
>
> As an aside, have you measured a 32-bit ruby binary running on the
> 64-bit system?
>

Yes, the Athlon64 performance were compared by running a 32bit Ruby on a 
64bit system in a 32bit chroot.

> I recall you mentioned trying a 32-bit ruby in a chroot ... but what was
> puzzling me was why the chroot was needed?

It isn't, but I have a chroot ready so it's easier for me to simply 
chroot into it when needing to run 32bit code. Few packages are 
available as 32bit on 64bit Gentoo :
- binary-only packages,
- packages that may link to 32 bit libraries like mplayer or firefox,
- common libraries needed by the 2 previous cases.

So the purpose of the chroot is to have a full-blown 32bit system at my 
disposal where I can install whatever is already packaged by Gentoo 
without looking for a binary or cross-compiling it myself. For example, 
if I want to compare PostgreSQL 32bit and 64bit performance, I only have 
to install PostgreSQL in the chroot with the package manager, make sure 
it isn't started in the main system and start it from the chroot.
Of course I still run with a 64bit kernel, so when I detect a change of 
behavior that I must be sure of I have to validate on a complete 32bit 
system but usually the kernel hasn't a big impact, globally running 
Linux 32bit code on a 64bit kernel instead of a 32bit one doesn't change 
the performance characteristics much.

>   I'm relatively new to
> 64-bit linux, but I have a couple servers now, running 64-bit debian
> systems, like:
>
> Linux fragbait 2.6.19.2-amd64.080215-grsec #1 SMP Sun Nov 18 06:48:46 
> PST 2007 x86_64 GNU/Linux
>
> And they have a /lib32 as well as a /lib64, and provided I install 
> (with apt-get) the 32-bit versions of whatever libraries are needed,
> they seem perfectly happy to run 32-bit binaries right alongside
> 64-bit binaries, no chroot needed...
>
> So it seems you ought to be able to run 32-bit ruby and 64-bit
> PostgreSQL side by side with no problem?

I could, but I'd have to do without Portage to maintain all things ruby 
dependent as I wouldn't be able to use it to install Ruby. The same is 
probably true on any distribution, if you want to test both 32bit and 
64bit binaries of the same package, it's not convenient to install them 
on the same system.

Lionel