doubt

Ken Moffat ken at linuxfromscratch.org
Sat Feb 11 16:04:14 PST 2006


On Sat, 11 Feb 2006, Bruno Pinto wrote:

> Hi guys!
>
> I want to do a LFS. I have an amd 64 bits laptop, so my doubt is if I
> should do a multilib 64system, all 64, or like if it was a normal
> i386?
>
> Can someone, please, tell me the pros and cons and give me an advice
> of what is the best option.

On a machine doing anything useful, the x86_64 code gives gcc a lot more 
registers to play with, and is typically 20% faster, but perhaps 20% 
bigger.  As long as you have a reasonable amount of memory, the extra 
space is not usually a problem.  But, I have no experience with what 
effect (if any) this might have on battery life (bigger data transfers, 
perhaps more pressure on cpu cache) for a laptop.

Multilib is extremely educational, but for blfs you *really* need to 
understand what you want to build - there isn't a lot of point 
persuading a whole set of libraries to build correctly as both -m32 and 
-m64 if you don't need them in a particular size (for multilib, the 
problems mostly come with building for 32-bit, but people have reported 
occasional problems with 64-bit apps finding the wrong libraries or 
pkgconfig files or whatever as well.  I'll go so far as to say that the 
only sensible reason for multilb on x86_64 is to allow the use of 32-bit 
binaries (browser plugins, or other binaries).  On multilib systems you 
have to watch unknown blfs applications to ensure any libraries (or 
pkgconfig files) will be installed to /usr/lib64 - a few apps don't 
respect --libdir when configured.  From experience, if you want to use a 
RealPlayer plugin on multilib you can expect some degree of pain when 
building the dependencies and when getting a 32-bit pango to sort-of 
work in the presence of a 64-bit pango.

Pure64 on x86_64 still has a few things to watch out for, but in 
general they also apply to 64-bit builds in a multilib, so you'll be hit 
by them anyway (e.g. config.{guess,sub} updates, --disable-fast-malloc 
in kde), and they will hopefully show up in a search of the blfs or clfs 
archives (well, if clfs is searchable).

If this is your first LFS, doing a straight i686 build will definitely 
be easier - if you have the disk space, reserve space for your _next_ 
system, build a regular LFS, decide what BLFS packages you want, and 
keep logs of what they install.  Then build a multilib or pure64 system 
for the second build.

Ken
-- 
  das eine Mal als Tragödie, das andere Mal als Farce


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