Optimisation

Gerard Beekmans gerard at linuxfromscratch.org
Tue Sep 5 05:49:53 PDT 2000


On Mon, 04 Sep 2000, you wrote:
> The main problem I have is that I am not familiar with exactly *what* may
> be causing the problem.  I was more or less asking if there are any
> packages that anyone KNOWS offhand doesn't work at such high optimisations.
>  I am really wanting everything possible to be optimised.  Is it possible
> to use optimisations when compiling glibc or should I compile it with the
> default -O2 (maybe -O3)

In addition to what others have said: it's not possible to tell what breaks 
and what doesn't. David mentioned him having problems with shadow password 
suite, I don't. Others have mentioned binutils and glibc problems, I don't. 
It's all very machine dependant. Till now I've compiled each and every 
package in the LFS book with -O3 -march=i686 -mcpu=i686 (and on shadowfax 
with -i586) and everything is working just dandy. Although very very 
ocasionally things don't work. Like KDE2-Beta4 - ksplash crashes wtih a 
segmentation fault whereas it doesn't do that on other systems.

So I have no idea who to blaim on that one: kde or binutils in combination 
with gcc and other X related packages that have been optimized. But KDE is 
the only package that doesn't run properly, and it's only the ksplash part 
that crashes, so I still wonder...

No, the reason that optimization works seemingly well here doesn't mean I 
have some super computer. It's the sum of the hardware that counts. Perhaps 
I'm lucky to have a stable CPU (though it's not that new or anything - intel 
celeron 533) or whatever else is caused. Perhaps it's because i'm the LFS 
project leader and software likes me a lot for that reason, who knows.

All I'm saying we can't tell which packages fail - because what fails for me 
doesn't mean it fails for you, or the other way around. That's the only 
reason why the book contains the vague lines "if you have problems, don't use 
it".

The 2.5.1 book won't contain optimization stuff anymore. It's almost a 
guarantee that something stops working properly. Perhaps Ian's problems can 
be tracked back to some package being optimized (like glibc or 
binutils-static or gcc-static or gcc-dynamic or others that are installed).

Instead those optimization instructions will be moved to an lfs-hint.



-- 
Gerard Beekmans
www.linuxfromscratch.org

-*- If Linux doesn't have the solution, you have the wrong problem -*-





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