Re: [gentoo-amd64] First Impressions

[Daniel Iliev]

Hemmann, Volker Armin wrote:
> On Wednesday 27 September 2006 07:50, Daniel Iliev wrote:
>
>
>> 1) I use CFLAGS="-march=athlon64 -mfpmath=sse -msse -msse2 -msse3
>> -m3dnow -mmmx -O3 -fomit-frame-pointer -pipe -fpic". P
>>
>
> -mfpmath=sse not needed. amd64 uses sse for math by default. remove that flag
> -msse not needed, see above
> -msse2 not needed, see above
> -msse3 can be set, but only if your CPU supports it. Not all CPUs do.
> Check /proc/cpuinfo for 'pni'
> -m3dnow just no. sse supersedes it. Also it is a '32bit flag'
> -mmmx see above
> -O3 don't do it. O2 is much, much safer and not really slower. It will prevent
> a lot of breakage.
> -fomit-frame-pointer not needed
> -pipe a good flag
> -fpic NO! Really, really really no! Don't do it! It is just wrong. Stop it
> now! This flag is not needed! Even for prelink on 32bit it was never needed
> (because everything that could compiled with that flag set it anyway).
> Please, read the documentation and remove that flag ASAP.
>
> so, march=k8 -O2 -pipe
> would be the result, if you remove all superflous and dangerous flags.
>
>
>
>> 2) I see too many flags that are disabled by the profile - the kind with
>> the parenthesis around them, like "(-3dnow)". Why? As I mentioned above
>> I enable some of these through my CFLAGS - e.g. (-mmx), (-mmxext),
>> (-sse) and (-sse2) and everything works perfect.
>>
>
> because 3dnow, mmx&co are useflags for 32bit code that was optimized for that
> extensions. If you use that code in 64bit apps, certain breakage is the
> result. And if something does not break, it will be A LOT slower.
>
> Don't use that flags. They are bad for amd64. Trust the devs, they know better
> than you or me.
>
Thank you very much for this reply. I'll follow your advise and remove
the redundant flags.
About trusting the devs - well, it depends. I trust them 100% if I need
a rock stable system. In that case I would not dare to divert from any
of the official instructions.
BUT. Devs always tent to advertise the safest ways - this brings users
no/less headaches and therefore less bug-reports ;-)
My case however is slightly different - I'm talking about my home
desktop which is dedicated for experiments and fun. So I'm not afraid to
break the system here and rebuild it again. In this particular moment my
purpose is to get the most out of the hardware no matter the stability.
So I'll leave -O3 ;-)

BTW, Everyone,
I'm observing something very interesting:
I was told not to go gentoo-amd64 for it was not stable. I was told not
to migrate because there were still many important programs pending to
be ported. I read almost everywhere about headaches and breakages.
Reading your replies in this thread also suggests strictly following the
official way otherwise - problems.
It is very strange - I was ready to meet tons of major problems but I
haven't met a single one yet. It is my opinion that the possibility of
problems on gentoo-amd64 is highly overrated. I installed it with no
problems, I obviously have tweaked it a lot beyond normal and what I see
is a perfectly working system. It appears that gentoo-amd64 team along
with the GNU, linux-kernel and all other nice guys who provide free/open
source software have done a great work and we owe them BIG THANKS. I
just wonder how come that so many people talk about some non-existing
problems.
How come that still in my first try I have bootstrapped from stage3,
made "emerge -e system", installed xfce4, gnome, firefox, thunderbird,
and a bunch of other packages along with all their dependencies, then
made "emerge -e world" and after all this compiling I had to do "emerge
--resume" only once when some package wanted mysql build with -fpic
flag. I'm I lucky or what? ;-)


-- 
Best regards,
Daniel


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