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urcindalo
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Location: Almeria, Spain

PostPosted: Thu Oct 27, 2005 8:30 am    Post subject: Before my first "emerge -e world" Reply with quote

Thanks for reading this.

I've been a Gentoo AMD64 user for 10 months. In fact, my first 10 months with PC hardware, since I'm still a Mac user.
But I must say that I'm cheeting on OS X with Gentoo AMD64 :D
I keep a very up-to-date system, rsync'ing everyday and performing several maintenance routines, like running the unclepine script.

However, I've thought of moving on from a very conservative setup:
Code:
CFLAGS="-march=k8 -O2"
CHOST="x86_64-pc-linux-gnu"
CXXFLAGS="${CFLAGS}"
to something like
Code:
CFLAGS="-march=k8 -O3 -pipe"
And to recompile everything, an "emerge -e world" is mandatory.

My question is: if something fails compiling, will I loose that package until I'm be able to compile it again, or will my system keep and use the old installation? I ask this because I see "emerge -e" tweaks the tree of installed packages to contain nothing, according to its man, but it is not clear to me if the "tweak" consists of removing them or inactivating them in any way prior to the new emerge.

Thanks in advance.
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Sleipnir
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Joined: 20 Sep 2005
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PostPosted: Thu Oct 27, 2005 8:40 am    Post subject: Reply with quote

If you recompile something and it fails the already installed package is still there. The overwrite
process starts after a successfull compilation. The only problem is that you maybe installed a
new and incompatible library for the existing executables on remerge...

Ergo: I think its save. ;-)

Edit:
I dunno if this makes a difference, but i specified -march=athlon64 for my AMD64....
The gcc manual says nothing about the differences between k8 and amd64. There are none :?:
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Codo
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PostPosted: Thu Oct 27, 2005 8:45 am    Post subject: Re: Before my first "emerge -e world" Reply with quote

urcindalo wrote:
However, I've thought of moving on from a very conservative setup:
Code:
CFLAGS="-march=k8 -O2"
CHOST="x86_64-pc-linux-gnu"
CXXFLAGS="${CFLAGS}"
to something like
Code:
CFLAGS="-march=k8 -O3 -pipe"
And to recompile everything, an "emerge -e world" is mandatory.

I suggest you to read carefully the man pages about gcc and comments about -O3. I've ran into minor (but annoying) issues with -O3 compiling. It makes your binaries bigger and is not a huge improvement on -O2. I ran -O3 for a while and then went back to -O2. I've heard -Os is good as well. Check on the gcc webpage...

urcindalo wrote:

My question is: if something fails compiling, will I loose that package until I'm be able to compile it again, or will my system keep and use the old installation? I ask this because I see "emerge -e" tweaks the tree of installed packages to contain nothing, according to its man, but it is not clear to me if the "tweak" consists of removing them or inactivating them in any way prior to the new emerge.

The answer is NO. emerge will only remove the previous package after it has successfuly installed the new one. But "successfuly installed" doesn't mean "working nice and clean", so there you are.
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Monkeh
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PostPosted: Thu Oct 27, 2005 8:57 am    Post subject: Reply with quote

Sleipnir wrote:
I dunno if this makes a difference, but i specified -march=athlon64 for my AMD64....
The gcc manual says nothing about the differences between k8 and amd64. There are none :?:


I believe k8 is used for 32-bit, athlon64 for 64-bit.
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urcindalo
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PostPosted: Thu Oct 27, 2005 9:49 am    Post subject: Reply with quote

OK. Thanks for your answers.

I think I'll try -march=athlon64 for the shake of change (my system was already 64 bit with k8 ) and will keep -O2.
What about -pipe? Will it break something important for the system stability? Will my system be faster with it?
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Monkeh
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PostPosted: Thu Oct 27, 2005 10:30 am    Post subject: Reply with quote

-pipe is used to speed up compiling, I believe. It has no effect on speed or stability that I know of. -fomit-frame-pointer is good though (but I don't know just how well it works on an AMD64).
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jtag
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Joined: 04 Jan 2005
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PostPosted: Thu Oct 27, 2005 10:53 am    Post subject: Reply with quote

Well according to http://gcc.gnu.org/onlinedocs/gcc-3.4.4/gcc/i386-and-x86_002d64-Options.html#i386-and-x86_002d64-Options
k8, opteron, athlon64 and athlon-fx
are all synonyms for
"AMD K8 core based CPUs with x86-64 instruction set support. (This supersets MMX, SSE, SSE2, 3dNOW!, enhanced 3dNOW! and 64-bit instruction set extensions.)"
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