[gentoo-user] CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[gentoo-user] CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[maxim wexler]

Hi group,

I note two schools of thought on the best CFLAGS for
the Pentium III processor.

One suggests using -O3 -pipe, the other, -O2 without
the pipe.

How much difference does this make? Is the extra level
of optimization with pipe the equivalent of the lower
level without?

-mw


 
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Re: [gentoo-user] CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Sascha Hlusiak]

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> One suggests using -O3 -pipe, the other, -O2 without
> the pipe.
>
> How much difference does this make? Is the extra level
> of optimization with pipe the equivalent of the lower
> level without?

From the gcc manpage:
-pipe
Use pipes rather than temporary files for communication between the various 
stages of compilation.  This fails to work on some systems where the 
assembler is unable to read from a pipe; but the GNU assembler has no 
trouble.

The pipe is only for speeding up the compiling process. It does not speed up 
binaries. 

The -O3 contains some more optimizations than -O2, which can result in much 
bigger applications and may be contraproductive. The -O2 is widely 
recommended, but I guess you won't feel a big difference anyway. See man gcc 
for a more detailled description. 


- Sascha

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Re: [gentoo-user] CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Andrey Gerasimenko]

On Mon, 09 Apr 2007 05:48:07 +0400, maxim wexler <blissfix@yahoo.com>  
wrote:

> Hi group,
>
> I note two schools of thought on the best CFLAGS for
> the Pentium III processor.
>
> One suggests using -O3 -pipe, the other, -O2 without
> the pipe.
>
> How much difference does this make? Is the extra level
> of optimization with pipe the equivalent of the lower
> level without?
>

Man gcc. -pipe allows to use pipes (memory) instead of temporary files  
(disk). -O controls the resulting binary sometimes making it fast, large,  
and unreliable. I have seen ebuilds that enforce -O2 even when -O3 is  
specified. This can create a faulty impression that -O3 always works fine.

-O and -pipe interact through the size of temporary files. Theoretically,  
-pipes may slow down compiles if there is not enough memory. Another  
factor that should be taken into account is the number of threads for  
make. For a PIII machine the generally recommended number is 2, but when  
the RAM is limited, say 384 megs, 1 thread with pipes works better.

Ideally you should measure compile times for large projects like Open  
Office and find out what works best on your system. I would start with 1  
thread -O2 and -pipe.

-- 
Andrei Gerasimenko
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Re: [gentoo-user] CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Neil Bothwick]

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Hello Andrey Gerasimenko,

> Ideally you should measure compile times for large projects like Open  
> Office and find out what works best on your system. I would start with
> 1 thread -O2 and -pipe.

That would be an incredible waste of time because the OOo build replaces
any -O? CFLAG with -O2. If you want to test this, use a more
representative ebuild, preferably for a package you can time with a watch
rather than a calendar.


-- 
Neil Bothwick

Accept that some days you're the pigeon, and some days you're the statue.

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[gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Alexander Skwar]

· maxim wexler <blissfix@yahoo.com>:

> One suggests using -O3 -pipe, the other, -O2 without
> the pipe.

The resulting binaries of a -O2 -pipe compile will be
the same as those of a -O2 (no pipe) compile. 

See http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Overall-Options.html#index-pipe-81

> How much difference does this make? Is the extra level
> of optimization with pipe the equivalent of the lower
> level without?

There's no extra level of optimization.

So the question boils down to: Is -O3 better than -O2? Answer: Depends.
On a system with not that much cache, it might not be.

Alexander Skwar
-- 
BOFH Excuse #16:

somebody was calculating pi on the server


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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Francisco Rivas]

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Hi all :D

I think what "-march=your_arch -O2" it's enough, because -O3 it's highest
but have some details
(http://gentoo-wiki.com/CFLAGS#-O2_or_-O3.3F). My guess is "-march=your_arch
-O2". I was compiled my entire system with those flags and my applications
no matter which have a very good functionality...

I hope give you some help to make your decision...

On 4/9/07, Alexander Skwar <listen@alexander.skwar.name> wrote:
>
> · maxim wexler <blissfix@yahoo.com>:
>
> > One suggests using -O3 -pipe, the other, -O2 without
> > the pipe.
>
> The resulting binaries of a -O2 -pipe compile will be
> the same as those of a -O2 (no pipe) compile.
>
> See
> http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Overall-Options.html#index-pipe-81
>
> > How much difference does this make? Is the extra level
> > of optimization with pipe the equivalent of the lower
> > level without?
>
> There's no extra level of optimization.
>
> So the question boils down to: Is -O3 better than -O2? Answer: Depends.
> On a system with not that much cache, it might not be.
>
> Alexander Skwar
> --
> BOFH Excuse #16:
>
> somebody was calculating pi on the server
>
>
> --
> gentoo-user@gentoo.org mailing list
>
>


-- 
['Cause without love I won't survive, I love you]. I

Francisco Rivas
2.6.19-gentoo-r5 x86
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e-mail : fjrivas@uc.edu.ve
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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[maxim wexler]

--- Francisco Rivas <taken2k4@gmail.com> wrote:

> Hi all :D
> 
> I think what "-march=your_arch -O2" it's enough,
> because -O3 it's highest
> but have some details
> (http://gentoo-wiki.com/CFLAGS#-O2_or_-O3.3F). My
> guess is "-march=your_arch
> -O2". I was compiled my entire system with those
> flags and my applications
> no matter which have a very good functionality...
> 
> I hope give you some help to make your decision...
> 

Interesting. Just completed emerge -uvDN world using
the "-03 -pipe" cflags in make.conf for the PIII arch.
I noticed as the output scrolled by that the flags I
set were being used for all packages *except* gcc
which used "-02 -pipe". 

-mw


       
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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Uwe Thiem]

On 10 April 2007, maxim wexler wrote:

> Interesting. Just completed emerge -uvDN world using
> the "-03 -pipe" cflags in make.conf for the PIII arch.
> I noticed as the output scrolled by that the flags I
> set were being used for all packages *except* gcc
> which used "-02 -pipe".

Some packages (ebuilds) set a maximum optimisation. Gcc is one of them, 
OpenOffice another one.

Uwe

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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Bo Ørsted Andresen]

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On Tuesday 10 April 2007 16:58:47 Uwe Thiem wrote:
> On 10 April 2007, maxim wexler wrote:
> > Interesting. Just completed emerge -uvDN world using
> > the "-03 -pipe" cflags in make.conf for the PIII arch.
> > I noticed as the output scrolled by that the flags I
> > set were being used for all packages *except* gcc
> > which used "-02 -pipe".
>
> Some packages (ebuilds) set a maximum optimisation. Gcc is one of them,
> OpenOffice another one.

It's done with `replace-flags -O? -O2` so it's not a maximum. -O0 or -O1 would 
be replaced too...

-- 
Bo Andresen

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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Francisco Rivas]

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Hi all..

Certainly some package have a maximun optimisation. I really believe, the
optimisation level is a very interesting thing bucause all depend of what
you need and you have all power of your system, only gentoo can give you
that.

it's very good to see a server compiling most of the applications, and
people with few resources in thier pc's can run a very good operating system
and no die trying... :P

Looking for more information on the web, I see
http://www.linuxjournal.com/article/7269.

In that article: "...The simplest way to achieve good performance is to rely
on the -O2 optimization level; if you're not interested in portability,
specify the target architecture using -march=. For space-constrained
applications, the -Os optimization level should be considered first.."

All is your decision based in what you need...

On 4/10/07, Uwe Thiem <uwix@iway.na> wrote:
>
> On 10 April 2007, maxim wexler wrote:
>
> > Interesting. Just completed emerge -uvDN world using
> > the "-03 -pipe" cflags in make.conf for the PIII arch.
> > I noticed as the output scrolled by that the flags I
> > set were being used for all packages *except* gcc
> > which used "-02 -pipe".
>
> Some packages (ebuilds) set a maximum optimisation. Gcc is one of them,
> OpenOffice another one.
>
> Uwe
>
> --
> A fast and easy generator of fractals for KDE:
> http://www.SysEx.com.na/iwy-1.0.tar.bz2
> Proof of concept of a TSP solver for KDE:
> http://www.SysEx.com.na/epat-0.1.tar.bz2
> --
> gentoo-user@gentoo.org mailing list
>
>


-- 
['Cause without love I won't survive, I love you]. I

Francisco Rivas
2.6.19-gentoo-r5 x86
udev v087 gnome 2.16.2
xorg-x11-7.1 hotplug v20040923-r2
e-mail : fjrivas@uc.edu.ve
msn : taken2k4@gmail.com

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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Tony Stohne]

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Hash: SHA1

Francisco Rivas said the following on 2007-04-10 17:29:
| ...
| Certainly some package have a maximun optimisation. I really believe,
| the optimisation level is a very interesting thing bucause all depend of
| what you need and you have all power of your system, only gentoo can
| give you that.
|
That's not entirely true. Take SuSE for instance. Using SRPMs and
setting your preferred compiler and linker flags, You can pretty much do
the same as in Gentoo, the difference being that Gentoo makes it a lot
easier :) since it - as opposed to the majority of Linux dists - is a
true source code distribution. (Phew! That was a long sentence).

| ...
|
| All is your decision based in what you need...
|
Agreed :)

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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Andrey Vul]

don't use -O3 unless you need _extreme_ performance
-O2 -finline-functions is close to -O3 but doesn't use -fno-home-register
For toolchain, I just stick to -O2. For power-hungry apps, I use -O2
-finline-functions
glibc developer said that inlining with gcc 4.2 screws up code, so on
the safe side, just use -O2 for toolchain, -O2 -finline-functions for
everything else
---------------------
Andrey Vul
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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[maxim wexler]

--- Andrey Vul <andrey.vul@gmail.com> wrote:

> don't use -O3 unless you need _extreme_ performance
> -O2 -finline-functions is close to -O3 but doesn't
> use -fno-home-register
> For toolchain, I just stick to -O2. For power-hungry
> apps, I use -O2
> -finline-functions
> glibc developer said that inlining with gcc 4.2
> screws up code, so on
> the safe side, just use -O2 for toolchain, -O2
> -finline-functions for
> everything else
> ---------------------
> Andrey Vul

Too late. Damage done. I decided to go with the
example make.conf which call the O3 level "decent".
> -- 
> gentoo-user@gentoo.org mailing list
> 
> 



       
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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Francisco Rivas]

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Hi all.. Oh god.. well damage done, but you learn the lesson rigth?.. I
believe yes. Actually all the people in the forum learn the lesson...

For the nex time remember use O2 :D
 I hope the damage was not horrible.. and you can recover all losted.

On 4/10/07, maxim wexler <blissfix@yahoo.com> wrote:
>
>
> --- Andrey Vul <andrey.vul@gmail.com> wrote:
>
> > don't use -O3 unless you need _extreme_ performance
> > -O2 -finline-functions is close to -O3 but doesn't
> > use -fno-home-register
> > For toolchain, I just stick to -O2. For power-hungry
> > apps, I use -O2
> > -finline-functions
> > glibc developer said that inlining with gcc 4.2
> > screws up code, so on
> > the safe side, just use -O2 for toolchain, -O2
> > -finline-functions for
> > everything else
> > ---------------------
> > Andrey Vul
>
> Too late. Damage done. I decided to go with the
> example make.conf which call the O3 level "decent".
> > --
> > gentoo-user@gentoo.org mailing list
> >
> >
>
>
>
>
>
> ____________________________________________________________________________________
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Francisco Rivas
2.6.19-gentoo-r5 x86
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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Davi]

Em Terça 10 Abril 2007 16:01, Francisco Rivas escreveu:
> Hi all.. Oh god.. well damage done, but you learn the lesson rigth?.. I
> believe yes. Actually all the people in the forum learn the lesson...
>
> For the nex time remember use O2 :D
>  I hope the damage was not horrible.. and you can recover all losted.
>

How can I rebuild my system with O2?? =P

I've configured my system with O3 and the HD space is going out... =P

TIA

-- 
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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Uwe Thiem]

On 10 April 2007, Davi wrote:
> Em Terça 10 Abril 2007 16:01, Francisco Rivas escreveu:
> > Hi all.. Oh god.. well damage done, but you learn the lesson rigth?.. I
> > believe yes. Actually all the people in the forum learn the lesson...
> >
> > For the nex time remember use O2 :D
> >  I hope the damage was not horrible.. and you can recover all losted.
>
> How can I rebuild my system with O2?? =P
>
> I've configured my system with O3 and the HD space is going out... =P

O3 binaries are larger than O2 binaries but not that much. So if you are about 
to be out of HD space with O3 binaries you will soon be out of it with O2 
binaries as well. You will need more HD space either way.

That said, you can rebuild your system to be O2 by editing /etc/make.conf 
(O3 -> O2) and the "--newuse" option for emerge. I don't think it's worth 
it. ;-)

Uwe

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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Bo Ørsted Andresen]

[-- Attachment #1: Type: text/plain, Size: 262 bytes --]

On Tuesday 10 April 2007 21:45:04 Uwe Thiem wrote:
> That said, you can rebuild your system to be O2 by editing /etc/make.conf
> (O3 -> O2) and the "--newuse" option for emerge. I don't think it's worth
> it. ;-)

You mean --emptytree.

-- 
Bo Andresen

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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Jesús Guerrero]

El Tue, 10 Apr 2007 20:45:04 +0100
Uwe Thiem <uwix@iway.na> escribió:

> >
> > How can I rebuild my system with O2?? =P
> >
> > I've configured my system with O3 and the HD space is going out...
> > =P
> 
> O3 binaries are larger than O2 binaries but not that much. So if you
> are about to be out of HD space with O3 binaries you will soon be out
> of it with O2 binaries as well. You will need more HD space either
> way.
> 
Yes. No way around that.

> That said, you can rebuild your system to be O2 by
> editing /etc/make.conf (O3 -> O2) and the "--newuse" option for
> emerge. I don't think it's worth it. ;-)
> 
No, --newuse is for use flags. He need to rebuild ALL the packages. So,
"emerge --emptytree world" would do.

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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Davi]

Em Terça 10 Abril 2007 16:56, Jesús Guerrero escreveu:
> No, --newuse is for use flags. He need to rebuild ALL the packages. So,
> "emerge --emptytree world" would do.


** Thinking: rebuild all = all packages = kde + Xorg + glibc + OOo + ... 
Humm... **

Well... I'm _very_ fine with -O3 flag... u.u'
I would like use the -O3 flag until format my HD instead recompile my entire 
system... =P


Thanks a lot!


-- 
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davividal@gmail.com
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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Jesús Guerrero]

El Tue, 10 Apr 2007 17:08:40 -0300
Davi <davividal@siscompar.com.br> escribió:

> Em Terça 10 Abril 2007 16:56, Jesús Guerrero escreveu:
> > No, --newuse is for use flags. He need to rebuild ALL the packages.
> > So, "emerge --emptytree world" would do.
> 
> 
> ** Thinking: rebuild all = all packages = kde + Xorg + glibc + OOo
> + ... Humm... **
> 
> Well... I'm _very_ fine with -O3 flag... u.u'
> I would like use the -O3 flag until format my HD instead recompile my
> entire system... =P


Well, you don't need to do so. Just change the flag.

Eventually, with the time, all the packages will be recompiled now or
later... There is no problem with that.

-- Jesús Guerrero
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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Davi]

Em Terça 10 Abril 2007 17:15, Jesús Guerrero escreveu:
> El Tue, 10 Apr 2007 17:08:40 -0300
>
> Davi <davividal@siscompar.com.br> escribió:
> > Em Terça 10 Abril 2007 16:56, Jesús Guerrero escreveu:
> > > No, --newuse is for use flags. He need to rebuild ALL the packages.
> > > So, "emerge --emptytree world" would do.
> >
> > ** Thinking: rebuild all = all packages = kde + Xorg + glibc + OOo
> > + ... Humm... **
> >
> > Well... I'm _very_ fine with -O3 flag... u.u'
> > I would like use the -O3 flag until format my HD instead recompile my
> > entire system... =P
>
> Well, you don't need to do so. Just change the flag.
>
> Eventually, with the time, all the packages will be recompiled now or
> later... There is no problem with that.
>
> -- Jesús Guerrero

Sure! But I don't want to wait 8~9 hours to compile OOo right _now_... =P

BTW, thanks for your help! =]

-- 
Davi Vidal
davividal@siscompar.com.br
davividal@gmail.com
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"===  ALL USERS PLEASE NOTE  ========================

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The function CAR now returns two values.  Since it has to go to the trouble 
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	(MULTIPLE-VALUE-BIND (THE-CAR THE-CDR) (CAR SOME-CONS) ...)

For symmetry with CAR, CDR returns a second value which is the CAR of the
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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Ryan Sims]

On 4/10/07, Davi <davividal@siscompar.com.br> wrote:
> Em Terça 10 Abril 2007 17:15, Jesús Guerrero escreveu:
> > El Tue, 10 Apr 2007 17:08:40 -0300
> >
> > Davi <davividal@siscompar.com.br> escribió:
> > > Em Terça 10 Abril 2007 16:56, Jesús Guerrero escreveu:
> > > ** Thinking: rebuild all = all packages = kde + Xorg + glibc + OOo
> > > + ... Humm... **
> > >
> > > Well... I'm _very_ fine with -O3 flag... u.u'
> > > I would like use the -O3 flag until format my HD instead recompile my
> > > entire system... =P
> >
> > Well, you don't need to do so. Just change the flag.
> >
> > Eventually, with the time, all the packages will be recompiled now or
> > later... There is no problem with that.
> >
> Sure! But I don't want to wait 8~9 hours to compile OOo right _now_... =P
>

What Jesús means is that if you change the flag now, over the course
of usual updates eventually everything will be recompiled.  There
shouldn't be any harm in having some -03 and some -02 binaries on your
system, so change your make.conf and let it happen incrementally with
your normal updates.

-- 
Ryan W Sims
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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Davi]

Em Terça 10 Abril 2007 19:03, Ryan Sims escreveu:
> On 4/10/07, Davi <davividal@siscompar.com.br> wrote:
> > Em Terça 10 Abril 2007 17:15, Jesús Guerrero escreveu:
> > > El Tue, 10 Apr 2007 17:08:40 -0300
> > >
> > > Davi <davividal@siscompar.com.br> escribió:
> > > > Em Terça 10 Abril 2007 16:56, Jesús Guerrero escreveu:
> > > > ** Thinking: rebuild all = all packages = kde + Xorg + glibc + OOo
> > > > + ... Humm... **
> > > >
> > > > Well... I'm _very_ fine with -O3 flag... u.u'
> > > > I would like use the -O3 flag until format my HD instead recompile my
> > > > entire system... =P
> > >
> > > Well, you don't need to do so. Just change the flag.
> > >
> > > Eventually, with the time, all the packages will be recompiled now or
> > > later... There is no problem with that.
> >
> > Sure! But I don't want to wait 8~9 hours to compile OOo right _now_... =P
>
> What Jesús means is that if you change the flag now, over the course
> of usual updates eventually everything will be recompiled.  There
> shouldn't be any harm in having some -03 and some -02 binaries on your
> system, so change your make.conf and let it happen incrementally with
> your normal updates.
>
> --
> Ryan W Sims

Sure! I get it and I already changed my make.conf... =]

thanks! =]

-- 
Davi Vidal
davividal@siscompar.com.br
davividal@gmail.com
--

Agora com fortune:
"Any path which narrows future possibilities may become a lethal trap. Humans 
are not threading their way through a maze; they scan a vast horizon filled 
with unique opportunities. The narrowing viewpoint of the maze should appeal 
only to creatures with their noses buried in sand. Sexually produced 
uniqueness 
and differences are the life-protection of the spices.

  -- The Spacing Guild Handbook"
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[gentoo-user] Re: Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Alexander Skwar]

Davi <davividal@siscompar.com.br> wrote:

> Em Terça 10 Abril 2007 16:56, Jesús Guerrero escreveu:
>> No, --newuse is for use flags. He need to rebuild ALL the packages. So,
>> "emerge --emptytree world" would do.
> 
> 
> ** Thinking: rebuild all = all packages = kde + Xorg + glibc + OOo + ...
> Humm... **
> 
> Well... I'm _very_ fine with -O3 flag... u.u'
> I would like use the -O3 flag until format my HD instead recompile my
> entire system... =P

Well, you can easily do a "rolling change". Ie. set the new CFLAG
now and go on as usual. Over time, all the packages will/might be
recompiled.

Alexander Skwar

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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Uwe Thiem]

On 10 April 2007, Jesús Guerrero wrote:
> El Tue, 10 Apr 2007 20:45:04 +0100
>
> Uwe Thiem <uwix@iway.na> escribió:
> > > How can I rebuild my system with O2?? =P
> > >
> > > I've configured my system with O3 and the HD space is going out...
> > > =P
> >
> > O3 binaries are larger than O2 binaries but not that much. So if you
> > are about to be out of HD space with O3 binaries you will soon be out
> > of it with O2 binaries as well. You will need more HD space either
> > way.
>
> Yes. No way around that.
>
> > That said, you can rebuild your system to be O2 by
> > editing /etc/make.conf (O3 -> O2) and the "--newuse" option for
> > emerge. I don't think it's worth it. ;-)
>
> No, --newuse is for use flags. He need to rebuild ALL the packages. So,
> "emerge --emptytree world" would do.

Yup. Sorry, my mistake.

Uwe

-- 
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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Dan Farrell]

On Tue, 10 Apr 2007 20:45:04 +0100
Uwe Thiem <uwix@iway.na> wrote:

> O3 binaries are larger than O2 binaries but not that much. So if you
> are about to be out of HD space with O3 binaries you will soon be out
> of it with O2 binaries as well. You will need more HD space either
> way.
> 
> That said, you can rebuild your system to be O2 by
> editing /etc/make.conf (O3 -> O2) and the "--newuse" option for
> emerge. I don't think it's worth it. ;-)
This thread contains a nice description of -02 -03 and -0s (size
optimization) which makes it clear that what is actually desired here
for space-saving concerns is -0s, not -03.  

I for some reason run -03
on all my emerges and allow the ebuilds to sort out the maximum
acceptible optimization level.  As far as I can tell, nothing's been
broken by that.  I don't run testing or anything, and it _is_ more
dangerous, but I'm doing it without problems.  For the record.  

Finally, as people have already said, --newuse is to recompile when you
change your use flags.  You want to rebuild the system and the world as
if none of the dependancies are already installed (so that they get
rebuilt too, even if not explicity a part of your world or system) and
the way to do that is -e (--emptytree).  Doing so after changing from
-03 to -0s may actually save a decent amount of space.  Furthermore, it
may actually perform pretty well too.  
-- 
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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Renat Golubchyk]

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On Tue, 10 Apr 2007 16:10:40 -0300 Davi <davividal@siscompar.com.br>
wrote:
> How can I rebuild my system with O2?? =P
> 
> I've configured my system with O3 and the HD space is going out... =P

Change your CFLAGS to have -O2 instead of -O3 and then run
"emerge -e world". If you don't have enough space then unmerge some
unneeded stuff before reemerging world.

Cheers,
Renat

-- 
Probleme kann man niemals mit derselben Denkweise loesen,
durch die sie entstanden sind.
                                              (Einstein)

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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Uwe Thiem]

On 10 April 2007, maxim wexler wrote:
> --- Andrey Vul <andrey.vul@gmail.com> wrote:
> > don't use -O3 unless you need _extreme_ performance
> > -O2 -finline-functions is close to -O3 but doesn't
> > use -fno-home-register
> > For toolchain, I just stick to -O2. For power-hungry
> > apps, I use -O2
> > -finline-functions
> > glibc developer said that inlining with gcc 4.2
> > screws up code, so on
> > the safe side, just use -O2 for toolchain, -O2
> > -finline-functions for
> > everything else
> > ---------------------
> > Andrey Vul
>
> Too late. Damage done. I decided to go with the
> example make.conf which call the O3 level "decent".

No real damage. Your system will work - and quite well, especially if you 
prelink the whole thing to overcome longer load times of O3 binaries.

Uwe

-- 
A fast and easy generator of fractals for KDE:
http://www.SysEx.com.na/iwy-1.0.tar.bz2
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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Daniel Iliev]

maxim wexler wrote:
>
> Too late. Damage done. I decided to go with the
> example make.conf which call the O3 level "decent".
>   
>> -- 
>> gentoo-user@gentoo.org mailing list
>>
>>
>>     


Exactly what kind of damage are you talking about? Don't you think if
there was a real problem with -O3, gentoo devs would have excluded it as
an option, especially when they have an easy to apply mechanism for
doing that (I have in mind the "filter-flags" && "replace-flags"
functions in the ebuilds)? All of my gentoo systems were build using -O3
and I haven't met a single problem with this setting. Of course there
are packages (like the already mentioned OO2 and some others) which
won't build with extreme optimization and the devs have taken care of
this by forcing appropriate C(XX)FLAGS. It is my opinion that the
statements like  "-O3 is wrong and can do damage" is nothing but FUD. It
is questionable if "-O3" helps building faster packages than those built
with "-O2" but for sure it won't do damage.

-- 
Best regards,
Daniel


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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Bo Ørsted Andresen]

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On Wednesday 11 April 2007 11:39:50 Daniel Iliev wrote:
> Exactly what kind of damage are you talking about? Don't you think if
> there was a real problem with -O3, gentoo devs would have excluded it as
> an option, especially when they have an easy to apply mechanism for
> doing that (I have in mind the "filter-flags" && "replace-flags"
> functions in the ebuilds)?

-O3 is replaced where necessary because it's supported by Gentoo. Unsupported 
flags are mostly not filtered as Gentoo devs don't wish to hide problems 
caused by stupid users. Bugs caused by unsupported flags are therefore mostly 
resolved invalid.

[SNIP]
> It is my opinion that the statements like  "-O3 is wrong and can do damage"
> is nothing but FUD.

It's true if you don't use Gentoo ebuilds.

-- 
Bo Andresen

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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Daniel Iliev]

Bo Ørsted Andresen wrote:
> On Wednesday 11 April 2007 11:39:50 Daniel Iliev wrote:
>   
>> Exactly what kind of damage are you talking about? Don't you think if
>> there was a real problem with -O3, gentoo devs would have excluded it as
>> an option, especially when they have an easy to apply mechanism for
>> doing that (I have in mind the "filter-flags" && "replace-flags"
>> functions in the ebuilds)?
>>     
>
> -O3 is replaced where necessary because it's supported by Gentoo. Unsupported 
> flags are mostly not filtered as Gentoo devs don't wish to hide problems 
> caused by stupid users. Bugs caused by unsupported flags are therefore mostly 
> resolved invalid.
>
> [SNIP]
>   
>> It is my opinion that the statements like  "-O3 is wrong and can do damage"
>> is nothing but FUD.
>>     
>
> It's true if you don't use Gentoo ebuilds.
>
>   


Sorry, I don't get it. Perhaps it is my poor English but I couldn't
understand two things:
 - Is -O3 supported by Gentoo or not?
 - What's the special thing about Gentoo ebuilds that makes -O3 dangerous?


-- 
Best regards,
Daniel


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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Davi]

Em Quarta 11 Abril 2007 07:56, Daniel Iliev escreveu:
> Sorry, I don't get it. Perhaps it is my poor English but I couldn't
> understand two things:
>  - Is -O3 supported by Gentoo or not?

Yes.

>  - What's the special thing about Gentoo ebuilds that makes -O3 dangerous?

Nothing. O3 isn't dangerous... =]


>
>
> --
> Best regards,
> Daniel

cya

-- 
Davi Vidal
davividal@siscompar.com.br
davividal@gmail.com
--

Agora com fortune:
"Zoe: "We're going to get the captain."

Kaylee: "Oh, good.... Can they do that?"

Jayne: "No.""
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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Bo Ørsted Andresen]

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On Wednesday 11 April 2007 12:56:43 Daniel Iliev wrote:
> Sorry, I don't get it. Perhaps it is my poor English but I couldn't
> understand two things:
>  - Is -O3 supported by Gentoo or not?

-O3 is supported by Gentoo.

>  - What's the special thing about Gentoo ebuilds that makes -O3 dangerous?

No no. The special thing about Gentoo ebuilds is that -O3 in make.conf is safe 
for all packages because those packages for which -O3 isn't safe are 
replacing it with -O2 in the ebuilds (or eclasses).

-- 
Bo Andresen

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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Francisco Rivas]

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Hi all..

I think what -O3 is not _dangerous_ when you know how to use, a few posts
ago someone mentioned not all of packages can be compiled using -O3, if I am
not wrong was GCC and OpenOffice.org.

The thing is: -O3 is not a _damage_ is an carefully flag to compile for some
packages..

In some webpages I people said : ".. -O3 is not used by developer because
come troubles when you want to do a debug..".

But:
 http://www.nersc.gov/vendor_docs/intel/f_ug2/dbg_opt.htm,
 http://linuxgazette.net/121/hegde.html,
http://publib.boulder.ibm.com/infocenter/macxhelp/v6v81/index.jsp?topic=/com.ibm.xlf81m.doc/pgs/ug42.htm
.

"...The following setting is the "Optimizations". You shouldn't use O3 as it
takes longer to compile, the generated code will be sometimes faster,
sometimes slower and almost always larger. For example, a program that was
compiled with the O2 level of optimization is 250KB large and is quite fast,
the same program compiled with the O3 level of optimization can take more
time to compile, produce a larger binary, depending on the code, even
500-700KB large and it can be slower or faster. Therefore, the O3
optimization level isn't recommended. Use O2 if you need the best
optimization without adding the risk of obtaining large binaries, which need
a long time to be loaded before being executed and are not always faster..."
take of http://www.softpedia.com/reviews/linux/Gentoo-Review-20543.shtml.


On 4/11/07, Bo Ørsted Andresen <bo.andresen@zlin.dk> wrote:
>
> On Wednesday 11 April 2007 12:56:43 Daniel Iliev wrote:
> > Sorry, I don't get it. Perhaps it is my poor English but I couldn't
> > understand two things:
> >  - Is -O3 supported by Gentoo or not?
>
> -O3 is supported by Gentoo.
>
> >  - What's the special thing about Gentoo ebuilds that makes -O3
> dangerous?
>
> No no. The special thing about Gentoo ebuilds is that -O3 in make.conf is
> safe
> for all packages because those packages for which -O3 isn't safe are
> replacing it with -O2 in the ebuilds (or eclasses).
>
> --
> Bo Andresen
>
>


-- 
['Cause without love I won't survive, I love you]. I

Francisco Rivas
2.6.19-gentoo-r5 x86
udev v087 gnome 2.16.2
xorg-x11-7.1 hotplug v20040923-r2
e-mail : fjrivas@uc.edu.ve
msn : taken2k4@gmail.com

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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Daniel Iliev]

Bo Ørsted Andresen wrote:
> On Wednesday 11 April 2007 12:56:43 Daniel Iliev wrote:
>   
>> Sorry, I don't get it. Perhaps it is my poor English but I couldn't
>> understand two things:
>>  - Is -O3 supported by Gentoo or not?
>>     
>
> -O3 is supported by Gentoo.
>
>   
>>  - What's the special thing about Gentoo ebuilds that makes -O3 dangerous?
>>     
>
> No no. The special thing about Gentoo ebuilds is that -O3 in make.conf is safe 
> for all packages because those packages for which -O3 isn't safe are 
> replacing it with -O2 in the ebuilds (or eclasses).
>
>   


Ah! Well, then it is exactly what I'm saying! ;-)

-- 
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Daniel


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Re: [gentoo-user] Re: CFLAGS "...-O3 -pipe" vs "...O2 <no pipe>"

[Jesús Guerrero]

El Tue, 10 Apr 2007 07:29:26 -0700 (PDT)
maxim wexler <blissfix@yahoo.com> escribió:

> 
> --- Francisco Rivas <taken2k4@gmail.com> wrote:
> 
> > Hi all :D
> > 
> > I think what "-march=your_arch -O2" it's enough,
> > because -O3 it's highest
> > but have some details
> > (http://gentoo-wiki.com/CFLAGS#-O2_or_-O3.3F). My
> > guess is "-march=your_arch
> > -O2". I was compiled my entire system with those
> > flags and my applications
> > no matter which have a very good functionality...
> > 
> > I hope give you some help to make your decision...
> > 
> 
> Interesting. Just completed emerge -uvDN world using
> the "-03 -pipe" cflags in make.conf for the PIII arch.
> I noticed as the output scrolled by that the flags I
> set were being used for all packages *except* gcc
> which used "-02 -pipe". 

Hello, 

If the ebuilds were that "smart" to let people mess up cflags on such
packages, people would need to reinstall Gentoo as much as they need to
reinstall Windows. Of course the reason would be a broken toolchain,
instead of a OS that gradually degrades whit the age.

That is specially true when you even make typos writing cflags. See -O2
vs. -02.

-- Jesús Guerrero
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