optimize build

Raccoon1400 · 2009-04-20 02:40:47

how would I optimize the build with makepkg? I was told that there was the -O3 option for gcc, but how can this be used in a pkgbuild?

What do these optimization flags gain me anyways?

Stefan Husmann · 2009-04-20 05:37:29

You can add that option to the CCFLAGS in makepkg.conf. But I do not recommend that.

Raccoon1400 · 2009-04-20 15:59:58

why don't you recommend it?

foutrelis · 2009-04-20 16:15:45

Raccoon1400 wrote:

how would I optimize the build with makepkg? I was told that there was the -O3 option for gcc, but how can this be used in a pkgbuild?

Probably in /etc/makepkg.conf, by changing the CFLAGS/CXXFLAGS variables. You can also override any of those variables by defining your own in ~/.makepkg.conf (~ is your home directory).

Raccoon1400 wrote:

What do these optimization flags gain me anyways?

There is a great optimization guide in Gentoo's documentation that explains the most common GCC flags.

Last edited by foutrelis (2009-04-20 16:16:18)

Stefan Husmann · 2009-04-20 18:15:05

Raccoon1400 wrote:

why don't you recommend it?

-O3 sometimes causes problems, and IMHO the speed gain is not worth it.

Wintervenom · 2009-04-20 18:43:31

-03:
- Produces larger binaries that use more memory, more CPU cache misses.
- More likely to break programs.
- Takes more time to compile.
- Insignificant gain, if any.

Last edited by Wintervenom (2009-04-20 18:44:00)

Raccoon1400 · 2009-04-20 19:10:05

are there any optimization options that are worth using?

Raccoon1400 · 2009-04-20 20:30:07

would it be better if only -march was used and not -mtune as well?

Wintervenom · 2009-04-20 20:57:00

-march=native -O2 -pipe is fine for just about everyone. It will automatically choose the best optimizations for the processor you have in your machine.

Last edited by Wintervenom (2009-04-20 20:57:50)

Raccoon1400 · 2009-04-20 21:04:01

I have this
CFLAGS="-march=x86-64 -mtune=generic -O2 -pipe"
CXXFLAGS="-march=x86-64 -mtune=generic -O2 -pipe"

Wintervenom · 2009-04-20 21:50:24

So you'd want:
CFLAGS="-march=native -O2 -pipe"
CXXFLAGS="$CFLAGS"

Xi0N · 2009-04-20 21:59:13

Wintervenom wrote:

So you'd want:
CFLAGS="-march=native -O2 -pipe"
CXXFLAGS="$CFLAGS"

Is it better to leave everything to autodetection instead of setting explicitly the optimal settings for your processor model? - the ones given in here i mean

Last edited by Xi0N (2009-04-20 22:02:50)

adamlau · 2009-04-22 01:21:13

Or you can add LDFLAGS with makepkg-git as such:

CFLAGS="-march=native -O2 -pipe -fomit-frame-pointer"
CXXFLAGS="-march=native -O2 -pipe -fomit-frame-pointer"
LDFLAGS="-Wl,-O1,--as-needed,--hash-style=gnu"

buddabrod · 2009-04-24 08:00:26

You can just add the LDFLAGS to you CFLAGS line so you dont need makepkg-git. LDFLAGS improve things imo more than playing around with CFLAGS.

I myself use only -march=native -Os -pipe -fomit-frame-pointer -Wl,O1,--as-needed,--hash-style=gnu,--sort-common -s
hash-style=gnu is there because by default it's hash-style=both which I dont need. Even when the gnu hash style was considered unstable I never had any problems with it.

shagrath · 2009-04-28 08:52:42

I have a serious question
Do the optimization strings in makepkg.conf influence when building with cmake? because I don't see any strings with "-march=native....".
For example when building kde.

buddabrod · 2009-04-28 14:09:33

Yes, they should. Try cmake VERBOSE=1 this should give you much more output.

shagrath · 2009-04-28 18:50:57

oh, thank you
I set -DCMAKE_VERBOSE_MAKEFILE=ON, and I can see them now! (lines i mean)

blasse · 2009-04-29 16:56:28

adamlau wrote:

Or you can add LDFLAGS with makepkg-git as such:
CFLAGS="-march=native -O2 -pipe -fomit-frame-pointer"
CXXFLAGS="-march=native -O2 -pipe -fomit-frame-pointer"
LDFLAGS="-Wl,-O1,--as-needed,--hash-style=gnu"

LDFLAGS=" " works just fine with recent makepkg, when added to makepkg.conf

Arch Linux

#1 2009-04-20 02:40:47

optimize build

#2 2009-04-20 05:37:29

Re: optimize build

#3 2009-04-20 15:59:58

Re: optimize build

#4 2009-04-20 16:15:45

Re: optimize build

#5 2009-04-20 18:15:05

Re: optimize build

#6 2009-04-20 18:43:31

Re: optimize build

#7 2009-04-20 19:10:05

Re: optimize build

#8 2009-04-20 20:30:07

Re: optimize build

#9 2009-04-20 20:57:00

Re: optimize build

#10 2009-04-20 21:04:01

Re: optimize build

#11 2009-04-20 21:50:24

Re: optimize build

#12 2009-04-20 21:59:13

Re: optimize build

#13 2009-04-22 01:21:13

Re: optimize build

#14 2009-04-24 08:00:26

Re: optimize build

#15 2009-04-28 08:52:42

Re: optimize build

#16 2009-04-28 14:09:33

Re: optimize build

#17 2009-04-28 18:50:57

Re: optimize build

#18 2009-04-29 16:56:28

Re: optimize build

Board footer