P4 2.8 HT Optimizations

genfool · n00b Joined: 20 Jul 2004 Posts: 24

I'm starting a new, clean install; I want to get it right. But I have a question. What optimizations can I make inside the make.conf?

Right now it's at:

CFLAGS="-O3 -mcpu=i686 -fomit-frame-pointer"
CHOST="i386-pc-linux-gnu"
CXXFLAGS="${CFLAGS}"

What can I do to optimize this as much as possible? I also don't know what the deal is with the sub architectures. I know my CPU is under x86, but I don't know what sub arch it's under. I want to optomize as much as possible, even if I don't really know what they mean just as long as they work well. BTW I read that -O2 or something already enable -fomit-frame-pointer, so why is -fomit-frame-pointer paired up with it? Isn't that repetetive?

edit: I printed out the book so that I don't hurt myself (104pp gg).

GentooBox · Veteran Joined: 22 Jun 2003 Posts: 1168 Location: Denmark

is it a stage1 ?

you should go with this if its a stage1:

genfool · n00b Joined: 20 Jul 2004 Posts: 24

It's stage 1. I read in some GCC manual that -O enables -fomit-frame-pointer, -O2 does what -O does, but with more optimizations, and -O3 has even more optimizations.

From GNU

"-O turns on the following optimization flags:

-fdefer-pop
-fmerge-constants
-fthread-jumps
-floop-optimize
-fif-conversion
-fif-conversion2
-fdelayed-branch
-fguess-branch-probability
-fcprop-registers

-O also turns on -fomit-frame-pointer on machines where doing so does not interfere with debugging."

Why shouldn't I use -O3? I'm not trying to go against your word, but I'm just curious why I should use -O2 instead.

Also, I've been looking for a site that would have information on most, if not all, architectures and sub archs that categorizes the processors.

I have HT technology, so should I have chosen smp kernel at boot, or was the default gentoo kernel fine? Is this kernel just the temporary kernel to run the installation, and the one I compile later is the permanent?

All help appreciated. Thanks.

Esben · Posted: Wed Jul 21, 2004 3:57 pm Post subject:

-O3 is not neccessarily faster than -O2; and some swear by -Os. -O2 is a safe maiddle road. Besides, sometimes things break at -O3, while the others are relative safe.

I would also add

GentooBox · Veteran Joined: 22 Jun 2003 Posts: 1168 Location: Denmark

genfool · n00b Joined: 20 Jul 2004 Posts: 24

I'm already booted in the "gentoo" kerenel or default kernel, so should I restart and choose smp kernel? Smp kernel is the kernel I used last time I installed. Hmm... The reason why I chose the gentoo kernel at boot was because it has a higher resolution plus a pretty decent bg, but I can easily restart at this point. Should I? Also, there was the code "mcpu=i686" and I was just wondering what that was for. Do you know any sites that have all those architectures/sub architectures? Thanks for the help so far; I'll probably use -O2.

Oh yeah, I guess I might as well ask this now. Okay, I'm probably just gonna reboot with SMP kernel (does it really make a difference?), but I was wondering how can I make myself a seperate partition for my home folder and then activate it? I have a boot, swap, and root partition right now.

Also.. MAKEOPTS="-j3" enables HT?

Esben · Posted: Wed Jul 21, 2004 5:24 pm Post subject:

MAKEOPT="-j3" enable make in parallel... which is an advantage if you have a multicore CPU as you do

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True trade is honest, but not merciful. Politics is dishonest, no matter how merciful... and war is neither honest nor merciful.... therefore, choose trade above politics, but politics above war.

genfool · n00b Joined: 20 Jul 2004 Posts: 24

Alright thanks for all the replies. Well I'm pretty impatient so I decided to boot into SMP kernel since it was no big, and I decided to try and make a /home partition. So now I have 4 partitions total.

/dev/hda1 is boot
/dev/hda2 is swap
/dev/hda3 is root
/dev/hda4 is home (I hope)

I saw that I had to mkdir for my boot and my root ie "mkdir /mnt/gentoo/boot" and then mount it with command "mount /dev/hda1 /mnt/gentoo/boot". So I decided to do that with home (I'm guessing as best as I can.) "mkdir /mnt/gentoo/home && mount /dev/hda4 /mnt/gentoo/home". Did I do it right? And why don't I have to mkdir for /mnt/gentoo?

Just incase you don't see my last post.. What's -mcpu=i686? Should I leave this out?

Esben · Posted: Wed Jul 21, 2004 6:55 pm Post subject:

The mounting stuff looks fine to me :-D

Remember to update the /etc/fstab with the /home partition when the guide tells you too...

-mcpu=i686 was the pre-3.0 cpu-switch, if I recall correctly. It has been supplanted with something like -mcpu=pentium4. Since you're probably not going to change the CPU on your box, you might as well use the -march=pentium4, which will enable the pentium4-specific instruction (-mcpu merely optimizes the instruction layout for a cputype).

If you really want to know more, you really should search. All you ask have been answered countless of times in these forums if you look...there is a lot more there than I can tell you

_________________
regards, Esben
True trade is honest, but not merciful. Politics is dishonest, no matter how merciful... and war is neither honest nor merciful.... therefore, choose trade above politics, but politics above war.

Beelzebubba · n00b Joined: 10 Dec 2003 Posts: 23 Location: Bologna (IT)

I have same processor as you, here is my cflags:

GentooBox · Veteran Joined: 22 Jun 2003 Posts: 1168 Location: Denmark

genfool · n00b Joined: 20 Jul 2004 Posts: 24

Nice. Thanks for all your replies. I was wondering what is this acovea that I've been reading about on the forums. It's a benchmark that shows what cflags should be turned on for your system? Do I use "emerge acovea" and it will install just like that, then do I have to config and make? I'm not sure what to do here, and I don't even know what ebuilds are although I'm starting to think they are really important. Sorry for all these questions. I just emerged system and I'm waiting for it to finish... So if I change my cflags, how can I re-optimize my system "emerge system" again?

GentooBox · Veteran Joined: 22 Jun 2003 Posts: 1168 Location: Denmark

GentooBox · Veteran Joined: 22 Jun 2003 Posts: 1168 Location: Denmark

oh, and yes, just do "emerge acovea" and emerge will download and install acovea for you.
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genfool · n00b Joined: 20 Jul 2004 Posts: 24

Awsome! Yeah, I understood what you said. I was just wondering how I figure out what version of GCC I have. I'm just guessing I have 3.4? Anyways, isn't the "scripts/bootstrap.sh" command the part that builds my compiler? I was going to try and get acovea earlier, but I'm still in the process of installing my gentoo, so I don't know if I have GCC yet, or if I can even use Acovea yet. If at all possible it would be nice if I could update my system with these new cflags after benchmarking. Is it possible? Thanks for all the help; been great.

edit

Okay, I still don't know what GCC version I have, but I was able to find "emerge -e world", so I guess I can just do that once I change my cflags.

ronnie · n00b Joined: 21 Jul 2004 Posts: 66

n3mo · Posted: Thu Jul 22, 2004 4:33 pm Post subject:

I think you could also use

GentooBox · Veteran Joined: 22 Jun 2003 Posts: 1168 Location: Denmark

taskara · Posted: Thu Aug 19, 2004 7:30 am Post subject:

hey mate,

you probably also want to look at this:

https://forums.gentoo.org/viewtopic.php?t=169054

It is a howto on getting your system happening with 2.6 headers and nptl (native posix threading library).

native posix is the fastest threading library around, and will help your p4 cpu.

You won't be able to test acovea on your pc until you actually have gentoo installed - so do one first.

I'd recommend staying with gcc 3.3.x atm if you want a smooth sailing system - but I personally use gcc 3.4.1.

Some (only a few these days) don't emerge with gcc 3.4

ATM I'd stick with

Esben · Posted: Thu Aug 19, 2004 2:40 pm Post subject:

taskara · Posted: Thu Aug 19, 2004 10:19 pm Post subject:

Ok thanks Esben - I'll have to start using that on my P4 too

What if you have a single cpu? should you use -j2?

Or is it only for "smp"?

cheers
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Esben · Posted: Fri Aug 20, 2004 7:50 am Post subject:

taskara · Posted: Fri Aug 20, 2004 8:01 am Post subject:

IC.. cheers

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