Tuning make.conf

[Julius Huang]

Hi,

On Mar 13, 2008, at 18:58 , Luca Presotto wrote:

>> You're *really* wasting your time.
> I supposed that!
>
>
>> Your system is doing no cpu cycles at all for most of
>> the time anyway. [cut]Also, makeopts and -pipe just make  
>> _compiling_ faster, not the
>> applications themselves!!!.
>
> I agree with everything. In any case I think that a faster  
> compiling will really be a good thing.
> I have been reading another time the man of make.conf and I still  
> have some doubts.
> Neither in the example either in the man page there is any  
> reference to "MAKEOPTS". Changing from -j1 to -j3 would really be a  
> huge difference!
>

Isn't -j depend on how many cpu/core and a faster harddisk / raid?

In our small lab we used to install New system on some Very Old SCSI  
for testing (18G SCSI 2 I think).
It takes 2x to 3x more time to build world / kernel than a New SCSI  
Ultra 320 HD on the Same machine no matter what we put in -j.

Faster / Higher IO through put always compile faster.

Also there may be problem buildworld and buildkernel if use -j IIRC,
other method is required to speed up compiler when build world / kernel.
Like not compile everything except what is Really need to be recompile.

> To be able to set this is very important.
> Then I don't want an ultra tweaked make.conf like gentooers do.  
> Just a reasonable one.
> (And you have convinced me, I won't recompile everything. Just to  
> have a good compiling when I will be upgrading)
>
> I have some doubts about the correct syntax, the man is ambiguous  
> in this point.
> If I write CPUTYPE= core2 will it automatically sets all the best  
> safe CFLAGS for my core or just set the -march=core2
> Should my make.conf be  like:
> MAKEOPTS==-j3
> CPUTYPE=core2
> CFLAGS= --O2 -pipe -fno-strict-aliasing
>
> or just:
> MAKEOPTS==-j3
> CPUTYPE=core2
>
> or maybe:
>
> MAKEOPTS==-j3
> CPUTYPE=core2
> CFLAGS+= --O2 -pipe -fno-strict-aliasing
>

I remember seeing some thread in Stable@, Question@, Performance@  
discuss about best CPUTYPE on AMD64 not long ago.

J.H.

>> Please take a look at the following pages, they have a lot more
>> information about this matter ;)
>> http://funroll-loops.info/
>> http://bugs.gentoo.org/show_bug.cgi?id=74072
>
> Actually that's really funny!! I think that's why there are so many  
> pages about gentoo and almost none about other OSes.
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