Re: Compiling for Athlon
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On Mon, 04 Feb 2002 16:07, Adam Stewart Edgar wrote:
> I was just wondering how hard would it be to take source debs and have
> them recompile with Athlon optimizations. I know all the debates about
> having optimized archs for the i386 family and I agree that having just
> i386 is best but if I chose to say write a script to recompile updated
> packages at night, how difficult would this be?
Pretty easy.
There is an excellent buildd as part of the Hurd project that I used at one
stage. I'm not so sure about the compiler -- pgcc exists but is a bit tricky
to get working, and gcc3.0.3 includes most of its optimisations anyway.
Personally I'd set it up using the hurd's buildd and then running dmirror so
your sources.list can include localhost.
However, is it worth it?
At most you'll see a 10% speed increase.
You'll use up a lot of bandwidth downloading the source packages. Since you
won't want to wait for it to compile packages when you apt-get dist-upgrade
you'll have to be running the buildd every night. You'll use a lot more
bandwidth if you make your packages available ;-)
You'll use heaps of CPU -- forget about doing anything else overnight and
even then you'll need a very grunty machine to keep up with unstable, you
might even need multiple machines depending on the number of packages you've
got installed. On a flash Athlon, KDE takes perhaps 4 hours to compile, I'd
be guessing you'd exceed 12 hours building about once a month. I'm not sure
how well the buildds cope with not keeping up with unstable, I guess pretty
smartly since we still have m68k.
You'll use a lot of disk space. Take your binary installed size and multiply
by 10, that is roughly what you'll need in total, unless you organise the
buildd so it deletes the source after each install.
You'll kill you disk. The amount of reading and writing going on in a buildd
is a lot, and you'd better hope you've got very reliable disks. If you've
got the ram then doing it on a ramdisk should help. It won't significantly
speed things up (linux caches after the first write) but it will save heaps
of writes.
You're essentially duplicating BSD's make world functionality. Since BSD was
designed for this, you're probably better of just installing BSD in the first
place.
But, in terms of effort to set up it isn't too bad, and it would be a pretty
cool thing to do.
Corrin
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