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Re: ppc64 port

Greetings,

Benjamin Herrenschmidt wrote:


On Tue, 2004-04-27 at 23:36, Cajus Pollmeier wrote:

Hi!

Just a simple query... I _may_ have a chance to get a ppc64
machine. Is anyone interested in such a port?

It's fun stuff and there seems to be a bunch of interest.


I know that it basically works with the 32 bit binaries, but the
installation is non trivial right now and having no 64 bit code
isn't optimal, too.
Well, the later is not true. 32 bits code tend to run faster than 64 bits code on ppc64. Unlike amd64 where you win by having access to more 
registers, on ppc64, you just end up having to use more instructions to
load a full constant in a register ;)
Well let's be careful here. As there old saying goes, there's lies, damn lies and benchmarks.
Yes some operations on PPC64 are slower than they are on PPC32 but that is not universally true. Given that things are a bit early in the life of PPC64 current performance is not necessarily a prediction of future performance. It's not like everyone is working on ppc32 performance and forgetting ppc64 entirely. 


Overall, we can go the gentoo way, and do a full 64 bits debian
distribution independant from the 32 bits one, or we can simply do like
other distributions do, and I think it makes some sense, is to have a biarch
distribution.

The main lot of packages stays 32 bits.
Let's review where some of the the other distros are at and what they are doing for x86_64 as well. Everyone (and I mean everyone) has the ability to run both 32 bit and 64 bit code. The design choice is what is the "default" mode. IE if a user just calls gcc, are they going to get a 64 bit app, or a 32 bit app. Install something like apache, will it be 64 bit or 32 bit... etc etc. 

1) SuSE SLES 8 for PowerPC64 - Default is 32 bit
2) SuSE SLES 8 for x86_64 - Default is 64 bit
4) Gentoo/ppc64 - Default is 64 bit
5) Gentoo/x86_64 - Default is 64 bit
6) Redhat Enterprise for PowerPC64 - Default is 32 bit
7) Redhat for x86_64 (fedora) - Default 64 bit
8) Redhat exterprise for x86_64 -Default 64 bit

and IIRC Debian x86_64 is 64 bit as well.


But we need a biarch gcc and the 2
libcs. Then, for each libxxxx package, we can build both the ppc and the ppc64
deb and they can be both installed at the same time.

But the first thing to have is a 64 bits kernel. That we really want. For
that, we need to be able to build it. So the first thing that need to be done
is to have a biarch toolchain. gcc 3.4 can be compiled biarch, but doing the
"initial" biarch build is very difficult. 
I wouldn't say that. Tedious yes, difficult no.
Besides, the debian x86_64 folks build bi-arch already. Just grab their build scripts. 

Regards,
Tom
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