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Re: Rebuilding Fedora

On Sun, 2004-10-24 at 22:16, Roland Kaeser wrote:

> I would like to thank You all for Your suggestions. But just for a small 
> sample, by all arguments. Try to recomile a samba for a actual CPU 
> plattform. When You run it as it comes with the dist, You will have 
> around 1 MByte/second transfer performance. After recompile its around 6 
> MBytes/second. The same on KDE, Apache etc. It's more than 5% Alan hmm?

Seriously, those numbers sound really suspect. First, on what kind of
computer is Samba CPU-limited to somewhere close to 1 MB/s? That sounds
extremely low; I don't have great statistics, but just opening large
files (10s of megabytes in any case) across a network I get transfer
speeds that are clearly several MB/s on modest hardware. With Red Hat
originated RPMs.

In most cases I sure wouldn't expect most of the network servers to be
limited by processing power at all, at least not on a 100 Mbps network
(I guess some new dynamics might show up using GB ethernet). If you're
really getting such bad performance it sounds like a pretty severe
misconfiguration. Are you sure that you were comparing identically
configured systems?

For Apache, I don't really have any experience with high-volume use of
it, but there are so many things that should be more important than
processor speed (at least for simple loads, with enough server-side
activity maybe processor speed can be critical) it would be extremely
surprising to see a significant speedup from optimizing for a specific
processor. I'm sure that hard data gathered in a well-controlled setting
would be appreciated!

On the KDE front, what programs are you looking at? There may be media
applications out there that don't have different libraries built for the
different processor types, and where you can get MMX/SSE/SSE2
optimizations if you optimize specifically. That's basically an example
of bad software design, at least when you're considering the possibility
of binary distribution. The right way to do it is to automatically load
libraries containing the special codepaths (there's built-in OS support
for this) or doing your own runtime detection. Also, considering that
there aren't all that many codecs shipped with Fedora, what applications
could be showing this?

> But I see, we could discuss weeks about this theme. The only thing i 
> need is a properly howto for recomiling the distribution. Please...

No, really, you're trying to fix some symptoms you're seeing instead of
solving the problem for real. If a Fedora system is really running at
only a fraction of the possible speed it's misconfigured somewhere, or
something is badly broken. If that's the default configuration, it
sounds like a bug to me.

If you still really want to rebuild everything, maybe try to look at
some of the projects that are providing recompiled versions of RHEL?
They have likely figured out a system for how to self-consistently build
the RHEL distributions, and Fedora should have the same base components.
If you know how to build the distributions, changing the default
optimization options should be relatively simple.


Per Bjornsson <perbj stanford edu>
Ph.D. Candidate, Department of Applied Physics, Stanford University

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