Performance testing (pass 1)

[Ulrich Drepper]

Panu Matilainen wrote:

> Yeah, I find it rather sickening: MS Office (Word) running in Wine starts AGES 
> before OO even gets around to show the stupid (because it gets in the way) 
> banner.

You're comparing apples and oranges, and I don't mean the programs here.

At a more fundamental level, you cannot compare regular ELF files with
PE files (the latter being that other OS's binary format).  PE has
nothing of the flexibility of ELF, it has direct binding, not much for
the dynamic loader equivalent to do.  And that code is in the kernel.

ELF provides many more possibility, which are all widely used and people
don't want to miss them.  But they come with a price: the dynamic linker
has quite a bit of work to do.  And because this is Unix, that part is
not in the kernel.

Now, if you want to do comparisons do as Ingo and Jakub already said:
compare a fully prelinked system.  In that case we basically have direct
linking.  There is still some overhead but it's minimal.

The problem is to get all applications and DSOs prelink-able.  Jakub has
done a lot of work in this area, especially to get GL working.  The
current code base should be mostly there.  I'm not sure about huge
projects like OO or even mozilla.  You can easily check it by looking at
the output adding

  LD_DEBUG=statistics

to the environment of the program provides.

So, install prelink, have the cron job do its work, and then do some
measurements.

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