Re: [libdv-dev] Lib status of libdv.

[Daniel K. <ko...@ta...>]

On Tue, Apr 10, 2001 at 10:31:21AM -0700, Charles 'Buck' Krasic wrote:
> In linux, shared libraries are mapped into process space with
> copy-on-write.  If your shared-library doesn't use pic, then a process
> using the library will not achieve any *memory* sharing benefit,
> because the shared library loader touches all places with absolute
> references which in turn triggers copy-on-write page faults for all
> the pages of the library.  You still get the disk space sharing
> benefit, and you get potentially a run-time performance benefit (over
> pic) for CPU intensive code (i.e. libdv).

Umm..., as far as I understood, the ELF loader wasn't capable of
performing such global relocations without the help of a compile-time
generated table, but then this really isn't the area I feel competent
in...

> I don't think it's worth the trouble to make a PIC version of libdv.
> We work so hard to get performance, why through it back for PIC? =20

Well, there's the much greater ease of maintainance with shared libs--
no need to recompile all your apps when the lib has been updated, but
the performance argument is one I very much tend to agree with. At
least now. Maybe it's time to raise this issue again when we're all
running 10 GHz machines that decode DV for breakfast. (Another issue
for me is Debian policy that requires a shared version of each lib
that is packaged, but I might get permitted an exception here.)

> ps I'd be very happy if you make a Debian package for libdv.  I've
>    been a RedHat user for a long time, so I'm not equipped to do it
>    myself.

Debian packages for the current unstable tree are available from

http://antares.tat.physik.uni-tuebingen.de/~kobras/debian/

(sorry, too lazy now to make it apt-able). Once the policy issue
is agreed upon, I intend to include them into the main distribution.
I've submitted all non-Debian-specific patches to SourceForge's
patch tracker already.

Best regards,

Daniel.

--=20
	GNU/Linux Audio Mechanics - http://www.glame.de
              Cutting Edge Office - http://www.c10a02.de
	      GPG Key ID 89BF7E2B - http://www.keyserver.net