[FFmpeg-devel] [PATCH] NellyMoser audio decoder

Michael Niedermayer michaelni
Wed Sep 12 02:57:37 CEST 2007


On Wed, Sep 12, 2007 at 02:43:10AM +0200, Michael Niedermayer wrote:
> > > (no i dont know of any such kernel but its possible in principle and would
> > > render shared libs even less usefull then they already are which would be a
> > > good thing)
> > 
> > Nope, it won't. Modules from static libs will not be in the same
> > page-boundary-relative locations in different binaries; moreover, only
> > the needed .o files will be included, and they'll each be patched with
> > different relocations. I don't see any way this could work..
> it can work if big things are aligned relative to pages ...
> and about relocations, i think there would be plenty of pages which contain
> none ...

also if you take an application like mencoder and run it twice with the same
input file (like for encoding on a system with several CPUs) then there will
be a very large amount of identical pages which you cannot share by any
amount of hardcoding tables
the same applies to lets say 2 instances of mutt looking at the same folder

but i suspect that even 2 mplayer/mencoder with different input files would
end up with quite a few identical pages which are not simple tables or
directly part of the object files
an example would be tables generated depening on user parameters, coefficient
tables for audio resampling which depend on input and output frequencies
similarely for video/imag rescaling

i really do thing theres a significant oppertunity to free up memory by
having the kernel/or a admin tool search and eliminate identical pages
which cannot be reached by any amount of hardcoded tables or shared libs

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Thouse who are best at talking, realize last or never when they are wrong.
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