Re: openoffice prelink

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> What do you think about OpenOffices prelinking?
I've not only prelinked my OpenOffice.org but my whole system and I must say,
eh, it works. But I'm not sure how big the gain is, the important thing is that there
is one.

> Does anybody know how it works,
> and is it useful on a live-CD where the machine and the CPU varies? 
I've attached a part of the man page of prelink which describes this (see EOM).
And yes, prelink would be perfectly usable on a live-CD.

> It should probably be included on the CD in some form,
> since if it gets installed on harddrive it might be useful.
Na, one could just do apt-get install prelink.

> What if the prelink was run at live-cd start-up? Would that be useful thinking
> that OO is opened on the live-cd (in demo purpose) maybe only once or twice...?
That can't be done, since prelink has to modify all binaries (and they are read-only).
Prelink would have to be run before the CD creation.

This brings this question to me:
What happened to the idea about installing directly from the
live system without having the original packages available?

*/ Christoffer Sawicki <[email protected]>

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DESCRIPTION
       prelink  is  a  program which modifies ELF shared libraries and ELF dynamically linked binaries, so that the time
       which dynamic linker needs for their relocation at startup significantly decreases and also due to fewer  reloca-
       tions  the  run-time  memory  consumption decreases too (especially number of unshareable pages). Such prelinking
       information is only used if all its dependant libraries have not changed since prelinking, otherwise programs are
       relocated normally.

       prelink  first  collects  ELF binaries which should be prelinked and all the ELF shared libraries they depend on.
       Then it assigns a unique virtual address space slot for each library and relinks the shared library to that  base
       address.   When  the  dynamic  linker  attempts to load such a library, unless that virtual address space slot is
       already occupied, it will map it into the given slot.  After this is done,  prelink  with  the  help  of  dynamic
       linker  resolves  all relocations in the binary or library against its dependant libraries and stores the reloca-
       tions into the ELF object.  It also stores a list of all dependant libraries together with their  checksums  into
       the binary or library.  For binaries, it also computes a list of conflicts (relocations which resolve differently
       in the binary's symbol search scope than in the smaller search scope in which the dependant library was resolved)
       and stores it into a special ELF section.

       At  runtime,  the dynamic linker first checks whether all dependant libraries were successfully mapped into their
       designated address space slots and whether they have not changed since the prelinking was done.   If  all  checks
       are  successful,  the  dynamic  linker just replays the list of conflicts (which is usually significantly shorter
       than total number of relocations) instead of relocating each library.
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