Re: prelink cron script
Wichert,
Read the glibc 2.3 release notes...
http://sources.redhat.com/ml/libc-alpha/2002-10/msg00048.html
also from the prelink manpage...
-----------------------------------------------------------------------
prelink is a program which modifies ELF shared libraries and ELF dynam-
ically linked binaries, so that the time which dynamic linker needs for
their relocation at startup significantly decreases and also due to
fewer relocations the run-time memory consumption decreases too (espe-
cially number of unshareable pages). Such prelinking information is
only used if all its dependant libraries have not changed since pre-
linking, 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 vir-
tual 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 relocations into
the ELF object. It also stores a list of all dependant libraries
together with their checksums into the binary or library. For bina-
ries, 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.
-----------------------------------------------------------------------
One can prelink a set of directories as defined in /etc/prelink.conf
but that process is rather slow. Redhat is considering using a cron
script approach to check for new files however with the amount of
churn in sid we have that isn't probably the best choice for us.
Redhat has also added postinst prelink scripts to some of their rpms.
Hoever as prelink is pretty system level, it seems to me more appropriate
to just let the user toggle autoprelink on for his machine and then
have both apt-get and dkpg prelink all of these binaries and libs
at install time. That eliminates the need to go hunting for them after
the fact which is much more time-consuming and requires maintaining
lots of timestamps.
Jack
ps I helped test prelink for Jakub on ppclinux and debian ppc sid.
It works really well so far with binaries in sid.
Reply to: