Re: RFC: ldconfig speedup

[Michael Schroeder <mls at suse dot de>]

On Tue, Jun 26, 2007 at 04:28:11PM +0200, Jakub Jelinek wrote:
> On Tue, Jun 26, 2007 at 10:12:14AM +0200, Andreas Jaeger wrote:
> > my colleague Michael Schröder improved ldconfig with an incremental mode
> > using a second cache that records inode number and times of a library
> > and then skips a library if it notices that the library is unchanged.
> > 
> > His patch adds a second cache below the current two ones.  I'm appending
> > his patch - and would like to have your comments on it.  I plan to
> > rework the patch this week and get it ready for inclusion and would
> > therefore need to know what you think about it.
> > 
> > Also, should we add a third cache - or just increase the CACHE_VERSION
> > and change the second cache to include the new data?
> 
> Can't we just stick the extra data into a separate file in /etc, which
> will go along with /etc/ld.so.cache?  This kind of data is only useful
> for ldconfig itself and not for ld.so.  Enlarging it (especially adding
> the data inline into the second cache, but to some extent even appending
> it to the file) will affect ld.so performance.

One file has the advantage that everything stays in sync. The lookup
speed shouldn't change that much, as ld.so uses a binary search
and thus never even looks at the extra data. But there's indeed a
tiny overhead, as the mmap() will map a couple more pages (24K on my
system), but it's just the single mmap call, not the lookup that is
slower.

Cheers,
  Michael.

-- 
Michael Schroeder                                   mls@suse.de
SUSE LINUX Products GmbH, GF Markus Rex, HRB 16746 AG Nuernberg
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