rtld optimizations

[Alexander Kabaev]

On Fri, 28 Jan 2011 00:47:37 +0100
Joerg Sonnenberger <joerg at britannica.bec.de> wrote:

> On Thu, Jan 27, 2011 at 06:24:18PM -0500, Alexander Kabaev wrote:
> > For starters, the number of libraries given binary is linked too is
> > completely and utterly irrelevant :) The change NetBSD guys claims
> > to revolutionize his application startup times only applies to
> > programs that dlopen (read - load dynamically) libraries with long
> > largely identical dependency chains and calls dlsym on them many,
> > many thousand times. I do not think you will find any real app out
> > there that fits this description close enough to actually
> > demonstrate the effect of the change that is distinguishable from
> > the statistical noise. Pressing ^C certainly not precise enough for
> > that.
> 
> (1) The program itself needs to have a large enough number of linked
> libraries.

That is wrong, of course. symlook_needed is only called when dlsym(<real
object handle>, <symbol name>) is called and the number of objects  on
main and global DAGS is very much an irrelevant detail hereirrelevant
here.

> (2) The program needs to dlopen() modules.

Yep.

> (3) The program needs to search for missing symbols often enough.
>
... by means of explicit dlsym() call.
 
> From memory, the real world example that fulfilled all three cases was
> Evolution. (1) and (2) are pretty typical though.
> 
Never claimed otherwise. It is just ones with nested trees deep enough
to matter is what in very short supply. I would be very interested in
seeing the Evolution benchmarked, but I dount very much than even
Evolution will manage to break through statistical noise.

-- 
Alexander Kabaev
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