Performance issue with systemd-coredump and container process linking 2000 shared libraries.

[Frank Ch. Eigler]

Hi -

> On our side Francois also told me this afternoon that he didn’t
> really reproduce the same thing with my reproducer posted here and
> the real systemd-coredump issue he witnessed live, and also noticed
> that with DEBUGINFOD_URLS unset/set to the empty string my
> reproducer has no problem anymore. [...]

Just doing the math from the debuginfod-client point of view (ignoring
other the later systemd side fix that moots this):

For an application that processes these elf/dwarf files sequentially,
queries for each synthetic solib are going to result in 2000 https-404
transactions, sans debuginfod caching.  If you're lucky (reusing a
dwfl object), elfutils may be able to reuse a long-lived https
connection to a server, otherwise a new https connection might have to
be spun up for each.  But even with reuse, we're talking about 2000
pingponging messages.  That will take a handful of minutes of elapsed
time just by itself.

If the calling code made these queries in parallel batches, it would
be much faster overall.

- FChE