[Bug testsuite/10671] semok/twenty.stp takes 15 minutes on slow/low-memory machine

["mjw at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

------- Additional Comments From mjw at redhat dot com  2009-09-22 10:09 -------
(In reply to comment #3)
> Then, random SIGINT/backtraces appear to
> implicate translate.cxx:4740, the call to dwfl_module_address_section().

Yes, this is another case where libdwfl decides to start relocating things just
because we want to get at the section header. In this case we only need the
shdr->sh_size, not the actual data. But there seems to be no way to get that
information, through libdwfl, without triggering a full relocation of the elf file.

This is actually part of a long standing discussion between Roland and myself:
http://sourceware.org/ml/systemtap/2008-q4/msg00597.html
The basic idea is that we try to build up a search table for addresses that can
be mapped to modules, and for that we want to know the size of the module.
Roland feels this should be done differently/isn't needed. But I don't know how
else we can get this working correctly without knowing the module sizes. Note
that it could very well be that the confusion is amplified by the fact that
previous versions of elfutils had some bugs in dwfl_module_relocate_address().
The thread referenced above is mainly about working around that bug.

IMHO, like in the other case, it would be nice if libdwfl would just let us get
at the "raw" elf section header/data without feeling the need to relocate it all
unless we explicitly request it does so.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|semok/twenty.stp takes 15   |semok/twenty.stp takes 15
                   |minutes on slow/low-memorry |minutes on slow/low-memory
                   |machine                     |machine


http://sourceware.org/bugzilla/show_bug.cgi?id=10671

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