Bug#911815: /usr/bin/perf_4.18: Please build perf against libbfd

["Steinar H. Gunderson" <sesse@debian.org>]

On Fri, Oct 26, 2018 at 01:12:51AM +0100, Ben Hutchings wrote:
> For future reference, that's the comment:
> 
> # perf can link against libbfd if available, but the result is
> # undistributable as they are licenced under GPL v2 and v3+
> # respectively.  Override detection of libbfd and insist that
> # cplus_demangle() can be found in libiberty (LGPL v2.1+).
> 
> Tagging this wontfix since we can't fix that problem.

But we can probably make the addr2line solution much faster?
perf runs:

        scnprintf(cmd, sizeof(cmd), "addr2line -e %s %016"PRIx64,
                  dso_name, addr);

        fp = popen(cmd, "r");

but the normal way of running addr2line is to run it and then start feeding
it addresses on stdin (ie. don't start the program anew for each and every
address we want to look up). I haven't tried, but it sounds like that would
reduce overhead significantly?

I also don't know if there's a cache somewhere in front of this? It seems to
look up the same addresses over and over and over again, at least in my case
(decoding a processor trace).

/* Steinar */
-- 
Homepage: https://www.sesse.net/