How can I get perf to find symbols in my program

Question

When using perf report, I don't see any symbols for my program, instead I get output like this:

$ perf record /path/to/racket ints.rkt 10000 $ perf report --stdio  # Overhead   Command      Shared Object  Symbol # ........  ........  .................  ...... #     70.06%  ints.rkt  [unknown]          [.] 0x5f99b8             26.28%  ints.rkt  [kernel.kallsyms]  [k] 0xffffffff8103d0ca      3.66%  ints.rkt  perf-32046.map     [.] 0x7f1d9be46650   

Which is fairly uninformative.

The relevant program is built with debugging symbols, and the sysprof tool shows the appropriate symbols, as does Zoom, which I think is using perf under the hood.

Note that this is on x86-64, so the binary is compiled with -fomit-frame-pointer, but that's the case when running under the other tools as well.

Answer 1

This post is already over a year old, but since it came out at the top of my Google search results when I had the same problem, I thought I'd answer it here. After some more searching around, I found the answer given in this related StackOverflow question very helpful. On my Ubuntu Raring system, I then ended up doing the following:

1. Compile my C++ sources with -g (fairly obvious, you need debug symbols)

2. Run perf as

   record -g dwarf -F 97 /path/to/my/program 

   This way perf is able to handle the DWARF 2 debug format, which is the standard format gcc uses on Linux. The -F 97 parameter reduces the sampling rate to 97 Hz. The default sampling rate was apparently too large for my system and resulted in messages like this:

   Warning: Processed 172390 events and lost 126 chunks!  Check IO/CPU overload! 

   and the perf report call afterwards would fail with a segmentation fault. With the reduced sampling rate everything worked out fine.

3. Once the perf.data file has been generated without any errors in the previous step, you can run perf report etc. I personally like the FlameGraph tools to generate SVG visualizations.

4. Other people reported that running

   echo 0 > /proc/sys/kernel/kptr_restrict 

   as root can help as well, if kernel symbols are required.