bitisony / perf-map-agent

A java agent to generate method mappings to use with the linux `perf` tool

A java agent to generate /tmp/perf-<pid>.map files for JITted methods for use with perf.

Build

cmake .
make

Use

Use ./perf-java <pid> <options> to create a perf-<pid>.map file for the current state of the JVM and run perf top -p <pid> for this process afterwards. perf-java expects libperfmap.so in the current directory.

Over time the JVM will JIT compile more methods and the perf-<pid>.map file will become stale. You need to rerun perf-java to generate a new and current map.

Note: If perf top still doesn't show any detailled info it's probably because of a permission problem. A common solution is to run the java program as a regular user with the agent enabled and then run a chown root /tmp/perf-<pid>.map to make the file accessible for the root user. Then run perf top as root. The perf-java script tries to do that.

Options

You can add a comma separated list of options to perf-java (or the AttachOnce runner). These options are currently supported:

• unfold: create extra entries for every codeblock inside a method that was inlined from elsewhere (named <inlined_method> in <root_method>)
• msig: include full method signature in the name string
• dottedclass: convert class signature (Ljava/lang/Class;) to the usual class names with segments separated by dots (java.lang.Class). NOTE: this currently breaks coloring when used in combination with flamegraphs.

Disclaimer

I'm not a professional C code writer. The code is very "experimental", and it is e.g. missing checks for error conditions etc.. Use it at your own risk. You have been warned!

License

This library is licensed under GPLv2. See the LICENSE file.