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 stringdottedclass: 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.