SA perf

SA perf collects symbols in CodeCache for perf map ( /tmp/perf-<PID>.map ) via SA.

How to use

Full time profiling

1. Build JVMTI agent

You have to JDK 6 or later.

$ cd agent
$ ant

2. Run driver script

Run saperf-driver.sh . This script runs java via perf record -g with -javaagent:saperf-agent.jar and -XX:-UseCodeCacheFlushing . You have to set JAVA_HOME environment variable.

• I recommend you to set -XX:-UseCodeCacheFlushing because HotSpot will collect unused CodeBlob from CodeCache. Thus perf report might report incorrect symbol(s) if CodeCache flushing is invoked. But this option might occur CodeCache full.

$ export JAVA_HOME=/path/to/jdk
$ ./saperf-driver.sh <options>

<optins> will be passed to java . If you want to run it on JDK 9 or later, you need to pass --jdk9 or --jdk10 to options of saperf-driver.sh

$ ./saperf-driver.sh --jdk9 <options>

$ ./saperf-driver.sh --jdk10 <options>

Partially profiling

Run collector script

You have to set JAVA_HOME environment variable.

$ export JAVA_HOME=/path/to/jdk
$ ./saperf-collector.sh <PID>

If you want to run it on JDK 9, you need to pass --jdk9 to options of saperf-collector.sh

$ ./saperf-collector.sh --jdk9 <PID>

Notes

• SA perf dumps all symbols in CodeCache to /tmp/perf-<PID>.map . So you might lost these files when you restart your machine.
• SA perf collects all symbols through CLHSDB . CLHSDB attaches to target process via ptrace systemcall. So target process will be suspended while collecting data from CodeCache.
• UseCodeCacheFlushing is introduced since 6u21. If you want to profile your app with JDK 6u20 or earlier, please remove this option from saperf-driver.sh .
• If you want to get complete mixed call stack in perf record -g, you need to add -XX:+PreserveFramePointer to java options. However it is introduced since 8u60.
• On JDK 9, saperf-collector.sh collects symbols in CodeCache via jcmd <PID> Compiler.codelist because JDK 9 has a bug JDK-8157947 that CLHSDB cannot load JavaScript. Compiler.codelist cannot collect stub routines. Thus you cannot check stubs in perf report .

License

The GNU Lesser General Public License, version 3.0