Profiling a running Java application in command line

user_221213 0
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I profile running Java applications often with VisualVM but it needs X to run on the machine.

I know I can connect through management port but that will be an offline sampled profiling which is not enough for me.

So I'm looking for a solution with which I can profile the CPU usage of the methods of a running Java application from command-line. It's enough for me to collect data on the server and then the collected data can be analyzed on a different machine.

Update:

It seems I need to be more specific. I want to profile a running Java application from command line, I don't want to stop it and rerun it.

jvm profiling command-line java performance
7 Answers

The most precise profiling can be achieved with https://github.com/jvm-profiling-tools/async-profiler.

This project is a low overhead sampling profiler for Java that does not suffer from Safepoint bias problem. It features HotSpot-specific APIs to collect stack traces and to track memory allocations. The profiler works with OpenJDK, Oracle JDK and other Java runtimes based on HotSpot JVM.

Here is my script to install and run it from command-line:

async-profiler.sh

if [ ! -d profiler ]; then
  mkdir profiler && cd profiler && curl -L https://github.com/jvm-profiling-tools/async-profiler/releases/download/v1.6-ea/async-profiler-1.6-ea-linux-x64.tar.gz | tar xvz
  echo 1 > /proc/sys/kernel/perf_event_paranoid
  echo 0 > /proc/sys/kernel/kptr_restrict
  #apt install openjdk-8-dbg
else
  cd profiler
fi

#jps

./profiler.sh -d 60 -f dump_`date +%Y-%m-%d_%H-%M-%S`.jfr `jps -q`

It assumes that app is run under same user and there is a single java process PID to be listed by jps. Profiling duration is 60 seconds.

No modification of app's startup options or app restart is needed.

GUI for examining dumps is built-in into IntelliJ IDEA Ultimate: https://www.jetbrains.com/help/idea/cpu-profiler.html.

user_6035160

One way to profile an "already started" JVM is to aggregate multiple jstacks taken over time.

You can for instance parse and display them as a FlameGraph (see details at the various answers for that link, I won't redundantly include them here).

user_324530
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