Challenges - Java Flame Graphs Introduction: Fire For Everyone!

I’ve got interested into flame graph and gone through an excellent post Java Flame Graphs Introduction: Fire For Everyone!

I tried the following script:

for i in {1..100}; do
  jstack <pid> >> iloveoldshit.jstk;
  sleep 0.1;
done
cat iloveoldshit.jstk | ./stackcollapse-jstack.pl | ./flamegraph.pl --color=green > jstack-flames.svg

and get the following error:

ERROR: No stack counts found

Being a beginner, I don’t know what happened. So I decided to go through source code. It turned out that stackcollapse-jstack.pl filter out some stacks[¹] with names like:

• C. CompilerThread
• Signal Dispatcher
• Service Thread
• Attach Listener
• epollWait
• socketAccept
• Socket.*accept0
• socketRead0

I run jstack against an idle tomcat. The dump was full of stacks that get filtered out by the script and stackcollapse-jstack.pl returned an empty output.

I managed to get it working by running jstack against a tomcat that’s handling requests.

Footnote