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