How do you Force Garbage Collection from the Shell?

Question

So I am looking at a heap with jmap on a remote box and I want to force garbage collection on it. How do you do this without popping into jvisualvm or jconsole and friends?<

Answer 1

just:

kill -SIGQUIT <PID>

Answer 2

Addition to user3198490's answer. Running this command might give you the following error message:

$ jcmd 1805 GC.run    
[16:08:01]
1805:
com.sun.tools.attach.AttachNotSupportedException: Unable to open socket file: target process not responding or HotSpot VM not loaded
...

This can be solved with help of this stackoverflow answer

sudo -u <process_owner> jcmd <pid> GC.run

where <process_owner> is the user that runs the process with PID <pid>. You can get both from top or htop

Answer 3

If you are using jolokia with your application, you can trigger a garbage collection with this command:

curl http://localhost:8558/jolokia/exec/java.lang:type=Memory/gc