Verbose or debugging logging for a Spring Boot isn't going to get you garbage collection information. You would need to set the JVM flags to enable garbage collection logging.
-XX:+PrintHeapAtGC -XX:+PrintGCDetails -XX:+PrintGCTimeStamps
You can also add `-Xloggc:/path/to/file.log` if you'd like to write the information to a file. Otherwise it just goes to STDOUT.
Where you put the JVM flags entirely depends on where you are running your app and how you are starting it up.
Hope that helps!