Garbage collector threads are rarely the reason your app performs badly or even runs out of memory. For 99.9% of the cases the cause would be in the application code. Don't expect command-line options that would fix an issue magically.
However, these tools let you track the inner working of your application from the GC point of view. When you experience a memory issue in your JVM process you can use these tools to narrow it down.
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Shai Almog
@shai.almog
Author, DevRel, Blogger, Open Source Hacker, Java Rockstar, Conference Speaker, Instructor and Entrepreneur