title: Release Java Heap Sapce
body: <p>I have an issue with java performance. I tried using GC1 but it didn't make things great. My only question is why the JVM keeps the java heap space even if it's not used ?
  As you can see in the picture first the batch work finish around 10:30 but the garbage collector wasn't triggered to clean. So I did it manually at 10:52 then the used space was freed but heap (8GB) is still allocated by the JVM. Why ?
  <a href="https://i.stack.imgur.com/EOmcS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/EOmcS.png" alt="Java Memory Problem"></a></p>