Why is my JVM having access to less memory than specified via -Xmx? - Plumbr

Why is my JVM having access to less memory than specified via -Xmx? – Plumbr

February 11, 2015 by Nikita Salnikov-Tarnovski “Hey, can you drop by and take a look at something weird”. This is how I started to look into a support case leading me towards this blog post. The particular problem at hand was related to different tools reporting different numbers about the available memory. In short, one of the engineers was investigating the excessive memory usage of a particular application which, by his knowledge was given 2G of heap to work with. But for whatever reason, the JVM tooling itself seemed to have not made up their mind on how much memory the process really has. For example jconsole guessed the total available heap to be equal to 1,963M while jvisualvm claimed it to be equal to 2,048M. So which one of the tools was correct and why was the other displaying different information? It was indeed weird, especially seeing that the usual suspects were eliminated – the JVM was not pulling any obvious tricks as:

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