Can JVisualVM “Heap Dump” button release memory?

Question

i have a very strange problem. I\'m working on an OSGi application, based on Eclipse Equinox; it was developed using OSGi Log Service (Equinox implementation) and now I\'m t

Answer 1

Can "Heap Dump" operation release almost 200 mbs? If yes, WHY?

Yes it can. I haven't studied the code but I am pretty sure it calls HotSpotDiagnosticMXBean.dumpHeap with the second argument set to true (it is the default if you call it form jconsole or the MBeans extension to JVisualVM). In my experience, doing so will trigger an explicit gc before it dumps the heap and that is probably the answer to the "Why?".

Answer 2

Why are you even bothered by GC? If the memory is properly released, there is no need to worry. But if you want to discover what causes heap to grow (even thou it's not a leak), look at this: How can I take a heap dump on Java 5 without garbage collecting first?.