garbage collection - Why does the java8 GC not collect for over 11 hours?

Question

Context: 64 bit Oracle Java SE 1.8.0_20-b26

For over 11 hours, my running java8 app has been accumulating objects in the Tenured generation (close to 25%). So, I manually clicked on the Perform GC button in jconsole and you can see the precipitous drop in heap memory on the right of the chart. I don't have any special VM options turned on except for XX:NewRatio=2.

Why does the GC not clean up the tenured generation ?

Answer 1

This is a fully expected and desirable behavior. The JVM has been successfully avoiding a Major GC by performing timely Minor GC's all along. A Minor GC, by definition, does not touch the Tenured Generation, and the key idea behind generational garbage collectors is that precisely this pattern will emerge.

You should be very satisfied with how your application is humming along.