JavaFX 8 Memory leak when Hiding Stage

Question

I have a JavaFX application that minimizes to tray when the X button is pressed. I have been monitoring the application via VisualVM for memory trends.

The weird part is, when the application is open, or minimized to taskbar, the memory is always GCed back to initial memory used. However, when it is minimized to tray (stage.hide(), systemTray.show()), the memory gets GCed, but in an upward trend (leak).

In VisualVM, the Old Gen space keeps going up, and once it hits the max after some time, the application will be unresponsive, and CPU spikes to 80%.

I notice that if I stage.show() on the app by double clicking the tray icon etc, GC will clear everything back to normal. However, if left for prolonged periods, it will simply fail to GC the old gen.

A heap dump shows javafx.scene.Scene#7 and javafx.scene.Node[]#2 as having the most retained space. Both will not appear if the stage is not hidden. Under references, it shows this[] -> dirtyNodes().

this     - value: javafx.scene.Node[] #2 <- dirtyNodes     - class: javafx.scene.Scene, value: javafx.scene.Node[] #2  <- value     - class: javafx.scene.Node$ReadOnlyObjectWrapperManualFire, value:    javafx.scene.Scene #7 

What is causing this and how can I solve this?

Answer 1

I never did find and answer to this. Instead, I would null the node on hide and restore it back on view. For intensive dynamic nodes/multiple nodes I created a hash map to store them in memory.

This has sort of become a habit for me in javafx8 to dispose all graphics and reassign on hide & view from hash map. The extra memory and cpu usage is negligible on modern desktops. Using this method, I have had 0 cpu usage apps and low memory apps (~100m) running when hidden on win8/10.