Question

We are currently developing an application which visualizes huge vector fields (> 250’000) on a sphere/plane in 4D. To speed up the process we are using VBOs for the vertices, normals and colors. To prepare the data before sending down to the GPU we are using Buffers (FloatBuffer, ByteBuffer, etc..).

Some data to the cylinders:
Each cylinder uses 16 * 9 + 16 * 3 = 192 floats -> 192 * 4 Bytes = 768 bytes.

After sending down the vertices we are doing the following cleanup:

// clear all buffers
vertexBufferShell.clear();
indexBufferShell.clear();

vertexBufferShell = null;
indexBufferShell = null;

We have monitored it with JConsole and we found out that the GarbageCollector is not run “correctly”. Even if we switch down the cylinder count, the memory does not get freed up. In the JConsole Monitoring Tool there is a button to Run the GC and if we do that manually it frees up the memory (If we have loaded a huge amount of cylinders and decrease it a lot, sometimes over 600mb gets cleaned by the GC).

Here an image of the JConsole:

Now the question is how can we clean up this Buffers by ourself in the code? Calling the clear method and set the reference to null is not enough. We have also tried to call System.gc() but with no effect. Do you have any idea?

Answer 1

There is any number of reason the memory usage could increase. I would say its not a memory leak unless the memory increases every time you perform this operation. If it only occurs the first time, it may be that this library needs some memory to load.

I suggest you take a heap dump or at least jmap -histo:live before and after to see where the memory increase is.

If you use a memory profiler like VisualVM or YourKit it will show you where and why memory is being retained.