I have a generic question about sketch performance.

I essentially have a window that allows the user to draw lines. I wanted to create a "layering" effect (not comparing the windows pixel array to delete if background pixels < other pixel color) where the users continuously draw layer upon layer of the drawn lines.

I know processing has a garbage collector, but i'm not sure if I am overlooking anything to be concerned about as the window continuously is updated with new lines/ and if anyone has suggestions for optimization. I am running a P2D render/high frame rate.