For a start, don't try to draw 3 million tiles on a screen that's likely to have around 2 million pixels. I'm guessing most of those tiles are off-screen, and

For a start, don't try to draw 3 million tiles on a screen that's likely to have around 2 million pixels. I'm guessing most of those tiles are off-screen, and you're creating a mesh for an entire game level, not just the visible area?