Optimization Techniques for GPU Programming [pdf]
To ones who are interested: "Programming Massively Parallel Processors: A Hands-on Approach" is a great book to learn CUDA programming, and it talks mostly about performance because, after all, GPU is about speed.Unlike normal programming books, it talks a lot about how GPUs work and how the introduced techniques fit in that picture. It's interesting even if you are just curious how a (NVIDIA) GPU works at code-level. Strongly recommended.