Nah, that's not it, I measure the CPU & GPU work separately, and 15ms happens between the kernel invocations. It also happens when I don't print out text. Than

Nah, that's not it, I measure the CPU & GPU work separately, and 15ms happens between the kernel invocations. It also happens when I don't print out text. Thanks for the idea though! I treat it as the first community contribution :D