Performance tuning in a garbage collected language is a slightly different skillset, but a lot of tools are the same (knowing how/when/why you allocate memory, the space complexity of your algorithms, etc). Sometimes it is easier, because generally a good GC wants to help, and isn't just an opaque black box but full of information about the memory usage of your app. There are fewer "knobs" to tweak in a GC language, but that doesn't mean "no knobs", and the focus on data structures, data usage, and (space complexity of) algorithms is a shared problem in the performance world, GC language or not. It seems well past time to stop thinking of GC languages as a "problem".