You are missing the point here – garbage collected languages (the "allocate it and forget about it" style, not refcounting like Objective-C) require much more memory to perform at the same level as a language where memory is explicitly allocated and deallocated.
Yes, I’m fairly familiar with garbage collectors and these are called tracing GCs. My point is that a big chunk of the system doesn’t use these, so you can’t just put the blame on one thing.
Would one percent be responsible for a system’s bad performance if that is “slow”?
