jart is a genius. What they’ve done with Blink, Cosmopolitan C, Redbean, and now llama.cpp is incredible. It gives me hope for the future of systems/low-level programming.
As you can see from comments up this thread (ref. various GitHub issues) - the people "gluing mmap" don't actually have a single clue. They can't properly measure memory consumption (they don't understand what the numbers they're seeing actually mean). They don't understand how paging, swapping or virtual memory work. They don't actually understand the concept of memory-mapped files, why they're there and how they work. They can't explain why their code behaves differently when using memory-mapped files.
Moments like this are here to remind you that there's actual knowledge and skill to building scalable and efficient software, and that hustling and copy-pasting StackOverflow examples will only get you so-far, as will "piecing together dataframe pipelines" in Python.
The trick she did overriding malloc & friends to validate that the optimization would be worth doing is, in my mind, one of the high-points of the paper. It's a very clever way of making a meaningful measurement, which was the keystone of the entire change.
I've never heard of, thought of, or used that trick, and the fact she had it in her arsenal to apply to this very specific situation is pretty impressive, to me at least.
Hopefully we should publicize this kind of achievement as a way to teach more devs about mmap... (this really should be common knowledge)