[bno1]

That's most likely reserved virtual memory. It's not committed, meaning it's not backed by physical memory.

[pojzon]

From what I could check those are all memory mapped files.

Required simply by ZGC to work, but still its super confusing and convoluted and our tooling is not aware of that at all.

[bno1]

Well yes, because on Linux you use mmap to reserve virtual memory.

I wouldn't say that tooling is not aware of all that. For example, top and htop display virtual memory and resident memory and shared memory. You need to look at resident memory if you want to know physical memory usage.