If you disable pagefile (like I did for some of my servers) and your program mallocs more than what you have in available space (even without ever dirtying a page) you will observe this.

I'm sure that this helps Windows a lot, even if it's not counted as actually used until the page is dirty.

Linux programs very often have virtual addresses many times the amount of physical ram, because there's never been any restriction. It's then very easy to just malloc huge chunks and use what you need and don't care about it too much.

Especially with many "tiny" allocations, python for example has huge sized objects which consume gobs of RAM dynamically, so any long running python process not only fragments memory but ends up having a bunch of objects consuming virtual memory...

idk why I felt the need to rant about this, but it's a difference that I've noted.