It talks about how a simple malloc implementation would doll out entries in a buffer of memory and manage free lists, but not how the implementation actually gets that buffer from the operating system, or return it to the system when done (mmap, munmap, for example).
I made a deliberate choice to not include that, mostly due to post size/complexity reasons. I decided that the focus of the piece was going to be on the task of effectively managing the memory you have in the face of calls to malloc/free. I decided against talking about any environment-specific information (brk, mmap, cache locality, multithreading, etc.)
May not have been the right call, but it kept the length fairly reasonable and I think it gives people enough of a nudge to dip their toes into the playground if they have time.
If you check the HTML comments on the page you'll find quite a lot of cut content. I wanted to do deep dives on real-world malloc implementations, but it ended up being very difficult to cover without making the post take over an hour to read.
