After this documentation was released in July 2003, I was approached by Prentice Hall and asked to write a book on the Linux VM under the Bruce Peren's Open Book Series.

The book is available and called simply "Understanding The Linux Virtual Memory Manager". There is a lot of additional material in the book that is not available here, including details on later 2.4 kernels, introductions to 2.6, a whole new chapter on the shared memory filesystem, coverage of TLB management, a lot more code commentary, countless other additions and clarifications and a CD with lots of cool stuff on it. This material (although now dated and lacking in comparison to the book) will remain available although I obviously encourge you to buy the book from your favourite book store :-) . As the book is under the Bruce Perens Open Book Series, it will be available 90 days after appearing on the book shelves which means it is not available right now. When it is available, it will be downloadable from http://www.phptr.com/perens so check there for more information.

To be fully clear, this webpage is not the actual book.

8.3 Freeing A Non-Contiguous Area

Figure 8.3: Call Graph: vfree()

The function vfree() is responsible for freeing a virtual area. It linearly searches the list of vm_structs looking for the desired region and then calls vmfree_area_pages() on the region of memory to be freed.

vmfree_area_pages() is the exact opposite of vmalloc_area_pages(). It walks the page tables freeing up the page table entries and associated pages for the region.