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.

1.1 General Kernel Literature

The second edition of Understanding the Linux Kernel was published in February 2003. It covers kernel 2.4.18 which contains a VM very similar to 2.4.20 that is discussed in this thesis. As it provides excellent coverage of the kernel, it deserves further discussion as a basis of comparison to this thesis.

First, the book tries to address the entire kernel and, while comprehensive, it misses VM details which are not of general interest. For example, it is detailed here why ZONE_ NORMAL is exactly 896MiB and exactly how per-cpu caches are implemented. Other aspects of the VM, such as the boot memory allocator, which are not of general kernel interest, are addressed by this thesis. In this thesis, the kernel is discussed entirely from the perspective of the VM alone and includes many subtle details that are missed by other literature.

Secondly, this thesis discusses the theory as well as the implementation so that a researcher can follow the origin of the idea rather than possible mistaking the implementation as being unique to Linux. By understanding the underlying idea behind an implementation, the reader can build a conceptual model of what to expect making the deciphering of the code much simpler.

Finally, this thesis includes a line by line code commentary to cover even the smallest details of the VM. This type of minutiae are not covered in general books as the reader would be overwhelmed with detail. Even a reader with a very strong conceptual model of the VM may encounter difficulties when examining the actual code which is a hurdle that this thesis helps them to overcome. Previously, researchers were required to read the source to find out many of these details which is why specialised research such as this thesis is needed. With a clear and complete understanding of this thesis, later VMs can be analysed and understood in a matter of days.