Memory allocation is a fascinating area, ripe in trade-offs and cutting-edge research. In this book, Bill Blunden manages to provide a pretty-good overview of the topic.



It begins with an introduction of the lowest levels - the hardware, namely the CPU memory management unit. Then it goes on to explain how operating systems manage memory - segmentation, paging, virtual memory and what's between them. Next, memory is examined on the programming-language level - compiler-level and heap allocation mechanisms in Fortran, COBOL, Pascal, C and finally Java.



The second part of the book is the practice: the author implements several manual memory management schemes (own implementations of malloc/free) in C++, and compares them in terms of performance and other characteristics (like memory fragmentation). Finally, he implements a couple of simple garbage collectors (reference-counting, and mark-sweep), and in the last chapter of the book also briefly mentions the important topic of sub-allocators (also known as "pools" or "arenas").



Overall, I enjoyed the book. But I do have a few points of (constructive) criticism. First of all, the book is a bit too conversational for such a technical work. It feels like a collection of blog posts, and thus also lacks in depth. For example, the section on memory management of Windows is quite disappointing. As much as I can admire the author's attempt to show his exploration process armed by various tracing and monitoring tools, much of this information is well known and has been described. Instead, I would expect a more thorough presentation of the topic.



The other problem is the C++ code. C++ code in books is a pet peeve of mine - for some reason it tends to be exceptionally bad in most of them, and this book is no exception. I won't go into examples because there are simply too many, so just a word of advice: if you intend to follow through this book actually implementing the code (always a good idea!) read about the algorithms the author describes, but write your own implementation. There's nothing good to learn from the C++ code in this book, so you might as well get some more practice on your own.