How InnoDB performs a checkpoint at Xaprb [by Baron Schwartz {of Perconna, MySQL vendor }
An article about MySQL InnoDB checkpoint-ing mechanism written by Perconna folks. Read comments as well, several PostgreSQL core committers have participated in the discussion.
"InnoDB’s checkpoint algorithm is not well documented. It is too complex to explain in even a long blog post, because to understand checkpoints, you need to understand a lot of other things that InnoDB does. I hope that explaining how InnoDB does checkpoints in high-level terms, with simplifications, will be helpful. A lot of the simplifications are because I do not want to explain the complexities of how the simple rules can be tweaked for optimization purposes, while not violating the ACID guarantees they enforce."