gistfile1.md

I’d read Poul Henning Kamp’s amusing ‘what’s wrong with 1975 programming‘ rant (also, take a gander at this unrelated but good article by the same chap) and suddenly had a brainwave: linux implements ‘copy on write’ semantics for memory blocks when a process forks. That means that my database could just ‘fork’ when it wanted to save a checkpoint. The child process gets an unchanging copy of all of the memory, just for the cost of a page-table copy in the OS; any writes in the parent process just cause the OS to do all the work for us, and duplicate the pages that are changing. The child can checkpoint at its leisure.