What goes into default Debian?

I once tried to make a build system with inferred dependency tracking using fanotify. On paper it's straightforward: fanotify gives a stream of events like "pid P opened file F for reading and G for writing", and from that we infer G depends on F. So we run the build and log all the file accesses and then process the log later and we have at least a rough idea of what file outputs use what other files as inputs. Easy.

Now try this with a build that has 4000 processes opening a million files on a dozen CPU cores. In nonblocking mode, the events can't be dequeued fast enough (there certainly isn't time to resolve filenames), and in blocking mode it dramatically slows down the build.

Same problem for incremental backups: the fanotify monitor plays along for a while, then a lot of files get updated at once and the monitor has to say "nope, can't do it, you'll have to do a full scan to find out what I missed."