I just landed bug 575667 into mozilla-central which adds more detailed reporting about the memory used by SQLite. Some people have been complaining to me that SQLite is using an awful lot of memory lately. My hunch was that most of this was the page cache (so you don’t have to hit the disk for every read), but with the next nightly those people can see for themselves. Now, instead of just indicating how much memory is being used, about:memory states how much is being used by the page cache and how much other memory is being used by SQLite. We are also planning to split this up more, but are waiting for the SQLite team to provide some APIs first.