Comment 5 for bug 501715

I found a few forum threads that seem to be about the same problem but haven't realized it's caused by ureadahead yet:

I'm observing the same thing at work (64-bit) and at home (32-bit). Even when I drop to single user mode with no processes running and unload all kernel modules, the memory usage is still about 300 MB and no indication where the memory is used. Very frustrating.

Since I don't reboot often it took me weeks to make the connection to ureadahead.