It appears there is a memory leak somewhere. I had 2 firefox windows (1
process), with about 25 tabs, and memory usage was showing about 240MB.
Closing some windows, including 1 or 2 with big web-accessed pdf files,
to a point where only about 10 tabs were open in 1 windows didn't
decrease it much. Exiting from the process, and re-launching it,
decreased total memory usage by about 320MB. If i were to guess, it
would be PDF plug-in, but it could also be something more generic. The
tabs in the first window that stayed thruout were open for about a month.
Just a note, in case someone wants to look into it.