Since installing Mac OS X 10.7.3 over a month ago, I have noticed a pattern of what appears to be continual erosion of available RAM on my MacBook over a few days, which continues until the available hard drive space is also diminished. If I take no corrective action, the hard drive space gets consumed and a warning message appears. The corrective action is to restart the machine, upon which the available hard drive space returns to a reasonable value.
I first observed this problem when printing a one-page detailed advertisement in contained in a PDF file using Adobe Reader with a scale to fit option - which slowed down the MacBook to a stop every time and used up the hard drive space. My solution was to use Preview for printing that PDF file.
Even when avoiding the Adobe scale to fit problem, occasionally RAM and then hard drive space got used up and operation was stopped and some “out of memory” message appeared when using other memory intensive applications, such as Adobe Photoshop Elements 10 and Garmin Lifetime Map Updater (GPS) - especially if I had restarted the MacBook more than three days ago or so,
It appears that these applications consume both real memory (RAM) and virtual memory (when my MacBook’s 2 GB RAM is insufficient). It also appears that when these applications are exited normally, they do not return all that memory to the pool for subsequent use by other applications.
I suspect that the disk space used for virtual memory by an application is not completely released on exit, and subsequent use accumulates the unreleased amount of disk space that was used for virtual memory - until the disk space is completely used up.
My strategy is to (1) restart before beginning a seriously memory-intensive task; and (2) occasionally monitor the available hard drive space at the bottom of a Finder window and restart the MacBook if it becomes unexplainably low.
The necessity and success of that second step (in restoring the “available” hard disk space) persuades me that Lion has a virtual memory leakage problem.