You can check the actual real memory usage of an application in Apple’s Activity Monitor (Activity Monitor is available in /Applications/Utilities).
Note that out of 16GB (above), nearly 8GB of memory is being used in one way or another. Here’s your guide to what the terms mean:
- The memory is completely unused.
- The memory is locked down and cannot be shared, or swapped to disk (system software and drivers require Wired memory).
- The memory is actively being used by programs and/or the system software.
- Typically means that the memory has been used to cache disk I/O. This is not a waste, it can greatly speed up some programs, like Photoshop.
- Ignore this; it’s a summary statistic.
- Virtual memory size, Page ins, Page outs, Swap used
- The Page ins and Page outs are useful: ideally these numbers stay a zero (but it’s normal for a small amount of paging to occur). If you see the numbers increasing steadily, install more memory; the system is being forced to swap data from real memory onto disk to share the real memory among programs. Check them before and after a time-consuming task: if they’ve changed more than a few percent, then you almost certainly will benefit from installing more memory. Ignore VM size.
Starting programs, running commands, etc will increase the memory requirements. The Real Memorycolumn is the one that matters—that’s the actual space the program is using in the memory chips.
Monitoring CPU Usage and disk activity
The graphical displays provided by Activity Monitor are excellent. Activity Monitor is found in the Utilities folder under Applications. Drag it into the dock so that it’s always readily available. Especially on dual display systems, it can be left open on the 2nd monitor for conveniently monitoring system performance.