Is your Mac running slow? Maybe there are some applications that are eating up all your memory and leaving none for others. The place to check this out is in your Mac’s Activity Monitor, which can be found in Utilities. At the bottom of the interface press the ‘System Memory’ tab.
You’ll see four types of memory: Wired, Active, Inactive, Free. Used is the total of the first three. Add up all four and you get the amount of RAM in your computer (which you can also verify by pressing Apple>About This Mac from the top left of your desktop).
You’ll also see something called VM size. This is the virtual memory in your Mac. Your computer can put it in your RAM or cache it to your hard drive to obtain the best running performance possible. This is called memory allocation. Pages ins and pages outs shows this distribution. For example if I see 879 MB of pages ins in my Activity Monitor, this means this same amount of RAM has been called up by an application.
You’ll notice that free memory is normally quite high right after starting up your Mac. Also, if an application needs some memory it will normally take that which is inactive. The only time you should really worry and think about adding more memory to your machine is if both free and inactive are low.
Activity Monitor isn’t the only application that can inform you on the state of your Mac. Also check out our list of alternative applications for Mac.