Activity Monitor: View system memory usage

View system memory usage

With Activity Monitor, you can view how Mac OS X allocates memory to different applications and how it uses virtual memory. You can view detailed information and a graph in the Activity Monitor Window. Or you can view just a graph in Activity Monitor’s Dock icon

Because of virtual memory, which is hard disk space used as memory, Mac OS X can use more memory than the amount of physical RAM you have. A hard disk is much slower than RAM, so your Mac runs more efficiently if you have enough RAM for your everyday activities. You can use Activity Monitor to make sure it does.

See system memory usage in the Activity Monitor window

You can view detailed information about system memory usage in the Activity Monitor Window

  1. Open Activity Monitor, in the Utilities folder in Launchpad.
  2. Click System Memory at the bottom of the Activity Monitor window.

    The following information is displayed:

    Option Description
    Free: Free memory is not being used and is immediately available.
    Wired: Wired memory contains information that must always stay in RAM.
    Active: Active memory contains information that is actively being used.
    Inactive: Inactive memory contains information that is not actively being used. Leaving this information in RAM is to your advantage if you (or a client of your computer) come back to it later.
    Used: Used memory is being used by a process or by the system. It’s the sum of wired, active, and inactive memory. If the system requires memory, it takes free memory before used memory.
    VM size: VM size is the total amount of virtual memory space reserved by the Mac OS X and your applications. The actual amount of virtual memory being used is likely to be much less, because Mac OS X and applications frequently reserve virtual memory space that they don’t use.
    Page ins: The amount of information copied from your hard disk to RAM. The numbers in parentheses are the rate at which information is currently being copied.
    Page outs: The amount of information copied from RAM to your hard disk. The number in parentheses is the rate at which the information is currently being copied. If your computer is performing its normal workload and that rate is above zero, adding RAM to your computer might improve performance.
    Swap used: The amount of hard disk space currently being used as virtual memory.

See the system memory usage in the Dock

You can see a graph of your computer’s system memory usage in Activity Monitor’s Dock icon.

  1. Open Activity Monitor, in the Utilities folder in Launchpad.
  2. Choose View > Dock Icon > Show Memory Usage.

Change the color of items in the graph

In the Activity Monitor window, you can change the colors used in the system memory usage graph. The colors are used in the graphs in the Activity Monitor window and in Activity Monitor’s Dock icon.

  1. Open Activity Monitor, in the Utilities folder in Launchpad.
  2. Click System Memory in the bar at the bottom of the Activity Monitor window.
  3. Click the color box next to each item.
Last Modified: May 8, 2012
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