Question about memory management

About OS X Memory Management and Usage

Reading system memory usage in Activity Monitor

Memory Management in Mac OS X

Performance Guidelines- Memory Management in Mac OS X

A detailed look at memory usage in OS X

Understanding top output in the Terminal

The amount of available RAM for applications is the sum of Free RAM and Inactive RAM. This will change as applications are opened and closed or change from active to inactive status. The Swap figure represents an estimate of the total amount of swap space required for VM if used, but does not necessarily indicate the actual size of the existing swap file. If you are really in need of more RAM that would be indicated by how frequently the system uses VM. If you open the Terminal and run the top command at the prompt you will find information reported on Pageins () and Pageouts (). Pageouts () is the important figure. If the value in the parentheses is 0 (zero) then OS X is not making instantaneous use of VM which means you have adequate physical RAM for the system with the applications you have loaded. If the figure in parentheses is running positive and your hard drive is constantly being used (thrashing) then you need more physical RAM.

Adding RAM only makes it possible to run more programs concurrently. It doesn't speed up the computer nor make games run faster. What it can do is prevent the system from having to use disk-based VM when it runs out of RAM because you are trying to run too many applications concurrently or using applications that are extremely RAM dependent. It will improve the performance of applications that run mostly in RAM or when loading programs.

Graffspree wrote:

Does memory manageemnt not kick in until memory is needed? Will it just susupend more and more until it needs to free RAM?

Memory management is always required sinc eyou are always using memory one way or another. Below is a link to an apple doc to help you understand how you could use your Activity Monitor (in Utilities) to understand the various memory info displayed:

Using Activity Monitor to read System Memory and determine how much RAM is being used

A lot of the Inactive memory is actually "Cached" data from your disk, so that if possible the OS can just reactive the inactive memory instead of doing a slow I/O reading the data from disk.

Another way to look at it is, if you just spent all that money for RAM, you would want your Mac to use it, so using it as cache is a way to give you your money's worth. Free RAM is wasted RAM.