What's the distinction in between Real, Virtual, Shared, and also Private Memory?

The various columns in Activity Monitor are a little complex

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2019-05-07 09:05:38
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Real mem connects to physical memory (real RAM components in your computer system). Digital Mem is just how much "phony" memory is alloted to the process, suggesting memory that is alloted on the irreversible storage space tool (disk drive, strong state drive, etc) for that process. Shared memory is physical (Real) memory that can be shown to various other procedures. Exclusive memory is "actual" memory that can just be made use of by the process it is alloted to.

These descriptions might aid too ... straight from activity monitor - - > aid - - > watching system memory use:

Here is a description of several of the details presented at the end of the memory pane:

  • Wired : Wired memory has details that has to constantly remain in RAM
  • Active : Active memory which contains details that is proactively being made use of.
  • Non-active : Inactive memory has details that is not proactively being made use of. Leaving this details in RAM is to your benefit if you (or a customer of your computer system) return to it later on.
  • Made use of : Used memory is being made use of by a process or by the system. Made use of memory is the amount of wired, energetic, and also non-active memory. If the system calls for memory it takes free memory prior to made use of memory.
  • Free : Free memory is not being made use of and also is quickly readily available.
  • VM dimension : Virtual memory, or VM, is hard drive space that can be made use of as memory. VM dimension is the quantity of disk space being made use of as memory. Mac OS X can make use of even more memory than the quantity of physical RAM you have. A hard drive is a lot slower than RAM, so the digital memory system instantly disperses details in between disk space and also RAM for reliable efficiency. Web page ins/outs : The variety of gigabytes of details Mac OS X has relocated in between RAM and also disk space
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2019-05-09 06:56:38
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Taken from my solution at Server Fault:

Mac OS X Memory Jargon:

Wired : This describes bit code and also such. Memory that needs to never be vacated the RAM. Additionally called resident memory.

Shared : Memory that is shared in between 2 or even more procedures. Both procedures would certainly show this quantity of memory so it can be a little bit deceptive regarding just how much memory is in fact in operation.

Actual : This is the "actual" memory use for an application as reported by task_info () - a harsh matter of the variety of physical web pages that the existing procedure has. (RSIZE)

Private : This is memory that a procedure is making use of only by itself that is made use of in Resident memory. (RPRVT)

Virtual : The complete quantity of address room while doing so that's mapped to anything - whether that's a randomly huge room for variables or anything - it does not relate to real VM usage. (VSIZE)

Active : Memory presently classified as energetic and also is made use of RAM.

Non-active : "Inactive memory is no more being made use of and also has actually been cached to disk. It will certainly continue to be in RAM till an additional application requires the room. Leaving this details in RAM is to your benefit if you (or a customer of your computer system) return to it later on." - Mac OS X Help

Free : The quantity of RAM in fact readily available with no information.


The most effective documents I recognize of (and also have actually had the ability to locate in followup study) is Apple's very own Managing Memory write-up on their programmer internet site.

Various other rewarding resources : Darwin - dev newsletter : [1 ], [2 ] and also an old write-up on MacOSXHints. In Addition Mike Ash has actually uploaded an excellent nonprofessional's intro on his blog

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2019-05-09 01:38:33
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