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On the ubuntu system monitor there are different types of memory listed: Virtual Memory, Resident Memory, Writeable Memory, Shared Memory & X Server Memory. What are the differences between them, and which reflects the actual RAM usage of the process?

Sorry if it's a newbie question :)

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2 Answers 2

up vote 4 down vote accepted
  • Virtual memory accounts for all the libraries and executable objects that are mapped into your process, as well as your stack space.

  • Resident memory is the amount of memory that is actually in RAM.

  • Writable memory is the amount of address space that your process has allocated with write privileges.

  • Shared memory is memory that may be simultaneously accessed by multiple programs with an intent to provide communication among them or avoid redundant copies.

  • X server memory is the amount used by the X server for the GUI-session.


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What about the column labelled "Memory"? Is that a new column. How is that different from all the other memory columns? It's values seem to be smaller than Resident Memory in most cases. Does that mean that it refers to a processes private memory only? – lsiden Sep 11 at 19:48

Some definitions and wiki pages:


Shared Memory: The amount of shared memory used by a task. It simply reflects memory that could be potentially shared with other processes.

Resident Memory: typically refers to physical RAM installed in the machine

X Server Memory: Self explanatory, the amount of memory the X server is using (X server controls your user interface)

Hope I have clarified some things for you.

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