Taskmanager and memory usage

Question

I'm a little bit confused about task manager and usage memory.

My question is:

the sum of all memory process is equal to physical memory used?

This is a picture of my task manager order by memory usage high to low:

http://imageshack.us/photo/my-images/525/immaginengq.png/

And this is the screen pf physical memory used in the same time:

http://imageshack.us/photo/my-images/13/immagine2vs.png/

But... the sum of all memory process is less then ~11 GB show in the second picture...

What's the true?

PS. Sorry for my bad english and thanks in advance

EDIT: OS is windows server 2003 enterprise edition 64bit (running on a virtual machine with 4 cpu and 24 GB ram)

Answer 1

Windows Vista and 7 will cache a certain amount of memory in case it needs to be used later. Thus, the total of all running processes can often be less than the memory actually being used. See techrepublic. As far as I know, Windows XP reported pretty much just actual usage.

Answer 2

Memory that contains useful information (such as the contents of files) is used, even if it's not currently being used by any running process.

Answer 3

There is an overlap in memory used by your applications. When an application is using a DLL, which is a shared library, the library is loaded into the physical memory only once, but every application using it sees an increase in its own memory usage. The Wikipedia article on shared libraries explains memory sharing quite well.

I see that your Windows is not in English, but if you try to translate the fields, I hope this information will help (taken from my Windows 7). The resource monitor can display working set, shareable memory and private memory for each process. Shareable memory and private memory are both combined into the working set of the application. Resident set is part of working set which is in physical memory (RAM) as opposed to being swapped on the hard drive.

So each shared library contributes towards the shareable memory of each application, which is a part of the working set. You have added up all working sets of all applications, I believe.