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If I go to task manager, I saw where all they go

enter image description here

Notice show processes from all users are ticked.

Now I have 8GB memory. If you look the above picture, the "greediest" program use at most 300mb of memory. So the the total is at most 2 GB. Yet if I look at the graph, task manager said I am using 7GB.

enter image description here

Note: Before answering, please try this in your computer first. Chance is the same problem is in your computer too all along. I have this issues in all of my computers running windows 7. It seems to be behavior rather than a bug.

The issue is basically this. There is a discrepancy between memory used by processes and memory used total. I just want some explanation. Some says memory commit but I want to see detail to strengthen my faith.

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Okay most of the answer says it's standard behavior. Good. Where can I learn more about it? I want detail. Cache. Caching what? – Jim Thio Aug 22 '12 at 4:19
up vote 3 down vote accepted

First of all, there is a lot of caching going on on all current (and older) windows systems that is not listed as processes in the taskmanager. You don't have any disadvantages of this.

From your tasklist I assume that you have one or several tools running which are sharing an instance of mongo-db. If this is an in-memory database, then this might be the thing that eats up your memory. You can track this down if you completely restart your system and then start the programs you are normally running, while watching the resource-monitor.

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well, even if mongodb is an in-memory database, which it isn't, why shouldn't it show up on process? – Jim Thio Aug 21 '12 at 10:37
There might be some strange kind of program behavior where database software does not show up correctly in the task-manager. For further investigation, you might want to use the Process-explorer – Michael K Aug 21 '12 at 10:40
Actually why not do it in your own computer. Chance is you have the same problem as I do. – Jim Thio Aug 21 '12 at 10:43
By having a look at the Process Explorer on my computer, I see processes using an overall of ~1GB memory. My system commit size is at 3,1GB and the used physical memory is at 2,7GB. Seems fine to me. What is using my memory? The system commit, like I said mostly consits of cached things and most of it is loaded into the RAM for fast access. – Michael K Aug 21 '12 at 10:47
At the time you took the screenshot, what was using your cpu that much? It is very likely that the same programs are using a lot of your memory, except you were running some kind of cpu stress test. – Michael K Aug 21 '12 at 10:48

Try this instead.

Open Task Manager, change to the 'Performance' tab, click 'Resource Monitor' then change to the 'Memory' tab.

I find this gives more in-depth information on what services, programs, etc. are using memory. See if you can identify the cause.

Do you have Microsoft SQL server installed?

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Thanks for the info upvoted. Why don't you try it yourself on your computer. The reason I said this is because the problem is still there on that resource monitor. – Jim Thio Aug 21 '12 at 10:38
Do you have MS SQL installed? – 0x0000001E Aug 21 '12 at 10:45
No. Actually other computers and other answerers report the same issue. The other answer says it's system commit or something. Please try that on your computer and you too will see differences between total memory used by processes and total memory used. – Jim Thio Aug 21 '12 at 10:51
@JimThio Maybe my answer was not clear enough. What you experience is standard behavior. Default. Normal. Have a look at any Windows 7 machine and try to add up the numbers. Also, you definitely want this behavior, because without massive caching, you system would run slow as a snail. You don't have any disadvantages of this, because if memory is needed for non-cached stuff, the cached memory will be overwritten. – Michael K Aug 21 '12 at 12:23
What is being cached in the memory and where can I learn more of it? – Jim Thio Aug 21 '12 at 15:07

The graph is showing the memory used by the system cache in addition to your process memory. System cache does not show up as memory used by processes.

See Microsoft's explanation of File Caching.

Windows is putting your free memory to good use by prefetching data from disk, based on some proprietary heuristics. There is nothing wrong with your system, and your system will actually perform better with this behavior.

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Why the downvotes? – Jim Thio Apr 3 '13 at 3:47
I didn't downvote anything? – M. Dudley Apr 3 '13 at 11:59

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