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My work computer (Windows 7 64-bit) spends a lot of time swapping memory when I switch between programs. This surprises me since I have 4 GB of RAM, and the programs I use aren't particularly RAM hungry (Outlook, Emacs, p4win, Firefox, various build tools). I downloaded RAMMap, and it shows over a gigabyte of memory used by "Metafile".

From the Sysinternals blog:

Metafile is part of the system cache and consists of NTFS metadata. NTFS metadata includes the MFT as well as the other various NTFS metadata files. ... In the MFT each file attribute record takes 1k and each file has at least one attribute record. Add to this the other NTFS metadata files and you can see why the Metafile category can grow quite large on servers with lots of files.

So I understand what the "Metafile" data is... I work on large builds comprising hundreds of thousands of files (none are that big, but they add up to several gigabytes). My question is how can I reduce the amount of memory used by "Metafile"? I'm not actively using all those files at once, so why does Windows need to keep info in RAM? Restarting my machine every time I sync a new build is really annoying.

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Builds are IO intensive, and thus Windows is keeping a large file system cache to improve performance. Unfortunately, build tools also use a lot of memory too and usually in large spikes, which is probably causing the swamping. As this is competing against the system cache. The best solution might be to add more memory. – tgiphil Jan 17 '11 at 18:42
@tgiphil, It's understandable that a lot of memory is used when checking out or making the build. However, it's still being used and still causes thrashing much later when I'm just working in a small area. Unfortunately IT won't give me any more memory. – Jay Conrod Jan 17 '11 at 19:37
I think Windows 7 is already optimizing your performance with caching. So to increase available memory and to reduce swap, close any unnecessary applications. You can get a good chunk of memory back by closing Outlook and Firefox, for example. If using Visual Studio and only need to compile, try a command line build instead. I hope this helps. BTW. With memory so low (6Gb under $100), it’s a excellent productivity investment. – tgiphil Jan 18 '11 at 3:28
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I believe that the system cache releases its memory when required, but glitches can happen. Below are listed some possibilities.

Your 64-bits system allocates the video memory in the first 4GB of memory. So if your video card has lots of memory, that memory is lost, as described in :
The usable memory may be less than the installed memory on Windows 7-based computers

You may examine the memory usage on the computer by opening the Device Manager and under the View menu, choose "Resources by connection". Expand the Memory node and see if you can figure out what, if anything, is occupying the memory. In some cases, memory can be increased by disabling unused devices such as firewire.

You can also try and do the exact opposite of what is described in this article :
Increase The FileSystem Memory Cache Size In Windows 7

You can also try to Disable Windows 7 SuperFetch.

If nothing helps, it would be useful for you to post a screenshot of the Task Manager tab named Performance.

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The +1 is for "Disable Superfetch". – Randolph West Jan 17 '11 at 22:00
No down grade, but Superfetch is most likely increasing his performance – not decreasing it - since build executables are generally executed frequently and will benefit from being cached. As for video card affecting available memory, it is not applicable on Windows 7 64bit with only 4Gb. The video card would be mapped above 4Gb, in this case. – tgiphil Jan 18 '11 at 3:19
@tgiphil: From the above-cited Microsoft article : "a video card that has 256 MB of on-board memory, that memory must be mapped within the first 4 GB of address space". – harrymc Jan 18 '11 at 5:55
At my organization, we also have tons of small files and a huge NTFS metafile in RAM. From what I can tell, Windows doesn't cache the Metafile like everything else and never really releases it from RAM. The computer will go up to 100% memory usage and then all your applications start crashing due to lack of memory. Of course this isn't Windows 7, it's Windows Server 2008 R2. – Phil Aug 17 '11 at 14:12
Also the "Increase FileSystem Memory Cache" link advises things that don't actually work. See tweakhound.com/blog/?p=1164 – Phil Aug 17 '11 at 14:24
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