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If you can, please explain these readings or supply a documentation link, thanks.

Task Manager:

The vertical Memory gauge is at 1.93GB.

Physical Memory (MB)

total 8191

cached 5417

available 6202

free 819

Kernel Memory (MB)

Paged 250

Nonpaged 57

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up vote 7 down vote accepted

Physical Memory

The Physical Memory is the amount of actual memory installed in your computer that Windows is currently able to access. The total of 8191MB is 8GB, so you have 8GB of RAM installed in your compuer.

Cached Memory

Currently, 5417MB (5.29GB) is used by the caching features of Windows 7 (file buffers, mapped files, superfetch, etc.). Cached memory is memory in use that can be dropped and retrieved at any time since the data exists elsewhere (on the network or on the disk, etc.).

Available Memory

Your Available Memory (6202MB or 6.05GB) the size of the cached memory plus whatever memory is backed by the page file. Windows 7 will sometimes "pre-swap" memory out to the page file before it is requested. This memory is "stale" (hasn't been accessed in a while) and is unlikely to be needed right away. By "pre-swapping" it out, it exists in both Physical Memory and the page file. If the program that allocated that memory needs it, there is no swapping involved since it is still in memory. On the other hand, if a different program makes a request for a large amount of memory and Windows has to start swapping memory out, it can just "drop" the pre-swapped memory since it is already in the page file. This helps make Windows seem snappier since it doesn't have to write it to disk before granting the allocation request. It looks like Windows has "pre-swapped" 785MB (Available Memory - Cached Memory) to the page file.

Free Memory

Free memory (819MB) is memory that is not in use by anything on the system. It is 100% completely unused. Usually you want this to be as low as possible because unused memory is wasted. (Of course, it could also be that with that much RAM, Windows just couldn't find something to fit in there - my 2GB system has 464MB available and 13MB free.)

Kernel Memory

Kernel Memory is a chunk of memory that is assigned to the core of Windows, the kernel. This memory is used by Windows for keeping track of low level objects (like window handles, file handles, GDI handles, etc.) and for drivers (like your video card, network card, etc.).

Paged Pool

Paged Kernel Memory (known as the "Paged Pool") for the Kernel is treated mostly like normal memory. It gets allocated when needed by drivers (or Windows directly) and can be swapped out when necessary to make more room.

Nonpaged Pool

Nonpaged Kernel Memory (known as the "Nonpaged Pool") is more delicate. Nonpaged memory is specially allocated so that it will never be swapped out in any occasion. This is necessary when the system is processing a device interrupt at such a high level it can't access the disk to swap memory back. In fact, if it did get swapped out (or the driver is accessing the wrong memory) this will lead to the well known BSOD "Page fault in non-paged area".

There is an awesome article written by Mark Russinovich, Pushing the Limits of Windows: Paged and Nonpaged Pool, that explains the paged and nonpaged pool of memory for the Kernel. If you're interested it is definitely worth the read!

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I had started to answer but then you posted your treatise...+1. – phoebus Dec 18 '09 at 5:26
A++ great superuser. – P a u l Dec 18 '09 at 5:36
I would add that the paged and nonpaged pool are not the ONLY memory used by kernel mode code. These are simply kernel mode versions of what's usually called a "heap" in user mode programming. There's a lot of kernel virtual address space that isn't in either of the pools. The pools are mostly used for relatively small and relatively short-term allocations. – Jamie Hanrahan Aug 30 '15 at 8:02

Physical Memory:

Physical Memory Total—This number represents the total amount of RAM installed on your computer.

Physical Memory Available—This number shows the amount of RAM available for CPU processes. This number will never go to zero because the operating system will swap data to the hard disk as the memory fills.

Physical Memory System Cache—This is the amount of RAM being used by the file cache.

Physical Memory Free- Physical memory currently not in use

Kernel Memory:

Kernel Memory Paged—This number shows the amount of virtual memory set aside for the kernel.

Kernel Memory Nonpaged—This is the amount of RAM dedicated to the operating system's kernel.

Most of this is explained in an old Win2K article, with the absence of physical memory free, which is straightforward.

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