Windows 7 mysterious memory usage

Question

I am using a windows 7 machine to play a game, among other things, which was running smoothly for years, up until now. It's not a big problem but sometimes I notice drops in fps from 60 to 40 for a couple seconds which is unacceptable having in mind the machine parameters and the game's requirements (plus, as I said, the game was running at 60 fps for years).

I am not sure if that is the cause of it but when I open the task manager I notice that there is a difference between the reported memory usage and the actual sum of the processes' used memory, see below.

When I sum the memory usage manually I get something like 1800MB, say 2GB, however the Performance tab is reporting a usage of 3.1GB?

What is the cause of this, and how can I diagnose the problem? I would really like to avoid having to re-install windows because there is quite some software that I'm using on that machine and I've done my best to keep it clean with that exact idea in mind - to not have to reinstall.

Answer 1

For seeing in detail how Windows uses the memory you should use RAMMap and not Taskmanager. This Microsoft blog explains what the data mean.

Answer 2

Some memory is under 'Cached'. It shows as 'used' but is available to the system when needed. Systems do that so when you use applications/files and close them, the next time you open them, they will open quicker (if the cache hasn't been overwritten by other apps).

Answer 3

It is completely normal for the sum of process memory usage to be less than total usage. In fact it could not be otherwise.

Firstly, there are some significant users of memory that are not processes. Some examples are: 1. Non paged pool 2. Resident portion of the Paged pool 3. The file cache. Oddly this is not included in "Cached" value shown in Task Manager. It is part of in use memory but is not identified in any way. There are some others but usually not very large.

Secondly, the memory usage column displayed does not account for full process usage. It shows the private memory usage of the process but not that used by the process executable and associated DLLs. To see full usage you must look at the "Working Set (Memory)" column. This is not shown by default but must be manually added. This includes some shared memory so there will be some double counting.

Windows memory usage is very complex and cannot be accounted for by simply adding up a column of numbers.

Your problem does not appear to be memory related.