[btschaegg]

Additionally, the number you come up with (as "MiB of RAM used by an application") might also depend on the OS features the application uses and not directly be obvious by its functionality.

Example: I've been doing some experiments around DWM thumbnails in MS Windows. My program doesn't really do much and shouldn't use too much memory (and doesn't, at least initially). I create a thumbnail for each visible window on the screen (say 5 of them), and -ding-, my process uses >400 MiB.

[smt88]

But Windows itself does this when you hover over a taskbar entry, right? Explorer is never that heavy for me.

Or is the process totally different?

[blattimwind]

A compositor doesn't create a separate image for stuff like this. Every window is rendered into a texture and things like thumbnails are simply a small texture-mapped quad; it's done for each frame by the GPU.