If you are speaking of shaders, these are small programs which can run a lot of copies on different data at the same time in the GPU. Assuming this GPU has its own VRAM (most do; however, some laptops share system memory), then there is some time spent uploading textures and shader programs to the GPU. The upload time is not necessarily all that long, but then computations are made on the various pieces of geometry as they are encountered. An example might be that in a given game there are a lot of scenes, but each scene is constructed of a limited number of pieces. If you've encountered all of those pieces in previous scenes, then a new scene (which you've never encountered before) won't require any kind of update from those pieces. There are also shader computations, but basically, if you encounter each of the components, and if the shader programs have been used once, then you'll mostly not get any more performance "burps" from that.
An exception is if you do not have enough VRAM. Not enough VRAM implies a new scene might need to throw away something not used in that scene in order to render that scene.
System RAM is what page files are about. Virtual memory uses the memory management unit (MMU) to map certain memory addresses to each individual program such that the memory appears to in some easier block to work with than if fragments from all over the memory were being used (the program does not have to manage that since the MMU is turning fragments into what looks like contiguous memory). Your disk (SSD, old style hard drive, so on) can be part of this, and the MMU can fake having more physical RAM by mapping drive space as ordinary memory. The problems include that this is exceptionally slow compared to RAM, and in modern days when you have solid state RAM, this can actually reduce the life of the solid state drive (wear leveling fights this failure, but constant thrashing of solid state memory still has consequences). You are far better off to completely turn of swap (paging) for both performance reasons and the life of the drive you swap to (assuming it is solid state). Even if you have a lot of RAM, if swap is enabled, then less used programs will still attempt to swap out.