No you won’t loose FPS, but if you would use up more video memory than your GPU has you would experience issues but no constant FPS drop (but 1000 MB pool size is fairly low).
The streaming pool contains all textures that are set to stream.
Basically if you’re close up to an object you want to see high details, so have a high texture resolution, but if you only see this object from far away or don’t see it at all, then you don’t need to have the full resolution texture loaded into memory. Therefore unreal engine generates mip maps (the same texture in smaller sizes) for all textures. In order to generate mip maps the size of the texture needs to be a power of two though (so something like 2048x2048 or 512x1024, …). So if you would have a texture size of 2048x2048 the first mip map would have a size of 1024x1024 then 512x512, …
The streaming pool size is the upper limit for this pool size. Therefore if the engine would like to stream in a higher resolution mip map it can’t do this if this would lead to going beyond this streaming pool size. You get to see the “TEXTURE STREAMING POOL OVER X MiB BUDGET” warning though. The X stands for the amount of Megabytes the engine would need to go beyond the current streaming pool size.
So if you’re far beyond the pool size you would eventually see blurry textures, since the engine would have to do with lower resolution mip maps (you can try this by setting the pools size to a small number like 200 MB).
[HR][/HR]
To see the video memory used by unreal engine you could use “stat D3D12RHI” if you’re running DX12, further there is also “stat memory” and for texture streaming “stat streaming” and if you would type in “stat streaming” auto completion would give some more suggestions. Basically if you never done this it might be useful to type in “stat” and try all the stat commands, and see what info they give.
And generally (I assume you already do this, but it is rather important for performance therefore I mention it) always test performance in standalone, else you will also see the performance used up by the editor.