Where is the Cache for Image-Sequence as Plane?

I’m getting low frame-rates when using Image-Sequance as Plane in the viewport. It eventually caches if i play through it once, but how do I see how much of it is cached? There’s no red bar in my timeline.

I’m working with a 2 minute video (720p) and i only have 8GB of RAM, so it would help to be able to see what portion of the video is cached.