@the8472, hah, so someone thought of the same thing. I'd try to leverage /etc/ld.so.preload with a config file as a more transparent solution, but your link proves the point that its possible.
hence why I said a config file based (i.e. include the path that stores one's media, won't matter what program you use to play it), but yes, page cache does play a role (but hence why I also said it be interesting to explore how different applications behave with and without it and how that impacts other system performance)
i.e. I really wonder for desktop workloads if one only caches "executable" data, how would that negatively impact perceived performance. I'd imagine it have some impact, but I'd be interested in seeing it quantified.
And if you only do it in a container you can also limit the page cache size of the container to avoid impacting the other workloads.