Ever further off topic :)

Of course Linux caches file data: in fact it won't work without it.
Absolutely everything that gets put in a page in memory (all file data,
anonymous mmaped pages, you name it) has to pass through the page cache
first. Executables *run* from the page cache: their text pages reside
nowhere else.

There *is* a cache of disk blocks (the buffer cache), but these days it's
used pretty much entirely for metadata (as this doesn't necessarily have a
page in memory devoted to it).