I think the information there is valuable because questions about memory usage in Linux keep coming up. The answer: "don't worry about it," is probably a good starting point. The page claims things that are just really misleading, though.
> There are no downsides, except for confusing newbies.
False. Populating the page cache involves lots of memory copies. It pays off if what's written is read back many times; otherwise, it's a net loss. It also costs cycles and memory to keep track of all these pages and maintain usage statistics so we know what page should be kept and which can be discarded. Unfortunately, Linux makes quantifying that cost hard, so it is not well understood.
> You can't disable disk caching. The only reason anyone ever wants to disable disk caching is because they think it takes memory away from their applications, which it doesn't!
People do want that, and they do turn it off. It's probably the number one thing database people do because they want domain-specific caching in userland and use O_DIRECT to bypass the kernel caches altogether. If you don't, you end up caching things twice, which is efficient/redundant.
> There are no downsides, except for confusing newbies.
False. Populating the page cache involves lots of memory copies. It pays off if what's written is read back many times; otherwise, it's a net loss. It also costs cycles and memory to keep track of all these pages and maintain usage statistics so we know what page should be kept and which can be discarded. Unfortunately, Linux makes quantifying that cost hard, so it is not well understood.
> You can't disable disk caching. The only reason anyone ever wants to disable disk caching is because they think it takes memory away from their applications, which it doesn't!
People do want that, and they do turn it off. It's probably the number one thing database people do because they want domain-specific caching in userland and use O_DIRECT to bypass the kernel caches altogether. If you don't, you end up caching things twice, which is efficient/redundant.