> Consider, for example, an application that is reading sequentially through a file. Each page of the file will be put into the page cache as it is read, but the application will never need it again; in this case, recent access is not a sign that the page will be used again soon.

Going off on a tangent here, but I've always felt there should be an easy way to read through files without causing the kernel to cache them into memory. When I grep through the odd multi-GB file I sometimes/often don't want that to be cached. Looking through the flags for open(2) I see O_DIRECT. Wonder if it'd make sense to expose that as an option in grep, or if there's a handy library somebody made that I could preload to anything to get that effect.

No need to make it an option for each text util. We use an O_DIRECT version of the (z)cat command as the start of pipelines with big files.

Related: The experimental async aware (io_uring optimized) Glommio API may eventually supplant POSIX I/O.

https://github.com/DataDog/glommio

"Modern storage is plenty fast. It is the APIs that are bad." https://itnext.io/modern-storage-is-plenty-fast-it-is-the-ap...