What does buffered, cached, free, slab and used mean when monitoring memory use on GKE?

Question

I am running some compute nodes on GKE and when I look on their memory usage in metrics explorer I see:

It is clear to me what used and free mean. But how about the other states?

The official documentation is quite terse on the subject.

Answer 1

That is standard terminology of Linux Kernel management:

buffered - Block device (e.g. harddisk) cache

cached - Parked file data (file content) cache

slab - Memory used by the kernel to cache data structures for its own use (caches like inode, dentry, etc)