[$] Rhashtables: under the hood

The first article in this series describedthe interface to the "rhashtable"resizable hash-table abstraction in Linux 4.15. While a knowledge ofthe interface can result in successful use of rhashtables, it oftenhelps to understand what is going on "under the hood", particularly whenthose details leak out through the interface, as is occasionally thecase with rhashtable. The centerpiece for understanding theimplementation is knowing exactly how the table is resized. So thisfollow-on article will explain that operation; it will also present theconfiguration parameters that were skimmed over last time and discusshow they affect the implementation.