[$] Hash table memory usage and a BPF interpreter bug

Anton Protopopov led a short discussion at the 2025 Linux Storage, Filesystem,Memory-Management, and BPF Summit about amount of memory usedby hash tables in BPF programs. He thinks that the current memory layout isinefficient, and wants to split the structure that holds table entries into twovariants for different kinds of maps. When that proposal proveduncontroversial, he also took the chance to talk about a bug in BPF's callinstruction.