[$] In search of faster this_cpu operations

The kernel's this_cpuoperations are meant to speed access to per-CPU variables. They aremore optimal on some CPUs than others, though. During amemory-management-track session at the 2026 Linux Storage,Filesystem, Memory Management, and BPF Summit, Yang Shi proposed afundamental, and somewhat controversial, change to how these operationswork in order to provide better performance on a wider range of architectures.