[$] Per-CPU memory for user space

The kernel makes extensive use of per-CPU data as a way to avoid contentionbetween processors and improve scalability. Using the same technique inuser space is harder, though, since there is little control over which CPUa process may be running on at any given time. That hasn't stopped MathieuDesnoyers from trying, though; in the memory-management track of the 2025Linux Storage, Filesystem, Memory-Management, and BPF Summit, he presenteda proposal for how user-space per-CPU memory could work.