[$] Three ways to rework the swap subsystem

The kernel's swap subsystem is complex and highly optimized - though notalways optimized for today's workloads. In three adjacent sessions duringthe memory-management track of the 2025 Linux Storage, Filesystem,Memory-Management, and BPF Summit, Kairui Song, Nhat Pham, and Usama Arifall talked about some of the problems that they are trying to solve in theLinux swap subsystem. In the first two cases, the solutions take the form ofan additional layer of indirection in the kernel's swap map; the third,which enables swap-in of large folios, may or may not be worthwhile in theend.