[$] Improving the merging of anonymous VMAs

The virtual memory area (VMA), represented by struct
vm_area_struct, is one of the core abstractions of the kernel's
memory-management subsystem; a VMA represents a portion of a process's
address space with the same characteristics. A memory-mapped file will be
represented by (at least) one VMA, as will the process's stack or a region
of anonymous memory. Efficiently managing VMAs and the logic around them
is crucial for good performance overall. Lorenzo Stoakes focused on one
specific problem area: the merging of anonymous VMAs, during the
memory-management track at the 2025 Linux Storage, Filesystem,
Memory-Management, and BPF Summit.