This article explains the Linux kernel reverse‑mapping (RMAP) mechanism, covering its historical background, core concepts, key data structures such as anon_vma and anon_vma_chain, and the detailed workflow for page creation, fork handling, and page reclaim or migration, with full code examples.
The article examines Linux kernel 6.9 memory-management locks—PG_locked, lru_lock, mmap_lock, anon_vma rwsem, mapping i_mmap_rwsem, and shrinker_rwsem—explaining their roles and presenting eight community-driven optimizations such as per-memcg lru_lock, per-VMA locks, speculative faults, and lock-less shrinker techniques to improve concurrency and performance.
The article explains Linux kernel reverse‑mapping (RMAP), describing its purpose for efficient page‑reclaim, the underlying data structures such as vm_area_struct, anon_vma and anon_vma_chain, and shows how anonymous and file pages are tracked and unmapped through detailed code examples.
This article explains the problem of memory fragmentation in Linux, describes the compaction algorithm that moves free pages together, and walks through the key kernel functions—alloc_pages_node, __alloc_pages_direct_compact, try_to_compact_pages, isolate_migratepages, migrate_pages, and unmap_and_move—detailing their roles in gathering movable pages and relocating them to create contiguous memory blocks.
