Page Frame Reclaiming
Page Frame Reclaiming The Page Frame Reclaiming Algorithm 1. Unified Page Cache & Dual-Caching Edge Case Unified Page Cache: Linux no longer separates the “disk/buffer cache” from the “page cache.” All file and block I/O goes through a single unified Page Cache indexed by (address_space, offset). The Dual-Caching Exception: Reading via a regular path (e.g., /app/data.db) uses the file inode’s address_space. Reading via the raw disk node (e.g., /dev/sda1) uses the block device inode’s address_space. Result: The exact same physical 4 KB block on disk can reside twice in RAM under two different address_space objects. Practical Impact: Rare in normal operation because accessing raw block nodes requires root privileges, and system tools handle raw access using unbuffered I/O (O_DIRECT). ...