Linux Memory Overcommit Modes Explained

Memory overcommit is a feature of Linux that determines how the kernel handles memory allocation requests from processes. Understanding memory overcommit is essential for preventing out-of-memory (OOM) crashes in production systems, optimizing application performance, debugging memory-related issues, and making informed decisions about system configuration. There are three overcommit modes available: 0, 1, and 2. Overcommit mode 1 allows processes to request more memory than what is physically available, while mode 2 imposes a hard limit on allocations and does not allow memory overcommit. Mode 0 uses heuristic overcommit, which decides if an allocation should be rejected or overcommitted based on its own algorithm. For Dragonfly, overcommit_memory=1 is often the best choice as it ensures allocations succeed during high-load scenarios, avoids costly copy-on-write operations, and keeps memory management predictable.