pmap

pmap is a command-line utility used to display the memory map of a running process on Unix-like systems. It reports how a process’s virtual address space is laid out, listing each mapped region along with its size, permissions, and the backing file or object. By revealing which parts of a process’s memory are code, data, shared libraries, or anonymous mappings, pmap helps diagnose memory usage patterns, fragmentation, and potential leaks.

In typical implementations, pmap reads information from the process’s memory mappings in the proc filesystem (for example /proc/[pid]/maps and /proc/[pid]/smaps on Linux) and presents it in a structured format. The output usually includes the start and end addresses of each region, the number of kilobytes, the access mode (read, write, execute), the file offset, the device and inode numbers, and the mapped file or object. Some variants provide an extended view that breaks down totals for private versus shared memory and resident set size (RSS).

Common usage is pmap [options] pid, where pid is the process identifier. Options in various implementations may alter the level of detail or formatting, with extended formats showing additional statistics such as total size and per-region private or shared memory. The exact flags and formatting can differ between Linux distributions and BSD/macOS variants, so users should consult the local manual page for precise syntax.

pmap is a diagnostic and profiling tool used by developers and system administrators to understand a process’s memory footprint, optimize memory usage, and diagnose anomalies in virtual memory behavior. It complements other tools that inspect memory and process resources.