pmap

Additional Notes

pmap reports the memory map of a running process. It shows each mapped memory region, its size, permissions, offset, device, inode, and the mapped file or mapping name (if any). This reveals exactly how a process uses memory: heap, stack, shared libraries, anonymous mappings, and mmap'd files.

System administrators and developers use pmap to diagnose memory leaks, understand memory usage patterns, find which shared libraries are loaded, identify large memory-mapped files, and troubleshoot out-of-memory conditions. It reads data from /proc/PID/maps and /proc/PID/smaps and presents it in a readable format.

Syntax

pmap [options] [pid...]

Parameters

• pid: Process ID(s) to inspect.

Common Options

• -x, --extended: Show extended output with RSS, dirty, and shared memory details.
• -XX: Show all available memory information (very detailed).
• -d, --device: Show device format output with offset and device numbers.
• -q, --quiet: Suppress header and footer lines.
• -A, --range low,high: Restrict output to a specific address range.
• -c: Read configuration from file.
• -p: Show PID in the footer.
• --help: Show help and exit.
• --version: Show version information.

Examples

pmap 1234

Show the memory map of PID 1234.

pmap -x 1234

Show extended memory details: RSS (resident set size), dirty pages, and mapping mode.

pmap -d 1234

Show the memory map in device format with read/write permissions.

pmap $(pidof bash)

Show the memory map of all running bash processes.

pmap -x -q 1234

Show extended output without headers, useful for scripts.

pmap -XX 1234 | sort -k2 -rn | head -10

Show the 10 largest memory mappings of a process.

Practical Notes

• The first column shows the virtual address of each mapping. The last column shows the mapped file (or [anon] for anonymous mappings, [heap] for heap, [stack] for stack, [vdso], [vvar], etc.).
• The RSS (Resident Set Size) column in -x mode shows how much of each mapping is currently in physical RAM.
• Heap growth over time can indicate memory leaks. Run pmap at intervals to compare.
• Shared libraries appear as read-only executable (r-x) mappings. Each loaded library adds one or more segments to the process map.
• Large anonymous mappings ([anon]) may indicate memory-mapped buffers, thread stacks, or JIT-compiled code.
• For a real-time memory usage overview, use top or htop. For detailed per-process maps, use pmap.
• The total memory shown by pmap may differ from ps or top because they account for shared pages differently.