pmap command in Linux with Examples

The pmap command in Linux is a powerful utility used to display the memory map of a process. A memory map provides insight into how memory is allocated and distributed within a running process. This can be incredibly useful for developers and system administrators when debugging memory issues, optimizing performance, or gaining an in-depth understanding of memory usage in Linux.

Syntax

pmap [options] pid [...]

where,

• pid: This represents the Process ID of the process whose memory map you want to display. You can find the pid of a process using commands like ps, top, or pgrep.

Basic Example

Key Options for the pmap Command

1. -x: Extended Format

This option displays the memory map in an extended format, which provides additional details such as the resident memory size (RSS), shared memory size, private memory size, and more.

Example:

pmap -x 9466

2. -p: Show Full Path

This option displays the full path to the files mapped in memory. It is helpful to know which files are being used by the process.

Example:

pmap -p 9466

3. -d: Device Format

This option displays memory in a device format, showing information like the device number and inode for mapped files.

Example:

pmap -d 9466

4. -q: Quiet Mode (No Column Names)

When using this option, pmap will display the memory map without the column names, making the output more compact. This is useful for scripts where column headers may not be necessary.

Example:

pmap -q -d 9466

5. -A: Display Memory Map for a Specific Range

This option is used to display results to the given range. Notice that the low and high arguments are single string separated with a comma.

Example:

pmap -A 000055a5908f8000, 00007fd264ed2000 11747

6. -XX: Display All Information Provided by the Kernel

The -XX option provides a complete and exhaustive output of the memory map, showing everything the kernel provides, including more detailed memory attributes like permissions and offsets.

Example:

pmap -xx [PID]

7. -n: Create a New Configuration

This option is used to create a new configuration.

Example:

pmap -n

8. -c: Read Default Configuration

If you want to revert to the default configuration or read an existing configuration, the -c option can be used. This is particularly useful when troubleshooting configuration issues.

Example:

pmap -c [PID]

9. -h: Display Help Text

To display a help message with all available options and usage information, use the -h option.

pmap -h

10. -v: Display Version Information

If you want to check the version of pmap that is installed on your system, use the -v option.

pmap -v

Conclusion

The pmap command is a versatile and essential tool for anyone needing to analyze process memory usage in Linux. pmap offers a range of options to display and investigate a process’s memory map in detail. By leveraging options like -x for extended format, -p for full file paths, and -XX for exhaustive kernel information, users can gain a comprehensive understanding of how memory is allocated and used in their system.