Ubuntu Tutorials - Herong's Tutorial Examples

∟Memory Management

∟pmap - Process Memory Map

This section provides a tutorial on how to install 'smem' and use it to report memory usage of each running process.

What Is "pmap"? - "pmap" is a Ubuntu command that reports the virtual memory map of a given process. Here are some examples of "pmap" command output:

1. Report virtual memory map for process ID 1998.

herong$ pmap 2666

2666:   /usr/bin/gnome-software --gapplication-service
000055a0683b7000    948K r-x-- gnome-software
000055a0686a4000     20K r---- gnome-software
000055a0686a9000      4K rw--- gnome-software
000055a06a349000  62240K rw---   [ anon ]
00007faba8000000  21900K rw---   [ anon ]
00007faba9563000  43636K -----   [ anon ]
...
00007fabbb539000     20K r-x-- libnss_dns-2.27.so
00007fabbb53e000   2048K ----- libnss_dns-2.27.so
00007fabbb73e000      4K r---- libnss_dns-2.27.so
...

 total          1345196K

The output shows that:

• The program code "/usr/bin/gnome-software" is distributed in 3 locations in the virtual memory.
• The data area is reported as "[ anon ] (anonymous mapping)" and scattered in multiple locations.
• Libraries (linked exclusively to the process and share with other processes) are also reported. libnss_dns-2.27.so is an example.

2. Report virtual memory map in the extended format, which provides 2 extra output fields and field headers.

herong$ pmap -x 1998

2666:   /usr/bin/gnome-software --gapplication-service
Address           Kbytes     RSS   Dirty Mode  Mapping
000055a0683b7000     948     504       0 r-x-- gnome-software
000055a0683b7000       0       0       0 r-x-- gnome-software
000055a0686a4000      20      20      20 r---- gnome-software
...
000055a06a349000   62240   53152   53152 rw---   [ anon ]
000055a06a349000       0       0       0 rw---   [ anon ]
00007faba8000000   21900   17352   17352 rw---   [ anon ]
... 
00007fabbb539000      20      20       0 r-x-- libnss_dns-2.27.so
00007fabbb539000       0       0       0 r-x-- libnss_dns-2.27.so
00007fabbb53e000    2048       0       0 ----- libnss_dns-2.27.so
...

total kB         1345196  162228  150928

Compare "pmap", "ps" and "smem" Reports - Here are the outputs of "pmap", "ps" and "smem" commands on process id 2666 (gnome-software).

herong$ pmap -x 2666
...
Address           Kbytes     RSS   Dirty Mode  Mapping
total kB         1345196  162228  150928

herong$ smem -P gnome-software 
  PID User    Command                       Swap     USS     PSS     RSS 
 2666 herong  /usr/bin/gnome-software --g  87120  153740  154670  162228 

herong$ ps -o pid,euser,%mem,rss,drs,trs,sz,vsz,comm | grep 2666 
  PID EUSER    %MEM    RSS     DRS  TRS     SZ     VSZ COMMAND
 2666 herong    4.3 161300 1344245  946 336298 1345192 gnome-software

Those outputs show that 3 commands report slightly different numbers. I am not sure why.

Table of Contents

 About This Book

 Introduction to Ubuntu Systems

 GNOME - Desktop Interface and Environment

 Shell - The Command-Line Interpreter

 Process Management

►Memory Management

 Layers of Memory and Access Speed

 List CPU Caches and Their Sizes

 Virtual Memory vs. Physical Memory

 Buffer Memory and Cache Memory

 Verify Cache Memory with "cp" Command

 What Is Swap Space

 Virtual Memory Mapping and Page Table

 "ps -o rss,drs,trs,vsz,sz" - Process Status Options

 smem - Process Memory Usage Report

►pmap - Process Memory Map

 /proc/{id}/maps - Process Memory Map

 /proc/{id}/smaps - Process Memory Map Details

 earlyoom - A Simple OOM Killer

 Files and Directories

 APT (Advanced Package Tool)

 Network Connection on Ubuntu

 Internet Networking Tools

 SSH Protocol and ssh/scp Commands

 Administrative Tasks

 References

 Full Version in PDF/EPUB

pmap - Process Memory Map - Updated in 2025, by Herong Yang