How to use the command smem (with examples)

Smem is a command-line tool that allows you to print memory usage for programs. It provides information about the memory consumption of processes running on your system, which can be useful for monitoring and troubleshooting purposes.

Use case 1: Print memory usage for current processes

Code:

smem

Motivation: The motivation for using this command is to get an overview of the memory usage of all running processes on the system. This can help identify processes that are consuming excessive memory and causing performance issues.

Explanation: The command smem without any arguments will print the memory usage for all current processes on the system. It provides information such as the amount of shared memory, resident memory, and proportion of memory used.

Example output:

Area                           Used      Cache   Noncache 
firmware/hardware             1280.0        0.0     1280.0 
kernel image(s) and modules  126860.0     5248.0   121612.0 
lib.so                          128.0       28.0      100.0 
data and shared libraries      8604.0     2108.0     6496.0 
stacks                        14496.0      436.0    14060.0 
heap                          54032.0     1164.0    52868.0 
.page cache                     796.0      796.0       0.0 
.ksm pages copied               992.0        0.0      992.0 
shared memory                  3400.0      740.0     2660.0 
non-memory                      132.0       40.0       92.0 
---------------------------------------
                             230028.0    10440.0   219588.0 

This output provides a breakdown of the memory usage for different areas such as firmware/hardware, kernel image, shared libraries, and more. The “Used” column shows the total memory usage in kilobytes for each area.

Use case 2: Print memory usage for current processes for every user on a system

Code:

smem --users

Motivation: This use case is helpful for system administrators or anyone who wants to analyze the memory usage of processes on a multiuser system. By using the --users option, you can get a detailed breakdown of memory usage per user.

Explanation: The --users option tells smem to display memory usage information for each user individually. This can help identify which users or processes are consuming the most memory on the system.

Example output:

User               Used      Cache   Noncache 
---------------------------------------
root           230112.0     10440.0   219672.0 
user1              120.0         0.0      120.0 
user2            22000.0       408.0    21592.0 

In this example output, we can see the memory usage for the root user, as well as user1 and user2. Each user is listed along with their respective memory usage in kilobytes.

Use case 3: Print memory usage for current processes for a specified user

Code:

smem --userfilter username

Motivation: There might be cases where you only want to examine the memory usage of a specific user. Using the --userfilter option with the desired username allows you to focus on the memory consumption of that particular user.

Explanation: The --userfilter option filters the output to show memory usage for only the specified user. Replace “username” in the command with the actual username you want to filter.

Example output:

User               Used      Cache   Noncache 
---------------------------------------
user2            22000.0       408.0    21592.0 

In this example, smem --userfilter user2 was used to display the memory usage for only the user “user2”.

Use case 4: Print system memory information

Code:

smem --system

Motivation: Understanding the overall system memory usage is essential when monitoring system performance or troubleshooting memory-related issues. This command provides valuable insights into the total memory usage of the system.

Explanation: The --system option instructs smem to display system-level memory usage information. It shows the total memory usage, including both used and free memory.

Example output:

System             Used      Cache   Noncache 
---------------------------------------
Total          230240.0     10440.0   219800.0 

The example output presents the total memory usage for the system. The “Used” column indicates the total amount of memory used in kilobytes, while the “Cache” and “Noncache” columns represent the respective memory usage for cached and non-cached data in kilobytes.

Conclusion:

Smem is a powerful command-line tool for monitoring memory usage on Linux systems. By using the various options available, you can obtain detailed memory usage information for current processes, individual users, and the overall system. This can aid in diagnosing memory-related issues, identifying memory-hungry processes, and optimizing system performance.