In-Depth Guide to Memory Usage! Efficient Monitoring and Management Methods for Ubuntu

By 佐川 直弘 | Naohiro Sagawa (運営者)

※記事内に広告を含みます。Amazonアソシエイトとして適格販売により収入を得ています。　

1. Introduction

Ubuntu is a lightweight yet highly functional Linux distribution that is widely supported by users. However, over prolonged use, your system may start to slow down. One of the main causes of this is “memory usage.” Especially in environments where multiple processes run simultaneously, such as development work or data processing, it is crucial to monitor and manage memory usage properly.

In this article, we will explain how to check memory usage in Ubuntu, introduce efficient management techniques, and provide troubleshooting methods. Whether you are a beginner or an intermediate user, you will find valuable information here, so be sure to read on!

The Importance of Memory Management in Ubuntu

Memory is a critical resource that directly affects system performance. When memory is insufficient, applications may slow down or even crash. Furthermore, increased swap memory usage leads to frequent read/write operations on the disk, which can degrade overall system performance. Therefore, properly monitoring memory usage allows you to maintain an efficient system.

Purpose of This Article

This article covers the following topics:

• Basic commands for checking memory usage
• How to examine detailed memory usage for the entire system and individual processes
• Methods for optimizing memory and using it efficiently
• Tools for troubleshooting and long-term monitoring

By understanding these topics, you will be able to manage Ubuntu memory usage effectively and improve your workflow.

2. Checking Memory Usage: Basic Commands

Ubuntu provides several commands that allow users to quickly check system memory usage. In this section, we will explain how to use these basic commands in a straightforward manner. Even beginners can easily follow along, so give them a try!

The free Command

The free command is a fundamental tool for checking overall memory usage on the system. Below is how to use it and how to interpret its output.

Usage Example:

free -m

Main Options:

• -m: Displays memory usage in megabytes (MB)
• -g: Displays memory usage in gigabytes (GB)
• -h: Displays memory usage in a human-readable format (automatically adjusts between MB and GB)

Sample Output:

              total        used        free      shared  buff/cache   available
Mem:           7989        2340         987         432        4661        5016
Swap:          2048          12        2036

Understanding the Output:

• total: Total system memory
• used: Amount of memory currently in use
• free: Amount of memory not being used
• buff/cache: Memory used for buffers and cache
• available: Memory that applications can actually use

This command is simple and intuitive, making it the first method you should try.

The top Command

The top command is a tool that displays real-time memory usage for each process.

Usage Example:

top

Sample Output (Excerpt):

PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
  1 root      20   0  225672   8956   5924 S   0.0  0.1   0:01.23 systemd
1234 user      20   0  135256  12320   8940 S   0.3  0.2   0:00.15 gnome-terminal

Understanding the Output:

• PID: Process ID
• %MEM: Percentage of memory used by the process
• COMMAND: Name of the running command

This command helps quickly identify which processes are consuming the most memory.

The htop Command

htop is an enhanced version of top that provides a more user-friendly and visually appealing display.

Installation:
On Ubuntu, install it with the following commands:

sudo apt update
sudo apt install htop

Usage Example:

htop

Features:

• Uses color to visually display memory usage
• Allows navigation with arrow keys to select and manage processes
• Provides filtering and sorting options

Since htop offers a more user-friendly interface, many Ubuntu users prefer it.

The vmstat Command

The vmstat command is a tool for checking overall system resource usage in real time.

Usage Example:

vmstat 5

Main Options:

• 5: Updates every 5 seconds

Sample Output:

procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 1  0     12  98736  43256 467321    0    0     3     5   55   99  2  0 97  0  0

Understanding the Output:

• free: Current available memory
• buff: Memory used as a buffer
• cache: Memory used for caching
• si/so: Swap-in and swap-out rates

This command is useful for monitoring memory status at regular intervals.

3. Analyzing Detailed Memory Usage

Beyond basic memory usage checks, Ubuntu provides tools and methods to obtain even more detailed information. This section explains how to analyze memory usage at the process level, which is especially useful for system administrators and intermediate to advanced users.

The pmap Command

The pmap command allows you to check the memory mapping information of a specific process. This tool is useful for understanding how a process is utilizing memory in detail.

Usage Example:

pmap <process ID>

Sample Output:

5600:   /usr/bin/python3
000055e45d7a2000   4K r-- /usr/bin/python3.8
000055e45d7a3000 124K r-x /usr/bin/python3.8
000055e45d7c2000   4K r-- /usr/bin/python3.8
...

Understanding the Output:

• Each line represents a memory segment used by the process.
• The leftmost value is the memory address range, and the rightmost part describes the usage (e.g., shared libraries or the main program).

pmap is useful for identifying which memory areas a process is occupying and diagnosing potential issues.

Checking /proc/[PID]/smaps

The /proc/[PID]/smaps file provides detailed memory usage information for each process. This file is particularly useful for advanced troubleshooting and investigating memory leaks.

Usage Example:

cat /proc/<process ID>/smaps

Sample Output (Excerpt):

7f9a9f3d0000-7f9a9f3f2000 rw-p 00000000 00:00 0
Size:               132 KB
Rss:                128 KB
Pss:                64 KB
...

Key Terms:

• Size: Total allocated memory
• Rss (Resident Set Size): Memory currently in physical RAM
• Pss (Proportional Set Size): Memory shared between processes, adjusted accordingly
• Shared_Clean/Shared_Dirty: Shared memory that remains unchanged/modified

Use Cases:

• Helpful when investigating potential memory leaks.
• Useful for analyzing high-memory-consuming processes in detail.

Checking /proc/meminfo

The /proc/meminfo file logs detailed system-wide memory usage, including swap and cache information. Checking this file allows you to obtain in-depth insights into system memory utilization.

Usage Example:

cat /proc/meminfo

Sample Output (Excerpt):

MemTotal:       16389276 kB
MemFree:         1234567 kB
Buffers:           56789 kB
Cached:          6789123 kB
SwapTotal:       2097148 kB
SwapFree:        2096123 kB

Key Metrics:

• MemTotal: Total physical memory
• MemFree: Unused memory
• Buffers: Memory used for file system buffering
• Cached: Memory used for caching
• SwapTotal/SwapFree: Total and available swap space

Regularly checking this information helps monitor system performance trends.

4. How to Optimize Memory Usage

To maintain a smooth working environment on Ubuntu, it is crucial to manage and optimize memory usage efficiently. In this section, we will explain specific methods to reduce unnecessary memory consumption and improve overall system performance.

Stopping Unnecessary Processes

If your system is running too many unnecessary processes, they may be consuming memory unnecessarily. Let’s review how to identify and stop these processes.

Steps:

1. Check running processes using top or htop

• Identify processes with high memory usage.
• Example: Use htop to display a list of processes and find those with a high %MEM.

1. Stop specific processes

• Use the kill command to stop a process.

sudo kill <process ID>

• If you need to force-stop a process, use:

sudo kill -9 <process ID>

3. Disable unnecessary services

• To prevent a service from starting automatically, use:

sudo systemctl disable <service name>

Managing Swap Memory

Swap space is a virtual memory area used when physical memory runs out. However, excessive swap usage can slow down your system. Here’s how to manage it properly.

Check swap usage:

free -m

Adding Swap Space:
If your system frequently runs out of memory, consider expanding the swap space.

1. Create a new swap file:

sudo fallocate -l 1G /swapfile

(This example creates a 1GB swap file.)

2. Change file permissions:

sudo chmod 600 /swapfile

3. Set it as swap space:

sudo mkswap /swapfile
sudo swapon /swapfile

4. Make the swap permanent by adding it to /etc/fstab:

/swapfile none swap sw 0 0

5. Long-Term Monitoring and Automation

Regularly monitoring memory usage and understanding trends is crucial for maintaining system performance. This section explains how to track and automate memory monitoring over time.

Using Monitoring Tools

Glances

Glances is a real-time monitoring tool for tracking overall system resources. It is lightweight and feature-rich, making it ideal for long-term memory monitoring.

Installation:

sudo apt update
sudo apt install glances

Usage:

glances

Features:

• Displays memory, CPU, disk, and network usage in real time.
• Supports web interface for remote monitoring.

6. FAQ (Frequently Asked Questions)

In this section, we answer common questions about managing memory usage in Ubuntu. These tips will be useful for both beginners and intermediate users.

Q1: What should I check first if my memory usage is high?

A1:
Start by using the following commands to check system-wide and per-process memory usage:

• free -m: Displays total and available memory.
• top or htop: Identifies processes consuming the most memory.

Q2: Is increasing swap memory usage a problem?

A2:
Swap usage is not necessarily a problem, but high usage may indicate insufficient physical memory. If swap usage is consistently high, consider the following steps:

1. Check swap usage using free -m.
2. If swap is frequently used, consider adding more physical RAM or expanding the swap space.
3. Review application and process memory usage, and terminate unnecessary ones.

Q3: How can I detect memory leaks?

A3:
If you suspect a memory leak, you can use the following tools to investigate:

• valgrind: A powerful tool for detecting memory leaks.
• Example usage:
  valgrind --leak-check=full ./your_application
• /proc/[PID]/smaps: Check detailed memory allocation per process.
• Example usage:
  cat /proc/<process ID>/smaps

Once a memory leak is identified, consider updating the application or investigating further for fixes.

Q4: How can I monitor memory usage over a long period?

A4:
For long-term monitoring, consider these methods:

• Use monitoring tools: Glances or Nagios for real-time tracking.
• Automate logging:
• Use scripts to periodically run free or vmstat and log results.
• Analyze log files to identify trends over time.

Q5: Can I automatically detect high memory usage processes and receive notifications?

A5:
You can use a script to monitor processes and send alerts when memory usage exceeds a certain threshold.

Example Script:

#!/bin/bash
THRESHOLD=80
MEMORY_USAGE=$(free | awk '/^Mem:/ {printf "%.0f", $3/$2 * 100}')

if [ $MEMORY_USAGE -gt $THRESHOLD ]; then
  echo "Memory usage has reached $MEMORY_USAGE%!" | mail -s "Memory Warning" user@example.com
fi

Schedule this script using crontab for periodic execution and automated alerts.

Q6: Are there risks in clearing the cache?

A6:
Clearing the cache may temporarily decrease system performance since cached data improves access speed. However, if memory is low, clearing the cache can free up space.

Clear cache safely:

sudo sync; echo 3 | sudo tee /proc/sys/vm/drop_caches

Q7: What should I do if an application crashes due to high memory usage?

A7:

1. Identify high-memory processes and terminate unnecessary ones.
2. Consider adding more RAM if needed.
3. Check application settings to limit resource usage if possible.

Q8: Is there a way to reset memory usage on Ubuntu?

A8:
While there is no direct way to reset memory usage, you can optimize the system using the following steps:

1. Stop unnecessary processes and services.
2. Clear caches.
3. Reboot the system if necessary.

These FAQs provide practical advice for managing memory usage effectively in Ubuntu.

7. Conclusion

In this article, we explored various aspects of memory management in Ubuntu, from basic checks to detailed analysis, optimization strategies, and long-term monitoring. Below is a summary of the key takeaways:

Summary of Key Topics

1. Checking Memory Usage

• We learned how to use basic commands such as free, top, and htop to check overall and per-process memory usage.
• We also explored tools like vmstat and ps for more detailed insights.

1. Detailed Analysis Methods

• Commands like pmap and /proc/[PID]/smaps allow for in-depth process-level memory inspection.
• The sar command helps track memory usage trends over time.

1. Optimizing Memory Usage

• We discussed how to stop unnecessary processes, manage swap space, and clear caches.
• We also covered how to detect and handle memory leaks.

1. Long-Term Monitoring and Automation

• Tools like Glances, Nagios, and Prometheus enable continuous monitoring.
• Automating memory checks with scripts ensures proactive management.

1. FAQ for Practical Solutions

• We answered common questions about memory management and troubleshooting.

The Importance of Memory Management

Proper memory management is essential for maintaining system stability and performance in Ubuntu. These strategies are especially useful in the following situations:

• When the system feels slow.
• When swap usage is consistently high.
• When specific applications consume excessive memory.

Next Steps

Apply what you’ve learned in this article by taking the following actions:

• Regularly use basic commands to monitor memory usage.
• Utilize advanced analysis and monitoring tools as needed.
• Implement scripts and automation for efficient memory management.

Final Thoughts

Understanding memory management can significantly improve your Ubuntu experience. We hope this article helps you optimize your system and handle any memory-related issues effectively.