Monitor Resource Usage: Check Memory Used by a Process in Linux

In the world of Linux, monitoring resource usage is a crucial task for system administrators and developers. Understanding how much memory a process is using is particularly important for optimizing system performance and troubleshooting issues. Fortunately, Linux provides a variety of tools and commands that allow you to monitor memory usage by a process.

In this article, we will explore 30 different methods to check the memory used by a process in Linux. From popular command-line tools like top, ps, and htop, to more specialized commands like smem, pmap, and cat /proc/[PID]/smaps_rollup, we will cover a wide range of options to suit your specific needs.

Whether you are a beginner or an experienced Linux user, this article will provide you with a comprehensive guide to monitoring memory usage by a process. By the end, you will have a solid understanding of the various tools and commands available, and be able to effectively monitor and manage memory usage in your Linux system.

1. top

The first tool we will explore is top. Top is a command-line utility that provides a real-time view of system processes, including their memory usage. By default, top displays processes sorted by CPU usage, but you can easily sort by memory usage by pressing the ‘M’ key.

To use top, simply open a terminal and type ‘top’ followed by the Enter key. You will be presented with a dynamic display of system processes, with the memory usage column prominently displayed. The memory usage is represented in kilobytes (KB), but you can change the units by pressing the ‘e’ key and selecting the desired unit.

Top also provides additional information such as CPU usage, process IDs (PIDs), and user information. It is a versatile tool that allows you to monitor memory usage in real-time and identify any processes that may be consuming excessive memory.

2. ps

Another popular command-line tool for monitoring memory usage is ps. Ps stands for “process status” and provides a snapshot of currently running processes on your system. By default, ps displays a limited set of information, but you can use various options to customize the output.

To check the memory used by a specific process using ps, you can use the ‘-o’ option to specify the columns you want to display. For example, to display the process ID (PID) and memory usage of all processes, you can use the following command:

ps -eo pid,pmem

This will display the PID and memory usage as a percentage for each process. You can also use the ‘-p’ option followed by a specific PID to check the memory usage of a single process.

Ps provides a flexible and customizable way to monitor memory usage by a process. By combining different options, you can obtain detailed information about the memory usage of specific processes or the entire system.

3. htop

Htop is an interactive process viewer for Linux that provides a more user-friendly and feature-rich alternative to top. Htop displays system processes in a hierarchical manner, making it easier to understand the relationships between processes.

Similar to top, htop allows you to sort processes by various criteria, including memory usage. To sort processes by memory usage, simply press the ‘F6’ key, then select ‘PERCENT_MEM’ from the list of available sort options.

Htop also provides color-coded memory usage bars, making it easy to identify processes that are consuming a significant amount of memory. Additionally, htop allows you to perform actions on processes, such as killing or renicing them, directly from the interface.

If you prefer a more interactive and visually appealing way to monitor memory usage, htop is an excellent choice. Its intuitive interface and powerful features make it a favorite among Linux users.

4. smem

Smem is a command-line tool that provides detailed memory usage statistics for processes in Linux. Unlike top or htop, which provide a real-time view of memory usage, smem focuses on historical data and provides a comprehensive overview of memory usage over time.

To use smem, simply install it using your package manager and run the ‘smem’ command. By default, smem displays memory usage in kilobytes (KB), but you can change the units by using the ‘-r’ option followed by the desired unit (e.g., ‘-r M’ for megabytes).

Smem provides a wealth of information, including resident memory, shared memory, and swap usage for each process. It also allows you to filter processes based on various criteria, such as process name or user.

If you need to analyze memory usage trends or identify processes that are consuming excessive memory over time, smem is a powerful tool that can provide valuable insights.

5. pmap

Pmap is a command-line tool that provides detailed information about the memory mappings of a process. Memory mappings are the regions of memory that a process has allocated for various purposes, such as code, data, and shared libraries.

To use pmap, simply run the ‘pmap’ command followed by the PID of the process you want to inspect. For example, to check the memory mappings of a process with PID 1234, you can use the following command:

pmap 1234

Pmap will display a list of memory mappings, along with information such as the start and end addresses, permissions, and the file or device associated with each mapping.

By analyzing the memory mappings of a process, you can gain insights into how memory is being used and identify any potential issues, such as memory leaks or excessive memory consumption.

6. free

The free command provides a summary of the system’s memory usage, including both physical and swap memory. While it does not provide detailed information about individual processes, it can give you a general idea of the overall memory usage on your system.

To use the free command, simply open a terminal and type ‘free’ followed by the Enter key. You will be presented with a table that displays the total, used, and free memory, as well as the amount of memory used for buffers and cache.

By default, the memory usage is displayed in kilobytes (KB), but you can change the units by using the ‘-h’ option. For example, to display the memory usage in megabytes (MB), you can use the following command:

free -h

The free command is a quick and easy way to get an overview of the system’s memory usage. While it does not provide detailed information about individual processes, it can be useful for identifying any memory-related issues or bottlenecks.

7. vmstat

Vmstat is a command-line utility that provides a wide range of information about system performance, including memory usage. It displays statistics about virtual memory, paging, and block I/O activity.

To use vmstat, simply open a terminal and type ‘vmstat’ followed by the Enter key. You will be presented with a table that displays various statistics, including the amount of free memory, the amount of memory used for buffers and cache, and the amount of memory used for active and inactive pages.

Vmstat also provides information about paging and swapping activity, which can be useful for identifying any memory-related issues or bottlenecks.

By default, vmstat displays statistics at regular intervals, but you can change the interval by using the ‘-n’ option followed by the desired interval in seconds. For example, to display statistics every 5 seconds, you can use the following command:

vmstat -n 5

Vmstat is a powerful tool for monitoring system performance, including memory usage. By analyzing the statistics provided by vmstat, you can gain insights into how memory is being used and identify any potential issues.

8. sar

The sar command is part of the sysstat package and provides a wide range of system performance monitoring capabilities, including memory usage. Sar collects and reports system activity information, allowing you to analyze historical data and identify trends.

To use sar, you first need to install the sysstat package using your package manager. Once installed, you can run the ‘sar’ command followed by the desired options and parameters.

For example, to display memory usage statistics for the current day, you can use the following command:

sar -r

This will display a table that shows various memory-related statistics, including the amount of free memory, the amount of memory used for buffers and cache, and the amount of memory used for active and inactive pages.

Sar allows you to collect and analyze system performance data over time, making it a valuable tool for monitoring memory usage and identifying any potential issues or bottlenecks.

9. cat /proc/[PID]/status

The /proc filesystem in Linux provides a wealth of information about running processes, including memory usage. By accessing the /proc/[PID]/status file, you can obtain detailed information about the memory usage of a specific process.

To check the memory usage of a process using the /proc/[PID]/status file, simply replace [PID] with the actual process ID. For example, to check the memory usage of a process with PID 1234, you can use the following command:

cat /proc/1234/status

The output will include various information about the process, including the amount of memory used, the amount of memory shared with other processes, and the amount of memory used for text, data, and stack segments.

By examining the /proc/[PID]/status file, you can gain insights into how memory is being used by a specific process and identify any potential issues or inefficiencies.

10. cat /proc/[PID]/statm

Similar to the /proc/[PID]/status file, the /proc/[PID]/statm file provides information about the memory usage of a specific process. However, the information provided by the statm file is more focused on memory segments and does not include detailed breakdowns.

To check the memory usage of a process using the /proc/[PID]/statm file, simply replace [PID] with the actual process ID. For example, to check the memory usage of a process with PID 1234, you can use the following command:

cat /proc/1234/statm

The output will include a single line with several numbers, representing the size of various memory segments used by the process. The first number represents the total program size, followed by the resident set size, shared pages, text size, and data and stack sizes.

While the information provided by the statm file is not as detailed as the status file, it can still give you a general idea of the memory usage of a specific process.

11. cat /proc/[PID]/smaps

The /proc/[PID]/smaps file provides a detailed breakdown of the memory usage of a specific process, including information about individual memory regions and their attributes.

To check the memory usage of a process using the /proc/[PID]/smaps file, simply replace [PID] with the actual process ID. For example, to check the memory usage of a process with PID 1234, you can use the following command:

cat /proc/1234/smaps

The output will include a list of memory regions, each with detailed information such as the start and end addresses, permissions, size, and the file or device associated with the region.

By analyzing the /proc/[PID]/smaps file, you can gain insights into how memory is being used by a specific process and identify any potential issues or inefficiencies.

12. cat /proc/[PID]/maps

The /proc/[PID]/maps file provides a similar breakdown of the memory usage of a specific process as the smaps file. However, the maps file provides a more concise and summarized view of the memory regions.

To check the memory usage of a process using the /proc/[PID]/maps file, simply replace [PID] with the actual process ID. For example, to check the memory usage of a process with PID 1234, you can use the following command:

cat /proc/1234/maps

The output will include a list of memory regions, each represented by a single line that includes the start and end addresses, permissions, offset, and the file or device associated with the region.

While the information provided by the maps file is not as detailed as the smaps file, it can still give you a good overview of the memory usage of a specific process.

13. cat /proc/[PID]/stat

The /proc/[PID]/stat file provides various statistics about a specific process, including memory usage. While the information provided by the stat file is not as detailed as the smaps or status files, it can still give you a general idea of the memory usage of a process.

To check the memory usage of a process using the /proc/[PID]/stat file, simply replace [PID] with the actual process ID. For example, to check the memory usage of a process with PID 1234, you can use the following command:

cat /proc/1234/stat

The output will include a single line with various fields, including the process ID, parent process ID, CPU usage, and memory usage. The memory usage is represented in kilobytes (KB).

While the information provided by the stat file is not as detailed as other files in the /proc filesystem, it can still give you a basic understanding of the memory usage of a specific process.

14. cat /proc/[PID]/statm

The /proc/[PID]/statm file provides a similar breakdown of the memory usage of a specific process as the stat file. However, the statm file provides a more concise and summarized view of the memory usage.

cat /proc/1234/statm

While the information provided by the statm file is not as detailed as other files in the /proc filesystem, it can still give you a good overview of the memory usage of a specific process.

15. cat /proc/[PID]/smaps_rollup

The /proc/[PID]/smaps_rollup file provides a summarized view of the memory usage of a specific process, including information about individual memory regions and their attributes.

To check the memory usage of a process using the /proc/[PID]/smaps_rollup file, simply replace [PID] with the actual process ID. For example, to check the memory usage of a process with PID 1234, you can use the following command:

cat /proc/1234/smaps_rollup