How do you determine which individual pages are resident on Linux

As a Linux user, it is essential to have a good understanding of how to determine which individual pages are resident on your system. This knowledge can help you optimize your system's performance and avoid memory issues. In this article, we will discuss different ways to identify resident pages on Linux, including using command-line tools and system monitoring utilities.

Understanding Resident Pages

Before we dive into ways of identifying resident pages on Linux, let's first understand what resident pages are. When a process in Linux accesses a file or program, kernel copies data into memory to speed up future access. This data is known as a page. Resident pages are pages that are currently present in physical memory of system.

Resident pages are essential for efficient memory management as they help reduce time required for system to retrieve data from hard disk. However, if a process requires more memory than what is available in physical memory, kernel has to move some pages from memory to swap space, which can slow down system's performance.

There are several ways to identify which pages are currently resident in memory on Linux.

Using /proc Filesystem

The /proc filesystem is a virtual filesystem that provides information about system's current state. It is a powerful tool for monitoring system's resources, including memory. /proc filesystem contains several directories and files, including /proc/[pid]/maps file, which can be used to determine resident pages of a process.

To use /proc filesystem, first, find process ID (PID) of process you want to monitor. You can use ps command to find PID. For example, to find PID of Firefox process, run following command −

ps aux | grep firefox

This will show a list of processes running on your system that contains word 'firefox'. Look for PID in second column of output.

Once you have PID, you can use /proc filesystem to find resident pages of process. For example, to find resident pages of Firefox process, run following command −

cat /proc/[PID]/smaps | grep Rss

This command will display a list of memory mappings for process and their resident memory usage in kilobytes.

Using pmap Command

The pmap command is a utility that shows memory usage of a process, including resident pages. To use pmap command, run following command, where [PID] is process ID −

pmap -x [PID]

This command will display memory usage of process in hexadecimal format, including resident pages, shared memory, and other memory segments.

Using top Command

The top command is a powerful utility for monitoring system's resources, including memory. top command displays a real-time view of system's processes and their memory usage. To use top command, run following command −

top

This will display a real-time view of system's processes and their memory usage. resident pages of a process can be found under RES column.

Using free Command

The free command is a system monitoring utility that displays amount of free and used memory in system. free command can be used to determine resident pages of system. To use free command, run following command −

free -m

This command will display total memory, used memory, free memory, and other memory usage statistics. resident pages of system can be found under used column.

Additionally, Linux users can also use vmstat command to determine resident pages on their system. vmstat command is a utility that reports virtual memory statistics, including resident pages. To use vmstat command, run following command −

vmstat -s | grep 'pages resident'

This command will display number of resident pages on system.

Another tool that Linux users can use to identify resident pages is htop command. htop command is an interactive process viewer that displays system's processes and their memory usage. To use htop command, run following command −

htop

This command will display an interactive view of system's processes and their memory usage. resident pages of a process can be found under RES column.

It is important to note that while identifying resident pages is important, it is not only factor that affects system's performance. Other factors, such as CPU usage, I/O operations, and network activity, can also impact system's performance. Therefore, it is recommended to monitor all system resources to ensure optimal performance.

Conclusion

In this article, we have discussed different ways to identify which individual pages are resident on Linux. We have seen how /proc filesystem, pmap command, top command, and free command can be used to determine resident pages. By using these tools, Linux users can monitor their system's memory usage and optimize its performance.

It is crucial to keep an eye on resident pages of system to prevent memory-related issues. By identifying which pages are resident, users can determine if their system has enough physical memory to handle workload. If not, they can take appropriate action to optimize system's performance or upgrade memory.

In summary, Linux provides several tools to monitor memory usage and determine which individual pages are resident on system. By utilizing these tools, Linux users can optimize their system's performance and avoid memory issues.