Q: I have a question, I want to monitor the memory usage of my Linux system. What views or command line tools are available under Linux?

A: In Linux systems, there are many ways to monitor memory usage. Here are some ways to view memory usage through view tools or the command line.

1. /proc/meminfo: The easiest way is to look at the /proc/meminfo file. This virtual file updates dynamically and provides detailed information about memory usage. It lists various memory metrics to cover most of your memory usage needs. In addition, you can also view the memory usage information of the process through /proc/<pid>/statm</pid> and /proc/<pid>/status</pid>.

2. free Command: This command can display the memory usage in the system, including used memory, free memory, cache and swap space, etc. You can use the free -h command to display memory usage in a human-readable way.

3. top Command: top The command can display various performance indicators of the system in real time, including memory usage. You can use the top command and press the Shift m key to sort processes by memory usage.

4. htop Tool: htop is an interactive process viewing tool that can display various performance indicators of the system, including memory usage, in a more friendly way. You can use the sudo apt install htop command to install and run htop.

5. glances Tool: glances is a versatile system monitoring tool that can summarize and display various performance indicators of the system, including memory usage. You can use the sudo apt install glances command to install and run glances.

These tools and commands provide different ways to monitor the memory usage of Linux systems. You can choose the appropriate tool to use according to your needs. Hope this information is helpful to you!

$ cat /proc/meminfo

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2.atop

atop command is a terminal environment monitoring command. It shows a combination of various system resources (CPU, memory, network, I/O, kernel) and is color-coded under high load conditions.

$ sudo atop

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3.free

The free command is a quick way to view memory usage. It is an overview of the information collected by /proc/meminfo.

$ free -h

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4.GNOME System Monitor

GNOME System Monitor is a view tool that displays the usage of CPU, memory, swap area and network in the recent period. It also provides a way to view CPU and memory usage.

$ gnome-system-monitor

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5.htop

The htop command displays the real-time memory usage of each process. It provides reports on the resident memory size of all processes, total program memory size, shared library size, etc. The list can be scrolled horizontally and vertically.

$ htop

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6.KDE System Monitor

The functions are the same as the GENOME version introduced in 4.

$ ksysguard

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7.memstat

memstat is a command that effectively identifies the use of virtual memory by executable(s), process(es) and shared libraries. Given a process ID, memstat can list the executable files, data and shared libraries associated with this process.

$ memstat -p 

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8.nmon

nmon是一个基于ncurses的系统基准测试工具，它可以监控CPU、内存、I/O、文件系统及网络资源等的互动模式。对于内存的使用，它可以实时的显示 总/剩余内存、交换空间等信息。

$ nmon

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9.ps

ps命令可以实时的显示各个进程的内存使用情况。Reported memory usage information includes %MEM (percent of physical memory used), VSZ (total amount of virtual memory used), and RSS (total amount of physical memory used)。你可以使用 “–sort”选项对进程进行排序，例如按RSS进行排序：

$ ps aux --sort -rss

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10.smem

smem命令允许你统计基于/proc信息的不同进程和用户的内存使用情况。内存使用情况的分析可以导出图表（如条形图和饼图）。

$ sudo smem --pie name -c "pss"

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11.top

top命令提供了实时的运行中的程序的资源使用统计。你可以根据内存的使用和大小来进行排序。

$ top

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12.vmstat

vmstat命令显示实时的和平均的统计，覆盖CPU、内存、I/O等内容。例如内存情况，不仅显示物理内存，也统计虚拟内存。

$ vmstat -s

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