Linux memory management artifact: smem tool

Hi everybody, I'm.

Today I want to introduce to you a very practical memory management tool in Linux systems: smem.

smem is a command line tool that can generate a variety of memory usage reports. Unlike other existing tools, smem can report PSS (Proportional Set Size, proportional occupied size), which is a more meaningful metric. It accurately measures the amount of memory used by libraries and applications in a virtual memory system.

Traditionally, since most physical memory is often shared among multiple applications, using resident set size (RSS) as a measure of memory usage overestimates actual memory consumption. In contrast, the PSS parameter measures the memory allocated by each application in each shared memory region, which provides a more realistic and accurate metric.

1. Install smem tool

If you are using Fedora 19 or above, smem is in the repository by default, so you can install it using yum:

$ sudo yum install smem

For Ubuntu users, you can use the apt-get command to install smem:

$ sudo apt-get install smem

If it cannot be installed normally, you can download its source code and install it directly at the address: https://www.selenic.com/smem/download/

2. Common usage of smem tool

By default, smem will display each running process and the memory used. Here, you can note the size of RSS relative to USS and PSS, and you can see that it is significantly higher than the other two.

$ smem

In addition, smem can also display the memory used by each library. This result is relatively long and may take some time, depending on your system.

$ smem -m

This command produces too many results. If we want to check the memory usage of a specific application, such as Firefox, then we can use it with the grep command and use -p## at the same time. # option to view memory usage as a percentage.

$ smem -m -p | grep firefox

smem The command can also display the memory usage of each user. You need to use the -u option:

$ smem -u -p

你还可以使用 -w 选项查看系统内存使用情况：

$ smem -w -p

3. 结果可视化输出

显示数字毕竟不直观，我们还可以使用 smem 生成图形图表来显示内存使用情况，一目了然。要达到这个目的，我们需要使用到除了不能生孩子啥都可以干的 Python 。

但光有 Python 还不行，还需要安装用于生成图表的 matplotlib 库。

Fedora 用户可以通过运行以下命令来安装它：

$ sudo yum install python-matplotlib

Ubuntu 用户可以通过运行下面命令获得它：

$ sudo apt-get install python-matplotlib

库安装之后，现在就可以以条形图或饼图的形式将获得的内存使用情况以可视化表示。

3.1 饼形图

使用 smem 以饼图的形式查看内存使用情况，需要加上 --pie 选项，如下所示：

$ smem --pie name -s pss

命令运行之后将生成一个饼图。请注意，这条命令里我们还加了 -s pss ，意思是显示 PSS 的内存使用情况。要获取 USS 和 RSS 的饼图，只需将命令中的 pss 替换为 uss 或 rss 即可。

从两个饼图中，可以看到 RSS 报告还有 41.74% 的未使用内存，而 PSS 报告有 53.02% 的未使用内存。可以看出来，RSS 显示的可用内存偏小，但实际还有很充足的内存空间。

3.2 柱状图

smem 的另一个很酷的特性是以柱状图的形式生成输出。有了这个功能，你可以一次性查看 USS、PSS 和 RSS 报告的内存使用情况。

要实现这个功能，需要加上 --bar 选项：

$ smem --bar pid -c "pss uss rss"

上面的命令将给出带有进程 ID 号的内存使用情况的输出结果。如果想要查看进程的名称，可以将 pid 替换为 name 即可。

命令运行之后，可以生成如下图所示的条柱状图。

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