{"id":962,"date":"2018-10-20T10:47:06","date_gmt":"2018-10-20T07:47:06","guid":{"rendered":"http:\/\/kifarunix.com\/?p=962"},"modified":"2024-03-11T20:05:08","modified_gmt":"2024-03-11T17:05:08","slug":"how-to-measure-memory-usage-in-linux","status":"publish","type":"post","link":"https:\/\/kifarunix.com\/how-to-measure-memory-usage-in-linux\/","title":{"rendered":"How to Measure Memory Usage in Linux"},"content":{"rendered":"\n
Linux provides a handful tools for measuring and checking memory usage. In this tutorial, we are going to learn a quite a number of these tools so that we can be able to troubleshoot any memory related issues.<\/p>\n\n\n\n
free<\/strong><\/h2>\n\n\n\n
free command is one of the most popular commands for checking free and used physical memory as well as swap space on Linux system. It also shows the buffers and caches used by the kernel. Below are basic examples of the free command.<\/p>\n\n\n\n
# free -h\n total used free shared buff\/cache available\nMem: 15G 6.1G 3.3G 574M 6.1G 8.5G\nSwap: 7.9G 0B 7.9G<\/pre>\n\n\n\n
The -h<\/strong> option shows the output fields automatically scaled to shortest three digit unit and display the units of print out. You may also use -b, -k, -m, -g<\/strong> to display the output in bytes, kilobytes, megabytes, gigabytes<\/strong> respectively.<\/p>\n\n\n\n
The displayed columns are:<\/p>\n\n\n\n
\n
total<\/strong> – shows the total installed memory (MemTotal and SwapTotal in \/proc\/meminfo)<\/li>\n\n\n\n
used<\/strong> – Used memory (calculated as total – free – buffers – cache<\/strong>)<\/li>\n\n\n\n
free<\/strong> – Unused memory (MemFree and SwapFree in \/proc\/meminfo)<\/li>\n\n\n\n
shared<\/strong> – Memory used (mostly) by tmpfs (Shmem in \/proc\/meminfo)<\/li>\n\n\n\n
buffers<\/strong> – Memory used by kernel buffers (Buffers in \/proc\/meminfo)<\/li>\n\n\n\n
cache<\/strong> – Memory used by the page cache and slabs (Cached and Slab in \/proc\/meminfo)<\/li>\n\n\n\n
buff\/cache<\/strong> – Sum of buffers and cache<\/li>\n\n\n\n
available – <\/strong>Estimation of how much memory is available for starting new applications, without swapping.<\/li>\n<\/ul>\n\n\n\n
\/proc\/meminfo<\/strong><\/h2>\n\n\n\n
\/proc\/meminfo<\/strong> reports a large amount of valuable information about the system’s RAM usage. To read this file, you can use cat<\/strong> command of paging commands like less<\/strong>.<\/p>\n\n\n\n
Much of the information in \/proc\/meminfo<\/strong> is used by the free<\/code>, top<\/code>, and ps<\/code> commands. The output of the free<\/strong> command is similar in appearance to the contents and structure of \/proc\/meminfo<\/strong>.<\/p>\n\n\n\n
Some of the information that you may be interested in the output of the \/proc\/meminfo include;<\/p>\n\n\n\n
\n
MemTotal<\/strong>: Total amount of usable RAM.<\/li>\n\n\n\n
MemFree<\/strong>: The amount of physical RAM left unused by the system.<\/li>\n\n\n\n
MemAvailable<\/strong>: An estimate of how much memory is available for starting new applications, without swapping.<\/li>\n\n\n\n
Buffers<\/strong>: The amount of temporary storage for raw disk blocks.<\/li>\n\n\n\n
Cached<\/strong>: The amount of physical RAM used as cache memory.<\/li>\n\n\n\n
SwapCached<\/strong>: The amount of memory that has once been moved into swap, then back into the main memory.<\/li>\n\n\n\n
SwapTotal<\/strong>: The total amount of swap available.<\/li>\n\n\n\n
SwapFree<\/strong>: The total amount of swap free.<\/li>\n<\/ul>\n\n\n\n
Note the the units of the \/proc\/meminfo is in kibibytes (KiB; 1 KiB equals 1024 B).<\/p>\n\n\n\n
top<\/strong><\/h2>\n\n\n\n
The top program provides a dynamic real-time view of a running system. This also enables you to check per process memory usage. To use top command to check per process memory, just run the command and press Shift+m <\/strong>to sort processes by memory usage in descending order.<\/p>\n\n\n\n<\/a>top-memory-usage<\/figcaption><\/figure>\n\n\n\n
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