Understanding and Monitoring Your Raspberry Pi’s Memory Usage

A step-by-step guide for checking memory space on your Raspberry Pi, including command line tools and visualization options. …


Updated September 19, 2023

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A step-by-step guide for checking memory space on your Raspberry Pi, including command line tools and visualization options.

The Raspberry Pi is a versatile computer system that can be used for various projects and tasks. One of the most important aspects to consider when using a Raspberry Pi is its memory usage. This article will guide you through checking your Raspberry Pi’s memory space, both in terms of total available space and how much is being used at any given time. We will cover the following topics:

  1. Command Line Tools for Checking Memory Space
  2. Visualizing Your Memory Usage with htop
  3. Conclusion

1. Command Line Tools for Checking Memory Space

Raspberry Pi comes with several built-in command line tools that allow you to check the memory space available and in use on your device. These are some of the most useful ones:

free

free is a command line tool that displays the total amount of RAM and swap space available, as well as how much is currently being used. You can run it by opening up a terminal window (either through SSH or directly on the Raspberry Pi) and typing free. The output will look something like this:

             total       used       free     shared    buffers     cached
Mem:       947680     253012     69478      12396        152      91324
-/+ buffers/cache:     13524     912356
Swap:            0          0          0

In this example, the Raspberry Pi has 94768 MB of total RAM, with 253012 MB used and 69478 MB free. The -/+ buffers/cache: line shows the difference between the actual usage and what is considered “free” by the system (i.e., memory that can be reclaimed if needed).

df

df stands for disk space, but it can also be used to check memory space. To display memory usage in a more human-readable format, you can run df -h. This command will show you the total size and available space of all mounted file systems, including your SD card and any USB drives connected to the Raspberry Pi:

Filesystem      Size  Used Avail Use% Mounted on
/dev/root       14G  2.5G   11G  19% /
devtmpfs        48M     0   48M   0% /dev
tmpfs          76M     0   76M   0% /dev/shm
tmpfs         3.9G     0  3.9G   0% /run
tmpfs          5.0M     0  5.0M   0% /run/lock
tmpfs          76M     0   76M   0% /sys/fs/cgroup
/dev/mmcblk0p1   23M   19M  3.4M  86% /boot

In this example, the SD card has a total size of 14 GB and is currently using 2.5 GB.

cat /proc/meminfo

The /proc/meminfo file contains detailed information about your Raspberry Pi’s memory usage. You can view it by running cat /proc/meminfo. This command will output a long list of values, including total RAM, free RAM, and swap space:

MemTotal:        947680 kB
MemFree:         69428 kB
MemAvailable:    93356 kB
Buffers:           152 kB
Cached:          9132 kB
SwapCached:          0 kB
Active:         24936 kB
Inactive:        7884 kB
Active(anon):     6104 kB
Inactive(anon):   3332 kB
Active(file):    1832 kB
Inactive(file):  1552 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:             0 kB
SwapFree:              0 kB
Dirty:                 0 kB
Writeback:             0 kB
AnonPages:        6072 kB
Mapped:            356 kB
Shmem:             124 kB
Slab:             2988 kB
SReclaimable:      2532 kB
SUnreclaim:         456 kB
KernelStack:        32 kB
PageTables:         76 kB
NFS_Unstable:          0 kB
Bounce:              0 kB
WritebackTmp:        12 kB
CommitLimit:      89608 kB
Committed_AS:     5344 kB
VmallocTotal:   34359738367 kB
VmallocUsed:       3500 kB
VmallocChunk:   3435973272 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
ShmemHugePages:        0 kB
ShmemPmdMapped:        0 kB
FileHugePages:         0 kB
FilePmdMapped:         0 kB
CmaTotal:              0 kB
CmaFree:               0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:      13600 kB
DirectMap2M:     956800 kB

Here you can see the total amount of RAM (MemTotal), as well as how much is currently free (MemFree) and available (MemAvailable).

2. Visualizing Your Memory Usage with htop

htop is a popular command line tool that provides a real-time, interactive view of your system’s processes and resources usage. It can be especially useful for monitoring memory space on the Raspberry Pi. To install htop, run:

sudo apt-get update
sudo apt-get install htop

Once installed, you can launch it by typing htop in your terminal window. The main screen will show a list of running processes, sorted by CPU usage. At the top of the screen, you’ll see information about your Raspberry Pi’s memory usage:

  • Tasks: The number of processes currently running.
  • Load average: A measure of the system load over the last 1, 5, and 15 minutes.
  • Memory: The total amount of RAM on your device, as well as how much is used, free, buffers, and cache.
  • Swap: The total amount of swap space and how much is currently being used.

You can use the arrow keys to navigate between processes, sort by different criteria (e.g., by memory usage or CPU time), and kill processes if necessary. Press F5 to refresh the display, and q to exit htop.

3. Conclusion

Checking your Raspberry Pi’s memory space is an important aspect of running any project on this device. The command line tools we covered (free, df, and cat /proc/meminfo) can provide detailed information about your system’s RAM, while htop offers a visual way to monitor processes and resource usage in real-time. With these tools, you can keep an eye on your Raspberry Pi’s memory usage and ensure that your projects have enough space to run efficiently.