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Running the htop command gives you a picture of the memory usage in a format like this: 

1.92G/5.83G

Question: how should I interpret the values taken from /proc/meminfo in order to calculate programmatically the memory used?

I am looking for something similar to this: Accurate calculation of CPU usage given in percentage in Linux? meaning that pseudocode is ok, I do not need something that can be compiled, just the logic. The source code of htop is a place to look for but I had no luck spotting the lines of code written for this...

$ cat /proc/meminfo MemTotal: 6110716 kB MemFree: 2076448 kB MemAvailable: 3800944 kB Buffers: 382240 kB Cached: 1496216 kB SwapCached: 0 kB Active: 2830192 kB Inactive: 796648 kB Active(anon): 1749940 kB Inactive(anon): 109808 kB Active(file): 1080252 kB Inactive(file): 686840 kB Unevictable: 48 kB . . . ...
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  • That depends on how accurate a picture you're wanting. For the 1.92G/5.83G stats you quote, simply take the numbers in the first two lines and convert from kB to GB (i.e. divide by 1024*1024)... Most of the rest of the lines are simply a breakdown of what's currently in use base on how it's being used, whether it's been modified or not, and a few other characteristics... Commented Dec 19, 2016 at 16:04
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    Hi @twalberg, thanks for your reply. So you are proposing something like [MemUsed] = [MemTotal] - [MemAvailable]? Commented Dec 19, 2016 at 16:20
  • I'm not really proposing anything, because it's not clear what kind of "picture" you're actually looking for. That might be a reasonable estimate, but it's not going to be exact - memory accounting in Linux (or really any significant OS, for that matter) is complex and not easily reduced to an equation in two variables... Commented Dec 19, 2016 at 16:24
  • the free command dumps the same as /proc/meminfo. Commented Dec 20, 2016 at 14:30

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htop author here. These are the calculations I make to get the numbers for the green, blue and yellow bars in the memory meter:

  • Total used memory = MemTotal - MemFree
  • Non cache/buffer memory (green) = Total used memory - (Buffers + Cached memory)
  • Buffers (blue) = Buffers
  • Cached memory (yellow) = Cached + SReclaimable - Shmem
  • Swap = SwapTotal - SwapFree

In the htop source code: linux/LinuxProcessList.c and linux/Platform.c.

htop screenshot

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6 Comments

How about blue? Also, what is « Buffers »?
Sorry, buffers was mislabeled yellow, it is blue. man proc says this about Buffers: "Relatively temporary storage for raw disk blocks that shouldn't get tremendously large"
@NicolasWormser 30% of RAM is “buffers”. What is it?
Why do you subtract shared memory from the cached memory (Cached + SReclaimable - Shmem)? The top command doesn't seem to do this for its buff/cache calculation.
@MattK, if I had to guess, it's probably because Shmem is included in the number for Cached, and he feels that it shouldn't count as true cached memory.
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