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I have a static memory splitting (configured in config file and confirmed by vcgencmd) of

arm=496M
gpu=16M

But when I run free -h I get

             total       used       free     shared    buffers     cached
Mem:          485M       184M       300M         0B        17M       128M
-/+ buffers/cache:        38M       446M
Swap:           0B         0B         0B

So, a total of 485 MB instead of 496 MB. Where did the 11 MB go? Also, the sum of columns used + free is 484 MB instead of 485 MB. How does the memory calculation work? free agrees with cat /proc/meminfo, as a side note.

Why are these numbers not matching?

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  • 2
    496*1000/1024=484. Different definitions of what is kilo is (1000 or 1024).
    – Gerben
    May 26, 2014 at 11:42

1 Answer 1

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on my system:

$ free
             total       used       free     shared    buffers     cached
Mem:        496948     260252     236696          0       6560     210968
-/+ buffers/cache:      42724     454224
Swap:       102396      21940      80456
$

260252 + 236696 = 496948, and you should drop -h switch to avoid rounding errors.

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  • This does it also show for me. 496948 / 1024 = 485MB. So, free -h calculates correctly. 496 MB * 1024 should be 507904 kB, however. So, there are still some MB missing.
    – Foo Bar
    May 26, 2014 at 7:06
  • there are megabytes of 1024kb size and there are megabytes of 1000kb size, you should not worry this much about it.
    – lenik
    May 26, 2014 at 7:18
  • I know about 2-based and 10-based prefixes, but some tools on the Raspberry Pi seem to use/name it not consistently, and now I'd like to know where the "bug" sits and which numbers to trust.
    – Foo Bar
    May 26, 2014 at 7:23

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