Too much reserved RAM: how to reclaim?

I’m on a RockPI-S with 256MB RAM.

Running Radxa Ubuntu image (18.04) with latest available kernel (4.4.143-47).

I only have access to about 177 MB RAM total:

            total            used          free      shared  buff/cache   available
Mem:         177980       35456       53436         308       89088      135584

because the kernel “reserves” a lot of RAM (89 MB), don’t know why (no graphics!):

[    0.000000] Memory: 171144K/260096K available (6910K kernel code, 518K rwdata, 2476K rodata, 384K init, 520K bss, 88952K reserved, 0K cma-reserved)

Can I reclaim some RAM back?
I’m a bit memory-constrained on some tasks. :frowning:

Try adding swiotlb=1024 to the kernel command line.
It should let you reclaim 62MB of RAM.


latest available kernel is 4.4.143-49


ubuntu ,not armbian

There is no Ubuntu for this board. Its only “Ubuntu” or Armbian in Ubuntu package relation … or some other 3rd party build.

Armbian Focal 20.04 with kernel 5.6.y (its untested nightly build, but probably works just fine)

No. When I wrote the message, the latest kernel from the official repository was 4.4.143-47.

To do that, take the latest Debian system,, as an example, add the following line at the end of file /boot/uEnv.txt and reboot ROCK Pi S.

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rock@rockpis:~$ free
              total        used        free      shared  buff/cache   available
Mem:         241840       35348      138944         308       67548      198432