[LEDE-DEV] Memory Usage of LEDE trunk on devices with only 32mb memory.

[mt]

Hi,

I'm not sure if that's a bug or inevitable so I'd thought I'd ask here 
about the position from the LEDE devs/community.

At the moment 32MB devices are pretty much unusable with LEDE and I'm 
not sure why.

A 1043NDv1 on CC 15.05 has 15MB free memory:

# cat /proc/meminfo
MemTotal:          28740 kB
MemFree:            7292 kB
MemAvailable:      15328 kB

With LEDE trunk it's only a few megabytes MemAvailable. I've seen 3MB to 
7MB but never more. So where are the additional 10-15MB usage are coming 
from?

This causes quite a few problems at the moment:

- opkg ist broken for these devices - the vfork patch caused problems 
and only did improve the problem for opkg update, opkg list / install 
etc.pp are still failing with out of memory error.

- luci is broken, at least if using luci-mod-admin-full, any hit to the 
router website triggers an oom for me or times out.

This is on the stock LEDE image, without additional packages (e.g. no 
vpn, olsr or batman)..

Is this a kernel issue? Is 4.4 that much bigger? Or where some changes 
in defaults/buffers from 3.18 to 4.4 that caused the increased memory 
usage?

Is 32mb device support something that's bug worthy or is the attitude: 
move on to 64mb devices?

Additionally where can I look to improve the situation? Any hints for 
debugging memory issues in the kernel?

regards & greetings from Weimar
Martin