[RPi1 rev.1] Linux OOM-Killer ending processes for no reason

[ajhlinuxuser]

Hi there,

I have been using an old Raspberry Pi 1 model B (rev.1 with only 256MB RAM) for MariaDB command line practice as well as some ssh connections, as non-graphical usage seemed a fitting use for the old but perfectly good device.

I am finding that as I have more simultaneous ssh commands running, the Linux Out-Of-Memory killer is ending ssh sessions. I now run just over 20 instances of ssh compared to less than 10 when I was not having problems. I even disabled the MariaDB daemon to free up memory.

But memory does not seem to be scarce, I have never seen free report more than 80MB used of the 256 total memory capacity.

Does anyone know why OOM-killer would be doing this? What things should I document in order to get this resolved?

References:

/proc/cpuinfo:
$this->bbcode_second_pass_code('', 'processor : 0
model name : ARMv6-compatible processor rev 7 (v6l)
BogoMIPS : 2.00
Features : swp half thumb fastmult vfp edsp java tls
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x0
CPU part : 0xb76
CPU revision : 7

Hardware : BCM2708
Revision : 0002
Serial : 00000000c20aabe5
')

'uname -a'
$this->bbcode_second_pass_code('', '[root@purity log]# uname -a
Linux purity 3.10.30-1-ARCH #1 PREEMPT Sun Feb 16 01:04:42 MST 2014 armv6l GNU/Linux')

running 'dmesg':
$this->bbcode_second_pass_code('', 'https://pastebin.com/8xY9HkVa')

My terminal at the exact moment when these ssh processes are being killed (followed by the 'free' command)
$this->bbcode_second_pass_code('', '
[adam@purity ~]$ ssh blah
Killed
[adam@purity ~]$ ssh blah
Killed
[adam@purity ~]$ ssh blah
Killed
[adam@purity ~]$ free
total used free shared buffers cached
Mem: 213944 73088 140856 1256 44 4608
-/+ buffers/cache: 68436 145508
Swap: 0 0 0
')

Lastly the load average goes up as high as 3, and then just logging into the Raspberry Pi becomes problematic:
$this->bbcode_second_pass_code('', '
$ ssh raspberry
packet_write_wait: Connection to 192.168.2.139 port 22: Broken pipe
$ ssh raspberry
ssh_exchange_identification: read: Connection reset by peer
')

I see that kswapd is taking up a lot of CPU time, but I don't have any swap set up, because I've never seen my usage breach the 100MB mark for the work I have used this Raspberry Pi for.

$this->bbcode_second_pass_code('', 'top - 23:44:54 up 19 days, 17:45, 28 users, load average: 4.51, 1.78, 0.87
Tasks: 179 total, 1 running, 178 sleeping, 0 stopped, 0 zombie
%Cpu(s): 2.1 us, 26.7 sy, 0.0 ni, 25.7 id, 40.9 wa, 3.7 hi, 0.8 si, 0.0 st
KiB Mem: 213944 total, 73896 used, 140048 free, 44 buffers
KiB Swap: 0 total, 0 used, 0 free. 4244 cached Mem

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
20 root 20 0 0 0 0 S 19.3 0.0 64:47.77 kswapd0
5914 adam 20 0 2912 496 160 R 4.5 0.2 0:10.63 top
46 root 20 0 0 0 0 S 3.4 0.0 18:53.24 mmcqd/0
5933 adam 20 0 3108 216 60 D 1.7 0.1 0:00.06 lquicK
5669 adam 20 0 6160 616 156 D 1.1 0.3 0:00.41 ssh
5649 adam 20 0 6160 616 156 D 0.8 0.3 0:00.44 ssh
5656 adam 20 0 6160 616 156 D 0.6 0.3 0:00.41 ssh
5745 adam 20 0 3312 316 0 S 0.6 0.1 0:00.16 bash
3 root 20 0 0 0 0 S 0.3 0.0 8:07.80 ksoftirqd/0
114 root 20 0 1672 48 0 S 0.3 0.0 5:41.61 rngd
5645 adam 20 0 10528 652 0 S 0.3 0.3 0:00.18 sshd
5666 adam 20 0 6160 616 156 D 0.3 0.3 0:00.39 ssh
5710 adam 20 0 10528 652 0 S 0.3 0.3 0:00.49 sshd
5744 adam 20 0 10528 652 0 S 0.3 0.3 0:00.04 sshd
5908 root 20 0 99300 336 120 D 0.3 0.2 0:01.83 systemd-jou+
5920 adam 20 0 10528 652 0 S 0.3 0.3 0:00.20 sshd
5926 adam 20 0 6160 508 48 D 0.3 0.2 0:00.56 ssh ')