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

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

Postby ajhlinuxuser » Sat Nov 17, 2018 4:49 am

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:
Code: Select all
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'
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[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':
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https://pastebin.com/8xY9HkVa


My terminal at the exact moment when these ssh processes are being killed (followed by the 'free' command)
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[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:
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$ 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.

Code: Select all
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         
ajhlinuxuser
 
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