Oom killer killed my python3 process while there was free memory

I am working on webserver on a linux embedded board without swap memory. Sometimes my webserver crashed when there was avaliable memory.

I set those configurations to prevent this but it didn't work.

overcommit_memory=2 overcommit_ratio=400 min_free_kbytes=1000,
Meminfo:

MemTotal:         241868 kB
MemFree:          157532 kB 
MemAvailable:     129380 kB
Buffers:               0 kB 
Cached:            22616 kB 
SwapCached:            0 kB 
Active:            53448 kB 
Inactive:           8852 kB
Active(anon):      45644 kB
Inactive(anon):     8448 kB
Active(file):       7804 kB
Inactive(file):      404 kB
Unevictable:           0 kB
Mlocked:               0 kB
HighTotal:             0 kB
HighFree:              0 kB
LowTotal:         241868 kB 
LowFree:          157532 kB 
SwapTotal:             0 kB 
SwapFree:              0 kB 
Dirty:                12 kB 
Writeback:             0 kB 
AnonPages:         39712 kB
Mapped:             8228 kB 
Shmem:             14392 kB 
KReclaimable:       4012 kB
Slab:              13148 kB
SReclaimable:       4012 kB 
SUnreclaim:         9136 kB 
KernelStack:         712 kB
PageTables:          872 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:      967472 kB
Committed_AS:     211544 kB
VmallocTotal:    1818624 kB
VmallocUsed:        3292 kB 
VmallocChunk:          0 kB 
Percpu:               84 kB 
CmaTotal:         131072 kB 
CmaFree:          121228 kB

Logs:

kworker/u2:1 invoked oom-killer: gfp_mask=0x2dc2(GFP_KERNEL|__GFP_HIGHMEM|__GFP_NOWARN|__GFP_ZERO), order=0, oom_score_adj=0

                [  pid  ] uid    tgid total_vm    rs pgtables_bytes swapents   oom_score_adj  name
[256776.750536] [    141]     0   141     2973       39    14336        0             0 rngd
[256776.759213] [    143]     0   143     9620      938    24576        0          -250 systemd-journal
[256776.768543] [    163]     0   163     2858      128    14336        0         -1000 systemd-udevd
[256776.777677] [    179]   992   179     6008       77    18432        0             0 systemd-timesyn
[256776.787171] [    435]     0   435      366       18     8192        0             0 atd
[256776.795496] [    436]     0   436      596       64     8192        0             0 crond
[256776.804098] [    437]   999   437      841       95    10240        0          -900 dbus-daemon
[256776.813047] [    444]     0   444     1455      112    12288        0             0 ofonod
[256776.821765] [    454]     0   454      376       30    10240        0             0 syslogd
[256776.830476] [    461]   998   461      684       44    12288        0             0 rpcbind
[256776.839183] [    468]     0   468     1256      932    12288        0             0 klogd
[256776.847852] [    469]     0   469     1299       81    12288        0             0 systemd-logind
[256776.857158] [    470]   993   470     1342       79    14336        0             0 systemd-resolve
[256776.866536] [    471]   996   471      947       81    12288        0             0 avahi-daemon
[256776.875745] [    472]   997   472      613      123    12288        0             0 rpc.statd
[256776.884678] [    477]   996   477      916       51    10240        0             0 avahi-daemon
[256776.893703] [    478]     0   478     3231      106    16384        0             0 tcf-agent
[256776.902526] [    482]     0   482      886       19    10240        0             0 agetty
[256776.911093] [    488]     0   488     4208     1681    26624        0             0 mydaemon
[256776.919901] [    490]     0   490     4834     2334    26624        0             0 python3
[256776.928492] [    597]     0   597    14636     5348    49152        0             0 python3
[256776.937084] [  12534]     0 12534      655       77     8192        0             0 sh
[256776.945600] [  19169]     0 19169    16437      309    30720        0             0 core
[256776.954004] [  19177]     0 19177     2154      142    14336        0             0 wpa_supplicant
[256776.963406] [  19179]   994 19179     1454      102    14336        0             0 systemd-network
[256776.972869] oom-kill:constraint=CONSTRAINT_NONE,nodemask=(null),task=python3,pid=597,uid=0
[256776.981576] Out of memory: Killed process 597 (python3) total-vm:58544kB, anon-rss:21392kB, file-rss:0kB, shmem-rss:0kB, UID:0 pgtables:49152kB oom_score_adj:0
[256777.041482] oom_reaper: reaped process 597 (python3), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB

The only way to stop it is to add more RAM (which you probably can't) or create a small swap file.

Some background info:
https://chrisdown.name/2018/01/02/in...e-of-swap.html

Originally Posted by selcukgk29 Sometimes my webserver crashed when there was avaliable memory.

Prove it - that meminfo needs to be immediately before the oom killer strikes.

[256776.981576] Out of memory: Killed process 597 (python3) total-vm:58544kB, anon-rss:21392kB, file-rss:0kB, shmem-rss:0kB, UID:0 pgtables:49152kB oom_score_adj:0

I'll believe the kernel until proven otherwise.

With those sysctls you need a (large) swap.

The board has 256 Mb ram. When I tested ram allocation test with

/dev/zero head -c 1000m |tail

, oom killed tail process at total-vm:159600kB.

[12781.161711] Out of memory: Killed process 14482 (tail) total-vm:159600kB, anon-rss:158240kB, file-rss:4kB, shmem-rss:0kB, UID:0 pgtables:165888kB oom_score_adj:0

But oom killed python3 at total-vm 58544kB before ?

python itself needs a lot of ram.