Output of free showed that my applications only use 2GB, swap was not used at all. Yet my applications were being killed (Skype, Firefox, Thunderbird). I watched it on htop and it looked like they allocated few megabytes and got killed. I had to reboot to fix the problem.My question is why and more importantly how to fix it when this happens again (I mean other than restart)? (EDIT3)It was very annoying, I lost quite a long post (Firefox was killed without any notice) and other things. Is it normal on Linux, killing applications b/c OOM on 80% free memory and with no attempt to use swap at all?EDIT: Distribution is Kubuntu 16.04.EDIT2: Log (small fragment, b/c of post length limit):[ 2687.946164] Xorg invoked oom-killer: gfp_mask=0x24040c0, order=3, oom_score_adj=0[ 2687.946167] Xorg cpuset=/ mems_allowed=0[ 2687.946171] CPU: 3 PID: 2109 Comm: Xorg Tainted: P           OE   4.4.0-59-generic #80-Ubuntu[ 2687.946172] Hardware name: MSI MS-7850/B85-G41 PC Mate(MS-7850), BIOS V2.9 03/30/2015[ 2687.946174]  0000000000000286 00000000828bbbc2 ffff880409ad38d8 ffffffff813f7583[ 2687.946176]  ffff880409ad3ab0 ffff880392c09c00 ffff880409ad3948 ffffffff8120ad5e[ 2687.946177]  0000000000000015 0000000000000000 ffff8802e4f47180 ffff8800033c2a00[ 2687.946179] Call Trace:...[ 2687.946394] Mem-Info:[ 2687.946396] active_anon:720752 inactive_anon:279235 isolated_anon:0[ 2687.946396]  active_file:729283 inactive_file:2048755 isolated_file:0[ 2687.946396]  unevictable:24 dirty:34175 writeback:29190 unstable:0[ 2687.946396]  slab_reclaimable:107795 slab_unreclaimable:37549[ 2687.946396]  mapped:269800 shmem:51809 pagetables:15581 bounce:0[ 2687.946396]  free:38642 free_pcp:46 free_cma:0[ 2687.946398] Node 0 DMA free:15900kB min:64kB low:80kB high:96kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15984kB managed:15900kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes[ 2687.946401] lowmem_reserve[]: 0 3401 15912 15912 15912[ 2687.946403] Node 0 DMA32 free:69016kB min:14432kB low:18040kB high:21648kB active_anon:393040kB inactive_anon:463048kB active_file:635316kB inactive_file:1758444kB unevictable:80kB isolated(anon):0kB isolated(file):0kB present:3613072kB managed:3532452kB mlocked:80kB dirty:26300kB writeback:23864kB mapped:226516kB shmem:47828kB slab_reclaimable:91324kB slab_unreclaimable:56464kB kernel_stack:2704kB pagetables:13724kB unstable:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no[ 2687.946406] lowmem_reserve[]: 0 0 12510 12510 12510[ 2687.946408] Node 0 Normal free:69652kB min:53084kB low:66352kB high:79624kB active_anon:2489968kB inactive_anon:653892kB active_file:2281816kB inactive_file:6436576kB unevictable:16kB isolated(anon):0kB isolated(file):0kB present:13074432kB managed:12810984kB mlocked:16kB dirty:110400kB writeback:92896kB mapped:852684kB shmem:159408kB slab_reclaimable:339856kB slab_unreclaimable:93732kB kernel_stack:11072kB pagetables:48600kB unstable:0kB bounce:0kB free_pcp:172kB local_pcp:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:128 all_unreclaimable? no[ 2687.946411] lowmem_reserve[]: 0 0 0 0 0[ 2687.946412] Node 0 DMA: 1*4kB (U) 1*8kB (U) 1*16kB (U) 0*32kB 2*64kB (U) 1*128kB (U) 1*256kB (U) 0*512kB 1*1024kB (U) 1*2048kB (M) 3*4096kB (M) = 15900kB[ 2687.946419] Node 0 DMA32: 6415*4kB (UME) 2655*8kB (UME) 1398*16kB (UME) 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 69268kB[ 2687.946424] Node 0 Normal: 10812*4kB (ME) 2620*8kB (UM) 72*16kB (M) 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 1*4096kB (H) = 69456kB[ 2687.946439] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=1048576kB[ 2687.946440] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=2048kB[ 2687.946441] 2829837 total pagecache pages[ 2687.946442] 0 pages in swap cache[ 2687.946443] Swap cache stats: add 0, delete 0, find 0/0[ 2687.946443] Free swap  = 16699388kB[ 2687.946444] Total swap = 16699388kB[ 2687.946444] 4175872 pages RAM[ 2687.946445] 0 pages HighMem/MovableOnly[ 2687.946445] 86038 pages reserved[ 2687.946446] 0 pages cma reserved[ 2687.946446] 0 pages hwpoisoned[ 2687.946447] [ pid ]   uid  tgid total_vm      rss nr_ptes nr_pmds swapents oom_score_adj name[ 2687.946453] [  445]     0   445     8850     1198      20       3        0             0 systemd-journal[ 2687.946454] [  478]     0   478    25742      381      17       3        0             0 lvmetad[ 2687.946456] [  492]     0   492    11323     1100      23       3        0         -1000 systemd-udevd[ 2687.946458] [ 1070]   100  1070    25596      640      21       3        0             0 systemd-timesyn[ 2687.946459] [ 1112]     0  1112     1100      333       8       3        0             0 acpid[ 2687.946461] [ 1116]     0  1116    41637     2192      36       3        0             0 thermald[ 2687.946462] [ 1118]     0  1118     7280      757      19       3        0             0 cron[ 2687.946463] [ 1120]   108  1120    91142     3432      78       3        0             0 whoopsie[ 2687.946465] [ 1122]   106  1122    10949     1230      27       3        0          -900 dbus-daemon[ 2687.946466] [ 1130]     0  1130     3964      622      14       3        0             0 anacron[ 2687.946467] [ 1132]     0  1132   112330     4027      71       3        0             0 NetworkManager[ 2687.946468] [ 1133]     0  1133    53957     4872      29       5        0             0 snapd[ 2687.946470] [ 1165]     0  1165    84379     2173      66       3        0             0 ModemManager[ 2687.946471] [ 1167]   104  1167    64099      871      27       3        0             0 rsyslogd[ 2687.946472] [ 1168]   122  1168    33544     4711      53       3        0             0 freshclam[ 2687.946473] [ 1170]   110  1170    11229      911      27       3        0             0 avahi-daemon[ 2687.946475] [ 1174]     0  1174     7157      789      18       3        0             0 systemd-logind[ 2687.946476] [ 1183]     0  1183    69059     2174      38       3        0             0 accounts-daemon[ 2687.946477] [ 1224]   110  1224    11197       85      26       3        0             0 avahi-daemon[ 2687.946479] [ 1270]     0  1270    70587     2236      41       3        0             0 polkitd[ 2687.946480] [ 1299]   126  1299    73695     6057      71       4        0          -900 postgres[ 2687.946481] [ 1302]   126  1302    73695     1019      58       4        0             0 postgres[ 2687.946482] [ 1303]   126  1303    73695     1425      59       4        0             0 postgres[ 2687.946483] [ 1304]   126  1304    73695     1019      57       4        0             0 postgres[ 2687.946485] [ 1305]   126  1305    73802     1637      62       4        0             0 postgres[ 2687.946486] [ 1306]   126  1306    37475      830      55       4        0             0 postgres[ 2687.946487] [ 1680]     0  1680     4030      892      13       3        0             0 dhclient[ 2687.946489] [ 1692] 65534  1692    13245     1056      31       3        0             0 dnsmasq[ 2687.946490] [ 1971]     0  1971     4868      572      14       3        0             0 irqbalance[ 2687.946491] [ 2027]   127  2027   940075   118111     325       7        0             0 java[ 2687.946493] [ 2049]     0  2049    26294     3360      41       3        0             0 sddm[ 2687.946494] [ 2099]     0  2099     5323      878      16       3        0             0 mysqld_safe[ 2687.946495] [ 2107]     0  2107    27240     1164      53       3        0             0 sendmail-mta[ 2687.946496] [ 2109]     0  2109    84298    54063     166       3        0             0 Xorg[ 2687.946498] [ 2254]   129  2254   151112    24593      89       3        0             0 mysqld[ 2687.946499] [ 2255]     0  2255     6551      344      18       3        0             0 logger[ 2687.946500] [ 2278]   128  2278    54060     3442      52       4        0             0 murmurd[ 2687.946502] [ 2299]     0  2299    60029     1474     113       4        0             0 nmbd[ 2687.946503] [ 2312]   120  2312     4275      408      14       3        0             0 nvidia-persiste[ 2687.946504] [ 2324]     0  2324    71846     2203     135       3        0             0 winbindd[ 2687.946506] [ 2325]     0  2325    71844     2273     136       3        0             0 winbindd[ 2687.946507] [ 2331]     0  2331    84508     3947     163       3        0             0 smbd[ 2687.946508] [ 2332]     0  2332    82479     1147     152       3        0             0 smbd[ 2687.946509] [ 2335]     0  2335    71845     1632     136       3        0             0 winbindd[ 2687.946511] [ 2336]     0  2336    71845     1031     134       3        0             0 winbindd[ 2687.946512] [ 2338]     0  2338    33686      884      60       3        0             0 veracrypt[ 2687.946513] [ 2339]     0  2339    78817      875      69       3        0             0 veracrypt[ 2687.946514] [ 2347]     0  2347    84508     1814     156       3        0             0 smbd[ 2687.946516] [ 2478]     0  2478    31094     2925      52       3        0             0 sddm-helper[ 2687.946517] [ 2490]  1000  2490    11345     1227      25       4        0             0 systemd[ 2687.946518] [ 2491]  1000  2491    15954      614      34       3        0             0 (sd-pam)[ 2687.946520] [ 2500]  1000  2500     1127      403       8       3        0             0 startkde[ 2687.946521] [ 2578]     0  2578     7534     4948      18       3        0             0 mount.ntfs[ 2687.946522] [ 2583]  1000  2583    41663      137      18       3        0             0 gpg-agent[ 2687.946523] [ 2586]  1000  2586     2785       80       9       3        0             0 ssh-agent[ 2687.946525] [ 2590]  1000  2590    10900      643      23       3        0             0 dbus-launch[ 2687.946526] [ 2596]  1000  2596    11038     1108      24       3        0             0 dbus-daemon[ 2687.946527] [ 2642]     0  2642    33690      970      62       3        0             0 veracrypt[ 2687.946528] [ 2643]     0  2643    78821      876      70       4        0             0 veracrypt[ 2687.946530] [ 2704]  1000  2704     1575       24       8       3        0             0 start_kdeinit[ 2687.946531] [ 2706]  1000  2706    66992     5454     113       3        0             0 kdeinit5[ 2687.946533] [ 2710]  1000  2710   104611     7283     150       3        0             0 klauncher[ 2687.946534] [ 2712]     0  2712    24833    22247      52       3        0             0 mount.ntfs[ 2687.946535] [ 2718]  1000  2718   377382    54973     375       4        0             0 kded5[ 2687.946536] [ 2732]  1000  2732   101975     7434     147       4        0             0 kaccess[ 2687.946538] [ 2743]  1000  2743    17577     1667      29       3        0             0 kwrapper5[ 2687.946539] [ 2746]  1000  2746   128035     9524     166       3        0             0 ksmserver[ 2687.946540] [ 2748]     0  2748    33690      986      61       3        0             0 veracrypt[ 2687.946542] [ 2749]     0  2749    78821      879      69       3        0             0 veracrypt[ 2687.946543] [ 2762]  1000  2762    99939     8388     145       3        0             0 kglobalaccel5[ 2687.946544] [ 2765]     0  2765    86884     2600      54       4        0             0 upowerd[ 2687.946545] [ 2768]  1000  2768   194905     8632     158       3        0             0 kactivitymanage[ 2687.946547] [ 2785]  1000  2785    44633     1163      23       3        0             0 dconf-service[ 2687.946548] [ 2792]  1000  2792   796368    30269     277       6        0             0 kwin_x11[ 2687.946549] [ 2796]  1000  2796  1371562     6937      87       5        0             0 baloo_file[ 2687.946551] [ 2802]  1000  2802  1679410    43163     355       8        0             0 krunner[ 2687.946552] [ 2818]     0  2818   108587     2972      48       3        0             0 udisksd[ 2687.946554] [ 2863]  1000  2863  1146275    97958     559       7        0             0 plasmashell[ 2687.946556] [ 2879]     0  2879     3199      637      10       3        0             0 mount.ntfs[ 2687.946557] [ 2882]  1000  2882   107872     3747      61       3        0             0 mission-control[ 2687.946559] [ 2894]     0  2894     4013      419      13       3        0             0 agetty[ 2687.946560] [ 2898]  1000  2898   140656     8810     162       4        0             0 polkit-kde-auth[ 2687.946561] [ 2905]  1000  2905    63342     4444      80       3        0             0 kscreen_backend[ 2687.946562] [ 2914]  1000  2914   100125     7779     143       3        0             0 xembedsniproxy[ 2687.946564] [ 2919]  1000  2919   114254    11562     173       3        0             0 charmtimetracke[ 2687.946565] [ 2926]  1000  2926   131566     3645     101       4        0             0 pulseaudio[ 2687.946567] [ 2927]   116  2927    45886      752      25       4        0             0 rtkit-daemon[ 2687.946568] [ 2928]  1000  2928    75967     9835     135       3        0             0 qstardict[ 2687.946570] [ 2932]  1000  2932   440694    28716     359       5        0             0 RetroShare06[ 2687.946571] [ 2945]  1000  2945    68633     1616      36       4        0             0 gvfsd[ 2687.946572] [ 2953]  1000  2953    85331     1850      32       4        0             0 gvfsd-fuse[ 2687.946573] [ 2972]  1000  2972   779950    43029     349       6        0             0 dropbox[ 2687.946574] [ 2978]  1000  2978   331520    24592     233      19        0             0 skypeforlinux[ 2687.946576] [ 2984]  1000  2984   141037    18264     189       3        0             0 yakuake[ 2687.946577] [ 2985]  1000  2985    84453     1369      32       3        0             0 at-spi-bus-laun[ 2687.946578] [ 2988]  1000  2988    51367     1877      33       4        0             0 gnome-keyring-d[ 2687.946579] [ 2997]  1000  2997   178857    12805     221       3        0             0 korgac[ 2687.946580] [ 2999]  1000  2999    10757      972      27       4        0             0 dbus-daemon[ 2687.946582] [ 3002]  1000  3002    51741     1317      36       3        0             0 at-spi2-registr[ 2687.946583] [ 3015]  1000  3015   626351    12095     116       5        0             0 copyq[ 2687.946584] [ 3037]  1000  3037    78126     7392     125       4        0             0 skypeforlinux[ 2687.946585] [ 3047]  1000  3047    37586     2507      57       3        0             0 obexd[ 2687.946587] [ 3059]  1000  3059    25344      999      51       3        0             0 gconf-helper[ 2687.946588] [ 3069]  1000  3069    15384     1472      35       3        0             0 gconfd-2[ 2687.946589] [ 3079]   107  3079     7067      328      20       3        0             0 uuidd[ 2687.946590] [ 3085]  1000  3085    87332     7609     126       3        0             0 copyq[ 2687.946592] [ 3100]  1000  3100    43529     3916      71       4        0             0 kdeinit4[ 2687.946593] [ 3103]  1000  3103    49619     4728      80       4        0             0 klauncher[ 2687.946595] [ 3117]  1000  3117    69575     6869     116       4        0             0 kded4[ 2687.946596] [ 3123]  1000  3123     2543      588      10       3        0             0 ksysguardd[ 2687.946597] [ 3125]  1000  3125    11789     1615      28       3        0             0 zsh[ 2687.946598] [ 3129]  1000  3129    97321     8939     141       3        0             0 knotify4[ 2687.946600] [ 3175]  1000  3175   121189    26207     204       6        0             0 skypeforlinux[ 2687.946601] [ 3274]  1000  3274   313212    42209     324      86        0           300 skypeforlinux[ 2687.946603] [ 3379]  1000  3379   123103     9279     157       3        0             0 kdeconnectd[ 2687.946604] [ 3387]  1000  3387    68391     6958     116       3        0             0 kuiserver[ 2687.946605] [ 3507]  1000  3507   342526    29181     257       4        0             0 doublecmd[ 2687.946606] [ 3521]  1000  3521   623171   332899    1038       6        0             0 firefox[ 2687.946607] [ 3544]  1000  3544   343564    91599     443       5        0             0 thunderbird[ 2687.946609] [ 3800]  1000  3800    81605     2254      45       4        0             0 gvfsd-http[ 2687.946610] [ 4353]     0  4353     1127      195       8       3        0             0 sh[ 2687.946611] [ 4354]     0  4354     1092      367       8       3        0             0 run-parts[ 2687.946612] [ 4510]     0  4510    68705     2415      68       3        0             0 cups-browsed[ 2687.946613] [ 5001]     0  5001     3160      736      12       3        0             0 sbackup[ 2687.946614] [ 5002]     0  5002   101153    19913      97       3        0             0 sbackup[ 2687.946615] [ 5038]     0  5038    10936      549      24       3        0             0 dbus-launch[ 2687.946617] [ 5039]     0  5039    10692      644      26       3        0             0 dbus-daemon[ 2687.946618] [ 5041]     0  5041    15355     1394      34       3        0             0 gconfd-2[ 2687.946619] [ 5046]     0  5046    10692      773      25       3        0             0 dbus-daemon[ 2687.946620] [ 5047] 65534  5047    26365     4559      54       4        0             0 sbackup-dbusser[ 2687.946622] [ 5055]  1000  5055   121399     8962     119       4        0             0 sbackup-indicat[ 2687.946623] [ 5080]     0  5080    68633     1553      34       3        0             0 gvfsd[ 2687.946624] [ 5085]     0  5085   101715     1820      33       4        0             0 gvfsd-fuse[ 2687.946625] [ 5093]     0  5093    46523     1340      26       3        0             0 gvfsd-metadata[ 2687.946626] [ 5865]     0  5865    80226    74366     162       3        0             0 tar[ 2687.946627] [ 5867]     0  5867     1192      427       8       3        0             0 gzip[ 2687.946628] [ 6688]  1000  6688     3183      805      11       3        0             0 bash[ 2687.946630] [ 6697]  1000  6697     3235      857      12       3        0             0 bash[ 2687.946631] [ 6698]  1000  6698     1853      164       9       3        0             0 tee[ 2687.946632] [ 7338]  1000  7338    46611     1396      28       3        0             0 gvfsd-metadata[ 2687.946634] [ 8551]   126  8551    73917     2014      63       4        0             0 postgres[ 2687.946635] [ 8552]   126  8552    73917     2022      63       4        0             0 postgres[ 2687.946636] [ 8554]   126  8554    73917     2051      63       4        0             0 postgres[ 2687.946637] [ 8556]   126  8556    73917     2051      63       4        0             0 postgres[ 2687.946639] [ 8559]   126  8559    73917     2051      63       4        0             0 postgres[ 2687.946640] [ 8560]   126  8560    73917     2051      63       4        0             0 postgres[ 2687.946641] [ 8562]   126  8562    73917     2051      63       4        0             0 postgres[ 2687.946642] [ 8643]   126  8643    73917     2051      63       4        0             0 postgres[ 2687.946644] [ 8645]   126  8645    73917     2051      63       4        0             0 postgres[ 2687.946645] [ 8648]   126  8648    73917     2051      63       4        0             0 postgres[ 2687.946646] [ 8649]   126  8649    73917     2051      63       4        0             0 postgres[ 2687.946647] [ 8652]   126  8652    73917     2051      63       4        0             0 postgres[ 2687.946648] [ 8653]   126  8653    73917     2051      63       4        0             0 postgres[ 2687.946649] [ 8656]   126  8656    73917     2038      63       4        0             0 postgres[ 2687.946650] [ 8657]   126  8657    73917     2036      63       4        0             0 postgres[ 2687.946652] [ 8659]   126  8659    73917     2051      63       4        0             0 postgres[ 2687.946653] [ 8661]   126  8661    73917     2051      63       4        0             0 postgres[ 2687.946654] [ 8663]   126  8663    73917     2051      63       4        0             0 postgres[ 2687.946655] [ 8665]   126  8665    73917     2051      63       4        0             0 postgres[ 2687.946656] [ 8667]   126  8667    73917     2051      63       4        0             0 postgres[ 2687.946658] [ 9415]  1000  9415   135556    80527     253       2        0             0 steam[ 2687.946659] [ 9417]  1000  9417    33897    13343      58       2        0             0 steam[ 2687.946660] [ 9418]  1000  9418     1127      176       8       3        0             0 sh[ 2687.946661] [ 9420]  1000  9420     3164      767      12       3        0             0 steamwebhelper.[ 2687.946663] [ 9422]  1000  9422   151458    19771     193       5        0             0 steamwebhelper[ 2687.946664] [ 9424]  1000  9424    78943     9566     131       4        0             0 steamwebhelper[ 2687.946666] [ 9542]  1000  9542   232518    13239     162      25        0           300 steamwebhelper[ 2687.946667] [ 9606]  1000  9606   233909    14334     165      26        0           300 steamwebhelper[ 2687.946668] [ 9734]   111  9734    76055     3464      50       3        0             0 colord[ 2687.946669] [10387]     0 10387    23345     1859      46       3        0             0 cupsd[ 2687.946671] [10389]     7 10389    20311     1396      41       3        0             0 dbus[ 2687.946672] [10390]     7 10390    20311     1441      43       3        0             0 dbus[ 2687.946673] Out of memory: Kill process 3274 (skypeforlinux) score 305 or sacrifice child[ 2687.946697] Killed process 3274 (skypeforlinux) total-vm:1252848kB, anon-rss:103412kB, file-rss:65424kBI suspect that it has to do something with not freeing io cache, unfortunately I did not save output of free.EDIT3: I thought that question in bold was clearly marked, but some people failed to read and started marking this whole post as put on hold as unclear what you're asking. I have provided all additional requested info and just to be sure edited title to be a question to avoid situation when someone ignores question text and marks it straight away as unclear what question is...EDIT4: Happened again, definitely related to high IO (reading from HDD). Output of free:              total        used        free      shared  buff/cache   availableMem:          15975        3535         294         151       12145       11867Swap:         16307           1       16306
Why is Linux kernel killing processes when it has 14GB free memory, and how to fix it?
ubuntu;kubuntu;out of memory