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A highly configurable OOM prevention daemon

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Nohang

Nohang is a highly configurable daemon for Linux which is able to correctly prevent out of memory (OOM) and keep system responsiveness in low memory conditions.

What is the problem?

OOM conditions may cause freezes, livelocks, drop caches and processes to be killed (via sending SIGKILL) instead of trying to terminate them correctly (via sending SIGTERM or takes other corrective action). Some applications may crash if it's impossible to allocate memory.

pic

Here are the statements of some users:

"How do I prevent Linux from freezing when out of memory? Today I (accidentally) ran some program on my Linux box that quickly used a lot of memory. My system froze, became unresponsive and thus I was unable to kill the offender. How can I prevent this in the future? Can't it at least keep a responsive core or something running?"

— serverfault

"With or without swap it still freezes before the OOM killer gets run automatically. This is really a kernel bug that should be fixed (i.e. run OOM killer earlier, before dropping all disk cache). Unfortunately kernel developers and a lot of other folk fail to see the problem. Common suggestions such as disable/enable swap, buy more RAM, run less processes, set limits etc. do not address the underlying problem that the kernel's low memory handling sucks camel's balls."

— serverfault

Also look at Why are low memory conditions handled so badly?

Solution

  • Use of earlyoom. This is a simple, stable and tiny OOM preventer written in C (the best choice for emedded and old servers). It has a minimum dependencies and can work with oldest kernels.
  • Use of oomd. This is a userspace OOM killer for linux systems whitten in C++ and developed by Facebook. This is the best choice for use in large data centers. It needs Linux 4.20+.
  • Use of nohang (maybe this is a good choice for modern desktops and servers if you need fine tuning).

The tools listed above may work at the same time on one computer.

See also

  • memlockd is a daemon that locks files into memory. Then if a machine starts paging heavily the chance of being able to login successfully is significantly increased.

Some features

  • Sending the SIGTERM signal is default corrective action. If the victim does not respond to SIGTERM, with a further drop in the level of memory it gets SIGKILL.
  • Impact on the badness of processes via matching their
    • names,
    • cgroup_v1,
    • cgroup_v2,
    • realpathes,
    • environs,
    • cmdlines and
    • euids with specified regular expressions
  • If the name of the victim matches a certain regex pattern, you can run any command instead of sending the SIGTERM signal (the default corrective action) to the victim. For example:
    • sysmemctl restart foo
    • kill -INT $PID (you can override the signal sent to the victim, $PID will be replaced by the victim's PID)
    • kill -TERM $PID && script.sh (in addition to sending any signal, you can run a specified script)
  • GUI notifications:
    • Notification of corrective actions taken and displaying the name and PID of the victim
    • Low memory warnings (displays available memory)
  • zram support (mem_used_total as a trigger)
  • Initial PSI (pressure stall information) support (demo)
  • Easy configuration with a well commented config file

Requirements

For basic usage:

  • Linux 3.14+ (since MemAvailable appeared in /proc/meminfo)
  • Python 3.3+ (not tested with previous)

To show GUI notifications:

  • notification server (most of desktop environments use their own implementations)
  • libnotify (Fedora, Arch Linux) or libnotify-bin (Debian GNU/Linux, Ubuntu)
  • sudo if nohang started with UID=0

To use PSI:

  • Linux 4.20+

Memory and CPU usage

  • VmRSS is about 10 - 12 MiB instead of the settings, about 10 MiB by default.
  • CPU usage depends on the level of available memory and monitoring intensity.

Download, install, uninstall

Please use the latest release version. Current version may be unstable.

To download the latest stable version (v0.1):

$ wget -ct0 https://github.com/hakavlad/nohang/archive/v0.1.tar.gz
$ tar xvzf v0.1.tar.gz
$ cd nohang-0.1

or to clone the latest unstable:

$ git clone https://github.com/hakavlad/nohang.git
$ cd nohang

To install:

$ sudo make install

To enable and start on systems with systemd:

$ sudo make systemd

To uninstall:

$ sudo make uninstall

For Arch Linux, there's an AUR package. Use your favorite AUR helper. For example,

$ yay -S nohang-git
$ sudo systemctl start nohang
$ sudo systemctl enable nohang

Command line options

./nohang -h
usage: nohang [-h] [-v] [-t] [-p] [-c CONFIG]

optional arguments:
  -h, --help            show this help message and exit
  -v, --version         print version
  -t, --test            print some tests
  -p, --print-proc-table
                        print table of processes with their badness values
  -c CONFIG, --config CONFIG
                        path to the config file, default values:
                        ./nohang.conf, /etc/nohang/nohang.conf

How to configure nohang

The program can be configured by editing the config file. The configuration includes the following sections:

  1. Memory levels to respond to as an OOM threat
  2. Response on PSI memory metrics
  3. The frequency of checking the level of available memory (and CPU usage)
  4. The prevention of killing innocent victims
  5. Impact on the badness of processes via matching their names, cgroups, realpaths, cmdlines and UIDs with certain regular expressions
  6. The execution of a specific command or sending any signal instead of sending the SIGTERM signal
  7. GUI notifications:
    • notifications of corrective actions taken
    • low memory warnings (or executing certain command instead)
  8. Verbosity
  9. Misc

Just read the description of the parameters and edit the values. Please restart nohang to apply the changes. Default path to the config after installing is /etc/nohang/nohang.conf.

Print table of processes with their badness values

Run sudo nohang -p to see the table of prosesses with their badness values, oom_scores, names, UIDs etc.

Output example
Config: /etc/nohang/nohang.conf
###################################################################################################################
#    PID     PPID  badness  oom_score  oom_score_adj        eUID  S  VmSize  VmRSS  VmSwap  Name             CGroup
#-------  -------  -------  ---------  -------------  ----------  -  ------  -----  ------  ---------------  --------
#    336        1        1          1              0           0  S      85     25       0  systemd-journal  /system.slice/systemd-journald.service
#    383        1        0          0          -1000           0  S      46      5       0  systemd-udevd    /system.slice/systemd-udevd.service
#    526     2238        7          7              0        1000  S     840     96       0  kate             /user.slice/user-1000.slice/session-7.scope
#    650        1        3          3              0        1000  S     760     50       0  kate             /user.slice/user-1000.slice/session-7.scope
#    731        1        0          0              0         100  S     126      4       0  systemd-timesyn  /system.slice/systemd-timesyncd.service
#    756        1        0          0              0         105  S     181      3       0  rtkit-daemon     /system.slice/rtkit-daemon.service
#    759        1        0          0              0           0  S     277      7       0  accounts-daemon  /system.slice/accounts-daemon.service
#    761        1        0          0              0           0  S     244      3       0  rsyslogd         /system.slice/rsyslog.service
#    764        1        0          0           -900         108  S      45      5       0  dbus-daemon      /system.slice/dbus.service
#    805        1        0          0              0           0  S      46      5       0  systemd-logind   /system.slice/systemd-logind.service
#    806        1        0          0              0           0  S      35      3       0  irqbalance       /system.slice/irqbalance.service
#    813        1        0          0              0           0  S      29      3       0  cron             /system.slice/cron.service
#    814        1       11         11              0           0  S     176    160       0  memlockd         /system.slice/memlockd.service
#    815        1        0          0            -10           0  S      32      9       0  python3          /fork.slice/fork-bomb.slice/fork-bomb-killer.slice/fork-bomb-killer.service
#    823        1        0          0              0           0  S      25      4       0  smartd           /system.slice/smartd.service
#    826        1        0          0              0         113  S      46      3       0  avahi-daemon     /system.slice/avahi-daemon.service
#    850      826        0          0              0         113  S      46      0       0  avahi-daemon     /system.slice/avahi-daemon.service
#    868        1        0          0              0           0  S     281      8       0  polkitd          /system.slice/polkit.service
#    903        1        1          1              0           0  S    4094     16       0  stunnel4         /system.slice/stunnel4.service
#    940        1        0          0           -600           0  S      39     10       0  python3          /nohang.slice/nohang.service
#   1014        1        0          0              0          13  S      22      2       0  obfs-local       /system.slice/obfs-local.service
#   1015        1        0          0              0        1000  S      36      4       0  ss-local         /system.slice/ss-local.service
#   1023        1        0          0              0         116  S      33      2       0  dnscrypt-proxy   /system.slice/dnscrypt-proxy.service
#   1029        1        1          1              0         119  S    4236     16       0  privoxy          /system.slice/privoxy.service
#   1035        1        0          0              0           0  S     355      6       0  lightdm          /system.slice/lightdm.service
#   1066        1        0          0              0           0  S      45      7       0  wpa_supplicant   /system.slice/wpa_supplicant.service
#   1178        1        0          0              0           0  S      14      2       0  agetty           /system.slice/system-getty.slice/getty@tty1.service
#   1294        1        0          0          -1000           0  S       4      1       0  watchdog         /system.slice/watchdog.service
#   1632        1        1          1              0        1000  S    1391     22       0  pulseaudio       /user.slice/user-1000.slice/session-2.scope
#   1689     1632        0          0              0        1000  S     125      5       0  gconf-helper     /user.slice/user-1000.slice/session-2.scope
#   1711        1        0          0              0           0  S     367      8       0  udisksd          /system.slice/udisks2.service
#   1819        1        0          0              0           0  S     304      8       0  upowerd          /system.slice/upower.service
#   1879        1        0          0              0        1000  S      64      7       0  systemd          /user.slice/user-1000.slice/user@1000.service/init.scope
#   1880     1879        0          0              0        1000  S     229      2       0  (sd-pam)         /user.slice/user-1000.slice/user@1000.service/init.scope
#   1888        1        0          0              0           0  S      14      2       0  agetty           /system.slice/system-getty.slice/getty@tty2.service
#   1889        1        0          0              0           0  S      14      2       0  agetty           /system.slice/system-getty.slice/getty@tty3.service
#   1890        1        0          0              0           0  S      14      2       0  agetty           /system.slice/system-getty.slice/getty@tty4.service
#   1891        1        0          0              0           0  S      14      2       0  agetty           /system.slice/system-getty.slice/getty@tty5.service
#   1892        1        0          0              0           0  S      14      2       0  agetty           /system.slice/system-getty.slice/getty@tty6.service
#   1893     1035       14         14              0           0  R     623    208       0  Xorg             /system.slice/lightdm.service
#   1904        1        0          0              0         111  S      64      7       0  systemd          /user.slice/user-111.slice/user@111.service/init.scope
#   1905     1904        0          0              0         111  S     229      2       0  (sd-pam)         /user.slice/user-111.slice/user@111.service/init.scope
#   1916     1904        0          0              0         111  S      44      3       0  dbus-daemon      /user.slice/user-111.slice/user@111.service/dbus.service
#   1920        1        0          0              0         111  S     215      5       0  at-spi2-registr  /user.slice/user-111.slice/session-c2.scope
#   1922     1904        0          0              0         111  S     278      6       0  gvfsd            /user.slice/user-111.slice/user@111.service/gvfs-daemon.service
#   1935     1035        0          0              0           0  S     238      6       0  lightdm          /user.slice/user-1000.slice/session-7.scope
#   1942        1        0          0              0        1000  S     210      9       0  gnome-keyring-d  /user.slice/user-1000.slice/session-7.scope
#   1944     1935        1          1              0        1000  S     411     21       0  mate-session     /user.slice/user-1000.slice/session-7.scope
#   1952     1879        0          0              0        1000  S      45      5       0  dbus-daemon      /user.slice/user-1000.slice/user@1000.service/dbus.service
#   1981     1944        0          0              0        1000  S      11      0       0  ssh-agent        /user.slice/user-1000.slice/session-7.scope
#   1984     1879        0          0              0        1000  S     278      6       0  gvfsd            /user.slice/user-1000.slice/user@1000.service/gvfs-daemon.service
#   1990     1879        0          0              0        1000  S     341      5       0  at-spi-bus-laun  /user.slice/user-1000.slice/user@1000.service/at-spi-dbus-bus.service
#   1995     1990        0          0              0        1000  S      44      4       0  dbus-daemon      /user.slice/user-1000.slice/user@1000.service/at-spi-dbus-bus.service
#   1997     1879        0          0              0        1000  S     215      5       0  at-spi2-registr  /user.slice/user-1000.slice/user@1000.service/at-spi-dbus-bus.service
#   2000     1879        0          0              0        1000  S     184      5       0  dconf-service    /user.slice/user-1000.slice/user@1000.service/dbus.service
#   2009     1944        2          2              0        1000  S    1308     35       0  mate-settings-d  /user.slice/user-1000.slice/session-7.scope
#   2013     1944        2          2              0        1000  S     436     32       0  marco            /user.slice/user-1000.slice/session-7.scope
#   2024     1944        4          4              0        1000  S    1258     55       0  caja             /user.slice/user-1000.slice/session-7.scope
#   2032        1        1          1              0        1000  S     333     18       0  msd-locate-poin  /user.slice/user-1000.slice/session-7.scope
#   2033     1879        0          0              0        1000  S     348     11       0  gvfs-udisks2-vo  /user.slice/user-1000.slice/user@1000.service/gvfs-udisks2-volume-monitor.service
#   2036     1944        1          1              0        1000  S     331     17       0  polkit-mate-aut  /user.slice/user-1000.slice/session-7.scope
#   2038     1944        5          5              0        1000  S     682     78       0  mate-panel       /user.slice/user-1000.slice/session-7.scope
#   2041     1944        2          2              0        1000  S     514     31       0  nm-applet        /user.slice/user-1000.slice/session-7.scope
#   2046     1944        1          1              0        1000  S     495     25       0  mate-power-mana  /user.slice/user-1000.slice/session-7.scope
#   2047     1944        2          2              0        1000  S     692     32       0  mate-volume-con  /user.slice/user-1000.slice/session-7.scope
#   2049     1944        3          3              0        1000  S     548     44       0  mate-screensave  /user.slice/user-1000.slice/session-7.scope
#   2059     1879        0          0              0        1000  S     263      5       0  gvfs-goa-volume  /user.slice/user-1000.slice/user@1000.service/gvfs-goa-volume-monitor.service
#   2076     1879        0          0              0        1000  S     352      7       0  gvfsd-trash      /user.slice/user-1000.slice/user@1000.service/gvfs-daemon.service
#   2077     1879        0          0              0        1000  S     362      7       0  gvfs-afc-volume  /user.slice/user-1000.slice/user@1000.service/gvfs-afc-volume-monitor.service
#   2087     1879        0          0              0        1000  S     263      5       0  gvfs-mtp-volume  /user.slice/user-1000.slice/user@1000.service/gvfs-mtp-volume-monitor.service
#   2093     1879        0          0              0        1000  S     275      6       0  gvfs-gphoto2-vo  /user.slice/user-1000.slice/user@1000.service/gvfs-gphoto2-volume-monitor.service
#   2106     1879        3          3              0        1000  S     544     42       0  wnck-applet      /user.slice/user-1000.slice/user@1000.service/dbus.service
#   2108     1879        1          1              0        1000  S     396     21       0  notification-ar  /user.slice/user-1000.slice/user@1000.service/dbus.service
#   2112     1879        1          1              0        1000  S     499     25       0  mate-sensors-ap  /user.slice/user-1000.slice/user@1000.service/dbus.service
#   2113     1879        1          1              0        1000  S     390     21       0  mate-brightness  /user.slice/user-1000.slice/user@1000.service/dbus.service
#   2114     1879        1          1              0        1000  S     534     22       0  mate-multiload-  /user.slice/user-1000.slice/user@1000.service/dbus.service
#   2118     1879        2          2              0        1000  S     547     29       0  clock-applet     /user.slice/user-1000.slice/user@1000.service/dbus.service
#   2152     1879        1          1              0        1000  S     218     22       0  gvfsd-metadata   /user.slice/user-1000.slice/user@1000.service/gvfs-metadata.service
#   2206        1        3          3              0         110  S     106     48       0  tor              /system.slice/system-tor.slice/tor@default.service
#   2229        1        3          3              0        1000  S     999     42       0  kactivitymanage  /user.slice/user-1000.slice/session-7.scope
#   2238        1        0          0              0        1000  S     150      9       0  kdeinit5         /user.slice/user-1000.slice/session-7.scope
#   2239     2238        3          3              0        1000  S     648     41       0  klauncher        /user.slice/user-1000.slice/session-7.scope
#   3959        1        1          1              0           0  S     615     18       0  NetworkManager   /system.slice/NetworkManager.service
#   3977     3959        0          0              0           0  S      20      4       0  dhclient         /system.slice/NetworkManager.service
#   5626     1879        0          0              0        1000  S     355      7       0  gvfsd-network    /user.slice/user-1000.slice/user@1000.service/gvfs-daemon.service
#   5637     1879        1          1              0        1000  S     623     14       0  gvfsd-smb-brows  /user.slice/user-1000.slice/user@1000.service/gvfs-daemon.service
#   6296     1879        0          0              0        1000  S     435      7       0  gvfsd-dnssd      /user.slice/user-1000.slice/user@1000.service/gvfs-daemon.service
#  11129     1879        3          3              0        1000  S     597     42       0  kded5            /user.slice/user-1000.slice/user@1000.service/dbus.service
#  11136     1879        2          2              0        1000  S     639     39       0  kuiserver5       /user.slice/user-1000.slice/user@1000.service/dbus.service
#  11703     1879        3          3              0        1000  S     500     45       0  mate-system-mon  /user.slice/user-1000.slice/user@1000.service/dbus.service
#  16798     1879        0          0              0        1000  S     346     10       0  gvfsd-http       /user.slice/user-1000.slice/user@1000.service/gvfs-daemon.service
#  18133        1        3          3              0        1000  S     760     49       0  kate             /user.slice/user-1000.slice/session-7.scope
#  18144     2038        1          1              0        1000  S     301     23       0  lxterminal       /user.slice/user-1000.slice/session-7.scope
#  18147    18144        0          0              0        1000  S      14      2       0  gnome-pty-helpe  /user.slice/user-1000.slice/session-7.scope
#  18148    18144        1          1              0        1000  S      42     26       0  bash             /user.slice/user-1000.slice/session-7.scope
#  18242     2238        1          1              0        1000  S     194     14       0  file.so          /user.slice/user-1000.slice/session-7.scope
#  18246    18148        0          0              0           0  S      54      4       0  sudo             /user.slice/user-1000.slice/session-7.scope
#  19003        1        0          0              0           0  S     310     12       0  packagekitd      /system.slice/packagekit.service
#  26993     2038       91         91              0        1000  S    3935   1256       0  firefox-esr      /user.slice/user-1000.slice/session-7.scope
#  27275    26993      121        121              0        1000  S    3957   1684       0  Web Content      /user.slice/user-1000.slice/session-7.scope
#  30374        1        1          1              0        1000  S     167     14       0  VBoxXPCOMIPCD    /user.slice/user-1000.slice/session-7.scope
#  30380        1        2          2              0        1000  S     958     27       0  VBoxSVC          /user.slice/user-1000.slice/session-7.scope
#  30549    30380       86         86              0        1000  S    5332   1192       0  VirtualBox       /user.slice/user-1000.slice/session-7.scope
#  30875        1        1          1              0        1000  S     345     26       0  leafpad          /user.slice/user-1000.slice/session-7.scope
#  32689        1        7          7              0        1000  S     896     99       0  dolphin          /user.slice/user-1000.slice/session-7.scope
###################################################################################################################
Process with highest badness (found in 55 ms):
  PID: 27275, Name: Web Content, badness: 121

oom-sort

oom-sort is an additional diagnostic tool that will be installed with nohang package. It sorts the processes in descending order of their oom_score and also displays oom_score_adj, Uid, Pid, Name, VmRSS, VmSwap and optionally cmdline. Run oom-sort --help for more info.

Usage:

$ oom-sort
Output example
oom_score oom_score_adj  UID   PID Name            VmRSS   VmSwap   cmdline
--------- ------------- ---- ----- --------------- ------- -------- -------
       23             0    0   964 Xorg               58 M     22 M /usr/libexec/Xorg -background none :0 vt01 -nolisten tcp -novtswitch -auth /var/run/lxdm/lxdm-:0.auth
       13             0 1000  1365 pcmanfm            38 M     10 M pcmanfm --desktop --profile LXDE
       10             0 1000  1408 dnfdragora-upda     9 M     27 M /usr/bin/python3 /bin/dnfdragora-updater
        5             0    0   822 firewalld           0 M     19 M /usr/bin/python3 /usr/sbin/firewalld --nofork --nopid
        5             0 1000  1364 lxpanel            18 M      2 M lxpanel --profile LXDE
        5             0 1000  1685 nm-applet           6 M     12 M nm-applet
        5             0 1000  1862 lxterminal         16 M      2 M lxterminal
        4             0  996   890 polkitd             8 M      6 M /usr/lib/polkit-1/polkitd --no-debug
        4             0 1000  1703 pnmixer             6 M     11 M pnmixer
        3             0    0   649 systemd-journal    10 M      1 M /usr/lib/systemd/systemd-journald
        3             0 1000  1360 openbox             9 M      2 M openbox --config-file /home/user/.config/openbox/lxde-rc.xml
        3             0 1000  1363 notification-da     3 M     10 M /usr/libexec/notification-daemon
        2             0 1000  1744 clipit              5 M      3 M clipit
        2             0 1000  2619 python3             9 M      0 M python3 /bin/oom-sort
        1             0    0   809 rsyslogd            3 M      3 M /usr/sbin/rsyslogd -n
        1             0    0   825 udisksd             2 M      2 M /usr/libexec/udisks2/udisksd
        1             0    0   873 sssd_nss            4 M      1 M /usr/libexec/sssd/sssd_nss --uid 0 --gid 0 --logger=files
        1             0    0   876 systemd-logind      2 M      2 M /usr/lib/systemd/systemd-logind
        1             0    0   907 abrt-dump-journ     2 M      1 M /usr/bin/abrt-dump-journal-oops -fxtD
        1             0    0   920 NetworkManager      3 M      2 M /usr/sbin/NetworkManager --no-daemon
        1             0 1000  1115 systemd             4 M      1 M /usr/lib/systemd/systemd --user
        1             0 1000  1118 (sd-pam)            0 M      5 M (sd-pam)
        1             0 1000  1366 xscreensaver        5 M      0 M xscreensaver -no-splash
        1             0 1000  1851 gvfsd-trash         3 M      1 M /usr/libexec/gvfsd-trash --spawner :1.6 /org/gtk/gvfs/exec_spaw/0
        1             0 1000  1969 gvfsd-metadata      6 M      0 M /usr/libexec/gvfsd-metadata
        1             0 1000  2262 bash                5 M      0 M bash
        0         -1000    0   675 systemd-udevd       0 M      4 M /usr/lib/systemd/systemd-udevd
        0         -1000    0   787 auditd              0 M      1 M /sbin/auditd
        0             0    0   807 ModemManager        0 M      1 M /usr/sbin/ModemManager
        0             0    0   808 smartd              0 M      1 M /usr/sbin/smartd -n -q never
        0             0    0   810 alsactl             0 M      0 M /usr/sbin/alsactl -s -n 19 -c -E ALSA_CONFIG_PATH=/etc/alsa/alsactl.conf --initfile=/lib/alsa/init/00main rdaemon
        0             0    0   811 mcelog              0 M      0 M /usr/sbin/mcelog --ignorenodev --daemon --foreground
        0             0  172   813 rtkit-daemon        0 M      0 M /usr/libexec/rtkit-daemon
        0             0    0   814 VBoxService         0 M      1 M /usr/sbin/VBoxService -f
        0             0    0   817 rngd                0 M      1 M /sbin/rngd -f
        0          -900   81   818 dbus-daemon         3 M      0 M /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only
        0             0    0   823 irqbalance          0 M      0 M /usr/sbin/irqbalance --foreground
        0             0   70   824 avahi-daemon        0 M      0 M avahi-daemon: running [linux.local]
        0             0    0   826 sssd                0 M      2 M /usr/sbin/sssd -i --logger=files
        0             0  995   838 chronyd             1 M      0 M /usr/sbin/chronyd
        0             0    0   849 gssproxy            0 M      1 M /usr/sbin/gssproxy -D
        0             0    0   866 abrtd               0 M      2 M /usr/sbin/abrtd -d -s
        0             0   70   870 avahi-daemon        0 M      0 M avahi-daemon: chroot helper
        0             0    0   871 sssd_be             0 M      2 M /usr/libexec/sssd/sssd_be --domain implicit_files --uid 0 --gid 0 --logger=files
        0             0    0   875 accounts-daemon     0 M      1 M /usr/libexec/accounts-daemon
        0             0    0   906 abrt-dump-journ     1 M      2 M /usr/bin/abrt-dump-journal-core -D -T -f -e
        0             0    0   908 abrt-dump-journ     1 M      2 M /usr/bin/abrt-dump-journal-xorg -fxtD
        0             0    0   950 crond               2 M      1 M /usr/sbin/crond -n
        0             0    0   951 atd                 0 M      0 M /usr/sbin/atd -f
        0             0    0   953 lxdm-binary         0 M      0 M /usr/sbin/lxdm-binary
        0             0    0  1060 dhclient            0 M      2 M /sbin/dhclient -d -q -sf /usr/libexec/nm-dhcp-helper -pf /var/run/dhclient-enp0s3.pid -lf /var/lib/NetworkManager/dhclient-939eab05-4796-3792-af24-9f76cf53ca7f-enp0s3.lease -cf /var/lib/NetworkManager/dhclient-enp0s3.conf enp0s3
        0             0    0  1105 lxdm-session        0 M      1 M /usr/libexec/lxdm-session
        0             0 1000  1123 pulseaudio          0 M      3 M /usr/bin/pulseaudio --daemonize=no
        0             0 1000  1124 lxsession           1 M      2 M /usr/bin/lxsession -s LXDE -e LXDE
        0             0 1000  1134 dbus-daemon         2 M      0 M /usr/bin/dbus-daemon --session --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only
        0             0 1000  1215 imsettings-daem     0 M      1 M /usr/libexec/imsettings-daemon
        0             0 1000  1218 gvfsd               3 M      1 M /usr/libexec/gvfsd
        0             0 1000  1223 gvfsd-fuse          0 M      1 M /usr/libexec/gvfsd-fuse /run/user/1000/gvfs -f -o big_writes
        0             0 1000  1309 VBoxClient          0 M      0 M /usr/bin/VBoxClient --display
        0             0 1000  1310 VBoxClient          0 M      0 M /usr/bin/VBoxClient --clipboard
        0             0 1000  1311 VBoxClient          0 M      0 M /usr/bin/VBoxClient --draganddrop
        0             0 1000  1312 VBoxClient          0 M      0 M /usr/bin/VBoxClient --display
        0             0 1000  1313 VBoxClient          1 M      0 M /usr/bin/VBoxClient --clipboard
        0             0 1000  1316 VBoxClient          0 M      0 M /usr/bin/VBoxClient --seamless
        0             0 1000  1318 VBoxClient          0 M      0 M /usr/bin/VBoxClient --seamless
        0             0 1000  1320 VBoxClient          0 M      0 M /usr/bin/VBoxClient --draganddrop
        0             0 1000  1334 ssh-agent           0 M      0 M /usr/bin/ssh-agent /bin/sh -c exec -l bash -c "/usr/bin/startlxde"
        0             0 1000  1362 lxpolkit            0 M      1 M lxpolkit
        0             0 1000  1370 lxclipboard         0 M      1 M lxclipboard
        0             0 1000  1373 ssh-agent           0 M      1 M /usr/bin/ssh-agent -s
        0             0 1000  1485 agent               0 M      1 M /usr/libexec/geoclue-2.0/demos/agent
        0             0 1000  1751 menu-cached         0 M      1 M /usr/libexec/menu-cache/menu-cached /run/user/1000/menu-cached-:0
        0             0 1000  1780 at-spi-bus-laun     0 M      1 M /usr/libexec/at-spi-bus-launcher
        0             0 1000  1786 dbus-daemon         1 M      0 M /usr/bin/dbus-daemon --config-file=/usr/share/defaults/at-spi2/accessibility.conf --nofork --print-address 3
        0             0 1000  1792 at-spi2-registr     1 M      1 M /usr/libexec/at-spi2-registryd --use-gnome-session
        0             0 1000  1840 gvfs-udisks2-vo     0 M      2 M /usr/libexec/gvfs-udisks2-volume-monitor
        0             0 1000  1863 gnome-pty-helpe     1 M      0 M gnome-pty-helper
        0             0 1000  1864 bash                0 M      1 M bash
        0             0    0  1899 sudo                0 M      1 M sudo -i
        0             0    0  1901 bash                0 M      1 M -bash
        0             0    0  1953 oomd_bin            0 M      0 M oomd_bin -f /sys/fs/cgroup/unified
        0          -600    0  2562 python3            10 M      0 M python3 /usr/sbin/nohang --config /etc/nohang/nohang.conf

Kthreads, zombies and Pid 1 will not be displayed.

Logging

To view the latest entries in the log (for systemd users):

$ sudo journalctl -eu nohang

See also man journalctl.

You can also enable separate_log in the config to logging in /var/log/nohang/nohang.log.

Known issues

  • Awful documentation
  • Non-optimal default settings (I do not know which settings are optimal for most users; you need a configuration for better experience)
  • No installation option for non-systemd users
  • No deb/rpm packages

Contribution

Please create issues. Use cases, feature requests and any questions are welcome.

Changelog

  • In progress

    • Added new CLI options:
      • -v, --version
      • -t, --test
      • -p, --print-proc-table
    • Possible process crashes are fixed:
      • Fixed crash at startup due to UnicodeDecodeError on some systems
      • Handled UnicodeDecodeError if victim name consists of many unicode characters (rfjakob/earlyoom#110)
      • Fixed process crash before performing corrective actions if Python 3.4 or lower are used to interpret nohang
    • Improve output:
      • Display oom_score, oom_score_adj, Ancestry, EUID, State, VmSize, RssAnon, RssFile, RssShmem, CGroup_v1, CGroup_v2, Realpath, Cmdline and Lifetime of the victim in corrective action reports
      • Added memory report interval
      • Added delta memory info (the rate of change of available memory)
      • Print statistics on corrective actions after each corrective action
      • Added ability to print a process table before each corrective action
      • Added the ability to log into a separate file
    • Improved GUI warnings:
      • Reduced the idle time of the daemon in the process of launching a notification
      • All notify-send calls are made using the nohang_notify_helper script, in which all timeouts are handled
      • Native python implementation of env search without running ps to notify all users if nohang started with UID=0.
      • Messages are sent to the helper via a temporary file in /dev/shm
      • Deduplication of frequently repeated identical notifications (for example, if the victim does not respond to SIGTERM)
    • Improved modifing badness via matching with regular expressions:
      • Added the ability to set many different badness_adj for processes depending on the matching Name, CGroup, cmdline, realpath and EUID with the specified regular expressions (issue #74)
      • Fix: replace re.fullmatch() by re.search()
    • Reduced memory usage:
      • Reduced memory usage and startup time (using sys.argv instead of argparse)
      • Reduced memory usage with mlockall() using MCL_ONFAULT (rfjakob/earlyoom#112) and lock all memory by default
    • Improve poll rate algorithm
    • Fixed Makefile for installation on CentOS 7 (remove gzip -k option).
    • Added max_post_sigterm_victim_lifetime option: send SIGKILL to the victim if it doesn't respond to SIGTERM for a certain time
    • Added post_kill_exe option (the ability to run any command after killing the victim)
    • Added warning_exe option (the ability to run any command instead of GUI low memory warnings)
    • Improved victim search algorithm (do it ~30% faster) (rfjakob/earlyoom#114)
    • Improved limiting oom_score_adj: now it can works with UID != 0
    • Fixed conf parsing: use of line.partition('=') instead of line.split('=')
    • Added oom-sort
    • Removed self-defense options from the config, use systemd unit scheduling instead
    • Added the ability to send any signal instead of SIGTERM for processes with certain names
    • Added initial support for PSI
    • Improved user input validation
    • Improved documentation
  • v0.1, 2018-11-23: Initial release

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A highly configurable OOM prevention daemon

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