# nohang
[](https://travis-ci.org/hakavlad/nohang)
[](https://repology.org/project/nohang/versions)
`nohang` package provides a highly configurable daemon for Linux which is able to correctly prevent [out of memory](https://en.wikipedia.org/wiki/Out_of_memory) (OOM) and keep system responsiveness in low memory conditions.
The package also includes additional diagnostic tools (`oom-sort`, `psi2log`, `psi-top`).
## What is the problem?
OOM conditions may cause [freezes](https://en.wikipedia.org/wiki/Hang_(computing)), [livelocks](https://en.wikipedia.org/wiki/Deadlock#Livelock), drop [caches](https://en.wikipedia.org/wiki/Page_cache) and processes to be killed (via sending [SIGKILL](https://en.wikipedia.org/wiki/Signal_(IPC)#SIGKILL)) instead of trying to terminate them correctly (via sending [SIGTERM](https://en.wikipedia.org/wiki/Signal_(IPC)#SIGTERM) or takes other corrective action). Some applications may crash if it's impossible to allocate memory.
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](https://serverfault.com/questions/390623/how-do-i-prevent-linux-from-freezing-when-out-of-memory)
> "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](https://serverfault.com/questions/390623/how-do-i-prevent-linux-from-freezing-when-out-of-memory#comment417508_390625)
> "The traditional Linux OOM killer works fine in some cases, but in others it kicks in too late, resulting in the system entering a [livelock](https://en.wikipedia.org/wiki/Deadlock#Livelock) for an indeterminate period."
— [engineering.fb.com](https://engineering.fb.com/production-engineering/oomd/)
Also look at these discussions:
- Why are low memory conditions handled so badly? [[r/linux](https://www.reddit.com/r/linux/comments/56r4xj/why_are_low_memory_conditions_handled_so_badly/)]
- Memory management "more effective" on Windows than Linux? (in preventing total system lockup) [[r/linux](https://www.reddit.com/r/linux/comments/aqd9mh/memory_management_more_effective_on_windows_than/)]
- Let's talk about the elephant in the room - the Linux kernel's inability to gracefully handle low memory pressure [[original LKML post](https://lkml.org/lkml/2019/8/4/15) | [r/linux](https://www.reddit.com/r/linux/comments/cmg48b/lets_talk_about_the_elephant_in_the_room_the/) | [Hacker News](https://news.ycombinator.com/item?id=20620545) | [slashdot](https://linux.slashdot.org/story/19/08/06/1839206/linux-performs-poorly-in-low-ram--memory-pressure-situations-on-the-desktop) | [phoronix](https://www.phoronix.com/forums/forum/phoronix/general-discussion/1118164-yes-linux-does-bad-in-low-ram-memory-pressure-situations-on-the-desktop) | [opennet.ru](https://www.opennet.ru/opennews/art.shtml?num=51231) | [linux.org.ru](https://www.linux.org.ru/forum/talks/15151526)]
## Solution
Use one of the userspace OOM killers:
- [earlyoom](https://github.com/rfjakob/earlyoom): This is a simple, stable and tiny OOM prevention daemon written in C (the best choice for emedded and old servers). It has a minimum dependencies and can work with oldest kernels. It is enabled by default on Fedora 32 Workstation (and F33 KDE).
- [oomd](https://github.com/facebookincubator/oomd): This is a userspace OOM killer for linux systems written in C++ and developed by Facebook. This is the best choice for use in large data centers. It needs Linux 4.20+.
- [systemd-oomd](https://man7.org/linux/man-pages/man8/systemd-oomd.service.8.html): Provided by systemd as `systemd-oomd.service` that uses cgroups-v2 and pressure stall information (PSI) to monitor and take action on processes before an OOM occurs in kernel space. It's used by default on [desktop versions of Fedora 34](https://fedoraproject.org/wiki/Changes/EnableSystemdOomd).
- [low-memory-monitor](https://gitlab.freedesktop.org/hadess/low-memory-monitor/): There's a [project announcement](http://www.hadess.net/2019/08/low-memory-monitor-new-project.html).
- [psi-monitor](https://github.com/endlessm/eos-boot-helper/tree/master/psi-monitor): It's used by default on [Endless OS](https://endlessos.com/).
- `nohang`: nohang is earlyoom on steroids and has many useful features, see below. Maybe this is a good choice for modern desktops and servers if you need fine-tuning. Previously it was used by default on [Garuda Linux](https://garudalinux.org/).
Use these tools to improve responsiveness during heavy swapping:
- MGLRU patchset is merged in Linux 6.1. Setting `min_ttl_ms` > 50 can help you.
- [le9-patch](https://github.com/hakavlad/le9-patch): [PATCH] mm: Protect clean file pages under memory pressure to prevent thrashing, avoid high latency and prevent livelock in near-OOM conditions. It's kernel-side solution that can fix the OOM killer behavior.
- [prelockd](https://github.com/hakavlad/prelockd): Lock executables and shared libraries in memory to improve system responsiveness under low-memory conditions.
- [memavaild](https://github.com/hakavlad/memavaild): Keep amount of available memory by evicting memory of selected cgroups into swap space.
- [uresourced](https://gitlab.freedesktop.org/benzea/uresourced): This daemon will give resource allocations to active graphical users. It's [enabled by default](https://fedoraproject.org/wiki/Changes/Reserve_resources_for_active_user_WS) on Fedora 33 Workstation.
Of course, you can also [download more RAM](https://downloadmoreram.com/), tune [virtual memory](https://www.kernel.org/doc/Documentation/sysctl/vm.txt), use [zram](https://www.kernel.org/doc/Documentation/blockdev/zram.txt)/[zswap](https://www.kernel.org/doc/Documentation/vm/zswap.txt) and use [limits](https://www.freedesktop.org/software/systemd/man/systemd.resource-control.html) for cgroups.
## 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;
- Customizing victim selection: impact on the badness of processes via matching their names, cgroups, exe realpathes, environs, cmdlines and euids with specified regular expressions;
- Customizing corrective actions: if the name or control group 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:
- `systemctl restart foo`;
- `kill -INT $PID` (you can override the signal sent to the victim, $PID will be replaced by the victim's PID).
- GUI notifications:
- Notification of corrective actions taken and displaying the name and PID of the victim;
- Low memory warnings.
- [zram](https://www.kernel.org/doc/Documentation/blockdev/zram.txt) support (`mem_used_total` as a trigger);
- [PSI](https://lwn.net/Articles/759658/) ([pressure stall information](https://facebookmicrosites.github.io/psi/)) support;
- Optional checking kernel messages for OOM events;
- Easy setup with configuration files ([nohang.conf](https://github.com/hakavlad/nohang/blob/master/conf/nohang/nohang.conf.in), [nohang-desktop.conf](https://github.com/hakavlad/nohang/blob/master/conf/nohang/nohang-desktop.conf.in)).
## Demo
`nohang` prevents Out Of Memory with GUI notifications:
- [https://youtu.be/ChTNu9m7uMU](https://youtu.be/ChTNu9m7uMU) – just old demo without swap space.
- [https://youtu.be/UCwZS5uNLu0](https://youtu.be/UCwZS5uNLu0) – running multiple fast memory hogs at the same time without swap space.
- [https://youtu.be/PLVWgNrVNlc](https://youtu.be/PLVWgNrVNlc) – opening multiple chromium tabs with 2.3 GiB memory and 1.8 GiB swap space on zram.
## Requirements
For basic usage:
- `Linux` (>= 3.14, since `MemAvailable` appeared in `/proc/meminfo`)
- `Python` (>= 3.3)
To respond to `PSI` metrics (optional):
- `Linux` (>= 4.20) with `CONFIG_PSI=y`
To show GUI notifications (optional):
- [notification server](https://wiki.archlinux.org/index.php/Desktop_notifications#Notification_servers) (most of desktop environments use their own implementations)
- `libnotify` (Arch Linux, Fedora, openSUSE) or `libnotify-bin` (Debian GNU/Linux, Ubuntu)
- `sudo` if nohang started with UID=0.
## Memory and CPU usage
- VmRSS is about 10–14 MiB instead of the settings, about 10–11 MiB by default (with Python <= 3.8), about 16–17 MiB with Python 3.9.
- CPU usage depends on the level of available memory and monitoring intensity.
## Warnings
- the daemon runs with super-user privileges and has full access to all private memory of all processes and sensitive user data;
- the daemon does not forbid you to shoot yourself in the foot: with some settings, unwanted killings of processes can occur;
- the daemon is not a panacea: there are no universal settings that reliably protect against all types of threats.
## Known problems
- The documentation is terrible.
- The ZFS ARC cache is memory-reclaimable, like the Linux buffer cache. However, in contrast to the buffer cache, it currently does not count to MemAvailable (see [openzfs/zfs#10255](https://github.com/openzfs/zfs/issues/10255)). See also https://github.com/rfjakob/earlyoom/pull/191 and https://github.com/hakavlad/nohang/issues/89.
- Linux kernels without `CONFIG_CGROUP_CPUACCT=y` ([linux-ck](https://wiki.archlinux.org/index.php/Linux-ck), for example) provide incorrect PSI metrics, see [issue](https://github.com/hakavlad/nohang/issues/25#issuecomment-643716504).
## nohang vs nohang-desktop
`nohang` comes with two configs: `nohang.conf` and `nohang-desktop.conf`. `nohang` comes with two systemd service unit files: `nohang.service` and `nohang-desktop.service`. Choose one.
- `nohang.conf` provides vanilla default settings without PSI checking enabled, without any badness correction and without GUI notifications enabled.
- `nohang-desktop.conf` provides default settings optimized for desktop usage.
## How to install
#### To install on [Fedora](https://src.fedoraproject.org/rpms/nohang/):
Orphaned for 6+ weeks, not available.
#### To install on RHEL 7 and RHEL 8:
nohang is avaliable in [EPEL repos](https://fedoraproject.org/wiki/EPEL).
```bash
sudo yum install nohang
sudo systemctl enable nohang.service
sudo systemctl start nohang.service
```
To enable PSI on RHEL 8 pass `psi=1` to kernel boot cmdline.
#### For Arch Linux there's an [AUR package](https://aur.archlinux.org/packages/nohang-git/)
Use your favorite [AUR helper](https://wiki.archlinux.org/index.php/AUR_helpers). For example,
```bash
yay -S nohang-git
sudo systemctl enable --now nohang-desktop.service
```
#### To install on Ubuntu 20.04/20.10
To install from [PPA](https://launchpad.net/~oibaf/+archive/ubuntu/test/):
```bash
sudo add-apt-repository ppa:oibaf/test
sudo apt update
sudo apt install nohang
sudo systemctl enable --now nohang-desktop.service
```
#### To install on Debian and Ubuntu-based systems:
Outdated and buggy nohang v0.1 release was packaged for [Debian 11](https://packages.debian.org/bullseye/source/nohang) and [Ubuntu 20.10](https://packages.ubuntu.com/source/groovy/nohang).
It's easy to build a deb package with the latest git snapshot. Install build dependencies:
```bash
sudo apt install make fakeroot
```
Clone the latest git snapshot and run the build script to build the package:
```bash
git clone https://github.com/hakavlad/nohang.git && cd nohang
deb/build.sh
```
Install the package:
```bash
sudo apt install --reinstall ./deb/package.deb
```
Start and enable `nohang.service` or `nohang-desktop.service` after installing the package:
```bash
sudo systemctl enable --now nohang-desktop.service
```
#### To install on Gentoo and derivatives (e.g. Funtoo):
Add the [eph kit](https://git.sr.ht/~happy_shredder/eph_kit) overlay, for example using layman or as a local repository.
Then update your repos:
```bash
sudo layman -S # if added via layman
sudo emerge --sync # local repo on Gentoo
sudo ego sync # local repo on Funtoo
```
Install:
```bash
sudo emerge -a nohang
```
Start the service:
```bash
sudo rc-service nohang-desktop start
```
Optionally add to startup:
```bash
sudo rc-update add nohang-desktop default
```
#### To install the latest version on any distro:
```bash
git clone https://github.com/hakavlad/nohang.git && cd nohang
sudo make install
```
Config files will be located in `/usr/local/etc/nohang/`. To enable and start unit without GUI notifications:
```bash
sudo systemctl enable --now nohang.service
```
To enable and start unit with GUI notifications:
```bash
sudo systemctl enable --now nohang-desktop.service
```
On systems with OpenRC:
```bash
sudo make install-openrc
```
To uninstall:
```bash
sudo make uninstall
```
## Command line options
```
./nohang -h
usage: nohang [-h|--help] [-v|--version] [-m|--memload]
[-c|--config CONFIG] [--check] [--monitor] [--tasks]
optional arguments:
-h, --help show this help message and exit
-v, --version show version of installed package and exit
-m, --memload consume memory until 40 MiB (MemAvailable + SwapFree)
remain free, and terminate the process
-c CONFIG, --config CONFIG
path to the config file. This should only be used
with one of the following options:
--monitor, --tasks, --check
--check check and show the configuration and exit. This should
only be used with -c/--config CONFIG option
--monitor start monitoring. This should only be used with
-c/--config CONFIG option
--tasks show tasks state and exit. This should only be used
with -c/--config CONFIG option
```
## How to configure
The program can be configured by editing the config file. The configuration includes the following sections:
0. Checking kernel messages for OOM events;
1. Common zram settings;
2. Common PSI settings;
3. Poll rate;
4. Warnings and notifications;
5. Soft threshold;
6. Hard threshold;
7. Customize victim selection;
8. Customize soft corrective actions;
9. Misc settings;
10. Verbosity, debug, logging.
Just read the description of the parameters and edit the values. Please restart the daemon to apply the changes.
## How to test nohang
- The safest way is to run `nohang --memload`. This causes memory consumption, and the process will exits before OOM occurs.
- Another way is to run `tail /dev/zero`. This causes fast memory comsumption and causes OOM at the end.
If testing occurs while `nohang` is running, these processes should be terminated before OOM occurs.
## Tasks state
Run `sudo nohang -c/--config CONFIG --tasks` 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
```
## Logging
To view the latest entries in the log (for systemd users):
```bash
sudo journalctl -eu nohang.service
#### or
sudo journalctl -eu nohang-desktop.service
```
You can also enable `separate_log` in the config to logging in `/var/log/nohang/nohang.log`.
## 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. Man page: [oom-sort.manpage.md](docs/oom-sort.manpage.md).
Usage:
```bash
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.
## psi-top
psi-top is script that prints the PSI metrics values for every cgroup. It requires `Linux` >= 4.20 with `CONFIG_PSI=y`. Man page: [psi-top.manpage.md](docs/psi-top.manpage.md).
Output example
```
$ psi-top
cgroup2 mountpoint: /sys/fs/cgroup
avg10 avg60 avg300 avg10 avg60 avg300 cgroup2
----- ----- ------ ----- ----- ------ ---------
some 0.00 0.21 1.56 | full 0.00 0.16 1.14 [SYSTEM_WIDE]
some 0.00 0.21 1.56 | full 0.00 0.16 1.14
some 0.00 0.15 1.11 | full 0.00 0.12 0.89 /user.slice
some 45.92 28.77 20.19 | full 45.05 28.17 19.56 /user.slice/user-1000.slice
some 1.44 4.67 9.24 | full 1.44 4.65 9.20 /user.slice/user-1000.slice/user@1000.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /user.slice/user-1000.slice/user@1000.service/pulseaudio.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /user.slice/user-1000.slice/user@1000.service/gvfs-daemon.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /user.slice/user-1000.slice/user@1000.service/dbus.socket
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /user.slice/user-1000.slice/user@1000.service/gvfs-udisks2-volume-monitor.service
some 0.25 1.97 4.05 | full 0.25 1.96 4.03 /user.slice/user-1000.slice/user@1000.service/xfce4-notifyd.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /user.slice/user-1000.slice/user@1000.service/init.scope
some 0.00 0.66 1.99 | full 0.00 0.66 1.97 /user.slice/user-1000.slice/user@1000.service/gpg-agent.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /user.slice/user-1000.slice/user@1000.service/gvfs-gphoto2-volume-monitor.service
some 0.93 0.75 0.20 | full 0.93 0.75 0.20 /user.slice/user-1000.slice/user@1000.service/at-spi-dbus-bus.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /user.slice/user-1000.slice/user@1000.service/gvfs-metadata.service
some 0.00 2.44 6.78 | full 0.00 2.43 6.74 /user.slice/user-1000.slice/user@1000.service/dbus.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /user.slice/user-1000.slice/user@1000.service/gvfs-mtp-volume-monitor.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /user.slice/user-1000.slice/user@1000.service/gvfs-afc-volume-monitor.service
some 44.99 28.30 19.41 | full 44.10 27.70 18.79 /user.slice/user-1000.slice/session-2.scope
some 0.00 0.31 0.53 | full 0.00 0.31 0.53 /init.scope
some 7.25 11.40 13.34 | full 7.23 11.32 13.24 /system.slice
some 0.00 0.01 0.02 | full 0.00 0.01 0.02 /system.slice/systemd-udevd.service
some 0.00 0.58 1.55 | full 0.00 0.58 1.55 /system.slice/cronie.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /system.slice/sys-kernel-config.mount
some 0.00 0.22 0.35 | full 0.00 0.22 0.35 /system.slice/polkit.service
some 0.00 0.06 0.20 | full 0.00 0.06 0.20 /system.slice/rtkit-daemon.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /system.slice/sys-kernel-debug.mount
some 0.00 0.14 0.62 | full 0.00 0.14 0.62 /system.slice/accounts-daemon.service
some 7.86 11.48 12.56 | full 7.84 11.42 12.51 /system.slice/lightdm.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /system.slice/ModemManager.service
some 0.00 1.82 5.47 | full 0.00 1.81 5.43 /system.slice/systemd-journald.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /system.slice/dev-mqueue.mount
some 0.00 1.64 4.07 | full 0.00 1.64 4.07 /system.slice/NetworkManager.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /system.slice/tmp.mount
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /system.slice/lvm2-lvmetad.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /system.slice/dev-disk-by\x2duuid-5d7355c0\x2dc131\x2d40c5\x2d8541\x2d1e04ad7c8b8d.swap
some 0.00 0.09 0.11 | full 0.00 0.09 0.11 /system.slice/upower.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /system.slice/udisks2.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /system.slice/dev-hugepages.mount
some 0.00 0.27 0.49 | full 0.00 0.27 0.48 /system.slice/dbus.service
some 0.00 0.00 0.00 | full 0.00 0.00 0.00 /system.slice/system-getty.slice
some 0.00 0.12 0.20 | full 0.00 0.12 0.20 /system.slice/avahi-daemon.service
some 0.00 0.18 0.30 | full 0.00 0.18 0.30 /system.slice/systemd-logind.service
```
## psi2log
psi2log is a CLI tool that can check and log PSI metrics from specified target. It requires `Linux` >= 4.20 with `CONFIG_PSI=y`. Man page: [psi2log.manpage.md](docs/psi2log.manpage.md).
Output example
```
$ psi2log
Starting psi2log
target: SYSTEM_WIDE
period: 2
------------------------------------------------------------------------------------------------------------------
some cpu pressure || some memory pressure | full memory pressure || some io pressure | full io pressure
---------------------||----------------------|----------------------||----------------------|---------------------
avg10 avg60 avg300 || avg10 avg60 avg300 | avg10 avg60 avg300 || avg10 avg60 avg300 | avg10 avg60 avg300
------ ------ ------ || ------ ------ ------ | ------ ------ ------ || ------ ------ ------ | ------ ------ ------
0.13 0.26 0.08 || 3.36 10.31 3.47 | 2.68 7.69 2.56 || 20.24 26.90 8.60 | 18.80 23.16 7.33
0.11 0.25 0.08 || 2.75 9.97 3.45 | 2.20 7.44 2.54 || 18.38 26.34 8.61 | 17.21 22.73 7.35
0.09 0.25 0.07 || 2.25 9.65 3.43 | 1.80 7.20 2.52 || 15.05 25.48 8.55 | 14.09 21.99 7.30
0.07 0.24 0.07 || 1.84 9.33 3.40 | 1.47 6.96 2.51 || 13.05 24.78 8.52 | 12.26 21.40 7.28
^C
Peak values: avg10 avg60 avg300
----------- ------ ------ ------
some cpu 0.13 0.26 0.08
----------- ------ ------ ------
some memory 3.36 10.31 3.47
full memory 2.68 7.69 2.56
----------- ------ ------ ------
some io 20.24 26.90 8.61
full io 18.80 23.16 7.35
$ psi2log -t /user.slice -l pm.log
Starting psi2log
target: /user.slice
period: 2
log file: pm.log
cgroup2 mountpoint: /sys/fs/cgroup
------------------------------------------------------------------------------------------------------------------
some cpu pressure || some memory pressure | full memory pressure || some io pressure | full io pressure
---------------------||----------------------|----------------------||----------------------|---------------------
avg10 avg60 avg300 || avg10 avg60 avg300 | avg10 avg60 avg300 || avg10 avg60 avg300 | avg10 avg60 avg300
------ ------ ------ || ------ ------ ------ | ------ ------ ------ || ------ ------ ------ | ------ ------ ------
28.32 11.97 3.03 || 0.00 1.05 1.65 | 0.00 0.85 1.33 || 0.55 7.79 7.21 | 0.54 7.52 6.80
29.53 12.72 3.25 || 0.00 1.01 1.64 | 0.00 0.82 1.32 || 0.81 7.60 7.17 | 0.44 7.27 6.76
29.80 13.32 3.44 || 0.00 0.98 1.63 | 0.00 0.79 1.31 || 0.66 7.35 7.12 | 0.36 7.03 6.71
29.83 13.86 3.62 || 0.00 0.95 1.62 | 0.00 0.77 1.30 || 0.54 7.11 7.08 | 0.30 6.80 6.66
29.86 14.39 3.80 || 0.00 0.91 1.60 | 0.00 0.74 1.29 || 0.44 6.88 7.03 | 0.24 6.58 6.62
30.07 14.94 3.99 || 0.00 0.88 1.59 | 0.00 0.72 1.28 || 0.36 6.65 6.98 | 0.20 6.36 6.57
^C
Peak values: avg10 avg60 avg300
----------- ------ ------ ------
some cpu 30.07 14.94 3.99
----------- ------ ------ ------
some memory 0.00 1.05 1.65
full memory 0.00 0.85 1.33
----------- ------ ------ ------
some io 0.81 7.79 7.21
full io 0.54 7.52 6.80
```
## Contribution
- Use cases, feature requests and any questions are [welcome](https://github.com/hakavlad/nohang/issues).
- Pull requests in `dev` branch are welcome.
## Documentation
- [nohang.manpage.md](docs/nohang.manpage.md)
- [oom-sort.manpage.md](docs/oom-sort.manpage.md)
- [psi2log.manpage.md](docs/psi2log.manpage.md)
- [psi-top.manpage.md](docs/psi-top.manpage.md)
- [FAQ.ru.md](docs/FAQ.ru.md)
- [CHANGELOG.md](CHANGELOG.md)
## License
This project is licensed under the terms of the [MIT license](LICENSE).