|
HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | SYSTEM REQUIREMENTS AND CONFIGURATION | USAGE RECOMMENDATIONS | OPTIONS | SIGNALS | SEE ALSO | NOTES | COLOPHON |
|
|
|
SYSTEMD-OOMD.SERVICE(8) systemd-oomd.service SYSTEMD-OOMD.SERVICE(8)
systemd-oomd.service, systemd-oomd - A userspace out-of-memory
(OOM) killer
systemd-oomd.service
/usr/lib/systemd/systemd-oomd
systemd-oomd is a system service that uses cgroups-v2 and pressure
stall information (PSI) to monitor and take corrective action
before an OOM occurs in the kernel space.
You can enable monitoring and actions on units by setting
ManagedOOMSwap= and ManagedOOMMemoryPressure= in the unit
configuration, see systemd.resource-control(5). systemd-oomd
retrieves information about such units from systemd(1) when it
starts and watches for subsequent changes.
Cgroups of units with ManagedOOMSwap= or ManagedOOMMemoryPressure=
set to kill will be monitored. systemd-oomd periodically polls
PSI statistics for the system and those cgroups to decide when to
take action. If the configured limits are exceeded, systemd-oomd
will select a cgroup to terminate, and send SIGKILL to all
processes in it. Note that only descendant cgroups are eligible
candidates for killing; the unit with its property set to kill is
not a candidate (unless one of its ancestors set their property to
kill). Also only leaf cgroups and cgroups with memory.oom.group
set to 1 are eligible candidates; see OOMPolicy= in
systemd.service(5).
oomctl(1) can be used to list monitored cgroups and pressure
information.
See oomd.conf(5) for more information about the configuration of
this service.
See org.freedesktop.oom1(5) and org.freedesktop.LogControl1(5) for
a description of the D-Bus API.
The system must be running systemd with a full unified cgroup
hierarchy for the expected cgroups-v2 features. Furthermore,
memory accounting must be turned on for all units monitored by
systemd-oomd. The easiest way to turn on memory accounting is by
ensuring the value for DefaultMemoryAccounting= is set to true in
systemd-system.conf(5).
The kernel must be compiled with PSI support. This is available in
Linux 4.20 and above.
It is highly recommended for the system to have swap enabled for
systemd-oomd to function optimally. With swap enabled, the system
spends enough time swapping pages to let systemd-oomd react.
Without swap, the system enters a livelocked state much more
quickly and may prevent systemd-oomd from responding in a
reasonable amount of time. See "In defence of swap: common
misconceptions"[1] for more details on swap. Any swap-based
actions on systems without swap will be ignored. While
systemd-oomd can perform pressure-based actions on such a system,
the pressure increases will be more abrupt and may require more
tuning to get the desired thresholds and behavior.
Be aware that if you intend to enable monitoring and actions on
user.slice, user-$UID.slice, or their ancestor cgroups, it is
highly recommended that your programs be managed by the systemd
user manager to prevent running too many processes under the same
session scope (and thus avoid a situation where memory intensive
tasks trigger systemd-oomd to kill everything under the cgroup).
If you're using a desktop environment like GNOME or KDE, it
already spawns many session components with the systemd user
manager.
ManagedOOMSwap= works with the system-wide swap values, so setting
it on the root slice -.slice, and allowing all descendant cgroups
to be eligible candidates may make the most sense.
ManagedOOMMemoryPressure= tends to work better on the cgroups
below the root slice. For units which tend to have processes that
are less latency sensitive (e.g. system.slice), a higher limit
like the default of 60% may be acceptable, as those processes can
usually ride out slowdowns caused by lack of memory without
serious consequences. However, something like user@$UID.service
may prefer a much lower value like 40%.
--dry-run
Do a dry run of systemd-oomd: when a kill is triggered, print
it to the log instead of killing the cgroup.
Added in version 253.
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
SIGHUP
Upon reception of the SIGHUP process signal systemd-oomd will
reload its configuration file.
Added in version 258.
systemd(1), systemd-system.conf(5), systemd.resource-control(5),
oomd.conf(5), oomctl(1), org.freedesktop.oom1(5)
1. "In defence of swap: common misconceptions"
https://chrisdown.name/2018/01/02/in-defence-of-swap.html
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-02-02. (At that
time, the date of the most recent commit that was found in the
repository was 2025-02-02.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
systemd 258~devel SYSTEMD-OOMD.SERVICE(8)
Pages that refer to this page: oomctl(1), oomd.conf(5), org.freedesktop.oom1(5), systemd.resource-control(5), systemd.scope(5), systemd.service(5), systemd.directives(7), systemd.index(7)
|
HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|