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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="oomd.conf" conditional='ENABLE_OOMD'
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>oomd.conf</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>oomd.conf</refentrytitle>
<manvolnum>5</manvolnum>
</refmeta>
<refnamediv>
<refname>oomd.conf</refname>
<refname>oomd.conf.d</refname>
<refpurpose>Global <command>systemd-oomd</command> configuration files</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><simplelist>
<member><filename>/etc/systemd/oomd.conf</filename></member>
<member><filename>/run/systemd/oomd.conf</filename></member>
<member><filename>/usr/local/lib/systemd/oomd.conf</filename></member>
<member><filename>/usr/lib/systemd/oomd.conf</filename></member>
<member><filename>/etc/systemd/oomd.conf.d/*.conf</filename></member>
<member><filename>/run/systemd/oomd.conf.d/*.conf</filename></member>
<member><filename>/usr/local/lib/systemd/oomd.conf.d/*.conf</filename></member>
<member><filename>/usr/lib/systemd/oomd.conf.d/*.conf</filename></member>
</simplelist></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>These files configure the various parameters of the
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> userspace
out-of-memory (OOM) killer,
<citerefentry><refentrytitle>systemd-oomd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
See <citerefentry><refentrytitle>systemd.syntax</refentrytitle><manvolnum>7</manvolnum></citerefentry>
for a general description of the syntax.</para>
</refsect1>
<xi:include href="standard-conf.xml" xpointer="main-conf" />
<refsect1>
<title>Prekill event</title>
<para><command>systemd-oomd</command> supports notifying external components before killing a control
group.
This is done by sending a notification over varlink to all sockets found in
<filename>/run/systemd/oomd.prekill.hook/</filename> folder. Each socket should implement the
<constant>io.systemd.oom.Prekill</constant> interface. The notification contains the control group path
to allow the hook to identify which control group is being killed. This allows external components to
perform any necessary cleanup or logging before the control group is terminated. The hook is not intended
as a way to avoid the kill, but rather as a notification mechanism.
Note that this is a privileged option as, even if it has a timeout, is synchronous and delays the kill,
so use with care.
The typically preferable mechanism to process memory pressure is to do what
<ulink url="https://systemd.io/MEMORY_PRESSURE/">MEMORY_PRESSURE</ulink> describes which is unprivileged,
asynchronous and does not delay the kill.
</para>
</refsect1>
<refsect1>
<title>[OOM] Section Options</title>
<para>The following options are available in the [OOM] section:</para>
<variablelist class='config-directives'>
<varlistentry>
<term><varname>SwapUsedLimit=</varname></term>
<listitem><para>Sets the limit for memory and swap usage on the system before <command>systemd-oomd</command>
will take action. If the fraction of memory used and the fraction of swap used on the system are both more than
what is defined here, <command>systemd-oomd</command> will act on eligible descendant control groups with swap
usage greater than 5% of total swap, starting from the ones with the highest swap usage. Which
control groups are monitored and what action gets taken depends on what the unit has configured for
<varname>ManagedOOMSwap=</varname>. Takes a value specified in percent (when suffixed with "%"),
permille ("‰") or permyriad ("‱"), between 0% and 100%, inclusive. Defaults to 90%.</para>
<xi:include href="version-info.xml" xpointer="v247"/></listitem>
</varlistentry>
<varlistentry>
<term><varname>DefaultMemoryPressureLimit=</varname></term>
<listitem><para>Sets the limit for memory pressure on the unit's control group before
<command>systemd-oomd</command> will take action. A unit can override this value with
<varname>ManagedOOMMemoryPressureLimit=</varname>. The memory pressure for this property represents
the fraction of time in a 10 second window in which all tasks in the control group were delayed. For
each monitored control group, if the memory pressure on that control group exceeds the limit set for
longer than the duration set by <varname>DefaultMemoryPressureDurationSec=</varname>,
<command>systemd-oomd</command> will act on eligible descendant control groups, starting from the
ones with the most reclaim activity to the least reclaim activity. Which control groups are monitored
and what action gets taken depends on what the unit has configured for
<varname>ManagedOOMMemoryPressure=</varname>. Takes a fraction specified in the same way as
<varname>SwapUsedLimit=</varname> above. Defaults to 60%.</para>
<xi:include href="version-info.xml" xpointer="v247"/></listitem>
</varlistentry>
<varlistentry>
<term><varname>DefaultMemoryPressureDurationSec=</varname></term>
<listitem><para>Sets the amount of time a unit's control group needs to have exceeded memory pressure
limits before <command>systemd-oomd</command> will take action. A unit can override this value with
<varname>ManagedOOMMemoryPressureDurationSec=</varname>. Memory pressure limits are defined by
<varname>DefaultMemoryPressureLimit=</varname> and <varname>ManagedOOMMemoryPressureLimit=</varname>.
Must be set to 0, or at least 1 second. Defaults to 30 seconds when unset or 0.</para>
<xi:include href="version-info.xml" xpointer="v248"/></listitem>
</varlistentry>
<varlistentry>
<term><varname>PrekillHookTimeoutSec=</varname></term>
<listitem><para>Sets the amount of time <command>systemd-oomd</command> will wait for pre-kill hooks
to complete, before proceeding with the control group termination. Pre-kill hooks work by placing
varlink socket to <filename>/run/systemd/oomd.prekill.hook/</filename> folder. Each socket should
implement interface for notification to work. <command>systemd-oomd</command> sends a notification
before killing a control group for each discovered socket. The timeout is intended to be global and
not per hook. If all hooks return earlier, the kill is performed as soon as possible. The timeout
must be at least 1s.
Defaults to 0, which means <command>systemd-oomd</command> will not wait and no notifications
will be sent.</para>
<xi:include href="version-info.xml" xpointer="v260"/></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>See Also</title>
<para><simplelist type="inline">
<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>systemd-oomd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>oomctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
</simplelist></para>
</refsect1>
</refentry>
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