Matteo Croce
15783e4657
Add to oomd the capability to define rulesets in /etc/systemd/oomd/rules.d/ and then reference them with a new config option OOMRule=
237 lines
12 KiB
XML
237 lines
12 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="oomd.conf" conditional='ENABLE_OOMD'
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>oomd.conf</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>oomd.conf</refentrytitle>
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<manvolnum>5</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>oomd.conf</refname>
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<refname>oomd.conf.d</refname>
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<refpurpose>Global <command>systemd-oomd</command> configuration files</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><simplelist>
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<member><filename>/etc/systemd/oomd.conf</filename></member>
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<member><filename>/run/systemd/oomd.conf</filename></member>
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<member><filename>/usr/local/lib/systemd/oomd.conf</filename></member>
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<member><filename>/usr/lib/systemd/oomd.conf</filename></member>
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<member><filename>/etc/systemd/oomd.conf.d/*.conf</filename></member>
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<member><filename>/run/systemd/oomd.conf.d/*.conf</filename></member>
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<member><filename>/usr/local/lib/systemd/oomd.conf.d/*.conf</filename></member>
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<member><filename>/usr/lib/systemd/oomd.conf.d/*.conf</filename></member>
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</simplelist></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>These files configure the various parameters of the
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> userspace
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out-of-memory (OOM) killer,
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<citerefentry><refentrytitle>systemd-oomd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
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See <citerefentry><refentrytitle>systemd.syntax</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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for a general description of the syntax.</para>
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</refsect1>
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<xi:include href="standard-conf.xml" xpointer="main-conf" />
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<refsect1>
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<title>Prekill event</title>
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<para><command>systemd-oomd</command> supports notifying external components before killing a control
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group.
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This is done by sending a notification over varlink to all sockets found in
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<filename>/run/systemd/oomd.prekill.hook/</filename> folder. Each socket should implement the
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<constant>io.systemd.oom.Prekill</constant> interface. The notification contains the control group path
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to allow the hook to identify which control group is being killed. This allows external components to
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perform any necessary cleanup or logging before the control group is terminated. The hook is not intended
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as a way to avoid the kill, but rather as a notification mechanism.
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Note that this is a privileged option as, even if it has a timeout, is synchronous and delays the kill,
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so use with care.
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The typically preferable mechanism to process memory pressure is to do what
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<ulink url="https://systemd.io/PRESSURE">Resource Pressure Handling</ulink> describes which is unprivileged,
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asynchronous and does not delay the kill.
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</para>
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</refsect1>
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<refsect1>
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<title>OOM Rulesets</title>
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<para><command>systemd-oomd</command> supports custom rulesets that define conditions and actions for
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OOM handling on a per-unit basis. Ruleset files use the <filename>.oomrule</filename> extension and are
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loaded from <filename>/etc/systemd/oomd/rules.d/</filename>,
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<filename>/run/systemd/oomd/rules.d/</filename>,
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<filename>/usr/local/lib/systemd/oomd/rules.d/</filename>, and
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<filename>/usr/lib/systemd/oomd/rules.d/</filename>.
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Units opt into rulesets via the <varname>OOMRules=</varname> setting in
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<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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which takes a space-separated list of ruleset names (the file name without the <filename>.oomrule</filename>
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extension).</para>
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<para>Each ruleset file contains a <literal>[Rule]</literal> section with the following options. At least
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one of <varname>MemoryPressureAbove=</varname> or <varname>SwapUsageMax=</varname> must be configured;
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rulesets with no conditions are ignored. If both are set, the conditions are combined with AND, i.e. the
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action is only triggered when both thresholds are exceeded simultaneously.</para>
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<variablelist class='config-directives'>
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<varlistentry>
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<term><varname>MemoryPressureAbove=</varname></term>
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<listitem><para>Sets the memory pressure threshold above which the rule's action will be triggered.
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The memory pressure represents the fraction of time in a 10 second window in which all tasks in the
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control group were delayed (PSI <literal>full avg10</literal>). Takes a value specified in percent
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(when suffixed with <literal>%</literal>), permille (<literal>‰</literal>) or permyriad
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(<literal>‱</literal>), between 0% and 100%, inclusive. If unset, this condition is not
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evaluated. A value of <literal>100%</literal> can never be exceeded and is
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therefore rejected with a warning; a value of <literal>0%</literal> makes the condition true on any
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observed pressure, which is usually not useful.</para>
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<xi:include href="version-info.xml" xpointer="v261"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>SwapUsageMax=</varname></term>
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<listitem><para>Sets the system-wide swap usage threshold above which the rule's action will be
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triggered. Takes a value specified in percent (when suffixed with <literal>%</literal>),
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permille (<literal>‰</literal>) or permyriad (<literal>‱</literal>),
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between 0% and 100%, inclusive. If unset, this condition is not evaluated. A value of
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<literal>100%</literal> can never be exceeded and is therefore rejected with
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a warning; a value of <literal>0%</literal> fires as soon as any swap is in use, which is usually
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not useful.</para>
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<xi:include href="version-info.xml" xpointer="v261"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>Action=</varname></term>
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<listitem><para>Specifies the action to take when the rule's conditions are met. Takes one of
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<literal>kill-all</literal>, <literal>kill-by-pgscan</literal>, or
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<literal>kill-by-swap</literal>. This setting is mandatory; rulesets without
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<varname>Action=</varname> are ignored.</para>
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<itemizedlist>
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<listitem><para><literal>kill-all</literal> sends <constant>SIGKILL</constant> to every process
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in the unit's cgroup hierarchy, including any descendant cgroups.</para></listitem>
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<listitem><para><literal>kill-by-pgscan</literal> selects and kills the descendant cgroup with
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the highest recent page scan (reclaim) rate.</para></listitem>
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<listitem><para><literal>kill-by-swap</literal> selects and kills the descendant cgroup with the
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highest swap usage.</para></listitem>
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</itemizedlist>
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<xi:include href="version-info.xml" xpointer="v261"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>LastingSec=</varname></term>
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<listitem><para>Sets the duration the conditions must be continuously met before the action is taken.
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Takes a time span value, see
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<citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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for details on the permitted syntax. Defaults to 0, i.e. the action is taken
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immediately when the conditions are met.</para>
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<xi:include href="version-info.xml" xpointer="v261"/></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>[OOM] Section Options</title>
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<para>The following options are available in the [OOM] section:</para>
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<variablelist class='config-directives'>
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<varlistentry>
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<term><varname>SwapUsedLimit=</varname></term>
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<listitem><para>Sets the limit for memory and swap usage on the system before <command>systemd-oomd</command>
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will take action. If the fraction of memory used and the fraction of swap used on the system are both more than
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what is defined here, <command>systemd-oomd</command> will act on eligible descendant control groups with swap
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usage greater than 5% of total swap, starting from the ones with the highest swap usage. Which
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control groups are monitored and what action gets taken depends on what the unit has configured for
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<varname>ManagedOOMSwap=</varname>. Takes a value specified in percent (when suffixed with "%"),
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permille ("‰") or permyriad ("‱"), between 0% and 100%, inclusive. Defaults to 90%.</para>
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<xi:include href="version-info.xml" xpointer="v247"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>DefaultMemoryPressureLimit=</varname></term>
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<listitem><para>Sets the limit for memory pressure on the unit's control group before
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<command>systemd-oomd</command> will take action. A unit can override this value with
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<varname>ManagedOOMMemoryPressureLimit=</varname>. The memory pressure for this property represents
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the fraction of time in a 10 second window in which all tasks in the control group were delayed. For
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each monitored control group, if the memory pressure on that control group exceeds the limit set for
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longer than the duration set by <varname>DefaultMemoryPressureDurationSec=</varname>,
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<command>systemd-oomd</command> will act on eligible descendant control groups, starting from the
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ones with the most reclaim activity to the least reclaim activity. Which control groups are monitored
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and what action gets taken depends on what the unit has configured for
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<varname>ManagedOOMMemoryPressure=</varname>. Takes a fraction specified in the same way as
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<varname>SwapUsedLimit=</varname> above. Defaults to 60%.</para>
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<xi:include href="version-info.xml" xpointer="v247"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>DefaultMemoryPressureDurationSec=</varname></term>
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<listitem><para>Sets the amount of time a unit's control group needs to have exceeded memory pressure
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limits before <command>systemd-oomd</command> will take action. A unit can override this value with
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<varname>ManagedOOMMemoryPressureDurationSec=</varname>. Memory pressure limits are defined by
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<varname>DefaultMemoryPressureLimit=</varname> and <varname>ManagedOOMMemoryPressureLimit=</varname>.
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Must be set to 0, or at least 1 second. Defaults to 30 seconds when unset or 0.</para>
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<xi:include href="version-info.xml" xpointer="v248"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>PrekillHookTimeoutSec=</varname></term>
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<listitem><para>Sets the amount of time <command>systemd-oomd</command> will wait for pre-kill hooks
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to complete, before proceeding with the control group termination. Pre-kill hooks work by placing
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varlink socket to <filename>/run/systemd/oomd.prekill.hook/</filename> folder. Each socket should
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implement interface for notification to work. <command>systemd-oomd</command> sends a notification
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before killing a control group for each discovered socket. The timeout is intended to be global and
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not per hook. If all hooks return earlier, the kill is performed as soon as possible. The timeout
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must be at least 1s.
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Defaults to 0, which means <command>systemd-oomd</command> will not wait and no notifications
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will be sent.</para>
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<xi:include href="version-info.xml" xpointer="v260"/></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para><simplelist type="inline">
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<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>systemd-oomd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>oomctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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</simplelist></para>
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</refsect1>
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</refentry>
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