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<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="iocost.conf" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>iocost.conf</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>iocost.conf</refentrytitle>
<manvolnum>5</manvolnum>
</refmeta>
<refnamediv>
<refname>iocost.conf</refname>
<refpurpose>Configuration files for the iocost solution manager</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para>
<filename>/etc/systemd/iocost.conf</filename>
<filename>/etc/systemd/iocost.conf.d/*.conf</filename>
</para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>This file configures the behavior of <literal>iocost</literal>, a tool mostly used by
<citerefentry><refentrytitle>systemd-udevd</refentrytitle><manvolnum>8</manvolnum></citerefentry> rules
to automatically apply I/O cost solutions to <filename>/sys/fs/cgroup/io.cost.*</filename>.</para>
<para>The qos and model values are calculated based on benchmarks collected on the
<ulink url="https://github.com/iocost-benchmark/iocost-benchmarks">iocost-benchmark</ulink>
project and turned into a set of solutions that go from most to least isolated.
Isolation allows the system to remain responsive in face of high I/O load.
Which solutions are available for a device can be queried from the udev metadata attached to it. By
default the naive solution is used, which provides the most bandwidth.</para>
</refsect1>
<xi:include href="standard-conf.xml" xpointer="main-conf" />
<refsect1>
<title>Options</title>
<para>All options are configured in the [IOCost] section:</para>
<variablelist class='config-directives'>
<varlistentry>
<term><varname>TargetSolution=</varname></term>
<listitem><para>Chooses which I/O cost solution (identified by named string) should be used
for the devices in this system. The known solutions can be queried from the udev metadata
attached to the devices. If a device does not have the specified solution, the first one
listed in <varname>IOCOST_SOLUTIONS</varname> is used instead.</para>
<para>E.g. <literal>TargetSolution=isolated-bandwidth</literal>.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<ulink url="https://github.com/iocost-benchmark/iocost-benchmarks">The iocost-benchmarks github project</ulink>,
<ulink url="https://github.com/facebookexperimental/resctl-demo/tree/main/resctl-bench/doc">The resctl-bench
documentation details how the values are obtained</ulink>
</para>
</refsect1>
</refentry>
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