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iocost.conf(5) — Linux manual page

IOCOST.CONF(5) iocost.conf IOCOST.CONF(5)

NAME top

 iocost.conf - Configuration files for the iocost solution manager

SYNOPSIS top

 /etc/systemd/iocost.conf /etc/systemd/iocost.conf.d/*.conf

DESCRIPTION top

 This file configures the behavior of "iocost", a tool mostly used
 by systemd-udevd(8) rules to automatically apply I/O cost
 solutions to /sys/fs/cgroup/io.cost.*.
 The qos and model values are calculated based on benchmarks
 collected on the iocost-benchmark[1] 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.

CONFIGURATION DIRECTORIES AND PRECEDENCE top

 The default configuration is set during compilation, so
 configuration is only needed when it is necessary to deviate from
 those defaults. The main configuration file is loaded from one of
 the listed directories in order of priority, only the first file
 found is used: /etc/systemd/, /run/systemd/,
 /usr/local/lib/systemd/ [2], /usr/lib/systemd/. The vendor version
 of the file contains commented out entries showing the defaults as
 a guide to the administrator. Local overrides can also be created
 by creating drop-ins, as described below. The main configuration
 file can also be edited for this purpose (or a copy in /etc/ if it
 is shipped under /usr/), however using drop-ins for local
 configuration is recommended over modifications to the main
 configuration file.
 In addition to the main configuration file, drop-in configuration
 snippets are read from /usr/lib/systemd/*.conf.d/,
 /usr/local/lib/systemd/*.conf.d/, and /etc/systemd/*.conf.d/.
 Those drop-ins have higher precedence and override the main
 configuration file. Files in the *.conf.d/ configuration
 subdirectories are sorted by their filename in lexicographic
 order, regardless of in which of the subdirectories they reside.
 When multiple files specify the same option, for options which
 accept just a single value, the entry in the file sorted last
 takes precedence, and for options which accept a list of values,
 entries are collected as they occur in the sorted files.
 When packages need to customize the configuration, they can
 install drop-ins under /usr/. Files in /etc/ are reserved for the
 local administrator, who may use this logic to override the
 configuration files installed by vendor packages. Drop-ins have to
 be used to override package drop-ins, since the main configuration
 file has lower precedence. It is recommended to prefix all
 filenames in those subdirectories with a two-digit number and a
 dash, to simplify the ordering. This also defines a concept of
 drop-in priorities to allow OS vendors to ship drop-ins within a
 specific range lower than the range used by users. This should
 lower the risk of package drop-ins overriding accidentally
 drop-ins defined by users. It is recommended to use the range
 10-40 for drop-ins in /usr/ and the range 60-90 for drop-ins in
 /etc/ and /run/, to make sure that local and transient drop-ins
 take priority over drop-ins shipped by the OS vendor.
 To disable a configuration file supplied by the vendor, the
 recommended way is to place a symlink to /dev/null in the
 configuration directory in /etc/, with the same filename as the
 vendor configuration file.

OPTIONS top

 All options are configured in the [IOCost] section:
 TargetSolution=
 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 IOCOST_SOLUTIONS is used instead.
 E.g. "TargetSolution=isolated-bandwidth".
 Added in version 254.

SEE ALSO top

 udevadm(8), The iocost-benchmarks github project[1], The
 resctl-bench documentation details how the values are obtained[3]

NOTES top

 1. iocost-benchmark
 https://github.com/iocost-benchmark/iocost-benchmarks
 2. 💣💥🧨💥💥💣 Please note that those configuration files must
 be available at all times. If /usr/local/ is a separate
 partition, it may not be available during early boot, and must
 not be used for configuration.
 3. The resctl-bench documentation details how the values are
 obtained
 https://github.com/facebookexperimental/resctl-demo/tree/main/resctl-bench/doc

COLOPHON top

 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年08月11日. (At that
 time, the date of the most recent commit that was found in the
 repository was 2025年08月11日.) 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~rc2 IOCOST.CONF(5)

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Pages that refer to this page: systemd.directives(7), systemd.index(7)

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