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NAME | SYNOPSIS | DESCRIPTION | CONFIGURATION DIRECTORIES AND PRECEDENCE | OPTIONS | SEE ALSO | NOTES | COLOPHON |
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IOCOST.CONF(5) iocost.conf IOCOST.CONF(5)
iocost.conf - Configuration files for the iocost solution manager
/etc/systemd/iocost.conf /etc/systemd/iocost.conf.d/*.conf
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.
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 either in
/usr/lib/systemd/ or /etc/systemd/ and contains commented out
entries showing the defaults as a guide to the administrator.
Local overrides can 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's shipped in /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 of the files. This
also defined a concept of drop-in priority to allow distributions
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.
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.
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.
udevadm(8), The iocost-benchmarks github project[1], The
resctl-bench documentation details how the values are obtained[2]
1. iocost-benchmark
https://github.com/iocost-benchmark/iocost-benchmarks
2. The resctl-bench documentation details how the values are
obtained
https://github.com/facebookexperimental/resctl-demo/tree/main/resctl-bench/doc
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 2023-12-22. (At that
time, the date of the most recent commit that was found in the
repository was 2023-12-22.) 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 255 IOCOST.CONF(5)
Pages that refer to this page: systemd.directives(7), systemd.index(7)
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HTML rendering created 2023-12-22 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. |
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