x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
IOCOST.CONF(5) iocost.conf IOCOST.CONF(5)
NAME
iocost.conf - Configuration files for the iocost solution manager
SYNOPSIS
/etc/systemd/iocost.conf /etc/systemd/iocost.conf.d/*.conf
DESCRIPTION
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
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 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
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".
SEE ALSO
udevadm(8), The iocost-benchmarks github project[1], The resctl-bench
documentation details how the values are obtained[2]
NOTES
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
systemd 254 IOCOST.CONF(5)
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