Ubuntu Manpage: iocost.conf - Configuration files for the iocost solution manager

Provided by: systemd_255.4-1ubuntu8.4_amd64

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 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.

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".

           Added in version 254.

NOTES