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.


       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's 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

       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:

           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

           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

        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

COLOPHON         top

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       This page was obtained from the project's upstream Git repository
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systemd 257~devel                                         IOCOST.CONF(5)

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