oomd.conf, oomd.conf.d — Global systemd-oomd configuration files
/etc/systemd/oomd.conf
/etc/systemd/oomd.conf.d/*.conf
/usr/lib/systemd/oomd.conf.d/*.conf
These files configure the various parameters of the systemd(1) userspace out-of-memory (OOM) killer, systemd-oomd.service(8). See systemd.syntax(7) for a general description of the syntax.
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.
The following options are available in the [OOM] section:
SwapUsedLimit=¶Sets the limit for memory and swap usage on the system before systemd-oomd
will take action. If the fraction of memory used and the fraction of swap used on the system are both more than
what is defined here, systemd-oomd will act on eligible descendant control groups with swap
usage greater than 5% of total swap, starting from the ones with the highest swap usage. Which
control groups are monitored and what action gets taken depends on what the unit has configured for
ManagedOOMSwap=. Takes a value specified in percent (when suffixed with "%"),
permille ("‰") or permyriad ("‱"), between 0% and 100%, inclusive. Defaults to 90%.
DefaultMemoryPressureLimit=¶Sets the limit for memory pressure on the unit's control group before
systemd-oomd will take action. A unit can override this value with
ManagedOOMMemoryPressureLimit=. The memory pressure for this property represents
the fraction of time in a 10 second window in which all tasks in the control group were delayed. For
each monitored control group, if the memory pressure on that control group exceeds the limit set for
longer than the duration set by DefaultMemoryPressureDurationSec=,
systemd-oomd will act on eligible descendant control groups, starting from the
ones with the most reclaim activity to the least reclaim activity. Which control groups are monitored
and what action gets taken depends on what the unit has configured for
ManagedOOMMemoryPressure=. Takes a fraction specified in the same way as
SwapUsedLimit= above. Defaults to 60%.
DefaultMemoryPressureDurationSec=¶Sets the amount of time a unit's control group needs to have exceeded memory pressure
limits before systemd-oomd will take action. Memory pressure limits are defined by
DefaultMemoryPressureLimit= and ManagedOOMMemoryPressureLimit=.
Must be set to 0, or at least 1 second. Defaults to 30 seconds when unset or 0.