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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | NOTES | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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CHOOM(1) User Commands CHOOM(1)
choom - display or adjust OOM-killer score
choom -p PID
choom -p PID -n number
choom -n number [--] command [argument ...]
The choom command displays or adjusts the Out-Of-Memory killer
score setting.
-p, --pid pid
Specifies process ID.
-n, --adjust value
Specify the adjust score value.
-h, --help
Display help text and exit.
-V, --version
Display version and exit.
Linux kernel uses the badness heuristic to select which process
gets killed in out of memory conditions.
The badness heuristic assigns a value to each candidate task
ranging from 0 (never kill) to 1000 (always kill) to determine
which process is targeted. The units are roughly a proportion
along that range of allowed memory the process may allocate from
based on an estimation of its current memory and swap use. For
example, if a task is using all allowed memory, its badness score
will be 1000. If it is using half of its allowed memory, its score
will be 500.
There is an additional factor included in the badness score: the
current memory and swap usage is discounted by 3% for root
processes.
The amount of "allowed" memory depends on the context in which the
oom killer was called. If it is due to the memory assigned to the
allocating task’s cpuset being exhausted, the allowed memory
represents the set of mems assigned to that cpuset. If it is due
to a mempolicy’s node(s) being exhausted, the allowed memory
represents the set of mempolicy nodes. If it is due to a memory
limit (or swap limit) being reached, the allowed memory is that
configured limit. Finally, if it is due to the entire system being
out of memory, the allowed memory represents all allocatable
resources.
The adjust score value is added to the badness score before it is
used to determine which task to kill. Acceptable values range from
-1000 to +1000. This allows userspace to polarize the preference
for oom killing either by always preferring a certain task or
completely disabling it. The lowest possible value, -1000, is
equivalent to disabling oom killing entirely for that task since
it will always report a badness score of 0.
Setting an adjust score value of +500, for example, is roughly
equivalent to allowing the remainder of tasks sharing the same
system, cpuset, mempolicy, or memory controller resources to use
at least 50% more memory. A value of -500, on the other hand,
would be roughly equivalent to discounting 50% of the task’s
allowed memory from being considered as scoring against the task.
Karel Zak <[email protected]>
proc(5)
For bug reports, use the issue tracker
<https://github.com/util-linux/util-linux/issues>.
The choom command is part of the util-linux package which can be
downloaded from Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>. This page is
part of the util-linux (a random collection of Linux utilities)
project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
bug report for this manual page, send it to
[email protected]. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2025-08-11. (At that time, the date of the most recent commit that
was found in the repository was 2025-08-05.) 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 [email protected]
util-linux 2.42-start-521-ec46 2025-08-09 CHOOM(1)
Pages that refer to this page: proc_pid_oom_score_adj(5)
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HTML rendering created 2025-09-06 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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