choom

CHOOM(1)                          User Commands                         CHOOM(1)



NAME
       choom - display and adjust OOM-killer score.

       choom -p PID

       choom -p PID -n number

       choom -n number [--] command [argument ...]

DESCRIPTION
       The choom command displays and adjusts Out-Of-Memory killer score
       setting.

OPTIONS
       -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 information and exit.

NOTES
       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.

AUTHORS
       Karel Zak <kzak@redhat.com>

SEE ALSO
       proc(5)

REPORTING BUGS
       For bug reports, use the issue tracker at
       https://github.com/karelzak/util-linux/issues.

AVAILABILITY
       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/>.



util-linux {release-version}       2021-06-08                           CHOOM(1)