jammy (1) choom.1.gz

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/>.