NAME

       choom - display and adjust OOM-killer score.

SYNOPSIS

       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)

AVAILABILITY

       The choom command is part of the util-linux package and is  available  from  Linux  Kernel
       Archive ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩.