man > proc_pid_oom_score_adj(5)

proc_pid_oom_score_adj(5)                File Formats Manual               proc_pid_oom_score_adj(5)

NAME
       /proc/pid/oom_score_adj - OOM-killer score adjustment

DESCRIPTION
       /proc/pid/oom_score_adj (since Linux 2.6.36)
              This  file  can  be  used to adjust the badness heuristic used 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: root processes are  given
              3% extra memory over other tasks.

              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 ex‐
              hausted, the allowed memory represents the set of mems assigned to  that  cpuset  (see
              cpuset(7)).  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  value  of oom_score_adj is added to the badness score before it is used to deter‐
              mine which task to kill.  Acceptable values range from  -1000  (OOM_SCORE_ADJ_MIN)  to
              +1000  (OOM_SCORE_ADJ_MAX).  This allows user space to control the preference for OOM-
              killing, ranging from always preferring a certain task or completely disabling it from
              OOM-killing.  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.

              Consequently, it is very simple for user space to define the amount of memory to  con‐
              sider  for each task.  Setting an oom_score_adj value of +500, for example, is roughly
              equivalent to allowing the remainder of tasks sharing the same system, cpuset, mempol‐
              icy, 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  al‐
              lowed memory from being considered as scoring against the task.

              For  backward compatibility with previous kernels, /proc/pid/oom_adj can still be used
              to tune the badness score.  Its value is scaled linearly with oom_score_adj.

              Writing to /proc/pid/oom_score_adj or /proc/pid/oom_adj will change the other with its
              scaled value.

              The choom(1) program provides a command-line interface for adjusting the oom_score_adj
              value of a running process or a newly executed command.

HISTORY
       /proc/pid/oom_adj (since Linux 2.6.11)
              This file can be used to adjust the score used  to  select  which  process  should  be
              killed  in  an  out-of-memory  (OOM) situation.  The kernel uses this value for a bit-
              shift operation of the process's oom_score value: valid values are in the range -16 to
              +15, plus the special value  -17,  which  disables  OOM-killing  altogether  for  this
              process.   A  positive  score increases the likelihood of this process being killed by
              the OOM-killer; a negative score decreases the likelihood.

              The default value for this file is 0; a new process inherits its parent's oom_adj set‐
              ting.  A process must be privileged (CAP_SYS_RESOURCE) to update this file, although a
              process can always increase its own oom_adj setting (since Linux 2.6.20).

              Since   Linux   2.6.36,   use   of   this   file   is   deprecated   in    favor    of
              /proc/pid/oom_score_adj, and finally removed in Linux 3.7.

SEE ALSO
       proc(5), proc_pid_oom_score(5)

Linux man-pages 6.7                          2023-11-24                    proc_pid_oom_score_adj(5)