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proc_pid_oom_score_adj(5) File Formats Manual proc_pid_oom_score_adj(5)
/proc/pid/oom_score_adj - OOM-killer score adjustment
/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
exhausted, 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 determine 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 consider 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, 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.
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.
/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 setting. 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.
proc(5), proc_pid_oom_score(5)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. 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]
Linux man-pages 6.9.1 2024-05-02 proc_pid_oom_score_adj(5)
Pages that refer to this page: proc_pid_oom_score(5)
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HTML rendering created 2024-06-26 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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