1CHOOM(1) User Commands CHOOM(1)
2
6 choom - display and adjust OOM-killer score.
7 choom -p PID
9 choom -p PID -n number
11 choom -n number [--] command [argument ...]
13
15 The choom command displays and adjusts Out-Of-Memory killer score
16 setting.
17
19 -p, --pid pid
20 Specifies process ID.
21 -n, --adjust value
23 Specify the adjust score value.
24 -h, --help
26 Display help text and exit.
27 -V, --version
29 Print version and exit.
30
32 Linux kernel uses the badness heuristic to select which process gets
33 killed in out of memory conditions.
34 The badness heuristic assigns a value to each candidate task ranging
36 from 0 (never kill) to 1000 (always kill) to determine which process is
37 targeted. The units are roughly a proportion along that range of
38 allowed memory the process may allocate from based on an estimation of
39 its current memory and swap use. For example, if a task is using all
40 allowed memory, its badness score will be 1000. If it is using half of
41 its allowed memory, its score will be 500.
42 There is an additional factor included in the badness score: the
44 current memory and swap usage is discounted by 3% for root processes.
45 The amount of "allowed" memory depends on the context in which the oom
47 killer was called. If it is due to the memory assigned to the
48 allocating task’s cpuset being exhausted, the allowed memory represents
49 the set of mems assigned to that cpuset. If it is due to a mempolicy’s
50 node(s) being exhausted, the allowed memory represents the set of
51 mempolicy nodes. If it is due to a memory limit (or swap limit) being
52 reached, the allowed memory is that configured limit. Finally, if it is
53 due to the entire system being out of memory, the allowed memory
54 represents all allocatable resources.
55 The adjust score value is added to the badness score before it is used
57 to determine which task to kill. Acceptable values range from -1000 to
58 +1000. This allows userspace to polarize the preference for oom killing
59 either by always preferring a certain task or completely disabling it.
60 The lowest possible value, -1000, is equivalent to disabling oom
61 killing entirely for that task since it will always report a badness
62 score of 0.
63 Setting an adjust score value of +500, for example, is roughly
65 equivalent to allowing the remainder of tasks sharing the same system,
66 cpuset, mempolicy, or memory controller resources to use at least 50%
67 more memory. A value of -500, on the other hand, would be roughly
68 equivalent to discounting 50% of the task’s allowed memory from being
69 considered as scoring against the task.
70
72 Karel Zak <kzak@redhat.com>
73
75 proc(5)
76
78 For bug reports, use the issue tracker at
79 https://github.com/util-linux/util-linux/issues.
80
82 The choom command is part of the util-linux package which can be
83 downloaded from Linux Kernel Archive
84 <https://www.kernel.org/pub/linux/utils/util-linux/>.
85util-linux 2.39.2 2023-06-14 CHOOM(1)