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3 .\" Copyright (C) 2023, Alejandro Colomar <alx@kernel.org>
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7 .TH proc_pid_oom_score_adj 5 (date) "Linux man-pages (unreleased)"
9 /proc/pid/oom_score_adj \- OOM-killer score adjustment
12 .IR /proc/ pid /oom_score_adj " (since Linux 2.6.36)"
13 .\" Text taken from Linux 3.7 Documentation/filesystems/proc.txt
14 This file can be used to adjust the badness heuristic used to select which
15 process gets killed in out-of-memory conditions.
17 The badness heuristic assigns a value to each candidate task ranging from 0
18 (never kill) to 1000 (always kill) to determine which process is targeted.
19 The units are roughly a proportion along that range of
20 allowed memory the process may allocate from,
21 based on an estimation of its current memory and swap use.
22 For example, if a task is using all allowed memory,
23 its badness score will be 1000.
24 If it is using half of its allowed memory, its score will be 500.
26 There is an additional factor included in the badness score: root
27 processes are given 3% extra memory over other tasks.
29 The amount of "allowed" memory depends on the context
30 in which the OOM-killer was called.
31 If it is due to the memory assigned to the allocating task's cpuset
33 the allowed memory represents the set of mems assigned to that
36 If it is due to a mempolicy's node(s) being exhausted,
37 the allowed memory represents the set of mempolicy nodes.
38 If it is due to a memory limit (or swap limit) being reached,
39 the allowed memory is that configured limit.
40 Finally, if it is due to the entire system being out of memory, the
41 allowed memory represents all allocatable resources.
45 is added to the badness score before it
46 is used to determine which task to kill.
47 Acceptable values range from \-1000
48 (OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX).
49 This allows user space to control the preference for OOM-killing,
50 ranging from always preferring a certain
51 task or completely disabling it from OOM-killing.
52 The lowest possible value, \-1000, is
53 equivalent to disabling OOM-killing entirely for that task,
54 since it will always report a badness score of 0.
56 Consequently, it is very simple for user space to define
57 the amount of memory to consider for each task.
60 value of +500, for example,
61 is roughly equivalent to allowing the remainder of tasks sharing the
62 same system, cpuset, mempolicy, or memory controller resources
63 to use at least 50% more memory.
64 A value of \-500, on the other hand, would be roughly
65 equivalent to discounting 50% of the task's
66 allowed memory from being considered as scoring against the task.
68 For backward compatibility with previous kernels,
69 .IR /proc/ pid /oom_adj
70 can still be used to tune the badness score.
76 .IR /proc/ pid /oom_score_adj
78 .IR /proc/ pid /oom_adj
79 will change the other with its scaled value.
83 program provides a command-line interface for adjusting the
85 value of a running process or a newly executed command.
88 .IR /proc/ pid /oom_adj " (since Linux 2.6.11)"
89 This file can be used to adjust the score used to select which process
90 should be killed in an out-of-memory (OOM) situation.
91 The kernel uses this value for a bit-shift operation of the process's
94 valid values are in the range \-16 to +15,
95 plus the special value \-17,
96 which disables OOM-killing altogether for this process.
97 A positive score increases the likelihood of this
98 process being killed by the OOM-killer;
99 a negative score decreases the likelihood.
101 The default value for this file is 0;
102 a new process inherits its parent's
105 A process must be privileged
106 .RB ( CAP_SYS_RESOURCE )
108 although a process can always increase its own
110 setting (since Linux 2.6.20).
112 Since Linux 2.6.36, use of this file is deprecated in favor of
113 .IR /proc/ pid /oom_score_adj ,
114 and finally removed in Linux 3.7.
117 .BR proc_pid_oom_score (5)