Messages in this thread Patch in this message | | | Date | Wed, 14 Jan 2009 20:06:06 +0300 | From | Evgeniy Polyakov <> | Subject | [take2] OOM documentation update [was: Linux killed Kenny, bastard!] |
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Updated version fixes some errors and extends description by adding swapping and children relation explaintaion.
Signed.
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index d105eb4..4aa1918 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -2311,6 +2311,33 @@ increase the likelihood of this process being killed by the oom-killer. Valid values are in the range -16 to +15, plus the special value -17, which disables oom-killing altogether for this process. +The process to be killed in an out-of-memory situation is selected among all others +based on its badness score. This value equals the original memory size of the process +originally and is then updated according to its CPU time (utime + stime) and the +run time (uptime - start time). The longer it runs the smaller is the score. +Badness score is divided by the square root of the cpu time and then by +the double square root of the run time. + +Swapped out tasks are killed first. Half of each child's memory size is added to +the parent's score if they do not share the same memory. Thus forking servers +are the prime candidates to be killed. Having only one 'hungry' child will make +parent less preferable than the child. + +/proc/<pid>/oom_score shows process' current badness score. + +The following heuristics are then applied: + * if the task was reniced, its score doubles + * superuser or direct hardware access tasks (CAP_SYS_ADMIN, CAP_SYS_RESOURCE + or CAP_SYS_RAWIO) have their score divided by 4 + * if oom condition happened in one cpuset and checked task does not belong + to it, its score is divided by 8 + * resulted score is multiplied by the two in the power of oom_adj when it is + positive, and divided otherwise, i.e. + points <<= oom_adj when it is positive and + points >>= oom_adj otherwise + +The task with the highest badness score is then killed. + 2.13 /proc/<pid>/oom_score - Display current oom-killer score -------------------------------------------------------------
-- Evgeniy Polyakov
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