Re: [PATCH v3] mm/oom_kill: show oom eligibility when displaying the current memory state of all tasks
From: Andrew Morton <akpm@linux-foundation.org>
Date: 2021-08-01 20:01:19
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On Fri, 30 Jul 2021 17:20:02 +0100 Aaron Tomlin [off-list ref] wrote:
quoted hunk ↗ jump to hunk
Changes since v2: - Use single character (e.g. 'R' for MMF_OOM_SKIP) as suggested by Tetsuo Handa [off-list ref] - Add new header to oom_dump_tasks documentation - Provide further justification The output generated by dump_tasks() can be helpful to determine why there was an OOM condition and which rogue task potentially caused it. Please note that this is only provided when sysctl oom_dump_tasks is enabled. At the present time, when showing potential OOM victims, we do not exclude any task that are not OOM eligible e.g. those that have MMF_OOM_SKIP set; it is possible that the last OOM killable victim was already OOM killed, yet the OOM reaper failed to reclaim memory and set MMF_OOM_SKIP. This can be confusing (or perhaps even be misleading) to the viewer. Now, we already unconditionally display a task's oom_score_adj_min value that can be set to OOM_SCORE_ADJ_MIN which is indicative of an "unkillable" task. This patch provides a clear indication with regard to the OOM ineligibility (and why) of each displayed task with the addition of a new column namely "oom_skipped". An example is provided below: [ 5084.524970] [ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj oom_skipped name [ 5084.526397] [660417] 0 660417 35869 683 167936 0 -1000 M conmon [ 5084.526400] [660452] 0 660452 175834 472 86016 0 -998 pod [ 5084.527460] [752415] 0 752415 35869 650 172032 0 -1000 M conmon [ 5084.527462] [752575] 1001050000 752575 184205 11158 700416 0 999 npm [ 5084.527467] [753606] 1001050000 753606 183380 46843 2134016 0 999 node [ 5084.527581] Memory cgroup out of memory: Killed process 753606 (node) total-vm:733520kB, anon-rss:161228kB, file-rss:26144kB, shmem-rss:0kB, UID:1001050000 So, a single character 'M' is for OOM_SCORE_ADJ_MIN, 'R' MMF_OOM_SKIP and 'V' for in_vfork(). index 003d5cc3751b..4c79fa00ddb3 100644--- a/Documentation/admin-guide/sysctl/vm.rst +++ b/Documentation/admin-guide/sysctl/vm.rst@@ -650,8 +650,9 @@ oom_dump_tasks Enables a system-wide task dump (excluding kernel threads) to be produced when the kernel performs an OOM-killing and includes such information as pid, uid, tgid, vm size, rss, pgtables_bytes, swapents, oom_score_adj -score, and name. This is helpful to determine why the OOM killer was -invoked, to identify the rogue task that caused it, and to determine why +score, oom eligibility status and name. This is helpful to determine why +the OOM killer was invoked, to identify the rogue task that caused it, and +to determine why
It would be better if the meaning of 'M', 'R' and 'V' were described here.
the OOM killer chose the task it did to kill. +/** + * is_task_eligible_oom - determine if and why a task cannot be OOM killed + * @tsk: task to check + * + * Needs to be called with task_lock(). + */ +static const char * const is_task_oom_eligible(struct task_struct *p)
Name seems inappropriate. task_oom_eligibility()?
+{
+ long adj;
+
+ adj = (long)p->signal->oom_score_adj;
+ if (adj == OOM_SCORE_ADJ_MIN)
+ return "M";
+ else if (test_bit(MMF_OOM_SKIP, &p->mm->flags)
+ return "R";
+ else if (in_vfork(p))
+ return "V";
+ else
+ return "";
+}