linux-kernel - Re: [PATCH] mm/oom: Add oom_score_adj value to oom Killed process message

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Date:   Thu, 22 Aug 2019 08:18:35 -0700
From:   Edward Chron <echron@...sta.com>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>,
        Johannes Weiner <hannes@...xchg.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Shakeel Butt <shakeelb@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Ivan Delalande <colona@...sta.com>
Subject: Re: [PATCH] mm/oom: Add oom_score_adj value to oom Killed process message

On Wed, Aug 21, 2019 at 12:19 AM David Rientjes <rientjes@...gle.com> wrote:
>
> On Wed, 21 Aug 2019, Michal Hocko wrote:
>
> > > vm.oom_dump_tasks is pretty useful, however, so it's curious why you
> > > haven't left it enabled :/
> >
> > Because it generates a lot of output potentially. Think of a workload
> > with too many tasks which is not uncommon.
>
> Probably better to always print all the info for the victim so we don't
> need to duplicate everything between dump_tasks() and dump_oom_summary().
>
> Edward, how about this?

It is worth mentioning that David's suggested change, while I agree with Michal
that it should be a separate issue from updating the OOM Killed process message,
certainly has merit.  Though, it's not strictly necessary for what I
was asking for.

If you have scripts that scan your logs from OOM events, having a regular format
to OOM output makes parsing easier. With David's suggestion there would always
be a "Tasks state" section and the vm.oom_dump_tasks still works but
it just prevents
all the tasks from being dumped not from dumping the killed process.

OOM output was reorganized not that long ago as we discussed earlier to provide
improved organization of data, so this proposal would be in line with
that change.

If there is interest in this I can submit a separate patch submission.

>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -420,11 +420,17 @@ static int dump_task(struct task_struct *p, void *arg)
>   * State information includes task's pid, uid, tgid, vm size, rss,
>   * pgtables_bytes, swapents, oom_score_adj value, and name.
>   */
> -static void dump_tasks(struct oom_control *oc)
> +static void dump_tasks(struct oom_control *oc, struct task_struct *victim)
>  {
>         pr_info("Tasks state (memory values in pages):\n");
>         pr_info("[  pid  ]   uid  tgid total_vm      rss pgtables_bytes swapents oom_score_adj name\n");
>
> +       /* If vm.oom_dump_tasks is disabled, only show the victim */
> +       if (!sysctl_oom_dump_tasks) {
> +               dump_task(victim, oc);
> +               return;
> +       }
> +
>         if (is_memcg_oom(oc))
>                 mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
>         else {
> @@ -465,8 +471,8 @@ static void dump_header(struct oom_control *oc, struct task_struct *p)
>                 if (is_dump_unreclaim_slabs())
>                         dump_unreclaimable_slab();
>         }
> -       if (sysctl_oom_dump_tasks)
> -               dump_tasks(oc);
> +       if (p || sysctl_oom_dump_tasks)
> +               dump_tasks(oc, p);
>         if (p)
>                 dump_oom_summary(oc, p);
>  }