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

[Edward Chron <echron@arista.com>]

On Thu, Aug 22, 2019 at 12:09 AM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Wed 21-08-19 15:25:13, Edward Chron wrote:
> > On Tue, Aug 20, 2019 at 8:25 PM David Rientjes <rientjes@google.com> wrote:
> > >
> > > On Tue, 20 Aug 2019, Edward Chron wrote:
> > >
> > > > For an OOM event: print oom_score_adj value for the OOM Killed process to
> > > > document what the oom score adjust value was at the time the process was
> > > > OOM Killed. The adjustment value can be set by user code and it affects
> > > > the resulting oom_score so it is used to influence kill process selection.
> > > >
> > > > When eligible tasks are not printed (sysctl oom_dump_tasks = 0) printing
> > > > this value is the only documentation of the value for the process being
> > > > killed. Having this value on the Killed process message documents if a
> > > > miscconfiguration occurred or it can confirm that the oom_score_adj
> > > > value applies as expected.
> > > >
> > > > An example which illustates both misconfiguration and validation that
> > > > the oom_score_adj was applied as expected is:
> > > >
> > > > Aug 14 23:00:02 testserver kernel: Out of memory: Killed process 2692
> > > >  (systemd-udevd) total-vm:1056800kB, anon-rss:1052760kB, file-rss:4kB,
> > > >  shmem-rss:0kB oom_score_adj:1000
> > > >
> > > > The systemd-udevd is a critical system application that should have an
> > > > oom_score_adj of -1000. Here it was misconfigured to have a adjustment
> > > > of 1000 making it a highly favored OOM kill target process. The output
> > > > documents both the misconfiguration and the fact that the process
> > > > was correctly targeted by OOM due to the miconfiguration. Having
> > > > the oom_score_adj on the Killed message ensures that it is documented.
> > > >
> > > > Signed-off-by: Edward Chron <echron@arista.com>
> > > > Acked-by: Michal Hocko <mhocko@suse.com>
> > >
> > > Acked-by: David Rientjes <rientjes@google.com>
> > >
> > > vm.oom_dump_tasks is pretty useful, however, so it's curious why you
> > > haven't left it enabled :/
> > >
> > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > > > index eda2e2a0bdc6..c781f73b6cd6 100644
> > > > --- a/mm/oom_kill.c
> > > > +++ b/mm/oom_kill.c
> > > > @@ -884,12 +884,13 @@ static void __oom_kill_process(struct task_struct *victim, const char *message)
> > > >        */
> > > >       do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID);
> > > >       mark_oom_victim(victim);
> > > > -     pr_err("%s: Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
> > > > +     pr_err("%s: Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB oom_score_adj:%ld\n",
> > > >               message, task_pid_nr(victim), victim->comm,
> > > >               K(victim->mm->total_vm),
> > > >               K(get_mm_counter(victim->mm, MM_ANONPAGES)),
> > > >               K(get_mm_counter(victim->mm, MM_FILEPAGES)),
> > > > -             K(get_mm_counter(victim->mm, MM_SHMEMPAGES)));
> > > > +             K(get_mm_counter(victim->mm, MM_SHMEMPAGES)),
> > > > +             (long)victim->signal->oom_score_adj);
> > > >       task_unlock(victim);
> > > >
> > > >       /*
> > >
> > > Nit: why not just use %hd and avoid the cast to long?
> >
> > Sorry I may have accidently top posted my response to this. Here is
> > where my response should go:
> > -----------------------------------------------------------------------------------------------------------------------------------
> >
> > Good point, I can post this with your correction.
> >
> > I will add your Acked-by: David Rientjes <rientjes@google.com>
> >
> > I am adding your Acked-by to the revised patch as this is what Michal
> > asked me to do (so I assume that is what I should do).
> >
> > Should I post as a separate fix again or simply post here?
>
> Andrew usually folds these small fixups automagically. If that doesn't
> happen here for some reason then just repost with acks and the fixup.
>

OK I will resubmit, wasn't sure if I should use --subject-prefix
"PATCH v2" or -v 2
or just resubmit but sounds like it should work either way.

> Thanks!
>
> --
> Michal Hocko
> SUSE Labs