On 2018/08/22 1:04, Johannes Weiner wrote:
> When the memcg OOM killer runs out of killable tasks, it currently
> prints a WARN with no further OOM context. This has caused some user
> confusion.
>
> Warnings indicate a kernel problem. In a reported case, however, the
> situation was triggered by a non-sensical memcg configuration (hard
> limit set to 0). But without any VM context this wasn't obvious from
> the report, and it took some back and forth on the mailing list to
> identify what is actually a trivial issue.
>
> Handle this OOM condition like we handle it in the global OOM killer:
> dump the full OOM context and tell the user we ran out of tasks.
>
> This way the user can identify misconfigurations easily by themselves
> and rectify the problem - without having to go through the hassle of
> running into an obscure but unsettling warning, finding the
> appropriate kernel mailing list and waiting for a kernel developer to
> remote-analyze that the memcg configuration caused this.
>
> If users cannot make sense of why the OOM killer was triggered or why
> it failed, they will still report it to the mailing list, we know that
> from experience. So in case there is an actual kernel bug causing
> this, kernel developers will very likely hear about it.
>
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> mm/memcontrol.c | 2 --
> mm/oom_kill.c | 13 ++++++++++---
> 2 files changed, 10 insertions(+), 5 deletions(-)
>
Now that above patch went to 4.19-rc3, please apply below one.
>From eb2bff2ed308da04785bcf541dd3f748286bfa23 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Date: Sat, 8 Sep 2018 22:26:28 +0900
Subject: [PATCH] mm, oom: Don't emit noises for failed SysRq-f.
Due to commit d75da004c708c9fc ("oom: improve oom disable handling") and
commit 3100dab2aa09dc6e ("mm: memcontrol: print proper OOM header when
no eligible victim left"), all
kworker/0:1 invoked oom-killer: gfp_mask=0x6000c0(GFP_KERNEL), nodemask=(null), order=-1, oom_score_adj=0
(...snipped...)
Out of memory and no killable processes...
OOM request ignored. No task eligible
lines are printed.
Let's not emit "invoked oom-killer" lines when SysRq-f failed.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
mm/oom_kill.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index f10aa53..92122ef 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -1106,8 +1106,10 @@ bool out_of_memory(struct oom_control *oc)
select_bad_process(oc);
/* Found nothing?!?! */
if (!oc->chosen) {
- dump_header(oc, NULL);
- pr_warn("Out of memory and no killable processes...\n");
+ if (!is_sysrq_oom(oc)) {
+ dump_header(oc, NULL);
+ pr_warn("Out of memory and no killable processes...\n");
+ }
/*
* If we got here due to an actual allocation at the
* system level, we cannot survive this and will enter
--
1.8.3.1
