On Fri, Jun 14, 2019 at 2:56 AM Michal Hocko <mhocko@xxxxxxxx> wrote:
>
> On Thu 13-06-19 21:55:50, Yafang Shao wrote:
> > In dump_oom_summary() oc->constraint is used to show
> > oom_constraint_text, but it hasn't been set before.
> > So the value of it is always the default value 0.
> > We should set it in constrained_alloc().
>
> Thanks for catching that.
>
> > Bellow is the output when memcg oom occurs,
> >
> > before this patch:
> > [ 133.078102] oom-kill:constraint=CONSTRAINT_NONE,nodemask=(null),
> > cpuset=/,mems_allowed=0,oom_memcg=/foo,task_memcg=/foo,task=bash,pid=7997,uid=0
> >
> > after this patch:
> > [ 952.977946] oom-kill:constraint=CONSTRAINT_MEMCG,nodemask=(null),
> > cpuset=/,mems_allowed=0,oom_memcg=/foo,task_memcg=/foo,task=bash,pid=13681,uid=0
> >
>
> unless I am missing something
> Fixes: ef8444ea01d7 ("mm, oom: reorganize the oom report in dump_header")
>
> The patch looks correct but I think it is more complicated than it needs
> to be. Can we do the following instead?
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 5a58778c91d4..f719b64741d6 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -987,8 +987,7 @@ static void oom_kill_process(struct oom_control *oc, const char *message)
> /*
> * Determines whether the kernel must panic because of the panic_on_oom sysctl.
> */
> -static void check_panic_on_oom(struct oom_control *oc,
> - enum oom_constraint constraint)
> +static void check_panic_on_oom(struct oom_control *oc)
> {
> if (likely(!sysctl_panic_on_oom))
> return;
> @@ -998,7 +997,7 @@ static void check_panic_on_oom(struct oom_control *oc,
> * does not panic for cpuset, mempolicy, or memcg allocation
> * failures.
> */
> - if (constraint != CONSTRAINT_NONE)
> + if (oc->constraint != CONSTRAINT_NONE)
> return;
> }
> /* Do not panic for oom kills triggered by sysrq */
> @@ -1035,7 +1034,6 @@ EXPORT_SYMBOL_GPL(unregister_oom_notifier);
> bool out_of_memory(struct oom_control *oc)
> {
> unsigned long freed = 0;
> - enum oom_constraint constraint = CONSTRAINT_NONE;
>
> if (oom_killer_disabled)
> return false;
> @@ -1071,10 +1069,10 @@ bool out_of_memory(struct oom_control *oc)
> * Check if there were limitations on the allocation (only relevant for
> * NUMA and memcg) that may require different handling.
> */
> - constraint = constrained_alloc(oc);
> - if (constraint != CONSTRAINT_MEMORY_POLICY)
> + oc->constraint = constrained_alloc(oc);
> + if (oc->constraint != CONSTRAINT_MEMORY_POLICY)
> oc->nodemask = NULL;
> - check_panic_on_oom(oc, constraint);
> + check_panic_on_oom(oc);
>
> if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
> current->mm && !oom_unkillable_task(current, NULL, oc->nodemask) &&
>
> I guess the current confusion comes from the fact that we have
> constraint both in the oom_control and a local variable so I would
> rather remove that. What do you think?
Remove the local variable is fine by me.
Thanks
Yafang
