Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel panic

[Yang Shi]

On 10/2/17 12:26 AM, Michal Hocko wrote:
> On Thu 28-09-17 01:25:50, Yang Shi wrote:
> > On 9/27/17 3:45 AM, Michal Hocko wrote:
> > > On Wed 27-09-17 08:53:35, Yang Shi wrote:
> > > > Kernel may panic when oom happens without killable process sometimes it
> > > > is caused by huge unreclaimable slabs used by kernel.
> > > >
> > > > Although kdump could help debug such problem, however, kdump is not
> > > > available on all architectures and it might be malfunction sometime.
> > > > And, since kernel already panic it is worthy capturing such information
> > > > in dmesg to aid touble shooting.
> > > >
> > > > Print out unreclaimable slab info (used size and total size) which
> > > > actual memory usage is not zero (num_objs * size != 0) when:
> > > >     - unreclaimable slabs : all user memory > unreclaim_slabs_oom_ratio
> > > >     - panic_on_oom is set or no killable process
> > >
> > > OK, this is better but I do not see why this should be tunable via proc.
> >
> > Just thought someone might want to dump unreclaimable slab info
> > unconditionally.
>
> If that ever happens then we will eventually add it. But do not add proc
> knobs for theoretical usecases. We will have to maintain them and it
> can turn into a maint. pain. Like some others in the past.

It has been removed since v8. Currently the only condition is 
unreclaimable slabs > user memory.

Thanks,
Yang

>