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

[Yang Shi]

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.

> Can we start with simple NR_SLAB_UNRECLAIMABLE > LRU_PAGES and place it
> into dump_header so that we get the report also during regular OOM
Yes.

Thanks,
Yang

>