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

From	"Yang Shi" <yang.s@alibaba-inc.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel panic
Date	2017-10-02 22:50 +0200
Message-ID	<uwfPb-ur-161@gated-at.bofh.it> (permalink)
References	<uu8RH-3yU-3@gated-at.bofh.it> <uu8RI-3yU-17@gated-at.bofh.it> <uui4G-1h8-25@gated-at.bofh.it> <uuojM-63X-29@gated-at.bofh.it> <uw3kS-4qv-13@gated-at.bofh.it>
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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

>

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[PATCH 0/3 v7] oom: capture unreclaimable slab info in oom message when kernel panic "Yang Shi" <yang.s@alibaba-inc.com> - 2017-09-27 03:00 +0200
  [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel panic "Yang Shi" <yang.s@alibaba-inc.com> - 2017-09-27 03:00 +0200
    Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel  panic Christopher Lameter <cl@linux.com> - 2017-09-27 09:20 +0200
      Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel  panic "Yang Shi" <yang.s@alibaba-inc.com> - 2017-09-27 19:30 +0200
        Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel  panic Christopher Lameter <cl@linux.com> - 2017-09-28 00:00 +0200
          Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel  panic "Yang Shi" <yang.s@alibaba-inc.com> - 2017-09-28 00:20 +0200
            Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel  panic Christopher Lameter <cl@linux.com> - 2017-10-01 08:50 +0200
              Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel  panic "Yang Shi" <yang.s@alibaba-inc.com> - 2017-10-02 22:50 +0200
    Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel  panic Michal Hocko <mhocko@kernel.org> - 2017-09-27 12:50 +0200
      Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel  panic "Yang Shi" <yang.s@alibaba-inc.com> - 2017-09-27 19:30 +0200
        Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel  panic Michal Hocko <mhocko@kernel.org> - 2017-10-02 09:30 +0200
          Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel  panic "Yang Shi" <yang.s@alibaba-inc.com> - 2017-10-02 22:50 +0200

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