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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ae112574-93c4-22a4-1309-58e585f31493@alibaba-inc.com>
Date:   Thu, 28 Sep 2017 01:25:50 +0800
From:   "Yang Shi" <yang.s@...baba-inc.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel
 panic



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

>