From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751892AbdJBPpZ (ORCPT ); Mon, 2 Oct 2017 11:45:25 -0400 Received: from out0-229.mail.aliyun.com ([140.205.0.229]:35709 "EHLO out0-229.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751193AbdJBPpY (ORCPT ); Mon, 2 Oct 2017 11:45:24 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R171e4;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01l10421;MF=yang.s@alibaba-inc.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---.91ZNTM0_1506959105; Subject: Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel panic To: Michal Hocko Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1506473616-88120-1-git-send-email-yang.s@alibaba-inc.com> <1506473616-88120-3-git-send-email-yang.s@alibaba-inc.com> <20170927104537.r42javxhnyqlxnqm@dhcp22.suse.cz> <20171002072607.sjikpsoaiyebmukd@dhcp22.suse.cz> From: "Yang Shi" Message-ID: Date: Mon, 02 Oct 2017 23:44:55 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20171002072607.sjikpsoaiyebmukd@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >