From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 808C66B0069 for ; Mon, 2 Oct 2017 11:45:27 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id p87so12840419pfj.4 for ; Mon, 02 Oct 2017 08:45:27 -0700 (PDT) Received: from out4433.biz.mail.alibaba.com (out4433.biz.mail.alibaba.com. [47.88.44.33]) by mx.google.com with ESMTPS id v63si6068361pfi.171.2017.10.02.08.45.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 02 Oct 2017 08:45:26 -0700 (PDT) Subject: Re: [PATCH 2/3] mm: oom: show unreclaimable slab info when kernel panic 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 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: owner-linux-mm@kvack.org List-ID: 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 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 > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org