Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936249AbdIYPzp (ORCPT ); Mon, 25 Sep 2017 11:55:45 -0400 Received: from out0-218.mail.aliyun.com ([140.205.0.218]:37503 "EHLO out0-218.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934482AbdIYPzo (ORCPT ); Mon, 25 Sep 2017 11:55:44 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R131e4;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e02c03308;MF=yang.s@alibaba-inc.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---.9-0cdGK_1506354921; Subject: Re: [PATCH 0/2 v4] oom: capture unreclaimable slab info in oom message 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: <1505947132-4363-1-git-send-email-yang.s@alibaba-inc.com> <20170925142352.havlx6ikheanqyhj@dhcp22.suse.cz> From: "Yang Shi" Message-ID: Date: Mon, 25 Sep 2017 23:55:19 +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: <20170925142352.havlx6ikheanqyhj@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 Content-Length: 1337 Lines: 30 On 9/25/17 7:23 AM, Michal Hocko wrote: > On Thu 21-09-17 06:38:50, Yang Shi wrote: >> Recently we ran into a oom issue, kernel panic due to no killable process. >> The dmesg shows huge unreclaimable slabs used almost 100% memory, but kdump doesn't capture vmcore due to some reason. >> >> So, it may sound better to capture unreclaimable slab info in oom message when kernel panic to aid trouble shooting and cover the corner case. >> Since kernel already panic, so capturing more information sounds worthy and doesn't bother normal oom killer. >> >> With the patchset, tools/vm/slabinfo has a new option, "-U", to show unreclaimable slab only. >> >> And, oom will print all non zero (num_objs * size != 0) unreclaimable slabs in oom killer message. > > Well, I do undestand that this _might_ be useful but it also might > generates a _lot_ of output. The oom report can be quite verbose already > so is this something we want to have enabled by default? The uneclaimable slub message will be just printed out when kernel panic (no killable process or panic_on_oom is set). So, it will not bother normal oom. Since kernel is already panic, so it might be preferred to have more information reported. We definitely can add a proc knob to control it if we want to disable the message even if when kernel panic. Thanks, Yang >