From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0B0A4C43441 for ; Fri, 16 Nov 2018 11:55:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CA79A20866 for ; Fri, 16 Nov 2018 11:55:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CA79A20866 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389558AbeKPWHm (ORCPT ); Fri, 16 Nov 2018 17:07:42 -0500 Received: from foss.arm.com ([217.140.101.70]:50256 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727963AbeKPWHm (ORCPT ); Fri, 16 Nov 2018 17:07:42 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 709E380D; Fri, 16 Nov 2018 03:55:39 -0800 (PST) Received: from [10.163.1.125] (unknown [10.163.1.125]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A24DA3F718; Fri, 16 Nov 2018 03:55:37 -0800 (PST) From: Anshuman Khandual Subject: Re: [PATCH 0/5] mm, memory_hotplug: improve memory offlining failures debugging To: Michal Hocko , Andrew Morton Cc: Oscar Salvador , Baoquan He , linux-mm@kvack.org, LKML References: <20181116083020.20260-1-mhocko@kernel.org> Message-ID: <8a91e93d-386d-f0bc-d639-a696bb37a34e@arm.com> Date: Fri, 16 Nov 2018 17:25:35 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181116083020.20260-1-mhocko@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/16/2018 02:00 PM, Michal Hocko wrote: > Hi, > this has been posted as an RFC [1]. I have screwed during rebasing so > there were few compilation issues in the previous version. I have also > integrated review feedback from Andrew and Anshuman. > > I have been promissing to improve memory offlining failures debugging > for quite some time. As things stand now we get only very limited > information in the kernel log when the offlining fails. It is usually > only > [ 1984.506184] rac1 kernel: memory offlining [mem 0x82600000000-0x8267fffffff] failed > without no further details. We do not know what exactly fails and for > what reason. Whenever I was forced to debug such a failure I've always > had to do a debugging patch to tell me more. We can enable some > tracepoints but it would be much better to get a better picture without > using them. > > This patch series does 2 things. The first one is to make dump_page > more usable by printing more information about the mapping patch 1. > Then it reduces the log level from emerg to warning so that this > function is usable from less critical context patch 2. Then I have > added more detailed information about the offlining failure patch 4 > and finally add dump_page to isolation and offlining migration paths. > Patch 3 is a trivial cleanup. > > Does this look go to you? > > [1] http://lkml.kernel.org/r/20181107101830.17405-1-mhocko@kernel.org > Agreed. It has been always difficult to debug memory hot plug problems without a debug patch particularly to understand the unmovable pages and their isolation failures in the range to be removed. This series is definitely going to help improve the situation.