From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi1-f197.google.com (mail-oi1-f197.google.com [209.85.167.197]) by kanga.kvack.org (Postfix) with ESMTP id 4D4746B095F for ; Fri, 16 Nov 2018 06:55:41 -0500 (EST) Received: by mail-oi1-f197.google.com with SMTP id n10-v6so13224161oib.5 for ; Fri, 16 Nov 2018 03:55:41 -0800 (PST) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id x7si11989310otk.273.2018.11.16.03.55.40 for ; Fri, 16 Nov 2018 03:55:40 -0800 (PST) From: Anshuman Khandual Subject: Re: [PATCH 0/5] mm, memory_hotplug: improve memory offlining failures debugging 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 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: owner-linux-mm@kvack.org List-ID: To: Michal Hocko , Andrew Morton Cc: Oscar Salvador , Baoquan He , linux-mm@kvack.org, LKML 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.