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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 35B93C32789 for ; Thu, 8 Nov 2018 07:16:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EC7812081C for ; Thu, 8 Nov 2018 07:16:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EC7812081C 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 S1726642AbeKHQu7 (ORCPT ); Thu, 8 Nov 2018 11:50:59 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:35502 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725724AbeKHQu7 (ORCPT ); Thu, 8 Nov 2018 11:50:59 -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 57416A78; Wed, 7 Nov 2018 23:16:52 -0800 (PST) Received: from [10.162.0.72] (p8cg001049571a15.blr.arm.com [10.162.0.72]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 499363F5BD; Wed, 7 Nov 2018 23:16:50 -0800 (PST) Subject: Re: [RFC PATCH 5/5] mm, memory_hotplug: be more verbose for memory offline failures To: Michal Hocko , linux-mm@kvack.org Cc: Andrew Morton , Oscar Salvador , Baoquan He , LKML , Michal Hocko References: <20181107101830.17405-1-mhocko@kernel.org> <20181107101830.17405-6-mhocko@kernel.org> From: Anshuman Khandual Message-ID: Date: Thu, 8 Nov 2018 12:46:47 +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: <20181107101830.17405-6-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 11/07/2018 03:48 PM, Michal Hocko wrote: > From: Michal Hocko > > There is only very limited information printed when the memory offlining > fails: > [ 1984.506184] rac1 kernel: memory offlining [mem 0x82600000000-0x8267fffffff] failed due to signal backoff > > This tells us that the failure is triggered by the userspace > intervention but it doesn't tell us much more about the underlying > reason. It might be that the page migration failes repeatedly and the > userspace timeout expires and send a signal or it might be some of the > earlier steps (isolation, memory notifier) takes too long. > > If the migration failes then it would be really helpful to see which > page that and its state. The same applies to the isolation phase. If we > fail to isolate a page from the allocator then knowing the state of the > page would be helpful as well. > > Dump the page state that fails to get isolated or migrated. This will > tell us more about the failure and what to focus on during debugging. > > Signed-off-by: Michal Hocko > --- > mm/memory_hotplug.c | 12 ++++++++---- > mm/page_alloc.c | 1 + > 2 files changed, 9 insertions(+), 4 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 1badac89c58e..bf214beccda3 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1388,10 +1388,8 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > page_is_file_cache(page)); > > } else { > -#ifdef CONFIG_DEBUG_VM > - pr_alert("failed to isolate pfn %lx\n", pfn); > + pr_warn("failed to isolate pfn %lx\n", pfn)> dump_page(page, "isolation failed"); > -#endif > put_page(page); > /* Because we don't have big zone->lock. we should > check this again here. */ > @@ -1411,8 +1409,14 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > /* Allocate a new page from the nearest neighbor node */ > ret = migrate_pages(&source, new_node_page, NULL, 0, > MIGRATE_SYNC, MR_MEMORY_HOTPLUG); > - if (ret) > + if (ret) { > + list_for_each_entry(page, &source, lru) { > + pr_warn("migrating pfn %lx failed ", > + page_to_pfn(page), ret); Seems like pr_warn() needs to have %d in here to print 'ret'. Though dumping return code from migrate_pages() makes sense, wondering if it is required for each and every page which failed to migrate here or just one instance is enough. > + dump_page(page, NULL); > + } s/NULL/failed to migrate/ for dump_page(). > putback_movable_pages(&source); > + } > } > out: > return ret; > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index a919ba5cb3c8..23267767bf98 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7845,6 +7845,7 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, > return false; > unmovable: > WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE); > + dump_page(pfn_to_page(pfn+iter), "has_unmovable_pages"); s/has_unmovable_pages/is unmovable/ If we eally care about the function name, then dump_page() should be followed by dump_stack() like the case in some other instances. > return true; This will be dumped from HugeTLB and CMA allocation paths as well through alloc_contig_range(). But it should be okay as those occurrences should be rare and dumping page state then will also help.