From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi1-f200.google.com (mail-oi1-f200.google.com [209.85.167.200]) by kanga.kvack.org (Postfix) with ESMTP id 8A2746B0590 for ; Thu, 8 Nov 2018 02:16:54 -0500 (EST) Received: by mail-oi1-f200.google.com with SMTP id b11-v6so12643960oii.19 for ; Wed, 07 Nov 2018 23:16:54 -0800 (PST) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id j188-v6si1326941oib.106.2018.11.07.23.16.52 for ; Wed, 07 Nov 2018 23:16:53 -0800 (PST) Subject: Re: [RFC PATCH 5/5] mm, memory_hotplug: be more verbose for memory offline failures 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 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: owner-linux-mm@kvack.org List-ID: To: Michal Hocko , linux-mm@kvack.org Cc: Andrew Morton , Oscar Salvador , Baoquan He , LKML , Michal Hocko 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.