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 B7BDCC43441 for ; Thu, 15 Nov 2018 09:42:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 78941223CB for ; Thu, 15 Nov 2018 09:42:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 78941223CB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.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 S2387970AbeKOTty (ORCPT ); Thu, 15 Nov 2018 14:49:54 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46656 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387911AbeKOTtx (ORCPT ); Thu, 15 Nov 2018 14:49:53 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2D71186673; Thu, 15 Nov 2018 09:42:49 +0000 (UTC) Received: from [10.36.117.224] (ovpn-117-224.ams2.redhat.com [10.36.117.224]) by smtp.corp.redhat.com (Postfix) with ESMTP id B5E3A5D759; Thu, 15 Nov 2018 09:42:47 +0000 (UTC) Subject: Re: Memory hotplug softlock issue To: Michal Hocko , Baoquan He Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, aarcange@redhat.com References: <20181114070909.GB2653@MiWiFi-R3L-srv> <5a6c6d6b-ebcd-8bfa-d6e0-4312bfe86586@redhat.com> <20181114090134.GG23419@dhcp22.suse.cz> <20181114145250.GE2653@MiWiFi-R3L-srv> <20181114150029.GY23419@dhcp22.suse.cz> <20181115051034.GK2653@MiWiFi-R3L-srv> <20181115073052.GA23831@dhcp22.suse.cz> <20181115075349.GL2653@MiWiFi-R3L-srv> <20181115083055.GD23831@dhcp22.suse.cz> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: <20181115083055.GD23831@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Thu, 15 Nov 2018 09:42:49 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15.11.18 09:30, Michal Hocko wrote: > On Thu 15-11-18 15:53:56, Baoquan He wrote: >> On 11/15/18 at 08:30am, Michal Hocko wrote: >>> On Thu 15-11-18 13:10:34, Baoquan He wrote: >>>> On 11/14/18 at 04:00pm, Michal Hocko wrote: >>>>> On Wed 14-11-18 22:52:50, Baoquan He wrote: >>>>>> On 11/14/18 at 10:01am, Michal Hocko wrote: >>>>>>> I have seen an issue when the migration cannot make a forward progress >>>>>>> because of a glibc page with a reference count bumping up and down. Most >>>>>>> probable explanation is the faultaround code. I am working on this and >>>>>>> will post a patch soon. In any case the migration should converge and if >>>>>>> it doesn't do then there is a bug lurking somewhere. >>>>>>> >>>>>>> Failing on ENOMEM is a questionable thing. I haven't seen that happening >>>>>>> wildly but if it is a case then I wouldn't be opposed. >>>>>> >>>>>> Applied your debugging patches, it helps a lot to printing message. >>>>>> >>>>>> Below is the dmesg log about the migrating failure. It can't pass >>>>>> migrate_pages() and loop forever. >>>>>> >>>>>> [ +0.083841] migrating pfn 10fff7d0 failed >>>>>> [ +0.000005] page:ffffea043ffdf400 count:208 mapcount:201 mapping:ffff888dff4bdda8 index:0x2 >>>>>> [ +0.012689] xfs_address_space_operations [xfs] >>>>>> [ +0.000030] name:"stress" >>>>>> [ +0.004556] flags: 0x5fffffc0000004(uptodate) >>>>>> [ +0.007339] raw: 005fffffc0000004 ffffc900000e3d80 ffffc900000e3d80 ffff888dff4bdda8 >>>>>> [ +0.009488] raw: 0000000000000002 0000000000000000 000000cb000000c8 ffff888e7353d000 >>>>>> [ +0.007726] page->mem_cgroup:ffff888e7353d000 >>>>>> [ +0.084538] migrating pfn 10fff7d0 failed >>>>>> [ +0.000006] page:ffffea043ffdf400 count:210 mapcount:201 mapping:ffff888dff4bdda8 index:0x2 >>>>>> [ +0.012798] xfs_address_space_operations [xfs] >>>>>> [ +0.000034] name:"stress" >>>>>> [ +0.004524] flags: 0x5fffffc0000004(uptodate) >>>>>> [ +0.007068] raw: 005fffffc0000004 ffffc900000e3d80 ffffc900000e3d80 ffff888dff4bdda8 >>>>>> [ +0.009359] raw: 0000000000000002 0000000000000000 000000cb000000c8 ffff888e7353d000 >>>>>> [ +0.007728] page->mem_cgroup:ffff888e7353d000 >>>>> >>>>> I wouldn't be surprised if this was a similar/same issue I've been >>>>> chasing recently. Could you try to disable faultaround to see if that >>>>> helps. It seems that it helped in my particular case but I am still >>>>> waiting for the final good-to-go to post the patch as I do not own the >>>>> workload which triggered that issue. >>>> >>>> Tried, still stuck in last block sometime. Usually after several times >>>> of hotplug/unplug. If stop stress program, the last block will be >>>> offlined immediately. >>> >>> Is the pattern still the same? I mean failing over few pages with >>> reference count jumping up and down between attempts? >> >> ->count jumping up and down, mapcount stays the same value. >> >>> >>>> [root@ ~]# cat /sys/kernel/debug/fault_around_bytes >>>> 4096 >>> >>> Can you make it 0? >> >> I executed 'echo 0 > fault_around_bytes', value less than one page size >> will round up to one page. > > OK, I have missed that. So then there must be a different source of the > page count volatility. Is it always the same file? > > I think we can rule out memory reclaim because that depends on the page > lock. Is the stress test hitting on memory compaction? In other words, > are > grep compact /proc/vmstat > counters changing during the offline test heavily? I am asking because I > do not see compaction pfn walkers skipping over MIGRATE_ISOLATE > pageblocks. But I might be missing something easily. > > It would be also good to find out whether this is fs specific. E.g. does > it make any difference if you use a different one for your stress > testing? > I am wondering why it is always the last memory block of that device (and even that node). Coincidence? -- Thanks, David / dhildenb