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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 996EFC43441 for ; Thu, 15 Nov 2018 07:54:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 642522089D for ; Thu, 15 Nov 2018 07:54:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 642522089D 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 S1728912AbeKOSAp (ORCPT ); Thu, 15 Nov 2018 13:00:45 -0500 Received: from mx1.redhat.com ([209.132.183.28]:57130 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728204AbeKOSAp (ORCPT ); Thu, 15 Nov 2018 13:00:45 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7B31A58E41; Thu, 15 Nov 2018 07:54:01 +0000 (UTC) Received: from localhost (ovpn-8-20.pek2.redhat.com [10.72.8.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D6D835D9CA; Thu, 15 Nov 2018 07:53:58 +0000 (UTC) Date: Thu, 15 Nov 2018 15:53:56 +0800 From: Baoquan He To: Michal Hocko Cc: David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, aarcange@redhat.com Subject: Re: Memory hotplug softlock issue Message-ID: <20181115075349.GL2653@MiWiFi-R3L-srv> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181115073052.GA23831@dhcp22.suse.cz> User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Thu, 15 Nov 2018 07:54:01 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. /* * fault_around_bytes must be rounded down to the nearest page order as it's * what do_fault_around() expects to see. */ static int fault_around_bytes_set(void *data, u64 val) { if (val / PAGE_SIZE > PTRS_PER_PTE) return -EINVAL; if (val > PAGE_SIZE) fault_around_bytes = rounddown_pow_of_two(val); else fault_around_bytes = PAGE_SIZE; /* rounddown_pow_of_two(0) is undefined */ return 0; }