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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 3F77CC83001 for ; Thu, 30 Apr 2020 07:21:25 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B644620838 for ; Thu, 30 Apr 2020 07:21:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B644620838 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.vnet.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 49CRdG086jzDrLK for ; Thu, 30 Apr 2020 17:21:22 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=linux.vnet.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=srikar@linux.vnet.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.vnet.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 49CRZ73551zDrCm for ; Thu, 30 Apr 2020 17:18:39 +1000 (AEST) Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 03U721bb087920; Thu, 30 Apr 2020 03:18:28 -0400 Received: from ppma03fra.de.ibm.com (6b.4a.5195.ip4.static.sl-reverse.com [149.81.74.107]) by mx0a-001b2d01.pphosted.com with ESMTP id 30me474bvn-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 30 Apr 2020 03:18:28 -0400 Received: from pps.filterd (ppma03fra.de.ibm.com [127.0.0.1]) by ppma03fra.de.ibm.com (8.16.0.27/8.16.0.27) with SMTP id 03U7AIWg001869; Thu, 30 Apr 2020 07:18:26 GMT Received: from b06cxnps4076.portsmouth.uk.ibm.com (d06relay13.portsmouth.uk.ibm.com [9.149.109.198]) by ppma03fra.de.ibm.com with ESMTP id 30mcu5af33-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 30 Apr 2020 07:18:25 +0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 03U7IN5349086470 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 30 Apr 2020 07:18:23 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9F9CB52051; Thu, 30 Apr 2020 07:18:23 +0000 (GMT) Received: from linux.vnet.ibm.com (unknown [9.126.150.29]) by d06av21.portsmouth.uk.ibm.com (Postfix) with SMTP id 8974252050; Thu, 30 Apr 2020 07:18:21 +0000 (GMT) Date: Thu, 30 Apr 2020 12:48:20 +0530 From: Srikar Dronamraju To: Michal Hocko Subject: Re: [PATCH v2 3/3] mm/page_alloc: Keep memoryless cpuless node 0 offline Message-ID: <20200430071820.GF19958@linux.vnet.ibm.com> References: <20200428093836.27190-1-srikar@linux.vnet.ibm.com> <20200428093836.27190-4-srikar@linux.vnet.ibm.com> <20200428165912.ca1eadefbac56d740e6e8fd1@linux-foundation.org> <20200429014145.GD19958@linux.vnet.ibm.com> <20200429122211.GD28637@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20200429122211.GD28637@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.676 definitions=2020-04-30_01:2020-04-30, 2020-04-30 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 bulkscore=0 lowpriorityscore=0 priorityscore=1501 mlxscore=0 impostorscore=0 spamscore=0 malwarescore=0 mlxlogscore=999 clxscore=1011 phishscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004300052 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Srikar Dronamraju Cc: Linus Torvalds , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Mel Gorman , "Kirill A. Shutemov" , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Christopher Lameter , Vlastimil Babka Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" * Michal Hocko [2020-04-29 14:22:11]: > On Wed 29-04-20 07:11:45, Srikar Dronamraju wrote: > > > > > > > > By marking, N_ONLINE as NODE_MASK_NONE, lets stop assuming that Node 0 is > > > > always online. > > > > > > > > ... > > > > > > > > --- a/mm/page_alloc.c > > > > +++ b/mm/page_alloc.c > > > > @@ -116,8 +116,10 @@ EXPORT_SYMBOL(latent_entropy); > > > > */ > > > > nodemask_t node_states[NR_NODE_STATES] __read_mostly = { > > > > [N_POSSIBLE] = NODE_MASK_ALL, > > > > +#ifdef CONFIG_NUMA > > > > + [N_ONLINE] = NODE_MASK_NONE, > > > > +#else > > > > [N_ONLINE] = { { [0] = 1UL } }, > > > > -#ifndef CONFIG_NUMA > > > > [N_NORMAL_MEMORY] = { { [0] = 1UL } }, > > > > #ifdef CONFIG_HIGHMEM > > > > [N_HIGH_MEMORY] = { { [0] = 1UL } }, > > > > > > So on all other NUMA machines, when does node 0 get marked online? > > > > > > This change means that for some time during boot, such machines will > > > now be running with node 0 marked as offline. What are the > > > implications of this? Will something break? > > > > Till the nodes are detected, marking Node 0 as online tends to be redundant. > > Because the system doesn't know if its a NUMA or a non-NUMA system. > > Once we detect the nodes, we online them immediately. Hence I don't see any > > side-effects or negative implications of this change. > > > > However if I am missing anything, please do let me know. > > > > >From my part, I have tested this on > > 1. Non-NUMA Single node but CPUs and memory coming from zero node. > > 2. Non-NUMA Single node but CPUs and memory coming from non-zero node. > > 3. NUMA Multi node but with CPUs and memory from node 0. > > 4. NUMA Multi node but with no CPUs and memory from node 0. > > Have you tested on something else than ppc? Each arch does the NUMA > setup separately and this is a big mess. E.g. x86 marks even memory less > nodes (see init_memory_less_node) as online. > while I have predominantly tested on ppc, I did test on X86 with CONFIG_NUMA enabled/disabled on both single node and multi node machines. However, I dont have a cpuless/memoryless x86 system. > Honestly I have hard time to evaluate the effect of this patch. It makes > some sense to assume all nodes offline before they get online but this > is a land mine territory. > > I am also not sure what kind of problem this is going to address. You > have mentioned numa balancing without many details. 1. On a machine with just one node with node number not being 0, the current setup will end up showing 2 online nodes. And when there are more than one online nodes, numa_balancing gets enabled. Without patch $ grep numa /proc/vmstat numa_hit 95179 numa_miss 0 numa_foreign 0 numa_interleave 3764 numa_local 95179 numa_other 0 numa_pte_updates 1206973 <---------- numa_huge_pte_updates 4654 <---------- numa_hint_faults 19560 <---------- numa_hint_faults_local 19560 <---------- numa_pages_migrated 0 With patch $ grep numa /proc/vmstat numa_hit 322338756 numa_miss 0 numa_foreign 0 numa_interleave 3790 numa_local 322338756 numa_other 0 numa_pte_updates 0 <---------- numa_huge_pte_updates 0 <---------- numa_hint_faults 0 <---------- numa_hint_faults_local 0 <---------- numa_pages_migrated 0 So we have a redundant page hinting numa faults which we can avoid. 2. Few people have complained about existence of this dummy node when parsing lscpu and numactl o/p. They somehow start to think that the tools are reporting incorrectly or the kernel is not able to recognize resources connected to the node. -- Thanks and Regards Srikar Dronamraju