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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 18 Mar 2020 07:50:12 -0000 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 02I7oBqa16973968 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 18 Mar 2020 07:50:11 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E13B342064; Wed, 18 Mar 2020 07:50:10 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DD8D042047; Wed, 18 Mar 2020 07:50:08 +0000 (GMT) Received: from linux.vnet.ibm.com (unknown [9.126.150.29]) by d06av24.portsmouth.uk.ibm.com (Postfix) with SMTP; Wed, 18 Mar 2020 07:50:08 +0000 (GMT) Date: Wed, 18 Mar 2020 13:20:08 +0530 From: Srikar Dronamraju To: Michal Hocko Cc: Christopher Lameter , Andrew Morton , Michael Ellerman , linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mel Gorman , Vlastimil Babka , "Kirill A. Shutemov" , Linus Torvalds Subject: Re: [PATCH 3/3] mm/page_alloc: Keep memoryless cpuless node 0 offline Reply-To: Srikar Dronamraju References: <20200311110237.5731-1-srikar@linux.vnet.ibm.com> <20200311110237.5731-4-srikar@linux.vnet.ibm.com> <20200316085425.GB11482@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20200316085425.GB11482@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) X-TM-AS-GCONF: 00 x-cbid: 20031807-0008-0000-0000-0000035F30D3 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20031807-0009-0000-0000-00004A808A63 Message-Id: <20200318075008.GE4879@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.645 definitions=2020-03-18_02:2020-03-17,2020-03-18 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 lowpriorityscore=0 suspectscore=0 priorityscore=1501 impostorscore=0 clxscore=1015 spamscore=0 bulkscore=0 phishscore=0 mlxlogscore=999 mlxscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003180037 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: * Michal Hocko [2020-03-16 09:54:25]: > On Sun 15-03-20 14:20:05, Cristopher Lameter wrote: > > On Wed, 11 Mar 2020, Srikar Dronamraju wrote: > > > > > Currently Linux kernel with CONFIG_NUMA on a system with multiple > > > possible nodes, marks node 0 as online at boot. However in practice, > > > there are systems which have node 0 as memoryless and cpuless. > > > > Would it not be better and simpler to require that node 0 always has > > memory (and processors)? A mininum operational set? > > I do not think you can simply ignore the reality. I cannot say that I am > a fan of memoryless/cpuless numa configurations but they are a sad > reality of different LPAR configurations. We have to deal with them. > Besides that I do not really see any strong technical arguments to lack > a support for those crippled configurations. We do have zonelists that > allow to do reasonable decisions on memoryless nodes. So no, I do not > think that this is a viable approach. > I agree with Michal, kernel should accept the reality and work with different Lpar configurations. > > We can dynamically number the nodes right? So just make sure that the > > firmware properly creates memory on node 0? > > Are you suggesting that the OS would renumber NUMA nodes coming > from FW just to satisfy node 0 existence? If yes then I believe this is > really a bad idea because it would make HW/LPAR configuration matching > to the resulting memory layout really hard to follow. > > -- > Michal Hocko > SUSE Labs Michal, Vlastimil, Christoph and others, do you have any more comments, suggestions or any other feedback. If not, can you please add your reviewed-by, acked etc. -- Thanks and Regards Srikar Dronamraju