From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965538AbdEZM2i (ORCPT ); Fri, 26 May 2017 08:28:38 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:48333 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753110AbdEZM2g (ORCPT ); Fri, 26 May 2017 08:28:36 -0400 Subject: Re: [PATCH V2 2/2]: powerpc/hotplug/mm: Fix hot-add memory node assoc To: Balbir Singh Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Reza Arbab , Thomas Gleixner , Bharata B Rao , Shailendra Singh , "Aneesh Kumar K.V" , Sebastian Andrzej Siewior References: <20170525171932.29159.89311.stgit@ltcalpine2-lp20.aus.stglabs.ibm.com> <9b006866-5a8e-dc05-d603-bfe8eb02eef2@linux.vnet.ibm.com> <20170526132305.19ef3590@firefly.ozlabs.ibm.com> From: Michael Bringmann Organization: IBM Linux Technology Center Date: Fri, 26 May 2017 07:28:27 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 MIME-Version: 1.0 In-Reply-To: <20170526132305.19ef3590@firefly.ozlabs.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 17052612-0052-0000-0000-0000020C0CFD X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007120; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000212; SDB=6.00865825; UDB=6.00430007; IPR=6.00645686; BA=6.00005375; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00015593; XFM=3.00000015; UTC=2017-05-26 12:28:32 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17052612-0053-0000-0000-000050B8949B Message-Id: <895fac95-bd7a-7006-5fef-5b9f75882bcb@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-05-26_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1703280000 definitions=main-1705260228 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >> arch/powerpc/mm/numa.c | 7 ------- >> 1 file changed, 7 deletions(-) >> >> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c >> index 15c2dd5..18f3038 100644 >> --- a/arch/powerpc/mm/numa.c >> +++ b/arch/powerpc/mm/numa.c >> @@ -907,13 +907,6 @@ void __init initmem_init(void) >> >> memblock_dump_all(); >> >> - /* >> - * Reduce the possible NUMA nodes to the online NUMA nodes, >> - * since we do not support node hotplug. This ensures that we >> - * lower the maximum NUMA node ID to what is actually present. >> - */ >> - nodes_and(node_possible_map, node_possible_map, node_online_map); >> - > > There is an overhead with turning this off if you have too many cgroups > with the memory controller. I think this fix was added for a pathological > test case. On my system I see 84 cgroups with 1 node, so the probable > overhead is 84*255*sizeof(struct mem_cgroup_tree_per_node). > > I tried some patches to reduce the overhead, but those need more overhauling > and rework. Is there some other way to add a node to a dynamic, running system without crashing? I have not encountered one as yet. > Balbir Singh. -- Michael W. Bringmann Linux Technology Center IBM Corporation Tie-Line 363-5196 External: (512) 286-5196 Cell: (512) 466-0650 mwb@linux.vnet.ibm.com