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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 31 Mar 2020 09:14:22 +0100 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 02V8DOkE50790826 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 31 Mar 2020 08:13:24 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 982FCA405C; Tue, 31 Mar 2020 08:14:27 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 211B9A405B; Tue, 31 Mar 2020 08:14:25 +0000 (GMT) Received: from linux.ibm.com (unknown [9.148.207.69]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Tue, 31 Mar 2020 08:14:25 +0000 (GMT) Date: Tue, 31 Mar 2020 11:14:23 +0300 From: Mike Rapoport To: Michal Hocko Subject: Re: [PATCH v3 0/5] mm: Enable CONFIG_NODES_SPAN_OTHER_NODES by default for NUMA References: <1585420282-25630-1-git-send-email-Hoan@os.amperecomputing.com> <20200330074246.GA14243@dhcp22.suse.cz> <20200330175100.GD30942@linux.ibm.com> <20200330182301.GM14243@dhcp22.suse.cz> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200330182301.GM14243@dhcp22.suse.cz> X-TM-AS-GCONF: 00 x-cbid: 20033108-0012-0000-0000-0000039B78A8 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20033108-0013-0000-0000-000021D883D5 Message-Id: <20200331081423.GE30942@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.676 definitions=2020-03-31_02:2020-03-30, 2020-03-31 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 adultscore=0 clxscore=1015 priorityscore=1501 lowpriorityscore=0 spamscore=0 malwarescore=0 impostorscore=0 suspectscore=5 bulkscore=0 mlxlogscore=855 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003310067 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200331_011439_350407_A671C188 X-CRM114-Status: GOOD ( 37.48 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mmorana@amperecomputing.com, Catalin Marinas , Heiko Carstens , "open list:MEMORY MANAGEMENT" , Paul Mackerras , "H. Peter Anvin" , sparclinux@vger.kernel.org, Alexander Duyck , linux-s390@vger.kernel.org, Michael Ellerman , x86@kernel.org, Christian Borntraeger , Ingo Molnar , Hoan Tran , Benjamin Herrenschmidt , Pavel Tatashin , lho@amperecomputing.com, Vasily Gorbik , Vlastimil Babka , Will Deacon , Borislav Petkov , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, Oscar Salvador , linux-kernel@vger.kernel.org, Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S. Miller" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Mar 30, 2020 at 08:23:01PM +0200, Michal Hocko wrote: > On Mon 30-03-20 20:51:00, Mike Rapoport wrote: > > On Mon, Mar 30, 2020 at 09:42:46AM +0200, Michal Hocko wrote: > > > On Sat 28-03-20 11:31:17, Hoan Tran wrote: > > > > In NUMA layout which nodes have memory ranges that span across other nodes, > > > > the mm driver can detect the memory node id incorrectly. > > > > > > > > For example, with layout below > > > > Node 0 address: 0000 xxxx 0000 xxxx > > > > Node 1 address: xxxx 1111 xxxx 1111 > > > > > > > > Note: > > > > - Memory from low to high > > > > - 0/1: Node id > > > > - x: Invalid memory of a node > > > > > > > > When mm probes the memory map, without CONFIG_NODES_SPAN_OTHER_NODES > > > > config, mm only checks the memory validity but not the node id. > > > > Because of that, Node 1 also detects the memory from node 0 as below > > > > when it scans from the start address to the end address of node 1. > > > > > > > > Node 0 address: 0000 xxxx xxxx xxxx > > > > Node 1 address: xxxx 1111 1111 1111 > > > > > > > > This layout could occur on any architecture. Most of them enables > > > > this config by default with CONFIG_NUMA. This patch, by default, enables > > > > CONFIG_NODES_SPAN_OTHER_NODES or uses early_pfn_in_nid() for NUMA. > > > > > > I am not opposed to this at all. It reduces the config space and that is > > > a good thing on its own. The history has shown that meory layout might > > > be really wild wrt NUMA. The config is only used for early_pfn_in_nid > > > which is clearly an overkill. > > > > > > Your description doesn't really explain why this is safe though. The > > > history of this config is somehow messy, though. Mike has tried > > > to remove it a94b3ab7eab4 ("[PATCH] mm: remove arch independent > > > NODES_SPAN_OTHER_NODES") just to be reintroduced by 7516795739bd > > > ("[PATCH] Reintroduce NODES_SPAN_OTHER_NODES for powerpc") without any > > > reasoning what so ever. This doesn't make it really easy see whether > > > reasons for reintroduction are still there. Maybe there are some subtle > > > dependencies. I do not see any TBH but that might be burried deep in an > > > arch specific code. > > > > I've looked at this a bit more and it seems that the check for > > early_pfn_in_nid() in memmap_init_zone() can be simply removed. > > > > The commits you've mentioned were way before the addition of > > HAVE_MEMBLOCK_NODE_MAP and the whole infrastructure that calculates zone > > sizes and boundaries based on the memblock node map. > > So, the memmap_init_zone() is called when zone boundaries are already > > within a node. > > But zones from different nodes might overlap in the pfn range. And this > check is there to skip over those overlapping areas. Maybe I mis-read the code, but I don't see how this could happen. In the HAVE_MEMBLOCK_NODE_MAP=y case, free_area_init_node() calls calculate_node_totalpages() that ensures that node->node_zones are entirely within the node because this is checked in zone_spanned_pages_in_node(). So, for zones from different nodes to overlap in the pfn range the nodes themself should overlap. Is this even possible? > The only way to skip over this check I can see is to do a different pfn > walk and go through memblock ranges which are guaranteed to belong to a > single node. > -- > Michal Hocko > SUSE Labs -- Sincerely yours, Mike. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel