Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751578AbdFOPna (ORCPT ); Thu, 15 Jun 2017 11:43:30 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:60033 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750814AbdFOPn3 (ORCPT ); Thu, 15 Jun 2017 11:43:29 -0400 Date: Thu, 15 Jun 2017 10:43:20 -0500 From: Reza Arbab To: Michal Hocko Cc: Andrew Morton , linux-mm@kvack.org, Mel Gorman , Vlastimil Babka , Andrea Arcangeli , Yasuaki Ishimatsu , qiuxishi@huawei.com, Kani Toshimitsu , slaoub@gmail.com, Joonsoo Kim , Andi Kleen , David Rientjes , Daniel Kiper , Igor Mammedov , Vitaly Kuznetsov , LKML , Michal Hocko Subject: Re: [PATCH] mm, memory_hotplug: support movable_node for hotplugable nodes References: <20170608122318.31598-1-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20170608122318.31598-1-mhocko@kernel.org> Organization: IBM Linux Technology Center User-Agent: NeoMutt/20170609 (1.8.3) X-TM-AS-GCONF: 00 x-cbid: 17061515-0008-0000-0000-00000242EA24 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007237; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000212; SDB=6.00875186; UDB=6.00435721; IPR=6.00655275; BA=6.00005423; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00015837; XFM=3.00000015; UTC=2017-06-15 15:43:27 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17061515-0009-0000-0000-000035AC926A Message-Id: <20170615154320.tzpkjxeuckkua2zm@arbab-laptop.localdomain> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-06-15_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-1706150270 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2154 Lines: 44 On Thu, Jun 08, 2017 at 02:23:18PM +0200, Michal Hocko wrote: >movable_node kernel parameter allows to make hotplugable NUMA >nodes to put all the hotplugable memory into movable zone which >allows more or less reliable memory hotremove. At least this >is the case for the NUMA nodes present during the boot (see >find_zone_movable_pfns_for_nodes). > >This is not the case for the memory hotplug, though. > > echo online > /sys/devices/system/memory/memoryXYZ/status > >will default to a kernel zone (usually ZONE_NORMAL) unless the >particular memblock is already in the movable zone range which is not >the case normally when onlining the memory from the udev rule context >for a freshly hotadded NUMA node. The only option currently is to have a >special udev rule to echo online_movable to all memblocks belonging to >such a node which is rather clumsy. Not the mention this is inconsistent >as well because what ended up in the movable zone during the boot will >end up in a kernel zone after hotremove & hotadd without special care. > >It would be nice to reuse memblock_is_hotpluggable but the runtime >hotplug doesn't have that information available because the boot and >hotplug paths are not shared and it would be really non trivial to >make them use the same code path because the runtime hotplug doesn't >play with the memblock allocator at all. > >Teach move_pfn_range that MMOP_ONLINE_KEEP can use the movable zone if >movable_node is enabled and the range doesn't overlap with the existing >normal zone. This should provide a reasonable default onlining strategy. > >Strictly speaking the semantic is not identical with the boot time >initialization because find_zone_movable_pfns_for_nodes covers only the >hotplugable range as described by the BIOS/FW. From my experience this >is usually a full node though (except for Node0 which is special and >never goes away completely). If this turns out to be a problem in the >real life we can tweak the code to store hotplug flag into memblocks >but let's keep this simple now. > >Signed-off-by: Michal Hocko Acked-by: Reza Arbab -- Reza Arbab