Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752440AbdFLI67 (ORCPT ); Mon, 12 Jun 2017 04:58:59 -0400 Received: from mx2.suse.de ([195.135.220.15]:43348 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752065AbdFLI66 (ORCPT ); Mon, 12 Jun 2017 04:58:58 -0400 Subject: Re: [PATCH] mm, memory_hotplug: support movable_node for hotplugable nodes To: Michal Hocko , Andrew Morton Cc: linux-mm@kvack.org, Mel Gorman , Andrea Arcangeli , Reza Arbab , 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 References: <20170608122318.31598-1-mhocko@kernel.org> From: Vlastimil Babka Message-ID: <40d41b19-607f-fbe4-d133-f1aecd548d7e@suse.cz> Date: Mon, 12 Jun 2017 10:58:53 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <20170608122318.31598-1-mhocko@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2195 Lines: 43 On 06/08/2017 02:23 PM, Michal Hocko wrote: > From: Michal Hocko > > 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: Vlastimil Babka