Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751186AbdFAMUd (ORCPT ); Thu, 1 Jun 2017 08:20:33 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:33410 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751056AbdFAMUc (ORCPT ); Thu, 1 Jun 2017 08:20:32 -0400 From: Michal Hocko To: linux-mm@kvack.org Cc: Andrew Morton , Mel Gorman , Vlastimil Babka , Andrea Arcangeli , Jerome Glisse , 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 Subject: [RFC PATCH] mm, memory_hotplug: support movable_node for hotplugable nodes Date: Thu, 1 Jun 2017 14:20:04 +0200 Message-Id: <20170601122004.32732-1-mhocko@kernel.org> X-Mailer: git-send-email 2.11.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4035 Lines: 96 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 --- Hi, I am sending this as an RFC because this is a user visible change change of behavior, strictly speaking. I believe it is a desirable change of behavior, thought, and it an explicit opt-in (kernel parameter) is required to see the change so I do not expect any breakage. I would still like to hear what other people think about this shift. I have tested it on a memory hotplug capable HW where the whole numa node can be hotremove/added. Does anybody see any problem with the proposed semantic? mm/memory_hotplug.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index b98fb0b3ae11..74d75583736c 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -943,6 +943,19 @@ struct zone *default_zone_for_pfn(int nid, unsigned long start_pfn, return &pgdat->node_zones[ZONE_NORMAL]; } +static inline bool movable_pfn_range(int nid, struct zone *default_zone, + unsigned long start_pfn, unsigned long nr_pages) +{ + if (!allow_online_pfn_range(nid, start_pfn, nr_pages, + MMOP_ONLINE_KERNEL)) + return true; + + if (!movable_node_is_enabled()) + return false; + + return !zone_intersects(default_zone, start_pfn, nr_pages); +} + /* * Associates the given pfn range with the given node and the zone appropriate * for the given online type. @@ -958,10 +971,10 @@ static struct zone * __meminit move_pfn_range(int online_type, int nid, /* * MMOP_ONLINE_KEEP defaults to MMOP_ONLINE_KERNEL but use * movable zone if that is not possible (e.g. we are within - * or past the existing movable zone) + * or past the existing movable zone). movable_node overrides + * this default and defaults to movable zone */ - if (!allow_online_pfn_range(nid, start_pfn, nr_pages, - MMOP_ONLINE_KERNEL)) + if (movable_pfn_range(nid, zone, start_pfn, nr_pages)) zone = movable_zone; } else if (online_type == MMOP_ONLINE_MOVABLE) { zone = &pgdat->node_zones[ZONE_MOVABLE]; -- 2.11.0