Messages in this thread | | | Date | Thu, 15 Jun 2017 10:43:20 -0500 | From | Reza Arbab <> | Subject | Re: [PATCH] mm, memory_hotplug: support movable_node for hotplugable nodes |
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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 <mhocko@suse.com>
Acked-by: Reza Arbab <arbab@linux.vnet.ibm.com>
-- Reza Arbab
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