On Wed, May 24, 2017 at 02:24:10PM +0200, Michal Hocko wrote:
74d42d8fe146 ("memory_hotplug: ensure every online node has NORMAL
memory") has added can_offline_normal which checks the amount of
memory in !movable zones as long as CONFIG_MOVABLE_NODE is disable.
It disallows to offline memory if there is nothing left with a
justification that "memory-management acts bad when we have nodes which
is online but don't have any normal memory".
74d42d8fe146 ("memory_hotplug: ensure every online node has NORMAL
memory") has introduced a restriction that every numa node has to have
at least some memory in !movable zones before a first movable memory
can be onlined if !CONFIG_MOVABLE_NODE with the same justification
While it is true that not having _any_ memory for kernel allocations on
a NUMA node is far from great and such a node would be quite subotimal
because all kernel allocations will have to fallback to another NUMA
node but there is no reason to disallow such a configuration in
principle.
Besides that there is not really a big difference to have one memblock
for ZONE_NORMAL available or none. With 128MB size memblocks the system
might trash on the kernel allocations requests anyway. It is really
hard to draw a line on how much normal memory is really sufficient so
we have to rely on administrator to configure system sanely therefore
drop the artificial restriction and remove can_offline_normal and
can_online_high_movable altogether.
I'm really liking all this cleanup of the memory hotplug code. Thanks!
Much appreciated.
Acked-by: Reza Arbab <arbab@xxxxxxxxxxxxxxxxxx>
--
Reza Arbab
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