Re: Question: new bind_zonelist uses only one zone type

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

Andi Kleen wrote:
> On IA64/SN2 ZONE_DMA is empty and at least in the part SGI was the only
> IA64 vendor actively interested in NUMA policy.
> 
> I assume you have a NUMA platform too. Do your machines have a contiguous
> memory map where there could be one or more nodes which only
> have ZONE_DMA?
> 

Fujitsu's PrimeQuest is NUMA and has memory in 0-4G areas in node 0.
It depends on installed memory whether node 0 contains only ZONE_DMA or not.

When using SPARSEMEM, it uses NUMA config. This means one-node-NUMA.
So, if I use SPARSEMEM on ia64 SMP machine with 5 Gbytes mem,
I can allocate just 1G bytes on mbind area.
(*)Maybe using mempolicy on one-node-NUMA make no sense.


>>> It is on my todo list to fix, but I haven't gotten around to it yet.
>>>
>>> Fixing it will unfortunately increase the footprint of the policy
>>> structures, so likely it would only increase to two. If someone beats me
>>> to a patch that would be ok too.
>> I don't have real problem now. It just looks curious.
> 
> Well it's a bit nasty to not be able to policy 4GB of your memory. Maybe
> if you have a few TB of it you won't care, but on smaller machines
> it likely will make a difference.
> 
It makes difference on my *numa emulation* environment, now ;)
But it's just emulation.

-- Kame.

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