Re: [PATCH RESEND part2 v2 1/8] x86: get pg_data_t's memory from other node

[Tang Chen <tangchen@cn.fujitsu.com>]

Hi Mel,

On 02/11/2014 07:08 PM, Mel Gorman wrote:
......
>>>> I think they should be warned if the ratio is high and have an option of
>>>> specifying a ratio manually even if that means that additional nodes
>>>> will not be hot-removable.
>>
>> I think this is easy to do, provide an option for users to specify a
>> Normal:Movable ratio. This is not phys addr, and it is easy to use.
>>
>
> Yes. It would even be some help if the parameter forced some NUMA nodes
> to be Normal instead of Movable regardless of what SRAT says. There
> still would be an administrative burden in discovering what nodes are
> now pluggable but they must have been dealing with this already.
>

OK, I will start this work, and send patches soon.

>>>>
>>>> This is all still a kludge around the fact that node memory hot-remove
>>>> did not try and cope with full migration by breaking some of the 1:1
>>>> virt:phys mapping assumptions when hot-remove was enabled.
>>
>> I also said before, the implementation now can only be a temporary
>> solution for memory hotplug since it would take us a lot of time to
>> deal with 1:1 mapping thing.
>>
>> But about "breaking some of the 1:1 mapping", would you please give me
>> any hint of it ?  I want to do it too, but I cannot see where to start.
>>
>
> Some hints on how it might be tackled were given back in November 2012
> https://lkml.org/lkml/2012/11/29/190 but I never researched it in
> detail.
>

Thank you very much. I will read it one more time, and start trying to
migrate some of the kernel pages first.

Thanks.

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