Re: question about memory-hotplug

[tgh <tianguanhua@ncic.ac.cn>]

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Thank you for your reply

Yasunori Goto 写道:
> Hello.
>
>   
>> hi
>>   I try to understand the memory_hotplug.c   ,but I am confused about 
>> the mechanism in it
>>  Does the mem_map is allocated when setup for all the memory page both 
>> the existing and the hotplug , or  does the mem_map is allocated 
>> dynamically when a chip of memory is hotpluged ?
>>  if mem_map is allocated dynamically,does the mem_map is maintained in 
>> the list or how to deal with it ?
>>  and if mem_map is allocated dynamically,does system need new node and 
>> new zone structure to manage the dynamically-allocated memmap ,or not ?
>>     
>
> Basically, memory hotplug code depends on sparsemem. So, I'll
> recommend that you should see mm/sparse.c too.
> In sparsemem code, mem_map is allocated dynamically, and 
> its pointed by mem_section[] array.
>   
In the traditional linux without sparsemem, there are node-zone-memmap 
mechanism for managing the physical memory,is it right?
while in the sparsemem mechanism, what is the architure of 
node-zone-memmap or node-zone-mem_section[]-mem_map like?

and if the sparsemem is on , buddy still does its work in a mem_map as 
before or does it work in a new way?
and how does virt-to-phy macro (or something like it) work,when there 
are a list of mem_map in the sparsemem system?

> (However, x86-64 code has original code. IIRC, its memmap was allcated 
>  statically....)
>   
does x86-64 not surpport the memory-hotplug,or how does it achieve the 
memory-hotplug ?
>   
>>  if  system need new node and new zone structure to manage the 
>> dynamically-allocated memmap,does system have to be a NUMA-surpport one 
>> or not?
>>     
>
> Pgdat and zone can be allocated dynamically for NUMA system,
> but memmap is not pointed by them if sparsemem is on.
>   
which structure points it ,mem_section[] does it? then what is the 
architure of the node-zone-mem_section[]-mem_map like?

> Thanks for your concern. :-)
>
> ---
> Yasunori Goto 
>
>
>
>
>   


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