Re: question about memory-hotplug

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

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Thank you for your reply

If sparsememory is on ,are there node and zone structures or not in the 
systme?

Thanks in advance


Yasunori Goto 写道:
>> In the traditional linux without sparsemem, there are node-zone-memmap 
>> mechanism for managing the physical memory,is it right?
>>     
>
> Yes.
>
>   
>> while in the sparsemem mechanism, what is the architure of 
>> node-zone-memmap or node-zone-mem_section[]-mem_map like?
>>     
>
> mem_section[] is "static array" which is defined in sparse.c.
> So, no pointer is necessary to point mem_section array.
> Its index can be found by only pfn like ((pfn >> PFN_SECTION_SHIFT)).
> Each mem_section has pointer of mem_map.
>
> In addition, each page->flags has area for saving mem_section's index.
> page_to_section() is (page->flags >> SECTIONS_PGSHIFT) & SECTIONS_MASK).
>
> Tracing __pfn_to_page() and __page_to_pfn in 
> include/asm-generic/memory_model.h will be good answer 
> for your understanding.
>
>   
>> 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?
>>     
>
> 2.6.10 or older kernel has bitmaps to manage buddy page. Current
> one doesn't have it. Its information is saved in page->private.
> Others are same.
> 1 section size is bigger than MAX_ORDER. So, current buddy system
> doensn't concern about section size. 
> This means memory hotplug unit size is section size. (At least now)
>
>   
>> 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 ?
>>     
>
> x86-64 supports both of sparse and non sparse. It is seleced by
> kernel config option.
>
> Bye.
>
>   


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