linux-kernel - Re: [PATCH 0/6] Sizing zones and holes in an architecture independent manner V9

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Date:	Tue, 22 Aug 2006 09:38:50 +0100 (IST)
From:	Mel Gorman <mel@....ul.ie>
To:	Keith Mannthey <kmannth@...il.com>
Cc:	akpm@...l.org, tony.luck@...el.com,
	Linux Memory Management List <linux-mm@...ck.org>,
	ak@...e.de, bob.picco@...com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linuxppc-dev@...abs.org
Subject: Re: [PATCH 0/6] Sizing zones and holes in an architecture independent
 manner V9

On Mon, 21 Aug 2006, Keith Mannthey wrote:

> On 8/21/06, Mel Gorman <mel@....ul.ie> wrote:
>> This is V9 of the patchset to size zones and memory holes in an
>> architecture-independent manner. It booted successfully on 5 different
>> machines (arches were x86, x86_64, ppc64 and ia64) in a number of different
>> configurations and successfully built a kernel. If it fails on any machine,
>> booting with loglevel=8 and the console log should tell me what went wrong.
>> 
>
> I am wondering why this new api didn't cleanup the pfn_to_nid code
> path as well. Arches are left to still keep another set of
> nid-start-end info around. We are sending info like
>

pfn_to_nid() is used at runtime and the early_node_map[] is deleted by 
then. As this step, I only want to get the initialisation correct. What 
can be replaced is the architecture-specific early_pfn_to_nid() function 
which I did for power and x86.

> add_active_range(unsigned int nid, unsigned long start_pfn, unsigned
> long end_pfn)
>
> With this info making a common pnf_to_nid seems to be of intrest so we
> don't have to keep redundant information in both generic and arch
> specific data structures.
>

To implement a common one of interest, the array would have to be 
converted to a linked list at the end of boot so it could be modified by 
memory hot-add, then pfn_to_nid() would walk the linked list rather than 
the existing array. pfn_valid() would probably be replaced as well. 
However, this is going to be slower (if more accurate in some cases) than 
the existing pfn_valid() and so I would treat it as a separate issue.

> Are you intending the hot-add memory code path to call add_active_range or 
> ???
>

Not at this time. I want to make sure the memory initialisation is right 
before dealing with additional complications.

> Thanks,
> Keith
>

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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