Date: Fri, 11 Aug 2006 00:05:32 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: moreau francis <francis_moreau2000@yahoo.fr>
Cc: apw@shadowen.org, alan@lxorguk.ukuu.org.uk, linux-kernel@vger.kernel.org
Subject: Re: Re : sparsemem usage
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On Thu, 10 Aug 2006 14:46:01 +0000 (GMT)
moreau francis <francis_moreau2000@yahoo.fr> wrote:
> 
> Why not implementing page_exist() by simply using mem_map[] ? When
> allocating mem_map[], we can just fill it with a special value. And
> then when registering memory area, we clear this special value with
> the "reserved" value. Hence for flatmem model, we can have:
> 
> #define page_exist(pfn)        (mem_map[pfn] != SPECIAL_VALUE)
>  
putting a special value to a page struct at mem_map + pfn ?

> and it should work for sparsemem too and other models that will use
> mem_map[].
> 
> Another point, is page_exist() going to replace page_valid() ?
what is page_valid() here ? pfn_valid() (in current kernel) ?

> I mean page_exist() is going to be something more accurate than
> page_valid(). All tests on page_valid() _only_ will be fine to test
> page_exist(). But all tests such:
> 
>     if (page_valid(x) && page_is_ram(x))
> 
> can be replaced by
> 
>     if (page_exist(x))
> 
> So, again, why not simply improving page_valid() definition rather
> than introduce a new service ?
> 
I welcome to do that if implementation is sane.
pfn_valid() --- check there is a page struct
page_exist() --- check there is a physical memory.

but discussing without patch is not very good. please post your patch.
Then we can discuss more concrete things.

-Kame

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