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Message-ID: <449ABC3E.5070609@innova-card.com>
Date: Thu, 22 Jun 2006 17:50:22 +0200
Reply-To: Franck <vagabon.xyz@gmail.com>
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To: Mel Gorman <mel@csn.ul.ie>
CC: Franck <vagabon.xyz@gmail.com>, Andrew Morton <akpm@osdl.org>,
       linux-kernel@vger.kernel.org
Subject: Re: 2.6.17-mm1
References: <20060621034857.35cfe36f.akpm@osdl.org> <449AB01A.5000608@innova-card.com> <Pine.LNX.4.64.0606221617420.5869@skynet.skynet.ie>
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From: Franck Bui-Huu <fbh.work@gmail.com>
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Mel Gorman wrote:
> On Thu, 22 Jun 2006, Franck Bui-Huu wrote:
>>
>> Should ARCH_PFN_OFFSET macro be used instead in order to make pfn/page
>> convertions work when node 0 start offset do not start at 0 ?
>>
> 
> What happens if you have ARCH_PFN_OFFSET as
> 
> #define ARCH_PFN_OFFSET (0UL)
> 
> ?

It's the default value (see memory_model.h). It means that pfn start
for node 0 is 0, therefore your physical memory address starts at 0.

> 
> What arch is this?
> 

well I'm working on MIPS, but you can take a look at ARM that does the
same thing better...

>> My physical memory start at 0x20000000. So node 0 starts at an offset
>> different from 0. I setup ARCH_PFN_OFFSET this way
>>
>>     #define ARCH_PFN_OFFSET    (0x20000000 << PAGE_SHIFT)
>>
> 
> If physical memory starts at 0x20000000, why is the PFN not
> 0x20000000 >> PAGE_SHIFT ?
> 

It is a typo... 

		Franck