Re: 2.6.17-mm1

[Mel Gorman]

On Thu, 22 Jun 2006, Franck Bui-Huu wrote:

> Andrew,
>
> Andrew Morton wrote:
> > All 1738 patches:
> >
> > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.17/2.6.17-mm1/patch-list
>
> Is the following patch really needed ?
>
> flatmem-relax-requirement-for-memory-to-start-at-pfn-0.patch
>
> """
> The FLATMEM memory model assumes that memory is in one contigious area
> based at pfn 0.  If we initialise node 0 to start at any other offset we
> will incorrectly map pfn's to the wrong struct page *.  The key to the
> memory model is the contigious nature of the memory not the location of it.
> Relax the requirement for the area to start at 0.
> """
>
> 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)

?

What arch is this?

> 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 ?

> Until now (2.6.17), it works well, but this patch breaks my machine.
>
> If you need more details about my memory mapping, feel free to ask.
>
> Thanks
>
> 		Franck

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