Re: [PATCH 6/6] Break out memory initialisation code from page_alloc.cto mem_init.c

[Mel Gorman]

On Tue, 9 May 2006, Nick Piggin wrote:

> Mel Gorman wrote:
>
> > page_alloc.c contains a large amount of memory initialisation code. This 
> > patch
> > breaks out the initialisation code to a separate file to make page_alloc.c
> > a bit easier to read.
>
> I realise this is at the wrong end of your queue, but if you _can_ easily
> break it out and submit it first, it would be a nice cleanup and would help
> shrink your main patchset.

The split-out potentially affects 10 other patches currently in -mm and is 
a merge headache for Andrew. My current understanding is that he wants to 
drop patch 6/6 until a later time. I guess this would be still true if the 
patch was at the other end of the queue.

> Also, we're recently having some problems with architectures not aligning
> zones correctly. Would it make sense to add these sorts of sanity checks,
> and possibly forcing alignment corrections into your generic code?

Yes, it is easy to force alignment corrections into the generic code. From 
that thread, there was this comment from Andy Whitcroft and your response;

> >1) check the alignment of the zones matches the implied alignment
> > constraints and correct it as we go.
> Yes. And preferably have checks in the generic page allocator setup
> code, so we can do something sane if the arch code gets it wrong.

With this patchset, it is trivial to move the start of highmem during 
setup. free_area_init_nodes() is passed the PFN each zone starts at by the 
architecture. If one wanted to force HIGHMEM to aligned, the 
arch_max_high_pfn value could be rounded down to MAX_ORDER alignment in 
free_area_init_nodes() before it calls free_area_init_node(). It doesn't 
matter if the PFN is in a hole. From there, an aligned mem_map should be 
allocated and memmap_init() will set the correct zone flags.

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