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Re: [discuss] 2.6.19-rc6: known regressions (v4): msg#00144

Subject: Re: [discuss] 2.6.19-rc6: known regressions (v4)
On Thu, 23 Nov 2006 12:01:41 +0000
mel@xxxxxxxxx (Mel Gorman) wrote:

> find_min_pfn_for_node() and find_min_pfn_with_active_regions() both depend
> on a sorted early_node_map[]. However, sort_node_map() is being called after
> fin_min_pfn_with_active_regions() in free_area_init_nodes(). In most cases,
> this is ok, but on at least one x86_64, the SRAT table caused the E820 ranges
> to be registered out of order. This gave the wrong values for the min PFN
> range resulting in some pages not being initialised.
> 
> This patch sorts the early_node_map in find_min_pfn_for_node(). It has
> been boot tested on x86, x86_64, ppc64 and ia64.
> 
> Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
> 
> diff -rup linux-2.6.19-rc6-clean/mm/page_alloc.c 
> linux-2.6.19-rc6-sort_in_find_min/mm/page_alloc.c
> --- linux-2.6.19-rc6-clean/mm/page_alloc.c    2006-11-15 20:03:40.000000000 
> -0800
> +++ linux-2.6.19-rc6-sort_in_find_min/mm/page_alloc.c 2006-11-23 
> 02:23:57.000000000 -0800
> @@ -2612,6 +2612,9 @@ unsigned long __init find_min_pfn_for_no
>  {
>       int i;
>  
> +     /* Regions in the early_node_map can be in any order */
> +     sort_node_map();
> +
>       /* Assuming a sorted map, the first range found has the starting pfn */
>       for_each_active_range_index_in_nid(i, nid)
>               return early_node_map[i].start_pfn;
> @@ -2680,9 +2683,6 @@ void __init free_area_init_nodes(unsigne
>                       max(max_zone_pfn[i], arch_zone_lowest_possible_pfn[i]);
>       }
>  
> -     /* Regions in the early_node_map can be in any order */
> -     sort_node_map();
> -
>       /* Print out the zone ranges */
>       printk("Zone PFN ranges:\n");
>       for (i = 0; i < MAX_NR_ZONES; i++)

Doesn't this mean that we can sort that map multiple times?

Seems a bit ... ungainly?


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