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

Andrew Morton
2006-11-23T19:14:17Z

On Thu, 23 Nov 2006 12:01:41 +0000
mel@skynet.ie (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@csn.ul.ie>
>
> 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?