On Tue 27-03-18 11:57:07, Wei Yang wrote:
> find_min_pfn_for_node() iterate on pfn range to find the minimum pfn for a
> node. The memblock_region in memblock_type are already ordered, which means
> the first hit in iteration is the minimum pfn.
I haven't looked at the code yet but the changelog should contain the
motivation why it exists. It seems like this is an optimization. If so,
what is the impact?
> This patch returns the fist hit instead of iterating the whole regions.
>
> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
> ---
> mm/page_alloc.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 635d7dd29d7f..a65de1ec4b91 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6365,14 +6365,14 @@ unsigned long __init node_map_pfn_alignment(void)
> /* Find the lowest pfn for a node */
> static unsigned long __init find_min_pfn_for_node(int nid)
> {
> - unsigned long min_pfn = ULONG_MAX;
> - unsigned long start_pfn;
> + unsigned long min_pfn;
> int i;
>
> - for_each_mem_pfn_range(i, nid, &start_pfn, NULL, NULL)
> - min_pfn = min(min_pfn, start_pfn);
> + for_each_mem_pfn_range(i, nid, &min_pfn, NULL, NULL) {
> + break;
> + }
>
> - if (min_pfn == ULONG_MAX) {
> + if (i == -1) {
> pr_warn("Could not find start_pfn for node %d\n", nid);
> return 0;
> }
> --
> 2.15.1
>
--
Michal Hocko
SUSE Labs
