On Fri, Dec 13, 2013 at 02:10:03PM +0000, Mel Gorman wrote:
> zone_local is using node_distance which is a more expensive call than
> necessary. On x86, it's another function call in the allocator fast path
> and increases cache footprint. This patch makes the assumption zones on a
> local node will share the same node ID. The necessary information should
> already be cache hot.
>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
> ---
> mm/page_alloc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 64020eb..fd9677e 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1816,7 +1816,7 @@ static void zlc_clear_zones_full(struct zonelist *zonelist)
>
> static bool zone_local(struct zone *local_zone, struct zone *zone)
> {
> - return node_distance(local_zone->node, zone->node) == LOCAL_DISTANCE;
> + return zone_to_nid(zone) == numa_node_id();
Why numa_node_id()? We pass in the preferred zone as @local_zone:
return zone_to_nid(local_zone) == zone_to_nid(zone)
Or even just compare the ->zone_pgdat pointers?
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