Re: [PATCH 3/7] mm: page_alloc: Use zone node IDs to approximatelocality

[Johannes Weiner]

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?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/