On Mon, Dec 16, 2013 at 03:25:07PM -0500, Johannes Weiner wrote: > 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 <[email protected]> > > --- > > 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: >
Initially because I was thinking "local node" and numa_node_id() is a per-cpu variable that should be cheap to access and in some cases cache-hot as the top-level gfp API calls numa_node_id(). Thinking about it more though it still makes sense because the preferred zone is not necessarily local. If the allocation request requires ZONE_DMA32 and the local node does not have that zone then preferred zone is on a remote node. -- Mel Gorman SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
