From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752193Ab3LPUZR (ORCPT ); Mon, 16 Dec 2013 15:25:17 -0500 Received: from zene.cmpxchg.org ([85.214.230.12]:50187 "EHLO zene.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751484Ab3LPUZN (ORCPT ); Mon, 16 Dec 2013 15:25:13 -0500 Date: Mon, 16 Dec 2013 15:25:07 -0500 From: Johannes Weiner To: Mel Gorman Cc: Andrew Morton , Dave Hansen , Rik van Riel , Linux-MM , LKML Subject: Re: [PATCH 3/7] mm: page_alloc: Use zone node IDs to approximate locality Message-ID: <20131216202507.GZ21724@cmpxchg.org> References: <1386943807-29601-1-git-send-email-mgorman@suse.de> <1386943807-29601-4-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1386943807-29601-4-git-send-email-mgorman@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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?