From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ee0-f48.google.com (mail-ee0-f48.google.com [74.125.83.48]) by kanga.kvack.org (Postfix) with ESMTP id C37A76B0035 for ; Tue, 17 Dec 2013 06:13:56 -0500 (EST) Received: by mail-ee0-f48.google.com with SMTP id e49so2764434eek.21 for ; Tue, 17 Dec 2013 03:13:56 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id e48si4551912eeh.92.2013.12.17.03.13.55 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 17 Dec 2013 03:13:55 -0800 (PST) Date: Tue, 17 Dec 2013 11:13:52 +0000 From: Mel Gorman Subject: Re: [PATCH 3/7] mm: page_alloc: Use zone node IDs to approximate locality Message-ID: <20131217111352.GZ11295@suse.de> References: <1386943807-29601-1-git-send-email-mgorman@suse.de> <1386943807-29601-4-git-send-email-mgorman@suse.de> <20131216202507.GZ21724@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20131216202507.GZ21724@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: Andrew Morton , Dave Hansen , Rik van Riel , Linux-MM , LKML 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 > > --- > > 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org