Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932760AbXHJKsA (ORCPT ); Fri, 10 Aug 2007 06:48:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754817AbXHJKrx (ORCPT ); Fri, 10 Aug 2007 06:47:53 -0400 Received: from gir.skynet.ie ([193.1.99.77]:36673 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754339AbXHJKrw (ORCPT ); Fri, 10 Aug 2007 06:47:52 -0400 Date: Fri, 10 Aug 2007 11:47:49 +0100 To: Christoph Lameter Cc: Lee.Schermerhorn@hp.com, ak@suse.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 3/4] Embed zone_id information within the zonelist->zones pointer Message-ID: <20070810104749.GA14300@skynet.ie> References: <20070809210616.14702.73376.sendpatchset@skynet.skynet.ie> <20070809210716.14702.43074.sendpatchset@skynet.skynet.ie> <20070809233300.GA31644@skynet.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.13 (2006-08-11) From: mel@skynet.ie (Mel Gorman) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1459 Lines: 34 On (09/08/07 18:44), Christoph Lameter didst pronounce: > > On Fri, 10 Aug 2007, Mel Gorman wrote: > > > > > +#if defined(CONFIG_SMP) && INTERNODE_CACHE_SHIFT > ZONES_SHIFT > > > > > > Is this necessary? ZONES_SHIFT is always <= 2 so it will work with > > > any pointer. Why disable this for UP? > > > > > > > Caution in case the number of zones increases. There was no guarantee of > > zone alignment. It's the same reason I have a BUG_ON in the encode > > function so that if we don't catch problems at compile-time, it'll go > > BANG in a nice predictable fashion. > > Caution would lead to a BUG_ON but why the #if? Why exclude UP? On x86_64 would have ZONE_DMA, ZONE_DMA32, ZONE_NORMAL, ZONE_HIGHMEM and ZONE_MOVABLE. On SMP, that's more than two bits worth and would fail t runtime. Well, it should at least I didn't actually try it out. However, I accept that the SMP check is less than than ideal. I considered comparing it against MAX_NR_ZONES but as it's an enum, it can't be checked at compile time. What else would make a better check? -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/