From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 10 Aug 2007 10:37:02 -0700 (PDT) From: Christoph Lameter Subject: Re: [PATCH 3/4] Embed zone_id information within the zonelist->zones pointer In-Reply-To: <20070810104749.GA14300@skynet.ie> Message-ID: References: <20070809210616.14702.73376.sendpatchset@skynet.skynet.ie> <20070809210716.14702.43074.sendpatchset@skynet.skynet.ie> <20070809233300.GA31644@skynet.ie> <20070810104749.GA14300@skynet.ie> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Mel Gorman Cc: Lee.Schermerhorn@hp.com, ak@suse.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Fri, 10 Aug 2007, Mel Gorman wrote: > 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. x86_64 does not support ZONE_HIGHMEM. The number of zones is depending on SMP? > 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? You could do a BUILD_BUG_ON() instead? -- 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