Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765299AbXILHu6 (ORCPT ); Wed, 12 Sep 2007 03:50:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1765529AbXILHuM (ORCPT ); Wed, 12 Sep 2007 03:50:12 -0400 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:50739 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1764688AbXILHuK (ORCPT ); Wed, 12 Sep 2007 03:50:10 -0400 Date: Wed, 12 Sep 2007 16:51:38 +0900 From: KAMEZAWA Hiroyuki To: Mel Gorman Cc: Lee.Schermerhorn@hp.com, akpm@linux-foundation.org, ak@suse.de, clameter@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 4/6] Embed zone_id information within the zonelist->zones pointer Message-Id: <20070912165138.5deb4db4.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20070911213127.23507.34058.sendpatchset@skynet.skynet.ie> References: <20070911213006.23507.19569.sendpatchset@skynet.skynet.ie> <20070911213127.23507.34058.sendpatchset@skynet.skynet.ie> Organization: Fujitsu X-Mailer: Sylpheed 2.4.2 (GTK+ 2.10.11; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1665 Lines: 50 On Tue, 11 Sep 2007 22:31:27 +0100 (IST) Mel Gorman wrote: > Using two zonelists per node requires very frequent use of zone_idx(). This > is costly as it involves a lookup of another structure and a substraction > operation. As struct zone is always word aligned and normally cache-line > aligned, the pointer values have a number of 0's at the least significant > bits of the address. > > This patch embeds the zone_id of a zone in the zonelist->zones pointers. > The real zone pointer is retrieved using the zonelist_zone() helper function. > The ID of the zone is found using zonelist_zone_idx(). To avoid accidental > references, the zones field is renamed to _zones and the type changed to > unsigned long. > At first, I welcome this patch. thanks!. A comment after reading all is, how about defining zonelist as following instead of encoding in pointer ? == struct zone_pointer { struct zone *zone; int node_id; int zone_idx; }; struct zonelist { struct zone_pointer _zones[MAX_ZONES_PER_ZONELIST + 1]; }; #define zonelist_zone(zl) (zl)->zone #define zonelist_zone_idx(zl) (zl)->zone_idx #ifdef CONFIG_NUMA #define zonelist_zone_nid(zl) (zl)->node_id #else #define zonelist_zone_nid(zl, i) (0) == If we really want to avoid unnecessary access to "zone" while walking zonelist, above may do something good. Cons is this makes sizeof zonlist bigger. Thanks, -Kame - 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/