From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262074AbTKGWd3 (ORCPT ); Fri, 7 Nov 2003 17:33:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262070AbTKGW1S (ORCPT ); Fri, 7 Nov 2003 17:27:18 -0500 Received: from zeus.kernel.org ([204.152.189.113]:15062 "EHLO zeus.kernel.org") by vger.kernel.org with ESMTP id S264364AbTKGV7i (ORCPT ); Fri, 7 Nov 2003 16:59:38 -0500 Date: Fri, 7 Nov 2003 13:58:06 -0800 From: Andrew Morton To: jbarnes@sgi.com (Jesse Barnes) Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] use NODES_SHIFT to calculate ZONE_SHIFT Message-Id: <20031107135806.3c929688.akpm@osdl.org> In-Reply-To: <20031105211608.GA23560@sgi.com> References: <20031105211608.GA23560@sgi.com> X-Mailer: Sylpheed version 0.9.6 (GTK+ 1.2.10; i586-pc-linux-gnu) 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 jbarnes@sgi.com (Jesse Barnes) wrote: > > Now that we have a proper NODES_SHIFT value, we need to use it to define > ZONE_SHIFT otherwise we'll spill over 8 bits if we have more than 85 > nodes. How does this look? The '+2' should really be > log2(MAX_NR_NODES), but I think this is an improvement over what was > there. You mean log2(MAX_NR_ZONES). How about we do it this way, so at least the duplicated information is on adjacent lines, and they are unlikely to get out of sync? diff -puN include/linux/mm.h~ZONE_SHIFT-from-NODES_SHIFT include/linux/mm.h --- 25/include/linux/mm.h~ZONE_SHIFT-from-NODES_SHIFT Fri Nov 7 13:51:22 2003 +++ 25-akpm/include/linux/mm.h Fri Nov 7 13:55:11 2003 @@ -322,8 +322,10 @@ static inline void put_page(struct page /* * The zone field is never updated after free_area_init_core() * sets it, so none of the operations on it need to be atomic. + * We'll have up to log2(MAX_NUMNODES * MAX_NR_ZONES) zones + * total, so we use NODES_SHIFT here to get enough bits. */ -#define ZONE_SHIFT (BITS_PER_LONG - 8) +#define ZONE_SHIFT (BITS_PER_LONG - NODES_SHIFT - MAX_NR_ZONES_SHIFT) struct zone; extern struct zone *zone_table[]; diff -puN include/linux/mmzone.h~ZONE_SHIFT-from-NODES_SHIFT include/linux/mmzone.h --- 25/include/linux/mmzone.h~ZONE_SHIFT-from-NODES_SHIFT Fri Nov 7 13:51:49 2003 +++ 25-akpm/include/linux/mmzone.h Fri Nov 7 13:57:19 2003 @@ -159,7 +159,10 @@ struct zone { #define ZONE_DMA 0 #define ZONE_NORMAL 1 #define ZONE_HIGHMEM 2 -#define MAX_NR_ZONES 3 + +#define MAX_NR_ZONES 3 /* Sync this with MAX_NR_ZONES_SHIFT */ +#define MAX_NR_ZONES_SHIFT 2 /* ceil(log2(MAX_NR_ZONES)) */ + #define GFP_ZONEMASK 0x03 /* _