From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 829D26B004F for ; Wed, 18 Mar 2009 10:18:29 -0400 (EDT) Received: from localhost (smtp.ultrahosting.com [127.0.0.1]) by smtp.ultrahosting.com (Postfix) with ESMTP id 0B72D304B5F for ; Wed, 18 Mar 2009 10:25:22 -0400 (EDT) Received: from smtp.ultrahosting.com ([74.213.174.254]) by localhost (smtp.ultrahosting.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 6tQUAdipUAs5 for ; Wed, 18 Mar 2009 10:25:15 -0400 (EDT) Received: from qirst.com (unknown [74.213.171.31]) by smtp.ultrahosting.com (Postfix) with ESMTP id C69D0304B5C for ; Wed, 18 Mar 2009 10:25:12 -0400 (EDT) Date: Wed, 18 Mar 2009 10:15:26 -0400 (EDT) From: Christoph Lameter Subject: Re: [PATCH 24/27] Convert gfp_zone() to use a table of precalculated values In-Reply-To: <20090318135222.GA4629@csn.ul.ie> Message-ID: References: <1237226020-14057-1-git-send-email-mel@csn.ul.ie> <1237226020-14057-25-git-send-email-mel@csn.ul.ie> <20090318135222.GA4629@csn.ul.ie> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Linux Memory Management List , Pekka Enberg , Rik van Riel , KOSAKI Motohiro , Johannes Weiner , Nick Piggin , Linux Kernel Mailing List , Lin Ming , Zhang Yanmin , Peter Zijlstra List-ID: On Wed, 18 Mar 2009, Mel Gorman wrote: > On Mon, Mar 16, 2009 at 03:12:50PM -0400, Christoph Lameter wrote: > > On Mon, 16 Mar 2009, Mel Gorman wrote: > > > > > +int gfp_zone_table[GFP_ZONEMASK] __read_mostly; > > > > The gfp_zone_table is compile time determinable. There is no need to > > calculate it. > > > > The cost of calculating it is negligible and the code is then freed later > in boot. Does having a const table make any difference? Should it not enable the compiler to determine the value at compile time and therefore make things like gfp_zone(constant) a constant? > > const int gfp_zone_table[GFP_ZONEMASK] = { > > ZONE_NORMAL, /* 00 No flags set */ > > ZONE_DMA, /* 01 Only GFP_DMA set */ > > ZONE_HIGHMEM, /* 02 Only GFP_HIGHMEM set */ > > ZONE_DMA, /* 03 GFP_HIGHMEM and GFP_DMA set */ > > ZONE_DMA32, /* 04 Only GFP_DMA32 set */ > > ZONE_DMA, /* 05 GFP_DMA and GFP_DMA32 set */ > > ZONE_DMA32, /* 06 GFP_DMA32 and GFP_HIGHMEM set */ > > ZONE_DMA, /* 07 GFP_DMA, GFP_DMA32 and GFP_DMA32 set */ > > ZONE_MOVABLE, /* 08 Only ZONE_MOVABLE set */ > > ZONE_DMA, /* 09 MOVABLE + DMA */ > > ZONE_MOVABLE, /* 0A MOVABLE + HIGHMEM */ > > ZONE_DMA, /* 0B MOVABLE + DMA + HIGHMEM */ > > ZONE_DMA32, /* 0C MOVABLE + DMA32 */ > > ZONE_DMA, /* 0D MOVABLE + DMA + DMA32 */ > > ZONE_DMA32, /* 0E MOVABLE + DMA32 + HIGHMEM */ > > ZONE_DMA /* 0F MOVABLE + DMA32 + HIGHMEM + DMA > > }; > > > > Hmmmm... Guess one would need to add some #ifdeffery here to setup > > ZONE_NORMAL in cases there is no DMA, DMA32 and HIGHMEM. > > > > Indeed, as I said, this is somewhat error prone which is why the patch > calculates the table at run-time instead of compile-time trickery. One would need to define some macros to make it simpler I guess Write something like #ifdef CONFIG_ZONE_DMA #define TZONE_DMA ZONE_DMA #else #define TZONE_DMA ZONE_NORMAL #endif for each configurable item. Then just add the T to the above table. -- 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