From: Mel Gorman <mel@csn.ul.ie>
To: Christoph Lameter <cl@linux-foundation.org>
Cc: Linux Memory Management List <linux-mm@kvack.org>,
Pekka Enberg <penberg@cs.helsinki.fi>,
Rik van Riel <riel@redhat.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Nick Piggin <npiggin@suse.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Lin Ming <ming.m.lin@intel.com>,
Zhang Yanmin <yanmin_zhang@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 24/27] Convert gfp_zone() to use a table of precalculated values
Date: Wed, 18 Mar 2009 13:52:23 +0000 [thread overview]
Message-ID: <20090318135222.GA4629@csn.ul.ie> (raw)
In-Reply-To: <alpine.DEB.1.10.0903161500280.20024@qirst.com>
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?
> 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.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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next prev parent reply other threads:[~2009-03-18 13:52 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-16 17:53 [PATCH 00/26] Cleanup and optimise the page allocator V4 Mel Gorman
2009-03-16 17:53 ` [PATCH 01/27] Replace __alloc_pages_internal() with __alloc_pages_nodemask() Mel Gorman
2009-03-16 17:53 ` [PATCH 02/27] Do not sanity check order in the fast path Mel Gorman
2009-03-16 17:53 ` [PATCH 03/27] Do not check NUMA node ID when the caller knows the node is valid Mel Gorman
2009-03-16 17:53 ` [PATCH 04/27] Check only once if the zonelist is suitable for the allocation Mel Gorman
2009-03-16 17:53 ` [PATCH 05/27] Break up the allocator entry point into fast and slow paths Mel Gorman
2009-03-16 19:30 ` Christoph Lameter
2009-03-16 17:53 ` [PATCH 06/27] Move check for disabled anti-fragmentation out of fastpath Mel Gorman
2009-03-16 17:53 ` [PATCH 07/27] Check in advance if the zonelist needs additional filtering Mel Gorman
2009-03-16 17:53 ` [PATCH 08/27] Calculate the preferred zone for allocation only once Mel Gorman
2009-03-16 17:53 ` [PATCH 09/27] Calculate the migratetype " Mel Gorman
2009-03-16 17:53 ` [PATCH 10/27] Calculate the alloc_flags " Mel Gorman
2009-03-16 17:53 ` [PATCH 11/27] Calculate the cold parameter " Mel Gorman
2009-03-16 17:53 ` [PATCH 12/27] Remove a branch by assuming __GFP_HIGH == ALLOC_HIGH Mel Gorman
2009-03-16 17:53 ` [PATCH 13/27] Inline __rmqueue_smallest() Mel Gorman
2009-03-16 18:55 ` Christoph Lameter
2009-03-16 17:53 ` [PATCH 14/27] Inline buffered_rmqueue() Mel Gorman
2009-03-16 17:53 ` [PATCH 15/27] Inline __rmqueue_fallback() Mel Gorman
2009-03-16 17:53 ` [PATCH 16/27] Save text by reducing call sites of __rmqueue() Mel Gorman
2009-03-16 17:53 ` [PATCH 17/27] Do not call get_pageblock_migratetype() more than necessary Mel Gorman
2009-03-16 17:53 ` [PATCH 18/27] Do not disable interrupts in free_page_mlock() Mel Gorman
2009-03-16 18:57 ` Christoph Lameter
2009-03-16 17:53 ` [PATCH 19/27] Do not setup zonelist cache when there is only one node Mel Gorman
2009-03-16 17:53 ` [PATCH 20/27] Use a pre-calculated value for num_online_nodes() Mel Gorman
2009-03-16 17:53 ` [PATCH 21/27] Do not check for compound pages during the page allocator sanity checks Mel Gorman
2009-03-16 17:53 ` [PATCH 22/27] Use allocation flags as an index to the zone watermark Mel Gorman
2009-03-16 17:53 ` [PATCH 23/27] Update NR_FREE_PAGES only as necessary Mel Gorman
2009-03-16 17:53 ` [PATCH 24/27] Convert gfp_zone() to use a table of precalculated values Mel Gorman
2009-03-16 19:12 ` Christoph Lameter
2009-03-18 13:52 ` Mel Gorman [this message]
2009-03-18 14:15 ` Christoph Lameter
2009-03-18 15:35 ` Mel Gorman
2009-03-18 17:21 ` Christoph Lameter
2009-03-18 18:17 ` Mel Gorman
2009-03-18 19:07 ` Christoph Lameter
2009-03-18 19:46 ` Mel Gorman
2009-03-19 0:04 ` KAMEZAWA Hiroyuki
2009-03-19 15:05 ` Christoph Lameter
2009-03-19 16:53 ` Christoph Lameter
2009-03-19 18:11 ` Mel Gorman
2009-03-19 18:15 ` Christoph Lameter
2009-03-19 18:37 ` Christoph Lameter
2009-03-16 17:53 ` [PATCH 25/27] Re-sort GFP flags and fix whitespace alignment for easier reading Mel Gorman
2009-03-16 17:53 ` [PATCH 26/27] Get the pageblock migratetype without disabling interrupts Mel Gorman
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