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From: Christoph Lameter <clameter@sgi.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: apw@shadowen.org
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: linux-mm@kvack.org
Subject: [rfc 06/10] Sparsemem: Vmemmap does not need section bits
Date: Mon, 03 Mar 2008 16:04:58 -0800	[thread overview]
Message-ID: <20080304000733.487348652@sgi.com> (raw)
In-Reply-To: <20080304000452.514878384@sgi.com>

[-- Attachment #1: sparsemem_vmemmap_does_not_need_section_flags --]
[-- Type: text/plain, Size: 1619 bytes --]

Sparsemem vmemmap does not need any section bits. This patch has
the effect of reducing the number of bits used in page->flags
by at least 6.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
 include/linux/mm.h |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

Index: linux-2.6/include/linux/mm.h
===================================================================
--- linux-2.6.orig/include/linux/mm.h	2008-03-03 15:45:07.047305876 -0800
+++ linux-2.6/include/linux/mm.h	2008-03-03 15:49:04.686432973 -0800
@@ -390,11 +390,11 @@ static inline void set_compound_order(st
  * we have run out of space and have to fall back to an
  * alternate (slower) way of determining the node.
  *
- *        No sparsemem: |       NODE     | ZONE | ... | FLAGS |
- * with space for node: | SECTION | NODE | ZONE | ... | FLAGS |
- *   no space for node: | SECTION |     ZONE    | ... | FLAGS |
+ * No sparsemem or sparsemem vmemmap: |       NODE     | ZONE | ... | FLAGS |
+ * classic sparse with space for node:| SECTION | NODE | ZONE | ... | FLAGS |
+ * classic sparse no space for node:  | SECTION |     ZONE    | ... | FLAGS |
  */
-#ifdef CONFIG_SPARSEMEM
+#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
 #define SECTIONS_WIDTH		SECTIONS_SHIFT
 #else
 #define SECTIONS_WIDTH		0
@@ -405,6 +405,9 @@ static inline void set_compound_order(st
 #if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= FLAGS_RESERVED
 #define NODES_WIDTH		NODES_SHIFT
 #else
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+#error "Vmemmap: No space for nodes field in page flags"
+#endif
 #define NODES_WIDTH		0
 #endif
 

-- 

  parent reply	other threads:[~2008-03-04  0:09 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-04  0:04 [rfc 00/10] [Patch] Page flags: Cleanup, reorg and introduce 5 new flags Christoph Lameter
2008-03-04  0:04 ` [rfc 01/10] Pageflags: Use an enum for the flags Christoph Lameter
2008-03-04  0:04 ` [rfc 02/10] Pageflags: Introduce macros to generate page flag functions Christoph Lameter
2008-03-04  0:04 ` [rfc 03/10] Pageflags: Convert to the use of new macros Christoph Lameter
2008-03-04  0:04 ` [rfc 04/10] Pageflags: Use proper page flag functions in Xen Christoph Lameter
2008-03-04  0:04 ` [rfc 05/10] Pageflags: Eliminate PG_xxx aliases Christoph Lameter
2008-03-04  0:04 ` Christoph Lameter [this message]
2008-03-04  0:04 ` [rfc 07/10] Kbuild: Create a way to create preprocessor constants from C expressions Christoph Lameter
2008-03-04  0:05 ` [rfc 08/10] Pageflags: Get rid of FLAGS_RESERVED Christoph Lameter
2008-03-04  0:05 ` [rfc 09/10] Get rid of __ZONE_COUNT Christoph Lameter
2008-03-04  0:05 ` [rfc 10/10] Pageflags: Land grab Christoph Lameter
2008-03-04  1:27   ` Andi Kleen
2008-03-04  5:38     ` Christoph Lameter

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