[RFC] free_area[] bitmap elimination [1/3]

[RFC] free_area[] bitmap elimination [1/3]

[Hiroyuki KAMEZAWA]

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This patch removes bitmap initialization.


-- 
--the clue is these footmarks leading to the door.--
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>



[-- Attachment #2: eliminate-bitmap-p02.patch --]
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Remove bitmap initialization in free_area_init_core()


---

 linux-2.6.8.1-kame-kamezawa/mm/page_alloc.c |   36 ----------------------------
 1 files changed, 1 insertion(+), 35 deletions(-)

diff -puN mm/page_alloc.c~eliminate-bitmap-p02 mm/page_alloc.c
--- linux-2.6.8.1-kame/mm/page_alloc.c~eliminate-bitmap-p02	2004-08-21 08:53:20.026423144 +0900
+++ linux-2.6.8.1-kame-kamezawa/mm/page_alloc.c	2004-08-21 08:53:20.033422080 +0900
@@ -1514,42 +1514,8 @@ static void __init free_area_init_core(s
 		zone_start_pfn += size;
 		lmem_map += size;
 
-		for (i = 0; ; i++) {
-			unsigned long bitmap_size;
-
+		for (i = 0; i < MAX_ORDER ; i++) {
 			INIT_LIST_HEAD(&zone->free_area[i].free_list);
-			if (i == MAX_ORDER-1) {
-				zone->free_area[i].map = NULL;
-				break;
-			}
-
-			/*
-			 * Page buddy system uses "index >> (i+1)",
-			 * where "index" is at most "size-1".
-			 *
-			 * The extra "+3" is to round down to byte
-			 * size (8 bits per byte assumption). Thus
-			 * we get "(size-1) >> (i+4)" as the last byte
-			 * we can access.
-			 *
-			 * The "+1" is because we want to round the
-			 * byte allocation up rather than down. So
-			 * we should have had a "+7" before we shifted
-			 * down by three. Also, we have to add one as
-			 * we actually _use_ the last bit (it's [0,n]
-			 * inclusive, not [0,n[).
-			 *
-			 * So we actually had +7+1 before we shift
-			 * down by 3. But (n+8) >> 3 == (n >> 3) + 1
-			 * (modulo overflows, which we do not have).
-			 *
-			 * Finally, we LONG_ALIGN because all bitmap
-			 * operations are on longs.
-			 */
-			bitmap_size = (size-1) >> (i+4);
-			bitmap_size = LONG_ALIGN(bitmap_size+1);
-			zone->free_area[i].map = 
-			  (unsigned long *) alloc_bootmem_node(pgdat, bitmap_size);
 		}
 	}
 }

_