Mel Gorman wrote:
> On (23/06/06 17:06), Franck Bui-Huu didst pronounce:
>> what do you think about this use of ARCH_PFN_OFFSET ?
>>
>
> I believe that arches calling free_area_init_node() directly, but using
> CONFIG_FLAT_NODE_MEM_MAP will have problems with this. There is no
> guarantee that pgdat->node_start_pfn will have any relation to
> ARCH_PFN_OFFSET.
I agree we shouldn't make this assumption.
what about this ?
-- >8 --
[PATCH] flatmem: tiny optimisation when memory do not start at 0
The FLATMEM memory model assumes that memory is in one
contigious area based at pfn 0. Some archictectures, like
ARM, use ARCH_PFN_OFFSET to relax this requirement but it
involves one more operation during page/pfn conversion.
Instead this patch modifies the address of mem_map to make
mem_map[ARCH_PFN_OFFSET] pointing at NODE_DATA(0)->node_mem_map.
The result is a slight gain on kernel code size.
It also relaxes this requirement in two more places:
free_area_init(...)
init_bootmem(...)
---
include/asm-generic/memory_model.h | 6 +++---
mm/bootmem.c | 4 ++--
mm/page_alloc.c | 18 ++++++++++++------
3 files changed, 17 insertions(+), 11 deletions(-)
diff --git a/include/asm-generic/memory_model.h b/include/asm-generic/memory_model.h
index 0cfb086..2faa12f 100644
--- a/include/asm-generic/memory_model.h
+++ b/include/asm-generic/memory_model.h
@@ -34,9 +34,9 @@ #else
*/
#if defined(CONFIG_FLATMEM)
-#define pfn_to_page(pfn) (mem_map + ((pfn) - ARCH_PFN_OFFSET))
-#define page_to_pfn(page) ((unsigned long)((page) - mem_map) + \
- ARCH_PFN_OFFSET)
+#define pfn_to_page(pfn) (mem_map + (pfn))
+#define page_to_pfn(page) ((unsigned long)((page) - mem_map))
+
#elif defined(CONFIG_DISCONTIGMEM)
#define pfn_to_page(pfn) \
diff --git a/mm/bootmem.c b/mm/bootmem.c
index d213fed..fd28eed 100644
--- a/mm/bootmem.c
+++ b/mm/bootmem.c
@@ -377,11 +377,11 @@ unsigned long __init free_all_bootmem_no
return(free_all_bootmem_core(pgdat));
}
-unsigned long __init init_bootmem (unsigned long start, unsigned long pages)
+unsigned long __init init_bootmem(unsigned long start, unsigned long pages)
{
max_low_pfn = pages;
min_low_pfn = start;
- return(init_bootmem_core(NODE_DATA(0), start, 0, pages));
+ return init_bootmem_core(NODE_DATA(0), start, ARCH_PFN_OFFSET, pages);
}
#ifndef CONFIG_HAVE_ARCH_BOOTMEM_NODE
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 253a450..3e97bc3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2118,15 +2118,16 @@ static void __init free_area_init_core(s
static void __init alloc_node_mem_map(struct pglist_data *pgdat)
{
+#ifdef CONFIG_FLAT_NODE_MEM_MAP
+ struct page *map = pgdat->node_mem_map;
+
/* Skip empty nodes */
if (!pgdat->node_spanned_pages)
return;
-#ifdef CONFIG_FLAT_NODE_MEM_MAP
/* ia64 gets its own node_mem_map, before this, without bootmem */
- if (!pgdat->node_mem_map) {
+ if (!map) {
unsigned long size, start, end;
- struct page *map;
/*
* The zone's endpoints aren't required to be MAX_ORDER
@@ -2147,7 +2148,13 @@ #ifdef CONFIG_FLATMEM
* With no DISCONTIG, the global mem_map is just set as node 0's
*/
if (pgdat == NODE_DATA(0))
- mem_map = NODE_DATA(0)->node_mem_map;
+ /*
+ * mem_map is assumed to be based at pfn 0 such that
+ * 'pfn = page* - mem_map' is true. Adjust map
+ * relative to node_mem_map to maintain this
+ * relationship.
+ */
+ mem_map = map - ARCH_PFN_OFFSET;
#endif
#endif /* CONFIG_FLAT_NODE_MEM_MAP */
}
@@ -2174,8 +2181,7 @@ #endif
void __init free_area_init(unsigned long *zones_size)
{
- free_area_init_node(0, NODE_DATA(0), zones_size,
- __pa(PAGE_OFFSET) >> PAGE_SHIFT, NULL);
+ free_area_init_node(0, NODE_DATA(0), zones_size, ARCH_PFN_OFFSET, NULL);
}
#ifdef CONFIG_PROC_FS
--
1.4.0.g64e8
-
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