Messages in this thread Patch in this message | | | From | Mel Gorman <> | Subject | [PATCH 1/1] Only use ARCH_PFN_OFFSET once during boot | Date | Thu, 6 Jul 2006 10:51:03 +0100 (IST) |
| |
The FLATMEM memory model assumes that memory is one contiguous region based at PFN 0 and uses the NODE_DATA(0)->node_mem_map as the global mem_map. As NODE_DATA(0)->node_mem_map may not be PFN 0, architectures optionally define ARCH_PFN_OFFSET as the offset between NODE_DATA(0)->node_mem_map and PFN 0. This offset is used every time page_to_pfn() or pfn_to_page() is called resulting in a small amount of code bloat and overhead.
This patch changes ARCH_PFN_OFFSET so that it is used only once during memory initialisation when working out where mem_map is. This gives a very small reduction in zImage size for architectures using ARCH_PFN_OFFSET. The patch also adds a small amount of documentation on what ARCH_PFN_OFFSET is for.
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
include/asm-generic/memory_model.h | 5 ++--- mm/page_alloc.c | 8 ++++++-- 2 files changed, 8 insertions(+), 5 deletions(-)
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.17-mm6-clean/include/asm-generic/memory_model.h linux-2.6.17-mm6-archpfnoffset_optimise/include/asm-generic/memory_model.h --- linux-2.6.17-mm6-clean/include/asm-generic/memory_model.h 2006-07-05 14:31:17.000000000 +0100 +++ linux-2.6.17-mm6-archpfnoffset_optimise/include/asm-generic/memory_model.h 2006-07-05 14:36:04.000000000 +0100 @@ -28,9 +28,8 @@ */ #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 -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.17-mm6-clean/mm/page_alloc.c linux-2.6.17-mm6-archpfnoffset_optimise/mm/page_alloc.c --- linux-2.6.17-mm6-clean/mm/page_alloc.c 2006-07-05 14:31:18.000000000 +0100 +++ linux-2.6.17-mm6-archpfnoffset_optimise/mm/page_alloc.c 2006-07-05 17:01:01.000000000 +0100 @@ -2157,10 +2157,14 @@ static void __init alloc_node_mem_map(st } #ifdef CONFIG_FLATMEM /* - * With no DISCONTIG, the global mem_map is just set as node 0's + * With FLATMEM, the global mem_map is just set as node 0's. The + * FLATMEM memory model assumes that memory is in one contiguous area + * starting at PFN 0. Architectures that do not start NODE 0 at PFN 0 + * must define ARCH_PFN_OFFSET as the offset between + * NODE_DATA(0)->node_mem_map and PFN 0. */ if (pgdat == NODE_DATA(0)) - mem_map = NODE_DATA(0)->node_mem_map; + mem_map = NODE_DATA(0)->node_mem_map - ARCH_PFN_OFFSET; #endif #endif /* CONFIG_FLAT_NODE_MEM_MAP */ } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |