From: Hiroyuki KAMEZAWA <kamezawa.hiroyu@jp.fujitsu.com>
Followings are patches for removing bitmaps from the buddy allocator. This
is benefical to memory-hot-plug stuffs, because this removes a data
structure which must meet to a host's physical memory layout.
This is one step to manage physical memory in nonlinear / discontiguous way
and will reduce some amounts of codes to implement memory-hot-plug.
This patch removes bitmaps from zone->free_area[] in include/linux/mmzone.h,
and adds some comments on page->private field in include/linux/mm.h.
non-atomic ops for changing PG_private bit is added in include/page-flags.h.
zone->lock is always acquired when PG_private of "a free page" is changed.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/include/linux/mm.h | 2 ++
25-akpm/include/linux/mmzone.h | 1 -
25-akpm/include/linux/page-flags.h | 2 ++
3 files changed, 4 insertions(+), 1 deletion(-)
diff -puN include/linux/mm.h~no-buddy-bitmap-patch-revist-intro-and-includes include/linux/mm.h
--- 25/include/linux/mm.h~no-buddy-bitmap-patch-revist-intro-and-includes Fri Oct 8 14:23:44 2004
+++ 25-akpm/include/linux/mm.h Fri Oct 8 14:23:44 2004
@@ -214,6 +214,8 @@ struct page {
* usually used for buffer_heads
* if PagePrivate set; used for
* swp_entry_t if PageSwapCache
+ * When page is free, this indicates
+ * order in the buddy system.
*/
struct address_space *mapping; /* If low bit clear, points to
* inode address_space, or NULL.
diff -puN include/linux/mmzone.h~no-buddy-bitmap-patch-revist-intro-and-includes include/linux/mmzone.h
--- 25/include/linux/mmzone.h~no-buddy-bitmap-patch-revist-intro-and-includes Fri Oct 8 14:23:44 2004
+++ 25-akpm/include/linux/mmzone.h Fri Oct 8 14:23:44 2004
@@ -22,7 +22,6 @@
struct free_area {
struct list_head free_list;
- unsigned long *map;
};
struct pglist_data;
diff -puN include/linux/page-flags.h~no-buddy-bitmap-patch-revist-intro-and-includes include/linux/page-flags.h
--- 25/include/linux/page-flags.h~no-buddy-bitmap-patch-revist-intro-and-includes Fri Oct 8 14:23:44 2004
+++ 25-akpm/include/linux/page-flags.h Fri Oct 8 14:23:44 2004
@@ -239,6 +239,8 @@ extern unsigned long __read_page_state(u
#define SetPagePrivate(page) set_bit(PG_private, &(page)->flags)
#define ClearPagePrivate(page) clear_bit(PG_private, &(page)->flags)
#define PagePrivate(page) test_bit(PG_private, &(page)->flags)
+#define __SetPagePrivate(page) __set_bit(PG_private, &(page)->flags)
+#define __ClearPagePrivate(page) __clear_bit(PG_private, &(page)->flags)
#define PageWriteback(page) test_bit(PG_writeback, &(page)->flags)
#define SetPageWriteback(page) \
_