no buddy bitmap patch revist : intro and includes [0/2]

Hi

Followings are patches for removing bitmaps from the buddy allocator, against 2.6.9-rc3.
This is benefical to memory-hot-plug stuffs, because this removes a data structure which must meet to a host's physical memory layout.

Difference from one I posted yesterday is using CONFIG_HOLES_IN_ZONE instead of HOLES_IN_ZONE and some fixes on comments.

This patch removes bitmaps in zone->free_area[] used in the buddy system. Instead of using bitmaps, this patch records a free page's order in a page struct itself using page->private field.

I removed "#define HOLES_IN_ZONE in asm/page.h" and added CONFIG_HOLES_IN_ZONE to Kconfig. An architecuture which has memory holes in a zone has to set this CONFIG. As far as I know, only ia64 with virtual memmap has to set this now.

In my performance test on ia64 SMP, there is no performance influence of this patch.

Kame <[email protected]> ============= patches for include files ==================

This patch set removes bitmaps from the page allocator.

Purpose:
This is one step to manage physical memory in nonlinear / discontiguous way and will reduce some amounts of codes to implement memory-hot-plug.

About this part:
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.

---

 test-kernel-kamezawa/include/linux/mm.h         |    2 ++
 test-kernel-kamezawa/include/linux/mmzone.h     |    1 -
 test-kernel-kamezawa/include/linux/page-flags.h |    2 ++
 3 files changed, 4 insertions(+), 1 deletion(-)

diff -puN include/linux/mm.h~eliminate-bitmap-includes include/linux/mm.h
@@ -209,6 +209,8 @@ 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~eliminate-bitmap-includes include/linux/mmzone.h
@@ -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~eliminate-bitmap-includes include/linux/page-flags.h
@@ -238,6 +238,8 @@ 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)						\

_

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to [email protected]. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"[email protected]"> [email protected] </a>