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Subject[PATCH] no buddy bitmap patch : intro and includes [0/2]
Hi,

Followings are patches for removing bitmaps from buddy allocator, against 2.6.9-rc3.
I think this version is much clearer than ones I posted a month ago.

The problem I was worried about was how to deal with memmap's holes in a zone.
and I decided to use pfn_valid() simply. Now, there is no messy codes :)

pfn_valid() is used when macro "HOLES_IN_ZONE" is defined.
It is defined only in ia64 now.

Here is kernbench result on my tiger4 (Itanium2 1.3GHz x2, 8 Gbytes memory)

Average Optimal -j 8 Load Run (Perfroming 5 run of make -j 8 on linux-2.6.8 source tree):

Elapsed Time User Time System Time Percent CPU Context Switches Sleeps
2.6.9-rc3 699.906 1322.01 39.336 194 64390 74416.8
no-bitmap 698.334 1321.79 38.58 194.2 64435.4 74622.2

If there is unclear point, please tell me.

Thanks.
Kame <kamezawa.hiroyu@jp.fujitsu.com>

=== patch for include files ===

This patch removes bitmap 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>


---

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
--- test-kernel/include/linux/mm.h~eliminate-bitmap-includes 2004-10-07 17:18:34.062982800 +0900
+++ test-kernel-kamezawa/include/linux/mm.h 2004-10-07 17:18:34.070981584 +0900
@@ -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
--- test-kernel/include/linux/mmzone.h~eliminate-bitmap-includes 2004-10-07 17:18:34.065982344 +0900
+++ test-kernel-kamezawa/include/linux/mmzone.h 2004-10-07 17:18:34.071981432 +0900
@@ -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
--- test-kernel/include/linux/page-flags.h~eliminate-bitmap-includes 2004-10-07 17:18:34.067982040 +0900
+++ test-kernel-kamezawa/include/linux/page-flags.h 2004-10-07 17:18:34.071981432 +0900
@@ -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) \
_

-
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