[patch 4/4] mm: less atomic ops

Nick Piggin
2006-01-18T10:41:09Z

In the page release paths, we can be sure that nobody will mess with our
page->flags because the refcount has dropped to 0. So no need for atomic
operations here.

Signed-off-by: Nick Piggin <npiggin@suse.de>

Index: linux-2.6/include/linux/page-flags.h
===================================================================
--- linux-2.6.orig/include/linux/page-flags.h
+++ linux-2.6/include/linux/page-flags.h
@@ -247,10 +247,12 @@ extern void __mod_page_state_offset(unsi
#define PageLRU(page) test_bit(PG_lru, &(page)->flags)
#define SetPageLRU(page) set_bit(PG_lru, &(page)->flags)
#define ClearPageLRU(page) clear_bit(PG_lru, &(page)->flags)
+#define __ClearPageLRU(page) __clear_bit(PG_lru, &(page)->flags)

#define PageActive(page) test_bit(PG_active, &(page)->flags)
#define SetPageActive(page) set_bit(PG_active, &(page)->flags)
#define ClearPageActive(page) clear_bit(PG_active, &(page)->flags)
+#define __ClearPageActive(page) __clear_bit(PG_active, &(page)->flags)

#define PageSlab(page) test_bit(PG_slab, &(page)->flags)
#define SetPageSlab(page) set_bit(PG_slab, &(page)->flags)
Index: linux-2.6/mm/swap.c
===================================================================
--- linux-2.6.orig/mm/swap.c
+++ linux-2.6/mm/swap.c
@@ -204,7 +204,7 @@ void fastcall __page_cache_release(struc
struct zone *zone = page_zone(page);
spin_lock_irqsave(&zone->lru_lock, flags);
BUG_ON(!PageLRU(page));
- ClearPageLRU(page);
+ __ClearPageLRU(page);
del_page_from_lru(zone, page);
spin_unlock_irqrestore(&zone->lru_lock, flags);
}
@@ -248,7 +248,7 @@ void release_pages(struct page **pages,
spin_lock_irq(&zone->lru_lock);
}
BUG_ON(!PageLRU(page));
- ClearPageLRU(page);
+ __ClearPageLRU(page);
del_page_from_lru(zone, page);
}

Index: linux-2.6/include/linux/mm_inline.h
===================================================================
--- linux-2.6.orig/include/linux/mm_inline.h
+++ linux-2.6/include/linux/mm_inline.h
@@ -32,7 +32,7 @@ del_page_from_lru(struct zone *zone, str
{
list_del(&page->lru);
if (PageActive(page)) {
- ClearPageActive(page);
+ __ClearPageActive(page);
zone->nr_active--;
} else {
zone->nr_inactive--;