[PATCH] shrink struct page
Reduce the size of the pageframe for NR_CPUS>4, CONFIG_PREEMPT back to the
minimal size by unionising both ->private and ->mapping with the pagetable
lock.
It uses an anonymous struct and hence requires gcc-3.x.
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7ff5424..df80e63 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -223,24 +223,27 @@
* & limit reverse map searches.
*/
union {
- unsigned long private; /* Mapping-private opaque data:
- * 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 {
+ unsigned long private; /* Mapping-private opaque data:
+ * 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.
+ * If page mapped as anonymous
+ * memory, low bit is set, and
+ * it points to anon_vma object:
+ * see PAGE_MAPPING_ANON below.
+ */
+ };
#if NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS
- spinlock_t ptl;
+ spinlock_t ptl;
#endif
- } u;
- struct address_space *mapping; /* If low bit clear, points to
- * inode address_space, or NULL.
- * If page mapped as anonymous
- * memory, low bit is set, and
- * it points to anon_vma object:
- * see PAGE_MAPPING_ANON below.
- */
+ };
pgoff_t index; /* Our offset within mapping. */
struct list_head lru; /* Pageout list, eg. active_list
* protected by zone->lru_lock !
@@ -261,8 +264,8 @@
#endif /* WANT_PAGE_VIRTUAL */
};
-#define page_private(page) ((page)->u.private)
-#define set_page_private(page, v) ((page)->u.private = (v))
+#define page_private(page) ((page)->private)
+#define set_page_private(page, v) ((page)->private = (v))
/*
* FIXME: take this include out, include page-flags.h in
@@ -815,7 +818,7 @@
* overflow into the next struct page (as it might with DEBUG_SPINLOCK).
* When freeing, reset page->mapping so free_pages_check won't complain.
*/
-#define __pte_lockptr(page) &((page)->u.ptl)
+#define __pte_lockptr(page) &((page)->ptl)
#define pte_lock_init(_page) do { \
spin_lock_init(__pte_lockptr(_page)); \
} while (0)