While splitting flags and pqflags might have been a good idea in theory

to separate locking, on most modern machines this is not enough
since operations on short types touch other short types that share the
same word in memory.

Merge pg_flags and pqflags again and now use atomic operations to change
the flags. Also bump wire_count to an int and pg_version might go
int as well, just for alignment.

tested by many, many. ok miod@

1 files changed, 28 insertions, 36 deletions

diff --git a/sys/uvm/uvm_page.h b/sys/uvm/uvm_page.h
index 9cce3418574..f0774112c6e 100644
--- a/sys/uvm/uvm_page.h
+++ b/sys/uvm/uvm_page.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_page.h,v 1.23 2007/04/04 17:44:45 art Exp $	*/
+/*	$OpenBSD: uvm_page.h,v 1.24 2007/04/13 18:57:49 art Exp $	*/
 /*	$NetBSD: uvm_page.h,v 1.19 2000/12/28 08:24:55 chs Exp $	*/
 
 /* 
@@ -103,18 +103,6 @@
  *	queues (P) [or both].
  */
 
-/*
- * locking note: the mach version of this data structure had bit
- * fields for the flags, and the bit fields were divided into two
- * items (depending on who locked what).  some time, in BSD, the bit
- * fields were dumped and all the flags were lumped into one short.
- * that is fine for a single threaded uniprocessor OS, but bad if you
- * want to actual make use of locking (simple_lock's).  so, we've
- * separated things back out again.
- *
- * note the page structure has no lock of its own.
- */
-
 #include <uvm/uvm_extern.h>
 #include <uvm/uvm_pglist.h>
 
@@ -128,10 +116,11 @@ struct vm_page {
 	struct uvm_object	*uobject;	/* object (O,P) */
 	voff_t			offset;		/* offset into object (O,P) */
 
-	u_short			pg_flags;	/* object flags [O] */
-	u_short			pg_version;	/* version count [O] */
-	u_short			wire_count;	/* wired down map refs [P] */
-	u_short			pqflags;	/* page queue flags [P] */
+	u_int			pg_flags;	/* object flags [O or P] */
+
+	u_int			pg_version;	/* version count [O] */
+	u_int			wire_count;	/* wired down map refs [P] */
+
 	u_int			loan_count;	/* number of active loans
 						 * to read: [O or P]
 						 * to modify: [O _and_ P] */
@@ -158,33 +147,36 @@ struct vm_page {
  *   PG_ ==> locked by object lock
  *   PQ_ ==> lock by page queue lock 
  *   PQ_FREE is locked by free queue lock and is mutex with all other PQs
+ *   pg_flags may only be changed using the atomic operations.
  *
  * PG_ZERO is used to indicate that a page has been pre-zero'd.  This flag
  * is only set when the page is on no queues, and is cleared when the page
  * is placed on the free list.
  */
 
-#define	PG_BUSY		0x0001		/* page is locked */
-#define	PG_WANTED	0x0002		/* someone is waiting for page */
-#define	PG_TABLED	0x0004		/* page is in VP table  */
-#define	PG_CLEAN	0x0008		/* page has not been modified */
-#define PG_CLEANCHK	0x0010		/* clean bit has been checked */
-#define PG_RELEASED	0x0020		/* page released while paging */
-#define	PG_FAKE		0x0040		/* page is not yet initialized */
-#define PG_RDONLY	0x0080		/* page must be mapped read-only */
-#define PG_ZERO		0x0100		/* page is pre-zero'd */
-
-#define PG_PAGER1	0x1000		/* pager-specific flag */
-
-#define PQ_FREE		0x0001		/* page is on free list */
-#define PQ_INACTIVE	0x0002		/* page is in inactive list */
-#define PQ_ACTIVE	0x0004		/* page is in active list */
-#define PQ_ANON		0x0010		/* page is part of an anon, rather
+#define	PG_BUSY		0x00000001	/* page is locked */
+#define	PG_WANTED	0x00000002	/* someone is waiting for page */
+#define	PG_TABLED	0x00000004	/* page is in VP table  */
+#define	PG_CLEAN	0x00000008	/* page has not been modified */
+#define PG_CLEANCHK	0x00000010	/* clean bit has been checked */
+#define PG_RELEASED	0x00000020	/* page released while paging */
+#define	PG_FAKE		0x00000040	/* page is not yet initialized */
+#define PG_RDONLY	0x00000080	/* page must be mapped read-only */
+#define PG_ZERO		0x00000100	/* page is pre-zero'd */
+
+#define PG_PAGER1	0x00001000	/* pager-specific flag */
+#define PG_MASK		0x0000ffff
+
+#define PQ_FREE		0x00010000	/* page is on free list */
+#define PQ_INACTIVE	0x00020000	/* page is in inactive list */
+#define PQ_ACTIVE	0x00040000	/* page is in active list */
+#define PQ_ANON		0x00100000	/* page is part of an anon, rather
 					   than an uvm_object */
-#define PQ_AOBJ		0x0020		/* page is part of an anonymous
+#define PQ_AOBJ		0x00200000	/* page is part of an anonymous
 					   uvm_object */
 #define PQ_SWAPBACKED	(PQ_ANON|PQ_AOBJ)
-#define	PQ_ENCRYPT	0x0040		/* page needs {en,de}cryption */
+#define	PQ_ENCRYPT	0x00400000	/* page needs {en,de}cryption */
+#define PQ_MASK		0xffff0000
 
 /*
  * physical memory layout structure
@@ -409,7 +401,7 @@ PHYS_TO_VM_PAGE(pa)
 	return(NULL);
 }
 
-#define VM_PAGE_IS_FREE(entry)  ((entry)->pqflags & PQ_FREE)
+#define VM_PAGE_IS_FREE(entry)  ((entry)->pg_flags & PQ_FREE)
 
 #endif /* _KERNEL */