Sat Jan 28 14:37:35 2012 UTC ()

Describe UVM object and explain lock sharing a little.


(rmind)

diff -r1.31 -r1.32 src/sys/uvm/uvm_object.h

--- src/sys/uvm/uvm_object.h 2011/06/12 03:36:03	1.31
+++ src/sys/uvm/uvm_object.h 2012/01/28 14:37:35	1.32

 @@ -1,14 +1,14 @@
-/*	$NetBSD: uvm_object.h,v 1.31 2011/06/12 03:36:03 rmind Exp $	*/
+/*	$NetBSD: uvm_object.h,v 1.32 2012/01/28 14:37:35 rmind Exp $	*/
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
  * All rights reserved.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
 @@ -20,36 +20,44 @@
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
  * from: Id: uvm_object.h,v 1.1.2.2 1998/01/04 22:44:51 chuck Exp
  */
 #ifndef _UVM_UVM_OBJECT_H_
 #define _UVM_UVM_OBJECT_H_
 /*
  * uvm_object.h
  */
 #include <sys/queue.h>
 #include <sys/rbtree.h>
 #include <uvm/uvm_pglist.h>
 /*
- * uvm_object: all that is left of mach objects.
+ * The UVM memory object interface.  Notes:
+ *
  * A UVM memory object represents a list of pages, which are managed by
  * the object's pager operations (uvm_object::pgops).  All pages belonging
  * to an object are owned by it and thus protected by the object lock.
+ *
  * The lock (uvm_object::vmobjlock) may be shared amongst the UVM objects.
  * By default, the lock is allocated dynamically using mutex_obj(9) cache.
  * Lock sharing is normally used when there is an underlying object.  For
  * example, vnode representing a file may have an underlying node, which
  * is the case for tmpfs and layered file systems.  In such case, vnode's
  * UVM object and the underlying UVM object shares the lock (note that the
  * vnode_t::v_interlock points to uvm_object::vmobjlock).
  */
 struct uvm_object {
 	kmutex_t *		vmobjlock;	/* lock on memq */
 	const struct uvm_pagerops *pgops;	/* pager ops */
 	struct pglist		memq;		/* pages in this object */
 	int			uo_npages;	/* # of pages in memq */
 	unsigned		uo_refs;	/* reference count */
 	struct rb_tree		rb_tree;	/* tree of pages */
 	LIST_HEAD(,ubc_map)	uo_ubc;		/* ubc mappings */
 };
 /*