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From: Andriy Gapon <avg@FreeBSD.org>
Date: Wed, 23 May 2012 12:51:49 +0000 (UTC)
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Subject: svn commit: r235829 - head/sys/vm
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Author: avg
Date: Wed May 23 12:51:49 2012
New Revision: 235829
URL: http://svn.freebsd.org/changeset/base/235829

Log:
  vm_pager_object_lookup: small performance optimization
  
  do not needlessly lock an object if its handle doesn't match
  
  Reviewed by:	kib, alc
  MFC after:	1 week

Modified:
  head/sys/vm/vm_pager.c

Modified: head/sys/vm/vm_pager.c
==============================================================================
--- head/sys/vm/vm_pager.c	Wed May 23 11:26:28 2012	(r235828)
+++ head/sys/vm/vm_pager.c	Wed May 23 12:51:49 2012	(r235829)
@@ -271,14 +271,15 @@ vm_pager_object_lookup(struct pagerlst *
 	vm_object_t object;
 
 	TAILQ_FOREACH(object, pg_list, pager_object_list) {
-		VM_OBJECT_LOCK(object);
-		if (object->handle == handle &&
-		    (object->flags & OBJ_DEAD) == 0) {
-			vm_object_reference_locked(object);
+		if (object->handle == handle) {
+			VM_OBJECT_LOCK(object);
+			if ((object->flags & OBJ_DEAD) == 0) {
+				vm_object_reference_locked(object);
+				VM_OBJECT_UNLOCK(object);
+				break;
+			}
 			VM_OBJECT_UNLOCK(object);
-			break;
 		}
-		VM_OBJECT_UNLOCK(object);
 	}
 	return (object);
 }