Customize ObjectCache for more efficient locking in removeExpiredObjectsInCache

components/resource/objectcache.cpp

@@ -11,13 +11,10 @@
  * OpenSceneGraph Public License for more details.
 */
 
-#include <osg/Version>
-
-#if OSG_VERSION_LESS_THAN(3,3,3)
-
 #include "objectcache.hpp"
 
-using namespace osgDB;
+namespace Resource
+{
 
 ////////////////////////////////////////////////////////////////////////////////////////////
 //
@@ -95,21 +92,29 @@ void ObjectCache::updateTimeStampOfObjectsInCacheWithExternalReferences(double r
 
 void ObjectCache::removeExpiredObjectsInCache(double expiryTime)
 {
-    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_objectCacheMutex);
+    std::vector<osg::ref_ptr<osg::Object> > objectsToRemove;
 
-    // Remove expired entries from object cache
-    ObjectCacheMap::iterator oitr = _objectCache.begin();
-    while(oitr != _objectCache.end())
     {
-        if (oitr->second.second<=expiryTime)
-        {
-            _objectCache.erase(oitr++);
-        }
-        else
+        OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_objectCacheMutex);
+
+        // Remove expired entries from object cache
+        ObjectCacheMap::iterator oitr = _objectCache.begin();
+        while(oitr != _objectCache.end())
         {
-            ++oitr;
+            if (oitr->second.second<=expiryTime)
+            {
+                objectsToRemove.push_back(oitr->second.first);
+                _objectCache.erase(oitr++);
+            }
+            else
+            {
+                ++oitr;
+            }
         }
     }
+
+    // note, actual unref happens outside of the lock
+    objectsToRemove.clear();
 }
 
 void ObjectCache::removeFromObjectCache(const std::string& fileName)
@@ -138,4 +143,4 @@ void ObjectCache::releaseGLObjects(osg::State* state)
     }
 }
 
-#endif
+}

components/resource/objectcache.hpp

@@ -1,3 +1,6 @@
+// Resource ObjectCache for OpenMW, forked from osgDB ObjectCache by Robert Osfield, see copyright notice below.
+// The main change from the upstream version is that removeExpiredObjectsInCache no longer keeps a lock while the unref happens.
+
 /* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield
  *
  * This library is open source and may be redistributed and/or modified under
@@ -11,17 +14,8 @@
  * OpenSceneGraph Public License for more details.
 */
 
-// Wrapper for osgDB/ObjectCache. Works around ObjectCache not being available in old OSG 3.2.
-// Use "#include objectcache.hpp" in place of "#include <osgDB/ObjectCache".
-
-#ifndef OSGDB_OBJECTCACHE_WRAPPER
-#define OSGDB_OBJECTCACHE_WRAPPER 1
-
-#include <osg/Version>
-
-#if OSG_VERSION_GREATER_OR_EQUAL(3,3,3)
-#include <osgDB/ObjectCache>
-#else
+#ifndef OPENMW_COMPONENTS_RESOURCE_OBJECTCACHE
+#define OPENMW_COMPONENTS_RESOURCE_OBJECTCACHE
 
 #include <osg/Node>
 
@@ -30,9 +24,9 @@
 
 #include <map>
 
-namespace osgDB {
+namespace Resource {
 
-class /*OSGDB_EXPORT*/ ObjectCache : public osg::Referenced
+class ObjectCache : public osg::Referenced
 {
     public:
 
@@ -70,7 +64,7 @@ class /*OSGDB_EXPORT*/ ObjectCache : public osg::Referenced
         /** Get an ref_ptr<Object> from the object cache*/
         osg::ref_ptr<osg::Object> getRefFromObjectCache(const std::string& fileName);
 
-        /** call rleaseGLObjects on all objects attached to the object cache.*/
+        /** call releaseGLObjects on all objects attached to the object cache.*/
         void releaseGLObjects(osg::State* state);
 
     protected:
@@ -88,5 +82,3 @@ class /*OSGDB_EXPORT*/ ObjectCache : public osg::Referenced
 }
 
 #endif
-
-#endif

components/resource/resourcemanager.cpp

@@ -7,7 +7,7 @@ namespace Resource
 
     ResourceManager::ResourceManager(const VFS::Manager *vfs, const double expiryDelay)
         : mVFS(vfs)
-        , mCache(new osgDB::ObjectCache)
+        , mCache(new Resource::ObjectCache)
         , mExpiryDelay(expiryDelay)
     {
 

components/resource/resourcemanager.hpp

@@ -8,13 +8,9 @@ namespace VFS
     class Manager;
 }
 
-namespace osgDB
-{
-    class ObjectCache;
-}
-
 namespace Resource
 {
+    class ObjectCache;
 
     /// @brief Base class for managers that require a virtual file system and object cache.
     /// @par This base class implements clearing of the cache, but populating it and what it's used for is up to the individual sub classes.
@@ -34,7 +30,7 @@ namespace Resource
 
     protected:
         const VFS::Manager* mVFS;
-        osg::ref_ptr<osgDB::ObjectCache> mCache;
+        osg::ref_ptr<Resource::ObjectCache> mCache;
         double mExpiryDelay;
     };
 

components/resource/resourcesystem.cpp

@@ -54,7 +54,6 @@ namespace Resource
 
     void ResourceSystem::updateCache(double referenceTime)
     {
-        // TODO: change ObjectCache to not hold lock while the unref happens
         for (std::vector<ResourceManager*>::iterator it = mResourceManagers.begin(); it != mResourceManagers.end(); ++it)
             (*it)->updateCache(referenceTime);
     }