diff --git a/panda/src/display/graphicsEngine.cxx b/panda/src/display/graphicsEngine.cxx
index 7b483eafd7..232cc296f6 100644
--- a/panda/src/display/graphicsEngine.cxx
+++ b/panda/src/display/graphicsEngine.cxx
@@ -45,6 +45,7 @@
 #include "geomVertexArrayData.h"
 #include "vertexDataSaveFile.h"
 #include "vertexDataBook.h"
+#include "vertexDataPage.h"
 #include "config_pgraph.h"
 
 #if defined(WIN32)
@@ -82,6 +83,7 @@ PStatCollector GraphicsEngine::_delete_pcollector("App:Delete");
 PStatCollector GraphicsEngine::_sw_sprites_pcollector("SW Sprites");
 PStatCollector GraphicsEngine::_vertex_data_small_pcollector("Vertex Data:Small");
 PStatCollector GraphicsEngine::_vertex_data_independent_pcollector("Vertex Data:Independent");
+PStatCollector GraphicsEngine::_vertex_data_pending_pcollector("Vertex Data:Pending");
 PStatCollector GraphicsEngine::_vertex_data_resident_pcollector("Vertex Data:Resident");
 PStatCollector GraphicsEngine::_vertex_data_compressed_pcollector("Vertex Data:Compressed");
 PStatCollector GraphicsEngine::_vertex_data_unused_disk_pcollector("Vertex Data:Disk:Unused");
@@ -501,6 +503,9 @@ remove_all_windows() {
   // any) has been flushed to disk.
   BamCache *cache = BamCache::get_global_ptr();
   cache->flush_index();
+
+  // And, hey, let's stop the vertex paging thread, if any.
+  VertexDataPage::stop_thread();
 }
 
 ////////////////////////////////////////////////////////////////////
@@ -758,6 +763,7 @@ render_frame() {
     size_t independent = GeomVertexArrayData::get_independent_lru()->get_total_size();
     size_t resident = VertexDataPage::get_global_lru(VertexDataPage::RC_resident)->get_total_size();
     size_t compressed = VertexDataPage::get_global_lru(VertexDataPage::RC_compressed)->get_total_size();
+    size_t pending = VertexDataPage::get_pending_lru()->get_total_size();
 
     VertexDataSaveFile *save_file = VertexDataPage::get_save_file();
     size_t total_disk = save_file->get_total_file_size();
@@ -765,6 +771,7 @@ render_frame() {
 
     _vertex_data_small_pcollector.set_level(small_buf);
     _vertex_data_independent_pcollector.set_level(independent);
+    _vertex_data_pending_pcollector.set_level(pending);
     _vertex_data_resident_pcollector.set_level(resident);
     _vertex_data_compressed_pcollector.set_level(compressed);
     _vertex_data_unused_disk_pcollector.set_level(total_disk - used_disk);
diff --git a/panda/src/display/graphicsEngine.h b/panda/src/display/graphicsEngine.h
index 4291fe3bd6..9b0e1d2ecb 100644
--- a/panda/src/display/graphicsEngine.h
+++ b/panda/src/display/graphicsEngine.h
@@ -362,6 +362,7 @@ private:
   static PStatCollector _sw_sprites_pcollector;
   static PStatCollector _vertex_data_small_pcollector;
   static PStatCollector _vertex_data_independent_pcollector;
+  static PStatCollector _vertex_data_pending_pcollector;
   static PStatCollector _vertex_data_resident_pcollector;
   static PStatCollector _vertex_data_compressed_pcollector;
   static PStatCollector _vertex_data_used_disk_pcollector;
diff --git a/panda/src/gobj/config_gobj.cxx b/panda/src/gobj/config_gobj.cxx
index ab338eb56f..bd23a8ce1c 100644
--- a/panda/src/gobj/config_gobj.cxx
+++ b/panda/src/gobj/config_gobj.cxx
@@ -307,9 +307,16 @@ ConfigVariableBool vertex_data_allow_reread
           "data to the page file, but it requires that bam files are not "
           "modified during program execution.  Set it false to prevent "
           "this, so that the vertex data will need to be written to a "
-          "page file when it is evicted."));
-
+          "page file when it is evicted.  Note that this is not fully "
+          "compatible with vertex-data-threaded-paging."));
 
+ConfigVariableBool vertex_data_threaded_paging
+("vertex-data-threaded-paging", true,
+ PRC_DESC("When this is true (and Panda has been compiled with thread "
+          "support) then a sub-thread will be spawned to evict vertex pages "
+          "to disk and read them back again.  When this is false, this "
+          "work will be done in the main thread, which may introduce "
+          "occasional random chugs in rendering."));
 
 ConfigureFn(config_gobj) {
   BufferContext::init_type();
diff --git a/panda/src/gobj/config_gobj.h b/panda/src/gobj/config_gobj.h
index a209ee2465..68065d974f 100644
--- a/panda/src/gobj/config_gobj.h
+++ b/panda/src/gobj/config_gobj.h
@@ -75,6 +75,7 @@ extern EXPCL_PANDA ConfigVariableFilename vertex_save_file_directory;
 extern EXPCL_PANDA ConfigVariableString vertex_save_file_prefix;
 extern EXPCL_PANDA ConfigVariableInt vertex_data_small_size;
 extern EXPCL_PANDA ConfigVariableBool vertex_data_allow_reread;
+extern EXPCL_PANDA ConfigVariableBool vertex_data_threaded_paging;
 
 #endif
 
diff --git a/panda/src/gobj/geomVertexArrayData.I b/panda/src/gobj/geomVertexArrayData.I
index 278cd57cde..4f1ce01493 100644
--- a/panda/src/gobj/geomVertexArrayData.I
+++ b/panda/src/gobj/geomVertexArrayData.I
@@ -369,12 +369,18 @@ get_object() {
 //     Function: GeomVertexArrayDataHandle::get_read_pointer
 //       Access: Public
 //  Description: Returns a readable pointer to the beginning of the
-//               actual data stream.
+//               actual data stream, or NULL if the data is not
+//               currently resident.  If the data is not currently
+//               resident, this will implicitly request it to become
+//               resident soon.
+//
+//               If force is true, this method will never return NULL,
+//               but may block until the data is available.
 ////////////////////////////////////////////////////////////////////
 INLINE const unsigned char *GeomVertexArrayDataHandle::
-get_read_pointer() const {
+get_read_pointer(bool force) const {
   check_resident();
-  return _cdata->_buffer.get_read_pointer();
+  return _cdata->_buffer.get_read_pointer(force);
 }
 
 ////////////////////////////////////////////////////////////////////
@@ -448,7 +454,7 @@ get_modified() const {
 INLINE string GeomVertexArrayDataHandle::
 get_data() const {
   check_resident();
-  return string((const char *)_cdata->_buffer.get_read_pointer(), _cdata->_buffer.get_size());
+  return string((const char *)_cdata->_buffer.get_read_pointer(true), _cdata->_buffer.get_size());
 }
 
 ////////////////////////////////////////////////////////////////////
@@ -464,7 +470,7 @@ get_subdata(size_t start, size_t size) const {
   check_resident();
   start = min(start, _cdata->_buffer.get_size());
   size = min(size, _cdata->_buffer.get_size() - start);
-  return string((const char *)_cdata->_buffer.get_read_pointer() + start, size);
+  return string((const char *)_cdata->_buffer.get_read_pointer(true) + start, size);
 }
 
 ////////////////////////////////////////////////////////////////////
diff --git a/panda/src/gobj/geomVertexArrayData.cxx b/panda/src/gobj/geomVertexArrayData.cxx
index 1325c4b8e7..ff188bab0d 100644
--- a/panda/src/gobj/geomVertexArrayData.cxx
+++ b/panda/src/gobj/geomVertexArrayData.cxx
@@ -43,8 +43,8 @@ ConfigVariableInt vertex_data_page_size
           "This also controls the page size that is compressed and written "
           "to disk when vertex data pages are evicted from memory."));
 
-SimpleLru GeomVertexArrayData::_independent_lru(max_independent_vertex_data);
-SimpleLru GeomVertexArrayData::_small_lru(max_independent_vertex_data);
+SimpleLru GeomVertexArrayData::_independent_lru("independent", max_independent_vertex_data);
+SimpleLru GeomVertexArrayData::_small_lru("small", max_independent_vertex_data);
 
 VertexDataBook GeomVertexArrayData::_book(vertex_data_page_size);
 
@@ -493,7 +493,7 @@ finalize(BamReader *manager) {
   if (_endian_reversed) {
     // Now is the time to endian-reverse the data.
     VertexDataBuffer new_buffer(cdata->_buffer.get_size());
-    reverse_data_endianness(new_buffer.get_write_pointer(), cdata->_buffer.get_read_pointer(), cdata->_buffer.get_size());
+    reverse_data_endianness(new_buffer.get_write_pointer(), cdata->_buffer.get_read_pointer(true), cdata->_buffer.get_size());
     cdata->_buffer.swap(new_buffer);
   }
 
@@ -570,12 +570,12 @@ write_datagram(BamWriter *manager, Datagram &dg, void *extra_data) const {
 
   if (manager->get_file_endian() == BE_native) {
     // For native endianness, we only have to write the data directly.
-    dg.append_data(_buffer.get_read_pointer(), _buffer.get_size());
+    dg.append_data(_buffer.get_read_pointer(true), _buffer.get_size());
 
   } else {
     // Otherwise, we have to convert it.
     unsigned char *new_data = (unsigned char *)alloca(_buffer.get_size());
-    array_data->reverse_data_endianness(new_data, _buffer.get_read_pointer(), _buffer.get_size());
+    array_data->reverse_data_endianness(new_data, _buffer.get_read_pointer(true), _buffer.get_size());
     dg.append_data(new_data, _buffer.get_size());
   }
 }
@@ -628,7 +628,7 @@ fillin(DatagramIterator &scan, BamReader *manager, void *extra_data) {
       // it immediately (and we should, to support threaded CData
       // updates).
       VertexDataBuffer new_buffer(_buffer.get_size());
-      array_data->reverse_data_endianness(new_buffer.get_write_pointer(), _buffer.get_read_pointer(), _buffer.get_size());
+      array_data->reverse_data_endianness(new_buffer.get_write_pointer(), _buffer.get_read_pointer(true), _buffer.get_size());
       _buffer.swap(new_buffer);
     }
   }
@@ -729,7 +729,7 @@ copy_data_from(const GeomVertexArrayDataHandle *other) {
 
   _cdata->_buffer.unclean_realloc(other->_cdata->_buffer.get_size());
   memcpy(_cdata->_buffer.get_write_pointer(),
-         other->_cdata->_buffer.get_read_pointer(),
+         other->_cdata->_buffer.get_read_pointer(true),
          other->_cdata->_buffer.get_size());
 
   _cdata->_modified = Geom::get_next_modified();
diff --git a/panda/src/gobj/geomVertexArrayData.h b/panda/src/gobj/geomVertexArrayData.h
index 270bfdf673..56c9e5829b 100644
--- a/panda/src/gobj/geomVertexArrayData.h
+++ b/panda/src/gobj/geomVertexArrayData.h
@@ -258,7 +258,7 @@ public:
   INLINE const GeomVertexArrayData *get_object() const;
   INLINE GeomVertexArrayData *get_object();
 
-  INLINE const unsigned char *get_read_pointer() const;
+  INLINE const unsigned char *get_read_pointer(bool force = true) const;
   unsigned char *get_write_pointer();
 
 PUBLISHED:
diff --git a/panda/src/gobj/simpleLru.I b/panda/src/gobj/simpleLru.I
index 44b04bbbcd..d5145f861c 100644
--- a/panda/src/gobj/simpleLru.I
+++ b/panda/src/gobj/simpleLru.I
@@ -25,6 +25,7 @@
 ////////////////////////////////////////////////////////////////////
 INLINE size_t SimpleLru::
 get_total_size() const {
+  MutexHolder holder(_global_lock);
   return _total_size;
 }
 
@@ -36,6 +37,7 @@ get_total_size() const {
 ////////////////////////////////////////////////////////////////////
 INLINE size_t SimpleLru::
 get_max_size() const {
+  MutexHolder holder(_global_lock);
   return _max_size;
 }
 
@@ -49,8 +51,11 @@ get_max_size() const {
 ////////////////////////////////////////////////////////////////////
 INLINE void SimpleLru::
 set_max_size(size_t max_size) {
+  MutexHolder holder(_global_lock);
   _max_size = max_size;
-  consider_evict();
+  if (_total_size > _max_size) {
+    do_evict();
+  }
 }
 
 ////////////////////////////////////////////////////////////////////
@@ -60,6 +65,7 @@ set_max_size(size_t max_size) {
 ////////////////////////////////////////////////////////////////////
 INLINE void SimpleLru::
 consider_evict() {
+  MutexHolder holder(_global_lock);
   if (_total_size > _max_size) {
     do_evict();
   }
@@ -121,35 +127,8 @@ operator = (const SimpleLruPage &copy) {
 ////////////////////////////////////////////////////////////////////
 INLINE SimpleLru *SimpleLruPage::
 get_lru() const {
-  return _lru;
-}
-
-////////////////////////////////////////////////////////////////////
-//     Function: SimpleLruPage::enqueue_lru
-//       Access: Published
-//  Description: Adds the page to the tail of the SimpleLru.  When it
-//               reaches the head, it will be the next to be evicted.
-////////////////////////////////////////////////////////////////////
-INLINE void SimpleLruPage::
-enqueue_lru(SimpleLru *lru) {
   MutexHolder holder(SimpleLru::_global_lock);
-
-  if (_lru != (SimpleLru *)NULL) {
-    remove_from_list();
-    _lru->_total_size -= _lru_size;
-    _lru = NULL;
-  }
-
-  _lru = lru;
-
-  if (_lru != (SimpleLru *)NULL) {
-    _lru->_total_size += _lru_size;
-    insert_before(_lru);
-  }
-
-  // Let's not automatically evict pages; instead, we'll evict only on
-  // an explicit epoch test.
-  //  _lru->consider_evict();
+  return _lru;
 }
 
 ////////////////////////////////////////////////////////////////////
@@ -218,6 +197,8 @@ set_lru_size(size_t lru_size) {
   if (_lru != (SimpleLru *)NULL) {
     _lru->_total_size -= _lru_size;
     _lru->_total_size += lru_size;
+    _lru_size = lru_size;
+  } else {
+    _lru_size = lru_size;
   }
-  _lru_size = lru_size;
 }
diff --git a/panda/src/gobj/simpleLru.cxx b/panda/src/gobj/simpleLru.cxx
index 2efd185c7e..4a201673bd 100644
--- a/panda/src/gobj/simpleLru.cxx
+++ b/panda/src/gobj/simpleLru.cxx
@@ -18,7 +18,11 @@
 
 #include "simpleLru.h"
 
-Mutex SimpleLru::_global_lock;
+// We define this as a reference to an allocated object, instead of as
+// a concrete object, so that it won't get destructed when the program
+// exits.  (If it did, there would be an ordering issue between it and
+// the various concrete SimpleLru objects which reference it.)
+Mutex &SimpleLru::_global_lock = *new Mutex;
 
 ////////////////////////////////////////////////////////////////////
 //     Function: SimpleLru::Constructor
@@ -26,7 +30,10 @@ Mutex SimpleLru::_global_lock;
 //  Description: 
 ////////////////////////////////////////////////////////////////////
 SimpleLru::
-SimpleLru(size_t max_size) : LinkedListNode(true) {
+SimpleLru(const string &name, size_t max_size) : 
+  LinkedListNode(true), 
+  Namable(name)
+{
   _total_size = 0;
   _max_size = max_size;
   _active_marker = new SimpleLruPage(0);
@@ -53,6 +60,38 @@ SimpleLru::
 #endif
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: SimpleLruPage::enqueue_lru
+//       Access: Published
+//  Description: Adds the page to the tail of the SimpleLru.  When it
+//               reaches the head, it will be the next to be evicted.
+////////////////////////////////////////////////////////////////////
+void SimpleLruPage::
+enqueue_lru(SimpleLru *lru) {
+  MutexHolder holder(SimpleLru::_global_lock);
+
+  if (_lru == lru) {
+    return;
+  }
+
+  if (_lru != (SimpleLru *)NULL) {
+    remove_from_list();
+    _lru->_total_size -= _lru_size;
+    _lru = NULL;
+  }
+
+  _lru = lru;
+
+  if (_lru != (SimpleLru *)NULL) {
+    _lru->_total_size += _lru_size;
+    insert_before(_lru);
+  }
+
+  // Let's not automatically evict pages; instead, we'll evict only on
+  // an explicit epoch test.
+  //  _lru->consider_evict();
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: SimpleLru::count_active_size
 //       Access: Published
@@ -77,10 +116,15 @@ count_active_size() const {
 //     Function: SimpleLru::do_evict
 //       Access: Private
 //  Description: Evicts pages until the LRU is within tolerance.
+//               Assumes the lock is already held.
 ////////////////////////////////////////////////////////////////////
 void SimpleLru::
 do_evict() {
-  MutexHolder holder(_global_lock);
+  if (_next == this) {
+    // Nothing in the queue.
+    return;
+  }
+
   // Store the current end of the list.  If pages re-enqueue
   // themselves during this traversal, we don't want to visit them
   // twice.
@@ -104,6 +148,25 @@ do_evict() {
   }
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: SimpleLru::do_validate_size
+//       Access: Private
+//  Description: Checks that _total_size is consistent.  Assume the
+//               lock is already held.
+////////////////////////////////////////////////////////////////////
+bool SimpleLru::
+do_validate_size() {
+  size_t total = 0;
+
+  LinkedListNode *node = _next;
+  while (node != this) {
+    total += ((SimpleLruPage *)node)->get_lru_size();
+    node = ((SimpleLruPage *)node)->_next;
+  }
+
+  return (total == _total_size);
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: SimpleLruPage::Destructor
 //       Access: Published, Virtual
diff --git a/panda/src/gobj/simpleLru.h b/panda/src/gobj/simpleLru.h
index 4183bbf3d4..fc0bc5c56a 100644
--- a/panda/src/gobj/simpleLru.h
+++ b/panda/src/gobj/simpleLru.h
@@ -21,6 +21,7 @@
 
 #include "pandabase.h"
 #include "linkedListNode.h"
+#include "namable.h"
 #include "pmutex.h"
 #include "mutexHolder.h"
 
@@ -30,9 +31,9 @@ class SimpleLruPage;
 //       Class : SimpleLru
 // Description : An implementation of a very simple LRU algorithm.
 ////////////////////////////////////////////////////////////////////
-class EXPCL_PANDA SimpleLru : public LinkedListNode {
+class EXPCL_PANDA SimpleLru : public LinkedListNode, public Namable {
 PUBLISHED:
-  SimpleLru(size_t max_size);
+  SimpleLru(const string &name, size_t max_size);
   ~SimpleLru();
 
   INLINE size_t get_total_size() const;
@@ -44,10 +45,11 @@ PUBLISHED:
   INLINE void begin_epoch();
 
 public:
-  static Mutex _global_lock;
+  static Mutex &_global_lock;
 
 private:
   void do_evict();
+  bool do_validate_size();
 
   size_t _total_size;
   size_t _max_size;
@@ -72,7 +74,7 @@ PUBLISHED:
 
   INLINE SimpleLru *get_lru() const;
 
-  INLINE void enqueue_lru(SimpleLru *lru);
+  void enqueue_lru(SimpleLru *lru);
   INLINE void dequeue_lru();
 
   INLINE void mark_used_lru() const;
diff --git a/panda/src/gobj/vertexDataBlock.I b/panda/src/gobj/vertexDataBlock.I
index a0c7a37e4a..4129125d37 100644
--- a/panda/src/gobj/vertexDataBlock.I
+++ b/panda/src/gobj/vertexDataBlock.I
@@ -43,12 +43,23 @@ get_page() const {
 //     Function: VertexDataBlock::get_pointer
 //       Access: Public
 //  Description: Returns a pointer to the start of the allocated
-//               memory for this buffer.
+//               memory for this buffer, or NULL if the data is not
+//               currently resident.  If the data is not currently
+//               resident, this will implicitly request it to become
+//               resident soon.
+//
+//               If force is true, this method will never return NULL,
+//               but may block until the data is available.
 ////////////////////////////////////////////////////////////////////
 INLINE unsigned char *VertexDataBlock::
-get_pointer() const {
+get_pointer(bool force) const {
   nassertr(get_page() != (VertexDataPage *)NULL, NULL);
-  return get_page()->get_page_data() + get_start();
+  unsigned char *page_data = get_page()->get_page_data(force);
+  if (page_data == (unsigned char *)NULL) {
+    return NULL;
+  } else {
+    return page_data + get_start();
+  }
 }
 
 ////////////////////////////////////////////////////////////////////
diff --git a/panda/src/gobj/vertexDataBlock.h b/panda/src/gobj/vertexDataBlock.h
index 3046b54586..6841cd5a6e 100644
--- a/panda/src/gobj/vertexDataBlock.h
+++ b/panda/src/gobj/vertexDataBlock.h
@@ -41,7 +41,7 @@ PUBLISHED:
   INLINE VertexDataBlock *get_next_block() const;
 
 public:
-  INLINE unsigned char *get_pointer() const;
+  INLINE unsigned char *get_pointer(bool force) const;
 
   friend class VertexDataPage;
 };
diff --git a/panda/src/gobj/vertexDataBuffer.I b/panda/src/gobj/vertexDataBuffer.I
index a45fc580d5..05ebe704a5 100644
--- a/panda/src/gobj/vertexDataBuffer.I
+++ b/panda/src/gobj/vertexDataBuffer.I
@@ -65,7 +65,7 @@ operator = (const VertexDataBuffer &copy) {
   MutexHolder holder(_lock);
 
   do_unclean_realloc(copy.get_size());
-  memcpy(_resident_data, copy.get_read_pointer(), _size);
+  memcpy(_resident_data, copy.get_read_pointer(true), _size);
   _source_file = copy._source_file;
   _source_pos = copy._source_pos;
 }
@@ -83,17 +83,23 @@ INLINE VertexDataBuffer::
 ////////////////////////////////////////////////////////////////////
 //     Function: VertexDataBuffer::get_read_pointer
 //       Access: Public
-//  Description: Returns a read-only pointer to the raw data.
+//  Description: Returns a read-only pointer to the raw data, or NULL
+//               if the data is not currently resident.  If the data
+//               is not currently resident, this will implicitly
+//               request it to become resident soon.
+//
+//               If force is true, this method will never return NULL,
+//               but may block until the data is available.
 ////////////////////////////////////////////////////////////////////
 INLINE const unsigned char *VertexDataBuffer::
-get_read_pointer() const {
+get_read_pointer(bool force) const {
   MutexHolder holder(_lock);
 
   if (_block != (VertexDataBlock *)NULL) {
     // We don't necessarily need to page the buffer all the way into
     // independent status; it's sufficient just to return the block's
     // pointer, which will force its page to resident status.
-    return _block->get_pointer();
+    return _block->get_pointer(force);
   }
   if (_resident_data == (unsigned char *)NULL && !_source_file.is_null()) {
     // If we need to re-read the original source, do so.
diff --git a/panda/src/gobj/vertexDataBuffer.cxx b/panda/src/gobj/vertexDataBuffer.cxx
index 838059098b..ced0008a5d 100644
--- a/panda/src/gobj/vertexDataBuffer.cxx
+++ b/panda/src/gobj/vertexDataBuffer.cxx
@@ -95,7 +95,7 @@ do_page_out(VertexDataBook &book) {
     // file.
     _block = book.alloc(_size);
     nassertv(_block != (VertexDataBlock *)NULL);
-    unsigned char *pointer = _block->get_pointer();
+    unsigned char *pointer = _block->get_pointer(true);
     nassertv(pointer != (unsigned char *)NULL);
     memcpy(pointer, _resident_data, _size);
   }
@@ -164,6 +164,6 @@ do_page_in() {
   nassertv(_resident_data != (unsigned char *)NULL);
   get_class_type().inc_memory_usage(TypeHandle::MC_array, _size);
 
-  memcpy(_resident_data, _block->get_pointer(), _size);
+  memcpy(_resident_data, _block->get_pointer(true), _size);
   _block = NULL;
 }
diff --git a/panda/src/gobj/vertexDataBuffer.h b/panda/src/gobj/vertexDataBuffer.h
index 9b3dbd6e52..0eed0eccb9 100644
--- a/panda/src/gobj/vertexDataBuffer.h
+++ b/panda/src/gobj/vertexDataBuffer.h
@@ -68,7 +68,7 @@ public:
   INLINE void operator = (const VertexDataBuffer &copy);
   INLINE ~VertexDataBuffer();
 
-  INLINE const unsigned char *get_read_pointer() const;
+  INLINE const unsigned char *get_read_pointer(bool force) const;
   INLINE unsigned char *get_write_pointer();
 
   INLINE size_t get_size() const;
diff --git a/panda/src/gobj/vertexDataPage.I b/panda/src/gobj/vertexDataPage.I
index 7d2560bb6d..91e8d6da20 100644
--- a/panda/src/gobj/vertexDataPage.I
+++ b/panda/src/gobj/vertexDataPage.I
@@ -26,9 +26,39 @@
 ////////////////////////////////////////////////////////////////////
 INLINE VertexDataPage::RamClass VertexDataPage::
 get_ram_class() const {
+  MutexHolder holder(_lock);
   return _ram_class;
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: VertexDataPage::get_pending_ram_class
+//       Access: Published
+//  Description: Returns the pending ram class of the array.  If this
+//               is different from get_ram_class(), this page has been
+//               queued to be processed by the thread.  Eventually the
+//               page will be set to this ram class.
+////////////////////////////////////////////////////////////////////
+INLINE VertexDataPage::RamClass VertexDataPage::
+get_pending_ram_class() const {
+  MutexHolder holder(_lock);
+  return _pending_ram_class;
+}
+
+////////////////////////////////////////////////////////////////////
+//     Function: VertexDataPage::request_resident
+//       Access: Published
+//  Description: Ensures that the page will become resident soon.
+//               Future calls to get_page_data() will eventually
+//               return non-NULL.
+////////////////////////////////////////////////////////////////////
+INLINE void VertexDataPage::
+request_resident() {
+  MutexHolder holder(_lock);
+  if (_ram_class != RC_resident) {
+    request_ram_class(RC_resident);
+  }
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: VertexDataPage::get_first_block
 //       Access: Published
@@ -38,7 +68,6 @@ get_ram_class() const {
 INLINE VertexDataBlock *VertexDataPage::
 get_first_block() const {
   MutexHolder holder(_lock);
-  check_resident();
   return (VertexDataBlock *)SimpleAllocator::get_first_block();
 }
 
@@ -66,6 +95,18 @@ get_global_lru(RamClass rclass) {
   return _global_lru[rclass];
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: VertexDataPage::get_pending_lru
+//       Access: Published, Static
+//  Description: Returns a pointer to the global LRU object that
+//               manages the VertexDataPage's that are pending
+//               processing by the thread.
+////////////////////////////////////////////////////////////////////
+INLINE SimpleLru *VertexDataPage::
+get_pending_lru() {
+  return &_pending_lru;
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: VertexDataPage::get_save_file
 //       Access: Published, Static
@@ -95,56 +136,56 @@ save_to_disk() {
   return do_save_to_disk();
 }
 
-////////////////////////////////////////////////////////////////////
-//     Function: VertexDataPage::restore_from_disk
-//       Access: Published
-//  Description: Restores the page from disk and makes it
-//               either compressed or resident (according to whether
-//               it was stored compressed on disk).
-////////////////////////////////////////////////////////////////////
-INLINE void VertexDataPage::
-restore_from_disk() {
-  MutexHolder holder(_lock);
-  do_restore_from_disk();
-}
-
 ////////////////////////////////////////////////////////////////////
 //     Function: VertexDataPage::get_page_data
 //       Access: Public
-//  Description: Returns a pointer to the page's data area.
+//  Description: Returns a pointer to the page's data area, or NULL if
+//               the page is not currently resident.  If the page is
+//               not currently resident, this will implicitly request
+//               it to become resident soon.
+//
+//               If force is true, this method will never return NULL,
+//               but may block until the page is available.
 ////////////////////////////////////////////////////////////////////
 INLINE unsigned char *VertexDataPage::
-get_page_data() const {
+get_page_data(bool force) {
   MutexHolder holder(_lock);
-  check_resident();
-  return _page_data;
-}
-
-////////////////////////////////////////////////////////////////////
-//     Function: VertexDataPage::check_resident
-//       Access: Private
-//  Description: Forces the vertex data into system RAM, if it is not
-//               already there; also, marks it recently-used.
-//
-//               Assumes the lock is already held.
-////////////////////////////////////////////////////////////////////
-INLINE void VertexDataPage::
-check_resident() const {
   if (_ram_class != RC_resident) {
-    ((VertexDataPage *)this)->make_resident();
-  } else {
-    ((VertexDataPage *)this)->mark_used_lru();
+    if (force) {
+      make_resident_now();
+    } else {
+      request_ram_class(RC_resident);
+      return NULL;
+    }
   }
-  nassertv(_size == _uncompressed_size);
+
+  mark_used_lru();
+  nassertr(_size == _uncompressed_size, _page_data);
+  return _page_data;
 }
 
 ////////////////////////////////////////////////////////////////////
 //     Function: VertexDataPage::set_ram_class
 //       Access: Private
-//  Description: Puts the data in a new ram class.
+//  Description: Puts the data in a new ram class.  Assumes the page
+//               lock is already held.
 ////////////////////////////////////////////////////////////////////
 INLINE void VertexDataPage::
 set_ram_class(RamClass rclass) {
   _ram_class = rclass;
   mark_used_lru(_global_lru[rclass]);
 }
+
+////////////////////////////////////////////////////////////////////
+//     Function: VertexDataPage::PageThread::Constructor
+//       Access: Public
+//  Description: 
+////////////////////////////////////////////////////////////////////
+INLINE VertexDataPage::PageThread::
+PageThread() : 
+  Thread("VertexDataPage", "VertexDataPage"),
+  _shutdown(false),
+  _working_cvar(_tlock),
+  _pending_cvar(_tlock)
+{
+}
diff --git a/panda/src/gobj/vertexDataPage.cxx b/panda/src/gobj/vertexDataPage.cxx
index 5650c668f0..5fbb4bb9a4 100644
--- a/panda/src/gobj/vertexDataPage.cxx
+++ b/panda/src/gobj/vertexDataPage.cxx
@@ -54,9 +54,13 @@ ConfigVariableInt max_disk_vertex_data
           "that is allowed to be written to disk.  Set it to -1 for no "
           "limit."));
 
-SimpleLru VertexDataPage::_resident_lru(max_resident_vertex_data);
-SimpleLru VertexDataPage::_compressed_lru(max_compressed_vertex_data);
-SimpleLru VertexDataPage::_disk_lru(0);
+PT(VertexDataPage::PageThread) VertexDataPage::_thread;
+Mutex VertexDataPage::_tlock;
+
+SimpleLru VertexDataPage::_resident_lru("resident", max_resident_vertex_data);
+SimpleLru VertexDataPage::_compressed_lru("compressed", max_compressed_vertex_data);
+SimpleLru VertexDataPage::_disk_lru("disk", 0);
+SimpleLru VertexDataPage::_pending_lru("pending", 0);
 
 SimpleLru *VertexDataPage::_global_lru[RC_end_of_list] = {
   &VertexDataPage::_resident_lru,
@@ -86,6 +90,7 @@ VertexDataPage(size_t page_size) : SimpleAllocator(page_size), SimpleLruPage(pag
   _uncompressed_size = _size;
   _total_page_size += _size;
   get_class_type().inc_memory_usage(TypeHandle::MC_array, (int)_size);
+  _pending_ram_class = RC_resident;
   set_ram_class(RC_resident);
 }
 
@@ -116,7 +121,9 @@ VertexDataPage::
 VertexDataBlock *VertexDataPage::
 alloc(size_t size) {
   MutexHolder holder(_lock);
-  check_resident();
+  if (_ram_class != RC_resident) {
+    make_resident_now();
+  }
   
   VertexDataBlock *block = (VertexDataBlock *)SimpleAllocator::alloc(size);
 
@@ -129,6 +136,27 @@ alloc(size_t size) {
   return block;
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: VertexDataPage::stop_thread
+//       Access: Published, Static
+//  Description: Call this to stop the paging thread, if it was
+//               started.  This may block until all of the thread's
+//               pending tasks have been completed.
+////////////////////////////////////////////////////////////////////
+void VertexDataPage::
+stop_thread() {
+  PT(PageThread) thread;
+  {
+    MutexHolder holder(_tlock);
+    thread = _thread;
+    _thread.clear();
+  }
+
+  if (thread != (PageThread *)NULL) {
+    thread->stop_thread();
+  }
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: VertexDataPage::make_block
 //       Access: Protected, Virtual
@@ -162,38 +190,58 @@ evict_lru() {
   switch (_ram_class) {
   case RC_resident:
     if (_compressed_lru.get_max_size() == 0) {
-      make_disk();
+      request_ram_class(RC_disk);
     } else {
-      make_compressed();
+      request_ram_class(RC_compressed);
     }
     break;
 
   case RC_compressed:
-    make_disk();
+    request_ram_class(RC_disk);
     break;
 
   case RC_disk:
-    gobj_cat.warning()
-      << "Cannot evict array data from disk.\n";
-    break;
-
   case RC_end_of_list:
+    gobj_cat.warning()
+      << "Internal error: attempt to evict array data " << this
+      << " in inappropriate state " << _ram_class << ".\n";
     break;
   }
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: VertexDataPage::make_resident_now
+//       Access: Private
+//  Description: Short-circuits the thread and forces the page into
+//               resident status immediately.
+//
+//               Intended to be called from the main thread.  Assumes
+//               the lock is already held.
+////////////////////////////////////////////////////////////////////
+void VertexDataPage::
+make_resident_now() {
+  MutexHolder holder(_tlock);
+  if (_pending_ram_class != _ram_class) {
+    nassertv(_thread != (PageThread *)NULL);
+    _thread->remove_page(this);
+  }
+
+  make_resident();
+  _pending_ram_class = RC_resident;
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: VertexDataPage::make_resident
 //       Access: Private
 //  Description: Moves the page to fully resident status by
 //               expanding it or reading it from disk as necessary.
 //
-//               Assumes the lock is already held.
+//               Intended to be called from the sub-thread.  Assumes
+//               the lock is already held.
 ////////////////////////////////////////////////////////////////////
 void VertexDataPage::
 make_resident() {
   if (_ram_class == RC_resident) {
-    // If we're already resident, just mark the page recently used.
     mark_used_lru();
     return;
   }
@@ -321,6 +369,8 @@ make_disk() {
   if (_ram_class == RC_resident || _ram_class == RC_compressed) {
     if (!do_save_to_disk()) {
       // Can't save it to disk for some reason.
+      gobj_cat.warning() 
+        << "Couldn't save page " << this << " to disk.\n";
       mark_used_lru();
       return;
     }
@@ -331,7 +381,7 @@ make_disk() {
     delete[] _page_data;
     _page_data = NULL;
     _size = 0;
-
+    
     set_ram_class(RC_disk);
   }
 }
@@ -419,6 +469,52 @@ do_restore_from_disk() {
   }
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: VertexDataPage::request_ram_class
+//       Access: Private
+//  Description: Requests the thread set the page to the indicated ram
+//               class (if we are using threading).  The page will be
+//               enqueued in the thread, which will eventually be
+//               responsible for setting the requested ram class.
+//
+//               Assumes the page's lock is already held.
+////////////////////////////////////////////////////////////////////
+void VertexDataPage::
+request_ram_class(RamClass ram_class) {
+  if (ram_class == _ram_class) {
+    gobj_cat.warning()
+      << "Page " << this << " already has ram class " << ram_class << "\n";
+    return;
+  }
+
+  if (!vertex_data_threaded_paging || !Thread::is_threading_supported()) {
+    // No threads.  Do it immediately.
+    switch (ram_class) {
+    case RC_resident:
+      make_resident();
+      break;
+
+    case RC_compressed:
+      make_compressed();
+      break;
+
+    case RC_disk:
+      make_disk();
+      break;
+    }
+    return;
+  }
+
+  MutexHolder holder(_tlock);
+  if (_thread == (PageThread *)NULL) {
+    // Allocate and start a new global thread.
+    _thread = new PageThread;
+    _thread->start(TP_low, true);
+  }
+
+  _thread->add_page(this, ram_class);
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: VertexDataPage::make_save_file
 //       Access: Private, Static
@@ -433,3 +529,149 @@ make_save_file() {
   _save_file = new VertexDataSaveFile(vertex_save_file_directory,
                                       vertex_save_file_prefix, max_size);
 }
+ 
+////////////////////////////////////////////////////////////////////
+//     Function: VertexDataPage::PageThread::add_page
+//       Access: Public
+//  Description: Enqueues the indicated page on the thread to convert
+//               it to the specified ram class.  
+//
+//               It is assumed the page's lock is already held, and
+//               the thread's tlock is already held.
+////////////////////////////////////////////////////////////////////
+void VertexDataPage::PageThread::
+add_page(VertexDataPage *page, RamClass ram_class) {
+  if (page->_pending_ram_class == ram_class) {
+    // It's already queued.
+    nassertv(page->get_lru() == &_pending_lru);
+    return;
+  }
+  
+  if (page->_pending_ram_class != page->_ram_class) {
+    // It's already queued, but for a different ram class.  Dequeue it
+    // so we can requeue it.
+    remove_page(page);
+  }
+
+  if (page->_pending_ram_class != ram_class) {
+    // First, move the page to the "pending" LRU.  When it eventually
+    // gets its requested ram class set, it will be requeued on the
+    // appropriate live LRU.
+    page->mark_used_lru(&_pending_lru);
+
+    page->_pending_ram_class = ram_class;
+    if (ram_class == RC_resident) {
+      _pending_reads.push_back(page);
+    } else {
+      _pending_writes.push_back(page);
+    }
+    _pending_cvar.signal();
+  }
+}
+
+////////////////////////////////////////////////////////////////////
+//     Function: VertexDataPage::PageThread::remove_page
+//       Access: Public
+//  Description: Dequeues the indicated page and removes it from the
+//               pending task list.
+//
+//               It is assumed the page's lock is already held, and
+//               the thread's tlock is already held.
+////////////////////////////////////////////////////////////////////
+void VertexDataPage::PageThread::
+remove_page(VertexDataPage *page) {
+  if (page == _working_page) {
+    // Oops, the thread is currently working on this one.  We'll have
+    // to wait for the thread to finish.
+    while (page == _working_page) {
+      _working_cvar.wait();
+    }
+    return;
+  }
+
+  if (page->_pending_ram_class == RC_resident) {
+    PendingPages::iterator pi = 
+      find(_pending_reads.begin(), _pending_reads.end(), page);
+    nassertv(pi != _pending_reads.end());
+    _pending_reads.erase(pi);
+  } else {
+    PendingPages::iterator pi = 
+      find(_pending_writes.begin(), _pending_writes.end(), page);
+    nassertv(pi != _pending_writes.end());
+    _pending_writes.erase(pi);
+  }
+
+  page->_pending_ram_class = page->_ram_class;
+}
+
+////////////////////////////////////////////////////////////////////
+//     Function: VertexDataPage::PageThread::thread_main
+//       Access: Protected, Virtual
+//  Description: The main processing loop for the sub-thread.
+////////////////////////////////////////////////////////////////////
+void VertexDataPage::PageThread::
+thread_main() {
+  _tlock.lock();
+
+  while (true) {
+    PStatClient::thread_tick(get_sync_name());
+
+    while (_pending_reads.empty() && _pending_writes.empty()) {
+      if (_shutdown) {
+        _tlock.release();
+        return;
+      }
+      _pending_cvar.wait();
+    }
+
+    // Reads always have priority.
+    if (!_pending_reads.empty()) {
+      _working_page = _pending_reads.front();
+      _pending_reads.pop_front();
+    } else {
+      _working_page = _pending_writes.front();
+      _pending_writes.pop_front();
+    }
+
+    RamClass ram_class = _working_page->_pending_ram_class;
+    _tlock.release();
+
+    {
+      MutexHolder holder(_working_page->_lock);
+      switch (ram_class) {
+      case RC_resident:
+        _working_page->make_resident();
+        break;
+        
+      case RC_compressed:
+        _working_page->make_compressed();
+        break;
+        
+      case RC_disk:
+        _working_page->make_disk();
+        break;
+      }
+    }
+    
+    _tlock.lock();
+
+    _working_page = NULL;
+    _working_cvar.signal();
+  }
+}
+
+////////////////////////////////////////////////////////////////////
+//     Function: VertexDataPage::PageThread::stop_thread
+//       Access: Public
+//  Description: Signals the thread to stop and waits for it.  Does
+//               not return until the thread has finished.
+////////////////////////////////////////////////////////////////////
+void VertexDataPage::PageThread::
+stop_thread() {
+  {
+    MutexHolder holder(_tlock);
+    _shutdown = true;
+    _pending_cvar.signal();
+  }
+  join();
+}
diff --git a/panda/src/gobj/vertexDataPage.h b/panda/src/gobj/vertexDataPage.h
index 8479534374..95e838d718 100644
--- a/panda/src/gobj/vertexDataPage.h
+++ b/panda/src/gobj/vertexDataPage.h
@@ -25,7 +25,10 @@
 #include "pStatCollector.h"
 #include "vertexDataSaveFile.h"
 #include "pmutex.h"
+#include "conditionVar.h"
+#include "thread.h"
 #include "mutexHolder.h"
+#include "pdeque.h"
 
 class VertexDataBlock;
 
@@ -53,27 +56,31 @@ PUBLISHED:
   };
 
   INLINE RamClass get_ram_class() const;
+  INLINE RamClass get_pending_ram_class() const;
+  INLINE void request_resident();
 
   VertexDataBlock *alloc(size_t size);
   INLINE VertexDataBlock *get_first_block() const;
 
   INLINE static size_t get_total_page_size();
   INLINE static SimpleLru *get_global_lru(RamClass rclass);
+  INLINE static SimpleLru *get_pending_lru();
   INLINE static VertexDataSaveFile *get_save_file();
 
   INLINE bool save_to_disk();
-  INLINE void restore_from_disk();
+  static void stop_thread();
 
 public:
-  INLINE unsigned char *get_page_data() const;
+  INLINE unsigned char *get_page_data(bool force);
 
 protected:
   virtual SimpleAllocatorBlock *make_block(size_t start, size_t size);
   virtual void evict_lru();
 
 private:
-  INLINE void check_resident() const;
+  class PageThread;
 
+  void make_resident_now();
   void make_resident();
   void make_compressed();
   void make_disk();
@@ -81,19 +88,48 @@ private:
   bool do_save_to_disk();
   void do_restore_from_disk();
 
+  PageThread *get_thread();
+  void request_ram_class(RamClass ram_class);
   INLINE void set_ram_class(RamClass ram_class);
   static void make_save_file();
 
+  typedef pdeque<VertexDataPage *> PendingPages;
+
+  class PageThread : public Thread {
+  public:
+    INLINE PageThread();
+    
+    void add_page(VertexDataPage *page, RamClass ram_class);
+    void remove_page(VertexDataPage *page);
+    void stop_thread();
+
+  protected:
+    virtual void thread_main();
+
+  private:
+    VertexDataPage *_working_page;
+    PendingPages _pending_writes;
+    PendingPages _pending_reads;
+    bool _shutdown;
+    ConditionVar _working_cvar;
+    ConditionVar _pending_cvar;
+  };
+  static PT(PageThread) _thread;
+  static Mutex _tlock;  // Protects the thread members.
+
   unsigned char *_page_data;
   size_t _size, _uncompressed_size;
   RamClass _ram_class;
   PT(VertexDataSaveBlock) _saved_block;
 
-  Mutex _lock;
+  Mutex _lock;  // Protects above members
+
+  RamClass _pending_ram_class;  // Protected by _tlock.
 
   static SimpleLru _resident_lru;
   static SimpleLru _compressed_lru;
   static SimpleLru _disk_lru;
+  static SimpleLru _pending_lru;
   static SimpleLru *_global_lru[RC_end_of_list];
 
   static size_t _total_page_size;
@@ -114,6 +150,8 @@ public:
 
 private:
   static TypeHandle _type_handle;
+
+  friend class PageThread;
 };
 
 #include "vertexDataPage.I"
diff --git a/panda/src/pstatclient/pStatProperties.cxx b/panda/src/pstatclient/pStatProperties.cxx
index dfe02fa754..ef9a035a7e 100644
--- a/panda/src/pstatclient/pStatProperties.cxx
+++ b/panda/src/pstatclient/pStatProperties.cxx
@@ -202,6 +202,7 @@ static LevelCollectorProperties level_properties[] = {
   { 1, "Vertex Data",                      { 1.0, 0.4, 0.0 },  "MB", 64, 1048576 },
   { 1, "Vertex Data:Small",                { 0.2, 0.3, 0.4 } },
   { 1, "Vertex Data:Independent",          { 0.9, 0.1, 0.9 } },
+  { 1, "Vertex Data:Pending",              { 0.6, 0.8, 1.0 } },
   { 1, "Vertex Data:Disk",                 { 0.6, 0.9, 0.1 } },
   { 1, "Vertex Data:Disk:Unused",          { 0.8, 0.4, 0.5 } },
   { 1, "Vertex Data:Disk:Used",            { 0.2, 0.1, 0.6 } },