--- a/hotspot/src/share/vm/gc_implementation/g1/dirtyCardQueue.cpp	Mon May 11 16:30:56 2009 -0700
+++ b/hotspot/src/share/vm/gc_implementation/g1/dirtyCardQueue.cpp	Mon May 18 11:52:46 2009 -0700
@@ -71,11 +71,11 @@
   _all_active = true;
 }
 
+// Determines how many mutator threads can process the buffers in parallel.
 size_t DirtyCardQueueSet::num_par_ids() {
-  return MAX2(ParallelGCThreads, (size_t)2);
+  return os::processor_count();
 }
 
-
 void DirtyCardQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
                                    int max_completed_queue,
                                    Mutex* lock, PtrQueueSet* fl_owner) {
@@ -85,8 +85,6 @@
 
   _shared_dirty_card_queue.set_lock(lock);
   _free_ids = new FreeIdSet((int) num_par_ids(), _cbl_mon);
-  bool b = _free_ids->claim_perm_id(0);
-  guarantee(b, "Must reserve id zero for concurrent refinement thread.");
 }
 
 void DirtyCardQueueSet::handle_zero_index_for_thread(JavaThread* t) {