--- a/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp	Tue Nov 22 04:47:10 2011 -0500
+++ b/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp	Tue Aug 09 10:16:01 2011 -0700
@@ -4244,9 +4244,11 @@
 
 bool CMSCollector::do_marking_mt(bool asynch) {
   assert(ConcGCThreads > 0 && conc_workers() != NULL, "precondition");
-  // In the future this would be determined ergonomically, based
-  // on #cpu's, # active mutator threads (and load), and mutation rate.
-  int num_workers = ConcGCThreads;
+  int num_workers = AdaptiveSizePolicy::calc_active_conc_workers(
+                                       conc_workers()->total_workers(),
+                                       conc_workers()->active_workers(),
+                                       Threads::number_of_non_daemon_threads());
+  conc_workers()->set_active_workers(num_workers);
 
   CompactibleFreeListSpace* cms_space  = _cmsGen->cmsSpace();
   CompactibleFreeListSpace* perm_space = _permGen->cmsSpace();
@@ -5062,6 +5064,8 @@
   ParallelTaskTerminator _term;
 
  public:
+  // A value of 0 passed to n_workers will cause the number of
+  // workers to be taken from the active workers in the work gang.
   CMSParRemarkTask(CMSCollector* collector,
                    CompactibleFreeListSpace* cms_space,
                    CompactibleFreeListSpace* perm_space,
@@ -5544,7 +5548,15 @@
   GenCollectedHeap* gch = GenCollectedHeap::heap();
   FlexibleWorkGang* workers = gch->workers();
   assert(workers != NULL, "Need parallel worker threads.");
-  int n_workers = workers->total_workers();
+  // Choose to use the number of GC workers most recently set
+  // into "active_workers".  If active_workers is not set, set it
+  // to ParallelGCThreads.
+  int n_workers = workers->active_workers();
+  if (n_workers == 0) {
+    assert(n_workers > 0, "Should have been set during scavenge");
+    n_workers = ParallelGCThreads;
+    workers->set_active_workers(n_workers);
+  }
   CompactibleFreeListSpace* cms_space  = _cmsGen->cmsSpace();
   CompactibleFreeListSpace* perm_space = _permGen->cmsSpace();
 
@@ -5884,8 +5896,17 @@
       // and a different number of discovered lists may have Ref objects.
       // That is OK as long as the Reference lists are balanced (see
       // balance_all_queues() and balance_queues()).
-
-      rp->set_active_mt_degree(ParallelGCThreads);
+      GenCollectedHeap* gch = GenCollectedHeap::heap();
+      int active_workers = ParallelGCThreads;
+      FlexibleWorkGang* workers = gch->workers();
+      if (workers != NULL) {
+        active_workers = workers->active_workers();
+        // The expectation is that active_workers will have already
+        // been set to a reasonable value.  If it has not been set,
+        // investigate.
+        assert(active_workers > 0, "Should have been set during scavenge");
+      }
+      rp->set_active_mt_degree(active_workers);
       CMSRefProcTaskExecutor task_executor(*this);
       rp->process_discovered_references(&_is_alive_closure,
                                         &cmsKeepAliveClosure,