--- a/src/share/vm/gc_implementation/shared/allocationStats.hpp	Wed Dec 16 15:12:51 2009 -0800
+++ b/src/share/vm/gc_implementation/shared/allocationStats.hpp	Wed Dec 23 09:23:54 2009 -0800
@@ -31,7 +31,7 @@
   // beginning of this sweep:
   //   Count(end_last_sweep) - Count(start_this_sweep)
   //     + splitBirths(between) - splitDeaths(between)
-  // The above number divided by the time since the start [END???] of the
+  // The above number divided by the time since the end of the
   // previous sweep gives us a time rate of demand for blocks
   // of this size. We compute a padded average of this rate as
   // our current estimate for the time rate of demand for blocks
@@ -41,7 +41,7 @@
   // estimates.
   AdaptivePaddedAverage _demand_rate_estimate;
 
-  ssize_t     _desired;          // Estimate computed as described above
+  ssize_t     _desired;         // Demand stimate computed as described above
   ssize_t     _coalDesired;     // desired +/- small-percent for tuning coalescing
 
   ssize_t     _surplus;         // count - (desired +/- small-percent),
@@ -53,9 +53,9 @@
   ssize_t     _coalDeaths;      // loss from coalescing
   ssize_t     _splitBirths;     // additional chunks from splitting
   ssize_t     _splitDeaths;     // loss from splitting
-  size_t     _returnedBytes;    // number of bytes returned to list.
+  size_t      _returnedBytes;   // number of bytes returned to list.
  public:
-  void initialize() {
+  void initialize(bool split_birth = false) {
     AdaptivePaddedAverage* dummy =
       new (&_demand_rate_estimate) AdaptivePaddedAverage(CMS_FLSWeight,
                                                          CMS_FLSPadding);
@@ -67,7 +67,7 @@
     _beforeSweep = 0;
     _coalBirths = 0;
     _coalDeaths = 0;
-    _splitBirths = 0;
+    _splitBirths = split_birth? 1 : 0;
     _splitDeaths = 0;
     _returnedBytes = 0;
   }
@@ -75,10 +75,12 @@
   AllocationStats() {
     initialize();
   }
+
   // The rate estimate is in blocks per second.
   void compute_desired(size_t count,
                        float inter_sweep_current,
-                       float inter_sweep_estimate) {
+                       float inter_sweep_estimate,
+                       float intra_sweep_estimate) {
     // If the latest inter-sweep time is below our granularity
     // of measurement, we may call in here with
     // inter_sweep_current == 0. However, even for suitably small
@@ -88,12 +90,31 @@
     // vulnerable to noisy glitches. In such cases, we
     // ignore the current sample and use currently available
     // historical estimates.
+    // XXX NEEDS TO BE FIXED
+    // assert(prevSweep() + splitBirths() >= splitDeaths() + (ssize_t)count, "Conservation Principle");
+    //     ^^^^^^^^^^^^^^^^^^^^^^^^^^^    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    //     "Total Stock"                  "Not used at this block size"
     if (inter_sweep_current > _threshold) {
-      ssize_t demand = prevSweep() - count + splitBirths() - splitDeaths();
+      ssize_t demand = prevSweep() - (ssize_t)count + splitBirths() - splitDeaths();
+      // XXX NEEDS TO BE FIXED
+      // assert(demand >= 0, "Demand should be non-negative");
+      // Defensive: adjust for imprecision in event counting
+      if (demand < 0) {
+        demand = 0;
+      }
+      float old_rate = _demand_rate_estimate.padded_average();
       float rate = ((float)demand)/inter_sweep_current;
       _demand_rate_estimate.sample(rate);
-      _desired = (ssize_t)(_demand_rate_estimate.padded_average()
-                           *inter_sweep_estimate);
+      float new_rate = _demand_rate_estimate.padded_average();
+      ssize_t old_desired = _desired;
+      _desired = (ssize_t)(new_rate * (inter_sweep_estimate
+                                       + CMSExtrapolateSweep
+                                         ? intra_sweep_estimate
+                                         : 0.0));
+      if (PrintFLSStatistics > 1) {
+        gclog_or_tty->print_cr("demand: %d, old_rate: %f, current_rate: %f, new_rate: %f, old_desired: %d, new_desired: %d",
+                                demand,     old_rate,     rate,             new_rate,     old_desired,     _desired);
+      }
     }
   }