8228609: G1 copy cost prediction uses used vs. actual copied bytes

src/hotspot/share/gc/g1/g1CollectedHeap.cpp

@@ -2883,7 +2883,6 @@ G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
                                 collector_state()->yc_type() == Mixed /* allMemoryPoolsAffected */);
 
     G1HeapTransition heap_transition(this);
-    size_t heap_used_bytes_before_gc = used();
 
     // Don't dynamically change the number of GC threads this early.  A value of
     // 0 is used to indicate serial work.  When parallel work is done,
@@ -3044,7 +3043,7 @@ G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
         double sample_end_time_sec = os::elapsedTime();
         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
         size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
-        g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
+        g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned);
 
         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());

src/hotspot/share/gc/g1/g1ParScanThreadState.cpp

@@ -82,16 +82,19 @@ G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint worker_id,
 }
 
 // Pass locally gathered statistics to global state.
-void G1ParScanThreadState::flush(size_t* surviving_young_words) {
+size_t G1ParScanThreadState::flush(size_t* surviving_young_words) {
   _dcq.flush();
   // Update allocation statistics.
   _plab_allocator->flush_and_retire_stats();
   _g1h->g1_policy()->record_age_table(&_age_table);
 
+  size_t sum = 0;
   uint length = _g1h->collection_set()->young_region_length();
   for (uint region_index = 0; region_index < length; region_index++) {
-    surviving_young_words[region_index] += _surviving_young_words[region_index];
+    surviving_young_words[region_index] += G1ParScanThreadState::surviving_young_words()[region_index];
+    sum += G1ParScanThreadState::surviving_young_words()[region_index];
   }
+  return sum;
 }
 
 G1ParScanThreadState::~G1ParScanThreadState() {
@@ -339,17 +342,19 @@ const size_t* G1ParScanThreadStateSet::surviving_young_words() const {
 void G1ParScanThreadStateSet::flush() {
   assert(!_flushed, "thread local state from the per thread states should be flushed once");
 
+  size_t copied_words = 0;
   for (uint worker_index = 0; worker_index < _n_workers; ++worker_index) {
     G1ParScanThreadState* pss = _states[worker_index];
 
     if (pss == NULL) {
       continue;
     }
 
-    pss->flush(_surviving_young_words_total);
+    copied_words += pss->flush(_surviving_young_words_total);
     delete pss;
     _states[worker_index] = NULL;
   }
+  _g1h->g1_policy()->record_copied_bytes(copied_words << LogBytesPerWord);
   _flushed = true;
 }
 

src/hotspot/share/gc/g1/g1ParScanThreadState.hpp

@@ -132,7 +132,7 @@ class G1ParScanThreadState : public CHeapObj<mtGC> {
     return _surviving_young_words + 1;
   }
 
-  void flush(size_t* surviving_young_words);
+  size_t flush(size_t* surviving_young_words);
 
 private:
   #define G1_PARTIAL_ARRAY_MASK 0x2

src/hotspot/share/gc/g1/g1Policy.cpp

@@ -60,6 +60,7 @@ G1Policy::G1Policy(STWGCTimer* gc_timer) :
   _reserve_factor((double) G1ReservePercent / 100.0),
   _reserve_regions(0),
   _rs_lengths_prediction(0),
+  _copied_bytes(0),
   _initial_mark_to_mixed(),
   _collection_set(NULL),
   _g1h(NULL),
@@ -553,11 +554,9 @@ bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_siz
 // Anything below that is considered to be zero
 #define MIN_TIMER_GRANULARITY 0.0000001
 
-void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
+void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned) {
   double end_time_sec = os::elapsedTime();
 
-  size_t cur_used_bytes = _g1h->used();
-  assert(cur_used_bytes == _g1h->recalculate_used(), "It should!");
   bool this_pause_included_initial_mark = false;
   bool this_pause_was_young_only = collector_state()->in_young_only_phase();
 
@@ -665,12 +664,9 @@ void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_sc
     }
     _analytics->report_rs_length_diff((double) rs_length_diff);
 
-    size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
-
-    if (_collection_set->bytes_used_before() > freed_bytes) {
-      size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
+    if (_copied_bytes > 0) {
       double average_copy_time = average_time_ms(G1GCPhaseTimes::ObjCopy);
-      double cost_per_byte_ms = average_copy_time / (double) copied_bytes;
+      double cost_per_byte_ms = average_copy_time / (double) _copied_bytes;
       _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress());
     }
 

src/hotspot/share/gc/g1/g1Policy.hpp

@@ -106,6 +106,8 @@ class G1Policy: public CHeapObj<mtGC> {
 
   size_t _pending_cards;
 
+  size_t _copied_bytes;
+
   G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;
 
   bool should_update_surv_rate_group_predictors() {
@@ -133,6 +135,10 @@ class G1Policy: public CHeapObj<mtGC> {
     _max_rs_lengths = rs_lengths;
   }
 
+  void record_copied_bytes(size_t copied_bytes) {
+    _copied_bytes = copied_bytes;
+  }
+
   double predict_base_elapsed_time_ms(size_t pending_cards) const;
   double predict_base_elapsed_time_ms(size_t pending_cards,
                                       size_t scanned_cards) const;
@@ -308,7 +314,7 @@ class G1Policy: public CHeapObj<mtGC> {
 
   // Record the start and end of an evacuation pause.
   void record_collection_pause_start(double start_time_sec);
-  void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc);
+  void record_collection_pause_end(double pause_time_ms, size_t cards_scanned);
 
   // Record the start and end of a full collection.
   void record_full_collection_start();