6963209: G1: remove the concept of abandoned pauses

Summary: As part of 6944166 we disabled the concept of abandoned pauses (i.e., if the collection set is empty, we would still try to do a pause even if it is to update the RSets and scan the roots). This changeset removes the code and structures associated with abandoned pauses.
Reviewed-by: iveresov, johnc

src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -2843,93 +2843,57 @@ G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
       g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
 #endif // YOUNG_LIST_VERBOSE
 
-      // Now choose the CS. We may abandon a pause if we find no
-      // region that will fit in the MMU pause.
-      bool abandoned = g1_policy()->choose_collection_set(target_pause_time_ms);
+      g1_policy()->choose_collection_set(target_pause_time_ms);
 
       // Nothing to do if we were unable to choose a collection set.
-      if (!abandoned) {
 #if G1_REM_SET_LOGGING
-        gclog_or_tty->print_cr("\nAfter pause, heap:");
-        print();
+      gclog_or_tty->print_cr("\nAfter pause, heap:");
+      print();
 #endif
-        PrepareForRSScanningClosure prepare_for_rs_scan;
-        collection_set_iterate(&prepare_for_rs_scan);
+      PrepareForRSScanningClosure prepare_for_rs_scan;
+      collection_set_iterate(&prepare_for_rs_scan);
 
-        setup_surviving_young_words();
+      setup_surviving_young_words();
 
-        // Set up the gc allocation regions.
-        get_gc_alloc_regions();
+      // Set up the gc allocation regions.
+      get_gc_alloc_regions();
 
-        // Actually do the work...
-        evacuate_collection_set();
+      // Actually do the work...
+      evacuate_collection_set();
 
-        free_collection_set(g1_policy()->collection_set());
-        g1_policy()->clear_collection_set();
+      free_collection_set(g1_policy()->collection_set());
+      g1_policy()->clear_collection_set();
 
-        cleanup_surviving_young_words();
+      cleanup_surviving_young_words();
 
-        // Start a new incremental collection set for the next pause.
-        g1_policy()->start_incremental_cset_building();
+      // Start a new incremental collection set for the next pause.
+      g1_policy()->start_incremental_cset_building();
 
-        // Clear the _cset_fast_test bitmap in anticipation of adding
-        // regions to the incremental collection set for the next
-        // evacuation pause.
-        clear_cset_fast_test();
+      // Clear the _cset_fast_test bitmap in anticipation of adding
+      // regions to the incremental collection set for the next
+      // evacuation pause.
+      clear_cset_fast_test();
 
-        if (g1_policy()->in_young_gc_mode()) {
-          _young_list->reset_sampled_info();
+      if (g1_policy()->in_young_gc_mode()) {
+        _young_list->reset_sampled_info();
 
-          // Don't check the whole heap at this point as the
-          // GC alloc regions from this pause have been tagged
-          // as survivors and moved on to the survivor list.
-          // Survivor regions will fail the !is_young() check.
-          assert(check_young_list_empty(false /* check_heap */),
-              "young list should be empty");
+        // Don't check the whole heap at this point as the
+        // GC alloc regions from this pause have been tagged
+        // as survivors and moved on to the survivor list.
+        // Survivor regions will fail the !is_young() check.
+        assert(check_young_list_empty(false /* check_heap */),
+               "young list should be empty");
 
 #if YOUNG_LIST_VERBOSE
-          gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
-          _young_list->print();
+        gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
+        _young_list->print();
 #endif // YOUNG_LIST_VERBOSE
 
-          g1_policy()->record_survivor_regions(_young_list->survivor_length(),
+        g1_policy()->record_survivor_regions(_young_list->survivor_length(),
                                           _young_list->first_survivor_region(),
                                           _young_list->last_survivor_region());
 
-          _young_list->reset_auxilary_lists();
-        }
-      } else {
-        // We have abandoned the current collection. This can only happen
-        // if we're not doing young or partially young collections, and
-        // we didn't find an old region that we're able to collect within
-        // the allowed time.
-
-        assert(g1_policy()->collection_set() == NULL, "should be");
-        assert(_young_list->length() == 0, "because it should be");
-
-        // This should be a no-op.
-        abandon_collection_set(g1_policy()->inc_cset_head());
-
-        g1_policy()->clear_incremental_cset();
-        g1_policy()->stop_incremental_cset_building();
-
-        // Start a new incremental collection set for the next pause.
-        g1_policy()->start_incremental_cset_building();
-
-        // Clear the _cset_fast_test bitmap in anticipation of adding
-        // regions to the incremental collection set for the next
-        // evacuation pause.
-        clear_cset_fast_test();
-
-        // This looks confusing, because the DPT should really be empty
-        // at this point -- since we have not done any collection work,
-        // there should not be any derived pointers in the table to update;
-        // however, there is some additional state in the DPT which is
-        // reset at the end of the (null) "gc" here via the following call.
-        // A better approach might be to split off that state resetting work
-        // into a separate method that asserts that the DPT is empty and call
-        // that here. That is deferred for now.
-        COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
+        _young_list->reset_auxilary_lists();
       }
 
       if (evacuation_failed()) {
@@ -2963,7 +2927,7 @@ G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
       double end_time_sec = os::elapsedTime();
       double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
       g1_policy()->record_pause_time_ms(pause_time_ms);
-      g1_policy()->record_collection_pause_end(abandoned);
+      g1_policy()->record_collection_pause_end();
 
       assert(regions_accounted_for(), "Region leakage.");
 

src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp

@@ -88,7 +88,6 @@ G1CollectorPolicy::G1CollectorPolicy() :
   _all_mod_union_times_ms(new NumberSeq()),
 
   _summary(new Summary()),
-  _abandoned_summary(new AbandonedSummary()),
 
 #ifndef PRODUCT
   _cur_clear_ct_time_ms(0.0),
@@ -1124,7 +1123,7 @@ double G1CollectorPolicy::max_sum (double* data1,
 // Anything below that is considered to be zero
 #define MIN_TIMER_GRANULARITY 0.0000001
 
-void G1CollectorPolicy::record_collection_pause_end(bool abandoned) {
+void G1CollectorPolicy::record_collection_pause_end() {
   double end_time_sec = os::elapsedTime();
   double elapsed_ms = _last_pause_time_ms;
   bool parallel = ParallelGCThreads > 0;
@@ -1134,7 +1133,7 @@ void G1CollectorPolicy::record_collection_pause_end(bool abandoned) {
   size_t cur_used_bytes = _g1->used();
   assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
   bool last_pause_included_initial_mark = false;
-  bool update_stats = !abandoned && !_g1->evacuation_failed();
+  bool update_stats = !_g1->evacuation_failed();
 
 #ifndef PRODUCT
   if (G1YoungSurvRateVerbose) {
@@ -1273,12 +1272,7 @@ void G1CollectorPolicy::record_collection_pause_end(bool abandoned) {
     gclog_or_tty->print_cr("   Recording collection pause(%d)", _n_pauses);
   }
 
-  PauseSummary* summary;
-  if (abandoned) {
-    summary = _abandoned_summary;
-  } else {
-    summary = _summary;
-  }
+  PauseSummary* summary = _summary;
 
   double ext_root_scan_time = avg_value(_par_last_ext_root_scan_times_ms);
   double mark_stack_scan_time = avg_value(_par_last_mark_stack_scan_times_ms);
@@ -1346,61 +1340,58 @@ void G1CollectorPolicy::record_collection_pause_end(bool abandoned) {
 
   double other_time_ms = elapsed_ms;
 
-  if (!abandoned) {
-    if (_satb_drain_time_set)
-      other_time_ms -= _cur_satb_drain_time_ms;
+  if (_satb_drain_time_set) {
+    other_time_ms -= _cur_satb_drain_time_ms;
+  }
 
-    if (parallel)
-      other_time_ms -= _cur_collection_par_time_ms + _cur_clear_ct_time_ms;
-    else
-      other_time_ms -=
-        update_rs_time +
-        ext_root_scan_time + mark_stack_scan_time +
-        scan_rs_time + obj_copy_time;
+  if (parallel) {
+    other_time_ms -= _cur_collection_par_time_ms + _cur_clear_ct_time_ms;
+  } else {
+    other_time_ms -=
+      update_rs_time +
+      ext_root_scan_time + mark_stack_scan_time +
+      scan_rs_time + obj_copy_time;
   }
 
   if (PrintGCDetails) {
-    gclog_or_tty->print_cr("%s%s, %1.8lf secs]",
-                           abandoned ? " (abandoned)" : "",
+    gclog_or_tty->print_cr("%s, %1.8lf secs]",
                            (last_pause_included_initial_mark) ? " (initial-mark)" : "",
                            elapsed_ms / 1000.0);
 
-    if (!abandoned) {
-      if (_satb_drain_time_set) {
-        print_stats(1, "SATB Drain Time", _cur_satb_drain_time_ms);
-      }
-      if (_last_satb_drain_processed_buffers >= 0) {
-        print_stats(2, "Processed Buffers", _last_satb_drain_processed_buffers);
-      }
-      if (parallel) {
-        print_stats(1, "Parallel Time", _cur_collection_par_time_ms);
-        print_par_stats(2, "GC Worker Start Time",
-                        _par_last_gc_worker_start_times_ms, false);
-        print_par_stats(2, "Update RS", _par_last_update_rs_times_ms);
-        print_par_sizes(3, "Processed Buffers",
-                        _par_last_update_rs_processed_buffers, true);
-        print_par_stats(2, "Ext Root Scanning",
-                        _par_last_ext_root_scan_times_ms);
-        print_par_stats(2, "Mark Stack Scanning",
-                        _par_last_mark_stack_scan_times_ms);
-        print_par_stats(2, "Scan RS", _par_last_scan_rs_times_ms);
-        print_par_stats(2, "Object Copy", _par_last_obj_copy_times_ms);
-        print_par_stats(2, "Termination", _par_last_termination_times_ms);
-        print_par_sizes(3, "Termination Attempts",
-                        _par_last_termination_attempts, true);
-        print_par_stats(2, "GC Worker End Time",
-                        _par_last_gc_worker_end_times_ms, false);
-        print_stats(2, "Other", parallel_other_time);
-        print_stats(1, "Clear CT", _cur_clear_ct_time_ms);
-      } else {
-        print_stats(1, "Update RS", update_rs_time);
-        print_stats(2, "Processed Buffers",
-                    (int)update_rs_processed_buffers);
-        print_stats(1, "Ext Root Scanning", ext_root_scan_time);
-        print_stats(1, "Mark Stack Scanning", mark_stack_scan_time);
-        print_stats(1, "Scan RS", scan_rs_time);
-        print_stats(1, "Object Copying", obj_copy_time);
-      }
+    if (_satb_drain_time_set) {
+      print_stats(1, "SATB Drain Time", _cur_satb_drain_time_ms);
+    }
+    if (_last_satb_drain_processed_buffers >= 0) {
+      print_stats(2, "Processed Buffers", _last_satb_drain_processed_buffers);
+    }
+    if (parallel) {
+      print_stats(1, "Parallel Time", _cur_collection_par_time_ms);
+      print_par_stats(2, "GC Worker Start Time",
+                      _par_last_gc_worker_start_times_ms, false);
+      print_par_stats(2, "Update RS", _par_last_update_rs_times_ms);
+      print_par_sizes(3, "Processed Buffers",
+                      _par_last_update_rs_processed_buffers, true);
+      print_par_stats(2, "Ext Root Scanning",
+                      _par_last_ext_root_scan_times_ms);
+      print_par_stats(2, "Mark Stack Scanning",
+                      _par_last_mark_stack_scan_times_ms);
+      print_par_stats(2, "Scan RS", _par_last_scan_rs_times_ms);
+      print_par_stats(2, "Object Copy", _par_last_obj_copy_times_ms);
+      print_par_stats(2, "Termination", _par_last_termination_times_ms);
+      print_par_sizes(3, "Termination Attempts",
+                      _par_last_termination_attempts, true);
+      print_par_stats(2, "GC Worker End Time",
+                      _par_last_gc_worker_end_times_ms, false);
+      print_stats(2, "Other", parallel_other_time);
+      print_stats(1, "Clear CT", _cur_clear_ct_time_ms);
+    } else {
+      print_stats(1, "Update RS", update_rs_time);
+      print_stats(2, "Processed Buffers",
+                  (int)update_rs_processed_buffers);
+      print_stats(1, "Ext Root Scanning", ext_root_scan_time);
+      print_stats(1, "Mark Stack Scanning", mark_stack_scan_time);
+      print_stats(1, "Scan RS", scan_rs_time);
+      print_stats(1, "Object Copying", obj_copy_time);
     }
 #ifndef PRODUCT
     print_stats(1, "Cur Clear CC", _cur_clear_cc_time_ms);
@@ -2176,33 +2167,27 @@ void G1CollectorPolicy::print_summary(PauseSummary* summary) const {
     print_summary(1, "Other", summary->get_other_seq());
     {
       NumberSeq calc_other_times_ms;
-      if (body_summary != NULL) {
-        // not abandoned
-        if (parallel) {
-          // parallel
-          NumberSeq* other_parts[] = {
-            body_summary->get_satb_drain_seq(),
-            body_summary->get_parallel_seq(),
-            body_summary->get_clear_ct_seq()
-          };
-          calc_other_times_ms = NumberSeq(summary->get_total_seq(),
-                                          3, other_parts);
-        } else {
-          // serial
-          NumberSeq* other_parts[] = {
-            body_summary->get_satb_drain_seq(),
-            body_summary->get_update_rs_seq(),
-            body_summary->get_ext_root_scan_seq(),
-            body_summary->get_mark_stack_scan_seq(),
-            body_summary->get_scan_rs_seq(),
-            body_summary->get_obj_copy_seq()
-          };
-          calc_other_times_ms = NumberSeq(summary->get_total_seq(),
-                                          7, other_parts);
-        }
+      if (parallel) {
+        // parallel
+        NumberSeq* other_parts[] = {
+          body_summary->get_satb_drain_seq(),
+          body_summary->get_parallel_seq(),
+          body_summary->get_clear_ct_seq()
+        };
+        calc_other_times_ms = NumberSeq(summary->get_total_seq(),
+                                        3, other_parts);
       } else {
-        // abandoned
-        calc_other_times_ms = NumberSeq();
+        // serial
+        NumberSeq* other_parts[] = {
+          body_summary->get_satb_drain_seq(),
+          body_summary->get_update_rs_seq(),
+          body_summary->get_ext_root_scan_seq(),
+          body_summary->get_mark_stack_scan_seq(),
+          body_summary->get_scan_rs_seq(),
+          body_summary->get_obj_copy_seq()
+        };
+        calc_other_times_ms = NumberSeq(summary->get_total_seq(),
+                                        7, other_parts);
       }
       check_other_times(1,  summary->get_other_seq(), &calc_other_times_ms);
     }
@@ -2213,20 +2198,6 @@ void G1CollectorPolicy::print_summary(PauseSummary* summary) const {
   gclog_or_tty->print_cr("");
 }
 
-void
-G1CollectorPolicy::print_abandoned_summary(PauseSummary* summary) const {
-  bool printed = false;
-  if (summary->get_total_seq()->num() > 0) {
-    printed = true;
-    print_summary(summary);
-  }
-  if (!printed) {
-    print_indent(0);
-    gclog_or_tty->print_cr("none");
-    gclog_or_tty->print_cr("");
-  }
-}
-
 void G1CollectorPolicy::print_tracing_info() const {
   if (TraceGen0Time) {
     gclog_or_tty->print_cr("ALL PAUSES");
@@ -2240,9 +2211,6 @@ void G1CollectorPolicy::print_tracing_info() const {
     gclog_or_tty->print_cr("EVACUATION PAUSES");
     print_summary(_summary);
 
-    gclog_or_tty->print_cr("ABANDONED PAUSES");
-    print_abandoned_summary(_abandoned_summary);
-
     gclog_or_tty->print_cr("MISC");
     print_summary_sd(0, "Stop World", _all_stop_world_times_ms);
     print_summary_sd(0, "Yields", _all_yield_times_ms);
@@ -2868,19 +2836,12 @@ void G1CollectorPolicy::print_collection_set(HeapRegion* list_head, outputStream
 }
 #endif // !PRODUCT
 
-bool
+void
 G1CollectorPolicy_BestRegionsFirst::choose_collection_set(
                                                   double target_pause_time_ms) {
   // Set this here - in case we're not doing young collections.
   double non_young_start_time_sec = os::elapsedTime();
 
-  // The result that this routine will return. This will be set to
-  // false if:
-  // * we're doing a young or partially young collection and we
-  //   have added the youg regions to collection set, or
-  // * we add old regions to the collection set.
-  bool abandon_collection = true;
-
   start_recording_regions();
 
   guarantee(target_pause_time_ms > 0.0,
@@ -2984,10 +2945,6 @@ G1CollectorPolicy_BestRegionsFirst::choose_collection_set(
     }
 
     assert(_inc_cset_size == _g1->young_list()->length(), "Invariant");
-    if (_inc_cset_size > 0) {
-      assert(_collection_set != NULL, "Invariant");
-      abandon_collection = false;
-    }
 
     double young_end_time_sec = os::elapsedTime();
     _recorded_young_cset_choice_time_ms =
@@ -3009,10 +2966,6 @@ G1CollectorPolicy_BestRegionsFirst::choose_collection_set(
     NumberSeq seq;
     double avg_prediction = 100000000000000000.0; // something very large
 
-    // Save the current size of the collection set to detect
-    // if we actually added any old regions.
-    size_t n_young_regions = _collection_set_size;
-
     do {
       hr = _collectionSetChooser->getNextMarkedRegion(time_remaining_ms,
                                                       avg_prediction);
@@ -3039,12 +2992,6 @@ G1CollectorPolicy_BestRegionsFirst::choose_collection_set(
     if (!adaptive_young_list_length() &&
         _collection_set_size < _young_list_fixed_length)
       _should_revert_to_full_young_gcs  = true;
-
-    if (_collection_set_size > n_young_regions) {
-      // We actually added old regions to the collection set
-      // so we are not abandoning this collection.
-      abandon_collection = false;
-    }
   }
 
 choose_collection_set_end:
@@ -3057,19 +3004,6 @@ choose_collection_set_end:
   double non_young_end_time_sec = os::elapsedTime();
   _recorded_non_young_cset_choice_time_ms =
     (non_young_end_time_sec - non_young_start_time_sec) * 1000.0;
-
-  // Here we are supposed to return whether the pause should be
-  // abandoned or not (i.e., whether the collection set is empty or
-  // not). However, this introduces a subtle issue when a pause is
-  // initiated explicitly with System.gc() and
-  // +ExplicitGCInvokesConcurrent (see Comment #2 in CR 6944166), it's
-  // supposed to start a marking cycle, and it's abandoned. So, by
-  // returning false here we are telling the caller never to consider
-  // a pause to be abandoned. We'll actually remove all the code
-  // associated with abandoned pauses as part of CR 6963209, but we are
-  // just disabling them this way for the moment to avoid increasing
-  // further the amount of changes for CR 6944166.
-  return false;
 }
 
 void G1CollectorPolicy_BestRegionsFirst::record_full_collection_end() {
@@ -3084,7 +3018,7 @@ expand_if_possible(size_t numRegions) {
 }
 
 void G1CollectorPolicy_BestRegionsFirst::
-record_collection_pause_end(bool abandoned) {
-  G1CollectorPolicy::record_collection_pause_end(abandoned);
+record_collection_pause_end() {
+  G1CollectorPolicy::record_collection_pause_end();
   assert(assertMarkedBytesDataOK(), "Marked regions not OK at pause end.");
 }

src/share/vm/gc_implementation/g1/g1CollectorPolicy.hpp

@@ -76,9 +76,6 @@ public:
   virtual MainBodySummary*    main_body_summary()    { return this; }
 };
 
-class AbandonedSummary: public PauseSummary {
-};
-
 class G1CollectorPolicy: public CollectorPolicy {
 protected:
   // The number of pauses during the execution.
@@ -148,7 +145,6 @@ protected:
   TruncatedSeq* _concurrent_mark_cleanup_times_ms;
 
   Summary*           _summary;
-  AbandonedSummary*  _abandoned_summary;
 
   NumberSeq* _all_pause_times_ms;
   NumberSeq* _all_full_gc_times_ms;
@@ -573,7 +569,6 @@ protected:
                          NumberSeq* calc_other_times_ms) const;
 
   void print_summary (PauseSummary* stats) const;
-  void print_abandoned_summary(PauseSummary* summary) const;
 
   void print_summary (int level, const char* str, NumberSeq* seq) const;
   void print_summary_sd (int level, const char* str, NumberSeq* seq) const;
@@ -886,7 +881,7 @@ public:
   virtual void record_collection_pause_end_CH_strong_roots();
   virtual void record_collection_pause_end_G1_strong_roots();
 
-  virtual void record_collection_pause_end(bool abandoned);
+  virtual void record_collection_pause_end();
 
   // Record the fact that a full collection occurred.
   virtual void record_full_collection_start();
@@ -999,7 +994,7 @@ public:
   // Choose a new collection set.  Marks the chosen regions as being
   // "in_collection_set", and links them together.  The head and number of
   // the collection set are available via access methods.
-  virtual bool choose_collection_set(double target_pause_time_ms) = 0;
+  virtual void choose_collection_set(double target_pause_time_ms) = 0;
 
   // The head of the list (via "next_in_collection_set()") representing the
   // current collection set.
@@ -1256,7 +1251,7 @@ class G1CollectorPolicy_BestRegionsFirst: public G1CollectorPolicy {
   // If the estimated is less then desirable, resize if possible.
   void expand_if_possible(size_t numRegions);
 
-  virtual bool choose_collection_set(double target_pause_time_ms);
+  virtual void choose_collection_set(double target_pause_time_ms);
   virtual void record_collection_pause_start(double start_time_sec,
                                              size_t start_used);
   virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
@@ -1267,7 +1262,7 @@ public:
   G1CollectorPolicy_BestRegionsFirst() {
     _collectionSetChooser = new CollectionSetChooser();
   }
-  void record_collection_pause_end(bool abandoned);
+  void record_collection_pause_end();
   bool should_do_collection_pause(size_t word_size);
   // This is not needed any more, after the CSet choosing code was
   // changed to use the pause prediction work. But let's leave the