8300769: Remove G1CollectionSet::_inc_bytes_used_before

Reviewed-by: ayang, iwalulya

src/hotspot/share/gc/g1/g1CollectionSet.cpp

@@ -59,10 +59,8 @@ G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy) :
   _collection_set_cur_length(0),
   _collection_set_max_length(0),
   _num_optional_regions(0),
-  _bytes_used_before(0),
   _inc_build_state(Inactive),
-  _inc_part_start(0),
-  _inc_bytes_used_before(0) {
+  _inc_part_start(0) {
 }
 
 G1CollectionSet::~G1CollectionSet() {
@@ -114,7 +112,6 @@ void G1CollectionSet::add_old_region(HeapRegion* hr) {
   assert(_collection_set_cur_length < _collection_set_max_length, "Collection set now larger than maximum size.");
   _collection_set_regions[_collection_set_cur_length++] = hr->hrm_index();
 
-  _bytes_used_before += hr->used();
   _old_region_length++;
 
   _g1h->old_set_remove(hr);
@@ -133,8 +130,6 @@ void G1CollectionSet::start_incremental_building() {
   assert(_collection_set_cur_length == 0, "Collection set must be empty before starting a new collection set.");
   assert(_inc_build_state == Inactive, "Precondition");
 
-  _inc_bytes_used_before = 0;
-
   update_incremental_marker();
 }
 
@@ -200,26 +195,6 @@ void G1CollectionSet::add_young_region_common(HeapRegion* hr) {
   assert(hr->is_young(), "invariant");
   assert(_inc_build_state == Active, "Precondition");
 
-  // This routine is used when:
-  // * adding survivor regions to the incremental cset at the end of an
-  //   evacuation pause or
-  // * adding the current allocation region to the incremental cset
-  //   when it is retired.
-  // Therefore this routine may be called at a safepoint by the
-  // VM thread, or in-between safepoints by mutator threads (when
-  // retiring the current allocation region)
-  // We need to clear and set the cached recorded/cached collection set
-  // information in the heap region here (before the region gets added
-  // to the collection set). An individual heap region's cached values
-  // are calculated, aggregated with the policy collection set info,
-  // and cached in the heap region here (initially) and (subsequently)
-  // by the Young List sampling code.
-  // Ignore calls to this due to retirement during full gc.
-
-  if (!_g1h->collector_state()->in_full_gc()) {
-    _inc_bytes_used_before += hr->used();
-  }
-
   assert(!hr->in_collection_set(), "invariant");
   _g1h->register_young_region_with_region_attr(hr);
 
@@ -334,8 +309,6 @@ double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1Survi
 
   verify_young_cset_indices();
 
-  _bytes_used_before = _inc_bytes_used_before;
-
   double predicted_base_time_ms = _policy->predict_base_time_ms(pending_cards);
   // Base time already includes the whole remembered set related time, so do not add that here
   // again.

src/hotspot/share/gc/g1/g1CollectionSet.hpp

@@ -156,11 +156,6 @@ class G1CollectionSet {
   // correspond to the first x entries in the collection set candidates.
   uint _num_optional_regions;
 
-  // The number of bytes in the collection set before the pause. Set from
-  // the incrementally built collection set at the start of an evacuation
-  // pause, and updated as more regions are added to the collection set.
-  size_t _bytes_used_before;
-
   enum CSetBuildType {
     Active,             // We are actively building the collection set
     Inactive            // We are not actively building the collection set
@@ -169,15 +164,6 @@ class G1CollectionSet {
   CSetBuildType _inc_build_state;
   size_t _inc_part_start;
 
-  // The associated information that is maintained while the incremental
-  // collection set is being built with *young* regions. Used to populate
-  // the recorded info for the evacuation pause.
-
-  // The number of bytes in the incrementally built collection set.
-  // Used to set _collection_set_bytes_used_before at the start of
-  // an evacuation pause.
-  size_t _inc_bytes_used_before;
-
   G1CollectorState* collector_state() const;
   G1GCPhaseTimes* phase_times();
 
@@ -273,14 +259,6 @@ class G1CollectionSet {
 
   void iterate_optional(HeapRegionClosure* cl) const;
 
-  size_t bytes_used_before() const {
-    return _bytes_used_before;
-  }
-
-  void reset_bytes_used_before() {
-    _bytes_used_before = 0;
-  }
-
   // Finalize the initial collection set consisting of all young regions potentially a
   // few old gen regions.
   void finalize_initial_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor);

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

@@ -103,8 +103,9 @@ void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 
   update_young_length_bounds();
-  // We may immediately start allocating regions and placing them on the
-  // collection set list. Initialize the per-collection set info
+
+  // We immediately start allocating regions placing them in the collection set.
+  // Initialize the collection set info.
   _collection_set->start_incremental_building();
 }
 
@@ -638,8 +639,6 @@ void G1Policy::record_young_collection_start() {
 
   phase_times()->record_cur_collection_start_sec(now.seconds());
 
-  _collection_set->reset_bytes_used_before();
-
   // do that for any other surv rate groups
   _eden_surv_rate_group->stop_adding_regions();
   _survivors_age_table.clear();

src/hotspot/share/gc/g1/g1YoungCollector.cpp

@@ -1020,7 +1020,6 @@ void G1YoungCollector::post_evacuate_collection_set(G1EvacInfo* evacuation_info,
 
   _g1h->record_obj_copy_mem_stats();
 
-  evacuation_info->set_collection_set_used_before(collection_set()->bytes_used_before());
   evacuation_info->set_bytes_used(_g1h->bytes_used_during_gc());
 
   _g1h->start_new_collection_set();

src/hotspot/share/gc/g1/g1YoungGCPostEvacuateTasks.cpp

@@ -465,6 +465,7 @@ class FreeCSetStats {
 
   void report(G1CollectedHeap* g1h, G1EvacInfo* evacuation_info) {
     evacuation_info->set_regions_freed(_regions_freed);
+    evacuation_info->set_collection_set_used_before(_before_used_bytes + _after_used_bytes);
     evacuation_info->increment_collection_set_used_after(_after_used_bytes);
 
     g1h->decrement_summary_bytes(_before_used_bytes);