Do the mark information reset more fine grained (like before this change) to not potentially make HeapRegion::hr_clear() too slow

Author: Thomas Schatzl

src/hotspot/share/gc/g1/g1ConcurrentMark.cpp

@@ -575,7 +575,6 @@ void G1ConcurrentMark::clear_statistics(HeapRegion* r) {
   for (uint j = 0; j < _max_num_tasks; ++j) {
     _tasks[j]->clear_mark_stats_cache(region_idx);
   }
-  _top_at_mark_starts[region_idx] = _g1h->bottom_addr_for_region(region_idx);
   _top_at_rebuild_starts[region_idx] = nullptr;
   _region_mark_stats[region_idx].clear();
 }
@@ -586,6 +585,16 @@ void G1ConcurrentMark::humongous_object_eagerly_reclaimed(HeapRegion* r) {
 
   // Need to clear mark bit of the humongous object. Doing this unconditionally is fine.
   mark_bitmap()->clear(r->bottom());
+
+  if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) {
+    return;
+}
+
+  // Clear any statistics about the region gathered so far.
+  _g1h->humongous_obj_regions_iterate(r,
+                                      [&] (HeapRegion* r) {
+                                        clear_statistics(r);
+                                      });
 }
 
 void G1ConcurrentMark::reset_marking_for_restart() {
@@ -1465,6 +1474,7 @@ class G1ReclaimEmptyRegionsTask : public WorkerTask {
           _g1h->free_region(hr, _local_cleanup_list);
         }
         hr->clear_cardtable();
+        _g1h->concurrent_mark()->clear_statistics(hr);
       }
 
       return false;

src/hotspot/share/gc/g1/g1HeapRegion.cpp

@@ -124,7 +124,7 @@ void HeapRegion::hr_clear(bool clear_space) {
 
   rem_set()->clear();
 
-  G1CollectedHeap::heap()->concurrent_mark()->clear_statistics(this);
+  G1CollectedHeap::heap()->concurrent_mark()->reset_top_at_mark_start(this);
 
   _parsable_bottom = bottom();
   _garbage_bytes = 0;

src/hotspot/share/gc/g1/g1HeapRegion.inline.hpp

@@ -187,9 +187,9 @@ inline void HeapRegion::reset_skip_compacting_after_full_gc() {
 }
 
 inline void HeapRegion::reset_after_full_gc_common() {
-  // After a full gc the mark bitmap in a movable region is invalid. Reset marking
+  // After a full gc the mark information in a movable region is invalid. Reset marking
   // information.
-  G1CollectedHeap::heap()->concurrent_mark()->clear_statistics(this); // FIXME?
+  G1CollectedHeap::heap()->concurrent_mark()->reset_top_at_mark_start(this);
 
   // Everything above bottom() is parsable and live.
   reset_parsable_bottom();

src/hotspot/share/gc/g1/g1RemSet.cpp

@@ -1133,6 +1133,7 @@ class G1MergeHeapRootsTask : public WorkerTask {
       // so the bitmap for the regions in the collection set must be cleared if not already.
       if (should_clear_region(hr)) {
         _g1h->clear_bitmap_for_region(hr);
+        _g1h->concurrent_mark()->reset_top_at_mark_start(hr);
       } else {
         assert_bitmap_clear(hr, _g1h->concurrent_mark()->mark_bitmap());
       }

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

@@ -555,7 +555,6 @@ class G1PostEvacuateCollectionSetCleanupTask2::ProcessEvacuationFailedRegionsTas
       bool clear_mark_data = !g1h->collector_state()->in_concurrent_start_gc() ||
                              g1h->policy()->should_retain_evac_failed_region(r);
 
-      cm->clear_statistics(r);
       if (clear_mark_data) {
         g1h->clear_bitmap_for_region(r);
       } else {