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

*** 302,316 ****
      _scan_chunks_shift = (uint8_t)log2_intptr(HeapRegion::CardsPerRegion / _scan_chunks_per_region);
      _scan_top = NEW_C_HEAP_ARRAY(HeapWord*, max_regions, mtGC);
    }
  
    void prepare() {
-     for (size_t i = 0; i < _max_regions; i++) {
-       _collection_set_iter_state[i] = false;
-       clear_scan_top((uint)i);
-     }
- 
      _all_dirty_regions = new G1DirtyRegions(_max_regions);
      _next_dirty_regions = new G1DirtyRegions(_max_regions);
    }
  
    void prepare_for_merge_heap_roots() {
--- 302,311 ----
*** 401,410 ****
--- 396,409 ----
          cur = 0;
        }
      } while (cur != start_pos);
    }
  
+   void reset_region_claim(uint region_idx) {
+     _collection_set_iter_state[region_idx] = false;
+   }
+ 
    // Attempt to claim the given region in the collection set for iteration. Returns true
    // if this call caused the transition from Unclaimed to Claimed.
    inline bool claim_collection_set_region(uint region) {
      assert(region < _max_regions, "Tried to access invalid region %u", region);
      if (_collection_set_iter_state[region]) {
*** 880,902 ****
      p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_refs_scanned(), G1GCPhaseTimes::ScanHRScannedOptRefs);
      p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_refs_memory_used(), G1GCPhaseTimes::ScanHRUsedMemory);
    }
  }
  
! // Creates a snapshot of the current _top values at the start of collection to
! // filter out card marks that we do not want to scan.
! void G1RemSet::prepare_region_for_scanning(HeapRegion* region) {
    uint hrm_index = region->hrm_index();
    if (region->in_collection_set()) {
      // Young regions had their card table marked as young at their allocation;
      // we need to make sure that these marks are cleared at the end of GC, *but*
      // they should not be scanned for cards.
      // So directly add them to the "all_dirty_regions".
      // Same for regions in the (initial) collection set: they may contain cards from
      // the log buffers, make sure they are cleaned.
      _scan_state->add_all_dirty_region(hrm_index);
!   } else if (region->is_old_or_humongous_or_archive()) {
      _scan_state->set_scan_top(hrm_index, region->top());
    }
  }
  
  void G1RemSet::prepare_for_scan_heap_roots() {
--- 879,903 ----
      p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_refs_scanned(), G1GCPhaseTimes::ScanHRScannedOptRefs);
      p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_refs_memory_used(), G1GCPhaseTimes::ScanHRUsedMemory);
    }
  }
  
! void G1RemSet::prepare_region_for_scan(HeapRegion* region) {
    uint hrm_index = region->hrm_index();
+ 
+   _scan_state->reset_region_claim(hrm_index);
    if (region->in_collection_set()) {
      // Young regions had their card table marked as young at their allocation;
      // we need to make sure that these marks are cleared at the end of GC, *but*
      // they should not be scanned for cards.
      // So directly add them to the "all_dirty_regions".
      // Same for regions in the (initial) collection set: they may contain cards from
      // the log buffers, make sure they are cleaned.
+     _scan_state->clear_scan_top(hrm_index);
      _scan_state->add_all_dirty_region(hrm_index);
!   } else {
!     assert(region->is_old_or_humongous_or_archive(), "All other regions should be in the collection set");
      _scan_state->set_scan_top(hrm_index, region->top());
    }
  }
  
  void G1RemSet::prepare_for_scan_heap_roots() {