8338440: Parallel: Improve fragmentation mitigation in Full GC

src/hotspot/share/gc/parallel/psParallelCompact.cpp

@@ -178,30 +178,30 @@ void SplitInfo::record(size_t split_region_idx, HeapWord* split_point, size_t pr
   }
 
   _split_region_idx = split_region_idx;
-  _split_destination = split_destination;
   _split_point = split_point;
   _preceding_live_words = preceding_live_words;
-  _split_destination_count = split_destination_count;
+  _preceding_destination = split_destination;
+  _preceding_destination_count = split_destination_count;
 }
 
 void SplitInfo::clear()
 {
   _split_region_idx = 0;
-  _split_destination = nullptr;
   _split_point = nullptr;
   _preceding_live_words = 0;
-  _split_destination_count = 0;
+  _preceding_destination = nullptr;
+  _preceding_destination_count = 0;
   assert(!is_valid(), "sanity");
 }
 
 #ifdef  ASSERT
 void SplitInfo::verify_clear()
 {
   assert(_split_region_idx == 0, "not clear");
-  assert(_split_destination == nullptr, "not clear");
   assert(_split_point == nullptr, "not clear");
   assert(_preceding_live_words == 0, "not clear");
-  assert(_split_destination_count == 0, "not clear");
+  assert(_preceding_destination == nullptr, "not clear");
+  assert(_preceding_destination_count == 0, "not clear");
 }
 #endif  // #ifdef ASSERT
 
@@ -484,7 +484,7 @@ bool ParallelCompactData::summarize(SplitInfo& split_info,
     }
 
     uint destination_count = split_info.is_split(cur_region)
-                             ? split_info.split_destination_count()
+                             ? split_info.preceding_destination_count()
                              : 0;
 
     HeapWord* const last_addr = dest_addr + words - 1;
@@ -1612,9 +1612,9 @@ void PSParallelCompact::forward_to_new_addr() {
 
           if (split_info.is_split(cur_region)) {
             // Part 1: will be relocated to space-1
-            HeapWord* split_destination = split_info.split_destination();
+            HeapWord* preceding_destination = split_info.preceding_destination();
             HeapWord* split_point = split_info.split_point();
-            forward_objs_in_range(cm, region_start + live_words, split_point, split_destination + live_words);
+            forward_objs_in_range(cm, region_start + live_words, split_point, preceding_destination + live_words);
 
             // Part 2: will be relocated to space-2
             HeapWord* destination = region_ptr->destination();
@@ -2056,7 +2056,7 @@ HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
     if (dest_addr == src_region_destination) {
       return split_info.split_point();
     }
-    region_start_destination = split_info.split_destination();
+    region_start_destination = split_info.preceding_destination();
   } else {
     region_start_destination = src_region_destination;
   }

src/hotspot/share/gc/parallel/psParallelCompact.hpp

@@ -121,22 +121,22 @@ class SplitInfo
   // Return true if this split holds data for the specified source region.
   inline bool is_split(size_t region_idx) const;
 
-  // A split region has two "destinations", living in two spaces. This method
-  // returns the split (first) one -- destination for the first live word on
-  // this split region.
-  HeapWord* split_destination() const {
-    assert(_split_destination != nullptr, "inv");
-    return _split_destination;
-  }
-
   // Obj at the split point doesn't fit the previous space and will be relocated to the next space.
   HeapWord* split_point() const { return _split_point; }
 
   // Number of live words before the split point on this region.
   size_t preceding_live_words() const { return _preceding_live_words; }
 
+  // A split region has two "destinations", living in two spaces. This method
+  // returns the first one -- destination for the first live word on
+  // this split region.
+  HeapWord* preceding_destination() const {
+    assert(_preceding_destination != nullptr, "inv");
+    return _preceding_destination;
+  }
+
   // Number of regions the preceding live words are relocated into.
-  uint split_destination_count() const { return _split_destination_count; }
+  uint preceding_destination_count() const { return _preceding_destination_count; }
 
   void record(size_t split_region_idx, HeapWord* split_point, size_t preceding_live_words);
 
@@ -146,10 +146,10 @@ class SplitInfo
 
 private:
   size_t       _split_region_idx;
-  HeapWord*    _split_destination;
   HeapWord*    _split_point;
   size_t       _preceding_live_words;
-  uint         _split_destination_count;
+  HeapWord*    _preceding_destination;
+  uint         _preceding_destination_count;
 };
 
 inline bool SplitInfo::is_split(size_t region_idx) const