8219003: SA: Refactor live regions iteration in preparation for JDK-8218922

Reviewed-by: eosterlund, ysuenaga

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/cms/CompactibleFreeListSpace.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -35,7 +35,7 @@ import sun.jvm.hotspot.runtime.*;
 import sun.jvm.hotspot.types.*;
 import sun.jvm.hotspot.utilities.*;
 
-public class CompactibleFreeListSpace extends CompactibleSpace {
+public class CompactibleFreeListSpace extends CompactibleSpace implements LiveRegionsProvider {
    private static AddressField collectorField;
    private static AddressField indexedFreeListField;
    private static AddressField dictionaryField;
@@ -93,10 +93,10 @@ public class CompactibleFreeListSpace extends CompactibleSpace {
    }
 
    public long used0() {
-      List regions = getLiveRegions();
+      List<MemRegion> regions = getLiveRegions();
       long usedSize = 0L;
-      for (Iterator itr = regions.iterator(); itr.hasNext();) {
+      for (Iterator<MemRegion> itr = regions.iterator(); itr.hasNext();) {
-         MemRegion mr = (MemRegion) itr.next();
+         MemRegion mr = itr.next();
          usedSize += mr.byteSize();
       }
       return usedSize;
@@ -154,8 +154,9 @@ public class CompactibleFreeListSpace extends CompactibleSpace {
        return addr;
    }
 
-   public List/*<MemRegion>*/ getLiveRegions() {
+  @Override
-      List res = new ArrayList(); // List<MemRegion>
+   public List<MemRegion> getLiveRegions() {
+      List<MemRegion> res = new ArrayList<>();
       VM vm = VM.getVM();
       Debugger dbg = vm.getDebugger();
       ObjectHeap heap = vm.getObjectHeap();

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/cms/ConcurrentMarkSweepGeneration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -66,6 +66,9 @@ public class ConcurrentMarkSweepGeneration extends CardGeneration {
   public void spaceIterate(SpaceClosure blk, boolean usedOnly) {
      blk.doSpace(cmsSpace());
   }
+  public void liveRegionsIterate(LiveRegionsClosure closure) {
+      closure.doLiveRegions(cmsSpace());
+  }
 
   public Generation.Name kind() {
     return Generation.Name.CONCURRENT_MARK_SWEEP;

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/epsilon/EpsilonHeap.java

@@ -80,6 +80,11 @@ public class EpsilonHeap extends CollectedHeap {
     return space;
   }
 
+  @Override
+  public void liveRegionsIterate(LiveRegionsClosure closure) {
+    closure.doLiveRegions(space());
+  }
+
   @Override
   public void printOn(PrintStream tty) {
      MemRegion mr = reservedRegion();

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/g1/G1CollectedHeap.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -32,8 +32,9 @@ import java.util.Observer;
 import sun.jvm.hotspot.debugger.Address;
 import sun.jvm.hotspot.gc.shared.CollectedHeap;
 import sun.jvm.hotspot.gc.shared.CollectedHeapName;
-import sun.jvm.hotspot.gc.shared.SpaceClosure;
+import sun.jvm.hotspot.gc.shared.LiveRegionsClosure;
 import sun.jvm.hotspot.gc.shared.PrintRegionClosure;
+import sun.jvm.hotspot.gc.shared.SpaceClosure;
 import sun.jvm.hotspot.memory.MemRegion;
 import sun.jvm.hotspot.runtime.VM;
 import sun.jvm.hotspot.runtime.VMObjectFactory;
@@ -137,6 +138,15 @@ public class G1CollectedHeap extends CollectedHeap {
         return CollectedHeapName.G1;
     }
 
+    @Override
+    public void liveRegionsIterate(LiveRegionsClosure closure) {
+        Iterator<HeapRegion> iter = heapRegionIterator();
+        while (iter.hasNext()) {
+            HeapRegion hr = iter.next();
+            closure.doLiveRegions(hr);
+        }
+    }
+
     @Override
     public void printOn(PrintStream tty) {
         MemRegion mr = reservedRegion();

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/g1/HeapRegion.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -32,6 +32,7 @@ import java.util.Observer;
 import sun.jvm.hotspot.debugger.Address;
 import sun.jvm.hotspot.debugger.OopHandle;
 import sun.jvm.hotspot.gc.shared.CompactibleSpace;
+import sun.jvm.hotspot.gc.shared.LiveRegionsProvider;
 import sun.jvm.hotspot.memory.MemRegion;
 import sun.jvm.hotspot.runtime.VM;
 import sun.jvm.hotspot.runtime.VMObjectFactory;
@@ -43,7 +44,7 @@ import sun.jvm.hotspot.types.TypeDataBase;
 // Mirror class for HeapRegion. Currently we don't actually include
 // any of its fields but only iterate over it.
 
-public class HeapRegion extends CompactibleSpace {
+public class HeapRegion extends CompactibleSpace implements LiveRegionsProvider {
     // static int GrainBytes;
     static private CIntegerField grainBytesField;
     static private AddressField topField;
@@ -86,8 +87,8 @@ public class HeapRegion extends CompactibleSpace {
     }
 
     @Override
-    public List getLiveRegions() {
+    public List<MemRegion> getLiveRegions() {
-        List res = new ArrayList();
+        List<MemRegion> res = new ArrayList<>();
         res.add(new MemRegion(bottom(), top()));
         return res;
     }

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/parallel/ImmutableSpace.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -73,7 +73,7 @@ public abstract class ImmutableSpace extends VMObject {
    }
 
    /** returns all MemRegions where live objects are */
-   public abstract List/*<MemRegion>*/ getLiveRegions();
+   public abstract List<MemRegion> getLiveRegions();
 
    /** Returned value is in bytes */
    public long capacity() { return end().minus(bottom()); }

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/parallel/MutableSpace.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -62,8 +62,8 @@ public class MutableSpace extends ImmutableSpace {
    }
 
    /** returns all MemRegions where live objects are */
-   public List/*<MemRegion>*/ getLiveRegions() {
+   public List<MemRegion> getLiveRegions() {
-      List res = new ArrayList();
+      List<MemRegion> res = new ArrayList<>();
       res.add(new MemRegion(bottom(), top()));
       return res;
    }

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/parallel/ParallelScavengeHeap.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -29,6 +29,7 @@ import java.util.*;
 
 import sun.jvm.hotspot.debugger.*;
 import sun.jvm.hotspot.gc.shared.*;
+import sun.jvm.hotspot.memory.MemRegion;
 import sun.jvm.hotspot.runtime.*;
 import sun.jvm.hotspot.types.*;
 
@@ -88,6 +89,35 @@ public class ParallelScavengeHeap extends CollectedHeap {
       return CollectedHeapName.PARALLEL;
    }
 
+   // Simple wrapper to provide toString() usable for debugging.
+   private class LiveRegionProviderImpl implements LiveRegionsProvider {
+      private String name;
+      private MutableSpace space;
+
+      public LiveRegionProviderImpl(String name, MutableSpace space) {
+         this.name = name;
+         this.space = space;
+      }
+
+      @Override
+      public List<MemRegion> getLiveRegions() {
+         return space.getLiveRegions();
+      }
+      @Override
+      public String toString() {
+         return name;
+      }
+   }
+
+   public void liveRegionsIterate(LiveRegionsClosure closure) {
+      // Add eden space
+      closure.doLiveRegions(new LiveRegionProviderImpl("eden", youngGen().edenSpace()));
+      // Add from-space but not to-space
+      closure.doLiveRegions(new LiveRegionProviderImpl("from", youngGen().fromSpace()));
+
+      closure.doLiveRegions(new LiveRegionProviderImpl("old ", oldGen().objectSpace()));
+   }
+
    public void printOn(PrintStream tty) {
       tty.print("ParallelScavengeHeap [ ");
       youngGen().printOn(tty);

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/serial/DefNewGeneration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -94,6 +94,11 @@ public class DefNewGeneration extends Generation {
     }
   }
 
+  public void liveRegionsIterate(LiveRegionsClosure closure) {
+    closure.doLiveRegions(eden());
+    closure.doLiveRegions(from());
+  }
+
   public void printOn(PrintStream tty) {
     tty.print("  eden");
     eden().printOn(tty);

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/serial/TenuredGeneration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -76,6 +76,10 @@ public class TenuredGeneration extends CardGeneration {
     blk.doSpace(theSpace());
   }
 
+  public void liveRegionsIterate(LiveRegionsClosure closure) {
+    closure.doLiveRegions(theSpace());
+  }
+
   public void printOn(PrintStream tty) {
     tty.print("  old ");
     theSpace().printOn(tty);

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/shared/CollectedHeap.java

@@ -28,6 +28,7 @@ import java.io.*;
 import java.util.*;
 
 import sun.jvm.hotspot.debugger.*;
+import sun.jvm.hotspot.gc.shared.*;
 import sun.jvm.hotspot.memory.*;
 import sun.jvm.hotspot.runtime.*;
 import sun.jvm.hotspot.types.*;
@@ -77,6 +78,8 @@ public abstract class CollectedHeap extends VMObject {
 
   public abstract CollectedHeapName kind();
 
+  public abstract void liveRegionsIterate(LiveRegionsClosure closure);
+
   public String oopAddressDescription(OopHandle handle) {
       return handle.toString();
   }

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/shared/ContiguousSpace.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -32,7 +32,7 @@ import sun.jvm.hotspot.memory.*;
 import sun.jvm.hotspot.runtime.*;
 import sun.jvm.hotspot.types.*;
 
-public class ContiguousSpace extends CompactibleSpace {
+public class ContiguousSpace extends CompactibleSpace implements LiveRegionsProvider {
   private static AddressField topField;
 
   static {
@@ -79,8 +79,8 @@ public class ContiguousSpace extends CompactibleSpace {
   }
 
   /** Returns regions of Space where live objects live */
-  public List/*<MemRegion>*/ getLiveRegions() {
+  public List<MemRegion> getLiveRegions() {
-    List res = new ArrayList();
+    List<MemRegion> res = new ArrayList<>();
     res.add(new MemRegion(bottom(), top()));
     return res;
   }

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/shared/GenCollectedHeap.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -28,6 +28,7 @@ import java.io.*;
 import java.util.*;
 
 import sun.jvm.hotspot.debugger.*;
+import sun.jvm.hotspot.gc.shared.*;
 import sun.jvm.hotspot.runtime.*;
 import sun.jvm.hotspot.types.*;
 import sun.jvm.hotspot.utilities.*;
@@ -134,6 +135,14 @@ abstract public class GenCollectedHeap extends CollectedHeap {
     }
   }
 
+  public void liveRegionsIterate(LiveRegionsClosure closure) {
+    // Run through all generations, obtaining bottom-top pairs.
+    for (int i = 0; i < nGens(); i++) {
+      Generation gen = getGen(i);
+      gen.liveRegionsIterate(closure);
+    }
+  }
+
   public void printOn(PrintStream tty) {
     for (int i = 0; i < nGens(); i++) {
       tty.print("Gen " + i + ": ");

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/shared/Generation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -184,6 +184,7 @@ public abstract class Generation extends VMObject {
 
   /** Iteration - do not use for time critical operations */
   public abstract void spaceIterate(SpaceClosure blk, boolean usedOnly);
+  public abstract void liveRegionsIterate(LiveRegionsClosure closure);
 
   public void print() { printOn(System.out); }
   public abstract void printOn(PrintStream tty);

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/shared/GenerationFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -65,6 +65,8 @@ public class GenerationFactory {
                   }
                   public void spaceIterate(SpaceClosure blk, boolean usedOnly) {
                   }
+                  public void liveRegionsIterate(LiveRegionsClosure closure) {
+                  }
                   public void printOn(java.io.PrintStream tty) {
                       tty.println("unknown subtype of Generation @ " + getAddress() + " (" +
                                   virtualSpace().low() + "," + virtualSpace().high() + ")");

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/shared/LiveRegionsClosure.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+package sun.jvm.hotspot.gc.shared;
+
+public interface LiveRegionsClosure {
+  public void doLiveRegions(LiveRegionsProvider lrp);
+}

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/shared/LiveRegionsProvider.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+package sun.jvm.hotspot.gc.shared;
+
+import java.util.List;
+
+import sun.jvm.hotspot.memory.MemRegion;
+
+public interface LiveRegionsProvider {
+  public List<MemRegion> getLiveRegions();
+}

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/shared/Space.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -89,9 +89,6 @@ public abstract class Space extends VMObject {
     return handle.addOffsetToAsOopHandle(size);
   }
 
-  /** returns all MemRegions where live objects are */
-  public abstract List/*<MemRegion>*/ getLiveRegions();
-
   /** Returned value is in bytes */
   public long capacity() { return end().minus(bottom()); }
   /** Returned value is in bytes */

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/shenandoah/ShenandoahHeap.java

@@ -25,6 +25,7 @@ package sun.jvm.hotspot.gc.shenandoah;
 
 import sun.jvm.hotspot.gc.shared.CollectedHeap;
 import sun.jvm.hotspot.gc.shared.CollectedHeapName;
+import sun.jvm.hotspot.gc.shared.LiveRegionsClosure;
 import sun.jvm.hotspot.debugger.Address;
 import sun.jvm.hotspot.runtime.VM;
 import sun.jvm.hotspot.types.Type;
@@ -77,6 +78,12 @@ public class ShenandoahHeap extends CollectedHeap {
         return committed.getValue(addr);
     }
 
+    @Override
+    public void liveRegionsIterate(LiveRegionsClosure closure) {
+        // Operation (currently) not supported with Shenandoah GC.
+        System.err.println("Warning: Operation not supported with Shenandoah GC");
+    }
+
     @Override
     public void printOn(PrintStream tty) {
         MemRegion mr = reservedRegion();

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/z/ZCollectedHeap.java

@@ -30,6 +30,7 @@ import sun.jvm.hotspot.debugger.Address;
 import sun.jvm.hotspot.debugger.OopHandle;
 import sun.jvm.hotspot.gc.shared.CollectedHeap;
 import sun.jvm.hotspot.gc.shared.CollectedHeapName;
+import sun.jvm.hotspot.gc.shared.LiveRegionsClosure;
 import sun.jvm.hotspot.runtime.VM;
 import sun.jvm.hotspot.runtime.VMObjectFactory;
 import sun.jvm.hotspot.types.Type;
@@ -39,7 +40,6 @@ import sun.jvm.hotspot.utilities.BitMapInterface;
 // Mirror class for ZCollectedHeap.
 
 public class ZCollectedHeap extends CollectedHeap {
-
     private static long zHeapFieldOffset;
 
     static {
@@ -119,6 +119,13 @@ public class ZCollectedHeap extends CollectedHeap {
         }
     }
 
+    @Override
+    public void liveRegionsIterate(LiveRegionsClosure closure) {
+        // Operation (currently) not supported with ZGC. Print
+        // a warning and leave the list of live regions empty.
+        System.err.println("Warning: Operation not supported with ZGC");
+    }
+
     @Override
     public BitMapInterface createBitMap(long size) {
         // Ignores the size

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/ObjectHeap.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -304,87 +304,48 @@ public class ObjectHeap {
     visitor.epilogue();
   }
 
-  private void addLiveRegions(String name, List input, List output) {
+  private static class LiveRegionsCollector implements LiveRegionsClosure {
-     for (Iterator itr = input.iterator(); itr.hasNext();) {
+    LiveRegionsCollector(List<Address> l) {
-        MemRegion reg = (MemRegion) itr.next();
+      liveRegions = l;
+    }
+
+    @Override
+    public void doLiveRegions(LiveRegionsProvider lrp) {
+      for (MemRegion reg : lrp.getLiveRegions()) {
         Address top = reg.end();
         Address bottom = reg.start();
         if (Assert.ASSERTS_ENABLED) {
-           Assert.that(top != null, "top address in a live region should not be null");
+          Assert.that(top != null, "top address in a live region should not be null");
         }
         if (Assert.ASSERTS_ENABLED) {
-           Assert.that(bottom != null, "bottom address in a live region should not be null");
+          Assert.that(bottom != null, "bottom address in a live region should not be null");
         }
-        output.add(top);
+        liveRegions.add(top);
-        output.add(bottom);
+        liveRegions.add(bottom);
         if (DEBUG) {
-          System.err.println("Live region: " + name + ": " + bottom + ", " + top);
+          System.err.println("Live region: " + lrp + ": " + bottom + ", " + top);
-        }
+      }
-     }
+    }
   }
 
-  private class LiveRegionsCollector implements SpaceClosure {
+     private List<Address> liveRegions;
-     LiveRegionsCollector(List l) {
-        liveRegions = l;
-     }
-
-     public void doSpace(Space s) {
-        addLiveRegions(s.toString(), s.getLiveRegions(), liveRegions);
-     }
-     private List liveRegions;
   }
 
   // Returns a List<Address> where the addresses come in pairs. These
   // designate the live regions of the heap.
-  private List collectLiveRegions() {
+  private List<Address> collectLiveRegions() {
     // We want to iterate through all live portions of the heap, but
     // do not want to abort the heap traversal prematurely if we find
     // a problem (like an allocated but uninitialized object at the
     // top of a generation). To do this we enumerate all generations'
     // bottom and top regions, and factor in TLABs if necessary.
 
-    // List<Address>. Addresses come in pairs.
+    // Addresses come in pairs.
-    List liveRegions = new ArrayList();
+    List<Address> liveRegions = new ArrayList<>();
     LiveRegionsCollector lrc = new LiveRegionsCollector(liveRegions);
 
     CollectedHeap heap = VM.getVM().getUniverse().heap();
-
+    heap.liveRegionsIterate(lrc);
-    if (heap instanceof GenCollectedHeap) {
-       GenCollectedHeap genHeap = (GenCollectedHeap) heap;
-       // Run through all generations, obtaining bottom-top pairs.
-       for (int i = 0; i < genHeap.nGens(); i++) {
-         Generation gen = genHeap.getGen(i);
-         gen.spaceIterate(lrc, true);
-       }
-    } else if (heap instanceof ParallelScavengeHeap) {
-       ParallelScavengeHeap psh = (ParallelScavengeHeap) heap;
-       PSYoungGen youngGen = psh.youngGen();
-       // Add eden space
-       addLiveRegions("eden", youngGen.edenSpace().getLiveRegions(), liveRegions);
-       // Add from-space but not to-space
-       addLiveRegions("from", youngGen.fromSpace().getLiveRegions(), liveRegions);
-       PSOldGen oldGen = psh.oldGen();
-       addLiveRegions("old ", oldGen.objectSpace().getLiveRegions(), liveRegions);
-    } else if (heap instanceof G1CollectedHeap) {
-        G1CollectedHeap g1h = (G1CollectedHeap) heap;
-        g1h.heapRegionIterate(lrc);
-    } else if (heap instanceof ShenandoahHeap) {
-       // Operation (currently) not supported with Shenandoah GC. Print
-       // a warning and leave the list of live regions empty.
-       System.err.println("Warning: Operation not supported with Shenandoah GC");
-    } else if (heap instanceof ZCollectedHeap) {
-       // Operation (currently) not supported with ZGC. Print
-       // a warning and leave the list of live regions empty.
-       System.err.println("Warning: Operation not supported with ZGC");
-    } else if (heap instanceof EpsilonHeap) {
-       EpsilonHeap eh = (EpsilonHeap) heap;
-       liveRegions.add(eh.space().top());
-       liveRegions.add(eh.space().bottom());
-    } else {
-       if (Assert.ASSERTS_ENABLED) {
-          Assert.that(false, "Unexpected CollectedHeap type: " + heap.getClass().getName());
-       }
-    }
 
     // If UseTLAB is enabled, snip out regions associated with TLABs'
     // dead regions. Note that TLABs can be present in any generation.
@@ -440,11 +401,9 @@ public class ObjectHeap {
     return liveRegions;
   }
 
-  private void sortLiveRegions(List liveRegions) {
+  private void sortLiveRegions(List<Address> liveRegions) {
-    Collections.sort(liveRegions, new Comparator() {
+    Collections.sort(liveRegions, new Comparator<Address>() {
-        public int compare(Object o1, Object o2) {
+        public int compare(Address a1, Address a2) {
-          Address a1 = (Address) o1;
-          Address a2 = (Address) o2;
           if (AddressOps.lt(a1, a2)) {
             return -1;
           } else if (AddressOps.gt(a1, a2)) {