6916623: Align object to 16 bytes to use Compressed Oops with java heap up to 64Gb

Summary: Added new product ObjectAlignmentInBytes flag to control object alignment.
Reviewed-by: twisti, ysr, iveresov

3 files changed, 24 insertions, 20 deletions

diff --git a/agent/src/share/classes/sun/jvm/hotspot/memory/CompactibleFreeListSpace.java b/agent/src/share/classes/sun/jvm/hotspot/memory/CompactibleFreeListSpace.java
index 48cb4edbc..e105be303 100644
--- a/agent/src/share/classes/sun/jvm/hotspot/memory/CompactibleFreeListSpace.java
+++ b/agent/src/share/classes/sun/jvm/hotspot/memory/CompactibleFreeListSpace.java
@@ -73,18 +73,11 @@ public class CompactibleFreeListSpace extends CompactibleSpace {
 
    public CompactibleFreeListSpace(Address addr) {
       super(addr);
-      if ( VM.getVM().isLP64() ) {
-         heapWordSize = 8;
-         IndexSetStart = 1;
-         IndexSetStride = 1;
-      }
-      else {
-         heapWordSize = 4;
-         IndexSetStart = 2;
-         IndexSetStride = 2;
-      }
-
-      IndexSetSize = 257;
+      VM vm = VM.getVM();
+      heapWordSize   = vm.getHeapWordSize();
+      IndexSetStart  = vm.getMinObjAlignmentInBytes() / heapWordSize;
+      IndexSetStride = IndexSetStart;
+      IndexSetSize   = 257;
    }
 
    // Accessing block offset table
diff --git a/agent/src/share/classes/sun/jvm/hotspot/oops/Oop.java b/agent/src/share/classes/sun/jvm/hotspot/oops/Oop.java
index cfaed9356..e5f254853 100644
--- a/agent/src/share/classes/sun/jvm/hotspot/oops/Oop.java
+++ b/agent/src/share/classes/sun/jvm/hotspot/oops/Oop.java
@@ -128,7 +128,7 @@ public class Oop {
 
   // Align the object size.
   public static long alignObjectSize(long size) {
-    return VM.getVM().alignUp(size, VM.getVM().getMinObjAlignment());
+    return VM.getVM().alignUp(size, VM.getVM().getMinObjAlignmentInBytes());
   }
 
   // All vm's align longs, so pad out certain offsets.
diff --git a/agent/src/share/classes/sun/jvm/hotspot/runtime/VM.java b/agent/src/share/classes/sun/jvm/hotspot/runtime/VM.java
index fda1e4f39..9798e74f5 100644
--- a/agent/src/share/classes/sun/jvm/hotspot/runtime/VM.java
+++ b/agent/src/share/classes/sun/jvm/hotspot/runtime/VM.java
@@ -93,6 +93,7 @@ public class VM {
   /** alignment constants */
   private boolean      isLP64;
   private int          bytesPerLong;
+  private int          objectAlignmentInBytes;
   private int          minObjAlignmentInBytes;
   private int          logMinObjAlignmentInBytes;
   private int          heapWordSize;
@@ -313,9 +314,15 @@ public class VM {
       isLP64 = debugger.getMachineDescription().isLP64();
     }
     bytesPerLong = db.lookupIntConstant("BytesPerLong").intValue();
-    minObjAlignmentInBytes = db.lookupIntConstant("MinObjAlignmentInBytes").intValue();
-    // minObjAlignment = db.lookupIntConstant("MinObjAlignment").intValue();
-    logMinObjAlignmentInBytes = db.lookupIntConstant("LogMinObjAlignmentInBytes").intValue();
+    minObjAlignmentInBytes = getObjectAlignmentInBytes();
+    if (minObjAlignmentInBytes == 8) {
+      logMinObjAlignmentInBytes = 3;
+    } else if (minObjAlignmentInBytes == 16) {
+      logMinObjAlignmentInBytes = 4;
+    } else {
+      throw new RuntimeException("Object alignment " + minObjAlignmentInBytes + " not yet supported");
+    }
+
     heapWordSize = db.lookupIntConstant("HeapWordSize").intValue();
     oopSize  = db.lookupIntConstant("oopSize").intValue();
 
@@ -492,10 +499,6 @@ public class VM {
   }
 
   /** Get minimum object alignment in bytes. */
-  public int getMinObjAlignment() {
-    return minObjAlignmentInBytes;
-  }
-
   public int getMinObjAlignmentInBytes() {
     return minObjAlignmentInBytes;
   }
@@ -754,6 +757,14 @@ public class VM {
     return compressedOopsEnabled.booleanValue();
   }
 
+  public int getObjectAlignmentInBytes() {
+    if (objectAlignmentInBytes == 0) {
+        Flag flag = getCommandLineFlag("ObjectAlignmentInBytes");
+        objectAlignmentInBytes = (flag == null) ? 8 : (int)flag.getIntx();
+    }
+    return objectAlignmentInBytes;
+  }
+
   // returns null, if not available.
   public Flag[] getCommandLineFlags() {
     if (commandLineFlags == null) {