BUG-2384: improve ImmutableUnkeyedListNode efficiency

With moderately-loaded BGP instance we are using quite a few on empty
unkeyed list nodes. The fact they are empty means we waste about 8 bytes
per instance just tracking empty list. Introduce a dedicated class to
take care of this common special case.

Change-Id: I3e94c637f5d7d47d39d274bae96850307f5c439d
Signed-off-by: Robert Varga <rovarga@cisco.com>

diff --git a/yang/yang-data-impl/src/main/java/org/opendaylight/yangtools/yang/data/impl/schema/builder/impl/ImmutableUnkeyedListNodeBuilder.java b/yang/yang-data-impl/src/main/java/org/opendaylight/yangtools/yang/data/impl/schema/builder/impl/ImmutableUnkeyedListNodeBuilder.java
index 66f81cadff5f75bc1b23cc9cbf915395830fda13..4f45293b80105fb9577c4439838dc27f61bee3c9 100644 (file)
--- a/yang/yang-data-impl/src/main/java/org/opendaylight/yangtools/yang/data/impl/schema/builder/impl/ImmutableUnkeyedListNodeBuilder.java
+++ b/yang/yang-data-impl/src/main/java/org/opendaylight/yangtools/yang/data/impl/schema/builder/impl/ImmutableUnkeyedListNodeBuilder.java
@@ -7,9 +7,11 @@
  */
 package org.opendaylight.yangtools.yang.data.impl.schema.builder.impl;
 
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Iterables;
+import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
-
 import org.opendaylight.yangtools.concepts.Immutable;
 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.NodeIdentifier;
@@ -21,9 +23,6 @@ import org.opendaylight.yangtools.yang.data.impl.schema.builder.api.NormalizedNo
 import org.opendaylight.yangtools.yang.data.impl.schema.nodes.AbstractImmutableNormalizedNode;
 import org.opendaylight.yangtools.yang.data.impl.schema.nodes.AbstractImmutableNormalizedValueNode;
 
-import com.google.common.collect.ImmutableList;
-import com.google.common.collect.Iterables;
-
 public class ImmutableUnkeyedListNodeBuilder implements CollectionNodeBuilder<UnkeyedListEntryNode, UnkeyedListNode> {
 
     private List<UnkeyedListEntryNode> value;
@@ -95,7 +94,11 @@ public class ImmutableUnkeyedListNodeBuilder implements CollectionNodeBuilder<Un
     @Override
     public UnkeyedListNode build() {
         dirty = true;
-        return new ImmutableUnkeyedListNode(nodeIdentifier, ImmutableList.copyOf(value));
+        if (value.isEmpty()) {
+            return new EmptyImmutableUnkeyedListNode(nodeIdentifier);
+        } else {
+            return new ImmutableUnkeyedListNode(nodeIdentifier, ImmutableList.copyOf(value));
+        }
     }
 
     @Override
@@ -109,6 +112,37 @@ public class ImmutableUnkeyedListNodeBuilder implements CollectionNodeBuilder<Un
         return withoutChild(key);
     }
 
+    protected static final class EmptyImmutableUnkeyedListNode extends AbstractImmutableNormalizedNode<YangInstanceIdentifier.NodeIdentifier, Iterable<UnkeyedListEntryNode>> implements Immutable, UnkeyedListNode {
+        protected EmptyImmutableUnkeyedListNode(final NodeIdentifier nodeIdentifier) {
+            super(nodeIdentifier);
+        }
+
+        @Override
+        public Iterable<UnkeyedListEntryNode> getValue() {
+            return Collections.emptyList();
+        }
+
+        @Override
+        public UnkeyedListEntryNode getChild(final int position) {
+            return null;
+        }
+
+        @Override
+        public int getSize() {
+            return 0;
+        }
+
+        @Override
+        protected boolean valueEquals(final AbstractImmutableNormalizedNode<?, ?> other) {
+            return Collections.EMPTY_LIST.equals(other.getValue());
+        }
+
+        @Override
+        protected int valueHashCode() {
+            return Collections.EMPTY_LIST.hashCode();
+        }
+    }
+
     protected static final class ImmutableUnkeyedListNode extends
             AbstractImmutableNormalizedValueNode<YangInstanceIdentifier.NodeIdentifier, Iterable<UnkeyedListEntryNode>>
             implements Immutable, UnkeyedListNode {