presize ArrayList

Change-Id: I0805991630a896da260b28a6cef7841593f020a9
diff --git a/providers/openflow/device/src/main/java/org/onlab/onos/provider/of/device/impl/OpenFlowDeviceProvider.java b/providers/openflow/device/src/main/java/org/onlab/onos/provider/of/device/impl/OpenFlowDeviceProvider.java
index 88cb1ac..f322270 100644
--- a/providers/openflow/device/src/main/java/org/onlab/onos/provider/of/device/impl/OpenFlowDeviceProvider.java
+++ b/providers/openflow/device/src/main/java/org/onlab/onos/provider/of/device/impl/OpenFlowDeviceProvider.java
@@ -172,7 +172,7 @@
          */
         private List<PortDescription> buildPortDescriptions(
                 List<OFPortDesc> ports) {
-            final List<PortDescription> portDescs = new ArrayList<>();
+            final List<PortDescription> portDescs = new ArrayList<>(ports.size());
             for (OFPortDesc port : ports) {
                 portDescs.add(buildPortDescription(port));
             }