[#1606] Reduce overhead during writes because of ChannelPromise validation

transport/src/main/java/io/netty/channel/DefaultChannelHandlerContext.java

@@ -812,17 +812,28 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
         return new FailedChannelFuture(channel(), executor(), cause);
     }
 
-    private void validatePromise(ChannelFuture promise, boolean allowUnsafe) {
+    private void validatePromise(ChannelPromise promise, boolean allowUnsafe) {
         if (promise == null) {
             throw new NullPointerException("promise");
         }
+
+        if (promise.isDone()) {
+            throw new IllegalArgumentException("promise already done: " + promise);
+        }
+
+        // check if the promise is of type DefaultChannelPromise and if so check if its validated already.
+        DefaultChannelPromise p = null;
+        if (promise instanceof DefaultChannelPromise) {
+            p = (DefaultChannelPromise) promise;
+            if (p.isValidated()) {
+                return;
+            }
+        }
+
         if (promise.channel() != channel()) {
             throw new IllegalArgumentException(String.format(
                     "promise.channel does not match: %s (expected: %s)", promise.channel(), channel()));
         }
-        if (promise.isDone()) {
-            throw new IllegalArgumentException("promise already done: " + promise);
-        }
         if (!allowUnsafe && promise instanceof VoidChannelPromise) {
             throw new IllegalArgumentException(
                     StringUtil.simpleClassName(VoidChannelPromise.class) + " not allowed for this operation");
@@ -831,6 +842,11 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
             throw new IllegalArgumentException(
                     StringUtil.simpleClassName(AbstractChannel.CloseFuture.class) + " not allowed in a pipeline");
         }
+
+        if (p != null) {
+            // mark as validated
+            p.validated();
+        }
     }
 
     private DefaultChannelHandlerContext findContextInbound() {

transport/src/main/java/io/netty/channel/DefaultChannelPromise.java

@@ -29,6 +29,7 @@ public class DefaultChannelPromise extends DefaultPromise<Void> implements Chann
 
     private final Channel channel;
     private long checkpoint;
+    private boolean validated;
 
     /**
      * Creates a new instance.
@@ -157,4 +158,12 @@ public class DefaultChannelPromise extends DefaultPromise<Void> implements Chann
             super.checkDeadLock();
         }
     }
+
+    final boolean isValidated() {
+        return validated;
+    }
+
+    final void validated() {
+        validated = true;
+    }
 }