stream: improve write performance

Author: ronag

lib/_stream_writable.js

@@ -493,30 +493,30 @@ function onwrite(stream, er) {
       onwriteError(stream, state, er, cb);
     }
   } else {
-    // Check if we're actually ready to finish, but don't emit yet
-    var finished = needFinish(state) || stream.destroyed;
-
-    if (!finished &&
-        !state.corked &&
+    if (!state.corked &&
         !state.bufferProcessing &&
         state.bufferedRequest) {
       clearBuffer(stream, state);
     }
 
-    if (sync) {
-      // It is a common case that the callback passed to .write() is always
-      // the same. In that case, we do not schedule a new nextTick(), but rather
-      // just increase a counter, to improve performance and avoid memory
-      // allocations.
-      if (state.afterWriteTickInfo !== null &&
-          state.afterWriteTickInfo.cb === cb) {
-        state.afterWriteTickInfo.count++;
+    if (state.ending || state.needDrain || cb !== nop) {
+      if (sync) {
+        // It is a common case that the callback passed to .write() is always
+        // the same. In that case, we do not schedule a new nextTick(), but
+        //  rather just increase a counter, to improve performance and avoid
+        // memory allocations.
+        if (state.afterWriteTickInfo !== null &&
+            state.afterWriteTickInfo.cb === cb) {
+          state.afterWriteTickInfo.count++;
+        } else {
+          state.afterWriteTickInfo = { count: 1, cb, stream, state };
+          process.nextTick(afterWriteTick, state.afterWriteTickInfo);
+        }
       } else {
-        state.afterWriteTickInfo = { count: 1, cb, stream, state };
-        process.nextTick(afterWriteTick, state.afterWriteTickInfo);
+        afterWrite(stream, state, 1, cb);
       }
     } else {
-      afterWrite(stream, state, 1, cb);
+      state.pendingcb--;
     }
   }
 }