stream: avoid tick in writable hot path

Author: ronag

lib/internal/streams/writable.js

@@ -396,7 +396,7 @@ function Writable(options) {
   destroyImpl.construct(this, () => {
     const state = this._writableState;
 
-    if (!state.writing) {
+    if ((state.state & kWriting) === 0) {
       clearBuffer(this, state);
     }
 
@@ -612,24 +612,30 @@ function onwrite(stream, er) {
     }
 
     if (sync) {
+      const needDrain = (state.state & kNeedDrain) !== 0 && state.length === 0;
+      const needTick = needDrain || (state.state & kDestroyed !== 0) || cb !== nop;
+
       // 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 (cb === nop) {
-        if ((state.state & kAfterWritePending) === 0) {
+        if ((state.state & kAfterWritePending) === 0 && needTick) {
           process.nextTick(afterWrite, stream, state, 1, cb);
           state.state |= kAfterWritePending;
         } else {
           state.pendingcb -= 1;
         }
-      } else if (state.afterWriteTickInfo !== null &&
-                 state.afterWriteTickInfo.cb === cb) {
-        state.afterWriteTickInfo.count++;
+      } else if ((state.state & kAfterWriteTickInfo) !== 0 &&
+                 state[kAfterWriteTickInfoValue].cb === cb) {
+        state[kAfterWriteTickInfoValue].count++;
+      } else if (needTick) {
+        state[kAfterWriteTickInfoValue] = { count: 1, cb, stream, state };
+        process.nextTick(afterWriteTick, state[kAfterWriteTickInfoValue]);
+        state.state |= (kAfterWritePending | kAfterWriteTickInfo);
       } else {
-        state.afterWriteTickInfo = { count: 1, cb, stream, state };
-        process.nextTick(afterWriteTick, state.afterWriteTickInfo);
-        state.state |= kAfterWritePending;
+        state.pendingcb--;
+        finishMaybe(stream, state, true);
       }
     } else {
       afterWrite(stream, state, 1, cb);
@@ -638,7 +644,8 @@ function onwrite(stream, er) {
 }
 
 function afterWriteTick({ stream, state, count, cb }) {
-  state.afterWriteTickInfo = null;
+  state.state &= ~kAfterWriteTickInfo;
+  state[kAfterWriteTickInfoValue] = null;
   return afterWrite(stream, state, count, cb);
 }
 
@@ -795,6 +802,8 @@ Writable.prototype.end = function(chunk, encoding, cb) {
   if (typeof cb === 'function') {
     if (err) {
       process.nextTick(cb, err);
+    } else if ((state.state & kErrored) !== 0) {
+      process.nextTick(cb, state[kErroredValue]);
     } else if ((state.state & kFinished) !== 0) {
       process.nextTick(cb, null);
     } else {