process: improve nextTick() performance

PR-URL: https://github.com/nodejs/node/pull/13446
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>

1 files changed, 95 insertions, 43 deletions

diff --git a/lib/internal/process/next_tick.js b/lib/internal/process/next_tick.js
index 61756f603c..e183c38263 100644
--- a/lib/internal/process/next_tick.js
+++ b/lib/internal/process/next_tick.js
@@ -10,6 +10,42 @@ exports.setup = setupNextTick;
 // Will be overwritten when setupNextTick() is called.
 exports.nextTick = null;
 
+class NextTickQueue {
+  constructor() {
+    this.head = null;
+    this.tail = null;
+    this.length = 0;
+  }
+
+  push(v) {
+    const entry = { data: v, next: null };
+    if (this.length > 0)
+      this.tail.next = entry;
+    else
+      this.head = entry;
+    this.tail = entry;
+    ++this.length;
+  }
+
+  shift() {
+    if (this.length === 0)
+      return;
+    const ret = this.head.data;
+    if (this.length === 1)
+      this.head = this.tail = null;
+    else
+      this.head = this.head.next;
+    --this.length;
+    return ret;
+  }
+
+  clear() {
+    this.head = null;
+    this.tail = null;
+    this.length = 0;
+  }
+}
+
 function setupNextTick() {
   const async_wrap = process.binding('async_wrap');
   const async_hooks = require('async_hooks');
@@ -27,7 +63,7 @@ function setupNextTick() {
   const { kInit, kBefore, kAfter, kDestroy, kAsyncUidCntr, kInitTriggerId } =
       async_wrap.constants;
   const { async_id_symbol, trigger_id_symbol } = async_wrap;
-  var nextTickQueue = [];
+  var nextTickQueue = new NextTickQueue();
   var microtasksScheduled = false;
 
   // Used to run V8's micro task queue.
@@ -55,27 +91,29 @@ function setupNextTick() {
   function tickDone() {
     if (tickInfo[kLength] !== 0) {
       if (tickInfo[kLength] <= tickInfo[kIndex]) {
-        nextTickQueue = [];
+        nextTickQueue.clear();
         tickInfo[kLength] = 0;
       } else {
-        nextTickQueue.splice(0, tickInfo[kIndex]);
         tickInfo[kLength] = nextTickQueue.length;
       }
     }
     tickInfo[kIndex] = 0;
   }
 
+  const microTasksTickObject = {
+    callback: runMicrotasksCallback,
+    args: undefined,
+    domain: null,
+    [async_id_symbol]: 0,
+    [trigger_id_symbol]: 0
+  };
   function scheduleMicrotasks() {
     if (microtasksScheduled)
       return;
 
-    const tickObject =
-        new TickObject(runMicrotasksCallback, undefined, null);
     // For the moment all microtasks come from the void until the PromiseHook
     // API is implemented.
-    tickObject[async_id_symbol] = 0;
-    tickObject[trigger_id_symbol] = 0;
-    nextTickQueue.push(tickObject);
+    nextTickQueue.push(microTasksTickObject);
 
     tickInfo[kLength]++;
     microtasksScheduled = true;
@@ -86,8 +124,9 @@ function setupNextTick() {
     _runMicrotasks();
 
     if (tickInfo[kIndex] < tickInfo[kLength] ||
-        emitPendingUnhandledRejections())
+        emitPendingUnhandledRejections()) {
       scheduleMicrotasks();
+    }
   }
 
   function _combinedTickCallback(args, callback) {
@@ -133,7 +172,8 @@ function setupNextTick() {
   function _tickCallback() {
     do {
       while (tickInfo[kIndex] < tickInfo[kLength]) {
-        const tock = nextTickQueue[tickInfo[kIndex]++];
+        ++tickInfo[kIndex];
+        const tock = nextTickQueue.shift();
         const callback = tock.callback;
         const args = tock.args;
 
@@ -174,7 +214,8 @@ function setupNextTick() {
   function _tickDomainCallback() {
     do {
       while (tickInfo[kIndex] < tickInfo[kLength]) {
-        const tock = nextTickQueue[tickInfo[kIndex]++];
+        ++tickInfo[kIndex];
+        const tock = nextTickQueue.shift();
         const callback = tock.callback;
         const domain = tock.domain;
         const args = tock.args;
@@ -210,45 +251,48 @@ function setupNextTick() {
     } while (tickInfo[kLength] !== 0);
   }
 
-  function TickObject(callback, args, domain) {
-    this.callback = callback;
-    this.domain = domain;
-    this.args = args;
-    this[async_id_symbol] = -1;
-    this[trigger_id_symbol] = -1;
-  }
-
-  function setupInit(tickObject, triggerAsyncId) {
-    tickObject[async_id_symbol] = ++async_uid_fields[kAsyncUidCntr];
-    tickObject[trigger_id_symbol] = triggerAsyncId || initTriggerId();
-    if (async_hook_fields[kInit] > 0) {
-      emitInit(tickObject[async_id_symbol],
-               'TickObject',
-               tickObject[trigger_id_symbol],
-               tickObject);
+  class TickObject {
+    constructor(callback, args, asyncId, triggerAsyncId) {
+      this.callback = callback;
+      this.args = args;
+      this.domain = process.domain || null;
+      this[async_id_symbol] = asyncId;
+      this[trigger_id_symbol] = triggerAsyncId;
     }
   }
 
+  // `nextTick()` will not enqueue any callback when the process is about to
+  // exit since the callback would not have a chance to be executed.
   function nextTick(callback) {
     if (typeof callback !== 'function')
       throw new errors.TypeError('ERR_INVALID_CALLBACK');
-    // on the way out, don't bother. it won't get fired anyway.
+
     if (process._exiting)
       return;
 
     var args;
-    if (arguments.length > 1) {
-      args = new Array(arguments.length - 1);
-      for (var i = 1; i < arguments.length; i++)
-        args[i - 1] = arguments[i];
+    switch (arguments.length) {
+      case 1: break;
+      case 2: args = [arguments[1]]; break;
+      case 3: args = [arguments[1], arguments[2]]; break;
+      case 4: args = [arguments[1], arguments[2], arguments[3]]; break;
+      default:
+        args = new Array(arguments.length - 1);
+        for (var i = 1; i < arguments.length; i++)
+          args[i - 1] = arguments[i];
     }
 
-    var obj = new TickObject(callback, args, process.domain || null);
-    setupInit(obj, null);
+    const asyncId = ++async_uid_fields[kAsyncUidCntr];
+    const triggerAsyncId = initTriggerId();
+    const obj = new TickObject(callback, args, asyncId, triggerAsyncId);
     nextTickQueue.push(obj);
-    tickInfo[kLength]++;
+    ++tickInfo[kLength];
+    if (async_hook_fields[kInit] > 0)
+      emitInit(asyncId, 'TickObject', triggerAsyncId, obj);
   }
 
+  // `internalNextTick()` will not enqueue any callback when the process is
+  // about to exit since the callback would not have a chance to be executed.
   function internalNextTick(triggerAsyncId, callback) {
     if (typeof callback !== 'function')
       throw new TypeError('callback is not a function');
@@ -259,17 +303,25 @@ function setupNextTick() {
       return;
 
     var args;
-    if (arguments.length > 2) {
-      args = new Array(arguments.length - 2);
-      for (var i = 2; i < arguments.length; i++)
-        args[i - 2] = arguments[i];
+    switch (arguments.length) {
+      case 2: break;
+      case 3: args = [arguments[2]]; break;
+      case 4: args = [arguments[2], arguments[3]]; break;
+      case 5: args = [arguments[2], arguments[3], arguments[4]]; break;
+      default:
+        args = new Array(arguments.length - 2);
+        for (var i = 2; i < arguments.length; i++)
+          args[i - 2] = arguments[i];
     }
 
-    var obj = new TickObject(callback, args, process.domain || null);
-    setupInit(obj, triggerAsyncId);
+    const asyncId = ++async_uid_fields[kAsyncUidCntr];
+    const obj = new TickObject(callback, args, asyncId, triggerAsyncId);
+    nextTickQueue.push(obj);
+    ++tickInfo[kLength];
+    if (async_hook_fields[kInit] > 0)
+      emitInit(asyncId, 'TickObject', triggerAsyncId, obj);
+
     // The call to initTriggerId() was skipped, so clear kInitTriggerId.
     async_uid_fields[kInitTriggerId] = 0;
-    nextTickQueue.push(obj);
-    tickInfo[kLength]++;
   }
 }