events: improve eventEmitter.once() performance

This commit improves once() performance by avoiding the creation of
wrapper functions.

These changes bring ~51% increase in performance when simply adding
once() event handlers, ~205% increase in the included ee-emit-once
benchmark, and a ~36% increase in the included ee-add-remove-once
benchmark.

This commit also adds new benchmarks, bumps the default number of
iterations for several of the existing benchmarks, and also
adds missing forced optimizations.

benchmark/events/ee-add-once.js

@@ -0,0 +1,35 @@
+'use strict';
+
+var common = require('../common');
+var EventEmitter = require('events');
+var v8 = require('v8');
+
+var bench = common.createBenchmark(main, {
+  n: [50e6]
+});
+
+function main(conf) {
+  var n = +conf.n;
+  var ee = new EventEmitter();
+  var listeners = [];
+
+  var k;
+  for (k = 0; k < 10; k += 1)
+    listeners.push(function() {});
+
+  // Force optimization before starting the benchmark
+  ee.once('dummy', listeners[0]);
+  ee._events = {};
+  v8.setFlagsFromString('--allow_natives_syntax');
+  eval('%OptimizeFunctionOnNextCall(ee.once)');
+  ee.once('dummy', listeners[0]);
+  ee._events = {};
+
+  bench.start();
+  for (var i = 0; i < n; ++i) {
+    for (k = listeners.length; --k >= 0; /* empty */)
+      ee.once('dummy', listeners[k]);
+    ee._events = {};
+  }
+  bench.end(n);
+}

benchmark/events/ee-add-remove-once.js

@@ -0,0 +1,41 @@
+'use strict';
+
+var common = require('../common');
+var EventEmitter = require('events');
+var v8 = require('v8');
+
+var bench = common.createBenchmark(main, {
+  n: [25e6]
+});
+
+function main(conf) {
+  var n = conf.n | 0;
+
+  var ee = new EventEmitter();
+  var listeners = [];
+
+  var k;
+  for (k = 0; k < 10; k += 1)
+    listeners.push(function() {});
+
+  for (k = listeners.length; --k >= 0; /* empty */)
+    ee.once('dummy', listeners[k]);
+  for (k = listeners.length; --k >= 0; /* empty */)
+    ee.removeListener('dummy', listeners[k]);
+  v8.setFlagsFromString('--allow_natives_syntax');
+  eval('%OptimizeFunctionOnNextCall(ee.once)');
+  eval('%OptimizeFunctionOnNextCall(ee.removeListener)');
+  for (k = listeners.length; --k >= 0; /* empty */)
+    ee.once('dummy', listeners[k]);
+  for (k = listeners.length; --k >= 0; /* empty */)
+    ee.removeListener('dummy', listeners[k]);
+
+  bench.start();
+  for (var i = 0; i < n; i += 1) {
+    for (k = listeners.length; --k >= 0; /* empty */)
+      ee.once('dummy', listeners[k]);
+    for (k = listeners.length; --k >= 0; /* empty */)
+      ee.removeListener('dummy', listeners[k]);
+  }
+  bench.end(n);
+}

benchmark/events/ee-add-remove.js

@@ -1,19 +1,35 @@
 'use strict';
-var common = require('../common.js');
-var events = require('events');
 
-var bench = common.createBenchmark(main, {n: [25e4]});
+var common = require('../common');
+var EventEmitter = require('events');
+var v8 = require('v8');
+
+var bench = common.createBenchmark(main, {
+  n: [50e5]
+});
 
 function main(conf) {
   var n = conf.n | 0;
 
-  var ee = new events.EventEmitter();
+  var ee = new EventEmitter();
   var listeners = [];
 
   var k;
   for (k = 0; k < 10; k += 1)
     listeners.push(function() {});
 
+  for (k = listeners.length; --k >= 0; /* empty */)
+    ee.on('dummy', listeners[k]);
+  for (k = listeners.length; --k >= 0; /* empty */)
+    ee.removeListener('dummy', listeners[k]);
+  v8.setFlagsFromString('--allow_natives_syntax');
+  eval('%OptimizeFunctionOnNextCall(ee.on)');
+  eval('%OptimizeFunctionOnNextCall(ee.removeListener)');
+  for (k = listeners.length; --k >= 0; /* empty */)
+    ee.on('dummy', listeners[k]);
+  for (k = listeners.length; --k >= 0; /* empty */)
+    ee.removeListener('dummy', listeners[k]);
+
   bench.start();
   for (var i = 0; i < n; i += 1) {
     for (k = listeners.length; --k >= 0; /* empty */)

benchmark/events/ee-add.js

@@ -0,0 +1,35 @@
+'use strict';
+
+var common = require('../common');
+var EventEmitter = require('events');
+var v8 = require('v8');
+
+var bench = common.createBenchmark(main, {
+  n: [100e5]
+});
+
+function main(conf) {
+  var n = +conf.n;
+  var ee = new EventEmitter();
+  var listeners = [];
+
+  var k;
+  for (k = 0; k < 10; k += 1)
+    listeners.push(function() {});
+
+  // Force optimization before starting the benchmark
+  ee.on('dummy', listeners[0]);
+  ee._events = {};
+  v8.setFlagsFromString('--allow_natives_syntax');
+  eval('%OptimizeFunctionOnNextCall(ee.on)');
+  ee.on('dummy', listeners[0]);
+  ee._events = {};
+
+  bench.start();
+  for (var i = 0; i < n; ++i) {
+    for (k = listeners.length; --k >= 0; /* empty */)
+      ee.on('dummy', listeners[k]);
+    ee._events = {};
+  }
+  bench.end(n);
+}

benchmark/events/ee-emit-multi-args.js

@@ -1,8 +1,12 @@
 'use strict';
-var common = require('../common.js');
-var EventEmitter = require('events').EventEmitter;
 
-var bench = common.createBenchmark(main, {n: [2e6]});
+var common = require('../common');
+var EventEmitter = require('events');
+var v8 = require('v8');
+
+var bench = common.createBenchmark(main, {
+  n: [25e6]
+});
 
 function main(conf) {
   var n = conf.n | 0;
@@ -12,6 +16,11 @@ function main(conf) {
   for (var k = 0; k < 10; k += 1)
     ee.on('dummy', function() {});
 
+  ee.emit('dummy', 5, true);
+  v8.setFlagsFromString('--allow_natives_syntax');
+  eval('%OptimizeFunctionOnNextCall(ee.emit)');
+  ee.emit('dummy', 5, true);
+
   bench.start();
   for (var i = 0; i < n; i += 1) {
     ee.emit('dummy', 5, true);

benchmark/events/ee-emit-once.js

@@ -0,0 +1,32 @@
+'use strict';
+
+var common = require('../common');
+var EventEmitter = require('events');
+var v8 = require('v8');
+
+var bench = common.createBenchmark(main, {
+  n: [25e6]
+});
+
+function main(conf) {
+  var n = conf.n | 0;
+
+  var ee = new EventEmitter();
+
+  function noop() {}
+
+  ee.once('dummy', noop);
+  ee.emit('dummy');
+  v8.setFlagsFromString('--allow_natives_syntax');
+  eval('%OptimizeFunctionOnNextCall(ee.once)');
+  eval('%OptimizeFunctionOnNextCall(ee.emit)');
+  ee.once('dummy', noop);
+  ee.emit('dummy');
+
+  bench.start();
+  for (var i = 0; i < n; i += 1) {
+    ee.once('dummy', noop);
+    ee.emit('dummy');
+  }
+  bench.end(n);
+}

benchmark/events/ee-emit.js

@@ -1,8 +1,12 @@
 'use strict';
-var common = require('../common.js');
-var EventEmitter = require('events').EventEmitter;
 
-var bench = common.createBenchmark(main, {n: [2e6]});
+var common = require('../common');
+var EventEmitter = require('events');
+var v8 = require('v8');
+
+var bench = common.createBenchmark(main, {
+  n: [50e6]
+});
 
 function main(conf) {
   var n = conf.n | 0;
@@ -12,6 +16,11 @@ function main(conf) {
   for (var k = 0; k < 10; k += 1)
     ee.on('dummy', function() {});
 
+  ee.emit('dummy');
+  v8.setFlagsFromString('--allow_natives_syntax');
+  eval('%OptimizeFunctionOnNextCall(ee.emit)');
+  ee.emit('dummy');
+
   bench.start();
   for (var i = 0; i < n; i += 1) {
     ee.emit('dummy');

benchmark/events/ee-listener-count-on-prototype.js

@@ -1,8 +1,12 @@
 'use strict';
-var common = require('../common.js');
-var EventEmitter = require('events').EventEmitter;
 
-var bench = common.createBenchmark(main, {n: [5e7]});
+var common = require('../common');
+var EventEmitter = require('events');
+var v8 = require('v8');
+
+var bench = common.createBenchmark(main, {
+  n: [5e7]
+});
 
 function main(conf) {
   var n = conf.n | 0;
@@ -12,6 +16,11 @@ function main(conf) {
   for (var k = 0; k < 10; k += 1)
     ee.on('dummy', function() {});
 
+  ee.listenerCount('dummy');
+  v8.setFlagsFromString('--allow_natives_syntax');
+  eval('%OptimizeFunctionOnNextCall(ee.listenerCount)');
+  ee.listenerCount('dummy');
+
   bench.start();
   for (var i = 0; i < n; i += 1) {
     ee.listenerCount('dummy');

benchmark/events/ee-listeners-many.js

@@ -1,8 +1,12 @@
 'use strict';
-var common = require('../common.js');
-var EventEmitter = require('events').EventEmitter;
 
-var bench = common.createBenchmark(main, {n: [5e6]});
+var common = require('../common');
+var EventEmitter = require('events');
+var v8 = require('v8');
+
+var bench = common.createBenchmark(main, {
+  n: [15e6]
+});
 
 function main(conf) {
   var n = conf.n | 0;
@@ -13,6 +17,11 @@ function main(conf) {
   for (var k = 0; k < 100; k += 1)
     ee.on('dummy', function() {});
 
+  ee.listeners('dummy');
+  v8.setFlagsFromString('--allow_natives_syntax');
+  eval('%OptimizeFunctionOnNextCall(ee.listeners)');
+  ee.listeners('dummy');
+
   bench.start();
   for (var i = 0; i < n; i += 1) {
     ee.listeners('dummy');

benchmark/events/ee-listeners.js

@@ -1,8 +1,12 @@
 'use strict';
-var common = require('../common.js');
-var EventEmitter = require('events').EventEmitter;
 
-var bench = common.createBenchmark(main, {n: [5e6]});
+var common = require('../common');
+var EventEmitter = require('events');
+var v8 = require('v8');
+
+var bench = common.createBenchmark(main, {
+  n: [90e6]
+});
 
 function main(conf) {
   var n = conf.n | 0;
@@ -12,6 +16,11 @@ function main(conf) {
   for (var k = 0; k < 10; k += 1)
     ee.on('dummy', function() {});
 
+  ee.listeners('dummy');
+  v8.setFlagsFromString('--allow_natives_syntax');
+  eval('%OptimizeFunctionOnNextCall(ee.listeners)');
+  ee.listeners('dummy');
+
   bench.start();
   for (var i = 0; i < n; i += 1) {
     ee.listeners('dummy');