events: optimize performance of add, remove, emit

If more than one handler is bound to an event type, avoid copying
it on emit and instead set a flag that regulates whether to make
a copy when a new event is added or removed.

Do not use delete or Object.create(null) when removing listeners,
instead set to undefined and modify other methods to account
for this.

benchmark/events/ee-add-remove.js

@@ -2,18 +2,30 @@
 const common = require('../common.js');
 const events = require('events');
 
-const bench = common.createBenchmark(main, { n: [25e4] });
+const bench = common.createBenchmark(main, {
+  n: [5e6],
+  events: [0, 5],
+  listeners: [1, 5]
+});
 
 function main(conf) {
-  const n = conf.n | 0;
+  let n = conf.n | 0;
+  const eventsCOunt = conf.events | 0;
+  const listenersCount = conf.listeners | 0;
 
   const ee = new events.EventEmitter();
   const listeners = [];
 
+  if (listenersCount === 1)
+    n *= 2;
+
   var k;
-  for (k = 0; k < 10; k += 1)
+  for (k = 0; k < listenersCount; k += 1)
     listeners.push(function() {});
 
+  for (k = 0; k < eventsCOunt; k++)
+    ee.on(`dummyunused${k}`, () => {});
+
   bench.start();
   for (var i = 0; i < n; i += 1) {
     const dummy = (i % 2 === 0) ? 'dummy0' : 'dummy1';

benchmark/events/ee-emit-multi.js

@@ -0,0 +1,36 @@
+'use strict';
+const common = require('../common.js');
+const EventEmitter = require('events').EventEmitter;
+
+const bench = common.createBenchmark(main, {
+  n: [2e7],
+  listeners: [1, 5, 10],
+});
+
+function main(conf) {
+  var n = conf.n | 0;
+  const listeners = Math.max(conf.listeners | 0, 1);
+
+  const ee = new EventEmitter();
+
+  if (listeners === 1)
+    n *= 5;
+  else if (listeners === 5)
+    n *= 2;
+
+  for (var k = 0; k < listeners; k += 1) {
+    ee.on('dummy', function() {});
+    ee.on(`dummy${k}`, function() {});
+  }
+
+  bench.start();
+  for (var i = 0; i < n; i += 1) {
+    if (i % 3 === 0)
+      ee.emit('dummy', true, 5);
+    else if (i % 2 === 0)
+      ee.emit('dummy', true, 5, 10, false);
+    else
+      ee.emit('dummy');
+  }
+  bench.end(n);
+}

benchmark/events/ee-emit.js

@@ -3,20 +3,27 @@ const common = require('../common.js');
 const EventEmitter = require('events').EventEmitter;
 
 const bench = common.createBenchmark(main, {
-  n: [2e6],
+  n: [2e7],
   argc: [0, 2, 4, 10],
   listeners: [1, 5, 10],
 });
 
 function main(conf) {
-  const n = conf.n | 0;
+  var n = conf.n | 0;
   const argc = conf.argc | 0;
   const listeners = Math.max(conf.listeners | 0, 1);
 
   const ee = new EventEmitter();
 
-  for (var k = 0; k < listeners; k += 1)
+  if (listeners === 1)
+    n *= 5;
+  else if (listeners === 5)
+    n *= 2;
+
+  for (var k = 0; k < listeners; k += 1) {
     ee.on('dummy', function() {});
+    ee.on(`dummy${k}`, function() {});
+  }
 
   var i;
   switch (argc) {

benchmark/events/ee-event-names.js

@@ -0,0 +1,30 @@
+'use strict';
+const common = require('../common.js');
+const EventEmitter = require('events').EventEmitter;
+
+const bench = common.createBenchmark(main, { n: [1e6] });
+
+function main(conf) {
+  const n = conf.n | 0;
+
+  const ee = new EventEmitter();
+
+  for (var k = 0; k < 9; k += 1) {
+    ee.on(`dummy0${k}`, function() {});
+    ee.on(`dummy1${k}`, function() {});
+    ee.on(`dummy2${k}`, function() {});
+  }
+
+  ee.removeAllListeners('dummy01');
+  ee.removeAllListeners('dummy11');
+  ee.removeAllListeners('dummy21');
+  ee.removeAllListeners('dummy06');
+  ee.removeAllListeners('dummy16');
+  ee.removeAllListeners('dummy26');
+
+  bench.start();
+  for (var i = 0; i < n; i += 1) {
+    ee.eventNames();
+  }
+  bench.end(n);
+}

benchmark/events/ee-listeners-many.js

@@ -2,7 +2,7 @@
 const common = require('../common.js');
 const EventEmitter = require('events').EventEmitter;
 
-const bench = common.createBenchmark(main, { n: [5e6] });
+const bench = common.createBenchmark(main, { n: [1e7] });
 
 function main(conf) {
   const n = conf.n | 0;

benchmark/events/ee-listeners.js

@@ -2,7 +2,7 @@
 const common = require('../common.js');
 const EventEmitter = require('events').EventEmitter;
 
-const bench = common.createBenchmark(main, { n: [5e6] });
+const bench = common.createBenchmark(main, { n: [5e7] });
 
 function main(conf) {
   const n = conf.n | 0;

benchmark/events/ee-once.js

@@ -2,19 +2,27 @@
 const common = require('../common.js');
 const EventEmitter = require('events').EventEmitter;
 
-const bench = common.createBenchmark(main, { n: [2e7] });
+const bench = common.createBenchmark(main, {
+  n: [5e6],
+  listeners: [1, 5]
+});
 
 function main(conf) {
-  const n = conf.n | 0;
+  let n = conf.n | 0;
+  const listeners = conf.listeners | 0;
+
+  if (listeners === 1)
+    n *= 2;
 
   const ee = new EventEmitter();
 
   function listener() {}
 
   bench.start();
-  for (var i = 0; i < n; i += 1) {
+  for (var i = 0; i < n; ++i) {
     const dummy = (i % 2 === 0) ? 'dummy0' : 'dummy1';
-    ee.once(dummy, listener);
+    for (var j = 0; j < listeners; ++j)
+      ee.once(dummy, listener);
     ee.emit(dummy);
   }
   bench.end(n);