node: improve nextTick performance

This commit uses separate functions to isolate deopts caused by
try-catches and avoids fn.apply() for callbacks with small numbers
of arguments.

These changes improve performance by ~2-16% in the various
nextTick benchmarks.

benchmark/misc/next-tick-breadth-args.js

@@ -0,0 +1,21 @@
+
+var common = require('../common.js');
+var bench = common.createBenchmark(main, {
+  millions: [2]
+});
+
+function main(conf) {
+  var N = +conf.millions * 1e6;
+  var n = 0;
+
+  function cb(arg1, arg2, arg3) {
+    n++;
+    if (n === N)
+      bench.end(n / 1e6);
+  }
+
+  bench.start();
+  for (var i = 0; i < N; i++) {
+    process.nextTick(cb, 512, true, null);
+  }
+}

benchmark/misc/next-tick-depth-args.js

@@ -0,0 +1,19 @@
+var common = require('../common.js');
+var bench = common.createBenchmark(main, {
+  millions: [2]
+});
+
+process.maxTickDepth = Infinity;
+
+function main(conf) {
+  var n = +conf.millions * 1e6;
+
+  bench.start();
+  process.nextTick(onNextTick, 512, true, null);
+  function onNextTick(arg1, arg2, arg3) {
+    if (--n)
+      process.nextTick(onNextTick);
+    else
+      bench.end(+conf.millions);
+  }
+}

src/node.js

@@ -328,23 +328,32 @@
     // Run callbacks that have no domain.
     // Using domains will cause this to be overridden.
     function _tickCallback() {
-      var callback, threw, tock;
+      var callback, args, threw, tock;
 
       do {
         while (tickInfo[kIndex] < tickInfo[kLength]) {
           tock = nextTickQueue[tickInfo[kIndex]++];
           callback = tock.callback;
-          threw = true;
-          try {
-            if (tock.args === undefined)
-              callback();
-            else
-              callback.apply(null, tock.args);
-            threw = false;
-          } finally {
-            if (threw)
-              tickDone();
+          args = tock.args;
+          if (args === undefined)
+            threw = doNTCallback0(callback);
+          else {
+            switch (args.length) {
+              case 1:
+                threw = doNTCallback1(callback, args[0]);
+                break;
+              case 2:
+                threw = doNTCallback2(callback, args[0], args[1]);
+                break;
+              case 3:
+                threw = doNTCallback3(callback, args[0], args[1], args[2]);
+                break;
+              default:
+                threw = doNTCallbackMany(callback, args);
+            }
           }
+          if (threw)
+            tickDone();
           if (1e4 < tickInfo[kIndex])
             tickDone();
         }
@@ -355,26 +364,35 @@
     }
 
     function _tickDomainCallback() {
-      var callback, domain, threw, tock;
+      var callback, domain, args, threw, tock;
 
       do {
         while (tickInfo[kIndex] < tickInfo[kLength]) {
           tock = nextTickQueue[tickInfo[kIndex]++];
           callback = tock.callback;
           domain = tock.domain;
+          args = tock.args;
           if (domain)
             domain.enter();
-          threw = true;
-          try {
-            if (tock.args === undefined)
-              callback();
-            else
-              callback.apply(null, tock.args);
-            threw = false;
-          } finally {
-            if (threw)
-              tickDone();
+          if (args === undefined)
+            threw = doNTCallback0(callback);
+          else {
+            switch (args.length) {
+              case 1:
+                threw = doNTCallback1(callback, args[0]);
+                break;
+              case 2:
+                threw = doNTCallback2(callback, args[0], args[1]);
+                break;
+              case 3:
+                threw = doNTCallback3(callback, args[0], args[1], args[2]);
+                break;
+              default:
+                threw = doNTCallbackMany(callback, args);
+            }
           }
+          if (threw)
+            tickDone();
           if (1e4 < tickInfo[kIndex])
             tickDone();
           if (domain)
@@ -386,6 +404,51 @@
       } while (tickInfo[kLength] !== 0);
     }
 
+    function doNTCallback0(callback) {
+      var threw = true;
+      try {
+        callback();
+        threw = false;
+      } finally {}
+      return threw;
+    }
+
+    function doNTCallback1(callback, arg1) {
+      var threw = true;
+      try {
+        callback(arg1);
+        threw = false;
+      } finally {}
+      return threw;
+    }
+
+    function doNTCallback2(callback, arg1, arg2) {
+      var threw = true;
+      try {
+        callback(arg1, arg2);
+        threw = false;
+      } finally {}
+      return threw;
+    }
+
+    function doNTCallback3(callback, arg1, arg2, arg3) {
+      var threw = true;
+      try {
+        callback(arg1, arg2, arg3);
+        threw = false;
+      } finally {}
+      return threw;
+    }
+
+    function doNTCallbackMany(callback, args) {
+      var threw = true;
+      try {
+        callback.apply(null, args);
+        threw = false;
+      } finally {}
+      return threw;
+    }
+
     function TickObject(c, args) {
       this.callback = c;
       this.domain = process.domain || null;

test/message/nexttick_throw.out

@@ -4,6 +4,7 @@
         ^
 ReferenceError: undefined_reference_error_maker is not defined
     at *test*message*nexttick_throw.js:*:*
+    at doNTCallback0 (node.js:*:*)
     at process._tickCallback (node.js:*:*)
     at Function.Module.runMain (module.js:*:*)
     at startup (node.js:*:*)

test/message/stdin_messages.out

@@ -12,6 +12,7 @@ SyntaxError: Strict mode code may not include a with statement
     at emitNone (events.js:*:*)
     at Socket.emit (events.js:*:*)
     at endReadableNT (_stream_readable.js:*:*)
+    at doNTCallback2 (node.js:*:*)
     at process._tickCallback (node.js:*:*)
 42
 42
@@ -29,7 +30,7 @@ Error: hello
     at emitNone (events.js:*:*)
     at Socket.emit (events.js:*:*)
     at endReadableNT (_stream_readable.js:*:*)
-    at process._tickCallback (node.js:*:*)
+    at doNTCallback2 (node.js:*:*)
 
 [stdin]:1
 throw new Error("hello")
@@ -44,7 +45,7 @@ Error: hello
     at emitNone (events.js:*:*)
     at Socket.emit (events.js:*:*)
     at endReadableNT (_stream_readable.js:*:*)
-    at process._tickCallback (node.js:*:*)
+    at doNTCallback2 (node.js:*:*)
 100
 
 [stdin]:1
@@ -60,7 +61,7 @@ ReferenceError: y is not defined
     at emitNone (events.js:*:*)
     at Socket.emit (events.js:*:*)
     at endReadableNT (_stream_readable.js:*:*)
-    at process._tickCallback (node.js:*:*)
+    at doNTCallback2 (node.js:*:*)
 
 [stdin]:1
 var ______________________________________________; throw 10