timers: refactor timer list processing

Instead of using kOnTimeout index to track a special list
processing function, just pass in a function to C++ at
startup that executes all handles and determines which
function to call.

This change improves the performance of unpooled timeouts
by roughly 20%, as well as makes the unref/ref processing
easier to follow.

PR-URL: https://github.com/nodejs/node/pull/18582
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Vladimir de Turckheim <vlad2t@hotmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/benchmark/timers/timers-timeout-unpooled.js b/benchmark/timers/timers-timeout-unpooled.js
new file mode 100644
index 0000000000..19f0f6a4af
--- /dev/null
+++ b/benchmark/timers/timers-timeout-unpooled.js
@@ -0,0 +1,36 @@
+'use strict';
+const common = require('../common.js');
+
+// The following benchmark sets up n * 1e6 unpooled timeouts,
+// then measures their execution on the next uv tick
+
+const bench = common.createBenchmark(main, {
+  n: [1e6],
+});
+
+function main({ n }) {
+  let count = 0;
+
+  // Function tracking on the hidden class in V8 can cause misleading
+  // results in this benchmark if only a single function is used —
+  // alternate between two functions for a fairer benchmark
+
+  function cb() {
+    count++;
+    if (count === n)
+      bench.end(n);
+  }
+  function cb2() {
+    count++;
+    if (count === n)
+      bench.end(n);
+  }
+
+  for (var i = 0; i < n; i++) {
+    // unref().ref() will cause each of these timers to
+    // allocate their own handle
+    setTimeout(i % 2 ? cb : cb2, 1).unref().ref();
+  }
+
+  bench.start();
+}