From 589b2a1244da2f04843652bda97ef55397cdf5b7 Mon Sep 17 00:00:00 2001
From: Trevor Norris <trev.norris@gmail.com>
Date: Tue, 25 Aug 2020 13:36:37 -0600
Subject: perf_hooks: add idleTime and event loop util
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Use uv_metrics_idle_time() to return a high resolution millisecond timer
of the amount of time the event loop has been idle since it was
initialized.

Include performance.eventLoopUtilization() API to handle the math of
calculating the idle and active times. This has been added to prevent
accidental miscalculations of the event loop utilization. Such as not
taking into consideration offsetting nodeTiming.loopStart or timing
differences when being called from a Worker thread.

PR-URL: https://github.com/nodejs/node/pull/34938
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Adrian Estrada <edsadr@gmail.com>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
---
 benchmark/README.md                         |  1 +
 benchmark/perf_hooks/bench-eventlooputil.js | 64 +++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+)
 create mode 100644 benchmark/perf_hooks/bench-eventlooputil.js

(limited to 'benchmark')

diff --git a/benchmark/README.md b/benchmark/README.md
index 6a40d7af3e1..dc02db4abd8 100644
--- a/benchmark/README.md
+++ b/benchmark/README.md
@@ -32,6 +32,7 @@ directory, see [the guide on benchmarks](../doc/guides/writing-and-running-bench
 | module          | Benchmarks for the `module` subsystem.                                                                           |
 | net             | Benchmarks for the `net` subsystem.                                                                              |
 | path            | Benchmarks for the `path` subsystem.                                                                             |
+| perf_hooks      | Benchmarks for the `perf_hooks` subsystem.                                                                       |
 | process         | Benchmarks for the `process` subsystem.                                                                          |
 | querystring     | Benchmarks for the `querystring` subsystem.                                                                      |
 | streams         | Benchmarks for the `streams` subsystem.                                                                          |
diff --git a/benchmark/perf_hooks/bench-eventlooputil.js b/benchmark/perf_hooks/bench-eventlooputil.js
new file mode 100644
index 00000000000..984b2b66aec
--- /dev/null
+++ b/benchmark/perf_hooks/bench-eventlooputil.js
@@ -0,0 +1,64 @@
+'use strict';
+
+const common = require('../common.js');
+const assert = require('assert').ok;
+const { performance } = require('perf_hooks');
+const { nodeTiming, eventLoopUtilization } = performance;
+
+const bench = common.createBenchmark(main, {
+  n: [1e6],
+  method: [
+    'idleTime',
+    'ELU_simple',
+    'ELU_passed',
+  ],
+});
+
+function main({ method, n }) {
+  switch (method) {
+    case 'idleTime':
+      benchIdleTime(n);
+      break;
+    case 'ELU_simple':
+      benchELUSimple(n);
+      break;
+    case 'ELU_passed':
+      benchELUPassed(n);
+      break;
+    default:
+      throw new Error(`Unsupported method ${method}`);
+  }
+}
+
+function benchIdleTime(n) {
+  bench.start();
+  for (let i = 0; i < n; i++)
+    nodeTiming.idleTime;
+  bench.end(n);
+}
+
+function benchELUSimple(n) {
+  // Need to put this in setImmediate or will always return 0.
+  setImmediate(() => {
+    const elu = eventLoopUtilization();
+    assert(elu.active + elu.idle > 0);
+
+    bench.start();
+    for (let i = 0; i < n; i++)
+      eventLoopUtilization();
+    bench.end(n);
+  });
+}
+
+function benchELUPassed(n) {
+  // Need to put this in setImmediate or will always return 0.
+  setImmediate(() => {
+    let elu = eventLoopUtilization();
+    assert(elu.active + elu.idle > 0);
+
+    bench.start();
+    for (let i = 0; i < n; i++)
+      elu = eventLoopUtilization(elu);
+    bench.end(n);
+  });
+}
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