From 5ef225853c0f81ba0a7d1ce888ab3b2d283eae0a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bartek=20Iwa=C5=84czuk?= <biwanczuk@gmail.com>
Date: Wed, 14 Jun 2023 16:21:06 +0200
Subject: perf: don't run microtask checkpoint if macrotask callback did no
 work (#19492)

Most of the time there's no firing timers, nor pending promise
rejections, so it's wasteful to run microtask checkpoint
additionally twice on each tick of the event loop.

Closes https://github.com/denoland/deno/issues/18871
Ref https://github.com/denoland/deno/issues/19451
---
 ext/web/02_timers.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'ext')

diff --git a/ext/web/02_timers.js b/ext/web/02_timers.js
index 19ebfaa0e..27e2e953d 100644
--- a/ext/web/02_timers.js
+++ b/ext/web/02_timers.js
@@ -54,8 +54,10 @@ const timerTasks = [];
 let timerNestingLevel = 0;
 
 function handleTimerMacrotask() {
+  // We have no work to do, tell the runtime that we don't
+  // need to perform microtask checkpoint.
   if (timerTasks.length === 0) {
-    return true;
+    return undefined;
   }
 
   const task = ArrayPrototypeShift(timerTasks);
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