LibWeb: Implement timer nesting level throttling

This clamps the interval of repeating timers to 4ms after they have run 5 times. This prevents CPU spinning for `setInterval()` calls with low timeouts.
Author: https://github.com/tcl3 Commit: https://github.com/LadybirdBrowser/ladybird/commit/7577fd2a57b Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/7734 Reviewed-by: https://github.com/rcorsi ✅
2026-05-01 12:07:14 +02:00 · 2026-02-02 20:03:53 +00:00 · 2026-02-11 16:34:54 +00:00
parent 24055b60ef
commit 7577fd2a57
4 changed files with 54 additions and 9 deletions
--- a/Tests/LibWeb/Text/input/html/timer-nesting-level-clamping.html
+++ b/Tests/LibWeb/Text/input/html/timer-nesting-level-clamping.html
@@ -0,0 +1,23 @@
+<!DOCTYPE html>
+<script src="../include.js"></script>
+<script>
+    asyncTest(done => {
+        // With 4ms clamping after nesting level 5, running for 100ms should yield
+        // roughly 5-6 unclamped calls plus approximately 25 clamped calls.
+        // Without clamping, we'd get thousands of calls.
+        // We test that the count is bounded, proving clamping is working.
+        const testDurationMilliseconds = 100;
+        let callCount = 0;
+
+        const id = setInterval(() => {
+            callCount++;
+        }, 0);
+
+        setTimeout(() => {
+            clearInterval(id);
+
+            println(`Callback count bounded (< 100 in 100ms): ${callCount < 100}`);
+            done();
+        }, testDurationMilliseconds);
+    });
+</script>