[Webkit-unassigned] [Bug 272156] New: setInterval average delay is larger than expected when it runs in Low Power Mode or in iframe

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=272156

            Bug ID: 272156
           Summary: setInterval average delay is larger than expected when
                    it runs in Low Power Mode or in iframe
           Product: WebKit
           Version: Safari 17
          Hardware: iPhone / iPad
                OS: iOS 17
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: fuweichin at gmail.com

Created attachment 470754

  --> https://bugs.webkit.org/attachment.cgi?id=470754&action=review

setInterval test results for various platforms/browsers and conditions/modes

For global function setInterval, the average delay detected may be 30% larger than the delay parameter value when Lower Power Mode is turned on or script runs in iframe. e.g. `setInterval(()=>{}, 66.66666666666667)` may actually scheduled at interval delay of 89ms.

For average delay of setInterval implementations, I must adimit mobile Safari can make it very accurate in normal conditions, since Chrome just ignores fractional part of the delay parameter, and desktop Firefox has no self-regulation to ensure an accurate average delay.

See demo [setInterval actual interval test](https://codepen.io/fuweichin/pen/PoayPbm) and attachment [setInterval test results for various platforms/browsers and conditions/modes].

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