Bug 299295 – playstation.com: Poor performance when rendering on homepage

• Component: DOM
• Status: RESOLVED DUPLICATE

[Ian Grunert]

Looks like there's a MutationObserver on this page which triggers during composite that takes ~3 seconds to complete on my machine. There's two composites during load; the main thread locks up for ~6-10 seconds.

Same page renders well on Firefox and Chromium.

[Alexey Proskuryakov]

Thank you for the report. My understanding is that this doesn't affect Safari or Safari Technology Preview by default, as the feature is disabled by default.

[Ian Grunert]

This was tested on Safari Version 18.6 (20621.3.11.11.3), with feature flags reset.

There's another user report in the wild: https://mastodon.social/@marioguzman/115232988279672103

[Radar WebKit Bug Importer]

<rdar://problem/161575207>

[Karl Dubost]

Ian, Thanks for the report. 
I wonder if you can reproduce consistently?
If yes, maybe it would be to use applefeedback://
to upload a sysdiagnose that would contain more information about possible performance issues. 


My own

1. with STP 227 on macOS Tahoe
2. Go to https://www.playstation.com/en-us/

Result:
page is loading.

I'm not seeing anything obvious

Testing on Firefox and Chrome, I get similar performances

Maybe on Shift-reload, we can notice a slight delay.
Yes I think I was able to reproduce it. Not always but sometimes.

[Karl Dubost]

I'm adding a sysdiagnose to the radar.

[Ian Grunert]

Created attachment 476899 [details]
safari timeline

I can reproduce it consistently. Compared to Chrome and Firefox, the videos for the carousel take significantly longer to appear, and scrolling after they appear is choppy due to a couple of long-running javascript tasks hogging the main thread.

I've attached a Safari timeline; there's three long running tasks:

* "Timer 16 Fired" takes 3.31 seconds 
* A MutationObserver Callback inside OtAutoBlock.js takes 3.05 seconds
* Microtask Dispatched takes 3.01 seconds

My fear with the MutationObserver callback is that this could be occurring on other sites; OtAutoBlock.js is from OneTrust (a vendor for cookie management in the GDPR age).

https://my.onetrust.com/s/article/UUID-cdb2fcad-1640-fdbd-e432-73c5536f0bbd?language=en_US

[Ian Grunert]

Created attachment 476900 [details]
webcontent instruments profile

Here's the instruments profile - there's three ~3s severe hangs, which lines up with what the Safari timeline shows.

[Ryan Reno]

Thank you for uploading an Instruments profile! This was fixed in https://bugs.webkit.org/show_bug.cgi?id=297591

[Ryosuke Niwa]

*** This bug has been marked as a duplicate of bug 297591 ***