User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Firefox/91.0

Steps to reproduce:

I dont know how to reproduce this bug.

Actual results:

It takes ages to fully load page, and to highlight visited links/websites and youtube title loads like 5-10sec after link is visited. While all of this is instant on edge or another firefox instance on different pc. I already tried some performance settings, tried fresh profile, tried safe mode, tried to reinstall firefox.

You can check out what I am talking about here, quick example https://streamable.com/rxdzs4 bear in mind this is not only happening on youtube etc, but youtube is great example. Firefox does not have any proxy settings enabled.

Same thing happened to this user https://www.reddit.com/r/firefox/comments/t91em2/youtube_is_loading_only_the_video_and_the_page/ and neither of us can figure out why it is happening.

about:support https://bin.snopyta.org/?7855599f1784cf67#8v4njsXi5bL5pwwc1vrBRAdTL2DxEniCbKcTyV7JUDJC

Expected results:

Visited links should highlight almost instantly, youtube video title should load way faster.

The Bugbug bot thinks this bug should belong to the 'Core::Graphics' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

I wasn't able to reproduce this issue on the latest Nightly 100.0a1 and Firefox 98 on Windows 10 x64.

Would you be so kind to answer several questions so that we can put together the STR?

1. On what other websites did you encounter this issue?
2. How do you access the video? Do you play the video directly on youtube.com?
3. Do you play the video in the same tab, new tab, new window?
4. Does the persist when using the latest Firefox release and latest Nightly build?

Could you please attach a txt file with a copy of the data from the about:support page because the data from PrivateBin has expired or has been deleted.

(In reply to Simona Badau from comment #2)

I wasn't able to reproduce this issue on the latest Nightly 100.0a1 and Firefox 98 on Windows 10 x64.

Would you be so kind to answer several questions so that we can put together the STR?

1. On what other websites did you encounter this issue?
2. How do you access the video? Do you play the video directly on youtube.com?
3. Do you play the video in the same tab, new tab, new window?
4. Does the persist when using the latest Firefox release and latest Nightly build?

Could you please attach a txt file with a copy of the data from the about:support page because the data from PrivateBin has expired or has been deleted.

1. The visited link highlighting happens on every website.
2. I simply open youtube.com, no extensions, no special procedure, no custom hardware. (I uploaded video to https://streamable.com/rxdzs4 where I showcase it)
3. Dont think I understood this question (maybe this does https://streamable.com/rxdzs4 )
4. Yes

https://bin.snopyta.org/?5dfff7f1f4599548#4hKZQXn28RdQpqAAez5U2zHn9s6cEMBbsReR9RbRfRmm

This does not seem to be "popular" issue as I only found one person thats this happening to. I tried nightly build, fresh profile, the firefox safe mode (forgot the exact name) and nothing solved this issue.

We don't think this is Graphics

Triage suggests this is not a graphics issue (perhaps networking?). Switching to general.

Could you try to capture a performance profile by following the instructions at https://profiler.firefox.com/. Then upload the profile and insert the link here.) Adding performance project flag and keywords and moving to Core::Performance until we can establish a more suitable component.

(In reply to Dave Hunt [:davehunt] [he/him] ⌚GMT from comment #7)

Could you try to capture a performance profile by following the instructions at https://profiler.firefox.com/. Then upload the profile and insert the link here.) Adding performance project flag and keywords and moving to Core::Performance until we can establish a more suitable component.

This is the profile on fresh profile showcasing the issue happening on youtube.
https://share.firefox.dev/3K1MoPI

In the screenshot I can see that you reproduced this in a private Firefox window. Does this also happen in non-private windows? If it does, could you capture another profile from it? The profile from comment 8 doesn't contain some essential information which was removed during the upload, because it was associated with a private window.

(In reply to Markus Stange [:mstange] from comment #9)

In the screenshot I can see that you reproduced this in a private Firefox window. Does this also happen in non-private windows? If it does, could you capture another profile from it? The profile from comment 8 doesn't contain some essential information which was removed during the upload, because it was associated with a private window.

https://share.firefox.dev/3tZkZbp

While recording this profile I've noticed that performance is consistently bit better when auto play is disabled (0-2s). When I enabled auto play then performance becomes as bad as mentioned in posts above.

Also I am not sure if I should create another bug report for the visited link highlighting delay (<a href="...">..</a>) highlight itself few seconds after page load instead of instantly, or its related to this which is hard to assume.

Thanks. I took another look through the profile and I can see that things are slow but it's unclear why. There's a super-late readystatechange event here: https://share.firefox.dev/3DwVdyu
Once that event fires, things start to get moving. But I'm not sure what it's waiting for. The network chart shows that all the interesting network requests have already completed long ago. And there's no "Extension suspend" marker in the parent process either.
There might be more interesting things happening on the Socket, Cache and Storage threads.

I'm moving this to the Network component.

(In reply to spam from comment #10)

Also I am not sure if I should create another bug report for the visited link highlighting delay (<a href="...">..</a>) highlight itself few seconds after page load instead of instantly, or its related to this which is hard to assume.

Yeah I'm not sure either. We could assume for now that it's related and re-test if there's a fix or a workaround.

Could you try to capture a http log?
The log may contain some privacy information, so you could send the log to necko@mozilla.com if you want.
Thanks.

(In reply to Kershaw Chang [:kershaw] from comment #12)

Could you try to capture a http log?
The log may contain some privacy information, so you could send the log to necko@mozilla.com if you want.
Thanks.

I have just sent you the logs.

Tried firefox forks such as librewolf and same thing is happening. I have a feeling that this is some kind of changed windows setting/patch/configuration... that just messes up something in firefox.

The socket thread and necko in general are not busy or delaying any events. They are really idle for long time periods.
The delay is not in necko.

Markus -- FYI: Dragana believes this is not a necko issue; so I'm moving this back to Performance for re-evaluation.

Dragana, can you forward the logs to me? Based on the profile I don't see where else the delay could be. But we clearly need better tools for this.

I have forwarded you the logs.

Thanks! You were right, it is indeed not a network issue.

In the meantime, bug 1764578 has come up, and pointed out that this problem is related to a high monitor refresh rate. In the profile in this bug, you can also see a refresh rate around 250Hz. So I'll mark this bug as a duplicate of bug 1764578 because that bug has more background.

I set refresh rate of both of my monitors to 60Hz and I can confirm that the issue was indeed fixed, both link highlighting and the youtube issue. Looking forward to seeing it fixed in the future. Thanks!!

Apparently Firefox 103 was supposed to fix this issue (i think this is the bug report https://bugzilla.mozilla.org/show_bug.cgi?id=1764578 ), but unfortunately for me it did not change anything, locking frame rate to 60 in about:config layout.frame_rate to 60 fixes all my issues