Loading lag on dynamically loaded pages




CSS Parsing and Computation
14 days ago
6 days ago


(Reporter: vojtech.vladyka, Unassigned)


({perf, regression})

58 Branch
perf, regression

Firefox Tracking Flags

(firefox58 fix-optional)




14 days ago
User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:58.0) Gecko/20100101 Firefox/58.0
Build ID: 20171107220115

Steps to reproduce:

1. Login to twitter
2. Scroll down quickly - you should see only background, foreground will come later (bad behaviour)
3. If you quickly scroll up, foreground is lost again and it takes time to re-render it

Actual results:

It loads after some time, but it was much faster in older versions. 
Only thing left on page is background but foreground loads really long time.

Bug was bisected using Mozregression tool. 
End of log (last good version)
2017-11-08T12:52:59: INFO : Running autoland build built on 2017-06-30 00:23:57.629000, revision ce2eee82
2017-11-08T12:53:02: INFO : Launching c:\Users\e878714\AppData\Local\Temp\tmpq_gtpd\firefox\firefox.exe
2017-11-08T12:53:02: INFO : Application command: c:\Users\e878714\AppData\Local\Temp\tmpq_gtpd\firefox\firefox.exe -profile c:\users\e878714\appdata\local\temp\tmpgzooor.mozrunner
2017-11-08T12:53:02: INFO : application_buildid: 20170629160321
2017-11-08T12:53:02: INFO : application_changeset: ce2eee8297d12142308cdfa050184621faea8e65
2017-11-08T12:53:02: INFO : application_display_name: Nightly
2017-11-08T12:53:02: INFO : application_id: {ec8030f7-c20a-464f-9b0e-13a3a9e97384}
2017-11-08T12:53:02: INFO : application_name: Firefox
2017-11-08T12:53:02: INFO : application_remotingname: firefox
2017-11-08T12:53:02: INFO : application_repository: https://hg.mozilla.org/integration/autoland
2017-11-08T12:53:02: INFO : application_vendor: Mozilla
2017-11-08T12:53:02: INFO : application_version: 56.0a1
2017-11-08T12:53:02: INFO : platform_buildid: 20170629160321
2017-11-08T12:53:02: INFO : platform_changeset: ce2eee8297d12142308cdfa050184621faea8e65
2017-11-08T12:53:02: INFO : platform_repository: https://hg.mozilla.org/integration/autoland
2017-11-08T12:53:02: INFO : platform_version: 56.0a1
2017-11-08T12:53:25: INFO : Unable to read VR Path Registry from C:\Users\e878714\AppData\Local\openvr\openvrpaths.vrpath
2017-11-08T12:53:25: INFO : [Child 620432] WARNING: pipe error: 109: file c:/builds/moz2_slave/autoland-w64-00000000000000000/build/src/ipc/chromium/src/chrome/common/ipc_channel_win.cc, line 346
2017-11-08T12:53:25: INFO : [Child 620432] WARNING: pipe error: 109: file c:/builds/moz2_slave/autoland-w64-00000000000000000/build/src/ipc/chromium/src/chrome/common/ipc_channel_win.cc, line 346
2017-11-08T12:53:26: INFO : Narrowed inbound regression window from [a7ea11ba, 07b3b72f] (3 builds) to [ce2eee82, 07b3b72f] (2 builds) (~1 steps left)
2017-11-08T12:53:26: DEBUG : Starting merge handling...
2017-11-08T12:53:26: DEBUG : Using url: https://hg.mozilla.org/integration/autoland/json-pushes?changeset=07b3b72fe522156b8a90dbd1e7b0754c571ac4b9&full=1
2017-11-08T12:53:28: DEBUG : Found commit message:
Bug 1373159 - Add a bunch of test cases for 'context-fill-opacity' and 'context-stroke-opacity'. r=heycam

MozReview-Commit-ID: AkSep6phtm8

2017-11-08T12:53:28: INFO : The bisection is done.
2017-11-08T12:53:28: INFO : Stopped

Bisection Informations:
app_name: firefox
build_date: 2017-06-30 00:24:06.192000
build_file: C:\Users\e878714\.mozilla\mozregression\persist\07b3b72fe522--autoland--firefox-56.0a1.en-US.win64.zip
build_type: inbound
build_url: https://queue.taskcluster.net/v1/task/R5NnkQ44RuOuKcex0qaopg/runs/0/artifacts/public%2Fbuild%2Ffirefox-56.0a1.en-US.win64.zip
changeset: 07b3b72fe522156b8a90dbd1e7b0754c571ac4b9
pushlog_url: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=a7ea11bae1ce47fb94c6e62696b474f492131101&tochange=07b3b72fe522156b8a90dbd1e7b0754c571ac4b9
repo_name: autoland
repo_url: https://hg.mozilla.org/integration/autoland
task_id: R5NnkQ44RuOuKcex0qaopg


14 days ago
Component: Untriaged → CSS Parsing and Computation
Keywords: perf, regression
Product: Firefox → Core


13 days ago
status-firefox58: --- → affected


9 days ago
Priority: -- → P3
status-firefox58: affected → fix-optional
The patches in the regression range seem irrelevant to the symptom. (assuming you are scolling up and down with loaded tweets)
I'm also having hard time to reproduce it on my Windows machine with corresponding Firefox version.
In your case, how much time did it take to re-render the page during scrolls?
It would be great if you could provide profile data for further investigation.

Flags: needinfo?(vojtech.vladyka)

Comment 2

6 days ago
I understand. 

Time varies with CPU load. At this moment I am on ~40% (measured using perfmon.exe, CPU is i5-7300U) and times are around 0.5s which is fairly visible in comparison to earlier versions where lag wasn't present at all or was very short (that spot was found using mozregression tool)

Profile is here https://perfht.ml/2hDo3YE It was made with latest nightly (issue is still present) If you need more profiles, don't hesitate to ask.

Flags: needinfo?(vojtech.vladyka)

Comment 3

6 days ago
By the way, on twitter, issue is more visible when scrolling quickly up from bottom of timeline.
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