1760749 - page timings delayed more than 10 sec with esr91.7.1 with devtools

Status: NEW

(DevTools :: Netmonitor, defect, P2)

Description

[lijingmu]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:98.0) Gecko/20100101 Firefox/98.0

Steps to reproduce:

1. I used Mozilla Firefox 78.5.0esr, to access the website https://aws.amazon.com/ and generate HAR file with devtools. The page timings are 2.5 seconds, from HAR are as below.
   "pageTimings": {
   "onContentLoad": 2429,
   "onLoad": 2432,
   "comment": ""
   },

2. When I changed to Mozilla Firefox 91.7.1esr. To visit the same website, the page load time is more then 17 seconds. The same issue can be found in other website, e.g. www.yahoo.com.
   "pageTimings": {
   "onContentLoad": 17499,
   "onLoad": 17513,
   "comment": ""
   },

3. When I disable --devtools, the page onLoad and onContentLoad time will be much faster. But I need this devtools to generate HAR file.

4. Right now the preference is as below:
   'devtools.toolbox.selectedTool': 'netmonitor',
   'devtools.netmonitor.enabled': true,

Expected results:

I have the same preference settings and access the same websites, but the page onLoad and onContentLoad time delayed from 2.5 sec to 17 sec. I hope you have some workaround or settings to resolve this.

Comment 1

[lijingmu]

environment:
firefox Mozilla Firefox 91.7.1esr
x86_64 Linux

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

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

Comment 3

[lijingmu]

I think this can be simply reproduced by

1. open latest FF with devtools opened, access the website https://aws.amazon.com/
2. save a HAR file
3. compare the onContentLoad and onLoad in pageTimings with version 78.

or use extensions to generate HAR as this one https://github.com/firefox-devtools/har-export-trigger

Comment 4

[Julian Descottes [:jdescottes]]

Honza to try to reproduce.
Not that HAR export was broken recently and fixed in 97, need to make sure that is still working in ESR.

Comment 5

[Alexandre Poirot [:ochameau]]

Har export was fixed in 97 via bug 1747804.

Comment 6

[Jan Honza Odvarko [:Honza] (always need-info? me)]

I tested this, some notes:

My STR:

1. Launch the lastest m-c (100 atm)
2. Open DevTools
3. Select e.g. the Memory panel (not the Network panel to avoid performance penalties caused by re-rendering during page load time)
4. Load www.yahoo.com, wait till it's loaded
5. Switch to the Network panel and see the load timing displayed at the bottom
6. Go to step #3 and get another measurement if needed

For 91: I am seeing the load time around 10 sec
For 100: I am seeing the load time around 2.6 sec

So, there seems to be something wrong.

Thanks for the report!

Honza

Comment 7

[lijingmu]

Access the same webpage https://aws.amazon.com/ with 102.3.0esr devtools enabled still see obvious delay. Would you please have a look at it? Thanks!

Mozilla   Firefox 78.5.0esr
"pageTimings": {
      "onContentLoad": 2653,
      "onLoad": 2659,
      "comment": ""
    },

Mozilla Firefox 102.3.0esr 
"pageTimings": {
      "onContentLoad": 19129,
      "onLoad": 19145,
      "comment": ""
    },

Comment 8

[lijingmu]

it becomes much better when disable devtools