1304393 - about:home is slow but about:newtab is fast

Status: RESOLVED INVALID

(Core :: DOM: Content Processes, defect)

Description

[Andrei Petcu]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0
Build ID: 20160920030429

Steps to reproduce:

Open a new tab with the about:home page (ctrl+click on the home button)
Here is a video https://vimeo.com/183656814
New profile, no addons.


Actual results:

It loaded about:home in 2.6 which is quite slow for a page that is loaded several times a day.


Expected results:

It should be instant just like about:newtab. It should be somehow preloaded.

Comment 1

[Andrei Petcu]

The default value of dom.ipc.processCount in about:config is 1. Only the first time I open an about:home tab is slow. If I open a second one it will be fast. If I close all about:home tabs and open a new one the first will be slow again and the second, third etc. will be fast.

If I increase dom.ipc.processCount to 4, then the first 4 tabs will be slow and the 5th, 6th, 7th etc. will be fast.

Since Mozilla plans to increase Firefox's dom.ipc.processCount to more than 1 this issue will surely pop up in the future.

Comment 2

[Mike Conley (:mconley) (:⚙️)]

This sounds like we're taking a long time spawning and using the new content process.

Would you mind getting a profile? That way, we can try to see what is taking the content process so long to spawn and be usable.

Instructions: https://github.com/mikeconley/getting-profiles-from-users/blob/master/49.0.x.md

Comment 3

[Andrei Petcu]

Somehow I was unable to reproduce it with processCount=1 and a common page (like Duck Duck Go). I reproduced it either with processCount=1 and about:performance or processCount=4 and Duck Duck Go. Here is the data, happy bug hunting :)

- dom.ipc.processCount=1
- current page=about:performance
https://cleopatra.io/#report=42c4f527f169cf7b44ddb06e61610b35b2e80ff4

- dom.ipc.processCount=4
- current page=https://duckduckgo.com
https://cleopatra.io/#report=ca84d29dea16002a24f8e46d5a5cfc69436b2394

Comment 4

[Mike Conley (:mconley) (:⚙️)]

Hrm, unfortunately, I don't think those profiles tell us much about this particular problem because I think by the time the content process starts gathering samples, the problem has gone away.

gw280, I seem to recall there being something you ran into when you were working on tresize where the content process took a long to start up for some reason... do you remember that? Do you remember what the issue was there?

Comment 5

[George Wright (:gw280) (needinfo me!)]

I recall we were wasting a lot of time loading the shim stuff when loading the addon tresize was using, which I fixed in bug 1179732.

Comment 6

[Andrei Petcu]

about:home is dead. resolving the issue.