1604204 - Firefox lags (hangs for 5+ seconds) when opening a new tab

Status: RESOLVED INCOMPLETE

(Core :: Widget: Gtk, defect)

Description

[Vitaly]

User Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/78.0.3904.108 Chrome/78.0.3904.108 Safari/537.36

Steps to reproduce:

Using Firefox 71 x64 on Linux, open a new (blank) tab, or switch to an
older inactive one.

Actual results:

Sometimes Firefox hangs (becomes unresponsive) for multiple seconds.
Opening the second one immediately after is fairly fast. I haven't found
a consistent pattern.

Here's a profile capture of one such occurrence:
https://perfht.ml/38K3qzq

Expected results:

I expect to see a blank tab within less than half a second.

I've tried this on a clean profile w/o plugins too: the problem seems to
remain (maybe to a lesser extent, but its hard to tell).

Some similar reports recommend checking "Prevent accessibility services
from accessing your browser" and setting the proxy to "no proxy" -- I did
both, no effect.

Comment 1

[Pablo]

Hi
I tried to replicate the issue using Ubuntu 18.04 and the latest Firefox Nightly release 73.0a1
But i see no issue with new tab delay

Could you please download the latest Firefox Nightly release from here: https://nightly.mozilla.org/ and retest the problem.

If you still have the issue please create a new profile, you have the steps here:https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles?redirectlocale=en-US&redirectslug=Managing-profiles#w_starting-the-profile-manager

Lastly test if the issue is reproducible in safe mode, here is a link that can help you:
https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode

Regards
Pablo

Comment 2

[Vitaly]

So, I've installed Nightly 73.0a1 (2019-12-20) and started with
a new profile. Overall it's pretty bad:

1. First I tried to open 7 new tabs (hitting Ctrl-T 7 times in a
   succession) using the default settings of a clean profile (with
   the profiler being the only new addon installed); here's the
   trace:

   https://perfht.ml/2sNCT3X

   Note that there are up to 1.5 second delays between tabs being
   opened, and the whole process takes at least 5 seconds. Firefox
   is barely responsive during the whole time.

2. Next, I changed the home page and the new tab page to be blank
   pages, restarted the browser, and tried to open 7 tabs the same
   way. Here's the trace:

   https://perfht.ml/2sb1jnZ

   Note that only 6 tabs got opened; due to lag probably. The delays
   are as bad as before, no noticeable change.

3. One more time, (after a browser restart) the same 7 Ctrl-Ts:

   https://perfht.ml/36U82Bf

   Only 5 tabs got opened this time. The lag is as before.

---

Overall Nightly is no better than 71. This is not surprising,
because the problem is now new.

Anyway. What I noticed in the original traces is that a new worker
process is seemingly being spawned during the lag. This got me
thinking, and I tried to change the "Content process limit"
setting from the default of 8 to 1, so that now new processes
are started. Lo and behold, this fixes the lag.

Does this mean I need to limit myself to single-threaded Firefox?

I'm not sure what makes starting new workers so slow on my
machine, of course.

Comment 3

[Vitaly]

If this makes any difference, the OS I'm running this on is
Ubuntu 18.04.3 LTS (amd64). The Nightly was launched from an
in-memory disk, although the profile is on an SSD. Safe Mode
makes no difference.

Comment 4

[Wayne Mery (:wsmwk)]

Vitaly does this still reproduce for you?

Comment 5

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

Redirect a needinfo that is pending on an inactive user to the triage owner.
:stransky, since the bug has recent activity, could you have a look please?

For more information, please visit auto_nag documentation.