1522671 - Clicking buttons in the about:config sometimes doesn't have an effect for several seconds

Status: RESOLVED WORKSFORME

(Firefox :: Settings UI, defect, P5)

Description

[Michael Cooper [:mythmon]]

In the new about config, clicking buttons such as "edit" or "toggle" sometimes doesn't change the value column for several seconds. The button stays in a pressed state. Sometimes it seems to stay that way until I move my mouse (even if my mouse doesn't leave the button).

This effect is inconsistent. Sometimes the UI seems just a bit out of sync, whereas other times there are noticeable lags that severely impact usability.

I have been able to reproduce this on a new profile, but not on other computers. I'm running Linux, the other systems I tested on were Windows and MacOS.

Comment 1

[:Paolo Amadini]

That's interesting, although I suspect that there is simply something else going on that blocks the parent process. We have to run the page there for security, but we don't get the benefits of using a content process, so we may see performance bugs that were typical before Electrolysis.

Can you get a profile of the jank with the Gecko Profiler Add-on?

Comment 2

[Michael Cooper [:mythmon]]

Here's a profile from a clean profile that didn't have any other tabs running. http://bit.ly/2RfBt8Z

Something of note: I had a lot of trouble reproducing this while my laptop was plugged in, but when unplugged it was a lot easier. The profile above was while running on battery power.

Edit: And here is another profile where I checked more boxes in the profiler, to capture more data: http://bit.ly/2RetatM

Comment 3

[Mike Conley (:mconley) (:⚙️)]

This is really strange. The profiles I'm looking at have huge (20ms!) gaps between the samples, but I can tell that the profiler is set to sample every 1ms...

mythmon, would you mind posting a profile with your laptop plugged in (with lag or without) to see how that changes the profiler output? Are you able to experience similar lag while working in about:preferences with your laptop unplugged?

It's hard to tell, but at this point, I'd guess that all of our threads are being starved for some reason... but it might also just be how we're profiling.

Comment 4

[Michael Cooper [:mythmon]]

Here's a profile while my laptop is plugged in. It didn't have any lag issues: http://bit.ly/2WjHPI1

I saw similar lag in about:preferences (though I've never noticed it before today).

This time I was able to reproduce the lag while plugged in, but not while I was profiling.

Comment 5

[Michael Cooper [:mythmon]]

I haven't had this problem in a long time, and I remember that I saw it in other places too.