791997 - nytimes.com in a background tab reflows the whole browser periodically

Status: RESOLVED INVALID

(Core :: Layout, defect)

Description

[Tim Taubert [:ttaubert] (inactive)]

While trying to investigate bug 786940, I opened like 20-30 of nytimes.com tabs and the whole browser quickly got unusable. I reduced my testcase to three background tabs (nytimes.com) and started profiling:

http://people.mozilla.com/~bgirard/cleopatra/?report=545d8568bfaae50a2fd8c8a3c823127cdd2125be

Now looks like we're reflowing all the time because of this:

http://b.scorecardresearch.com/c2/3005403/cs.js
http://pastebin.mozilla.org/1829083 (beautified version)

There's some function that is repeatedly called using setTimeout() that triggers reflows. Even worse, it's triggering whole-browser reflows somehow.

If you enable paint flashing you can easily see that just one nytimes.com tab opened in the background causes the whole browser window to reflow periodically (I think every second). This easily sums up with lots of tabs of course.

Comment 1

[Tim Taubert [:ttaubert] (inactive)]

Argh, that's related to bug 786484. With browser.newtab.preload=false the only thing that's repainted is the nytimes.com tab itself.

Comment 2

[Tim Taubert [:ttaubert] (inactive)]

Also, the stupid script manages to redraw the whole nytimes content every second. Which probably still is very costly even if throttled down in the background. Not sure we can do anything about that.

Comment 3

[Boris Zbarsky [:bzbarsky]]

That profile shows the profiler itself doing changes in chrome, if I read it right.

If you disable the profiler, do you still see nytimes in a background tab causing repaints of the whole chrome?

But yes, in general nytimes has some "ticker" script that keeps changing the page on a timer, so if you have lots of them open it can start to chew up a good bit of CPU...

Comment 4

[Boris Zbarsky [:bzbarsky]]

Redraws in a background tab just don't happen, which should not be costly at all.

Comment 5

[Tim Taubert [:ttaubert] (inactive)]

The profiler doesn't make a difference for me. As soon as I disable browser.newtab.preload everything's fine again. We'll work around bug 786484 in bug 780123 which doesn't fix the underlying layout bug. Somehow the extra <browser> element makes the layout invalidation not behave as it should.

Comment 6

[Boris Zbarsky [:bzbarsky]]

OK, let's take this up in bug 786484.

Comment 7

[Tim Taubert [:ttaubert] (inactive)]

IIRC the original issue reported was purely caused by bug 786484. I think we can close this one.