804290 - Drawing table with many <img> tags is very slow

Status: NEW

(Core :: Layout: Images, Video, and HTML Frames, defect)

Description

[Phoenix]

Attachment: HTML Testcase

A friend of mine provide me attached testcase, I've made a quick search and didn't find corresponding bug, so creating new.
In current nightly loading this testcase taking 90 seconds, IE10 loads it instantly.

Comment 1

[Phoenix]

Attachment: Profiling data from Gecko Profiling Addon

Also attaching data from Gecko Profiling Addon

Comment 2

[Boris Zbarsky [:bzbarsky]]

Isn't the problem just that it has a bunch of images that are 404 and have no width/height specified in the HTML and hence force relayout partway through the load?  Note that IE doesn't handle such images correctly, in general...

(You can test by replacing the spacer gifs with divs to see whether the images are the real problem, by the way.)

Comment 3

[Phoenix]

Replaced <img> tags with <div>s, loading page takes 7 seconds...

Comment 4

[Boris Zbarsky [:bzbarsky]]

OK.  Is that still significantly slower than other browsers?  If so, might be worth filing a separate bug on the variant with <div>s.

Comment 5

[Phoenix]

(In reply to Boris Zbarsky (:bz) from comment #4)
> OK.  Is that still significantly slower than other browsers?
Yes, IE9 loads same testcase in near one second (don't have IE10 here yet), and replacing divs with just spaces doesn't cut load time significantly, it drops from 7 to 6 seconds

Comment 6

[Boris Zbarsky [:bzbarsky]]

Attachment: Testcase that does some self-timing

If you unzip this and try it from local disk, what do the two alerts show in IE for you?  In Firefox?

What I see is about 800ms for the first alert and about 2s for the second in Firefox.  For comparison, Chrome is at about 1500ms and hang and Opera at about 900ms and 1500ms.

Note that this testcase just measures parse and layout without incremental layout going on.  When I just load the page without the display:none bit I get incremental layout which obviously makes total pageload slower.

Comment 7

[Phoenix]

(In reply to Boris Zbarsky (:bz) from comment #6)
> If you unzip this and try it from local disk, what do the two alerts show in
> IE for you?  In Firefox?
My numbers:
IE9: 1232/3889 and table is instantly drawed
FF19: 875/3471 but total page load time is near 8 seconds

Comment 8

[Boris Zbarsky [:bzbarsky]]

In IE9, you mean instantly drawn after the second alert comes up, right?

Comment 9

[Phoenix]

Yes

Comment 10

[Boris Zbarsky [:bzbarsky]]

OK.  Sounds like you should file a second bug in the Graphics component then, with info from about:support about your GPU and such.  I can't reproduce the 4+second lag you describe; for me the paint is instant after the second alert (on Mac, though, not Windows).

Comment 11

[Phoenix]

Retested, there is a little confusion, when I said that total time is near 8 seconds I'm not mean that after second timer page continue to load for another four seconds, but that if I measure page load time with external clock, then in moment when second alert shows 3471, clock shows near 8 seconds, and IE's clock's time is near 4 seconds, but I found the reason for that, Profiler Addon was not disabled during tests, after it's removal new FF19 numbers are 840/1979 and complete time is near same 4 seconds as with IE, so only problem with original testcase remains.

Comment 12

[Phoenix]

Attachment: HTML Testcase with image

Finished another check, presence or absence of image in image tag doesn't matter, updating original testcase with image for consistency