235694 - Javascript ticker causes serious cpu usage in mozilla browsers

Status: RESOLVED DUPLICATE of bug 137584

(SeaMonkey :: General, defect)

Description

[Benny Brunner]

User-Agent:       
Build Identifier: Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.6) Gecko/20040206 Firefox/0.8

On most web pages, Firefox either frizzes completely (the spinning ball), or it
takes ages for the spinning ball to disappear. The problem gets worse when I'm
using a HTTP proxy server.
Hardware: Mac G4, 533Mhz DP, 1GB SDRAM. Software: MacOS 10.3.2 with the very
latest security and other updates. 

I've noticed this problem with earlier versions of the browser too!

Reproducible: Always
Steps to Reproduce:
1. Enabling HTTP proxy server
2. Visiting http://www.ynet.co.il/
3. Opening links in new tabs

Actual Results:  
Firefox either frizzes or it takes way too long for the spinning ball to stop
spinning.

Expected Results:  
Just function smoothly.

I didn't add any new theme and/or skin and/or extensions to Firefox.

Comment 1

[Wayne Woods]

Confirmed on OS X 10.2.8, 20040226 Firefox/0.8.0+

Unlike Benny, I'm not using a html proxy, and the browser doesn't hang or crash
nearly as much for me. What loading the page does do, however, is cause a huge
cpu spike, which lasts until I close the page. I can get it to crash by
selecting "Save Page As..." from the File menu.

The cpu usage also goes up enormously on the standard Mozilla browser when
loading the same page, (I can't get it to crash when trying to save the page,
though), so I'll set product to Browser.

From narrowing down the code, it appears that the problem isn't in the main
quoted page at all, but in another page that is called from it:

http://www.ynet.co.il/Ext/Comp/Ticker/Dhtml_Ticker/0,10016,L-184,00.html

That page seems to be some sort of dynamic HTML scrolling text. Narrowing the
problem code down further is difficult, as removing all manner of different
blocks of code can make the bug go away. I'll see if I can narrow it down
further tomorrow, if nobody has identified the problem before then.

Comment 2

[Wayne Woods]

My knowledge of javascript is very poor, so I'm hoping someone else can look at
this bug soon.

I'm attaching a test case which shows the slow scrolling of the text, compared
to Safari. If you're running CPU Monitor, you'll see that it spikes quite
dramatically as well. Unfortunately I haven't been able to pare it down as much
I liked. Also, having removed a lot of code, it runs much faster than the
original, but is still jerky and slow compared to what it should be.

- When I load the page, the Console log warns me:
Warning: ATSUMeasureText has been deprecated.  Use ATSUGetUnjustifiedBounds instead.

- If I replace the Hebrew text with English, it scrolls MUCH faster, and the
system usage doesn't go up nearly as much. Also, the Console log no longer gives
me that warning. So I hope that pins down the main problem.

- Choosing "Save Page As..." still causes the browser to crash on these pages,
regardless of English or Hebrew text and system performance. I'm wondering if
that's a separate bug entirely, but also related to Javascript.

Comment 3

[Wayne Woods]

Attachment: Reduced test case

Note slow and jerky scrolling compared to Safari, high cpu usage, and warning
in console.log. Crashes browser if you attempt to "Save Page As..."

Comment 4

[Wayne Woods]

Please ignore the comment about crashing when trying to save the page. It now
appears that part is an unrelated Firebird bug. Sorry for the spam.

Comment 5

[Wayne Woods]

Sorry for more bug spam, but I have something more to add.

The problem also exists on Windows builds, although the system resource usage
seems less serious.

I tested it out on an Athlon 2600+ at work, using recent builds of both Firefox
and Mozilla.

Loading http://www.ynet.co.il/Ext/Comp/Ticker/Dhtml_Ticker/0,10016,L-184,00.html
in Internet Explorer results in relatively smooth-scrolling text and a cpu usage
of around 1-2%.

Loading the page in either Firefox or Mozilla results in jerkier text and an
average cpu usage of around 30-50%.

Comment 6

[Gérard Talbot]

> Loading http://www.ynet.co.il/Ext/Comp/Ticker/Dhtml_Ticker/0,10016,L-184,00.html
> in Internet Explorer results in relatively smooth-scrolling text and a cpu usage
> of around 1-2%.

Please always check for duplicates.




*** This bug has been marked as a duplicate of 137584 ***