501158 - Firefox freezes for several seconds during page load, tab switches

Status: RESOLVED WORKSFORME

(Firefox :: General, defect)

Description

[nivtwig]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2a1pre) Gecko/20090628 Minefield/3.6a1pre
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2a1pre) Gecko/20090628 Minefield/3.6a1pre

Firefox freezes and is unresponsive (try to switch between tabs, for example) for several seconds during page loads from the ynet.co.il web site, for news articles from this site, probably due to pages with many user comments on the article . This is a major news site in Israel.

When opening multiple tabs of news articles from this site, and since the website refreshes the tabs automatically after some period of time, Firefox slows down and freezes a lot for several seconds.

This happens even when I use Adblock Plus to block all the flash ads on this page , so it probably is not related to flash 

Tested on an Intel Celeron 3.2Ghz machine with 2GB RAM, Windows 7, but I believe it is a problem with all platforms. 
The bug is both on Firefox 3.5 and on the trunk (Minefield)

Based on the URL from bug 401679 . I opened another bug since that bug summary was about 100% CPU usage, and the main problem here is not the(almost) 100% CPU, which might be expected since it is a long page with ~2000
comments, but the lack of application responsiveness for some seconds when the
page loads .


Reproducible: Always

Steps to Reproduce:
1. open the URL . Block flash ads on the page using adblock plus to filter the flash ads performance influence .
2. Try to switch between tabs quickly during page load
3.
Actual Results:  
Firefox freezes and is unresponsive for several seconds during page load

Expected Results:  
firefox should be responsive and not freeze during page load

Comment 1

[Ria Klaassen (not reading all bugmail)]

Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.2a1pre) Gecko/20090629 Minefield/3.6a1pre

Can you specify the steps to reproduce?
I loaded http://www.ynet.co.il/articles/0,7340,L-3465625,00.html and opened all the links of the blue buttons on the right in new tabs, but I see no problem here, not even with all the flash ads. I have a rather fast connection.

Comment 2

[nivtwig]

I am not sure you understood what I meant, and don't understand why you opened the links of the blue buttons on the right in new tabs. The links of the blue buttons are links to sections of the site, not to news articles, if that is what you meant - to try to open several articles.

Anyway, I guess you need a relarively slow machine (Notice I used Intel Celeron 3.2GHz). What is your machine specs?

Detailed steps to reproduce:
1) Open several tabs from static and simple html pages like from www.mozilla.org . 
2) Open the URL I specified, with flash ad blocking.
3) Before and during the ynet.co.il page load (until it completely loads) try to switch quickly between 2 tabs repeatedly, by clicking with the mouse on the tabs . 
Instead of switching between 2 tabs , you can also try moving your mouse over the bookmarks toolbar quickly and repeatedly and see the icons highlighted/selected .

You should notice that during the page load, sometimes there are freezes for several seconds (1-2), when firefox is unresponsive and tabs do not switch with the mouse click. Or in the case of the bookmarks toolbar, the icons/bookmarks are not selected/highlighted.

Comment 3

[Ria Klaassen (not reading all bugmail)]

Thanks; no alas, I can't reproduce it (tested with a new profile). 
This is an Intel Pentium Dual T3200 2.00 GHz and 3.000 MB RAM.
Does safe-mode or a new profile make difference?
http://support.mozilla.com/en-US/kb/Safe+Mode
http://support.mozilla.com/en-US/kb/Basic+Troubleshooting#Make_a_new_profile

Comment 4

[nivtwig]

I tried with both safe-mode and a new profile, and the freezes are still happening the same as before.
I believe you don't see it because of your fast, dual core computer. 
Or maybe it is your fast internet connection - Mine is quite fast too 1.5Mb/s, but maybe the website, or ads are not served quickly enough and the browser freezes on waiting for reading them . 

I believe it is the first reason - your fast computer T3200 is with a PassMark score of 1062 and is much faster than the Celeron 3.2G with a PassMark of 381 . It is ~3x faster if the Passmark scores are linear with time.

The CPU benchmarks data is from :
http://www.cpubenchmark.net/cpu_list.php

Comment 5

[nivtwig]

In addition to comment #3 , can somebody with a slower computer confirm this ?

Comment 6

[Tyler Downer [He/Him]]

Well, running with Vista (SP2) on an AMD Athlon 64 3500+ (2.20GHz) with 2 GB RAM and Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.2a1pre) Gecko/20090629 Minefield/3.6a1pre (.NET CLR 3.5.30729) ID:20090629044912 (I think it is the slowest machine so far :), I get a slight hang while switching, but nothing dramatic. It simply does not switch to the other tab as quickly as usual (maybe a second). Confirming for now though.

Comment 7

[nivtwig]

(In reply to comment #6)
> Well, running with Vista (SP2) on an AMD Athlon 64 3500+ (2.20GHz) with 2 GB
> RAM and Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.2a1pre)
> Gecko/20090629 Minefield/3.6a1pre (.NET CLR 3.5.30729) ID:20090629044912 (I
> think it is the slowest machine so far :)

Thanks. 
I think your computer is not the slowest machine so far . It has a Passmark score of 510, while my Intel Celeron 3.2Gghz is the slowest - it has a Passmark score of 381 . So your machine is about 33% faster.

Comment 8

[Emerson Prado]

(In reply to comment #5)
> In addition to comment #3 , can somebody with a slower computer confirm this ?

I had this issue quite bad in my Celeron 2.4GHz w/ 1MB of DDR400 RAM, running on Win2k. I reported this in Bug 508961 (quite similar to this one, IMHO).
But I'm messing with the plugins (oddly, safe mode didn't help here) and found out disabling some stuff might help. Java Quick Start addon and M$ DRM plugins seemed to make quite a difference - didn't freeze so far after accessing some "hard" pages as Yahoo mail.
Leave it as my 2 cent.

Comment 9

[Wayne Mery (:wsmwk)]

I would be very surprised if this were not a duplicate of another bug. 

In looking at bug 445713 and this bug, using Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.3a5pre) Gecko/20100518 Minefield/3.7a5pre, and Shockwave Flash 10.0 r45

With and without flash adverts displaying (using flashblock) I did not see the issue described in bug 445713. I do however see a slight performance issue, more readily seen using the ideas of  bug 445713 and the tab switch described in this bug: 
1. using flashblock, enable only the flash item [1] below RSS RSS עולם	|	לרשימת כל ה-
   
 2. page down twice
3. page up three times
4. down arrow three times quickly

results: scrolling of second and third down arrow are not immediately seen, there is a delay of 1-3 seconds. sometimes the first downarrow is also not immediate. in fact, the delay in down arrow reaction can been seen with any multiple up or down arrow actions when any part of the flash advert is visible on the page.  CPU does not spike.

I also, but less reliably, see tab switch delay.

offhand I would say this performance issue is flash or display related. does not qualify as a hang. and very much needs a reduced testcase.

[1] the flash advert links to http://rpdigital.pas-rahav.com/mizrachiLive/?ref=calcalist_bigbox_ros&browser=41

Comment 10

[Wayne Mery (:wsmwk)]

nivtwig, do you also see this with version 5 or 4?

Comment 11

[nivtwig]

(In reply to comment #10)
> nivtwig, do you also see this with version 5 or 4?

I see now a tab switch delay which is far less noticeable, for what I think is a tenth of a second, but this is now a smaller problem for 2 reasons:

1) I am using now a much faster computer and CPU (about 5x) :), and I can't test with the old CPU.
I am using now Intel dual core E6500 2.93GHZ with a Passmark score of 2029, versus the Intel Celeron 3.2Ghz I used in the previous tests, with a Passmark score of 381 .

2) The web page has changed somewhat : Previously there were about 2000 comments on the page. Now not all comments are displayed on the page, only the last 300, and you can click on a link to see the rest. I think the loading of the many comments was the part of the page that caused the freezes previously, and now that there are much less comments, it can explain why it loads more smoothly without freezes (or less noticeable ones).

So, I think you can close this bug since the testcase (the web page) is not good anymore. If someone sees a better "freeze" testcase than this they will open another bug.

Comment 12

[Wayne Mery (:wsmwk)]

nivtwig, thanks for the update. WFM is accurate enough I think.