A testcase i found on Bugzilla

stravinsky · Unread post by **stravinsky** » 2012-10-17, 07:57

<!DOCTYPE HTML>
<style type="text/css">
span {opacity:0.5;}
</style>
<body>
<div>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
</div>
<div>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
</div>
<div>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
</div>
<div>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
<span>Hello</span>
</div>

This code scrolls poorly on ALL VERSION OF MOZILLA BASED BROWSERS. , specially with HWA enabled. Just copy the code inside the <div> tag ten-twelve times and open it.
Try scrolling. Grab the scrollbar and try to quickly scroll the page up and down. The page will lag w.r.t. the scroll bar.

EDIT: http://www.2shared.com/document/YyIiidTX/testcase.html Similar page but with enough length to make it actually scrollable.

Unread post by **Moonchild** » 2012-10-17, 09:52

Smooth for me on 15.2

Do note that I properly tagged the code to make it normal html to test. meaning adding HTML HEAD and BODY opening and closing tags. The code as pasted is not properly encoded.

stravinsky · Unread post by **stravinsky** » 2012-10-17, 10:44

Moonchild wrote:Smooth for me on 15.2

Probably because the code is too small in length to make the page actually scrollable. I have attached a file. Try that.
See the CPU usage while quick scrolling. It is high.

dark_moon · Unread post by **dark_moon** » 2012-10-17, 10:57

Yes can confirm this.

There is 1 sec delay and the scrolling isn't smooth. And the cpu goes to 15+ %

stravinsky · Unread post by **stravinsky** » 2012-10-17, 17:33

Makes me wonder what all is the code doing under the hood to make such simple HTML so expensive.

Unread post by **Moonchild** » 2012-10-19, 08:35

CPU is indeed high, if I make it a lot more copies to scroll.
Compositing is the issue.

Transparency is expensive if you apply it to a lot of small objects that are drawn reflowed (not positioned). Basically it's not the kind of webdesign you should be doing, anyway

The code may be "simple" from a source point of view, but it's not simple from a rendering point of view.

stravinsky · Unread post by **stravinsky** » 2012-10-19, 14:15

So you found the relevant bug then ?

Basically it's not the kind of webdesign you should be doing, anyway

Yet lots of webpages use these type of 'silly' codes frequently. So mozilla has to optimize for it. Because you can bet that Chrome is already optimizing for it.

Unread post by **Moonchild** » 2012-10-19, 14:25

Then Chrome is optimizing for something that you wouldn't find "in the wild". And as said I have to copy/paste a LOT of these snippets to make it actually detrimental. How many web pages do you know that have hundreds of reflowed transparent elements? IMO this kind of extreme case is (should be) low priority to "fix"

stravinsky · Unread post by **stravinsky** » 2012-10-19, 16:26

This test case performs quite worse on the nightlies. So its a side-effect of recent bugs.

lyceus · Unread post by **lyceus** » 2012-10-20, 01:59

Smooth and fast scroll here, but well with an AMD Phenom X4 and 8 GB ram maybe it's not a surprise.

stravinsky · Unread post by **stravinsky** » 2012-10-20, 03:01

lobocursor wrote:Smooth and fast scroll here, but well with an AMD Phenom X4 and 8 GB ram maybe it's not a surprise.

Why would a Ph X4 be obviously smoother ? AMD Ph X4 are comparable to intel core2quad. Which are decidedly old compared to the IvyBridge generation. And PM uses one core anyway.
That 8GB RAM is useful only if you had been forced to use pagefile in absence of that RAM.....

lyceus · Unread post by **lyceus** » 2012-10-21, 02:57

stravinsky wrote:
lobocursor wrote:Smooth and fast scroll here, but well with an AMD Phenom X4 and 8 GB ram maybe it's not a surprise.
Why would a Ph X4 be obviously smoother ? AMD Ph X4 are comparable to intel core2quad. Which are decidedly old compared to the IvyBridge generation. And PM uses one core anyway.
That 8GB RAM is useful only if you had been forced to use pagefile in absence of that RAM.....

Well if I remember the 8GB ram means that more windows functions works in pure ram and leave the process free of disk writes. WIN XP 64 may be old, but is less taxing than Windows Vista/7 64 bits, so basically I'm trying to kill bugs with a cannon, old but still a cannon. Also few people has 8 GB RAM for start, I do the test in a non common configuration.

Pale Moon forum

A testcase i found on Bugzilla

A testcase i found on Bugzilla

Re: A testcase i found on Bugzilla

Re: A testcase i found on Bugzilla

Re: A testcase i found on Bugzilla

Re: A testcase i found on Bugzilla

Re: A testcase i found on Bugzilla

Re: A testcase i found on Bugzilla

Re: A testcase i found on Bugzilla

Re: A testcase i found on Bugzilla

Re: A testcase i found on Bugzilla

Re: A testcase i found on Bugzilla

Re: A testcase i found on Bugzilla