596446 - [Mac] The CPU usage while playing Flash 10.1 on 4.0b6 is ~80% vs ~40% on 3.6.9

Status: RESOLVED DUPLICATE of bug 591687

(Core Graveyard :: Plug-ins, defect)

Description

[jarrodsyoung]

User-Agent:       Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.9) Gecko/20100824 Firefox/3.6.9
Build Identifier: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0b6) Gecko/20100101 Firefox/4.0b6

While watching any Youtube video, 4.0b6 experiences twice the CPU tax that Safari 5 or Firefox 3.6.9 needs for the same video. Tested with a 320p video.

Using a 2010 13inch MacBook Pro on Snow Leopard with latest Flash 10.1. The CPu is 2.4 Ghz Core 2 Duo with 4 gigs of RAM and the NVIDIA 320M graphics card.

Firefox 4.0b6 was installed after removing all previous library/preference files and cache folder.

Reproducible: Always

Steps to Reproduce:
1. Use Firefox 3.6.9 or Safari 5 to watch any Youtube video on 320p.
2. Use Firefox 4.0b6 for the same video.
3. Notate processor usage differences.
Actual Results:  
Firefox 4.0b6 uses 82.3% CPU.

Expected Results:  
The same amount as Safari 5 or Firefox 3.6.9 which was 42.1%.

Comment 1

[jarrodsyoung]

Observation on 4.0b6: http://imgur.com/ih9lE.png

Observation on Safari 5: http://imgur.com/0JhJr.png

Comment 2

[Scoobidiver (away)]

Try to compare FF 3.6.9 and 4.0b6 in safe mode :
http://support.mozilla.com/en-US/kb/safe+mode

Comment 3

[l.g.moz]

I have been experiencing the same problem on a 2008 macbook with all firefox 4 betas or nightlies.
Tried the safe mode, but it does not change anything.
Comparing the processes, it looks like the flash process is doing the same thing for firefox and safari, but the firefox process is on top of that working extra hard(the cpu % is always higher than that of the flash process), while the safari process is close to zero.
On youtube, if I scroll down so that the video does not appear, the firefox process drops close to zero while the flash process continues as before. Is the firefox process re-rendering what the flash process is doing?
On a side note, this behavior also occurs in google chrome 6 (other versions not tested).

Comment 4

[Scoobidiver (away)]

With a new profile, on my Pentium T4300 2.1 GHz, under Windows 7, the CPU usage is :
* 25 % for FF 3.6.10
* 25 % for FF 4.0b6
* 25 % for FF 4.0b6 without HW acceleration

So, it seems that is specific to Mac OS.
The results are identical when HW acceleration is enabled or disabled (safe mode), so according to me, it is a Core plugin issue.

Comment 5

[juan becerra [:juanb]]

It seems plugin or oopp related, so moving to plugins.