463984 - APNG decode takes a lot of CPU

Status: RESOLVED INVALID

(Core :: Graphics: ImageLib, defect)

Description

[Mike Beltzner [:beltzner, not reading bugmail]]

Spun off from bug 437829, which complains that the new APNG throbber has significant performance implications:

From bug 437829 comment 0:

>1) Type chrome://global/skin/icons/loading_16.png into the urlbar
>   Firefox CPU: 55-70%
>
>2) Type chrome://global/skin/throbber/Throbber-small.gif into the urlbar
>   Firefox CPU: 15-20%

Yikes.

Comment 1

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

I think Joe was looking at this.

Comment 2

[Damon Sicore (:damons)]

So, why would this block 3.1 if it's in 3?

Comment 3

[Martijn Wargers (dead)]

Why not?

Comment 4

[Peter Weilbacher]

(In reply to comment #2)
> So, why would this block 3.1 if it's in 3?

Because it is one of the top complaints of people on older machines that the CPU goes to 100% while loading a page. Apparently just because of that APNG throbber.

Comment 5

[Jeff Muizelaar [:jrmuizel]]

Profiling the large APNG that joe made (https://bugzilla.mozilla.org/attachment.cgi?id=348033) doesn't show anything unusual on OS X. Does anyone actually have any evidence that APNG is the problem here?

Comment 6

[Martijn Wargers (dead)]

See testcases in bug 437829, compare https://bugzilla.mozilla.org/attachment.cgi?id=324188 (using gif image) with https://bugzilla.mozilla.org/attachment.cgi?id=324187 (using png image).

Comment 7

[Wayne Mery (:wsmwk)]

The following obviously isn't a profile and I'm not sure any or all of the testcases are useful, but fwiw...

(In reply to comment #6)
> See testcases in bug 437829, compare
> 1. https://bugzilla.mozilla.org/attachment.cgi?id=324188 (using gif image) with
> 2. https://bugzilla.mozilla.org/attachment.cgi?id=324187 (using png image).

3. https://bugzilla.mozilla.org/attachment.cgi?id=348033

windows vista, AMD Turion 1.80GHz

        FF304  FF31b2pre 20081011 
1. gif  ~50%   ~16%
2. png  ~50%   ~50%
3. joe 4-10%   2-6%   during first ~5 seconds display
          0%     0%   after >5 sec display

(In reply to comment #4)
> (In reply to comment #2)
> > So, why would this block 3.1 if it's in 3?
> 
> Because it is one of the top complaints of people on older machines that the
> CPU goes to 100% while loading a page. Apparently just because of that APNG
> throbber.

older machines might not be the only area for complaint:
- machines on slow network connections
- opening multiple tabs at once, such as
  * bookmark group
  * session restart and startups with multiple pages

Comment 8

[Jeff Muizelaar [:jrmuizel]]

(In reply to comment #6)
> See testcases in bug 437829, compare
> https://bugzilla.mozilla.org/attachment.cgi?id=324188 (using gif image) with
> https://bugzilla.mozilla.org/attachment.cgi?id=324187 (using png image).

The png image has a frame rate of 32.25fps where as the gif image has a frame rate of 10fps so comparing these isn't really that useful.

Unless there's evidence that the same animation in APNG takes more cpu then the gif version, I'm going to close this bug. The issue about the desired framerate can be dealt with in bug 437829.