Open Bug 905432 Opened 11 years ago Updated 2 years ago

High CPU usage on


(Core :: Web Painting, defect)

26 Branch




(Reporter: vincent-moz, Unassigned)



User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:26.0) Gecko/20100101 Firefox/26.0 (Beta/Release)
Build ID: 20130814030204

Steps to reproduce:


Actual results:

Firefox takes much CPU time (92% on the machine from which I report the bug, with this Firefox version).

Expected results:

CPU usage should remain low, possibly after some time (configurable).

Note: There are scrolling images near the bottom of the page. But CPU usage is almost as high when these images are not visible. If I disable Javascript via about:config, the problem disappears.

Chromium takes about 30% CPU time (but it's also too high).
The images are the problem. If you place your mouse on them, so they stop scrolling, CPU usage goes back to 0%. I think it's a layout problem (and a known one).
If you search Core:Layout for anything related to CPU and scrolling images quite a few come back. It would take a while to figure out which to count as the main bugs and which are duplicates so I'll go ahead and add this to the bunch.
Assignee: general → nobody
Component: JavaScript Engine → Layout: View Rendering
Ever confirmed: true
Related bug: probably 693105.
Component: Layout: View Rendering → Layout: Web Painting
Severity: normal → S3
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