When I access following page in Ohloh Code Search, Firefox hangs up and CPU spikes up after showing the page contents. http://code.ohloh.net/file?fid=7UyJXxx8y6GGv1-VeJSJ0JP9jIs&cid=hOh6fvYhQFU&s=ITfMouseTrackerACP&fp=491344&mp&projSelected=true#L0 I can reproduce this bug on both Firefox 31 and Nightly. And also I can reproduce this with safe mode. On Google Chrome, I cannot reproduce this.

Setting accessibility.force_disabled = 1 seems to fix the high CPU usage problem.

Thank you, Alice-san. I tested again. If I change the pref, I can load mxr (e.g., http://mxr.mozilla.org/mozilla-central/source/layout/base/nsPresShell.cpp) smoother. So, something of a11y has serious performance issue on a lot of page. Alexander Surkov, do you know something about this?

When I load nsPresShell.cpp of mxr, the profiler said: http://people.mozilla.org/~bgirard/cleopatra/#report=af9390cc747b20f8d53d8befbfb612330e991980 According to the result of profile, following methods spend almost half of the time: mozilla::a11y::Accessible::InvalidateChildrenGroupInfo() mozilla::a11y::EventQueue::CoalesceReorderEvents(mozilla::a11y::AccEvent *) mozilla::a11y::EventQueue::CoalesceEvents()

bug 1041070 might help with it

(In reply to alexander :surkov from comment #4) > bug 1041070 might help with it Yeah, I confirmed that the patch of bug 1041070 fixes this bug.

I tested at nsPresShell.cpp in mxr. In the default settings, perhaps by the fix of bug 1041070, the time to hang up is much shorter than I've experienced before. However, I still need long time to render the page. If I disable a11y module with |accessibility.force_disabled = 1|, I don't see any hanging up. surkov: Do you think that remaining cost is necessary? Or can improve with some hack? (e.g., using interruptable handling like layout)

I bet we have some perf a11y issues to fix. Can you share a link at perf report?

Okay, I'll do that later.

It's odd. I cannot reproduce this with prof-build on my development machine... http://people.mozilla.org/~bgirard/cleopatra/#report=7b5f1d61b58e90f4478f7ea9b5fede66de77ae3e I'll investigate what happens more. And if it's not caused by a11y module, I'll file another bug.

Hi! Is this still a problem with current Firefox?

I cannot access the website, but I don't experience this bug on dxr nor searchfox anymore. marking this as WFM.