Open Bug 1496899 Opened 6 years ago Updated 2 years ago

JS demo throttles if you navigate away from the page, and then return


(Core :: Layout, defect, P3)




Tracking Status
firefox-esr60 --- wontfix
firefox62 --- wontfix
firefox63 --- wontfix
firefox64 --- wontfix
firefox65 --- fix-optional


(Reporter: mayankleoboy1, Unassigned)




(Keywords: nightly-community, perf, regression)

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:64.0) Gecko/20100101 Firefox/64.0

Steps to reproduce:

1. Create new profile
2. Go to
It is fast
3. Enter in the same tab, and go there
4. Press the back arrow to come back to the JS demo

Actual results:

Demo becomes very slow
Or atleast the animation slows down.

Expected results:

not so
on returning back, there is no CPU starvation. So this looks more of a throttling issue
Summary: JS demo slows if you navigate away from the page, and then return → JS demo throttles if you navigate away from the page, and then return
i can reproduce the issue on Win10 Nightly64.0a1 x64.

Regression window:

Regressed by: Bug 1145439
Blocks: 1145439
Component: General → Canvas: 2D
Keywords: perf, regression
Happy to take a patch in nightly; if it seems low risk enough please feel free to request uplift to 65 beta.

Layout (or maybe DOM) is probably a better place to triage for now. Seth is no longer around who introduced the regression, but the regressing bug mostly modified features in those areas.

Component: Canvas: 2D → Layout

The priority flag is not set for this bug.
:dbaron, could you have a look please?

For more information, please visit auto_nag documentation.

Flags: needinfo?(dbaron)

CCing :tnikkel, it seems to me that we need to update Document::mVisibilityState when the document is restored from the BFCache.
Setting P3, it might be severer but it's been an issue since firefox 40.

Flags: needinfo?(dbaron)
Priority: -- → P3
Severity: normal → S3
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