Created attachment 8630974 [details] profile.json User Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:42.0) Gecko/20100101 Firefox/42.0 Build ID: 20150707030206 Steps to reproduce: 1) Open about:addons 2) Smooth scroll the page 3) Observe the jank. A performance recording confirms a lot time spent on painting and style recalculations. Attaching the profile recording. Actual results: Janky scrolling on about:addons page. Expected results: Smooth scrolling on about:addons page.
OS: Unspecified → Windows 8.1
Hardware: Unspecified → x86_64
Status: UNCONFIRMED → NEW
Component: Untriaged → Layout
Ever confirmed: true
Product: Firefox → Core
Can you still reproduce the issue with latest stable Firefox or latest Nightly?
Well, the paints and recalculation styles are almost all gone in a new performance recording from the latest Nighlty, but now there are a lot of GC work with a huge "Non-incremental GC" that takes a whooping ~500 ms also when just staying idle on the addons page (and also when scrolling, which janks APZ scrolling of course)! Note: this seems (I say seems, as I don't see a visual jank of ~500ms while scrolling with APZ) to happen only when recording a performance recording. Note2: this seems to happen only on internal pages such as the about:addons page and also a "new tab" page (blank page or non blank, doesn't matter), but NOT on tabs with sites where scrolling is smooth and no such GC work. Attaching a performance recording when staying idle on the about:addons page, and one with smooth scrolling the page (APZ enabled).
Based on comment #2 and the profiles, is this something the JS team can/should look at? mccr8?
Flags: needinfo?(continuation) → needinfo?(terrence)
Moving ni? to Jon.
Flags: needinfo?(terrence) → needinfo?(jcoppeard)
(In reply to Mikel from comment #2) It's possible that the performance recording triggers extra GCs. I can see this happening in your supplied profile data, but not for anything like 500ms. I tried to reproduce this but I don't see any long non-incremental GCs myself. Since it doesn't seem to happen in normal use I'm going to close this. Please reopen if you disagree.
Status: NEW → RESOLVED
Last Resolved: 2 years ago
Resolution: --- → WORKSFORME
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