Tab switch spinners can occur anytime that the content process hasn't given us a layer tree in enough time to composite them in response to a user switching tabs. I want to know when, in a tabs lifetime, those spinners are likely to occur. I'm going to break a tabs lifetime down into three discrete chunks: 1) Tab is new* and has never been seen 2) Tab is not new* and has never been seen 3) Tab is one we've seen before, and we're switching back to it. My hypothesis is that we tend to show a lot of spinners in case (1). If so, I suspect there are ways we can address those. * newness is the fuzzy part of this. I need to settle on a solid definition of newness - perhaps as a measure of time since the tab was created.

Hey liuche, got time for a quick data-review?

Comment on attachment 8844118 [details] Bug 1342464 - Add regression tests for the FX_TAB_SWITCH_SPINNER_TYPE probe. https://reviewboard.mozilla.org/r/117652/#review119648 ::: browser/base/content/test/tabs/browser_tabSpinnerTypeProbe.js:156 (Diff revision 1) > + * probe works. This means that we show a spinner for a tab that we've never > + * seen before, and not enough time has passed since its creation that we consider > + * it "old" (See the NEWNESS_THRESHOLD constant in the async tabswitcher for > + * the exact definition). > + */ > +add_task(function* test_unseenOld_spinner_type_probe() { This function name seems wrong.

Comment on attachment 8843334 [details] Bug 1342464 - Collect Telemetry on when a tab switch spinner is shown. , data-review=liuche https://reviewboard.mozilla.org/r/117100/#review119780 ::: dom/interfaces/base/nsITabParent.idl:59 (Diff revision 4) > * If aForward is false, navigate to the last focusable element or document. > */ > void navigateByKey(in bool aForward, in bool aForDocumentNavigation); > > readonly attribute boolean hasContentOpener; > + readonly attribute boolean hasPresented; Can you comment that this means we've previously received layers for this tab when switching to it. ::: toolkit/components/telemetry/Histograms.json:5101 (Diff revision 4) > + "expires_in_version": "60", > + "kind": "categorical", > + "bug_numbers": [1301104], > + "alert_emails": ["mconley@mozilla.com"], > + "releaseChannelCollection": "opt-out", > + "description": "Firefox: If the spinner interstitial displays during tab switching, record if the tab being switched to has been seen before. If not, record if the tab is 'old' (> 1000ms since creation) or 'new'.", Might want to make clear that "seen" means that it's content was visible.

Comment on attachment 8843334 [details] Bug 1342464 - Collect Telemetry on when a tab switch spinner is shown. , data-review=liuche https://reviewboard.mozilla.org/r/117100/#review120188 Clear description (and +1 to billm's suggestion), has expiration - r+ (data-review only)

Pushed by mconley@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/aae7b99fbe2f Collect Telemetry on when a tab switch spinner is shown. r=billm,liuche, data-review=liuche https://hg.mozilla.org/integration/autoland/rev/3313b3efefea Add regression tests for the FX_TAB_SWITCH_SPINNER_TYPE probe. r=mossop

Pushed by kwierso@gmail.com: https://hg.mozilla.org/integration/autoland/rev/d1c9574f8a26 Convert line endings to satisfy eslint

Pushed by archaeopteryx@coole-files.de: https://hg.mozilla.org/integration/autoland/rev/f8d82fa1218c More lint for the lint gods. r=Aryx

https://hg.mozilla.org/mozilla-central/rev/aae7b99fbe2f https://hg.mozilla.org/mozilla-central/rev/3313b3efefea https://hg.mozilla.org/mozilla-central/rev/d1c9574f8a26 https://hg.mozilla.org/mozilla-central/rev/f8d82fa1218c