Open Bug 1500465 Opened 11 months ago Updated 2 months ago
Need APIs to measure touch scrolling input latency on desktop and Gecko
47 bytes, text/x-phabricator-request
|Details | Review|
The performance team wants to add level 1 telemetry probes for touch scrolling latency, most importantly on Windows and Android/GeckoView. We may also want to have a Talos test that measures this latency. We will need to have APIs to get the time that passes between the OS touch event and the composite that presents this touch move to the screen.
11 months ago
The touch events already have a timestamp on them (if not we can add one), so those can be used to track the time from when the OS gives us the event to the point where APZ uses that event to mutate the scroll position. However past that point there's a many-to-one collapsing where multiple touch events can have their effect show up on the screen in a single composite. So we'd somehow have to track all the touch events that were processed by APZ between samplings, and hand that bag of information to the compositor at sample time (or just expose it via an API to be read after a sampling). Then when the compositor presents the frame it can record the telemetry probes for those touch events. This assumes we only care about touch events that are eventually processed by APZ, and not touch events that preventDefault()'d but then drive some JS scrolling. That would be much harder to track.
Priority: -- → P3
Attachment #9074622 - Attachment description: Bug 1500465 - Measure touch scroll latency and connect to telemetry. r=mstange → Bug 1500465 - Measure touch scroll latency and connect to telemetry.
Pushed by firstname.lastname@example.org: https://hg.mozilla.org/integration/autoland/rev/40010303c474 Measure touch scroll latency and connect to telemetry. r=kats
Backout by email@example.com: https://hg.mozilla.org/mozilla-central/rev/c4b20b18bf97 Backed out changeset 40010303c474 on request of christina_ for causing OOM crashes in automation. a=backout
Status: RESOLVED → REOPENED
Resolution: FIXED → ---
Target Milestone: mozilla70 → ---
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