1919845 - Add the ability to annotate flows between markers

Status: ASSIGNED

(Core :: Gecko Profiler, enhancement)

Description

[Jeff Muizelaar [:jrmuizel]]

Perfetto (flow_ids) and ETW (activityID)(docs) both have support for this kind of thing.

I believe adding these annotations and exposing them in the UI would be valuable for better understanding what's happening in profiles and help when comparing to Chrome.

Comment 1

[Jeff Muizelaar [:jrmuizel]]

Attachment: Bug 1919845. Add support flows in markers

Comment 2

[Jeff Muizelaar [:jrmuizel]]

Here's an an example profile that has some flows for image decoding: https://share.firefox.dev/3Uky4su

Comment 4

[Markus Stange [:mstange]]

Since the meaning of a flow ID depends on the marker's timestamp, I worry that we might get into trouble when we use flow IDs with "backdated" markers. We'll need to say something like this somewhere: "When using Flow IDs generated from a pointer, make sure this pointer was valid at the time of the marker timestamp". It may be tricky for the implementation to enforce this.

Comment 5

[Markus Stange [:mstange]]

I've filed https://github.com/firefox-devtools/profiler/issues/5178 for the front-end part.

Comment 6

[Markus Stange [:mstange]]

For interval markers, is the flow ID associated with the start timestamp or the end timestamp of the marker? I can think of ways to cause trouble with either choice.
I don't have a suggestion for a solution. Maybe we can pick the start timestamp for now and see how much trouble we run into.