1779685 - Add events to profile.profileGatheringLog

Status: RESOLVED FIXED

(Core :: Gecko Profiler, task, P2)

Description

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

Since bug 1676271, profiles contain a profileGatheringLog, but currently it only stores the start and end timestamps.
We want to capture the most useful events that happen during this phase, e.g.: profile requests and responses, progress, errors, etc.

This will be useful for fixes to bug 1758643 and bug 1779367, to document why we need to discard some data because of issues during the gathering process.

Here's an example profile with the new data: https://share.firefox.dev/3cfxrO2 , open the web console and inspect profile.profileGatheringLog, it should look like this:

{
  "91168": {
    "events": [
      [ 762491.7001, "Generated parent process profile, size:", 89156614 ],
      [ 762522.4514, "Added exit profiles, total size so far:", 89156631 ],
      [ 762533.0517, "Waiting for pending profile, pid:", 77304 ],
      [ 762533.0774, "Waiting for pending profile, pid:", 94216 ],
      [ 762754.0895, "Got profile from pid, with size:", 77304, 53061201 ],
      [ 763810.0778, "Requested progress from pid:", 94216 ],
      [ 763810.6212, "Got response from pid, with progress:", 94216, 73.29 ],
      [ 764810.7392, "Requested progress from pid:", 94216 ],
      [ 764811.1027, "Got response from pid, with progress:", 94216, 97.89 ],
      [ 765003.995, "Got profile from pid, with size:", 94216, 90143930 ],
      [ 765097.7483, "Finished gathering, total size:", 405950395 ]
    ],
    "profileGatheringLogBegin_TSms": 757591.8512,
    "profileGatheringLogEnd_TSms": 765145.2974
  }
}

Comment 1

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

Attachment: Bug 1779685 - Factor ChunkedJSONWriteFunc::Length() out of CopyDataIntoLazilyAllocatedBuffer() - r?florian

This will be useful to see how big profiles get during gathering, and
potentially to avoid making them too big if possible.

Comment 2

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

Attachment: Bug 1779685 - Add useful information to profile.profileGatheringLog.events - r?florian

This may be useful to advanced profiler users, to see how the multi-process
profile gathering went.

(Some information, like missing processes, could be useful to expose to all
users, but this should be done in future tasks, with corresponding front-end
work.)

Note: There are no direct tests, as this is intended for advanced human users,
and the format is not guaranteed to stay stable.

Depends on D151901

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/42b6aac07798
Factor ChunkedJSONWriteFunc::Length() out of CopyDataIntoLazilyAllocatedBuffer() - r=florian
https://hg.mozilla.org/integration/autoland/rev/2b1c4f14a2cf
Add useful information to profile.profileGatheringLog.events - r=florian

Comment 4

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/42b6aac07798
https://hg.mozilla.org/mozilla-central/rev/2b1c4f14a2cf