LoAF: Report worker congestion from a saturated task queue [chromium/src : main]

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Joone Hur (Gerrit)

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Jul 30, 2026, 2:34:48 AM (yesterday) Jul 30
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Joone Hur added 2 comments

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File-level comment, Patchset 25:
Joone Hur . resolved

As discussed, I've added queue_time to TaskTimeObserver::DidProcessTask and removed base::TaskObserver from the LoAF monitor, so the worker congestion monitor uses a single task observer to get the queue time. PTAL.

File third_party/blink/renderer/core/frame/animation_frame_timing_monitor.h
Line 87, Patchset 20: // base::TaskObserver. Captures each task's scheduled start time (queue_time /
Noam Rosenthal . resolved

Maybe we can add queue_time to TaskTimeObserver instead? WDYT @shas...@chromium.org

Scott Haseley

Sounds reasonable to me. I guess the caveat is it's not always set, but probably fine to document given GetDesiredExecutionTime() has the same behavior.

It would be good to use one or the other rather than a different type of observer for main vs. worker, if possible. IIRC the main difference is TaskTimeObserver ignores tasks that run in nested run loops, which should only affect the main thread (% devtools pausing, I think).

Joone Hur

Done

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Scott Haseley (Gerrit)

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Jul 30, 2026, 5:23:03 PM (12 hours ago) Jul 30
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Scott Haseley added 4 comments

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File-level comment, Patchset 26 (Latest):
Scott Haseley . resolved

LG % a few comments. I'll wait for Noam to take another pass, but the guts of it LG.

File base/task/sequence_manager/task_time_observer.h
Line 31, Patchset 26 (Latest): TimeTicks queue_time) = 0;
Scott Haseley . unresolved

Can we rename this:

```suggestion
                              TimeTicks desired_execution_time) = 0;
```

given it maps to `GetDesiredExecutionTime()`?

File third_party/blink/renderer/core/frame/animation_frame_timing_monitor.cc
Line 81, Patchset 26 (Latest): FinalizeCongestedMoment();
Scott Haseley . unresolved

Will this entry be consumed by anything? I think the worker will stop running tasks after this?

Line 272, Patchset 26 (Latest): // A congested moment is an interval during which the task queue stays
Scott Haseley . unresolved

nit: there are multiple task queues with different priorities, so "the task queue" is a bit of a simplification. It's probably worth rephrasing (here and below), and I think it's find, but please double-check that this matches the model you're using here (i.e. `desired_execution_time` of `task_N+1` can be less than `desired_execution_time` of `task_N`).

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    Noam Rosenthal (Gerrit)

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    Jul 30, 2026, 5:27:12 PM (12 hours ago) Jul 30
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    Noam Rosenthal . resolved

    Really nice work.
    I would want to see how the processing model looks like in the spec, but iterating on top of this prototype seems good.

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