runtime: expose schedule latency in TaskMeta / Task Hooks - #8282
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Add an explicit tracking knob and expose the sampled task schedule latency through TaskMeta. Reuse the histogram poll timestamp where possible and preserve grouped histogram accounting for LIFO polls. Document activation and interval semantics and cover current-thread, multi-thread, LIFO, disabled, and non-poll callback behavior.
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August 9, 2026 14:19
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Motivation
#7986 exposes a task-schedule-latency histogram and metric. For tools like dial9, it is very helpful to have this statistic available on a per-poll basis.
Solution
Expose
schedule_latency() -> Option<Duration>onTaskMeta.This is off by default. When disabled, schedule_latency returns
None. It is enabled by callingtrack_task_schedule_latency(); happy to workshop the name. It can be enabled separately from the histogram: if you are tracking the individual latencies there's no specific need to also put them in a histogram. Enabling the histogram also exposes it toTaskMeta.Assisted by GPT 5.6 Sol