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Sometimes one span covers more than one kind of operation. Let users pass extra arguments to the span-end probe so tracers can split its latency by category. To that end extend span_with_probe! with a probe_args option: a [u64; N] array expression:(N = 0..=3) whose values are exposed to the tracer as the probe's arguments after the span duration (arg0). The macro emits a per-span probe function of matching arity and a stapsdt note with one -8@<reg> descriptor per argument, so each call site chooses how many values it passes. The probe function pointer is type-erased (as *const ()) in the shared SpanProbe, which carries the args in a fixed [u64; 4] array; Drop casts it back to the right fn(u64, ..) arity. Spans without probe_args keep a duration-only probe, and tracers reading only arg0 are unaffected.
Add a cache_task span that alternates cache hits and misses, passing a hit flag as arg1 via probe_args. The bpftrace script buckets the single probe's durations by outcome with /arg1 == 1/ and /arg1 == 0/ filters.
oga35767-eng
approved these changes
Sep 21, 2026
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Sometimes one span covers more than one kind of operation. Let users pass extra arguments to the span-end probe so tracers can split its latency by category.