future-util: opts#31061
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Pull request overview
This PR optimizes ssx future utility helpers to reduce overhead (scheduler round-trips / allocations) and adds a dedicated rpbench benchmark to measure ignore_shutdown_exceptions behavior across common success/failure paths.
Changes:
- Reworks
ssx::ignore_shutdown_exceptionsto fast-path already-ready successful futures and use a shared shutdown-exception filter. - Reimplements
ssx::spawn_with_gate_thento avoidtry_with_gateand filter shutdown exceptions in athen_wrappedcontinuation. - Adds
future_util_rpbenchbenchmark to exerciseignore_shutdown_exceptionswith ready-success, shutdown-failure, and non-shutdown-failure inputs.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| src/v/ssx/future-util.h | Optimizes shutdown-exception filtering and gate-spawn helper to reduce overhead on common paths. |
| src/v/ssx/tests/future_util_bench.cc | Adds perf benchmarks focused on ignore_shutdown_exceptions fast path and exception filtering. |
| src/v/ssx/tests/BUILD | Registers a new rpbench target for the future-util benchmark. |
dotnwat
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Jul 9, 2026
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how much goose value does this add?
Cover already-resolved futures for success, gate closure, abort, and non-shutdown propagation. Keep producers out of line so callers cannot specialize for a known future state. Release/Bazel baseline (inst / tasks / allocs): ready 289 / 0 / 1 gate closed 22.87K / 0 / 3 abort 22.56K / 0 / 3 non-shutdown 24.44K / 0 / 4
Return already-successful futures directly. Handle failures with one
continuation that classifies once. Shutdown errors are swallowed; other
errors are returned in a failed future. This removes the coroutine frame
and a second unwind.
Release/Bazel deltas vs b0d4b296:
produce 1 KiB:
inst 56.13K -> 55.06K (-1.07K, -1.9%)
tasks 34 -> 34 (0, 0.0%); allocs 94 -> 90 (-4, -4.3%)
raft quorum ack, 16 B:
inst 159.82K -> 157.84K (-1.98K, -1.2%)
tasks 105 -> 105 (0, 0.0%); allocs 265 -> 254 (-11, -4.2%)
ready:
inst 289 -> 85 (-204, -70.5%)
tasks 0 -> 0 (0, 0.0%); allocs 1 -> 0 (-1, -100.0%)
gate closed:
inst 22.87K -> 15.50K (-7.37K, -32.2%)
tasks 0 -> 0 (0, 0.0%); allocs 3 -> 2 (-1, -33.3%)
abort requested:
inst 22.56K -> 15.19K (-7.37K, -32.7%)
tasks 0 -> 0 (0, 0.0%); allocs 3 -> 2 (-1, -33.3%)
non-shutdown:
inst 24.44K -> 17.30K (-7.14K, -29.2%)
tasks 0 -> 0 (0, 0.0%); allocs 4 -> 3 (-1, -25.0%)
Combine gate release and exception filtering in one then_wrapped
continuation. Return immediately when the gate is closed, and reuse the
shared shutdown filter on failure. Each successful call saves one task
and one allocation.
Release/Bazel deltas vs c23ee68:
produce 1 KiB:
inst 55.45K -> 55.30K (-150, -0.3%, noise)
tasks 34 -> 33 (-1, -2.9%); allocs 90 -> 89 (-1, -1.1%)
raft quorum ack, 16 B:
inst 157.82K -> 157.10K (-720, -0.5%, noise)
tasks 105 -> 100 (-5, -4.8%); allocs 253 -> 249 (-4, -1.6%)
future_util_rpbench:
all four cases unchanged in inst, tasks, and allocs
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CI test resultstest results on build#86940
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/microbench |
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Performance change detected in https://buildkite.com/redpanda/redpanda/builds/86950#019f4af0-35d2-41e5-8ac5-1b869c3d5e26: See https://redpandadata.atlassian.net/wiki/x/LQAqLg for docs |
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Remove task/scheduler-roundtrips and allocs from future-utils.
Backports Required
Release Notes