mirror of
https://github.com/OPCFoundation/UA-.NETStandard.git
synced 2026-10-24 19:13:02 +08:00
romanettandClaude Opus 5.5
bd38870cf7
## Summary The 1-core client stall in the server load harness (`--client-cores 1`, write->notify p99 0.7-1.7 s) was caused by the harness, not the OPC UA client. `StartServerChild` started `PumpServerOutput` with `Task.Run`. The pump blocks in a synchronous `StreamReader.ReadLine` on the server's stdout for the whole run, so it held one thread-pool worker permanently. With `DOTNET_PROCESSOR_COUNT=1` the pool's minimum is one worker, so all other work items waited for the pool's starvation injection. That is why `DOTNET_ThreadPool_ForceMinWorkerThreads=8` and two processors both hid the stall. **Evidence:** 14 `dotnet-stack` samples of the constrained client during the measurement window. In every sample, the only blocked pool worker was in `ReadFile <- StreamReader.ReadLine <- Program.PumpServerOutput <- StartServerChild`, and the other workers were idle. No `Opc.Ua` frame was blocked. **Fix:** run the pump on a dedicated background thread. ## Numbers `run --scenario sub --sessions 25 --subs 20 --nodes 100 --pub 500 --write-interval 100 --duration 10 --warmup 6 --client-cores 1 --client-memory 512`, 5 alternating rounds (ms): | round | base write->notify p99 | fix write->notify p99 | base write p99 | fix write p99 | |---|---|---|---|---| | 1 | 659 | 61 | 619 | 12 | | 2 | 885 | 310 | 859 | 15 | | 3 | 306 | 303 | 52 | 23 | | 4 | 1717 | 455 | 408 | 81 | | 5 | 234 | 193 | 148 | 67 | The baseline stalled (> 600 ms) in 3 of 5 runs and the fix in 0 of 5 (max 492 ms). The remaining ~300 ms p99 comes from the 500 ms publishing interval. ## Test plan - [x] Harness Release build (net10.0) - [x] Alternating A/B runs above 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>