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threading_performance_report.md

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+# WeaselDB Threading Performance Analysis Report
+
+## Summary
+
+WeaselDB achieved 1.3M requests/second throughput using a two-stage ThreadPipeline, with 396ns serial CPU time per request. Higher serial CPU time means more CPU budget available for serial processing.
+
+## Performance Metrics
+
+### Throughput
+- Non-blocking: 1.3M requests/second over unix socket
+- Blocking: 1.1M requests/second over unix socket
+- 8 I/O threads with 8 epoll instances
+- Load tester used 12 network threads
+- Max latency: 4ms out of 90M requests
+
+### Threading Architecture
+- Two-stage pipeline: Stage-0 (noop) → Stage-1 (connection return)
+- Lock-free coordination using atomic ring buffer
+- Each request "processed" serially on single thread
+
+### Non-blocking vs Blocking Acquisition
+
+**Non-blocking acquisition (`mayBlock=false`)**:
+- Throughput: 1.3M requests/second (maintained with up to 1200 loop iterations)
+- Stage-0 CPU: 100% (10% futex wake, 90% other)
+- Serial CPU time per request: 396ns (1200 iterations, validated with nanobench)
+- 100% CPU usage when idle
+
+**Blocking acquisition (`mayBlock=true`)**:
+- Throughput: 1.1M requests/second (800 loop iterations)
+- Stage-0 CPU: 100% total (18% sched_yield, 8% futex wait, 7% futex wake, 67% other)
+- Serial CPU time per request: 266ns (800 iterations, validated with nanobench)
+- 0% CPU usage when idle
+
+### Request Flow
+```
+I/O Threads (8) → HttpHandler::on_batch_complete() → ThreadPipeline
+                                                          ↓
+                                                   Stage 0: Noop thread
+                                                   (396ns serial CPU per request)
+                                                          ↓
+                                                   Stage 1: Connection return
+                                                          ↓
+                                             Server::release_back_to_server()
+```
+
+### Pipeline Configuration
+- Stage 0: 1 noop thread
+- Stage 1: 2 worker threads for connection return
+- Atomic counters with shared ring buffer
+
+### Memory Management
+- Transfer ownership of the connection along the pipeline
+
+## Test Configuration
+
+- Server: test_config.toml with 8 io_threads, 8 epoll_instances
+- Load tester: ./load_tester --network-threads 12
+- Build: ninja
+- Command: ./weaseldb --config test_config.toml