65 lines
2.6 KiB
Markdown
65 lines
2.6 KiB
Markdown
# WeaselDB Threading Performance Analysis Report
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## Summary
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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.
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## Performance Metrics
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### Throughput
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- Non-blocking: 1.3M requests/second over unix socket
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- Blocking: 1.1M requests/second over unix socket
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- 8 I/O threads with 8 epoll instances
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- Load tester used 12 network threads
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- Max latency: 4ms out of 90M requests
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### Threading Architecture
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- Two-stage pipeline: Stage-0 (noop) → Stage-1 (connection return)
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- Lock-free coordination using atomic ring buffer
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- Each request "processed" serially on single thread
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### Non-blocking vs Blocking Acquisition
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**Non-blocking acquisition (`mayBlock=false`)**:
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- Throughput: 1.3M requests/second (maintained with up to 1200 loop iterations)
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- Stage-0 CPU: 100% (10% futex wake, 90% other)
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- Serial CPU time per request: 396ns (1200 iterations, validated with nanobench)
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- Theoretical maximum serial CPU time: 769ns (1,000,000,000ns ÷ 1,300,000 req/s)
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- Serial efficiency: 51.5% (396ns ÷ 769ns)
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- 100% CPU usage when idle
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**Blocking acquisition (`mayBlock=true`)**:
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- Throughput: 1.1M requests/second (800 loop iterations)
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- Stage-0 CPU: 100% total (18% sched_yield, 8% futex wait, 7% futex wake, 67% other)
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- Serial CPU time per request: 266ns (800 iterations, validated with nanobench)
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- Theoretical maximum serial CPU time: 909ns (1,000,000,000ns ÷ 1,100,000 req/s)
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- Serial efficiency: 29.3% (266ns ÷ 909ns)
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- 0% CPU usage when idle
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### Request Flow
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```
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I/O Threads (8) → HttpHandler::on_batch_complete() → ThreadPipeline
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↓
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Stage 0: Noop thread
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(396ns serial CPU per request)
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↓
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Stage 1: Connection return
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↓
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Server::release_back_to_server()
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```
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### Pipeline Configuration
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- Stage 0: 1 noop thread
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- Stage 1: 2 worker threads for connection return
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- Atomic counters with shared ring buffer
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### Memory Management
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- Transfer ownership of the connection along the pipeline
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## Test Configuration
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- Server: test_config.toml with 8 io_threads, 8 epoll_instances
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- Load tester: ./load_tester --network-threads 12
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- Build: ninja
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- Command: ./weaseldb --config test_config.toml
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