ClawPerfBench

Performance benchmarking tool for LLM Serving backends with multi-turn long-context workloads.

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Built on EvalScope's perf infrastructure, adding:

• Multi-turn context model: System Prefix + User Prefix + History + Current Input
• Append-mode compaction: Clear history, grow user prefix when context reaches limits
• User arrival scheduling: Burst, steady, or Poisson arrival patterns
• System metrics polling: Prometheus endpoint support for vLLM, SGLang, MindIE
• Per-user + per-turn metrics: TTFT, TPOT, ITL with compaction tracking
• Prefix cache simulation: Trie-based HBM + external prefix cache hit rate tracking in mock server

Installation

pip install clawperf

For the mock server used in testing:

pip install clawperf[mock-server]

For development:

pip install clawperf[dev]

Install from source (recommended for development):

git clone https://github.com/Potterluo/ClawPerf.git
cd ClawPerf
uv sync --extra dev --extra mock-server

Quick Start

Run a benchmark

clawperf \
  --endpoint http://localhost:8000/v1/chat/completions \
  --model qwen3-32b \
  --num-users 5 \
  --user-arrival steady:2 \
  --max-turns 10 \
  --output results.json

Start mock server (for testing)

clawperf-mock-server --port 8080

End-to-end test with mock server

# Start mock server
clawperf-mock-server --port 8080

# Run benchmark against it
clawperf \
  --endpoint http://localhost:8080/v1/chat/completions \
  --model Qwen/Qwen2.5-7B-Instruct \
  --tokenizer Qwen/Qwen2.5-7B-Instruct \
  --num-users 4 \
  --max-turns 5 \
  --max-context-tokens 200000 \
  --metrics-endpoint http://localhost:8080/metrics \
  --backend vllm \
  --verbose

CLI Options

User Configuration

Option	Default	Description
--num-users	1	Total concurrent users
--user-arrival	burst	Arrival pattern: burst, steady:<seconds>, or poisson:<lambda>

Context Configuration

Option	Default	Description
--system-prefix-tokens	15000	System prefix token count
--system-prefix-source	random	Source: random or a file path
--user-prefix-tokens	5000	Per-user prefix token count
--input-tokens-per-turn	5000	Input tokens per turn
--output-tokens-per-turn	1000	Output tokens per turn
--max-context-tokens	128000	Context window limit
--compaction-prefix-increment	5000	User prefix growth on compaction

Run Configuration

Option	Default	Description
--max-turns	100	Maximum turns per user

API Configuration

Option	Default	Description
--endpoint	(required)	LLM API endpoint URL
--model	(required)	Model name
--api-key	(empty)	API key
--tokenizer	(defaults to model)	Tokenizer path
--ignore-eos	True	Ignore EOS token
--request-timeout	600	Request timeout in seconds

System Metrics

Option	Default	Description
--metrics-endpoint	None	Prometheus metrics URL
--metrics-interval	5	Polling interval in seconds
--backend	vllm	Backend: vllm, sglang, or mindie

Output

Option	Default	Description
--output	results.json	Output JSON file path

Output Format

Results are saved as JSON with:

{
  "config": { ... },
  "summary": {
    "prefix_cache_token_hit_rate": 0.7981,
    "prefix_cache_hit_tokens_delta": 712012,
    "prefix_cache_query_tokens_delta": 892165,
    "total_compactions": 0,
    ...
  },
  "users": [
    {
      "user_id": 0,
      "aggregate": {
        "total_output_tokens": 3000,
        "ttft": { "avg": 150.2, "P50": 140, "P99": 200 },
        "tpot": { "avg": 3.2, "P50": 3.0, "P99": 5.0 },
        "throughput_tok_s": 12.5,
        "error_count": 0,
        "compaction_count": 2
      },
      "turns": [
        {
          "turn_id": 1,
          "success": true,
          "ttft_ms": 150.2,
          "e2e_latency_ms": 3200.5,
          "tpot_ms": 3.2,
          "input_tokens": 25000,
          "output_tokens": 1000,
          "context_tokens": 25000,
          "compaction_triggered": false
        }
      ]
    }
  ],
  "system_metrics": [ ... ],
  "timeline": [ ... ]
}

Testing Philosophy

ClawPerfBench is designed to simulate the real workload of an Agent system — not single-shot API calls, but sustained multi-turn conversations that push LLM serving backends to their limits.

Why multi-turn matters

Real Agent systems (like OpenClaw) don't send one-off requests. They maintain long conversations: a system prompt, user-specific context, and growing history. Each turn re-sends the entire accumulated context, creating exponentially growing prompts. This is fundamentally different from single-request benchmarks and exposes backend behaviors that single-shot tests miss:

• Prefix cache effectiveness: Does the KV-block cache actually reuse tokens across turns? A single-request benchmark can't measure this.
• Compaction under load: When context hits the window limit, how does the system handle truncation? Does it recover gracefully or spiral into overflow?
• Latency degradation: As context grows from 25K to 200K tokens, TTFT and TPOT change dramatically. Per-turn metrics reveal this progression.
• Concurrent pressure: Multiple users with independent conversations create mixed prefix cache states — some sharing the system prefix, others diverging at user-specific paths.

Simulating real users

Each simulated user maintains an independent conversation state with its own growing prefix and history. Users arrive according to configurable patterns (burst, steady, Poisson) — mimicking how real traffic builds up, not an artificial flood of identical requests.

What we measure

What	Why it matters
TTFT per turn	First-token latency grows with context size — the key UX metric for Agent systems
TPOT per turn	Generation speed should stay stable; degradation indicates compute bottlenecks
Prefix cache hit rate	Token-level reuse fraction across turns — the efficiency metric for KV caching
Compaction events	When and how often context overflows — determines conversation continuity
Per-user breakdown	Different users have different prefix paths; aggregate stats hide per-user variance

Context Model

Each user's context follows this structure:

[System Prefix] [User Prefix] [History] [Current Input]

When context reaches --max-context-tokens, append-mode compaction fires:

1. The base context (system + user prefix + input, without history) is checked first. If it already exceeds the limit, compaction is skipped and the turn is marked as context_overflow — this prevents infinite compaction loops.
2. Otherwise, history is cleared and the user prefix grows by --compaction-prefix-increment tokens.
3. New random content fills the enlarged user prefix.

This simulates how real LLM serving systems handle context overflow with prefix caching.

Prefix Cache Simulation

The mock server simulates vLLM's KV-block prefix cache using a trie:

• HBM trie: Represents GPU KV cache. Queried first for longest prefix match. Always updated after every request (mimicking vLLM storing all KV blocks regardless of hit/miss).
• External trie: Represents CPU/disk prefix cache. Queried on HBM miss. Also always updated after every request.
• Token-level hit rate: prefix_cache_hit_tokens / prefix_cache_query_tokens — the fraction of prompt tokens that reuse cached KV blocks. This is the meaningful metric; request-level (binary) hit rate is not reported.
• Eviction: When the trie exceeds max_prefixes (200), oldest leaf nodes are evicted.

User Arrival Scheduling

• burst: All users start immediately
• steady:2: Users arrive every 2 seconds
• poisson:0.5: Users arrive following a Poisson process with rate 0.5

Architecture

ClawPerf reuses EvalScope's core perf components:

• AioHttpClient: Async HTTP with streaming, proper timeout/connector config
• OpenaiPlugin: Request building, response parsing, local token counting
• BenchmarkData: Single-request data container (TTFT, ITL, E2E timing)
• MetricsAccumulator: Real-time metrics aggregation

And adds its own orchestration layer for multi-turn, multi-user workloads.

Key modules:

Module	Role
cli.py	Argparse entry point, config creation, runner launch
config.py	BenchmarkConfig dataclass, arrival mode parsing
runner.py	BenchmarkRunner orchestrator, user loop, result finalization
context.py	UserContext context assembly, compaction with infinite-loop guard
scheduler.py	Burst/steady/Poisson async generators
system_metrics.py	SystemMetricsPoller with backend-specific metric mappings
tokenizer.py	TokenizerManager wrapping ModelScope/HuggingFace tokenizers
mock_server.py	FastAPI mock LLM server with trie-based prefix cache simulation

Development

uv sync --extra dev --extra mock-server
pytest
ruff check

License

Apache License 2.0