Files
sglang/benchmark/hicache
laoyao0822 9a9893e571 Model CP scheduler admission with cache-hit pressure
Add an offline benchmark that reuses PrefillAdder to model how L1 cached tokens, L2 HiCache hits, and extend tokens shape CP shared-KV prefill batch admission. The tool makes scheduler stop reasons and fake L2 load-back capacity pressure observable without starting a model.

Constraint: The benchmark must stay CPU/offline and avoid depending on CUDA execution or live services.

Constraint: L2 cached tokens are modeled as host_hit_length, so successful load-back both increases prefix_len and consumes fake L1 capacity.

Rejected: Build an ETE benchmark first | too slow for isolating scheduler admission behavior.

Rejected: Reimplement scheduler logic from scratch | would drift from PrefillAdder semantics.

Confidence: high

Scope-risk: narrow

Directive: Treat duration_us as Python admission overhead only; it is not an ETE latency metric.

Tested: Remote pytest test/registered/unit/managers/test_prefill_scheduler_admission_bench.py: 4 passed as part of 6 targeted tests.

Tested: Remote synthetic benchmark run with --cp-max-total-cached-tokens showed second 4096-token cached request stopped with OTHER.

Not-tested: Real traffic trace import from production logs.
2026-06-10 22:21:59 +08:00
..

Run synthetic multi-turn benchmark

# SGLang server with radix cache disabled
python -m sglang.launch_server --model-path Qwen/Qwen2.5-14B-Instruct --port 30000 --disable-radix-cache

# SGLang server with radix cache on and first-come-first-serve policy
python -m sglang.launch_server --model-path Qwen/Qwen2.5-14B-Instruct --port 30000 --schedule-policy fcfs

# The default SGLang server with radix cache on and long-prefix-match policy
python -m sglang.launch_server --model-path Qwen/Qwen2.5-14B-Instruct --port 30000

# SGLang server with hierarchical radix cache enabled
python -m sglang.launch_server --model-path Qwen/Qwen2.5-14B-Instruct --port 30000 --enable-hierarchical-cache

python bench_multiturn.py --model-path Qwen/Qwen2.5-14B-Instruct

Note: The performance gain of hierarchical caching depends on the ratio of reusable tokens to GPU memory capacity. The more tokens to be reused, the larger the model, and the more constrained the GPU memory size, the greater the benefit one can expect from hierarchical caching.

Benchmark with more datasets

Download Dataset

./download.sh {sharegpt|ultragpt|loogle|nextqa|all}

This script will automatically download the required dataset to the current working directory

Multiturn Benchmark

Supported Datasets

  • sharegpt
  • ultrachat
  • loogle

Example Usage:

python3 bench_serving.py --model mistralai/Mistral-7B-Instruct-v0.3 --backend sglang \
--dataset-path longdep_qa.json --dataset-name loogle --request-rate 10 --num-prompts 10  \
--port 8001 --enable-multiturn --disable-shuffle

This uses mistralai/Mistral-7B-Instruct-v0.3 model with sglang as backend. The dataset is longdep_qa.json. We send 10 conversations with 10 req/s to port 8001. We enable multiturn chat without shuffling the order of conversations (i.e. following the original order in the dataset file).

Note:

The requests of multiple conversations are sent in a round robin fashion. For example, if we have 3 conversations A, B, C whose rounds are [2, 3, 4] correspondingly, multiturn chat will send the requests to the backend in the following order: [A1, B1, C1, A2, B2, C2, B3, C3, C4] This has implications on the cache reuse patterns: the cache reuse distance is the largest under this request pattern (which means a prefix-aware local scheduler in the backend can yield the most benefit compared to a FIFO scheduler)

Shared Prefix Benchmark

Supported Datasets

  • loogle

Example Usage:

python3 bench_serving.py --model mistralai/Mistral-7B-Instruct-v0.3 --backend sglang \
--dataset-path longdep_qa.json --dataset-name loogle --request-rate 10 --num-prompts 10  \
--port 8001 --enable-shared-prefix --disable-shuffle

Note:

Shared Prefix benchmark sends the questions for the same prompt together. For example, if we have 3 shared prefix A, B, C, which have [2, 3, 4] questions correspondingly, the shared prefix benchmark will send the requests to the backend in the following order: [A+Q1, A+Q2, B+Q1, B+Q2, B+Q3, C+Q1, C+Q2, C+Q3].

Multi Modality Benchmark (WIP)

Supported Datasets:

  • nextqa

Example Usage:

Server:
python3 -m sglang.launch_server --model-path lmms-lab/LLaVA-NeXT-Video-7B  --tp 2 --dp 1 --port 8001 \
--host 0.0.0.0 --mem-fraction-static 0.9 --tokenizer-path llava-hf/llava-1.5-7b-hf \
--json-model-override-args "{\"architectures\": [\"LlavaVidForCausalLM\"], \"model_type\":\"llava\", \"mm_spatial_pool_stride\":2}"

Client:
python3 bench_serving.py --model lmms-lab/LLaVA-NeXT-Video-7B --backend sglang  --dataset-path \
NExTVideo  --dataset-name nextqa --request-rate 10 --num-prompts 1 --disable-shuffle --port 8001 \ --enable-multiturn --max-frames 16 --tokenizer llava-hf/llava-1.5-7b-hf --fixed-output-len 2048

Note: for the server args, tokenizer-path, overriding architecture are necessary.

Supported Backend

  • sglang (oai)
  • vllm (oai)
  • lmdeploy (oai)