Files
sglang/benchmark/hicache
laoyao0822 2c94b8de23 Ground HiCache backup overlap policy in measured tails
The per-layer backup path did not explain end-to-end performance by inspection alone, so add a focused benchmark that compares all-layer tail backup against per-layer forward-overlap backup under the same page_first_direct layout. The benchmark reports total latency, over-forward-only latency, submit overhead, and winner so short-extend fallback decisions are based on measured cost rather than request-size intuition.

Constraint: CUDA benchmark execution is remote-only; this local commit only records the benchmark driver.

Rejected: Adding more online logs for this question | the user asked for benchmark evidence and logs would perturb scheduler behavior.

Confidence: high

Scope-risk: narrow

Directive: Do not infer production policy from per_extra alone; per-layer CPU submission can be hidden inside the forward timing interval, so total latency is the safer comparison metric.

Tested: Local py_compile benchmark/hicache/bench_cp_hicache_backup_overlap.py.

Tested: Remote benchmark logs generated under /mnt/beegfs/cjy/cp_hicache_backup_overlap_bench_20260527_*.log.

Not-tested: Full SGLang test suite; benchmark is standalone and CUDA execution was remote-only.
2026-05-28 03:43:05 +08:00
..
2025-08-28 23:44:26 -07:00

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)